摘要:

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ISSN:0365-6217    

DOI:10.1039/AR93835FP001

出版商:RSC    

年代:1938

数据来源: RSC

摘要:

ANNUAL REPORTSON THEPROGRESS OF CHEMISTRY.RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.1. INTRODUCTION AND S m m y .THESE Reports do not represent an attempt at a condensed, anda t the same time complete account of the advances made in nuclearphysics during the current year. They are brief summaries of themost important papers which have appeared, the criterion ofimportance being set by the Reporters in an arbitrary manner.It is proposed to provide next year an article on nuclear theory,so that, for the present, attention will be confined to results of amore empirical nature.The “Mesotron.”-From a fundamental point of view there isno doubt that greatest interest is centred round a growing beliefin the existence of a new particle of matter, which must be regardedas fundamental in the same sense as the proton, neutron, and theelectrons. In the literature this particle has been called by variousnames, but it seems generally agreed now that it shall be termed theThis particle, firstsuggested theoretically by H.Yukawa, has been observed only inthe cosmic radiation. Theory indicates that the large penetratingpower of some components of the cosmic radiation is not com-patible with the properties of a particle such as the electron. Onthe other hand, great contidence in the theory has arisen from itssuccess in explaining the production of cosmic ray “ showers,”which are assumed to arise from a cascade process of production ofpairs of electrons.It is possible, however, to account for the great penetratingpower of the anomalous component of the cosmic rays by assumingit to consist of particles of mass intermediate between that of theproton and the electron.Such particles should lose energy by theproduction of radiation in passing through matter at a smaller ratethan electrons, but, on the other hand, they should produce adetectably greater ionisation per unit path when they are movingslowly, i.e., with energies of 10 m.v. or less. Photographs of suchmesotron ” (Le., “ intermediate ” particle). ( 8 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.particles have been obtained by various workers, notably by E. J.Williams. The mass of the particle determined from penetrationobservations, and from the ionisation near the end of the path,lies between 10 and 200 times the electron mass, with a probabilitythat this ratio lies around 150.Attempts have been made in the past to explain the attractiveforce between proton and neutron in the nucleus in terms of anexchange of charge between these particles.The assumption thatthis exchange takes place as a result of a virtual emission of anelectron did not meet with much success. However, the newparticle has proved extremely promising in this sphere, for itsgreater mass, and its higher spin of unity, enable a comprehensivetreatment of nuclear forces to be developed.In view of the fundamental importance of the new particle, aspecial article has been contributed by Professor R. Peierls, andforms the second section of this Report. A more condensed accountis given by P.M. S. Blackett.1Technical.-Technical advances made in the sphere of atomicphysics have been in the direction of improvement of existingmethods rather than the development of new ones. This is par-ticularly so in the production of high-speed ions for nuclear studies.Methods of direct acceleration of particles by high voltages havebeen improved, mainly by the extension of the multiplicationcircuit to give 2 m.v. by Messrs. Philips of Eindhoven, and by thestill further development of the electrostatic belt generator workingunder pressure. Thus, D. B. Parkinson, R. G. Herb, E. J. Bernet,and J. L. McKibben l a have given a detailed account of an apparatusproducing small beams of ions with energies as great as 2.4 m.v.,and W.H. Wells2 has reported the progress made with the verylarge apparatus constructed by the Westinghouse Co., which shouldproduce at least 5 m.v. and M. E.Rose4 have shown that the maximum energy of the particles ob-tained from the cyclotron is limited by loss of resonance with theelectric field, owing to the relativistic increase of mass. Theyshowed that to maintain resonance at high energies, the magneticfield of the cyclotron must increase with the radius of curvature ofthe paths of the ions, and that this is not compatible with focusingconditions. J. Churgin and R. R. Wilson also have discussedH. A. Bethe and M. E. RoseNature, 1938,142, 692.Bull. Amer. Physical SOC., 1938, 13, No. 7, 15.Ibid., 1938, 53, 362.Oompt. rend.Acad. Sci. U.R.S.S., 1938, 19, 237.Physical Rev., 1938, 63, 408.la Physical Rev., 1938, 53, 642.a Physical Rev., 1937, 52, 1254OLIPHANT : INTRODUCTION AND SUMMARY. 9the stability of ionic orbits in the cyclotron, and recent (unpublished)considerations have indicated that by increasing the radio-frequencypower, and hence the D voltage, the production of ions of energies asgreat as 50 m.v. or more should be possible. It has been pointedout by L. H. Thomas 7 that if a cylindrical variation of the magneticfield, with period x / 2 , be superimposed upon a magnetic field increas-ing from the centre outwards, stable orbits may be obtained and re-sonance preserved. L. I. Schiff* has shown that a cylindricalperiodicity of 2x13 has some advantages, in that the amplitude of thevariations required to produce focusing is less.These variations inthe magnetic field are combined with a corresponding modificationin the electric field, i.e., in the latter case the D-shaped electrodesare replaced by “ triants ” provided with three-phase power. Thusit becomes possible that the energies of particles available fornuclear studies may be increased very much in the future by thebuilding of still larger cyclotrons.R. R. Wilson9 has shown that the currents actually circulatingin the cyclotron, and which may be utilised to strike internal targets,may be of the order of milliampbres. Very powerful sources indeedof artificial radioactive elements have been prepared by using theseinternal targets.It is evident that the cyclotron is by far the mostpowerful accelerating system so far produced.Nuclear Isomerism and Element No. 43.-Considerable advance inknowledge of isomeric nuclei has been gained during the presentyear, and information on some of the work is given in the section ofthe Report contributed by Dr. P. B. Moon.Isomeric nuclei are atomic species with identical atomic chargesand mass numbers, but with differing energy states, the state ofhigher energy being “ metastable ” in the sense that the transitionto the lower state is sufficiently delayed for the higher energy stateto have an appreciable lifetime. Recent discussion of the problemof nuclear isomerism has been given by N. Feather and E. Bretscher loand W. Bothe? Feather and Bretscher have discussed theisomerism of U-X, and U-2, in the natural disintegration ofuranium.They concluded that the U-2 is formed from U-X, by it(p-y) branching in the ratio 665 : 1. A level scheme is proposed toaccount for the facts on the basis of C. F. von Weizsacker’s hypo-thesis l2 that for small energy differences the y-transition betweenPhysical Rev., 1938, 54, 580.Ibid., pp. 240, 1031.* Ibid., p. 1114.lo Proc. Roy. Soc., 1938, A, 165, 530.11 Nuovo Cim., 1937, 14, 601.l2 See Ann. Reports, 1937, 34, 2110 RADIOACTIVITY AND SUB-ATOMIU PHENOMENA.the isomers may be inhibited by a large difference in angularmomentum. However, M. H. Hebb and G. S. Uhlenbeck 13 haveshown that these conditions may lead to a considerable internalconversion, so that the transition should lead more often to emissionof a conversion electron than a y-ray.At the same time, the life-time of the metastable isomeric state will be much reduced.B. Pontecorvo l4 has shown that the isomeric nucleus, 105Rh, ofgreater energy emits a line of 8-rays corresponding to the internalconversion of the y-radiation. E. Segrk and G. T. Seaborg 15 haveshown that bombardment of molybdenum with deuterons, or slowneutrons, gives an active molybdenum isotope of half-life 65 hours,which decays by 8-emission to a second radioactive element whichemits only a line spectrum of @-rays. Chemical separation shows thatthis is an element of atomic number 43. It is shown both by absorp-tion methods and by use of a magnetic spectrograph that the electronsemitted have energy of about 110 k.v., corresponding to the internalconversion of a y-ray of 130 k.v.energy.16 Some X-rays are emittedalso, identified by absorption observations in neighbouring elementsas the K, radiation from element 43. Some y-rays are observed.The simplest assumption to account for these observations is thatthe activity is due to an isomeric form of element 43, which decaysto a more stable form by internal conversion, and by emission ofy-rays, with a half-life of 6 hours. P. Abelson 1' has since obtainedX-ray spectra giving confirmation of these conclusions, using intensesources prepared in the Berkeley cyclotron. This is probably thefirst reliable evidence of the existence of an element of atomicnumber 43.M.L. Pool and L. L. Quill I* have suggested that 159Gd, whichgives @-decay periods of 3-5 minutes and 17 hours, and 175Yb (2.1hours, and 14 hours) are further cases of nuclear isomerism.A. C. G. Mitchell and L. M. Langer l9 have shown that the captureof slow neutrons by 1151n leads to the formation of two isomericforms of 116In, one of period 13 secs. and t,he other 54 mins. Ay-ray is associated with the decay of the latter but not with theformer period. The branching ratio (13 secs. : 54 mins.) in formationis independent of the method of excitation, and is 1.12 0.06,and a level scheme can be prepared which will account for all thel3 Physica, 1938, 5, 605.l4 Physical Rev., 1938, 54, 542.Is Ibid., p. 772.l6 Cf.D. C. Kalbfell, Bull. Amer. Physical Soc., 1938, 13, NO. 6 : PhysicalRev., 1938, 54, 543.1' Unpublished.1* Physical Rev., 1938,53, 437. 1g Ibid., p. 505OLIPHANT : INTRODUCTION AND SUMMARY. 11observed facts. M. L. Pool 20 also has given evidence for the exist-ence of isomeric pairs of radio-iridium. M. L. Pool and E. C.Campbell 2 1 have discussed the isomerism of 106Ag, 24.5-min.radio-isotope, and 106Ag, 8.2-day ground state. The idea of nuclearisomerism is of great importance, and it is likely to lead to consider-able advances in the understanding of nuclear-energy states.Radioactive Decay by K-Electron Capture.-A number of strikingexamples have been recorded of transformations of positron-emitting bodies by the capture of electrons from the H-shells of theelements concerned.M. L. Pool and E. C. Campbell 21 have inves-tigated the decay of the isomeric 106Ag nucleus of 8.2 hours half-life,and find that the relative probabilities of H-electron capture,negative p-emission, and positive p-emission are in the ratio640 : 40 : 1. E. J. Williams and E. Pickup 22 showed that H-electroncapture in the decay of a radio-element formed from titanium bybombardment with fast deuterons is 1000 times that of the alter-native process of positron emission. L. H. Rumbaugh, L. R.Hafstad, and R. B. Roberts 23 give evidence that 7Be decays to 'Liby K-electron capture. L. Alvarez 24 has discussed critically thefact that evidence of emission of K-radiation is no real evidencealone of K-electron capture by a radioactive nucleus, for this mayarise from internal conversion of y-rays.It is necessary to provethat a nucleus of charge 2 is transformed into one of (Z- l), and thatthe characteristic radiation of (2-1) is emitted after the process.67Ga, formed by deuteron or a-particle bombardment of zinc,emits X-rays, electrons, and y-rays. The electrons are identified byabsorption and magnetic spectrographic methods as a line spectrumwith lines of 90 and 99 k.v., corresponding with the K- and L-conversion of a 100 k.v. line. The X-radiation is identified asZn-K, and -KB. Absorption of the y-rays in lead and copperindicates an energy of 0.2-0.3 m.v. All the data are in accord withthe view that 67Ga is transformed into 67Zn by electron capture,and that this 67Zn then emits a K-X-ray quantum in half the cases.The excited state of 67Zn then emits either a 100 k.v.or a 0 . 2 4 - 3m.v. y-ray quantum or both, the 100 k.v. line being stronglyinternally converted. Finally, another quantum of Zn-Kradiation is emitted in about half the cases (Auger coefficient 0.5).Similarly, the same author 25 has discussed electron capture in thetransformation of 22Na into 22Ne, of 'Be into 'Li, of a vanadiumradio-isotope, and other cases.20 Phyysiccsl Rev., 1938, 53. 611.22 Nature, 1938, 141, 199.24 Ibid., 53, 606.21 Ibid., p. 272.28 Phyakd Rev., 1930,64,657.86 Ibiol., 64, 48612 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.Existence of 5He.-F. Joliot and I. Zlotowski 26 have described amethod for identifying particles produced in nuclear transformationsby passing them through a magnetic field of 16,000 Gauss producedby means of coils of wire carrying 6000 ampbres, placed around aWilson expansion chamber.The tracks of heavy particles are thuscurved. Further, they give evidence27 for the formation of astable isotope of helium of mass 5, through collision between a-particles and deuterons. Examination of the particles emittedfrom a thin film of heavy paraffin, bombarded with poloniumor-particles, showed that they consisted of deuterium and hydrogenparticles in the proportion 3 : 2. The energy of the deuterons is inaccord with the assumption that they are elastically projected in thecollision, but the energy of the protons is 0.5 m.v.greater than thatof projected protons. The a-particles have not sufficient energyto break up the deuterium nucleus, so the only possible reaction toaccount for the production of the protons appears to be4He+2D+5He+1H-Qwhere Q is 0.1-0-3 m.v. The mass of the 5He atom can be calculatedfrom this equation and is 5.0106 -& 0.0005, and this should be astable species. On the other hand, H. Staub and W. Stephens28find, in agreement with J. H. Williams, W. G. Shepherd and R. D.H a ~ b y , ~ ~ that a group of or-particles of range 7.6 cm. occurs duringthe reaction of deuterons with 7Li. It is:assumed that this arises fromthe reaction 'Li(2D, 4He)5He, and this leads to the conclusion that5He is unstable by 0-8 m.v. The same authors claim to have found agroup of neutrons corresponding in energy to the break up of suchan unstable 5He.Helium of mass 5 is not known to occur in natural sources ofthe gas.Existence of 3H.-R.Sherr, L. Smith, and W. Bleakney30 haveused the Hertz diffusion method to concentrate any 3H which maybe present in water. They find no evidence for a concentration inexcess of one part in 1012 of ordinary hydrogen. On the otherhand, E. Hudspeth and T. W. Bonner31 were able to determinethe mean range for the 3H particles emitted in the reaction2H(2D, p)3H, indicating that 3H must be stable during the timerequired for the particles to traverse the chamber.Stability of 8Be.-A number of nuclear reactions have been studiedin past years which have led to the formation of an atomic species*Be.This isotope is not known in Nature, though the mass cal-26 J . Phys. Radium, 1938, 9, 593.28 Physical Rev., 1938, 54, 236.30 Ibid., 1938, 54, 388.27 Ibid., p. 403.28 Ibid., 1937, 51, 888.s1 Ibid., p. 308OLTPHANT : INTRODUCTION AND SUMMBRY. 13culated from the reactions indicated that it should be stable byabout 0.2 m.v. Further information concerning this isotope hasaccumulated during the current year. 0. Laaff32 claims, on thebasis of counting experiments in which he detected the simultaneousentry of two a-particles into his chamber, that 8Be produced inthe process 11B(p, a)sBe, is unstable, and breaks up into twoa-particles with the emission of 0.2 m.v. of energy.E. Gluckauf and F. A. Paneth33 have shown that the photo-disintegration of 9Be by y-radiation from radium leads to the pro-duction of measurable quantities of helium, the quantity formedbeing in accord with the assumption that the reaction leads to theformation of two a-particles and a neutron, rather than of 8Be and aneutron. F.Kirchner, 0. Laaff, and H. Neuert,3* using the methodof 0. Laaff, have reported similar results, showing that 8Be is un-stable by between 40 and 120 k.v.The most precise measurement of the mass of 8Be reported so faris due to S. K. Allison, E. R. Graves, L. S. Skaggs, and W. M. Smith,35who have determined the energy of the reaction gBe(p, D)8Be to be0.562 & 0-006 m.v. This is an absolute determination based onthe electrostatic deflection of the deuterons, and it leads to a mass of8.00739, which is atable with respect to a-particle disintegration by0.31 & 0.06 m.v.It is seen that there is not yet sufficient evidence to reach a definiteconclusion whether 8Be is a stable atomic species, or whether itbreaks up spontaneously into two a-particles, but the balance ofevidence is in favour of stability.Trans-uranium E2ements.-In recent years considerable attentionhas been given to the possibility of the formation of elements ofatomic number greater than 92 (uranium) by bombarding uraniumand thorium with neutrons.36 A number of different @-active bodieswere found, with chemical properties compatible with those to beexpected of chemical elements beyond uranium.Finally, 0. Hahnand F. Strassmann370 showed that isotopes of barium (atomicnumber 56) were produced as a consequence of the bombardmentof uranium with neutrons.L. Meitner and 0. R. Frisch 37b interpretthis as indicating that the assumption of the formation of trans-32 Ann. Physik, 1938, 32, 743.33 Proc. Roy. SOC., 1938, A , 165, 229.ap Physical Rev., 1938, 53, 794.35 Bull. Amer. Phy8?kl Soc., 1938, 13, No. 7, 14.36 L. Meitner, F. Strassmann, and 0. Hahn, 2. Physik, 1938, 109, 538.In this paper three isomeric z2aRa nuclei and three 22eAc nuclei are reported ;cf. (We) I. Curie and P. Savitch, J . Phys. Radium, 1937,8,385 ; Compt. rend.1938,206, 1643.37a Naturwiss., 1939, 27, 11. 37b Nature, 1939, 143, 24014 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.uranium elements is false, and that one must conclude that auranium nucleus becomes unstable when a neutron is captured, andbreaks up into isotopes of two elements of much lower atomicnumber (e.g., if one of these is the other must be 36Kr)' Eitheror both of these may be radioactive, and may decay by one or morep-transformations to a stable isotope of another element.Theenergy available in the whole transformation process may be asgreat as 200 m.v. We understand (unpublished) that F. Joliot andE. Fermi each independently have reached the same conclusions,and that the recoiling fragments of the uranium nucleus have beendetected and identified.It appears, therefore, that there is no evidence as yet that radio-active elements beyond uranium can be formed in transformationof heavy elements by neutrons, and that previous assumptions thatthese elements exist are erroneous.Natural Radioactivity.-Advances in the field of natural radio-activity have not been marked in 1938.A. Bramley and A. K.Brewer 38 have remeasured the radioactivity of potassium, andwhen this is corrected for the abundance of the radioactive isotope40K, they find for the half-life a value of (14.2 & 3) x lo8 years.C. W. Bennett 39 has photographed in the cloud chamber the tracksof internal conversion electrons corresponding with the energydifferences between the two observed groups of a-particles fromactinium, and S. P. Choong and J. Sumgue4* have obtained inform-ation about the 7-rays from various products of actinium active-deposit.T. R.Wilkins and A. J. Dempster41 have deposited separatedisotopes of samarium upon a photographic plate in a mass-spectro-graph, and have shown that, after it has been left for several monthsand then developed, tracks of a-particles appear in the emulsiononly beneath the line corresponding to the isotope 148Sa. Theapparent half-life of 1.2 x 1012 years obtained by G. von Hevesyand M. Pahl 42 must therefore be reduced by a factor of 7, since theabundance of 148Sa is 14% of the whole.It has been shown by H. Suess 43 that the radioactivity of potas-sium in minerals may be used to determine the age of the materials,and 0. Hahn and E. Walbig 44 point out that the geological age ofrubidium-bearing minerals may be found from mass-spectroscopic38 Physical Rev., 1938, 53, 502.30 Proc.C a d . Phil. Soc., 1938, 34, 282.40 J . Phys. Radium, 1938, 9, 437.41 Physical Rev., 1938, 54, 315.4 2 8. physikal. Chem., 1934, A, 169, 147.Natumoiss., 1938, 26, 411.44 2. anorg. Chem., 1938,236, 78OLTPHL" : INTRODUCTION AND SUMMARY. 15determinations of the product of the disintegration of s7Rh, vix.,87Sr. Measurements of this nature are reported by A. K. Brewer.45Atom Building in the Interior of Stars.-Tt is natural to assume thatthe chemical elements have been formed in cosmological processesfrom hydrogen. H. A. Bethe and C. L. Critchfield 46 have discussedthe probability of the simplest of the building processes, vix., theformation of deuterium by the combination of two hydrogenatoms.Fermi's theory is used in calculating the positron emissionof the process H + H -+ D + ef. They show that a t the centreof the sun the energy evolution by this process should amount toabout 2 ergs per g. per sec., and this alone is almost sufficient toaccount for the whole observed evolution of energy. C. F. vonWeizsacker47 has shown that evolution of energy can only beexpected in stellar interiors from reactions involving light nuclei,and he has discussed the conditions necessary for the formation ofall elements in comparable amount. G. Gamow 48 gives a relationbetween the features of star distribution along the main sequenceand the pro ton-proton reaction.Transformatiom Produced by Proton Bombardment.-An interestingfeature of the experiments upon the bombardment of elements byfast particles is the observation that protons of high energy are ableto enter nuclei very readily and eject neutrons.These reactionshave been studied in greatest detail by workers in Rochester. Thus,L. A. Du Bridge 49 reports that the reactions produced are almostalways of the (p-n) type, though a reaction of the (p-p) typeleading to formation of a radioactive isomeric state of 1151n hasbeen found. Over thirty (p-n) reactions leading to radioactiveisotopes already formed in other ways have been found, and twentyreactions are reported leading to new active isotopes. Definiteeffects are produced by 6.5 m.v. protons in elements as heavy asosmium, while there is some evidence for an effect produced inthorium, though most elements heavier than tellurium show noeffect.Nuclear Physics in Biology an& Medicine.-The study of nuclearphysics since 1934 has shown that practically every element in theperiodic table may be rendered radioactive, and, during the pastyear a great deal of work has been done, notably by G.von Hevesy,upon the use of atoms, " labelled " by the presence of radioactiveisotopes, to elucidate some of the complicated chemical processesgoing on in biological material. The most recent authoritative45 J . A ~ T . Chem. Soc., 1938, 60, 691.46 Physical Rev., 1938, !5& 248.48 Physical Rev., 1938, 68, 9074g BuU. AWT. Physical SOC., 1938, 13, No. 7, 19.4 7 Phyaikal. Z., 1938, 39, 63316 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.account of such work has been published by J.H. Lawrence,50 aless recent article being that by G. von H e ~ e s y . ~ l Full referenceswill be found in these papers. As radioactive isotopes of all thebiologically important elements are now available in quantitywherever a cyclotron of sufficient size is installed, great advances inthis powerful method of attack are to be expected in the nearfuture. I n medicine, radio-sodium, and particularly radio-phos-phorus, promise to be of use in the treatment of certain diseases,and the selective deposition of elements in tissues (phosphorus inbone, iodine in thyroid, etc.) introduces a new method of selectiveirradiation. Laboratory and clinical work on the selective actionof neutrons in the destruction of neoplastic tissues, and in the treat-ment of malignant growths, is being carried out in a number ofcentres. 62M.L. 0.2. THE MESOTRON.During the last two years, convincing evidence has been found infavour of the suggestion that there exists, in cosmic rays, a hithertounknown charged particle of a mass intermediate between those ofthe electron and the proton. For the name of this particle,mesotron” now seems to be agreed upon, but in earlier papersone finds the names “ U-particle,”, “ heavy electron,” “ Yukon,”‘‘ barytron,” and ‘‘ meson.”For a convincing proof one would have to give a detailed analysisof cosmic-ray phenomena,l but we shall outline the type of experi-ment which serves as evidence for each of its main properties.The mesotron carries one positive or negative electronic charge.This can be deduced from its ionising power.The rate of productionof ions on passage through matter is governed by collisions that donot involve close approach; it depends, therefore, not on the struc-ture of the particle, but only on its charge and velocity, and ispractically independent of the latter provided the particle hasnearly the velocity of light. Now, it is known that the density ofions along the cloud-chamber tracks of all fast cosmic-ray particlesis equal to that produced by a fast electron. Hence, if any of thesetracks belong to the new particle, its charge must, within the limitsof error, be equal to the electronic charge. Since it is unlikely todiffer from it by a small fraction, it is reasonably certain that it isjust one electronic charge.That there are positive as well as nega-60 “ Handbook of Physical Therapy,” American Medical Association, 1938.ti1 Nuovo Cim., New Series, Anno 15, no. 5 , 279.62 See J. H. Lawrence, op. cit.6 4H. Eder and W. Heisenberg, Ergebn. exakt. Ndumb8., 1938, 17, 1PEIERLS: THE MESOTRON. 17tive mesotrons follows from the fact 2 that one knows the numbersand behaviour of positive and negative cosmic-ray particles to bevery nearly the same.This was in thefirst instance deduced from its penetrating power, the propertywhich led to its discovery. The data on the passage of cosmic raysthrough air and other materials, which were referred to in lastyear’s Report 3 and have since been extended: show that a part ofcosmic-ray particles, predominant at energies above about 2 x lo8volts, lose energy less rapidly and produce fewer showers thanelectrons ought to do on the quantum t h e ~ r y .~ This discrepancycannot be due to a failure of the theory, since a fraction of theobserved particles show a behaviour in accord with the theory forelectrons. This suggested that the remaining particles were notelectrons but new particles of greater penetrating power. Theenergy loss of fast electrons is, on the quantum theory, mainly dueto the emission of radiation in passing through atoms, and that dueto this cause is, except in very heavy elements, proportional toe4/m2, e being the charge and m the mass. This formula is likelyto hold for any new kind of particle as well, since again the maincontribution is from collisions not involving close approach, andtherefore the structure of the particle is unimportant.Since thecharge of the new particle cannot be appreciably smaller than thatof the electron, its mass must be greater, in order to explain itssmaller energy loss.The mesotron is lighter than the proton. We have seen that theionisation depends on the velocity as well as on the charge, andonce the velocity of the particle is appreciably less than that oflight, i e . , its kinetic energy is less than the relativistic rest energymc2 (c = light velocity), it produces noticeably more ions than afast particle. Now one knows the distribution of momenta ofparticles in cosmic rays from magnetic-deflection measurementsin a cloud chamber,2 and if many of them were protons, one couldestimate the chance of photographing them while they have amomentum less than Mc (M being the proton mass) and producemore ions on their track than fast particles.Actually, far fewersuch dense tracks have been observed, and this proves thatThe mesotron is much heavier than the electron.a P. M. S. Blackett, Proc. Roy. SOC., 1937, A, 159, 1.Ann. Reports, 1937, 34, 26.E.g., P. 31. S. Blackett and J. G. Wilson, Proc. Roy. SOC., 1937, A, 160,306; P. M. S. Blackett, {bid., 1938, 165, 11; S. H. Neddermeyer and C. D.Anderson, Physical Rev., 1937, 51, 884.W. Heitler, “ The Theory of Radiation,” Oxford, 1936; H. J.Bhabhaand W. Heitler, Proc. Roy. SOC., 1937, A, 159, 432; J. F. Carlaon and J. K.Oppenheimer, Physical Rev., 1937, 51, 22018 RADIOACTIVITY AND SUB-ATOMIC PENNOMENA.particles with momenta less than Mc must still move with nearlythe velocity of Light, and hence they cannot have proton mass.A few tracks have now been observed for which one knows thevelocity (which is less than c), from the number of ions, and themomentum, from the deflection by a magnetic field.G Fromvelocity and momentum one can fmd the mass of the particle, whichis in most cases between 100 and 300 times the electron mass. Thesephotographs constitute the most direct evidence in favour of thenew particle. The wide variation of the mass values is probablyaccounted for by the difiiculties involved in determining the iondensity and curvature of the tracks, but the possibility is not ruledout that the mass is not the same for all these particles.The bestestimate on the present evidence is in the neighbourhood of 150electron masses.The mesotron is not stable, but undergoes a radioactive decay.This idea, which was &st suggested by Yukawa from the theory dis-cussed on p. 19, gave a natural explanation7 of the otherwiseinexplicable fact that the intensity of cosmic rays which travelobliquely through the atmosphere, compared with that of thevertical ones, is weaker than could be accounted for by the absorp-tion in air (known from the altitude dependence of the vertical rays).If the mesotron decays spontaneously, the difference may be dueto the longer path, and hence longer time, of travel for oblique rays.To obtain agreement, the mean life of a mesotron at rest must thenbe assumed to be about 2 x sec.(A rapidly moving mesotronseems to live longer owing to the relativity time dilatation.) Oneof the disintegration products must be an electron. These disinte-gration electrons can be distinguished from those produced bycollisions of the mesotron with atoms or nuclei by comparing theelectrons generated in different media by penetrating cosmic rays.lThe number of disintegration electrons produced per unit time doesnot depend on the nature and density of the medium through whichthe rays are travelling. The data are in favour of the existence ofsuch disintegration electrons and lead to a mean life of the same orderof magnitude as the above.The mesotron is not a part of the incident radiation reaching theearth from outside, but is generated by it in the upper atmosphere.This follows from the preceding statement about the short life ofmesotrons, but there is independent evidence from the absenceof a latitude effect 1 in the penetrating component of cosmic rays.For fullerreferences, cf.Euler and Heisenberg, Zoc. cit., p. 7 (ref. 1).* B.Q., E. J. Williams and E. Pickup, Nature, 1938, 141, 684.7 P. M. S. Blackett, Nature, 1938, 142, 692.8 E.g., A. Ehmert, 2. Physik, 1937, 106, 761PEIERLS : THE MESOTRON. 19It is likely that the process leading to a production of mesotrons isthe collision of fast electrons with atomic nuclei.So far, we have based our Report entirely on the experimentalevidence as the more conclusive proof, but it is of interest to realisethat the existence of mesotrons and all the above-mentionedproperties were predicted on purely theoretical grounds by H.Yukawa.9It is knownfrom the binding energies of light nuclei and from the scattering ofneutrons and protons by protons lo that the forces holding the con-stituents of a nucleus together are short-range forces having anappreciable action only over distances of the order of 3 x 10-13 cm.At larger distances, the forces decrease rapidly, at any rate morequickly than the inverse-square law.Yukawa tried the assumptionthat these forces are transmitted by a field, just as the electric forcebetween two charges is transmitted by the electromagnetic field.Thisassumption is extremely plausible, since a direct action at a distance(even at a distance as small as those involved in nuclear processes)would be incompatible with the postulate of relativity. However,since the nuclear forces do not satisfy the inverse-square law, thefield transmitting them must satisfy equations different from thoseof the electromagnetic field. I n other words, the wave equationYukawa tried to develop a theory of nuclear forces.must be replaced by another one. From general requirements ofrelativity, the only suitable equation appears to bein which k is a constant of the dimension of an inverse length.According to this wave equation, a static central field will have apotential whose variation with the distance r is given byV(r) = const.e-”/rThis potential gives a force of the required range if the constant kis chosen to be of the order of 3.5 x 10l2 cm.-l. Yukawa nowremarked that in quantum theory this field must be associated withparticles in the same way as the electromagnetic field is associatedwith light quanta. A difference is that the modified wave equationnow leads t o waves which are propagated, not with light velocity,@ PTOC. Ph9-8. Math. SOC. Japan, 1936,17,48 ; 1938,19,712 ; H. Yukawa andS. Sakata, ibid., p. 1084; H. Yukawa, S. Sakata, and M. Taketani, {bid., 20,319.lo Cf. H. A. Bethe and R. F. Bacher, Rev. Mod. Physics, 1936,s. 8220 RADIOACTrVrrY BND SUB-ATOMIC PHENOMENA.but with a velocity depending on the frequency V, and hence on theenergy hv of the associated particle in the same way as the energyand velocity of a material particle of mass h/2xEc are connected.The field which produces the nuclear forces is the de Broglie wavefield of these particles.On this theory the mass of the particle isof the order of 120 electron masses, i.e., of the same order as thatof the mesotron found in cosmic rays.From the behaviour of nuclear forces in large nuclei, in whichthey show saturation like chemical valency forces, one can concludethat the nuclear forces must be of the type of exchange forces, justas one now knows the chemical forces to be exchange forces betweenthe electrons in the atoms.This feature is reproduced by theYukawa theory if one adds the assumption that the particlesassociated with the wave field each carry one electronic charge.The analogy with the electromagnetic field can be carried stillfurther. The fact that charged particles produce electromagneticfields is responsible for the other fact that if a charged particlemoves with suflicient energy in a field of force, it can produce orabsorb light quanta. Similarly, neutrons or protons which producenuclear forces must, if they have sufficient energy, be able to producemesotrons. Only, since the mesotron is charged, a neutron will,on emitting a negative mesotron, become a proton, whereas aproton, on emitting a negative mesotron, may turn into a neutron.Conservation of angular momentum (spin) then makes it evident that,since both neutron and proton each have a spin of half a unit(h/Zx), the spin of the mesotron must be equal to zero or a wholenumber of units, and indeed this is an essential requirement ofYukawa’s theory.There is no evidence on the spin of the mesotronswhich are observed in cosmic rays, but all known facts are at leastcompatible with the assumption that they have integral spin andmay therefore be identified with Yukawa’s particle.Yukawa further supposed that the process of a neutron turninginto a proton on the emission of a negative mesotron took place in thep-decay of atomic nuclei, but that in the same elementary act themesotron was further split into an electron and a “neutrino.”The first part of this process is linked with the interaction of neutronsand protons with the mesotron field, and is therefore quantitativelyconnected with the nuclear forces.The second part is connectedwith the spontaneous disintegration of a mesotron into an electronand a neutrino, and thus the probability of the latter can be deducedfrom the observed constant of P-radioactivity. In this way onearrives at a mean life of Q x 10-6 sec. for the mesotron, in satisfactoryagreement (in view of the crude estimates involved in both values)with the cosmic-ray value of 2 x quoted aboveMOON : NEUTRONS. 21The det.ailed theory of nuclear forces was, following Yukawa,investigated by a number of authors.ll Although the theory givesqualitatively the right type of force, it is unable to explain the forcebetween like particles, for example, between two protons, which isknown to be comparable to the force between neutron and proton.The proton field consists of positive mesotrons, and acts only uponneutrons, but not upon other protons.The forces between lightparticles could be accounted for if one assumed the existence, besidesthe charged mesotrons, of neutral particles of about the same mass.12At present it seems likely that the spin of the mesotron is oneunit. It must be an integer if one accepts Yukawa’s theory, and ifit were zero, this would produce repulsion between a neutron and aproton, instead of attraction, whereas values of 2 units or more wouldlead to theoretical difficulties in other respects.In spite of the plausibility of thisYukawa theory and its extensions,and in spite of its success in predicting the observed properties ofthe mesotron, it meets with difficulties regarding the nature of thenuclear forces at very close approach.For this reason it is not,at present, possible to develop a mathematically consistent theory ofthe r6le of the mesotron in the nuclear interactions. One may hope,however, that by further modifications of the theory these difficultieswill be overcome.R. P.3. NEUTRONS.Although publications dealing with neutrons are still verynumerous, the advances of the past year have consisted mainly inthe refinement and extension of our information about processesalready known. This seems an appropriate time a t which to takestock of our knowledge, and, while concentrating attention uponthe developments of the past year, the Reporter will not hesitate torefer briefly to work discussed in earlier Reports.Production, Detection, and Properties of Free Neutrons.-Althoughneutrons are not known to be emitted during spontaneous radio-active change, the ejection of one or more neutrons from a nucleusbombarded with high-speed particles or with y-rays is very common.Scores of such nuclear reactions are known, but only a few are ofpractical importance as neutron sources, either for convenience, highyield, freedom from other radiations, or suitability of the energy-11 H.Frohlich, W. Heitler, and N. Kemmer, Proc. Roy. Soc., 1938, A, 166,154; H.J. Bhabha, ibid., p. 501; N. Kemmer, Proc. C a d . Phil. SOC., 1938,34, 354.l2 N. Arley and W. Heitler, Nature, 1938, 142, 168; N. Kemmer, Zoc. cit22 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.distribution of the neutrons for the experiment for which they areneeded.2D + 2D = 3He + ln. This reaction, important for high yieldand absence of y-rays, has been further studied. E. Baldinger,P. Huber and H. Staub have measured, with an ionisation chambercontaining He, the number and ionising power of helium nucleiprojected in elastic collisions by neutrons from a target of trideutero-phosphoric acid bombarded by deuterons of energies up to 0.13m.v.2 From the number of projected nuclei, and with a know-ledge of the cross-section for scattering of neutrons by helium nuclei,the number of neutrons passing through the chamber may becalculated.From the geometry of the apparatus, the total rate ofgeneration of neutrons may then be found ; the authors’ result was1.2 x neutron per deuteron, when referred to a target of puredeuterium and a deuteron energy of 0.1 m.v., and agrees reason-ably well with those of R. B. Roberts and of R. Ladenburg andM. H. Kanner.4.5It now seems certain that some of the earlier estimates of theyield of this reaction were far wrong. From the ionising power(which gives the energy) of the projected nuclei, the energy-distribution of the neutrons may be deduced. In agreement withprevious work, a fairly homogeneous group of neutrons of about2.5 m.v. was found; slower neutrons around 1 m.v.wereconsidered to be due to scattering of these in neighbouring objects.The total energy released in the reaction, of which part goes to the3He nucleus, is 3.1 m.v., as against 3-4 & 0.1 m.v. found byP. G. Kruger, W. E. Shouff, R. E. Watson, and P. W. Stallmanfrom measurements of the projected deuteron tracks produced bythese neutrons in a cloud chamber containing some deuterium.T. W. Bonner 7 finds that the group of slower neutrons is of homo-geneous energy 1.08 m.v., and ascribes them to the 3He nucleusbeing left in an excited state.7Li + 2D = SBe + In. The energies of neutrons produced bythis reaction have been studied by W. E. Stephens by way ofhelium nuclei projected by them in a cloud chamber. He reportstwo groups of energies, 14-01 and 11.1 m.v., corresponding withdisintegration energies 15.05 5 0.2 and 11.8 & 0.4 m.v.The2 m.v. = million electron-volts in contexts where an energy is concerned.3 Physical Rev., 1937, 51, 810.6 For a critical summary of work up to the end of 1937 on yields fromthis and other reactions, see C. J. Bakker, W. de Groot, and F. M. Penning,Nederl. Tijds. Natuurk., 1938, 5, 102.6 Physical Rev., 1938, 53, 1014.Helv. Physica Acta, 1938, 11, 245.Ibid., 52, 911.Ibid., p. 771. Ibid., p, 223MOON : NEUTRONS. 23group of lower energy is five times the more intense. These resultswere obtained with deuterons of energies up to 0.93 m.v. M. 1;.Pool: using 5.7 m.v. deuterons from a cyclotron, finds energies upto 20.8 m.v.in the forward direction. The angular distributionof neutrons agrees with the reaction 'Li + 2D = 4He + 4He + Inrather than with the production of SBe.QBe + 4He = 12C + In. The a-particle bombardment ofberyllium, which for this purpose is mixed with radium or radon, isstill an important source because of its small size and convenience,and is a suitable standard of comparison for the strength of anyother neutron source. The number of neutrons emitted per secondfrom 1 millicurie of radon mixed with beryllium powder is still ratheruncertain, Amaldi's value of 25,000 being usually employed. Theenergy-distribution is complex, depending upon the energy of thebombarding a-particles, and extends up to several m.v.lOThe irradiation of deuterium by y-rays isuseful as a source of neutrons of known energy. Since the bindingenergy of the deuteron is 2.2 m.v., a y-ray of energy E gives anavailable -energy of ( E - 2.2) m.v., which is shared nearly equallybetween the neutron and the proton.The Detection of Neutrons.-Although no great advances in themethods of detection of neutrons have been made during the pastyear, a summary of the present position may be useful.Since neutrons interact only with nuclei and not with electrons,they cannot be detected directly by the methods (ionisation chamber,cloud chamber, etc.) available for particles which ionise gases ;they are detected by the ionising particles which they produceby collisions with atomic nuclei.Four cases may be dis-tinguished :(i) If the neutron is fast and the struck nucleus light, an elasticcollision will project the nucleus with sufficient velocity for itsionisation to be detectable.Examples of this method have alreadybeen given.(ii) An inelastic collision of a neutron (fast or slow) with a nucIeusmay cause a transmutation with the immediate expulsion of anionising particle such as an a-particle or a proton. An importantexample is the reaction loB + ln --+ 'Li + 4He, which is employedin the '' boron chamber "-an ionisation chamber with boron-linedwalls or filled with boron trifluoride-coupled to a valve amplifierto magnify the ionisation caused by each a-particle.(iii) A neutron-produced transmutation may yield a radioactiveproduct whose activity, measured subsequently by any appropriate2D + y + lH + ln.Physhl Rev., 1938, 53, 711.lo See T.Bjerge, Proc. Roy. Soc., 1938, A, 164, 24324 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.method, gives an indirect measure of the intensity of the neutronradiation.(iv) The nuclear transmutation and/or subsequent radioactivedisintegration may be accompanied by y-radiation. Since y-raysthemselves can be detected only indirectly, this is an insensitivemeans of detecting neutrons.Mass ofthe Neutron.-If energy E (ergs) is required to disintegratea particle of mass ml (g.) into two particles of masses m2 and m3, theequivalence of mass and energy requires that ml + E/c2 = m2 + m3,c being the velocity of light. If the masses are expressed on thescale l60 = 16, and the binding energy E is measured in m.v.,the equation becomes m, + 0.00107E = m2 + m3.A determinationof the energy required to disintegrate the deuteron into a neutronand a proton thus enables the mass of a neutron to be found interms of those of the proton and the deuteron. A determination bythis means, by J. Chadwick, N. Feather, and E. Bretscher leadingt o a value of 1.00902 was discussed in last year's Report, but it hassince been pointed out 11 that this value must be amended to 1-00893if the newer data l2 for the connection between the range and theenergy of slow protons are accepted as correct. An independentdetermination of the binding energy of the deuteron which does notinvolve this range-energy relation has led to the result 1.00895.13Xpin of the Neutr0n.A.Schwinger l4 has pointed out that experi-ments on the scattering of neutrons by ortho- and para-hydrogencould resolve any doubt that the spin of the neutron is & (in unitsof h / 2 x ) , and not p; the experiments of F. G. Brickwedde, J. R.Dunning, H. J. Hoge, and J. H. Manley l5 confirm the value 4.Magnetic Moment of the Neutron.-The experiments of 0. R.Frisch, H. von Hdban, and J. Koch, mentioned last year, have nowbeen published in full; l6 the vdue of about -2 nuclear magnetonsstill hoIds.17Collisions of Neutrons with Nuclei.-(i) Fast neutrons (energy -1m.v.) . The usual initial process in neutron-nucleus collisionsl1 H. A. Bethe, Physical Rev., 1938, 53, 313.1s D. B. Parkinson, R. G. Herb, J.C. Bellamy, and C. M. Hudson, ibicE.,13 G. Stetter and W. Jentsch, 2. Physik, 1938, 110, 214.1* Physical Rev., 1937, 52, 1076.1 6 Ibid., 1938, 54, 266; cf. Ann. Reports, 1937, 34, 23.1 7 A nudear magneton = Bohr magneton X (mass of electron)/(mass ofproton) = magnetic moment due to orbital motion of a proton rotating in anorbit with angular momentum hI27r. The negative sign means that thedirections of spin and magnetic moment are related as they would be for arotating negative charge.1937, 52, 76.Physical Rev., 1938, 53, 719MOON : NEUTRONS. 25is believed to be the combination of the neutron with the nucleusand the sharing of its kinetic energy and energy of combination withall the nuclear particles. The excited nucleus may now get rid ofits energy by the re-emission of a neutron (equivalent to scatteringof the original neutron, elastically or inelastically according towhether it carries away the whole of the original kinetic energy ornot); or by the emission of y-radiation, so much energy beingradiated that neither the neutron nor any other particle can escapefrom the nucleus, which therefore remains an isotope of the originalnucleus; or by the emission of a charged particle (a-particle orproton).The probabilities of these competing processes willdepend upon the nature of the initial nucleus and the energy of theneutron, but it is clear that for fast neutrons inelastic scatteringmust be much more probable than elastic scattering, which requiresthe whole of the excess energy to become concentrated once moreon a single neutron.It is, of course, possible that a neutron may Lcgraze” the surfaceof a nucleus without “ sticking ” to it, and be scatteredwithout muchloss of energy.The ratio of elastic scattering to all other processestherefore measures the ratio of “ non-sticking ” to “ sticking ” colli-sions. D. C. Grahame and G . T. Seaborg Is find that for fast radon-beryllium neutrons and for several elements, the ‘‘ sticking proba-bility” is of the order of 0.4. A. Soltan19 also finds it to be lessthan unity.NucEear transmutations produced by fast neutrons. 1. (n, 7 )Processes.20 Although these processes are frequently reportedwith fast neutrons, they happen to such a remarkable extent withslow neutrons that great care must be taken to remove all possi-bility that they may be due to a relatively small proportion of slowneutrons produced by scattering in neighbouring bodies.Ex-periments believed to be free from this possibility have recentlybeen made by E. T. Booth and C. Hurst, by H. Reddemann, and byH. von Halban and L. Kowarski, who are agreed on the existence of(n, y ) processes for fast neutrons. The last authors21 find thatneutron-capture occurs most readily for those elements whichabsorb slow neutrons strongly-a somewhat disturbing result,since the strong capture of slow neutrons is assumed to be due tothe accidental correspondence of a nuclear resonance level with thenarrow band of energies in which slow neutrons can be obtained inPhysical Rev., 1938, 53, 795.1* Natumoiss., 1938, 26, 124.20 The symbol (n, 7 ) indicates a process in which a neutron enters the nucleusSimilar notations will be used for other nuclear and a y-ray comes out.reactions.21 Nature, 1938, 142, 39226 RADIOACTIVITY AND SW-ATOIKIO PHENOMENA.large numbers; since the energies of the fast neutrons spread over aband much wider than the separation of neighbouring resonances,little selectivity as between different elements (and certainly not thesame selectivity as for slow neutrons) would have been expected.The net loss of one neutron is a commonprocess under fast-neutron bombardment ; the resulting isotope,having a greater ratio of charge to mass than the stable isotope fromwhich it was formed, will often be positron-radioactive.Theidentification of 151Gd, 163Er, and 159Dy made by this processenabled M. L. Pool and L. L. Quill 22 to predict the existence of thestable isotopes 152Gd, 164Er, and 159Dy, which have since beenconfirmed rnass-~pectrographically.~3 In this work seventeen (n,2%) reactions were found with rare-earth elements.The ejection of a proton is common with fastneutrons. If the resulting isotope is radioactive, it usually emitsan electron, the original nucleus being thereby regenerated.A number of instances are known of theejection of an a-particle by a fast neutron.Fast neutrons lose energy by scattering inpassing through matter, and if the matter is rich in hydrogen and freefrom strongly absorbent nuclei, elastic collisions with protons rapidlyreduce the neutrons to thermal velocities, though quantum restric-tions as to the amounts of energy which a proton bound in amolecule can take up from a neutron hinder the establishment ofthermal equilibrium, particularly at low temperatures.Two purelyelectrical methods of separating neutrons of defined velocities inthe thermal range have recently been described,24+ 25 and with oneof them the approximately Maxwellian velocity-distribution of the(‘ thermal ” neutrons has been verified somewhat more accuratelythan hitherto. Neutrons of all higher energies, on their way towardsthermal equilibrium, are of course also present, but most of theobserved “ slow neutron phenomena ” seem to arise from neutronsbelow about 100 volts.(n, y ) Processes with slow neutrons.The cross-sections forcapture of slow neutrons by many nuclei (e.g., boron, lithium,cadmium, silver, iodine, gold) reach, for certain velocities of neutronswithin this range, values enormously greater than the nucleardimensions. Considerable information as to the positions, widths,and heights of these absorption bands has been obtained by in-direct methods,26 but progress during the past year has been slow2. (n, 2n) Processes.3. (n, p ) Processes.4. (n, a) Reactions.(ii) Slow neutrons.22 Physical Rev., 1938, 53, 437.24 L. W. Alvarez, ibid., 54, 609.26 G. E. F. Fertel, P. B. Moon, G. P. Thomson, and C. E. Wynn-Williams,2e See H. A. Bethe, Rev. Mod. Physics, 1937, 9, 71 ($0 60, 61, 62).A.J. Dempster, ibid., p. 727.N ~ U T ~ , 1938,w,a29MOON : ARTIFICIAL RADIOACTMTY. 27and the subject seems to await new methods of attack. In thisconnection, papers by S. Nishikawa, S. Nakagawa, and I. Sumoto 27and by A. E. Downing and C. D. Ellis 28 are of interest. Theseauthors develop a method due originally to von Halban in whichthe thickness of hydrogenous material through which neutronsmust pass in order that their velocities may change from oneabsorption band to another is used to give information about therelative positions of the two bands.(n, a) Processes. The capture of slow neutrons by boron and bylithium is accompanied by the immediate emission of an @-particle,and there is good evidence that the dependence of capture cross-section upon velocity does not show the sharp resonances charac-teristic of the (n, y ) process but varies inversely as the neutronvelocity.Details of energies involved in the reaction loB + In =5'Li + 4He are still obtained differently by different authors. Thebest experimental method to date seems to be that of J. C. Bower,E. Bretscher, and C. W. Gilbert,29 who measure the total length oflithium and helium tracks in a cloud chamber, and fix the proportionto be assigned to each nucleus by ionisation-density measurementsalong the tracks. They find the lithium particle to have a range of4.3 5 0.2 mm. in air, and the helium particle to have one of 7-0 &0.3 mm. It is disappointing that there should be little agreementbetween these results and those of M.8. Livingston and J. G.Hoffman,30 who find by an ionisation-chamber method two groups ofhelium particles of ranges 8.0 and 6.6 mm.P. B. M.4. ARTIFICIAL RADIOACTIVITY.This section of the Report deals with the spontaneous (delayed)changes which occur in may of the nuclei produced by the bombard-ment of stable elements by protons, neutrons, y-rays, etc. Theyear's progress in the field of artificial radioactivity is notable fortwo reasons. The first is that nuclear isomerism (Le., the existence oflong-lived nuclei of the same mass and charge but different pro-perties) has now been recognised in a considerable number ofelements and is no longer reckoned a8 a rarity; the second is theexperimental proof of a new type of nuclear transformation-theabsorption of a K-electron into the nucleus.These advances areimportant, not only for their own interest, but also because theyhave indirectly brought into prominence the idea of competition27 Sci. Papers Inst. Phys. Chem. Res. Tokyo, 1937, 34, 1.28 Nature, 1938, 142, 793.29 Proc. C a d . Phil. SOL, 1938, 34, 290.ao Physical Rev., 1938, 53, 22728 RADIOACTrVITY AND SW-ATOMIC PHENOEdENA.between the various processes by means of which a nucleus may getrid of energy.Types of Xlpontuneous Nuclear Change.-The Reporter believesthat the discussion of the developments of the past year can be madeboth more concise and more intelligible if an account is first givenof the ways in which nuclei may spontaneously lose energy atmeasurable times after their f ~ r m a t i o n .~ ~ If it be granted thatnuclei are composed of neutrons and protons, two nuclei can differonly in respect of (i) charge Z (equal to the number of protons),(ii) mass-number A (equal to the number of protons + number ofneutrons), and (iii) internal configuration. Differences of internalconfiguration will be associated with differences of internal energy,and the existence of “ isomeric ” nuclei having identical values of2 and A but different properties must necessarily be referred todifferences of internal energy. Since a nucleus having energygreater than that of its “ground state ” normally radiates thatenergy as a y-ray without measurable delay, we can only explainnuclear isomers by the existence of one or more energylevels abovethe ground state which have a probability of y-ray emission per unittime enormously less than usual.If this probability is zero, theisomer of higher energy will be, as regards y-emission, completelystable; however, the most general assumption to make, and theone which fits the experimental facts, is that the radiation prob-ability is low but finite, so that the isomer is “metastable”against y-emission. The reason for the low radiation probabilitydoes not matter for our present purpose, but it is generally supposed,following a suggestion of C. F. von Wei~sacker,,~ to arise from alarge difference of nuclear spin between the states.We now have the following four ways in which a given nucleusin a given state of energy can spontaneously change :1.Electron (p-particle) emission Z + Z + lZ - - + Z - l2 unchanged 1 2. Positron emission3. Capture of K-electron4. Emission of y-rayThere will be a definite probability per unit time for the nucleus tochange in each of these four ways; if we denote these probabilitiesby p l , p2, p,, p4, the total probability of change per unit time isP = p1 + p 2 + p3 + pa, and the number N of nuclei remaining inthe original state after time t is related to the original number, No,by the equationN = N , e-Pf81 a-Radioactivity will be mentioned only incidentally, being characteristica2 Naturwks., 1936, 24, 813; see Ann. Reporta, 1937, 34, 21.only of very heavy nucleiMOON : ARTIFICIAL RADIOACTIVITY.29Now the magnitudes of the transition probabilities p,, p 2 , pa, p4,vary enormously from one nucleus to another. One or more ofthem may be zero,33 the corresponding transition being energeticallyimpossible. On the other hand, the probability of one of theseprocesses [particularly (4), if there exists a lower state of energywith a not very different value of the nuclear spin] may be so highthat the corresponding mean lifetime is a very small fraction of asecond. However this may be, the wide range of possible valuesfor the p’s usually ensures that one of the four processes has a prob-ability much higher than the combined probabilities of the otherthree, so that it alone is effective. On the other hand, we shalloccasionally find that the two most probable processes have com-parable probabilities, so that some nuclei are transformed in one wayand some in another, the “ branching ratio ” being the ratio of thetwo transition probabilities.The number of the original nucleiremaining, and hence the rate of occurrence of the two competingprocesses, will decrease with time with the single decay constant P.Such branching transformations, the competing processes beinga- and p-emission, are already familiar among the naturallyoccurring unstable nuclei of high atomic number. Several examplesamong the artificial radio-elements will be found in Table I.Secondary Processes.-Any single nucleus, after having changedby one of the above four processes, may or may not be completelystable. It is very commonly left in a state of energy above its groundstate and emits one or more y-rays in reaching the ground state;since it is exceptional for y-radiation to have the low probability perunit time required to explain nuclear isomerism, such y-radiationwill usually occur immediately. It is, of course, possible that thenucleus may arrive into a state of appreciable lifetime as regards y‘radiation, or that it may undergo transformation by one or more ofthe other three processes; if so, we return to the starting pointexcept that, the nucleus being now of different atomic number ordifferent state of energy, the four transition probabilities will all bedifferent and the type(s) and time-constant of transformation mayhave no similarity to those of the former nucleus.We thus have thepossibility of a ‘‘ chain ” of spontaneous transformations ; auchchains are highly characteristic of natural radioactivity, but rare inthe lighter elements.More important in practice are secondary processes brought aboutoutside the nucleus by the radiations emitted in the primary trans-formation, which will all decay in intensity at the same rate as theprimary process. The most important of these are as follows :(i) If the primary process is positron emission, the annihil-33 For a stable nucleus in its ground state all four are, of course, zero30 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.Ha0LiBeBCI0FNeNoUSAlSiPSc1AKCascTiVC rInFecoHicuZn0.Oe15S OBPKrRbSrYZrNM Ol aRURhPd43CdInSrSbTeIIecsBaLaCePrNdI1SmmGdTbDYHoErTuYbLUHfTawRe0sIrPtAuHgT1MOON : ARTIFICIAL RADIOACTIVITY.311134-1 2 4 0 1 2 1 6 2 4 1 2 6 1 0 2 0 6 0SECONDS 1 2 6 1 0 2 0 6 0 HOURS 1 2 4 6 10 2 0 40 GO100M1NUT.U DAYS[+ = positron emission ; - = electron emission ; k = electron capture ;* The unstable 8Be nucleus thus formed disintegrates immediately into twoa = a-particle emission].or-particles32 RADIOACTIVITY AND SUB-ATOIMC PHENOMENA.ation of these positrons in passing through matter will givey -radiation.(ii) If the primary process is K-electron capture, the vacancy inthe K-shell will lead to the emission of X-rays characteristic of theproduct element of atomic number 2-1.(iii) If the primary process is y-radiation, a line spectrum ofelectrons will be produced by the " internal conversion " of the y-rayenergy in the electronic structure of the emitting atom.Electronsmay similarly be produced by y-rays emitted as the nucleus " settlesdown " after other forms of transformation.It will be realised that the radiations emitted as the result ofspontaneous disintegration of a single variety of nucleus may bequite complex; when it is also remembered that the disintegrationof a stable element by any one kind of nuclear bombardmentfrequently produces several nuclear varieties, the difficulty ofdetermining the mode of transformation of certain unstable nucleiwill be understood. Although some of the inferences mentionedbelow and included in Table I may have to be revised, it seems likelythat the majority are not far wrong.Nuclear Isomerism-Among the instances of nuclear isomerismnow re~ognised,~~ the following seem, for one reason or another,specially interesting,Scandium. It now seems certain35s36 that the positron-emitters of 52-hour and &hour half-periods obtained by bombardingscandium with fast neutrons are both due to Wc.The 4-houractivity had previously been assigned to %c, and its productionfrom the only stable isotope (45Sc) had been taken as evidence for a(n, 3n) reaction. No evidence of this type of reaction now exists.Similarly, the activity obtained by W. Gentner by irradiatingscandium with energetic y-rays must be due to the reaction45Sc(y, 12)44Sc and not to 4%c(y, 2n)43Sc. It seems possible that46Sc has three electron-emitting isomers of half-lives about an hour,two and a year or more.Altogether there appear to beat least seven radioactive isotopes of scandium.Rhodium. The 44-sec. and 4.2-min. electron-emitting bodiesobtained by the irradiation of rhodium with slow neutrons have beenshown to be 1wRh isomers, produced by the reaction lo3Rh(rt, y)lo4Rh.B. Pontecorvo38 finds evidence that the isomer of higher energydecays mainly by the emission of y-radiation with the 4-min. period9p See Table I.9 5 W. E. Burcham, M. Goldhaber, and R. D. Hill, Nature, 1938, 141, 610.86 J. M. Cork and R. C. Thornton, Physical Rev., 1938, 53, 866.87 This has been omitted from Table I.88 Physical Reu., 1938, 54, 642MOON : ARTIFICIAL RADIOACTIVITY.33to the ground state, which emits 8-rays and has the 44-sec. half-period, thereby becoming palladium. If such a chain rertction istaking place, the number of rays emitted in the early stages ofirradiation should vary with time in a more complicated way than ifa single decay process were involved. Unfortunately, the very muchgreater intensity of p-rays of 44-sec. period from the direct productionof the ground state in the original nuclear reaction makes thisverification impossible. It also seems likely that some of the nucleiin the upper state go directly by @-emission to palladium, so that wehave a 7-P branching. The accompanying figure indicates thesuggested processes :103Rl "Pdlo4Rh (ground state)The y-rays emitted in the transition from the upper level to theground state are not themselves observed ; what are actuallymeasured are the electrons from their internal conver~ion.~~ E.C.Crittenden and R. F. Bacher *O report experiments supportingPontecorvo's conclusions.K-Electron Cupture.-The possibility of this process of nuclearchange was suggested by H. Yukawa and S. Sakata 41 on the followinglines. The emission of a positron from a nucleus may be considered asdue to the simultaneous occurrence of two processes : (i) the creationof a positron-electron pair, (ii) the combination of the electron with anuclear proton which is thereby transformed into a neutron.Theemission of a positron is therefore energetically possible if the energyset free by the combination of a nuclear proton with an electron is atleast equal to that required to provide the rest-energy of a positronand an electron (2mc2, or about 1 m.v.). On the other hand, thecapture of an orbital electron by the nucleus is energetically possibleif the combination of the electron with one of the nuclear protonsreleases any positive amount of energy ; this process is thereforeenergetically more probable than positron emission, and though it isgeometrically less favourable because the K-electrons rarely comeclose to the nucleus, it may be expected to occur in those instanceswhere the energy available from the change of a proton into aneutron lies between 0 and 2mc2, and as a branch process even when39 Theoretical reasona are given by M.H. Hebb and G. E. Uhlenbeck,Physica, 1938, 5, 605.4Q Physical Rev., 1938,54, 862.41 Proc. Phys. Math. SOC. Japan, 1935, 17, 467; ibid., 1936, 18, 128.REP.-VOL. XXXV. 34 RADIOACTIVITY AND SUB- ATOMIC PHENOMENA.the available energy is above 2mc2. G. J. Sizoo 42 later showedthat under certain conditions a branching between electron captureand ebctron emission might be expected.A survey of the experimental evidence for electron capture, bothof the Yukawa and of the Sizoo type is given by L. W. Alvarez,43who was largely responsible for establishing the existence of thephenomenon, which is usually best observed by way of the charac-teristic X-rays of the product element which arise from the fillingof the vacancy in the K-shell.Alvarez showed that 67Gadisintegrates with the emission of X-rays characteristic of zinc butemits no positrons. This, then, is an example of pure electroncapture. The first example of positron emission-electron capturebranching-is that of a zinc isotope (probably s5Zn) of 8 months44* 45 0. Oldenberg 46 showed that lS0Ta, obtained byirradiating tantalum with fast neutrons, decays by electron captureto 18*Hf. Some @-rays are also observed, and it is probable 43 thatthey also come from the lWTa nucleus, so that we have here anexample of electron emission-electron capture branching. A mostinteresting suggestion by von Weizsacker 47 is that the naturalradioactivity of potassium is a branching reaction of this type.Since the radioactive isotope is 4oK, electron capture would yield4OA, the production of which from potassium might explain itsrelatively high natural abundance.The isotope 7Be, which may beobtained by the reactions 6Li(D, n)7Be and 1°B(D, oc)'Be, decays witha half-life of 43 days and emits y-rays only. The decay process isthe capture of a K-electron with the formation of 'Li in an excitedstate, the transition to the ground state giving the observed y-ray.48For other examples of electron capture, reference may be made toAlvarez's paper and to Table I.Data concerning Stable and Radioactive Nuclei.-To the summariesreferred to in last year's Report may be added an article by K.Diebner and E. Grassmann 49 surveying data obtained between 1937and March 1938, and tables by Gregoire 50 corrected to October lst,1938. Table I of this Report shows in semi-graphical form the half-lives, types of disintegration, and mass numbers of radioactive nucleiup to 2 = 81, publications available to the Reporter up to the endof 1938 being included.Chemical Aspects.-Chemical and physicochemical methods4 4 Ibid., 53, 946.45 J. J. Livingood and G. T. Seaborg, ibid., 54, 239.4 6 Ibid., 53, 35.48 R. B. Roberts, N. P. Heydenburg, and G. L. Locher, Physical Rev., 1938,40 Physikal. Z., 1938, 39, 469.Physica, 1937, 4, 467. 43 Physical Rev., 1938, 54, 486.4 7 Physikal. Z., 1937, 38, 623.63, 1016.J . Physique, 1938, 9, 419MOON : ARTIFICIAL RADIOACTIVITY. 36continue to be of great service. The identification of activity asbelonging to a particular nucleus is rarely accepted unless it beshown that the activity is carried with the correct fraction in achemical separation of the elements to which it might belong. Thepartial separation of active from inactive nuclei is of great valueas a means of concentrating the activity; a recent example is theconcentration of radioactive copper from a neutron-irradiated zincsolution by electrolysis with a rotating cathode.51 The concen-tration of radioactive gallium by extraction with ether is describedby Alvarez .43An important application of a micro-chemical method is affordedby the work on the y-ray disintegration of 9Be.52 J. W. J. Fay,E. Gliickauf, and F. A. Paneth 53 have shown that the helium contentof beryls cannot be explained by the disintegration of a hypotheticalsBe, and is probably not connected with beryllium at all.The applications of radioactive indicators to problems in chemistryhave been surprisingly few 54 in view of the fact that radioactiveforms of all but two or three of the elements are known. It is truethat for many elements no radio-isotope of convenient period isknown, and that supplies of most of them can only be had fromlaboratories where a cyclotron or other powerful source of fastparticles is available. In this last respect the situation will improve,and one may hope that this branch of the subject may require fullerconsideration in future Reports, With this application in view,Table I has been arranged so as to emphasise the half-lives of theradioactive nuclei.P. B. M.P. B. MOON.M. L. OLIPHANT.R. PEIERLS.51 J. Steigman, Physical Rev., 1938, 53, 771.62 See this Report, p. 13.64 But see 0. Hahn, 2. Elektrochern., 1938, 44, 497; J. J. Livingood andG. T. Seaborg, J . Amr. Chem. SOC., 1938, 80, 2524. For references tobiochemical applications, see this vol., pp. 15, 16, and 347.53 Proc. Roy. Soc., 1938, A , 165, 238

ISSN:0365-6217    

DOI:10.1039/AR9383500007

出版商:RSC    

年代:1938

数据来源: RSC

摘要:

GENERAL AND PHYSICAL CHEMISTRY.1. INTRODUCTION.THERE has been a growing tendency in recent Reports on Generaland Physical Chemistry to select a number of topics and review theprogress made over two or three years in order that the treatmentmay be made more critical and also more useful to the non-specialistfor whom the Reports are intended. In the following sections ofthis Report this policy has been carried even further, since thereseems to be a desire for such a modXcation of the articles. Thechoice this year has been dictated partly by the state of the par-ticular branch of physical chemistry and partly by the topics dealtwith in the past two years. It is hoped that this arrangement willnot curtail the scope of the Reports, the number of referencesquoted being nearly the same as in previous years.Again, spacewill not permit of a really comprehensive review, since the maximumnumber of papers to which reference can be made represents only10% of the total published.The Report is divided into four sections. The first, by G. B. B. M.Sutherland, is concerned with infra-red and Raman spectra. Herethe tendency is to stress the importance of the application of thesetechniques to the solution of chemical problems rather than to thedetermination of the structure and force constants of polyatomicmolecules. Within recent years there has been much discussionabout the more fundamental aspects of the adsorption of gases bysolids in simple and sufficiently well-defined systems. A summaryand critical discussion of this subject is given by J.K. Roberts withspecial reference to its possible application, in due course, to themechanism of heterogeneous catalysis. In this connection mentionmay be made of the second edition of N. K. Adam’s well-knownbook on the “ Physics and Chemistry of Surfaces ” (Oxford), whichhas been brought thoroughly up-to-date. As in the first edition, theproperties of the liquid-gas interface receive the greatest pro-minence. During the year under review E. F. Burton has produceda third edition of the “ Physical Properties of Colloidal Solutions ”(Longmans), and H. B. Weiser has completed Vol. I11 of his “ Inor-ganic Colloid Chemistry ” (Chapman and Hall, London), dealingwith the colloidal salts.The subject matter of chemical kinetics covers such a wide fieldthat an annual report is absolutely necessary, but only a few aspectSUTHERLAND : SPECTROSCOPY.37can be treated in any one article. This year, attention has beendevoted mostly to reactions connected with solids, the reason forthe choice being that a summary of the present position of this,the most intractable branch of kinetics, has not been attemptedrecently. Two books on kinetics must be mentioned, the firstby G. M. Schwab, H. S. Taylor, and R. Spence on “ Catalysis fromthe Standpoint of Chemical Kinetics ” (Macmillan), which deals withthe subject in the most comprehensive manner, and the second byFarrington Daniels on “ Chemical Kinetics ” (Cornell UniversityPress), who limits himself to a small number of topics which are con-sidered from a practical standpoint.The last section of the Report, by F.P. Bowden and J. N. Agar,is a critical discussion of the nature of electrode processes.H. W. M.2. SPECTROSCOPY.This Report will be concerned entirely with the infra-red andRaman spectra of polyatomic molecules, as it is not possible toinclude even the briefest review of electronic spectra in the spaceavailable. In previous years 1 general surveys have been made ofthe principles on which the interpretation of vibration-rotationspectra are based; this year it is proposed to deal with some of themore novel applications to specific physicochemical problems.Important advances in the general theory since 1936 will be brieflynoted, and the earlier tables of data on the structural constants ofsimple polyatomic molecules revised where necessary.It is hopedthat this will round off the treatment of this branch of spectroscopyso that next year’s Report may be devoted mainly to a compre-hensive review of electronic spectra. A book of considerableimportance which has appeared since the last Report is the supple-mentary volume of Kohlrausch’s “ Smekal-Raman-Effekt ’’ which,in addition to an excellent review of the developments in this fieldas a whole, contains references to over 1200 publications which haveappeared between 1931 and the end of 1937. Tables of the actualfrequencies are no longer included: for these one must refer toLandolt-Bornstein ‘‘ Tabellen ” or the Annual Tables of the ConseilInternational des Unions S~ientifiques,~ neither of which unfor-tunately goes beyond 1935.Another publication of interest is“ Spectroscopy in Science and Industry,” * which is really a summary1 L. A. Woodward, Ann. Reports, 1934, 31, 21; G. B. B. M. Sutherland,ibid., 1935, 32, 53; 1936, 33, 53.2 “ Smekal-Raman-Effekt,” Erglinzungsband 1931-37, Julius Springer,1938.8 Gauthier-Villars, Paris, 1936.4 John Wiley and Sons or Chapman and Hall, 193838 GENERAL AND PHYSICAL CHEMISTRY.of the Conference on Spectroscopy held a t the MassachusettsInstitute of Technology in July, 1937.The Hydrogen Bond and Association.-The existence of some formof a “ hydrogen bond ” in the structure of certain chemical com-pounds has been recognised for some years, although the exactnature of such a bond has been, and still is, the subject of muchdiscussion and controversy.Within the past two years it hasbecome clear that infra-red spectroscopy offers an entirely new butvery promising approach to this problem. This is not because thehydrogen bond itself gives a characteristic absorption, but becausethe existence of such a bond alters the position and intensity ofcharacteristic absorption bands due to certain groups in the mole-cule. For instance, some of the best known examples of a hydrogenbond occur either within (intramolecular) or between (extramole-cular) molecules containing a hydroxyl group. Now this group hasa fundamental frequency of vibration very close to 3700 cm.-l,which is practically unaffected by changes in the rest of the moleculebut is extremely sensitive to any alteration in the hydroxyl bond,since the vibration is almost entirely confined to that group. Iftherefore the hydrogen atom of the hydroxyl group becomes involvedin either an intra- or extra-molecular linkage, then one would expectthe characteristic hydroxyl absorption to be affected.The firstworkers to observe such an effect were 0. R. Wulf and U. Liddeland R. Freymana6 The former noticed that the absorptioncorresponding to the first harmonic of the fundamental hydroxylvibration was missing in substances such as o-nitrophenol and methylsalicylate where there is supposed to be a chelate ring formed by anintramolecular hydrogen bond ; the last observed that the intensityof the characteristic hydroxyl band in certain alcohols increasedwith temperature, whereas in other cases a change in temperaturecaused a change in the position of maximum absorption.Thiswork was very quickly extended and developed both by the originaland by a host of other workers.’ It was soon established that,in general, there are two characteristic regions of absorption from6 J . Amer. Chem. SOC., 1935, 57, 1464; see also G. E. Hilbert, 0. R. Wulf,U. Liddel, and S. B. Hendricks, Nature, 1935,135, 147; J . Amer. Chem. Soc.,1936, 58, 548,2247.Compt. rend., 1932,195, 39; Ann. Physique, 1933, 20, 243.7 J. Errera and P. Mollet, Nature, 1936,138, 882; Compt. rend., 1937, 204,259; J. J. Fox and A. E. Martin, Proc.Roy. SOC., 1937, A , 162, 419; A.Buswell, V. Deitz, and W. Rodebush, J. Chem. Physics, 1937, 5, 501; W.Gordy, .ibid., p. 284; Physical Rev., 1936,60, 1151; R. M. Badger and S. H.Bauer, J. Chem. Physics, 1936, 4, 711 ; 1937, 5, 605, 839; M. M. Davies andG. B. B. M. Sutherland, ibid., 1938, 6, 755, 767; R. Freymann, ibid., p. 497.The last reference gives a brief r6sum6 of Freymann’s snd his co-worker’sresults from 1932 t o July 1938SUTHERLAND : SPECTROSCOPY. 39the fundamental vibration of the hydroxyl group. The first is anarrow symmetrical band with its centre somewhere between2-73 p and 2.86 p (according to the molecule under investigation) ; thesecond is a very wide unsymmetrical band, stretching roughly from2-9 p to 3-2 p, in which the position and intensity of maximumabsorption vary both with temperature and with concentration.It was observed that for alcohols dissolved in an inert solvent suchas carbon tetrachloride an increase of temperature or an increase indilution always had the effect of strengthening the narrow band andweakening the broad one.The former was accordingly associatedwith the unperturbed hydroxyl group, and the latter with a moleculein which the hydrogen of this group has been affected throughassociation with other molecules. In other words, the presence of ahydrogen bond is indicated by the appearance of the wide “ associ-ation band,” as it is sometimes called. In the case of the intramole-cular bond, the sharp or “ monomeric ” hydroxyl band is entirelymissing and the wide association band is superimposed on thecharacteristic CH absorption at 3.1 p.This explains Wulf andLiddel’s early result, from which it was at first wrongly concludedthat the presence of an intramolecular bond caused the completedisappearance of hydroxyl absorption.The case of the carboxylic acids is particularly interesting, inthat for these we have more information about the strength ofthe hydrogen bond than in the alcohols or the chelated compounds.Here the hydroxyl absorption shows very similar characteristics tothose found in the alcohols, the monomeric band being a t 2-83 p(as compared with 2.75 p in the alcohols), and the association bandof the dimer extends from 3.0 p to 3-3 p. The fact that the associ-ation band is fully as wide as in the alcohols indicates that theexplanation offered by J.Errera,8 vix., that the width of theassociation band is due to different polymers, cannot be the correctone. We shall return to this question of the width of the associationband. An additional feature with the carboxylic acids is thatabsorption bands due to bonds other than the hydroxyl one arefound to be affected by association. Thus several workers showedthat the position of the characteristic carbonyl bond absorption at5.7 p was shifted to shorter wave-lengths by raising the temperatureof acetic acid either in the vapour or in dilute solution in carbontetrachloride. More recently,1° this shift has been proved to be dueto the existence of two distinct bands, one characteristic of the8 J.Errera and H. Sack, Trans. Far&y Soc., 1938,34, 728.* R. H. Gillette and F. Daniels, J . Amer. Chenz. SOC., 1936,68, 1139; E. L.f(insey and J. W. Ellis, J . Chem. P h y d , 1937,5,399; W. Gordy, ibid., p. 284.lo M. M. Davies and G. B. B, M, Sutherland, see Ref. (7)40 GENERAL AND PHYSICAL CHEMISTRY.carbonyl bond in the monomer, the other characteristic of the samebond in the dimer. The relative intensity of these can be alteredin just the same way as the intensities of the monomeric and dimerichydroxyl bands. There is this important Berence, that the mono-meric band is not appreciably narrower than the association band.A similar shift but in the opposite direction in the band a t 7 p hasbeen resolved into two bands presumably due to the G O single bondin the monomer and in the dimer. This interpretation is not socertain, for the experimental curves are complicated by the presenceof other absorptions in the same region.By employing the empiricalrelations which exist between force constant and internucleardistance, it is estimated that association increases the C=O distanceby approximately 0.016 A. and decreases the G O distance by aboutthe same amount.This method of investigation has been made more than quali-tative by measuring the intensity of absorption due to the monomerichydroxyl group (in the photographic region) at various temperaturesand assuming it to be proportional to the number of molecules in themonomeric form. were able toconfirm reasonably well the value obtained from vapour-densitymeasurements of 16,400 cals. per mole for the heat of association.R.C . Herman and R. Hofstadter l1 reached a similar conclusionworking on the intensity of the dimeric fundamental OD band inacetic deuteracid. Both these sets of measurements were on theacid in the vapour. More recently Davies and S~therland,~ workingwith the acid in solution, have obtained a much lower value(6000--10,000 cals. per mole). They conclude, however, that thisvalue is probably spuriously low, for the absorption coefficient insolution seems to vary with temperature.The conclusions regarding the nature of the hydrogen bond to bedrawn from these experiments are still being crystallised, and muchmore experimental work is required, particularly on the behaviourof the OH deformation frequency.Certain general deductions mayalready be formulated, of which the first concerns the change in the0-H distance when the hydrogen atom becomes involved in ahydrogen bond. From the comparatively small alteration in thevibration frequency, it is clear that the change in the internucleardistance must also be small : it may be estimated as not greaterthan 0.1 A. Thus in the formic acid dimer the 0-H distances mustbe very close to 1.07 and 1.60 A. if we take the value given by electrondiffraction for the 0-0 distance, viz., 2.67 A. In the alcohols,where the change in the frequency is less than in the acids, the alter-ation in the 0-H distance must be correspondingly smaller.TheIn this way Badger and BauerJ . O h . Phpik?, 1938,6,640SUTHERLAND : SPECTROSCOPY. 41question as to whether there is a simple relation between the shiftin the frequency and the energy of formation of the hydrogen bondhas not been satisfactorily settled, although several suggestionshave been made.12 The fact that the changes in frequency andinternuclear distance are relatively small when the hydrogen bondis formed indicates that the source of the energy of association is tobe sought rather in ordinary classical electrostatic interactions thanin quantum-mechanical effects, although the latter must certainlyplay some part in the acids. The importance of the contributionof electrostatic terms has been shown by the calculations of R.H.Gillette and J. Sherman13 and also of E. A. Moel~yn-Hughes.~~In this connexion, a recent theory proposed by E. Bauer and M.Magat 15 is of particular interest. These authors have been ableto give a quantitative account of the large change in the hydroxylfrequency observed for water in going from the vapour to the liquidand the solid state by considering purely classical electrostatic effects.The essential feature of their treatment is that, in calculating theeffect of neighbouring molecules on a specified water molecule, themolecules are not regarded as dipoles which interact, but the inter-action between individual ‘< effective ” charges is computed. In thisway the alteration in the hydroxyl frequency is related t o the distancebetween two neighbouring atoms by taking the Bernal-Powlermodel as a basis.According to this theory, the 0-H distancealters from 0-972 A. in water vapour to a mean value of 0.985 A. inliquid water at normal temperatures, and to 0.989 A. in ice at 0 ” ~ .The well known diffuseness of the Raman bands of water is thusexplained as being due to the different internuclear distances whichexist between the oxygen atoms in the liquid state. The width of theassociation band in the alcohols receives a similar explanation, thenarrowing of the band with rise of temperature being interpretedas due to the transition from “ libration ’’ about a fixed position to“free rotation.” It is not so easy to see how the width of theassociation band in the carboxylic acids can be explained on thistheory.It should be added that Bauer and Magat can also explainwhy the change in the deformation frequency of the hydroxylgroup is in the opposite direction to the change in the bond frequencyin going from the gaseous to the liquid state. In connexion withBauer and Magat’s treatment of the spectrum of liquid water,mention should also be made of a very interesting paper by P. C.Cross, J. Burnham, and P. A. Leighton l6 on the Raman spectrumla R. M. Badger and 8. H. Bauer; J. J. Fox and A. E. Martin, lorn. cit.,Ref. (7).J. Amer. Chm. SOC., 1936, 58, 1136.J. Amer, Uhmn, ~ o c . , 1937, 69, 1134.l4 J., 1938, 1243.l6 J . Phy8. Radhn, 1938,9, 3142 GENERAL AND PHYSICAL CHEMISTRY aof water a t different temperatures up to the critical point.Theyinterpret the changes in the structure of the bands in terms of theperturbed radial frequencies in a broken-down ice structure, buttheir method has been criticised by Bauer and Magat becausecertain arbitrary interactions are introduced to get agreement withexperiment.Free Rotation.-The problem of free rotation about a single bondis another subject on which the spectroscopist can now give thephysical chemist considerable help. Evidence on this point maybe obtained from either infra-red or Raman spectra. In each caseit may be detected through its effect on the symmetry of the molecule(and consequently on the selection rules governing the appearanceof vibration frequencies in absorption or scattering), but in theabsorption case its effect on the rotational structure of the bands mayalso be detectable.In ethane the effect of a restricting potential on the appearanceof the vibration-rotation spectrum has been very fully investigatedby J.B. Howard,17 who concludes that, although there is no definiteevidence for or against free rotation from a purely vibrationalanalysis, yet the rotational fine structure of certain bands in theinfra-red indicates a minimum value of 2000 cals. per mole for thepotential restricting rotation. This would appear to be confirmedby the measurements of the heat capacity by G. B. Kistiakowsky,J. R. Lacher, and F. Stitt,ls although it is not in agreement with theanalysis of the vibrational spectrum made by E.Bartholomb andJ. Kar~ei1.l~ Another simple molecule for which the existence of arestricting potential has been established from the rotational struc-ture is methyl alcohol. Here, A. Borden and E. F. Barker 2O haveshown that the rotation of the hydroxyl group about the C-0 bondis restricted by a potential barrier of 500 & 100 cm.-l. In the caseof formic acid, S. H. Bauer and R. M. Badger 21 deduce that the re-stricting potential is so high that the hydroxyl group may be re-garded as clamped firmly in the cis-position. This conclusion hassince been questioned by I. E. Coop, N. R. Davidson, and L. E.Sutton,22 whose measurements of the dielectric polarisation indicatethat free rotation or a transition to the trans-position may takeplace between 40" and 140".Analysis of the rotational structureof certain bands of methylamine 23 has indicated that here also therotation is very restricted at ordinary temperatures.The detection of free rotation by its effect on the Raman spectrum17 J . Chem. Physics, 1937, 5, 451.Is 2. physikal. Chem., 1938, B, 39, 1.g1 Ibi&., 1937, 5, 852.23 H, W, Thompson and H. A. Skinner, ibid,, p, 775,l8 Ibict., 1938, 6, 407.2o J . Chem. Physics, 1938,6, 553.22 Ibi&., 1938, 6, 905SUTHERLAND : SPECTROSCOPY. 43of the molecule has been considered by S. Mizushima, Y. Morino,and their co-workers24 in a series of papers dealing with thehalogenated ethanes, the o-hnlogenophenols, the carboxylic acidmonomers, sulphur monochloride, and other substances containingG C , G O and S-S bonds.This method does not give reliable resultsunless supplementary information from infra-red spectra or dipolemoments is available.Rotation in the Solid State.-The idea that certain molecules mightbe free to rotate about their equilibrium positions in the crystallinelattice was introduced by L. Pauling 25 in 1930 in order to accountfor the entropy of hydrogen and for anomalous peaks occurringin the specific-heat and the polarisation curves at certain (transition)temperatures. There have been several attempts to get directspectroscopic proof of this phenomenon, but so far without muchsuccess. G. Hettner 26 has investigated the infra-red absorptionspectrum of hydrogen chloride above and below the transition point(98" IC.) at which rotation is supposed to set in.Instead of findingsigns of rotational structure, he obtained above 98" K. a singlemaximum, but below this temperature he found a doublet therelative intensities of whose components varied with temperature.A little later, P. Shearin,27 using higher dispersion, claimed to havefound individual rotation lines below the transition point in thesame substance. This work of Shearin's has not been confirmed in arecent investigation by E. Lee, G. B. B. M. Sutherland, and C . K.W U , ~ ~ who, using dispersion equal to Shearin's, have exactly re-peated Hettner's result below the transition point. The latterauthors have also investigated deuterium chloride, where they find,not two, but three maxima.Infra-red studies have also been madeon hydrogen bromide, hydrogen iodide,29 carbon dioxide,3O and theammonium saltsYB1 but so far without producing any clear-cutevidence. From Raman spectra the evidence is also rather unsatis-factory in that no actual rotational structure has been detected froma solid. A. C. Menzies and H. R. Mills32 have investigated theRaman spectra of ammonium chloride and bromide above andbelow the transition points. In the case of the chloride, the appear-ance of a low lattice frequency below the transition point is accountedfor by rotation setting in at that temperature. Such a conclusionrequires further substantiation, however, particularly in view of the24 Sci. Papers Inst. Phys. Chem. Res. Tokyo, 1937, 32, 220.26 Physical Rev..1930, 46, 430.27 Physical Rev., 1935, 48, 299.29 J. Zunino, 2. Physik, 1936, 100, 335.31 R. Pohlman, ibid., 1932,79, 394.32 Proc. Roy, SOC.. 1935, A, 148, 407.This papercontains references to all the previous work.26 8. Physik, 1934, 89, 234.28 Nature, 1938, 142, 169.30 W. Dahlke, ibid., 102, 36044 GENERAL AND PHYSICAL CHEMISTRY.fact that later work33 on the Raman spectrum of ammoniumchloride indicates that there are many unexplained peculiarities inthis spectrum and that the whole question of the interpretationof such very low Raman frequencies is still very imperfectly under-stood.Force Constants and Bond Character.-In the Reports for 1936methods of obtaining the values of the force constants characterisingthe resistance offered by a bond to stretching were reviewed, and asmall list was given of fairly well accepted values for some of thecommoner linkages.The only significant advance to be reportedin methods of treatment is a development of the general method ofMannebach in a systematic manner by 0. Redlich and H. Tompa.34When more data are available from isotopic molecules this methodis bound to become the only really satisfactory one. Meanwhile,the more approximate methods based on the valency force fieldcontinue to yield useful and interesting results. Thus, H. W.Thompson and J. W. Linnett35 have concluded that resonancehybrids probably exist in carbon suboxide and cyanogen, where thevariations in the C-C, C-0, and C-N force constants from normalvalues are real.This last is the crucial point in all approximatemethods which suffer from the defect that one can seldom be surewhether variations in the values of a force constant found in goingfrom one molecule to another are real or are due to neglect ofinteraction terms in the potential function. It is never safe toconclude, because a certain set of force constants will reproduce theobserved frequencies, that these are the correct set, since an infinitenumber of sets exist f u m g that condition. Unless the isotopicfrequencies have been predicted and verified, or the effect of smallinteraction terms carefully considered, one should accept values offorce constants and deductions based on them with considerablecaution. For instance, it is possible to correlate the frequencies inthe spectrum of tetrachloroethylene with a set of potential constantsgiving an abnormally low value (6.2 x lo5 dynes/cm.) for the G Cforce constant, J. Duchesne36 and, later, H.W. Thompson andJ. W. Linnett 37 have interpreted this as arising from resonatingstructures thus :c1 c1 Cl /C1>"=C<,,and >fC"c1 c1 \ClRecently, however, Duchesne3* has shown that a more completepotential function (of the Mannebach type) yields equally good33 F. T. Holmes, J . Chm. Physics, 1936,4, 88.86 J., 1937, 1384, 1399.87 J., 1937, 1393.84 Ibid., 1937,5, 629.96 Nature, 1937, 139, 288.38 Nature, 1938,142, 256SU!I!HERLAND : SPECTROSCOPY. 45agreement with a value for the W force constant which is practi-cally the same as that in ethylene (8.5 x lo5 dyneslcm.).Whichis the correct interpretation is still uncertain.The complete potential function for the water molecule has beenvery thoroughly investigated by G. W. King,39 who shows that thesubstitution of deuterium for hydrogen does not change the potentialfunction within the accuracy of measurement of the vibrationallevels. This enables the value of the angle to be calculated as 107"22', agreeing quite satisfactorily with that obtained from rotationalana'lysis,82 vuix., 105". All the potential constants are determined forthe complete potential function (allowance being made for cubicand quartic terms). This shows that valency and central forceconstants are equally important and that the cross terms are notnegligible, a t least with respect to the lowest frequency.Theproblem of the most suitable potential function for the ethylenemolecule has engaged the attention of several workers,a but is notyet satisfactorily cleared up, as there is still some doubt regardingthe assignments of some of the fundamental frequencies. For thosefrequencies of which the assignment is not in question, the generalisedfunction of C. Mannebach and A. Verleysen 40 gives the best agree-ment as tested by prediction of the isotopic frequencies in tetra-deuteroethylene. A modified valency force field suggested by H. W.Thompson and J. W. Linnett?O which seemed to give excellentcorrelation of the ethylene frequencies, is found to give poor agree-ment when used to predict the isotopic freq~encies.~l More recently,J. J.Fox and A. E. Martin40 have tried modifying Thompson andLinnett's function by the addition of two more cross terms. Theseauthors do not consider the problem as a whole but are moreinterested in showing that the value for the G H force constantis intermediate between that found for the same bond in formalde-hyde and in acetylene. It had previously been pointed out bySutherland and Dennison*O that the difference in the C-H forceconstant in methane and in acetylene corresponded to a dif€erencein the G H distance in those two molecules. Following this,Thompson and Linnett 42 tried to correlate the different C-H forceconstants with differences in the G H distances in different molecules,J.Chm. Physics, 1937, 5, 405, 413.40 G. B. B. M. Sutherland and D. M. Dennison, Proc. Roy. SOC., 1936, A ,148,250; J. M. Delfosse, Ann. SOC. sci. Bruxelles, 1935,55,114; L. G. Bonner,J . Amer. Chem. SOC., 1936,58,34; C . Mannebach and A. Verleysen, Ann. Xoc.sci. Bruxelles, 1936, 56, 349; 1937, 57, 31; Y. Tchang, ibid., 1938, 58, 87;H. W. Thompson and J. W. Lhnett, J., 1937, 1376; J. J. Fox and A. E.Martin, Proc. Roy. Soc., 1938, A , 167, 257.41 G. B. B. M. Sutherland and G. K. T. Conn, Nature, 1937,140, 644.J., 1937, 139646 GENERAL AND PHYSICAL CHEMISTRY.largely as a test of the empirical relations of Badger and Clarkbetween force constant and internuclear distance (see next section).Although Fox and Martin would seem to have established that theC-H bond in ethylene is intermediate in length between those inacetylene and in formaldehyde, their other conclusion regardingthe assignment of one of the ethylene frequencies has since beenquestioned by G. K.T. Conn and G. B. B. M. S~therland?~ whosework on the spectrum of tetradeuteroethylene leads them to stillanother assignment of the ethylene frequencies.Force Constant and Internuclear Distance .-The empirical relationbetween force constant and bond length has been further investi-gated. C. H. Douglas Clark and J. L. Stovest4 working on a verywide range of non-hydride diatomic molecules and “ di-atoms,”claim t o have demonstrated that Clark’s relation gives a better fitthan either Badger’s 45 or H. S.Allen and A. K. long air'^.^^ H. W.Thompson and J. W. Linnett 42 investigated the applicability ofBadger’s and of Clark’s relation to the C-0, C-H, and G-C linkagesin various polyatomic molecules, and in so far as reliable values offorce constants and distances were available, found that both gavereasonable agreement, Clark’s being somewhat superior. In theReport for 1936 only Badger’s form of the relation was quoted,vix.,where re is the equilibrium internuclear distance, ke is the bondforce constant, and cij and dij are constants depending on thepositions of the constituent atoms in the periodic table. Clark4’gives the relation in the formre = (cij/ke)* + dijwhere kqr is a constant depending on the periods in which the twoatoms are situated, n is the “ group number ” (defined as the sum ofthe number of valency electrons of both atoms), and we the funda-mental frequency.It will be noticed that this equation relates, notthe force constant, but the vibration frequency to the internucleardistance. Such a formulation is clearly wrong from the dynamicalpoint of view, since it implies that a change of mass (e.g., isotopic)which produces a change in the frequency must therefore produce achange in the interatomic distance. Of course, except for deuterium,the isotope effect is small, but formally the relation is wrong andshould be written in the formre = (kfT[ken)’4 3 Proc. Roy. Soc., 1939, A., in the press.44 Phil. Mag., 1936, 22, 1137.d6 Phil. Mag., 1935, 19, 1032.46 J .Chem. Physics, 1935, 3, 710.47 Ibid., 1934, 18, 459SUTHERLAND : SPECTROSCOPY. 47Because of this fact, H. S. Allen and A. K. Longair 46 proposed theformula,w,r,Sp* = Kwhere p is the reduced mass of the di-atom and K is a period con-stant. All of these relations are obviously approximations to thetruth, and which is most successful depends partly on the choice ofarbitrary constants to be varied in going from one molecule toanother. For instance, Allen and Longair's has only one adjustableconstant, whereas each of the others has two. Moreover, Clarkvaries his value of lip within a group where Badger keeps cijconstant. The theoretical basis for such relations has been soughtby R. A. Newing48 and more recently by G. B. B. M. S~therland.~~Starting from a general expression for the mutual potential energyof the two atoms of the formv=pp-ct/,*n .. . . . (1)the latter author has shown that relations of the type found byBadger and by Allen and Longair are to be expected, the differentrelations arising from the particular values chosen for the exponentsm and n in (1). For instance, n = 4 gives the Allen-Longairrelation, whereas m = 1 gives the Badger relation. From the sameassumption it may also be shown that a relation of the formD = lcer,2/mnexists between the dissociation energy D and the internucleardistance re. Such a relation had been deduced empirically by R.Mecke 50 several years earlier. The empirical connexion betweenforce constant, inter-nuclear distance, and heat of rupture of a,bond has also been considered in a very suggestive paper by J.J.Fox and A. E. Martin.50aAdvances in General Theory.-Except in the evaluation of forceconstants mentioned earlier, progress here is largely concernedwith the interaction between vibration and rotation in polyatomicmolecules. This is essentially an extension of the work of E.Teller and L. Tisza 51 and of M. Johnston and D. M. Dennison 52 (seeAnn. Reports, 1935), who considered the perturbations in rotationalstructure caused by a degenerate vibration which itself gives riseto an internal angular momentum. H. H. Nielsen 53 has consideredthe very interesting case of formaldehyde, where the vibrations of4a Phil. Mag., 1935,19, 759.6o Leipziger Vwtrage, 193 1.6l 2.Physik, 1932, 73, 791.b3 J . Chem. Physics, 1937, 5, 818.4g Proc. Indian Acad. Sci., 1938,8, 341.J . , 1935, 2106.Physical Rev., 1935, 48, 86848 GENERAL AND PHYSICAL CHEMISTRY.the methylene group as a unit in two planes perpendicular throughthe G O axis are so close that they partly overlap, giving a pseudo-doubly degenerate vibration of the type referred to above. Theresulting perturbations in the rotational structure have been com-puted, the general effect being to enhance the intensity and diminishthe spacing of the rotational lines on the sides of the bands adjacentto one another. The agreement with the observed spectrum is verysatisfactory 54 and enables those two frequencies to be assignedwith certainty, showing that all previous interpretations of theformaldehyde spectrum were wrong. A somewhat similar problemin which the rotational structures of one of'the methane bands isperturbed by the close proximity of another fundamental has beensatisfactorily cleared up by H.A. Jahn and W. H. J. Childs.55Such phenomena are bound to be of frequent occurrence in theperpendicular bands of molecules possessing three-fold or higheraxes of symmetry. Their elucidation is more than a matter ofspectroscopic interest since it yielda information about the potentialconstants of the molecule.An important paper by R. M. Badger and 1;. R. Zumwalt 5f3 hasjust appeared on the shapes of the envelopes of the absorptionbands of asymmetrical rotators. It will be recalled (see Ann.Reports, 1935) that this was one of the few outstanding problemsin the theory of vibration-rotation spectra.As the great majorityof molecules fall into this class and have moments of inertia so greatthat their rotational fine structure cannot be resolved, a knowledgeof the theoretical envelopes and their dependence on the values ofthe moments of inertia is clearly of the first importance. Thegeneral treatment of the effect of non-rigidity on the equations forthe asymmetrical rotator including centrifugal distortion has beengiven by C. Eckart 57 and also by E. B. Wilson and their co-w~rkers.~~Two other papers are worthy of attention in this section. The firstdeals with a mechanical method of solving the secular determinantalequation arising in the normal vibration problem ; 59 the second is asystematic treatment by H. J.Bernstein60 of the symmetricalmodes of vibration of a series of typical molecules having two-,three-, and four-fold axes of symmetry.64 E. S. Ebers and H. H. Nielsen, J. Chem. Physics, 1937, 5, 822.65 Nature, 1938,141, 916; H. A. Jahn, Proc. Roy. SOC., 1938, A, 168, 469.66 J. Chem. Physics, 1938, 6, 711.67 Physical Rev., 1935, 47, 552; A. Weinberg and C. Eckart, J . Chem.68 E. B. Wilson and J. B. Howard, ibid., 1936, 4, 260; E. B. Wilson, ibid.,6s D. P. MacDougall and E. B. Wilson, ibid., p. 940.6o Ibid., 1938,6, 718.Physics, 1937, 5, 617.p. 313; 1937, 5, 617SUTHERLAXD : SPECTROSCOPY. 49Structural Problems.Gnear MokcuZes.-Part of a band in the spectrum of 1aC160, hasbeen observed in atmospheric absorption by A.H. Nielsen,61 theagreement with the predicted position from A. Adel and D, M.Dennison’s potential constants G2 being perfect. Certain anomaliesin the fine structure of the bands of carbon disulphide have beennoted by C. R. Bailey.63 The spectrum of diacetylene has beenconsidered by several workers G4 and on current analyses appears toyield an abnormally low value for the C-C single-bond force constan$(2.85 x lo5 dyneslcm.) although the C =C and G-H force constantsare practically the same as in acetylene. The spectra of carbon sub-oxide,65 cyanogen,66 and various acetylene derivatives 67 have alsoreceived considerable attention, and approximate values for thebond force constants derived. The case of methylacetylene isparticularly interesting because in this molecule G.Herzberg, B’.Patat, and H. Verleger 68 were able to resolve the rotational finestructure and show that the C-C single-bond distance was 1.462 &0-005 A., which is considerably smaller than the normal value forthis distance, vix., 1.50 &- 0.02 A.Xpherical Molecules.-The absorption spectrum of tetradeutero-methane has been investigated by A. H. Nielsen and H. H. Niel~en.~~The agreement with predictions based on Johnston and Dennison’streatment 62 of methane is not very satisfactory. There are certainanomalies in the rotational structure indicating interaction betweenvibration and rotation of a higher order than that considered byJohnston and Dennison which probably accounts for the lack ofagreement.Additional structure of a similar kind has been foundby E. Lee and G. B. B. M. Sutherland 70 in the spectrum of germane,and had also been found in silane by W. B. Steward and H. H.N i e l ~ e n , ~ ~ although the latter may possibly be an isotope effect.Physical Rev., 1938, 53, 983. 62 Ibid., 1933,43, 716; 44, 99.68 Nature, 1937, 140, 851.64 B. T i m and R. Mecke, 2. Physik, 1935, 94, 1 ; T. Wu and Y. Shen,Chinese J. Physk?, 1936,2,128 ; G. Glockler and F. T. Wall, J . Chem. Physics,1937, 5, 813.6s H. W. Thompson and J. W. Linnett, J., 1937, 1291; W. Engler andK. W. F. Kohlrausch, 2. physikal. Chem., 1936, B, 34, 214; R. C. Lord andN. Wright, J. Chem. Physics, 1937,5,642.6 6 S. C. Woo, J . Chinese Chem.SOC., 1935, 3, 301; H. W. Thompson and5. W. Linnett, J., 1937, 1399.67 G. Glockler and F. T. Wall, Physical Rev., 1937, 51, 529 [see also Ref.(64)j; R. M. Badger, J. Chem. Physics, 1937, 5, 178.68 J. Physical Chem., 1937, 41, 123.69 Physical Rev., 1938, 54, 118.70 Proc. Carnb. Phil. SOC., 1939, in the press.7 1 Physical Rev., 1935, 47, 82850 GENERAL AND PHYSICAL CHEMISTRY.The work of Jahn and Childs on methane has already been noted.55The assignments of the fundamental frequencies and the values ofthe bond constants in tetramethylmethane and tetramethylsilanehave been investigated by 3’. T. Wall and C. R. Eddy.72 The finestructure in the Raman frequencies of carbon tetrachloride has beenshown to be entirely accountable as an isotope effect and not dueto a lack of symmetry in the carbon valencies, but it has not beensufficiently resolved to enable one to use it as a discriminant betweenthe various types of force field which have been proposed for thismolecule.v3Symmetrical-top MoZecuEes.-The spectroscopic data on the methylhalide molecules have been critically re-examined by Sutherland,74who arrives at values for the carbon-halogen distances which aremarkedly different from those obtained by the diffraction method.New work on the spectra of the pyramidal molecules trideutero-phosphine and arsine by G. B. B. M. Sutherland, Cheng-Kai Wu, andE. LeeT5 has enabled them to obtain quite accurate values forthe dimensions of those molecules. One of the double frequenciesof ammonia which has always been difficult to assign has finallybeen fixed by E.F. Barker 76 as having its centre at 3407 cm.-l andnot at 3450 cm.-l as given in the 1936 Report. Earlier work on theRaman spectrum of boron trifluoride has been shown to containspurious lines,77 and C. R. Bailey, J. B. Hale, and J. W. Thompson’sassignment 78 of the fundamentals, based on the infra-red spectrum,has been confirmed. A. Borden and E. F. Barker 2O have made thefirst satisfactory study of the infra-red spectrum of methyl alcoholvapour. Their values for the two larger moments of inertia are35.18 x 10-40 g.-cm.2 and 33.83 x 1040 g.-cm.2, i.e., the moleculeis practically a symmetrical top. If one assumes that the dimensionsof the methyl group are the same as in the methyl halides and the0-H distance is equal to that in water, one arrives at a value forthe G O distance of 1.425 & 0.005 A., which agrees well with thediffraction value 79 of 1-44 j= 0.02 A.The spectra of methyl anddeuteromethyl deuteralcohols have also been investigated by E. F.Barker and G. Bosschieter,“ but the assignment of the fundamentalfrequencies is not yet quite certain.72 J . Chem. Phys?ks, 1938,6, 107.7 3 C. K. Wu and G. B. B. M. Sutherland, ibid., p. 114.74 Trans. F a r h y SOC., 1938,34, 325.7 5 Trans. Paraday SOC., 1939, in publication.v 6 Physical Rev., 1937, 52, 250.7 7 D. M. Yost, D.DeVault,and E. N. Lassettre, J . Chem. Physics, 1938,6,424.7 8 Proc. Roy. Soc., 1937, A , 161, 107; J . Chern. Physics, 1937, 5, 275.79 L.0. Brockway, J. Y. Beach, and L. Pauling J . Amer. Chem. SOC., 1935,57, 2693. 80 J . Chem. Physics, 1938,6, 563SUTHERLAND : SPECTROSCOPY. 51Asymrnetrical-top Molecules.-The pure rotation spectrum of waterhas been reinvestigated and satisfactorily interpreted for the &sttime by H. M. Randall, D. M. Dennison, N. Ginsburg, and L. R.Weber.81 The dimensions given by Mecke 82 are confirmed butthe large effects due to centrifugal forces had to be carefully computcdbefore satisfactory agreement could be obtained. The spectrumof hydrogen sulphide has been the subject of some controversy.The values of the moments of inertia given in the former Report(1936) are not in question, but A. D. Sprague and H. H. Nielsen 83have suggested that a value of 85" for the vertical angle is necessaryin order to account for the gross structure of certain of the fundamen-tal absorption bands.On the other hand, B. L. Crawford and P. C.Cross a have defended Cross's original choice of 92" on the basis ofthe intensities of the individual lines in the band at 10,100 A. Whichis the correct value will be uncertain until the structure of the funda-mental bands has been interpreted in detail. For the present, thehigher value is to be preferred, since it depends on a more detailedanalysis of band structure. The correct vibrational analysis of theformaldehyde spectrum would appear to have been given for the&st time by E. S. Ebers and H. H. N i e l ~ e n . ~ ~ The frequencies givenin the 1936 Report should be replaced by the following set : 2875,2780, 1750, 1500, 1278 and 1165 cm.-l.These frequencies aresatisfactorily correlated by a valency force field, an excellent checkbeing provided by the frequencies of the dideuteroformaldehydemolecule which the same authors have observed. From an analysisof the rotational structure of a band of formic acid in the photo-graphic region, s. H. Bauer and R. M. Badger 21 have evaluated themoments of inertia of this molecule as 85.2, 74.4, and 10.81 x 10"g.-cm.2. Several important papers on the absorption spectra ofmonomeric and dimeric forms of both light and heavy formic andacetic acid have also appeared,e6 but the complete vibrational an-alyses have still to be accomplished. The absorption spectrum ofhydrogen peroxide has been investigated by C. R.Bailey and R. R.GordonYa7 who find that their results, coupled with earlier data onthe Raman spectrum of this molecule, support the model proposedfor it by W. G. Penney and G. B. B. M. Sutherland.88 Severalpapers have appeared on the spectra of light and heavy ethylene,8981 Physical Rev., 1937, 52, 160.83 J . Chem. Phymka, 1937, 5, 85.85 Ibid., 1938, 6, 311.8 6 R. C. Herman and It. Hofstadter, ibid., pp. 631, 534, 540.87 Trans. Faraduy SOC., 1938,34, 1133.8 8 Ibid., 1934, 30, 898; J . Chem. Physica, 1934, 2, 492.8g M. de Hemptinne, J. Jungers, and J. M. Delfosae, ibid., 1938, 8, 319;82 Ann. Reports, 1935, 32, 61.84 Ibid., p. 621.also Refs. (40), (4l), (43)62 GENERAL AND PHYSICAL CHEMISTRY.but the assignment of a few of the fundamental frequencies is stillopen to question and much of the theoretical work will have to berepeated in view of premature assumptions regarding those assign-ments. The spectrum of allene has also been investigated, andthe value obtained for the moment of inertia (97.0 x 10-40 g.-cm.2)shows that the C-C distance must be virtually the same as in ethylene(1.33 A.).An assignment of the vibration frequencies has also beenproposed.91 The absorption spectrum of carbonyl chloride has beeninvestigated by C. R. Bailey and J. B. Hale, and the fundamentalfrequencies assigned. The force constants calculated from a valencyforce field indicate that resonance occurs between different struc-t u r e ~ .~ ~ The infra-red and Raman spectra of certain uranyl saltshave been studied by G. K. T. Conn and C. K. W U , ~ ~ who concludethat the uranyl group is probably not linear.Deuterium Cmpounds.-A useful collection of the data availableon the spectra of deuterium compounds up to the end of 1936 hasbeen prepared by G. Charn~etier.~~G. B. B. M. S.3. THE ADSORPTION OFGASES ON PLANE METAL SURFACES.1. Introduction.Some experiments on the interchange of energy between gasatoms and solids in which Knudsen's thermal accommodation co-efficient was measured showed that the accommodation coefficientof helium on tungsten is profoundly affected both in magnitude andin the nature of its temperature variation when all adsorbed filmsare removed from the surface of the meta1.l The accommodationcoefficient with an ordinary metal, when no particular precautionsare taken to ensure a bare surface, is about 0.3 a t room temperatureand this rises to 0.36 a t 90" K.With a clean surface, on the otherhand, the temperature variation is as shown in Fig. 1. It will beseen that at 79" K. the very low value of 0-025 is obtained. Thecurve suggests that, as the absolute zero is approached, the accom-modation coefficient approaches the value zero, i.e., the collisionsof the gas atoms with the solid become more and more nearly per-fectly elastic. No doubt, however, at sufficiently low temperaturesadsorption of helium would begin and ultimately condensation inQo E. Eyster, J . Chem. Physics, 1938,6,680.91 J.W. Linnet and W. H. Avery, ibid., p. 686.93 Trans. Faraday SOC., 1938, 34, 1483.04 " Tables Annuellea de Constants et DonnQes Numeriques," Hermann &C. R. Bailey and J. B. Hale, Phil. Mag., 1938, 25, 98.Cie., Paris, 1937.1 J. K. Roberts, Proc. Roy. SOC., 1932, A, 135, 192ROBERTS: THE ADSORPTION OF GASES. 53bulk would take place, so that the lowest portions of the curve wouldnot be realised in practice. The following physical picture explainswhy the collisions become elastic at low temperatures. Supposethe solid can be regarded as an assembly of Planck oscillators all ofidentical frequency v : this assumption mas made by Einstein whenhe first worked out the quantum theory of the temperature variationof the specific heat of solids.When a gas atom interacts with suchan assembly, energy transfers can only take place in amounts ofnhv, where n can have the values 0, 1, 2, 3, etc. At temperaturesat which the mean thermal energy is smaller than hv, a considerablenumber of the atoms of the solid will be in the ground state. WhenAccommodation coeflcient, a, of helium with tungsten as a function oftemperature.a gas atom interacts with such an atom, the only possible inter-change of energy that can take place is that the gas atom givesup energy to the solid atom, and the smallest amount of energy thatthe solid atoms can take is hv. The number of gas atoms that haveenergy hv to give up becomes progressively smaller as the tempera-ture gets lower, and thus the proportion of gas atoms which canundergo a change of energy on interacting with the solid becomessmaller and smaller as the temperature approaches the absolutezero.It is evident that similar considerations will apply whenaccount is taken of the fact that all the oscillations are not of thesame frequency. The detailed theory of this effect has been givenby A. F. Devonshire,2 who has developed the earlier work of Fowler,Jackson, Mott, and others.With neon, the change in the magnitude of the accommodationcoefficient is even greater. At room temperature for an ordinarya Proc. Roy. Soc., 1937, A, 158, 269. References to the eaxlier work aregiven here54 GENERAL AND PHYSICAL CHEMISTRY.metal when no particular precautions are taken to ensure a baresurface the value is 0.6, and for clean tungsten it is about 0.06.The difference between the temperature variation for helium andfor neon is of interest from the point of view of interatomic forcesbut will not be discussed here.The large change mentionedsuggested that the accommodation coefficient of neon would be asensitive indicator for studying the adsorption on bare tungsten oftraces of other gases mixed with the neon.The first gas chosen for study in this way was hydrogen, andsome results obtained are illustrated in Fig. 2 in which the0admitted-70 0 10 20Erne, m!'nutes,FIU. 2.Effect of hydrogen o n the accommodation coeflcient of neon :Curve (a), 295' K. ; curve (b), 79" K.accommodation coefficient of neon with a clean tungsten surfaceis plotted as a function of the time in experiments at 295" K.andat 79" E. Even when every precaution is taken to remove adsorb-able impurities from the neon, traces remain, and their effect isshown by the small drift a t the beginning of the experiment. Atthe point shown by the arrow, a trace of hydrogen sufficient toproduce a pressure of mm. of mercury was admitted, and theaccommodation coefficient of the neon immediately began to rise.The pressure of the neon was about 0.1 mm., so the rise was notdue to any direct effect of the hydrogen in transferring heat. Weare therefore forced to the conclusion that the hydrogen is adsorbedon the bare tungsten, and that the presence of the adsorbed filmalters the accommodation coefficient of neon.Other experimentsin which different amounts of hydrogen were admitted showedthat, if its partial pressure was 10 times as great, the final valuROBERTS: THE ADSORPTION OF OASES. 55of the accommodation coefficient was not affected. This suggestssaturation, i.e., that the film is complete, at the lower pressure.This was conf%med by experiments by a Merent method (see p. 56).This result is in marked contradiction with what had been foundin earlier work3 on the adsorption of hydrogen on tungsten, inwhich the ordinary methods were used and the metal was in theform of a powder. There was no rapid adsorption even a t com-paratively high pressures, but only a slow take-up of gas and all thephenomena associated with the term activated adsorption, whichwe shall not discuss.The essential point is that, since no rapidadsorption was observed and since the present experiments haveshown that on bare tungsten the complete film is formed rapidlyat very low pressures, it must be concluded that in the earlier powderexperiments the tungsten was not bare when the hydrogen wasadmitted, in spite of the fact that these particular experiments withtungsten powder were carried out with great care.Some general consequences of this result may now be noted.K. F. Bonhoeffer and A. Farkas4 have measured the rate of theortho-para hydrogen conversion on tungsten and other metals a troom temperature and have suggested that the mechanism of thisconversion is that hydrogen molecules strike the tungsten surface,are adsorbed with dissociation, recombine on the surface, and thenre-evaporate in the equilibrium proportion corresponding to thetemperature of the metal.This suggestion requires the assumptionthat re-evaporation of hydrogen from an adsorbed film on tungstenoccurs rapidly and continuously a t room temperature. The presentexperiments, and particularly those described below, show that thisre-evaporation does not, in fact, occur, and that the film is extremelystable. It is evident that in the experiments of Bonhoeffer andFarkas the tungsten was not bare but was covered with a filmof hydrogen, or possibly of oxygen not removed before the experimentbegan. The conversion must take place above this first layer eitherby exchange with the atoms in the first layer, if they are hydrogen,or by some interaction between hydrogen molecules in a possiblesecond layer.The details are irrelevant to the present discussion,and in any case are still a matter of speculation, but it is importantto point out that the mechanism of Bonhoeffer and Farkas cannotbe maintained, although it appears to be widely accepted andapplied in other ways. Similar remarks would apply to the ex-change reaction between hydrogen and deuterium.In this connexion it may be mentioned that it has also beenW. Frankenburger and A. Hodler, Trans. Faraday Soc., 1932, 28, 229.2. physikal. Chem., 1931, B, 12, 231. For a general account see A.Farkas, “ Orthohydrogen, Parahydrogen and Heavy Hydrogen,” pp. 96-101,Crtmb. Univ. Press (1935)56 GENERAL AND PHYSICAL CHEMISTRY.shown by the two independent methods that at room temperatureand a t liquid-air temperature on a bare tungsten surface nitrogenat pressures of the order of lo4 mm.of mercury is rapidly adsorbedto a considerable extent. Some experiments by R. S. Burdon6with another metal, mercury, are of interest too. He has shown that,if a new mercury surface is formed in the presence of hydrogen,a complete film is adsorbed which is stable when the pressure isreduced to lo4 mm. of mercury, but that unless this precaution istaken, i.e., unless the mercury surface is formed in the presence ofthe hydrogen to ensure that the gas comes into contact with baremetal atoms, no such adsorption is observed.2. Measurement of Heat of Adsorption on a Filament.It is of interest to study the properties of films formed under theseconditions as widely as possible, and in order to do this a methodhas been developed for measuring the heat of adsorption on a finefilament, the filament itself being used as a calorimeter.' Theprinciple of the method is the same as that of any method in whichheats of adsorption are measured calorimetrically, the only differ-ences being that the amounts of gas involved are very small, sothe work must be done a t very low pressures and a Pirani gaugemust be used for their measurement, and that the amounts of heatinvolved are small, the temperature rise of the filament being onlyabout 0.01".To measure this rise, the aament is put in a sensitiveWheatstone bridge so that the change in its resistance when ad-sorption takes place may be determined.The precautions neces-sary to produce and maintain a clean surface must, of course, betaken.The apparent superficial area of the effective part of the filamentwas 0.55 cm.2. If we assume, as is usually done following Langmuir,that the 110 plane is the important one in the surface, the numberof tungsten atoms in the surface is p x 7.8 x 1014. If the 100plane is the important one,8 the number of tungsten atoms in thesurface is p x 5.5 x 1014, where p is a roughness factor which willprobably lie between 1 and 2. The total numbers of hydrogenmolecules adsorbed in five independent experiments were 4.2, 4.4,4-3, 3-3 and 3.8 x 10f4.Thus, which ever plane is important, witha reasonable value of Q we have one atom of hydrogen for eachatom of tungsten. The experiments showed that, until the film was5 J. K. Roberts, Nature, 1936,137,669; A. B. Van CIeave, Tram. FurachySOC., 1938, 34, 11746 Proc. Physical SOC., 1935, 47, 460.7 J. K. Roberts, Proc. Roy. SOC., 1936, A, 159, 4-45.8 R. P. Johnson, PhyaicaE Rw., 1938, 64, 469ROBERTS: THE ADSORPTION OF GASES. 57complete, the whole of the hydrogen wm taken up by the tungsten,i.e., that the equilibrium pressure was lower than could be detectedby the gauge (< about 10-7 mm.).The variation of heat of adsorption with amount adsorbed infour experiments is shown in Fig. 3. The results for any givenexperiment are plotted with the same symbol, and the relativevalues for different amounts adsorbed in any particular experimentcould be determined much more accurately than the absolute values,which are used in comparing different experiments.It will be seenthat the relation between heat of adsorption and amount adsorbedis approximately linear. K. IF'. Herzfeld9 pointed out that forcesFIG. 3.J-'ar&t&n of heat of crdsorptwn of hydrogen on tungsten with amount adsorbed.between adsorbed particles can give rise to variation in the heatof adsorption as the surface becomes covered, and in order to discussthese results it is necessary to have a theory of adsorption whichtakes these forces into account.3. Mobile and Immobile Adsorbed Films.In considering the interpretation of these results in terms of theforces between adsorbed particles it is necessary to distinguishcarefully between mobile and immobile films and to discuss thesetwo general types separately from the theoretical point of view.By a mobile film we mean one in which the energy of activationnecessary to enable a particle to move from the site on which itis &orbed to a neighbouring unoccupied site is small compared9 J .Amer. Chem. Soc., 1929, ljl, 280858 GENERAL AND PHYSICAL CHEMISTRY.with kT. In such a film, particles will move freely from site to site,and at any instant the distribution of particles on the surface underthe influence of their mutual forces will be an equilibrium Boltzmanndistribution.If, on the other hand, the energy of activation necessary toenable a particle to move from the site on which it is adsorbed is > kT, the particles will not move freely over the surface but willremain fixed on the sites on which they are first adsorbed.In animmobile film of this type the distribution of particles on the surfaceat any instant will not necessarily be an equilibrium Boltzmanndistribution. It should be mentioned that an equilibrium distribu-tion can be set up on the surface by the processes of evaporationand condensation themselves, but, if the energy of activation formigration is greater than kT, much more will the heat of evaporationbe greater than kT and the probability that a particle will evaporatewill be even smaller than that it will migrate. During the occurrenceof any process with an immobile film we shall assume that theparticles remain fixed where they are fist adsorbed.The theoretical problem is to determine for any type of film theaverage distribution of particles on the surface for any given totalnumber of adsorbed particles.The exact solution of this problem,taking into account the fact that the energy of a single adsorbedatom in its lowest state is a continuously varying function of itsposition on the surface, would be extremely complicated. A generalindication of the behaviour that would be expected can be obtainedby simplifying the problem along the lines first followed by Langmuirin his treatment of the case when there is no interaction. It iswell known that he made a great advance when he suggested that,owing to the lattice structure of the solid, there would be a stronglocalisation of adsorption forces at definite places on the surface,particularly if these forces were chemical in origin.The effect ofthis can be represented by assuming that there is a definite number,say n,, of sites per unit area available for adsorption. We retainthis assumption and assume further lo that, when two particles areadsorbed on neighbouring sites, there is an interaction energy Vbetween them, but, if they are on more distant sites, the interactionenergy is negligible;* V is positive if the potential energy arisesfrom repulsive forces. We suppose throughout that the probabilitylo See R. Peierls, Proc. Camb. Phil. SOC., 1936, 32, 471, who develops atheory h t given by Fowler when discussing attractive forces in connexionwith critical Condensation conditions.A similar treatment can be applied,as here, to repulsive forces. * For a discussion of this assumption, see J. K. Roberts, ‘‘ Some Problemsin Adsorption,” Section 2.7, Cambridge Physical Tracts, Camb. Univ. Press,in course of publicationROBERTS: THE ADSORPTION OF GASES. 59that a molecule condenses, when it strikes a vacant site, is indepen-dent of the state of occupation of neighbouring sites.Let us consider an immobile film in which each molecule in thegas phase occupies one site on the surface. There is no appreciablere-evaporation. It is evident that at each stage in the adsorptionprocess the number of occupied neighbouring sites around any sitewill on the average be Ox, where x is the number of neighbours toa given site and O is the fraction of the total number of sites whichare occupied.Thus the heat of adsorption per molecule will bewhere qo is the heat of adsorption on a bare surface; i.e., the heatwill be a linear function of 8.For a mobile film, on the other hand, the particles will alwaystend to arrange themselves in the configuration of lowest energy,FIG. 4.State of lowest energy for a quadratic lattice at 6 = 0.5 when there is a repulsiveforce between particles on neighbouring sites.and the thermal motion will resist this tendency and give actual con-figurations in accord with Boltzmann’s law. Consider a surface inwhich each site for adsorption has four neighbouring sites tw inFig.4, in which the sites for adsorption are at the intersections ofthe lines. The adsorbed molecules are represented by circles. Itwill be seen that up to O = 0-5 the particles can arrange themselvesas shown in the figure, so that the interaction energy is zero. Hence,up to 8 = 0-5 for this model, in the state of lowest energy the heatof adsorption will remain constant at qo. It will then drop sharplyto q0 - 4 V as illustrated by the curve marked u in Pig. 5. Ifthe fact that the particles are distributed according to Boltzmann’slaw is taken into account, detailed calculations show that the effectis to round the corners of this curve l1 to a greater or less extentaccording to the value of VIkT. This is shown in the figure forvarious values of 7 = e-v/kT.11 J, S , Wang, Proc.Roy, Soc,, 1937, A, 161, 12760 GENERAL AND PHYSICAL CHEMISTRY.At the other extreme we can consider a model in which thepotential energy is uniform all over the surface so that there istwo-dimensional lateral free motion in the adsorbed film.12 Forvalues of 0 not greater than 0-5 there will be a general similaritybetween the shape of the curve representing the variation of heatof adsorption with 0 and those in Fig. 5. In general, for all mobilefilms with repulsive forces there will be a tendency for the heatof adsorption to vary slowly with 0 a t the beginning of the formationof the film.Similar considerations apply to adsorption with dissociation,lland for the sake of definiteness we shall assume, as is generally done,that, when hydrogen is chemi-sorbed on a metal, dissociationFIG.6 .Variation of heat of adsorption with fraction of surface covered for a quadraticlattice. Curve a, q = 0 ; curve b, q = 6.6 x lo-&; curve c , 7 = 0.082;c u m d, 7 = 0.368. '7 = e-VlkT.occurs.13 It is not necessary to discuss adsorption with dissociationin detail here as the aim is to give a general account of the physicalresults. The essential point is that the experimental behaviour isin accord with what would be expected for an immobile film andnot with what would be expected for a mobile h with the highinteraction energy necessary to account for the large change in heatof adsorption as the surface becomes covered.A further point isthat it can be shown that, for a film formed with dissociation, thekinetics of formation is different for a mobile and for an immobileThe generalconsiderations brought forward would apply, apart from changes in detail,to any other type of adsorption in which each adsorbed molecule occupiesmore than one site.1% F. J. Wilkins, ibid., 1938, A, 164, 496.13 For a discussion of this assumption see J. K. Roberts, op. citROBERTS: THE ADSORPTION OF GASES. 61film.14 In order to investigate the condensation of hydrogen ontungsten at room temperature, R. C. L. Bosworth15 has used amodification of I. Langmuir and K. H. Kingdon’s method l6 formeasuring contact potentials, improved by A. L. Reimann17 anddeveloped by Bosworth and E.K. Rideal l8 to study some propertiesof sodium films on tungsten. He has shown that the kinetic be-haviour is in accord with what would be expected for an immobilefilm, but not for a mobile one (for a fuller discussion of this, seeRoberts 13).4. Holes and Gaps in Immobile Adsorbed Films.that, unless each gasmolecule occupies one site and one site only on the surface, immobilefilms will necessarily have gaps in them; i.e., when adsorption hasfinished taking place, there will still be vacant sites left on thesurface on which no further adsorption can occur; in other words,the molecules will not be packed as tightly on the surface as ispossible. These vacant sites will probably be important centres ofcatalytic activity.19 The reason for the occurrence of these vacantsites or holes in the adsorbed film can be understood by consideringas an example adsorption of diatomic molecules with dissociation.We suppose that the two atoms into which the molecule dissociatesoccupy two neighbouring sites on the surface and that, if a moleculefrom the gas strikes a place on the surface where two neighbouringsites are vacant, the probability of its condensing is independent ofthe state of occupation of neighbouring sites. It is evident that,as the film is built up, certain single vacant sites will be found to becompletely surrounded by occupied sites.Such sites will be ableto play no part in the adsorption process and will remain bare. Byusing a model of the surface and occupying it by choosing pairsof sites a t random by drawing cards, it was found that 8% of thetotal number of sites remained bare.The proportion of bare siteswill, of course, depend on the type of adsorption.21Suppose that there is oxygen present in the gas phase. Theseuncovered tungsten atoms will undoubtedly exert a greaterIt has been pointed out by the Reporter1* J. K. Roberts, Proc. Roy. SOC., 1937, A, 161, 141.l~. Proc. Camb. Phil. SOC., 1937, 33, 394.l6 Physical Rev., 1929, 34, 129.l7 Phil. Mag., 1935, 20, 594.l* J. K. Roberts, Nature, 1935, 135, 1037.2o For a general discussion of the use of modeb to obtain the properties ofimmobile I~IIU, see J. K. Roberts, Proc. Camb. Phil. SOC., 1938, 34, 399.a1 See, e.g., idem, ibid., p. 577, where a different type of adsorption is con-sidered in which there is no dissociation but each particle occupies more thanone site.Proc.Roy. SOC., 1937, A, 162, 162 GENERAL AND PHYSICAL CHEMISTRY.\ 0.3r.? 3 + k0.2B E 3 sg2 ?o+EkS k 42 0,0 .c,bc! 3 3 00 0 - 00ROBERTS: THE ADSORPTION OF GASES. 63accommodation coefficient a of neon at room temperature wasmeasured. Since there was always it residual trace of oxygen inthe neon in this experiment, the value of a showed a drift with time,and in Fig. 6 the value extrapolated to the instant at which thecurrent i was cut off is plotted as ordinate in each experiment.It will be seen that heating the wire to 1100" or 1200" K. for oneminute reduced the accommodation coefficient to 0.20.This valuepresumably corresponds to the presence of the well-known stablefilm, and the higher values which persisted when the wire wasonly heated to 1100" K. or lower are due to the presence of a secondless stable one. Removal of the first or stable film began at about1750"~. Heating the wire to temperatures between about 1500"and 1700" K. caused an increase in the value of the accommodationcoefficient. This effect occurred consistently, and was presumablydue to some rearrangement in the film, a possible interpretation beingthat the first film becomes mobile a t these temperatures, thus allow-ing the gaps to move about and so to come together and be filledup from the residual traces of oxygen in the gas phase. VanCleave's results are therefore consistent with, although they cannotbe taken as definitely establishing, the view that the stable filmcontains holes or gaps.5. The Production of Atomic Hydrogen by Hot Tungsten.Among processes involving the adsorption of hydrogen on tungsteaone of the most interesting is the production of atomic hydrogenby the hot metal, and it has recently been possible to give a satis-factory account of this process.This is probably the simplestchemical surface reaction that is known, and because of this it ispossible to consider in some detail the various mechanisms by whichthe reaction can proceed. We shall see that it is difficult to dis-tinguish between these mechanisms. This makes one realise verystrongly that, in more complicated surface reactions involving anumber of gases where numerous combinations of mechanisms couldbe proposed, the fact that a given mechanism accounts for theobserved kinetics does not necessarily mean that the mechanism iscorrect.The first experiments on this subject were carried out by I.L a n g m ~ i r .~ ~ When a tungsten filament is heated to a sufficientlyhigh temperature in hydrogen contained in a glass vessel, the wallsof which are cooled in liquid air, he showed that there is a continuousdiminution of pressure, and interpreted this as being due to theproduction by the hot tungsten of atomic hydrogen which isadsorbed on the surface of the glass.23 J. Amer. Chem. SOC., 1912, 34, 1310; 1915, 37, 417; see also Gen. ElectricRev., 1926, 29, 16364 GENERAL AND PHYSICAL CHEMISTRY.To obtain quantitative data in this connexion, it is obviouslyessential to use an efficient method of trapping the hydrogen atoms,since, if it can be assumed that every atom produced is trappedbefore it recombines with another atom, the rate of disappearanceof gas, which is obtained from the volume of the vessel and the rateof diminution of pressure, gives a measure of the rate of productionof atoms.Langmuir's measurements themselves showed that glasscooled in liquid air is not consistently efficient in this way, since therate of production of atoms under definite conditions appeared fromthem to be very variable. Atomic hydrogen is known to react withmolybdenum oxide. G. BryceM therefore carried out some ex-periments in which, in order to trap the atoms, this oxide was de-posited to a depth of more than 50 layers on the walls of the tubecontaining the hydrogen.Subsidiary experiments indicated theefficiency and lack of fatigue effects in the oxide as a trappingagent. Bryce showed that the earlier estimates of the rates atvarious temperatures of the tungsten were too low by factors whichwere all greater than 200. He showed, too, that the rate varies rapidlywith the temperature of the tungsten, and determined the law ofthis variation. Uncertainties due to inefficient trapping in theearlier experiments had obscured this effect.After correcting for the effect of temperature distribution in thefilament, Bryce showed that the number n of atoms produced percm.2 per second is given byn = 2.5 x 10241/i;e-45*000/RTwhere p is the pressure of the hydrogen in mm.of mercury, thetemperature of the gas being 0"; T is the absolute temperature ofthe tungsten, and R is in calorie units. This formula applies overa temperature range of 1148-1420" K. and a pressure range of2.4-37 x 103 mm. of mercury. It will be seen that, over thisrange of conditions at a given filament temperature, the rate ofproduction is proportional to the square root of the hydrogenpressure.To account for these results theoretically, we must consider theprocesses occurring a t the surface of tungsten in the presence ofhydrogen. The equilibrium condition in the gas phase for thereaction H, = 2H iswhere p1 and pz are the partial pressures (in dynes per cm.2) of atomicand molecular hydrogen and K is the equilibrium constant withpressures measured in atmospheres.Consider a tungsten boxmaintained at the required temperature and containing hydrogen,231 = 103dKdg . . . . . (1)24 Proc. Camb. Phil. Soc., 1936, 52, 640ROBERTS: THE ADSORPTION OF GASES. 65the surface of the tungsten being quite free from oxygen and otheradsorbed impurities. The processes occurring at the surface mustthemselves be able to set up and maintain the degree of dissociationof the hydrogen corresponding to the temperature of the walls andthe pressure quite apart from any reactions taking place in the gasphase. Three pairs of surface reactions must be considered and,according to the principle of detailed balancing, each pair mustbalance individually.These are :(i) (a) Evaporation of atoms from the adsorbed film. ( b ) Atomfrom gas hits bare surface and is adsorbed.(ii) (a) Two neighbouring adsorbed atoms combine and evaporateas a molecule. ( b ) Molecule strikes the surface wheretwo neighbouring sites are bare and is adsorbed asatoms.(iii) (a) Gas atom strikes adsorbed atom, combines with it, andthe two evaporate as a molecule. ( b ) Gas moleculestrikes bare surface, one atom is adsorbed, and the othergoes into the gas phase.If we neglect the effect of interactions between adsorbed atoms andwrite down the condition for the balance of these processes, it canbe shown 25 by using equation (1) that each pair leads to the con-ditionwhere A , which is constant a t constant temperature, can be repre-sented in three different ways given by0 / ( l - 0) = AdT2 .. . . . (2)I n these equations pL1 = 2/(2xm1kT), p2 = 1/(2xm,kT), Y is thenumber of atoms evaporating per second per unit area from acomplete film, a is the probability that a gas atom striking a baresurface is adsorbed, q is the number of molecules evaporating persecond per unit area from a complete film due to the recombinationof adsorbed atoms, and p the probability that a molecule strikinga bare surface is adsorbed ; y is the probability that a gas atom strik-ing an adsorbed atom combines with it and the two evaporate asa molecule, and 6 the probability that a molecule striking a baresurface breaks up so that one atom is adsorbed and the other escapesinto the gas phase.Equation (2) is the isotherm for this type ofadsorption.It will be seen that, of the processes enumerated above, (i) ( a )and (iii) ( b ) both give rise to the presence of atoms in the gas phase.We shall now show 26 that the d$ law is obtained, if, under the con-26 J. K. Roberts, Ptoc. C a d . Phil. SOC., 1936, 32, 154.* 6 J. K. Roberts and G. Bryce, .ibid., p. 653.REP.-VOL. XXXV. 66 GENERAL AND PHYSICAL CHEMISTRY.ditions of the experiments, (i) (a) is the important process and thesurface is very sparsely covered, i e . , 0 is small. It is obtainedequally if (iii) ( b ) is the important process and the surface is nearlycompletely covered, ie., 0 is nearly unity.Further, we shall showthat the temperature variation in the rate of production is thesame for the two processes. Thus, it is not possible with the resultsavailable to distinguish between them from kinetic considerationsalone, and it is not easy to extend the range of the experimentalconditions widely.The rateof evaporation of atoms from the film is v0, and, with the firstvalue of A given in (3), this rate isAt constant temperature this is proportional to 4%. Equation(2) actually gives the fraction of surface covered when the gas isat the same temperature To as the wire. Since, a t the filamenttemperatures with which we are concerned, the degree of dissociationis small, it can be taken as giving to a first approximation thefraction of surface covered when the wire is at To and the gas a t0".To this approximation we can treat p1 and the condensationcoefficient a as constants. The variatim with temperature of therate of production of atoms is then due entirely to the variationwith temperature of 1/K.Now consider process (iii) ( b ) . When 0 is nearly unity, equation(2) becomes 1/(1 - 0 ) = Ad&. The rate of production of atomsis @,(l - 0)/p, or, from the last equation, Sd&/Ap2. The lastvalue of A from (3) being used, this becomes 103(y/p1)l/Kdg.This, as we have said, is also a t constant temperature proportionalto dE. If we regard y as independent of T, we have again thatthe temperature variation in the rate of atom production is dueentirely to the temperature variation of 1/K.The values of Khave been calculated from the data given by W. F. Gia~que,~' butusing the value 101,000 cals. for the heat of dissociation fromspectroscopic data instead of the older value 102,800 used by him.These values of K being used, the relative rates of production ofatomic hydrogen a t the tungsten surface at various temperaturescan be obtained immediately if the above view is correct. Thus,if the rate a t one temperature (the highest) is taken as known, therates a t other temperatures can be calculated. The results of thesecalculations and also the measured rates are given in the accompany-ing table. When account is taken of the approximations in the cal-culation, the agreement between calculated and observed valuesis very satisfactory.J .Amer. Chem. Soc., 1930, 52, 4816.When 0 is small, equation (2) becomes 0 = Ad%.ye = 103(a/p~)l/Kl/& . . . . . (4ROBERTS : THE ADSORPTION OF CASES. 67The Reporter 14 has shown that, when the interaction betweenadsorbed pa,rticles is taken into account, the above considerationsTemp., sec. x a t p = 1-25 x mm. of mercury.Production of H atoms per cm.2 perOK. Obs. Cdc.1338 1151243 32 221148 7 41420 316 w;)are not affected, and has discussed this whole question more fullyel~ewhere.1~I n order to decide whether process (i) ( a ) or process (%) ( b ) isthe important one, it is necessary to determine whether, under theconditions obtaining in Bryce’s experiments, the surface is sparselyor nearly fully covered with hydrogen.Bosworth l5 has investigatedthis problem, using the contact-potential method, and has con-cluded that the surface is nearly fully covered. Thus we mustsuppose that the production of atomic hydrogen in the range ofconditions considered is predominantly due to the process in whicha molecule hits a bare place on the surface and one atom is adsorbedand the other passes into the gas phase.In addition, some important qualitative observations on theeffect of oxygen poisoning on the rate of production of atomichydrogen have been made by G. Bryce,zg who has shown that someof the inferences drawn by earlier workers in this field will have to bemodified. For example, the removal of poisoning oxygen in the pres-ence of hydrogen, which was attributed by Langmuir to a flank attackof the hydrogen on the adsorbed oxygen, is shown to take place inan exactly similar way when hydrogen is absent.6.The Removal and Pormation of Adsorbed Filmson Tungsten.I. Langmuir and D. S. Villars 29 h s t measured the heat of evapora-tion of oxygen from tungsten by measuring the temperature variationof the evaporation rate. Similar measurements have recently beencarried out by M. C. Johnson and F. A. T7ick3* by measuring thetime variation of the thermionic emission from a filament with anoxygen film on it. In order to carry out these measurements, theydeveloped a method using a suitable oscillograph to follow therapid changes involved, and Johnson and A. F. Henson 31 have usedthe method to study the deposition of oxygen films a t very highTrans.Faraday Soc., 1937, 33, 782.2s J . Amr. Chern. SOC., 1931, 53, 486.30 Pmo. Roy. SOC., 1935, A, 151, 296.31 Ibid., 1938, A, 165, 14868 GENERAL AND PHYSICAL CHEMISTRY.temperatures. Their results suggest the possibility that the oxygenfilm thus formed is of a different nature from that formed a t ordinarytemperatures.13 Bosworth and Rideal 32 have also given a prelim-inary account of a determination of the heat of evaporation ofoxygen, using the same method and detecting the film by measuringthe contact potential. The Reporter 2o has discussed the generaltheory of the method.When oxygen is admitted to tungsten already covered with hydro-gen, the Reporter,' using the heat of adsorption method describedin Section 2, has shown that the oxygen is adsorbed and that eachmolecule which goes on to the surface throws off a molecule ofhydrogen.7.The Theory of Adsorption.An important advance in the fundamental theory of adsorptionwas made by R-. H. Fowler 33 when he showed that the Langmuiradsorption isotherm can be deduced from statistical considerationswithout postulating any particular mechanisms for condensationand evaporation. He 34 later extended the statistical theoryto include the effects of attractive interactions between adsorbedparticles, and showed that with sufficiently large attractiveforces critical phenomena would occur, and a t temperatures belowthe critical temperature there would, a t a given stage in the ad-sorption process, be a rapid increase in the equilibrium amountadsorbed with increase of pressure.This same problem was latertreated by R. P e i e r l ~ , ~ ~ using the method which Bethe first developedfor studying order and disorder problems in alloys. Fowler andPeierls both considered the formation of one layer only of adsorbedatoms, and the extension of the theory to two layers has been carriedout by G. P. D ~ b e . ~ ~used the method of Peierls in discussing the effect ofrepulsive forces between adsorbed particles, and later 37 obtainedan approximate theory to cover the effect of dipole interactions.Other applications of the method have already been discussed.Mention should be made of papers by G. S. Rushbro~ke,~~ T. S.Chang, 39 and by E.A. Guggenheim 40 in which some of the assump-tions underlying the theory are discussed.The mechanisms of evaporation and condensation have been dis-cussed in a number of papers by J. E. Lennard-Jones and hisJ. S. Wang32 Physim, 1937, 4, 925; 1938, 5, 170.83 Proc. Camb. Phil. SOC., 1935, 31, 260.34 Ibid., 1936, 32, 144.3O Ibid., 1938, 34, 587.38 Ibid., p. 424.40 Proc. Roy. SOC., 1938, A , 169, 134.3 5 Ibsbid., p. 471.37 Ibid., pp. 238, 412.39 Ibid., p. 224MELVILLE : CHEMICAL KINETICS. 69collaborator^.^^ One of the most interesting results is that evena t low temperatures evaporation in two stages is relatively frequent,i.e., the particle is first excited from the ground state to a highervibrational level and then receives a further quantum of energyfrom the solid which causes it to evaporate.J.K. R.4. CHEMICA4L KINETICS.Just as physical chemistry in these reports has been divided intoa number of well-established divisions, so chemical kinetics hasbeen similarly classified. The method is convenient, for the progressmade each year may be clearly summarised and assessed; but theconsequence is that some branches of the subject are left out orare only cursorily examined. In this Report, therefore, many ofthe customary topics, such as photochemistry, unimolecular re-actions, oxidations and explosions, reactions in solution, have beenpurposely omitted in order to make way for a discussion of a varietyof processes connected in one way or another with the solid state.Such reactions include heterogeneous catalysis, diffusion in solids,thermal decomposition of solids, photo-processes in solids, etc.Itmust be admitted that the progress made in these lines of researchis less striking and often less clear cut than in gaseous or liquidkinetics, but there is no doubt, in spite of greater experimentaldifficulties, that material advances are being made which put thesubject on a more satisfactory footing and justifgr a discussion of it.First, attention is devoted to the mechanism of heterogeneouscatalysis. Here, deuterium has been of great value in discriminatingbetween reaction mechanisms. The original novelty of the discoveryof deuterium reactions has disappeared and has been replaced bya more thorough attack in which all possible methods have beenemployed in close collaboration.Connected with heterogeneouscatalysis is the mechanism of diffusion of gases through metals.Here a beginning has been made in isolating and measuring the rateof the interface reaction and the velocity of diffusion through themetal itself. There is, however, still lacking a theory which willcorrelate velocity of diffusion with the associated energy of activa-tion. An essentially similar process occurs in the interdiffusionof solids where qualitative criteria are now beginning to emerge.Somewhat more complicated is the thermal decomposition of solids,for example, of detonating substances and the dehydration of salthydrates, although some degree of order is now apparent in this4l J.E. Lennard-Jones and A. I?. Devonshire, Proc. Roy. Soc., 1936, A,156, 6, 29; C. Strachan, ibid., 1937, A , 158, 691; J. E. Lennard-Jones andE. T. Goodwin, ibid., 1937, A, 163, 10170 GENERAL AND PHYSICAL CHEMISTRY.field. Not less complicated are photo-reactions in solids, but for-tunately it has been possible to choose simple systems-alkali halidelattices-with which to experiment. The result has been to givefundamental significance to the nature of the absorption spectraand to gain an insight into the primary and secondary photo-processes.Moreover, evidence is not lacking that that knowledge can be appliedto the more familiar reactions, such as the photo-decomposition ofsilver halides or the fluorescence and phosphorescence of sulphides,in order to bring reason into the wide variety of observational datacollected over a long period of years.Heterogeneous Gas Reactions.-Although there have been recentreports on various phases of heterogeneous catalysis, it wouldappear to be opportune to survey the subject with especial referenceto recent developments.As is well known, the basic theory wasput forward many years ago by I. Langmuir and illustrated by aseries of experiments in comparatively simple systems. Somewhatlater, C. N. Hinshelwood further extended the enquiry by addinga number of systems falling into well defined types. Briefly, whatthe theory did was to attempt, from the observed pressure andtemperature dependence of the reaction, to give a picture of thenature and concentration of the adsorbed entities and their precisemode of interaction.Since these early developments, a long listof reactions on as many different catalysts has been investigatedwithout resulting in any material advance in the theory of such pro-cesses. In some reactions, for example, it is not possible to correlatethe observed pressure dependence with temperature dependenceaccording to the Langmuir theory. This does not, of course, reflecton the theory for, even had the systems been suitable for the applica-tion of the theory, and some were not, there are certain problemswhich had eluded experimental investigation. A case in point maybe quoted. At a nickel surface hydrogen will hydrogenate ethaneto methane. By the older method, the kinetics may be determinedand the mechanism worked out as far as the method will allow.But it is not possible to say whether the ethane is dissociated totwo methyl radicals or to an ethyl radical and a hydrogen atom, orwhether the hydrogen is dissociated into atoms which in turnattack adsorbed ethane, nor for that matter is it possible to definethe rate-determining step in the reaction.The newer technique,utilising para-hydrogen, deuterium, and deuterides, has advancedthe problem another whole stage, but the complete solution is notby any means in sight. What deuterium has done is to provideanswers to specific questions which had hitherto been only matters1 See, e.g., “ Kinetics of Chemical Change in Gaseous Systems,” 3rd edn.,Oxford, Chap.8MELVILLE : CHEMICAL KINETICS. 71for uncertain and often wild speculation. It is convenient to con-sider this section according to the under-mentioned subdivisions.H. S. Taylor andJ. C. Jungers 2 demonstrated qualitatively that deuterium exchangedwith ammonia on a synthetic-ammonia catalyst (iron, potassium,and aluminium oxides) a t temperatures lower than those a t whichammonia is readily formed, the evidence being the change in theultra-violet absorption spectrum of the ammonia. By employingortho-deuterium and carrying out a systematic investigation of thekinetics on an evaporated iron catalyst, A. Farkas was able to gaina definite idea of the mechanism. The advantage in using ortho-deuterium is that a measurement may be made of its rate of con-version alongside of that of exchange reaction, so that the rate ofdissociation of deuterium may be obtained.Two objections mightbe raised in this connexion. The first is that the ortho-deuteriumconversion might be due to the paramagnetism of the catalyst, andthe second that the mechanism of the conversion isD(ads.) + o-D, --+ pD2 + D(ads.),i.e., an exchange reaction with the deuterium already adsorbed onthe surface of the catalyst. With a number of catalysts it has beenshown that the reaction H2 + D, ---+ 2HD goes a t about the samespeed as the ortho-deuterium conversion ; this disposes of the firstobjection but not directly of the second, and therein lies a possibleweakness of the method.At temperatures in the neighbourhood of 200°, exchange betweendeuterium and ammonia is much slower than that of the ortho-deuterium conversion, in spite of the fact that the velocity of thelatter reaction is strongly inhibited by the presence of ammonia.That ammonia is strongly adsorbed is shown, not only by the factthat the exchange reaction is of zero order with respect to ammoniapressure, but also because inhibition by ammonia becomes irreversibleif ammonia is allowed access to the catalyst a t 20°, when a smallamount of hydrogen can be detected.As in all reactions of this nature, there are essentially twomechanisms by means of which exchange d a y occur, vix.,Exchange of deuterium with saturated hydrides.D , + D + DD + NH, --+ NH,D (f)H + D + H D (9)I) + NH,+ NH,D + H (I) NH, ---+ NH, + H (d)](II) (e)D,-+D+DH + D-f HD(All the molecules are supposed to be adsorbed on the catalyst.)J .Amer. Chem. SOC., 1935, 57, 660.Trans. Furadcay Soc., 1936, 32, 41672 GENERAL AND PHYSICAL CHEMISTRY.Since the velocity of conversion is greater than that of exchange(e.g., 100 : 1 at 155"), reactions (a), (c), (d), and (9) are not rate-determining. On account of the slight decomposition of ammoniaon admission to a fresh catalyst, Farkas concluded that mechanism(11) is the correct scheme. These conclusions are supported in partby the observation that the apparent energy of activation forexchange, 15 kg.-cals., is somewhat greater than that for conversion,8 kg.-cals.In a similar manner, deuterium exchanges with water on typicalhydrogenation catalysts which exhibit activated adsorption ofhydr~gen.~ In fact, the water content of such catalysts may beestimated by determining the equilibrium point for the exchange.Likewise, a platinum wire catalyst is effective for this reaction.5Again the para-ortho interconversion is more rapid than exchange,and in a,ddition, the former reaction is inhibited by the water vapour.There is also some degree of reversible poisoning by water vapour.These observations parallel those with ammonia, and therefore thequestion arises : Does exchange occur between adsorbed atomicdeuterium and adsorbed water or fragments of the water moleculesuch as hydroxyl radicals ? The indirect evidence from irreversiblepoisoning of the catalyst for the para-conversion would indicatethat the latter alternative is correct.A variety of organic molecules,e.g., ethyl ether, benzene, acetone, ethyl alcohol, n-butanol and 2-ethylhexanol, exhibit exchange in presence of a platinum catalyst .*Naturally, all hydrogen atoms are not equally reactive. For example,those in the alcoholic hydroxy-group exchange more rapidly thanthose attached to a carbon atom. Roughly, two types of behaviourmay be distinguished : (i) reactions in which the para-conversionis much faster than exchange, and (ii) those in which these changesoccur at about the same speed. Such a classification is, of course,dependent both on the temperature of the catalyst and on the pres-sure of the molecule undergoing exchange.Ethyl ether, benzene,and acetone belong to the first class, but ethyl alcohol may bebrought into this class if its pressure is reduced from a few mm. to0.01 mm. in presence of 20 mm. of deuterium. If it is assumed thatthe hydride is dissociated, then, when the conversion is fasterthan exchange, the velocity of the latter process is governed by therate of dissociation of the hydride. On the other hand, when thepara-conversion goes at the same speed as the exchange, then therate of dissociation of deuterium is the rate-determining step, forH. S . Taylor and H. Diamond, J . Amer. Chem. SOC., 1934,56,1821; 1935,A. Farkas, Trans. Faraduy SOC., 1936, 32, 922.A. Farkas and L. Frarkas, i b d . , 1937, 33, 378.57, 1256MELVILTAE : CHEMICAL KINE'ITCS.73in this circumstance the strong adsorption of the hydride limits thearea upon which the deuterium molecule may dissociate. Theexchange is thus controlled by the replacement of these hydrogenatoms with deuterium. In the same paper a scheme is worked outto account for this behaviour and its relation to exchange occurringa t the liquid cataIyst interface.Exchange with unsaturated molecules. With such compounds thereis the additional complication of hydrogenation to be taken intoaccount, and the question arises whether the exchange is intimatelybound up with the hydrogenation or whether the two processes areindependent of each other. With ethylene on nickel, hydrogenationoccurs to the exclusion of exchange at low temperatures (20"), whilethe reverse happens a t higher temperatures (200°).7 Ethane doesnot undergo exchange under these conditions, and moreover, atlow temperatures the para-hydrogen conversion is inhibited stronglyby the ethylene except when the ethylene pressure is low.Some-what similar behaviour * is obtained with a platinum catalyst, thepara-conversion possessing practically the same apparent energy ofactivation as the hydrogenation reaction. The ratio of conversionrate to hydrogenation rate depends on the relative pressures. Above150°, there is an inversion of the temperature coeficient of thehydrogenation, similar to that observed for nickel: the para-conversion then proceeding relatively much faster. In so far asexchange is concerned, two mechanisms are again possible, uiz.,(l) $- c2H4 --+ C2H4D } Associative mechanismC,H,D + C,H,D + H} Dissociative mechanism (2) C,H, --+ C,H, + HC,H, + D --+ C,H,DFrom the similarity in apparent energies of activation for para-conversion and hydrogenation, A.and L. Farkas suggest that thelatter involves dissociation of the hydrogen when addition toethylene immediately occurs if an ethylene molecule is in theneighbourhood. The exchange reaction, on the other hand, has amuch higher energy of activation. This is attributed to the occur-rence of reaction (2), the equilibrium being displaced towards theright, thus decreasing the concentration of adsorbed ethylene mole-cules. This cuts down the velocity of the hydrogenation reactionand is the cause of the inversion of the temperature coefficient.7 A.Farkas, L. Farkas, and E. K. Rideal, PTOC. Roy. SOC., 1934, A , 146,630.* A. Farkas and L. Farkas, J. Amer. Chem. Soc., 1938, 60, 22.E. K. Rideal, J., 1922, 121, 309; H. zur Strassen, 2;. physikal. Chem.,1934, A , 169, 8174 GENERAL AND PHYSICAJJ CHEMISTRY.Exchange of deuterium with liquid benzene, first demonstrated byI. Horiuti, G. Ogden, and M. Po1anyi,lo is also catalysed by nickeland platinum. Under different conditions-platinum in the gasphase-hydrogenation proceeds at a comparable speed,ll theinteresting observation being made that the para-conversion is notnow inhibited by benzene. Again, it would appear that hydrogen-ation and exchange have essentially different mechanisms, for therate of the former is proportional to the first power of the hydrogenpressure and independent of the benzene pressure, whereas theexchange rate is independent of the hydrogen pressure and pro-portional to the 0.4 power of the benzene pressure.It is suggestedthat the dissociative mechanism holds good for exchange, but thatbenzene is only adsorbed on certain selected portions of the surfacein which the geometrical arrangement of the platinum lattice is mostfavourable. Adsorption is complete on those regions.Exchange reactions between hydrides and deuterides. It will berealised from the foregoing discussion that the para-hydrogen con-version and the rate of formation of HD molecules from H, andD, provide important information about adsorbed hydrogen, butsuch observations do not allow any absolutely definite conclusionsto be drawn about the nature of the interaction of the hydride withthe catalytic surface.To find whether or not a hydride is dis-sociated on such a surface, the interaction of the hydride with thecorresponding deuteride must be investigated. For those moleculeswhich yield absorption spectra in the quartz ultra-violet, a qualita-tive analysis will serve to demonstrate the appearance of inter-mediate deuterides. Owing to the complexity of such spectra,infra-red spectra possess many advantages, although the techniqueis more laborious. W. S. Benedict, K. Morikawa, R. B. Barnes,and H. S. Taylor l2 have described the details of the analyticaltechnique for the methanes and ethanes, which absorb strongly intwo regions, e.g., a t 2000-3200 cm.-l owing to valency vibrations,and at 900-1300 cm.-l owing to deformation vibrations. It hasproved possible to estimate the mole-fraction of any individualintermediate deuteride, and thus to say whether a hydride mixtureis in a state of equilibrium.Employing a nickel catalyst, K.Morikawa, W. S. Benedict, andH. S. Taylor 13 showed that methane and tetradeuteromethanegave the equilibrium amounts of the intermediate methanes whenlo Trans. Fsraday SOC., 1934, 30, 663; cf. also I. Horiuti and M. Polanyi,11 A. Farkas and L. Farkas, ibirE., 1937. 33, 827.1s J . Chem. Physics, 1937, 5, 1.13 J. Amer. Chem. SOC., 1936, 58, 1445.ibid., p. 1164MELVILLE : CHEMICAL KINETICS.76put into contact with the catalyst. Moreover, the velocity andapparent energy of activation for the exchange reactionD, + CH4 -> CH,D + HD were about the same as those for theinteraction of hydride and deuteride. Also it is very probable thatunder the conditions-high temperature, ZOO", active bulk catalysts-the para-conversion would have been very fast. Hence it isestablished straight away that, not only is methane dissociated intomethyl and atomic hydrogen, but that this reaction is the rate-determining step in the exchange reaction. If the deuterium isreplaced by its oxide, the velocity of the exchange is much decreasedowing to displacement of adsorbed methane by the oxide. Withethane, hydrogenation to methane occurs in addition to exchange.The infra-red technique, supplemented by appropriate chemicalanalysis,l4 showed again that the exchange rate is governed by thedissociation of the hydrocarbon to ethylene and atomic hydrogen.On the other hand, hydrogenation to methane, which involves split-ting of the molecule into two methyl groups, occurs much less readily.The reactions of propane have been analysed in a similar manner, thereactivity of the molecule being somewhat greater than that ofethane. In this way the order in which the various bonds in ahydrocarbon are broken on a nickel catalyst may be determined.The order is as follows, the reactivity increasing down the series :(CH, --+ CH3 + H) > (C,H, -+ 2CH3) > (C3H8 --+ C2H5 + CH,)Mention has already been made of the difficulty in decidingbetween the mechanisms for exchange a.nd hydrogenation of un-saturated compounds.It is evident that exchange between hydridesand deuterides will decide the issue for exchange of hydride withdeuterium. Experiments l5 with ethylene have shown that noexchange between hydride and deut'eride occurs under conditionswhere the exchange reaction with deuterium is very fast. Theassociative mechanism for exchange must therefore operate withethylene. Whether it occurs with other unsaturated molecules isyet to be seen. For ethylene, at any rate, the results mean thatboth hydrogenation and exchange are similar, in that if anotherhydrogen atom combines with the associative complex before thelatter dissociates ethane will be formed.The problem then is toreconcile the dissimilar kinetics of the two reactions with theessential similarity in mechanism. Such a correlation is indeedd a c u l t and emphasises the remarks made at the beginning of thisreport ; but there is, of course, the possibility that in hydrogenationK. Morikawa, W. S . Benedict, and H. S . Taylor, J . Amer. Chem. SOC.,1936,58, 1795.> (CZHG--+ CZ&, + H) > (C3HS + C,H, + H) > (H2 + ZH).16 G. H. Twigg and 0. K. T. COM, private communication76 GENERAL AND PHYSICAL CHEMISTRY.the addition of two hydrogen atoms, even from the same molecule,may occur consecutively but so rapidly that the half-hydrogenatedstate does not exist, under some conditions, long enough to havethe opportunity to dissociate.Relutive Velocities of Reactions of Hydrogen and Deuterium.--This question may be considered in two stages.First, measurementsof the relative velocities of a number of such reactions have beenmade to determine to what extent zero-point energy controls therate of heterogeneous reactions. Secondly, the experience so gainedmay be applied to discriminate between reaction mechanisms whenother methods fail. It is probably true to say that the second stagehas not yet been reached although much work has had this objectin view.In surface reactions hydrogen may react more quickly thandeuterium by a factor of d2, owing to the greater speed of thehydrogen molecule or atom either in getting to the surface or inmigrating along it.Besides this factor there is another effect tobe taken into consideration. If the reaction involves the activationof a hydrogen bond, then, in virtue of the fact that the zero-pointenergy of a hydride is at most 41% greater than that of a deuteride,the energy of activation required for the deuteride may be larger,since zero-point energy is known to contribute to the activationenergy of reactions.16 Some time ago H. Eyring and A. Sherman l7estimated that the difference in zero-point energy of surface hydridesand deuterides of metals commonly used as catalysts was not greaterthan about 700 cals. At 300" K., the maximum possible ratio ofrates will be exp(7OOIRT) = 3, while at 600" K. the ratio is only1.7. The reactions which have been studied are the ortho-paraconversion of hydrogen and deuterium, on nickel l8 and platinum,lgthe reduction of nitrous oxide and oxygenY2O and of ethane tomethane on nickel,21 the reduction of copper oxide,22 the reductionof light and heavy ethylene by hydrogen and by deuterium on nickeland on copper.23 In nearly every reaction the hydrogen reacts morequickly than the deuterium, and sometimes the ratio of rates isgreater than can be accounted for by the simple mass factor of16 For a summary, see H.W. Melville, Science Progress, 1937, 31, 499.1 7 J . Chem. Physics, 1933, 1, 348.1 8 E. Fajans, 2. physikal. Chem., 1935, B, 28, 247.Is A. Farkas and L. Farkas, J. Amer. Chem. SOC., 1938, 60, 22.2o H. W. Melville, J., 1934, 797.2 1 K. Morikawtt, W.S. Benedict, and H. S. Taylor, ref. (14).22 H. W. Melville and E. K. Rideal, Proc. Roy. SOC., 1935, A , 153, 82.23 T. Tucholski and E. K. Rideal, J., 1935, 1701 ; 0. Boris, J. C. Jungers,and H. S . Taylor, J . Amer. Chem. Soc., 1938, 60, 1982; G. G. Jones andJ. C. Jungers, ibid., p. 1999 ; R. N. Pease and A. Wheeler, ibid., 1935,57, 1149MELVILLE : CHEMICAL EMETICS. 77d.%. Experimentally, however, it is extremely m c u l t to measurethe difference in the energies of activation for hydrogen and deuter-ium, since the experimental error in the individual determinationsis often of the same order of magnitude as the difference. Thesame state of affairs exists for the decomposition of ammonia anddeuteroammonia 24 and of phosphine and trideuterophosphine 25 ontungsten, the ratio of rates giving, without correction for a massfactor, a difference of a few hundred calories.A fair general sum-mary of the present position of this section of kinetics would bethat, in a number of heterogeneous processes involving both hydrogenand deuterium, hydrogen reacts faster because of the greater zero-point energy possessed by the hydrogen bond, but the full effectof this factor is annulled to a large extent by the existence of zero-point energy in the transition state. In those reactions wheresuch a difference is observed it may be concluded that the rate-determining step does involve the activation of the hydrogen bond.Further than this it would probably be unsafe to go, and thereforethe method will in general be insufficiently accurate to be of anyuse in settling reaction mechanism. The so-called tunnel effectoriginally looked for by E.Cremer and M. Polanyi26 does notappear to play any significant part in the above-mentioned reactions.Activated Adsorption.-By studying the relative rates of ad-sorption of hydrogen and deuterium on those solids exhibiting thephenomenon, it was also hoped to gain some further informationabout this process. Measurments have been made on oncopper,28 on chromic oxide, and Zn0,Cr20,.29 Sometimes hydrogenis more quickly adsorbed than deuterium ; the reverse happens underdifferent conditions on the same adsorbent. The phenomena appearto be so complicated that in this particular instance the interpreta-tion of the experiments with deuterium certainly has not clarifiedthe problem.Diflmion of Gases through Metals.-Although this type of inter-action of gases with solids was quantitatively studied more than30 years ago and sporadically since that time, there has been arevival of interest within the past two or three years. This is dueto developments in technique permitting measurements over a24 J.C. Jungers and H. S. Taylor, J . dmer. Chem. SOC., 1938, 60, 679.26 R. M. Barrer, Trans. Parnduy SOC., 1936, 32, 490.26 2. physikal. Chem., 1932, €3, 19, 443.27 J. Pace and H. S. Taylor, J . Chem. Physics, 1934, 2, 578; R. Klar,Naturwiss., 1934, 22, 822.28 H. W. Melville and E. K. Rideal, Proc. Roy. SOC., 1935, A , 153, 85;R. A. Beebe, E. L. Wilber, and S.Goldwasser, J . Amer. Chem. SOC., 1935,67, 2527.zu J. Pace and H. S. Taylor, ref. (27)78 GENERAL AND PHYSIUAL CHEMISTRY.wider range of conditions, and also to the fact that the reactions ofthe hydrogen modifications and of deuterium have supplied newdata which must be incorporated in any theory of diffusion. Itwas established by 0. W. Richardson, J. Nicol, and T. Parnell30that the diffusion coefficient (D) of hydrogen through platinum isgiven by D = const.p*e-ED’RT. dTd-l, where p is the pressure onone side of the platinum, the other side of the metal being in avacuum, ED is a characteristic constant, and d the thickness of themetal. Later experiments with other metals fully supportedthe validity of the equation.31Before enquiring further into the significance of the factors inthe above equation, the first question which arises is whetherdiffusion of the gas occurs along the intercrystalline cracks orthrough the lattice itself.Since the rate of diffusion is sometimessubject to the treatment and condition of the metallic surface, itwould appear that intercrystalline cracks are important in thisconnection. With iron, however, C. J. Smithells and C. E. Ransley 32have shown that diffusion must take place through the lattice, sincethe rate is not markedly altered by substituting a polycrystallinetube for a tube consisting of a single crystal. It is not impossiblethat this may prove to be a general phenomenon for hydrogen-metal systems. The appearance of the d$ term in the diffusionequation has always been taken to imply that hydrogen atomsmigrate through the lattice.There is, however, no doubt that themolecule as such loses its identity in the process, for ifpara-hydrogenor a mixture of hydrogen or deuterium is used the correspondingequilibrium mixture issues from the other side of the Atlow pressures, on the other hand, the rate varies with the pressureaccording to a power higher than $34 (the pressure at which thedeviation occurs is higher the lower the temperature). None theless surprising is the fact that the square-root law holds up to atleast 112 atmosphere^.^^ In view of the fact that the rate ofdiffusion is inversely proportional to the thickness, the generalpicture of the diffusion process is that a concentration gradient isset up inside the metal, the magnitude of the gradient being pro-portional to the square root of the hydrogen pressure.Such amechanism implies that the rate-determining step is not the transfer30 Phil. Mag., 1904, 8, 1.31 For a summary, see C. J. Smithells, “Gases and Metals,” Chap. 2,Chapman and Hall, London.32 Proc. Roy. SOC., 1935, A , 150, 172.83 A. J. Gould, W. Bleskney, and H. S. Taylor, J . Chem. Physics, 1934,84 C. J. Smithells and C. E. Ransley, Proc. Roy. SOC., 1935, A, 150, 172;2, 366.1936, A, 157, 1936MELVILLE : CHEWCfi KINETICS. 79of hydrogen molecules to atoms just inside the metal surface, i.e.,the interface reaction, but the transport of the atoms within thelattice. Hence, in order to explain the low-pressure dependenceof rate upon pressure, Smithells and Ransley suggested that hydrogenmolecules adsorbed on the surface controlled the concentration ofatoms just inside.The concentration of molecules is supposed tobe given by the simple form of the Langmuir isotherm. At highenough pressures this concentration is independent of pressure,and hence the l/r, law is obeyed ; at low pressures the concentrationof molecules is proportional to p and thus the rate of diffusion to$12. At very high pressures, on this hypothesis, there ought tobe a limit to the concentration of dissolved hydrogen atoms, where-upon the diffusion rate should become independent of pressure.J. S. Wang36 has put forward a mechanism which evades thisdifficulty and also accounts for the high and low pressure rates.Besides the two processes envisaged above, i.e., (a) gas moleculesstrike the surface of the metal and are dissociated, and (b) the passageof adsorbed atoms just inside the metal, an additional process isadded, vix., ( c ) a molecule strikes a vacant place on the surface ofthe metal, one atom is adsorbed, and the other penetrates insidethe metal.It is evident from these results that the phenomena at the gas-metal interface merited further study. Again, the rates of diffusionof deuterium have been compared with those of hydrogen for themetals copper, nickel, and palladium 22* 36 in the hope that furtherlight might be brought to bear on the problem.As in heterogeneousreactions, the diffusion rate for hydrogen is somewhat higher thanthat for deuterium, but the same difficulty arises here as wasencountered in interpreting the results for heterogeneous reactions,uiz., that the difference in overall energy of activation cannot beaccurately determined without making certain assumptions, whichare not easy to verify.However, it would appear that the differenceis of the order of a few hundred calories.Experiments with palladium deserve special mention because,not only may the relative rates of d8usion be measured at com-paratively low temperatures, but also the relative solubilities underthe same ~onditions.~~*3~ The heats of solution of hydrogen and ofdeuterium are calculated from the variation of solubility withtemperature. The apparent energy of activation for diffusion,s6 Proc.Camb. Phil. SOC., 1936, 32, 657.36 A. Farkm and L. Farkas, Proc. Roy. SOC., 1934, A, 144, 477; W. Jostand A. Widmann, 2. physikal. Chem., 1935, By 29, 247; A. Farkas, Trans.Faraday SOC., 1936, 32, 1667.37 A. Sieverts, 2. physikal. Chem., 1935, 174, 36980 GENERAL AND PHYSICAL CHEmSTRY.ED, is thus corrected by subtracting half the heat of solution togive the true energy of activation for diffusion. It turns out thathydrogen is more soluble than deuterium) the heat of solution beinggreater by a few hundred calories, presumably owing to a zero-pointenergy effect, thus producing a greater concentration gradient in themetal and thereby causing the hydrogen to diffuse more rapidly.On correcting for solubility, however, it is found that part of thedifference in diffusion rate is actually due to the difference of afew hundred calories in the true energy of activation for diffusion.By measuring the velocity of the para-hydrogen conversion simul-taneously with diffusion, A.Farkas 36 determined the velocity ofthe transformation of molecular into atomic hydrogen at the gas-metal interface. With some specimens of palladium the latterprocess was far faster than the diffusion rate, and hence the rateof diffusion was not governed by the boundary process. This meansthat the velocity of the boundary process was sufficient to maintainthe concentration of atoms just inside the metal at an equilibriumvalue very nearly equal to that obtaining if there had been nodiffusion through the metal.Conditions were also found where therates of conversion and diffusion were of the same order of magnitude,indicating that in some circumstances the boundary process maybecome the rate-determining step.Finally, mention may be made of the " constant " in the diffusionequation. In spite of big variations in the value of the apparentenergy of activation for diffusion, the constant is of a similar orderof magnitude for a number of metals, as was pointed out by Smithellsand Ransley. It is probable that, if allowance had been made forvariation of solubility with temperature) a closer concordancewould have been obtained. The theoretical significance is not yetknown.Diflwion in Solids.-The first demonstration of the interdiffusionof two solids was made many years ago in the system gold-lead byRoberts-Austen.Later, the self-diffusion coefficient of lead wasmeasured by J. Gr6h and G. von Hevesyy3* using as radioactiveindicators thorium-B and radium-D, and found to be very muchsmaller than that of gold in lead. At 165") for example, the re-spective diffusion coefficients are 1.2 x and 5.8 xsec.-l. In order to explain this observation, Hevesy 39 suggestedthat the high mobility of gold is due to the attractive forces betweenits atoms being smaller than those between lead atoms. Hence aqualitative criterion for diffusion would be that the more akin aAnn. Physik, 1920, 63, 85.G. von Hevesy and W. Seith, 2. Elektrochem., 1931, 37, 528; G.vonHevesy, ibid., 1933, 39, 491MELVILLE : CHEMTCAL KINETICS. 81metal is t o lead, the smaller should be its diffusion coefficient.W. Seith40 confirmed this idea when he found the diffusion co-efficients decreased in the order silver, cadmium, mercury, bismuth,thallium, tin. For example, at 250", the coefficients for the systemsPb-Au, Pb-Sn, and Pb-Pb are respectively 3.5 x lo-', 1.5 X 10-l1,5.1 x 10-11 cm.2 sec.-l. One condition that the diffusion shouldoccur in a, homogeneous system is that the two components shouldform a solid solution. Aless soluble metal might diffuse more quickly, but with the complica-tion of the formation of a two-phase system. The production ofradio-active gold has made possible the measurement of the diffusioncoefficient of g0ld.~1 At 917" it has the value cm.2 sec.-l,and on extrapolation to 165", 6 x compared with 1-2 x 10-14cm.2 sec.-l for lead.Reactions in 8oEids.-The question of reactivity in solids is muchmore complicated than that of heterogeneous catalysis or even ofdiffusion in solids, mainly because of the immobility of the atomsand molecules constituting the interface and hence of the fact thatinteraction only occurs between nearest neighbours in a lattice.The simplest type of reaction is the polymorphic transformation,but this is more properly dealt with by the X-ray crystallographer,for information about the nature of reaction is best obtained byX-ray technique.Of more purely chemical interest, however, arethe decomposition of detonating substances and the dehydration ofsalt hydrates, both of which have received very wide attentionfrom the kinetic point of view, with the result that the data can beco-ordinated to form a homogeneous whole.Thesesolids include molecules such as the alkali and alkaline-earth azides,lead azide, nitrogen tri-iodide, lead styphnate, mercury fulminate,Hg(ONC),, etc.The general behaviour exhibited by these sub-stances is that on gentle heating they decompose after the lapse ofan induction period, the rate at first increasing and then finallydecreasing with time. At higher temperatures, detonation mayoccur after the expiry of an induction period. If the product ofthe reaction is a solid, the decomposition will occur at the solid-solid interface and presumably also start from such an interface.It is well known that many solid reactions do not take place if thecrystals are as nearly as possible perfect.Imperfections or im-purities in a crystal are, however, conducive to reaction and are prob-ably normally present in the crystals of the detonating substance.The induction period is thus due to the time required for these*O 2. Elektrochem., 1933, 39, 33; 1935, 41, 872.4 1 H. A. C. McKay, Trans. Faraday Xoc., 1938, 33, 845.Gold just comes within this restriction.Detonating substances may first of all be considered82 GENERAL AND PHYSICAL CHEMISTRY.imperfections or nuclei to grow to an effective size. Such sourcesof imperfection can be produced artiticially by a-particles,42 fastelectrons, X-rays, hydrogen, mercury and argon ions,*3 and ultra-violet light,44 and the induction period is then reduced or eliminated.The exact nature of the primary process is not yet known in anyone case.Once the detonation wave is started, it travels with themaximum possible speed, for it traverses a layer of atoms in a crystalin about sec., i.e., in a period comparable with a latticevibration. There is therefore no time lag in the transmission ofenergy from one layer to the next in a crystal. The questionarises, as in all reactions of this nature-in gases, liquid, or solids-whether the energy is specifically transmitted to adjacent moleculesor whether it is spread over a wider volume, thereby raising thetemperature of a small locality of atoms as a whole.This is ELvery dif6cult point to settle, and in fact the discrimination mayonly be artificial. It might be anticipated, however, that if thelatter mechanism is important, a sufficient increase in the numberof centres would not only remove the induction period but also.increase the velocity of the ensuing reaction. Actually, there isno significant increase in reaction velocity. Energy considerationsalso throw an interesting light on the mechanism of detonation,as has been shown by W. E. Garr1er.~5 The activation energy forthe decomposition of lead azide is 38 kg.-cals. This energy, togetherwith the exothermic heat of reaction, if transmitted without loss,would only activate three or four molecules of azide and wouldconsequently not start a spherical detonation wave in which mole-cules must be activated.The simultaneous decomposition of twomolecules within the requisite time interval would suffice for thepropagation of the detonation wave. Even below the detonationtemperature, such a coincidence may easily occur within the courseof the induction period, since at 290" 1016 molecules per cm.2or 30 layers of molecules decompose per second. The probabilitythat two adjacent molecules will decompose within l O - l 3 sec. is4 X i.e., simultaneous reaction would occur 4 x lo4 times persec./cm.2. On the same basis, ternary events may be completelyexcluded.So-called nitrogen tri-iodide, NI,,NH3, may be put in a class byitself, for at pressures below 2 x 10-2 mm.even at 0" detonationoccurs irnmediatel~.~~ In presence of ammonia, but not of iodine,42 W. E. Garner and C. H. Moon, J., 1933, 1398.13 H. Kallman and W. Schrankler, Naturwiss., 1933, 21, 379.44 Cited by W. E. Garner, Trans. Faraday S'oc., 1938, 33, 908.4 b J., 1934, 720; Trans. Paraday SOC., 1938, 33, 985.46 W. E. Garner and W. E. Latchem, Trans. Faraday SOC., 1936, 32, 667;F. R. Meldrum, ibid., 1938, 34, 947MELVIUB : CHEMICAL KINETICS. 83stable decomposition may be observed. It is suggested that NI,molecules either are or furnish the nuclei for initiation of detonation.Ammonia represses the formation of NI,, and so no detonationwave can be started.In dealing with the slow decomposition of detonating substances,general features may be mentioned in that there is an inductionperiod preceding reaction which initially increases exponentkdlywith time.W. E. Garner and D. J. B. Marke *7 sought to eliminatethe troublesome interface by working with sodium and potassiumazides under conditions in which the resultant alkali metal wasimmediately removed. Unfortunately, it is only in presence of thesaturated vapour of the metal, and therefore of an interface, thatthe decomposition rates became reproducible. These reactions maythen be compared with those of the alkaline-earth azides, lead azide,and lead styphnate. From the following summarising table it willRange of temp.Energy of activ-Substance. NaN,. ICN,. BaN,. CaN, .for decompn. 240-275" 222-255" 100-1 30' 60-130"ation, kg.-cals.34-4 35.1 21 1s-19Substance. Srh', . a-PbN,. P-PbN,. Pb[ C,H( N0,~,0,].Range of temp.Energy of activ-be observed that the lower the temperature a t which decompositionoccurs the lower is the energy of activation. This regularity doesnot apply to some molecules, such as mercury fulminate, troty1,4*C,H,(NO,),, picric acid, tetryl, C,Hz(N02)3NH*CH2*N02, and liquidnitroglycerol, which decompose a t much lower temperatures thanwould be expected firom the observed energy of activation. Withazides there is also another regularity. In some heterogeneousreactions it has been found that the rate of reaction per cm.2 ofthe catalyst is equal to vN, where N is the number or moleculesper ern., and v a factor having the dimensions of a frequency anda numerical value about 1013 sec.-1, i.e., a frequency comparableto that of the lattice.The decomposition of the azides falls withinthis category, and it might fairly be concluded that these decom-positions are normal interface reactions. The existence of aninduction period and the exponential rate-time character of theinitial stage of the decomposition remain to be explained. Again,the period of induction may be attributed to the growth of nucleii.To explain the subsequent increase of rate, a conception current in47 J., 1936, 657.4n S. Z . Roginski, Physikal. 2. Sovietunwn, 1932, 1, 649.for decompn. 100-130" 222-260' 200-270" 226-255Oation, kg.-cals. 18 3s (37) (4084 GENERAL AND PHYSICAL CHEMISTRY.homogeneous reactions is employed.49 Many oxidations, e.g., theslow oxidation of hydrocarbons, exhibit a similar behaviour of re-action rate with time, and these reactions are known to be of thebranching-chain type.By assuming that a similar general mechan-ism holds for solid reactions, without specifying the exact natureof the reaction centres, it is easy to derive an expression consistentwith the experimental results. If N is the number of reactioncentres generated per sec., and K is the number of times per sec.that two molecules are activated instead of one (i.e.? that the chainbranches, in kinetic parlance), thenW/dt = No +- KNor In N = Kt + In No/K.Since N is proportional to the rate of increase of pressureIn dp/dt = Kt + ln No/K.Chains are terminated when they encounter a crack or molecules ofthe product of the reaction, which keeps the branching reaction incheck.Unfortunately, the information obtained by such studiescannot give direct evidence of the nature of the chain propagators,but it would appear that some carriers do have a relatively longlifetime in that, should the reaction be stopped during the in-duction period by lowering the temperature, then on the crystalsbeing reheated, the reaction starts where it left off. There are there-fore some who would oppose the chain hypothesis on thesegrounds, but in view of the close analogy with gaseous chain re-actions, the corresponding reactions in solids cannot be so lightlydismissed in spite of lack of detail about the mechanism.The mechanism of the dehydration of salt hydrates may be putinto the same category, although there is a marked difference in thatthe reaction is strongly endothermic.The interesting observationis that the energy of activation for dehydration is practically equalto that osthe heat change in the reaction for the copper sulphatehydrates. Hydration will therefore be a reaction of zero energyof activation. Again, the absolute rates are in agreement withthose calculated from the simple theory (see p. 83) from the ob-served energy of activation. Observations by W. E. Garner andhis co-workers 51 on the rate of nuclear growth have shown that theenergy of activation is practically the same as that for the evolutionof water after the induction period. Individual variations in4@ W.E. Garner and H. R. Hailes, Proc. Roy. SOC., 1933, A, 139, 588.50 See, e.g., The Faraday Society Discussion, 1938, pp. 822-1082.6 1 N. F. €I. Bright and W. E. Garner, J., 1934, 1372; W. E. Garner andW. Southon, ibid., 1935, 1706; W. E. Garner and H. V. Pike, ibid., 1937,1665MELMLLE : CHEMICAL KINETICS. 85nuclear growth in different directions give rise to variety of nuclearshapes, but it is likely that the energy of activation is not greatlydifferent in these directions. To explain the slow rate of nucleargrowth, J. A. Cooper and W. E. Garner 52 suggest that, owing tocontraction of the solid, a negative tension is set up which reducesthe vapour pressure and therefore the rate of evaporation.Photo-processes in Solids.-Within the last few years a numberof significant advances have been made in the photochemistry ofsolids.Absorption spectra of simple crystals with and withoutimpurities may now be interpreted, some idea of the processes under-lying fluorescence have been obtained, and a new light has beenbrought to bear on the theory of the photographic plate. Theenlightenment is due to the application of the modern theory ofsolids to the problem and to the discovery of new facts in sufficientlysimple systems.Absorption in the visibleand ultra-violet is due to excitation of electrons which may, aswith free atoms, be raised to a discrete series of energy levelssucceeded by a continuum representing ionisation. The discretelevels in the solid are blurred because of lattice vibrations andperturbation by crystalline fields.The blurring due to latticevibrations can be diminished but not eliminated by working at lowtemperatures, as has been shown by J. T. Randa11.53 Exceptionsto the above-mentioned behaviour occur when the absorbing groupsare well screened from external influence. For example, compoundsof the rare earths and transition elements, complex ions such asUO,++, and organic molecules containing conjugated double bondshave sharp energy levels in the solid state. In a solid, then, thecriterion for ionisation is not a continuous broad band, but the onsetof photoconductivity. Photochemical action may result from suchexcitation, but this phase of the subject will be omitted in this report.Once the electron is excited to a discrete level, it either falls backto the ground level with the emission of radiation as fluorescencein some sec., or the electronic energy is dissipated as heatand no radiation is emitted.In the former circumstance thefluorescent quantum is usually smaller than that absorbed, sinceelectronic energy is partly dissipated as heat before fluorescenceoccurs. The decay of fluorescence follows the usual exponentiallaw, I = lo exp( - d), where I , and I are the intensities at zero timeand at time t respectively and a is a constant, since only one electronis concerned in the emission process. R. W. Gurney and N. F. MotPWe deal first with absorption spectra.61 Trans. Faraday SOC., 1936, 32, 1739.53 Nature, 1938,142, 113; cf.also C. J. Milner, Tram. Faraduy SOC., 1939,35, 101. 64 Ibid., p. 6986 GENERAL AND PHYSICAL CHEMISTRY.have suggested another way in which electronic energy is used,'uiz., to produce phosphorescence, one of the main characteristicsbeing a much longer decay period than that of fluorescence. Whenin the discrete level the electron may receive energy from the latticeto raise it into a true continuous level or conduction band. Theelectron then moves away from its original position, leaving apositive hole behind. The electron may then be trapped in a boundenergy level or it may combine eventually with a positive holewhereupon radiation is emitted. The intensity of emitted radiationwill thus be proportional to the product of the concentration ofholes and electrons, and hence the decay law will be of the secondorder.Randall's observation that the intensity of fluorescence increases/IConfi+rational co-ordinates.FIU.7.Potential-energy diagram of a crystal exhibiting fluorescence and phosphorescence.with decreasing temperature among a number of pure substances,e.g. , manganese, lead, cadmium, and samarium salts, not exhibitingphoto-conductivity, has suggested to Gurney and Mott a generalmechanism for fluorescence which is best explained by means ofa diagram. The potential energy of the absorbing centre may be re-presented for simplicity in a two-dimensional diagram as a functionof configurational co-ordinates (Fig. 7). On absorption of a quan-tum, the Franck-Condon principle comes into operation, with theresult that there is a vertical transition in the diagram to theupper excited state possessing considerable vibrational energy.This is lost to the lattice in a period of the order of a lattice vibration,i.e., 10-13 sec., long before fluorescence occurs, in 10-8 sec.Inconsequence, a quantum of lower frequency is emitted. In ordeMELVILLE : CHEMICAL KINETICS. 87to explain the temperature dependence, it is postulated that thepotential-energy curves cross. At this point the excited state willhave a high probability of reverting to the ground state with largevibrational energy, but without emission of radiation. In order toreach point C, however, energy must be acquired from the lattice.At low temperatures this is so infrequent an occurrence that nearlyevery absorbed quantum is emitted as a fluorescent quantum; athigh temperatures fluorescence may not be detectable. Thus,under suitable conditions fluorescence may be a much more commonphenomenon than was once supposed.The most striking examples of the luminescence of solids areprovided by those solids which from a chemical point of view areimpure.Examples are calcium and zinc sulphides containing avariety of metallic sulphides. Many of these substances are ofill-defined chemical constitution and cannot be obtained in largecrystals. R. Hilsch, R. W. Pohl, and their collaborators 55 havediscovered that alkali halide crystals activated with small amounts(0.001--0.01%) of the corresponding thallous halide exhibit bothfluorescence and phosphorescence and are, in general, systems moresuitable for experimental work.The absorption spectrum of suchcrystals consists of broad bands lying at a longer wave-length thanthe first fundamental band of the pure alkali halide itself. With thechlorides there are three absorption peaks of the A , B, and C bands.For example, potassium chloride has its first fundamental banda t 1636 A., the A , B, and C bands lying a t 2530, 2110, and 1976 A.respectively. A systematic investigation has shown that theabsorption maxima are practically independent of the cation in anyone halide. The anion has a small effect, the iodides absorbing a ta somewhat longer wave-length than the chlorides, the bromidesbeing intermediate between the two.On irradiation there is nodecomposition as with the pure thallous halide and there is no photo-conductivity. P. Seitz 56 therefore concludes that absorption isdue, not to the halide ion, but to the thallium, and that the systemis initially raised to a discrete level. No doubt, with light of shortenough wave-length the electron might be raised into the conductionband. First, if theabsorption were due to the halide, the bands should have a doubletstructure, whereas none is shown ; 57 secondly, absorption shouldlie further into the ultra-violet. The reason for the latter statementis that the halogen-thallium transition should lie close to thehalogen-rubidium which is much further into the ultra-violet-Two facts are in favour of this supposition.E d G au/’5 5 For a summary, see R.Kilsch, Proc. PhysicaE Soc., 1937, 49, 40. P 4 &Gt ,& 56 J. Chem. Physics, 1938, 6, 150.57 R. W. Pohl, Proc. Physical SOC., 1937, 49,,,5. f88 GENERAL AND PHYSICAL CHEMISTRY.1 6 8 4 ~ . for rubidium chloride. In point of fact, the C band forRbCl(T1) is at 1 9 4 4 ~ . If this assumption be made, it is possibleto correlate the position of three absorption bands with the corres-ponding transitions in the free atom.56To simplify the discussion, reference will be confined to thepotassium chloride phosphor. If light is absorbed in the A , B, orC bands, fluorescence is emitted in two superimposed bands lyingon the long wave-length side of the absorption bands. Moreover,any absorption band is effective, the quantum efficiency is of theorder of unity, and the relative intensities of the emission bandsare independent of which excitation band is employed. Just asabsorption spectra may be due to a multiplicity of levels in the crystal,so the fluorescent emission spectra may be accounted for by postulat-ing suitable crossing of potential-energy curves, so that the systemfinally reaches a level such that either fluorescent band may be emitted.Apartfrom the longer decay period, which is increased a t lower tempera-tures, only light in the B and C bands is effective.Moreover, theintensity is proportional to the square of the intensity of the excitingradiation ; the decay, however, follows a first-order equation andis quickened by infra-red radiation. The effect seems to be due 56to the co-operation of two thallium ions producing such a conditionthat the system may reach a metastable region.Entry into thatregion is dependent on the square of the incident intensity; escapefrom it, at a rate proportional to the concentration of the metastablestate, is facilitated by supply of energy from the lattice or by infra-red radiation. The existence of the metastable minimum thusensures the production of phosphorescence owing to the tardy escapeof energy by radiation.A somewhat different state of affairs exists with zinc sulphidephosphors. Pure zinc sulphide, either wurtzite or blende, doesnot phosphoresce, but the disturbance produced by having the twocrystal modifications in juxtaposition is sufficient to producephosphorescence.Similarly, sulphides of copper, silver, etc., alsoinduce phosphorescence. The criterion for the functioning of asulphide activator seems simple. For example, lead sulphide willactivate calcium and strontium sulphides but not zinc sulphide.By employing radioactive thorium-B-an isotope of lead-it canbe shown that lead does not enter the zinc sulphide lattice.5* Inthis manner in terdiffusion of metallic sulphides may be followedby measuring the phosphorescent intensity of successive layers ofphosphor^.^^ The reason for the occurrence of diffusion into theThe phosphorescence has rather different characteristics.58 H. Kading and N. Riehl, Angew. Chem., 1934, 47, 263.5Q E.Tiede, Ber., 1932, 65, 364; N. Riehl, Ann. Physik, 1937, 29, 654MELVILLE : CHEMICAL KINETICS. 89zinc sulphide lattice appears to be one of size. If the metallicatom can be accommodated without distortion in the vacant tetra-hedra of the zinc sulphide lattice, diffusion and therefore phos-phorescence are observed; if not, the energy of activation fordiffusion is so high that it effectively stops that process.Phosphorescence is optically an efficient process in spite of thefact that the absorption coefficient is unaltered by the additionof the activator. The energy acquired by the lattice must reachthe activator without loss, for the impurity is on the average at least20 atomic diameters away from the scene of absorption. A clueto the mechanism of emission is provided by the fact that, for somephosphors, the crystal exhibits photoconductivity, and that therate of decay is of the second order, the velocity being temperature-dependent.60 The second-order decay law certainly proves theparticipation of two particles in the emission process-photocon-ductivity shows that one is an electron.The other must be apositive hole left behind. The latter also may migrate in thesense that a neighbouring electron destroys it with the simultaneouscreation of an adjacent positive hole. When positive hole andelectron come together in presence of the activator, the functionof the latter is to provide a discrete level by means of which theenergy of combination of electron and positive hole may be emittedas radiation.Besides the phenomenon of the transfer of energy in crystals,there is also an interesting example of the transfer of energy fromthe solid to the gas phase, discovered by H.Kautsky.61 Dyes suchas porphyrin , tryptoflavin, and chlorophyll, when adsorbed onsilica or alumina gel, absorb radiation and re-emit it without im-parting any appreciable fraction to the support. I n presence ofoxygen, however, the fluorescence is quenched and the oxygenmolecule is excited to a low-lying metastable level. Such oxygenmolecules readily oxidise some substances, e.g., leuco-malachite-green, in which the colour change is evidence of reaction. Thismay be demonstrated by mixing together gel particles containingthe two dyes. In absence of oxygen the leuco-compound is un-changed.There is an optimum pressure for the effect - ca.mm. At low pressures only a fraction of the energy is removed bythe impact of the oxygen molecules, and at high pressures themetastable oxygen molecules are deactivated by collisions withnormal molecules on diffusing to the leuco-compound.H. W. M.6o A. L. Reimann, Nature, 1937, 140, 501.61 Biochem. Z., 1937, 291, 27190 GENERAL AND PHYSICAL CHEMISTRY.5. IRREVERSIBLE ELECTRODE PROCESSES.If an electrode reaction is carried out a t an appreciable rate theelectrode potential may be different from the reversible value.The reaction is then an irreversible one, and the electrode is saidto be “ polarised ” or to exhibit an “ overpotential.” The over-potential a t an electrode is defined as the potential difference betweenthis electrode and a similar reversible electrode in the same solution.It is possible to distinguish three main causes of irreversibility.Activation Overpotential, V .-Consider the general case of adissolved ion which moves up to the electrode surface, is discharged,and finally evolved as an atom or molecule. The process may occurin several stages each of which may require a definite energy ofactivation, but it is clear that the reaction velocity will be controlledby the slowest of these stages, which is usually that requiring thehighest energy of activation.FIG.8. FIG. 9.Let W be the energy of activittion of the slowest stage when theelectrode is at its reversible potential. We may expect that theenergy of activation will be some function of the electrode potential.If the ion is negative, for example, the discharge will be facilitated bymaking the electrode more positive.If the overpotential is V ,the alteration in the energy of activation will be aVF, where 61represents this function, and the new energy of activation will beW - aBP (Fig. 8). Experiment has shown that for many reactionsa is a constant.I€ the distribution of energy among the reacting species is Maxw-ell-ian, the number reacting per second, N . is given byN=Noe-(W-aVF)IRT . . * (1)where No is the number present at the electrode ~urface.BOWDEN AND AGAR : IRREVERSIBLE ELECTRODE PROCESSES. 91If N is measured by the current density, i,h i = const.+ aV&’/RT . . . . (2)and a In i/aY = 2.303 a log i/aV = aP/RT . . (31so that the overpotential plotted against the logarithm of the currentdensity should give a straight line the slope of which is equal toaF/2*303RT.The height of the energy barrier ( W - aVP) may be obtained fromthe temperature coeficient of the current density (C.D.) (at constantoverpotential) sinceor from the temperature coefficient of the overpotential (at constantC.D.) since(a In N/aT), = 2.303 (a log ilaT), = (W - aVP)/RT2 . (4)(aV/aT), = - ( W - a Y F ) / a F T . . . . ( 5 )It should be emphasised that the relations (2)-(5) are derivedwithout any particular assumptions as to mechanism. The onlyassumptions made are that some energy of activation is required,that this is influenced by the electrode potential, and that theenergy distribution is Maxwellian.* This type of overpotential,which is due to the existence of a high energy of activation in theelectrode reaction, may be called “ activation overpotential,” V,.The overpotentials of hydrogen and oxygen are of this kind.The relation (2) may be written in the form :v, = b(l0g i - log io) .. . . . (6)where b is equal to 2.303 RT/aF. Tafel2 showed that the over-potential of hydrogen followed this equation. This relation is ofvery wide applicability, and is illustrated in Fig. 9. It will be seenthat if the straight line, AB, corresponding to the experimentalobservations is extrapolated to V , = 0 (i.e., to the reversiblehydrogen potential in this solution), the intercept is equal to log i,;i, is thus the rate of deposition of hydrogen at the reversible potential.A t this potential, however, the deposition of hydrogen is exactlybalanced by the reverse process, viz., electro-solution of hydrogen ;both processes have the velocity i,, so the net rate of deposition is zero.At any potential the observed C.D.is actually equal to thedifference between the rate of deposition of hydrogen ions and therate of electro-solution of hydrogen. In most cases the latter rateF. P. Bowden, Proc. Roy. SOC., 1929, A , 126, 107.J. Tafel, 2. physikal. Chem., 1905, 50, 641.* Similar relations could be derived on the assumption that the potentialchange increased the current density by increasing the number of reactingparticles on the electrode surface, and had no direct influence on the height ofthe energy barrier92 GENERAL AND PHYSIOAL CHEWSTRY.only becomes negligible in comparison with the deposition rate whenthe cathodic overpotential is greater than about 50 millivolts.Atlower overpotentials the net C.D. is significantly less than the rateof deposition of ions. Since equations (1) and (5) apply to the rateof deposition alone, the observed net C.D. does not obey this lawa t low overpotentials. The experimental V-log i curve is no longerlinear under these conditions (BC, Fig. 9).I t i s evident that the rate of deposition at the reversible potential,i.e., i,, is the most useful measure of the catalytic activity of the electrodefor this reaction.If io is large, then the metal is an active one, andthe overpotential is small. If i, and the constant b are known, itis easy to calculate the overpotential V, a t any current density i bymeans of equation ( 5 ) ; b is, of course, given by the slope, aV/a log i,of the linear portion AB of the curve in Fig. 9.The presence of very small traces of oxidising substances (in thecase of hydrogen overpotential) or of reducing substances (in thecase of oxygen overpotential) will cause V to fall below its theoreticalvalue. This is particularly marked at low C.D.’s, and the curvema.y take the form AXY (Fig. 9). This form is frequently observedin solutions which have not been rigorously purified.In the past, the variation of the overpotential with the currentdensity has not been sufficiently appreciated.Many workers re-strict their observations to the “ minimum ” overpotential. Thisis defined as the potential at which bubbles first appear on theelectrode surface, or a t which some supposed discontinuity isobserved in the relation between current and potential. It is clearthat this “ overpotential ” is characteristic of only one arbitraryC.D., and the information it can give is limited.Concentration Overpotential, V,.3-The passage of current maycause a change in the concentration of the electrolyte close to theelectrode a t which reaction is taking place, and cause it to fall fromC, to C,. This concentration change may alter the reversiblepotential of this electrode.In practice the reference electrode isusually situated outside the region affected by concentration changes,so that the measured potential difference between the two electrodes,i.e., the overpotential, may include a term V , whereV, = (RTjnP) In C,]Co . . . . (7)V , may be calledfor general review of earlier work.the “ concentration overpotential.”*3 See F. Foerster, “ Elektrochemie wiisseriger Losungen ”, Leipzig, 1922,4 J. N. Agar and F. P. Bowden, Proc. Roy. SOC., 1938, A, 169, 206. * In order to avoid the confusion which arises from the loose use of theword “ polarisation,” the term “ concentration polarisation,” which is some-times used for potential changes of this nature, is not employed hereBOWDEN AND AGAR : IRREVERSIBLE ELECTRODE PROCESSES.93When a steady state is reached, the rate of removal of an ion by de-position must be equal to the rate a t which it is supplied from the bulkof the solution where its concentration is supposed to remain constant.The ion is supplied by (i) migration, (ii) convection, (iii) diffusion.It is difficult to give a complete solution of the bydrodynamicalproblems involved in the last two processes. It is therefore necessaryto proceed by semi-empirical and approximate methods. I n thisconnexion the concept of the diffusion layer 5* 6* has been foundvery useful. There can be no motion of fluid across the electrodesurface itself, and therefore convection cannot take place at anypoint on this surface. On the other hand, in the bulk of the solution,a t sufficiently large distances from the electrode, the concentrationis practically uniform, and in this part of the system diffusion playslittle part.On this basis it is considered that the electrode iscovered with a " diffusion layer " of thickness 6. Outside thislayer the concentration is that of the bulk of the solution. Insidethe layer it is assumed that convection is negligible and that thereactant is supplied to the surface by diffusion and migration alone.The rate of diffusion through the layer, per sq. cm. of surface area,is equal to k(Co - C,)/S, where k is the diffusion coefficient of thesubstance concerned. Since Ce cannot become less than zero, therate of diffusion cannot exceed kCo/S. If the C.D. a t an electrodeis made to exceed this value (the limiting C.D., i t ) the current mustpartly be carried by the deposition of some other ion.This willgenerally take place a t a higher potential than the original process,and a sharp rise in the potential therefore occurs when the C.D.reaches the limiting value. Experimental determinations of 6generally rest on measurements of the limiting diffusion rate.I n unstirred solutions the motion of the liquid is mainly due tothe density differences which accompany the concentration changes.For this reason 6 varies slightly with the concentration difference,(Co-Ce), but has a value about 0.05 em. in most 7 I nstirred solutions 6 decreases It isusually of the order 0~001-0~005 * e g It can be shownas the rate of stirring increases.A. A.Noyes and W. R. Whitney, 2. physikal. Chem., 1897, 23, 689; W.Nernst, ibid., 1904, 47, 52; F. Weigert, ibid., 1907, 60, 513; T. R. Rosebrughand W. Lash Miller, J. Physical Chem., 1910, 14, 816.See S. Glasstone and A. Hickling, " Electrolytic Oxidation and Reduc-tion," 1935, for a good general review.R. E. Wilson and M. A. Youtz, J. I n d . Eng. Chem., 1923, 15, 603; S.Glasstone and G. D. Reynolds, Truns. Furaday SOC., 1933,29,399 ; S. Glasstone,J., 1929, 690; Trans. Electrochem. Soc.,1931,69, 277.W. Nernst and E. S. Merriam, 2. physilcal. Chem., 1905, 53, 235.E. Brunner, ibid., 1904, 47, 56; 1906, 58, 194 GENERAL AND PHYSICAL CHEMISTRY.theoretically that in stirred solutions 6 is independent of the con-centration d8erence.10Some of the important differences between activation over-potential V, and concentration overpotential Vc are set out below.*(i) Efject of stirring.I n the case of concentration overpotentialthe value of the limiting current it is always increased by stirring,SO that V, will fall.V, is profoundly affected by thenature and physical state of the electrode surface; V, is in generalunaffected by these factors. If, however, the surface irregularitiesare very large so that they penetrate beyond the diffusion layer, theymay cause small variations in Vc..(iii) Temperature coefficient. Both V, and V, decrease as thetemperature rises. The value of dV,/dT varies, of course, from onereaction to another, but for a number of reactions in aqueoussolution, it is cu.2 or 3 millivolts per degree; - dV,/dT is smaller,since it depends on the temperature coefficient of diffusion and isusually a fraction of a millivolt per degree.V, is proportional to the logarithm of theC.D. (equation 6). The relation between Vc and the C.D. is usuallydifferent from this.V, grows rapidly when the current is switchedon. The potential change is proportional to the quantity of electri-city passed, and the electrode has a capacity of ca. 20 microfaradsper sq. cm.11 The growth of Vc is in most cases much slower, thepotential does not change linearly with the quantity of electricitypassed, and the apparent ‘( capacity ” is usually several thousandmicrofarads per sq. cm.4Resistance Overpotential.-If there is an appreciable resistancebetween the solution and the electrode, the passage of the currentwill produce a potential drop across this resistance which may obeyOhm’s law.We may call this the “ resistance overpotential,” V,.The resistance may be due to the electrolyte itself, either becauseit is dilute or because local concentration changes have made it sonear the electrode. I n other cases it may be due to a poorly con-ducting oxide or other film on the surface of the electrode. Thesefilms occur, for example, on aluminium anodes.13Since the resistance is often a complex function of i, the relationbetween V, and i is not simple. If i is large, V, may reach very highvalues indeed. A distinguishing characteristic of V, is that itshould, in general, cease the instant the current is switched off.Stirring has little or no effect on V,.(ii) The nature of the surface.(iv) Current density.(v) Rate of growth.lo J.N. Agar, Diss., Cambridge, 1938.l1 Soe, e.g., A. Frumkin, Act. sci. ind., 373, Paris, 1936BOWDEN AND AGAR : IRREVERSIBLE ELECTRODE PROCESSES. 95The decay of V,, though rapid, is exponential.12 The decay of V ,is usually slower than that of V,. Many investigations of the anodicformation of oxide and other films have been made. This workhas been summarised by U. R. Evans,13 and we do not deal furtherwith this subject here.It is clear that all three types may occur simultaneously and themeasured overpotential may be made up of V , + V, + Vr. It isnot always easy to separate them experimentally, and much work iscomplicated by the fact that no clear distinction is made between thevarious causes of irreversibility.The Electrodeposition of Hydrogen.-The electrodeposition ofhydrogen from aqueous solutions is nearly always a highly irrever-sible process; it is only in exceptional cases, e.g., on platinisedplatinum or other speciaUy active electrodes, that the reaction canoccur at an appreciable rate without a large overpotential.At agiven C.D. this hydrogen overpotential, on most metals, may showwide and uncontrolled variations according to the physical state anddegree of contamination of the surface. This irreproducibilityaffects all solid metals and is probably greatest on the catalyticallyactive metals.It is possible, however, t o obtain reproducible results on mercurysurfaces and on other liquid surfaces such as gallium and Wood’sd10y.14 If high currents are used, the overpotential includes termsdue to V,, V,, and V,.If the C.D. is kept low, however, V, andV become negligibly small and the irreversibility is essentiallydue t o activation overpotential. The use of small currents makes itimperative that traces of dissolved oxygen or other impurities shouldbe removed from the solution (see X Y , Fig. 9).Experiment 1n 2p 15-17 has shown that in acidsolutions the relation between the overpotential and the logarithmof the current (equation 6) holds for currents cf lo-’ to lo3 amp./cin.2. If high currents are used, deviations occur.l* If, however,the solution is violently stirred or is in rapid motion so that con-centration changes are prevented, the relation nisy hold good forMercury cathode.1 2 F.P. Bowden and E. K. Rideal, Proc. Roy. Soc., 1928, A, 120,59.13 “ Metallic Corrosion, Passivity and Protection,” 1937, pp. 13 ff., 42 ff. ;seo also J. A. V. Butler and J. D. Pearson, Trans. Paraday SOC., 1038, 34,806.l4 F. P. Bowden and E. A. O’Connor, Proc. Roy. SOC., 1930, A, 128. 318.F. P. Bowden and E. K. Rideal, ibid., 1928, A , 120, 59.S. LeWina and V. Sarinsky, Acta Physicochim. U.R.S.S., 1937, 6, 491.l7 F. P. Bowden and H. F. Kenyon, Nature, 1935,135,105; H. F. Kenyon,l8 F. P. Bowden, Trans. Faraduy SOC., 1928,24, 473.Diss., Cambridge, 193796 GENERAL AND PHYSICAL CHEMISTRY.much bigher C.D.’s.19 At currents below 10-7 amp./cm.2, theoverpotential usually falls below its theoretical value.Recentexperiments have shown that, if the cathode is completely enclosedand the polarising current is passed through the glass walls so that ad1traces of oxygen are excluded, the theoretical relationship is obeyeddown to currents of 10” or 10-10 amp. /cm.2.20I n acid solutions at room temperature b = 0.120 volt,l* 2, 15-18021provided the electrode is not contaminated. Since b = 2.303 RT/MP,c( = 0.5. Experiments carried out at different temperatures 1* 2show that b is proportional to the absolute temperature, so o! isindependent of temperature. As will be shown later, this value ofa (ca. 0.5) is found for a large number of metals and also for thedeposition of oxygen from acid solutions.The deposition of hydrogen from alkaline solutions on to mercuryis complicated by the simultaneous deposition of sodium and theformation of amalgam, and little work has been done in this field,but it has recently been shown l7 that amalgam formation is unim-portant a t very low currents and equation ( 5 ) is again obeyed.The value of a is, however, different.I n alkaline solutions ( ~ / 5 -sodium hydroxide) a = ca. 0.25, which is one half of the value foundin acid solutions under similar conditions. This low value of M hasalso been observed in buffered solution of pH 0*8-6-6.18 At lowcurrents a = 0.5, but on increasing the current a break occurs andthe slope of the line changes so that M now has a value of 0.25.The current at which this break occurs becomes progressively loweras the pH is increased.It seems probable that this change is due tothe fact that the buffering agents fail to prevent the solution nearthe cathode from becoming alkaline at high currents.* Theseexperiments suggest that the mechanism of deposition in alkalinesolution is different from that in acids.Several investigators 16* 23* 2* have studied the effect of changesof pH on the overpotential in acid solutions. According to thetheory developed by A. Frumkin25 (see below) the overpotentialshould be independent of the p E in pure acid solutions, but should19 B. Kabanov, Acta Physicochim. U.R.S.S., 1936, 5, 193; J , Phys. Chem.Russia, 1936, 8, 486.20 F.P. Bowden and K. E. Grew, in course of publication; K. E. Grew, Diss.,Cambridge, 1936.21 E. Baars, t3itzungsber. Ges. Befiird. Natumikw. Marburg, 1928, 63, 213;E. Baars and C. Kayser, Z. Elektrochem., 1930, 36,429.22 Acta Physicochirn. U.R.S.S., 1937,7, 405.25 S. Glasstone, J., 1924, 125, 2646.24 J. Heyrovsky, Rec. Trav. chim., 1925, 44, 499; P. Heyrasymenko, ibid.,s6 8. physikal. Chem., 1933, A, 164,121.* But see Lewina and Sarinsky.22p. 503BOWDEN AND AGAR : IRREVERSIBLE ELECTRODE PROCESSES. 97become 0-058 volt greater (more negative) for each ten-fold decreasein the hydrogen-ion concentration, if a large excess of a foreignelectrolyte is present. I n agreement with this, S. Lewina andV. Sarinsky l 6 ~ 22 have found that the overpotential is the same in0.01, 0.1, and 1.0N-hydrochloric acid, but increases by 0.04-0.05volt per ten-fold decrease in hydrogen-ion concentration in similarsolutions containing an excess of lanthanum chloride.On the otherhand, Bowden 1.18 found that the overpotential was independentof pH at low C.D.’s in buflered solutions containing a large quantityof foreign electrolytes. Recent experiments of C. Wagner andW. Traud 26 in acid solutions of various pE, but all M with respect tocalcium chloride, also indicate a much smaller change in the over-potential than Frumkin’s theory requires. Although the presentposition is not very satisfactory, the experimental evidence showsthat in most cases the overpotential is practically independent ofthe pE, provided it is not too high.This is in general agreementwith earlier 23The height of the energy barrier can be determined from the tem-perature coefficient of the overpotential or of the C.D. 1 (equations3 and 4). Experiment shows that both these relations give the sameresult. The values of the energy of activation obtained in this wayare given in Table I.Overpotential of hydrogen isotopes. After the discovery anddevelopment of the electrolytic method for preparing heavy28 many measurements of the isotopic separation factor(8) were reported; 29 the results were extremely divergent. It waspointed out by R. H. Fowler 3O that the fractionation could not bedue to a difference in the ionic mobilities of the isotopes, but mustbe caused by the difference in the speeds at which the isotopesreact a t the cathode.A comparison by Bowden and Kenyon17 ofthe overpotentials of hydrogen and deuterium showed that theydiffered by an amount which was adequate to account for theobserved separation factors.The kinetics of electrodeposition from O-B~-sulphuric acid ona mercury cathode were very similar for both isotopes (a = 0.52 ineach case) but the overpotential of deuterium was considerablyhigher than that of hydrogen. At a given C.D. the cathode potentialfor deuterium was 0.115 volt more negative (on the saturated26 2. Elektrochem., 1938, 44, 391.27 E. W. Washburn and H. C. Urey, Proc. Nut. A d . Sci., 1932, 18, 496.28 G. N. Lewis and R. T. MacDonald, J. Chem. Physks, 1933, 1, 341.Ann.Reporta, 1934,31,13; H. C . Urey and G. K. Ted, Rev. Mod. Physics,1935, 7, 34; J. A, V. Butler, 2. Elektrochem., 1938, 44, 55.* Proc. Roy. Soo., 1934, A, 144,462.REP.-VOL. XXXV. 98 GENERAL AND PHYSICAL CEKEMISTRY.calomel scale a t 25"). This difference in overpotential means thatthe electrodeposition of hydrogen from light water thus occursabout ten times faster than the deposition of heavy hydrogen fromheavy water at the same cathode potential. The measurement ofthe temperature coefficient shows that the respective energies ofactivation are 118-0 kg.-cals. for hydrogen and 20.9 kg.-cals. fordeuterium. I n 0.2~-potassium hydroxide solution a is 0-24 in eachcase and the cathode potential (on the saturated calomel scale) ofthe deuterium at any given current is 0-159 volt more negative.The energies of activation W in alkaline solution are 8.65 kg.-cals.forhydrogen and 10.7 kg.-cals. for deuterium. Later measurements byJ. Novak 31 on a dropping-mercury cathode in acid gave a differencein the cathode potentials of 0.087 volt a t 20" and 0-071 volt a t 60°,but this should be contrasted with the work of J. Heyrovskf and0. H. Muller.32Investigations of separation coefficients under carefully con-trolled conditions have been made by J. Horiuti and G . Okamoto33and by H. F. Walton and J. H. Wolfenden.34 The former pointout that cathodes of nickel, gold, silver, copper, platinum, and lead(with alkaline electrolyte) all give values of 8 about 6, and that tin,mercury, and lead (with acid electrolyte) give values of 3.1, 3.1, and3.0 respectively.Walton and Wolfenden confirm this division ofcathodes with two groups. With silver, platinum, and nickel theyfind values of S at room temperature of 5-7, falling considerablywith increase of temperature. With mercury and tin, X is about 3;in the case of mercury it falls slightly with rising temperature, and inthat of tin there is actually an increase of S with temperature.With the exception of this anomalous behaviour of tin, the resultsare in agreement with the theory of Horiuti and Okamoto (seep. 104).Numerous experiments show that the logarithmicrelation (6) between overpotential and C.D. holds true for thedeposition of hydrogen on most meta1s.l. Some typical results ofrecent work with different metals are collected in the followingtable.As previously stated, the activity of solid electrodes variesconsiderably, so the results are not always reproducible.In this table u is obtained experimentally from the slope of theV-logi curve; i, is obtained by extrapolating this curve toV = 0 and is a measure of the rate of deposition when the over-potential is zero. The energy of activation W is calculated fromOther metals.31 CoU. Czech. Chem. Cmm., 1937, 9, 207.32 Ibid., 1935, 7, 281.33 Sci. Papers Imt. Phys. Chem. Res. Tokyo, 1936, 28, 231.34 Trans. Faraday Soc., 1938, 34, 436; Nature, 1936, 138, 468BOWDEN AND AGAR : IRREVERSIBLE ELECTRODE PROCESSES. 99TABLE I.The Overpotential of Hydrogen on Different Metals.*2.303RTElectrode.Solution. = -* bP "' sq. amp.' cm.Mercury 0-2N-H,SO, 0.52 6 x lo-''0*2N-D,SO, 0.52 0.8 X lo-"O-lN-HCl 0.49 1.7 X lo-''0.2N-NaOH 0.24 6.9XlWO.2N-NaOD 0.24 2*3x 10-,0.35N-HCl 0 . 4 - 4 . 5 10-1'in MeOHHCl in EtOH0*014*6N- 0.5 2X10-11m, kg.-cala. Remarks. Reference.18.0 25' 17, cf. 120.9 25O 17 - 220 168.65 25' 1710.7 280- - 36- - ibGallium 0*2N-H,SO,Wood's alloy ,,Polished Ag 9,Etched Ag Y,Xickel ,>Bright 9 ,platinum fSPOWY Y, platinumBright 0.2N-NaOHgatinumN-KOHPalladium N-H,SO,Palladium 0.2N-H,SOI0.2N-NaOHLead BN-HaSO,Tantalum 2N-H,SO,Bismuth ?,Copper -Cobalt 11Antimony 9 ,Carbon $90.50.40.50-60.520.75-4.3-0.8-0.60.51 0 2 4 . 50.50 .4 4 - 50.30-280 . 8 4 . 50 . 5 4 - 40-5(falling)0.2(variable)0.51.6 X 10-7 15.2l x 10-8 16.43 . 2 ~ lCk* -6x 10J -6 x -0.1-2 X lo-' 6-7ca. lo-' -0.1-5 X lo-' -2 x 10-6 91 x 10-6 1010-6 to 10-0 -5x lo-'* to -1C-8 -2 x 10-0 -lo-" -- - - -8 x 10-1187'P7O2 5025" ; i, very dependenton state of surfaceQ decreases with timeI22O ; i, very dependenton state of surfaceActivated by anodicoxidationElectrode cleaned byflaming-3 ) 9 9 -IResults variable; silr-face possibly con-taminated,s 9,1415 I ,199,1, 3613738394237431144461,*,43* Some further values of Q (or a) are given in a useful review by K. Wirtz.'* t Values of Q a8 large as 2 have been observed on particularly active Pt and Pd electrodes.'O, 'I, "It seems probable that the overpotential in these cases is concentration overpotential, due to thechange in concentration of dissolved hydrogen near the electrode.4035 S.Lewina and M. Silberfarb, Acta Physicochim. U.R.S.S., 1938, 4, 275.36 M. Volmer and H. Wick, 2. physikal. Chem., 1935, A, 172,429.37 F. P. Bowden and J. N. Agar, unpublished; J. N. Agar, Diss., Cambridge,38 G. Masing and G. Laue, 2. physikal. Chem., 1936, A, 178, 1.3e C. A. Knorr and E. Schwartz, 2. Elektrochem., 1934, 40, 38; 2. physikal.Chem., 1936, A , 178, 161.40 L. Kandler and C. A. Knorr, 2. Elektrochem., 1936,42,669; L. Kandler,C. A. Knorr, and C. Schwitzer, 2. physikal. Chem., 1937, A , 180, 281.41 M. G. Raeder and K.W. Nilsen, Chem. Zentr., 1935, ii, 3640; NorgesTekn. Hobkole Auhundl,, Ti1 26 iirs Jubileet, 1935,263.p 2 F. P. Bowden and H. P. Stout, unpublished.43 T. Erdoy-Gruz and H. Wick, 2. physikal. Chem., 1932, A , 162, 53.44 K. Wirtz, ibid., 1937, B, 36, 435.45 F. P. Bowden and L. E. Price, unpublished.1938.L. P. Hanunett et al., J . Amr. Chem. SOC., 1924,46, 7; 1925,47, 1215;1933, 55, 70.47 L. P. Hammett, Trans. Faraduy soc., 1933, 29, 770.4* 2. Elektrochem., 1938 44, 303100 GENERAL AND PHYSICAL CHEMISTRY.the temperature coefficient of overpotential (equation 4 or 5 ) .The characteristic overpotential on the metal a t any C.D. can beobtained from the values of i, and a in this table. For example,the overpotential in acid solution on a mercury cathode a t a currentof amp./cm.2 and a t 25" isV = 2-303 (log i - log i,) d[log ( - log (6 x - 2.303 x 8-31 x 298 -0.5 x 96,500= 0.72 voltI n acid solution the majority of the metals give CI = ca.0.5when the surface is clean. The notable exceptions to this areplatinum and palladium. On these metals a may be initially veryhigh 21s 37s 39* 41 (ca. 1) and may fall w-ith time." 39 The value of ais greatly influenced by traces of contaminants such as arseniousoxide. On lead, cobalt, and antimony, cc is low and variable.It will be seen that i, varies over a wide range on the differentmetals. For a high-overpotential metal, e.g., mercury, i, is assmall as 10-l2 to 10-11 amp./cma2; for a low-overpotential metal,e.g., palladium, it may be as large as to 10-5 to 10-4 amp.lcm.2.On specially " activated " surfaces the value may be higher ~ t i l l .4 ~The results for etched and for polished silver l5 show clearly that i,is also influenced by the physical state of the surface. This makesit difficult to compare the overpotentials of different metals. Ifthe electrodes are liquid, this difficulty is removed and experimentshows that, a t the same temperature and overpotential, hydrogenis deposited some 30 times faster on gallium than it is on mercury.14The increase in i, on solid surfaces which have been " activated "is partly due to an increase in the red accessible area of the elec-trode.15 The height of the energy barrier varies from 18 kg.-cals.(20.9 kg.-cals. for deuterium) on mercury, down to less than halfthis value on the low-overpotential metals such as platinum.It isinteresting to note that the overpotential of hydrogen in alcoholicsolutions is nearly the same as that observed in aqueous solutions.Several authors 36* 393 46 have investigated the deposition ofhydrogen on the catalytically active metals a t low overpotentials,where the logarithmic relation breaks down. Volmer and Wick 36find a roughly linear relation between current and potential nearthe reversible potential (platinum, gold, and iridium electrodes).In addition, they observed that a t potentials considerably morepositive than the reversible value, the electrosolution of hydrogen onplatinum approximately obeys a logarithmic relation analogous to(6).But this behaviour does not seem to be general,39* 46 and therBOWDEN AND AGAR : IRREVERSIBLE ELECTRODE PROCESSES. 101is little doubt that the characteristics of the reaction at low over-potentials and in the anodic range depend markedly on the previoustreatment of the electrode.F. P. Bowden 15* 49 has measured the qua'ntity of electricityrequired to change the potential of a platinurn electrode from thereversible hydrogen to the reversible oxygen potential. Thisquantity is sufficient to remove a unimolecular film of hydrogenand deposit a unimolecular film of oxygen on the electrode surface.J. A. V. Butler and G . Armstr~ng,~o using the same method, find asimilar result (see also J. A. V. Butler and J. n. Pearson 52).Frumkin and others 51 have measured the amount of hydrogenadsorbed a t various potentials and also the adsorption of ions in thedouble layer.They find that the chemical potential of the adsorbedhydrogen is proportional t o the amount adsorbed, and 'that thequantity of hydrogen adsorbed a t the reversible potential againcorresponds to a complete monolayer. This interesting work alsoshows that hydrogen is more strongly adsorbed from alkaline thanfrom acid solutions.The overpotential of both hydrogen and oxygen is decreasedwhen ultra-violet light falls on the electrode surface.53 The mag-nitude of the photo-current increases with the overpotential andwith the frequency of the light. Its effect is due, not to electronemission, but to an acceleration of the surface reaction.53 Ultra-violet light mill also liberate hydrogen from various aqueous solutions,and some separation of the isotopes may be effected in thatway.54The Overpotential of Oxygen.-The deposition of oxygen cannotbe studied on most metals because the metal dissolves or is attackedby the oxygen.Bowden showed that the kinetics of electro-deposition of oxygen from acid solution on to a platinum anodeclosely resembles that of hydrogen on other metals. The over-potential was high and equations (3), (4), and (5) were obeyed; ccwas again equal to 0.5, i, = 3.7 x 10-l1 amp./sq. cm. a t 14", and theenergy of activation W = 18.7 kg.-cals.49 Proc. Roy. SOC., 1929, A, 125, 446.5O Ibid., 1932, A , 137,604 ; J. A. V. Butler, G.Armstrong, and F. Himsworth,ibid., 1933, A, 143, 89.51 A. F r d i n and A. Slygin, Compt. rend. A d . Sci. U.R.S.S., 1934, 2,167; Acta Physicochim. U.R.S.S., 1935,3,791; A. Slyginand W. Medwedowsky,ibid., 1936, 4, 911 ; A. Frumkin and A. Slygin, ibid., 1936,5,819; B. Erschlerand M. Proskurnin, ibid., 1937, 6, 195; B. Erschler, ibid., 1937, 7, 327;B. Erschler, G. Deborin, and A. Frumkin, ibid., 1935, 8, 565.52 Trans. Paraday Soc., 1938,34, 1163.53 F. P. Bowden, ibid., 1931, 27, 505.54 A. Farkes and L. Farkas, ibid., 1938, 34, 1113, 1120102 GENERAL AND PHYSICAL CHEMISTRY.T. P. Hoar 55 found that this relation also held for alkalinesolutions and for the reverse process, the electro-solution of oxygen,although a was not always 0.5 F. P.Bowden and H. W. Keenan 5 6found that o! on a platinum anode was cn. 0.54 in very dilute alkalinesolutions but increased steadily as the hydroxyl-ion concentrationincreased, reaching a value of 1-74 in 14~-sodium hydroxide. Insolutions of sodium hydroxide the overpotential decreased as thehydroxyl-ion concentration increased, but in solutions of sulphuricacid it was independent both of pE and of the sulphate-ion con-centration. V. Vitek 57 finds that on a dropping-mercury electrodethe electro-reduction of dissolved oxygen occurs in two stages,He attributes these to the reduction to hydrogen peroxide and thenceto water.*The overpotential of the halogens is usually very small unlesshigh currents are 58 Much of the experimental work iscomplicated by the fact that concentration overpotential becomesimportant at high C.D.’s (see p.109).OverpotentiaE of Metals.-It has been known for some time that thedeposition of metals is accompanied by an overpotential which isusually small (a few millivolts) except for the transition elementsiron, cobalt, and nickel,59 for which it is quite large. Except inthe case of mercury it is not due entirely to concentration changes.The discharged meta,l ions eventually find their way into the crystallattice and the intermediate stages are not clearly understood.The kinetics of deposition have been investigated by T. Erdey-Grfizand M. Volmer.600 If the discharge of the ion is the slow processthe relation between overpotential and current will be similar toequation (6).If the discharge is rapid the slow process may be theincorporation of the ions into the crystal lattice. There is evidencethat deposition only occurs at certain active centres. If the numberof these active centres is constant, there will be a linear relationbetween the C.D. and the overpotential. If fresh active centres arecontinually being formed the relation will be more complex.5 5 Proc. Roy. Soc., 1933, A , 142, 628: see also W. Roiter and R. Jampol-skaja, Acta Physicochim. U.R.S.S., 1937, 7, 47.56 Unpublished; see also H. W. Keenan, Diss., Cambridge, 1936.5 7 Coll. Czech. Chem. Comm., 1935, 7, 537.F. Chmg and H. Wick, 2. physikal. Chew&., 1936, A , 172, 448.58 N. Thon, Compt. rend., 1932, 197, 1312; W. Roiter and W.Jusa, ActsPhysicochim. U.R.S.S., 1936, 4, 135; see S. Glasstone, “ Electrochemistry ofSolutions,” 1937, p. 452, for refs. to earlier work.60 2. physikal. Chem., 1931, A , 157, 165.61 T. Erdey-Grhz, ibid., 1935, A , 172, 157; T. Erdey-GrGz and E. Frankl,* See also Ann. Reports, 1937, 34, 110.ibid., 1936, A , 178, 266; T. Erdey-Gniz and R. Kardos, ibid., p. 255BOWDEN AND AUAR : IRREVERSIBLE ELECTRODE PROCESSES. 103Erdey-GrGz and Volmer find that at low currents the relation islinear and that deviations occur at high currents. They considerthat overpotential is due to the slow migration of ions to the activecentres. This has been criticised by B. Hunt,62 who considers thatthe metal ions accumulate in the double layer until a continuouslattice can be formed over the face of a particular crystal.J.Hoekstra63 observed that the linear relation holds good for highC.D.’s if the electrode is continuously scraped. He also found thatdeposition on most metals took place in layers of ca. 1000 atoms inthickness * except in the case of iron, nickel, and cobalt, in whichsmall nodules were formed. E. Miiller and H. Borchman 64 find thatthe deposition is affected by the nature of the anion. Satisfactorygrowth of single crystals is only obtained in a solution of complexsalts.Theories of Hydrogen Overpotential.-The deposition of hydrogenmust occur in several stages. The H30f ion moves up to thecathode, loses its charge, combines with another hydrogen atom, andescapes from the surface as gaseous hydrogen. Each of thesestages may be slow, but it is probable that the controlling stage iseither (a) the neutralisation of the ion or (b) the formation of theH-H bond of the molecule H2.Either of these may have a largeenergy of activation. It was a t one time thought that stage ( a )would in all cases be rapid, and attention was concentrated on ( b )as the rate-determining process responsible for the hydrogen over-potential.(1) In its simplest form this mechanism 2* 65 (the “ Tafel ” or“catalytic” mechanism) postulates that the slow stage of thereaction is the recombination of atoms adsorbed on the electrodesurface. It is assumed that the rate of recombination is equalto kn2, where n is the number of adsorbed atoms per sq. em.It is further supposed that the overpotential V is given byV = (RT/P) In n/no, where no is the number of adsorbed atomsper sq.cm. a t the reversible potential. Combination of theseequations leads to the relation* - (7)or to i = i 0 (e2VFIRT - 1) . . . . * (8)i = k?z2 = kno2 . e2VFiRT = i, . e2VFIRTif we take account of the fact that the actual observed current i isequal to the rate of recombination less the rate of spontaneousdissociation into atoms.65 The latter is supposed to be independent82 TTWM. Electrochem. SOC., 1934, 65, 95.63 Rec. Trav. chim., 1931, 50, 339.84 2. Elektrochem., 1933, 39, 341. Ibid., 1934, 40, 38. * Cf. Erdey-Grbz and Volmer,6104 GENERAL AND PHYSICAL CHEMISTRY.of the potential and is equal to i,. At high overpotentials the twoexpressions (7) and (8) are indistinguishable.According to thissimple theory a = 2; this is contrary to experiment in nearly allcases. The assumptions made in this treatment will break down,however, if the surface is approaching saturation with adsorbedhydrogen,66 particularly if there are considerable repulsive forcesbetween the adsorbed atoms. Under these conditions cc can be muchless than 2, and, in fact, tends to zero for a completely saturatedsurface.Horiuti and his co-workers 66 have given a detailed treatment ofthe kinetics of recombination of adsorbed hydrogen atoms on anickel electrode, by the transition state method, taking into accountthe varying degree of occupation of the surface, and the repulsiveforces between the adsorbed atoms.Another mode of formation of hydrogen molecules has recentlybeen considered by the same author^.^^*^^ This is the reactionbetween a hydrogen atom, adsorbed on the negatively chargedelectrode, and a hydrogen ion in solution : H30+ + H-Me+H, + H,O + Me.This so-called “ electrochemical ” mechanismhas certain points in common with the earlier theories of Bowden 1and of J. H e y r ~ v s k f . ~ ~ A thorough statistical mechanical treat-ment of this mechanism has also been given by J. Horiuti et a2.6*and G . O k a m ~ t o . ~ ~In the last ten years the view that the neutralisation of theH,O + ion may be the rate-determining process has been developed,in slightly different forms, by several a~thors.~O--~~ According toR. W.Gurney’s 71 theory, the H,O+ ions in the solution near thecathode (within a few A.) are neutralised by electrons from themetal which “ leak ” through the potential barrier at the surface,forming free hydrogen atoms and water molecules. This process ishighly endothermic, and the energy of activation is in the first placedue to this fact. It is increased by the high repulsive potentialenergy of the neutral complex H,O which is the initial product ofneutralisation. Gurney calculates the probability that an electron613 G. Okamoto, J. Horiuti, and K. Hirota, Sci. Papers Inst. Phys. Chem.Res. Tokyo, 1936, 29, 223.6 7 Rec. Trav. chim., 1926,44, 499; 1927,46, 582.6 8 Bull. Chem. SOC. Japan, 1938,13, 216.e9 J . Fac. Sci. Hokkaido Imp. Univ., 1937, (iii), 2, 115.70 M.Volmer and T . Erdey-GrGz, 2. physikal. Chem., 1930, A, 150, 203.Proc. Roy. Soc., 1931, A, 134, 137; Physikal. 2. Sovietunion, 1933, 4,360 ; R. H. Fowler, Trans. Faraduy Soc., 1932, 28, 368.72 2. physikal. Chem., 1932, A , 160, 116.73 Acta Physicochim. U.R.S.S., 1935, 2, 506.J4 Proc. Roy. SOC., 1936, A , 157, 423; 8ee also Trans. Faraday SOC., 1924,19,734; 1932,28, 379BOWDEN AND AGAR : IRREVERSIBLE ELECTRODE PROCESSES. 105and a hydrogen ion between them have sufficient energy for thisprocess, and shows that this quantity, which is proportional to theC.D., is an exponential function of the potential. It is also possibleto explain why a is commonly equal to 0-5 on this basis. On theother hand, B. Topley and H. Eyring 7 5 have pointed out that thistheory leads to an impossibly high energy of activation.It alsosuggests that the overpotential should be practically independent ofthe nature of the e l e ~ t r o d e , ~ ~ whereas experiment shows that thisis not the case.The other neutralisation theories all postulate an adsorbedhydrogen atom instead of a free atom as the product of the reaction.As the heat of adsorption of hydrogen atoms on metals is usuallyconsiderable, this reaction is much " easier " than the productionof free hydrogen atoms, and the difficulty with regard to the energyof activation disappears. A. Prumkin 72 pointed out that thisprocess can be regarded as a proton jump from the acid H,O+ tothe negatively charged metallic surface, which behaves as a base inthe generalised sense of J.N. B r o n ~ t e d . ~ ~ The fractional value ofa is analogous to the fractional exponent in Bronsted's relation 78connecting the catalytic constants of various acids with theirdissociation constants. This view has been developed by J. Horiutiand M. Polanyi.'3 They consider the case of deposition on a nickelsurface, and construct Morse functions giving the potential energyH,O+-H and the Ni-H bonds in terms of the respective nuclearseparations. It is assumed that the height of the energy barrier isgiven by the height of the point of intersection of the two Morsecurves. This clearly depends on the separation of the H,O+ ionfrom the surface, but, using a reasonable value for this quantity,Horiuti and Polanyi find that the energy of activation at the rever-sible potential lies between 20 and 30 kg.-cals.J. A. V. Butler 74has developed a similar treatment, differing in some details, andfinds W = 7-27 kg.-cals. for this reaction. Obviously thesecalculations will not give accurate values of W , but they show thatthis stage of the reaction may well have an energy of activation ofthe same order as that observed.It is easily shown * that a cathodic overpotential will reduce Wby EVF, where O < a< 1. The exact value of a depends on therelative slopes of the two Morse curves at the point of intersection,and is likely to be of the order of 0.5. At the same time the energy75 Nature, 1934, 133, 292.76 See N. K. Adam, L ' Physics and Chemistry of Surfaces," 2nd edition,7 7 Rec.Trav. chim., 1923, 42, 718; T. M. Lomy, Chem. and Ind., 1923,* See, e.g., Horiuti and Polanyi.'aOxford, 1938, p. 332.42,43.Cbm. Reviews, 1928, 5, 321106 GENERAX AND PHYSICAL CHEMISTRY.of activation of the reverse process-the transition of a proton froman adsorption position on the surface to a water molecule-is in-creased by (1 - a) VP. These changes will alter the forward andthe reverse reaction velocities by factors of eaVF’RT and e-(l-a)rF’RTrespectively. As the net rate of deposition, i, is the difference ofthese two velocities, this leads to i = i, (eJ‘*12RT - e-vF‘2RT) if a =0.5’0.At high overpotentials this relation reduces to the usual logarith-mic equation of the type (6) or (1). It also suggests that there willbe a similar logarithmic relation on the anodic side of the reversiblepotential.This theory indicates that the energy of activation, W ,will be lowest on metals with a large heat of adsorption forhydrogen, 73 in general agreement with experiment .48The effect of changes of pH on the overpotential due to a mechan-ism of this type has been investigated by F r ~ m k i n . ~ ~ Adopting0. Stern’s theory 79 of the double layer, he assumes that the rate ofthe reaction depends directly on the concentration of hydrogen ionsadsorbed a t the interface and on the potential difference across thenon-diffuse, “ Helmholtz ”, part of the double layer. The ratio ofthe concentration of adsorbed ions at the surface to the bulk con-centration in turn depends on the diffuse potential, c.The < potentialand the Helmholtz potential together make up the total potentialdifference across the interface. Using the expressions developedby Stern, Frumkin shows that the overpotential should be inde-pendent of pa in solutions of pure acids, but should become 0.058volt more negative for a unit increase of p E in solutions containingan excess of a foreign electrolyte.The three processes considered above are summarised schemati-cally in Fig. 10.It will be seen that stage I must take place in all cases; it maybe followed either by IIa or by IIb. The reaction will in fact proceedby the faster of the two alternative processes, IIa and IIb. As in-dicated above, the reaction velocity and the overpotential are con-trolled by the slower of the two stages I and I1 (cf.G. Okamoto 67).It is now generally accepted that no one mechanism can explainall the features of hydrogen overpotential on different metals.P*In particular, the behaviour of platinum and similar metals is verydifferent from that of mercury. This division into two classes isbrought out very clearly by measurements of the isotopic separationfactor 33. 34 [about 7 for platinum, nickel, silver, etc. ; about 3 formwcury, tin, lead (in acid)], and of its temperature coefficient.34It is interesting to note that this classification includes silver andnickel in the platinum rather than the mercury group.79 2. Elektrochem., 1924, 30, 508. Ann. Reports, 1937, 34, 108BOWDEN AND AGAR : IRREVERSIBLE ELECTRODE PROCESSES.107Evidence from several sources indicates that hydrogen is notand the simple appreciably adsorbed on mercury s~rfaces,6~*(1.)theory sketched(IIa.)FIG. 10.on p. 103 should therefore apply to the “ Tafel ”mechanism (IIa). As this leads to a value of a which is 4 times toolarge, stage IIa cannot determine the reaction rate on mercury.On similar grounds it has been considered that the electrochemicalmechanism IIb does not control the velocity on mercury, since thiswould also be expected to give a value of cc greater than unity.Frumkin therefore supposes 81 that the process is in this case con-trolled by the neutralisation stage. On the other hand, Horiutiand his co-workers 68* 69 arrive a t the value a = 0-6 for mercury,after a detailed investigation of this mechanism.They also calculatethe actual C.D. at a specified overpotential, and the isotopic separ-ation factor, and show that these are in agreement with experiment.In addition, their theory predicts a low value for the temperaturecoefficient of the separation factor, although not as low as thatactually observed. Further support for this mechanism comesfrom the observation of the difference between the separation factor,and the ratio of deposition rates a t a specified potential in purelight and heavy waters l7 (see p. 98). It has been pointed out thatthis is readily explicable if two atoms take part in the rate-deter-mining process.34On platinum, nickel, and similar metals the situation is radicallydifferent, since the evidence indicates that these metals are coveredwith a fairly complete layer of adsorbed hydrogen on the cathodic81 Acta Physicochim. U.R.X.S., 1937, 7, 475108 GENERm AND PHYSICAL CHEMISTRY.side of the reversible potential.g2 Low values of cc are thereforeexplicable by any of the three mechanisms, I, IIa, IIb.The valueof the separation factor shows, however, that the slow step on thesemetals is generally different from that on mercury. In the case ofnickel the theoretical treatment of Horiuti and his co-workers 66. G9suggests strongly that IIa is the rate-controlling process. Theycalculate the values of the isotopic separation factors and of theenergy of activation, which agree with experiment, and show thatthis mechanism provides a good semi-quantit'ative explanation ofthe anodic electro-solution of hydrogen on nickel in alkaline solutions.Some other characteristics (e.g., high and variable values of 21* 39similarity of kinetics in alkaline and acid solutions37*38*46) of theoverpotential on metals of this class support the above view (seetable).On the other hand, it is difficult to explain the observationsof Volmer and Wick 36 on the anodic reaction, on this basis ; it isalso to be expected that when the surface becomes saturated withhydrogen atoms, no further increase of the deposition rate canoccur 333 74 ( a = 0), and the potential should rise until some alter-native process sets in. It is difficult to disentangle such potentialincreases a t high C.D.'s from resistive effects, and they may occurin some cases.But there is no such break shown in the results ofKabanov,lg who has measured the overpotential on platinum up to100 amps./sq. cm., or in the work summarised in the table. Itthus seems most probable that more than one mechanism may beresponsible for the overpotential on these metals according to thestate of the surface, the potential, etc.Some further information about the mechanism of overpotentialcan be obtained from experiments on other related processes.These include (a) isotopic exchange between gas and solution a tan electrode,839 84 ( 6 ) the ortho-para-hydrogen interconversion onelectrode surfaces,83 (c) the diffusion of hydrogen into and throughthe electrode * ' 9 88Although a certain amount of work on these lines has alreadybeen carried out, the results cannot yet be clearly interpreted.There is, however, evidence for the following statements.(i) Theinterchange reaction on platinum Bas practically the same velocityas the ortho-para c o n v e r ~ i o n . ~ ~ * ~ ~ As the latter depends on thesplitting of molecules into atoms, it would appear that the sameprocess controls the transference of a hydrogen particle from thesolution to gas phase, or vice versa, on the electrodes used. (ii) Ex-83 See refs. (49)-(52).83 D. D. Eley and M. Polanyi, Trans. Paraday SOC., 1936, 32, 1388.84 35. Calvin, ibid., p. 1428; M. Calvin and H. Dyas, ibid., 1937, 33, 1492.J. A. V. Butler, 2.Elektrochem., 1938, 44, 55BOWDEN AND AGAR : IRREVERSIBLE ELECTRODE PROCESSES. 109periments on diffusion of cathodically liberated hydrogen throughiron and palladium 86, 8'. 88 suggest that the activity of hydrogenatoms on the surface may reach very high values. It seems thatthe recombination is again a slow process, particularly on poisonedelectrodes.87 In this connexion it may be mentioned that C. A.Knorr and E. Schwartz 65 found a close relation between the rateof solution of gaseous hydrogen in palladium wires, and the valueof i, for the electrodeposition of hydrogen on the same wires(saturated with hydrogen).The subject is clearly very complicated, and it is difficult to cometo a final conclusion. More precise experimental work is required,and it is especially important to co-ordinate overpotential measure-ments with the other phenomena which are associated with theelectrode reactions.Concentration Overpotential.-Although concentration overpoten-tial plays an important part in a great many electrode reactions,3* 4 nthere are comparatively few in which it is known to be the onlycause of irreversibility. This is the case in the deposition of mercuryor of iodine from aqueous solutions.58 Concentration overpotentialis also very important in the deposition of chlorine and 89but it has been shown that a small activation overpotential alsooccurs in the case of chlorine.58 This activation overpotentialbecomes relatively more important if the concentration over-potential is diminished by vigorously stirring the solution.Several investigations of overpotential in fused salts have beenmade re~ently,~.91 and the existence of concentration over-potential has been established in some case^.^^ s~ It seems likelythat activation overpotential is generally negligible a t temperaturessuch as those used in this work. This is exemplified by a recentinvestigation of the electrodeposition of oxygen from fused sodiumhydroxide.* In contrast to the state of affairs in aqueous solutions,** A. Coehn and W. Specht, 2. Physik, 1930,62, 1; C . G. Fink, H. C. Urey,and D. B. Lake, J . Chem. Physics, 1934, 2, 105, 301; T. N. Morris, J . SOC.Chem. Ind., 1935, 54, 7 T.A. H. W. Aten and M. Zieren, Rec. Trav. chim., 1929, 48, 944; 1930, 49,641; P.C. Blokker, ibid., 1936,55, 979; P. C. Blokker and A. H. W. Aten,i b d . , 1931, 50, 943.L. Sabinina and L. Polonskaja, J . Phys. Chem. Russia, 1935, 6, 107;S . Makareva, ibid., 1934, 5, 1380 (see A,, 1937, 33, 24).R. Luther and F. J . Brislee, 2. physihl. Chem., 1903, 45, 216; G. Pflei-derer, ibid., 1909, 68, 49; E. Newbery, J., 1921, 113, 477.90 S. Karpatschev and W. Patzug, 2. physikal. Chem., 1935, A, 173, 383;S. Karpatschev and 0. Poltaratskaja, Acta Physicochim. U.R.X.S., 1937,6, 275.@l S. Karpatschev and S. Rempel, J. Phys. Chem. Russia, 1936, 8, 134;S. Karpatschev and 0. Poltaratska, J. Phg&aZ Ckm., 1936 40, 763110 GENERAL AND PHYSICBL CHEMISTRY.it is found that activation overpotential is negligibly small even athigh C.D.’s. The irreversibility observed, which is considerable,is a concentration overpotential due to the liberation of water atthe anode.In connexion with the electrolysis of fused salts, it has beenpointed outg2 that many metals, when deposited from such elec-trolytes, go into solution to some extent in the melt.This affectsthe apparent current efficiency and also the electrode potential,until the melt becomes saturated.The dependence of the concentration a t an electrode on time wasinvestigated theoretically in an important paper by H. J. S. Sand,93and has also been considered by Rosebrugh and Lash Miller.5 Theexpressions derived can be adapted to the calculation of the growthof concentration overpotential from the moment that current isswitchedLord Rothschildg4 has shown that the potential of a calomelelectrode may change when a current is passed through it.Thischange, which is of considerable practical importance, is evidentlydue to concentration changes in the electrolyte near the electrodesurface.Dropping Electrodes.-Numerous papers on the dropping-mercuryelectrode by J. HeyrovskS; and his collaborators have been publishedduring the last few years. Useful summaries have been givenby him 95 and by 0. Gatty and E. C. R. Sp0oner.~6The Double Layer and Electro-capillarity .-The potential differenceswhich generally exist a t an interface must originate in a separationof electric charges of opposite signs. H. von Helmholtz 97 supposedthat this charge was confined to a monolayer, whereas Gouyg8 andChapman98 considered that there was a region of diffuse charge inthe solution. Neither view is entirely satisfactory by itself, but thesynthesis of the two views accomplished by Stern 79 seems to givea t least a qualitatively correct picture.Any change of electrode potential must involve a change in thecharge of the double layer as a whole (both the diffuse and the“Helmholtz ” portion). This can occur either (a) by a direct92 P. Drossbach, 2. Elektrochern., 1938,44, 288 (and earlier work).93 Phil. Mag., 1901, 1, 45.94 PTOC. Roy. Soc., 1938, €3, 125, 283.9s Act. sci. ind., 90, Paris, 1934; J. Heyrovskf and J. Klumpar, Coll.O 6 “ Electrode Potential Behaviour of Corroding Metals in Aqueous Solu-97 “ Gesammt. Abh.,” 1879, 1, 925.98 G. Gouy, Ann. Chim. Phys., 1903, [vii], 29, 145 (and see Frumkin,ll forCzech. Chem. C o r n . , 1938,10, 153 (bibliography).tion~,’’ Oxford, 1938 (Appendix 111).further references); D. L. Chapman, Phil. Mag., 1913, 25, 475BOWDEN AND AGBR : WEVELCSIELE ELECTRODE PROCESSES. 111transition of ions across the metal-solution interface or (b) throughan external circuit. I n the case of mercury in contact with solutionsof acids or simple salts there is a considerable range of potential inwhich both the dissolution of mercury ions and the deposition ofhydrogen are extremely slow. At such an electrode, which is ‘‘ com-pletely polarisable,”99 all the increase in the charge of the doublelayer must pass through an external circuit and can be measured.The ratio of increment of charge to increment of potential is thecapacity of the double layer, which may be regarded as an electro-static condenser. The capacity can be measured in the mannerindicated either by observations of the rate of increase of potentialat a steady small current,15* or by the use of aIternatingcurrent.lo” 103 Alternatively, the charge on a mercury surfacecan be measured at different potentials by a dropping elec-It is also possible t o calculate the capacity from electro-capillarydata. According to the theory originally developed by G.Lippmann 107 and Helmholtz,97 C = d20/d V 2 , where C is the capacity,0 the surface tension, and V the potential across the interface.In recent years a rigid thermodynamical theory of electro-capillarityhas been developed,99* lo8 and the above relation has been deducedwithout resorting to the somewhat crude physical picture requiredby earlier deTivations. It may also be noticed that the total poten-tial V across the interface between two different media cannot bemeasured, and in this sense is without physical meaning.109 Forthe present purpose, however, it is only changes in V which are ofimportance.The very extensive series of experiments on electro-capillaritycarried out by Gouy 98 show that the double layer capacity is about20 PF. over a considerable range of potential. Outside this rangetrode.104, 105, 106OB 0. Koenig, J. Physical Chem., 1934, 38, 111.loo F. Kriiger, 2. physikal. Chcm., 1903, 45, 1 ; H. Brandes, ibid., 1929, A,101 T. Erdey-Gr6z and G. Kromrey, ibid., 1931, A, 157, 213.102 M. Proskurnin and A. Frumkin, Trans. Paraday Soc., 1935, 31, 112;103 T. Borissova and M. Proskurnin, Acta Physicochim. U.R.S.S., 1936,lo4 A. Frumkin, 2. physikal. Chem., 1923, A , 103, 43, 55.105 J. St. L. Philpot, Phil. Mag., 1932, 13, 775.lo6 D. Ilkovic, Coll. Czech. Chem. Comm., 1936, 8, 170.107 Ann. Chim. Phys., 1875, 5, 494.108 S. R. Craxford, 0. Gatty, and others, Phil. Mag., 1933, 14, 849; 1934,17, 54; 1935,19, 965; 1936, 22 359.109 E. A. Guggenheim, J. Physical Chem., 1929, 33, 842; 1930, 34, 1640;“ Modern Thermodynamics,” 1933, Chap. 10.142, 97and see Gatty and Spooner, op. cit., p. 485.4, 819112 GENERAL AND PHYSICAL CHEMISTRY.the capacity increases somewhat, and there is also evidence of anintermediate maximum at about -0.5 volt on the calomel scale.This corresponds to the electro-capillary maximum. These resultsare obtained in the majority of simple salts, but in solutions of“ capillary active ” substances, the situation is less simple, anddifferent values of the capacity are observed.110 Experimentswith dropping electrodes lo4-lO6 give similar results. On thecathodic side of the capillary maximum the capacity is of the order20 VF., and practically independent of the nature of the ions in thesolution. On the anodic side higher values are observed,105 andthese depend to some extent on the nature and particularly thepolarisability of the anion present.Until recently, all attempts to measure the capacity by thedirect method gave lower values than the other two rnethods,l5* lo1although it was shown lol that the variation of the capacity with thepotential was closely parallel to that observed by Gouy. Thisdiscrepancy has now been cleared up. Proslruriliii and Frumkin lo2measured the capacity a t a freshly formed mercury surface by analternating-current method, and found values almost identical withthose observed by Gouy. If the surface were contaminated, however,a value about 4 tirnes lower was observed. Bowden and Grew,*Oworking at very low C.D.’s, find that if a mercury surface is protectedfrom contamination by being completely enclosed in glass, it hascapacity of 20 pF./Sq. c.mThe direct method of measuring capacities can be applied to nearlyall metals. With liquid gallium and Wood’s metal, Bowden andO’Connor l4 found a value identical with that for mercury. Morerecently, electro-capillary experiments have been carried out withgallium,lll and these lead to a capacity of about 20 yF./sq. em.In the case of solid metals the capacity depends upon the realsurface area and is always greater than that for mercury.15Direct surface-tension experiments cannot be carried out on solidmetals ; but the angle of contact of bubbles or oil drops on thesurface depends on the metal-solution surface tension ,112 and thevariation of this with potential can be calculated from observationsof the contact angle.l13 In this way an “ electro-capillary ” curvefor platinum has been obtained. This work has been summarisedby Frumkin.llA. Frumkin, 2. Physik, 1926, 35, 792.A. Murtazajew and A. Gorodetzkajs, Acta Physicochim. U.R.S.S., 1936,l l a G. Moller, Ann. Physik, 1908, [iv], 27, 665; 2. physikal. Chem., 1908,113 A. Frumkin, B. Kabanov, and others, 2. physikal. Chem., 1933, A, 165,4, 75 ; A. Frumkin, Physilcal. 2. Sovietunwn, 1933, 4, 239.85, 226.433; Phy&kal. I;. Sovietunion, 1932,1, 255; 1934, 5,418BOWDEN AND AGAR : IRREVERSIBLE ELECTRODE PROCESSES. 113A good account of electro-capillary phenomena in general, and ofoverpotential, has been given recently by N. I<. Adam.l14 Aninteresting experimental and theoretical account of the electrodepotentials of corroding metals has been published by Gatty andS p ~ o n e r . ~ ~ Evidence is brought forward for the existence of in-hibitive hydride films on iron and several other metals. The electro-chemical basis of corrosion in general has been fully treated inEvans's recent book l3 on that subject.We thank Mr. G. C. Barker, Dr. H. F. Kenyon, and Mr. H. P.Stout for valuable assistance.F. P. B. ; J. N. A.J. N. AGAR.F. P. BOWDEN.H. W. MELVILLE.J. K. ROBERTS.G . B. B. M. SUTHERLAND.Op. cit.; see also A. Frumkin, Ergebn. exakt. Naturwiss., 1928, 7, 235;Gatty and Spooner, op. oit., Appendix V

ISSN:0365-6217    

DOI:10.1039/AR9383500036

出版商:RSC    

年代:1938

数据来源: RSC

摘要:

INORGANIC CHEMISTRY.1. INTRODUCTION.DURING the past year work in Inorganic Chemistry has continuedalong well-defined lines, and progress has been more in the nature ofelucidation of older problems rather than of a fundamental type.It is not to be inferred, however, that work in this branch haslacked interest. The use of more exact or more powerful methodshas led to a clearer insight into the course of reactions and into thestructure of inorganic substances, and it is in these directions thatadvances have been made.Although an enormous number of observations on the ozonecontent of the atmosphere have been carried out since the timeof C. F. Schonbein (1845) doubt of the accuracy of the data (or evenof its presence) has always existed owing to the lack of a sufficientlydelicate specific reagent for this compound.by first concentrating the morevolatile products in a known volume of air by condensation, followedby separation by fractional distillation, have conclusively shownthat ozone is present in the air and have estimated its concentrationin London and a t Kew.The ozone purified in this manner fromother oxidising agents, especially oxides of nitrogen, can be deter-mined by the potassium iodide-starch method or spectroscopically.These observers find that the average concentration of ozone inLondon air is 1.1 xBy means of a balloon and a self-registering ultra-violet spectro-graph, efforts have been made to determine the vertical distributionof ozone in the atmosphere. V. H. Regener’s2 measurements seemto indicate that the ozone concentration decreases from a heightof 14 km.to a sharp minimum between 5 and 12 km. Althoughreasons for this concentration change have been put forward, it isperhaps unsafe to discuss them, for, owing to the complications inthe method due to absorption of light by dust particles and Rayleighscattering, the results are not free from criticism. It is to be hopedthat Paneth, as indicated in his letter, will extend his observationsto higher altitudes.By measurement of the absorption in a limited region of thea Naturwiss., 1938, 28, 166; 2. Physik, 1938, 109, 642.F. A. Paneth and J. L. Edgarvol. yo.Nature, 1938, 142, 112TERREY : INTRODUCTION. 115spectrum, G. Dejardin, A. Arulf, and D. Cavassilas have computedthat the thickness of the ozone layer, reduced to normal temperatureand pressure, is 0.200 cm.The difficulties of this method,however, apply equally here, and the estimated accuracy is probablyunreal.In the atmosphere, the argon : neon ratio is of the order 520 : 1,but in celestial sources neon is much more abundant. H. A. Russelland D. N. Menze14 explained this on the supposition that theatmosphere lost most of its neon in earlier times when the earthtemperature was very high. Support for this view has been broughtforward by (Lord) Rayleigh 5 from an examination of the neon andargon content of granite. Four samples from different sourceswere examined, and it was found that the quantities per g. ofgranite were of the order 10-6 C.C.of neon and 4 x C.C. ofargon, Le., a ratio of about 40 : 1.The realisation that fluorine could be readily prepared in apparatusother than platinum * has led to a more extended investigationof this element, and most of its physical properties have now beendetermined, e.g., viscosity, surface tension, molecular heat offusion, entropy,6 and electrode potential. L. 0. Brockwayhas measured the internuclear distance in the molecule by electrondiffraction, obtaining a value of 1.45 A., and hence for the covalentradius of the atom a value of 0-73 A. The distance calculated fromother fluorides, e.g., methyl fluoride, is 0.64 A., so that in the fluorinemolecule the distance is about 14% greater than the value expectedfor a normal covalent single bond.A Raman spectrum could notbe detected.8Purification from ~xygen,~ a common impurity, can be broughtabout by the fact that the latter element is more readily adsorbedby charcoal at low temperatures than fluorine, five adsorptions at- 180" being sufficient to decrease the oxygen content from 3.5%to 0.4%.In the solid form fluorine reacts normally very vigorously withhydrogen except in capillaries or in old glass vessels, where anexplosion could not be induced at room temperatures even underirradiation. This inhibition is thought to be due to silicon tetra-fluoride acting as a negative catalyst.10Proc. Nat. Amd. Sci., 1933, 19, 997.5%.C m p t . rend., 1937, 205, 809.Nature, 1938, 141, 410.E. Kanda, Bull. Chem. SOC.Japan, 1937,12, 463,469,511.J . Amer. Chem. SOC., 1938, 60, 1348.C. S. Garner and D. M. Yost, ibid., 1937, 59, 2738.E. Kanda, Bull. Chem. SOC. Japan, 1937, 12, 455.lo Idem, ibid., p. 521.* For the latest type of fluorine generator, see A. L. Heme, J. Amr.Chem. SOC., 1938, 60, 6096116 IINOTtBANIC CHEMISTRY.The white product formed when fluorine acts on tellurium hasbeen shown to be the tetrafluoride l1 and not the difluoride asformerly supposed.As mentioned in last year’s Reports,12 the decompositionof bromine dioxide takes place in stages. The brown productformed has since been shown to be Br,O, identical with that obtainedby W. Brenschede and H. J. Schumacher l3 by the action of bromineon specially active mercuric oxide.The composition of iodous sulphate has been finally settled byJ.I. 0. Masson and C . Argument,14 who find that the product formedin concentrated sulphuric acid is the anhydrous salt I,O,,SO,. Thissulphate is prepared by acting on a mixture of iodine pentoxide andiodine with concentrated sulphuric acid. If the acid concentrationis reduced to that of H,SO,,H,O decomposition into the initialproducts takes place, and in fuming sulphuric acid the com-pound undergoes transition into a white crystalline sulphateI,o,,4s03,xH,o. Dilution of the fuming acid leads first to theregeneration of iodine and iodine pentoxide, which then react withthe re-formation of I,O,,SO,. This fact has induced the authorsto put forward the view that in passing from the concentrated to thefuming acid, a transition of the tervalent iodine takes place andthat in the fuming acid it is present in the form of a complex,possibly a negative one, whilst in the concentrated acid the bare ionI+++ is present.Iodine is soluble in the acid solution of the yellow sulphate,giving a deep brown colour, the concentration of the iodine takenup per molecule of I,O, present varying from 3.44 I, to 11.07 I, asthe acid strength changes from H,SO,,H,O to nearly H,S04.Fromthe reactions of these solutions with organic molecules, e.g., chloro-benzene, which result in the formation of iodo- and not iodoniumcompounds, and from the fact that if the initial ‘‘ oxide ” solute isexpressed as 1,O then exactly 1,O is consumed and the remaining(x - 2) atoms of iodine are precipitated as element, it is concludedthat the iodine is present in the univalent form.These results are expressed by equations thus :I+++ + I, = 31+I+ + nI, = I+, + 2nI+l+2n + RH = RI + H+ + nI,The view that the iodine atoms were present as iodine ofR.Whytlaw-Gray, T. H. Henry, and G. A. R. Hartley, Nature, 1938,142, 952.l2 Ann. Reports, 1937, 34, 139.Ibid., p. 138. l4 J., 1938, 1702TERREY : INTRODUCTION. 117solvation 15 or taken up as a micelle was rejected on the groundsthat it would necessitate a very complicated and artificial mechanismfor aromatic iodinations. It is interesting to note that if theauthors’ views are accepted we have a parallel between the positiveions of univalent iodine I+, 13+, Is+, etc., and the negative ions I-,13-, I,- of the iodides and polyiodides.Further attempts to demonstrate the polar nature of iodinemonochloride have been carried out by C.Sardonnini and N.Borghello 16 by the electrolysis of this substance in acetic acid andin nitrobenzene. The cathode and the anode chamber wereseparated by glass diaphragms, and platinum electrodes were used.In acetic acid, although the concentration of both halogens increasedat the anode, the ratio I to C1 decreased, and the results agreed withthe view that the solution contains a small amount of I+ and IC1,-ions, the latter having a much higher migration velocity.Reactions between iodine monochloride and a number of saltshave been investigated. Briefly, the results may be summarisedby stating that in some cases chlorides are formed, in others iodides,and some give addition compounds.Thus ammonium, potassium,and rubidium chlorides (but not those of lithium and sodium)form addition compounds of the type MCl,ICl, as do the acetatesof the heavy metals lead, copper, and cadmium : [M,(OAc),]I,Cl.The nitrates and sulphates of sodium and potassium and a numberof cyanides yield chlorides, but the sulphides of cadmium, lead,zinc, and silver are converted into iodides. Cyanates and thio-cyanates give chlorides and I(CON), and I( CNS), respectively.E. Zintl and W. Morawietz 18 have attempted to classify oxidesaccording to the polarisability, (charge on ion)/(radius of ion), of thepositive ion. Those which form glass-like oxides all have valuesof elr between 7 and 15.Oxides having values of this quotientgreater than 15 constitute the volatile oxides with molecular lattices,and those with e/r < 7 are the salt-like oxides with co-ordinationlattices as their structure. In the case of the latter, the authorsattempted to determine the co-ordination number of the ion by thepreparation of ortho-salts. This possibility rests on the assumptionthat when a sufficient amount of a strongly basic oxide is presentall oxygen bonds of the acid oxide are broken down and that thewhole of the oxygen present may be looked upon as co-ordinated tothe acid-forming element .19l5 Cf. A. C. D. Rivett and J. Packer, J., 1927, 1342.Atti R. Accad. Lincei, 1937, [vi], 25, 46.J. Cornog, H.W. Horrabin, and R. A. Karges, J . Amer. Chem. SOC., 1938,60, 429.I8 2. anorg. Chem., 1938, 236-237, 372.Is In the paper the grounds for this assumption are discussed118 INORGANIC CHEMISTRY.The ortho-salts were made by heating decreasing amounts ofsodium oxide with the acid oxide or a salt in a vacuum and thensubjecting the product to X-ray examination. When the spectrumof Na20 was no longer visible it was inferred that the maximumcombining power of base to acidic oxide had been attained, and thecomposition of the product was determined at that stage. Theresults are given in the subjoined table, the number below thecentral element indicating its co-ordinating value.NaOH Na,BeO, Na,BO, Na,C03 Na,NvO, Na,SO,,~Na,O NaC10,1 3 3 3 4 4 4Na,AlO, Na4Si04 Na3NIITOQ Na,SeO,,QNs,O4 3 4Na,AgOz2Na,Sn,O,Na,IO,6Na,PbO,,Na,O Na3P04 Na,TeO,4 4 6The formation of ortho-salts of nitric and nitrous acids is ofinterest.Sodium hydroxide showed no tendency to combinewith sodium oxide : the ion [OHO]--- analogous to the bifluorideion FHF- seems incapable of existence. It should be noted that inthe preparation of these ortho-salts, sodium oxide must be used.Energy considerations prevent in certain cases the formation whenthe hydroxide or carbonate is substituted. Moreover, the valueof the co-ordination number derived in this way is not always inagreement with that obtained from consideration of ionic size.Confirmation of the existence of the oxide of lead, Pb,O,,, reportedlast year,20 could not be obtained by A.Baroni,21 who, inthe decomposition of lead dioxide or by the action of oxygen on themonoxide under pressure, could only detect the well-known speciesPb20, and Pb,04. His X-ray and magnetic work further tends toconfirm the view that Pb20 does not exist,22 but that it is a mixtureof the metal and tetragonal PbO.Working under different conditions, L e . , by heating the dioxidewith aqueous sodium hydroxide in a pressure bomb, G. L. Clark,N. C. Schieltz, and T. T. Quirke 23 found, in addition to crystals ofPb20, and Pb30,, large single crystals of Pb,O,, the three oxidesbeing formed at temperatures of 260-275", 355-375", and 295-310" respectively under their conditions.Five papers 24 have been published on the higher oxides of nickel.2o Ann.Reports, 1937, 34, 150.22 Cf. Ann. Reports, 1937, 84, 150.2s J . Amer. Chem. Soc., 1937, 59, 2305.24 F. Frazqoia and (Mlle.) M. L. Delwaulle, Compt. rend., 1937, 204, 1042;205, 282; B. A. Petrov and B. Ormont, J . @en. Ohm. Russia, 1938, 8, 563;D. P. Bogatzki, ibid., 1937, 7, 1397; J. H. Krepelks and M. Blabolil, Coll.Czech. Chem. Comm., 1937. 9, 497.a1 A. Baroni, Qazzetta, 1938, 68, 387TERREY : INTRODUCTION. 119Possibly the best way of looking upon these oxides, whether madefrom the ignition of nickel nitrate or by the action of oxidisingagents on nickel salt solutions, is as a series of solid solut.ions ofNiO and NiO,. According to Bogatzki, the intermediate oxidesdiffer from NiO only in their larger space lattice constant. Thepossibility of replacing bivalent nickel in the nickel oxide latticeby higher-valent nickel giving rise to non-stoicheiometric or" Berthollide " oxides, must be borne in mind, and even the factthat Ni,O, itself may actually be non-existent.A disconcerting result, especially to analytical chemists, is theobservations of A.Westgren and K. Dihlstrom 25 that the productformed by heating antimonic acid for 3 hours a t 780" was not thetetroxide, Sb,O,, but SbIIIO(OH),SbV,O, , a structure apparentlyconfirmed by comparison with the isomophous compound BiTa206P.The above procedure is the one commonly recommended for thequantitative determination of antimony as Sb,O, and has beenchecked by many observers, and to the Reporter it must appearthat SbO(OH),Sb,O, is capable of losing water (and oxygen) with-out change of structure, a feature observed also in CaSO,,$H,O.It is only when the last traces of water are removed that the latticebreaks down from the face-centred cubic of the hydrated compoundto the rhombic form of the tetroxide.It has long been known that when ammonium dichromate isgently ignited a black solid residue is left, which on stronger heatingchanges over into a green mass universally assumed to be chromicoxide.K. Fishbeck and H. Spengler,26 who carried out thedecomposition in a vacuum at a temperature of 160--250", concludedthat the black product was Cr2Q,,H,0. Closer examination byE. H. Harbord and A. King,Z7 however, reveals the fact that thissubstance is not homogeneous and that on heating it evolves notonly water but nitrous oxide and nitrogen: moreover, strongignition did not result in the formation of Cr,O,, but of an oxidecontaining more oxygen, possibly a non-stoicheiometric compound.A still lower oxide of sulphurY28 S,O, is said to exist> in the yellowsolution formed when $0 is passed into dry carbon tetrachloride.It decomposes rapidly into sulphur and the dioxide, but can bestabilised in this solvent to some extent by the addition of dryhydrogen chloride.The evidence for its existence is based on theobservation that on treatment of the carbon tetrachloride solutionwith sodium hydroxide, equivalent amounts of sodium sulphideand sulphite are formed.26 2.anorg. Chem., 1938, 235, 163; K. Dihlstrom, ibid., 1938, 236, 57.28 B. S , Rao, Current Sci., 1938, 6. 386,z 8 Ibid., 1938, 235, 183. 27 J . , 1938, 955120 INORGA?SIC CHEMISTRY.By the reduction of dilute hydrochloric acid solutions of rheniumwith zinc and with cadmium respectively, the hydrated forms of thetwo lower oxides Re,0,2H,O and ReO,H,O have been isolated.29Both exist in the form of black powders insoluble in hydrochloricacid or sodium hydroxide, but rapidly attacked by oxidising agentssuch as nitric acid or bromine water.P. Baumgarten and H. Erbe 30 have made an extended study ofthe oxidation of sulphite solutions, using substances capable ofyielding stable compounds with the unstable intermediates asindicators. All the latter possessed pronounced co-ordinativecharacteristics and included pyridine, urea, dioxan, glycine,ammonia, boric acid, and alkali fluoride.Three types of sulphiteoxidation were distinguished : (1) Cupric salts and Caro’s acid,HSO,, which with pyridine as indicator gave pyridiniumsulphonicacid in addition to sulphate and dithionate :SO,(O*OH)O- + C,H5N:+ISO3-- = C,H,N+SO,O- + SO,-- + OH-(2) Anodic oxidation and potassium persulphate, which do notyield the above pyridinium salt but in the absence of an indicatorgive a greater yield of dithionate. (3) Hydrogen peroxide, whichgives almost exclusively sulphate.These results are explained on the assumption of the productionof ions A and B. Whether the ion is discharged at (u) or (b) depends2Cu++ + C,H,N + SO,-- = 2Cu+ + C6H5N+S0,0-..: 0 :: 0 :(A*)..: o : s : (a) ..*...: o :: s : o : (b): 0 :(B-1......on the oxidising agent, ( B ) being the intermediate when pyridinium-sulphonic acid is produced, whereas (A) is prominent when dithionateis formed.The probable reaction in the latter case isC,H,N + A- + C,H,N - A S,O,” + C5H,NWith hydrogen peroxide the main process is in all probability animmediate transference of oxygen from H,O, to SO3”, thus :H,O, + SO,” = SO,” + H20S. R. Das 31 has made a study of the sulphur allotropes, and hasshown that roll sulphur, flowers of sulphur, milk of sulphur, and thegummy deposits of colloidal sulphur are all S, (orthorhombic2s R. C. Young and J. W. Irvine, J . Amer.Chem. Xoc., 1937,59,2648.so Ber., 1937, 70, 2235. 31 Indian J . Physics, 1938, 12, 163TERREY : INTRODUCTION. 121sulphur). Hydrolysis of sulphur monochloride gives a white form,definitely crystalline but different from S,, into which, however, itis easily converted by heating to 88". Fresh plastic sulphur isamorphous, giving a diffuse band which coincides with one of thebands of liquid sulphur. No change in the structure of sulphurwas observed on cooling to - 183".A reinvestigation of Bridgman's observation that whitephosphorus was irreversibly converted into a black modification at12,000 atm. and about 200" has been undertaken by R. B. Jacobs.3,This black form differs from the ordinary black crystalline modific-ation in being amorphous and having a lower density.Prolongedheating of this amorphous powder at 125" yielded a brilliant violetmodification of red phosphorus.Further support for regarding the diammoniate of diborane 33as being a monoammonium NH,+H,BNH,BH,-, in which anatom of nitrogen is interposed in the boron chain, has been obtainedfrom a study of BzH~N.~' This compound, which has m. p. - 66.5"and b. p. 76-2", is easily prepared by the action of B,H, onB,H6,2NH,. Acids hydrolyse it, giving 5 mols. of hydrogen, 2mols. of boric acid and one ammonium ion. It reacts with anequal volume of trimethylamine, giving a stable.. .. .. white solid which, on heating, gives borine tri-B : N : B : H methylamine and takes up one molecule of ammonia,,H H H forming B,H7N,NH3.In liquid ammonia the latterreacts with sodium, forming NaNH,,B,H,N. These (1.1 reactions are in harmony with the structure (I), whichis supported by the electron-diffraction work of S. H. Bauer,36 whofinds a B-N-B skeleton.Some interesting new derivatives of the silyI radical have beenprepared by H. J. Emelhus and N. Miller 37 by the interaction ofmonochlorosilane and amines. For instance, with methylaminethe following reaction takes place :.. .. ..3CH3*NH, + 2SiH3C1 = CH3*N(SiH3), + 2CH3-NH,,HC1The product, methyldisilylamine, is a liquid, b. p. 325", hydrolysedby alkali and decomposed by hydrochloric acid :CH3*N(SiH3), + 3HC1= 2SiH,C1 + CH,*NH,,HClWith trimethylamine a stable, solid, quaternary compound is formed,N(CH,),,SiH,Cl. This is decomposed by water into trimethyl-32 J .Chem. Physics, 1937, 5, 945.33 Cf. Ann. Reports, 1937, 34, 152.34 H. I. Schlesinger and A. B. Bury, J . Amer. Chem. Xoc., 1938,60,290.35 H. I. Schlesinger, D. M. Ritter, and A. B. Bury, &id., p. 2297.86 Ibid., p. 524. 37 Nature, 1938, 142, 996122 INORGANIC CHEMISTRY.amine hydrochloride and disiloxane, (SiH3)20, and is hydrolysedby alkali :N(CH,),,SiH,CI + 3NaOH = Na,SiO, + NaCl + N(CH,), + 3H2This salt has a dissociation pressure of 1 atm. at 91". This dissoci-ation is not reversible at higher temperatures, owing to the dis-proportionation of the SiH,Cl formed :2SiH3C1 = SiH, + SiH,CI,It is a useful silylating agent, for it reacts with alcohols to formsilyl alkyl ethers :EtOH + NMe,(SiH,)Cl = SiH,OEt + NMe,,HClMonochlorosilane and dimethylamine react at room temperature,forming N(SiH,)Me,.This tends to unite with an excess of themonochlorosilane, giving an unstable quaternary salt. As pointedout by the investigators, there is a decrease in the stability of thequaternary salts as CH, is replaced by SiH, :NMe,Cl Stable NMe( SiH,),CI Not formedNMe,SiH,CI Moderately stable N( SiH,),Cl Not formedNMe,( SiH,),Cl UnstableA new view for the change in colour under varying conditionso€ cobalt salt solutions has been put forward by J. N. Pearce andL. R. D a ~ s o n . ~ ~ Of the older ideas, one school ascribed the changeof the red solution on the addition of chlorides to the formation ofthe complex ion CoCl,--, whereas another concluded that the degreeof hydration of the cobalt ion changed : in the red solution it wasco-ordinated to six molecules of water, whereas in the blue it wastetra-co-ordinated, a view based on the fact that the colour changewas linked with the hydrating power of the added cation.Pearceand Dawson point out that the first of the above theories seemsinadequate in that equimolecular concentrations of added chloridedo not produce equivalent colour changes. They find from anexamination of the spectrum that the absorption band is widenedby added salt, the extent of which depends directly on the ioniccharge and inversely on the ionic volume of the added cation.The new view regards the cobalt atom in dilute solution as beingstrongly hydrated, the sheath of water molecules preventing itsclose approach to the chlorine ion.Addition of strongly hydratingcations removes this sheath and permits electrostatic attractionto bring the cobalt and chlorine ions closer together. This causes adistortion of the electronic system of the cobalt ion, with change inits absorption spectrum.Da J . Chem. Physics, 1938,6, 128TERREY : INTRODUCTION. 123The rare earths have continued to receive attention. Byheating the oxides of lanthanum, cerium, praseodymium,neodymium, samarium, and ytterbium with ammonium iodideat 400" the anhydrous iodides of these elements were prepared,excess of ammonium iodide being removed by vacuumsublirnati~n.~~ The products were obtained in the form of green,hygroscopic powders readily soluble in organic solvents suchas alcohol or pyridine.On exposure to the air, hydrolysis takesplace and basic salts are formed.G . Beck and W. Nowacki 40 have shown that the lower fluorideand sulphide of europium can be respectively obtained by reducingthe tervalent fluoride in a stream of hydrogen and the sulphate ina current of hydrogen sulphide. It is interesting to note thatEuF, has the fluorite structure with cell dimensions approximatingto those of SrF,. Elementary europium has been isolated by theelectrolysis of the trichloride in a sodium chloridepotassiumchloride eutectic mixture.41From observations of the amount of oxygen taken up whenpraseodymium was heated under pressure in that gas, W. Prandtland G . Rieder 42 have demonstrated that praseodymium is quinque-valent in the completely oxidised state, whereas under similarconditions terbium tends to quadrivalency.Seeking better methods for the separation of the rare earths,W.Prandtl and S. Mohr 43 have studied the ferro- and ferri-cyanidesand their solubility in water and dilute hydrochloric acid. By theaction of alkali ferrocyanide on an acid solution of a rare-earth salt,ferrocyanides of the type NaMFe(CN),,nH,O are obtained. Withferrocyanic acid, basic salts are formed, e.g., with lanthanum,LaOH[LaFe(CN),],,18H20. Ferricyanides give compounds of thegeneral type MFe(cN),,nH,O. These are more soluble than theferrocyanides.Isotherms, determined a t 25" and 50" for the ternary system,cerium group nitrates-nitric acid-water, show that the solubilitiesdo not decrease in the order of increasing atomic number, but thatthe solubility of lanthanum nitrate is anomalously low, the orderfound being Ce > Pr > La > Nd > Sm.In the solid form thenitrates exist as hexa-, tetra-, and tri-hydrates. Observations by5. Newton Friend and D. A. Halla in the cases of lanthanum andpraseodymium on the loss of water from the characteristic hexa-hydrates could only codrm the existence of the monohydrate forlanthanum and the dihydrate for praseodymium.39 W. A. Taebel and B. S. Hopkins, 2. alzorg. Chem., 1937,235,62.co Natuzcmoiss., 1938, 28, 496.42 2. anwg. Chem., 1938, 238, 225.4s Ibid., 1938, 236, 243; 23'7, 160.41 F. Trombe, C-t. red., 1938, 206, 1380.44 J., 1938, 1920124 INORGANIC CHEMISTRY.It has been known for some years that when nitrogen dioxidewas dried over phosphoric oxide union occurred and a glassy com-pound was formed.This was looked upon as an addition compoundP205,xN02’45 but E. M. Stoddart46 finds that in the interactionoxygen is evolved and that the addition compound is reallyP20,,2N0 :N,O, + P20, = P205,2N0 + 0 2This observation rules out Smith’s evidence that intensive dryinginhibited the reaction between nitric oxide and oxygen. H. B.Baker’s evidence4’ is now the only indication that drying caninfluence this reaction.”No further definite developments have been made since thelast Reports with regard t o elements nos. 43, 61, 87, and 93.H. Hulubei’s claims 48 to have observed lines corresponding to theLa, La,, Lp, and L., of element 87 in the alkali concentrates frompollucite have not been confirmed.The same applies to his observ-ations on the presence of a transuranium element no. 93 in mineralscontaining uranium and rhenium.49 Fermi’s contention, however,that transuranium elements resulted from the disintegration ofactivated uranium has been well substantiated by other w~rkers.~OH. Jensen 51 has suggested that stable nuclei of elements No. 43 and61 may not occur. This suggestion is based on Mattauch’s rule,which states that if two isobares differ in nuclear charge by unity,one of them must be unstable. Considering element 61, the adjacentmembers &d and &m have many isotopes. This points to anunstable nucleus for an element of atomic number 61.A similarstate of affairs occurs with 43. The existence of long-lived p-activeisotopes is also considered unlikely.Work has continued throughout the year on polynuclear metalliccomplexes and on co-ordination compounds. These are discussed inseparate sections of this Report, as is also the separation of isotopes.Investigations on reactions in solvents other than water also receiveda good deal of attention, in particular the solvents with high di-electric constants and good ionising properties-ammonia, sulphurdioxide, and hydrogen fluoride. The earlier work on ammonia iswell summed up by A. Findlay in the Franklin Memorial Lecture : 524 5 J. W. Smith, J., 1928, 1886.47 J., 1894, 65, 611.49 H.Hulubei and (Mlle.) Y . Couchois, ibid., 1938, 207, 333.50 For a very full account of work on the transuranium elements, see L. L.Quill, Chem. Reviews, 1938, 23, 87.51 Naturwiss., 1938, 26, 381.52 J . , 1938, 583.* See, however, in this connection E. M. Stoddart, J., 1939, 5.4 6 J . , 1938, 1459.Compt. rend., 1936,202, 1927; 1927,205, 854WHYrrBW-GRAY : ATOMIC WEIGHTS. 125other solvents such as the alcohols, alkyl halides, acetone, nitro-benzene, and benzene have been used, particularly by V. A. Plotnikovand his co-~orkers.~~ H. T.2. ATOMIC WEIGHTS.1936-1938.In view of the rapid extension of the study of nuclear trans-formations and their accompanying energy changes, as well as themarked developments in mass spectrography, it is not surprisingthat purely physical evidence is becoming of increasing importancein this field of chemistry.Apart from the comparatively large errors in certain atomicweight values indicated by earlier work on mass spectra and usuallycorrected by chemical revision, data are now available for theexamination of smaller differences, and in some cases atomic weightvalues have been revised solely on the strength of physical evidence.This is the case for the new values H = 1.0081, He = 4.003, and0 s = 190.2 in the Eighth Report of the Committee on AtomicWeights of the International Union.It is now impossibleadequately to review the progress in atomic weight research withoutreference to the new physical material now available.Develop-ment has extended mainly in two directions : (1) the measurementof the relative masses of atoms (isotopic weights) either withimproved mass spectrographs or by means of nuclear reactionenergies, (2) the determination of the relative proportions of theisotopes in complex elements (abundance ratios). Notable progressin both directions has been made during the last two years.F. W. Aston has measured by the doublet method with his second-order focusing mass spectrograph the masses of 21 isotopes rangingfrom hydrogen to mercury with an accuracy approaching 1 part inlo5, and just recently he has examined five more, making availablethe packing fractions and isotopic weights of 24 species determinedto a higher order of accuracy. Similar work has been publishedby K.T. Bainbridge and E. B. Jordan for a number of the lighterelements, vix. , hydrogen, deuterium, carbon, helium, beryllium,boron, neon, and argon, an instrument of specially high resolutionagain being used, whilst A. J. Dempster4 has published work onthe heavier elements.Primarily, the new data are of great importance in nuclear physics,53 For summary, see Mem. Inst. Chem. Ukrain. Acad. Sci., 1937, 4, No. 3.J., 1938, 1101.Proc. Roy. Soc., 1937, A , 163, 391 ; Nature, 1938, 141, 1096.Physical Rev., 1936, 49, 883; 1937, 51, 384. Ibid., 1938, 53, 64126 INORGANIC CHEMISTRY.for they furnish an independent check on energy change^,^ but theyalso afford the chemist more accurate values for the packing fractionswhich, taken in conjunction with the abundance ratios, enablemore reliable estimates of the atomic weights of a number of elementsto be made.It is interesting to note that the values for the isotopicweights from nuclear reactions and from mass spectrography showa remarkable concordance. M. S. Livingston and H. A. Bethehave critically examined the data available up to 1937 and havepublished what they judge to be the most accurate values for theisotopic weights from lH to 4oA.A striking contribution to the measurement of abundance ratioshas been made by A. 0. Nier. Using a mass spectrograph speciallydesigned for this purpose, he determines the relative proportions ofthe isotopes in complex elements by an electrometric methodinstead of by photometry of the lines on a photographic plate.He has examined A,'# K, Rb, Zn, Cd,' Hg, l o Xe, Kr, Be,8 Ca,Ti, S,9 Pb,ll Sr, Ba, Tl10 and Os,I5 as well as I, As, Cs,* Bi.10 Nonew isotopes have been detected in the last group, which are singleto a high degree.A number of new rare isotopes have been foundamongst the complex elements. In other cases some atomic speciesreported previously have not been detected, such as the threeisotopes of lead, 205,209, and 210.Since his values are regarded by the Committee on Atoms of theInternational Union as superseding the older ones, it is satisfactoryto note that these new ratios lead to atomic weigbts differing inmost cases but slightly from the international figures: osmiumwas a striking exception and its atomic weight has been corrected.Nier 11 also reports that he has found the isotopic constitutionof common lead to vary appreciably in twelve samples of knownorigin and of different geological age.In most of these the computedatomic weight agrees satisfactorily with the chemical valuepreviously determined from the same sample, but it is evident thatlead of constant isotopic composition is not invariably found evenin the oldest formations, and that its atomic weight may varywithin small limits. Nier attributes the variation to contaminationwith radiogenic leads present in igneous rocks.Many other measurements of isotopic abundance ratios havebeen made recently, notably for Pd, Pt, Ir, Rh, and Co, by M. B.5 See J. Mattauch, Physikal. Z., 1937, 38, 951; 2.anorg. Chem., 1938,236, 209.Rev. Mod. Physics, 1937, 9, (3).Physical Rev., 1937, 52, 133.Ibid., 1938, 53, 282.lo Ibid., 1938, 54, 275.7 Ibid., 1936, MI, 1041 ; see also Ann. Reports, 1937, 34, 8.J . Amer. Chem. SOC., 1938, 60, 1671WHYTLAW-GRAY : ATOMIC WEIGHTS. 127Sampson and W. Bleakney,l2 for the rare earth group by A. J.Dempster,13 for Li, K, and Rb by A. K. Brewer,l4for Pb l6 and Nd l7by J. Mattauch and V. Hauk. A useful summary of work up tothe end of 1937 is given by Otto Hahn.18In view of this rapid progress, it would be premature to attemptto correlate in detail the physical and chemical data, but thesignificance of the former in relation to the chemical atomic weightsis evident.It is well to bear in mind that isotopic weights deduced from massspectra may, as Aston 19 has emphasised, be affected by cumulativeerrors especially when they are based on a long chain of relation-ships.The same applies even more to the calculation from energyrelations. There is, however, a high probability that a final resulthas been reached when the chemical and physical values agreeclosely.The cases of cadmium 21 and tellurium,20 for which, on accountof errors in the mass spectrum, the chemical values have been foundto be nearer the truth, have been mentioned in earlier reports.Another instance is neodymium,22 for which the mass spectrumvalue, Nd = 143.5, is less than the chemical value, Nd = 144.27,founded on the work of G. P. Baxter and H. C. Chapin23 in 1911by nearly 0-8 unit.A careful revision by 0. Honigschmid andF. Wittner,** who compared anhydrous neodymium chloride withsilver by the standard procedure, has been published recently andgave Nd = 144.273. The discovery of two new isotopes by A. J.D e m p ~ t e r , ~ ~ viz., 14*Nd and 150Nd, does not explain the discrepancy,for they are only present in small amounts. J. Mattauch and V.Hauk 26 have now revised the isotopic constitution of this element,using a more developed technique, and their measurements giveNd = 144.29 & 0.03 and thus bring the two values into satisfactoryagreement. Among the rare earths, holmium22 still presents anoutstanding discrepancy ; lesser differences are shown by samarium,thulium, and terbium. Chemical revision of gadolinium 27 anderbium 28 has brought about a close agreement. The new work ofl2 Physical Rev., 1936, 50, 732.I4 ]bid., 1936, 49, 867.l6 Naturwiss., 1937, 25, 763.l 8 Ber., 1938, 71, 1.2o Ann.Reports, 1934, 31, 95.2 2 Ibid., 1934, 31, 370, 94; Proc. Roy. Soc., 1934, A, 146, 46.23 J . Amer. Chem. SOC., 1911, 33, 1.24 2. anorg. Chem., 1938, 235, 220.2 6 Naturwiss., 1937, 25, 780.'.: Ann. Reports, 1936,33, 135 ; C. R. Naeser and B. S. Hopkins, J . Amr.28 0. Honigschmid and F. Wittner, 2. anorg. Chem., 1937, 232, 113.la Ibid., 1938, 53, 727.l6 Ibid., 1937, 52, 885.lo Nature, 1935, 135, 541.21 Ibid., 1936, 33, 142.Ibid., p . 780.25 Physkl Rev., 1937, 51, 289.Chcm. SOC., 1935, 57, 2183128 INORGANIC CHEMISTRY.G. P. Baxter and F.D. Tuemmler 29 and of W. Kapfenberger 30 onthe analysis of europous chloride does not show as close aconcordance as is to be expected, though it is clear that the truevalue for europium lies below 152, the present international figure.The inter-national value for this element was in 1936 changed from 12-00t,o 12.01 on the evidence of gas-density measurements whichindicated a value greater than 12-00. Mass-spectrograph datafrom reliable and independent sources, although confirming 12.01,do not give values agreeing to the third place of decimals. Aston’s 31latest value for 12C on the l60 scale is 12-00355, a result from anumber of very carefully checked doublet measurements. E. B.Jordan and K. T. Bainbridge,32 however, find lZC = 12.00398,a difference approaching 1 part in 20,000.The latter value issupported by evidence from nuclear-energy changes. 6* 33 Fromthe viewpoint of the chemist this difference is, however, small.A larger uncertainty lies in the abundance ratio 12C : 13C of the twoisotopes. Aston’s value for this is 140 5 14 : 1, found some yearsago. More recent measurements give lower values. Thus A. R.Brosi and W. D. hark in^,^^ from measurement of the relativeintensities of the band heads in the Swan spectrum, find 92-2 53.7/1. F. A. Jenkins and L. S. Ornstein35 by a similar methodfound 106 5 11/1, whilst A. L. Vaughan, J. H. Williams and J. T.Tate 36 with the mass spectrograph obtained 91 -6 2-2/1. Aston’sfigure, however, is still the international value.The chemicalatomic weight calculated from Aston’s data, the factor 1.000275 37being used to convert to the chemical scale, is C = 12.0074, whilsta 12C/13C ratio of 92 combined with the figure of Bainbridge andJordan gives C = 12.0115. The limiting-pressure method usedwith the density microbalance gives for the gases oxygen, carbonmonoxide and dioxide, and ethylene 36 values in substantial agree-ment with the latter figure, i.e., C = 12.010. however,using the standard method of limiting densities but with an improvedtechnique, finds for a comparison of the same gases with oxygenC = 12.0070.The completion of two important investigations on the chemical2Q J . Amer. Chem. SOC., 1938, 60, 602. 30 2. anorg. Chem., 1938, 236, 273.31 Proc.Roy. SOC., 1937, A , 163, 403. 32 Physical Rev., 1937, 51, 384.33 M. S . Livingston and H. A. Bethe, Rev. Mod. Physics, 1937, 9, 246 ; seealso J. Mattauch and R. Herzog, Naturwiss., 1937, 25, 147.34 Physical Rev., 1937, 52, 472.35 Proc. K . Akad. Wetensch. Amsterdam, 1932, 35, 1212.36 Ann. Reports, 1936, 33, 144.37 W. R. Smythe, Physical Rev., 1934, 45, 299.88 Bull. SOC. chirn. Belg., 1938, 47, 427.An example of finer differences is that of carbon.EWHYTLAW-GRAY : ATOMIC WEIGHTS. 129side has recently supplied strong evidence in favour of the higherfigure. G . P. Baxter and A. H. Hale,39 by the combustion inoxygen over a platinum catalyst of carefully purified specimensof chrysene, C, 8H12, triphenylbenzene, c24H18, and anthracene,C14H10, have obtained a series of 27 values for carbon ranging from12.0080 to 12.0118.Quantities of hydrocarbons of 3-6 g. were usedin each experiment. The final value with all corrections madeis C = 12.0102 (H = 1.0081). In this work carbon is compareddirectly with oxygen. A. F. Scott and F. H. Hurley, j~n.,~O havedetermined the ratio of benzoyl chloride to silver. The benzoylchloride, prepared from highly purified benzoic acid from thiophen-free toluene, and phosphorus trichloride, was fractionally distilledin a vacuum in an all-glass apparatus. The silver equivalent of thevarious final fractions was determined by the standard opalescencemethod. The mean is computed from eight closely concordantvalues, the extremes being 12-0099 and 12.0106.The final meanwith H = 1-0081 is C = 12.0100. The evidence from all thesesources makes the higher value more probable, and the internationalcommittee in their Eighth Report assign to carbon the value 12.010.A. F. Scott and F. H. Hurley, jun.,4l have also pointed out that thenew value for carbon leads to a slightly lower value for sodium inthe ratios Na2C0,/2Ag, Na2C0,/2AgBr, and Na,CO,/I,O,, the meangiving Na = 22.993 in agreement with the value Na = 22.994found by C. R. Johnson,42 and lower than the accepted value by0.004 unit.The atomic weight of phosphorus, to which attention was directedin the Annual Report for 1934, has quite recently been redeterminedby the analysis of phosphorus oxychloride by 0. Honigschmid andW. Menn.43 The preparation of this substance in a high state ofpurity was accomplished by first subjecting the commercial productto fractional distillation to remove the greater part of the trichloride,followed by treatment of the product with phosphoric anhydrideto eliminate any pentahalide, and subsequent fractional recrystallis-ation.The material so obtained was distilled in a vacuum througha fractionating column in a sealed glass apparatus a number oftimes, until the fractions gave closely concordant results on analysis.The sealed bulbs containing the final oxychloride were, afterweighing, broken below the surface of aqueous ammonia in astoppered flask, the glass fragments collected on a fritted filter,weighed, and the chlorion content of the solution determined bystandard methods.The results give values for the atomic weight39 J . Amer. Chem. SOC., 1937, 59, 506.41 Ibid., p 2078.43 2. anorg. Chem., 1937,235, 129.40 Ibid., p. 1905.42 Ann. Reports, 1935, 32, 95.REP.-VOL. XXXV. 130 INORGANIC CHEMISTRY.from the two ratios POCl, : 3Ag : 3AgCl varying from 30.986 to30.975, with a final mean of P = 30.978 when C1= 35.475 andAg = 107-880. The current value P = 31.02 is based on theanalysis of the trichloride and tribromide carried out 25 years agoby Baxter and his collaborators.44 Since this element is single andno rare isotopes have been reported, and moreover, its packingfraction is accurately known, any uncertainty has been removedby the close agreement of the chemical with the physical figureP = 30-975, calculated from Aston's recent value with the factor1.000275.This again accords very closely with P = 30-977 foundfrom the limiting density of phosphine in 1930 by M. Ritchie 45 asa result of very careful measurements.The claim of A. K. Brewer to have proved that plants assimilateselectively the 41K isotope was noted in 1936.46 He 47 now finds thatthe potassium from some animal tissues shows a similar displace-ment of the 39K/41K ratio. These observations so far are withoutindependent confirmation. That the rare 40K isotope is responsiblefor the radioactivity of this element has been proved by W. R.Smythe and A. Hernmendinger48 and confirmed by others.49It seems likely that 40K disintegrates by a dual change to 40Caand 40A, and that the bulk of the argon in the atmosphere has beenformed in this way.49*5* An interesting account of all this workis given by Brewer.47Equally interesting is recent work on the other naturally radio-active alkali metal rubidium, the p-radiation from which has beenshown to be due to the less abundant of its two isot~pes,~l vix.,87Rb.The ratio 85Rb/87Rb has been determined by A. K. Brewer 52in minerals from various localities and he found no appreciablevariation. His value 2.61 is rather lower than A. 0. Nier's 2-68,and he calculates the atomic weight to be Rb = 85-456. The inter-national value is Rb = 85-48, based on the ratios RbCl : Ag andRbBr:Ag determined by standard methods in 1936 by E. H.Archibald and J. G. Ho01ey.~~ s7Rb disintegrates to 87Sr, and 0.Hahn, F.Strassmann, and E. Walling,54 from 1 kg. of a Canadian44 a. P. Baxter, C. J. Moore, and A. C. Boylston, 2. anorg. Chem., 1912, 74,365; G. P. Baxter and C. J. Moore, ibid., 1913,80, 185.45 Proc. Roy. SOC., 1930, A, 128, 551. 46 Ann. Reports, 1936, 33, 140.47 Ind. Eng. Chem., 1938, 30, 893. 48 Physical Rev., 1937, 51, 178.49 C. F. Weizsiicker, Physikal. Z., 1937, 38, 623; A. Bramley and A. K.Brewer, Physical Rev., 1938, 53, 502.6o A. Branley, Science, 1937, 86, 424.6 1 J. Mattauch, Physikal. Z., 1937, 38, 958; W. R. Smythe and A.Hemmendinger, PhysicaZ Rev., 1937, 51, 1052; W. Walcher, Physikal. Z . ,1937, 38, 961.5a J . Amer. Chem. Soc., 1938, 60, 691.63 Ibid., 1936, 58, 70, 618. 64 Nuturwiss., 1937, 25, 189WHYTLAW-GRAY : ATOMIC WEIGHTS.131lithium mica containing rubidium, have isolated 250 mg. of strontiumcarbonate, which J. Mattauch 55 proved by examination with themass spectrograph to consist almost entirely of s7Sr. The principalconstituents of strontium are the three isotopes 86, 87, and 88in the approximate proportions of 10, 7, and 83%. The isotopicweight of S7Sr on the chemical scale is 86-90. The atomic weightof the element is 87.63. The separation of larger amounts of thepractically pure isotope will enable the isotopic weight to bedetermined by chemical analysis. It is evident that strontiumextracted from minerals containing rubidium will have an atomicweight below the normal value.The difference in the atomic weights of oxygen from water andfrom air, first reported by M.Dole and confirmed by N. Moritaand T. T i t a ~ G , ~ ~ has again been confirmed. E. R. Smith and H.Matheson 5' find that water containing oxygen from air is 8-6 partsper million heavier than that containing oxygen derived from water.T. 0. Jones and N. 3'. Hall,58 from an exchange reaction on platinumabove 1800°, find 7 p.p.m. Dole found a difference of 6 and Moritaand Titani 7 p.p.m.Further data have appeared on the deuterium content of normalwater. J. L. Gabbard and M. Dole 59 find H/D = 690011 in LakeMichigan water, N. Morita and T. Titani,60 in tap water fromOsaka and from Cambridge, U.S.A., 6200/1, and L. Tronstad andJ. Brun,61 in water from Rjukan, 5960/1. The mean valueapproximates to 6000/1, rather greater than earlier estimates but notsufficient to affect the fourth decimal place in calculating the atomicweight of chemical hydrogen from mass-spectrum analysis.The relative abundance of the oxygen isotopes l60 and l80 is nowconsidered to be expressed more exactly by the value 530 & 10found by W.R. Smythe 62 than by the older value of R. Mecke andW. H. J. Childs, zlix., 630 &- 60.63 The factor for correction to thechemical scale hence becomes 1.000275.In the last two years a number of papers have been publishedby E. Moles and his pupils 38* 64 on normal and limiting densitiesof gases and the atomic weights derived from them. Moles has5 6 See Ann. Reports, 1936, 33, 141. 6B Naturwiss,, 1937, 25, 170, 189.6 7 J.Res. Nat. Bur. Stand., 1936, 1'7, 625.6o Bull. Chem. Boc. Japan, 1938, 13, 419.61 Trans. Paraday Soc., 1938, 34, 766.62 Physica;Z Rev., 1934, 45, 299. 2. Physik, 1931, 68, 362.64 E. Moles and T. Toral, Monatsh., 1936, 69, 342; E. Moles and J. Sancho,Anal. Fis. Qudm., 1934, 32, 931; 1936, 34, 865; E. Moles, J . Chim. physique,1937, 34, 49; Compt. rend., 1937, 205, 1391; E. Moles and C. Roquero, Anal.Pis. Quim., 1937, 35, 263; E. Moles and A. Escribano, Compt. rend,, 1938,207, 66; E. Moles and T. Salazar, Anal. pis. Quim., 1934,32, 954.6 8 J . Amer. Chem. Soc., 1937, 59, 259. 6s Ibid., p. 181132 INORGANIC CHEMISTRY.greatly improved the technique of the standard methods, and takeselaborate precautions t o avoid small errors. For instance, rubberconnexions carrying mercury are dispensed with.The mercuryin the manometer and the gas-leading tubes is kept at a constanttemperature either by water circulating from a thermostat or byimmersion in ice. Mercury never comes in contact with tap grease,No gas other than pure dry air ever enters the lower manometerchamber, and the gas pressurq in the density bulbs or volumeteris equalised through a gauge filledwith Apiezon oil. The employmentof fritted-glass filters prevents any oil or mercury fog from enteringthe density bulbs. Adsorption is measured for each gas on glassof the same composition as the density bulbs, and a correctionappropriate to the filling pressure is applied. Moles claims toreach an accuracy of about 1 part in lo5 in his density values.Thisis borne out by his work on oxygen.Since 1933 he has published with his co-workers five papers onthe density of this standard gas and made 99 determinations of thenormal litre weight. The results, which agree to a very closeapproximation, give as a mean the value 1.42894 & 0.00001 at O",sea level, lat. 45" (g = 9800616).I n these investigations there is always the possibility that thelimiting density values are affected by errors due to the form takenby the p y p graph in extrapolating to zero pressure. There is nouncertainty about the permanent gases, the pu-p values of which arelinear to a high degree, but with gases such as ammonia, sulphurdioxide, and carbon dioxide, which are easily liquefied, strictlylinear relationship cannot be assumed without strong evidence.A critical discussion 65 of this and of other sources of error, andalso of modern work on the physicochemical determination ofthe molecular and atomic weights of gases, has just been publishedby the Institut International de Cooperation Intellectuelle as theresult of a meeting of a number of workers in this field.From general theoretical considerations, it would appear thatthe pv-p isothermals for liquefiable gases are slightly curved,the slope of the graph becoming smaller towards lower pressures.This curvature is small even with a gas like carbon dioxide, butW.H. Keesom 66 contends that it must be allowed for when resultsof the highest accuracy are required, and that the second term inequations of the type pv = A + Bp + Cp2, etc., which representsthe behaviour of gases at high pressures, is of significance from 1atmosphere downwards." Les Determinations physico-chimiques des Poi& Moleculaires etAtomiques des Gaz," Paris, 1938.6 6 Ibid., pp.105-109 and 165WRYTLAW-GRAY : ATOMIC WEIGHTS. 133Direct experimental results in the neighbourhood of 1 atmosphere,such as those of W. Cawood and H. S. appear to givea linear pv-p relationship. It is doubtful, however, whetherany data are yet available of sufficient accuracy to detect a slightcurvature with certainty. W. H. Keesom points out that Moles'sresults for carbon dioxide, ammonia, and silane, when extrapolatedon a pv-p basis, although apparently linear, can be representedequally well by an equation of the second degree.Moles,68 however,finds that the densities per unit pressure of all the liquefiable gasesexamined, i.e., carbon dioxide, ethylene, silicon tetrafluoride, andammonia, are a linear function of p to a high order of accuracyover the pressure range from 1 t o 1 /4 atmosphere.The extrapolation of the " litre weights " determined at pressuresfrom 1 to 1/4 atmosphere and reduced afterwards t o unit pressure,i.e., 1 atmosphere, as a linear function of p is not equivalent to alinear extrapolation of pv. The first assumes Wlpv and the secondpv/W to be linear, where W is the weight of the gas in litres fillingthe density bulb a t 0". Actually,the differences between the two methods of extrapolation are small,and again it may be doubted whether the accuracy of the experi-mental data is sufficient to decide between them. D.Berthelot'soriginal assumption was that, for the permanent gases at least,pv-p was strictly linear. Nobody would wish to dispute thisnow, but further experimental work of a, high order of precisionon the compressibilities of the liquefiable gases is clearly desirable.The method of '' limiting pressures " G9 would appear in this connexionto be superior to that of '' limiting densities " since it allows gases tobe compared a t lower pressures and so avoids so long an extrapol-ation. In comparison with the older methods it has the sole dis-advantage that the microbalance requires a careful surface compens-ation to eliminate the effect of adsorption on account of the greaterratio of surface to volume in small bulbs.On the other hand,adsorption on vitreous silica is less than on glass.In the publication cited 65 new results for silane and hydrogensulphide are reported by R. Whytlaw-Gray and W. Cawood and byCawood; using the silica microbalance, they give Si = 28.112 andE. Moles also reports fresh results with arnmonia,70 silicontetrafl~oride,'~ sulphur and hydrogen sulphide. From13' J . , 1933, 619.13* Op. cit., pp. 185-192.13* W. Cawood and H. S. Patterson, PhiE. Tram., 1936, A, 236, 77.7 0 E. Moles and J. Sandro, And. Pis. Quim., 1936, 34, 866.'1 E. Moles and T. Toral, 2. anorg. Chem., 1938, 236, 225.72 E. Moles, T. Toral, and A. Escribano, Compt.r e d . , 1938, 206, 1726.They cannot both be linear.S = 32.065134 INORUANIC CHEMISTRY.the limiting densities, he h d s S = 32.062 (SO,), S = 32.065 (H,S),N = 14.008, and F = 18.995. A. 0. Nier from his abundanceratios finds S = 32.064.I n calculating the value for fluorine from silicon fluoride, Molestakes Si = 28.104, a value distinctly greater than the internationalvalue Si = 28-06, but which is supported by the work of P. F.Weatherill and P. S. Brundage 73 and also by that of 0. Honigschmidand M. Steh~heil.~~ The mass-spectrum value is Si = 28.12,calculated from Aston's latest values for 28Si and 29Si, for 30Si thevalue from energy changes and for the abundance ratios the figuresgiven in the third report of the Committee on Atoms of the Inter-national Union.75 If reliance can be placed on the accuracy of theabundance ratios the current value for the atomic weight of siliconwould appear to be too low.I n addition to the investigations mentioned, new chemical workon the atomic weights of the following elements has also beenpublished during the period under review : arsenic, 76 aluminium,77radiogenic leads,78 lead,79 lutecium,sO and ruthenium.81R.W.-G.3. THE SEPARA'I'ION O F ISOTOPES.Since F. W. Aston's announcement in 1913 that a partial separ-ation of the isotopes of neon had been effected, many attempts toseparate the isotopes of the stable elements have been made. Thework done in this field up to 1933 has been reviewed by Aston'l andhis survey of the separations actually achieved to that date " showsthat from the practical point of view they are, with two exceptionsvery small.I n cases where the method can deal with fair quantitiesof the substance, the order of the separation is small, while in thecase of complete separation the quantities produced are insignifi-cant." The two exceptions referred to by Aston are the separationof the neon isotopes by continuous diffusion and of the hydrogenisotopes by electrolysis. The progress made in separating hydrogenand deuterium has been described in recent Annual Reports and73 J . Amer. Chem. SOC., 1932, 54, 3932.74 2. anorg. Chem., 1924, 141, 101.76 J. H. Khpelka and M. KoEnar, CoZZ. Czech. Chem. Comm., 1936, 8, 485.7 7 J. I. Hoffmann and G. E.F. Lundell, J . Bee. Nat. Bur. Stand., 1937, 8, 1.78 G. P. Baxter, J. H. Faull, jun,, and F. D. Tuemmler, J . Amer. Chem. Soc.,1937,59,702; G. P. Baxter and W. M. Kelley, ibid., 1938, 60, 62.7g J. P. Marble, ibid., 1937, 59, 653.76 J . , 1938, 1110.0. HCmigschmid, Natumuiss., 1937, 25, 748.K. Gleu and K. Rehm, 2. anorg. Chem., 1938, 235, 352.1 " Mass Spectra and Isotopes," 1933, pp. 219-233.a Ann. Reports, 1935,32,41; 1937,34,32WALKER : THE SEPPARATION OF ISOTOPES. 135will not come within the scope of the present article. The success-ful separation of the hydrogen isotopes by means of electrolysis anddiffusion undoubtedly stimulated the efforts to increase the separ-ation of the isotopes of other elements, and considerable progress inthis direction has been made since the publication of Aston’s survey.The ultimate goal of complete separation, however, has beenachieved with only a very limited number of elements. An ex-cellent summary of the results obtained up to 1936 has beenpublished by G.Cham~etier.~Although the methods leading to the partial or complete separ-ation of isotopes are of interest in themselves, there are many im-portant applications of the results of such separations in chemistry,physics, and biology. In the first place one may quote Aston’sremark that “ in physics all constants involving, e.g., the densityof mercury or the atomic weight of silver may have to be redefined,while in chemistry reconstruction may be necessary for that partof the science the numerical foundations of which have hithertorested securely upon the constancy of atomic weights.’’ Accordingto H.C. Urey and L. J. GreiffS5 owing to the possibility of isotopicseparation occurring in chemical reactions, there is a “ limit to theprecision with which atomic weights may be determined and thislimit has already been reached for several of the lighter elements.”There are, moreover, many problems in the fields of nuclear trans-formations, radioactivity, and spectroscopy which can be completelyor partly solved by using separated isotopes. The use of fraction-ated isotopes as indicators in the study of chemical exchangereactions and biological processes is becoming of increasing impor-tance, and in this type of work even partly separated isotopes willin many cases provide a useful tool.It should be borne in mindthat what is meant by an appreciable separation ‘‘ depends upon theuses for which the isotopic mixtures are being prepared. If theprincipal purpose is to study the properties of pure isotopic com-pounds a nearly complete separation is desiked. On the other hand,if they are to be used as tracers or for studying many exchangereaction problems, the extent of the separation is determined by thedilution factor in the experiments and the sensitiveness of themethod of analysis.’’ Another factor of practical importance isthe length of time required to effect a separation of amounts ofmaterial which are sufficient for the special application.In the literature dealing with the separation of isotopes, theBull. SOC.chim., 1936,3, 1701 ; cf. also Ann. Reports, 1937,34,43; 1935,Op. cit., p. 219.H. C. Urey, J. R. Huffman, H. G. Thode and M. Fox, J . Chern. Physics,32, 51.J . Amer. Chem. SOC., 1935, 57,321.1937, 5, 857136 INORGANIC CHEMISTRY.extent of separation of a mixture of two isotopic elements or com-pounds is commonly expressed quantitatively by means of a separ-ation or fractionation factor. If, for example, n, and n2 are thenumbers of light and heavy atoms in a mixture before, and N, andN , the corresponding numbers after, a single separation process,then, if N1/N,>n1/n2, the separation factor for the light isotope isdefined as q = (N1/N2)/(n1/n2). This simple-process separationfactor must be distinguished from the total or over-all enrichmentfactor, A , which expresses the results of a number of successiveseparation stages.In general, if there are x single stages, A = p.It will be convenient to deal in turn with the more importantseparation methods and to describe briefly the results achieved ineach case, with special reference to the period since 1933.(1) Separation by Means of Mum-ray Analysis.-It was realisedquite early that one of the most promising methods for the completeseparation of isotopes would consist in the adaptation of the massspectrograph itself for this purpose. In the ordinary forms of thisinstrument separation of the atoms according to their masses doesoccur, but the amounts which are separated even in a few hoursare very small since the positive-ion beams are of the order of 10-8amp.or less. Attention has been directed, therefore, to increasingthe ion beam capacity. The earlier attempts of M. Morand toseparate the isotopes of lithium and of K. P. Jakowlew to separatethose of neon by mass-spectrograph methods did not give anysignificant separation.The first successful results by this method were obtained in 1934by M. L. Oliphant, E. S. Shire, and B. M. Crowther in the Caven-dish laboratory, and by W. R. Smythe, L. H. Rumbaugh, and S. S.West 10 in California. The Cambridge workers described two massspectrographs using the combined action of crossed electrostatic andmagnetic fields, by means of which the isotopes 6Li and 7Li wereseparated in quantities of about g.The lithium ions wereobtained from a platinum filament coated with a mixture of3Li2C03,A1203,3Si02 and activated by preliminary heat treatment.An ion current of several hundred micro-amps. could be taken fromsuch a source for several hours. In one form of the apparatus thebeam of lithium ions was passed through a magnetic field of 4000gauss and an electric field, which was so adjusted as to allow theions of one isotope t o follow a straight path through the narrowchannel formed by the edges of the electrically charged plates,Compt. Tend., 1926,182,460; Ann. Physique, 1927,7, 164.a Z. Physik, 1930,64,378.* PTOC. Roy. SOC., 1934,146,922. 10 Physical Rev., 1934,45, 724WALKER : THE SEPARATION OF ISOTOPES. 137while the ions of the other isotope were deflected and preventedfrom passing out of the end of the channel.The isotopes werecollected one at a time on small metal plates carried on a glass tubefilled with liquid nitrogen. After collection, the isotopes were fixedby admitting a puff of hydrogen chloride into the apparatus to formlithium chloride. The completeness of the separation effected wasconfirmed by bombardment experiments with protons and deu-terons, the range and nature of the resulting particles being charac-teristic of the particular isotope.In the high-intensity mass spectrometer devised by the Americanworkers, positive ions from an extended source of comparativelylarge area were focused electrostatically to form a nearly planebeam, which was then passed through a magnetic field whose boun-daries were so shaped that all particles of a certain mass werefocused on a slit beyond the field. The highest convenient ioncurrent obtainable was 0.1 milliamp., which deposited 1 mg.of 39Kin 7 hours. Practically complete separation from 41K was obtained.In similar experiments with lithium ions, several samples of 6Li and7Li of about 1 pg. were collected. Quantities of 18 pg. of 6Li and200 pg. of 7Li were also prepared by L. H. Rumbaugh and L. R.Hafstad l1 for disintegration experiments.An interesting application of the use of pure isotopes separatedby means of a high-intensity mass spectrometer is furnished by thework of W. R. Smythe and A. Hemrnendinger,l2 who were able toobtain quantities of the order of several mg.of the three isotopes ofpotassium having mass numbers 39,40, and 41. Activity measure-ments with these samples showed that only 40K is radioactive:The same workers l3 further improved the resolving power of theirinstrument and separated the isotopes of rubidium. Measurementsof the radioactivity of samples collected at masses 84, 86, 87, 88,and 90 proved that only 87Rb is active. W. Walcher l4 has alsodescribed a mass spectrograph of high intensity by means of whichsamples of 90 pg. of 85Rb and of 30 pg. of 87Rb were collected inabout 15 hours. In this case the purity of the products was shownby investigation of the hyperfine structure of the Rbr resonanceline a t 7800 A.An improved but still comparatively simple mass spectrograph,similar to those described by M.L. Oliphant and his co-workers,has been used recently by E. L. Yates l5 for the separation of 30 pg.of 7Li and of 2 pg. each of loB and llB, as well as for the preparationl1 Physical Rev., 1936, 50, 681.l2 Ibid., 1937, 51, 178. l3 I b i d . , p . 1052.l4 Physikal. Z., 1937, 38, 961; 2. Physik, 1938, 108, 376.l5 Proc. Roy. Soc., 1938, 168, 148138 INORGANIC CHEMISTRY.of several pg. of 12C free from 13C. The separated isotopes obtabedin these experiments were examined in disintegration experimentsand found to be very pure.Summing up the work carried out so far on the separation ofisotopes by the use of high-capacity mass spectrographs, it may besaid that the method gives separated isotopes of a high degree ofpurity.Although the yields obtained are small and of no use forchemical experiments, they are sufficiently large to be of value formany physical purposes.( 2 ) Separation by Means of Diffwion Methods.-(a) Hertz'smethod. Since the rate of diffusion of gases through an aperturewhich is small in comparison with the mean free path of the mole-cules is inversely proportional to the square root of the mass of themolecules a change in composition must occur when two or moregases which differ in molecular weight are allowed to diffuse throughsuch an aperture. This was the principle first applied by Aston inhis early attempts to separate the isotopes of neon of masses 20 and22. Diffusion was allowed to take place through a porous materialsuch as pipe-clay.The difference in mass of the components of anisotopic mixture is in general small, and only a very slight separationis obtained in a single process. Fractionation methods must there-fore be resorted to. The weakness of the earlier diffusion experi-ments of Aston and of others lay in the use of only one fractionationunit in a single operation. The technique was enormously improvedin 1932 by G. Hertz,16 who introduced the use of porous-walleddiffusion units so designed that a number of them could be used in'series. Mercury-diffusion pumps were incorporated in the appar-atus to circulate the gases through the various units, thus makingthe whole process continuous and automatic. At one end of theseries of pumps the gas becomes enriched with respect to the heaviercomponent; at the other end it is enriched with respect to thelighter constituent.Since the system is a closed one, eventuallya state of equilibrium is reached in which the composition of thegas mixture circulating in the various units changes progressivelyfrom one unit to the next. As the total separation factor increasesexponentially with the number of units, in principle any desiredseparation can be obtained by using a sufficient number of them.With his first apparatus consisting of 24 units Hertz was able toobtain, in addition to the results with hydrogen, a considerableseparation of the two main isotopes of neon. A later apparatus,17using about 50 stages, by means of which pure hydrogen and16 8.Physik, 1932, 79, 108.17 H. Harmsen, ibid., 1933,82,589; H. Harmsen, G. Hertz, and W. Schiitze,ibid., 1934, 90, 703WALKER : W E SEPAFCATION OF ISOTOPES. 139deuterium were prepared, also gave practically pure 22Ne. D. E.Wooldridge and F. A. Jenkins have described a similar apparatuscontaining 34 porous-walled units with which they obtained gaseousmethane having 16% of 13CH4 instead of the normal 1%. Theyhave also reported the concentration by this method of 15N innitrogen from the normal 0.6% to 6%.The difficulty of preventing the accumulation of impuritiesduring operation of the porous-walled units led G. Hertz l9 to modifythe technique of the diffusion method. In the more recent forms ofapparatus the porous tubes are dispensed with, and use is made ofthe stream of mercury vapour in the pump as the diffusion medium.The essential principle of the modified Langmuir pump devised byHertz is that only the centre portion of the stream of mercuryvapour is used to pump away the gas, which has to diffuse throughthe mercury vapour stream in a direction perpendicular to it.Thegreater the diffusion velocity of the gas, the more it will penetrateinto the centre of the mercury vapour stream, which will thereforebe enriched with respect to the lighter component of the gas. Apartfrom this modification in the nature of the diffusion medium, thetechnique of the newer method is much the same as in the porous-walled type, and a large number of pumps is used in series.Thesame over-all separation factor is achieved in a shorter time in thenewer apparatus. The degree of enrichment will depend, of course,on certain factors, such as the diffusion constant of the gas beingused, the streaming velocity of the mercury vapour, and the geo-metrical dimensions of the pumps.20s21*22 Under the best oper-ating conditions the Hertz method is able to produce highly concen-trated or even completely separated materials, but the yields areonly of the order of a few C.C. (at N.T.P.) of enriched gas per 24 hours'operation.With the newer apparatus, G. Hertz l9 obtained a marked separ-ation of the isotopes 2oNe and 22Ne. Using a similar method,H. Barwich and W. Schiitze 23 separated normal argon ("A : 38A :36A = 99.64 : 0.06 : 0.30) into light and heavy fractions, whichwere found by means of mass-spectrograph analysis to contain90-89, 0-51, 8.6 and 99.74, 0.046, 0-23%, respectively, of the threeisotopes.H. Kopfermann and H. with the same appar-atus, carried out a 300-hour run in which the volume of gas at thePhysical Rev., 1936, 49, 404, 704; cf. also D. E. Wooldridge and W. R.Smythe, ibid., 1936, 50, 233.lo 2;. Physik, 1934,91, 810. 20 H. Barwich, ibid., 1936, 100, 166.21 R. Scherr, J . Chem. Physics, 1938, 6, 251.23 D. MacGillevry, Rec. Trav. chirn., 1937, 56, 330; Trans. Paraday SOC.,23 2. Physik, 1937,105, 395.1937, 33, 433.2o Ibid., 1937, 105, 389140 INORGANIC CHEMISTRY." heavy " end was replaced every 6 hours by normal argon. From1 litre of normal argon (at 700 mm.pressure) they obtained 500 C.C.(at 1 mm. pressure) of a mixture containing S6A and 40A in the ratio1 : 1. H. by diffusion of a sample of nitrogen containingabout 1.9% of 15N, got a product in which the concentration of theheavy nitrogen was increased to 20%. A battery of 51 Hertzpumps has also been used 26 to obtain a partial separation of WH4and WH4. A run of 30 hours' pumping yielded 300 C.C. of methaneat 1.8 mm. containing about 30% of 13C, as indicated by the inten-sities of the isotopic Swan bands.(b) &m2utionaZ diffusion. Although the attempts at separ-ating isotopes by centrifuging have been generally abandoned asimpracticable, the development of a new air-driven centrifuge hasencouraged J. W. Beams and his co-workersZ7 t o re-examine thefeasibility of the method.They have announced preliminaryattempts t o separate the isotopes of chlorine in the form of carbontetrachloride by a modification of a method fist suggested by R. S.Mulliken,28 using a vacuum type tubular centrifuge which separatessubstances of different molecular weight while in the vapour state.By this means carbon tetrachloride has been separated into light,medium, and heavy fractions, but in the preliminary papers no dataare given a8 to the extent of the separation achieved. The method,however, appears to be a promising one, since the separation is quitefast and comparatively large quantities can be centrifuged.(c) Thermal diflmion. K. Clusius and G. Dickel 29 have describedpartial separations of the isotopes of chlorine in hydrogen chlorideand of neon which depend, in part at least, on the application of theprinciples of thermal diffusion.In their apparatus a vertical hotsurface, consisting of an electrically heated wire, is placed oppositea cold surface, and between the two is a gas mixture. As a resultof thermal diffusion, the relative concentration of the heaviermolecules at the cold surface is greater than at the hot surface.In addition, owing t o a thermal syphoning effect, the gas rises at thehot surface, flows over to the cold surface at the top of the column,sinks down the cold surface, and at the foot flows over again to thehot surface. Consequently, two streams of gas are constantlymoving past one another which are not in equilibrium with respect26 Naturwhs., 1938, 28, 445.26 P.Capron, J. M. Delfoase, M. de Hemptinne and H. S. Taylor, J. Chem.Physics, 1938, 6, 656.*' J. W. Beams and F. B. Haynes, Phy&xzl Rev., 1936, 50, 491; J. W.Beams and A. V. Maaket, ibid., 1937,51,384; J. W. Beams and L. B. Snoddy,J. Chem. Physics, 1937, 5, 993.t 8 J . Amr. Chem. Soc., 1922,44,1033; 1923,45,1592.'@ Natuwiss., 1938, 26, 546WALKEB: THE SEPmA'MON OF ISOTOPES. 141to thermal diffusion. The simultaneous working of both processescauses an enrichment of the heavier component at the bottom andof the lighter component a t the top of the apparatus. With neona fraction was obtained from the " heavy " end of the apparatus inwhich the ratio of Z2Ne : 20Ne had been increased from the normalvalue of 1 : 9.28 to 1 : 2.20.Normal hydrogen chloride (23% H37Cl,77% H35Cl) gave a gas consisting of 40% H37Cl and 60% H35Cl atthe base of the apparatus(3) Separation by Means of Electrochemical Methods.-Thesuggestion that isotopes might be separated by electrolysis hadbeen made in 1923 by J. Kendall and E. D. C15ttenden.~~ Followingon the success with hydrogen and deuterium further attempts havebeen made to separate the isotopes of other elements by the electro-lytic method.The possibility of the electrolytic separation of the oxygenisotopes l6O and 1 * 0 (assuming 1'0 to be negligible in amount) wasdiscussed by E. W. Washburn and H. C. U r e ~ . ~ 1 I n the prolongedelectrolysis of ordinary water resulting in an enrichment withrespect to D,O, it is necessary to determine whether all the densityincrease of the water is due to deuterium or can be ascribed in partto the heavy oxygen isotope.The early experiments in this direc-tion led to rather conflicting results.32 It was shown, however,by P. W. Selwood, H. S. Taylor, J. A. Hipple, and W. Bleakney33that the failure of some of the earlier workers to obtain heavy oxygenenrichment in the water resulting from a number of electrolysisstages was due to equilibration of the oxygen isotope ratio in thewater to, or nearly to, that of the carbon dioxide used to neutralisethe concentrated alkali solutions before distillation, Experimentsin which neutralisation was accomplished by means of ammoniumchloride or hydrogen chloride showed that when 117 litres of 0 .5 ~ -sodium hydroxide were electrolysed with nickel anodes down to1 c.c., there was a steady but slow increase in concentration of l*O(determined by the mass spectrograph) from 0.202% to 0.222%,i.e., an increase of only 10% corresponding to a separation factor of1.01. H. L. Johnston34 carried out a fractional electrolysis ofpotassium hydroxide solution, using iron electrodes which wereknown to give a large separation of the isotopes of hydrogen. Thelight water from each stage was obtained by recombining the hydro-gen and oxygen from the first 25% of the electrolysis. Since threestages of electrolysis were known to reduce the deuterium contenta* Proc. Nat. A d . Sci., 1923, 9, 75.81 Ibid., 1932, 18, 496.52 Cf. refs. (33) and (36).33 J . Amer. Chem. SOC., 1935, 57, 642 ; Phy8ical Rev., 1935, 47, 800.34 J . Amer. Chem. SOC., 1935, 57, 484142 INORGANIC CHEMISTRY.of the recovered gases to a negligible amount, density changes inlater stages must result from the electrolytic separation of theoxygen isotopes only. In fact, during the first three or four electro-lyses the density of the light water decreased comparatively rapidly,after which there was a slower steady decrease with increasingnumber of electrolyses. From these experiments the separationfactor of l80 from l60 was found to be 1.008. W. H. Hall and H. L.Johnston35 also determined the amount of heavy oxygen in theelectrolyte from commercial cells which had been in continuousoperation for over seven years.The excess density due to 180gave a separation factor of 1.008. A somewhat greater value forthis separation factor has been obtained by L. Tronstad and J.B r ~ n , ~ ~ vix., 1.034, and other values have also been recorded.Undoubtedly, the value of the separation factor will depend on theconditions of electrolysis. It is clear, however, that the electrolyticmethod is not very practicable for the preparation of water con-taining heavy oxygen in high concentration. It has been estimated34that “reduction of the entire ocean by electrolysis to a residualcubic mm. would less than double the concentration of the heavyisotopes of oxygen,’’ unless, of course, electrode materials or otherconditions of electrolysis were found which gave a more efficientseparation.The electrolytic method of separating isotopes has been moresuccessful in the case of the element lithium, although in some ofthe earlier attempts no significant separation was obtained.37- 38, 39Recently, however, T.I. Taylor and H. C. Urey 4O and L. Holleck 41have shown that 6Li is deposited preferentially with respect to ‘Liat a mercury cathode, and have effected a partial but appreciableseparation of these two isotopes. Taylor and Urey electrolysed800 C.C. of a 10% solution of lithium hydroxide in a cell containinga nickel anode above a rapidly stirred mercury cathode, till onlyabout 1 g. of the hydroxide was left in the cell. Mercury wasallowed to flow continuously through the cell to remove the lithiumamalgam as it was produced. Twenty such runs were carried out,and the residual solutions were united, concentrated, and electro-lysed further.The ratio of the initial to the h a 1 residual lithiumwas about 600 : 1. Mass-spectrograph analysis showed that the86 J . Amer. Chem. SOC., 1935, 57, 1515.86 Trans. Faraday SOC., 1938, 34, 766; cf. a h N. Morita, J . Chem. SOC.37 J. Kendall, Proc. Roy. SOC. Edinburgh, 1937, 57, 182.s 0 A. Eucken and K. Bratzler, 2. physikal. Chem., 1935, A , 174, 269.so G. Champetier and P. Regnaut, Bull. SOC. chim., 1937, 4, 692.4 O J . Chem. Physics, 1937, 5, 697.I1 2. Elektrochem., 1938, 44, 111.Japan, 1936, 57, 176WALmR: THE SEPARATION OF ISOTOPES. 143ratio 7Li : 6Li, which was 12-5 : 1 in the hydroxide used, had beenincreased in the final residue to 14.2 : 1, corresponding to a simple-process separation factor of 1,020.Later experiments 42 withlithium chloride gave a fractionation factor of 1.039. Holleck alsoelectrolysed a solution of the chloride fractionally at a mercurycathode from which the deposited lithium was continuously removed.He concentrated 9000 g. of lithium chloride in three stages down toa final deposited fraction of 5.6 g., in which the lithium was foundto have an atomic weight of 6.894 compared with a value of 6.941in the original material. These figures correspond to an enrichmentof 6Li by 71% of the concentration originally present.G . N. Lewis and R. T. Macdonald 43 have obtained a marked separ-ation of the isotopes of lithium by a method which, though not adirect electrolytic one, depends on the difference in electrodepotential of the two isotopes.They showed that if fine drops oflithium amalgam are allowed to fall through a solution of a lithiumsalt, the ratio of 7Li : 6Li is not the same in the two phases, and 6Liis carried preferentially by the amalgam. They carried out theprocess in a fractionation column consisting of a vertical glass tube18 m. high and of 4 mm. internal diameter, which was filled with asolution of a lithium salt (the chloride in alcohol, or the bromide inalcohol-dioxan). Over half a ton of lithium amalgam ( 0 - 5 4 . 7 Mwith respect to lithium) was prepared, and in each experiment 10litres of the amalgam were used in a 24-hour run, after which thematerial at the foot of the column was removed for analysis.Inone of the best runs the atomic weight of the lithium in the saltfrom the foot of the column had been decreased from 6.940 to 6.855,i.e., an increase in the ratio of 6Li : 7Li from 1 : 11.6 to 1 : 5.1 hadbeen effected. This is an enrichment comparable with that ofHolleck.With lithium, therefore, quite considerable isotopic separationshave been achieved by electrolytic and electrochemical methods,and this work may lead to further attempts with other elements.The fractional electrolysis of a solution of mercurous nitrate hadbeen tried some years previously by J. Kenda11,44 who claimed tohave obtained a very slight separation of the mercury isotopes, butthe observed changes in density of the metal were disappointinglysmall.(4) Separation by Means of Fractional Distillation.-One of themethods tried by Aston in his first attempts to separate the isotopesof neon was that of fractional distillation over charcoal cooled in4 2 T.I. Taylor and H. C. Urey, J. Chem. Physics, 1938,6,429.43 J . Ame~. Chem. SOC., 1936, 58, 2519.44 Ibid., 1933,55,2612 ; see also ref. (37)144 INORGANIC CHEMISTRY.liquid air, but no measurable separation was achieved. The moresuccessful attempts of W. H. Keesom and H. van Dijk 45 by recti-fication of neon at or near its triple point, which were recorded byAston in his survey, have since been considerably improved upon.In a glass rectifying apparatus for the separation of relatively largequantities, fractions of atomic weight 20.091 and 20.574 (normalatomic weight, 20.183) have been obtained.46 In later experiments 47neon of atomic weight 21.157 was prepared.It may be recalledthat H. C. Urey and his co-workers effected the first concentrationof deuterium by the method of fractional distillation near the triplepoint. Small increases in the concentration of l80 have been foundin residues from the fractional distillation of liquid air and liquidoxygen.48~ 49* 50In 1933 G. N. Lewis and R. E. Cornish 61 announced that bymeans of fractional distillation they had produced small changes inthe density of water due t o separation of the isotopes of hydrogenand of oxygen. Since then several workers have tried to improvethe fractional distillation method for the preparation of water whichis denser than the normal owing to an increased concentration of theheavy isotopes of oxygen.Density increases due to concentrationof deuterium must, of course, be eliminated or allowed for, asin the electrolytic production of " heavy '' oxygen water. M. H.Wahl and H. C . Urey 52 measured the relative vapour pressuresof H2l6O and H2l8O by using a simple distillation process, inwhich case the ratio of the vapour pressures is equal to the simple-process fractionation factor q. They found that Q decreases from1.089 at 11-25' to 1.062 at 46.35", giving an extrapolated valueof 1.025 at 100". Since these values differ only slightly fromunity, efficient fractional distillation columns must be used inorder to obtain a reasonable separation of the oxygen isotopes.The conditions necessary to obtain the best results, and thedetailed working of a fractionating column, consisting of alternatestationary and rotating cones to provide a large surface, have beendescribed by J. R.Huffman and H. C. U r e ~ . ~ 3 During the timetheir still was run it produced about 200 C.C. of water containing0435% of H2180, and it is considered capable of producing water45 Proc. K . Akad. Wetensch. Amsterdam, 1931,34,42.4 6 Ibid., 1934, 37, 615.4a E. R. Smith, J. Chem. Physics, 1934, 2, 298.4g R. Klar and A. Krauss, Naturwiss., 1934, 22, 119.D. F. Stedman, Canadian J . Res., 1935,13, 114.61 J . Amer. Chem.SOC., 1933, 55, 2616.62 J . Chem. Physics, 1935, 3, 411.63 Ind. Eng. Chem., 1937, 29, 531 ; see also G. B. Pegram, H. C. Urey, and47 Ibid., 1935, 38, 809.J. R. Huffman, Physical Rev., 1936, 49, 883WALK.ER: THE SEPmATION OF ISOTOPES. 146three times as concentrated. A still built by H. E. Watson 54 hasalready given water with a, total increased density of 700 parts permillion (approximately half due to deuterium). D. F. Stedman 50has also recorded small separations of the oxygen isotopes by thedistillation of water. Although the concentrations of heavy oxygenwater obtained so far are not very large, they are sufficient for manypurposes, such as the study of oxygen exchange reactions in solution,55since measurements of the density of water can be carried outaccurately to 1 part per million.An attempt has also been made56 to concentrate 15N by thefractional distillation of liquid ammonia, but only slight separationhas been effected in the preliminary experiments.( 5 ) Separation by Chemical Exchange Methods.-The markeddifferences in chemical properties of hydrogen and deuteriumcompounds are now well known.Equilibrium constants involvinghydrogen and deuterium, calculated from statistical theory usingspectroscopic data, have in many cases been confirmed by experi-ment and have formed the basis of methods for separating the twoisotopes. In recent years, heterogeneous equilibria in exchangereactions involving isotopes of elements other than hydrogen havebeen used to effect isotopic separations.H. C. Urey and L. (7.Greiff showed theoretically that slight differences in the chemicalproperties of isotopic compounds of the lighter elements shouldexist, and calculated the separation factors of several exchangereactions. For example, the equilibrium between liquid water andgaseous carbon dioxidegives a separation factor of 1.047 at O", and favours the concentrationof l80 in the carbon dioxide. This was confirmed experimentallyby L. A. Websfer, M. H. Wahl, and H. C. U r e ~ . ~ ~ In most of theother examples given by Urey and Greiff the theoretical separationfactors are also small, and the separation that can be expected in asimple-process equilibrium of this type is very slight. To effectreasonable separations, the exchange of isotopes between the liquidand the gas phase must be allowed to proceed continuously in afractionating column in which counterflow of liquid and gas ismaintained.The principles and technique of chemical exchangeseparations are therefore essentially the same as those of fractionaldistillation. The process consists in the flow of liquid phase down-ward through a column of high efficiency, at the bottom of whichC1602 + 2H2180 e ClSO2 + 2H216054 Cf. S. C. Datta, J. N. E. Day, and C. K. Ingold, J . , 1937, 1969.6 5 See, e.g., ref. (64).5 6 M. H. Wahl, J. R. Huffman, and J. A. Hipple, J . Chem. Physics, 1936,3, 434. bv Xbid., p. 129146 INORGANIC CHEMISTRY.the gas from the liquid phase is liberated by boiling and returnedupward through the column.Preliminary experiments by H.C. Urey and his co-workers 58demonstrated the usefulness of chemical exchange methods forconcentrating the isotopes 15N and 13C, and improved separationshave since been obtained. Using the 35 ft. column originally devisedfor the fractional distillation of water,53 H. C. Urey, M. Fox, J. R.Huffman, and H. G. Thode 59 have studied the exchange reactionswith aqueous and alcoholic solutions, and1WH3 (gas) + 14NH4+ (soln.) 14NH3 (gas) + 15NH4+ (soln.)with solutions of the nitrate and sulphate. The two most successfulruns yielded 61 g. of ammonium chloride in which the nitrogencontained 2.5% of 16N (i.e., a 66fold increase), and larger amountsof not quite so concentrated material. By means of the exchangereaction between ammonia and ammonium nitrate, using an ar-rangement of two distillation columns in cascade, a 46-fold increasein 15N has now been effected and a sample containing 14.5% ofheavy nitrogen obtained.60 A column has also been designed togive a production of 1.5 g.of 15N per 24 hours in concentrations ofabout 60%. In the same paper a %fold increase in the concentrationof 34S in a solution of sodium hydrogen sulphate by exchangereaction with sulphur dioxide has been recorded, and further con-centrations are foreshadowed.An interesting application of chemical exchange methods in aliquid-solid system has been used by T. I. Taylor and H. C. Urey 4** 42to effect a partial separation of the isotopes of alkali metals. Thisdepends on the fact that when a complex hydrated aluminosilicate ofthe zeolite type is shaken with a solution containing an alkali-metalion, an exchange of the positive ion takes place, and partial re-placement occurs according to the equilibrium A+ + BZ = Bf + AZ.Taylor and Urey assumed that with a mixture of twoisotopes, e.g., 6Li and 7Li, one isotope would be taken up morereadily than the other. The fractionation factor for a single processis then given by the distribution of the two isotopes between the twophases, vix., q = (6LiZ/7LiZ)/(6Li+/7Li+). The value of q, how-ever, is only slightly greater than unity, as in most isotopic exchangereactions, and so the separation effect is multiplied by using long6 8 H. C. Urey and A. H. W. Aten, Physical Rev., 1936,50,575; H.C. Urey,A. H. W. Aten, and A. S. Keston, J . Chem. Physics, 1936,4,622.J. Amer. Chem. Soc., 1937, 59, 1407; me also ref. (6).6o H. G. Thode, J. E. Gorham, and H. C. Urey, J . Chem. Physics, 1938,6,296WALKER: THE SEPARATION OF ISOTOPES. 147columns of zeolite, about 30-100 feet long. If a solution oflithium chloride is added at the top of such a column originallyfilled with a sodium zeolite and distilled water, all the way down thecolumn one lithium isotope is held back more than the other, andthe fist lithium chloride coming through at the bottom should havea changed isotope ratio. Afterthe column has been converted into a lithium zeolite, a solution ofsodium chloride is passed through it. One lithium isotope is re-placed more readily than the other by the sodium ion, and the laatlithium chloride coming through, called the tailing sample, shouldhave the isotope ratio changed in the opposite direction to that ofthe leading sample.In other experiments the procedure was some-what modified by using the principles of chromatographic analysis.Taylor and Urey found that the normal ratio of 7Li : 6Li of 11.7 : 1(determined mass-spectrographically) was increased to 12.3-13.3 : 1 in the leading samples and decreased to 8-8-8-9 : 1 in thetailing samples. This means that 6Lif is preferentially taken upby the zeolite, and is not so readilyremoved as 7Li+. Further ex-periments on the influence of the solvent and of the specific natureof the zeolite are being made.The same general procedures were also tried for potassium andfor the nitrogen isotopes in the ammonium ion.I n both casessmall changes in the isotope ratio were observed, but in a directionopposite to that found with lithium, i.e., the heavier isotope wasmore readily taken up by the zeolite. This suggests that the pro-cess responsible for the fractionation is essentially an equilibriumone rather than one due to differences in the rate of diffusion orreaction, since, otherwise, the light isotopes would all diffuse faster,resulting in changes of the isotopic ratio in the same direction.Other chemical methods have been used to obtain small separ-ations of isotopes. For example, H. S. Taylor and A. J. Gould 61obtained a partial separation of the oxygen isotopes in the de-composition of 30% hydrogen peroxide in presence of colloidalplatinum. Slight fractionation of the isotopes of oxygen, chlorine,bromine, and nitrogen in chemical reactions have been reported byE.Ogawa,62 and R. S. Bradley 63 observed a small chemical separation of the chlorine isotopes when carbon tetrachloride was heatedwith sodium amalgam. The reaction 4Na + CCl, = C + 4NaC1occurs almost quantitatively, and the S5Cl reacts preferentially to(6) Separation by Photochemical Methods.-These have not re-ceived much further study, and brief mention will be made only of63 Nature, 1936, 137, 403.This is called the leading sample.37~1.61 J . Amer. Chem. SOC., 1934,56, 1823.62 Bull. Chem. Soc. Japan, 1936, 11, 420148 INORGANIC CHEMISTRY.two other papers in which the separation of isotopes by photo-chemical means has been reported since the publication of Aston’ssurvey.W. Kuhn and H. Martin 64 have published a more detailedaccount of their method, which resulted in a partial separation ofthe isotopes of chlorine. A photochemical method has also beenused by K. Zuber 65 to effect a partial separation of 2mHg and 202Hgby selective irradiation of ordinary mercury vapour with twocomponents of the mercury resonance line at 2537 A.In the experiments carried out so far on the separation of iso-topes, only about 16 elements have been used. An examinationof the International Table of stable isotopes for 1938 66 shows that,of the elements from hydrogen to bismuth in the Periodic Table,about 20 are simple, i.e., are represented by only one mass number.The remaining elements are complex and consist of from 2 to 10isotopes, the lighter elements usually having not more than 2 or 3isotopes.With the doubtful exception of the mass number 5 ,which may belong to an isotope of lithium, all the mass numbersfrom 1 to 209 have been appropriated by known stable isotopes.Some mass numbers are represented more than once, owing t o theexistence of isobares, and in the 1938 table about 270 differentkinds of atom are included in the above range of mass number.It is obvious, therefore, that in the attempts to separate the iso-topes of individual elements there is still a very large field forexperiment, and no doubt further advances will be made duringthe next few years.0.J. W.4. POLYNUCLEAR METALLIC COMPOUNDS.Our knowledge of polynuclear metallic compounds is a t presentconfined largely to compounds in which the metallic atoms show acovalency of 4 or of 6. Werner investigated the 6-covalent metalliccompounds in some detail, and showed that the two (or more)octahedra could be linked through one, two, or three “ bridging ”groups. The chief bridging groups known to Werner were:-OH, -0-, -02-, -NH,, -NH-, -NO,, and a compound such as8hO/(NH,),Co’ ‘ Co(NH,), Br, he termed octammino-p-dihydroxy-H c -J dicobaltic tetrabromide, the symbol p indicating the bridgingG4 2. physikal. Chem., 1933, B, 21, 93. 6s Nature, 1935, 136, 796.6 6 0. Hahn, Ber., 1938,7’1, 1 ; also Union Internat.Chim., 1938, pp. 3-14MANN : POLYNUCLEAR METALLIC COMZ'OUNDS. 149groups. The study of similar derivatives of 4-covalent metals hadbeen largely neglected until recently, and this Report is confinedtherefore mainly to the considerable progress which has been achievedin the elucidation of the structure of the polynuclear 4-covalentmetallic compounds during the last few years.Since 1857, when H. St. C. Deville and L. Troost showed that thevapour densities of aluminium and ferric chlorides corresponded to&,CIS and Fe,C16 respectively, it has been recognised that moleculesof certain metallic chlorides can unite in pairs, and P. Pfeiffer 2 firstsuggested the structure (I) for aluminium chloride. Decisiveevidence for this bridged structure has now been obtained forderivatives of gold, palladium, aluminium, cadmium, and mercury,and considerable evidence has also been obtained for derivatives ofplatinum, zinc, copper, and silver.These metals will be discussed inturn.Gold.-The vapour density of auric chloride between 150" and260" has been shown by W. Fischer3 to correspond to thec1, p. /c1 Br\ /Brq /Br Et\ /$$Br% / Etcl/A1~\tcl;AL\cI Br/Au kBrPU\Br WBr/ 'Et(1.1 (11.) (In. 1bimolecular form Au,CI,, and the molecular weight of auric bromidein boiling bromine has been shown by A. Burawoy and C. S. Gibson *to correspond similarly to Au2Br6, which is formulated as (11)." Diethylmonobromogold," originally prepared by C. S. Gibson andW. J.Pope,5 has been shown by Gibson and his co-workers to havea molecular weight corresponding to [Et2AuBrl2 in benzene andbromoform, and the bridged structure (111) was therefore allotted tothis compound. This structure for the crystalline compound wasdecisively proved by X-ray analysis,' which showed that themolecule was planar and that the intervalency angles in the ringwere those shown in (111). The compound should therefore betermed tetraethyl-p-dibromodigold. " Monoethyldibromogold " 6also showed in bromoform solution a molecular weight correspondingto [EtAuBr,], and was therefore formulated as the unsymmetrical(IVA) and the symmetrical form (IVB), the latter being theoreticallycapable of cis-trans-isomerism. Only one form was actuallyisolated, however." Di-n-propylcyanogold " proved to have themolecular formula [Pr2AuCN],, and the structure (V) having aEt,A~m*;<T) AUCompt. rend., 1857, 45, 821.* Werner-PfeiEer, " Neuere Anschauungen auf dem Gebiete der Anorgan-ischen Chemie," 6th Edition, 1923, p. 285.2. anorg. Chem., 1929, 184, 333. J., 1935, 217.ti J., 1907, 91, 2061. J., 1930, 2531; 1934, 860I60 INORQANIC CHEMISTRY.planar 12-membered ring was allotted to it.? Decisive evidence forthe structures (IV) and (V) has not yet appeared.Pr,Au-CN+AuPr2I CN+ Br Et, /Brk /Br N I + Et\*u/Brk*u/ AuEt’ hBr’ \Br Br/ hBr/AU\EtPr2 u+NC-AuPr,(ma. 1 (WB. 1 (V. )Palladium and Platinum.-It has been known for many yearsthat platinum, when heated with phosphorus pentachloride,gave two compounds of composition [(PCl,),PtCl,] and[(PCl,)PtCl,].These reacted with alcohols (ROH) to give thecorresponding ester derivatives, whose molecular formul2e wereshown to be [{P( OR),),PtCl,] and [{P( OR),)PtCl2I2, respectively.Palladium gave analogous derivatives.F. G. Mann and D. Purdie 8 have prepared similar “ bimolecular ”compounds of aliphatic tertiary phosphines and arsines by theinteraction of the corresponding dichlorobisphosphine( or arsine)-palladium and ammonium palladochloride in alcoholic solution :[(R,P),PdCl,] + (NH,),[PdCl,] = [R3P,PdCI2], + 2NH4C1The arsine compounds were also prepared by thermal decom-position :Z[(R,As),PdCl,] = [R,As,PdCl,], + R,Asa method which cannot be employed for the phosphine derivatives,since the compounds [ (R,P),PdCl,] distil unchanged on heating.The phosphine- and arsine-dipalladium compounds so obtainedcrystallise readily from many organic solvents and usually havesharp m.p.’s, and the first detailed study of the structure andreactions of a series of bridged dimetallic compounds has thus beenpossible.These bridged phosphine and arsine compounds can theoreticallyexist in the unsymmetrical (VIA) and in the cis- and trum-symmet-rical (VI, B and c) forms. In the crystalline state only one formoccurs : since, however, the crystalline n-propyl (and the n-butyl)phosphine and arsine derivatives are isomorphous, corresponding7 A. Burawoy, C. S. Gibson, G. S. Hampson, and H. M. Powell, J . , 1937,1690.J . , 1936, 873MANN : POLYNUCLEAR METALLIC COMPOUNDS.151phosphine and arsine compounds must have the same structure, anddifferences in reaction must therefore be due essentially to differences1 c1‘Pd/ ‘Pd’C1’ \Cl/ \PR,(VIC.) JInteratomic distances (A.) :Pd-Br, 2.45 ; Pd-As, 2.50 & 0.05 ;Pd-Pd, 3.55.(VII. )in stability. Similar bridged compounds containing the bromine,iodine, nitro-, and thiocyanato-radicals have also been prepared.A detailed crystallographic examination proved that the iso-morphous trimethylarsine tetrachloro- and tetrabromo-compounds,[ (Me,As),Pd,X,], possessed planar molecules of the trans-symmetrical type, the dimensions of the tetrabromo-molecule beingshown in (VII).gThere is evidence, both physical and chemical, however, thatthese dipalladium compounds, although crystallising in only oneform, give in organic solvents a tautomeric mixture of the threepossible forms (VI; A, B, and c).A. E. Finn has found the dipolemoment of the n-butylphosphine derivative, [ (Bu,P),Pd,Cl,], inbenzene a t 25” to be 2-34 D., and that of the arsine derivative,[(Bu,As),Pd,CI,], to be 2-52 D. The expected moments, if thesecompounds existed in each of the three forms, would be, for theunsymmetrical form (VIA), 12-14 ; for the cis-symmetrical (VIB),7-8 ; for the trans-symmetrical (VIc), 0. The experimental valuesindicate therefore a mixture either of (VIB) and (VIc), or of all threeforms.The chemical evidence for the existence of the symmetrical forms(VI, B and C) in solution is summariaed under two headings :(i) The butylphosphine (or arsine) compound, when treated incold solution with two equivalents of a monoacid base, e.g., p -toluidine, gives solely two molecules of the very soluble compound(VIII), the bridged ring splitting diagonally as shown.The sameproduct would clearly be given by the cis-symmetrical form (VIB),since in unbridged non-chelated palladium compounds such as(VIII), the interconversion cis tram occurs a t room tempera-ture, the more stable tram-form being usually the sole final product. lo0 F. 6;. Mann and A. F. Wells, J., 1938, 702; A. F. Wells, Proc. Roy. Soc.,l o F. G. Mmn, D. Crowfoot, D. C. Gattiker, and N. Wooster, J., 1935, 1642.1938, A , 167, 169152 INORGANIC CHEMISTRY.The t etranit ro- compound, [( Bu,P),Pd,( NO,),], similarly gives[(Bu,P)(C,H,,Me~NH,)Pd(NO,),], and in both reactions the p -toluidine may be replaced by aniline, pyridine, or quinoline.Inview of the evidence given below for the facile interchange of groups,both bridged and unbridged, in the dipalladium compounds, thisreaction with p-toluidine has a further significance, in that it showsthat the scission of the bridged compounds must be severely con-trolled by specific factors : if the groups concerned were entirelyfree for mutual rearrangement, the reaction would proceed as inequation (l), since the second of these dichloro-compounds is almost[(Bu3P)ClPdCI,PdC1(PBu3)] L-’-j [ (Bu3P),PdCI,] +insoluble in the usual solvents employed.(ii) The butylphosphine tetrachloro-compound gives a similarreaction with ammonia, but all the chlorine is evicted from the com-plex, giving the triammino-compound (IX), a reaction which isreadily reversed by hydrochloric acid.The compound (IX) is20 H MeNH[(C,H4Me*NH2)2Pdcl,l (1)C(Bu3P) (NH3)Pdcl21 (X).unstable on prolonged exposure to air, losing two molecules ofammonia and giving the non-ionic monoammino-compound (X),which in turn, under the influence of a vacuum or of hydrochloricacid, readily regenerates the original bridged tetrachloro-compound.The chemical evidence originally adduced by Mann and Purdiefor the existence of the unsymmetrical form (VIA) was based partlyon two reactions. When the butylphosphine tetrachloro-compoundwas treated in solution with one equivalent of ad-dipyridyl, itappeared to undergo a simple ‘‘ vertical splitting ” (2).Further-more? the tetrachloro-compound when treated with potassiumoxalate gave the bridged dichloro-oxalate (XI), in which the oxalategroup in accordance with previous experience was considered to bechelated to one palladium atom by the normal operation of twocovalencies, thus necessitating the unsymmetrical structure.This structure was apparently confirmed by the fact that thedichloro-oxalate gave a similar reaction with dipyridyl (3), thMANN : POLYNUCLEAR METALLIC COMPOUNDS. 153unbridged dichloride and mono-oxalate being formed. Preciselyparallel reactions were given also by the butylphosphine tetranitro-compound. The dipole moment of the dichloro-oxalate was found,however, by Finn to be 3.55 D., whereas the structure (XI) would[(Bu3P),PdC1,1PdC12] + dpy = [(Bu,P)~P~CI,] + [dpy PdCI,] .(2)require it moment of 12-14 D. Hence Finn suggested that theoxalate group bridged the palladium atoms in the dichloro-oxalate,which could therefore exist theoretically in the unsymmetricalform (XIIA) and in the cis- and trans-symmetrical forms (XII, Band c). A tautomeric mixture of these three forms would explain,(XIIa. ) (XIIB.)the observed moment. The dichloro-oxalate has therefore beenfurther investigated by J. Chatt, P. G. Mann, and A. F. Wells,llwho find that the Pd-Pd distance in this compound is 5 . 4 8 ~ .Now when the palladium atoms are bridged by chlorine atoms,gthe Pd-Pd distance is known t o be ca.3.4 A. ; if, however, thepalladium atoms are bridged by an oxalate group, the calculatedPd-Pd distance is ca. 5.3 A. Furthermore, the crystallographicevidence shows almost certainly that the molecule has a centre ofsymmetry. The oxalate group therefore must bridge the palladiumatoms, and the molecule in the crystal probably has the trans-symmetrical structure (XIIc).In addition, the dichloro-oxalate reacts with two equivalentsof p-toluidine thus :2C,H,Xe-NH, [ (BU~P)C~P~C~O,P~CI(PBU~)] - ->[ (Bu,P)(C6H4MeoNH2)PdC2O4] + [(Bu,P)(C6H4MeDNH,)PdCI,]The interpretation of this reaction is very diEcult on the basis ofstructure (XI), but relatively simple on that of (XIIc). It is clear,however, from the structure of the dichloro-oxalate that the actionl1 J., 1938, 2086154 INORGANIC CHEMISTRY.of dipyridyl cannot be the simple “vertical splitting’’ shown in(2) and (3), and that these reactions cannot be cited as evidence forthe unsymmetrical structure (VIA).The probable mechanism of theaction of dipyridyl and of p-toluidine is discussed by these authors.The chief chemical evidence for the unsymmetrical structure istherefore the following :(i) The butylarsine tetrachloro-compound (isomorphous with thebutylphosphine derivative), when cautiously treated with ammonia,[(B%h)2PdCI21 [ (NH3)2PdC1z1Both products on exposure to air lose two mole-(ii) The same compound readily reacts with excess potassiumreacts as in (4).cules of ammonia as shown.nitrite, giving [ (Bu,As),Pd(NO,),] :[ ( Bu3As),PdC1,PdC1,] ---+ 6KNOP[(Bu3As),Pd(NO,),I + K,[Pd(NO2)41 + 4Kc1 - (5)(iii) The corresponding dichloro-dithiocyanate, in which the-SCN groups are known to bridge the palladium atoms, reacts withexcess potassium thiocyanate to give [(Bu,As),Pd(SCN),] :[ (Bu~As),P~(SCN)~P~CI,] ---+ CKGNS[(Bu,As),Pd(SCN),] + K,[Pd(SCN),] + 2KCI .(6)I n an attempt to synthesise a bridged compound which mustnecessarily have the unsymmetrical structure, J. Chatt and F. G.Mann l2 have prepared the disulphide compound (XIII), in whichR = Et and also n-octyl, the diarsine compound (XIV), and alsothe compound (XV), in which R = Me and also n-butyl. If theser R Ph Ph R R I \ / \ /H,F/’ pd/’l \ c i [H2c>qfl H,C/A”” pd/” \ C d [\)\AsH /\/*SkPd/CI \ C jPh Ph R/ \R(XIII.) (XIV.) (XV.)chelated compounds reacted with ammonium palladochloride, thebridged compounds so formed must have the unsymmetricalNature, 1938, 142, 709MANN : POLYNUCLEAR METaLLIC COMPOUNDS. 155structure ; actually, however, none of these compounds would formbridged derivatives. This inability cannot be due to the chelatedring as such, since several chelated-ring, bridged dipalladiumcompounds are known (e.g., XVI 13), in all of which, however, the(XVI.)chelated ring is joined to the metal by one co-ordinate and onecovalent link, and the symmetrical structure is thus possible.The three reactions given above provide very strong prima facieevidence for the unsymmetrical structure of the tetrachloro-com-pound. The failure to isolate a compound which must necessarilyhave the unsymmetrical bridged structure raises doubt, however,as to whether compounds possessing this structure are sufficientlystable to exist other than in solution, and then only in tautomericequilibrium with the symmetrical forms.Alternatively, the threereactions may be more complex than the equations indicate, andmay not therefore provide the required evidence.The remarkable mobility of the constituent groups in thesebridged palladium compounds has recently been demonstrated byJ. Chatt and F. G. Mann,l* who, by treating the butylphosphineEt Et -2 [ Bu3p4 pd/’ ‘ pd/“ ‘Pd’ S ‘Pd’ ;+ L Cl’ ‘C1’ ‘PBu, C1’ \S’ ‘PBu,Et(XVII. ) (XVIII. ) 1 (VIc.) rU3”Pd/ c1 ‘Pd’C1’ ‘Cl’ \PBu,tetrachloro-compound with ethylthiol, have prepared the compounds[(Bu3P),Pd2C13(SEt) J and [(Bu3P),Pd2Cl,(SEt),].The latter doesnot react with dipyridyl or p-toluidine, and therefore cannot possessthe PdC1,Pd ring, i e . , the -SEt radicals bridge the palladium atomsand the compound has the structure (XVIII). The mono-ethylthiol compound (XVII) in solution gives an equilibrium mixturel3 C. R. Porter, J., 1938, 368; see also Section 5 of this Report, p. 164.1‘ J., 1938, 1949156 INORGANIC CHEMISTRY.of the bisethylthiol compound (XVIII) and the original tetrachloro-compound (VIc). This is shown by considerable physical andchemical evidence : for example, when solutions of the bis-thiolcompound (XVIII) and the tetrachloro-compound (VIc) are mixed,the least soluble monothiol compound (XVII) crystallises out.Chemical reagents, however, shift the equilibrium point to the right,the monothiol compound (XVII) in solution reacting as a mixture of(XVIII) and (VIc).It is probable that the labile nature of the groups in these bridgeddipalladium compounds is not a specific property of the bridgedstructure as such, but is due primarily to the loose co-ordination ofgroups in complex palladium compounds generally.A detailed crystallographic investigation of palladium dichloridehas recently been made by A.I?. We1ls,l5 who found it to consistof long chains of palladium atoms bridged by chlorine atoms (XIX),the C1-Pd-C1 angle within the ring so formed being 87".TheJ (XIX.) (XX.)fact that the corresponding angle in the bridged trimethylarsinecompound (VII) is 86" confirms the essential identity of the ringstructure in the two compounds, and the PdCl, units in (XIX) aredoubtless united through a series of co-ordinate links as shown,although, of course, when once the chain is formed there is no essentialdifference between the links involved.The above work on bridged compounds elucidates the probableconstitution of many palladium and platinum compounds to whichunlikely structures have been attributed by past workers. Forinstance, A. Gutbier and C. Fellner l6 have described several saltsof amine hydrochlorides with palladium dichloride, to which theyassigned the general formula B,H[PdCl,]. It is almost certain thatthese compounds have the double formula (BH),[Pd,Cl,] and thestructure (XX), in which the anion contains two palladium atomsbridged through chlorine atoms.The formation of this [Pd,Cl,]ion enables each palladium atom to acquire the desired six electrons(precisely as in the above bridged phosphine and arsine compounds),and hence the bridging process presumably stops at this stage. Incrystalline palladium dichloride (XIX), the bridging process gives sixelectrons to each palladium atom with the exception of the terminalmetallic atoms, which acquire only four electrons. This deficiency ofelectrons on the terminal palladium atoms is thus probably intimatelyl6 2. Krist., 1938, 100, 189. l6 2. anorg. Chem., 1916,95,169MA" : POLYNUCLEAR METALLIC COMPOUNDS.157associated with the indefinite length of the bridged chain. Severalother palladium and platinum compounds, which past investigatorshave formulated as containing either direct metal-to-metal links oralternatively 5-covalent metallic atoms, are discussed by F. G. Mannand D. Purdie,8 and their probable bridged structure indicated.Aluminium.-Decisive evidence 1' has only recently been obtained(by electron diffraction methods) that aluminium chloride, bromide,and iodide have the bridged structure (I), the 4-covalent aluminiumcomplex being tetrahedral, and the unbridged halogen atoms beingtherefore in a plane at right angles to that of the ring.Cadmium, Zinc, and Mercury.-G. J. Burrows l8 and his co-workers have briefly described two types of complex compoundwhich phenyldimethylarsine gives with cadmium, zinc, andmercuric halides.The first is given the formula (PhMe,As),MX,,where M = Cd, Zn or Hg, and X = halogen, and the second theformula (PhMe,As)MX,. Although no molecular-weight deter-minations are recorded, the second type of compound undoubtedlyhas the bridged formulation (as VI), but owing t o the tetrahedraldisposition of these metallic atoms, the four terminal unbridgedgroups will lie in a plane at right angles to that of the bridged ring,as in aluminium chloride.The structure and reactions of the compounds which the lowertrialkyl-phosphines and -arsines give with the above metallic halidesare being examined in detail in the Cambridge laboratories.Cad-mium bromide is found to give three distinct derivatives : (i) Thenormal unbridged tetrahedral com-this should exist in three forms similarto (VIA, B, and c ) , but crystallo-Et3P\ Cd/ Br \ c-,/BJ? pound [ (R,P),CdBr,]. (ii) TheBr/ kBr/ sPEt, bridged compound [(R,P),Cd,Br,] ;graphic evidence shows that the ethyl compound has the trans-symmetrical structure (XXI). (iii) A compound of composition(R,P),(CdBr,), ; crystal analysis indicates that this " sesqui "product is a new type of complex compound, and not a latticecombination of two molecules of (i) with one of (ii).Mercuric halides also give phosphine compounds of types (ii)and (iii). The bridged derivative [ ( Pra3P) ,Hg,Br,] possesses acentre of symmetry and therefore also has the trans-symmetricalstructure (as XXI).The iodide, [(Pra3P),Hg,14], occurs in twocrystalline forms 9 of correct molecular weight, one colourless and theother yellow, but it is not yet certain whether they are isomericforms or merely dimorphic forms of the same substance.. Bridged1 7 K. S. Palmer and N. Elliott, J. Amer. Chem. SOC., 1938, 60, 1852.J . Proc. Roy. SOC. N.S.W., 1936, 'SO, 62, 218, 222.3 (XXI.158 INORGANIC CHEMISTRY." mixed-metal " compounds, e.g., [ (Pra3P)BrCdBr2HgBr(Pra3P)],have also been prepared and are under examination.Copper and Xiher.-Four-covalent copper appears t o form atleast three types of polynuclear compound.(i) The addition products of the lower trialkyl-phosphines and-arsines with the cuprous halides, previously considered to be[R,P(As)+CuX], have now been shown by Mann, Purdie, andWells l9 to have a fourfold molecule, the ethylarsine-cuprous iodideEt3 As(XXII.) Tetrakis(monoiodotriethy1arsinecopper).The broken lines represent the edges of the tetrahedron formed by the fourcopper atoms, the apex occupied by the central copper atom being tiltedforward to show a11 the four bonds joined to this atom.The iodine atombehind the rear face of the tetrahedron is not shown. The unbroken lineswithout barbs represent covalent links, those with barbs co-ordinate links.derivative thus being [ E~,AS+CUI]~. Crystallographic analysisof this compound showed that the four copper atoms occupy theapices of a regular tetrahedron (XXII); the iodine atoms aresituated each above the central point of one face of this tetrahedron,so that they also form a tetrahedron external to that of the copperatoms.Beyond each copper atom is an arsenic atom lying on theelongation of the axis joining the centre of the inner tetrahedronto the copper atom. The iodine atoms have thus become 3-covalent,being joined to the three neighbouring copper atoms by one covalentand two co-ordinate links. The formation of the fourfold moleculelD J., 1936, 1503M A " : POLYNUCLEAR METALLIC COMPOUNDS. 159has thus enabled each of the tetrahedral 4-covalent cuprous atoms tobecome joined by a covalent link to one iodine and by co-ordinatelinks to one arsenic and two iodine atoms, and thus by acquiringseven electrons to attain the electronic structure of krypton.Thecrystallographic evidence also shows, not only that the 4-covalentarsenic atom is tetrahedral, but also that the 3-covalent iodine atomcan be regarded as being a t the apex of a tetrahedron with itsvalencies directed to the remaining three apices, and in this respectresembles 3-covalent sulphur.It is noteworthy, however, that G. J. Burrows and E. P. Sanford 2ohave shown that the molecular weights of certain cuprous deriva-tives of phenyldimethylarsine, e.g., [PhMe,As+CuI], indicatedecisively that these compounds have the " unimolecular "formula.(ii) There is little doubt that the cuprous compounds ofempirical composition dpy CuI l9 and(P~M~,AS)~CUI 2O have the doubled bridgedcrystalline form or instability has so farhindered investigation.(iii) D.P. Mellor, G. J. Burrows, and B. S. Morns 21 have describedtwo compounds of formula (PhMe,As),Cu,Cl,, obtained by theconstitution (as XXIII), but indifferent(XXIII.)Iaction of the arsine on cupric chloride. The two forms are blue andbrown, severally, and give satisfactory molecular weights in nitro-benzene solution. The authors consider that part of the copper hasundergone reduction to the cuprous state by the excess of arsine, andthat isomeric bridged compounds are thus formed (XXIV, A and B),both containing a tetrahedral cuprous and a uniplanar cupriccomplex. These formuh satisfy the necessary stereochemical andelectronic conditions, and decisive evidence for the structure of thecompounds would therefore be of great interest.Trialkyl-phosphines and -arsines also combine with silver iodide 22to give fourfold molecules, and since [Pra,As+AgI], is strictlyisomorphous with [Et,As-+CuI],, the silver compounds have astructure identical with (XXII), and the silver atoms thus attain theelectronic state of xenon.Aurous halides, however, give only" unimolecular " compounds, [R,P(As)+AuX], and the goldto J. Proc. Roy. SOC. N.S.W., 1936, 69, 182.31 Nature, 1938, 141, 414.32 F. G. Mann, A. F. Wells, and D. Purdie, J., 1937, 1828160 INORGANIC CHEMISTRY.atoms do not attempt to reach the electronic structure of radon.G. J. Burrows and R. H. Parker 23 have described some additionproducts of phenyldimethyl- and diphenylmethyl-arsine with silversalts, to which they assign ionic formulae such as [(PhMe,As),Ag]Cland [(Ph,MeAs),Ag]NO,. Since some of these compounds arefreely soluble in organic solvents, such formuh are unlikely, andit is more probable that they are bridged compounds [(R,As),AgCl],similar in type to (VIc).F.G. M.5. CO-ORDINATION COMPO~JDS.It will cause no surprise that the study of co-ordination compoundscontinues to be prosecuted with unabated vigour, when it is realisedhow far the co-ordination theory, in its modern form, has becomeinterwoven into the fabric of chemistry. It would be impossible tosurvey co-ordination compounds on such a broad basis ; accordingly,the scope of the present Report has been restricted to complexmetallic compounds generally, as has been the practice former1y.lThe main trend of investigation has continued to centre round thedetermination of the structure of co-ordination compounds with allthe powerful physical methods at the disposal of the modernchemist-a refurbishing of old observations in the light of present-day knowledge.It is only within the last few years that the amminated derivativesof ruthenium have been the subject of a comprehensive study.Some preliminary investigations have already been reported ,,and these have been followed by some ten memoirs by K.Gleu andhis co-workers on the ruthenium ammines. It is found that theaction of ammonia on ruthenium trichloride leads to the colourlesscrystalline hexammine [Ru,6NH,]C13 , from which a number of saltscontaining the anion [Ru,6NH3]+++ can be prepared by doubledecomposition.With boiling concentrated hydrochloric acid, theforegoing hexammines furnish yellow, sparingly soluble[RuC1,5NH3]CI,. With aqueous ammonia, followed by ammoniumdithionate, this pentammine gives [RUOH(NH,)~]S,O, in colourless,sparingly soluble crystals which are changed into the aquo-pentammine [Ru(NH,)5H,0],(S,06)3,2H20 by aqueous dithionic23 J . Amer. Chem. Soc., 1933, 55, 4133.Ann Reports, 1036, 33, 157.K. Gleu and K. Rehm, 2. anorg. Chem., 1936, 227, 237; K. Gleu, W.Ibid.,p. 171.Breuel, and K. Rehm, ibid., 1938, 235, 201; K. Gleu and W. Breuel, ibid.,p. 211 ; K. Gleu and K. Rehm, ibid., p. 352 ; K. Gleu, W. Cuntze, and K. Rehm,ibid., 1938, 237, 89; K.Gleu and W. Cuntze, ibid., p . 187; K. Gleu andW. Breuel, ibid., p p . 197,326, 335, 350BURSTALL : CO-ORDINATION COMPOUNDS. 161acid. The chloropentammine [RuCl(NH,),]Cl, also forms thestarting point for a series of tetrammines, since it reacts with sodiumbisulphite with formation of Na,[Ru( SO,H),(NH,),( S0,),],6H20and [Ru(SO,H),(NH,),]. The latter sulphite is acidic and affordsan ammonium salt (NH,),[Ru( S0,),(NH3),],4H,0 whereaswith hydrochloric acid a remarkable orange ruthenammine[RuC~(NH,)~SO,]C~ containing neutral co-ordinated sulphur dioxideis formed. From this sulphito-chloride a number ofsimilarly constituted salts, such as [RuBr(NH,),SO,]Br and[RU(NH,),SO,,H~O](NO~)~, can be obtained by double decompos-ition. With ammonia the sulphito-chloride yields the sulphite[RuSO~(NH,)~],~H,O, which with mineral acid furnishes a pent-ammine series [RU(NH,)~SO,]X, containing sulphur dioxide.Thesebivalent ruthenammines are all diamagnetic. Oxidation of thechloride [RuCl(NH,),SO,]Cl with iodine chloride, or of the corre-sponding bromide with bromine, leads to the tetrammines[RuCI,(NH,),]Cl,H,O and [RuBr,(NH,),]Br,H,O, which have atram-configuration since they differ markedly from the corre-sponding cis-derivatives. The constitution of the cis-tetramminesfollows from their method of formation, which consists in treatingthe hydroxo-salt [RuOH,5NH,]S206 with oxalic acid, whereby theyellow oxalate [RuC20,,4NH,]S,O, is formed ; hydrochloric acidthen yields the cis-chloride [RuC32(NH,),]Cl,~H20.The prolongedaction of hydrogen chloride on this cis-tetrammine yields non-ionic [RuCl,(NH,),] as a sparingly soluble, red deposit. Thecompounds of tervalent ruthenium are all paramagnetic witha moment of about 2 Bohr magnetons.L. W. N. Godward and W. Wardlaw4 have obtained greencrystalline salts of the types X,[RuCl,] and X,[RuCl,,H,O]containing bivalent ruthenium in a complex cation. These authorsprepared pyridinium 2 : 2’-dipyridylium, and ethylenediammoniumsalts of the former type, and a trimethylammonium compound of thelatter series by addition of these bases in hydrochloric acid to thedeep blue solution resulting from electrolytic reduction of rutheniumtrichloride in 6~-hydrochloric acid. These stable salts are dia-magnetic .It has been found that the polypyridyls form a series of complexruthenium derivatives containing the nitric oxide group., WithK2[RuNOCI5], 2 : 2’-dipyridyl behaves as a chelate group and yieldsthe green internal complex [NORuCl, dipy] and the red salt[NORuCl 2dipy][NORuCl,].An extrusion of nuclear chlorine iseffected by the tridentate base 2 : 2‘ : 2”-tripyridyl, resulting in the( S i r ) G. T. Morgan and F. H. Burstall, J . , 1938,1676.REP.-VOL. XXXV. F4 J . , i93a,i42z162 INORGANIC CHEMISTRY.formation of brown, water-soluble [NORuCI, tripy]Cl,S&H,O, and afurther atom of chlorine is displaced to the anion when the quadri-dentate base 2 : 2’ : 2” : 2”’-tetrapyridyl is introduced into a moleculeof nitrosoruthenium pentachloride, the salt [NORuCl tetrpy]C1,,5H20being formed.During the past few years considerable interest has beenmanifested in the structure of four-covalent metallic compounds.It was found that univalent compounds of copper, silver, and goldwith a co-ordination number of four were tetrahedral in structure,whereas corresponding derivatives of bivalent copper and silverand tervalent gold possessed a planar configuration.A planarsymmetry has also been shown to be present in certain four-covalentcompounds of platinum, palladium, and nickel. An excellentsummary of these facts has already been given.6 It has now beenfound by X-ray analysis that a planar arrangement is also apparentin the a-form of [CoC1,,2C5H,N], which possesses a tram-configur-ation. This fact is of special interest, since a tetrahedral arrange-ment has already been found for the ion [CoCI,]”,* thus showing thatboth types of spatial configuration can be manifested in unchelatedderivatives of a bivalent metal. The structure of p-[CoC1,,2C5H,N]is still uncertain, but it has been found that pink [MnC1,,2C,H5N]is isomorphous with the a-[CoC1,,2C5H5N] and must thereforepossess a tram-planar configuration.A change in structure witha change in valency has also been discovered among derivativesof tin, lead,g and thallium.10 In potassium stannous chloride,K2[SnC1,],2H2O, the four chlorine atoms are arranged in a planewith the tin atom, whereas in quadrivalent stannic iodide thedistribution of halogen is tetrahedral. Similarly, with bivalentlead in [PbCI2,2CS(NH,),], the arrangement of addenda is planarin contrast to the tetrahedral configuration of such quadrivalentlead compounds as Pb(C,H,),.Among thallium derivatives, thecomplex salts [Tl 4CS(NH,),]NO, (or Cl)containing the univalent element are planar,CH3\ whereas in the tervalent thallic compoundCH,/ \o-& (I) a tetrahedral structure is regarded asI n the foregoing survey of (1.1planar and tetrahedral types, it has beenassumed that it is the central metallic atom which controls thearrangement of the co-ordinating units, but it is clear that other/CH3T1\CH, most probable.6 Ann. Reports, 1936, 33, 158.7 E. G. Cox, A. J. Shorter, W. Wardlaw, and W. J. R. Way, J., 1937, 1566.a H. M. Powell and A.F. Wells, J., 1935, 359.0 E. G. Cox, A. J. Shorter, and W. Wardlaw, Nature, 1937,139,72.10 J., 1938, 1886BURSTALL : CO-ORDINATION COMPODNDS. 163considerations must be taken into account. The co-ordinatingaddenda may, owing to rigidity or size, be unable to take up anarrangement in keeping with the disposition of a metallic atom.This is particularly evident among the metallic derivatives of por-phyrin and its allies (notably the phthalocyanines), where a rela-tively rigid macrocyclic ring imposes a planar structure on itsmetallic derivatives.11 It is claimed that a similar imposition ofa planar structure is apparent among the complex metallic saltscontaining 2 : 2’ : 2”-tripyridyl (tripy) and 2 : 2’ : 2” : 2”’-tetra-pyridyl (tetrpy), which are unable to encircle a tetrahedron with-out considerable distortion of the molecule.12 The former, tri-dentate, base yields two series of well-defined salts : (a) thosecontaining one molecule of base having formula (11) (where M isCuII, AgII, Zn, Cd, Hg, Pd, and Pt, and X is a univalent acid(111.)radical), and ( b ) those with two molecules of the triamine exempli-fied by (111), where M is FeII, CoIIor 111, Ni, RuII, 0811, and CrIII,and X is a univalent acid radical. Although (111) is octahedral, itis concluded that the two molecules of base are at right anglesto one another and planar with respect to the central metallicatom.These salts are also notable for their unusual colour andexceptional stability. Complex salts with the quadridentate base2 : 2’ : 2” : 2”’-tetrapyridyl contain only one molecule of base butyield types (IT) (where M is FeII, CoII, Ni, CuII, Zn, Cd, andPtII, and X is a univalent acid radical) and (V) (where M is CoIIIand IF).These derivatives differ considerably in colour andstability from the foregoing salts with 2 : 2’ : 2”-tripyridyl.11 Ann. Reports, 1937, 34, 369.l2 (Sir) G. T. Morgan and F. H. Burstall, J., 1937,1649; 1938,1672164 INORCXNIC CHEMISTRY.The converse of the method whereby a zhetal ion is constrained totake up a planar configuration hasalso been attempted. l3 A chelategroup is chosen such that metallicderivatives of the type R2M can-not be planar. These conditionsprevail in metallic compounds ofN ethyl tetramethylpyrromethene-Co2Et Me/l - II-CH- Me Me-co2Et -1N N\/ -bMeMeH\-CH--/\Me 4 : 4'-dicarboxylate of type (VI), co,~+,.--- I t- Me MeII /ICO,Et which must be non-planar owingto the mutual interference of four WI.1 ..(M = CO, Ni, CU, Zn, Cd, and Pd.) methyl groups which operate in asimilar manner to that of 2 : 2'-di-substituted diphenyl derivatives. The effect is shown diagram-matically for the palladium compound in (VII).(VII.)An interesting addition to the chemistry of ethylenediamine-cupric salts has been made by F. W. Chattaway and H. D. K.Drew,14 who have shown that the complex salt [CuC12,en] is reallythe dimeric cuprichloride [Cu,2en]CuC14.It follows that the corresponding sulphate [CuSO,,en],3H2O maybe regarded as a dimeric cuprisulphate [Cu,2en][Cu(S04),,6H20],whereas hydrated cupric sulphate (blue vitriol), CuSO,,SH,O, maybe formulated as [Cu,4H20][Cu(S0,),,6H20], As bearing on thelatter structure, it is significant that X-ray analysis of coppersulphate l5 shows only four molecules of water surrounding thel4 J ., 1937, 947.C. A. Beevers and H. Lipson, Proc. Roy. Soc., 1934, A , 146,570.la C. R. Porter, J., 1938, 368BURSTAIL : CO-ORDINATION COMPOUNDS. 165copper atom, the fifth being associated with two other water mole-cules and two oxygen atoms of a sulphate group. The tendencyof ethylenediamine to form stable complex cupric salts is wellknown, but it has now been found that this effect is greatlyreduced in N-alkylated ethylenediamines. 16 Nevertheless,the perchlorates[Cu(NMeH*CH,*CH2*NH2)](C1O4),,[Cu( NHE t*CH,*CH,*NHEt)] (ClO,),,[Cu( NEt2*CH2*CH2*NH2),]( C104)2,[NHMe*CH,*CH,.NEt, Cu/OH' Cu NEt,*CH,*CH,*NHMe](C104),and' OH/were obtained from alcoholic solution, but definite salts could not beisolated with NHPh*CH,*CH,.NEt,.Attention may be directed tothe complex salts 17 containing 3-methyl-4 : 5-phenanthroline (VIII) : <\- [Fe(Ci3Hi,N2),I(C10,), [Ag(CisHioN2)21N03 Ci-<> Me [Ni(C, 3H182) 31 (C104) 2 [cu (c1 3HioN,) 21 (c104 )a ,2HO(VIII.)in which, it is claimed, the methyl group exerts no marked effecton the co-ordinating power of the two nitrogen atoms of the organicbase.Co-ordination compounds of the alkali metals of well-definedtype l8 are less plentiful than those ofthe transition elements, but furtheradditions l9 have been made recentlyby the production of alkali-metal saltsof di-2-hydroxy-1 -naphthyl sulphide(IX ; X = S), di-2-hydroxy-l-naphthyl-k / methane (IX; X = CH,), and di-2- MVX.) hydroxy-l-naphthyl selenide (IX ; X =(M = ~ i , N*, K, Rb.) Se).These compounds, which arenormally hydrated (2 or 4H,O), aretypical covalent derivatives, being soluble in organic solvents. Thepresence of a stable eight-membered ring is particularly noteworthy.Recently, H. D. K. Drew and N. H. Pratt,20 investigating theV/"$\o 0P. Pfeiffer and H. Glaser, J. pr. Chem., 1938, [ii], 161, 134.l7 P. Pfeiffer and W. Cristeleit, ibid., p. 127.la See Ann. Reports, 1933,30, 98.W. J. Evam and 8. Smiles, J., 1937, 727; V.Dvorkovitz and 8. $milee,J., 1938,2022. eo J., 1937, 606166 INORGANIC CHEMISTRY.interaction of molecular proportions of cobaltous chloride andethylenediamine in a limited supply of air, found that the pink,insoluble cobaltochloride [CoOH( en),H,O]CoCl, was formed, andthat addition of hydrochloric acid to the filtrate furnished green[CoCl,(en),]CoC14,H20, both products being trans-derivatives. Withmore concentrated hydrochloric acid the former cobaltochloridedecomposed with rupture of one ethylenediamine ring and formationof [CoCI, en NH,*CH,*CH,*NH,]CI, a dihydrate of which was earlierrecorded by S. M. Jorgensen.21The way in which physical measurements assist in the determin-ation of the structure of co-ordination compounds is well shownin a reinvestigation of the red and black forms of nitrosopentammino-cobalt salts by (Mrs.) J.L. Milward, W. Wardlaw, and W. J. R.Way.22 The red chloride [NOCo,5NH3]CI, obtained from thenitrate [NOCO,~NH~](NO,)~,O-~H,O by cold concentrated hydro-chloric acid is diamagnetic and yields the purpureo-chloride[ CoC1,5NH,]C12 on decomposition with hydrochloric acid. It is,th$refore, regarded as a genuine tervalent cobaltic salt (X) in whichnitric oxide is attached to cobalt in the same way as it is to carbonin organic nitrosyls. The corresponding black chloride, however,[ ON-Co,5NH3]CI, [ 6=&-50,5NH3] C1, [O=&=Co,5NH3] C1,(X.) (XI.) (XII.)is paramagnetic and yields a solution containing bivalent cobaltafter decomposition with hydrochloric acid.In view of theseresults, the foregoing authors concluded that the black chloride isa hybrid of the two structures (XI) and (XII) in which the cobaltatom will act as if it were substantially bivalent. These electronicstructures may also be applied to the complex nitrosorutheniumsalts already described (p. 161).Some interesting work has recently been carried out 23924 on thecomplex cyanides of rhenium, the only known members of whichare salts of the hypothetical acid H,[ReO,(CN),]. The Britishauthors24 prepare these salts either by reduction of alkali per-rhenate with hydrazine hydrate in presence of alkali cyanide, orbetter, by boiling hydrated rhenium dioxide with aqueous alkalicyanide and oxidising the product with hydrogen peroxide.Theseoxycyanides are normally yellow, brown, or red, but acid salts with2 : 2'-dipyridyl, (CloH8N2H)2H[Re02(CN),],4H,0, and phen-anthridine, (C,3H9NH)BH[Re0,(CN),], are pale blue. Rheniumis quinquevalent in these cyanides.21 J . pr. Chern., 1889,39, 24. 23 J., 1938, 233.2* W. Klemm and G. Frischmuth, 2. anorg. Ghem., 1937,230,215,Z4 (Sir) G, T. Morgan and G. R. Davies, J . , 1938,1858BURSTALL : CO-ORDINATION COMPOUNDS. 167Platinum salts combine with an enormous range of inorganic andorganic groups or molecules and many of these complex salts havebeen known for over 100 years. Yet the constitution of the isomericdiammines of type [PtC1,,2NH3] is still the subject of controversy.It is believed, on the one hand, that there are only two isomerswhich have a cis-(XIII) and a trans-(XIV) planar arrangementoriginally proposed by Alfred Werner, and on the other hand, thatH N 4pt/c1H.?N~ \ci(XIII; /%cis-.)H N h P pC1’ \NH,(XIV; a-trans-.)/NH3ClPt,there are three isomers : (a) the u-trans-diammine (XIV), (b) ap-diammine which is regarded as a substituted ammonium salt (XV),and (c) a y-isomeride [H3NC1PtNH3CI] (XVI) which is intermediatebetween (a) and (b), these structures being proposed by H.D. K.Drew, F. W. Pinkard, W. Wardlaw, and E. G. COX.^^ RecentlyF. W. Chattaway and H. D. K. Drew26 have brought forwardfurther evidence in favour of the structure (XV) for the p-dichloride.Interactions of p-[PtCI,,SNH,] and palladous chloride in hydro-chloric acid, or potassium palladochloride, furnish the twocompounds [Pt (NH,),CI],PdCI, and [Pd(NH3),]PdC14 in black andgreyish-black crystals respectively.The former salt arises fromaerial oxidation, and both salts are readily dissociated on warmingwith water. The authors conclude that these experiments showthat the p-dichloride can and does act in the ionic forms[Pt(NH3),C1]CI and [Pt (NH,),]Cl,, but an alternative formulation(XVII) cannot be entirely excluded. Itis significant that p-diammines contain-[(NH3)2pt(CI~pdc12] ing addenda other than ammonia have not(XVII. ) - so far yielded similar compounds, a factwhich lends some support to the view27that the p-salts [PtCI,X,] are of two types: (1) a large class ofconventional cis-structure (XIII), and (2) a small class, includingthe ammonia compounds, in which chlorine atoms are united withnitrogen (XV).It was also observed that neither u- nor y-[PtCl,(NH,),] reacted with palladous chloride, but A. A. Grunbergand F. M. Filinov,28 operating with potassium platinichloride,find that the equilibriumc1[PtX,(NH&] + K,[PtCI,] [Pt&(NH3)21 + KdPtXd(X = C1, Br, CNS, or I) is established with both cis- and trans-26 J . , 1932, 993. s6 J., 1938, 198.27 H. D. K. Drew and H. Tress, J., 1933, 38; 1936,1212.z 8 Bull. Awd. Sci. U.R.S.S., Ser. Chim., 1937, 1245168 INORGANIC CHEMISTRY.compounds. New light on the behaviour of diamminoplatinoussalts in aqueous solution has resulted from a study of their electricalconductivities : H. J. S. King 29 finds that there are two classes ofdiammine : (1) those which are practically non-electrolytes, suchas the dichlorides and dihydroxides, and (2) those which areconductors, such as the cis- and trans-dinitrates, -dipicrates, and-sulphates.In the latter group the conductivity is such as toindicate the formation in solution of diaquo-salts of the typeexemplified by [Pt(NH3)2(H,0)2](N03)2 which, however, could notbe separated in the hydrated condition. Addition of ammonia to asolution of the dinitrate sets up an equilibrium which conductivitymeasurements indicate is in accordance with the schemeThe aquohydroxo-nitrate could not be isolated, but the hydroxo-nitrates (cis and tram) [Pt(NH,),(OH)NO,] were obtained in thesolid state, and became hydrated on dissolving in water, withformation of univalent cations.Among co-ordination compounds of platinum, those containingolefins are of considerable interest owing to the difficulty of providingan adequate electronic interpretation of their structure.30 Fromthe mixture resulting from heating sodium chloroplatinate andalcohol, yellow dimeric (PtCl,C,H,), (XVIII) and the saltK[PtC1,C2H4] can be isolated by suitable meam.31 This processrepresents the classical preparation of Zeise, but a more convenientmethod32 of obtaining the former covalent derivative consists inbubbling ethylene through a suspension of platinic chloride inbenzene at 70".( XVIII .)- - (XIX.)Corresponding styrene, amylene, and cycbhexene derivativescan also be prepared, either by interactions of the olefin with platinicchloride in glacial acetic acid suspension or by heating the ethylene-platinous chloride with the less volatile hydrocarbon.The olefmis eliminated from these compounds by heat alone, the action ofhydrochloric acid, or excess pyridine. The stereochemistry ofthe Zeise aeries of salts R1[C,H4PtC13] is interesting. With aqueouspyridine the salt [C2H,Pt(C,H,N)C1,] is formed and it is thought29 J., 1938, 1338. Ann. R ~ ~ O T ~ S , 1936, 33, 177.t.1 J. S. Anderson, J., 1934,971; 1936,1042.8s M. S, Kharasch and T. A. Ashford, J . Amer, Chem. SOC., 1936.58, 1733BURSTALL CO-ORDINA!IXON COMPOUNDS. 169that this pyridine compound 33 has a trans-configuration (XIX),since excess pyridine yields truns-[PtCl,(C,H,N),].The action ofethylene on K[(C,H,N)PtCl,] (a Cossa-type salt) yields an isomericproduct of cis-configuration (XX). With hydrochloric acid, both cis-and trans-derivatives furnish C,H,NH[C,H,PtCl,]. Ammonia canreplace pyridine in the foregoing reactions.34It has been found that palladium salts also combine with hydro-carbons. Olefins replace benzonitrile in the complex [PdC1,,2C6H,*CN]with formation of compounds of type [RPdCl,],, where R =ethylene, styrene, cycbhexene, and isobutylene, which are less stablethan the platinous derivati~es.~, By means of a distributiontechnique, it has also been found that silver salts co-ordinate withcertain hydrocarbons such as butadiene, cyclohexene, etc., althoughsolid compounds were not obtained in every case.36That metallic lakes of mordant dyes are co-ordination complexesis probably accepted in principle by most chemists, for it providesthe most satisfactory explanation for the formation of theseinteresting and important substances. In an important memoir,H. D. K. Drew and J. K. Landquist 37 have considerably clarifiedthe position with regard to the copper lakes of o-substituted azo-dyes. The copper lake of 2-hydroxyazobenzene (XXI) is anhydrousand shows no tendency to take up further addenda of co-ordination,and the formation of a six-membered chelate ring rather than afive-membered ring is inferred from the marked similarity betweenthis copper complex and that of salicylideneaniline (XXII), whichmust on structural grounds possess two six-membered rings.Similar constitutions have been deduced for the copper complexesof other 2-hydroxyazo-dyes. The copper compounds of o-carboxy-azo-dyes show perceptible differences from the foregoing hydroxy-33 I. I. Tscherniaev and A. D. Gelmann, Compt. rend. Acud. Sci. U.R.S.S. ,1936, 4, 181 ; Ann. Sect. Platine, 1937, 14, 77.A. D. Gelmann, Sci. Rep. Leningrad State Univ., 1936, 2, 6 ; Compt.rend. A d . Sci. U.R.S.S., 1937, 16, 351.M. S. Kharaaoh, R. C. Seyler, and F. R. Mayo, J . Amer. Ohern. SOC.,1938, 60, 802.*6 S. Winstein and H, J. Lucas, ibid., p. 836. 5 7 J.. 293a,292170 INORGANIC CHEMISTRY.derivatives. Azobenzene-o-carboxylic acid yields the dihydratedsalt (XXIII), which only furnishes the anhydrous salt (XXIV)NPhNPh H,O -\-N., II /O-CO\ -+,O-CO’+ .i> -<CO-O/CukN-<MPhCO-O/H,O 11NPh(XXIII.) (XXIV.)with some difficulty. With azo-dyes containing both an o-hydroxy-and an o-carboxy-group, such as o-carboxybenzeneazo- @-naphthol,there is production of a covalently unsaturated copper salt (XXV)which manifests its tendency to form four-covalent compounds byuniting with one molecule of aniline or pyridine. A similar degreeof co-ordinative unsaturation prevails in the copper salt of 2 : 2’-dihydroxyazobenzene (XXVI) and other oo‘-dihydroxyazo-dyes.0-cu-0co--o/(XXV.) (XXVI.)This unimolecular, intensely coloured, copper salt (XXVI) yieldscrystalline monopyridine and monoquinoline derivatives, thusincreasing the co-ordination(XXVII.)The similarity of (XXVI) to the copper derivative of salicylidene-o-aminophenol (XXVII) confirms the view that only one nitrogenatom is united to copper.The removal of one o-hydroxy-group to the m- or the p-positionleads to a copper lake of totally different type, as exemplified in(XXVIII). Two molecules of the dye then combine with oneatom of copper, and the two m- or p-hydroxy-groups areuncombined. The constitution of copper lakes of azo-dyescontaining sulphonic acid groups is more speculative, but thBURSTALL : CO-ORDINATION COMPOUNDS. 171primary reaction appears to be the formation of ionic cupric salts(R*SO,),Cu which may be followed by conversion into an internalcomplex with suitable reagents (mild alkali), providing that thereis a hydroxy-group in the a-position to the azo-group; a copperlake of type (XXVIII) is then formed in which the free hydroxy-groups are replaced by sulphonic acid groups. Numerous internalcomplex metallic compounds bearing a certain resemblance to thecopper lakes just described have been prepared. The salicylidenederivatives 3 8 9 3 9 can all be included in the general formulae (XXIX)and (XXX) (where R is an aryl group, -NH*CO*NH,, or H, X is*CH,*CH2- or o-C,H,<,-~-~o\M/o-<CH-N~ %=CH\X/o\M’”=CH(XXX.) i,,,l \o- --?I (XXIX. )and M is a bivalent metal, Cu, Zn, Ni). Attempts to resolvecompounds of the type (XXX) were unsuccessful. Very similarto the foregoing are the metallic aldimine~,~~ which are the same as(XXIX) and (XXX) with the oxygen atoms replaced by imino-groups. Certain pyrrole derivatives yield metallic complexes 38of the type (XXXI), as well as those containing a bridge groupI11(XXXI.) (XXXII.)(compare XXX) which unites two pyrrole units. Hydroxytriazensalso act as powerful chelate groups, forming highly-coloured metallicsalts (XXXII) which, from their solubility in organic media andlow melting points, are typical covalent derivatives.M Semi-carbazide and substituted semicarbazides also act as chelate groupswith metal ions, yielding complex derivatives (XXXIII) containingone, two, or three organic molecules to one atom of meta1.41n42Aminoguanidhe acts in a very similar manner, yielding derivativesof the type (XXXIV).s* P. Pfeiffer, T. Hesse, H. Pfitzner, W. Scholl and H. Thielert, J. p. Chem.,1937, [ii], 149, 217; P. Pfeiffer, W. Christeleit, T. Hesse, H. Pfitzner and H.Thielert, ibid., 1938, [ii], 150, 261.39 L. Hunter and J. A. Marriott, J., 1937, 2000.40 (Miss) M. Elkins and L. Hunter, J., 1938, 1346.41 K. A. Jensen and E. Ranke-Madsen, 2. art.org. Chern.. 1936,227,25.42 G. S. Smith, J., 1937, 1354172 INORGANIC CHEMISTRY.I n the foregoing survey, the co-ordination compounds have allbeen meta,Uic complexes, and it is fitting therefore to conclude withreference to co-ordination between non-metals or metalloids.J x2Good examples of these substances are the sulphilimines43R2S+N*S02*C7H7, phosphinimines R,P+N*SO,~C,H,, and arsini-mines R,As+N-SO,*C,H,, which arise from the interaction oforganic sulphides, phosphines, and arsines respectively with chlor-amine-T, CH,*C,Hp*S02~NNaCl,3H20. These derivatives are struc-turally analogous to the corresponding oxides R2S+0, R,P+O,and R,As+O. F. H. B.F. H. BURSTAIL.F. G. MA”.H. TERREY.0. J. WALKER.R. WHYTLAW-GRAY.4s F. G. Mann, J., 1932,958; F. G. Mann and E. J. Chaplin, J., 1937, 527

ISSN:0365-6217    

DOI:10.1039/AR9383500114

出版商:RSC    

年代:1938

数据来源: RSC

摘要:

CRYSTALLOGRAPHY.1. INTRODUCTION.IN the early days of X-ray crystallography there was naturally atendency to select for examination substances which occurred inlarge, well-formed crystals and presented no technical mculties,and for this reason many structures were prematurely and imperfectlyanalysed. The numerous references in current literature toimproved methods for studying substances in all stages of aggreg-ation and a t almost any temperature or pressure serve to emphasisethe fact that there is now no reason for selecting one substancerather than another for analysis other than its relatively greaterimportance. An absolute standard of importance in crystallo-graphy is a somewhat barren conception, and we find that thedeterminative factor is usually the significance of a substance forone or more of the many sciences which require structural inform-ation for their full development; the mere enumeration of thesesciences sufficiently emphasises the key position occupied bycrystallography.I n the present Report special sections are devotedto topics which have obvious connections with metallurgy, soilscience and ceramics, and biochemistry, and the general sectionson inorganic and organic structures record advances which, in manycases, have been inspired by theoretical chemistry, and in othersprovide accurate data for a more detailed examination of theproblems of chemical binding. In many fields, however, thecontributions of crystallography are not yet as extensive as theyshould be; for example, the Faraday Society’s stimulating dis-cussion on reactions in solids emphasised the great need of structureanalysis specscally organised for the development of this subject.An encouraging feature of current researches is the increasingtendency to use other physical methods in conjunction with X-rays, and on this account alone the appearance of the first book inEnglish on the fundamentals of crystal physics3 is particularlyR.B. Jacobs, Physical Rev., 1937, 51, 999; 54, 325; 0. P. Hendershot,Rev. Sci. Instr., 1937, 8, 436; C. Gamertsfelder and N. S. Gingrich, ibid.,1938, 9, 154; F. Schossberger, 2. Krist., 1937, 98, 259; 1938, 99, 341;W. Hme-Rothery and P. W. Reynolds, PTOC. Roy. Soc., 1938, A, 167, 25;A. Goetz, R. B. Jacobs, and 0.B. Jackson, Physikal. Z., 1937,38,998.Trans. Faraday Soc., 1938, 34, 822.W. A. Wooster, “ A Text-book on Crystal Physics,” Cambridge Univ.Press, 1938174 CRYSTALLOGRAPHY.timely. The value of optical and magnetic methods has beenestablished for some time, and the introduction of infra-red anddielectric measurements on single crystals foreshadows the develop-ment of techniques which will not only yield results of great interestin themselves but will considerably assist structure analysis,particularly of organic compounds. The correlation of structuralinformation from X-ray analysis with the energy values and otherdata derived from thermal, infra-red, and dielectric measurementsfor appropriate key substances should afford a means of shorteningconsiderably the analysis of many compounds and of predictingthe properties of others unsuited to exact analysis.In thisconnection a survey of crystal structures in relation to thermalconductivity is of interest.Physical properties are particularly valuable also in the studyof those substances which do not conform to the strict geometricallaws of crystallography and consequently are not always susceptibleof exact analysis by X-rays. These substances, which are now sonumerous as to call for detailed classification and figured largelyin a recent discussion of the German Bunsen Society, fall intofour main types according as the kind of irregularity is :(1) Occupation of equivalent lattice points by different(2) Non-occupation of some lattice points.(3) Occupation of inter-lattice points by molecules, atoms,(4) Rotation or variable orientation of molecules or groups.molecules, atoms, or ions.or ions.Some aspects of (2) and (3) were discussed in these Reports lastyear; alloys afford frequent examples of (l), and (4) is of commonoccurrence among organic compounds. These irregularities, whichhave so far been studied chiefly by thermodynamic and electricalmethods, are of great theoretical interest and are intimatelyconnected with, inter alia, problems of plasticity, diffusion, and thestructure of liquids.E. G . C.2. TECHNIQUE.There have appeared during the past year various publicationswhich in the Reporter’s opinion ignore certain fundamental limit-ations of structure analysis and give an erroneous impression ofE.g., R.C. Evans, Phil. Mag., 1937, 24, 70; G. Busch, Helv. PhysicaActa, 1938,11, 269; J. W. Ellis and J. Beth, J . Chem. Physics, 1938,6, 221.H. D. Megaw, 2. Krist., 1938,100, 58.W. Nowacki, ibid., p. 77.7 F. C . Frank, Nature, 1938,142, 1166COX : TECHNIQUE. 175its present power, and it may therefore be opportune to surveybriefly the existing position of the technique of the subject.As is well known,8 the objects of experimental technique are,first, to determine the cell dimensions and space group ofthesubstance under investigation, and secondly, to determine for asmany planes (h, k, I ) as possible the integrated reflection intensitiesand thence the squares of the structure amplitudes B2hkl.Theobject of interpretative technique is to find an atomic arrangementconsistent with all the experimental data, i.e., with the B2’s; thisobject may be attained by “ trial and error ” or by direct synthesisleading to one-, two-, or three-dimensional electron distributions.Improved methods for determining cell dimensions, analysingphotographs, measuring intensities, etc. (including the increasinguse of strictly monochromatic radiation), continue to be devised,and it is fair to say that in general there is no serious obstacle to thedetermination of a series of P2’s adequate both in number andin accuracy for the purposes of an ordinary structure analysis.Interpretative technique is, however, not yet free from a majordifficulty arising from the fact that the quantity P required fordirect Fourier synthesis is in general complex and therefore has aphase angle which cannot be deduced from the experimental valueof F2.In many cases an approximate structure can be found bytrial and error, and the phase angles so determined utilised in anF-synthesis which if necessary must be successively refined, butthe laborious nature of trial and error calculations has led to theintroduction of the so-called direct (Patterson) methods of synthesisin which the experimentally observed P2’s are used, so that theresulting contour diagrams give, not atomic positions, but inter-atomic vectors. In not too complicated cases the informationobtained in this way enables the B-synthesis to be effected. Anelegant algebraic method of analysis has been proposed by M.A ~ r a m i , ~ which, in the absence of data on phase angles, yields thesame information as the Patterson method, over which it is claimedto have some advantage on account of the slow convergence of theP2-series.The algebraic method, however, is clearly less generalin its scope, since it fails in just those cases which are most difficultof solution by other methods, vix., those in which the highestavailable values of h, k, or 1 are less than the number of parametersin the structure; it is significant that essentially the same methodRecent accounts of the methods of crystal analysis are given in“ Angewandte Kristallatrukturlehre,” E. Brandenberger, Berlin, 1938, and in“ Rontgenanalyse von Kristallen,” J.M. Bijvoet and N. H. Kolkmeijer,Amsterdam, 1938.Physical Rev., 1938, [ii], 54, 300176 CRYSTALLOGRAPHY.(in a less general form) has had no application, so far as the Reporteris aware, since its publication lo over five years ago.It is clear that, corresponding to a given F2 series (whichsummarises the experimental data), there is an infinity of F-series,only one of which represents the actual crystal structure; most ofthese can be eliminated by applying the criterion that the electrondensity in a real crystal must everywhere be positive (or zero),but since it is always possible to find an F sufficiently small toenable its phase angle to be varied without producing any negativeelectron densities, it is not possible in general to determine a uniqueF-series corresponding to an F2-series. The final test of the correct-ness of a proposed structure must be the agreement between observedF2’s and the values calculated from the atomic positions andscattering factors.In this connection the determination of accurateatomic scattering factors is of considerable importance.llIn discussing many aspects of structural crystallography (e.g.,space-group theory) it is convenient to regard the actual atomicarrangement as being replaced by a point distribution; thisprocedure, however, is liable to be misleading when used in thediscussion of the interpretation of vector maps l2 (P2-syntheses) iffor no other reason than that the important conception of resolvingpower is inapplicable to point distributions.It is generally acceptedthat the resolving power in a Fourier synthesis of the type used instructure analysis is determined by the ordinary diffraction theory ; 13this indicates that it is impossible to distinguish two peaks in acontour map if their distance apart is less than 0.61d0, where do isthe lower limit to the spacing of the planes whose F’s (or P2’s) areutilised to synthesise the contour map. Consideration of resolvingpower reveals a significant difference between P-series and P2-series. The former represents the electronic distribution in acrystal, and consequently peaks (representing atoms) cannot occurcloser than an atomic diameter, i.e., 1 A. or more; since do can bemade less than 1 A. (for truly crystalline substances), it follows thatindividual atoms can always be resolved by means of a suitableF-series, however complex the structure, the only difiiculty being,as pointed out above, the determination of the phases of the F’s.On the other hand, since an F2-series exhibits maxima correspondingto the separation of pairs of maxima in the corresponding P-series,their number increases rapidly with the volume of the unit cell,and their average distance apart becomes less than the resolving10 K.Banerjee, Proc. Roy. SOC., 1933, A , 141, 188.11 E.g., G. W. Brindley and P. Ridley, Proc. Physical SOC., 1938,50, 96.l2 I. Langmuir and D. M. Wrinch, Nature, 1938,142, 581 ; D. M. Wrinch,18 W. L. Bragg and J. West, Phil. Mag., 1930, 10, 823.ibd., p.955; E. H. Neville, ibid., p. 994COX : !FECHRIQUE. 177power. I n organic compounds there are roughly 60 atoms per1000 A.3, so that the three-dimensional P2-synthesis for such asubstance exhibits roughly 3600n2 maxima, where 103n A.3 is thevolume of the unit cell; in practice, this may be reduced to (say)900n2 on account of symmetry, but even so, the average separationof maxima becomes less than the resolving power (say 0.5 A.) whenn exceeds 4, and the probability of two maxima being unresolvableis evidently very high for much smaller unit cells. If the structurecontains a small number of heavy atoms, the maxima due to thesewill stand out on the almost uniform background due to the lighteratoms. Experience shows that the value of the Patterson methodlies in this ; it can be relied upon to fix the positions of heavy atoms,and in some cases to identify peaks corresponding to distancesbetween heavy and light atoms, but except in the simplest cases(e.g., pentaerythritol) it cannot determine the positions of light atoms(e.g., carbon, nitrogen and oxygen). (It should be noted that thepreceding discussion applies to three-dimensional summations andthat conditions are less favourable in the case of two-dimensionalseries on account of the much greater probability of maxima over-lapping.) Apart from the effects of heavy atoms, the peaks observedin the Patterson diagrams of complicated organic molecules are dueto the superposition of many interatomic vectors, and can be usedto determine only the general outlines of the structure; e.g., in thecase of insulin l4 the lower limit of spacing for which reflections wereobserved was 7 A., so that the resolving power of the P2-series is ofthe order of 4 A., and therefore, although the synthesis may be usedto test an assumed structure, it is clearly impossible at present todeduce a unique atomic arrangement in detail from it.A further suggestion l2 in connection with the P2-series is that,if the structure of a substance can be represented by a, continuouselectron distribution (P-series), then the associated F2-series shouldshow maxima corresponding, not only to distances between maxima(atoms) in the electron distribution, but also to distances betweenminima (regions, between atoms, of low electron density).l5 It isreadily seen, however, that maxima in the P2-series due to thissecond cause are negligible.I n two-dimensional syntheses oftypical organic compounds the mean electron density is about2 e J ~ . ~ while the maxima (e.g., at the centres of carbon atoms)exceed 7 e J ~ . ~ . Since the minimum possible electron density iszero, the heights of peaks in the F2-series due respectively to atom-atom and minimum-minimum distances w i l l be roughly in the ratio(7-.2)2 to (2-0)2, Le., 6 to 1, so that no error will be introduced by1* seep. 201.l5 I. Lmgmuir and D. M. Wrinch, Zoc. cit., ref. (12)178 CRYSTALLOGRAPHY.assuming that all observed peaks are associated with interatomicvect ors .The preceding discussion has emphasised limitations of syntheticmethods which are recognised by crystallographers, and it is ofinterest to note that in a number of widely different structureanalyses carried out in the past year an almost identical procedurehas been adopted, vuix., use of P2-synthesis to locate heavy atoms,calculation of phase angles of the more important P's followed byB-synthesis, and finally, refinement of atomic co-ordinates bytrial and error methods.A development of interpretative techniquewhich may be expected in the near future is the simplification andimprovement of structure amplitude calculations and their extendedapplication by the method of Fourier transformations. Thismethod,16 which provides a means of systematising trial and errorcalculations, is likely to be of particular value in the case of thosesubstances where the approximate shape of the molecule can beassumed from chemical evidence but where little or no assistancecan be derived from optical or magnetic data; the chief obstacleto its employment at present is undoubtedly the laborious natureof the calculations.Although the analysis of complex structures is still a matter ofsome difliculty, the available methods are more than adequate forthe complete determination of simple structures, and the questionarises as to whether it is possible to push the analysis in such casesbeyond the mere determination of atomic positions and to obtainelectron-density distributions of sufficient accuracy to discriminatebetween the various types of chemical binding.It is evident thatin analyses of the required precision, various considerations wouldloom large which are of small importance in ordinary crystalanalyses. It would be necessary to use strictly monochromaticradiation, and to ascertain whether under the conditions of theexperiment the incident X-ray beam contained a plane-polarisedcomponent. The actual measurement of intensities would requireconsiderably higher accuracy than is usually attained, and thecorrections for extinction and " indirect excitation '' 1' wouldrequire to be much more carefully estimated. Although experi-mental details are not yet available, R. Brill and his co-workers l*claim to have attained the necessary precision in Fourier analysesof sodium chloride, diamond, hexamethylenetetramine, andmagnesium, typical representatives of ionic, covalent, van der16 See, e.g., P.P. Ewald, 2. Krbt., 1935, 90, 493.1 7 M. Renninger, Naturwiss., 1937, 25, 43; 2. Krist., 1937, 97, 107.18 H. G. Grimm, R. Brill, C. Hermann, and C. Peters, NatumOiSrr., 1938,26,29,479; R. Brill, Angew. Chem., 1938,51,277BRADLEY : TERNARY ALLOY SYSTEMS. 179Waals, and metallic structures respectively. For the first twosubstances their results are in accordance with expectation : theelectron density falls to zero between chlorine and sodium ions butremains at a level of nearly 2 e / ~ . ~ between the carbon atoms indiamond, indicating the real existence of covalent bonds. Theirconclusions with regard to hexamethylenetetramine and magnesiumare, however, not likely to command general acceptance withoutconsiderably more evidence.The contour diagram of the formersubstance shows at certain points between molecules a density ofnearly le/A.2, which is interpreted as indicating some form ofhydrogen bond between the nitrogen and carbon atoms of adjacentmolecules, and small protuberances in the contour lines aroundcarbon atoms are said to represent hydrogen atoms. In the case ofmagnesium, the electron density between atoms differs from zeroby an amount corresponding to the distribution of the conductivityelectrons uniformly throughout the structure. It appears froma remark made by the authors that they are uncertain of the phaseangle of F222 for diamond, and the same uncertainty probably occursfor other weak reflections; it should also be pointed out that thedetection of an electron density due to conductivity electrons iscontrary to all modern views, according to which conductivityelectrons can give rise only to incoherent scattering of X-rays.P. Debye,lg in connection with the development of a method fordetermining the number of conductivity electrons from observationson incoherent scattering, has shown that the coherent scattering(contributing to lattice reflections utilised in structure analysis) iscompletely negligible.E. G. C.3. TERNARY ALLOY SYSTEMS.The X-ray powder method is a powerful means for investigatingcomplicated ternary alloy systems. It gives information which isnot obtainable by use of the older methods, and enables phase-diagrams to be worked out from the beginning with reasonablespeed and accuracy.Until comparatively recently X-ray work was almost entirelyconfined to binary systems.Here its contribution mostly consistedin the fundamental task of solving the structures. Its applicationto problems of phase equilibria consisted for the most part in thenore accurate delineation of the phase boundaries, the generaloutlines of all the most important binary systems having alreadybeen drawn by the classic methods of metallography.Microscopic methods are less easy to apply to complicated ternary19 Physikal Z., 1937,38, 161 ; cf. W. Scharwiichfer, ibid., p. 165180 CRYSTALLOGRAPHY.systems, for the microscope cannot give the composition of a ternaryphase where this is mixed with a second or third constituent.It istherefore very diEcult to trace the course of the complicatedreactions occurring in ternary alloy systems. X-Rays provide anecessary tool for this purpose, and whether used in conjunctionwith the microscope or separately, they are probably essential forthe complete understanding of many ternary systems of technicalimportance. Above all, X-rays offer an infallible means for theidentification of structures , whether solid solutions or compounds.A n accurate measurement of the lattice spacings leads to a know-ledge of the exact composition of a solid solution which is inequilibrium with a given compound, a point which is often ofconsiderable importance.Of course, many ternary equilibrium diagrams have alreadybeen partly worked out by the older methods, though these are moreand more being supplemented by X-ray data.Very important workhas recently been done by M. L. V. Gayler 1 on the dental amalgams,which are alloys of silver, tin, and mercury. As part of this research,the constitution of the ternary alloys was determined. It issuggested that seven invariant reactions take place, and on thisbasis a new theory is proposed to explain the changes occurringduring the setting of dental amalgams. Another importantinvestigation on a ternary system recently carried out by the usualthermal and microscopic methods, but supplemented by X-rays,is that of W. 0. Alexander2 on the copper-nickel-aluminiumsystem.Of primary importance is the study of the reactions taking placeduring solidification, which has in the past proceeded mainly fromthe interpretation of thermal curves.No doubt, high-temperatureX-ray powder photographs will play an important part in futuredevelopments. Cameras such as that recently designed by W.Hume-Rothery and P. W. Reynolds will soon be an indispensableadjunct to studies of ternary systems. At present the use of high-temperature X-ray cameras is mainly confined to binary systems,as, e.g., in the work of E. A. Owen and E. L. Yates4 on thecoefficient of expansion of iron-nickel alloys.It is, however, at lower temperatures that the use of X-rays isespecially valuable. Here, thermal curves may give misleadingresults, for the alloys are often too sluggish to react during the timeof cooling.Long periods of annealing, followed by X-ray powder1 J . Inst. Metals, 1937, 60, 379, 407.Ibid., 1938, 62, advance copy.Proc. Roy. SOC., 1938, A, 167, 25.Proc. Physical Soc., 1937, 49, 17, 178BRADLEY : TERNARY ALLOY SYSTEMS. 181photographs, should reveal the true equilibrium conditions. Itwill then be possible to distinguish between the different types ofreaction which may take place in ternary systems. As an alloy iscooled from the molten state to room temperature, any one of thefollowing reactions may take place :A + BA + B + C (peritectoid if solid, peritectic if C is liquid)A + B + CA + B += C + D (bigenetic solution D)A B + C + D (trigenetic solution D)(Read from left to right on heating, right to left on cooling.)The reactants in the above equations may all have differentstructures, though this is not necessarily the case.For example,C (eutectoid if solid, eutectic if C is liquid)D (monogenetic solution D)CUboth A and B may be face-centred cubic but with differentcompositions.On the assumption that these reactions have been carried tocompletion down t o a given temperature, it is possible to investigatethe isothermal phase equilibrium diagram at that temperature.This consists of a mosaic of single-phase, two-phase, and three-phase areas, a typical example, with some of the more complicatedregions omitted, being shown in the figure (A. J. Bradley and H.Lipson 5).The single-phase axem am in general bounded by curved6 Proc, Roy. Soc., 1938, A , 167, 421182 CRYSTALLOGRAPHY.lines, and the three-phase areas are triangles, the corners of whichgive the compositions of the three phases. In a two-phase regionthe compositions of the phases, though no longer invariant, can befound for any given alloy from the directions of the tie-lines whichare indicated by dashes (shown in the x1 + a region only). Thisis a specially valuable contribution of the X-ray method, thoughW. Koster and W. Dannohl have shown that magnetic measure-ments may sometimes be used for the same purpose.The first important investigation of a ternary alloy system bypurely X-ray methods was that of E. Persson on the copper-manganese-aluminium system.Later, F. R. Morral s examinedthe iron-rich iron-aluminium-carbon system. Following thesepioneer investigations, A. G. H. Anderson and E. R. Jette madea more comprehensive survey of the iron-chromium-silicon system,which was important on account of the use of a new method forfixing phase boundwies in ternary systems. Finally, A. J. Bradleyand A. Taylor lo and A. J. Bradley and H. Lipson have workedout complete constitutional diagrams for given heat-treatments inthe case of the iron-nickel-aluminium and copper-nickel-aluminiumsystems. I n preparing such preliminary phase-diagrams theessential point is to fix the positions of the corners of the three-phase fields, which is readily done from a comparison of a smallnumber of photographs.have devised a method forapplying lattice-spacing measurements to the determination ofphase boundaries in ternary systems, the principle of which is thatthe lattice spacing contours show abrupt changes in direction oncrossing from a two-phase field to a single-phase area.I n practice,difficulties may sometimes arise where the changes in direction areonly slight, especially when the lattice spacing contours in thesingle-phase fields show serious departures from Vegard's law.The phase boundaries can then be fixed solely from a visual estimateof the proportions of the phases present in two-phase alloys.Though not leading to highly accurate results, this method issufficiently reliable for the construction of a first approximatephase diagram, as, e.g., in the case of the above iron- and copper-nickel-aluminium systems.I n these diagrams it is surprising to find alloys consisting of two-phases which have, not merely the same type of structure, but alsoA.G. H. Andersen and E. R. Jette6 2. Metallk., 1935, 2'7, 220.8 J . Iron Steel Inst., 1934, 130, 419.Trans. Amer. SOC. Metals, 1936, 24, 375.10 Proc. Roy. SOC., 1938, A , 166, 353.l1 Trans. Amer. SOC. Metals, 1936, 24, 519.2. Physik, 1929, 57, 115BRADLEY : TERNARY ALLOY SYSTEMS. 183almost the same lattice spacings. For example, in the formersystem there is a range of alloys containing two body-centred cubicphases in equilibrium, whereas in the latter system two face-centredcubic structures are often present in the same alloy.At certaincompositions, lattice spacings are absolutely identical, and the onlydifferences are the presence of superlattices in one phase, but notin the other. Even this distinction may not always be found, sothat the interpretation of isolated X-ray photographs is to beavoided a t all costs. A complete range of compositions must beexamined if trustworthy results are to be obtained.Some interesting results have been obtained in structuralinvestigations on ternary systems. It is often found that theternary intermetallic compounds and solid solutions are analogousin structure to certain phases found in binary systems ; e.g., F. Lavesand S. Werner l2 have found that the binary alloy Mg,Zn is iso-morphous with Mg,Cu,All,, both being cubic (Oh).This falls intoline with the earlier observation that MgCuAl is isomorphous withMgZn,, while MgNiZn is isomorphous with MgCu,. Both these twotypes of structure are also found in each of the ternary systemsMg-Cu-Zn, Mg-Ag-Zn, Mg-Cu-Si, and Mg-Co-Zn.13 In accordancewith the principle first laid down by Hume-Rothery, analogousstructures are in each case found a t about the same ratio of valencyelectrons to atoms.The application of this rule to the phases found in ternary systemsis d a c u l t in the case of the transition elements. For example,P. Rahlfs l4 has found four new phases of a body-centred cubictype with superlattices. These are : (Cu,Ni),Sn, a’ = 5.946 A . ;(Cu,Ni),Sb, a’ = 5.857 A. ; Ni,MgSn, a’ = 6.097 A. ; Ni,MgSb,a’ = 6.050 A.It thus appears that nickel may replace copper asthough it, too, were univalent, whereas in general this element mustbe reckoned as null-valent when applying the Hume-Rothery rule.On the other hand, in the copper-nickel-aluminium system copperreplaces nickel quite extensively in the phases Ni,M and NizAl3,which extend up to the compositions NizCuAl and NiCuAl,respectively. Such facts show the need for avoiding too literal aninterpretation of the Hume-Rothery rule.F. Laves l5 has shown that it is possible to prepare a continuousseries of ternary solid solutions extending between the compositionAgCd, and pure magnesium. All these alloys have the same typeof hexagonal close-packed structure, suggesting that the bindingforces in metallic magnesium are not essentially different from thosel2 2.Krist., 1936, 95, 114.13 F. Laves and H. Witte, Metallw., 1936,15, 15, 840.l4 Ibid., 1937, 16, 640. Nai?uwh8., 1936, 84, 742184 CRYSTALLOGRDHY.in AgCd,, which is regarded as a typical Hume-Rothery compound.On the other hand, W. Hume-Rothery and G. V. Raynor l6 haveshown that the extension of ternary solid solutions depends onfactors other than electron concentration. For example, Mg,Sndoes not dissolve any appreciable quantity of aluminium or indiumeven when the compositions are made up to give the correctproportions of electrons to atoms. The same workers l7 haverecently discussed the various other factors which must be takeninto consideration in formulating a theory of alloys, the chief ofwhich is the size-factor.K.Riederer l8 has examined the structures found in the systemAl-Mg-Zn and finds a body-centred cubic structure for AI,Mg,Zn,with 160 atoms in the unit cell. He has also investigated theAl-Mg-Cd system,lg drawing up a ternary diagram for 230". H.Witte20 has examined some Mg-Zn-Ag alloys, also using X-raymethods.It is beyond the scope of the present account to describe the manyinvestigations of ternary alloy systems which are being carried outby other methods. Reference may be made to the investigationsof W. Koster and his co-workers,21 on the systems Co-Mn-Al,Co-Mn-Cu, Fe-Co-V, Mn-A1-T1, and Mn-Cd-T1. Other recentresults are those of J. L. Haughton 22 on the system Ag-Al-Mg, andof D. Hanson and W.T. PeU-Walpolez3 on Sb-Cd-Sn. C. H. M.Jenkins, E. H. Bucknall, C. R. Austin, and G. A. Mellor24 haveinvestigated the Fe-Cr-Ni system. A. J. B.4. CRYSTAL CHEMISTRY.With the progress of crystal chemistry the number of essentiallynew structure types discovered each year diminishes, particularlyamong simple substances, and it is interesting to observe thaturanium, one of the last of the elements to be analysed,l appears tohave a structure unlike that of any other, consisting of a hexagonalclose-packed arrangement deformed in such a way that each atom isbonded to four neighbours only, two bonds being collinear and theother two a t 127" to each other in a plane at right angles to thefirst pair.The structures of various oxides, halides, sulphides, and otherrelatively simple compounds have been determined, but the majorityPhil.Mag., 1938, [vii], 25, 335.1 7 Ibid., 26, 129.Is Ibid., 1938, 30, 16.21 2. Metallk., 1938, 30, 281, 330.Za Ibid., 1937,61, advance copy.l8 2. Metallk., 1936, 28, 312.8. angew. Min., 1937, 1, 83.2a J . Inst. Metals, 1938, 62, 175.a4 J . Iron Steel Inst., 1937, (2), 187.1 C, W. Jacob and B. E. Warren, J. Arner. Chem, SOC., 1937,59,2588COX : CRYSTAL CHEMISTRY. 185of publications during the year have been devoted to more complexstructures. Although, in general, the increase in complexity ofsubstances studied has been accompanied by an increase in theextensiveness of the data employed for their analyses, this is notuniversally the case, and some proposed structures fall short of theaccuracy desirable, on account of the small number of reflectionintensities employed.In order that atoms shall be located with anaccuracy of a few hundredths of 1 A., it is necessary, except in thesimplest cases, to employ at least 100 intensities; visual estimatesof many intensities are likely to give a better picture of the structurethan the most accurate measurement of a few.Structures containing linear groups include sodium cyanide,,sodium isocyanate,3 potassium hydrofluoride KHF,,* and ammoniumchlorobromoiodide.6 In the cubic modification of the cyanide(NaC1 structure) the CN groups are rotating, and both in this andin the low-temperature orthorhombic form the G N distance is1-06 A., the same as N-N in the iso-electronic nitrogen molecule.For sodium isocyanate, the structure of which is similar to thatof sodium azide, the distances are given as C-N, 1.21 A.and G O ,1-13 A. The detailed analysis of the triple halide confirms earlierwork ; the C1-I and Br-I distances are 2-38 and 2.50 A., respectively,very slightly greater in each case than the sum of the neutral radii.Linear HgCl, groups are also found in NH4HgC1,,6 which shouldtherefore be regarded as NH4C1,HgC1,, and in K,HgC14,2H,0,7 theHg-C1 distance being about 2.4 A., although in the latter case theHgC1, groups deviate slightly from strict linearity. The similarityof the cell dimensions of K,HgCl,,H20 and K,SnC1,,2H20 is probablynot significant.An accurate analysis of sodium bromate * has yielded a Br-0distance of 1.78 A.; although this is probably slightly too high(cf.1-0 = 1-79 A. in sodium periodate), previous values wereundoubtedly too low. The bromine atom is displaced from theplane of the oxygens, its valency angle being 112O. The planarnature of the BO, group, on the other hand, has again beendemonstrated in sodium metaborate and potassium pentaborate,KH2(H30)2B5010 ; lo the latter substance contains the quinquevalention (I), in which the central boron atom is surrounded tetrahedrally2 H. J. Verweel and J. M. Bijvoet, 2. Krist., 1938,100,201.* V. Caglioti and G. Giacomello, Ric. sci., 1938,9,545.6 (Miss) R. C. L. Mooney, 2. Krkt., 1938,98, 324.7 C. H. MecGillavry, J. H. De Wilde, and J. M. Bijvoet, ibid., p.212.* (Miss) J. E. Hamilton, ibid., p. 104.0 S. Fang, ibid., 99, 1,M. Bassihre, Compt. rend., 1938, 206, 1309.E. J. Harmsen, ibid., 100, 208.lo W. H, Zachariasen. ibid., 1937, 98, 266186 CRYSTALLOGRAPHY.by four oxygens a t 1.53 A., an appreciably greater distance thanin the BO, triangle (1.35 A.). The environment of the oxygenatoms not in the complex ion is considered to afford evidence thatthey form hydroxonium ions, but it seems doubtful whether thealternative view that they are water molecules and that the complex0 0 HO OH0 2-0 B-o>~<o-B<~ O-B/o B-0 0-BO / (1.1 HOion is univalent (11) can be excluded. The ion B,O, in sodiummetaborate is found to have configuration and interatomic distancesidentical with those in the isomorphous potassium salt; it is ofinterest that this isomorphism results in a compromise wherebyboth sodium and potassium have a co-ordination number of 7instead of the more usual 6 and 8-10 respectively.Among substances containing AX, groups, accurate revisionshave been made of the structures of silver permanganate,ll sodiumperiodate,12 and czesium chromateYf3 while in accordance with thepredictions l4 of A.Strunz, durangite, NaA1F(As04), appears 15to be fully isostructural with titanite, CaTiO(Si04), and olivenite,Cu2(OH)As04,1s has the andalusite structure, containing the peculiartrigonal bipyramidal co-ordination of five oxygens to copper. Thesame co-ordination, although more symmetrical, occurs in themolecules of the trimethylstibine dihalides, SbMe,X,.l' Anunexpected discovery is the existence of square ICl, groups inKIC14,1* with I-C1 = 2-34 A., very slightly less than in [ClIBrI-.Since the ordinary theory of square co-ordination postulatingsp2d bonds is considered inapplicable in this case, it is suggestedthat this is essentially an octahedral (d2sp3) co-ordination with twovacant positions. In substances of the type AAlF419 (A = NH,,K, Rb, or Tl), as expected, the aluminium does not form an ionAlF, but has the usual octahedral co-ordination which is also foundin the closely related substances T12A1F,,20 chiolite, 3NaA1F4,4NaF,21and cryolite, Na3AlF6.22 On the other hand, the planar configur-l2 E.A. Hazlewood, ibid., 98, 439.l4 See Ann. Reports, 1937, 34, 164.l7 A.F. Wells, ibid., p. 367.11 K. Sasvari, 2. Krist., 1938, 99, 9.13 J. J. Miller, ibid., 99, 32.15 P. Kokkoros, 2. Krist., 1938, 99, 38.18 H. Heritsch, ibid., p. 466.18 (Miss) R. C . L. Mooney, ibid., 98, 377.19 C. Brosset, 2. anorg. Chem., 1938, 239, 301.20 Idem, ibid., 1937, 235, 139.21 Idem, ibid., 1938, 238, 201 ; V. Caglioti and G. Giacomello, Naturwiss.,20 S . von Nbray-Szab6 and K. Sasvari, 2. Krwt., 1938,99,27,1938, 26, 317BANNISTER : CLAY MINERALS. 187ation of auric gold is confirmed by the analysisz3 of Cs2Au2C1, andCs2AgAuC1,, which have modified perowskite structures containingsquare [AuCI,]- and linear [AgCI,]- and [AuCI,]- ions. There is anappreciable difference between the Ad-C1 and AuIII-Cl distances(2.30 and 2-42 A., respectively).Further examples of the squareco-ordination of palladium are provided by palladous chloride 24and (AsMe,)Pd,X, (X = C1 or Br) ; 25 the former is built of infinitechains (111), in marked contrast with>pd<~&pd<~~>pd< the rutile atructure of palladous fluoride,and the same four-membered ring withalmost identical angles (86" at the palla-dium atoms) occurs in the trimethylarsine derivatives, the analysisof which affords a good example of the value of triple Fouriersummations. This investigation also illustrates the difliculty oflocating exactly the lighter carbon atoms on account of the swampingeffect of the heavier ones ; on the other hand, a recent analysis 26 ofplatinum phthalocyanine has shown that, when necessary, thesediificulties can be overcome by sufficient refinement of experimentaland interpretative procedure, and the results in this particular caseprovide some justification for the application of the Abbe diffractiontheory to electron-density maps in that the effect of the first twominima and maxima around the platinum atom are clearly discernibleat distances corresponding closely with those predicted by the theory.I n conclusion, attention may be directed to a useful survey of theprogress of inorganic crystal chemistry during the past ten yearsby F.Machatschki.27(111.)E. G. C.5. CLAY MINERALS.Minerals based upon (Si,Al),O, Sheets.Micas.-Mauguin's early measurements and calculations of micaformulae have been extended by many workers. R.E. Stevens1has published seventeen new chemical analyses of lepidolite, andalthough he does not give physical data, he marks the limits ofsubstitution in the lithium micas. H. D. Miser and R. E. Stevensgive KLiMg,Si40,,F2 as the formula of a mineral resemblingsericite from Magnet Cove, Arkansas, and identify it as the rarelithium mica taeniolite. J. Holzner has recalculated a number23 N. Elliott and L. Pauling, J . Amer. Chem. SOC., 1038,60, 1846.z4 A. F. Wells, 2. Krist., 1938, 100, 189.26 Idem, Proc. Roy. SOC., 1938, A , 167, 169.J. M. Robertson, private communication.27 Naturwiss., 1938, 26, 67, 86.Ibid., p. 104.Amer. Min., 1938, 23, 607.2;. Krist., 1936, 95, 435188 CRYSTALLOGRAPHY.of mica analyses and his results, coupled with those of Stevens, showthat, referred to 48 (0, OH, F) the octahedral cations totalapproximately 8 in muscovite, 4KAl,Si3A1010(OH),, and 12 inphlogopite, 4KMg,Si,A1010( OH),.The departures from roundnumbers are much more considerable for biotite and lepidolite,where the octahedral cation sum vanes fkom 10 to 12. G.Nagelschmidt4 has made a study of the powder patterns of micawith a view to their identification in soil fractions, and finds thatthey belong to either of two types, the muscovite or the phlogopite-biotite type. Hydromus~ovite,~ sericite, illite,6 the potassium-bearing clay mineral of Ross and Kerr, and Endell and Hofmann’sglimmerton ” are all hydrated muscovite which cannot bedistinguished with any certainty by X-ray methods from ordinarymuscovite. E.Maegdefrau and U. Hofmann 7 have also confirmedthat glauconite is a mica of the muscovite type low in potassiumand high in water content. Chemical analysis, specific gravity, andX-ray measurements of a hydromuscovite from Ogofau, Carmarthen-shire, show that the unit cell contains 48 (0, OH), and that replace-ment of oxygen by hydroxyl groups [037(OH)11 instead of O,(OH),]is balanced by a diminution in the potassium content from 4 to3.88 atoms per unit celL5 The departure of the ideal water contentof a mica from 4H20, in conjunction with the variation in atomicreplacements, is probably sufficient to account for the departurefrom the comparatively ideal formulae of muscovite and phlogopiteof the lithium, iron, and sericitic micas.Jackson and West’sanalysis of muscovite still remains the only serious contribution tothe crystal-structure studies of the mica family. Biotite androscoelite, two members meriting particular attention, still awaitsolution. A hydxated muscovite from Schmiedefeld, Thuringia,formerly determined as fine-grained pyrophyllite, contains 1.08%of V203.8 It is possible that the vanadium content of the triassicred marl of the south-west of England and the Permian shales ofOlsnitz, Saxony, is due to a similar vanadium-bearing layer-structuremineral. M. Mehmel has studied the decomposition of biotite byacid, alkali, and heat treatment, using X-ray methods to identifythe products, and has obtained results of interest in the investigationof sediments.Talc and PyrophyZZite.-The structures of talc and pyrophyllite6 A.Brammall, J. G. C. Leech, and F. A. Bannister, Min. Mag., 1937,24,* R. E. Grim, R. H. Bray, and W. F. Bradley, Amer. Min., 1937,@, 813.‘I 2. Krbt., 1937, 98, 31.8 H. Jung, Chem. Erde, 1937, 11, 38.a Ibid., p. 307; Portschr. Min., 1937,22. autoreferctte, XLVII.2. Krbt., 1937, 97, 514.607BANNISTER : CLAY MINERALS. 189have been partly confirmed by the interpretation of single-crystalphotographs.1° A chemically analysed sample of the former wasused. The unit cell dimensions (in A.) are :Pyrophyllite, A1,Si4010 (OH) 2.a ..................... 5.15 & 0.02 5.27 -J= 0-02b ..................... 8.88 5 0.02 9.13 f 0.03/3 .....................lOO"45' f 30' lOO"15' f 15'Talc, Mg3Si,010 ( OH) 2.c 18.60 f 0.04 18.88 f 0.05 .....................It is found that "agreement with observed intensities is verypoor and thus all structures strictly compatible with space-grouprequirements are eliminated as was the case for dickite." Thestructures are concluded to have been correctly determined byJ. W. Gruner within the layer, and to be fixed along the a and cdirections, but individual [Al,Si,O,,(OH),], or [Mg,Si,O,,(OH),],layers are shifted at random by some multiples of b/6 along theb axis.Chlorites and Vermiculites.-Although Pauling and McMurchy 'swork on the chlorite family is consistent with the evidence of powderphotographs, no recent single-crystal studies have confirmed theproposed structures.J. Holzner l1 has published chemical analysesof iron chlorites, and obtains fairly satisfactory agreement with thePauling formulae by calculation on a basis of 14 oxygens per unit cell.Cookeite, occurring as small curved flakes on the pegmatites ofMaine, U.S.A., and at Ogofau, Carmarthenshire, probably possessesa chlorite-like structure in which the alternating talc-likeand brucite-like layers are replaced by pyrophyllite-likelayers [Al,Si,AlO,,( OH),]-l and lithium-bearing gibbsitelayers [La,( OH),]+ l, leading to the approximate formula,LiAl4Si,AlOl0( OH),. The cell dimensions determined on singlecrystals are a = 5.13, b = 8.93, c sin p = 28.30 A.5 One of themost interesting chlorites awaiting X-ray study is cronstedtite,the analyses of which can only be reconciled with the chlorite-typestructure by including in the tetrahedral layer 4-6 ferric ions withsilicon to make up the usual 16.Gruner's structure for the vermiculites has been coniirmed in themain by S.B. Hendricks and M. E. Jefferson,12 who used singlecrystals of several chemically analysed specimens of vermiculite.They obtained a = 5.33 &- 0.05, b = 9.18 3: 0-05, c = 28-85 If0.10 A., p = 93'15' 5 15', i.e., about 4" smaller than Gruner's value.Fourier analysis of the (001) diffractions shows that talc-like layersare interleaved with layers of water molecules. The layers are10 S. B. Hendricks, 2. Krist., 1938, 99, 264.Neues Jahrb. Min., 1938, A, 73, 389.Amer. Min., 1938, 23, 851190 CRYSTALLOGRAPHY.stacked precisely as in muscovite for the a direction, but a partlyrandom stacking of layers is found for the b direction as in talcand pyrophyllite (see above).Vermiculites form mixed structureswith both the chlorites and the micas. Any mixture of mica,vermiculite, chlorite, pyrophyllite, and talc or kaolin layers mightbe encountered, particularly in soils. Different samples ofj efferisite from Brinton's quarry, West Chester, Pennsylvania, maybe either vermiculite, vermiculite-mica, or vermiculite-chlorite,so that " considerable variation can be expected even in a restrictedlocality." The various mixed structures may be differentiated by(1) the (001) spectra, (2) the swelling produced on heating, whichreveals the presence of vermiculite layers.Hendricks and Jeffersonalso suggest that the layers of water molecules in vermiculites formhexagonal nets in which the oxygen atoms are probably coplanar.One-quarter of the hydrogen ions, i.e., one hydrogen ion of alternatewater molecules within the net, join the net to oxygen ions in theadjacent silicate layer. The proposed structure accounts for one-half the water being expelled from the mineral without change ofthe X-ray patterns.Both J. W. Gruner l3 and I. Fankuchen l4 have studied thestilpnomelane group of minerals. Gruner, who used the powdermethod, interpreted his data on the basis of a monoclinic pseudo-hexagonal cell : a = 5.23-5-27, b = 9.08-9.12, c = 12-07-12-18 A.Fankuchen's single-crystal measurements in A.are :Or thohexagonal. Rhombohedral.a. b. C. a. a.Stilpnomelane ............ 22-0 38.0 37.9 17.9 76"Ferrostilpnomelane ... 22.1 38.1 36-2 17.6 78"- - Parsettensite ............ 22-5 39.0 38.0The Laue photographs of single flakes reveal complete asterismwith hexagonal symmetry, and the character of the spots onoscillation photographs leads to a possible explanation : The 16small pseudo-cells may vary in composition throughout the truecell and be packed not quite in perfect regularity. The structureis probably like that of chlorite, consisting of interleaved, alternate,distorted mica sheets and layers containing K, (OH), and Mg.Fankuchen's study accompanies optical, chemical and dehydrationdata by C. 0. Hutton.14 No attempt, however, has been made tocount the atoms in the unit cell; formulae are deduced by assuming14 (0,OH) per unit cell.No suggestion is made that one or moreof these minerals have a mixed-layer structure like those foundamongst the vermiculites.CZays.-Resumh of recent work on the clay minerals include Sir13 Amer. Min., 1937, 22, 912. l4 See Min. Mag., 1938,25, 172BANNISTER : CLAY MINERALS. 191William Bragg’s,15 in which physical properties are shown to beclosely connected with crystal-structures, W. von Engelhardt’s,lein which chemical analyses and a useful bibliography are given,and A. Brammall and J. G . C. Leech’s on layer-structures and base-exchange.17 J. de Lapparent l8 has classified the clay minerals in amanner running counter to the usually accepted structure work.Many problems on the mineralogy of clays await solution, and aconfused nomenclature often obscures published work containingimportant data.In addition to papers listed in this report,additional abstracts of studies on clay minerals (other than crystal-structure analyses) are given in a special section on clays in theMineralogical Abstracts. l9 Abstracts of papers on clay technologyare given in the Transactions of the Ceramic Society.Much attention has been given to the determination of clayminerals in soils. F. A. van Baren 2O has made a study of changesin refractive index produced by interaction of the mineral with theimmersion liquid. Von Engelhardt 21 has described a simplemethod of measuring the refractive index of submicroscopic mineralparticles based on measurement of the relative intensity of lightscattered from a suspension of the mineral in media of variousrefractive indices.Powder photographs showing marked orientation of clay mineralsdeposited by slow evaporation from water on to a flat surface areuseful for identification.22 Mineral constituents of Spsoil fractionshave been successfully determined by the powder method,23 and thepublished photographs show that great improvements in techniquehave been made.The time is ripe for redeterminations of thecomponents of other composite materials, particularly slate.Recent work on clay minerals has been concentrated on thecrystal-structure and properties of montmorillonite, the chiefcomponent of Fuller’s earth 24 and bentonites, nontronite orchloropal, and the recently discovered magnesium-bentonite 25from Hector, San Bernardino Co., California, the last being closein composition to saponite and lucianite.All these mineralsl5 Proc. Roy. Inst., 1938, 30, 39.l6 Portschr. Min., 1937, 21, 276.l7 Science Progress, 1937, 31, 641 ; Sci. J. Roy. Coll. Sci., 1937, 7, 69; 1938,l8 2. Krist., 1937, 98, 233.2o Z . Krbt., 1936, 95, 464.z1 W. von Engelhardt, Zentr. Min., Abt. A , 1938, 212.22 G. L. Clark, R. E. Grim, and W. F. Bradley, 2. Krist., 1937,96, 322.z3 G. L. Clark, F. F. Riecken, and D. H. Reynolds, ibid., p. 273.24 E. F. Newton, Proc. Geol. ASSOC., 1937, 48, 175.26 W. F. Foshag and A. 0. Woodford, Amer. Min., 1936, 21, 238.8, 43.lB Min.Abstr., 1938, 7, 94192 CRYSTALLOGRAPHY.give the same powder patterns but dXerent a and b spacings(in A,) : 26a ........................ 5.15 5.23 5-24b ........................ 8.95 9.11 9.16The powder data are consistent with the structures of these mineralsconsisting of pyrophyllite or talc-like layers interleaved with layersof water molecules. The remarkable property of montmorilloniteof shrinkage along the c direction on dehydration provides in somemeasure a confirmation of the proposed structure, but considerablediscussion has attended the structural details, which cannot ofcourse be decided by single-crystal work. E. Maegdefrau andU. Hofrnann2’ find only (hkO) and (001) diffractions on powderphotographs, and conclude that the neutral [AI,Si,O,& OH),],layers are stacked in parallel superposition but in random orientationabout the normal to the layers.S. B. Hendricks and C. S. Ross,~*however, point out that the presence of (hEO) reflections impliessome regularity in the orientation of the layers about the layernormal and in their relative translations. These authors, fromoptical and electron-diffraction studies, consider that ‘‘ individualmontmorillonite crystals contain many aluminosilicate layers andthat these layers have a rather regular arrangement with respectto one another as long as a few orders of reflection from (001) canbe observed.”The exact interpretation of the dehydration data of montmoril-lonite is also in question. G. Nagelschmidt 29 and, later, Maegdefrauand Hofmann 27 concluded that the c-spacing varies continuouslyas a function of the water content.W. F. Bradley, R. E. Grimand G. L. Clark,30 however, regard their own data obtainedby wetting dehydrated material as evidence for the existenceof five hydrates containing 2, 8, 14, 20, and 26 molecules of waterand with corresponding c-spacings 9.6, 12.4, 15-4, 18.4, and 21.4 A.8. B. Hendricks and M. E. Jefferson31 consider that the structureof montmorillonite is made up of aluminosilicate layers (seeabove) interleaved with extended hexagonal nets of watermolecules as in the vermiculites, and that the former layers havea relative shift with respect to one another of n/6 along the bdirection. The distance between two neighbouring oxygen ions ofthe water layer is about 3.0 A., and this spacing is consideredto produce the sharp and intense diffraction on the powderMontmorillonite. Nontronite.Mg-bentonite.26 G. Nagelschmidt, Min. Mag., 1938,25, 140.27 2. Krist., 1937, 98, 299.2Q Ibid., 1936, 93, 481.81 Arner. Min., 1938, 23, 863.28 Ibid., 1938, 100, 251.so Ibid., 1937, 97, 216BANNISTER : CLAY MINERALS. 193photographs of 3.1 A. This proposal is more in accord with whatis known of other hydrates, no close-packed arrangement of watermolecules having yet been encountered. The reversible dehydrationproperties of montmorillonite compared with vermiculite areattributed to the very small particle size of the one mineral,and also to the presence of ions external t o the pyrophyllitelayers which account for the base-exchange properties of the mineral.G.Nagelschmidt and H. Z. Schofield26 have produced datasuggesting that the base-exchange capacities of the montmorillonitefanlily (excluding magnesium bentonite) are closely related to theexcess cations (Ca, Na, Mg, K) present. This work supports theview that a large fraction of the base-exchange cations enter intothe crystal lattice and are not merely adsorbed at the surface of theparticles. Sir William Bragg 15 has suggested that the mechanism ofbase-exchange in montmorillonite takes place via the water moleculesheets of the structure.Gruner’s structure for dickite has now been confirmed by S. B.Hendri~ks,~2 who reports that single crystals are piezo-electric.The stacking of layers along the b direction, however, is a randomone, as for vermiculites, pyrophyllite, talc, and montmorillonite.Gruner’s kaolinite structure is also supported by X-ray and electron-diffraction photographs by Hendri~ks.~3 Anauxite is supposedto have a similar structure but with vacant Al and (OH) positions;hence, the excess silica which distinguishes the mineral fromkaolinite.J. W. Gruner 34 has measured the unit cell dimensionsand specific gravities of seven chemically analysed specimens ofkaolinite and anauxite. He obtains almost identical unit cellvolumes but lower specific gravities for anauxite, and rejectsHendricks’s conclusion, suggesting instead that tetrahedral SiO,groups of the tetrahedral layers are replaced by octahedral A10,(OH)4groups.F. Machatschki,35 however, refutes this structure asrequiring some distortion of the anion packing, and gives analternative solution in which six-fold and four-fold co-ordinationpositions (the latter being all vacant in the ideal kaolinite structure)of the Al(0,OH) octahedral layer are statistically and partiallyoccupied by aluminium and silicon ions respectively. Further X -ray and electron-diffraction studies have been carried out onhalloysite and metahalloysite.32 The former is the fully hydratedmineral AZ,0,,2Si02,4H20. Of Ross and Kerr’s halloysite samples,2, 8, and 9 proved to be metahalloysite, the remainder being truekaolinite. Using fully hydrated halloysite from Djebal Debar,Hendricks showed that the electron and X-ray data are consistent32 Amer.Min., 1938, 23, 295. 33 2. Krist., 1936, 95, 247.34 Amer. Min., 1937, 22, 855. as Ibid., 1938, 23, 117.REP.-VOL. XXXV. 1 94 CRYSTALLOGRAPHY.with a structure in which neutral [Al,Si,O,(OH),], layers are inter-leaved with [(H,O),], layers. More recently, he has suggested 31 thathydrated halloysite contains the extended hexagonal water moleculesheets postulated for montmorillonite and the vermiculites. Thereis only one layer of water molecules present between the alumino-silicate layers, however, and on dehydration the metahalloysitewould be more tightly bonded between layers. This is consideredto explain the irreversible character of the dehydration at EiO".%F. A. B.6. ORGANIC STRUCTURES.Although but few exact analyses of organic structures have beenreported during the past year, much useful work continues to bedone in preliminary investigations of all classes of compounds, andthe value of the X-ray method in studies of semicrystalline, high-molecular substances has been shown in many publications, some ofwhich, bearing on the structure of the proteins, are discussed inSection 7 of this Report.I n the case of another high polymer,cellulose, an attempt has been made by S. T. Gross and G. L. Clark 1to effect a definite decision between the lattices proposed by K. H.Meyer and by E. Sauter. It appears to the Reporter that thediscussion on which they base their conclusion in favour of theformer author's view is not sufficiently exhaustive, and that thesituation still remains as summarised in last year's Report.,Apart from X-ray investigations, various electrical and thermalmeasurements on organic compounds have furnished usefulcontributions to the important field of studies concerned with therelations between structure and thermodynamic properties ; aninteresting example of this type of work is afforded by A.R.Ubbelohde's determination of the lattice energies of some long-chain compounds, the results of which afford confirmation of A.Miiller's 5 theoretical calculations. It is very unfortunate, how-ever, that in some investigations of long-chain compoundsinsufficient attention has been given to the question of purity;these substances are not readily obtained in a state of high purity,96 M.Mehmel, Chem. Erde, 1937, 11, 1; Fortschr. Min.., 1937, 21, 80.1 2. Krist., 1938, 99, 357.8 W. 0. Baker and C. P. Smyth, J . Amer. Chem. SOC., 1938, 60, 1229;A. Muller, Proc. Roy. SOC., 1938, A , 166, 316; A. R. Ubbelohde and J. W. H.Oldham, Nature, 1938, 142, 74; J. M. Robertson and A. R. Ubbelohde, Proc.Roy. Xoc., 1938, A , 167, 136.Ann. Reports, 1937, 34, 189.Trans. Faraday SOC., 1938, 34, 282.Proc. Roy. SOC., 1936, A, 154, 624COX : ORGANIC STRUCTURES. 195for which neither mixed melting points nor long spacings separatelyare adequate criteria.6Last year the similarity between the hydroxyl-bond systemsof pentaerythritol and resorcinol was commented upon,' and somesimilarity might be expected to persist in the dimorphic forms intowhich both are transformed a t higher temperatures.This provesnot to be the case, however; analysis of high-temperature (p)resorcinol shows that a rearrangement of the molecules takes placewhereby a denser packing, resembling that of aromatic hydrocarbonmolecules, is attained. The influence of the hydroxyl bonds thusappears to be diminished, although this is shown more by theirdeflection from a tetrahedral distribution than by their increase inlength, which is scarcely more than the experimental error. Theenergy required to stretch and deflect the hydroxyl bonds ispresumably more than compensated by the lower van der Waalsand polarisation energies achieved in the closer packing '(cf. the caseof the transition ice I -+ ice I11 9 ) .The bond lengths in p-resorcinol are the same as in the low-temperature form, but theC-OH bonds are deflected out of the symmetrical position by 3"in the plane of the ring, and one of them is also deflected about3" out of the plane. The diminution in rigidity implied by thisdistortion is probably not due to a large increase in thermal motionof the atoms, but may be a consequence of the molecule's beingraised to an excited state a t the higher temperature; in a moleculeof this kind, with several possible arrangements of bonds of nearlythe same energy, such an excitation is possible if it results in thenew crystalline form's having lower free energy.The transition of pentaerythritol, on the other hand, is of normaltype, with increase in volume on going to the cubic high-temperatureform, and although a detailed analysis has not been made, there isno doubt that rotation of all the hydroxyl groups occurs in the cubicform.1° The fact that the substance remains solid for over 70"above the transition point suggests that the rotation is of such anature as to permit the continued existence of some kind of hydroxylbonding.F.Francis, F. J. E. Collins, and S. H. Piper,PToc. Roy. Soc., 1937, A ,155, 691 ; S . H. Piper, J . SOC. Chem. Ind., 1937, 50, 6 1 ~ ; J. W. H. Oldhamand A. R. Ubbelohde, J . , 1938, 201. ' Ann. Reports, 1937, 34, 182.J. M. Robertson and A. R. Ubbelohde, Proc. Roy. SOC., 1938, A , 167,(Sir) W. H. Bragg, Proc. Roy. Inst., 1938, 30, 283.122.lo I.Nitta and T. Watanab6, Bull. Chern. SOC. Japan, 1938, 13, 2 8 ;C. Finbak, Tids. Kjemi, 1937, 17, 146; E. G. Cox and F. J. Llewellyn,unpublished196 CRYSTALLOGRAPHY.The analysis of pentaerythritol tetra-acetate l1 has provided thefirst accurate determination of the structure of an ester group, andaffords a good example of the use of triple Fourier summations.12All angles between single bonds in the molecule are found to betetrahedral within experimental error, and the O=C-C andOXC-0 angles are equal to 125", in agreement with stereochemicaltheory. The bond distances are C-C = 1.52 A., C-0 = 1.41 A.,and C=O = 1-33 A . ; the last is appreciably greater than thevalue 1.24 A. calculated from the sum of the bond radii and foundexperimentally in oxalic acid dihydrate, whereas the second appearssomewhat small.It may be that the C=O distance is increasedsomewhat in ester groups, but it is difficult to see why this should beso, and it seems likely on the internal evidence that the uncertaintyin bond lengths is rather greater than the ammount (0.03 A . ) assignedby the authors. The possibility of this, in a careful analysis of thiskind, supports the view that the results of Fourier syntheses should,in general, be submitted to the test of structure-factor calculationswith small variations in the parameters, and emphasises the veryapproximate nature of the bond distances given by the numerousanalyses of organic compounds based on a relatively small numberof qualitative intensity measurements.In a preliminary account l3 of the analysis of succinic acid, theinteratomic distances are given as C-C = 1.51 and 1-52 A., andC-0 = 1-28 and 1-31 A.; the conjugation present in oxalic acidno longer occurs, so that the C-C distances revert to the normalsingle-bond length. It is noteworthy that all analyses of the lasttwo years agree in suggesting that the pure single bond betweenaliphatic carbon atoms is 1-52 A. rather than 1.54 A.Onaccount of resonance between the various possible bond arrange-ments, the molecule of 2 : 5-diketopiperazine l4 is flat, with allangles in the ring 120°, and bond lengths C-0 = 1-25, N-C(keto) =1-33, N-C(methy1ene) = 1.41, and C-C = 1.47 A. The last twodistances are unusually low, since resonance would not be expectedto cause links to the methylene carbon atom to assume any double-bond character.It is probable, again, that the uncertainty in thelengths is rather greater than the 0.03 A. indicated by the authors,although it is notable that the N-C(methy1ene) distance in hexa-methylenetetramine l5 is also given as 1-42 A. The dimensions ofthe *NH*CO* group correspond closely with those found in urea.I511 T. H. Goodwin a)nd R. Hardy, Proc. Roy. SOC., 1938, A , 164, 369.12 Idem, Phil. Mag., 1938, 25, 1096.l3 H. J. Venveel and C. H. MacGillavry, Nature, 1938,142, 161.1* R. B. Corey, J. Amer. Chem. SOC., 1938, 60, 1598.1s R. W. G. Wyckoff and R. B. Corey, 2. Krist., 1934, 89, 462.Several interesting ring compounds have been examinedCOX : ORGANIC STRUCTURES.197The packing of the molecules proves to be very much as suggestedby J. D. Bernal; l6 they are connected in long ribbons by centro-symmetrical arrangements of -NH . . . . O= bonds of length2.84 A., similar to those in isatin.17 There is no hint of anyN . . . . CH2 interaction such as has been proposed in the case ofhexamethylenetetramie.ls A somewhat similar substance iscyanuric acid, whose flat six-membered ring has sixequal C-N distances of 1.37 A., unlike cyanuric triazide,20 in whichC-N and C=N distances of 1.38 and 1.31 A. respectively can bedistinguished. The tendency for one of the KekulB forms topredominate is thus removed when the unsymmetrical azide groupis replaced by -OH, and indeed, the mean G O distance of 1.27 A.suggests that the biggest contribution to the resonance structureof cyanuric acid is made by the form (I).I n this crystal also thereappear to be -NH . . . . O = bonds of about 2.8 A. Thenature of the intermolecular forces in acetaldehyde-ammonia,21CH,-CHO,NH,, on the other hand, is somewhat obscure. Chemicaland X-ray evidence combine to show that this substance has thestructure (11) + 3H20 (and is the cis-isomer). It is suggested thatH CH,\N/(111.)3-six water molecules are united by hydrogen bonds to form a puckeredring, and that the crystal is built of sandwiches of these and(CHMe*NH), hexagons, held together by NH . . . . H,O bonds;the length of 3.4 A. assigned to these bonds, however, is incompatiblewith anything stronger than van der Waals binding.The tri-cyanomelamine ion (111) appears22 to be very similar to the iso-electronic cyanuric triazide, but accurate measurements of bondlengths are not yet available.l6 2. Krist., 1931, 78, 363.l7 E. G. Cox, T. H. Goodwin, and (Miss) A. I. Wagstaff, Proc. Roy. SOC.,1936, A , 157, 399.l* Seep. 179.In E. H. Wiebenga and N. F. Moerman, 2. Krist., 1938, 99, 217; Nature,2o Ann. Reports, 1935, 32, 233.21 N. F. Moerman, 2. Krist., 1938, 98, 447.22 J. L. Hoard, J. 4mer. Chem, SOC., 1938,60, 1194.1938, 141, 122198 CRYSTALLOGRAPHY.X-Ray investigations of aromatic compounds are too numerousto be discussed individually; outstanding among them are theanalyses of p-resorcinol (see above) and of t01an.~~ The detailsof the latter structure, which was mentioned briefly last year,24show that the length of the C E C bond is 1-19 A., in good agreementwith the value found spectroscopically in acetylene, so that thecontribution of excited structures involving a double bond betweenthe central carbon atoms is probably small.It is to be observed,however, that the electron displacement in a triple bond may beenough to cause the X-ray value for its length to be slightly shorterthan the same bond measured spectroscopically, since in the lattercase the internuclear distance is determined. The C-C bondsconnecting the central atoms to the benzene rings are only 1-40 A.,as compared with 1.44 A. in stilbene; this contraction in a singlebond adjacent to a triple one is difficult to account for in terms ofresonance, although an explanation of another kind can probablybe given.25 A similar contraction is found spectroscopically inseveral acetylene derivatives.A somewhat different case, forwhich no theoretical explanation is available, is the short C-CH,distance (1.47 A.) in durene,2G and it is interesting to note that arevision 27 of the structure of hexamethylbenzene, in which thesame distance can be measured more accurately, yields the value163 A. E. G. C .7. PROTEINS.For the purposes of summarising recent developments in theX-ray study of protein structure, a more convenient introductioncould hardly be found than T. W. J. Taylor’s Report last year on“ The Chemistry of Proteins and Related Substances.” The presentsection may be considered as being a crystallographic continuationof that report.A simple, and perhaps not altogether surprising, generalisationseems to have been reached in the X-ray classification of the fibrousproteiq2 in that they all appear to fall into no more than two maingroups, the keratin-myosin group (including its p-sub-group) and2s J.M. Robertson and (Miss) I. Woodward, Proc. Roy. SOC., 1938, A , 164,24 Ann. Reports, 1937,34, 187 ; cf. J. M. Robertson, J . , 1938,131.25 W. G. Penney and G. J. Kynch, Proc. Roy. SOC., 1938, A , 164, 409.26 J. M. Robertson, ibid., 1933, A, 142, 659.27 Idem, J. SOC. Chem. I d . , 1938,57, 1056.436.Ann. Report& 1937, 34, 302.W. T. Astbury, C m p t . rend. Trav. Lab.Carlsberg (S~rensen Jubilee Vol.),1938,22, 45; Trans. Paraday SOC., 1938,34, 377; Kolloid-Z., 1938,83, 130ASTBURY : PROTEINS. 199the collagen group. The normal state of the former group is that ofthe regularly-folded cc-form, but this may be converted into thefully-extended @-form by stretching or by means, of the type ofdenaturation, which also serve to disrupt the intramolecular folds.The chief muscle protein, myosin,2*3 turns out to be extraordinarilylike the hair protein, keratin, in its labile or “ supercontracting ) )form, i.e., when the disulphide bridges so characteristic of thekeratins have been largely broken down,* both as regards molecularconfiguration and elastic properties ; and the conclusion has beendrawn that the contraction of muscle is the consequence of a furtherfolding of the cc-form of myosin analogous to the supercontractionof keratin.The keratin-myosin group includes also the fibrous proteins ofthe epidermisIt undoubtedly connotes something very fundamental in the make-up of living things, some configuration that, suitably graded insensitivity by modifications introduced during differentiation,must be used widely as the basis of long-range elasticity.Anextreme modification used by birds and reptiles, as opposed tomammals (which use ct-keratin), is “ feather keratin,” which occursin a slightly constrictedOutside the keratin-myosin group all, or almost all, other naturalprotein fibres fall into the collagen group, which includes suchstructures as connective tissue, tendons, cartilage, elastoidin,’ etc.Fibres of the collagen group (except elastin) exist normally in whatappears to be a stereochemically fully-extended configuration-not the trans-configuration of the P-proteins, but perhaps a cis-configuration s-but they contract strongly in hot water a t ratherspecific temperatures.The contracted form then shows long-rangeelasticity like that of the keratin-myosin group, and this property,taken into consideration with the X-ray photograph^,^^ makesit clear that once more we must postulate the folding and anfoldingand probably those of myo-epithelial tissueW. T. Astbury and S. Dickinson, “X-Ray Studies of the MolecularStructure of Muscle ” (in preparation).J. B. Speakman, Nature, 1933, 132, 930; 1936, 138, 327; J .Text. Inst.,1936, 27, P231.K. M. Rudall, Ph.D. Thesis, Leeds, 1936; A. Giroud and G. Champetier,Bull. SOC. Chirn. biol., 1936, 18, 656; J. C. Derksen and G. C . Heringa, Polskaffaz. lekarska, Szymonowicz Festschr., 1936, 15, 532; J. C. Derksen, G. C.Heringa, and A. Weidinger, Acta Neerland. Morph., 1937,1, 31.W. T. Astbury and T. C . Marwick, Nature, 1932,130,309 ; W. T. Astbury,Trans. Faraday SOC., 1933, 29, 193; Kolloid-Z., 1934, 69, 340; C h m . Week-blad, 1936, 33, 778. ’ W. T. Astbury and R. Lomax, J . , 1935, 846; G. Champetier andE. Fawe-Fremiet, J. Chim. physique, 1937, 34, 197.IJ W. T. Astbury, Chem. Weekblad, 1936, 33, 778200 CRYSTALLOCIRAPHY.of polypeptide chains. The highly elastic protein of the ligamenturnnuchae, elastin, apparently gives the collagen fibre photograph onlyon ~tretching,~ from which it is a fair conclusion that elastin is amember of the collagen group characterised by a thermal-trans-formation temperature below ordinary temperatures.2The fact that, according to X-rays, all the fibrous proteins fallinto two, or very few, main configurational groups provides stillanother argument against perpetuating any real distinction between“ fibrous ” and ‘‘ globular ” proteins; for one of the implicationsof the results obtained by T.Svedberg and his collaborators withthe ultra-centrifuge is surely that in the whole of the protein fieldonly a few configurations are used out of the enormous number oftheoretical possibilities.A similar inference may be drawn fromthe recent results of M. Bergmann and C. NiemannYga which showalso-and this is supported by X-ray data l-that the Svedberggeneralisation of multiple molecular weights, deduced from thestudy of “ globular ” proteins, holds for fibrous proteins too. Moreimpressive still, however, is this, that within one and the sameconfigurational group of the fibrous proteins there are wide variationsin chemical constitution like those found between members of eachof Svedberg’s moleoular-weight groups.1°That there are great variations of molecular shape within eachof the various molecular-weight groups is also evident from T.Svedberg’s data: indeed, X-rays indicate that the range ofvariation includes even the fully-extended, or p-, pr0teins.l. l2 I nproteins as we know them now, configuration is not decided by strictchemical constitution, and neither shape nor chemical constitutionis the chief factor in fixing molecular weight.The apparent codictbetween chemical constitution and configuration may be resolved,nevertheless, by some such concept as unifies the aromaticcompounds, which are all based on the benzene ring and itshomologues.Similar intramolecular folds are probably used in the structureof both fibrous and globular proteins, but their precise nature stilleludes us, though crystallographic cell dimensions, number ofmolecules per cell, molecular weight, and in some cases space-groupalso, have been worked out for the following globular proteins:* H.Kolpak, Kolloid-Z., 1935,73, 129.J . BioZ. Chem., 1936, 115, 77 ; 1937, 118, 301.10 W. T. Astbury, Royal Society Discussion on Protein Structure, Nov.,11 Nature, 1937, 139, 1051 ; Id. Eng. Chern., 1938,10, 113.l2 W. T. Astbury and F. 0. Bell, Cold Spring Harbor Symposia on Qumti-1938.tative Biology, 1938, 6ASTBURY : PROTEINS. 201insulin,l3 excelsin,l4* 15 lactoglobulin,16 chymotrypsin,17 hzemo-globin,17 pepsin,l8 and tobacco-seed g10bulin.l~ Insulin has alsobeen submitted to a Patterson analysis,13 but the interpretation forthe present is under discussion. D. M. Wrinch 2o argues that thecorrect solution is the cage-like structure she had proposed forboth insulin 21 and pepsin.22 This structure, the “ G, cyclol,” besidesbeing of the right sort of shape for insulin and pepsin, is built from288 residues and therefore offers a very striking geometricalexplanation of the Svedberg 35,000 group and the findings of M.Bergmann and C.Niemann; but it is difficult to reconcile it withthe great variations in shape within the group, and with the evidencethat the larger protein molecules are formed by the union ofrelatively small sub-units, all of a similar density and probably of afibrous nature.12The liberation of polypeptide chains when globular proteins formmonolayers has now been placed beyond l2 Multi-layersprepared by the technique of I. Langmuir and K. B l ~ d g e t t , ~ ~ andconsisting of up to 1764 monolayers of egg albumin, have beendetached from their metal base and examined mechanically,optically, and by X-rays.The conclusion is that such multilayersof egg albumin consist of polypeptide chains roughly oriented inthe direction of movement of the slide, and laid down with theirside chains approximately perpendicular to the surface. Theside-chain spacing is about 98 A., agreeing closely with the thicknessper monolayer given by direct measurement of the multilayerthickness, which was obtained first by means of an optical arrange-ment independent of the optical constants of the flms themselves,and then even by means of an ordinary screw micrometer ! E.Stenhagen25 has since obtained similar results from 40 layers of al3 (Miss) D. Crowfoot, Nature, 1935, 135, 691; Proc. Roy. SOC., 1938, A ,164, 580.l4 W.T. Astbury, S . Dickinson, and K. Bailey, Biochem. J., 1935, 29, 2351.l5 W. T. Astbury, S. Dickinson, and F. 0. Bell, unpublished results.l6 (Miss) D. Crowfoot and D. Riley, Nature, 1938,141, 521.l7 J. D. Bernal, I. Fankuchen, andM. Perutz, ibid., p. 521.l8 J. D. Bernal and (Miss) D. Crowfoot, ibid., 1934, 133, 794.lo (Miss) D. Crowfoot and I. Fankuchen, ibid., 1938, 141, 521.2o J . Amer. Chem. SOC., 1938, 60, 2005; Nature, 1938, 142, 955; D. M.Wrinch and I. Langmuir, J . Amer. Chem. SOG., 1938, 60, 2247; Nature, 1938,142, 581 ; E. H. Neville, ibid., p. 994.21 D. M. Wrinch, Trans. Paraday Soc., 1937, 33, 1368.22 Idem, Phil. Mag., 1937, 24, 940.23 W. T. Astbury, F. 0. Bell, E. Gouter, and J. van Ormondt, Nature, 1938,24 K. M. Blodgett, J .Amer. Chem. Soc., 1935, 57, 1007; I. Langmuir, V. J.25 Trans. Faradrcy Soc., 1938, 34, 1328.142, 33.Schaefer, and D. M. Wrinch, Science, 1937, 85, 76202 CRYSTALLOGRAPHY.lipo-protein photographed with the condensing monochromatordesigned by I. Fankuchen.26The most far-reaching protein discovery for years is that of thenature of the tobacco mosaic and related viruses, which have beenfound to be chemical individuals of the nucleo-protein class. X -Ray examinations have been carried out by R. W. G. Wyckoff27and J. D. Bernal 28 and their collaborators, but mostly by the lattergroup, who have made an intensive study of three strains of tobaccovirus and two of cucumber virus. The units in pure preparationsof these are apparently" rod-like bodies about 150 A.thick whendry. All the preparations, except the most dilute solutions, areactually liquid-crystalline : the rods fit together laterally in two-dimensional hexagonal close packing, but have no regularity ofpacking in the direction of their length. The X-ray pattern iscoinposite, one part-the intramolecular pattern-being a fibrediagram that remains practically unchanged in all preparationsfrom solutions up to the dry gel, and the other-the intermolecularpattern-a system of side reflections whose spacings vary with theproportion of water present. The lateral separation of the rodsis increased to about 210 A. in the wet gel, and to as much as 450 A.in a 137L solution, and all the while the particles remain distributeduniformly in a two-dimensional hexagonal arrangement IThe intramolecular pattern, which repeats along the fibre axisat intervals of about 69 A., shows, of course, that the giant moleculesare built up from sub-units that are relatively small.J. D. Bernal 31now favours a sub-unit of dimensions about 11 x 10 x 10 A., buthe originally suggested 22 x 20 x 20 A . ~ ~however, from the nucleic acid content (5%) and X-ray data onthe proteins and nucleic acids339 l2 (see below) that the largerdimensions correspond a t any rate to the smallest possible chemicalIt can be26 Nature, 1937, 139, 193; Physical Rev., 1938, 53, 909.27 R. W. G. Wyckoff and R. B. Corey, J. Biol. Chem., 1936,116,51.28 F. C. Bawden, N. W. Pirie, J. D. Bernal, and I. Fankuchen, Nature, 1936,20 H. S. Loring, M. A. Lauffer, Vf. M. Stanley, F. C. Bawden, N. ?V. Pirio,30 J. D. Bernal, I. Fankuchen, and D. P. Riley, ibid., p. 1075.31 Private communication.32 W. T. Astbury and W. AT. Stanley, Discussion on Stanley's paper at33 W. T. Astbury and F. 0. Bell, Nature, 1938, 141, 747.* There is some disagreement 29 as to whether the true unit is really rod-shaped : there is evidence that it may be almost round like that of the tomato" bushy-stunt " virus, but is aggregated into rods by the methods of isolation.Bushy-stunt virus crystallises in rhombic dodecahedra and gives X-rayphotographs corresponding to a body-centred cubic lattice.30138, 1051 ; J. D. Bernal and I. Fankuchen, ibid., 1937,139,923.K. M. Smith, and W. D. MacClement, ibid., 1938,142, 841.Cold Spring Harbor Symposium, 1938ASTBURY : PROTEINS. 203sub-unit, for the volume they include is associated with just onenucleotide, in combination with about 54 arnino-acid residues.The dimensional data on the nucleic acids have been obtainedprincipally from an X-ray study of thymonucleic acid and itscompound with clupein.33* l2 The unit in pure preparations ofsodium thymonucleate, the viscous solutions of which show streamingdouble r e f r a ~ t i o n , ~ ~ appears to be a column of some 2,000 flat, orflattish, nucleotides piled on top of one another a t 3.3, A. apart.This distance is almost exactly equal to the spacing of the sidechains in a fully-extended polypeptide, with the result that clupein,for instance, a simple polypeptide of about 28 residues, 21 of whichare arginine residues,35 combines readily with thymonucleic acidto form a fibrous compound that gives an X-ray photographremarkably like that of the sodium compound : the outstandingperiod along the fibre axis of 3.3, A. remains unchanged. Thefibres of clupein thymonucleate are optically negative with respectto their length, just as are the nucleic acid-containing 36 bands of t h esalivary chromosomes with respect to the chromosome length,37from which it may be inferred that if the protamine-thymonucleicacid compounds in the chromosomes are similar to clupein thymo-nucleate, then the protein chains must run along their length.Thus for the f i s t time we arrive experimentaZly at a reasonablemolecular basis for the physicochemical properties of thechromosomes and their linear genic pattern; for protein chains,perhaps modulated by combination with nucleic acid, are naturallywhat we first think of as likely bearers of such properties.W. T. A.W. T. ASTBURY.F. A. BANNISTER.A. J. BRADLEY.E. G. Cox.R. Signer, T. Caspersson, and E. Hammarsten, Nature, 1938, 141, 122.K. Linderstrtam-Lang, Trans. Faraday SOC., 1935, 31, 324; K.Linderstrtam-Lang and K. E. Rasmussen, Compt. rend. Trav. Lab. Carlsberg,1935, 20, 1.36 T. Caspersson, Skand. Arch. Physiol., 1936, 73, Suppl. No, 8.37 W. J. Schmidt, Naturwiss., 1937, 25, 506

ISSN:0365-6217    

DOI:10.1039/AR9383500173

出版商:RSC    

年代:1938

数据来源: RSC

摘要:

ORGANIC CHEMISTRY.1. INTRODUCTION.THE study of the mechanisms of chemical reactions, which has notreceived much attention in recent Reports, continues to provide afruitful field of research, and our knowledge of many changes inwhich organic compounds participate has been enriched by theresults of a large number of recent investigations. In the presentReport the policy of presenting certain topics with a reasonableamount of detail has been adopted and the consideration of muchimportant work is postponed until a future occasion. A series ofkinetic studies of replacements in aliphatic compounds have shownthat in the reaction Z + RX --+ RZ + X (e.g., OH' + RC1+ROH + Cl'), the removal of the group X and the addition of Z mayoccur either simultaneously (" bimolecular mechanism ") or con-secutively (" unimolecular mechanism "). The predominance ofone mechanism or the other is conditioned, inter aZia, by the natureof R and of the medium.The examination of a number of replace-ments a t an asymmetric carbon atom under kinetically controlledconditions has thrown light upon much that was obscure in connec-tion with the Walden inversion ; the st'eric course of the substitutiondepends largely upon its mechanism. Olefin elimination from alkylhalides and other compounds may proceed by a " bimolecular "or by a " unimolecular " mechanism, and similar possibilities havebeen demonstrated in anionotropic and allied changes. The in-vestigation of prototropic systems has been continued ; this hasincluded the measurement of speeds of isomerisation, halogenation,racemisation and deuterium exchange.The introduction of deu-terium into the aromatic nucleus follows the ordinary substitutionrules.The general problem of the influence of substituent groups uponreactions has been approached from two points of view : (a) by theanalysis of reaction velocities on the basis of the kinetic equation,k = PZe-E'RT, and (b) by the interpretation of chemical andphysicochemical data in the light of permanent and time-variableelectronic effects, each operating by two distinct mechanisms.Halogens and alkyl groups present peculiar features, as also, ofcourse, do groups standing in the ortho-positions in aromaticcompounds, and efforts have been made to trace the origin of thesepeculiaritiesINTRODUCTION. 205The aim of the Report on fatty acids and other long-chain com-pounds is to present to the organic chemist an account of theadvances in our knowledge of the structure of higher aliphaticcompounds arising out of studies of crystallisation and melting.Some of the developments have been treated separately in earlierReports, but in view of the complementary nature of the researchesit appeared worth while to attempt a general survey.As in someof the topics there are a t least fifteen years’ publications to be re-viewed, it will not be possible this year to deal with purely chemicalwork on higher aliphatic compounds, except for a few methods ofpreparation. The main departure from the earlier work in thisfield is the recognition that very different criteria of purity mustbe applied in dealing with higher aliphatic compounds from thosefound sufficient for lower aliphatic OF for aromatic substances.Binarysystems from pure homologues have thrown light on the behaviourof naturally occurring mixtures and have brought out the analogybetween liquid crystals and some forms of aliphatic compounds.The crystal structure of long-chain compounds has been made fairlyclear by X-ray methods; X-ray analysis of films is also used foridentification of pure compounds and for confirmation of the resultsof other methods of analysing mixtures. There have been manycontributions to the study of polymorphism, alternation of meltingpoints in homologous series, and compound formation.Many advances have been made in the chemistry of the terpenessince they were last reviewed in these Reports for 1935.Interestingsyntheses have been effected in the monoterpene group. Theabnormal rearrangement of the isoprene residues in Artemesia ketonehas been conf%med by the synthesis of the tetrahydro-derivative.Thujane has been prepared from I-menthone and also from acyclopentene derivative, and the cycbpropane nature of the thujanegroup is established by the synthesis of umbellularic acid, a de-gradation product of umbellulone. Carane has been prepared froma cyczohexene derivative, syntheses of verbanone, 6-pinene andpinane from cyclobutane derivatives have been described andfenchone has been obtained from camphenonic acid.Newinvestigations have removed several difficulties from camphorchemistry. For instance, oxidation of a-campholenic acid yieldsa-campholonic, and not pinonic acid as previously reported, moreattractive structures have been suggested for sulphocamphylic andthe related camphylic acids, and a study of camphenilyl chlorideand camphenilene shows that the constitution of the latter,put forward on Raman spectra, evidence, is inconsistent withdegradation experiments. Two different syntheses of ketones,probably structurally identical with the cyperones, indicat206 ORGANIC CHEMISTRY.that these sesquiterpene ketones are of the eudalene type,derived from head-to-tail union of three isoprene units. Re-searches on eremophilone have led to the conclusion that thestructure cannot be based on the skeleton of 1 : 9-dimethyl-7-isopropyldecalin ; two alternatives have been suggested, but afinal solution of the problem has not been made.The constitutionof the caryophyllenes is still uncertain; a structure advanced someyears ago is disproved by the synthesis of homocaryophyllenic acidand a new structure containing a fusion of four- and seven-memberedrings has been suggested. New alcohols, known as the betulenols,have been investigat,ed and a relationship between these compoundsand the caryophyllenes has been established. A novel structurecontaining a cydopentene ring has been tentatively advanced for thesesquiterpene alcohol, lanceol, and it is worthy of note that thecyclopentene system is present in the naturally occurring ketone,jasmone, C,,H,,O.The constitution of ledol has been amendedon the grounds of its relationship to the azulenes, and the structureof irene, an important degradation product of irone, has been con-firmed synthetically.The term '' steroid " is employed as a generic term for the naturalproducts, including the sterols, bile acids, heart poisons, saponinsand sex hormones, which are characterised by the common skeleton(I), and the undiminished activity in this field justifies a furtherreport on the chemistry of these substances. Most of the workduring the last two years has been stimulated by discoveries in thegroup of steroidal sex hormones, which have the physiologicalactivities characteristic of the gonads.Removal of the side chainfrom the sterols is now effected on a manufacturing scale and in-vestigations have been directed towards the production, fromandrostane intermediates, e.g., trans-dehydroandrosterone (11), ofmore active substances such as testosterone (the most activemale natural hormone) or compounds of therapeutic advantage.The preparation of compounds of protracted physiological activityhas received attention and other investigations on the brominationand subsequent dehalogenation of the steroids have led to unsaturatedcompounds showing both oestrogenic and androgenic activity.The possibility of transition from one group of hormones to anotherhas been examined. A route to the oestrone (111) series either fromandrostane intermediates or from sterols (by removal of the 17-sidechain after aromatisation of ring I) has been opened.The pregnane(IV) series includes progesterone, the hormone of the corpus luteumof the ovary, and the " life maintenance '' hormone of the adrenalcortex. It seems less practicable to obtain these important butinaccessible substances by arresting the degradation of the sterol sidINTRODUCTION. 207chain, than to synthesise them from 17-ketoandrostane derivatives,and reactions of the latter type are being examined. Of the newnatural products which have been isolated, the adrenal corticalsteroids are most important. The investigations of T. Reichstein,including the analysis of complex tissue extracts, the separation ofthe highly active corticosterone, the artificial preparation and laterthe isolation of deoxycorticosterone, and the elucidation of theconstitution of the compounds, form a remarkable chapter in thechemistry of natural products. Of the structural questions whicharise, one of importance concerns the position of an inert oxygenatom, investigation into which has had repercussions in the heartpoison group.The steroids of urine are now recognised as trans-Meformation products of the body steroids, and much new work in thisfield has been done, but neither the biochemical nor the structuralproblems can be regarded as settled. The " Vitamin D problem "is still not completely solved on the structural side. On the bio-logical side it now appears that the precursors are either ergosterolor 7-dehydrocholesterol, and calciferol and " vitamin D3" thecorresponding natural antirachitic vitamins.In recent years developments in the heterocyclic division havecentred around natural products, particularly those of pronouncedphysiological activity.The isolation in 1936 of c4ocopherol withvitamin E activity and the inevitable concentration of research inthis field led to an amazingly rapid solution of the structural problem.Progress has been made in other directions and several topics whichhave been developing steadily are reviewed in the present Report.Dioxan, discovered in 1907, has recently come into prominence as asolvent useful both for cryoscopic determinations and as a medium fororganic reactions, and an addition product with sulphur trioxide ha208 ORGANIC CHEMISTRY.been advocated as a sulphonating agent.a-Tocopherol has beensynthesised from +-cumoquinol and phytol. The synthesis isambiguous, but the degradation evidence favours the phenolicchroman (V) and not the alternative coumaran structure. Thestructure of equol, a phenol isolated from horse urine, has beenlimited to alternative coumaran or chroman formulae. The effectof alkali on Derris constituents has been examined, an importantadvance has been made in the chemistry of rottlerin, the structureof which is now limited to one of two chromen formulz, and a novelstructure containing a ring composed of one oxygen atom and ninecarbon atoms has been advanced for usnic acid. The observationthat high-temperature bromination of 2 : 2’-dipyridyl leads to sub-stitutionin the a-positions has been used in preparing and establishingthe structures of a series of polypyridyls.Important improvementshave been discovered in the preparation of glyoxalines and benz-iminazoles, and a new type of heterocyclic compound has beenprepared from o-phenylenediarnine and glucose. The bacterialpigments oxychlororaphine, pyocyanine and the pigment of Chromo-bacterium iodinum contain the phenazine nucleus and syntheses ofthe first two have been described. Important contributions tophenazine chemistry have been made, including the isolation ofcrystalline phenazyl radicals. An examination of the Americanspecies of Dicentra and Corydalis has revealed the presence ofthirty alkaloids hitherto undiscovered in the Asiatic plants, and theisolation of some new bases of the narcotine type is noteworthy.The constitution of the bis-isoquinoline alkaloid, cepharanthin, hasbeen limited to two formulax A relationship has been discoveredbetween alkaloids of the Senecio and the HeEiotropium species; onhydrolysis the alkaloids give acids of unknown structure and oneof three C, bases, all of which yield the same reduction product ofstructure (VI).R.K. C u o w .R. D. HAWORTH.F. B. KIPPING.J. C. SMITH.H. B. WATSON.2. REACTION MECHANISMS.The classification of reagents as ‘‘ negative-centre seeking ” and“positive-centre seeking’’ is a very old one, and the terms“ kationoid ” and (‘ anionoid ” have been used by Lapworth andothers to describe these two types.Since, however, the classificationdepends solely upon the affinity of the reagent for electrons or foWATSON : REACTION MECHANISMS. 209nuclei, independently of its state of electrification, the nomenclature“ electrophilic ” and “ nucleophilic ” has been suggested by C. K.Ingold1 as more appropriate. An electrophilic reagent is definedas one which acquires electrons or a share in electrons belongingto some other atom or ion, and a nucleophilic reagent as onewhich transfers electrons to or shares its electrons with a foreignnucleus.It is evident that when an electrophilic reagent attacks a moleculeit will do so at a point where the electron density is high relativelyto the nuclear field; moreover, the greater the electron density(relatively to the field), the more facile the reaction.Commonelectrophilic reagents are those which bring about the replacementof hydrogen of the aromatic nucleus (hence the op-orientation andthe facility of substitution when an electron-releasing group such as-O-CH, is present) or add a t olefinic linkages (where electron-repulsive groups cause increased speed) .2 A nucleophilic reagent,on the other hand, seeks a point of low electron density (againrelatively to the nuclear field), and the greater the deficiency ofelectrons the more rapid the reaction. Nucleophilic reagentsinclude the hydroxyl ion (as in alkaline hydrolyses which are nor-mally favoured by electron-attractive groups) and the reagents whichadd a t carbonyl carbon (e.g., in >CO + CN’+ >C(CN)mO‘,the first step in cyanohydrin formation).Acids, defined in theLowry-Bronsted generalised sense as proton donators, and oxidisingagents (electron acceptors) are included in the larger class of elec-trophilic reagents, and bases (again defined in the generalised manner)and reducing agents (which donate electrons) are similarly includedin the class of nucleophilic reagents.Whereas electrophilic reagents seek the most negative, andnucleophilic reagents the most positive point of a molecule, a numberof instances have been observed in which either of these points maybe attacked. One criterion of this type of reaction is that sub-stitution in an aromatic compound is always op, whether thedirecting group be of the op-type (when normally all positions arenegative but the o- and p - are the most negative) or of the m-directive type (when all positions are positive but the o- andp- aremost positive).The actual substituting reagent is here a freeneutral organic radical (produced by the symmetrical rupture of acovalent bond) ; reference was made in last year’s Report to thereactions of these radicals in the liquid phase.4 The incompletenessJ . , 1933, 1120; Chem. Reviews, 1934, 15, 226.C. K. Ingold and (Mrs.) E. H. Ingold, J . , 1931, 2354.D. H. Hey and W. A. Waters, Chem. Reviews, 1937, 21, 169.Ann. Reports, 1937, 34, 282210 ORGANIC CHEMISTRY.of the octet of one carbon atom renders the radical an electrophilicreagent, and the presence of an unshared electron renders it nucleo-philic; it thus combines the properties of the two common types ofreagent.5 The similarity of the behaviour of neutral radicals insolution to that of radicals in the gas phase has now been demon-strated further, and their reactions have been applied to the pre-paration of a number of derivatives of diphenyl and p-terphenyl,6and also of aromatic compounds of antimony and tellurium ;reaction occurs less readily or not at all with non-metallic elementssuch as sulphur, selenium, phosphorus, boron, carbon and silicon.'In striking contrast with aromatic substitution, which has beenthe subject of a multitude of researches during several decades,substitution at a saturated carbon atom has received relativelylittle attention until recently.In the past few years, however, theinvestigation of aliphatic substitution has , made very substantialprogress, and the knowledge so gained has thrown much light uponthe phenomenon of optical inversion. This work is summarised inthe paragraphs which follow, and some of the recent researches uponprototropic and anionotropic systems are then dealt with. A some-what arbitrary selection of topics has resulted in the omission ofreference to much of the recent work upon reaction mechanisms, andthis shortcoming is illustrated by the absence of any consideration ofintramolecular rearrangements or of the Kharasch peroxide effect.Any attempt to review the whole field in one Report would inevitablyhave reduced this section to a mere catalogue of the more importantresearches, however, and of the two evils the former has beenpreferred.AEiphatic Substitution.-The term " substitution " is here used todesignate the replacement of any group by any other.Substitutionby electrophilic and by nucleophilic reagents may be representedby the following general schemes, which refer to cases where thereaction involves the rupture either of one bond (" three-centresystem ") or of two (" four-centre system") :Electrophilic SubstitutionZ + R--jX+ R-Z + XY-!Z + R-[X+ R-'7 + Y-X5 C. K. Ingold, Chem. and Ind., 1937, 57, 112.6 W. S. M. Grieve and D. H. Hey, J., 1938, 108; I. M. Heilbron, D. H. Hey,and R. Wilkinson, ibid., pp. 113, 699; E.C. Butterworth and D. H. Hey,ibid., p. 116 ; H. France, I. M. Heilbron, and D. H. Hey, ibid., p. 1364 ; E. C.Butterworth, I. M. Heilbron, D. H. Hey, and R. Wilkinson, ibid., p. 1386.F. B. Makin and W. A. Waters, ibid., p. 843; W. A. Waters, ibid.,p. 1077WATSON : REACTION MEC€IANISMS. 211Nucleophilic SubstitutionZ + R+X+ R-'7 + X 1 - S N Yi-Z + R!-X --+ R-Z + Y-X(The dotted lines indicate the fate of the electron pairs originallyforming the covalent bonds which are broken.)In a comprehensive discussion of substitution processes in solution,E. D. Hughes and C. K. Ingold 8 have suggested that reactions of anyof these types may proceed by either of two mechanisms, which theyname the " bimolecular '' (S,2 ; S,2) and " unimolecular " (SE1 ; S,1)mechanisms.Substitution requires the addition of one group andthe removal of another, a.nd in a bimolecular process these steps arenow regarded as proceeding simultaneously ; the formation of thetransition complex involves the bringing up of the reagent and thestretching of the bond which is ultimately to be ruptured. Hughesand Ingold visualise an alternative mechanism of substitution,however. If the group which is to be replaced is not bound toostrongly, solvation may reduce the energy of ionisation by an amountcomparable in magnitude with the bond strength,* and a rupture ofthe bond at measurable speed may precede an almost instantaneousreaction of the ion with the attacking reagent, i.e., bond fission andbond formation may be separated into stages, of which theformer controls the rate.Such a mechanism is not possible whenthe group is held very firmly, as is the case with groups linked to thearomatic nucleus, and the theory applies essentially to substitutionat a saturated carbon atom and in solution. Ingold, Hughes, andtheir collaborators have carried out extensive studies of nucleophilicsubstitutions of this type.10For cases where one bond is broken the two mechanisms ofnucleophilic substitution are formulated :Z+RI-X+R-Z+X . . . S N 2slowRi-X- R+ + X ) . . . .rapidR+ + Z 4 R-ZIt is evident that reactions occurring by these mechanismswiu be bimolecular (s,2) and unimolecular (&I) respectively.Mechanism S,1 will be favoured relatively to S,2 by large electronrelease from R, strong electron-affinity in X, low nucleophilica J., 1936, 244 F.London, 2. Elektrochem., 1929,35, 652.lo See summary by E. D. Hughes, Trans. Fnraduy Soc., 1938,34. 185. * This answ01's the objection that an ionisation mechanism would involvetoo great an energy of activation (A. R. Olson and H. H. Voge, J. Amer. Chem.SOL, 1934, 56, 1690)212 ORGANIC CHEMISTRY.activity (basicity) and low concentration of the reagent 2, and highionising capacity of the solvent. The corresponding mechanisms forelectrophilic substitution (SE2 and S,l) and the factors favouringmechanism S,1 may be deduced similarly.The new experimental evidence which is put forward in favour ofthe view outlined above relates to the degradations of 'onium saltsand the hydrolysis of alkyl halides; Hughes and Ingold furtherquote various observations from the literature which are in accordwith their views.If the group R be varied in the direction ofincreasing electron release, the effect will be to oppose the attackof the nucleophilic reagent which is necessary for mechanism SN2,and to facilitate the ionisation which is the rate-determining step inmechanism SN1; a sufficiently large range of variation in theelectron-repulsion by R would be expected to lead first to a re-tardation of the reaction by mechanism SN2, and then to a change ofmechanism to SN1, followed by an increase of speed (this reversal ofthe effect of electron-repulsion is due, of course, to the fact that inmechanism SN1 the nucleophilic reagent Z is not attacking themolecule itself, and the measured speed is that of an ionisation whichis facilitated by a flow of electrons from R).There will thus be amechanistic critical point, on either side of which one mechanismpredominates, and, except in the neighbourhood of this point,reaction by the other mechanism will be almost negligible. While,however, increasing electron release by the group R will lead todiminishing velocity in the region where mechanism S,2 operates,the observed retardation may be small or even irregular, since anincreasing opposition to the approach of the reagent (process abelow) is to some extent counteracted by an increased facility in the m f aexpulsion of the group replaced (process b) ; Z + R - X+ RZ + X.Once the mechanistic critical point has been reached, however,the reaction, now proceeding by the SN1 mechanism, will be un-conditionally facilitated by increasing electron release, and a rela-tively large effect is likely to be observed.Some justification for the above predictions was found in studiesof the elimination of alcohols from quaternary ammonium hydr-oxides l1 (Z = OH; X = hAlk3), and an examination of thecorresponding hydrolysis of trialkylsulphonium hydroxides and salts( Z = OH, Br, etc.; X = SAlk,) gave evidence of a more definitecharacter.12 The decomposition of trimethylsulphonium hydroxide,l1 E.D. Hughes and C . K. Ingold, J., 1933, 69; E. D. Hughes, C. K..Ingold, and C. S. Patel, ibid., p. 526.la E.D. Hughes and C. K. Ingold, J . , 1933,1671 ; J. L. Gleave, E. D. Hughes,and C. K. Ingold, J . , 1935, 236.- - WATSON : REACTION MECHANISMS. 213OH + CH,*SMe, = CH,*OH + SMe,, and that of the corre-sponding triethyl compound, both in water at loo”, proved to be ofthe first order with respect to each of the ions concerned; bothreactions were bimolecular, the former being the more rapid.Methyldiisopropyl- and dimethyl-tert. -butyl-sulphonium hydroxidesdecomposed to yield isopropyl and tert.-butyl alcohol respectively,and both reactions were kinetically of the Jirst order ; moreover,even considerable additions of extraneous hydroxide ions had noeffect in the case of the tert.-butyl compound, and the completereplacement of hydroxyl by other ions (i.e., the use of sulphoniumsalts instead of the hydraxide) was without influence.The latterreaction (elimination of tert.-butyl alcohol) was much more rapidthan the former; actually the ratio of the velocity coefficientsBuylPrs was about 2600, whereas the ratio Me/Et was about 9.The anticipated relationships were thus realised, since the fourgroups Me, Et, PrB and Bur stand in ascending order of electronrepulsion (+ I ) , and the mechanistic critical point (for diluteaqueous solutions a t 100”) was located at some point between ethyland isopropyl. Confirmatory evidence was found in a study of theeffects of different anions upon the decomposition of the trimethyl-sulphonium cation. Five anions were employed; in order ofdescending basicity they were OH‘, OPh’, COs”, Br’ (Cl’).Inethyl-alcoholic solution the decomposition of the phenoxide, likethat of the hydroxide, was of the first order with respect to each ion(ie., kinetically bimolecular), and the carbonate, bromide andchloride decomposed by a unimolecular change, the speed not beinginfluenced by extraneous anions. For the first two anions thevelocities varied in the order OH’ >OPh’, whereas the decomposi-tions of the carbonate, bromide and chloride gave speeds whichwere equal within the limits of experimental precision. It is clearthat, while the speed of the bimolecular change will depend upon thebasicity of the reagent anion, changes in the latter will not affect therate of the unimolecular mechanism, since the reagent is here ex-cluded from the measurable stage The anticipated effects of changesin the anion were thus observed.An examination of the kinetics of the hydrolysis of a series ofalkyl halides has also led to results which are in harmony with thetheory of Hughes and Ingold.The alkaline hydrolysis of methyland ethyl halides in alcohol or aqueous alcohol is bimolecular, theethyl compound reacting the more slowly (by a factor of aboutl/10).13 E. D. Hughes, C. K. Ingold, and U. G. Shapiro’s investig-ation of the hydrolysis of isopropyl halides in aqueous alcohol haslS C. A. L. de Briiyn and A. Steger, Rec. Truv. chim., 1899, 18, 41, 311;+G. H. Grant and C. N. Hinshelwood, J., 1933, 258214 ORGANIC CHEMISTRY.shown that the bimolecular and the unimolecular reactions proceedhere at comparable speeds ; the former was slower (about 1/25) thanthe corresponding reaction of the ethyl halides (in this case moderateconcentrations of alkali lead also to the elimination of propylene,and by suitable adjustment of the conditions and determination ofthe propylene the individual velocity coefficients for the threereactions were determined) .14 The hydrolysis of tert.-butyl halides(in aqueous alcohol or aqueous acetone) was found to be unimolecular,and addition of alkali had no influence; l5 the speed was greaterthan that for the isopropyl halides under comparable conditions by afactor of about lo4. Further, a notable increase in the speed ofhydrolysis of tert.-butyl halides was caused by increase of the watercontent of the solvent, as would be expected on the view that thevelocity is governed by the ionisation of the halide.Clearly, achange of solvent is likely to cause a movement of the mechanisticcritical point, and in the case of a suitable compound might actuallylead to a change in the order of the reaction.Increase in the length of a n-alkyl group beyond two carbon atonisdoes not bring about any large increase in the inductive effect, andit is therefore to be expected that other primary, secondary andtertiary groups will give reaction mechanisms of the same type asthose established for ethyl, isopropyl and tert.-butyl respectively ;this has been verified in the hydrolysis of P-n-hexyl bromide,l6P-n-octyl bromide l7 (both similar to isopropyl halides), and thetert.-amyl halides l8 (similar to tert.-butyl halides).Relationships of the same type as those observed among theprimary, secondary and tertiary aliphatic halides are found in thearalphyl series CH,, CH,Ph, CHPh,, CPh,.The kinetics of thealkaline hydrolysis of benzyl chloride are of no simple type l9 andindicate simultaneous bimolecular and unimolecular reactions ;benzhydryl chloride in aqueous alcohol gives a first-order reactionindependent of added hydroxyl ionsY2O and the same applies to a-phenylethyl chloride.21 The ease of ionisation of triphenylmethylhalides is well known. It is clear that the hydrolysis of benzyl chloridestands on the border line between the unimolecular and the bimole-cular mechanisms, and this explains the fact that alkaline hydrolysis(where S,2 is favoured by a relatively high concentration of OH’) isE.D. Hughes, J., 1936, 256; K. A. Cooper and E. D. Hughes, J., 1937,S. C. J. Olivier, Rec. Trav. chim., 1937, 56, 247.I7 E. D. Hughes and U. G. Shapiro, J . , 1937, 1192.l8 E. D. Hughes and B. J. MacNulty, ibid., p. 1283.l o S. C. J. Olivier and A. P. Weber, Rec. Truv. chim., 1934, 53, 869.*O A. M. Ward, J., 1927, 2285.l4 J., 1936, 225; E. D. Hughes and U. G. Shapiro, J . , 1937, 1177.1183.21 Idem, ibid., p. 445WATSON : REACTION MECHANISMS. 215accelerated by electron-attractive substituents in the nucleus,whereas in absence of alkali (where conditions are not favourable toSN2) these substituents cause a decrease of speed. Benzylidenechloride and benzotrichloride have both been shown to undergo uni-molecular hydr01ysis.l~ In the degradation of a series of aralphyl-trimethylammonium hydroxides (R*NMe,*OH, where R = CH,,CH,Ph, CHPh,) in aqueous solution a change from S,2 to SN1 isobserved a t R = CHPh,.22All the above “hydrolytic ” reactions, when they occur inaqueous-alcoholic solution, are actually combined hydrolyses andalcoholyses.The reagent YZ is here both water and the alcohol(i.e., Z = OH and OR).A notable observation has been made by E. D. Hughes, C. K.Ingold, and A. D. Scott 23 in connection with the alcoholysis ofa-phenylethyl chloride. Using sodium methoxide ( 3 . 5 ~ ) inanhydrous methyl alcohol or sodium ethoxide (2-8s) in anhydrousethyl alcohol at 70°, they find that the bimolecular reaction is ofmajor importance (in contrast with the unimolecular change inaqueous alcohol referrred to above) ; in the former case 61 yo and inthe latter of the total alcoholysis proceeds by the bimolecularmechanism under these conditions.The smaller ionising power ofthe medium (as compared with aqueous alcohol) depresses reactivityby the S,1 mechanism, and the greater reactivity of the alkoxide ion(as compared with hydroxyl) favours the S,2 mechanism.Hughes and Ingold’s theory of aliphatic substitution has beenchallenged by W. Taylor. In a study of the reactions (hydrolysis +alcoholysis) of methyl, ethyl and tert.-butyl bromides in 60% and80% alcohol in absence of added hydroxide, he found these to bekinetically of the first order, the velocities giving the sequenceBUY ))) Me>Prfl>Et 24 (the value for Prs was taken from theresults of Hughes, Ingold, and Shapiro).This sequence was re-garded as evidence against the theory of Hughes and Ingold, whichpredicts for reactions by the unimolecular mechanism (if they couldall be realised) Bu”>Prfl>Et >Me. Since, however, a bimolecularreaction inevitably becomes pseudounimolecular if one reagent ispresent in large excess, the results provide no test of mechanism, aswas pointed out by L. C. Bateman and E. D. Hughes; 25 on theother hand, the relative speeds Me >Et (for the bimolecular mechan-ism) and Bur))) Prb (for the unimolecular mechanism) are to beanticipated on Hughes and Ingold’s theory. In a subsequentexamination of the hydrolysis of the halides in acetone containing5% or 10% of water (again water in excess; the ratio of the initial24 I b i d ., p . 992.2 2 E. D. Hughes and C. K. Ingold, J., 1933, 09.23 J . , 1937, 1201. z6 Ibid., p. 1187216 ORGANIC CHEMISTRY.concentrations [H,O] /[RBr] in the experiments recorded varied from25 to 70), the same sequence of velocities was obtained.26 Taylorhas also measured 27 the speed of hydrolysis of tert.-butyl bromideand of benzhydryl chloride in acetone containing quantities of waterup to 10% (initial ratio [H,O]/[RBr] from 3-4 to 47). In the case oftert.-butyl bromide he emphasises the proportionality betweenvelocity and water concentration for the hydrolysis by 1 yo and 2%of water; he does not observe such proportionality in the case ofbenzhydryl chloride, however.On the grounds outlined above,together with certain calculations of the equilibrium concentrationsfor tert.-butyl chloride and benzhydryl chloride 27 and a furtherobservation to which reference is made below, Taylor concludes that,contrary to the view of Hughes and Ingold, the hydrolysis of analkyl halide always proceeds by a bimolecular mechanism in whichwater appears as a direct reagent.28If, as Taylor suggests, the hydrolysis of tert.-butyl halides is abimolecular process, it would still, of course, give first-order kineticswhen water is present in excess. Hughes and Ingold have pointedout, however,s that, if the water molecule acts as a reagent, itfunctions either as an acid or as a base, and then a stronger acid(e.g., H,O+) or base (e.g., OH-) will act more powerfully; if this doesnot occur, then in the rate-determining stage the water is acting assolvent only.The velocity of hydrolysis of tert.-butyl chloride wasshown to be unaffected by acids or bases, and it was largely on thisfact that their views of the reaction mechanism were first based.L. C. Bateman and E. D. Hughes have more recently treated tert.-butyl chloride with small quantities of water in formic acid medium ; 25the ionising power of this solvent is so high that it is not likely to bechanged perceptibly by the addition of small proportions of water.They find that the velocity in the initial stages (Le., previous tointerference by the reversed reaction) is independent of the con-centration of water, and, for the whole reaction, constant values ofthe velocity coefficient were obtained by use of the appropriateexpression for a first-order reaction with second-order reversal.They isolated tert.-butyl alcohol, but no tert.-butyl formate, as theproduct of the reaction in moist formic acid.Taylor finds 29 thattert.-butyl chloride is esterified by a mixture of formic acid and cal-cium formate, and suggests that the first-order reaction observed byBaternan and Hughes was a pseudounimolecular esterification. In arecent publi~ation,~~ L. C. Bateman, E. D. Hughes, and C. K.26 J., 1938, 840.27 J . , 1937, 1853; J . Amer. Chem.Soc., 1938,60, 2094.28 J., 1937, 1962. ao Ibid.,p. 1852.3u J. Amer. Chem. Soc., 1938,60, 3080WATSON : REACTION MECHANISMS. 217Ingold report that the introduction of chloroacetate ions into asolution of tert.-butyl chloride in moist formic acid leads to the pro-duction of tert.-butyl chloroacetate, the measured reaction velocitynot being increased; it appears, therefore, that Taylor’s result wasprobably due solely to the formate ions which he introduced.L. P. Hammett and his co-~orkers,~l like Hughes and Ingold,recognise that in the hydrolysis and alcoholysis of alkyl halidesthere are two competing reaction paths which differ in mechanismand in their dependence upon the structure of the halide. Theyfind that the presence of small quantities of water brings about alarge increase in the speed of alcoholysis of benzhydryl chloride,32and examination of the reaction products has shown that this largervelocity is not due to an independent hydrolysis of the halide,but to a speeding-up of the alcoholysis.They describe the changeas “ polymolecular,” and envisage the formation of a solvationcomplex of alkyl halide with solvent, within which the rearrange-ments necessary for reaction occur ; they further suggest that thesubstitution of a water molecule for one of alcohol in this complexmight then increase the speed on account of a greater affinity ofhalide ions for water than for alcohol. C. K. Ingold33 notes thecontrast between this large increase of velocity when small pro-portions of water are added to alcoholic solutions of benzhydrylchloride and the complete lack of any such catalytic influence bysimilar small quantities of water upon the speed of hydrolysis oftert.-butyl chloride in formic acid (where a constant value of theunimolecular velocity coefficient is found) .25 He suggests that,since water is a much better ionising solvent than ethyl alcohol,small quantities will greatly increase the rate of ionisation of thealkyl halide, whereas, since formic acid, like water, is a stronglyionising solvent, 110 such effect would there be expected.The reaction undergone by tert.-butyl chloride in aqueous alcoholicsolution is a simultlaneous hydrolysis and alcoholysis, giving amixture of tert.-butyl alcohol and tert.-butyl ethyl ether, and A.R.Olson and R. S. Kalford34 have given a quasi-thermodynamictreatment of reaction rates in such binary solvent mixtures. Usingan expression involving the specific velocities for pure alcohol andpure water, and the partial vapour pressures of these constituentsand of the tert.-butyl halide, and supposing that the solvent takespart in the reaction, they calculate the rates a t intermediate solvent31 J. Steigman and L. P. Hammett, J . Amer. Chem. SOC., 1937, 59, 2536;32 Compare 5. F. Norris and A. A. Morton, ibid., 1928, 50, 1795.33 Trans. Faraday SOC., 1938,34, 221.3 4 J . Amer. Chem. SOC., 1937, 59, 2644.N.T. Farinacci and L. P. Hammett, ibid., p. 2542218 ORGANIC CHEMISTRY.compositions from those observed at two extremes, and also deter-mine the anticipated composition of the reaction productcorresponding to each solvent mixture.The calculated rates arein agreement with experimental values, and Olson and Halfordtherefore assume the reaction to be bimolecular. They did notascertain whether their calculated compositions of the product alsoagreed with experiment, however. L. C. Bateman, E. D. Hughes,and C. K. Ingold 35 have pointed out that, since the solvent doubtlessenters into the transition state for any reaction in solution (theimportant r d e of the solvent is emphasised in all the theories towhich reference has been made above), Olson and Halford’s expres-sion applies equally well to the measurable stage of the unimolecularmechanism. They show further that, since the products of abimolecular mechanism are formed in the rate-measured stage,whereas those of a unimolecular mechanism are not (for they areformed in subsequent rapid reactions the velocities of which cannotbe found), the real test is to determine whether the calculatedcomposition of the product agrees with experiment; only if suchagreement is obtained can it be concluded that the products areformed in the rate-measured stage and hence that the reaction isbimolecular.They have determined the proportions of alcoholand ether in the product of the combined hydrolysis and alcoholysisof tert.-butyl chloride in three mixtures of water and methyl alcoholand three of water and ethyl alcohol, and find that the proportionof ether is always two to three times larger than that calculated byOlson and Halford.The differences are much greater than theerrors in experiment or calculation, and thus a further test has shownthe reaction to be unimolecular. Recent work on the Waldeninversion has provided yet another method of distinguishingbetween the bimolecular and the unimolecular mechanisms ; thisis dealt with below.The Walden Inversion.-The inversion of configuration whichfrequently accompanies the replacement of a group linked to asaturated carbon atom, discovered by Walden over forty years ago,has been exemplified by numerous instances where either an opticallyactive compound is converted into its stereoisomeride by two re-placements or the same replacement leads to stereoisomeric productswhen the reagent or the conditions are varied.The diflicultiesencountered in detecting the actual change in which inversion takesplace and in elucidating the conditions which determine its occurrencehave been due partly to the absence of reliable methods of relatingsign of rotation to configuration, but also to a lack of knowledge ofthe mechanism of substitution a t a saturated carbon atom. Aa= J., 1938, 881WATSON : REACTION MECHANISMS. 2 19notable advance towards the solution of the problem has been maderecently. Aided by methods, devised by Kenyon and others, fordetermining the relative stereochemical configurations of alliedcompounds, Ingold, Hughes, and their co-workers have been able tocarry their researches on aliphatic substitution (see precedingsection) into this field, and to link the steric course of a reactionwith its mechanism and hence with the factors by which mechanismis determined, vix., the structure of the reacting compound and theconditions under which the replacement occurs.A list of relative configurations was drawn up twenty-five yearsago by P.F. Pra~&land,~~ on the basis of a statistical survey of therecorded effects of different reagents upon replacements a t anasymmetric carbon atom, and the recent researches have largelyconfirmed the conclusions there reached. The assumption made byG. W. Cl~ugh,~' vix., that similarity of configuration is accompaniedby similarity in the effects of structural and external conditions,appears to have yielded less satisfactory results, although it may beused within prescribed limits.38 A number of theoretical methodsby which attempts have been made to relate structure to rotationare summarised by E.D. H~ghes.3~ J. Kenyon and H. Phillipshave used a chemical method which has enabled them to establishconfigurations with a good degree of certainty. The followingscheme is typical of the numerous series of transformations whichthey have carried out during the past few years :The (+) and (-) symbols indicate the observed signs of rotation.Of these replacements, it may be assumed that only the reactionsof the p-toluenesulphonate with acetate or chloride ions involve therupture of one of the linkages of the asymmetric carbon atom, andtherefore an inversion is possible only in these two stages.Sincethe acetate obtained by direct acetylation of the secondary alcohol,a reaction presumably not iiivolving the asymmetric carbon atom,36 J., 1913, 103, 713.88 K. Freudenberg and A. Lux, Ber., 1928, 61, 1083; Ann. Reports, 1929,8s Trans. Paraday SOC., 1938, 34, 202.s1 J., 1918, 113, 526.20, 86220 ORGANIC CHEMISTRY.has the same sign of rotation as the alcohol, whereas that preparedby the reaction of acetate ion with the p-toluenesulphonate has theopposite sign, it may be concluded that inversion occurs in the latterreplacement, and hence that the alcohol and the acetate having thesame sign of rotation are alike in configuration. By analogy this willapply also to the chloride, but this view demands the assumption thatchloride and acetate ions have similar steric effects.The sameconclusion regarding the configuration of the chloride is drawn (bymaking a very similar assumption) from observations of replace-ments in the sulphinic esters :?(/OH Cl*SO*C,HJ yc/ (+) O*SO*C7H:pR'/ \OHR'/ \H( - ) R / H0" \C/ +C7H,*S0,ClR'/ \H R, (-)On the basis of a procedure of the type outlined above, Kenyon,Phillips, and their co-workers have a,ssigned configurations toderivatives of a-benzylethyl alcohol,40 @-n-octyl alcoholtl ethyllactate,42 a-phenylethyl alcoh01,4~ and ethyl p-hydroxy- P-phenyl-propionate.44 The replacement of the sulphonate or sulphinategroup (e.g., by OAc, OH) led t o inversion in all cases where theconfiguration of the product was known, and there was thus con-siderable justification for the assumption that its replacement bychlorine would have the same effect.Moreover, this is in harmonywith recent views regarding the Walden inversion,45 and its correct-ness is rendered the more probable since, in the case of @-n-octyli0dide,~6 and also of a-phenylethyl bromide 47 and of a-bromopro-pionic acid,48 the replacement of a halide ion by one of the same kind(I by I, or Br by Br) has been shown to occur at a rate which is40 H. Phillips, J., 1923, 123, 44.41 Idem, J., 1925,127, 2564; A. J. H. HOUSS~., J. Kenyon, andH. Phillips,4 2 J. Kenyon, H. Phillips, and H. G. Turley, J., 1925, 127, 399; Ann.4 3 J. Kenyon, H. Phillips, and F. M. H. Taylor, J., 1933, 173.4 4 J.Kenyon, H. Phillips, and G. R. Shutt, J., 1936, 1663; Ann. ReportsJ . , 1929, 1700; Ann. Reports, 1929, 26, 87.Reports, 1926, 23, 110.1935, 32, 244.Refs. 54, 55, 56.46 E. D. Hughes, F. Juliusburger, S. Masterman, B. Topley, and J. Weiss,47 E. D. Hughes, F. Juliusburger, A. D. Scott, B. Topley, and J. Weiss,48 W. A. Cowdrey, E. D. Hughes, T. P. Nevoll, and C. L. Wilson, J., 1938,J., 1935, 1525.J., 1936, 1173.209WATSON : REACTION MECILXNISMS. 221quantitatively equivalent to the speed of racemisation. In the workhere referred to, the organic halide in acetone solution was treatedwith sodium iodide (or lithium bromide) containing the radioactiveisotope of the halogen, and the rate of exchange of halogen (e.g.:RI + NaI* = RI* + NaI, where I* represents the radioactiveisotope) was determined by measurement of the intensities ofradioactivity of the alkyl halide or the alkali halide after knowntime intervals.The velocity of racemisation was found polari-metrically, and in all three instances the rates of exchange andracemisation were equivalent within experimental error. Thereseems to be little doubt, therefore, that inversion occurs when ahalide ion replaces another anion, and that the configurationsarrived a t by Kenyon and Phillips are correct. A knowledge of theseconfigurations was essential in the recent work now to be described.The earlier theories of the Walden inversion 49 postulated theinitial formation of an addition product, and the opposite view, thatof an ionisation process as the first step, has been considered byT.M. Lowry 50 and by J. Kenyon and H. Phillip~.~1 The remaininga l t e r n a t i ~ e , ~ ~ vix., that substitution involves a simultaneous additionof one group and removal of the other, as was suggested in connectionwith the Walden inversion by G. N. Lewis,53 has appeared in recenttheories due to A. R. Olson Olsonpostulates inversion in every substitution, and Meer and Polanyipredict inversion for certain types of substitution. When an anionicgroup X (e.g., OH, Cl) is linked to the asymmetric carbon atom, thedipole associated with the bond has the direction 6-X, and anSummarised in Ann. Reports, 191 1 , 8, 60 ; also P. F. Frankland, ref. 36.A. Meisenheimer (Annulen, 1927, 456, 126) has more recently put forward adevelopment of views of this type.and N.Meer and M. Polanyi.55*5O DeuxiAme Conseil de Chimie Solvay, 1925, p. 39.61 Trans. Paraday SOC., 1930, 26, 451.5 2 A comprehensive survey of theories of the Walden inversion wouldalso include reference to the postulates of B. Holmberg (Ber., 1926, 59, 125)and H. N. K. Rordam (J., 1928, 2447; 1929, 1282; 1930,2017). The formerbases his argument upon the relative distances C ++X and B++Y(" reaction distances J J ) in the compound R,CX and the reagent BY, but itis difficult to understand the meaning of the term when the reagent is ananion; he considers, however, that inversion will be the general rule in thiscase, as is indicated by his experimental results.Rordam distinguishesbetween replacements brought about by an anion and those brought about bya molecule (e.g., PCl,) which itself removes the replaced group. He supposesthat the position taken up by the entering group will depend upon the phaseof oscillation of the three radicals still linked t o the asymmetric carbon atoma t the moment of entry.53 '' Valence and the Structure of Atoms and Molecules."5 4 J . Chem. Physics, 1833, 1, 418.56 2;. physikal. Cham., 1932, B, 19, 164.1923, p. 113222 ORGANIU CHEMISTRY.approaching negative ion, under the influence of the electrostaticforces, therefore attacks the carbon atom on the side away from thegroup X; “ the group which is to be displaced determines a uniquepath for the entering group such that the system requires less energythan it would for any other path.” The conclusion is thus reachedthat inversion always occurs in the bimolecular replacement of ananionic group by a negative ion,56 and in addition to the evidenceprovided by Olson and Polanyi themselves, relating mainly toreactions between halide ions and alkyl halides or halogeno-acids,57this view is supported by the results, already referred to, of investig-ations by Kenyon and Phillips and by E.D. Hughes and his co-worker~.~~. 47* 48 Meer and Polanyi distinguish between thesereplacements by an anion (“ negative mechanism ”) and those inwhich the attack is by a cation (“ positive mechanism ”) ; theyconsider that the latter would not in general lead to inversion,although doubt is expressed regarding certain in~tances.~8In a detailed discussion of the problems presented by the stericcourse of substitution, W.A. Cowdrey, E. D. Hughes, C. K. Ingold,S. Masterman, and A. D. Scott 59 employ the theory of simultaneousaddition and dissociation in conjunction with that of initial dissoci-ation, and the knowledge of reaction mechanism gained by thekinetic studies to which reference has already been made (precedingsection) is applied to the prediction and interpretation of thesteric course of the substitution. Their general conclusions arethat bimolecular substitutions ( SN2, S,2 ; see preceding section) areinvariably accompanied by inversion, whereas unimolecular substi-tution (S,l, S,l) may lead to inversion, retention of configuration,or racemisation, the actual result being dependent upon othercircumstances.Inversion of configuration in a bimolecular substitution is ascribed,not to the direction of the dipole ‘c-2, but to the fact that, onaccount of forces of shorter range than dipole forces, the mostfavourable method of attack is along the line of this linking, i.e.,J.Walker’s observation of inversion in the replacement by OH ofNMe, in 2-piperityltrimethylammonium hydroxide ; 6o the bond toCompare B. Holmberg, ref. 52; J. Steigman and L. P. Hammett, ref. 31 ;J. Kenyon and H. Phillips, ref. 51 ; P. A. Levene, A. Rothen, and M. Kuna,J. BioE. Chem., 1937, 121, 747. “ The moIecule is turned inside out like anumbrella in a strong wind ” (Ann.Reports, 1936, 32, 95).67 A. It. Olson and F. A. Long, J. Amer. Chem. SOC., 1934,56,1294; A. R.Olson and H. H. Voge, ibicE., p. 1690; E. Bergmann, M. Polyani, and A. L.Szabo, 2. physikal. Chem., 1933, 20, 161; Trans. Faraday SOC., 1936, 32, 843.J., 1934, 308.y ____-__ h-- , CX.O Such a view is confirmed by J. Read and+68 M. Polanyi, “ Atomic Reactions,” 1932, p. 63.6a J., 1937, 1252WATSON : REACTION ME(IEANISMS. 223be ruptured is C-NR,, and the electrostatic forces would heredirect the attacking anion to a position giving a retained con-figuration, whereas the experimental results indicate that the attackis on the opposite side. The configuration of the product of aunimolecular substitution, in which the first step is the formation ofa carbon anion or cation, is determined, according to Ingold andhis co-workers, by the life of the ion.The available examples relateto nucleophilic substitutions (S,l), where the positive ion is flat.If this ion has a relatively long life (as will be the case if the reactivityof the ion itself or of the medium is low, or if the dilution of thereagent is high), substitution at either side will occur with equalfacility, giving a racemic product. A cation of short life, however,will be shielded by the receding anion during the period in which theposition of substitution is determined, and substitutions withinversion will outnumber those in which the configuration is retained ;the net result is a predominating inversion, but with more or lessracemisation.In special instances, however (see later), there may beconsiderable retention of configuration. These predictions havebeen tested by a kinetic and polarimetric study of the hydrolysisand alcoholysis of p-n-octyl halides, a-phenylethyl halides anda-bromopropionic acid, its anion, and its ester.Of these examples, the simplest is that of the p-n-octyl halides,where only neutral, saturated substituents are present a t the seatof substitution. E. D. Hughes and U. G. Shapiro 17 have shown thatin general (as is the case with other secondary halides ; see precedingsection) the substitution occurs by both the bimolecular and theunimolecular mechanisms ( SN2 and S,l) , but suitable conditionscame one or the other mechanism to take almost complete control.E.D. Hughes, C . K. Ingold, and S. Masterman 61 find that thebimolecular hydrolysis or alcoholysis proceeds with inversion ofconfiguration and an almost quantitative preservation of rotatorypower, while the unimolecular substitution takes place with pre-dominating inversion but Considerable racemisation ; this is incomplete agreement with the predictions outlined above. Thephenyl substituent in a-phenylethyl halides introduces resonancewhich tends both to stabilise and to flatten the ion. The bimole-cular hydrolysis of this halide cannot be realised experimentally,21but E. D. Hughes, C. K. Ingold, and A. D. Scott 62 have shown thatbimolecular alcoholysis leads to inversion with a high retention ofrotatory power, while unimolecular hydrolysis and alcoholysis leadto inversion with very extensive racemisation.The aryl groupincreases both the relative importance of mechanism S,1 and theextent to which racemisation accompanies substitution by thisf61 J . , 1937, 1196. 62 Ibid., p. 1201224 ORGANIC CHEMISTRY.mechanism. The definite character of the above results and theiragreement with theoretical predictions make it justifiable to drawtwo conclusions,59 vix. : (a) in the homogeneous hydrolysis andalcoholysis of alkyl halides, whatever mechanism be involved,inversion predominates, and this rule may be employed in relatingconfiguration to sign of rotation ; (b) extensive racemisation alwaysaccompanies the unimolecular mechanism and is absent in thebimolecular mechanism ; this provides an additional method ofdetermining mechanism.The groups -CO*OH and -CO*OR are strongly electron-attractive ; their attachment a t the seat of substitution thereforefavours reaction by the bimolecular mechanism, and W.A. Cowdrey,E. D. Hughes, and C. K. Ingold63 find that the hydrolysis andalcoholysis of a-bromopropionic acid and its methyl ester occur withinversion and no appreciable racemisation. The presence of thenegatively charged carboxylate group (an electron-repelling group)in the a-bromopropionate anion, on the other hand, favours mecha-nism S,1; it also tends to stabilise the ion and to preserve a pyra-comidal configuration, since the ion is a betaine / \ ; this-0 C+structure is likely to remain until a new group enters the positionvacated by the one expelled, and the result will be a considerableretention of configuration, An investigation of the hydrolysis andalcoholysis of sodium a-bromopropionate by Cowdrey, Hughes, andIngold 63 has demonstrated the occurrence of reaction by bothmechanisms ; mechanism S,2 proceeds, as usual, with inversion,while S,1 gives an almost complete retention of the original con-figuration.The above results have been tabulated very clearly byE. D. Hughes.39The reactions of akyl halides with silver oxide or with solublesilver salts (e.g., RC1 + AgNO, + H,O = ROH + AgCl + HNO,)involve a heterogeneous attack by silver ions upon the halideadsorbed on the surface of solid silver oxide or halide.64* 65* 66 Itmay be supposed 59 that the C-halogen bond of the adsorbed halideis stretched and thereby weakened, this making it possible for anadsorbed silver ion to remove the halogen; finally, reaction occursbetween the ion and an adsorbed reagent or solvent molecule.Thisview, which postulates a heterogeneous ionisation, leads to theexpectation of a similarity between these processes and homogeneousunimolecular hydrolysis (SNl), and the results of Ingold, Hughes, and63 J . , 1937, 1208.6s E. D. Hughes, C. K. Ingold, and S . Masterman, J., 1937, 1236.66 W. A. Cowdrey, E. D. Hughes, and C. K. Ingold, ibid., p. 1243.6 4 G. Senter, J., 1910, 97, 346; 1911,99, 95WATSON : REACTION MECHANISMS. 225their co-workers have shown that such a similarity actually exists,The hydrolysis and alcoholysis of p-n-octyl halides by means of silveroxide, nitrate or acetate in aqueous alcohol gives predominating in-version and some racemisation ; a-phenylethyl chloride under similarconditions behaves in the same way, but more extensive racemisation0ccurs.6~ The alcoholysis of methyl a-bromopropionate by silvernitrate in methyl alcohol leads to inversion with racemisation, whilein presence of either silver oxide or silver nitrate substitution in thea-bromopropionate ion is far more rapid than in the undissociatedacid or its ester (even in fairly concentrated solutions of mineralacid the reaction of a-bromopropionic acid with aqueous silvernitrate proceeds almost entirely through the giving a pre-dominating retention of configuration but some accompanyingracemisation.66 The anticipated analogy of the heterogeneousreaction with unimolecular homogeneous substitution is thus realised.In their discussion of these problems, Ingold and his collaborator^^^have applied their views to numerous observations from theliterature, and have also constructed tables showing relationshipsbetween molecular configuration and the sign of optical rotation ina number of compounds; in general their configurations are inagreement with those of F r a ~ k l a n d .~ ~ Recorded data for the re-placement of hydroxyl by halogen through the agency of phosphorusor sulphur halides or of halogen acids are also considered. Thefacts relating to these substitutions indicate that inversion is thegeneral rule ; 68 in substitutions by thionyl chloride, however,inversion is not observed if a phenyl group is attached to the asym-metric carbon atom, although this peculiarity disappears if atertiary amine is present.69 The reactions with hydrogen halidesappear to give racemisation in addition.The mechanisms putforward by Ingold and his collaborators to represent these changesare all of the same type, and may be illustrated by reference to thereplacement of hydroxyl by chlorine through the agency of thionylchloride. The first step postulated is the formation of a compoundR*O*SOCl, which can then undergo three distinct changes, asfollows : R-C1+ SO2 . . . . . . . SNiROH+ d \SO+ R-O*SOf Cl-+ C1-R + SO, . sN2R+ + SO, + C1-+ C1-R -/- SO2 .s N 1A suppression of ionisation by the nitric acid liberated in the reactionaccounts for a downward drift in the second-order velocity coefficients for thehydroxylation of a-halogenated acids by aqueous silver nitrate (G. Senter,ref. 64; H. Euler, Ber., 1906, 39, 2726).0 /Ic1/ \66 Compare P. F. Frankland, ref. 36.6 9 J. Kenyon, A. G. Lipscomb, and H. Phillips, J., 1930, 415.REP.-VOL. XXXV. 226 ORGANIC CHEMISTRY.The fist change (SNi) is a " rearrangement " (actually a nucleophilicsubstitution in which two bonds are ruptured) which results in aretention of the original configuration ; SN2 and S,1 are respectivelybimolecular and unimolecular substitutions in the cation ofR*O*SOCl, and lead to inversion (S,2) and inversion with race-misation (&I) in accordance with the principles already established.A phenyl substituent at the point of substitution will promotereaction by S,i (configuration retained) owing to its capacity forelectromeric electron-release, but a tertiary base will favour theionisation mechanisms which lead to inversion owing to the pro-duction of its hydrochloride.The application to other recordedobservations may be found in the original paper, together with listsof compounds having corresponding configurations.Elimination Reactions.-Olefin elimination frequently occurs sideby side with substitution in saturated compounds (e.g., alkyl halides,quaternary ammonium hydroxides, etc.), and the demonstration of adual mechanism for the latter suggests a similar possibility for theformer.The mechanism of elimination reactions put forward byW. Hanhart and C. K. Ingold 70 may be writtenZ + H~-CR2-CR2i-X + Z-H + CR2=CR, + X . . E2In this bimolecular reaction, a basic reagent Z extracts a protonsimultaneously with the separation of an anionic group X ; thehydrogen and the anionic group must be linked to adjacent carbonatoms in order that octets may be preserved. Since the formul-ation of this mechanism, studies of olefin elimination have beenreported in various papers by C. K. Ingold and his collaborators,and in their most recent contribution to the subject they bringforward evidence of a unimolecular mechanism,* vix.,slowH-CR,--CR,/--X + H-CR,-CR,+ + X-H~-CR,-CR,+ ----+ H+ + CR2=CR,rapidIn a search for reactions proceeding by the unimolecular mechan-ism, the non-basic but strongly ionising solvents sulphur dioxideand formic acid were used; these media can ionise alkyl halides butcannot bring about substitution or bimolecular (pseudounimole-cular) elimination (as, e.g., in H,O + N0,*C,H,*CH2*CH2*NMe,=H,Oi + NO,*C,H,*CH:CH, + NMe,, where water is a sufficientlystrong base to remove the proton, and the presence of a stronger base'O J., 1927, 997; Ann.RepOTl8, 1930, 27, 143.* W. Taylor (ref. 28) has proposed a bimolecular mechanism for aEE elimin-This does not appear to differ from+ation reactions (as for all substitutions).Ingold's E, mechanismWATSON : REACTION MECIZANISMS. 227increases the speed) .71 The halides chosen for the investigationwere a-phenylethyl chloride and tert.-butyl chloride, both of whichundergo substitution by the unimolecular mechanism S,1, and alsocontain a hydrogen in the correct position for the eliminationreaction. In both sulphur dioxide and formic acid the halides wereshcwn to come spontaneously into equilibrium with olefin and hydro-gen chloride.72 The work was extended to aqueous media by astudy of the elimination reactions accompanying substitution inp-n-octyl, tert.-butyl, and tert.-amyl halides in aqueousThe speed of the elimination reaction was measured by estimation ofthe olefin a t given time intervals; this was found to give first-orderkinetics, but, in view of the basic nature of the medium, the reactionmechanism was not thereby established.The following test wastherefore applied. The postulated rate-controlling process forboth substitution and elimination is the same, 'uix., the ionisation ofthe alkyl halide, RX + Rf + X-, and the subsequent (rapid)step is a reaction of the organic cation alone :%%O> R*OH+ H+. . . . . S,1The total velocity (that of the ionisation) will therefore depend uponthe nature both of the alkyl group R and of the halogen, but therelative speeds of substitution and elimination (which govern theproportion of olefin in the product) are independent of the halogenand depend only upon the group R. For two halides having thesame alkyl group (e.g., p-n-octyl chloride and bromide), therefore,the ratios of the velocity of elimination (kEJ to the total velocity(k,) should not be very different.Absolute equality of these ratioscannot be expected, since other factors intervene (e.g., the shieldingof the cation by the departing anion).74 Nevertheless, the propor-tion of the total first-order reaction which results in elimination(kEl/kl) should depend essentially upon R, and be modified to arelatively small degree by changes in the halogen. The experimentalresults are summarised below :Ratio of Ratio RatioR. k , values kE,lkt kE,/klRCl/RBr. for RCl. for RBr.8-n-Octyl (100" in 6076 alcohol) 33 0.13 0.1444 0.17 0-13 ~ ~ ~ ~ : ~ ~ $ }(25" in 80% alcohol){ 39 0-33 0.2671 E. D. Hughes and C. K. Ingold, J., 1933, 523.72 E. D. Hughes, C. K. Ingold, and A.D. Scott, J . , 1937, 1271.73 E. D. Hughes, C. K. Ingold, and U. G. Shapiro, ibid., p. 1277; K. A.Cooper, E. D. Hughes, and C. K. Ingold, ibid., p. 1280; E. D. Hughes andB. J. MacNulty, ibid., p. 1283.74 Compare this report, p. 223228 ORGANIC CHEMISTRY aThe significant feature is the contrast between the large differencesin velocity and the accompanying smaZZ differences in the kEl/kl ratiowhen alkyl chlorides are compared with the corresponding bromides.This is in harmony with the predictions of Ingold and Hughes.Prototropic Changes.-Prototropic systems (e.g., HX-Y=Z 2X-Y-ZH) may be classified as (a) thermodynamically balancedand (b) thermodynamically unbalanced. In those of the formerclass, both tautomerides are of the same order of stability and thecatalysed transformation of the one into the other may be followedby analytical methods. This procedure is not applicable to systemsof the second type, however, since the concentration of one formis at no time sufficiently high for measurement. Many keto-enolsystems belong to this class, and the velocity of the prototropicchange may here be determined by Lapworth’s halogenation method.Most carbonyl compounds react instantaneously with halogenssubsequently to a catalysed prototropic change which is the rate-determining step ; simple monocarboxylic acids and their derivativesare not included in this generalisation, for they give no evidence ofprototropy (e.g., the speed of bromination of acetyl bromide isdirectly proportional to the concentration of the halogen).l J.B.Conant and G. H. Carlson 2 have introduced a third method for themeasurement of rates of prototropic changes ; this can be employedin cases where the atom from which the mobile proton migrates is acentre of asymmetry, and where the rate of loss of optical activity cantherefore be determined (e.g., R*CO*CHR1R2 + ROC( OH):CR1R2).By a combination of the second and the third of the above methods,P. D. Bartlett and his collaborators have estimated the relativecontributions made by the two groups capable of providing aproton in ketones of the type >CH*CO*CH<, where one cc-carbonis asymmetric; the halogenation is a measure of the sum of thechanges into the isomeric enols, whereas the loss of optical activityis determined by the change into one of these.They have shown, forexample, that in the acid-catalysed prototropy of menthone in glacialacetic acid, 79% of the prototropic change involves the hydrogenlinked to Ca. The acid-catalysed racemisation of menthone,phenylmethylacetophenone and phenylisobutylacetophenone innon-hydroxylic solvents has recently been studied by R. P. Bell andhis co-workers ; the absence of basic characters in the medium hereintroduces some special features.l H. B. Watson, J . , 1925,127,2067 ; 1928,1137 ; Chem. ReUieW8,1930,7,173.J. Amer. Chem. Xoc., 1932, 54, 4048; Ann. Reports, 1934, 31, 197.P. D. Bartlett and J. R. Vincent, J . Amer. Chem. SOC., 1933, 55, 4992;4 R. P. Bell and E. F. Caldin, J., 1938,382; R.P. Bell, 0. M. Lidwell, andP. D. Bartlett and C. H. Stauffer, ibid., 1935, 57, 2580.J. Wright, ibid., p. 1861WATSON : REACTION MECHBNISMS. 229Reference was made two years ago to the measurements ofspeeds of prototropic reactions by C. K. Ingold and C. L. Wilson,,who employed all of the above methods. This work has now beenextended to include yet a fourth method, vix., the determination ofthe rate a t which hydrogen is exchanged for deuterium.' Threedifferent systems have been investigated :(A) Ketones. (1.) R*CO*CHR'R' t ROC( OH):CR1R2 (11.)(I = 2-o-carboxybenzylindan- 1 -one ; Ph*CO*CHMeEt)(B) Unsaturated nitriles.*/CHZ-CHZ \C-CH,*CN CH/ C*2-CH2)C:C*.cN\CH,-CH, (IV.1CH2(111.) \CH,-CH/(C) Methyleneazomethines.(V.) R1R2CH*N:CR3R4 f R1R2C:N*CHR3R4 WI.1(R1 and R3 = Ph ; R2 = Me or p-Ph*C,H, ; R4 = H, Ph or p-C,H4C1)In all comparisons the conditions were standardised as completelyas possible, and the results may be summarised as follows :(A) For ketones, the speeds of racemisation, bromination anddeuterium exchange, all base-catalysed, are equal within the limitsof experimental uncertainty.* The rates of the acid-catalysedracemisation and bromination are also equal (this equality wasfound for methylethylacetophenone by Bartlett and Stauffer).3(B) In the case of the unsaturated nitriles, the less stable iso-meride (111) exchanges hydrogen for deuterium far more rapidlythan it is converted into (IV).(C) In the methyleneazomethine system the speeds of racemisationand interconversion are equal, and this equality has been confirmedby G.T. Borcherdt and H. Adkins for the case where R1= R3 =Ph, R2 = Me, and R4 = p-C,H,Cl. The rate of deuterium exchangeis much greater, however.6 Ann. Reports, 1936, 33, 232.6 C . K. Ingold and C. L. Wilson, J., 1933, 1493; 1934, 93, 773; C. L.Wilson, J., 1934, 98; S. K. Hsu, C. K. Ingold, and C. L. Wilson, J., 1935,1778; S. K. Hsii and C. L. Wilson, J., 1936, 623.7 C. I(. Ingold, E. de Salas, and C. L. Wilson, J . , 1936, 1328; S. K. Hsii,C. K. Ingold, and C. L. Wilson, J., 1938, 78; E. de Salas and C. L. Wilson,ibid., p. 319. Surnmarised by C. L. Wilson, Trans. Faraday SOC., 1938, 34,175.8 See also A. Kandiah and R. P. Linstead, J., 1929, 2139.0 J . Amer. Chem:Soc., 1938, 60, 3.* D.J. G. Ives and G. C. Wilks ( J . , 1938,1455) have more recently observedequal rates of racemisation and exchange in the phenyl-p- tolyldeuteroacetateion230 ORGANIC CHEMISTRY.Ingold and Wilson interpret their results on the basis of thecommonly accepted view that the first step in the base-catalysedchange (" basic mechanism ") is the transfer of the mobile proton tothe catalyst; in catalysis by acids (" acid mechanism ") trans-ference of this proton to an acceptor in the medium is made moreeasy by initial co-ordination of the molecule with the acid. Thispoint of view is essentially that put forward by A. Lapworth andA. C. 0. Hann,l* and it has more recently been expressed fully byK. J. Pedersen,ll who points out that it implies that there is nodifference in principle between the acidic characters of a $-acid(e.g., ketone, nitro-compound) and of a true acid (e.g., enol, iso-nitro-compound), since both are genuine acids although the formeris much weaker than the latter.The equality of the speeds of base-catalysed racemisation,bromination and deuterium exchange for the ketones studied byIngold and Wilson indicates that all three reactions are controlledby the same fundamental process, which, in accordance with theionisation theory of prototropy, is believed to be the removal ofthe or-proton with formation of the mesomeric anion C-C-0(a resonance structure between c-C-0 and C=C-6).This ionis regarded as the active agent in bromination and deuteriumexchange, and the measured (equal) speeds are therefore equated tothe speed of ionisation ; even if the thermodynamically unstableenol is formed, the union of the ions will be practically instantaneousand the result will be the same.R. H. Kimball l2 has found, how-ever, that the I-menthyl ester of d-P-keto-a-phenyl-n-butyric acid(in cyclohexane) loses its optical activity about three times as rapidlyas it passes into its enolic form (which here constitutes about 71%of the equilibrium mixture); it appears, therefore, that the asym-metry is lost in the ion, which may subsequently accept a protoneither to regenerate the ketone or to form enol (since both forms are,in this case, of comparable stability, and their rates of productionfrom the mesomeric ion are therefore of the same order).The rateof tautomeric conversion is therefore less than that of ionisation(and hence of racemisation). The difference in the speeds of iso-merisation and deuterium exchange for the unsaturated nitrile (111)is interpreted similarly; every anion formed from (111) leads todeuterium exchange with the medium, but not every anion yields(IV), some reverting to (111). An analogous observation has beene--h-710 J . , 1902, 81, 1512.11 J . Physical Chem., 1933, 37, 751; 1934, 38, 581, 601; Trans. Far&y12 J . Amer. Chem. SOC., 1936,58, 1963; Ann. Reports, 1936,33, 234.SOC., 1938, 34, 237WATSON : REACTION MECHANISMS. 231made by D. J. G . Ives for the three-carbon system in the vinylacet-ate ion; the speed of the exchange reaction is greater than that ofthe conversion into crotonate ion.In the methyleneazomethinesystem, also, the tautomerides are of similar stability, and everyionisation process would be expected to lead to loss of opticalactivity but not to isomerisation. Here, however, the observedvelocities are equal. It is therefore suggested that the anion doesnot attain kinetic independence, but that the removal of the oneproton and the addition of the other occur in one synchronised act;under these conditions racemisation would not be more rapid thanisomerisation (the greater rate of deuterium exchange is ascribedto the operation of some additional mechanism). Systems havingmobile hydrogen can be arranged in a series of descending acidity;such a series passes from carboxylic acids HO-C=O, throughketones HC-(3-0 and nitro-compounds HC-N=O, to unsaturatedhydrocarbons HC-C=C and methyleneazomethines HC-N=C,and Ingold and Wilson consider that the kinetic independence of theanion shows a steady decrease until in the last member the dissoci-ation and reassociation processes overlap in time and the anionnever becomes free.The ionisation theory of base-catalysed prototropy, in postul-ating the direct removal of a proton from its combination withcarbon, thus implies an analogy of prototropic systems with themore powerfully acidic systems (e.g., carboxylic acids) in whichhydrogen linked to oxygen is ionisable.It has been suggested14that the primary process may rather be analogous to cyanohydrinformation or the alkaline hydrolysis of esters, in which the base isadded a t carbonyl carbon.The anion would then be formed intwo steps instead of one, as follows :e - HX-Y=Z + OR- + HX-Y <:R---+ X-Y-Z + HORAs might be anticipated, electron-attractive substituents in aketone molecule facilitate base-catalysed prototropy and operateagainst the acid-catalysed reaction.* This has been demonstrated,for example, in a series of nuclear-substituted acetophenones.15The favourable influence of electron-attractive groups upon base-13 J., 1938, 91.14 H. B. Watson, W. S. Nathan, and L. L. Laurie, J . Chem. Physics, 1935,3, 170.15 W. S. Nathan and H. B. Watson, J., 1933, 217; D. P. Evans, V. G.Morgan, and H. B. Watson, J., 1935,1167 ; V.G. Morgan and H. B. Watson,ibid., p. 1173.* A similar remark does not apply to acid hydrolysis of esters; see p. 238232 ORGANIC CHEMISTRY.catalysed prototropy has been observed in a number of systems(e.g., three-carbon tautomerism,16 prototropy of ay-diphenylpropenesand ay-diphenylmethyleneazomethines) ,17 and quite recently it hasbeen shown that the halogen atom in a-bromo-pp-diphenylpro-pionylmesitylene very greatly increases the ease with which thecompound is converted into enol.18 It follows, of course, that insystems where prototropy may occur by either the “ acidmechanism ” or the “ basic mechanism,” the presence of electron-attractive groups in the vicinity of the reactive centre will tend tocause the change to follow the latter route.This is found, forexample, in the bromination of ethyl acetoacetate and of ethylpyruvate.lY A further example has been revealed in a study of thebromination of a series of halogenated acetones in 50% and 75%acetic acid containing hydrogen chloride ; 2* as the number of halogenatoms in the molecule increases, the isocatalytic point movessteadily to a region of higher acid concentration, until aaa-tribromo-and ns-tetrabromo-acetones are brominated by the ‘‘ basic mechan-ism ” even in presence of Z~-hydrogen chloride. In view of thispowerful effect of halogen substituents in promoting reaction bythe “ basic mechanism,” it is not surprising that the speed of inter-action of acetone with alkaline hypobromite or hypoiodite (haloformreaction) is governed by the rate of prototropic change of the acetoneitself, the subsequent stages being relatively instantaneous 21 (thecase of hypochlorite is peculiar and a slow reaction of OC1- ion withthe enol is suggested).The susceptibility of the higher halogenatedacetones to base-catalysed prototropy is, of course, to be correlatedwith the stability of their hydrates and other addition compounds.Moreover, an electrometric study of dilute aqueous solutions of anumber of halogenated acetones 22 has shown that in such solutionsthe mono- and di-chlorinated ketones exchange chlorine forhydroxyl, hexachloroacetone suffers haloform cleavage, and penta-chloro- and as-tetrabromo-acetones undergo both these changes.The accumulation of halogen substituents a t the a-position rendersthe carbonyl group more and more reactive towards nucleophilicreagents, and the CX, group (which must stand adjacent tocarbonyl to make the haloform cleavage possible) 23 is eliminated16 C.K. Ingold, C. W. Shoppee, and J. F. Thorpe, J., 1926, 1477.17 C. W. Shoppee, J., 1930, 968; 1931, 1225; 1932, 696.I* E. P. Kohler and H. M. Sonnichsen, J. Amer. Chem. SOC., 1938,60, 2650.10 K. J. Pedersen, ref. 11 ; H. B. Watson rtnd E. D. Yates, J., 1933, 220.2O H. B. Watson and E. D. Yates, J., 1932, 1207.21 P. D. Bartlett, J. Amer. Chem. Soc., 1934, 56, 967.22 E. G. Edwards, D. P. Evans, and H. B. Watson, J., 1937, 1942.2s See summary by R. C. Fmon and B. A. Bull, Chm, Reviews, 1934,15,2 75WATSON : REACTION MECHANISMS.233in the same manner as the OR group of an ester in alkalinehydrolysis.Anionotropic Systems.-Some ten years ago, H. Burton and C. K.Ingold brought forward evidence in favour of the view that theinterconversion of the tautomerides in an anionotropic system (asin a prototropic system) involves the ionisation of the migratinggroup : 24++ A I \CHR=CH-CHR’X -+ CHR-CH-CHR’ + x-CHR-CH-CHR’ + X-CHRX-CH=CHR’This mechanism was based upon the effects of variations in thenature of the substituent R’, of the anionic group X, and of themedium. It was intended to apply primarily to changes in ionisingmedia, and in solvents of poor ionising power or in the absence ofa solvent it is quite conceivable, as E. D. Hughes has suggested,25that the interconversion might occur without separation of X :CH CH/d\ / \CHR CHR‘+ CHR CHR’ .. (11)\ z-x6 XThe two mechanisms are clearly the analogues of S,1 and SN2 foraliphatic substitution.26 Their simultaneous operation may explainthe observation, made by J. Kenyon, S. M. Partridge, and H.Phillip~,~’ that the anionotropic change of an optically active formof CHMe:CHCHPhX, where X is OH or o-O*CO*C,H,*CO,H, takesplace with some racemisation but predominating inversion, as muchas 70% of the optical activity being preserved; 28 changes in themedium are here without a marked influence, and the authorssuggest a non-ionic mechanism.Investigations of the replacement of the anionic group X by adifferent group Y have led to interesting results.It is evidentthat the group Y may become linked either to the carbon atom fromwhich X is removed (C,) or to another carbon atom (C,,), and alsothat the substitution may occur in one synchronous act or by the2 4 Ann. Reports, 1928, 25, 127.2s Trans. Faraday SOC., 1938, 34, 194.2R See this Report, p. 21 1.2; J., 1937, 207.28 See Hughes and Ingold’s theory of the Walden inversion; this Report,p. 222234 ORGANIC CHEMISTRY.addition of Y after the ionisation of X. The following possibilitiesare therefore presented : 29 +----------., CHRZCH-CHR’X + CHR-CH-CHR’ + X--+ /I CHR=CH-CHR’Y7- CHR-CH-CHR’ + Y- 4 CHRY-CHICHR’/I CHRXCH-CHR’Y +4 CHRY-CHZCHR’ + Y- + CHGCH-CHR’Xx- . ( I I U )x- . (IIb)The analogy of these schemes with the two possible mechanisms ofanionotropic change, and with the SN1 and sN2 mechanisms ofaliphatic substitution is obvious.Since the formation of twoisomeric substances by either mechanism cannot be excluded, theisolation of a mixed product 3O may not be proof of the intermediateformation of a carbon cation, and the same remark applies to observ-ations of simultaneous substitution and anionotropic change.31Evidence in favour of the occurrence of substitution by mechanismI1 (in addition to mechanism I) is provided by W. G. Young andJ. I?. Lane’s observation that the reactions of hydrogen bromideunder standardised conditions with CHMe:CH*CH,*OH and withCHMe( OH)*CH:CH, give mixed products containing different pro-portions of the isomeric bromides ; 29 if the substitution occurred bythe ionisation mechanism alone, the mesomeric ion CHMeCH-CH,would be formed initially in each case, and identical products wouldbe expected from the two isomeric alcohols.Substitutions by themechanisms I and I1 will be unimolecular and bimolecular respect-ively; in agreement with this, J. Meisenheimer and G. Beutter 32have found that the reaction of cinnamyl chloride with potassiumacetate gives second-order kinetics in acetic anhydride medium,but in acetic acid the kinetics are between first and second order(a mixed product was obtained in the latter case only).J. Kenyon and his collaborators have observed a pronouncedloss of optical activity in a number of replacements of the anionicgroup of optically active derivatives of ally1 alcohol; 33 e.g., thereplacement of the -O*CO*C,H,*CO,H group of ay-dimethylallylhydrogen phthalate to give the formate, acetate or methyl ether.A more detailed study was made of the hydrogen phthalate andz 9 C.L. Arcus and J. Kenyon, J., 1938,1912; W. G. Young and J. F. Lane,J . Amer. Chem. Soc., 1938,60, 847; E. D. Hughes, ref. 25.30 C. Prbvost, Cow@ rend., 1928, 187, 1052.31 H. Burton, J . , 1928, 1650.33 H. W. J . Hills, J. Kenyon. and H. Phillips, J., 1936, 576; J. Kenyon,S. M, Partridge, and H. Phillips, ref, 27 ; C. L. Arcus and J. Kenyon, ref. 29.+ -3a Annalen, 1933, 508, 58WATSON : REACTION MECHANISMS. 235chloride of y-methyl-a-n-propylallyl alcohol, CHMe:CH*CHPraX.In the case of the hydrogen phthalate, formic or benzoic acid gavean inactive product, and acetic acid also brought about racemisationbut with some retention of optical activity (inverted configuration) ;the chloride gave an inactive product with acetate ions, and mainlyracemisation but a small retention of activity (again inverted con-figuration) when converted into the alcohol (by aqueous sodiumcarbonate) or the methyl ether (by potassium carbonate in methylalcohol).The residual optical activity was in each case due to aderivative of the original y-methyl- a-propyl compound, and neverto its anionotropic (a-methyl-y-propyl) form, as indicated by thecomplete inactivity of its reduction product [which for y-methyl-a-propyl would be inactive CHPr,X and for a-methyl-y-propyl wouldbe active CHMe(C,H,,)Y]. Arcus and Kenyon consider that thereplacement occurs principally by the ionic mechanism (QY whichwould lead to racemisation, and the small preservation of opticalactivity is attributed either to some reaction by a bimolecularmechanism (IIa) or to a shielding of one side of the a-carbon atomby the receding anion.=It is remarkable that the alkaline hydrolysis of y-phenyl-a-methylallyl, ay-dimethylallyl and y-methyl-a-n-propylallyl hydrogenphthalates by concentrated ( 5 ~ ) sodium hydroxide gives an almostquantitative preservation of the original configuration ; 35 decreasein the concentration or strength of the base leads to increasingracemisation.Arcus and Kenyon suggest a simple explanation.In neutral solution, the hydrogen phthalate exists largely as theundissociated ester-acid CHR:CH*CHR'*O*CO*C,H4*C02H, and theanionisation of the group O*CO*C6H4-C02H is facilitated by theelectron-attractive character of carboxyl, by the capacity forelect.ron-release possessed by the double bond, and by the electron-repulsion of the alkyl groups R and R' (and still more by phenyl).But in strongly alkaline solution the entity concerned is the ionCHR:CH*CHR'j*O*iCO-C,H,.C02-y and the electron repulsion of thenegative pole, by opposing the fission of the molecule a t (a), causesthe hydrolysis to proceed by the normal mechanismF6 whichinvolves fission at ( b ) with elimination of CHR:CHCHR'*O- as ananion.The linkages of the asymmetric carbon atom are not heredisturbed, and hence the stereochemical configuration is retained.H.B. W.(4 (b)s4 Compare p. 223.36 J. Kenyon, S. M. Partridge, and H. Phillips, J., 1936, 85; H. W. J.Hills, J. Kenyon, and H. Phillips, ref. 33 ; C. L. Arcus and J. Kenyon, ref. 29.86 M. Polanyi and A. L. Szabo, Trans. B'a~aday Soc., 1934, 30, 508. Thecorresponding mechanism for esterifleation has recently been demonstratedby I. Roberts and H, C. Urey (J, Rmer. Chem. SOC., 1938, 60, 2391)236 ORGANIC CHEMISTRY.3. INFLUENCES OF GROUPS UPON REACTIVITY.Modern views concerning the nature of the influences whichsubstituent atoms and groups exert upon the reactions of organiccompounds are based upon the electronic theory of valency, andtheir progress has therefore gone hand in hand with the develop-ment of that theory. But the theoretical superstructure which hasbeen erected has a broad foundation of experimental observations,which include, inter alia, comparisons of reaction velocities, measure-ments of the dissociation constants of acids and bases, determina-tions of the proportions of isomeric products (especially in aromaticsubstitution), and, of late years, the study of spectroscopic andother physical properties, notably the dipole moment.Some ofthe more important of the many recent contributions to thegeneral problem are summarised below, and certain cases of a specialcharacter are then considered.The General Problem from the Standpoint of Reaction Kinetics.-The vast majority of kinetic measurements have been conductedin solution, and simple comparisons of reaction velocities underfixed conditions have led, in the past, to important conclusions;in conjunction with other evidence they have given, for example,the familiar (‘ polar sequence ” NO,>Hal>H>Alkyl forelectron-attractive character.It has now become clear, however,that the mere comparison of velocity coefficients at a single tempera-ture does not extract in full measure the information which a studyof reaction speeds is capable of yielding, and it may, indeed, leadto wrong conclusions.* The measured velocity indicates theresultant effect of more than one factor, and the kinetic study ofthe reaction is not complete until some further analysis has beenmade. The kinetic equation k = PZe-E’RT, where E is the energyof activation, 2 is the collision frequency, and P denotes the pro-portion of sufficiently energised collisions which actually leads tothe formation of the reaction products, provides a simple physicalpicture of the inner mechanism of the change, and its use has beenabundantly justified by C.N. Hinshe1wood.l Since it may beassumed that 2 does not vary to any great extent from reaction toreaction, changes in velocity may be due to variations in E, in P, orin both. For reactions which have been studied kinetically, thevalues of E cover a range of many thousand calories, and P variesover about twelve powers of 10; these parameters frequently rise1 J., 1937, 635; Trans. Faraday SOC., 1938, 34, 105.* The results of E. W. Timm and C. N. Hinshelwood (ref. 10) upon theacid-catalysed hydrolysis of the chloroacetic esters provide a particularlyinstructive exampleWATSON : INFLUENCES OF GROUPS UPON REACTIVITY. 237or fall simultaneously when the medium or the pressure 3 changes,and in a catalysed reaction P increases very considerably on passingfrom an uncharged to a, charged catalystb4 A number of factorswhich may influence the value of P have been enumerated by C. N.Hinshelwood and C . A. Wid~ler.~One method of studying the influences of substituent groups isto determine the values of E and P, to as high a degree of approxima-tion as is possible,* when each member of a, series of compoundsWering only in one group takes part in a given reaction. Twocases can here be distinguished; the variable substituent may be(a) well removed from the point of reaction, when local disturbanceswill be eliminated, or (b) quite close to the reactive centre.In a number of instances of the former type, it has been shownthat changes in velocity are due almost entirely to variations inthe energy of activation, any variations in the value of P beinginsignificant.The most convenient series of reactions for studyare those of benzene derivatives with a variable substituent placedrn or p to the point of reaction, and the cases which have beeninvestigated include the following : chlorination of phenolic ethers,6benzoylation of anilines, 7 alkaline hydrolysis of benzoic esters, 8 andthe reaction of methyl iodide with dimethylaniline~.~ Very con-siderable changes in E , leading to large differences in velocity,are accompanied in these examples by almost negligible variationsin the value of P,t and it would appear justifiable to conclude that,a R.A. Fairclough and C. N. Hinshelwood, J., 1937, 538,1573; 1938,236;C. N. Hinshelwood, Trans. Farachy Soc., 1938, 34, 138. A correlation oflog PZ with 1 IdE is suggested from theoretical considerations.3 M. W. Perrin, Trans. Faraduy Xoc., 1938, 34, 144.4 G. F. Smith, J., 1934, 1744; A. T. Williamson and C. N. Hinshelwood,Trans. Faruday Soc., 1934, 30, 1145; C. N. Hinshelwood and A. R. Legard,J., 1935, 687.6 J., 1936, 371.A. E. Bradfield and B. Jones, J., 1928, 1006, 3073; A. E. Bradfield,W.0. Jones, and F. Spencer, J., 1931, 2907; A. E. Bradfield, Chem. andInd., 1932, 51, 254.E. G. Williams and C. N. Hinshelwood, J., 1934, 1079.C. K. Ingold and W. S. Nathan, J., 1936,222; D. P. Evans, 5. J. Gordon,and H. B. Watson, J., 1937, 1430.O K. J. Laidler, J., 1938, 1786.* The accuracy with which these values can be determined is not high,and is subject to some uncertainty. Caution should therefore be exercisedbefore significance is attached to m 2 Z differences (compare E. D. Hughes,C. K. Ingold, and U. G. Shapiro, J., 1936, 228). V. K. LaMer and (Miss)M. L. Miller ( J . Amer. Chem. SOC., 1935, 57, 2674) find indications of sub-stantial variations of E and P with temperature in certain cases ; the possi-bility of changes in reaction mechanism should not be overlooked, however,It followsfrom the kinetic equation that, if PZ remains constant, the graph will be aThis is shown conveniently by plotting log& against E238 ORGANIC CHEMISTRY.as a general rule, a substituent occupying a position which is wellremoved from the point of reaction influences the velocity almostentirely by its effect upon the energy of activation; E is raised orlowered according to the nature of the reaction and of the group.There are certain instances, however, in which appreciable changesin P are caused by substituents in the rn- or p-positions.The mostnotable are the acid hydrolysis of benzoic esters, the alcoholysisof benzoyl chlorides,ll and the hydrolysis of arylsulphuric acids ; 12P here increases or decreases with E, but its effect is never suffi-ciently great to outweigh the variations in the energy of activation,and these reactions may possess some complicating feature to whichthe changes in P are to be ascribed.13 The kinetic study of theacid hydrolysis of benzoic esters has revealed another interestingfact ; like alkaline hydrolysis, it is favoured by electron-attractivesubstituents, whereas the reverse would have been anticipated.C.N. Hinshelwood, K. J. Laidler, and E. W. Timm l4 concludethat the step which governs the value of E is the attack of a watermolecule upon the carbonyl carbon ; since, in the acid-catalysedreaction, this involves the removal of hydroxyl ions from watermolecules, whereas in alkaline hydrolysis these ions are alreadypresent in high concentration, the energy of activation is considerablyhigher (by 5000-7000 cals.) in the former case than in the latter.15Variation of a substituent group standing in close proximity tothe point of reaction generally causes simultaneous variations inE and P; this has been demonstrated in the esterification reactionsof aliphatic acids,16 the addition of alkyl halides to tertiary bases,l7and in reactions of aromatic compounds having groups in the o-position .I8In a theoretical consideration of the factors which determinethe energy of activation, C.N. Hinshelwood, K. J. Laidler, andE. W. Timm 1* arrive at the conclusion that '' there should be ageneral tendency for the influence of the substituent on the activa-10 E.W. Timm and C. N. Hinshelwood, J., 1938, 862.11 G. E. K. Branch and A. C. Nixon, J . Amer. Chem. SOC., 1936, 58, 2499.12 G. N. Burkhardt, C. Horrex, and (Miss) D. I. Jenkins, J., 1936, 1649.13 Compare D. P. Evans, V. G. Morgan, and H. B. Watson (J., 1935, 1167)on the bromination of nuclear-substituted acetophenones where mall, butregular, variations in P are observed.14 J . , 1938, 848.16 W. B. S . Newling and C. N. Hinshelwood, J . , 1936, 1357.16 C. N. Hinshelwood and A. R. Legard, ref. 4.1 7 C. A. Winkler and C. N. Hinshelwood, J . , 1935, 1147.1s See p. 244.straight line of slope - 2*303RT, while a greater or smaller slope indicatesan increase or decrease in PZ, which it is doubtless justifiable to attributeto variation in P rather than in the collision frequency 2WATSON : INFLUENCES OF GROUPS UPON REACTIVITY.239tion energy to follow the direction indicated by its effect on theattraction of the reagent to the seat of reaction.” This is found,of course, in a large majority of instances. Circumstances areenvisaged, however, in which the effect of the substituent upon thebond which is to be ruptured will become of increasing importanceand may take control ; aliphatic substitution by the unimolecularmechanism might perhaps be regarded as an extreme instance of thiskind, for the reagent is here not concerned in the rate-determiningstage.lgReference was made in last year’s Report 2O to the linear relation-ship, noted by L. P. Hammett 21 and by G. N. Burkhardt,22 whichfrequently exists between the logarithms of the velocity coefficientsfor different reactions of similarly constituted compounds, or be-tween the logarithms of the velocity coefficients and those of thedissociation constants of the appropriate substituted acids or bases.For a series of m- or p-substituted aromatic compounds, where Pdoes not vary (and it is to such compounds that most of the observedlinear relationships refer), the variations in log k are a measure ofchanges in the energy of activation, while those in log K are ameasure of differences in the free energy of ionisation.The rela-tionship may therefore be written AE1 = uAE2, where AEl andAE2 are the changes in E caused by any given substituent (ie., thedifferences of the E values for the substituted and the unsubstitutedcompound) in the two processes.23 This means that, for differentsubstituents, a constant fraction of the effect is transmitted througha given structure.24 A linear relationship is to be anticipated onlywhen the effect of the group in the different systems involves theoperation of the same factors, and when similar paths are availablefor its transmission (as in benzoic and cinnamic esters, for in-stance) ; 25 these limitations arise from the time-variable natureof certain electronic effects and the necessity for a conjugatedsystem to make possible the transmission of effects by the tautomericmechanism.Hinshelwood describes a as the ‘‘ transmission co-efficient ”. Hammett analyses the observed effect on the basis ofl9 See this Report, p.211.2o Ann. Reports, 1937, 34, 52.21 L. P. Hammett and H. L. Pfluger, J . Amer. Chem. SOC., 1933, 55, 4079;L. P. Hammett, Chem. Reviews, 1935, 17, 125; J . Amer. Chem. SOC., 1937,59, 96; Trans. Faraday SOC., 1938, 34, 156.22 Nature, 1935,136,684; G. N. Burkhardt, W. G. K. Ford, and E. Singleton,J., 1936, 20.2s C. N. Hinshelwood, J., 1937, 640; E. Tommila and C. N. Hinshelwood,J . , 1938, 1801.24 C. N. Hinshelwood, Trans. Faraday Soc., 1938, 34, 172.J. F. J. Dippy and H. B. Watson, J., 1936, 436; H. B. Watson, Trans.Paraday SOC., 1938, 34, 174240 ORGANIC CHEMISTRY.the equation A log Ic = 09, where o is a " substituent constant "dependent upon the nature of the group, and p a " reaction constant ''dependent upon the reaction and the external conditions.The General Problem from the Standpoint of the Electronic Theoryof Va1ency.-Four distinct polar effects of groups are nowrecognised.26 Two are polarisations (permanent effects), vix., (1)the inductive effect and (2) the mesomeric effect, and two polarisa-bilities (time-variable), viz., (3) the inductomeric effect and (4) theelectromeric effect.Of these effects, (1) and ( 3 ) do not involve co-valency changes and are capable of transmission through saturahedsystems. Effects (2) and (4) operate by 6he tautomeric mechanism,and, since they involve covalency changes, can be transmitted onlyin conjugated systems; they depend upon the phenomenon ofquantum-mechanical resonance.27The classical dissociation constants of carboxylic acids, deter-mined by Ostwald and others, have long been employed as criteriaof the polar influences of substituents.A number of accuratethermodynamic constants have been obtained during recent years,in most cases for isolated acids. J. F. J. Dippy and his collabora-tors,28 using an expeditious conductometric method, have now deter-mined values for the thermodynamic constants of a large numberof acids, principally of the benzoic, phenylacetic , p-phenylpropionicand cinnarnic series, in aqueous solutions a t 25". These valuesare strictly comparable, and provide data from which the effectsof groups in aromatic combination may be deduced with a gooddegree of certainty. Certain saturated and olefinic acids are alsoincluded.Dippy finds that the dissociation constants of the m-substituted acids in the benzoic, phenylacetic and p-phenylpropionicseries show a linear relationship with the dipole moments of thecorresponding substituted benzenes. This is quite distinct fromthe earlier correlation of log K with p.29 Further justification hasbeen found for the use of dissociation constants referring to a singlesolvent and a single temperature in deducing the order of acid26 See R. Robinson, " Outline of an Electrochemical (Electronic) Theoryof the Course of Organic Reactions," Institute of Chemistry, 1932; J. SOC.Dyers and Colorists, Jubilee Issue, 1934, p. 65; C. K. Ingold, Chem. Reviews,1934, 15, 225.27 See N. V. Sidgwick, Ann.Reports, 1934, 31, 37; J., 1936, 533; 1937,694; C. K. Ingold, ref. 26; J., 1933, 1120.2 8 J. F. J. Dippy and F. R. Williams, J., 1934, 161, 1888; 1935, 343;J. F. J. Dippy, H. B. Watson, and F. R. Williams, ibid., p. 346; J. F. J.Dippy and R. H. Lewis, J., 1936, 644; 1937, 1008, 1426; J. W. Baker,J. F. J. Dippy, and J. E. Page, J . , 1937, 1774; J. F. J. Dippy and J. E. Page,J., 1938, 357; J. F. J. Dippy, J., 1938, 1222.29 W. S . Nathan and H. B. Watson, J., 1933, 890; J. F. J. Dippy andH. B. Watson, ref. 25; H. B. Watson, Trans. Paraday SOC., 1938, 34, 165WATSON : INFLUENCES OF GROUPS UPON REACTIVITY. 241strengths; for example, a series of acids stand in the same orderin n-butyl alcohol or chlorobenzene as in water,30 and the sequenceappears to remain when the temperature is ~hanged.3~ Of recentstudies of the strengths of bases, the most extensive is that ofN.F. Hall and M. R. Sprinkle.32Sutton’s rule, which relates the differences between the dipolemoments of aromatic compounds ArylX and of their aliphaticanalogues AlphylX with the op- or m-directive influences of thegroups X in aromatic substitution, has been confirmed by L. G.Groves and S. S ~ g d e n , ~ ~ using new values for the dipole moments inthe vapour state. The same authors have calculated the values ofthe mesomeric moments in substituted benzenes 34 (certain approxi-mations and assumptions being necessary with regard to valencyangles and induction within the molecule), and they find that, where-as op-directive groups give quite large mesomeric moments (e.g.,C6H,C1 0.97, C6H5*OH 1.12 Debye units), those due to m-directivegroups are small (e.g., C6H5*N0, 0.29, C,H,*COMe 0.17).R. J. B.Marsden and L. E. Sutton 35 find 1.55 D. for the mesomeric momentof NMe,, and the mesomeric effects of the sulphoxide, nitroso- andiodoxy-groups have been discussed by D. L. Hammick and R. B.Williams.36 Comparison of the dipole moments of p-substitutedphenols, phenolic ethers and anilines with those calculated by vectoraddition of the moments of the corresponding monosubstitutedbenzenes has revealed an appreciable difference between the twosets of values 37; in other words, the mesomeric effect of a groupin aromatic combination is not a constant quantity, but is influencedby other groups present, and this may explain, inter alia, the devi-ation of p-substituted benzoic acids from the log K--I_L relationshipwhich their m-isomeridea obey.38The proportions of o-, m-, and p-isomerides formed in replacements30 L.A. Wooten and L. P. Hamnett, J. Amer. Chem. SOC., 1935, 57, 2289;L. P. Hammett, Trans. Faraduy SOC., 1938,34, 162 ; D. C. Griffiths, J., 1938,818. Compare Ann. Reports, 1934, 31, 79, and I. M. Kolthoff, J. J. Lingane,and W. D. Larson, J . Arner. Chem. SOC., 1938,60, 2512.31 L. P. Hammett, J. Chern. Physics, 1936, 4, 613; cf. J. F. J. Dippy, J . ,1937, 1776.32 J. Arner. Chem. SOC., 1932, 54, 3469.3p J., 1937, 1992.s5 J., 1936, 599.83 J., 1935, 971.These are based upon dipole moments in the vapourThey have also calculated values for NH,, OH, and OMe ;All are based on dipole moments in benzenephase.these are referred to later.solutions.36 J., 1938, 211.3 7 G.M. Bennett and S. Glasstone, Proc. Roy. SOC., 1934, A , 145, 71.38 H. B. Watson, ref. 29.Compare Ann. Reports, 1929, 26, 132; Marsden and Sutton, ref. 35242 ORGANIC CHEMISTRY.of nuclear hydrogen by electrophilic reagents have formed one ofthe foundation stones of the electronic theory of reactivity. Therelative velocities of nitration (by acetyl nitrate in acetic anhydride)at the various positions in ethyl benzoate40 and thehalogenobenzenes *l have now been determined. The total velocity(referred to that for unsubstituted benzene) was found by a com-petitive method, and by combining the figures so obtained with theproportions of the isomerides in the product, the " partial ratefactors " for the o-, m- and ppositions (indicating their relativereactivities) were calculated. The results are summarised below :Partial rate factors.1 1 143 3 55Compound. 0.rn. PaC6HGC,H5*CH3C,H,.CO,Et 0.0028 0.0079 0.0009C,H5C1 0.030 O*OOO 0.139'cGH5Br 0.037 0-000 0.106The total rates of nitration of the halogenobenzenes were found tobe as follows (C,H, = 1) : PhF 0.15, PhCl 0.033, PhBr 0.030,PhI 0.18. The sequence H>I-F>Cl>Br has been confirmedby a dilatometric methodj2 The results for toluene and ethylbenzoate are in accordance with expectation. The electron-repulsive methyl group makes all positions more reactive towardsan electrophilic reagent, but the o- and p-positions far more so thanthe m-position; carbethoxyl, on the other hand, by reason of itselectron-attractive character, deactivates all positions, again o andp more than m.The new figures relating to the halogenobenzenes bring up againthe vexed question of the effects of halogens when linked to thebenzene nucleus.This has been discussed fully by G. Baddeley,G. M. Bennett, S. Glasstone, and B. Jones.43 The observed effectsof halogens in aliphatic compounds lead to the orderF>Cl>Br>I for their inductive effects. From their behaviourin aromatic compounds it is necessary to postulate also a mesomericeffect decreasing in magnitude in the same order, vix.,F>Cl>Br>I; this order was first suggested by G.Baddeleyand G. M. Bennett,44 and L. G. Groves and S. Sugden34 have morerecently found the following values (Debye units) for the mesomeric8s C. K. Ingold and (Miss) F. R. Shaw, J., 1927, 2918; Ann. Reports, 1927,24, 152; C. K. Ingold, A. Lapworth, E. Rothstein, and D. Ward, J., 1931,1959; Ann. Reports, 1931, 28, 115.' 0 C. K. Ingold and (Miss) M. S. Smith, J., 1938, 905.(Miss) M. L. Bird and C. K. Ingold, ibid., p. 918.G. A. Benford and C. K. Ingold, ibid., p. 929.r a J., 1935, 1827.44 J., 1933, 261. Compare G. M. Bennett, ibid., p. 1112WATSON : INFLUENCES OI? GROUPS UPON REACTIVITY. 243moments in the four halogenobenzenes : F 1, C1 0.97, Br 0.89,I 0.87. The chemical evidence relating to the mesomeric effect isgiven in the paper by Bennett and his co-workers, who also discussthe origin of this effect.A polarisability of the halogen-nucleusbond, decreasing in the order I>Br>Cl>F, is also postulated;this may be either an inductomeric43 or an electromeric45polarisabilit y .The replacement of nuclear hydrogen by deuterium is an electro-philic substitution, and is subject to the rules which govern othersubstitutions by electrophilic reagents. Thus, the effects ofnuclear groups upon the speed of deuteration give the usual sequenceO->NMe,>OMe>H>S03H,46 and phenol and aniline aredeuterated exclusively in the o- and p-p~sitions.~~ortho-Substituted Compounds.-N. V. Sidgwick and R. K. Callow’spostulate 48 of a hydrogen bond in o-substituted phenols where thesecond group contains an electron-donating atom (e.g., CHO, CO,R,NO,, C1) and where the process “ completes ” a five- or more fie-quently a six-membered “ chelate ring ”, has received abundantc~nfirmation,~~ and the difficulty which once existed with respectto “ two-covalent ” hydrogen has now been removed.50 The viewhas been applied by G. E.K. Branch and D. L. Yabroff 51 to ex-plain the unusually high dissociation constant of salicylic acid (ascompared with the isomeric acids), and by W. Baker 52 in connectionwith the further increase in strength brought about by the intro-duction of hydroxyl in the remaining o-position; if it be supposedthat chelation occurs mainly in the anion (where it would be favouredby the negative charge), the resulting decrease in electron-avail-ability of the carboxylate group accounts for the high strength.Recent confirmation of Sidgwick’s view is found in observations ofthe Raman spectra of salicylaldehyde and ethyl salicylate,= andin the removal of marked differences in the behaviour of the stereo-isomeric o-hydroxybenzophenoneoximes by acylation of the phenolichydroxyl or by salt formation.1114; Bird and Ingold, ref.41; J. W. Baker, J . , 1936, 1448.*& A. E. Oxford and R. Robinson, J., 1927, 2239; R. Robinson, J., 1933,46 C. K. Ingold, C. G. Raisin, and C. L. Wilson, J . , 1936, 1637. *’ A. P. Best and C. L. Wilson, J., 1938, 28.40 See summaries by E. N. Lassettre, Chem. Reviews, 1937, 20, 259, and6o Ann.Reports, 1933, 30, 112; 1934, 31, 40.61 J . Amer. Chem. SOC., 1934, 56, 2568.6a Nature, 1936, 137, 236.6s L. Kahovec and K. W. F. Kohlrausch, 2. physikal. Chem., 1937, B, 38,54 A. H. Blatt, J . Amer. Chem. SOC., 1938, 60, 205.J., 1924, 125, 527; Ann. Reports, 1924, 21, 104.W. Baker, Ann. Reports, 1936, 33, 283.119244 ORGANIC CHEMISTRY.Internal hydrogen-bond formation is not restricted to phenoliccompounds. The work of von Auwers and others has shown thatamides and anilides are normally associated in solution, but thatthere is little or no association in anilides having a nitro- or aldehydo-group in the o-position (a similar lack of association occurs whenboth amide hydrogens are replaced, for no hydrogen is then availablefor bond formation).H. 0. Chaplin and L. Hunter 55 have nowdemonstrated the absence of molecular association in a furthernumber of compounds where an electron-donating group is situatedin the o-position with respect to an acylamido-group ; they includeo-nitroacylanilides, o-acetamidoazo-compounds, ethyl . o-acetamido-benzoate, o-acetamidoacetophenone, l-acetamidoanthraquinone and8-acetamidoquinoline. The authors interpret this lack of associa-tion by postulating a hydrogen linkage between the nitrogen of theamide group and a suitably placed atom of electron-donating charac-ter (0 of CO,Et, COR or NO,; N of 3l:NA.r or quinoline). Ex-tension of this work has indicated, however, that such chelation isgreatly reduced by the presence of an additional group in either the6-position or the 3-position (this " group " may be the second nucleusof a naphthalene derivative).This occurs, for example, if CH,,Br or NO, is introduced into the 6-position in o-nitroacetanilide,and, of the isomeric compounds (I) and (11), (I) shows considerableassociation and (11) does not [i.e., (I) is not chelated]. ChelationNHAc NO,is similarly reduced by the presence of a group (NO,, CH,, CO,Et,Br) in the 3-position in o-nitroacetanilide, but introduction of Bror CH, (OEt is ineffective) into position 4 in 2 : 3-dinitroacetanilideresults in increased chelation. These phenomena are attributed tosteric interference by the group in the 6- or the 3-position; theauthors suggest that the acetamido-group or the o-substituent isthereby excluded from the plane of the benzene nucleus, and itwill then be difficult for these groups to position themselves suitablyfor hydrogen-bond formation.A group in position 4 will have asimilar steric effect upon one in position 3, however, and so preventit from exerting its full effect. At the same time, of course, themutual interaction of these groups occupying adjacent positions isnot impossible.The considerable evidence of chelation in compounds where twogroups stand in o-positions with respect to each other suggests thepossibility that similar processes may contribute to the familiar66 J., 1937, 1114; 1938, 376, 1034WATSON : INFLUENCES OF GROUPS UPON REACTIVITY. 245unreactivity of many o-substituted benzene derivatives.It has longbeen realised that the Victor Meyer conception of steric retardationby a purely geometrical effect is not capable of embracing all the facts,and the necessity for some additional or alternative explanationhas been emphasised by the observation that “ steric hindrance ”is in some cases associated with a high energy of activation. Forinstance, D. H. Peacock 56 has found that the values of E for thereactions of o-toluidine with benzyl chloride and 2 : 4-dinitrochloro-benzene are distinctly higher than the corresponding values relatingto m- and p-toluidines, and C. N. Hinshelwood and A. R. Legard’sstudy of the esterification of o-nitrobenzoic and s-trimethylbenzoicacids 4 has revealed a considerable increase in E and also a rise inthe value of P due to the presence of the groups in o-positions.A purely geometrical effect would lead to a low velocity by reducingP rather than by increasing E.The ortho-effect appears t o operate only when the reacting groupcontains an electron-donating atom (e.g., NR,, CORY C0,R).Thus,it is manifested in the reactions of benzoyl chlorides but not in thoseof benzyl chlorides; 57 o-substituted phenols do not appear toexhibit such an effect, and it may be noted in this connection thatimino-ethers (with C-OR) differ from the isomeric amides (withG O ) in that they are not ass~ciated.~g A kinetic study of thealkaline hydrolysis of o-substituted benzoic esters 59 has indicated afurther necessary condition : the substituent must be capable ofacting as electron-acceptor.With nitroxyl, chlorine or methyl inthe o-position the hydrolysis is relatively slow, the low velocity beingdue to a reduction of the P factor (as compared with its value for theunsubstituted, m-substituted or p-substituted esters) by about apower of 10; the values of E are slightly less than those for theisomeric p-substituted esters. The three groups referred to mayall be regarded as possible electron-acceptors; chlorine on the basisof Sidgwick’s covalency rule, nitroxyl on grounds put forward byG. M. Bennett and G. H. Willis,60 and methyl by virtue of anability to form a hydrogen bond under favourable conditions (sucha linkage was suggested tentatively by Sidgwick a’nd Callow foro-nitrotoluene, and other possible examples are discussed later 61).Fluorine, however, presents an instance where the acceptance ofelectrons is definitely impossible (it cannot expand its valency groupb6 Nature, 1932,129, 57; A.Singh and D. H. Peacock, J . Physical Chem.,1936, 40, 669.67 S. C. J. Olivier, Rec. Truv. chim., 1929,48, 227; 1930,49,697. CompareG. M. Bennett and B. Jones, J., 1935, 1815.68 H. 0. Chaplin and L. Hunter, J., 1937, 1114.59 D. P. Evans, J. J. Gordon, and H. B. Watson, ref. 8.60 J., 1929, 256. 61 See p. 250246 ORGANIC CHEMISTRY.beyond eight), and in ethyl o-fluorobenzoate the criteria of theortho-eff ect disappear completely ; its behaviour is almost identicalwith that of the p-isomeride. The indications are, therefore, thatthe operation of the ortho-eff ect demands electron-donating andelectron-accepting groups, and it is no great step to postulateinteraction between these two groups to give either a co-ordinatebond or a hydrogen bond.62In the anilides and phenols to which reference has been made,there is evidence of chelation under ordinary conditions ; this is,of course, to be attributed to the ionisable character of the hydrogenin the acylamino- or hydroxyl group.Ethyl salicylate is includedin this category, but there is no reason whatsoever to suppose thatthe corresponding esters containing nitroxyl, halogen OT methyl arechelated. The suggestion is therefore made that the interaction ofgroups to give a co-ordinate bond or a hydrogen bond occurs onlyin the transition complex.The first step in alkaline hydrolysis maybe writtenAs the hydroxyl ion approaches, an electron-pair begins to recedefrom carbon, to come under the sole control. of oxygen (which there-fore acquires an increasing negative charge), and the system climbsthe energy valley to the pass which represents the transition state.It is not improbable that, simultaneously with these processes, theunshared electrons of oxygen (now in relatively high energy levels)will interact with a suitably placed acceptor. If chelation doesoccur at this stage, the energy required for the formation of thetransition complex is not likely to be affected to any great extent;perhaps the electromeric change G O may be rendered rather/srOEt I ,..OHC.:' 8(A.) /\,'\,OI II 6,\/easier, in accordance with the slightly low value of E.But if theapproaching reagent is an acid catalyst (as in esterification processes)which attacks the group a t oxygen, the decreased electron avail-ability of this atom will operate against reaction, and E will be62 J. F. J. Dippy, D. I?. Evans, J. J. Gordon, R. H. Lewis, and H. B. Watson,J., 1937, 1421WATSON : INFLUENCES OF GROUPS UPON REACTIVITY. 247raised, as Hinshelwood and Legard found. The chelation processesfor alkaline hydrolysis and acid-catalysed esterification are repre-sented, on this view, by the curved arrows in (A) and (B).It is clear that the effect of the process in either case is to transfera negative charge from oxygen of carbethoxyl or carboxyl to theo-substituent, and the portion of the complex upon which thereaction depends is rendered less negative in (A) and more positivein (B); i.e., in (A) it becomes less and in (B) more highly charged.Now it is well known that a relatively high P value is characteristicof reactioas involving either an ion or a charged catalyst; thecharge may make the complex more stable, so that it is better ableto exist while the processes leading to the completion of the reactionare taking place (instead of falling apart to give the original reagents).The effect of chelation upon that part of the complex where theseprocesses must occur is thus in the direction which will lead to aEower P factor in (A) and a higher value of P in (B), as is foundexperimentally.Alternatively it may be argued that the transferof negative charge may lead to the less facile elimination of OEtfrom (A) and the more ready reaction of (B) with an alcohol molecule ;again the change in P would be in the direction indicated by ex-periment, since the value of this factor will depend, inter aEia, uponthe proportion of the complexes which actually leads to products.*The relatively high dissociation constants of o-substituted benzoicacids 63 may be due, in some cases, to chelation in the anion, assuggested by Branch and Yabroff for salicylic acid. This inter-pretation does not hold throughout, however, and other factorssuch as the bulk of the substituent doubtless intervene; in fact,steric hindrance of the Victor Meyer type can rarely be neglectedas a possible contributory effect in considerations of the behaviourof o-substituted compounds.Groups in the o-positions decreasethe strengths of bases; the position of the substituent is here notalways suitable for a chelation process (e.g., o-chloroaniline wouldrequire a four-membered ring, which is most unlikely), but it wouldappear, nevertheless, that the unshared electron pair of the nitrogenmust be torn away from some constraint before the necessary unionwith a proton can occur. The reduced strength is not explicableon the basis of a bulk effect, which would operate unfavourablyupon the reversed change in the equilibriumR*NH, + H,O 2 R*NH3+ + OH-(in dilute solution where the ba.se is in constant contact with watermolecules), thus giving an increase in strength ; increased stability83 See table given by J.F. J. Dippy and R. H. Lewis, J., 1937, 1426.* On this point, see H. B. Watson, “ Modern Theories of Organic Chemistry,”Oxford University Press, 1937, p. 161248 ORGANIC CHEMISTRY.of the hydroxide is not impossible in view of the effect of o-substitu-ents upon benzaldehydecyanohydrins.64W. C. Davies and H. W. Addis 65 find that dimethyl-o-toluidine isactually stronger than its pisomeride (although o-toluidine isweaker than p - ) , whereas an ortho-effect is indicated in its reactionswith alkyl halides. If NMe, has a greater mesomeric effect thanNH, (as the electron-repulsive character of the methyl groups makesprobable, and as is indicated by the values of the dipole momentsof aniline a,nd dimethylaniline 6 6 ) , this will render the protons ofthe o-methyl group less reactive, but they may nevertheless interactin some way with the unshared electrons of the nitrogen in a highlyenergised transition complex.AZkyZ Croups.-The absence of a dipole moment in all paraffinsmakes it necessary to suppose that alkyl groups exert only thosepolar effects which are impressed on them by other groups presentin the molecule.67 Since the substituents commonly encounteredare attractors of electrons, alkyl groups normally exhibit a ratherfeeble electron repulsion, but it is not impossible that they mightin certain circumstances display the opposite effect.*The electron-repulsive characters of alkyl groups should increasein magnitude as the m-series is ascended (Me<Et<Pra<Bua,etc.), and also in series such as Me<Et<PrS<Buy, for thehigher groups are all derived from the lower by successive replace-ments of H by CH,.This sequence is found in a number of in-stances which have been enumerated in recent papers.68* 69 In then-series the differences become smaller as the length of the chainincreases, and the dipole moments of homologous alkyl halides andother compounds have been found to reach a constant value atan early stage in the series (e.g., a t Pra for chlorides and bromides64 A. Lapworth and R. H. F. Manske, J . , 1928, 2546.65 J., 1937, 1622.6 6 Recent values for the vapours are PhNH, 1.48 and PhNMe, 1.61 D.(L.G. Groves and S. Sugden, J., 1937, 1782). Using values for benzene solu-tions, R. J. B. Marsden and L. E. Sutton (ref. 35) have calculated the mesomericmoments as PhNH, 1-12 and PhNMe, 1.55.67 C . K. Ingold, Chem. Reviews, 1934, 15, 238.68 E. E. Ayling, J . , 1938, 1014.69 D. P. Evans, J. J. Gordon, and H. B. Watson, ibid., p. 1439.* The mesomeric moments of phenol and anisole C1.12 and 0 . 4 0 ~ . re-spectively; Groves and Sugden (ref. 34), but Marsden and Sutton (ref. 35)calculate the reverse order, viz., 0.84 and 1-03] and the relative strengthsof certain hydroxy- and methoxy-substituted acids might indicate such areversal of character when alkyl groups are linked to oxygen (the effect ofincrease in the size of the group is in the usual direction), but an interpretationof this kind (suggested by J.F. J. Dippy, J., 1938, 1224) must at present betreated with reserveWATSON : INFLUENCES OF CROUPS UPON REACTIVITY. 249and at Bua for iodides 70) ; a similar tendency to a constant value hasfrequently been observed in the effects of the groups upon chemicalchanges, and in the chlorination of a series of phenolic ethersRO*C,H,X an actual decrease in the effect is found when R reachesn-heptyl.71 If the alkyl group is removed some distance from thereactive centre, as, for example, by interposition of an aromaticnucleus, the differences become very small and are not easy to detector to interpret with any degree of certainty; this has been found insome recent investigation^,'^ and it constitutes one of the difficultieswhich have been encountered in the study of the influences of alkylgroups.In a large number of instances the observed effects of alkyl groupsdo not follow the theoretical order.These peculiarities are some-times due to a change in reaction mechanism, and not to any ab-normality on the part of the group itself,73 and in such casesirregularity is observed only when primary groups are comparedwith secondary or tertiary, or secondary with tertiary, for all primary(secondary or tertiary) groups appear to give a reaction of the samemechanistic type. E. E. Ayling 68 has suggested that n-alkylgroups show divergence from the theoretical sequence only whenthey are not themselves participating in the reaction but are exert-ing their influence upon the reacting group.Two causes of abnormal behaviour have been suggested duringrecent years.J. W. Baker and W. S. Nathan 74 have dealt withinstances where methyl exhibits a capacity for electron releasesuperior to that of higher groups; for example, in the nitration ofpalkyltoluenes substitution occurs predominantly ortho to themethyl group, and Baker and Nathan quote a number of otherinstances to which their view is applicable (e.g., the singular lack ofreactivity of some compounds containing the isobutyl group 75).Briefly, the view is that the C-H electron pairs of methyl can comeunder the control of the adjacent nucleus, giving rise (in a conjugatedsystem) to an effect which is superimposed upon and is of the samesign as the inductive effect; it is of a permanent character, andmay accelerate or retard a chemical change, and its magnitude70 L.G. Groves and S. Sugden, J., 1937, 158; E. G. Cowley and J. R.71 B. Jones, J., 1935, 1831.72 E.g., idem, J . , 1938, 1414.74 J., 1935,1844.Partington, J., 1938, 977.Compare idem, J . , 1936, 1854.73 See this Report, p. 212.A rather similar suggestion was made by G. N. Burkhardtand M. G. Evans (Nem. Manchester Lit. Phil. Soc., 1933, 77, 37, and quotedby G. N. Burkhardt, C. Horrex, and Miss D. I. Jenkins, J., 1936, 1657).B. V. Tronov andL. V. Ladigina, Ber., 1929, 62, 2844; B. V. Tronov and N. C. Ssibgatullin,aid., p. 2850; W. C. Drtvies, J., 1938, 1866.7 5 G. M. Bennett and F. M. Reynolds, J., 1935, 131250 ORGANIC CHEMISTRY.decreases as the hydrogen atoms of methyl are replaced (Me>Et>PrS), becoming zero in tert.-butyl.The co-operation of suchan effect with the inductive effect (which increases in magnitudefrom Me to Buy) may account for the peculiar order of the dissocia-tion constants of the p-alkylbenzoic acids (Me<Et-PrS >Bu779,for the order primary< secondary >tertiary for the strengths ofaliphatic amines, and for the equality of the strengths of propionicand isobutyric acids.77 A similar equality is found in the energiesof activation for the alkaline hydrolysis of propionic and isobutyricesters, whereas the series of n-esters give results in accordance withthe sequence of the inductive effects of the alkyl groups; 69 thesame influence can be traced in the acid-catalysed prototropy ofthe homologues of a~etophenone.~~ In these cases the largerinductive effect of the secondary alkyl group appears to be balancedby its smaller electron-release by the Baker-Nathan mechanism.The second suggestion has been made in order to account forpeculiarities of a different type.In 1930, G. M. Bennett andA. N. Mosses 79 postulated for the methyl group a direct polar effectof opposite sign to its inductive effect. This would, of course, havegreatest influence a t a point of the molecule which can approachthe methyl group closely, and the rather high dissociation constantof n-butyric acid (as compared with propionic and n-heptoic acids)was cited as an example of its operation.The same view has recentlybeen applied by E. E. Ayling 68 to the explanation of a number ofphenomena, including his own observations of the Hantzsch pyridinecondensation; for a series of aliphatic aldehydes RCHO the yieldof product is unexpectedly high for R = Pra. I n a study of theacid-catalysed prototropy of phenyl alkyl ketones, D. P. Evans 78has observed a notable rise in the energy of activation, and also anincrease in the P factor, on passing from acetophenone to propio-phenone; in actual magnitude the increase in E was twice as greatas that found when a p-nitro-group was introduced into the nucleus,but further lengthening of the chain produced little effect. Evanshas suggested that a hydrogen bond is formed, in the transitioncomplex, between the carbonyl oxygen and the p-carbon atom ofpropiophenone and higher ketones. This is actually a modification(or perhaps a more precise definition) of the original view of BennettThe actualdifferences are small, but reasom are given for accepting them as real andsignificant.The possibility of an effect opposite insign to the inductive effect and greatest in the tertiary group is suggested asan alternative to Baker and Nathan’s view.78 D.P. Evans, J., 1936,785 ; D. P. Evans and J. J. Gordon, J., 1938,1434.79 J., 1930, 2364.76 J. W. Baker, J. F. J. Dippy, and J. E. Page, J., 1937, 1774.7 7 J. F. J. Dippy, J., 1938, 1222SMITH: FATTY ACIDS AND OTHER LONQ-CHAIN COMPOUNDS. 251and Mosses. It is in harmony with the fact that the values of Efor the base-catalysed prototropy of the same ketones show noanomaly, but rise steadily in accordance with the inductive effectsof the alkyl groups, whereas a t propiophenone there is a decreasein the value of P; the position is here similar t o that found in thealkaline hydrolysis of o-substituted benzoic esters:* and the analogyextends further, for, in the hydrolysis of a series of aliphatic esters,a fall in P is observed for ethyl isobutyrate and ethyl trimethyl-acetate.69 Lapworth and Manske's dissociation constants of thecyanohydrins of phenyl alkyl ketones have also been discussedin the light of this view.In an accurate redetermination of the dissociation constants ofa series of aliphatic acids (up to n-nonoic) J.F. J. Dippy" findsthat the values for n-butyric and the higher acids are displacedupwards as compared with those for acetic and propionic acids,and he considers that this is due to some degree of chelation in theanions of the former acids. The " chelate ring " which is " com-pleted " by the hydrogen bond is here six-membered, as is thatpostulated, for example, in salicylic acid. The chelation suggestedby Evans in the prototropy of ketones (and the hydrolysis of aliphaticesters) leads to a " five-membered ring," on the other hand. Thecontradiction is only apparent, however, since the " chelate rings ) )contain different numbers of double linkages, and the electron-donating atom will interact with the hydrogen atom most favourablyplaced.The above suggestions appear to embrace a considerable pro-portion of the instances where alkyl groups place themselves inan order different from that of their inductive effects.There are,however, certain observations which do not admit of interpretationalong these lines. One obvious case is the abnormal basic strengthof diethylaniline, and the same peculiar effect of two ethyl groupsappears in the very high energy of activation for the alkalinehydrolysis of diethylacetic ester.69 This effect is quite unexplained.The order of strengths of the p-alkyldimethylanilines 82 also seemsto defy interpretation.H. B. W.4. FATTY ACIDS AND OTHER LONG-CHAIN COMPOUNDS..Methods of Xynthesis and Preparation.-The outstanding advancein methods of building up paraffinoid chains is the modification180 See this Report, p.245. 81 J., 1930, 1976.82 W. C. Davies, ref. 75. (Mrs.) G. M. Robinson, J,, 1930, 745252 ORGANIC CHEMISTRY.of the Robinson synthesissynthesis involves the following stages :of keto-acids. In its present form theCH,*CO*CHNa*CO,Et + Br*[CH2]lo*C02Et --+Na(I.) CH3'C0*CH(C02Et) [cH21 looco ZEt C&.[CH,]a.COCI 3(11.) CH,*[CH2lm*C0*C(CO2Et) (CO*CHJ*[CH2]1o*CO2Et -/Ethyl a-acetylbrassylate (I) is obtained in good yield from thereadily available ll-bromoundecoic The complex (11)resulting from the condensation of the sodio-derivative of (I) withan acid chloride is submitted to a graded hydrolysis and yields thelong-chain keto-acid, accompanied by varying amounts of 13-ketotetradecoic acid.These higher keto-acids are readily reducedby the Clemmensen4 method, and thus twelve carbon atoms areadded at a time to the original acid (or acid chloride). Stearic acidyields n-triacontanoic acid, undecoic and lauric acids yield tri-cosanoic and tetracosanoic acids respectively.6 Starting frombehenoyl chloride, tetratriacontanoic acid and then hexatetra-contanoic acid (C4,Hg202) were synthesised.' 15-Phenylpentadecoicacid and 22-phenylbehenic acid * and also ketones, e.g., 12-nonaco~anone,~ have been made, the last by a modification of theprocess. Another modification led to the synthesis at the CulionLeper Colony of dl-chaulmoogric acid.10The alcohols from decanol to octadecanol are now commercialproducts, but even the " purest " grades need much further purifi-cation.l1 Paraffins have been made readily accessible by modifi-cations in the methods of reducing the iodides.12Puri$cation.-In 1898, L. E. 0. de Visser l3 a t the Apollo CandleP (Mrs.) G. M. Robinson and R. Robinson, J., 1925,127, 175; 1926, 2204;Ann. Reports, 1925, 22, 80.R. Ashton and J. C. Smith, J., 1934, 435, 1308.4 E. Clemmensen, Ber., 1913,46,1837 ; H. R. Le Sueur and J. C. Withers, J . ,5 (Mrs.) G. M. Robinson, J . , 1934, 1543.6 R. Ashton, R. Robinson, and J. C. Smith, J., 1936, 283.1915,107, 736.F. Francis, (Miss) A. M. King, J. A. V. Willis, and F. J. E. Collins, J.,1937, 999.8 G. M. Hills and R. Robinson, J . , 1936, 281.* S. H. Piper, A. C. Chibnall, S. J. Hopkins, A.Pollard, J. A. B. Smith, and10 G. A. Perkins and A. 0. Cruz, J . Amer. Chem. Soc., 1927, 49, 1070; Ann.11 J. W. C. Phillips and S. A. Mumford, J . , 1933, 235; 1934, 1657.12 (Miss) P. C. Carey and J. C. Smith, J., 1933, 346.la Rec. Trav. chim., 1898, 17, 182.E. F. Williams, Biochem. J . , 1931, 25, 2072.Reports, 1927, 24, 88SMITH: FATTY ACIDS AND OTEER LONG-CHAIN COMPOUNDS. 253Works, Schiedam, crystallised stearic acid fifty-one times andpalmitic acid thirty-six times from alcohol. Actually such a pro-cedure was not sufficiently varied, and his products were slightlycontaminated probably with each other and with traces of ethylesters; but de Visser set a standard which has not often beenreached, and in this field of higher aliphatic compounds physicalchemists have really merited the gibe of making very accuratemeasurements on very impure substances.The main difficulty liesin separating substances from the homologues with which they areusually associated and with which they form solid solutions. Anotherfactor is that, as the binary systems on pages 261-262 show, thedepressions of melting point by admixture with homologues aresmall. Carboxylic acids show relatively large depressions, yet1 yo of palmitic acid lowers the melting point of stearic acid by only0.24"; l3 as an extreme example the addition of 20 molecules yo oftetracosanoic acid to tricosanoic acid lowers the melting point byonly 0.45"; 6 the melting point of a hydrocarbon is usually raisedsteadily by the addition of a higher homologue.Temperatures should therefore be correct to & 0.1", preferably to&- 0-05", which entails the use of 1-3 grams of the substance and astandardised thermometer in the liquid.For pure substances themelting point and freezing point then differ by less than 0*05",unless there is a transition near the melting ~ 0 i n t . l ~When only small amounts of substance are available, the pro-cedures described by Chibnall or by F. Francis and F. J. E. C011ins,15using capillary tubes, give uniform results. Melting points given byheating in capillary tubes in the usual manner are 0-5-2' too highand when taken rapidly l6 lead to very high values which causeconfusion in the literature.Generally the separation of homologues is best attained byfractional distillation a t low pressure through efficient columns 14~17followed by crystallisation from a series of solvents ; until the purityexceeds SOY0, crystallisation is of little use.(Molecular distillation,which depends on the rate of evaporation rather than on the partialvapour pressure, is being increasingly used.18) In separating asubstance (by crystallisation in a solvent) from an impurity withl4 J. C. Smith, J., 1931, 802.l6 P. A. Leveno and F. A. Taylor, J . Biol. Chem., 1924,59,905.l7 E. Jantzen and C. Tiedcke, J . pr. Chern., 1930,127, 277; L. Keffler andJ. H. McLean, J . Soc. Chem. Ind., 1935, 54,362 T; E. Klenk, 2. physwb. Chem.,1931, 200, 56; 1936, 242, 250; W. Diemair and W. Schmidt, Bwchern. Z.,1937, 294, 348; A.Klem, Nature, 1938, 142, 616.l8 E. W. Washburn, Bur. Stand. J . Res., 1929,2,476; K. C. D. Hickman,Ind. Eng. Chem., 1937, 29, 968 ; (Miss) H. Gilchrist and (Miss) B. Karlik, J.,1932, 1992.l6 J . , 1936, 137254 ORGANIC CHEMISTRY.which it forms mixed crystals it is generally advantageous to allowthe solution to cool very slowly. Even then as many as ten crys-tallisations may be necessary in order to obtain a specimen of 99%purity and a further ten crystallisations to reach 99.9%. Thebest known of the higher aliphatic compounds, palmitic and stearicacids, may not yet have reached 99.9% purity, as some change intechnique may show. De Visser,13 by crystallisation from alcohol,raised the freezing point of palmitic acid to 62.62' and of stearic acidto 69.32"; use of different solvents changed these values to 62.66"and 69-41' respectively ; l4 distillation, combined with twentycrystallisations from various solvents, brought the values to 62-75'and 69~62O.l~X-Ray Andy& of FiZrns.-Interest in long-chain compoundswas much stimulated by the results of X-ray investigations. It wasshown 20* 21 that thin films of a homologous series of substancescould yield X-ray photographs in which some of the distances(the d, spacings) varied linearly with the number of carbon atomsin the homologue.The lines are due to reflections from planesseparating the molecules, and the methylene chain is a more or lessrigid zigzag between these planes. A. Muller 22 likens solid paraffinsnear their melting point to closely packed hexagonal pencils.There appears to be only one type of chain, but in the earlierstages of the development of the subject other forms were consideredin order to accommodate the facts that in the ethyl esters the in-crement of the d, spacing per CM, group was 1.22 A.whereas in theacids it was 1 . 0 ~ . (actually 2 . 0 ~ . for the double molecule).23 Itwas realised later that the chains could adopt various angles oftilt, but that in some esters the axis of the chain was a t right anglesto the end plane (a " vertical chain "). I n most of the acids thechains were "tilted" and moreover the acids existed as doublemolecules. When the photographs of acids were compared withthose of ketones in which the position of the carbonyl group wasknown,24 the relative intensities of the orders of reflection showed thatthe two carboxyl groups must be together, as is now accepted forthe associated forms.25 Shorter spacings (d, and d,) of between 4and 5 A., representing the breadth and thickness of the chain,remain almost constant in a homologous series.19 J.B. Guy and J. C. Smith, unpublished result.20 A. Muller, J., 1923, 123, 2043.21 S. H. Piper and E. N. Grindley, Proc. Physical SOG., 1923, 85, 269; Ann.za Trans. Furuduy SOC., 1933, 29, 990.23 A. Muller and G. Sheerer, J . , 1923, 123, 3156.24 W. B. Saville end G. Shearer, J., 1925, 127, 591.25 N. V. Sidgwick, Ann. Reports, 1933, 30, 115.Reports, 1923, 20, 242; 1925, 22, 254SMITH: FATTY ACIDS AND OTHER LONG-CHAIN COMPOUNDS.255In some cases the increase of length for each CH, added is greaterthan would be expected for a methylene chain with the carbonvalency angle of 109°28’.2G In the acids the longest spacing (A)shows an increase of 1.4 A. per CH, group, whereas 1.22 A. wouldcorrespond to an angle of 109°28’.27 S. H. Piper 28 found thatACH, corresponded to an angle of 111O46’ in the acid salts of thefatty acids (R=CO,H,R*CO,K), and T. Malkin 29 calculates that thevalency angle in the vertical forms of ethyl esters is 118”.It was pointed out by L. Pauling 3O that rotation of long chainsshould be possible in the solid state. J. D. Bernal 31 showed that indodecyl alcohol and octadecylamine hydrochloride the moleculesacquired a higher degree of symmetry with rise in the temperatureand that this could be accounted for if the chain began to rotate.A.Miiller3, showed that all paraffins from C,,H, to C,,H,,acquired higher (hexagonal) symmetry near the melting point, andthat the rapid rise in polarisation of ketones (near the m. p.) wasaccompanied by a large expansion of crystal l a t t i ~ e . ~ ~ a That thechains rotate in “ vertical ” transparent crystal forms is now awidely accepted view 33 and explains the similarity of these crystalsto liquid crystals, as is pointed out in the section on BinarySystems.Obviously the method of measuring the spacings in films hasyielded very valuable results, but many outstanding problems canbe solved only by detailed analysis of single crystals,34 as has beendone with the dibasic acid~,3~ nonacosz~ne,~~ triacontane 37 and cetyl~ a l r n i t a t e .~ ~ Work on unimolecular films on liquid and solid sur-faces has been reviewed by N. K. Adam.39 X-Ray analysis ofliquid paraffins has shown that the chains are roughly parallel evenin the liquid ~tate.~O The diffraction of electrons by long-chain26 Ann. Reports, 1931, 28, 384.27 S. H. Piper, T. Malkin, and H. E. Austin, J., 1926, 2310.28 J . , 1929, 234.30 Physical Rev., 1930, 36, 430.31 Nature, 1932, 129, 870; 2. Krist., 1932, 83, 153.32 Nature, 1932, 129, 436; Proc. Roy. SOC., 1932, A, 138, 514.32a Proc. Roy. Xoc., 1938, -4, 166, 316.33 Ann. Reports, 1937, 34, 184; T. Malkin, J., 1936, 726; W. 0. Baker and34 Ann. Reports, 1935,32,227.35 W.A. Caspari, J . , 1928, 3235; 1929, 2709.36 A. Muller, Proc. Roy. Soc., 1938, A , 120, 437.37 R. Kohlhaas and K. H. Soremba, 2. Krist., 1938, 100, 47.38 R. Kohlhaas, ibid., 1938, 98, 418.3g “ The Physics and Chemistry of Surfaces,” 2nd Edn., Oxford, 1938.4O G. W. Stewart, PhysicaE Rev., 1928, 31, 174; B. E. Warren, ibid., 1933,29 J., 1931, 2796.C. P. Smyth, J . Amer. Chem. Xoc., 1938, 60, 1229.44,969256 ORGANIC CHEMISTRY.compounds has yielded results in excellent agreement with those fromX-ray studies.41Polymorphism.-Crystal analysis with the help of X-ray measure-ments, by detecting different cell dimensions for compounds undervarying conditions, has not only indicated polymorphism but has insome cases given an explanation of the phenomenon.Previous to 1920 only a few higher aliphatic compounds wereknown in more than one crystalline form, examples being theglycerides, oleic acid and cetyl acetate, but it is now recognised thatthe majority of long-chain compounds are polymorphous.Themore systematic aspects of polymorphism in the fatty acids,42* 899 279 43alcohols,45 and dicarboxylic acids 35 were emphasisedby the X-ray studies; isobutyl palmitate and stearate were visiblydimorph~us.~~ Hexadecane, ethyl palmitate and ethyl stearatewere handled for some years without recognition of their polymor-phism, although there was some confusion over the differencebetween the X-ray spacings of “ melted ” and of ‘( pressed ” films.When the polymorphism of these esters was pointed 0 ~ t , l ~ 1 4 ~ it wasobvious that “melted” films were composed of the metastable,transparent forms and that pressing with a spatula would hastenthe change to the stable, opaque forms.Moreover, in mixtures ofesters the transparent forms were stabilised, l 4 yielding longerspacings than either of the pure component^.^^Examination of binary systems of homologues produced some of theconditions under which metastable forms were detectable, so thathexadecane, octadecane and cetyl iodide were seen to bedimorph~us.~~ Adopting the binary system technique, J. W. C.Phillips and S. A. Mumford 49* 55* 56 made an extended study ofpolymorphism. Cooling curves have been used by Phillips andM ~ m f o r d , ~ ~ M a l k k ~ , ~ ~ and (Miss) J.D. Meyer and E. E. Reid,5*optical methods by D. Vorlander and W. Selke46 and by C.Weygand and W. G r i i n t ~ i g . ~ ~W. E. Garner and F. C. Randall 89 noticedthat, when nonoic and undecoic acids were cooled about 20” belowCarboxylic acids.4 1 P. A. Thiessen and T. Schoon, 2. physikal. Chem., 1937,36, B, 216.42 A. Gascard, Ann. Chim., 1921, 15, 332.43 G. M. de Boer, Nature, 1927, 119, 634; S. H. Piper, Trans. Paraday SOC.,44 A. Muller and W. B. Saville, J., 1925, 127, 599.46 T. Malkin, J. Amer. Chem. SOC., 1930, 52, 3739.413 D. Vorlhnder and W. Selke, 2. physikal. Chem., 1927, 129, 435.4 7 J. W. C. Phillips and S. A. Mumford, J . , 1931, 1732.48 J. C. Smith, J., 1932, 737.50 J . Amer. Chem. SOC., 1933, 55, 1574.51 2. anorg.Chem., 1932, 206, 304, 313.1929, 25, 348.4Q J . , 1932, 898SMITH: FATTY ACIDS AND OTHER LONG-CHAIN COMPOUNDS, 257the freezing points, they changed enantiotropically into opaqueforms ; in general, two forms are visibly detectable for “ odd ” acidsfrom C, to CZ5, whereas “even” acids appear to be of one type.X-Ray analysis, however, shows the existence of three forms (A,B, and C spacings) for ‘‘ even ” acids and of four forms (A’, B‘, C’and D’ spacings) for “odd” acids.*3 Forms with A (and A’)spacings seem the least easily obtained and have a vertical chain;they are said to occur in palmitic and stearic acids only when theseare fairly and only in mixtures when the chain length is 23 to27 carbon atoms.52 The solvent used for crystallising the acid 53and the temperature to which the film is heated have a big effect onthe spacings obtained.Films of ‘‘ even ” acids (lauric to stearic)which show A and B spacings will on heating near the m. p. showonly C spacings.43 As the history of the specimen does not appear toaffect the m. p. of an acid, it must be assumed that the same formis always present at the melting point. The acid sodium or potas-sium salts (R-CO,H,R*CO,Na) yield only an A spacing, so theiridentification by X-rays is simple.28Only a tilted form with double molecules has sofar been observed for the methyl esters of even acids. Methylesters of odd acids crystallise either in double molecules with anangle of tilt of 67.5” or in single molecules with 75” tilt,29* 54 but theposition is not quite clear, as it is found that the heats of transitionand crystallisation of methyl nonadecoate are practically identicalwith those of ethyl nonadecoate where both forms are of singlemolecules .97At least three kinds of polymorphism are ob-served 5 4 4 7 , 55, 56, 14, 57,49, 58 : (1) for esters up to ethyl myristatethe opaque p-forms of both even and odd members are stable andthe transparent a-forms are metastable (monotropic polymorphism) ;(ii) from ethyl myristate to ethyl eicosanoate a-forms of the oddmembers are stable near the melting point and change enantio-tropically to the P-forms on cooling; a-forms of the even membersare metastable (except in mixtures) and change monotropicallyto the p-forms; (iii) above ethyl eicosanoate the a-forms of bothMethyl esters.Ethyl esters.52 S .H. Piper, A. C. Chibnall, and E. F. Williams, Biochem. J., 1936, 30,53 F. Francis, F. J. E. Collins, and S. H. Piper, PTOC. Roy. SOC., 1937, A ,64 J. W. C. Phillips and S. A. Mumford, J., 1934, 1657.5 5 Idem, J., 1932, 898.5 6 Idem, Rec. Trav. chim., 1933, 52, 175, 181.5 7 (Miss) P. C. Carey and J. C. Smith, J., 1933, 635.58 S. H. Piper, A. C. Chibnall, and E. F. Williams, Biochem. J., 1934, 28,100, 112.158, 691 ; Ann Reports, 1937, 34, 183.2175.REP.-VOL. XXXV. 258 ORGANIC CHEMISTRY.odd and even members are stable near the melting point (mono-tropic polymorphism). These complications are partly due to theintersection of the melting point curves (m. p. plotted againstnumber of carbon atoms) ; the a-m.p. curve (both “ even ” and“ odd ”) begins below the P-curves, but, rising more steeply, inter-sects the p-“ odd ” curve near ethyl pentadecoate and the p-“ even ”curve near ethyl eic~sanoate.~~ All the a-(transparent) forms havevertical chains and the m. p.’s fit on a smooth curve.29 Thereis some evidence for the existence of lower-melting y - f ~ r m s . ~ ~ Themelting point of ethyl hexatetracontaiioate (C,,Hgl*CO,Et), 90.5”,is higher than that expected by extrapolation of the a-m. p. curve,and a P-form is ~uggested.~3n-Propyl, n-butyl and n-amyl esters of higher fatty acids have beenmuch less fully inve~tigated.5~~ 60.46~61AZcohoZs. The melting-point curve (m. p. against no. of C atoms)for the a-forms intersects the p-m.p. curve a t C13. For dodecylalcohol the transparent a-form changes monotropically to the opaqueP-form. Tetradecyl alcohol, like the higher members of the series,solidifies in the a-form and changes enantiotropically to the @-form onfurther All the alcohols above dodecyl are in the a-format the m. p.’s,4, which are sometimes unsharp because of the transi-tions taking place in the solid; the a-forms have vertical chains( r ~ t a t i n g ) . ~ ~ For the ‘‘ even ” members the P-forms have tiltedchains; the “ odd ” p-forms are opaque but they are not tilted.It has been shown that they are vertical, non-rotatingAcetates and formates. The polymorphism of the “ even”acetates is very similar to that of ethyl esters with the same numberof carbon atoms.,* Heptadecyl acetate readily yields a y-f~rm.~‘.54Cetyl formate exists in transparent and opaque forms.12Hulides. These have not been fully investigated. Cetyl iodideis dimorphous ; 48 the “ even ” iodides from C,, to C,, have a- andp-forms ; C32, CM, C36 iodides have so far given only a - f ~ r r n s . ~ ~ ~ 29Cetyl chloride (but not cetyl bromide) is dimorph~us.~~For “ even ” paraffins there are transparent verticalforms with rotating chains and also opaque tilted forms. With purehexadecane the transparent form has not been obtained, butaddition of 1 yo of octadecane causes this form to crystallise on coolingand then change suddenly to the opaque crystals; addition of moreoctadecane stabilises the transparent form.Similarly the trans-parent crystals of octadecane are not obtained from the pure sub-63Parufins.s~ N. K. Adam, Proc. Roy. SOC., 1922, A , 101,516.6o G. S. Whitby, J . , 1926, 1458.61 T. Malkin, Trans. Paraahy SOC., 1933, 29, 977.62 D. A. Wilson and E. Ott, J . Chem. Physics, 1934, 2, 231.63 T. Malkin, J . , 1935, 726SMITH: FATTY ACIDS AND OTHBR LONB-CRBT" COMPOUNDS. 269stance.48 Above octadecane the polymorphism becomes enantio-tropic and the transparent form is stable near the melting point.From hexacosane onwards the paraEns can exist in a thirdmodification with a more highly tilted chain.Q The existence of thesetypes of polymorphism explains the contrast between petroleum jellyand paraffin wax. " Odd " paraffins above undecane, on cooling,crystallise in transparent, vertical, rotating forms, which on furthercooling change into opaque, vertical, non-rotating forms, and thereverse changes occur on heating.The " odd " parafks do notcrystallise with tilted chains.9* 44* G4# G5In general (and with the possible exception of the acids) a longerchain, a higher temperature, an odd number of carbon atoms, orthe presence of impurity favours crystallisation in vertical forms.Binary Xystems.-The collection of binary systems on pp. 261-262illustrates many of the types predicted 66 for substances whichform solid solutions. Roozeboom's Type 11, a continuous seriesof solid solutions with a maximum, is absent, but it is rarely foundin organic systems (examples are d- and Z-~arvoxime,~7 n-propyland n-butyl gallate 68).The narrow range of temperatures coveredby each of these systems, compared with systems of inorganiccompounds, and the low heat conductivity of the substances makethe determination of solidus points difiicult, and it is doubtfulwhether equilibrium is established between solid and liquidphases. 69The systems on p. 261 are mainly those of the #-forms of thesubstances, transparent crystals with rotating chains.31 D. Vor-lander 7O has pointed out from the study of the optical propertiesthe similarity between liquid crystals and the transparent forms oflong-chain compounds in that both possess freedom of movementround a long axis. In discussing isomorphism among liquid crystals,he quotes two binary systems, p-azoxyanisole-p-azoxyphenetole(Fig. XIV) and p-azoxyanisole-p-methoxycinnamic acid (Fig.XV).71 Both pairs, in the equilibrium between the liquid crystaland the solid, give a eutectic and show no mixed crystal formation.6 5 A. Muller, Proc.Roy. SOC., 1928, A , 120, 437; 1930, A, 127, 417; 1932,66 H. W. B. Roozeboom, 2. physikal. Chem., 1899,30, 385.67 J. H. Adriani, ibid., 1900, 33, 469.6 8 R. M. Harris and J. C. Smith, J., 1935, 1220.69 E. Jantzen, 2. angew. Chem., 1931, 44, 482; W. Briill, Naturwiss., 1934,70 2. K,rist., 1931, 79, 61; I). Vorliinder with K. Ost, Bey., 1938, 71, 1688.7 1 A. Prins, 2. physikal. Chem., 1909, 67, 689; A. C. de Koch, ibid., 1904,(Miss) P. C. Carey and J. C. Smith, J., 1933, 1348.A , 138, 514.22, 436.See also T.48, 129260 ORGANIC CHEMISTRY.For the equilibrium, liquid crystal-amorphous liquid, both pairsform a continuous series of mixed crystals.Thus in the liquidcrystal form in each case the molecules possess a higher degree ofsymmetry. The first pair very readily form mixed (liquid) crystals ;the second pair, as would be expected from their differing structures,form mixed crystals rather less readily, the liquidus curve showinga minimum. The higher aliphatic binary systems now providea confirmation of VorlBnder's views.Crystals of ethyl palmitate and ethyl stearate are sufficientlysimilar in the opaque (p) form to yield mixed crystals, a discon-tinuous series with a eutectic (Fig. VII) ; in the a-form the crystalsare so similar that they yield an unbroken series of mixed crystalswithout a minimum.Mixtures of " odd-even " esters (Fig. VIII)show the closest conformation possible, the mixed melting-pointcurve being a straight line. As the carbon chain of the ester becomesshorter, the ability to assume the or-form decreases until at ethyldecoate apparently only the p-form (Figs. IX, X, XI) exists. Itseems in Fig. I that the @-forms of the paraffins are tending towardsa eutectic, 'while the a-forms (rotating chains) give a continuousseries of solid solutions ; rather surprisingly the (R-) paraffins seemto form solid solutions less readily than do the (a-)ethyl esters, as isshown by the minimum in the curve (Fig. I). The higher members,however, give straight line mixed melting-point curves (Fig. 111).The @-forms of the paraffins give larger depressions of meltingpoint and this part of the system can be followed as a transitiontemperature in the solid phase (Figs.I1 1, IV). Chibnall and hiscollaborators have used these transition temperatures in the analysisof paraffins from plant waxes. For example, an equimolecularmixture of C,,HGo and CS1HGP has a sharp melting point (65.6")at almost the same temperature as that of pure C,,H,, (65-7"),but the transition temperatures show the dif€erence between thepure hydrocarbon and the mixture.In the " even" alcohols the a-forms are stable at the meltingpoint, and the curve shows moderate ease of mixed crystal for-mation (Fig. V), while in the " even-odd " alcohol systems there is adiscontinuity (Fig. VI).This discontinuity shows that there ispersistence of one crystal lattice up to 50 molecules yo and then asudden change to the lattice of the other component (compare thesystems, cadmium-mercury and cadmium-magnesium 72). If inthe " odd " alcohols also the a-form is stable at the melting point,the reason for this abrupt change is not obvious.It is interesting to compare these aliphatic systems with thoseof pairs of the bromides of phosphorus, arsenic, antimony and72 " International Critical Tables," Vol. 11, p. 429SMITH: FATTY ACIDS AND OTHER LONG-CHAIN COMPOUNDS. 261bismuth,73 those of the diphenylene oxides, sulphides and selenides,dioxides, disulphides and di~elenides,'~ and the aromatic systems : 75the more similar the components of a system, the more readily aremixed crystals formed.Most of the binary systems on p.262 show a eutectic, which73 N. A. Pugin and J. Makuc, 2. anorg. Chem., 1938,237, 177.74 N. M. Cullinane and C. A. J. Plummer, J., 1938, 63.76 H. G. G r i m , M. Gunther, and H. Tittus, 2. physikal. Chem., 1931,B, 14,169262 ORGANIC CHEMISTRY.indicates that solid solutions are formed with some difficulty. Inthe acids (Figs. XVI, XVIIu and b ) the forms stable at the meltingpoint have tilted chains, while with tricosanoic and tetracosanoicacids (Fig. XVIIc) at least some of the mixtures crystallise with avertical chain (A spacing).52 If these A forms really are stableat the melting point, this system also shows the greater ease withwhich vertical forms yield solid solutions.The systems oleic-palmitic, elaidic-palmitic and oleic-elaidic acids (Fig. XVIII) aremade up almost entirely of the crystals from the higher-meltingcomponent in each case; these crystals are opaque and probablyhave a tilted chain. The X-ray data for the unsaturated acids arein need of revision.23In the two substituted undecoic acid systems (Fig. XXII) differentpositions of the substituent 8s well as a, shorter chain length brinSMITH: FATTY ACIDS AND OTHER LONG-UHAIN COMPOUNDS. 263about a larger depression in melting point, and the depressions withacetic and butyric acids (Fig. XXIII) are of the order expected forcomponents which do not form solid solutions. Amides, anilides(Fig.XIX), methyl esters and iodides (Figs. XX and XXI) are alsosystems of opaque forms. The other point of interest is their bearingon the question of compound formation.I. 4811. 1, transition cc+ p; 2, solidus; 3, liquidus. C17H36-111. IV. Transition points cc + p of the paraffin in III.gV. 14 For systems of alcohols C,, to Ca, see ChibnalL5*XIII.54 Xor dodecyl-tetradecyl and tetradecyl-hexadecylXIV . p - Az ox yanis ole-p -az ox yphene t ole. 70*XV. p-Azoxyanisole-p-methoxycinnamic acid. 708 71XVI.l3~ 53* 79 Other “ even-even ” acid 78 Chibnalland collaborator^.^^^ 58XVII. ‘‘ Odd-even ” acids : (a) margaric-palmitic, ( h ) margaric-stearic ;79 ( c ) tricosanoic-tetracosanoic.6* 7 9 ~ 52 For other “ odd-even ” systems, see ref.52.XVIII. Oleic acid-elaidic acid ; 8O oleic-palmitic ; 81 elaidic-palmitic (J. C. Smith, unpublished).XIX. (J. B. Guy and J. C. Smith, unpublished). XX. (idem,ibid.). XXI.48 XXII a ; B2 b.83 XXIII.78Compound Formution.-Mixtures of ‘‘ even ” acids from dodecoicto eicosanoic give melting-point curves similar to that in Fig. XVI;formation of a compound with a non-congruent melting point isgenerally inferred. Few ‘‘ even-odd ” systems have been investi-gated with pure acids, but they seem to indicate less stable and notnecessarily 1 : 1 compounds (Fig. XVIIa, b, and perhaps c). Thisbehaviour of carboxylic acids would be expected, since they existas double molecules in solution 84 and, for the lower members, a t7 6 S. L. LangedijkandW. C.B. Smithuysen, Rec. Trav.chim., 1938,57,1050.7 7 G. T. Morgan and A. R. Bowen, J. SOC. Chem. Ind., 1924,43, 346 T.7 8 L. A. Bhatt and H. E. Watson, J . Indian Inst. Sci., 1930, 13, A , 141.79 J. C. Smith, J., 1936, 625.For C16H34-C16H32, see ref. (76).C,,H,, is very similar.64v1.64 v11.14 ~ 1 1 1 . 5 7 ~ 5 6 1 x . 5 6 x . 5 6 XI. 56 x11.56acetates, see ref. 54.H. N. Griffiths and T. P. Hilditch, J., 1932, 2315.A. Lapworth, (Mrs.) L. K. Pearson, and E. N. Mottram, Biochem. J.,1925, 19, 7 ; J. C. Smith, unpublished resuIts.82 P. L. Harris and J. C. Smith, J., 1935, 1108.83 (Miss) M. L. Sherrill and J. C. Smith, J., 1937, 1501.P. W. Robertson, J., 1903, 83, 1425; H. N. Brocklesby, Canadian J .Res., 1936, 14, B, 222; C. R. Bury and H. 0. Jenkins, J., 1934, 688;M.Trrtutz and W. Moschel, 2. anorg. Chem., 1926,155,13264 ORGANIC CHEMISTRY.temperatures above the boiling point ; 85 a ring formula is generallyaccepted.25 If acids X and Y exist as X-X and Y-Y units, someX-Y units should occur in a mixture, and similarly the amides andanilides should yield equimolecular compounds.The unsaturated acid system, oleic-elaidic, and the unsaturated-saturated system, oleic-palmitic, give no sign of compound for-mation (Fig. XVIII) (elaidic-palmitic is it doubtful case), nor dothe systems in Figs. XXII and XXIII. Methyl ester and alkyliodide systems (Figs. XX and XXI) show " compounds " with non-congruent melting points.X-Ray spacings show that the saturated and the unsaturatedacids crystallise in double molecules ;23 methyl (but not ethyl)esters,29 methyl (but not ethyl) ketones,24 alkyl iodides 29 andalcohols 45$ 62 form double molecules.That is, the " reactive "ends come together in the middle and the pattern repeats itself aftereach two molecules. In solution, molecular-weight determinationsshow that the saturated acids are ma,inly in double molecules andthat unsaturated acids are less as~ociated.~~ The presence of im-purities can obliterate the changes in a liquidus curve which indicatethe compounds between acid^.^^^^^ Lack of symmetry may con-ceivably prevent crystallisation of a compound between a saturatedand an unsaturated acid, but on the other hand it may be the demandsof symmetry (or the ease of packing) which cause methyl esters tocrystallise in double molecules.The position is not clear andattempts to solve this aliphatic and other similar problems by X-raymethods 27p 37 and by measurement of dielectric constant 86s 87 orof fluidity 88 have met with little success.Thermal Investigations.-Heats of crystallisation, transitiontemperatures, and specific heats of several series of long-chainpompounds have been systematically examined. *9-98s5 (Miss) T. M. Fenton and W. E. Garner, J . , 1930, 694; V. C. E. Burnop,86 E. Eisenlohr and G. Meier, Ber., 1938, 71, 1005.87 K. Hrynakowski and J. Jeske, ibid., p. 1415.88 R. H. Ewell, J . Chem. Physics, 1937, 5, 967.W. E. Garner and F. C. Randall, J . , 1924,125, 881.90 W. E. Garner, F. C. Madden, and J.E. Rushbrooke, J . , 1936, 2491.91 W. E. Garner and J. E. Rushbrooke, J., 1927, 1351.92 W. E. Garner and (Miss) A. M. King, J., 1929, 1849.93 (Miss) A. M. King and W. E. Garner, J . , 1931, 578.94 W. E. Garner, (Miss) K. Van Bibber, and (Miss) A. M. King, J . , 1931, 1533.9 5 (Miss) A. M. King and W. E. Garner, J . , 1934, 1449 (summarising paper).9 6 Idem, J., 1936, 1368 (summarising paper).97 Idem, ibid., p. 1372.g8 G. S. Parks and H. M . Huffman, Ind. Eng. Chem., 1931, 23, 1138; H. M.Huffman, G. S. Parks, and M. Barmore, J . Amer. Chem. SOC., 1931, 53, 3876;G. S. Parks, H. M. Huffman, and S. B. Thomas, ibid., 1930,52,1032.J . , 1938, 1614SMITH: FATTY ACIDS AND OTHER LONG-CHAIN COMPOUNDS. 265In any homologous series where similar crystal forms are stablea t the melting point the heat of crystallisation per CH, group isconstant.Where the crystal form alternates, as in the " odd "and " even " members of the fatty acids, the heat of crystallisationalternates and has its minimum a t about the same point in the seriesas does the melting 98 The heat of crystallisation (&)of even-number fatty acids (above C,,), plotted against the numberof carbon atoms (n), gives a straight line, as also does &/T, whereT = m. p. in degrees absolute :& = 1-030n - 3.61 ; &/T = 0.002652n - 0.0043Hence T = (1.030% - 3.61)/(0.002652n - 0.0043)This equation for T predicts a maximum (the convergence tempera-ture) of 115" c. for the series.g0 Similar equations are derived for theodd acidsYg2 the ethyl 959 54 and methyl 97 esters, and the paraffins.94[E.B. Moulling9 finds that, for paraffins of n carbon atoms, log(n - a), plotted against melting point, gives a straight line fromn = 27 to n = 8 and probably lower. The analogy between anacid and a paraffin of double the number of carbon atoms is pointedout .]Defining the melting point as the temperature a t which the prob-ability of detachment of a molecule from a surface is equal to theprobability of its attachment, Garner and his pupils develop a theoryof melting from the X-ray model of the crystal. On the surface themolecule will be attached by i ( n - 2)CH, groups and by the twoend groups ; in melting, a molecule will leave the surface in stages inwhich one point of attachment may be broken at a time and equationsare derived in terms of energies of activati~n.~O*~~ This prob-ability factor is held responsible 93 for the minimum in the meltingpoints of homologous series between C, and C , (the theory does notdeal specifically with the transparent forms in which the chains arerotating below the melting point).Besides the probability factor an important contribution tomelting in the case of the lower members must be made by the endgroups.The heat of crystallisation of each CH, group for the acidsabove decoic is 1.030 kg.-cals. and from this the heat of crystallisationof the end groups is calculated to be - 1.55 kg.-cals. All homolo-gous series give negative values (from -0-53 to -3.90 kg.-cals.) forthe two terminal groups in members with more than ten carbonFor other formulae for calcu-lating m.p.'s in homologous series, see also J. B. Austin, J . Amer. Chem. SOC.,1930, 52, 1049; V. K. Nikiforov and I. I. Korolkov, J . Gen. Chem. Russia,1937, 7, 2139; R. Kobuyashi, J. SOC. Chem. I n d . Japan, 1937, 40, 341 B ;C. D. Nenizescu, $. Titeica. and I. Irimescu, Naturwiss., 1938. 28, 629.99 Proc. Camb. PhiZ. SOC., 1938, 34, 459266 ORGANIC CHEMISTRY.atoms.96 From the area of cross section of the crystal cell it seemsthat the end groups, whatever their nature, are in an " expanded "state and can move about much more freely than the rest of thechain; on melting, the end groups approach more closely and givea positive heat value.g1 For the lower members (perhaps c6upwards) this negative heat of crystallisation lowers the meltingpoint, but its effect is felt less and less as the methylene chainbecomes longer.In all series there is a convergence temperatureof about 120" as the methylene chain becomes the dominantfactor.g1* 96 As regards the first members of a series there are manydisturbing factors, especially from the terminal groups. If it isassumed that the heat of crystallisation of the CH, group is constantright down the series, then the heat of crystallisation of the endgroups changes from negative to positive :$2.77 +0.58 -0.52 -1.07 -1-55 -1-55 -1.62 -1-44 -1.59kg.-cals.The value for acetic acid (+ 2.77 cals.) is greater than the totalheat of crystallisation of butyric acid (+ 2.62), although butyricacid has two CH, groups.96 When one end grouping is very polar,as in the acids, the amides or the alcohols, the degree of associationmust have a large effect on the heat of crystallisation.Accordingto Garner and Rushbrookegl the main cause of the very highmelting points of the lower amides is the exceptionally high heat ofcrystallisation of the (- CO*NH,), group in the associated compound.Crystalline form should have a big effect on the melting point,and X-ray studies on the acids from formic to decoic show irregularspacings up to hexoicThe thermal investigations divide crystals of long-chain substancesvery sharply into those with vertical and those with tilted chains.Vertical forms have a low heat of crystallisation, a high specificheat, a large cross-section, and a large coefficient of expan-si0n,9~* 95* 96 indicating that the molecules possess relatively greatmobility (as would be expected with a rotating chain).In the tilted forms, although the angle of tilt varies considerablyfrom series to series, the variation in the heat of crystallisation perCH, group in the different series is relatively small.The specificheat of the solid in equilibrium with the liquid is normal, i.e., it isless than that of the liquid.Ca c4 c6 c8 c10 c l B c14 c16 CzoThese data are summarised : 9 4 ~ 95* 96Heat of crystn. Specific heat Area of crossForm. per CH,, kg.-cals. of solid form. section, A.,.Vertical . . . . . . . . 0.61 - 0.84 0.63 - 1.05 19.9Tilted . .. . . . . . 0.97 - 1.08 0.43 - 0.48 18.4a -+ p Transitions of " odd " acids are regarded as an exampleg9cr R. E. Gibbs, J . , 1924,125, 2622SMITH: FATTY ACIDS AND OTHER LONG-CHAIN COMPOUNDS. 267of unilateral transition in the solid state 92s exemplified by thesimultaneous occurrence of three spacings (corresponding to threecrystal forms) on the same photograph of an “ odd ” acid.*3 Theheats of transition cc --+ for hydrocarbons are approximately fourtimes as great as those for the fatty acids.94 For the hydrocarbonsit is a change from rotating to non-rotating forms, followed in the‘‘ even ” hydrocarbons by a tilt of the molecule ; for acids, usuallyonly a change of tilt is incurred.A. R. Ubbelohde2 has determined specific heats of paraffins andobserved marked pre-melting.K. H. Meyer and A. van der Wyk3discuss the effect of the heat of fusion on the solubility of paraffins.Alternation in Melting Point.-This is a subject which has attractedthe attention of most chemists who have worked with homologouscompounds. All homologous series show alternation in meltingpoint between ‘‘ even ” and “ odd ” members early in the series :the alcohols after amyl alcohol show only slight alternation, a gentlezigzag when the melting points are plotted against the numberof carbon atoms; the paraffins zigzag more decidedly as far asfor the acids, alternation persists so that the melting pointof C21H4,02 is just equal to that of C2,H,002. The dicarboxylicacids provide an extreme case, the melting points of odd and evenmembers falling on two converging curves.Alkyl iodides29 andbromides are unusual, for in both cases the melting point curve ofthe “ odd ” lies above that of the “ even ” members.Several theories have been put forward to explain this alternationand a bibliography is given by T. MaU~in.~~ G. Tamrna~~n,~ workingwith the lower fatty acids, ascribed alternation to the existence ofpolymorphism in the even members, though the evidence wasscanty. W. E. Garner and F. C. Randall 89 decided from the heatsof crystallisation of odd and even acids that alternation was due to“ a difference in crystalline structure ”. W. A. Caspari 35 analysedwell-developed crystals of the dicarboxylic acids and found that theeven-number acids crystallised with two molecules and the “ odd ”acids with four molecules in the unit cell, as should be required by thesymmetry in the two cases.He inferred that “this difference incrystal structure cannot be unconnected with the alternation inmelting point.”T. Malkin 29 noted that when the melting points of the transparentforms of ethyl esters were plotted there was no alternation, andsimilarly with transparent forms of hydrocarbons, methyl ketones,1 E. Ban, 2. physikal. Chem., 1928,137, 63.a Trans. Faraday SOC., 1938, 34, 282, 292.3 Helv. Chim. Acta, 1937, 20, 1313.4 2. anorg. Ohm., 1920, 109, 221268 ORGANIC CHEMISTRY.and alcohols (compare C. Weygand and W. Griinzig on the gly-cerides 51) ; the opaque forms of the esters, however, showeddecided alternation.Malkin infers that alternation is a propertyof crystals with tilted chains. He shows diagrammatically 299 6 1 how“ even ” tilted chains may be separated by closely packed planes,all similar, whereas “ odd ” tilted chains should be separated byplanes alternately loosely and closely packed. The loose packingin “ odd ” chains is thought to cause easier separation and so lowermelting. This theory, which has been extended to the glyceride^,^has been vehemently criticised by P. E. Verkade and J. C O O ~ S , ~ one oftheir objections being that alkylmalonic acids, although crystallisingwith vertical chains, yet show alternation in melting point. Ob-viously these are cases where the measuring of long spacings willnot give the necessary information and detailed crystal analysis isurgently required.The alternation of various properties of the liquid state reportedby 0.Biach has been disproved by more exact measurements :alternation is confined to propertes of the crystalline state.*J. C. S.5 . TERPENES.Monoterpenes.Syntheses.-The structure shown below for Artemesia ketone wasadvanced by Y. Asahina and E. Yoshitomil and Y. Asahina andS. Takagi2 from a study of the oxidation products of the ketoneand those of its tetrahydro-derivative; it showed an abnormalarrangement of the isoprene residues and was therefore open tocriticism.3 The structure, however, has now been established bythe synthesis of the tetrahydro-ketone from aa-dimethylbutyrylchloride and isobutylzinc iodide :CHMe,*CH,*ZnI + Cl*CO*CMe,Et .1 CHMe,*CH,-CO*CMe,Et Tetrahydroartemesia ketone5 c.CH,:CMe*CH,*CO*CMe,*CH:CH, Artemesia ketoneE.Clarlcson and T. Malkin, J., 1934, 666; Ann. Reports, 1934, 31,159; T. Malkin and Riad el Shurbagy, J . , 1936, 1628; Ann. Reports, 1936,6 Rec. Trav. chim., 1933, 52, 747. 2. physikal. Chem., 1905, 50, 43.8 P. E. Verkade, J. Coops, and H. Hartman, Rec. Traw. chim., 1926,45, 585.1 J . Pharm. SOC. Japan, 1917, 424, 1. Ibid., 1920,464,837.3 J. L. Simonsen, “ The Terpenes,” I, 90.L. Ruzicka, T. Reichstein, and R. Pdver, HeZv. Chim. Actu, 1936,19, 646.33, 220KIPPING : TERPENES. 269Some interesting syntheses have been performed in the thujane,carane and pinane series. S. K. Ranganathan and E. 0. Phillip~,~and G.R. Ramage and J. L. Simonsen 6 simultaneously synthesisedcis- and trans-1 -isopropylcycZopropane-1 : 2-dicarboxylic acid by thecondensation of ethyl a-isopropylacrylate with ethyl diazoacetate :CH,:CPrfl*CO,E t ~ cH2(rW30,Et vN,CH*CO,Et H*CO,EtUmbelluloneThe same acids have been obtained by H. N. Rydon from ethylisopropylfumarate and diazomethane. The cis-acid was resolved byRanganathan and by Rydon and the Z-form was shown to be iden-tical with umbellularic acid, obtained by the degradation of um-bell~lone.~P. C. Guha and B. Nath 10 have shown that 2 : 4-dibromomenth-one, obtained by the bromination of Z-menthone in chloroformsolution, yields thujane when it is reduced by the Clemmensenmethod. v I v)p C6) \(WO ,Et(1.) - b' @IThujaneIP.C. Guha and S. Krishnamurthyll have converted (I) into thecorresponding cyclopentene derivative by reduction and dehydrationand then into the bicycZo[O : 1 : 3lhexane derivative with the aid ofdiazomethane ; after having been hydrolysed and decarboxylated,the last product yielded thujane.Carane has been similarly synthesised l2 from ethyl l-methyl-A3 - cyc lo h exene - 4 - car b ox y la t e .Syntheses of verbanone, 6-pinene and pinane have been carriedout by G. Komppa and A. Klami.13 Methyl pinononate was con-verted by the Reformatsky reaction, dehydration, hydrolysis andreduction successively into (11). The destructive distillation of the' Cf. K. von Auwers and F. Konig, Annalen, 1932, 496, 27, 252 ; J. OwenJ .Indian Chem. SOC., 1936, 13, 419. J., 1936, 828.and J. L. Simonsen, J., 1933, 1225.J., 1936, 829. @ I?. Tutin, J., 1906, 89, 1104.lo Ber., 1937, 70, 931.l2 P. C. Guha and D. K. Sankaran, Current Sci., 1938, 6, 606.Ber., 1937, 70, 788.Ibid., p. 2112270 ORGANIC CHEMISTRY.lead salt of this acid then gave dl-verbanone, which can be reducedto pinane, as already shown by H. Wienhaus and P. Schumm.14dl-6-Pinene was prepared by the reduction of verbanone to thealcohol, which was then dehydrated :_3 yo-+ 6 \CHMe*CH2*CO2HMethyl pinononate (11.) Verbanone 6 -PineneWOMeA new synthesis of dl-fenchone from camphenonic acid is describedby G. Komppa and A. Klami.15 The acid is converted successivelyinto the acyl chloride, aldehyde (hydrogen and palladium-bariumsulphate), and alcohol (hydrogen, platinum dioxide, and ferrous sul-phate) (111) ; the last-named compound yields fenchone when itschloride is reduced :-bO,HCamphenonic acid (111.) FenchoneCampholenic Acid, etc.-According to F.Tiemann,16 when a-campholenic acid is oxidised, one of the products is phonic acid;such a reaction, however, would involve a change from the cyclo-pentane to the cyclobutane system and would be unique in terpenechemistry. G. Komppa and S. Beckmannl' could not confirmTiemann's results : the first oxidation product of campholenicacid is the dihydroxy-acid (IV), which, when heated with dilutesulphuric acid, gives a-campholonic acid and 2 : 6-diketocamphane.Contrary to Tiemann's statement the acid does not give bromoformwith sodium hypobromite, and the 2 : 6-diketocamphane is identicalwith that obtained by Y.Asahina, M. Ishidate, and T. Takamoto l8by the oxidation of E-bornyl acetate :u-Campholenic acid (IV.) u-Campholonic acid DiketocamphaneXulphocamphylic Acid and the Camphylic Acids.-The structureof sulphocamphylic acid, obtained by the action of sulphuric acidon camphoric acid, and those of the a- and p-camphylic acids, pro-duced from the sulpho-acid by fusion with alkaline hydroxides, have14 Annalen, 1924, 439, 20.l6 Ibid., 1896, 29, 3014.l6 Ber., 1935, 68, 2001.l7 Ibid., 1936,69,2783. 1* Ibid., p. 349KIPPING : TERPENES. 271been reinvestigated by J. R. Lewis and J. L. Simonsen.lg Both thecamphylic acids absorb two molecules of hydrogen in the presenceof a catalyst, the former yielding dihydro-a-campholytic acid andthe latter dihydroisolauronic acid ; both form additive productswith a-naphthaquinone and both on ozonolysis give methyl iso-propyl ketone and oxalic acid.On the basis of these results thestructures shown below are assigned to a- and p-camphylic acids :H,*CH*CO,Ha-Cmphylio Dihydro-u- /?-Camphylic acid Dihydroisolauronicacid campholytic acid acidWith hydrogen bromide p-camphylic acid yields isobromodihydro-p-camphylic acid, to which the structure (V) is assigned on thebasis of its decomposition into bromoform and as-dimethylsuccinicacid by ozonolysis, followed by treatment with sodium hypobromite :CH,-YMe2 CHBr-YMe, S0,H-CH-C)Me2 SO,H*CH-YMe,CH, *CO ,H CHBr-C=CO,H CH,--C*CO,H CH,*C*C02HWhen sulphocamphylyl bromide is heated, bromodihydro- p-camphylic acid is obtained; this product, as now shown, yieldsbromoform and trans-aa-dimethylglutaconic acid on successivetreatment with ozone and sodium hypobromite and therefore mustbe (VI), as the only other possible formula (V) has already beenassigned.The structure (VII) for sulphocamphylic acid, suggestedby the foregoing results, is thus established ; moreover, the so-calledsulphopimelic acid (VIII) ,2* obtained by oxidation of (VII) withnitric acid, gives, when heated, cis- and trans-dimethylglutaconicacids and not terebic acid as supposed by Koenigs.“ Camphenilene ” and Related Compounds.-P. Snitter 21 des-cribed a hydrocarbon, “ camphenilene,” prepared from campheniloland from camphenilyl chloride, as a crystalline solid, m.p. /I\/ 26.5” ; he concluded, solely on the evidence of the Rarnan p> spectrum, that it was a slightly impure sample of a com-pound of the structure (IX). Previously it had been(Ix’) shown that the ‘‘ camphenilene ” obtained in the sameway by W. Jagelki and by S. V. Hintikka and G. Komppa2219 J., 1936, 734; 1937, 457.20 J. Kachler, Annalen, 1873, 189, 179; W. Koenigs and J. Hoerlin,Ber., 1893, 28, 812, 2045.21 Bull. Inst. Pin., 1933, 200.22 Ber., 1899, 32, 1503; Annalen, 1912, 387, 292.1 CO2H fiMe I $Me I GMe(V-) (VI.) (VII.) I (VIII.272 ORGANIC CHEMISTRY.consisted mainly of ~ a n t e n e . ~ ~ Now, if the structure (IX) werecorrect, it would provide the first exception to the Bredt rule.24Snitter’s camphenilene was therefore reinvestigated by G.Grattonand J. L. S i m ~ n s e n , ~ ~ who proved conclusively that it is mainlysantene, together with a little apocyclene. The same conclusion wasreached by G. Komppa and G. A. Nyman.26These facts show the unreliability of purely physical methods forthe determination of structure and throw grave doubt, for example,on the work of G. Dupont and R. D~lon,~’ where such evidenceis also used for the determination of the constitutions of the pyrolysisproducts of a-pinene.P. Lipp and J. Daniels 28 have now shown that camphenilyl chlor-ide with sodium phenoxide gives mainly apobornylene ; they couldnot detect any santene in their product.G. Komppa and G. A.Nyman 29 conclude from a study of the hydrolysis of “ camphenilylchloride ” with lime that the compound is mainly apobornyl chloride,since camphenilol, p-fenchocamphorol and a-isofenchocamphorol(a stereoisomeride of a-fenchocamphorol) are thereby produced.Similarly 4-methylcamphenilol gives mainly epibornyl chloride withphosphorus pentachloride.Apobornyl chloride Camphenilol Apocyclene Santene(Camphenilylchloride)Apobornylene p-Fenchocamphorol a-FenchocamphorolAn interesting synthesis of camphenilone is described by G.Komppa and 0. Komppa : 3O cydopentadiene is condensed withpp-dimethylacrylic acid, and, after the catalytic reduction of theethylenic linkage in the product, the acid is converted successivelyinto the azide, amine and alcohol.The alcohol is then oxidisedto a mixture which contains camphenilone :23 G. Komppa and S. V. Hintikka, BUZZ. Soc. chi,m., 1917, [iv], 21, 147.24 J. L. Simonsen, “The Terpenes,” 11, 1.54.25 J., 1935, 1621.27 Cornpt. rend., 1935, 201, 219.-29 Ibid., p. 1813.26 Ber., 1936, 69, 334.28 Ber., 1936, 69, 586.Ibid., p. 2606RIPPING : TERPENES. 273Sesquiterpenes.Cyperones.-The main constituent of oil of Cyperus rotundus isa ketone, d-a-cyperone, C15H220, which is readily purified with theaid of its semi~arbazone.~~ Catalytic hydrogenation convertscyperone into a tetrahydro-derivative, and reduction with sodiumand alcohol yields dihydro- a-cyperol ; this alcohol yields eudalenewhen it is heated with selenium, and a keto-alcohol, together withformaldehyde, on ozonolysis.Furthermore dihydro-a-cyperyl3 : 5-dinitrobenzoate, on ozonolysis, gives a ketone which yields iodoformwith Puson’s reagent.32 The isoprene rule being assumed valid, thisevidence indicates the structure of the carbon skeleton, the con-jugation of one double bond with the carbonyl group, and thepresence of the second ethylenic linkage as -C(CH,):CH,. Thealcohol formed from tetrahydro-a-cyperone and methylmagnesiumiodide yields 1 : 2-dimethyl-7-isopropylnaphthalene when it is de-hydrogenated, a fact which indicates position 2 for the keto-groupof cyperone ; dihydro-a-cyperol must therefore be represented by(I) and cyperone by (11), (111) or (IV) :a-Cyperone yields a hydroxymethylene derivative which, byreduction and dehydrogenation, gives 1 : 3-dimethyl-7-isopropyl-naphthalene; the structure of this is proved by synthesis,33 and itsformation excludes formula (11) for cyperone.Structure (IV) isinadmissible, as the ozonolysis of a-cyperone semicarbazone givesa product, CI5H,,O4N,, whereas the semicarbazone of (IV) wouldclearly lose two carbon atoms when thus oxidised; a-cyperone istherefore represented by (111). p-Cyperone, which is formed bythe action of aqueous oxalic acid on the a-ketone, is regarded asa stereoisomeride, since its semicarbazone and that of a-cyperonegive the same degradation products. Substances structurallyidentical with cyperone have been synthesised by two independentA. E.Bradfield, B. H.Hegde, E. S. Rao, J. L. Simonsen, and A. E. Gillam, J.,1936, 667.32 R. C. Fuson and C. W. Tullock, J. Amer. Chem. SOC., 1934, 56, 1638.33 A. E. Bradfield, R. R. Pritchard, and J. L. Simonsen, J., 1937, 763.31 B. H. Hegde and B. S. Rao, J. SOC. Chem. Ind., 1935, 54, 3 8 7 ~ 274 ORGBNIC CHEMISTRY.methods,34 which are of importance as furnishing the only directevidence for the existence of the angle methyl group at position9 in those sesquiterpenes which give eudalene on dehydrogenation.In one synthesis the condensation of the sodium derivative ofZ-dihydrocarvone with ethyl p-chloropropionate yielded (V) ; thisproduct, with zinc and ethyl a-bromopropionate, gave a mixtureof which the main fraction afforded on hydrolysis a ketone (VI),closely resembling p-cyperone :Dihy drocarvone W e ) (VI.1The substance (V) was purified from any(VII) it might contain by means of itsalkali-soluble condensation product withethyl oxalate (cf.ref. 35).The second cyperone synthesis is moredirect and consists in the condensation ofthe methiodide of 1-diethylaminopentan-3-one with l-dihydro-carvone, in the presence of sodamide: the resulting diketone isreadily cyclised to (VIII) :lfEt2,MeI(VII.)H2.CH2.C02Et(VIII.)The complete identity (structural and configurational) of the syn-thetic products (VI) and (VIII), made respectively at Bangor anda t Oxford, with one another and with natural cyperone is not claimed,but sufficient similarity in the properties of various derivativesestablishes the validity of the above structures.Eremophilone and Hydroxyeremophi1one.-It was considered in1932 36 that the structures of the three ketones, eremophilone,hydroxyeremophilone and hydroxydihydroeremophilone, had beendecided. During the investigation of a-cyperone, however, it becamenecessary to prepare 1 : 3-dimethyl-7-isopropylnaphthalene (p.273)34 P. S. Adamson, F. J. McQuillin, R. Robinson, and J. L. Simonsan,J . , 1937, 1576.35 A. E. BracEeld, E. R. Jones, and J. L. Simonsen, J . , 1936, 1137.36 Ann. Reports, 1932, 29, 155KIPPING : TERPENES. 27 5in order to identify it with the substance formed by the dehydro-genation of the reduction product of hydroxymethylene-cc-cyperone.The simplest way to do this appeared to be by the dehydrogenationof the alcohol formed from eremophilone [then considered to be(IX)] with the aid of methylmagnesium iodide.It was then foundthat the two naphthalene derivatives were notidentical and, the structure of the product fromcyperone having been decided by synthesisthat the compound from eremophilone is 1 : 5-dimethyl-7-is0propylnaphthalene.~~ The position of the carbonylgroup of eremophilone is thus fixed a t 5 and not a t 3. A con-firmation of this evidence is afforded by the fact that hydroxy-met h y lene - eremophilone yields 1 : 6 - dimet hy 1 - 7 -is0 pr o p y h a p h t ha1 -ene on reduction and dehydrogenation. It has also been shown 36that the eremophilone structure contains a double bond conjugatedwith that of the carbonyl group.Now, if the carbonyl group isat position 5, and the methylene group at 6 (formation of hydroxy-methylene derivative, etc.), it would be impossible to have anap-ethylenic linkage (4 : 9) together with the angle methyl groupat 9, a position assigned to it on account of the formation of eudalenefrom eremophilone. A reinvestigation of the ozonolysis of hydroxy-(above), it was proved by subsequent workeremophilone benzoate3' has shown that the final product of theprolonged action of ozone is a keto-acid, C10H1603, which is isolatedas its semicarbaeone, C,,H,,O,N, (not C13Hl,0,N,,2C2H60 aspreviously assumed 38) ; this keto-acid is reduced to a saturatedacid, CloH1802, by the Clemmensen method. Now, if the assumptionof a head-to-tail isoprene arrangement is abandoned, formula (X)and (XI) are possible for eremophilone and hydroxyeremophilonerespectively, and the acid CloH1,O2 would then be (XII).2 : 2-DimethylcycEohexylacetic acid was therefore synthesised,but it was different from the acid derived from hydroxyeremophil-one ; the suggested structures must therefore be dismissed unlessit be assumed that a methyl group migrates at some stage.It was5 7 A. E. Bradfield, N. Hellstrom, A. R. Penfold, and J. L. Simonsen, J . ,1938, 767.as A. E. Bradfield, A. R. Penfold, and J. L. Simonsen, J., 1932, 2756276 ORGANIC CHEMISTRY.subsequently shown39 that the methyl ester of the acid CloH1,O2yields o-xylene when it is dehydrogenated with selenium ; the acidis therefore (XIII) and its formation from (XI) would be extremelyunlikely.The most probable formula for hydroxyeremophilonethus appears to be (XIV), in which the isoprene rule is not followed ;(XIII.) (XIV.)other evidence that this is possible in the polyterpene series canbe advanced.40 It would also appear that formula (-XV) (previouslysuggested by Simonsen 37), which is made up of isoprene residues,although not in the familiar head-to-tail arrangement, might accountfor the facts if it be assumed that during dehydrogenation the anglemethyl is eliminated and a ring widening a t the gem-dimethyl groupoccurs; in the present state of our knowledge such changes appearby no means imp~ssible.~~ Ring widening could also occur duringthe dehydrogenation of the ester of the acid CloH1,O2.CuryophyZ2enes.-The syntheses and resolutions of the norcaryo-phyllenic acids by H.N. Rydon42 have now been followed by theconversion of d-cis-norcaryophyllenic acid into homocaryophyllenicacid by the ordinary ester reduction to the glycol, and the treatmentof the latter with phosphorus tribromide, potassium cyanide andhydrolysing agents successively.43- C02H --CH2*C02HhCO2H ‘cH2*co2HNorcaryophyllenic acid Homocaryophyllenic acidF. W. Semmler and E. W. M a ~ e r , ~ ~ by the oxidation of caryo-phyllene, isolated a keto-acid, C11Hls03, from which, by the actionof sodium hypobromite, L. Ruzicka and A. H. Wind45 and C. R.Ramage and J. L. Simonsen 46 prepared a homocaryophyllenic acid.From a comparison of the dianilides of the natural and the syntheticacid it is now thought43 that they are probably identical, but a39 J.L. Simonsen, private communication.4O J. C. E. Simpson, J., 1938, 1313.4 1 Ann. Reports, 1936, 33, 294; N. N. Chatterjee, J. Indian Chem. SOC.,42 J., 1936, 593; 1937, 1340; Ann. Reports, 1935, 32, 325.43 C. R. Ramage and J. L. Simonsen, J., 1937, 73.44 Ber., 1911, 44, 3662.45 Helu. Chim. Acta, 1931, 14, 422.1936, 13, 588.46 J., 1936, 742KIPPING : TERPENES. 277definite conclusion cannot be reached. The validity of the abovestructure for homocaryophyllenic acid being granted, Ramage andSimonsen’s structure for @-caryophyllene 47 must now be abandoned,as it would give (I) for homocaryophyllenic acid :$lH,*CMe:CH,- C0,H --C02H_3 hCH2*CH2Ac JCH,*CH2*C02€I/I-Caryophyllene (R.and S.) (1.1Ruzicka’s structure 48 accounts satisfactorily for the formation ofhomocaryophyllenic acid, of the keto-acid (11)’ and of a diketo-acid, C14H220P (111), which forms the chief product of the ozonolysisof caryophyllene :H2*CO*CH3- --CH,AcCH,-CMe:CH, /--CH,*CO,H I/I-Caryophyllene (L.R.) (11.) (111.)On the other hand, a ketone, CI0Hl8O, and a diketone, C13H2202,which are also oxidation products, cannot be satisfactorily derivedfrom this structure; the formation of clovene by isomeric change-CH,*COMe - l A C 0 2 H - --3{7H*CO,H COMe (VI.)(V.)and its oxidation to an acid without the loss of carbon would alsobe hard to explain. There is, however, no evidence that theseketones are not derived from a-caryophyllene, which may be presenteven in the most highly purified samples of 8-caryophyllene, and it47 J., 1935, 1581; Ann.Reports, 1935, 32, 327.48 J. SOC. Chem. Ind., 1935, 54, 509278 ORGANIC CHEMISTRY.is therefore unsound to consider them in a discussion of the structureof p-caryophyllene. H. N. Ryd0n,4~ stimulated by recent work onthe azulenes,s0 suggests for caryophyllene the structure shownbelow. The diketo-acid, C14H2204, would then become (IV) and itcould be degraded finally to (V), in conformity with the results ofL. Ruzicka, W. Zimmermann, and K. H ~ b e r . ~ lThe formation of the keto-acid, CI1Hl,O, (VI), is also explained.For the production of the diketone, C1,H2,0, (VII), Rydon assumesthe presence of an isomeric caryophyllene :--I-@Me - CH2*C02H__f -CO*CHMe, - l?C02€I(VII .)The formation of the tricyclic clovene and its oxidation product,clovenic acid, would be easily accounted for : -10 - I / / -l-,GJ \I ;I%”.. lp(VIII.)Clovene (different projections of O2Hsame s true ture)On the other hand, clovenic acid readily yields an anhydride butit cannot be brominated. These facts are obviously not in accord-ance with Rydon’s structure. An equally good formula for caryo-phyllene is (VIII) and a decision between these alternatives wouldbe possible if the structure of caryophyllenic acid were determined.By the oxidation of acetamidodihydrocaryophyllene, a crystallineketone has been prepared with the carbonyl group in the tail; itis hoped that the degradation of this compound will yield valuableresults.52BetuZenob.-Three closely related sesquiterpene alcohols, a-, p-and y-betulenols, have been isolated from birch-bud oil by fractionalreaction with phthalic anhydride.53 All these alcohols yield amonocyclic dicarboxylic acid, betulenolic acid, ClOHISO4, onvigorous oxidation with permanganate, followed by nitric acid ;this product gives a dimethyl ester which is easily hydrolysed byN [lo-alcoholic potassium hydroxide and therefore does not containa tertiary carboxyl group; further oxidation gives oxalic andaa -dime t h ylsuccinic acids.4# J.SOC. Chern. Ind., 1938, 57, 123.61 Helv. Chim. Acta, 1936, 19, 343.62 C. R. Ramage and J. L. Simonsen, private communication.6s Ber., 1938, 71, 612.so Ann.Reports, 1937, 34, 396KIPPING : TERPENES. 279The identity of betulenolic acid with natural homocaryophyllenicacid has been proved by Simonsen and Ramage43 and by W.T r e i b ~ . ~ ~The chief component of birch-bud oil, the or-alcohol, can beoxidised to a saturated dicyclic hydroxy-dicarboxylic acid, C,H,,O,,which on further oxidation gives betulenolic acid; on this basisa-betulenol has the formula (IX) and the acid, (X), the structurediscussed above for homocaryophyllenic acid being assumed :The following formulze are suggested for the isomeric betulenols :BetulenolsLanceo1.-This sesquiterpene alcohol, C1,H,,O, was first isolatedfrom the wood of Santalurn Eanceolaturn by A. R. Penfold : 54 the usualmethods now show that it is a primary monocyclic alcohol containingthree ethylenic linkages, which are not ~onjugated.~~ When itis oxidised with ozone, formaldehyde and hydroxyacetone are foundin the portion volatile in steam; the latter was identified as itsI COMeLance01COMe(X1.josazone, and the possibility of methylglyoxal being present iseliminated by the fact that the double bonds are not conjugated.The non-volatile portion, on further oxidation with silver oxide,yields 1md.ic acid, and a crystalline acid, C,H,,O,, which onozonolysis is converted into 8-acetylbutane-ap-dicarboxylic acid.From a consideration of all the structures which could yield this64 J.Proc. Roy. Soc., N.S.W., 1928, 62, 60; 1932, 66, 240.55 A. E. Bradfield, E. M. Francis, A. R.Penfold, and J. L. Simonsen, J . ,1936, 1619280 ORGANIC CHEMISTRY.acid on ozonolysis it is finally concluded that the acid C,Hl,O, isprobably (XI) : some of the alternatives were excluded by a com-parison of the acid C,HI2O4 with synthetic acids.The structure shown is then advanced for lanceol and the formationof (XI) from it is explained as above. An alternative structurecontaining an isopropylidene instead of an isopropenyl group wouldyield (XI) directly on ozonolysis, the cyclopentene ring beingassumed to be unattacked; the failure to detect acetone amongthe products of oxidation, however, renders such an alternativeunlikely.Ledol.-The constitution previously advanced for ledol (XII) 56 hasbeen amended by G. Komppa and G. A. Nyman 57 on the groundof the dehydrogenation of ledol to azulenes [skeleton (XIII)].Itis pointed out that a substance (XII) would be expected to yieldcadalene on dehydrogenation ; this is actually only a minor product.If, however, the cyclopropane ring is present as in (XIV), the form-ation of an azulene is readily explained on the assumption thatduring dehydrogenation the bond between the carbon atoms com-mon to the two rings undergoes fission, giving a 7 : 5 dicyclicstructure.(XII.) (XIV.) (XV.)This view is supported by the fact that copame (XV) does not giveazulene on dehydrogenation.Irone.-The classical work of F. Tiemann and P. Kruger 58 onirone and its dehydration product, irene, led to erroneous con-clusions with regard to the structures of these compounds, as wasfirst shown by L.Ruzicka, C. F. Seidel, and H. Schinz; 59 theseinvestigators proved that irone is C,,H,,O (and not C1,H,,O) andthat irene is C14H2,. Irene yields 1 : 2 : 6-trimethylnaphthalene ondehydrogenation and from this fact, and other evidence, is assignedthe constitution (XVII). This structure has now been confirmedby a synthesis of irene by M. T. Bogert and P. M. Appelbaum.60m-Tolylmagnesium bromide, with ethylene oxide, gave p-m-tolyl-5 6 G. Komppa, Norske Vidensk. Xelsk. Skr., 1933, 1.67 Compt. rend. Trav. Lab. Carlsberg, 1938, 22, 272.5 8 Ber., 1893, 26, 2675; 1895, 28, 1754.5O Helv. Ghim. Acla, 1933, 16, 1143.6O J . Amer. Chem. SOC., 1938, 60, 930CALLOW : STEROIDS. 281ethanol, and the Grignard reagent of the corresponding bromideyielded, with methyl isopropyl ketone, the tertiary alcohol (XVI).When this alcohol was heated with sulphuric acid, 1 : 1 : 2 : 6-tetramethyltetralene (XVII) was formed, which was proved to be,CHMe,Me*q*OH /\A/\ (Y _f C ! 2 ) ! 4 --+ *( //(XVII.)BrCH,-CH2 C%(XVI.)identical with irene, obtained from irone, both by a comparison oftheir physical properties and by a study of their oxidation products.Ruzicka and his co-workers (loc. cit.) advanced two possiblestructures for irone, (XVIII) and (XIX) : the former explains theformation of irene in a simple manner but is difficult to reconcilewith the production of ppy-trimethylpimelic acid by the ozonolysisof irone ; the latter (XIX) would account readily for the productionof this acid but not for the formation of irene.(XVIII.) Irone-6-CH:CHAc (XIX.)F.B. K.6. STEROIDS.Stereoisomerism and Nomenclature.-Before considering the pre-parative work which has been carried out in the field of steroidchemistry during the last two years, it is appropriate to considera major theoretical problem which is slowly being cleared upconcurrently with these detailed investigations, namely, that ofthe spatial configuration of substituent groups in steroids, and togive some attention to the vexing question of nomenclature ofstereoisomeric compounds, which, as a result of the attempts toreduce confusion by introducing new systems, is acquiring a chaoticappearance to observers outside the field.Much of the latest stereochemical theory of the steroids is dueto L.Ruzicka and his co-workers, who, in a series of papers havedealt with the assignment of configuration, relative to adjacentL. Ruzicka, Helv. Chirn. Acta, 1933, 16, 327; 1934, 17, 1407; L. Ruzicka,M. W. Goldberg, J. Meyer, H. Briingger, and E. Eichenberger, ibid., 1934.17, 1395; L. Ruzicka, M. W. Goldberg, and H. Wirz, ibid., 1935, 18, 61;L. Ruzicka and M . W. Goldberg, ibid., 1936, 19, 99; L. Ruzicka and H.Kagi, ibid., 1936, 19, 842; 1937, 20, 1557; cf. Ann. Reports, 1934, 31, 207282 ORGANIC OHEMISTRY.centres of asymmetry, to epimeric steroid alcohols with hydroxylgroups in positions 3 or 17, and to the junctions of the rings.In view of the complexity of the matter, no apology is needed forrecapitulating the theory now generally accepted.Practically allknown steroid compounds belong to one of two ring-systems :(1) the cholestane, allocholane, allopregnane, or androstane type,or (2) the coprostane, cholane, pregnane, or aetiocholane type.These differ in the orientation of the hydrogen on C, relative to the10-methyl group, which is trans in type 1 and cis in type 2.Ruzicka’s hypothesis assumes that cholestanol has the configuration(I), denoted by trans, trans-anti-trans-nti-trans.?rBHdFurther, isomerism of 3-hydroxyl compounds cis or trans to thehydrogen on C, gives four sub-types : Ia (3-trans-OH, as in chole-stanol) ; Ib (3-&OH, as in epicholestanol) ; IIa (3-trans-OH, asin epicoprostanol) ; IIb (3-cis-OH, as in coprostanol).The nexttype of isomerism found is that of 17-hydroxyl compounds, whichmay be cis or trans relative to the 13-methyl group. The con-figurations suggested have been supported by a series of chemicaland physical observations in the papers mentioned, the mostimportant generalisation being the Auwers-Skita rule applied toreduction of 3-ketones.K. Miescher and W. H. Fischer 2 have expounded the applicationof the Auwers-Skita rule to the stereochemistry of epimeric alcoholswith special reference to the steroids, and revealed how speculativethe generalisations applying to epimeric cycloparaffin alcohols withone adjacent substituent in the ring may become when they aretransferred to epimeric 3-hydroxysteroids in which there are threesubstituents.As a result, however, of reviewing the behaviour ofthe 3-hydroxysteroids, particularly in the light of their ability toform glucosides, it is concluded that compounds can be classifiedas “ cisoid ” (non-reactive hydroxyl group) or “ transoid ” (re-active hydroxyl group) in behaviour. The above authors suggestusing these terms, abbreviated to “ c ” and “ t,” as prefixes to thenames ; thus cholestanol is t-cholestanol. The result is discordantwith the Ruzicka “ cis ” and “ trans ” nomenclature only in thea Relv. Chim. Acta, 1938, 21, 336CALLOW : STEROIDS. 283cases of coprostanol, which is cis but “ transoid ”, and epi-copro-stanol, which is trans but “ cisoid.” This anomaly is comparedwith that of the cis-decalols.In the latest paper from Ruzicka’s lab~ratory,~ the work ofG.Vavon and B. Jakubowicz* has been extended to examinationof the rates of hydrolysis of the acetates and benzoates of fourtypes of epimeric pairs : (a) cholestanol and epicholestanol, (b)coprostanol and epicoprostanol, (cl) 17-trans- and 17-cis-hydroxy.androstan-3-one, (cz) 17-trans- and 17-cis-testosterone, and (d)cholesterol and epicholesterol. All the compounds denoted as tramby Ruzicka were more readily hydrolysed than the cis-epimerides.Finally, when the assumed configurations are built up in a seriesof models, a mechanical explanation is apparent for the sterichindrance assumed to be responsible for the lowered reactivity inthe cases in which it is found. The property of forming digitonidesalso can be correlated with the conformation of the molecule.The anomalous esterifications of Miescher and Fischer are dismissedfor the reason that reactions not taking place in homogeneoussolution may not be controlled by simple factors only.The ancillary problem of nomenclature of stereoisomerides is ina controversial state.Definition of the configuration of the hydroxylgroup at C, relative to a hydrogen atom at C,, which is of variableconfiguration and in many cases is non-existent, as in Ruzicka’ssystem, introduces difficulty and confusion. The alternative ofusing the methyl group a t C,, as a standard of reference, suggestedby R. Schoenheimer and E. A. Evans and adopted in the lastReport,6 has not won favour, particularly as some of the designationscis and trum become reversed.L. F. Fieser 7 has suggested that‘‘ the configuration at C3 common to cholesterol, dihydrocholesterol,coprosterol, ergosterol and similar steroids is appropriately desig-nated where necessary by the classical prefix p, while the epimers ofthese substances are 3(cc)-hydroxy-compounds, as are the bile acidsand androsterone.” Provided that the mistake responsible for thehistorical name “ p-cholestanol ” is ignored, and, further, that 0:and p are kept within parentheses, adjacent to a position numeral,and confusion with other uses of the Greek alphabet thus avoided,this proposal actually provides a convention for defining arbitrarilyL. Ruzicka, M. Furter, and M. W. Goldberg, Helu. Chim.Acta, 1938, 21,498.E d . Soc. chim., 1933, [iv], 53, 581.J. Biol. Chem., 1936, 114, 567; cf. R. I<. Callow and F. G. Young, Proc.Ann. Reports, 1936, 33, footnote, p. 343.Roy. Soc., 1936, A , 157, 194.7 “ A Supplement to the Chemistry of Natural Products Related toPhenanthrene,” New York, 1937, p. 399284 ORGANIC CHEMISTRY.the position of the 3-hydroxyl group relative to the steroid skeletonas a whole. A. Butenandt * uses the new prefix n- and the oldterm epi- in the same sense as (a)- and (cc)-, respectively. Fieser'sproposal, however, has been adopted by several workers, and ananalogous system of labelling hydroxyl groups similarly oriented ina series of compounds has been extended to the 17-9 and the 20-positions 10 in the pregnane skeleton.I n this Report Fieser'ssystem has been adopted for systematic names, whilst certain'' trivial " names have been retained on account of their familiarity.i-Cholesterol and the " Abnormal " Cholesteryl Ethers.1somerismwhich is to be explained on structural rather than spatial groundsoccurs in the i-sterols, in which a novel and surprising form ofmolecular rearrangement has been postulated to explain the resultsof an attempt to epimerise the hydroxyl group of cholesterol.The work was based on that of W. Stoll l1 and of T. Wagner-Jaureggand L. Werner,12 who described two series of isomeric ethers-(a) " normal," lawo-rotatory, and (b) " abnormal," strongly dextro-rotary-formed when the p-toluenesulphonate, or the chloride orbromide of cholesterol reacted with alcohols (a) alone, or (b) inthe presence of potassium acetate, respectively. The dextrorotationof the, " abnormal " ethers was anornalou~,~~ and certain of theirproperties were peeuliar, if they were to beMe C8H17 considered as derivatives of epicholesterol.E.S. Wallis, E. Fernholz, and F. T. Gephart l4treated cholesteryl p-toluenesulphonate withpotassium acetate in acetic anhydride and )(" (11.1 obtained the acetate of i-cholesterol, which wasnot identical with any of the known isomerides(allo-, epi-, or epiallo-) whose existence was explicable l5 on the basisof epimerisation of the 3-hydroxyl group or shift of the ethyleniclinkage from 5 : 6 to 4 : 5. i-Cholesterol exhibited no unsaturation.It was assigned the structure (11) with a bridge linking between C,and C,.J.H. Beynon, I. M. Heilbron, and F. S. Spring l6 confirmed thiswork, and the analogy with the " abnormal " ethers, but did notaccept the 6-position of the hydroxyl group. E. G. Ford, P.ppp8 Cf. A. Butenandt and G. Miiller, Ber., 1938, 71, 191.T. Reiclistein and K. Giitzi, Helv. Chim. Acta, 1938, 21, 1185.10 R. E. Marker, 0. Kamm, E. L. Wittle, T. S. Oakwood, E. J. Lawson,l1 2. physiol. Chem., 1932, 207, 147; 1937, 246, 13.l2 Ibid., 1932, 213, 119.l3 Cf. R. K. Callow and F. G. Young, Proc. Roy. SOC., 1936, A , 157, 194.l4 J . Amer. Chem. Soc., 1937, 59, 137.and J. F. Laucius, J . Amer. Chem. SOC., 1937, 59, 2291.Cf. Ann. Reports, 1936, 33, 341. l6 J., 1937, 1459CALLOW : STEROIDS.285Chakravorty, and E. S. Wallis I 7 then reported the isolation ofi-cholestanone (111) , by oxidation of i-cholesterol. i-Cholestanonewas converted successively into a-3-chloro-6-keto-cholestane (IV)," heterocholestenone " (V) , and 6-ketocholestane, thus clinching theposition of the oxygen atom. I. M. Heilbron, J. Hodges, and P. S.Spring l8 accept this conclusion, but contest the intermediatestages, since they obtain '' heterocholestenone," to which theyassign the " i "-structure (111), directly from i-cholesterol, and(111.) (IV.) (V.)consider the i-cholestanone of the American workers inhomogeneous.Androstane and pregnane derivatives belonging to the i-series havebeen obtained by analogous methods.19Enol Esters of A4-3-Keto-steroids.-Owing to the effect whichesterification of sex hormone alcohols has in prolonging their physio-logical action when they are injected, numerous esters with acidsof all types have been prepared.20Following this line of investigation, the preparation of the acetateof the enolic form of cholestenone 21 led tothe preparation of enol esters of the hormonesprogesterone and testosterone,22 which wereshown to have the A3: 5-structure (VI) rathertraction of the biological activity was foundbut not with those from pro-E.Schwenk, G. Fleischer, and B. Whitman 24 report the prepara-l7 J . Amer. Chern. Soc., 1938, 60, 413. 18 J., 1938, 759.lB A. Butenandt and W. Grosse, Ber., 1936, 69, 2776; 1937, 70, 1446.2o Cf. K. Miescher, A. Wettstein, and E.Tschopp, Biochem. J . , 1936, 30,1977; Schweiz. med. Woclz., 1936, 66, 763; K. Miescher, H. Kagi, C. Scholz,A. Wettstein, and E. Tschopp, Biochem. Z . , 1937, 294, 39; K. Miescher andC. Scholz, Helv. Chim. Acta, 1937, 20, 263, 1237.21 L. Ruzicke and W. H. Fischer, Helv. Chim. Acta, 1936, 19, 806; €3. H.Inhoffen, Ber., 1936, 69, 2141.22 L. Ruzicka and W. H. Fischer, Helv. Chim. Acta, 1936, 19, 1371;U. Westphal, Naturwiss., 1936, 24, 696; Ber., 1937, 70, 2128.23 K. Miescher, W. H. Fischer, and E. Tschopp, Nature, 1937, 140, 726.24 J . Arner. Chem. Xoc., 1938, 60, 1702.RO than the A2 : *-structure. The expected pro-(VI-)with the testosteronegesterone286 ORGANIC CHEMISTRY.tion of the enol ethyl ethers from cholestenoiie and testosteronepropionate and benzoate by interaction with ethyl orthoformate.I. M.Heilbron, T. Kennedy, F. S. Spring, and G. Swain25 haveprepared enol-acetates of ergostatrienone and lumistatrienone,spectroscopically identical, to which the A3 : : 7-structures areassigned, of ergostatetraenone (A3 : : : 9), and of isoergostatrienone.The last-named compound is assigned the A2 : : %tructure.Bromination and Debromination.-Investigations on the bromina-tion of sterol derivatives, having as their object the aromatisationof ring I, or, at least, the preparation of heavily unsaturated com-pounds, were referred to in the last Report, and these havecontinued ac tively.26H. H. Inhoffen and Huang-Minlon27 have obtained the mostpromising result in preparing A1 : 4-cholestadien-3-one (VIII) bydebrominating 2 : 4-dibromocholestan-3-one (VII) with pyridine.(VII.) (VIII.)Partial hydrogenation yielded Al-coprostenone (IX) .The authorsconsider both these compounds suitable starting materials forpreparing steroids in which ring I is aromatic.A preliminary announcement 28 has beenmade of the conversion of dibromoandro-stanedione into products which on thermal f&19 decomposition give a phenol with weakestrogenic activity which may be iso-equilin (X).Preparation of A4-3-Ketones.-A generalreaction which enables one to prepare theimportant A4- 3 -ketones from A5-3 -h ydroxy-compounds deservesparticular mention, as its application to the preparation of testo-Me0Ho\\/+y(X-125 J., 1938, 869.26 Ann.Reports, 1936, 33, 343; A. Butenandt, G. Schramm, and H.Kudssus, Annalen, 1937, 531, 176; I. M. Heilbron, E. R. H. Jones, and F. S.Spring, J., 1937, 801 ; I. M. Heilbron, H. Jackson, E. R. H. Jones, and F. S.Spring, J., 1938, 102; T. Barr, I. M. Heilbron, E. R. H. Jones, and F. 8.Spring, ibid., p. 334; H. H. Inhoffen, Ber., 1937, 70, 1695; L. Ruzicka,P. A. Plattner, and R. Aeschbacher, Helv. Chim. Acta, 1938, 21, 866; E.Schwenk and B. Whitman, J . Amer. Chem. Soc., 1937, 59, 949.2a H. H. Inhoffen, Naturwiss., 1937, 25, 125. Ber., 1938, 71, 1720CALLOW : STEROIDS. 287sterone and progesterone or allied compounds has been of specialvalue. The method of reducing ketones with aluminium alkoxides 29is reversed with respect to the sterol, by suitable adjustment ofthe proportion of reactants, and the A5-hydroxy-compound is re-fluxed with a considerable excess of acetone, benzene, and aluminiumtert. -butoxide .30New Degradations of the l?-Side-chain.-One more importantMe COClMe CO*CH,*OAc Me CO*CH,*OAc' Zn + NaOAc0(XVI.)Me CO*CH,*OHdegradation has been added to the series of " partial syntheses "of hormones from sterols and bile acids.M. Steiger and T. Reich-stein elaborated a method of preparing 3( p)-hydroxy-A6-aetiochol-enic acid (XI) from stigmasterol31 and proceeded32 to build upthe corticosterone side-chain in position 17 by the series of reactionsshown (XI-XVII). The product, deoxycorticosterone, or 21 -29 H. Meenvein and R. Schmidt, Annalen, 1925, 444, 221; W.Ponndorf,2. angew. Chem., 1926, 39, 138.$0 R. V. Oppenauer, Rec. Trav. chim., 1937, 56, 137.31 Helv. Chim. Acta, 1937, 20, 1040.32 Nature, 1937, 139, 925; Helv. Chim. Acta, 1937, 20, 1164288 ORGANIC CHEMISTRY.hydroxyprogesterone, has recently 33 been found in adrenal extracts,though present in smaller amount than corticosterone. It is evenmore active than corticosterone and, in view of the high degree ofspecificity of this type of hormone activity to structure, this factis accounted as evidence in favour of the assumed positions of threeof the four oxygen atoms in corticosterone itself.Degradations from sterols direct to the pregnane series have beenreported by N. I. Tavastsherna34 and by W. Dirscherl and F.Hani~ch.~5 The latter authors oxidised cholestenone directly toprogesterone with chromium trioxide, but the yield is not stated,and it might be inferred, from the activity in attempting to reachprogesterone from other directions, that it is not good.The de-gradation of a saturated heart poison genin, vuix., periplogenin, toprogesterone has been claimed in a patent.36The reported degradation of ergosterol to oestrone 37 has beencontroverted from more than one quarter. A. Windaus and M.Deppe 38 were unable to obtain from tetradehydroneoergosterol(XVIII) by the method of the American workers, a substance withring I aromatic, and only isolated a product which they proved to beepineoergosterol (XIX) .(XVIII.) (XIX.) (XX.)P. N. Chakravorty and E. S. Wallis 39 confirmed the German workand oxidised epineoergosterol to a ketone, C,,H,,O, which may be17-keto-A3 : : : 9-oestratetraene (XX).R. E. Marker ** has, how-ever, defended his original work, firstly on the grounds of the analogousreduction of 13-naphthol to ar-tetrahydro-13-naphthol in 8% yieldby E. Bamberger and M. K i t ~ c h e l t , ~ ~ and, secondly, by reportingthe reduction of ring I1 of equilenin and of R- and p-dihydroequilenin.The crude reduction product of equilenin yielded oestrone on oxida-tion ; 01- and 13-dihydroequilenin yielded R- and p-oestradiol,33 T. Reichstein and J. v. Euw, Helv. Chim. Acta, 1938, 21, 1197.3Q Arch. biol. Nauk, 1935, 50, 141.35 2;. physiol. Chem., 1938, 252, 49.36 B.P. 452,321, 10.3.37. Switz., 23.3.36 and 9.2.37.37 R.E. Marlier, 0. Kamm, T. S. Oakwood, and J. F. Laucius, J. Amer.Chem. Soc., 1936, 58, 1503; Ann. Reports, 1936, 33, 361.38 Ber., 1937, 7Q, 76. 39 J . Amer. Chem. Soc., 1938, 60, 1379.40 I'bid., p. 1897. O1 Ber., 1890, 23, 885CALLOW : STEROIDS. 289respectively. Experimental details of the reduction of tetradehydro-neoergosterol are promised for a later publication. L. Ruzicka,P. Muller, and E. Morgeli 42 report independent investigations onthe same Lines as those of Marker and his co-workers. They did,in fact, obtain up to 20% of phenolic material from the reduction ofequilenin by sodium and amyl alcohol, but considered that thepossibility of a practicable degradation of ergosterol to cestrone wastoo remote for the investigation t o be continued.The hexahydro-equilenin they actually isolated, which they formulated as (XXI),had no androgenic activity. The estrogenic activity was so smallthat it was not consistent with the report by I. A. Remesov 43 thatthe substance obtained by degradation of neoergosterol, andformulated as 17-keto-A5 : : 9-cestratriene (XXII), possesses activitycomparable with that of cestrone.Transition from the Androstane to the Pregnane 8eries.-Since theinteraction of methyl- and ethyl-magnesium halides with 17-keto-androstanes took place readily, it was natural that efforts shouldbe made to introduce more reactive groups in the same way. S.Kuwada and M. Yago 44 described the reaction of vinylmagnesiumbromide with A5-androsten-3( p)-o1-17-one (" trans-dehydroandro-sterone ") and claimed the formation of 17-vinyl-A5-androstene-3(p) : 17-dio1, but this work cannot be confirmed.45 A.Butenandtand D. Peters,45 however, have started a very promising series ofreactions with interaction of the acetate with allylmagnesium brom-ide. The 17-allylandrostenediol so obtained was converted by anOppenauer oxidation 3O into 17-allyltestosterone, from which wasobtained the 17 : 21-diene, the 17 : 20 : 21 : 22-tetrol, and twoisomeric 17 : 21 : 22-triols which diEered in the configuration atW. A. Yarnall andE. S. Wallis 46 claimed to have condensed ethyl a-chloropropionatewith A5-androsten-3( p)-ol-17-one and to have converted the productinto pregnane derivatives, but the work has not yet been confirmed,42 Iielv.Chim. Actca, 21, 1394.43 Bull. Exp. Biol. Med., 1936, 1, 181; Rec. Trav. chim., 1936, 55, 797.44 J . Pharm. Soc. Japan, 1936, 56, 109; Chem Zentr., 1937, I, 3808.4 6 L. Ruzicka, K. Hofmann, and H. F. Meldahl, Helv. Chim. Actcc, 1938,46 J . Amer. Chem. Soc., 1937, 59, 951.since they gave the same 20-aldehyde.21, 371; A. Butenandt and D. Peters, Ber., 1938, 2'1, 2688.REP.-VOL. XXXV. 290 ORGAXIC CHEMISTRY.nor have experimental details been published. Another form ofDarzens condensation, with ethyl dichloroacetate, was attemptedby A. Ercoli and L. Mamoli,4’ but only the ester was obtained.The addition of acetylene to the 17-carbonyl group was achievedindependently by J. Kathol, W. Logemann, and A. Serini48 andby L. Ruzicka and K.H0fmann.4~ The latter authors condensedpotassium acetylide in liquid ammonia with A5-androsten-3( P)-ol-17-one (“ trans-dehydroandrosterone ”) and androstan-3( p)-ol-17-oneto give the corresponding 17-ethinyl- 17-hydroxy-compounds. Sub-sequently 5O 17-ethinyl-A5-androstene-3( p) : 17-dio1 (XXIII) wasconverted by ozonisation,and the ethylenic linkage,acid (XXIV).CiCHafter protection of the hydroxyl groupinto 3( p) : 17-dihydroxy-A5-aetiocholenicCO,H CSCH( XXIII . ) (XXIV.) (XXV.)L. Ruzicka, K. Hofmann, and H. F. Meldahl 51 converted (XXIII)by reduction into the vinyl derivative, and by oxidation withaluminium tert.-butoxide into ethinyltestosterone (XXV) , a sub-stance with the physiological properties of progesterone. Vinyl-testosterone was prepared by L.Ruzicka, K. Hofmann, and H. F.Meldahl 52 by analogous methods.Another route to pregnane derivatives from ethinylandrostanecompounds is reported by L. Ruzicka and H. F. Meldahl,53 who foundthat 17-ethinyl-A5-androstene-3( p) : 17-diol in glacial acetic acidin the presence of acetic anhydride and mercuric oxide togetherwith the boron fluoride-ether catalyst 54 readily added on aceticacid and gave rise to 3( p) : 17-diacetoxy-A5-pregnen-20-one (XXVI).The goal of the investigation, the preparation of 17-hydroxypro-gesterone, was attained (a) by partial saponification of (XXVI) tothe 17-monoacetate and oxidation by Oppenauer’s method, or (b)by addition of acetic acid to 17-ethinyltestosterone (XXV).H. H. Inhoffen, W.Logemann, W. Hohlweg, and A. Serini5547 Chim. e l’Ind., 1937, 19, 435. 48 Naturwiss., 1937, 25, 682.49 Helv. Chim. Acta, 1937, 20, 1280.61 Ibid., p. 371. 62 Ibid., p. 597. 65 Ibid., p. 1760.s4 G. F. Hennion, H. D. Hinton, and J. A. Nieuwland, J. Amer. Chem.SOC., 1933, 55, 2858.66 Ber., 1938, 71, 1024; cf. H. H. Inhoffen and W. Hohlweg, Naturwiss.,1938, 26, 96.Ibid., 1938, 21, 88CALLOR : STEROIDS. 291applied the process of acetylene condensation to aestrone, equilin,and equilenin and obtained the corresponding ethinyl compounds.TH,*OHCH*OH GFC YH3 co(XXVI.) (XXVII. ) (XXVIII.)17-Ethinylc~stratriene-3 : 17-diol (XXVII) was converted by re-duction into the vinyl compound, and the latter by osmium tetroxideoxidation into 17-(cr~-dihydroxyethyl)oestradiol (XXVIII).S.Kuwada and M. Miyasaka 56 attacked the problem of attachingcarbon atoms to position 17 by preparing the cyanohydrin (XXIX),and were followed independently by A. Butenandt and J. Schmidt-CN(XXIX.)COMe(XXXII. ) (XXXI.)The cyanohydrin proved to be somewhat difficult todeal with, as it lost the nitrile group readily. The German workersdehydrated the acetate with phosphoryl chloride in pyridine togive the A16-unsaturated nitrile (XXX), which was then converteds0 J . Pharm. SOC. Japan, 1937, 57,96; 1938,58, 116; Chem. Zentr., 1937,11, 1825.57 Naturwiss., 1938, 26, 253; Ber., 1938, 71, 1487; cf. J. Schmidt-Thom6,Angew. Chem.., 1938, 51, 494; W. Schoeller and A. Serini (Schering A.-G.),D. R.-P. 657,017292 ORGANIC CHEMISTBY.into the acid (XXXI) by sodium hydroxide at 180".Reductionwith Raney nickel yielded 3( p)-hydroxy-A5-aetiocholenic acid (XI) ,an intermediate in the degradation of stigmasterol to progester-A possible alternative to this path to progesterone, which is amatter of six stages, is provided by the interaction of (XXX) withmethylmagnesium iodide to give As: 16-pregnadien-3-ol-20-oneK. Miescher and A. Wett~tein,~S following the same line, foundconditions under which the cyanohydrin diacetate was convertedby hydrochloric acid into the amide (XXXIII) and thence into0ne.319 32(XXXII).(XXXIII.) (XXXIV. )3( p) : 17-dihydroxy-A5-aetiocholenic acid (XXIV), identical withthe product from 3( p) : 17-dihydroxy-17-ethinyl-A5-androsteneobtained by L.Ruzicka and K. Hofmann.*a They also preparedfrom A5-andros ten- 3 ( p) -01-20-one acetate the 17 -8pirohydant oinA. Serini and W. Logemann 59 attempted to get an actual com-pound of the adrenal cortical group from one of the androstanegroup by oxidation of 3( p) : 17-dihydroxy-17-vinylandrostane(XXXVI) with osmium tetroxide :YH,*OH(XXXIV).f l E 2 g>oso, CH*OHp ~ $ l ~ z ~ ~ l ~ Me (-OHMe (-OH 2 M f l A M*HO HO( XXXVI . ) (XXXVII.),A/ HOThe resulting allopregnane-3 : 17 : 20 : 21-tetrol (XXXVII), and theA5-pregnene-3 : 17 : 20 : 21-tetrol and A*-pregnene-17 : 20 : 21-triol-%one, prepared by analogous methods, are not, however, likely tobe identical with natural adrenal cortical compounds owing to the58 Helv.Chirn. Acta, 1938, 21, 1317. 6a Ber., 1938, 71, 1362CALLOW : STEROIDS. 293difference of configuration a t position 17. This question will beconsidered a t the end of the following section.Adrenal Steroids.-In the last two years the chemistry of con-stituents of the adrenal cortex has developed with great rapidity,and the result of the work of E. C. Kendall, T. Reichstein, and0. Wintersteiner and their respective associates has been not merelythe isolation of two compounds which possess the characteristicphysiological activity of the adrenal cortex in high degree, but alsothe isolation of a large group of other related compounds of theandrostane and pregnane series and the partial or complete elucida-tion of their constitution. In view of the volume and complexityof this work, it is fortunate that reference can be made to severalreviews,6* in which accounts are given which are both detailed andconsecutive.The compounds isolated are enumerated in the table, with theirprovisional designations, and the constitution assigned, with theappropriate references.The separation of this series of compounds has not only greatimportance on account of the isolation and consequent determinationof the constitution of substances of high hormonal activity but haspotential value from the physiological point of view when theproblem of the relations of these substances to each other in vivocan be attacked.As an example of the separation of a group ofnatural compounds by methods involving only the gentlest treat-ment, the work of Reichstein and his collaborators will serve as amodel for many other investigations.The highly hydroxylatedcharacter of the side-chains in some cases, with the resulting solu-bility in water, was a factor which enabled separation by processesof partition. The possibility of separation by ketone reagents ledto the next step, application of the Girard-Sandulesco reagent T(trimethylearbohydrazidomethylammonium chloride 88) to thefractional formation of water-soluble derivatives of the ketonicsubstances, followed by their fractional decomposition. 72* 75Fractionation of hydroxyl compounds or of their acetates by elutionof (‘ chromatographic ” adsorption columns followed, 81 and, sincereducing ketols were separable as acetates, but not recoverable byordinary methods of hydrolysis, a new technique of hydrolysis byalkali carbonates was elaborated 89 and applied.82# 83The determination of the constitution of these compounds hasproceeded by the steps of showing the presence of the steroid nucleus,8O T.Reichstein, Ergeb. Vitamin- u. Hormonforsch., 1938, 1, 334; Abder-halden’s “Hmdb. der biol. Arbeitsmet.,” 1938, Abt. V, Teil 3B, 8. 1367;0. Wintersteiner and P. E. Smith, Ann, Rev. Biochem., 1938, 7 , 253;K. Miescher, Angew. Chena., 1938, 51, 551Steroids from the Adrenal Cortex.Systematic names.aZZoPregnane-3 : 11 : 17 : 20 : 21-pent01aZloPregnane-3 : 11 : 17 : 21-tetrol-20-onealloPregnane-3 : 17 : 21-triol-11 : 20-dioneA4-Pregnene-11 : 17 : 20 : 21-tetrol-3-0110A4-Pregnene-11 : 17 : 21-friol-3 : 20-dioneA4-Pregnene-17 : 21-diol-3 : 11 : 20-trioneaZZoPregnane-3 : 17 : 20 : 21-tetrolaZloPregnane-3 : 17 : 21-triol-20-oneaZZoPregnane-3 : 11 : 21-triol-20-oneaEEoPregnane-3 : 21-diol-11 : 20-dioneAd-Pregnene-11 : 21-diol-3 : 20-dione (Corticosterone)Ad-Pregnene-17 : 21-diol-3 : 20-&one114-Pregnen-21-01-3 : 11 : 20-trioneaZZoPregnme-3 : 17 : 20-triols (stereoisomeridea)aEloPregnane-3 : 17-diol-20-oneA4-Pregnen-21-01-3 : 20-dione (Deoxycorticosterone)alloPregnan-3-01-20-oneA4-Pregnene-3 : 20-dione (Progesterone)Androstane-%(fi) : 1 l-di01-17-oneA4-Androstene-3 : 11 : 17-trione (Adrenosterone)References.Isolation.Constitution.62, 64, 72 70,7461, 62,68,72 7068,72 7068,77 70, 78,7962, 63, 64, 65, 70, 71, 78, 79 866, 67, 68,7581 8182 8283 8669,81 69,8264, 66, 76, 77 69, 78, 80 964 66, 69, 7875,81 8175 8783 84858683 8372, 73 72, 7372, 78 75,79a83 86 CALLOW : STEROIDS.295followed by clearing up the nature of the side-chain, recognitionof the pregnane skeleton, and provisional allocation to position11 of the relatively inert hydroxyl or ketone group which some ofOH[XXXVIII;(XXXIX;(XL;R = CH(OH)*CH,mOH, R’ = OH]R = CO*CH,.OH, R’ = OH)R = CO*CH,*OH, R’ = :O)them possess. The first three substances in the table (XXXVIII,.XXXIX, XL) are oxidised by chromium trioxide to give a saturated61 0. Wintersteiner and J. J. Pfiffner, J . Biol. Chem., 1935, 109, Sci.Proc.,29, c. Idem, ibid., 1935, 111, 599.63 Idem, ibid., 1936, 114, Sci. Proc., 30, lxxx; ibid., 1936, 116, 291; E. C.Kendall, H. L. Mason, C. S. Myers, and W. D. Allers, ibid., 114, Sci. Proc.,30, lvii.H. L. Mason, C. S. Myers, and E. C. Kendall, ibid., 1936, 114, 613.66 Idem, Proc. Staff Meeting8 Mayo Clinic, 1936, 11, 351 ; J . Biol. Chern.,66 E . C. Kendall, H. L. Mason, W. H. Hoehn, and B. F. McKenzie, Proc.67 Idem, ibid., 1937, 12, 270.6a H. L. Mason, W. M. Hoehn, B. F. McKenzie, and E. C. Kendall, ibid.,70 H. L. Mason, W. M. Hoehn, and E. C. Kendall, ibid., 1938, 124, 459.71 H. L. Mason, ibid., p. 475.72 T. Roichstein, Helv. Chim. Acta, 1936, 19, 29.73 Idem, ibid., p. 223. 74 Idem, ibid., p. 402. 7 6 Idem, ibid., p. 1107.7 6 T.Reichstein, E. Laqueur, I. E. Uyldert, P. de Fremery, and R. W.7 7 P. de Fremery, E. Laqueur, T. Reichstein, R. W. Spanhoff, and I. E.7 8 T. Reichstein, Helv. Chim. Acta, 1937, 20, 953.70 Idem, ibid., p. 978.80 M. Steiger and T. Reichstein, Nature, 1938, 141, 202; Helv. Chim. Acta,82 T. Reichstein and T. Giitzi, ibid., p. 1185.*3 T. Reichstein and J..v. Euw, ibid., p. 1197.84 M. Steiger and T. Reichstein, Nature, 1937, 139, 925.135 D. Beall and T. Reichstein, ibid., 1938, 142, 479; D. Beall, Biochem.86 T. Reichstein, H e b . Chim. Acta, 1938, 21, 1490.87 T. Reichstein and K. Giitzi, ibid., p. 1497.88 A. Girard and G. Sandulesco, ibid., 1936, 19, 1095.8Q T. Reichstein and J, V. Euw, ibid,, 1938, 21, 1181,1936, 116, 267.S t a g Meetings Mayo Clinic, 1937, 12, 136.Idem, J .Biol. Chem., 1937, 119, Sci. Proc., 31, lvi.1937, 120, 719.Spanhoff, Proc. K. Akad. Wetensch. Amsterdam, 1936, 39, 10.Uyldert, Nature, 1937, 139, 26.1938, 21, 161. 81 Idem, ibid., p. 546.J . , 1938, 32, 1957296 ORGANIC CHEMISTRY.triketone (XLI) with one non-reactive oxygen, and this is reducedby Clemmensen’s method to the known hydrocarbon androstaneThe next three substances can be degraded to adrenosterone, fromwhich (XLI) is obtained by catalytic hydrogenation. Degradationof the side-chain of (XXXVIII) occurred with lead tetra-acetate,or with periodic acid with the consumption of three and two equi-valents of oxygen, respectively, indicating three adjacent carbinolgroups. The product (XLIII), a dihydroxy-ketone, formed a mono-acetate and also, with difficulty, a diacetate. Oxidation of the(XLII) .OH(XXXVIII.) (XLIII.) (XLIV.)monoacetate yielded the diketone (XLIV), and the unreactivehydroxyl group was, therefore, secondary. Either (XLIII) or(XLIV) could be transformed into the 3 : 11 : 17-triketone (XLI).Both the 3 : 11-diol-17-one and the 3-01-11 : 17-dione compoundswere precipitable with digitonin, indicating a 3-hydroxyl groupand cholestanol configuration.The 17-position for the side-chain,already suggested by the formation of some androstan-17-one asa by-product in the reduction of the 3 : 11 : 17-triketone, and byother considerations, was rigidly proved by the transformation ofcorticosterone into allopregnane 80 by the following steps CALLOW : STEROIDS.297ll-Substituted derivatives. The ‘‘ inert,” third oxygen atom ofthe adrenal steroids, in view of the fact that no a- or P-diketo-compounds have been obtained, might be in position 6, 7, 11, or12. The supposedly “inert” positions 11 and 12 have beenfavoured, but 6 and 7 are not rigidly excluded. Since position12 has been dismi~sed,~’ position 11 has been provisionallyaccepted by all the workers concerned, pending some direct proof.Unreactive hydroxylic or ketonic groups have been found in othernatural steroids, and by a process of elimination or other type ofindirect evidence, position 11 has been assigned to this substituent,e.g.) in dig~xigenin,~* the stereoisomeric ~armentogenin,~~ anduranetriolg2 from the urine of pregnant mares.Attempts toprepare reference comGounds with 11 -substitution have been madefrom several directions. R. E. Marker and E. J. Lawson 93 reportedthe preparation of 3 : ll-dihydroxy-12-ketocholanic acid by bromin-ation and hydrolysis of 12-keto-3-acetoxycholanic acid, but failedto isolate a product of reduction of the 12-keto-group. J. Barnettand T. Reichstein 94 pursued a somewhat similar course in preparingthe isomeric 11 -hydroxy-12-ketocholanic acids ; they described theinteresting properties of the 11 : 12-diketo-acid, which has stablethe enolic (XLVI) and ketonic (XLVII) forms, and obtained acompound which they formulated as (XLVIII) by Raney reductionof the ester monoxime, but failed to attain the desired ll-derivative.(XLVI.) (XLVII.) (XLVIII.)M.Steiger and T. Reichstein 95 proceeded to test the assumptionthat digoxigenin and corticosterone both contained 11 -hydroxylgroups by attempting to degrade both compounds t o aetiocholanicacids with substituents in positions 3 and 11. The two series ofproducts proved to be different, and it was concluded that in oneseries the assumed constitution must be incorrect. W. M. Hoehnand H. L. Mason 96 prepared authentic aetiocholanic acid derivativesu0 R. Tschesche and K. Bohle (with H. Grasshof), Ber., 1936, 69, 793.91 R. Tschesche Etnd K. Bohle, ibid., p. 2497.%2 R. E. Marker, 0. Kamm, T. S. Oakwood, E. L. Wittle, and E. J. Lawson,94 Helv. C h h . Acta, 1938, 21, 926.86 J. Amer. Ohem. Soc., 1938, 60, 1493, 2666,J .Amer. Chem. SOC., 1938, 60, 1061. O3 Ibid., p. 1334.Ibid., p, 828298 ORGANIC CHEMISTRY.with hydroxyl or carbonyl in positions 3 and 12 from deoxycholicacid, and these were foundg7 to be identical with products fromdigoxigenin. The assumed constitution of adrenal steroids remains,at least, unassailed, but the formulze of digoxigenin and sarmento-genin require revision. The method of degradation of digoxigenindevised by M. Steiger and T. Reichstein may be expected to givevaluable information when applied to other heart poisons. Itconsists of permanganate oxidation of the diacetate (XLIX), followedby elimination of the tertiary hydroxyl group, and reduction of thedouble linking by Raney nickel, to give 3 : 12-dihydroxyaetio-cholanic acid as shown in formulae (XLIX) to (LII).A processof oxidation, bromination, debromination to the 3-keto-A*-acid, andreduction yielded the corresponding aetioallocholanic acid.>o YH,*COC=CHCon$guration at Cl,. A further problem remaining to be settledin the adrenal steroid group is that of the configuration at Cl,.This is part of a general problem which arose in a comparativelyshort period in connexion with all three groups of sex hormones.aZloPregnan-3 (8) -01-20-one 98 and A5-pregnen-3 (p)-ol-20-one 99 wereshown to be converted by alkali into " is0 "-compounds, the form-ation of which was explained by alteration of the configuration atCl,. The latter had considerably decreased dextrorotation, andno longer gave insoluble digitonides.The isomeric oestradiols 1showed analogous differences, and isomeric dihydroequilenins 2 were97 H. L. Mason and W. M. Hoehn, J . Amer. Chem. SOC., 1938,60, 2824.9 8 A. Butenandt and L. Mamoli, Ber., 1935, 68, 1845.99 A. Butenandt and G. Fleischer, Ber., 1937, 70, 96.Ann. Reports, 1936, 33, 361; 0. Wintersteiner, J . Amer. Chem. SOC.,1937,59,765 ; A. Butenandt and C . Goergens, 2. physiol. Chem., 1937,248,129.R. E. Marker, 0. Kamm, T. S. Oakwood, and F. H. Tendick, J , Amer.Chem, Soc,, 1937, 39, 768; R. E. Marker, ibid., 1938, 60, 1897CALLOW : STEROIDS. 299prepared. Isomeric androstane-3( a ) : 17-diols were separated,3 andthe isomeride formed in greater amount by reduction of androsteronewas allotted, on the basis of superior rea~tivity,~ the configurationwith the 17-hydroxyl and the 13-methyl group trans to each other.The interesting possibility of correlating digitonide formation,relative dextrorotation, and higher physiological activity has beendis~ussed,~ but the position is still obscure and awaits systematicinvestigation.As far as concerns products obtained by additionof hydrogen cyanide, acetylene, or alkylmagnesium halides to theketo-group in position 17, there is evidence from identity oftransformation products and of colour reactions 6 that they belongto the same group with trans-configuration. In particular, T.Reichstein and K. Gatzi point out that all the pregnane derivativesobtained by interaction of acetylene or ethylmagnesium halideswith androstan-3( p)-ol-17-one or A5-androsten-3( p)-ol-17-one can bereduced to the same albpregnane-3 : 17-diol.These, which composewhat they call the 17(a)-series, are not precipitated by digitonin,but the natural adrenal steroids with 3(p)- and 17-hydroxyl groupsare precipitated by digitonin and belong to the 17(p)-series. It doesnot seem clear a t the moment whether a-cestradiol (higher dextro-rotation and physiological activity, precipitable by digitonin,principal natural product) is a 17(p)- or a 17(a)-hydroxy-compound,and it affords a good example of the uncertainties in configurationalrelations which remain to be made clear. In the meantime, anexplanation is afforded for the difference of the synthetic 8 and thenatural aZlopregnane-3(p) : 17 : 20 : 21-tetrol, which are respectively17 (a)- and 17( p)-hydroxy-compounds, and are conventionally repre-sented as (LIII) and (LIV).VH,*OHHC*OH OHL.Ruzicka and H. Kiigi, Helv. Chim. Acta, 1936,19, 842.L. Ruzicka and M. W. Goldberg, ibid., p. 99; L. Ruzicka and H. Kzigi,ibid., 1937, 20, 1557.0. Wintersteiner, Cold Spring Harbor Symposia on Quantitative Biology,1937, 5, 25.* K. Miescher and A. Wettstein, Helv. Chim. Acta, 1938, 21, 1317;H. Kagi and K. Miescher, Chem. and In&., 1938, 57, 276; cf. L. Ruzicka,K. Hofinann, and H? F. Meldahl, Helv. Chhim. Acta, 1938, 21, 597.a A. Serini and W, Logemann, Ber,, 1938.71, 1362, 7 Ibid., p. 1185300 ORGANIC CHEMISTRY.Urinary Steroids.-The possibility of a connexion between steroidspresent in the adrenal cortex and certain of those excreted in theurine was discussed in the last R e p ~ r t , ~ and is now more firmlyestablished, at least in the case of certain abnormal conditions.10The isolation of androsterone and A5-androsten-3( ~)-ol-17-one fromthe urine of normal women l1 and of androsterone from the urineof pregnant women l2 shows that these compounds are a t least notspecific to the male organism, but leaves open the question whetherthey are derived from the adrenal cortical secretion.G. C. Butlerand G. F. Marrian l3 suggest that the pregnane-3(a) : 17 : 20-trio1isolated by them from a pathological urine may be the intermediatestage in a breakdown to the aetiocholan-3(a)-ol-17-one present inthe same urine and typify the in viwo degradation of steroids of thepregnane or allopregnane series to those of the aetiocholane orandrostane series, respectively, beginning with the introduction ofthe tertiary hydroxyl group in position 17.The investigations of R.E. Marker and his co-workers into thesteroids of urine, carried out with large amounts of material, haveled to the isolation of a series of pregnane derivatives which maybe looked upon as excretory transformation products of the steroidsof the corpus Zuteum of the ovary, and of the adrenal cortex. Fromthe urine of pregnant mares there have been obtained pregnanediol,14aZZopregnanedi01,~~ pregnanedione, dlopregnanedione, allopregnan-3-01-20-0ne~ uran-11 -01-3-one,15 urane-3 : 11 -diol,16 A4-pregnenediol,17pregnanetriol-A l8 (later named uranetriol 19), pregnanetriol-B,and ( '2) albpregnane-3@) : 11 : 20 : 21-tetr01.~~ Pregnanetriol-B,originally isolated by G.F. Marrian and his co-workers,21 wasD Ann. Reports, 1936, 33, 360.10 Cf. the discussion by R. K. Callow, Proc. Roy. SOC. Med., 1938, 31, 841.11 (Mrs.) N. H. Callow and R. K. Callow, Biochem. J., 1938, 32, 1759.12 R. E. Marker and E. J. Lawson, J. Amer. Chem. SOC., 1938, 60, 2928.18 J . Biol. Chern., 1938, 124, 237; Nature, 1938, 142, 400.14 R. E. Marker, 0. Kamm, H. M. Crooks, T. S. Oakwood, E. J. Lawson,and E. L. Wittle, J . Amer. Chem. SOC., 1937, 59, 2297. For a review of thenatural and the synthetic pregnanediols and pregnanolones, cf. R. E. Marker,0. Karnm, E. L. Wittle, T. S. Oakwood, E.J. Lawson, and 5. F. Laucius,ibid., p. 2291.15 R. E. Marker, E. J. Lawson, E. L. Wittle, and H. M. Crooks, ibid.,1938, 60, 1559.16 R. E. Marker, E. Rohrmann, and E. L. Wittle, ibid., p. 1561.1 7 R. E. Marker and E. R o ~ ~ M , ibid., p. 1565.18 R. E. Marker, 0. K a m , H. M. Crooks, T. S. Oakwood, E. L. Wittle,lQ R. E. Marker, 0. Kamm, E. L. Wittle, and E. J. Lawson, ibid., p. 1061.2o R. E. Marker, E. J. Lawson, E. Rohrrnann, and E. L. Wittle, ibid., p. 1555.81 E. R. Smith, D. Hughes, G. F. Marrian, and G. A. D. Haslewood, Nature,1933, 132, 102; G. A. D. Haslewood, G. F. Marrian, and E. R. Smith,Biochem. J,, 1934, 28, 1316.and E. J. Lawson, ibid., p. 210CALLOW : STEROIDS. 301assigned 22 the constitution of pregnane-3(a) : 4 : 20-triol.A. D.Odell and G. F. Marrian23 have since obtained evidence againstthis formulation, and propose instead pregnane- or allopregnane-3(a) : 6 : 20-triol.The “ urane ” derivatives have been assigned 19 a structurewhich is stereoisomeric with that of the pregnane derivatives invirtue of a difference in orientation a t CQ, and uranetriol and preg-nanediol are formulated as (LV) and (LVI), respectively. A numberYHS CH-OH QH3 CH-OHPV.1 (LVI.) (LVII.)of derivatives have been prepared,lQ* 24 including the parent hydro-carbon, but since the proposed structure was based very largely onanalogy with assumed structures of sarmentogenin and digoxigeninwhich are no longer tenable 95s 97 (cf. p. 298)’ it seems justifiableto delay reporting further on this work until controversial pointsare settled.Pregnane-3( a ) : 20( a)-diol, aZZopregnane-3( a) : 20(a)-diol, and aZZo-pregnane-3@) : 20(a)-diol have been isolated from bull’s ~ r i n e .2 ~The urine of pregnant women yielded aZZopregnan-3( a)-ol-20-0ne,~~pregnan-3(a)-ol-20-0ne,~7 and pregnan-3(or)-ol,l2 The first-namedcompound was styled the androgenic principle of human pregnancyurine,2s but A. Butenandt and A. Heusner2Q find that it has noandrogenic activity.R. E. Marker and his co-workers30 have further isolated two22 R. E. Marker, 0. Kamm, E. L. Wittle, T. S. Oakwood, and E. J. Lawson,J . Amer. Chem. Soc., 1938, 60, 1067.23 J . Biol. Chem., 1938, 125, 333.24 R. E. Marker, E. L. Wittle, and T. S. Oakwood, J. Amer. Chem. SOC.,26 R.E. Marker, E. L. Wittle, and E. J. Lawson, ibid., p. 2931.::g R. E. Marker, 0. Kamm, and R. V. McGrew, ibid., 1937, 59, 616.97 R. E. Marker and 0. Kamm, ibid., p. 1373.28 R. E. Marker, 0. Krcmm, D. M. Jones, E. L. Wittle, T. S. Oakwood,29 Angew. Chem., 1938, 51, 493; 8. physiol. Chem., 1938, 256, 236,3O R. E. Marker, E. Rohrmann, E. L. Wittle, and E. J. Lawson, J. Amer.Chem. Soc., 1938, 60, 1512; R. E. Marker, E. Rohrmann, E. J. Lawson,and E. L. Wittle, ibid., p. 1901 ; R. E. Marker and E. Rohrmann, ibid., p. 2927.1938, 60, 15W.and H. M. Crooks, a i d . , p. 768302 ORGANIC CHEMISTRY.isomeric hexahydrocestradiols (LVII), cestranediol-A and cestrane-diol-B from the urine of non-pregnant women. The second of thesecompounds is identical with a reduction product of oestroneY3l andhas the same configuration at C,, as or-cestradiol.A new excretory product of the male hormone group detectedin extracts of men's urine is aetiocholane-3(a) : 17-di01,~~ but thecircumstances in which it was isolated compel the reservationthat it may not exist in the urine as such, but be formed duringsubsequent treatment.I n a highly ingenious but speculative paper based on the chemicalwork reported in papers on steroids in urine and tissues, thirty-nineof which are from his own laboratory, R.E. Marker33 producesa general scheme for the metabolism of the steroidal hormones inthe body. The schemes of biogenesis of steroids of simpler typefrom cholesterol are shown to be open to serious objections, as, forinstance, the difficulty of removing the side-chain from position 17except by the most violent methods, and the difficulty of introducinga hydroxyl group into the 1 l-position postulated for the inert oxygenof the adrenal cortical group and certain wane compounds.Ascheme for the biological reduction of progesterone has been con-structed on the assumption that two types of change take place:(a) reduction of the 4 : 5-double linking to give either cis- or trans-derivatives (coprosta,ne or cholestane type), followed by reductionof the 3-carbonyl group to give 3(a)-hydroxy-compounds, and ( b )the reduction of the A4-3-keto-grouping successively to As-3( p)-hydroxy- (cholesterol type) and 3( p)-trans-derivatives (cholestanoltype). So far, generalisation and experimental facts correspond,for the compounds isolated fit in, and only two hypothetical productsare included. Extension of the same generalisation to the malehormone group, however, entails the assumption that A4-androstene-3 : l7-dione is the original hormone, and eight out of twelve com-pounds in the resulting scheme have not been isolated from eithergland or urine.These speculations become entirely independent of experimentalfacts when A4: 8-pregnadiene-17 : 21-diol-3 : 11 : 20-trione (LVIII)is proposed as the hypothetical common precursor of the C,,, C19,a,nd C,, sex hormones and the adrenal cortical steroids.Thejustification of these adventurous hypotheses not only by isolationof further substances from natural sources and by synthetical work,but also by observations of a more physiological type, will be awaitedwith interest.81 W.Dirscherl, 2. physiol. Chem., 1936, 239, 53.52 A. Butenandt, K. Tscherning, and H. Dannenberg, ibid., 1937, 2.68, 205.33 J . Amer. Ckern. SOC., 1938, 60, 1725CALLOW : STEROIDS. 303The Vitamins-D and their Precursors.-Further work has beencarried out on the occurrence and composition of natural pro-vitamins-D; so far, only two compounds have been found,OHMe CHMe*CH,*CH2*CH2Prs(LIX.)O:p~~O*CH2*OHA,,\/-7-dehydrocholesterol ( A5 : 7-cholestadien-3-ol) in pig’s skin 34 andin the common whelk,35 and ergosterol in other invertebrates 35 andin wheat-germ 0il.36 7-Dehydro-sitosterol and -stigmasterol werenot found.Further A5 : 7-steroids which are potential provitaminshave been prepared. G. A. D. Haslewood 37 obtained 3( p)-hydroxy-A5 : 7-choladienic acid from methyl 3 : 7-dibenzoyloxy-A5-cholenateby the action of dimethylaniline, a method which is superior tothe pyrolytic one previously used for introducing the C,-8 doublebond. A5 : 7-Androstadiene-3( @) : 17-dio1, obtained by analogousmethods,3* is a potentially interesting compound, not only fromthe physiological point of view, but also in view of the possiblepreparation of a “ vitamin-D ” perhaps more amenable to physicalmethods in determination of its structure than the compounds wit,hlong side-chains in position 17.Vitamin-D3 has been obtained crystalline from tunny-liver oil,and the presence of a small amount of admixed calciferol has beenrec~gnised.~~Synthetic vitamin-D, has been ~rystallised,~l and a detailedstudy of the irradiation products of 7-dehydrocholesterol 42 has ledto the isolation of lumisterol-3 and tachysterol-3, analogous to theproducts from ergosterol.Ozonisation of vitamin-D, yielded aketone, probably (LIX), in complete analogy with calciferol.“ Vitamin-D4 ” (from irradiation of 22 : 23-dihydroergosterol) hasbeen isolated and ~haracterised.~~Halibut-liver oil also contains ~itarnin-D~.~O34 A. Windaus and F. Bock, 2. physiol. Chern., 1937, 245, 168.36 F. Bock and F. Wetter, ibid., 1938, 256, 33.36 A. Windaus and F. Bock, ibid., p. 47.a7 J., 1938, 224.38 A. Butenmdt, E. Hausmann, and J. Paland (with, in part, D.von3O H. Brockmann and A. Busse, Naturwiss., 1938, 26, 122; 2. physiol.40 H. Brockmann, 2. physiol. Chem., 1937, 245, 96.4 1 F. Schenck, Naturwiss., 1937, 25, 159.42 A. Windaus, M. Deppe, and W. Wunderlich, Annalen, 1937, 533, 118.43 A. Windaus and G. Trautmann, 2;. physiol. Chem., 1937, 247, 185.Dresler and U. Meinerts), Ber., 1938, 71, 1316.Chem., 1938, 256, 252304 ORGANIC CHEMISTRY.The flat contradiction between the conclusions of X-ray crystallo-graphy and of chemistry as to the structure of calciferol still remainsunresolved. K. v. A ~ w e r s , ~ ~ however, considers that measurementsof n and dispersive power are concordant with the Windaus formula,rather than with a 4-ring structure. An examination of the physicalDehydroergosterolLumisterol (LXIII.)constants of calciferol in a large series of samples 45 showed a vari-ation in the optical rotation which was relatively greater than that ofthe ultra-violet absorption : the significance of this is not under-stood. Further work on lumisterol confirms the hypothesis thatit differs from ergosterol simply in the steric position of the 10-methyl44 Annalen, 1938, 533, 255.45 F.W. Anderson, A. L. Bacharach, and E. L. Smith, Analyst, 1937, 62,430CALLOW : STEROIDS. 305group, as postulated by K. Dimroth46 and by A. Windaus andK. Dimr~th.~' These authors, finding that ergosterol (LX) andisopyrocalciferol (LXI) yielded the same dehydroergosterol (LXII),whilst lumisterol (LXIII) and pyrocalciferol (LXIV) yielded thesame dehydrolumisterol (LXV), proposed a scheme which may berepresented as on p, 304.An alternative scheme, according to which the relations might beexplained by variation of orientation round C3 and Cg, insteadof round C, and Cl0, was ahown48 to be impossible, on account ofthe non-identity of epiergoeterol with either lumisterol or pyro-calciferol and of epilumisterol with either ergosterol or isopyrocal-ciferol.The results of comparative studies of analogous ergosteroland lumisterol derivatives by chemical and ultra-violet spectro-graphic methods 49 are concordant with these conclusions.The constitution of tachysterol has been discussed by W. Grund-rnanq60 who considers that the possibilityMe 'gH17 of its being a stereoisomeride of calciferolcan be ruled out. The evidence so far ciq obtained from ozonolysis of adducts withcitraconic anhydride 51 or with methylacetylenedicarboxylate, or from directoxidative degradation, suggests theA5(I0) : : 8-structure (LXVI) rather than the A1(l0) : : '-structurepreviously discussed.A.Windaus and K. Buchholz52 have oxidised calciferol byOppenauer's method to the corresponding ketone. This has notbeen obtained crystalline, but it has the same absorption spectrumas calciferol : its antirachitic activity is 11300 of that of calciferol.An interesting side-line to the calciferol problem is the behaviourof pyrocalciferol and isopyrocalciferol on irradiation.63 Theseappear to be transformed directly into well-characterised compounds,photopyrocalciferol and photoisopyrocalciferol, which contain doublelinkings that are not conjugated but are probably in the 4 : 5- and7 : 8-positions.The reactions are reversed on heating.The occurrence of photochemical change in steroids containingconjugated double linkings not in the " provitamin " or 5 : 7-positionis a new development. A6 : 8-Cholestadien-3-ol, obtaine'd as a by-4~ Ber., 1936, 69, 1123.48 I. M. Heilbron, T. Kennedy, F. S. Spring, and G. Swain, J., 1938, 869.4g A. Burawoy, J . , 1937,409; I. M. Heilbron, G. L. Moffet, and F. S. Spring,60 2. physiol. Chem., 1938, 252, 151.61 Laucht, Dissert., Gottingen, 1936, quoted by W. Grundmann, Eoc. cit.62 2. physiol. Chern., 1938, 256, 273.6s K. Dimroth, Ber., 1937, 70, 1031.\/-\/ (LXVI.) I47 Ibid., 1937, 70, 376.ibid., p.411306 ORGANIU CHEMISTRY.product in the preparation of A5 7-cholestadien-3-ol,~ is converted 55by ultra-violet irradiation into A6 : 8-coprostadien-3-ol by a changeof configuration on C,. This is regarded as completely analogouato the change of configuration on C,, in A5: 7-comp~unds, for ineach case the primary change is in a position “loosened” by theconjugated system. The two A6 : 8-compounds and the A5: ’-compound give the same “ pinacol ” on insolation in alcohol con-taining eosin, and this is confirmed by preparation of the samenorsterol (ring I1 aromatic) by distillation of the pinacol from allthree sources. Other transformation products of the stereoisomericA6 : 8-compounds are analogous, e.g., the maleic acid adducts, theA*-3 : 6 : 7-triols, dihydro-derivatives-or-(A8* 14) and &(A8* 9)-anda “ dienol-B, ” (A7 : 14) compound.A photochemical reaction commonly regarded as characteristicof A5: 7-compounds, the formation of a peroxide on irradiation inalcohol containing eosin in presence of oxygen, has been found tooccur with A2 : 4-cholestadiene, which is obtained by dehydrationof cholesterol with alumina under special conditions.56 The initialdisagreement as to the properties of the compound formed has beenexplained in a somewhat unexpected way by the observation57 thatthe product obtained by irradiation with a tungsten-filament lampis isomerised by exposure to sunlight. The first product is shown 57to be A3-cholestene 2 : ti-peroxide, since the properties of the productof hydrogenation indicate that it must be cholestane-2 : 5-diol.Synthesis of Steroids.-Although this Report has dealt only withnatural products and the relations between them, it should bementioned that there has been increasing activity in the explorationof routes to the synthesis of natural steroids.It seems likely that the next major advancein the chemistry of the steroids will be inthis direction.This work has not yetreached a stage a t which it could usefullyMe0 \A/ (LXVU.) be reported in detail, but an exception maybe made in referring to the recent synthesis 58of a compound closely related to cestrone, namely, x-norequileninmethyl ether (LXVII), obtained from the product of cyclising/v\ 9, f II3 - p -naphthylcyclopentan-l -one-2 -acetic acid.R.K. C .64 A. Windaw, 0. Linsert, and H. J. Eckhardt, Annalen, 1938, 534, 22.16 A. Windaus and G. Ziihlsdorff, ibid., 1938, 536, 204.H. E. Stavely and W. Bergmann, J. Org. Chem., 1937, 1, 675; E. L.Skau and W. Bergmann, J. Amer. Chem. SOC., 1938, 60, 986; A. Butenandtand H. Kudssus, 2. physiol. Chem., 1938, 253, 1, 224.68 A. Koebner and R. Robinson, J., 1938, 1994.E. L. Skau and W. Bergmann, J. Org. Chem., 1938, 3, 166HAWORTH : HETEROCYCLIC COMPOUNDS. 3077. HETEROCYCLIC COMPOUNDS.(a) Oxygen Ring Compounds.Dioxan Derivatives .-Dioxan (diethylene dioxide), prepared fromethylene glycol and PP'-dichlorodiethyl ether by the action ofsulphuric acid and alkali respectively, is a useful solvent for cryo-scopic and ebullioscopic work, and on account of its miscibility withwater and stability towards acids, alkalis and oxidising agents, itprovides a suitable medium for many organic reactions. 2 : 3-Dichlorodioxan, obtained together with smaller amounts of tetra-and hexa-chloro-derivatives by direct ~hlorination,~ is hydrolysedby the action of warm water to glycol and glyoxal, and the hydroly-sate may be used as a convenient source of the latter.3*4 Thechlorine atoms of the dichloro-derivative are replaceable by alkoxy-groups, and it reacts with glycols and catechol derivatives to givedicyclic compounds such as (I).3v5 This compound (I) occurs incis- and trans-forms, which have been oriented by measurement of0the dipole 2 : 3-Dichlorodioxan reacts with Grignardreagents to give 2 : 3-dialkyl or -diary1 derivativesY5*7 but undercertain conditions methylmagnesium iodide yields dioxen (11),from which 2-phenyldioxan may be prepared by addition of hydrogenchloride and subsequent treatment of the unstable 2-chlorodioxanwith phenylmagnesium bromide.8 Dioxan readily forms doublecompounds, and recently the solid product (111) has been preparedby treatment with sulphur trioxide in carbon tetrachloride solution.1 L.Anschutz and W. Brocker, Ber., 1926, 59, 2844; K. Hess andH. Frahms,ibid., 1938,71, 2627; U.S.P. 1,681,861.B.P. 363,895.J. Boeseken, F. Tellegen, and P. C. Henriquez, Rec. Truv. chim., 1931,C. L. Butler and L. N. Critcher, J . Amer. Chem. SOC., 1932, 54, 2987.J.Boeseken, F. Tellegen, and P. C. Henriquez, Rec. Truv. chim., 1935,54,7 R. K. Summerbell and R. Christ, J . Amer. Chem. SOC., 1933, 55, 4547;8 R. K. Summerbell and L. N. Bauer, ibi&., 1935,57,2364.0 C. M. Suter, P. B. Evans, and J. M. Keifer, ibid., 1938,60, 538.50, 909.6 R. K. Summerbell and R. Christ, ibid., p. 3778.733.R. K. Summerbell and L. N. Bauer, ibid., 1936, 58, 759308 ORGANIC CHEMISTRY.The product (111) is a more vigorous sulphonating and sulphuratingagent than the corresponding pyridine-sulphur trioxide adduct.Benzene, naphthalene and anisole are sulphonated with increasingfacility at the ordinary temperature, phenol and aniline give 0- andN-sulphonates respectively, alcohols yield alkyl hydrogen sulphates,and ethylenes are converted into the corresponding carbyl sulphates.More complicated dioxan derivatives have been encountered byW.Madelung and M. E. Oberwegner.1° Desyl chloride (IV) isconverted into the oxides (V) and (VI) when treated with potassiumhydroxide in toluene and with sodium methoxide respectively.On standing, (VI) is converted into the cis-form of the dioxanderivative (VII), from which the trans-form is obtained by treat-ment with methyl-alcoholic hydrogen chloride ; the trans-form of(VII) is also produced directly from benzoin on treatment withmethyl-alcoholic hydrogen chloride. Dehydration of (VII) leadsto (VIII), from which four stereoisomeric tetrahydro-derivatives(IX) have been prepared. A dioxan structure (X) has been intro-0 OMe “730 P h d ‘4Ph phbo/cHph Me’ h b O PhCPh*CO*CHPhb u ebl PhW.) (V.1 (VI.) (VII-10 0I?h& )HPh P h h )HClPhCH CHPh CH-CPhP h ( 8 P hPhC 8Ph\ / 0 \ / 0 \ / 0(VIII.) (X.1duced for the “chloro-diphenacyls” obtained by the action ofsodium ethoxide on o-chloroacetophenone,ll but no satisfactoryexplanation has been advanced for the rearrangement of (X) duringreduction to cc p -dibenzoylethane. *The Tocopherols.-The isolation, from the unsaponifiable fractionof wheat germ and cotton seed oils, of compounds possessingvitamin-E activity was discussed in these Reports for 1937 (p. 410).10 W. Madelung and M. E. Oberwenger, Annalen, 1931, 490, 201; 1936,626, 196.11 0. Widmas, ibid., 1913, 400, 90.* Similar peculiar rearrangements have been reported for bimolecular lacto-lides (M.Bergmann, A. Miekeley, and E. von Lippmasn, Ber., 1929,62,1467 ;M. Bergmann and A. Miekeley, ibid., p. 2297)HAWORTH : HETEROCYCLIC COMPOUXDS. 309The substances, previously known as neotocopherol l2 and cumoto-pherol,l3 have now been proved identical with p-tocopherol.14* 15* l6The first indication of the constitution of the tocopherols was ob-tained by thermal decomposition at 350"; a- and p-tocopherolyielded duroquinol (I) and $-cumoquinol (11) l3 respectively.Examination of a number of synthetic esters of the quinoh (I)and (11) showed that they differed from the tocopherols in absorptionMe Me(1.1 (11.) (111.) (Iv.)spectra and in their reactions with oxidising and hydrolyticagents.l4s 16918 Consequently it was suggested that the C,, sidechain of the tocopherols was attached to the quinol nucleus by acarbon-carbon linkage, and a compound of structure (111) or (IV),synthesised from quinol and ally1 bromide,l* resembled theEIO&-VH,Me CH,(V.1 Me o/CH*[CHM~*(CH,),],*CHM~,Metocopherols in absorption spectrum.This synthetic reaction hasbeen extended and modified, and racemic a-tocopherol, (V) or (VI),has been obtained from $-cumoquinol (11) by condensation withphytyl bromide,lS phytol 2O or phytadiene.21 The syntheticla P. Karrer, H. Salomon, and H. Fritzsche, Hek. Chim. Acta, 1937, 20,1422.W. John, 2. physiol. Chem., 1937, 250, 11.l4 P. Karrer, H. Salomon, and H. Fritzsche, Helv. Chim. Acta, 1938,21,309.l6 F.Bergel, A. R. Todd, and T. S. Work, J., 1938,253.l6 W. John, E. Dietzel, and P. Gunther, 8. physiol. Chem., 1938,252, 201.l7 E. Fernholz, J . Amer. Chern. SOC., 1937, 59, 1154.lo P. Karrer, H. Fritzsche, B. H. Ringier, and H. Salomon, Helv. Chirn. Actac,2o F. Bergel, (Miss) A. M. Copping, (Miss) A. Jacob, A. R. Todd, and T. S.a1 L. I. Smith, H. E. Ungnade, and W. W. Prichard, Science, 1938, $8,40.E. Fernholz, ibid., 1938, 60, 700.1938, 21, 520, 820.Work, J., 1938, 1382310 ORGANIC CHEMISTRY.racemate, which shows marked vitamin-E activity, has been resolvedlgand the d-bromocamphorsulphonate is identical with that obtainedfrom natural a-tocopherol. The synthesis outlined above is am-biguous and difficulties have been encountered in differentiatingbetween the alternative structures (V) and (VI), but the latterchroman structure (VI) is now favoured by the specialists in thisfield.When a-tocopherol is oxidised with chromic acid or potassiumpermanganate,l*s22 the aromatic nucleus is destroyed and a y-lactone, C21H,402, is obtained. The alcoholic group of the corre-sponding hydroxy-acid is inert and therefore probably tertiary incharacter, and the lactone is formulated as (VII). Burther evidencein support of (VI) is obtained by oxidising a-tocopherol with silvernitrate or ferric chloride. A quinone is produced and this is regardedas (VIII) because the di-p-bromobenzoate of the correspondingquinol is not attacked by chromic acid.23 The formation of theMe CH,Od\/ \Me1 A TH2 \ 0 C-[(CH,),*CHMe],*MeM A H (VIII.)&H2O-Qf(CH,),*CHMe],*MeMe Me (VII.)quinone (VIII) may be followed by potentiometric titration withauric chloride, and the tertiary nature of the hydroxyl group of(VIII) is also indicated by its stability to aluminium isobutoxide.24Examination of a number of synthetic products shows that re-moval of methyl groups from the aromatic nucleus or modification ofthe side chain of a-tocopherol reduces the vitamin-E a~tivity.~5The coumaran (IX) is inactive,26 but a variety of duroquinol ethers 27and the compound (X) 28 show activity in large dosages.p-Tocopherol has inferior vitamin-E activity, but its chemical2a 0.H. Emerson, Science, 1938, 88, 40.2s W. John, E. Dietzel, P. Gunther, and W.Emte, Naturwiss., 1938,26,366.24 P. Karrer, R. Escher, H. Fritzsche, H. Keller, B. H. Ringier, and25 P. Karrer and K. A. Jensen, ibid., p. 1622; W. John, P. Gunther, and26 F. Bergel, (Miss) A. Jacob, A. R. Todd, and T. S. Work, J., 1938, 1375.27 F. Weider and T. Moll, 2. physiol. Chem., 1938,254, 39,88 W. John and P. Gunther, ihid., p. 51.H. Salomon, Helv. Chim. Acta, 1938, 21, 939.M. Schmeil, Ber., 1938, 71, 2637HAMrOItTH : HETEROCYCLIC COMPOUNDS. 31 1properties are similar to those of ec-tocopherol. The compounds arenot isomeric, and although the structure of @-tocopherol has not beenestablished, the formation of +-cumoquinol instead of duroquinol onpyrolysis suggests that it is probably the lower homologue ofcc- t ocopherol.EquoZ.-Similar difjEiculty in distinguishing between chroman andcoumaran structure has been encountered in an investigation onequol.This optically active dihydroxyphenol, C15HlP03, isolatedfrom horse urine,29 yields a number of phenols and phenolic acids onfusion with alkalis. One of the products is an optically inactive,unsaturated, trihydroxyphenol, which as a result of recent work 30is regarded as (I11 ; R = H), and the structure is confirmed by asynthesis of the methyl ether (111; R = Me). Condensation ofresorcinol with p-hydroxyphenylacetonitrile gave the trihydroxy-deoxybenzoin (IV; R‘ = R” = H), the trimethyl ether (IV;(111.) (IV.1R’ = Me, R” = H) of which yielded (IV; R’ = R”= Me) on treat-ment with methyl iodide and sodium ethoxide.Pondorff reductionof (IV; R’ = R” = Me) and subsequent dehydration of the second-ary alcohol yielded (111; R = Me). On the basis of this evidencestructure (I) or (11) has been advanced for equol, but a decisionbetween the alternatives has not been made.Derris Constituents.-The structures of the constituents of derrisroot were reviewed in these Reports for 1937 (p. 346), and the re-actions of Z-rotenone were interpreted on the basis of structure (I),which contains three asymmetric carbon atoms a t 7, 8, and 20.E-Dehydrorotenone (11), with asymmetry a t position 20, and Z-isorotenone (111), with asymmetry a t positions 7 and 8, are obtainedby the action of iodine and acetic-sulphuric acid respectively onrotenone (I). As both these derivatives (11) and (111) are levo-rotatory, it is legitimate to assign a levorotatory contribution toa* G.F. Marrian and G. A. D. Haslewood, Biochem. J., 1932, 26, 1227;80 F. Wessely, H. Herschel, and G. Sohlogl-Petaival, Mowtah,, 1938, 71,G. F. Marrian and D. Beall, ibid., 1935, 29, 1686.215312 ORGANIC CHEMISTRY.C,, and also to the combination of C, and C,. When I-rotenone (I)is treated with alkali in benzene, methyl alcohol or acetone, but notin water, it is converted into mutarotenone, which is an equilibriummixture of rotenone and d-epirotenone. As d-epirotenone may beMe0 coOHMe0I CO OHoxidised to I-dehydrorotenone (11) and isomerised by acetic-sulphuric acid to d-isorotenone, it follows that d-epirotenone isderived from rotenone by inversion of both C, and c8.A similarinversion of both C, and c8 must also be postulated in order to accountfor the formation of a dl-enol ether of type (IV) from I-isorotenone,and the inversions are explained by enolisation of C, and fission ofring C with the production of intermediate compounds of type (V).Me0A I CO OH* (IX.)0 ICH-CH@O*This suggestion is supported by the observation that, in the presenceof alkali, a-toxicarol (VI) is equilibrated with the isomeric P-toxicarol,and structure (VIII) assigned to the latter is consistent with theintermediate production of (VII) by enolisation and ring scission.On dehydrogenation, @-toxicarol is converted into dehydro- @-toxicarol (type 11), which differs from dehydro-a-toxicarol.ThiHAWORTE : HETEROCYCLIC COMPOUNDS. 313proves that a- and p-toxicarol contain different ring systems. Furtherreduction of the chromen ring of p-toxicarol yields a dihydro-derivative, which may be converted into a dehydrodihydro-derivative(type 11), and the conversion of the last into the acid (IX), identicalwith the acid obtained similarly from a-toxicarol, completes the proofof the structure (VIII) for p-to~icarol.~~Further investigations on the constituents of derris have revealedthe presence of Z-toxicarol, which is converted into optically inactivea-toxicarol by the action of alkali,31s32 and structures (X) and (XI),the former of which is more consistent with the analytical results,have been suggestedS3 for a substance fist isolated from derris byT. A.B ~ c k l e y . ~ ~RottEerin.-This yellowish-brown phenol, which was isolated in1855 from the Indian colouring matter and anthelmintic drugknown as kamala, has formed the subject of numerous researches,and the molecular formula of rottlerin has been a subject of con-troversy. H. Brockmann and K. Maier 35 have recently suggestedthe C30H2808 formula, which agrees with earlier analytical re~ults.~6Rottlerin contains two ethylenic linkages and five hydroxyl groups,which may be acylated or alkylated. Alkaline fission of rottlerinand tetrahydrorottlerin yields the dihydroxyphenol, rottlerone,and its tetrahydro-derivative respectively, together with C-methyl-phlor~glucinol.~~ The conversion of tetrahydrorottlerone intop-phenylpropionic acid and 5 : 6-dihydroxy-2 : 2-dimethylchromanunder the influence of hot concentrated alkali led to the suggestionof structure (I) or (11) for rottlerone.37 The C-methylphloro-glucinol derivative (111) has been obtained by the action ofdiazoaminobenzene on rottlerin and the structure has been estab-lished ~ynthetically.~~ Analogy with the work of R.Boehm38indicated that the reaction with diazoaminobenzene was due to thepresence of a methylenebisphloroglucinol group and it was inferredthat the C-methylphloroglucinol and rottlerone residues are unitedas in (IV) or (V). Rottlerin is isomerised by boiling with alcohol tois~rottlerin,~~ which contains a single ethylenic bond and does notR. S. Ccthn, R. F. Phipers, and J. J. Boam, J., 1938, 513, 734.** F.Tattersfield and J. J. Martin, J. Soc. Chem. Id., 1937,56,77~.S. H. Harper, Chem. and Ind., 1938, 57, 1609; R. S. Calm and J. J.Boam, J . , 1938, 1818.84 J. SOC. C&m. Id., 1936, 55, 2 8 5 ~ .8s Annalen, 1938,535, 175.86 A. McGookin, F. P. Reed, and A. Robertson, J., 1937, 748. K. S.Narang and B. S. Ray (Current Sci., 1936, 6,608) prefer the C3fH3008 formulaproposed by A. Hoffman and L. Faier (Arch. Phum., 1933, 271, 97).87 A. McGookin, A. B. Percival, and A. Robertson, J . , 1938, 309,88 Anden, 1901,318, 262314 ORGANIC CHEMISTRY.react with diazoaminobenzene. On the basis of structure (V) forrottlerin, formula (VI) was suggested for isorottlerin. A finaldecision between structures (IV) and (V) for rottlerin has not beenmade.Structure (IV) can accommodate two isomeric isorottlerins ;the isolation of one form only does not exclude structure (IV),as steric factors may inhibit the formation of the other isomer.CO*CH:CHPhI(1.1CO*CH:CHPh4-Arylresorcinols of known constitution are readily soluble in alkaliand the sparing solubility of rottlerone has been used as an argumentin favour of (I) and (IV) for rottlerone and rottlerin respectively.37Usnic Acid.-Considerable progress has been made since thechemistry of usnic acid, which occurs in many lichens, was lastreviewed (Ann. Reports, 1933, 30, 224). It is now generally agreedthat the acidicproperties of usnic acid, C,,HI60,, are due to a reactivep-diketonic group. The presence of a coumaran nucleus is indicatedby the frequent isolation of coumaran derivatives from degradationexperiments.Thu8 alkali converts usnic acid into sccetoscetic aciHAWORTH : HETEROCYCLIC COMPOUNDS. 315and usnetic acid (I; R = CH,*CO,H), which is decarboxylated tousnetol (I ; R = Me), and the structure of the latter has been provedYOMe VOMe COMeHO,CI.!JMe C/O\R %!() OH HO le@CHMe O\QO(11.) (111.) (IV. 1by synthesis.39 The orientation of the furan ring of (I; R =CH,*CO,H) is proved by oxidation with hydrogen peroxide to thetribasic acid (I1 ; R = CH2*C02H).40 The isonitroso-derivative of(I1 ; R = CH,*CO,H) was converted into the nitrile (I1 ; R = CN),which yielded the known 3-methylfuran-2-carboxylic acid on decarb-oxylation and subsequent hydrolysis.As usnetic acid differs fromthe synthetic isomer derived by interchanging the Me and CH,*CO,Hgroups in (I ; R = CH,*C02H),41 its structure is rigidly established.More recently, compounds (111) and (IV) have been obtained bydegradation of dihydrousnic acid 42 and the suggested structureshave received synthetical c~nfirmation.~~RCH, CHYOMeCH0 (VIII.) 8 (VII.)When usnic acid is heated with absolute and 96% alcohol at 150",it is converted into acetousnetic ester (V; R = C0,Et) 44 anddecarbousnic acid (V ; R = COCH,) respe~tively.~~~ 46 The latter39 F. H. Curd and A. Robertson, J., 1933, 1174.40 Y. Asahina and M. Yanganita, B~T., 1937,70, 1500.*l H. F. Birch, D. G. Flynn, and A. Robertson, J., 1936, 1834.4a Y. Asahina and M. Yanganita, Ber., 1938,71, 2260.43 M.Yanganitrt, ibid., p. 2269.44 Y. Asahina, M. Yanganita, and S. Mayeda, ibid., 1937, YO, 2462.46 F. H, Curd and A. Robertson, J . , 1937, 894,0. Widman, Annalen, 1900,310,230; 1902,324,13316 ORGANIC CHEMISTRY.p-diketone (V; R = CO*CH,) is dehydrated by sulphuric acid todecarbousnol, which is regarded as (VI ; R = H).43 There can beno steric objection to this novel structure (VI; R = H), whichcorresponds spatially to a phenanthrene system. Interactionbetween the carbonyl group and the furan oxygen atom, similar tothat between the carbonyl and the methylimino-group in the alkaloidcryptopine, may be responsible for the inhibition in decarbousnolof certain @-diketonic properties. Usnolic acid, obtained from usnicacid by isomerisation with sulphuric acid, is a carboxylic acid,which yields decarbousnol (VI; R = H) on decarboxylation, andstructure (VI; R = C0,H) is consistent with the properties ofusnolic acid.The optical inactivity of the compounds discussed above is inagreement with the suggested formula Usnic acid has, however,been obtained in d-, I-, and dl-modifications, and many of theproperties, including the optical activity of the acid, are interpretedsatisfactorily on the basis of the recently introduced 42 structure(VII; R = H).Hydrolysis a t the 11 : 12-bond and subsequentaromatisation to the C-methylphloroglucinol type accounts for theoptically inactive degradation products ; the side chain liberatedduring the hydrolysis may either recombine with the nuclearCOCH, group, as in the formation of (VI), or suffer degradation tostructure (IV) or (I).Dihydrousnic acid is assumed to be thesecondary alcohol produced by reduction of the exposed carbonylgroup in position 3, and formation of (111) and (IV) is preceded bydehydration of this secondary alcoholic group.Structure (VII; R = H) for usnic acid also gives a satisfactoryexplanation of the properties of usnonic acid, Cl,Hl,08, which isprepared by the action of potassium permanganate or lead tetra-acetate on usnic acid.42* 44* 45 Usnonic acid is optically active andas it is reduced by zinc and acetic acid to optically active usnicacid, it is regarded as (VII; R = OH). When heated with alcoholat 150", usnonic acid is converted into optically active hooxy-acetousnetic ester (VIII), but it is reduced by zinc and acetic acid toinactive acetousnetic ester (V; R = C0,Et).Such behaviour isconsistent with structure (VII; R = OH) for usnonic acid; thechinol-benzene rearrangement responsible for the loss of opticalactivity is prevented by the hydroxyl group of (VIII), but replace-ment of the group by hydrogen leads to rapid rearrangement to theinactive aromatic form.(b) Nitrogen Ring Compmndt?.Pyridine and PoZypyridyls.-When pyridine is brominated in thevapour phase at high temperatures and in the presence of a catalystHAWORTH : HETEROCYCLIC COMPOUNDS. 317an abnormal reaction leading to substitution in the a-positionspredominates. Thus a t 300” in the presence of carbon or pumice,3-bromo- and 3 : 5-dibromo-pyridines are obtained in 39% and15% yields respectively, but a t 500”, 48% and 36% yields of 2-bromo- and 2 : 6-dibromo-pyridines respectively are produced.With a ferrous or cuprous bromide catalyst, however, abnormalattack of the 2- and 6-positions occurs a t 3 O O O .l Equally remarkableresults have been obtained in the benzene series and chloro- andbromo-benzene are substituted in the m-positions above 450°.2This work has been extended at the Teddington laboratories andan interesting series of polypyridyls, giving a multitude of metallic(1.1 (11.1 (111.)co-ordination compounds, has been ~btained.~ 2 : 2’-Dipyridyl (I)has been prepared in 70% yields by dehalogenation of 2-bromo-pyridine with copper in boiling diphenyl solution, and under similarconditions a mixture of 2-bromo- and 2 : 6-dibromo-pyridine isconverted into 2 : 2’ : 2”-tripyridyl (11) and 2 : 2’ : 2” : 2”’-tetra-pyridyl (111).This reaction proves the constitution of bases (11)and (111), which, however, may be more conveniently prepared bydehydrogenating pyridine with ferric chloride: and 2 : 2’-dipyridylwith iodine respectively. When 2 : 2’-dipyridyl is brominated at500”, 6-bromo- and 6 : 6’-dibromo-derivatives are obtained, and thestructures of the substitution products are established by theconversion of the former, or a mixture of the latter with 2-bromo-pyridine, into 2 : 2‘ : 2“ : 2”’-tetrapyridyl (111) by dehalogenationwith copper. Similar high-temperature bromination of (11) gave6-bromo- and 6 : 6”-dibromo-tripyridyl, and dehalogenation of theformer yielded 2 : 2‘ : 2” : 2’” : 2”” : 2””’-hexapyridyl, which,however, is best prepared by the action of iodine on 2 : 2’ : 2”-tripyridyl (11).Dehalogenation of a mixture of 6 : 6”-dibromo-2 : 2’ : 2”-tripyridyl and 2-bromopyridine yielded 2 : 2’ : 2“ : 2”’ : 2””-pentapyridyl.G2ucuzidone.-The formation of quinoxaline derivatives fromo - p heny lenediamine and a - ke t o - acids has been investigated .5H. J. den Hertog and J. P. Wibaut, Rec. Trav. chim., 1933, 51, 381, 940.J. P. Wibaut, L. M. F. Lande, and G. Wallagh, ibid., 1933, 52, 794;1937, 56, 65; J. 2. Wibaut and M. von Loon, ibid., 1937, 56, 815.F. H. Burstall, J., 1938, 1662; (Sir) G. T. Morgan and F.H. Burstall, ibid.pp. 1672, 1675.G. T. Morgan and F. H. Burstall, J., 1932, 20; 1934, 1498.6 H. Ohle, Ber., 1934, 67, 155; H. Erlbach and H. Ohle, ibid., p. 555;H. Ohle and W. Gross, ibid., 1935, 68, 2262318 ORGANIU CHEMISTRY.Condensation with a-ketogluconic acid yielded the quinoxaline( I ; R' = OH, R" = CO,H), the structure of which was indicatedby oxidation to 2 : 3-dihydroxyquinoxaline, and by conversion intothe hydrazone (11) by the action of phenylhydrazine. The hydrazone(11) was also obtained from the condensation product of o-phenyl-enediamine and dibromopyruvic acid.In 1887, P. Griess prepared similar quinoxalines from glucoseand o-phenylenediamine. The compounds have been reinvestigatedand it has been shown that fructose, glucose, and sucrose yieldthe quinoxaline (I; R' = H, R" = CH,*OH), but galactose andthe pentoses give benziminazole derivatives.6 The quinoxalineMe(y'1 /\wco v=o RU N A (IV.1I \\ /Jco"/\(111.)derivative ( I ; R' = H, R" = CH,*OH) is degraded to quinoxalineunder the influence of light,' and it is converted into glucazidone(111; R = H), together with a, little hydroxyglucazidone (111;R = OH) by the action of sulphuric acid.6 Glucaaidone (111; R =H(V.) \\)C=oR Ph(VI4 (VIII.)H), unlike (I ; R' = H, R" = CH,*OH), is optically inactive andnon-reducing, and it is oxidised by potassium permanganate toquinoxaline-2-carboxylic acid.With methyl iodide, glucazidone(111; R = H) gives a quaternary salt, which is oxidised by ferri-cyanide to the compound (IV; R = H), and the action of phenyl-6 K.Maurer and B. Schiedt, Ber., 1934, 67, 1980; K. Maurer, B. Schiedt,andH. Schroeter, ibid., 1935, 68, 1716.7 R. Kuhn and F. Bar, ibid., 1934, 67, 898HAWORTH : HETEROUYCLIC COMPOUNDS. 319magnesium bromide on glucazidone leads to a secondary aminewhich is regarded as (V; R = H) because it is oxidised to 3-phenyl-quinoxaline-2-carboxylic acid. The structure (I11 ; R = OH)assigned to hydroxyglucazidone is supported by the conversion ofthe O-methyl ether into (IV; R = OMe) and (V; R = OMe).When the quinoxaline (I ; R‘ = OH, R” = CH,-OH) is treated withsodium methoxide, a red product containing (VI) is obtained.This substance , which gives an acetyl derivative and a semicarbazone,yields quinoxaline-2-carboxylic acid on oxidation , reacts witho-phenylenediamine to give the diquinoxaline (VII), and the anilof (VI) polymerises to a compound for which structure (VIII) issuggested.*Clyoxaline Derivatives.-The early Radziszewski synthesis ofglyoxalines from glyoxal, formaldehyde, and ammonia has beenmodified with great improvement in yield and application.Whena mixture of an cc-hydroxy-aldehyde or -ketone is allowed to reactin the cold with ammonia and an aldehyde in the presence of copperacetate, the glyoxaline derivative is precipitated in excellent yieldas a complex copper salt.g The hydroxy-ketone and aldehydecomponents may be aromatic or aliphatic, and cyclohexanone hasbeen used in the preparation of tetrahydrobenzoglyoxalines.l oWhen fructose is employed as the hydroxy-ketonic component,4-hydroxymethylglyoxaline is obtained, presumably by scission ofthe fructose into trioses, and the observation is of considerableinterest in connection with the biological formation of histidinederivatives. l1Cupric ions also have a marked influence on the yields of benz-iminazoles obtained by the Ladenburg-Hinsberg synthesis fromo-phenylenediamines and aldehydes and extensive applications of themethod are described.12Phenaxine Derivatives.-The physiological activity of phenazinederivatives and the frequent occurrence of the phenazine nucleus inthe structure of the bacterial pigments has led to much activity inthis field.Oxychlororaphine, the yellow pigment of Bacillus chlororaphis,has been shown to be the amide (I; R = CO-NH,) of phenazine-l-carboxylic acid (I; R = C0,H).The phenazine nature of thepigment was first proved by hydrolysis and decarboxylation tophenazine, and the position of the amido-group was established by* K. Maurer and B. Boettger, Ber., 1938,71, 1383, 2092.R. Weidenhagen and R. Herrmann, ibid., 1935, 68, 1953, 2205.lo R. Weidenhagen and H. Wegner, ibid., 1938,71, 2124.l1 Idem, ibid., 1937, 70, 570.l2 R. Weidenhagen, ibid., 1936,59,2263 ; R. Weidenhagen and V. Weededibid., 1938,71,2347320 ORGANIC CHEMISTRY.synthesis, Wohl’s method being used. Nitrobenzene and anthranilicacid were heated with potassium hydroxide; a small yield of(I; R = C0,H) was obtained and the corresponding amide (I;R = CO-NH,) was identical with oxychlororaphine.l3 A secondsynthesis has been effected under milder conditions ; 1 -methyl-1 : 2 : 3 : 4-tetrahydrophenazine, obtained from o-phenylenediamineand 1 -methylcycZohexan-2 : 3-dione, was dehydrogenated to 1 -methylphenazine, which on oxidation gave (I; R = C0,H).14co(1.1 (11.1 (111.) w.13’.Wrede and E. Strack l5 showed that pyocyanine, the bluepigment of B. pyocyuneus, underwent oxidative N-demethylationto l-hydroxyphenazine (I; R = OH) when its alkaline solutionswere exposed to air. Structure (I; R = OH) was established bysynthesis from 3-methoxy-o-benzoquinone and o-phenylenediamine,and subsequent demethylation with hydrobromic acid. Reductionwith zinc and acetic acid converted pyocyanine into a dihydro-derivative, which was regarded as (11) and gave pyocyanine onautoxidation.Pyocyanine was therefore formulated as (111) andit was synthesised by the action of alkalis on l-hydroxyphenazinemethosulphate. Pyocyanine has also been synthesised in 45 yoyields by exposing aqueous solutions of phenazine methosulphate tosunlight for one day.16 The above experiments, however, do notestablish the relative positions of the OH and NH groups in dihydro-phenazine (11), but it has been shown that oxalyl chloride convertsdihydrophenazine into a cyclic compound (IV),17 thus provingstructure (11) for dihydrophenazine and supporting (111) forpyocyanine. The physical properties of the pigment are, however,more in agreement with the dipole modification (V) .The crystalline purple pigment, C,,H804N,, of Chromobacteriumiodinum has been proved to be a phenazine derivative.18 Catalytic13 F. Kogl and J.J. Postowsky, Annulen, 1930, 480, 280; F. Kogl andB. Tonnis, ibid., 1932,497, 265.14 G. R. Clemo and H. McIlwain, J., 1934, 1991.15 2. physiol. Chem., 1925, 142, 803; 1928, 177, 177; 1929, 181,58; Ber.,16 H. McIlwain, J., 1937, 1708. 1’ H. Hillemann, Ber., 1938,71, 46.18 G. R. Clemo and H. McIlwain, J., 1938,479.1929, 62, 2051HAWORTH : HETEROCYCLIC COMPOUNDS. 321reduction yielded a colourless substance, C1,HlOO2N,, which under-went autoxidation to a dihydroxyphenol, C12H802N2 ; this gavephenazine on distillation with zinc. The pigment liberates iodinefrom iodides, the absorption spectrum resembles those of the di-N-oxides prepared by the action of hydrogen peroxide on phenazineeI Me(V- )04 OH(VII.)or 1 -hydroxyphenazine, and structure (VI) has been advanced forthe pigment.The position of the hydroxyl groups is indicated by theformation of metallic lakes from the dihydroxyphenol, Cl,H80,N,.It will be convenient to refer a t this point to a number of observ-ations made in a more general study of phenazine derivatives.1 : 2 : 3 : 4-Tetrahydrophenazine and its derivatives, obtained fromappropriate o-phenylenediamines and cyczohexane- 1 : 2-diones, havebeen reduced either to 1 : 2 : 3 : 4 : 9 : 10-hexahydrophenazine, whichhas been isolated in cis- and trans-forms, or to 1 : 2 : 3 : 4 : 5 : 6 : 7 : 8-octahydr~phenazine.~~ 1 : 2 : 3 : 4-Tetrahydrophenazine andbenzaldehyde condense to give 1 ; 4-dibenzylphenazine : 2o theisomeric dibenzylidene structure is excluded by the stability of theproduct towards oxidising agents.The reactivity of the 1- and4-methylene groups in tetrahydrophenazine has numerous analogiesin heterocyclic chemistry and the activity of tetrahydroacridineand 7-aza-5 : 6-benzohydrindene 21 may be cited as recent examples.Examination of the N-alkylphenszonium salts has shown thatfacile substitution occurs in the 2-, 4-, and 10-positions and thatoxidative N-demethylation, similar to that mentioned above in thecase of pyocyanine, is frequently observed. In absence of airN-methylphenazonium hydroxide solutions decompose into form-aldehyde, phenazine and N-methyl-9 : l0-dihydrophenazineY22but in presence of oxygen the last is partially oxidised and 5%yields of 2-keto-N-methylphenazine (VII) are produced. Theconversion of phenazine methosulphate into pyocyanine, mentionedabove, is accompanied by phenazine and the decomposition providesa further example of N-demethylation and substitution in position4.When treated with potassium cyanide and with sodium sulphite,ln G. R. Clemo and H. McIlwain, J., 1936, 258, 1698.2o H. McIlwain, J., 1937, 1701.21 W. Borsche and R. Manteuffel, Annalen, 1938, 534, 56.z 2 H. McIlwain, J., 1937, 1704.REP.-VOL. XXXV. 322 ORGANIC CHEMISTRY.phenazine methosulphate is converted into compounds regarded as(VIII; R = CN) and (VIII; R = S03Na) respectively.Thesestructures, which postulate substitution in the 2-position, are basedon analogy, but structure (VIII;conversion of the nitrile, by heatR = CN) is consistent with theand subsequent hydrolysis, into(X-1 (XI.)phenazine-2-carboxylic acid. Nuclear methylation , assumed to be inposition 2, is observed during the prolonged action of methyl sulphateon phenazine, and substitution in position 10 is encountered in theformation of 9 : 10-dimethyl-9 : 10-dihydrophenazine together withphenazine when phenazine methiodide is treated with methyl-magnesium iodide.23The reduction of the pale yellow phenazines to the colourless9 : 10-dihydro-compounds and the reverse dehydrogenation proceedthrough intermediate green salts.These salts were investigated byA. Hantzsch, who showed their resemblance to the quinhydrones, butsuggested a unimolecular radical structure. Potentiometric measure-ments show clearly that the reduction of a phenazine salt occursin two stages, and the intermediate green salt may be formulatedas the radical (IX) or its equivalent (X).24 Reduction of phenazinemethosulphate with one atom of hydrogen gives a green sulphate,the cation of which is the radical (X ; with NMe instead of NH).Addition of a second hydrogen atom yields colourless 9-methyl-9 : 10-dihydrophenazine, and the reverse changes may be followediodometri~ally.~3 Bases corresponding to the semiquinonoid salt(X) have been isolated. R = CN), obtainedfrom potassium cyanide and phenazine methosulphate, is autoxi-dised to a blue crystalline radical (XI), and the N-ethylphenazylradical (XI ; with H and E t instead of CN and Me respectively) wasobtained by the action of air on 9-ethyl-9 : 10-dihydrophenazine.In these cases the unimolecular structure was supported by cryoscopicmeasurements.22 In the same way the red salts of pyocyanine arereduced to intermediate green salts possessing a radical cation, andsimilar coloured radicals have been encountered during reduction ofla~toflavin,~~ pyridine alkyl halides,26 and ane~rin.~'The nitrile (VIII;29 H. Hillemann, Ber., 1938, 71, 34.24 L.Michaelis, Chem. Reviews, 1936, 16, 243.25 R. Kuhn and R. Strtjbele, Ber., 1937,70,753.26 P. Karrer and F. Benz, Helv. Chim. Acta, 1936, 19, 1028 ; P.Karrer and2 7 F. Lipmann and G. Perlman, J . Amer. Chem. SOC., 1938, 60, 2574.3'. J. Stare, ibid., 1937, 20,418HAWOR!MX : HETEROCYCLIC COMPOUNDS. 323Crystalline blue compounds known as phenazhydrins 28 areobtained by mixing equimolecular proportions of phenazine anddihydrophenazines. The phenaz-hydrins differ from the phenazylradicals and resemble the quin-hydrones, in dissociating to paleyellow solutions. Molecular-weightdeterminations cannot be made, buta resonance structure (XII) is re-quired to exphin the observationthat the phenazhydrin obtained from phenazine and 1-methyl-9 : 10-dihydrophenazine is identical with that obtainedfrom 1 -methylphenazine and 9 : 10-dihydrophenazine. TheAH\\ H yP"yJ KO d N(XIX.)[ @ 'y' HJr2(XIII.) Me (XIV.)phenazhydrin salts, which yield green solutions, are, however,assigned the radical structure (X), and in agreement with these viewsit was found that phenazine and 9 : 10-dimethyl-9 : 10-dihydro-phenazine, although incapable of forming a phenazhydrin, yieldeda complex green hydrochloride (XIII). The resonance structurefor the phenazhydrins receives indirect support from the recentobservation 29 that quinhydrone is diamagnetic ; this excludes theradical formula but supports the resonance structure for quinhydrone.Reduc-tion with zinc and water produces a green pigment, known aschlororaphine, which is occasionally found in cultures of B. chkro-raphis. This pigment was first regarded as a bimolecular complexof oxychlororaphine with its dihydro-deri~ative,1~ but later theradical structure (XIV) was introduced.= Potentiometric studiesin acid solution 30 support the radical structure of the chlororaphinecation, but the constitution of the base must be regarded as uncertain.Chlororaphine dissociates in neutral solvents ; this does not neces-sarily exclude the radical formula, but the general resemblancewith the quinhydrones and phenazhydrins favours the bimolecularresonance formula for the pigment.Alkaloids.-(a) isoQuinoline alkaloids.Base (I), synthesised by28 G. R. Clemo, and H. McIlwain, J., 1934, 1991; 1935, 738.ao L. Michaelis, M. P. Schilbert, R. K. Riber, J. A. Kuck, and S. Granick,30 B. Elema, Rec. Trav. chim., 1933, 52, 669.The structure of oxychlororaphine has been discussed.J .Amer. Chem. SOC., 1938, 60, 1678324 ORGDIC CHEMISTRY.standard methods, has been resolved and the E-form is identicalwith natural ~alsolidine.~~ Structure (11; R' = R" = H), assignedto corypalline, an alkaloid obtained from Corydalis pallida or theseeds of C. a ~ r e a , ~ ~ n has been confirmed by syntheses of the ethyland the benzyl ether, and acid hydrolysis of the latter yielded aphenol identical with corypalline.M e 0 7 \7H2MeOl/\ /NH /NMe /NMeCH2 € V a C $ H 2 M e O Y CH2 \QH2CHMe CH CHl/O\CH COGR2 R2(111.)l P \ CH COThe investigation of corypalline €orms part of a detailed examin-ation made during the last six years on the alkaloidal constituentsof American species of Dicentra, CorydaEis, and AdE~rnina.3~ Basesof the protopine, berberine, aporphine and narcotine types havebeen isolated, and the use of improved experimental methods hasled not only to the isolation of many known bases but also to thediscovery of some thirty new alkaloids.Protopine is a universalconstituent of these American fumariaceous plants, but its associ-ation with cryptopine and a-aEEo-cryptopine in twelve species has notbeen observed previously in Asiatic varieties ; this may be due partlyto the use of superior methods and not necessarily to alkaloidalvariations within the species. Corydaline and phenolic bases,including corypalmine, isocorypalmine, and scoulerine, have beenisolated from both American and Asiatic Varieties. Tetrahydro-palmatine, which occurs as the d-form in the Asiatic plants, ispresent in 1- and dl-forms in C .aurea 32h and C. caseana 329* 33 and adihydroxyphenol, known as aurotensine, which gives 1 -tetrahydro-palmatine on methylation, is obtained from C. a ~ r e a . ~ ~ p The apor-phine bases include dicentrine, glaucine, corytuberine, corydine,31 E. Spath and F. Dengel, Ber., 1938,71, 113.32 R. H. F. Manske, Canadian J. Res., (a) 1932, 7, 258; (b)ibid., p. 264;(c) 1933, 8, 142; ( d ) ibid., p. 210; ( e ) ibid., p. 404; (f) ibid., p. 407; ( 9 ) ibid.,p. 592; ( h ) 1933, 9, 436; (i) 1934, 10, 521; (j) ibid., p. 765; (k) 1936, 14,325; ( I ) ibid., p. 347; (m) ibid., p. 354; (n) 1937, 15, 159; ( 0 ) ibid., p. 2'74;( p ) ibid., 1938,16, 81 ; (4) ibid., p. 153.33 Private communication from Dr. ManskeHAWORTH : HETEROCYCLIC COMPOUNDS. 326and bulbocapnine, and a new phenolic base, glaucentrine, obtainedfrom three species of American Di~entra,~~g~i$j is proved by methyl-ation to be an O-demethylglaucine.Bases of the narcotine group have not been previously isolatedfrom the Fumuriacece, but the structures of a number of newlydiscovered bases of this type have been established by standardoxidative hydrolysis to phthalaldehydic acids and 1 -hydroxy-2-methyltetrahydroisoquinolines. The structure (111 ; RlRl =R2R2 = CH,O,), derived for the alkaloid bicuculline 32a9 b whichhas been isolated from nine American species, has been confirmed~ynthetically,~~ and bicucine 32h represents the correspondinghydroxy-acid. Adlumine, isolated as d- and Z-forms from Adluminafungosa 32d and C. semperiuens 32f or C. scoulerei 321 respectively, andcorlumine, obtained from C. siberica and C. scoulerei,32z* arediastereoisomeric forms 32e*k of (111; R1 = OMe, R2R2 = CH,02).Corlumidine, 32k* 2, n a phenol present in C. scoulerei, yields corlumineon methylation , and as ethylation and subsequent hydrolysis givethe carbinol base (11; R’ = Et, R” = OH), which was alsoprepared by an unambiguous synthesis, structure (IV) is estab-lished for corlumidine. C ~ r d r a s t i n e , ~ ~ ~ obtained from C. aurea,probably represents the tetramethoxy-analogue (I11 ; R1 = R2 =OMe).The constitutions of other bases isolated from the fumariaceousplants are uncertain, but relationships are frequently apparent.For instance, capaurine and ~apauridine,3~h from C. aurea, areisomeric bases, C,,H,,O,N, containing one hydroxy- and fourmethoxy-groups ; these must be differently oriented, as the alkaloidsyield isomers on methylation. Adl~rnidine,~~d from Adluminafungosa, and ~apnoidine,~~f, 1 from C. scoulerei and C. semperivens, areisomeric methoxyl-free compounds, C,,H,,O,N, probably belongingto the narcotine class. The phenolic dimethoxy-base, ~ u l a r i d i n e , ~ ~ ~from D. cucullaria, its methyl ether, ~ularine,3~~ obtained fromD. cucullaria, eximia, formosa, and oregana, and N-demethyl-cularineF2p from D. eximia, form a related group of bases containingan oxygen atom of unknown function.Structure (V) is consistent with the properties of narcotoline, anew phenolic base isolated from Papaver ~ornniferum,~~ whichyields narcotine on methylation and meconine on heating withacetic anhydride. Anolobine, C,,H,,O,N, a phenolic secondaryamine containing a methylenedioxy-group, has been isolated fromthe bark of Asimina t r i l ~ b a . ~ ~ Methylation and alkali treatment34 P. W. G. Groenewoud and R. Robinson, J . , 1936, 199.35 F. Wrede, Arch. Exp. Path. Pha~m., 1937, 184, 331.36 R. 8. F. Manske, C a d i a n J. Res., 1938,16,76326 ORGANIC CHE116ISTRY.yield an optically inactive methin, C,oH,303N, which gives 4-methoxyphthalic acid on exhaustive methylation and subsequentoxidation. Of the two structures (VI) and (VII; R = H) capableof accounting for these results, the latter is excluded because themethin C20H,,03N differs from that obtained from laureline(VII; R = Me).37CH,/NMel/O\CH CO&eOMeThe structure of colchicine, the alkaloid of the autumn crocus, isstill uncertain. Structures (VIII; R = Me) and (VIII; R = H)were suggested for colchicine and its hydrolysis product, colchiceine ,respectively as a result of the investigations of A. Windaus in 1923.The position of the three methoxyl groups was supported by oxid-ation to trimethoxyphthalic acid, and degradation to 9-methyl-phenanthrene and certain nitrogenous naphthalene derivativesproved that the methyl and the acetamido-group were attached tothe 9- or the 10-position. The orientation of ring C was unsettled,but this is now limited to two possibilities. A. Windaus showed that,when treated with iodine, colchicine was converted into an iodo-phenol regarded as (IX ; R = H), the methyl ether (IX ; R = Me)of which gave an iodomethoxyphthalic acid on oxidation. R.Grewe 38 has synthesised the acid (X), which is identical withthe colchiceine degradation product, and it follows that the iodo-phenol must have either structure (IX; R = H) suggested byA. Windaus, or an alternative derived by interchanging the iodineatom and the hydroxyl group. Structure (VIII ; R = H) representscolchiceine as the hydroxymethylene form of a phenolic aldehydeand on general grounds the aromatic form would be regarded asstable. However, the absorption spectrum of colchiceine (VIII ;R = H) resembles that of colchicine (VIII; R = Me) 39 and it isconcluded that colchiceine exists in the hydroxymethylene form.G. Barger and A. Girardet, Helv. Chim. Actu, 1931,14,481; E. Schittler,ibid., 1932,15, 394.as Rer., 1938, 71, 245. a* I(. Bursian, ibid., p. 745HAWORTH : HETEROCYCLIC COMPOUNDS. 327The appearance of two new bands in the spectrum of the base inammoniacal solution indicates partial transformation to the aromaticstate, but the stability of the hydroxymethylene form and thefailure to obtain an adduct with maleic anhydride are not consistentwith the arrangement of double bonds in structure (VIII).40Me\ / co(VIII.)The structure of cepharanthin, the main bisisoquinoline alkaloidof Stephania cepharuntha, has been limited to the alternatives (I)and (11) .41 Ozonisation of the methin base gave 6-methoxydiphenylCH2 CH2QH QHO N \VH2MoN\ H2g/ Dye H 2 " < O v \ /NMeCH2QHz<$'>cH2 0 ----c\ M e O N /NMe \QH2-0 r/""'vether-3 : 4-dialdehyde and a dibasic dialdehyde, which on Hofmanndegradation yielded trimethylamine and a divinyl-dialdehyde.40 A n arrangement with one ethylenic linkage in ring B and a displacementof either the methyl or the acetamido-group to a neighbouring carbon atomwould overcome this difficulty.4 1 H. Kondo, Y. Yamashita, and I. Keimatsu, J. Pharm. Xoc. Japan, 1934,S4, 108; H. Kondo and I. Keimatsu, ibid., 1935, 55, 25, 63; Ber., 1938, 71,2553328 ORGANIC CHEMISTRY.The latter mas reduced by catalytic and by Clemmensen methodsto a diphenyl ether which wasidentical with a synthetic ether z:())!l H2c<EoMe of structure (111). Cepharanthin(111.) is the first methylenedioxy-representative of the bisisoquin-oline group, but attempted demethylenation led to profounddecomposition and conversion into the trimethoxy-analogue,tetrandin or oxyacanthin O-methyl ether (see Ann. Reports, 1933,30, 246), was not realised.(b) Senecio and Heliotropium alkaloids (see Ann. Reports, 1936,33,377). The table includes some of the numerous alkaloids whichhave been isolated from Senecio and Heliotropium species, togetherwith their alkaline hydrolysis products.EtAlkaloid.Products of hydrolysis.7 * >Acid. Base. Ref.Retrorsine, Cl,H2,0sN Retronecic, ClOHl6O, Retronecine, C,H,,O,N 42, 43Senecionine, C laHI sOllN Senecic, C loH1404 46, 47Platyphylhqe, CiaHa,OaN Platynecic CleH1401 PlatynGiine C 0 N 48Trichodesmme, dl-Lactic icid and Retronecind, C:H:6,0tN 49methyl asobutyl ketoneLasiocarpine, C,,Hg,O,N Angelic and Heliotridine, CllHISOIN 50lasiocarpic, C,H,,O,Jacobine Cl8HS10 N Jaconecic, C,,,Hl8Ol , f 42, 44Seneciphilline, Cls$asO,N Seneciphyllic, C1,HI4O6 I , I S 45Heliotrine, CiaHa,OsN Heliotric, C 8H1604 ,, ,, 51The first five alkaloids are derived from Senecio species, tricho-desmine occurs in Trichodesma incanum and lasiocarpine andheliotrine were isolated from Heliotropium lasiocarpin. The Seneciobases contain eighteen atoms and yield on alkaline hydrolysis anacid containing ten carbon atoms and a dihydroxy-tertiary base,usually retronecine, containing eight carbon atoms. It has beenshown that reduction of retr~necine,~~ platynecine 48 or heliotridine 63yields the same product, CSHISN, known as heliotridan (11), anda relationship between the Senecio and the Heliotropium bases istherefore established. Reduction of the methin base of (I) gave apyrrolidine derivative (11),54 which was converted into the base42 R. H. F. Manske, Canadian J . Res., 1931,5,664.43 G. Barger, T. R. Seshadri, H. E. Watt, and T. Yabuta, J., 1935, 11.44 G. Barger and J. J. Blackie, J., 1937, 684.45 R. A. Konovalova and A. P. OrBkhof, Bull. SOC. chirn., 1937, 4, 2037.46 G. Barger and J. J. Blackie, J., 1936, 743.4 7 R. H. F. Manske, Canadian J . Res., 1936,14,8.4 8 R. A. Konovalova, Bull. Acud. Sci. U.R.S.S., 1937, 961.49 G. P. Menschikov, Ber., 1935, 68, 2039.60 Idem, ibid., p. 1110.51 Idem, Bw., 1932, 65, 974.6% L. Konovalova and A. P. OrBkhof, Bull. SOC. chim., 1937, 4, 1285.53 G. P. Menschikov, Ber., 1933, 66, 875; 1935, 68, 1051.64 Idem, Ber., 1936, 68, 1555HAWOR!FE : HETEROCYCLIC COMPOUNDS. 329(1 11) by Hofmann degradation and subsequent reduction.55 ThisCH,-CH,*CH,*CH*CHMe*CH,*CH,NMe,(111.)1 5 (fj CH,-CH,*CH,Med-(1.1 (11.)tertiary base (111) was also obtained by reduction of the methinbase prepared from (IV), which was synthesised as follows : 56MeO*[CH2],*I + CHMeEt.CN A(1) (2) Redn. HBr of oxime E t M e H ( + ,Meof CH ,I,*CO*CH MeEt(IV.) MeN-The tertiary base (111) must be derived from either (11) or (IV) and,as the pyrrolidine derivative (11) differs from the synthetical base(IV), its structure and that of heliotridan (I) are established. Asynthesis of dl-heliotridan has also been reported. 55 Consequentlyheliotrin and retronecine are monoethylenic dihydroxy-derivativesof (I) differing in orientation of the hydroxyl groups and/or ethyleniclinkage, and platynecine corresponds to a saturated dihydroxy-derivative of (I).The structures of the acids obtained by hydrolysis of the alkaloidsare not settled. Although the majority contain ten carbon atoms,they exhibit great variation in structure. Aliphatic, cyclic, saturatedand unsaturated representatives have been obtained, and hydroxyl,methoxyl, carbonyl and lactonic groups have been detected. Thefrequent occurrence of the C,, acids, the isolation of angelic acidfrom lasiocarpine, and the presence of C-methyl groups 46 suggesta terpenoid structure for the acids. In the alkaloids, the acidicfragment is combined by an ester linkage with the dihydroxy-base ; inheliotrin and the Senecio bases one hydroxyl group only is esterified,but lasiocarpine and trichodesmine may contain two ester linkages.R. D. H.66 G. P. Menschikov, Bull. A d . Sci. U.R.S.S., 1937, 1035.6 6 Idem, J. Gen. Chem. Rzcrrs&z, 1937, '7, 1632

ISSN:0365-6217    

DOI:10.1039/AR9383500204

出版商:RSC    

年代:1938

数据来源: RSC

摘要:

BIOCHEMISTRY.AN^ BIOCHEMISTRY.Introduction.INVESTIGATIONS in biochemistry cover such a wide field that itcan invariably be said, with truth, that considerable progress hasbeen made.As in past years, vitamins have been dealt with at some length :the progress is so marked that it is impossible to neglect the subject.In particular might be mentioned the identification and synthesisof vitamin E, the work on nicotinic acid, and the rapid advance ininvestigations on the other components of B, and on vitamin K.Valuable contributions to chemical methods for determiningcertain vitamins are discussed in another section. Subjects whichhave not received much attention, certainly during the past two years,include the hormones, enzymes,l the chemistry of micro-organisms,2carcinogenic substance^,^ chemical changes in muscle, yeast meta-bolism, and biological oxidations and reductions ; in all thesefields important advances have been made.Amongst other subjectswhich offer special interest to biochemists are the proteins : thisimportant field is adequately dealt with in another section of theseReports (p. 366).The use of isotopes in the study of metabolism is in its infancy,but sufficient has already been accomplished to show that themethod will prove of real value. The success of the chemicalstudies on heparin has led to important clinical applications,and the work done during the past year on sulphanilamide andrelated drugs has more than justified the statement made last yearthat the discovery of these drugs was “ probably the most importantadvance in chemotherapy for many years.”The Vitamins.The vitamin story may now be regarded as approaching the endof what is possibly the most important chapter, that dealing with1 Reviews of the recent work on several of the enzymes will be found inErgebn. Enzymforsch., 1938,7, and in earlier volumes.* E.g., the many papers by H. Raistrick and his colleagues (in the Biochem.J., etc.) ; cf.also a chaper by H. Raistrick in “ Perspectives in Biochemistry ”(Camb. Univ. Press, 1937).8 An interesting account of some of the recent work is given by E. C. Dodds(Lancet, 1938,235, 351)WORMALL: AN=. 331the identification of those vitamins which are required for theprevention of certain widespread deficiency diseases in man.Thisstatement does not suggest that those vitamins which have not yetsuccumbed to intensive chemical attack are not needed by man, nordoes it mean that all the vitamins required by man have been dis-covered. The list of “ recognised ” vitamins five years hence willprobably be considerably longer than the present-day list, but inview of the very general character of investigations on this subjectit will be rather surprising if some serious vitamin deficiency diseasehas so far been missed. In dealing with the vitamins, experiencehas shown that it is unwise to make dogmatic statements about thenumber of possible vitamins, or to accept or discredit, withoutallowing sufficient time for an adequate test, any new observation.Furthermore, we must be prepared for discoveries showing thattwo or more closely related substances possess similar vitaminactivities, as has already occurred with vitamins A, D and E.The present-day knowledge of the chemical properties of thevitamins cannot be indicated more clearly than by a list of thosevitamins which are now available as synthetic products.In thislist are vitamin B,, two members of the B,-complex (riboflavin andnicotinic acid), C, E and possibly A. In addition, D is readilyavailable commercially as a crystalline product and crystalline B,(another member of the B,-complex) has recently been isolated.Perhaps one of the most valuable publications on vitaminsduring the past year is the first volume of a series of monographsby L.J. Harris.4Vitamin A (Axerophthol 5).-The nature and distribution of thesuggested second factor (A,) has aroused considerable interest.J. R. Edisbury, R. A. Morton, G. W. Simpkins, and J. A. Lovernhave determined the vitamin A content of various tissues of rabbitsand many kinds of fish, and have attempted to correlate the resultswith possible functions of this vitamin; as yet, no definite con-clusions as to the participation of the vitamin in fat exchange orassimilation can be reached. Factor A, tends to replace vitamin Ain freshwater fish, but does not seem to occur in mammals. Similarstudies on Russian fish have been made by A. E. Gillam, I. M.Heilbron, W. E. Jones, and E. Lederer,‘ who have also tried toseparate and identify the 6930 A.chromogen (A,). Although thisattempt was not successful, they obtained evidence that this factor4 “ Vitamins and Vitamin Deficiencies.” Vol. 1. Historical and Intro-ductory. Vitamin B, and Beri-beri. L. J. Harris (J. and A. Churchill), 1938.The name suggested by P. Kmer (cf. H. v. Euler, P. Karrer, andU. Solmssen, HeZv. Chim. Acta, 1938,21, 211).Biochem. J., 1938,32, 118. Bid., p. 406332 BIOCHEMISTRY.is the C,, honiologue of vitamin A, with six ethylenic linkages.They suggest formula (I) for factor A,.8Biological tests suggest that A, contributes to the total vitamin Aactivity of A-concentrates, but more extensive investigation will beneeded before this factor is accepted as vitamin A,.8 E. Ledererand F. H. Rathmann9 have shown that A, gives with antimonytrichloride a second absorption band a t 6500 A.and that withconcentrates rich in A, nearly half the absorption a t 6200 A. is dueto overlapping, necessitating a redetermination of the A, /A2ratios. These authors have also shown that the rat and frog canabsorb A, from the intestine and can accumulate it in the liver.A, appears to be, therefore, a specific product of the liver metabolismof certain species of freshwater fish, and its absence from the liverof mammals can be attributed to its absence from their food. Thisconclusion receives support from the investigations of A. E. Gillam,lowho has shown that A, is absent from the livers of mammals andbirds, but present in the livers of animals known to feed on fish,and in the liver of a rat fed with a concentrate containing A,.Up tothe present, therefore, there is no indication that A,, although itmight have a biological value equal to A,, plays any significant r6Iein mammalian nutrition.T. Thorbjarnarson and J. C. Drummond 11 have found that thestorage of vitamin A in the liver is facilitated by the presence offat in the diet. The administration of choline, which preventsdeposition of liver-fat, causes a low storage of vitamin A. Fatleaving the liver may take vitamin A with it, but the retention offat does not necessarily mean the retention of the vitamin. Theadministration of large doses of A to rats and guinea-pigs causes nosymptoms of true hypervitaminosis according to I. Ikegaki,12 and* The results of H.v. Euler, P. Karrer, and U. Solmssen (Helv. Chim.Acta, 1938, 21, 211) and of P. Karrer, A. Ruegger, and A. Geiger (ibid.,p. 1171) suggest, however, that some modification of this formula may benecessary. With Karrer's classification, formula, (I) represents p-apa-6-c aro t inol .Compt. rend., 1938,206,781 ; Biochem. J . , 1938,32,1252.10 Biochem. J., 1938, 32, 1496.l1 Ibid., p. 5 .12 2. Vitarninforsch., 1938, 7, 113WORMAILL: ANIMAL. 333the vitamin is only toxic to rats if given in doses in excess of 100,000I.U. per day.13Several investigators have studied the prevalence of vitamin A-deficiency in man, using methods which vary from the determinationof the vitamin in the serum and urine to a measurement of darkadaptation.The last-named method is based on the finding thatindividuals who have a, partial or complete deficiency of this vitaminshow some degree of " night-blindness " after exposure to brightlight, and several modifications of the original method of P. C. Jeansand 7;. Zentmire 14 have been described. Most of the investigationshave reported a considerable amount of vitamin A-deficiencyamongst the poorer populations even in the countries where thestandard of nutrition is supposed to be high. M. K. Maitra and L. J.Harris l5 have shown, for example, that 22-36% of elementaryschool-children in the east of London and in Cambridge were in the" definitely subnormal " group, whereas none of the boys at a publicschool was in this category. When treated with vitamin A for fourweeks, 39 out of 40 in the former group became normal or showedimprovement, whereas untreated controls remained subnormal.H. Jeghers 16 has found partial vitamin A-deficiency not uncommonin adults, and several other authors have reported on this method andthe results of their surveys.17Crystalline ant hraquinone -2 - car box ylic and 2-napht hoic esters ofvitamin A, prepared by T.H. Mead,l* have been tested biologicallyby K. H. Coward and S. W. E'. Underhill.lg From the potency ofthese esters, the potency of vitamin A alcohol is calculated to be3.32 x lo6 I.U. per g., i.e., twice the activity of the internationalstandard of p-carotene (1.667 x lo6 units per g.). These resultssuggest that one molecule of p-carotene is converted into onemolecule of vitamin A in the animal body, and not two as hasgenerdly been supposed.Vitamin B, (Aneurin or Thiamin) .-Interesting accounts of thechemistry and the biological significance of this vitamin are given byla E.B. Vedder and C. Rosenberg, J. Nutrition, 1938,16,57.l4 J . Amer. Med. ASSOC., 1934,102,892 ; cf. also P. C. Jeans, E. Blanchard,l5 Lancet, 1937, 233, 1009; cf. also M. A. Abbasy and L. J. Harris, Chem.l6 Ann. Intern. Med., 1937,10, 1304; J . Amer. Med. ASSOG., 1937,109, 756.l7 J. R. Mutch and H. D. Griffith, Brit. Med. J . , 1937, ii, 565; B. L. Isaacs,F. T. J u g , and A. C. Ivy, J . Amer. Med. ASSOC., 1938, 111, 777; C. Schuckand W. 0. Miller, Arch. Intern. Med., 1938,61, 910; N. T. Gridgeman and H.Wilkinson, Lancet, 1938,234,905; C.E. Palmer, Amer. J . Publ. Health, 1938,28, 309.and Z. Zentmire, ibid., 1937, 108, 451.and Ind., 1938,57,86 ; B. Ahmad and L. J. Harris, ibid., p. 1190.Chem. and Ind., 1938, 57, 1189.Ibid., p. 1189334 BIOCHEMISTRY.R. R. Williams,2* whose brilliant work leading to the establishmentof the formula and to the synthesis of this vitamin has been dealtwith in previous Reports. These papers and the very comprehensivereview by L. J. Harris will furnish the most exacting reader with afull account of the work on the anti-neuritic vitamin up to about themiddle of 1938, and will indicate the trend of modern views on therelationship between this vitamin and various enzymic systemsconcerned with carbohydrate metabolism.The full fruition of thechemical attacks on B, appears to be indicated by the recentadoption of crystalline vitamin B, hydrochloride as the internationalstandard, in place of the adsorbate hitherto used.The study of the relationship between B, and co-carboxylase,stimulated by the recognition of the latter as the pyrophosphoricester of vitamin B1,21 has been continued by many investigators.The synthesis of co-carboxylase from the vitamin by the action ofyeast, animal tissues or by simple chemical processes is effectedquite readily,22 and there is much support for the view that in theanimal body vitamin B, may play a r6le similar to that of co-carboxylase in yeast.23 The conversion of the vitamin into co-carboxylase by liver slices or (‘ brei ” is at an optimum at about pH8.5 and the synthesis is inhibited by iodoacetic acid but is littleaffected by fluoride.24 The results of S.Ochoa and R. A. Peters 25confirm the view that co-carboxylase is a very significant form ofvitamin B, in animal tissues; in some, such as brain and liver, itappears to be predominant. These authors find that the adminis-tration of B, leads to an immediate accumulation of both B, and itspyrophosphoric ester in the liver, and they make the interestingobservation that this is the first time that the liver has been broughtinto prominence in the metabolism of this vitamin.The importance of the vitamin in carbohydrate metabolism asa component of the pyruvic acid oxidation system is fully reviewedby R. A.Peters,26 and B. S. Platt 27 gives an account of the studies20 Science, 1938, 87, 559; J. Amer. Med. Assoc., 1938,110, 727.21 K. Lohmann and P. Schuster, Naturwiss., 1937, 25, 26; Biochem. Z.,1937, 294, 188.2s H. W. Kinnersley and R. A. Peters, Chem. and Ind., 1937, 56, 447; H.von Euler and R. Vestin, Naturwiss., 1937, 25, 416; H. Tauber, Science, 1937,86, 180; J. Amer. Chem. Soc., 1938,60,730; J . Biol. Chem., 1938,123,499;125, 191; M. A. Lipschitz, V. R. Potter, and C. A. Elvehjem, Biochem. J.,1938,32,474; H. W. Kinnersley and R. A. Peters, ibid., p. 697.23 Cf. discussion by L. J. Harris, ref. (4).zil S. Ochoa and R. A. Peters, Nature, 1938,142, 356.25 Chem. and Ind., 1938,57,471; Biochena. J . , 1938,32,1501.Trans. Roy. Soc. !Prop. Med.Hyg., 1938, 31, 483.27 l b i d . , p. 493WORMALL : ANIMAL. 335which have shown that in beri-beri there is an increase in the bloodpyruvic acid. The action of the vitamin is not confined to carbo-hydrate metabolism, but also concerns fat metabolism, possiblyby an indirect process. E. W. McHenry 28 has shown, for example,that B, and choline have a complementary effect in increasing theweights of young rats, and that B, administered to rats maintainedon a low-choline diet causes a marked increase in liver fat. Inthe rat and pigeon, B, causes fat formation from carbohydrate,apparently in the liver, and subsequently choline, flavin and B,promote fat migration from the liver to the depots.29Several authors have made determinations of the amount ofvitamin B, in the serum or the urine, and have attempted to assessthe clinical significance of the results. E.N. Rowlands and J. F.Wilkinson30 have, for example, used a modification of the methodof W. H. Schopfer 31 (which involves the use of Phycomyces blakes-leeanus) for determining the blood vitamin B,, and have reportedgross deficiencies in alcoholic neuritis, nutritional neuritis, scurvyand “ malnutrition.” L. J. Harris, P. C. Leong, and C. C. Ungley 32have continued their study of the excretion of B, in the urine, asdetermined by the “ bradycardia ” method, and conclude that theurinary excretion furnishes a useful guide to the state of nutritionof the subject with regard to this vitamin. These authors havealso alluded to “ conditioned deficiency ” of vitamin B, as a causeof polyneuritis in various diseases, such conditioned deficiency beingdiagnosed by urine tests.A carbohydrate-tolerance test for B, hasrecently been devised by G. G. Banerji and L. J. andit seems possible that this test may be of considerable valuefor surveys of the level of nutrition of large groups of thepopulation.Vitamin B,-Complex.-Several vitamins of the B-group have beendiscovered in recent years, and much confusion has arisen, and stillexists, with regard to the nomenclature. Following the separationand identification of B,, the other members of this ill-assortedfamily have been given various designations. Least confusionis probably caused when the term B, is used for the B groupminus B,.Under this classification there are now at least foures Biochem. J., 1937, 31, 1616; J. Physiol., 1937, 89, 287; Science, 1937,86, 200.2Q Private communication from Dr. E. W. McHenry.** Brit. Med. J . , 1938, ii, 878,1110; cf., however, criticism by H. M. Sinclair,81 Cf. Ann. Reports, 1937, 34, 401.38 Lancet, 1938, 234, 539.33 Chtm. and Ind.¶ 1938,57, 1190.ibid., pp. 1060, 1111.For the other literature on this subject, seeref. (4)336 BIOCHEMISTRY.different well-characterised vitamins, of which the first two havebeen identified and synthesised :(1) Riboflavin (a more satisfactory name than lactoflavin).(2) Nicotinic acid (the pellagra-preventing or anti-black-tongue(3) Vitamin B, (the rat-dermatitis preventing factor).(4) The chick-antidermatitis factor.The filtrate factor34 may be identical with (4) and the yeasteluate factor with B6,35 but the above list is probably by no meanscomplete.Pigeons require factors which have been designated B, andB, (though these may not differ from the " recognised " componentsof the B,-complex), and certain animal species may need factorsother than those listed above. Little is known, however, about thechemical properties of these additional factors.The discovery, reported last year, that nicotinic acid ornicotinamide will cure black-tongue in dogs 36 and pellagra in m2un,37has been followed by many confirmatory reports.38 Spectacularresults follow the administration, orally or by injection, of nicotinicacid or nicotinamide to patients suffering from pellagra, and similartreatment cures pellagra in monkeys 39 or in pigs.4o The dramaticresults which follow the addition of 60 mg.of nicotinic acid dailyfor three months to the diet of pigs suffering from pig-dermatitisare beautifully shown in photographs presented by H. Chick, T. F.Macrae, A. J. P. Martin, and C . J. Martin.40The observation*l that nicotinic acid (or some substance whichgives a similar colour reaction) is absent from the urine of pellagrins,34 Cf. Ann. Reports, 1937, 34, 404.a6 C. E. Edgar, M. M. El Sadr, and T. F. Macrae, Chem. and Ind., 1938,57,1111; Biochem. J . , 1938,32, 2200.36 C. A. Elvehjem, R. J. Madden, F. M. Strong, and D. W. Woolley, J .Amer. Chem. SOC., 1937, 59, 1767; J . Biol. Chem., 1938, 123, 137; cf.alsoW. J. Dann and Y . Subbarow, J . Nutrition, 1938,16,183.37 P. J. Fouts, 0. M. Helmer, S. Lepkovsky, and T. H. Jukes, Proc. SOC.Exp. Biol. Med., 1937, 37, 405; L. J. Harris and A. Hassan, Nature, 1937,140, 1070; D. T. Smith, J. M. Ruffin, and S . G. Smith, J . Amer. Med. ASSOC.,1937,109,2054.3 8 T. D. Spies, Lancet, 1938, 234, 252; T. D. Spies, C. Cooper, and M. A.Blankenhorn, J . Amer. Med. Assoc., 1938,110, 622 ; T. D. Spies, W. B. Bean,and R. E. Stone, ibid., 1938,111,584 (who report that " they have not observeda case of acute pellagra which has not responded promptly t o nicotinic acid " ) ;cf. also ref. (42) ; R. S. Mathews, ibid., p. 1148; A. C. Alport, P. Ghdioungui,and G. H m a , Lancet, 1938,235, 1460.factor).3B L.J. Harris, Nature, 1937,140, 1070; Biochem. J . , 1938,32, 1479.40 Ibid., pp. 10, 844.4 1 S. P. Vilter, T. D. Spies, and A. P. Mathews, J . Amer. Chem. SOC., 1938,60, 731WORMALL : ANIMAL. 337but is excreted by normal individuals, and by pellagrins whoreceive nicotinic acid or amide, may be taken as support, if this isneeded, for the view that pellagra is associated with a deficiency ofthis acid. As a potent therapeutic agent for treatment of pellagra,nicotinic acid is certain to be of inestimable value, but there can beno doubt that pellagra-producing diets must often be deficient in anumber of other ~ubstances.~~ Furthermore, it is generally agreedthat where the diet contains a reasonable proportion of dairyproduce and meat, there is no pellagra, and, to quote the words ofJ.C. Drumrnond,43 this problem " is not a question of nicotinic acid ;it is simply one of 2. s. d."Many authors have tested the pellagra or black-tongue curingpowers of substances related to nicotinic acid. p-Aminopyridineis ineffective,44 and it appears probable that only those pyridinederivatives which are capable of oxidative or hydrolytic conver-sion into nicotinic acid (or amide) in the body are active in thisrespect.45Vitamin B, (for which the name adermin has been suggested) hasrecently been obtained crystalline 46 and has been given the empiricalformula C8H,,0,NCI. The chick antidermatitis factor is acidic andcontains one or more hydroxyl or amino-gr~ups.~'Vitamin C (Ascorbic Acid).-The urinary excretion of this vitaminby the normal individual and by patients suffering from variousdiseases has been studied by many authors Although the suggestionthat there may be a relationship between a deficiency of this vitaminand an increased tendency t o certain infections 48 has been thesubject of criticism,49 there is a considerable amount of evidencethat in some infections the ascorbic acid excretion is subnormal andthat the patients are " unsaturated " with regard to this vitamin.4 2 Cf.J. M. Grant, E. Zschiesche, and T. D. Spies, Lancet, 1938, 234, 939.4 3 In a preface to " Science and Nutrition," A. L. Bacharach (Watts andCo.), London, 1938.44 F. M. Strong, R. J. Madden, and C. A. Elvehjem, J. Amer. Chern. SOC.,1938, 60, 2564; Y .Subbarow and W. J. Dann, ibid., p. 2565. 8-Amino-pyridine is also without action in monkey pellagra (private communicationfrom Dr. L. J. Harris).46 D. W. Woolley, F. M. Strong, R. J. Madden, and C. A. Elvehjem,J . B i d . Chern., 1938, 124, 715.46 P. Gyorgy, J . Amer. Chem. SOC., 1938,60, 953; R . Kuhn and G. Wendt,Ber., 1938,71, 780, 1118; J. C. Keresztesy and J. R. Stevens, J . Amer. Chem.SOC., 1938,60,1267 ; A. Ichiba and I(. Michi (cited from P. W. Wiardi, Nature,1938,142, 1158).*' D. W. Woolley, H. A. Waisman, 0. Mickelsen, and C. A. Elvehjem,J . Biol. Chem., 1938, 125, 716.4 8 Cf. Ann. Reports, 1937, 34, 407.49 Cf. review by L. G. Parsons, Lancet, 1938, 234, 123338 BIOCHEMISTRY.In diseases such as pulmonary tuberculosis, osteomyelitis, rheuma-toid arthritis, rheumatic fever, whooping cough and sometimes indiabetes there is often a hypovitaminosis C , as shown by a diminishedurinary excretion and a delay in the excretion of ascorbic acidadded to the diet.Whether this deficiency is due to an increasedrate of metabolism concurrent with the pyrexia, a deficiency in thediet, a lowered renal threshold (to account for the low plasma-ascorbic acid), a decreased absorption of the vitamin, an increasedutiliaation of the vitamin by the leucocytes and other cells, or tosome cause unrelated to the infection, there appears to be justifi-cation for the addition of suitable sources of vitamin C to patientssuffering from, and convalescing after, diseases of this type.The possible significance of ascorbic acid in immunologicalreactions has received much attention, but the reports made areoften of a conflicting nature.It is perhaps too early to attemptto reach any definite conclusions as to any possible antitoxic actionof the vitamin, the alleged protective action against anaphylacticshock, or the reported stimulation, by the vitamin, of specificantibody production. The view that vitamin C has a protectiveaction against diphtheria toxin has, however, been contested byS. S. Zi1va.mVitumin E (a-, p- and y-Tompherob).-This vitamin has nowsuccumbed to the intensive chemical attack made by investigatorsin several laboratories, and work carried out during the past twelvemonths has added the last chapter to its story.There is now almostunanimous agreement as to the structure of a- and p-tocopherols(C29H5002 and C,8HasOz respectively), two substances with vitaminE activity which can be separated from the oils of wheat-germ, rice-germ and cotton-seed. The fertility of vitamin E-deficient rats isrestored by the addition of 3 mg. of the a-compound or 5 mg. of thep-compound to the diet.51The observation of E. Fernholz 62 that x-tocopherol yields duro-quinol when heated and the similar work of W. John 53 have beenfollowed by the suggestion, made independently and practicallysimultaneously by four groups of workers, that the tocopherols arecoumarans or chromans with side chains.s4 Synthesis of cc-toco-61 A. L. Bacharach (Nature, 1938,142, 35), using the purified allophanates,records 1-2 and 1.9 mg. for the mean fertility doses of a- and ,%tocopherolrespectively for rats.Brit. J .Exp. Path., 1937, 18, 449.62 J . Amer. Chem. SOC., 1937,59, 1164.aa 8. physiol. Chem., 1937, 250, 11.54 E. Fernholz, J. Amer. Chem. SOC., 1938, 60, 700; W. John, 8. physiol.Chem., 1938, 252, 222; F. Bergel, A. R. Todd, and T. S. Work, J., 1938,253 ; F. Bergel, A. Jacob, A. R. Todd, and T. S. Work, Nature, 1938,141,646 ;P. Karrer, H. Salomon, and H. Fritzsche, Helv. Chim. Acta, 1938, 21, 309WORMALL : ANIMAL. 339pherol has been effected by different methods by P. Kaxrer, H.Fritzsche, B. H. Ringier, and H. S a l ~ m o n , ~ ~ F. Bergel, A. Jacob,A. R. Todd, and T. S. Work,56 and L. I. Smith, H. E. Ungnade,and W.W. Pri~hard,~' and the products shown to be identical, inchemical and biological tests, with the natural product.58 Prom thisevidence a-tocopherol was given formula (11) or (111), i.e., it has acoumaran or chroman structure, but it is now generally acceptedthat the chroman structure (111) is the correct one.CH3QH2 QH3CH2-CH*QH2QH2 p 3 3(11.)CH2-CHCH2-CH,*CH,-CH( CH,)H3C CH,(111.) CH,-CH*QH,p 2 p%CH2-CH*CH2*CH,*CH2CH ( CH3),p-Tocopherol differs from the a-compound in having only twomethyl groups in the aromatic nucleus, and 3'. Bergel, A. M.Copping, A. Jacob, A. R. Todd, and T. S. Work 59 have recentlyobtained a synthetic product, from m-xyloquinol and phytol, whichappears to be isomeric or identical with @-tocopherol.60 The puretocopherols isolated from wheat-germ-oil, etc., account for only afraction of the total vitamin E activity of the oil.This may be66 Helv. Chim. Acta., 1938, 21, 520, 820; Nature, 1938, 141, 1057;P. Karrer and V . Demole, Schweiz. med. Woch., 1938, 68, 954.66 Nature, 1938, 142, 36.5 7 Science, 1938, 88, 37.6 8 The biological tests on the product obtained by Smith and his colleaguoswere made by H. M. Evans, G. A. Emerson, and 0. H. Emerson (Science, 1938,88, 38).68 J . , 1938, 1382.6o The positions of the two methyl groups in the aromatic nucleus of p-tocopherol have not yet been established. In addition to the isomermentioned, the other two have now been synthesised, from phytol and o-and p-xyloquinol, and found to have about the same activity as 6-tocopherol(private communication from Prof.A. R. Todd). P. Karrer and H. Fritzsche(Helv. Chim. Acta, 1938, 21, 1234) have also recently synthesised the threepossible ,9-tocopherols, and found all three active340 BIOCHEMISTRY.due to loss during the preparation or to the existence of othertocopherols or related compounds with anti-sterility properties,and in this connection it would be useful to have more informationabout y-tocopherol, which according to 0. H. Emerson, G. A.Emerson, A. Mohammad, and H. M. Evans 6 l has an activity aboutone-half or one-third that of a-tocopherol.The considerable loss of vitamin E during saponification is referredt o by A. R. Moss and 5. C. DrummondYg2 who have recently describeda new method for the isolation of a- and p-tocopherols, involvingadsorption by alumina from solution in light petroleum; by thismethod, 2 kg.of wheat-germ oil yielded 1 g. of a-tocopherol allo-phanate and 0-75 g. of p-tocopherol allophanate.Space will not permit a description of the recent work on thephysiological activity of vitamin E, but if this were possible, littlecould be added to the excellent account given by A. L. B a ~ h a r a c h . ~ ~This author reviews the subject of the relationship between vitaminE and the gonads and the anterior pituitary, and investigationsdealing with the use of the vitamin in the treatment of sterility inwomen and for veterinary purposes. The same author and hiscolleagues G4 have made valuable contributions in connection withthe biological assay of this vitamin, and the relationship betweendosage and response to vitamin E.65Vitamin K.-Satisfactory evidence of a true vitamin deficiencyin chickens, leading to a lengthening of the blood-clotting time,was presented in 1935 by H.Dam66 and independently by H. J.Almquist and E. L. R. Stokstad.67 An account of this work andsom2 of the earlier observations which led to the recognition ofvitamin K were given in these Reports for 1936.68 This fat-solublevitamin is found in green leafy tissue (alfalfa, cabbage, spinach,etc.) and in moderate amounts in tomato, hempseed and soya-bean61 J . Biol. Chem., 1937-8,122, 99.62 Biochem. J., 1938, 32, 1953. A similar method was previously describedin an I. G. Patent (see footnote to this paper by A.R. Moss and J. C.Drummond).133 Nutrit. Abs. Reu., 1938, 7, 811; cf. also H. A. Mattill, J. Amer. Med.ASSOC., 1938, 110, 1831. For work on the effect of vitamin E deficiency onthe length of gestation and on lactation, see M. M. 0. Bmrie (Biochem. J.,1938, 32, 1467, 1474).64 A. L. Bacharach, E. Allchorne, and H. E. Glynn, Biochem. J., 1937,31, 2287 ; A. L. Bacharach, Nature, 1938,142, 35, 675 ; A. L. Bacharach andE. Allchorne, Biochem. J., 1938, 32, 1298; cf. also K. E. Mason and W. L.Bryan, ibid., p. 1785.65 A. L. Bacharach, ibid., p. 2017.6 6 Nature, 1935, 135, 652; Biochem. J., 1935, 29, 1273.6 7 Nature, 1935, 136, 31; J . Biol. Chem., 1935, 111, 105.6 8 Ann. Reports, 1936, 33, 394WORMALL : ANIMAL. 341oil? Hog-liver fat is a good source, but the liver of normal chickscontains very little.70 A deficiency of the vitamin in the diet ofchickens leads to subcutaneous and intramuscular hzemorrhage,with prolongation of the clotting time of the blood. Intravenousinjection of the vitamin restores the clotting time to normal within4-6 h0urs,~1 but the vitamin has no in vitro action on blood from K-avitaminous chicks.The ingestion of large doses does not renderthe coagulability of the blood " supernormal." 72 The precise r6le ofthe vitamin in the blood-clotting mechanism is at present not known,but the view that it is a component of prothrombin will probablyhave to be abandoned, since it has been shown that prothrombinpreparations may have little vitamin K activity.71 Erosions andlesions of the chick gizzard lining have been associated with K-deficiency, but more recent work has shown that this defect isrelated to a deficiency of certain components of the bile, notablycholic acid, '3Considerable progress has been made during the past two years byH.J. Almquist and by H. Dam and their colleagues in efforts toisolate the pure vitamin. Highly active concentrates are viscousoils, though a colourless crystalline solid has been obtained atlow temperat~re,~~ and more recently S. A. Thayer, D. W. Mac-Corquodale, S. B. Binkley, and E. A. Doisy claim to have isolatedthe vitamin as a crystalline solid, m. p. 69". The chemical andphysical properties of this vitamin have been summarised recentlyby A.A. Klose, H. J. Almquist, and E. Me~chi,~6 who conclude thatthey are consistent with those of a complex low-melting unsaturatedhydrocarbon containing an aromatic grouping. The rapid progressmade, and the recent improvements effected in the assay of the~itarnin,~7 leave little doubt that the structure of this substance (orsubstances) will soon be elucidated.The significance of the vitamin for mammals is not so clearlyestablished, but H. Dam and J. Glavind ' 8 report a mild K-avi-gs For a list of the principal sources of this vitamin see refs. (66) and (67),and H. Dam and J. Glavind, Biochem. J . , 1938,32,485.70 H. J. Almquist and E. L. It. Stokstad, J. Nutrition, 1936,12,329.7l H. Dam, J. Glavind, L. Lewis,and E. Tage-Hansen, Skand.Arch. Physiol.,72 H. Dam and J. Glavind, Biochem. J . , 1938,32, 1018.73 For a fuller description of this work, see H. J. Almquist, Science, 1938,74 H. J. Ahnquist, Nature, 1937, 140, 25; J. Biol. Chem., 1937, 120, 635.75 Science, 1938, 88, 243.7 6 J . Biol. Chem., 1938, 125, 681.7 7 H. Dam and J. Glavind, Biochem. J., 1938, 32, 1018; H. J. Almquist,78 Acta Med. Xcand., 1938, 96, 108.1938, 79, 121.87, 538; H. J. Almquist and E. Mecchi, J . Biol. Chem., 1938,126,407.E. Mecchi, and A. A. Hlos0, ibid., p. 1897342 BIOCHEMISTRY.taminosis in rabbits. Interesting and promising results have beenobtained in clinical tests on man, for a marked reduction in theclotting time of the blood of patients with obstructive jaundice hasbeen observed following the injection of emulsions of vitamin K.79The suggestion has been made that treatment of this condition withthe vitamin may completely replace the old bile therapy.80Vitamin P.-About two years ago, A.Szent-Gyorgyi and hiscolleagues 81 suggested that fruit juices, Hungarian red pepper,etc., contain a substance (which they called vitamin P) whichregulates the permeability of the capillaries, and they suggestedthat experimental scurvy, as in the guinea-pig, is a deficiencydisease caused by the combined lack of vitamins C and P. Fromthe results of chemical investigations these authors suggested thatthe vitamin is a flavone or flavonol glucoside (" citrin ") and laterthat the crystalline substance hesperidin has vitamin P activity inguinea-pigs.Clinical trials with patients suffering from variousdiseases in which there is a low capillary resistance, gave promisingresults .S. S. Zilva 82 has made exhaustive efforts to confirm these findingswith guinea-pigs, but finds that neither citrin nor hesperidin willdelay the onset of scurvy or the fatal termination of the disease inthese animals on a scorbutic diet ; post-mortem examinationrevealed extensive fresh haemorrhages. Zilva also found that acondition similar to that reported by Szent-Gyorgyi could beobtained simply by giving suboptimal doses of vitamin C. Th.Moll 83 also has obtained negative results, and at the present timeunequivocal experimental proof of a deficiency disease due to adietary deficiency of a vitamin P is lacking.The possibility that" citrin " preparations and nearly pure hesperidin may contain someclosely related substance which is the active agent could accountfor some but not all of these discrepancies.Therapeutic tests with hesperidin or " citrin " have sometimesgiven promising results and several authors 85 have reported satis-factory results following the administration of these preparationsby mouth, or by injection, to patients suffering from certain diseasesin which there is an increased permeability of the capillaries. The7s H. Dam and J. Glavind, refs. (78) and (80).80 Idem, Lancet, 1938,234, 720.81 For the references, see ref. (82).82 Biochem. J., 1937,31,916, 1488; Nature, 1937,140,588.83 Klin. Woch., 1937, 16, 1653.84 Cf.H. Lotze, Deutsche med. Woch., 1938, 64, 477.a6 S. Ruaznyhk and A. Szent-Gyorgyi, Nature, 1936, 138, 27; S. Lajos,Klin. Woch., 1937, 16, 1615; T. Jersild, Lancet, 1938, 234, 1445; H.Scarborough and C. P. Stewart, ibid., 235, 610WORMALL: AMMAL. 343position with regard to vitamin P is, however, still obscure. Thefailure of other workers to confirm, with animals, the originalobservations of A. Szent-Gyorgyi, and the absence of large-scalewell-controlled clinical tests, suggest that the time has not yetarrived for the full recognition of vitamin P.Imulin, Diabetes and the Glywtropic Factor of the AnteriorPituitary.The chemistry of insulin has been dealt with briefly at varioustimes in these Reports,86 but this is perhaps a convenient opportunityto review the progress made.By the use of various inactivatingagents, considerable progress has been made in determining groupswhich may be concerned with the activity of this hormone, andmany investigators have undoubtedly visualised the possibility ofsynthesising some relatively simple compound possessing theseactive groups and having a hypoglycaemic power similar to that ofinsulin. In the most optimistic dreams these insulin-substituteshave been resistant to the action of proteolytic enzymes and havetherefore been effective when given by mouth. These dreamshave not yet materialised.The chemical attack on insulin has been made by numerousauthors, including K. Fre~denberg,~’ C. R. Harington,88 H.J e n ~ e n , ~ ~ D. A. Scott and 0. Wintersteiner and their colleaguesand many others.91 The hormone is inactivated by a variety ofagents, including proteolytic enzymes, alkalis, acid-alcohol, cysteine,glutathione, ascorbic acid, iodine, acetic anhydride, formaldehyde,phenyl isocyanate, benzyl chloroformate, and keten ; in someinstances the loss of hypoglycaemic power can be attributed to adefinite change in part of the protein molecule.So far there is87 K. Freudenberg and various colleagues, 2. physiol. Chem., 1928,175, 1 ;1929,180,212; 1930,187, 89; 1931, 202, 97, 128, 159, 192; 1932,204,233;213, 226, 248; 1935, 233, 159; cf. review by I(. Freudenberg, Monatah.,1936,69, 144.** C. R. Harington and A. Neuberger, Biochem. J., 1936, 30, 809; C. R.Harington and T. H. Mead, ibid., p. 1698.For the earlier papers, see H.Jensen and E. A. Evans, Phyaiol. Rev.,1934,14, 188; cf. also J . BioZ. Chem., 1935,108,l; H. Jensen, E. A. Evans,W. D. Pennington, andE. D. Schock, ibid., 1936,114,199.Cf. review by H. Jensen and E. A. Evans, ref. (89). For other workon the chemistry of insulin, see K. G. Stern and A. White, J . Biol. Chem.,1937,117,95; 1938,122,371 ; A. White and K. G. Stern, ibid., 1937,119,215.Its Production, Purificationand Physiological Action.” Hutchinson’s Scientific and Technical Public-ations. London, 1936) and H. F. Jensen (“Insulin. Its Chemistry andPhysiology.” The Commonwealth Fund. New York, 1938) give fullreviews of this literature.Ann. Reports, 1936, 33, 396 ; 1937, 34, 309.D. W. Hill and F. 0.Howitt (“Insulin344 BIOCHEMISTRY.evidence that changes in the S-S groups, in the tyrosine (e.g., theintroduction of two iodine atoms o r t h to the hydroxyl group),and possibly in the free amino-groups, cause loss of activity. In afew cases, reactivation of the inactive product can be effected byremoval of the new groups or by a reversal of the chemical changewhich causes inactivation. Up to the present, however, theseobservations have not rendered possible the preparation of a simpleror synthetic insulin, but the evidence which has accrued maysome day help to solve the problem as to the exact function ofthis hormone in carbohydrate metabolism.In another direction much progress has been made in the pasttwo or three years. This refers to the preparation of insulinderivatives which, after injection into the body, exert their activityfor a longer period than does ordinary insulin.The outstandingsuccess in these efforts was attained in 1936 by H. C. Hagedorn,B. N. Jensen, N. B. Krarup, and I. Wod~trup.~~ These authorsfound that the addition of protamine to insulin leads to the formationof a salt (protamine-insulin) which is less soluble at about pH 7than is ordinary insulin; absorption of the injected material istherefore less rapid, and the complex continues to exercise a hypo-glycaemic action for about 12 hours compared with 5-6 hoursfor ordinary insulin. Clinical tests showed that protamine-insulingives very satisfactory results in the treatment of diabetes,particularly those cases where control of the blood-sugar withordinary insulin is not too satisfactory.Various protarnineshave been used to form these complexes. H. C. Hagedorn andhis colleagues used those derived from the sperm of the rainbowtrout (satmiridin) and from mackerel (scornbrine), but other basicproteins give similar results ; amongst others, spermine 93 (preparedfrom the pancreas) and histones have been used.Afurther step forward was made by D. A. Scott and A. M.Fisher. Following on their work on the rhle of zinc in the crystallis-ation of insulin, these authors found that the addition of a smallamount of zinc (as zinc chloride, sulphate, etc.) led to a markedprolongation of the hypoglycaemic action of the hormone,g4 andthey subsequently observed that zinc has a similar effect onprotamine-insulin 95 (with amounts of zinc as small as 1 mg.Zn/500units). The mixture called protamine zinc insulin is now used92 J . Amer. Med. AGSOC., 1936,106, 177; H. C. Hagedorn, Proc. Roy. SOC.Med., 1937, 30, 11.93 A. M. Fisher and D. A. Scott, J. Pham. Exp. Ther., 1936,58, 93; 1937,61, 21.94 D. A. Scott and A. M. Fisher, ibid., 1935, 55,206.9 5 Idem, J . Biol. Chem., 1936, 114, lxxxviii; J . Pharrn. Exp. Ther., 1936,58, 78; 1937,61, 21WORMALL : ANIMAL. 345extensively for the treatment of diabetes, and most authorities onthe subject agree that it has many advantages over ordinary insulin.Severe cases of this disease can usually be controlled by two injectionsof protamine zinc insulin per day,96 and, if necessary, a little ordinaryinsulin can be added to the mixture to deal with the glucoseabsorbed shortly after a carbohydrate-containing meal.Thevalue of the " new insulins " has been discussed by G. Graham,97who also gives an interesting account of the changes in the treatmentof diabetes during the past fifteen years.The addition of zinc stabilises in some way the suspension ofprotamine-insulin, but the delay in the response to insulin (orprotamine-insulin) is not yet fully explained. Zinc, or some othermetal, may be responsible for the combination of insulin andp r ~ t a m i n e , ~ ~ and the presence of zinc in the pancreas and the readycrystallisation of the hormone when zinc is present 98 suggest thatthis metal may be a factor in the liberation and action of insulinin the body.Various other metals have been tested and somefound to have an action similar to that of zinc.9gDuring recent years renewed interest has been shown in therelationship between the anterior pituitary and carbohydratemetabolism. B. A. Houssay and A. Biassotti found in 1931 thatthe removal of the pituitary gland greatly reduced the symptomsof diabetes produced by removal of the pancreas, and later experi-ments by Houssay and his colleagues showed that intact animalsFor the earlier work on this subject, see H. C. Hagedorn et al., ref. (92);0. Leyton, Brit. Med. J., 1936, i, 443; R. D. Lawrence and N. Archer, ibid.,p. 487; H. F. Root, P. White, A. Marble, and %. H. Stotz, J. Amer. Med.ASSOC., 1936, 106, 180; R.B. Kerr, C. H. Best, W. R. Campbell, and A. A.Fletcher, Canadian Med. Assoc. J., 193G, 34, 400. For more recent work, seeH. C. Hagedorn (Schweiz. med. Woch., 1938, 68, 37) and G. Graham, ref. (97).D. A. Scott, Biochern. J., 1934, 28, 1592; D. A. Scott and A. M. Fisher,ibid., 1935,254 1048 ; Trans. Roy. SOC. Canada, 1938,32,55. Analyses, by theseauthors, of crystalline zinc-insulin, cobalt-insulin, cadmium-insulin andnickel-insulin show that the metals concerned are chemically combinedconstituents of the compounds. The same authors ( J . Clin. Invest., 1938,17, 725) have also found that the zinc content of t,he pancreas of diabetics,at autopsy, is only one-half that normally present.99 For the literature, see E. M.Bavin and W. A. Broom (Quart. J.Pharm.,1937, 10, 327), who report that magnesium and iron behave like zinc inthat small quantities prolong the hypoglycaemia, whereas large amountscompletely inhibit the normal insulin response. These authors (W. A. Broomand E. M. Bavin, ibid., p. 334) have also shown that the addition of zinc totannic acid-insulin prolongs the hypoglycaemic effect of this complex.g7 Lancet, 1938, 235, 1, 62, 121.Endocrinology, 193 1 , 15, 5 1 1.Summarised by B. A. Houssay, N e w Engl. J . Med., 1936,214,961, 971 ;cf. also H. M. Evans, K. Meyer, M. E. Simpson, and F. L. Reichert, Proc. SOC.Exp. Biol. Med., 1932, 29, 857346 BIOCHEMISTRY.could be rendered temporarily diabetic by the injection of extractsof the anterior pituitary.These observations have been confirmedby many investigators, and the suggestion naturally arose as to thepossibility that diabetes in man might be due, in some cases, tohyperactivity of the anterior pituitary. Although no final answercan yet be made to this question, considerable progress has beenrecorded during the past three years as a result of the work ofF. G. Young and several other authors. By prolonged injectionsof large amounts of crude saline extracts of fresh anterior pituitaryglands, F. G. Young has succeeded in producing a permanentdiabetic condition in normal dogs.3 These animals have lived forlong periods (over one year) after the cessation of the injections,and have, during this period, shown hyperglycaemia, glycosuriaand excretion of ‘‘ acetone-bodies.” The dogs retained full vigour,and no insulin treatment was found necessary; to abolish theglycosuria with a normal (high-protein) diet, these dogs requiredabout 60 units of insulin per day.These crude ox anterior pituitaryextracts have a diabetogenic action on dogs, sometimes on catsand rabbits, but not to any appreciable extent on mice, rats andguinea-pigs? More recent studies on the “ diabetogenic factor ”of the anterior pituitary have confirmed the view that this factor 5is probably complex ; the glycotropic and thyrotropic factors ofthis gland are possibly constituents of this complex, but prolactinis not.6 Somewhat similar views as to the complexity of thisprinciple have been put forward by C. N. H. Long,’ who considersthat there are two components, one heat-labile and the other heat-stable. It would be unwise at present to speculate as to whetherthis complex is responsible, wholly or in part, for the occurrenceof diabetes in man, but it is almost certain that our knowledgeabout this disease will be considerably enriched by these funda-mental investigations.The observation that some of these dogs,rendered diabetic by pituitary extracts, have little or no islettissue in the pancreas * may help towards the solution of thisproblem.Mention has been made above of the glycotropic factor of theLancet, 1937, 233, 372. This observation has been confirmed byF. G. Young, Biochem. J . , 1938,32, 513.The term “diabetogenic hormone” adopted by some authors is aptt,o be misleading, and its use should not be encouraged [see F.G. Young, ref.(a)]. Recent work on the various hormones of the anterior pituitary has beenwell summarised by J. B. Collip (Edin. Med. J., 1938,45, 782).J. Campbell and C . H. Best (Lancet, 1938,234,1444).6 F. G. Young, Biochem. J . , 1938,32, 524.Medicine, Baltimore, 1937, 16, 215.K. C. Richardson and F. G. Young, Lancet, 1938,234,1098WORMBLL: ANIMAL. 347anterior pituitary, a factor which may be a component of the morecomplex diabetogenic factor. The work of 0. Cope and H. P.Marks9 showed that the injection of extracts of this gland intonormal rabbits neutralised the effect of insulin subsequentlyinjected, and more recent work by F. G. Young has thrown consider-able light on the nature and properties of the active agent.This" anti-insulin '' or " glycotropic " 10 factor does not significantlyalter the blood-sugar of fasting rabbits, nor does the injection oflarge amounts cause glycosuria or ketonuria in dogs (k., the sub-stance is not diabetogenic by itself), but it produces a completeinsensitivity to the hypoglycaemic action of insulin. It is notidentical with prolactin,ll or with the thyrotropic and gonado-tropic hormones or the oxytocic or vasopressor substances of thepituitary.12 The mechanism of the anti-insulin effect of the glyco-tropic substance has been studied by several investigators l3 andit is fairly generally agreed that the hyperglycaemic action dfadrenaline is not essentially concerned with this response ; theglycotropic substance appears rather t o act by antagonising theaction of insulin both in the liver and in the peripheral tissues.12Isotopes in the Study of Metabolism.It was perhaps only to be expected that biochemists wouldexplore the possibility of using heavy hydrogen as a new weaponfor attacks on many of the unsolved problems of metabolism.Previous to the discovery of this isotope, G.von Hevesy l4 had studiedthe fate of lead containing one of its radioactive isotopes (Ra-D),but this method of labelling an element has very limited possibilities.A much wider field was opened by the discovery of deuterium andlater heavy nitrogen (N16), accompanied by the elaboration ofsensitive methods for the detection and determination of verysmall amounts of the heavy isotopes.The first workers to use deuterium for the study of intermediatemetabolism were R.Schoenheimer and D. Rittenberg, whointroduced the label or " tag " by catalytic reduction of unsaturatedJ . Physiol., 1934, 83, 167.l o The expression " glycotropic " was first suggested by F. G. Youngl1 F. G. Young, Chem. and Ind., 1937,56, 292; Biochem. J., 1938,32,524;l2 Idem, Biochem. J . , 1938,32, 1521.l3 H. P. Himsworth and D. B. M. Scott, J . Physiol., 1938, 91, 447; 92,183; F. G. Young, ref. (12); H. P. Marks and F. G. Young, J . Physiol., 1938,93, 61.(Lancet, 1936, 231, 297).Chem. and Ind., 1938,57, 1190.l4 Biochem. Z., 1926,173, 175348 BIOCHEMISTRY.fats in the presence of deuterium.15 The saturated fats obtained,and in later experiments sterols, bile acids, etc., cannot be distin-guished from the natural analogues by ordinary chemical methods.In this way deuterium is attached to carbon with the production ofcompounds which are so little different from the “normal”compounds that one is probably justified in believing that theanimal body will treat the labelled and the natural products inexactly the same way.The body has extraordinary powers fordistinguishing between certain optical isomers, and there arenumerous observations which show that a very slight change in onegroup of a very large molecule may have a profound effect on thephysiological or pharmacological action of a compound, but as yetthere is no evidence that the metabolism of stearic acid containingtwo atoms of deuterium per molecule differs from that of the naturalacid. Furthermore there is good reason to believe that the removalof deuterium from, and its introduction into, fatty acids and othercompounds are not due to a mere physical exchange of hydrogenand deuterium (R.Schoenheimer and D. Rittenberg Is). Normalconstituents of our food can thus be administered to animals in sucha form that many molecules have labels attached to them, andperhaps even more important, methods are available for the detectionof the label in various €ractions of the animal body. The sensitivityof these methods is such that some of the labelled products can bereadily detected when diluted with more than 1,000 times theirweight of natural product.An excellent review of the use of isotopes in the study of inter-mediate metabolism is given by R.Schoenheimer and D. Rittenberg, l6who discuss the position up to the end of 1937. Since this field hasnot been covered in these Reports, a brief account of some of themain results might be welcomed. The feeding of deutero-fats leadsto the deposition of a large part of the fat in the fat depots, withsmaller amounts in the liver, etc.17 B. Cavanagh and H. S. Raper l8in similar studies showed that the absorption of deuterium-containing fat is almost complete, and that considerable amounts1 5 J. Biol. Chein., 1935, 111, 163; D. Rittenberg and R. Schoenheimer,ibid., p. 169; R. Schoenheimer, D. Rittenberg, and M.Gmff, ibid., p. 183;R. Schoenheimer and D. Rittenberg, ibid., 193G, 113, 505; 114, 381; R.Schoenheimer, D. Rittenberg, B. N. Berg, and L. Rousselot, ibid., 1936, 115,635. W. E. van Heyningen, D. Rittenberg, and R. Schoenheimer (ibid., 1938,125, 495) have recently described two methods for the preparation of fattyacids containing deuterium. In one method the exchange occurs at thea-carbon atom only.1 6 Science, 1938, 8’7, 221; cf. also review by A. Krogh, Enzymologia, 1938,17 R. Schoenheimer and D. Rittenberg, J. Bid. Chern., 1035, 111, 175.5, 185.Nature, 1936, 137, 233WORMALL: ANIMAL. 349of the fatty acids containing deuterium enter into the lipines oforgans such as the liver and kidney; this observation offers strongsupport for the view that the lipines are actively concerned in themetabolism of fat.Investigations dealing with the theory of fatty acid desaturationhave yielded interesting and fundamental results.This theory,that fatty acids can be desaturated in the liver and possibly otherorgans, was previously supported by evidence which was notentirely convincing, but the work of R. Schoenheimer and D.Rittenberg now appears to show quite definitely that this changedoes occur. Deutero-unsaturated acids were isolated from mice whichhad received deutero-stearic acid,lg and evidence of the reversechange, i.e., the saturation of unsaturated fatty acids, has alsobeen obtained.2* Desaturation does not appear to be effectedduring the absorption of fatty acids by the intestinal wa11,21 and sofar these experiments have not established the site of this process;in all probability the responsibility will largely fall on that hard-worked organ, the liver.In further experiments with deutero-fats R. Schoenheimer and D. Rittenberg have confirmed the viewthat stearic acid can be converted into palmitic acid,22 and theyhave shown also that administered deutero-butyric and -hexoicacids are not used for the synthesis of -higher fatty acids for fat-storage, but are rapidly and completely oxidised in the body.23In these investigations it is improbable that the changes observedare due t o simple exchange of hydrogen between the substancesconcerned and the water in which they are dissolved, sincedeuterium-free fatty acid 24 and cholesterol 25 were isolated fromchicks which had developed in heavy water-enriched eggs, anddeuterium-free lysine from mice whose body fluids had containedheavy water for more than three months.26 The claim that proteolyticenzymes may introduce carbon-bound deuterium into amino-acidsfrom heavy water 27 is not confirmed by G.L. Poster, A. S. Keston,I>. Rittenberg, and R. Schoenheimer.28H. M. Barrett, C. H. Best, and J. H. Ridout 29 have recently madeIs R. Schoenheimer and D. Rittenberg, J . Biol. Chern., 1936, 113, 505.2o D. Rittenberg and R. Schoenheimer, ibid., 1937, 117, 485.21 Cf. R. Schoenheimor and D. Rittenberg, Science, 1938, 87, 221.22 R. Schoenheimer and D. Rittenberg, J . Biol. Chem., 1937, 120, 155,23 D. Rittenberg, R.Schocnheimer, and E. A. Evans, ibid., p. 503.2 * R. Schoenheimer and D. Rittenberg, ibid., 1936, 114, 381.25 D. Rittenberg and R. Schocnheimer, ibid., 1937, 121, 235.2 6 Cf. ref. (21).2 7 J. A. Stekol and W. H. Hamill, J. Biol. Clzern., 1937,120,531.28 [bid., 1938, 124, 159.2s J . Yhysiol., 1938, 93, 367; cf. also H. M. Barrett, C. H. Best, and J. H.Ridout, J . Biol. Chem., 1938, 123, iii350 BIOCHEMISTRY.use of deuterium as an indicator for the study of the source of the fatwhich accumulates in the liver when animals are maintained ona diet poor in lipotropic factors or when certain extracts of theanterior pituitary gland are admini~tered.~~ Using a speciallydevised rapid and relatively simple micro-density method for thedetermination of deuterium oxide, these authors have confirmedthe view that the fat depots supply most if not all of the fat whichaccumulates in the liver during fasting, or after administration ofanterior pituitary extracts, or when mice are exposed to carbontetrachloride vapour.When animals containing deutero-fat inthe fat reserves are fed on a diet which is low in protein and otherlipotropic factors but rich in carbohydrate, they accumulate liver-fat which does not come from the depots but most probably fromthe food carbohydrate. These authors have also obtained evidenceof the in vitro and in vivo stability of the label of deutero-fats.The metabolism of proteins and amino-acids is now being inves-tigated by similar methods. R. Schoenheimer, D. Rittenberg,M.Fox, A. S. Keston, and S. Ratner31 have introduced heavynitrogen into glycine and hippuric acid, and have shown that thelatter can be absorbed from the intestinal tract without beinghydrolysed; the results suggest also that glycine may be useddirectly for hippuric acid formation. A. Krogh and H. H. Ussing 32have used a rather different method for the study of proteinmetabolism. The maintenance of a fairly constant concentrationof heavy water in an animal results in the introduction of deuteriuminto amino-acids, attached in part to the asymmetric carbon atomsin the growing foetus but to other carbon atoms in the matureorganism. The proteins of the viscera of these animals showedthis exchange of hydrogen to a greater extent than did the proteinsof muscle and skin, owing presumably to the less reactive elastin,collagen and keratin.33 The lipide of the rat showed no similarexchange of hydrogen and deuterium.Radioactive elements have been used by many authors for3O For a review of this work on lipotropic factors, etc., see D.L. Maclean,J. H. Ridout, and C. H. Best, Brit. J. Exp. Path., 1937, 18, 345; C. H. Bestand J. H. Ridout, Amer. J . Physiol., 1938,122,67 ; C. H. Best and J. Campbell,J . Physiol., 1938,92, 91 ; H. J. Channon, G. N. Jenkins, and J. A. B. Smith,Biochem. J . , 1937, 31, 41 ; H. J. Channon, J. V. Loach, and G. R. Tristram,{bid., 1938, 32, 1332.31 J . Amer. Chem. SOC., 1937, 59, 1768; cf. also H. H. Ussing (Nature,1938, 142, 399), who has used deutero-amino-acids for the study of proteinmetabolism.32 Compt.rend. Trav. Lab. Carlsberg, 1938,22,282 ; cf. also J. A. Stekol andW. H. Hamill, Proc. Xoc. Exp. Biol. Med., 1937, 35, 591, and G. L. Foster,D. Rittenberg, andR. Schoenheimer, J . Biol. Chem., 1938,125, 13.33 H. H. Ussing, Skand. Arch. Physwl., 1938, 78, 225WORMALL: ANIMAL. 361the study of biological problems. The use of natural radio-elementsis obviously rather limited, but a much wider application is possiblewith artificially produced radio-elements (e.g., the isotopes ofcarbon, phosphorus, sodium and calcium) .34 Labelled (radioactive)phosphorus, prepared from sulphur by neutron bombardment,was injected subcutaneously, as sodium phosphate, into a rabbitby L. A. Hahn, G. C. Hevesy, and E.C. L~ndsgaard.~~ Within27 days, 45% of this phosphorus was excreted in the urine and 11 yoin the faces, and the average time a phosphorus atom remains inthe body was found to be 30 days. An exchange of phosphorusatoms by bone still continues after the lapse of 21 days. A similarexchange occurs in teeth, and the replacement of 1% of thephosphorus of a human tooth by phosphorus derived from thefood takes about 250 days.36 Ingestion of radioactive phosphorus(as Na2HP0,) by fasting rats is followed by the appearance of thisisotope in the phospholipins of all the tissues examined, and theresults suggest that the liver and intestine and possibly the kidneyparticipate in phospholipin ~ynthesis.~' A considerable amountof this radioactive phosphorus is used for lipin formation within30 minutes of the injection of the phosphate.38 Similar conclusionsare reached by W.E. Cohn and D. M. Greenberg, who state that brainhas a slow turnover of phosphorus, but other tissues show a rapiduptake in the &st 10 hours.39Other isotopes have not escaped attention, and amongst thosewhich have given promising results are the radioactive isotopes ofsodium,m potassium,41 sulphur,42 iodine and iron. The value ofwhat has been described as " this scientific game of tag " need notbe emphasised, and it seems almost certain that the use of labelled34 Cf. G. von Hevesy and F. A. Paneth, Science Progress, 1937,32,38.35 Biochem. J . , 1937, 31, 1705.36 G. Hevesy, J. J. Holst, and A. Krogh, Kgl. Danske Vdenskab.Selskab,1937,13, 34.s7 I. Perlman, S. Ruben, and I. L. Chaikoff, J . Biol. Chem., 1937-8,122,1G9 ;B. A. Fries, S. Ruben, I. Perlman, and I. L. Chaikoff, i b i d . , 1938,123, 587.3B M. J. L. Dols, B. C. P. Jansen, G. J. Sizoo, and F. Berendregt, Nature,1938,141, 77.3s J . Biol. Chem., 1938, 123, 185; cf. also S. F. Cook, K. G. Scott, and P.Abelson (Proc. Nat. Acad. Sci., 1937, 23, 528), who had previously shown thatradio-phosphorus is deposited in all the tissues of growing chicks examinedbut principally in bone and muscle.40 J. G. Hamilton and R. S. Stone, Proc. SOC. Exp. Biol. Med., 1937, 35,595; J. G. Hamilton, Proc. Nat. Acad. Sci., 1937,23, 521.41 D. M. Graenberg, M. Joseph, W. E. Cohn, and E. V. Tufts, Science, 1938,87, 438.4 2 H.Borsook, G. Keighley, D. M. Jost, aid E. Maillillan, ibid., 1937, 86,525352 BIOCHEMISTRY.elements will undoubtedly throw much light on many of themysteries of fat and possibly protein metabolism. Other aspectsof biochemistry in which one may confidently anticipate usefulprogress as a result of the use of these isotopes are those concernedwith some of the hormones, enzyme action, the chemistry ofimmunity, and the action of certain drugs.Chemotherapy .Xulpknilamide and Related Brugs.-The claim 43 that thediscovery of sulphanilamide, prontosil, and related compoundswas probably the most important advance in chemotherapy formany years has been fully substantiated and amazing progresshas been made in this branch of “ chemical warfare ” during thepast year.The main efforts have been devoted to a search for newsulphonamide derivatives more powerful and possibly less toxicthan sulphanilamide, and to investigations on the mode of actionof these drugs. Under the first heading might be included thepreparation of new derivatives for the treatment of bacterialinfections which resist the action of prontosil and sulphanilamide,and in this field the discovery of M. & B. 693, mentioned below,is of outstanding importance.The literature on sulphanilamide (IV) and its congeners is nowso colossal that it is not possible to mention more than a few of thepublished papers. Excellent comprehensive reviews of the discoveryof the drugs of this group and the work done in this field are givenby L.P. Garr~d,*~ P. H. Long and E. A. Bliss,45 C. L e ~ a d i t i , ~ ~and L. E. H. Whitb~.~’ The value of these drugs for the treatmentof the majority of hemolytic streptococcal infections is, to quotethe words of L. P. Garrod, “now a matter of almost universalexperience and not one demanding proof.’’ Amongst other diseasesin which successful results are frequently obtained with sulphanil-amide administration are certain staphylococcal, pneumococcal,meningococcal and gonococcal infections, gas gangrene, typhoidfever, undulant fever, and certain skin infections. There is not,however, unanimous agreement as to the efficacy of sulphanilamidetreatment in all these infections. It is generally agreed that thereare many infections (e.g., tuberculosis,*8 syphilis, rheumatic fever,4 4 Lancet, 1938, 234, 1125, 1178. 49 Ann.Reports, 1937, 54, 398.45 Ann. Intern. Med., 1937, 11, 575.4 6 Schweiz. 2. allg. Path. Bakt., 1938,1,365. 17 Lancet, 1938, 235, 1095.48 A. R. Rich and R. H. Follis (Bull. Johns Hopkins Hosp., 1938, 62, 77)found, however, that sulphanilamide has a distinct inhibitory effect on thedevelopment of tuberculous lesions in guinea-pigs infected with a humanstrain. Less striking results were obtained by G. A. H. Buttle and H. J.Parish (Brit. Med. J., 1938, ii, 776)WORMALL : ANIMAL. 353and leprosy) where this drug has no curative or preventive action.The treatment of virus diseases (e.g., infantile paralysis, influenza,and encephalitis) with sulphanilamide is usually ineffe~tive.~~The discovery of prontosil and the later observation that theless complex sulphanilamide has a similar therapeutic value havebeen followed by numerous attempts to obtain compounds witha higher efficiency, a lower toxicity or a wider range of actionon bacteria.Thousands of these derivatives have been preparedand tested by in vitro experiments; several have given sufficientlypromising results to warrant trial on man. The informationobtained, even where the results were of a negative character, willcertainly be of considerable value when sufficient evidence is avail-able to correlate the in vitro and in vivo effects with the chemicalconstitutions of these compounds. It has already been establishedthat the sulphonamide group is not the only one effective in thisclass, for certain sulphones have an activity equal to that of~ulphanilamide.~~ Substitution in the amino-group or replace-ment of one hydrogen of the sulphonamido-group does notnecessarily produce inactive products, but few other generalisationscan be made at present.The testing of these compounds islargely a matter of ‘‘ tedious empirical trial and error ” (L. E. H.Whitby 47).The most promising of the new derivatives is undoubtedly 2-(paminobenzenesu1phonamido)pyridine (M. & B. 693 or T. 693)(V). L. E. H. Whitby51 has shown that this substance ischemotherapeutically active, in experimental infections in mice,against pneumococci of Types I, 11, 111, V, VII, and VIII.Sulphanilamide has relatively little action on these organisms, andsince M.& B. 693 is at least as lethal to certain other organisms(haemolytic streptococci, meningococci, etc.) as is sulphanilamideand its toxicity is apparently less than that of the la~t-named,~~49 F. 0. MacCallum and G. M. FindIay (Lancet, 1938, 235, 136) found,however, that sulphanilamide and a glucose derivative of 4 : 4’-diamino-diphenylsulphone protect a large percentage of mice against the virus oflymphogranuloma inguinale introduced intracerebrally. C. Levaditi (Compt.rend. Xoc. Biol., 1938, 127, 958; 128, 138) also found certain sulphonamideseffective in the treatment of virus infections in small animals.50 Cf. Ann. Reports, 1937, 34, 421.61 Lancet, 1938,234, 1210.52 R. Wien, Quart.J . Pharm., 1938,11,217. Cf., however, E. K. Marshall,A. C. Bratton, and J. T. Litchfield (Science, 1938, 88, 597), who have reachedthe opposite conclusion and advise caution in the use of 2-sulphanilamido-pyridine.REP.-VOL. XXXV. 354 BIOCHEMISTRY.it is receiving extensive clinical trials. Almost invariably satis-factory results have so far been reported. A marked reductionin the mortality rate amongst patients with lobar- and broncho-pneumonia has been observed 53 and successful results have beenobtained in cases of gonorrhoea 54 and pneumococcal meningiti~.~~The mode of action of these drugs has been the subject of manyinvestigation^.^^ The theory most commonly accepted in thiscountry is that they exert a bacteriostatic action, thus preventingthe rapid development of the organisms; the body is then able toovercome the infection by its normal defence mechanisms, e.g.,by phagocytosis by the leucocytes.Sulphanilamide has someaction on the capsules of streptococci 67 and M. & B. 693 has asimilar action on the pneumococcus capsule,58 and this directaction may play a part in the inactivation of the organisms. Thework of J. S. Lockwood 59 suggests that sulphanilamide exerts itsaction by preventing streptococci from utilising serum proteinsfor growth purposes, possibly by the inactivation of an enzyme.Other investigators have suggested that these drugs neutralisetoxins produced by bacteria or that they stimulate phagocyticactivity or other defence mechanisms, but the evidence in favourof these hypotheses does not appear to be conclusive.The marked specificity of many of these drugs is anotherinteresting feature.The selective action on certain bacteriaM. Telling and W. A. Oliver, Lancet, 1938,234, 1391 ; G. M. Evans andW. F. Gaisford, ibid., 235, 14; J. M. Christie, ibid., p. 281; S . C. Dyke andG. C. K. Reid, ibid., p. 1157.54 V. E. Lloyd, D. Erskine, and A. G. Johnson, Lancet, 1938, 234, 1305;T. Anwyl-Davies, Practitioner, 1938,141, 496; F. J. T. Bowie, Brit. Med. J.,1938, ii, 283. R. C. L. Batchelor, R. Lees, M. Murrell, and G. I. H. Braine(Brit. Med. J., 1938, ii, 1142) have recently reported on the treatment of 102cases of gonococcal infection with M. & B. 693, and conclude that this drug isthe most potent anti-gonococcal agent available at present.S6 For the literature, see ref.(47).66 Cf. reviews, refs. (44) and (47). A. Fleming (Lancet, 1938, 235, 74, 564)has carried out a full investigation of the antibacterial power of M. & B. 693against haemolytic streptococci and pneumococci, and has shown that theincreased antibacterial power of the blood of patients taking this drug liesin the serurn. This drug does not, however, prevent capsulation ofpneumococci. E. A. Bliss and P. H. Long (J. Arner. Med. ASGOC., 1937, 109,1524) conclude that sulphanilamide controls streptococcal and certain otherinfections in mice largely by a bacteriostatic action. In the control ofinfections of tho urinary tract, a bactericidal action is also exerted (P.H.Long and E. A. Bliss, South. Med. J., Alabama, 1938,31,308).5 7 C. Levaditi and A. Vaisman, Compt. rend. SOC. Biol., 1935,119,946; 120,1077.5 8 L. E. H. Whitby, Lancet, 1938,234,1210; M. Telling and W. A. Oliver,ibid., p. 1391.5B J . Immunol., 1938, 35, 155WORMALL : ANIMAL. 355suggests a specific combination with " receptor " groups in theorganism, and this phenomenon might prove of value in bacterio-logical and immunological investigations. Whether the prolongedadministration of these drugs will lead to the development ofdrug-resistant strains of the organisms has not been established,but it is perhaps fortunate that there is now available a largenumber of widely differing drugs of this type for the eradicationof these undesirable strains.The outstanding success of this work on sulphanilamide, etc.,has naturally led to their fairly widespread use for almost anyailment from the common cold to rheumatism.Routineadministration of the compounds for all types of infection is stronglydeprecated by most authorities in this field, and it should beremembered that practically all these sulphonamides frequentlyproduce some or all of the toxic effects referred to last year.60 Thesesymptoms, occurring often in 50% of the treated cases, are usuallyof a mild character, and can be controlled, but some fatalities havebeen recorded. The exact significance of the increased amount ofporphyrin excreted in the urine following the administration ofsulphanilamide to hospital patients 61 has not been established,but it may be connected with hypersensitiveness to the drug, asshown by dermatitis in some cases.E.K. Marshall and his colleagues have made important contrib-utions on the absorption and excretion of sulphanilamide and manyof its derivatives. Using a colorimetric method for the determin-ation of these substances,62 they have continued their studies onthe behaviour of the drugs in various animals.63 They haveobserved that sulphanilamide given orally in solution is absorbedmuch more rapidly than when given in solid form, and that excretionof the drug in the urine is more rapid in the mouse than in the rat,dog or man.Some Chemical Aspects of Immunity.It is impossible to do justice to this important and rapidlydeveloping subject in the space remaining for animal biochemistry.60 Ann.Reports, 1938, 34, 423. A more complete account of the toxicityof sulphanilamide and the effects of large doses administered to variousanimals is given by E. K. Marshall, W. C. Cutting, and K. Emerson ( J . Amer.Med. ASSOC., 1938, 110, 252. Cf. also P. H. Long, Ohio State Med. J . , 1938,34, 977).C. Rimington and A. W. Hemmings, Lancet, 1938,234,770.62 E. K. Marshall, J . BioZ. Chem., 1937,122,263; E. K. Marshall and J. T.6s E. K. Marshall, W. C. Cutting, and W. L. Cover, Bull. Johns HopkinsLitchfield, Science, 1938, 88, 2273.Hosp., 1938,63,318; E. K. Marshall and W. C. Cutting, ibid., p. 328356 BI 0 CHEMISTRY.All that can be attempted is to indicate one or two of the advanceswhich have been made in recent times and to show how immuno-chemical methods are being used to help to solve some ofthe problems of biochemistry.Excellent reviews 64 are availablefor those who wish to have a full account of this subject.The chemical basis of the specificity of antigens has beenextensively studied by the use of conjugated antigens, in whichcertain known groups have been attached to antigenic proteins(e-g., serum globulin). For the preparation of these conjugatedantigens K. Landsteiner and H. Lamp1 in 1917 first made use ofthe property of proteins of coupling, by virtue of the phenolic andiminazole groups which they contain, with diazonium compoundsin alkaline solution, and during the past twenty years this methodhas been used, with very successful results, by numerous workers.Other reactions have been described for the introduction of newgroups into proteins, but these have usually been of limited applic-ation.In a recent general method devised by R. E”. Clutton,C. R. Harington, and T. H. Mead,65 a compound containing acarboxyl group is converted into the acid azide, which is coupled,under mild conditions, with a protein. Using this technique,R. F. Clutbon, C. R. Harington, and M. E. Yuill 66 have shownthat both insulin and gelatin become antigenic when coupled withglucosidotyrosine ; the antibodies produced by these complexeswill react with glucosidotyrosyl-globulin, but for some unknownreason, not with the antigen used for the immunisation. In afurther study the same authors 67 have prepared thyroxyl deriv-atives of serum globulin and albumin, and of thyroglobulin, andhave found that immunisation with these complexes producesantisera which when injected into rats will protect against thenormal physiological effects of exogenously administrated thyro-globulin or thyroxine.The possible extension of this work toantisera against artificial compounds of proteins with otherphysiologically active compounds will be awaited with considerableinterest.There is much evidence, chemical as well as immunological,that a large variety of compounds are capable of reacting withproteins to form complexes quite different in immunological64 “ The Specificity of Serological Reactions,” by K. Landsteiner (CharlesC.Thomas, Baltimore, 1936) ; “ The Chemistry of Antigens and Antibodies,”by J. R. Marrack (H. M. Stationery Office, London, 1938). Shorter reviewsare given, in the Ann. Rev. Biochem., by M. Heidelberger (1933,2, 503 ; 1935,4, 569) and by K. Landsteiner and M. W. Chase (1937,6, 621).6 5 Biochem. J . , 1937, 31, 764.6 6 Ibid., 1938, 32, 1111.67 Ibid., p. 1119WORMALL : ANIMAL. 357properties from the original protein. Several types of hyper-sensitivity in man can undoubtedly be explained on the basis thatthe active agent combines with the body proteins to produce acomplex which is “foreign” and antigenic to the body. Strongevidence in support of this view has been obtained by K. Landsteinerand M. W. Chase,6S who have shown that true anaphylactic sensitis-ation can be effected in guinea-pigs by the cutaneous application ofsimple chemical substances, including 2 : 4-dinitrochlorobenzene,a typical incitant of contact dermatitis in man.Although theformation of antigenic conjugates will not account for all types ofallergic response, these and similar immuno-chemical studiesshould throw much light on many aspects of allergy, includinghypersensitivity to certain drugs, to hormones such as insulin, andto chemical substances which frequently produce dermatitis inindustrial workers.Other investigations to which reference should be made arethose dealing with the mechanism of the antigen-antibody reaction,in particular the quantitative theory of the precipitin reactionpropounded by M.Heidelberger.G9 Other workers 70 have isolated,from bacteria, antigens which when injected produce an activeimmunity similar to that produccd by the whole bacterial cells,and in certain instances the non-protein nature of the bacterialantigens is strongly suggested; in one case at least the complexconsists mainly, if not entirely, of polysaccharide linked to aphosphatide. Another interesting problem is that of the anti-hormones, the study of which was stimulated by the discoveries ofJ. B. Collip and his colleagues,71 but lack of space preventsa discussion of this and many other fascinating aspects of immunity.Sufficient has perhaps been said to indicate the progress which hasbeen made and the bright prospects for the future.The rabbit hasalready worked wonders as a relatively inexpensive chemicalassistant, and the delicate and highly specific immunological testsare certain to be of considerable use in the future study of thenormal as well as the pathological animal.A. WORMALL.6 8 J . Exp. Med., 1937, 66, 337, and earlier papers.6D See H. E. Stokinger and M. Heidelberger (ibid., p. 251) andM. Heidelberger ( J . Amer. Chem. SOC., 1938,60,242) for tho literature.‘O For the literature, see W. W. C. Topley, H. Raistrick, J. Wilson, M.Stacey, S. W. Challinor, and R. 0. J. Clark, Lancet, 1937, 232, 252; W. T. J.Morgan, Biochem. J . , 1937, 31, 2003.A discussion of the early work in this field is given by G. F. Marrian andG. C . Butler (Ann. Rev. Biochem., 1937, 6, 303; cf.also 0. Wintersteiner andP. E. Smith, ibid., 1938,7,253)368 BIOCREMISTRY .PLANT BIOCHEMISTRY.Introductory.Any attempt to summarise the progress in any branch of chemistryfor one year involves drastic selection, and the choice of somehundred odd references from the many hundreds available is alwaysinvidious. In the first part of this year's Report on Plant Bio-chemistry an attempt has been made to indicate some of the sub-stances-carbohydrates, enzymes, pigments, etc.-in which theplant chemist is interested. The plant chemist, as distinct from thestructural organic chemist, may still be said to blaze the trail forhis colleague, although the distance between them is ever decreasing.The problem of starch is still engaging the attention of chemists theworld over, and a reconciliation between results and theories basedsolely on chemical grounds and those derived from a study ofenzymic reactions appears to be very much nearer than was formerlythe case.The survey of the anthocyanins commenced in 1931 continues,and of particular interest in this field is the discovery of new typesbased on hydroxy-cyanidins and -pelargonidins.Nitrogenousanthocyanins also are reported.For reasons of space, only a brief review of some chemical aspectsof micro-organisms has been possible, and a summary of importantwork on the substances necessary for the growth of higher andlower plants is held over until next year.Some Plant Products.Starch and Amyhse.s.-It is proposed in succeeding paragraphs todiscuss starch mainly with reference to amylase action, but apreliminary reference to the more chemical aspects may be made.Views on the constitution of starch have by no means reachedfinality, but it may be said that two theories stand out beyond others.On the one hand there is the well-established calculation of Haworthand his school, based on the end-group assay method, which indicatesa chain length for the starch molecule corresponding to 25-30glucose units combined through a-glycosidic links.These primaryunits are associated into physical aggregates of much largerdimensions. On the other hand Staudinger has long held the viewthat macro-molecules as distinct from molecular aggregates existin starch, a view based largely on physical considerations.Inrecent experiments described by H. Staudinger and E. Husemann 1 9 2it was shown that after acetylation of potato, and later of wheatstarch, a regenerated starch was obtained in which the degree ofl Annulen, 1937, 527, 196. * Ber., 1938,71, 1067NORRIS : PLANT. 359polymerisation was practically unchanged. Phosphorus-free starchwas used, which by osmotic pressure measurements had a molecularweight of 286,000, corresponding to a polymerisation degree of 1770.By rapid hydrolysis with N-hydrochloric acid another preparationwas obtained with a polymerisation degree of only 600. Theregenerated compounds after acetolysis possessed polymerisationdegrees of 1640 and 530 respectively. It is suggested that themacro-molecules are extremely sensitive to chemical disruptionand the presence of only a trace of atmospheric oxygen in thesolvent exerts an enormous effect on the degree of polymerisation.This probably explains why such results have not hitherto beenobtained, and the slight lowering in degree of polymerisationobserved is of no significance in view of the great difficulty ofavoiding disturbing influences.The results were confirmed byviscosity measurements.It is suggested that the starch macro-molecules must be quitedifferent from the cellulose micelles. The structure of starch isenvisaged as consisting of short branched coils, the glucose chainsbeing linked from chain to chain through the aldehyde and hydroxylgroups. Such a conception fulfils physical requirements and alsoaccounts for the occurrence of tetramethyl glucose in the proportionsobtained by methylation methods, and for the lack of aldehydicproperties in starch itself.The activity of preparations of amylases has been investigatedby J.Blom, A. Bak, and B. B~-aae,~ who find that the effects ofheating, acidifying or adsorbing on starch are reflected in thesubsequent action of the enzymes. Thus there are changes in thepower to liquefy and saccharify starch, and the action on the starch-iodine property is modified. A study of the changes effected bypretreatment of the amylase preparation is of use in revealing thepresence of one or the other of the only two forms discovered, namely,the liquefying a-amylase and the saccharogenic p-amylase.Theauthors confirm that the usual preparations of malt amylase aremixtures of the two types and find similar mixtures in preparationsfrom Aspergillus oryxce; one form only was present in the case ofbacterial and pancreatic amylases.In a further contribution4 on the decomposition of starch byamylases these authors employ a commercial preparation, super-clastase, shown to contain only cc-amylase. The starch is de-composed only to the extent of 40%, after which the action of theamylase ceases or becomes exceedingly slow. Dextrins are firstformed and in the later stages of the action the enzyme is catalysingthe breakdown to maltose of such dextrins. The products of theIbid., 1938, 252, 251. 2. physiol. Chem., 1937, 250, 104360 BIOCHEMISTRY.action were studied, not by the more usual method of fractionalprecipitation with alcohol, but after fermentation of the maltosewith brewer’s or baker’s yeast.The progressive changes in iodine coloration effected duringhydrolysis of starch by the two amylases? indicated in a previousreferen~e,~ have been studied quantitatively by C.S. Hanes andM. Cattle,5 who have examined the absorption characteristics of thecompounds produced during the action. They find that the twoamylases are directly distinguishable from very early stages of therespective reactions by the manner in which the absorptioncharacteristics change. Moreover, it is claimed that by plottingcolour, or absorption, and reducing power relationships, it is possibleto correlate changes in iodine coloration and the liberation ofreducing groups as hydrolysis proceeds.These considerations maybe said to have two important bearings on studies on starch and itsenzymic breakdown: firstly, these methods provide a basis ofadditional refinement in the investigation of amylase action ;secondly, they have a direct bearing on theories of the constitutionof starch. It is considered that “colouring groups ” are evenlydistributed along the molecular chain structure of starch such thatthe molecule may be divided into a number of portions whichcontain equivalent numbers of “ colouring groups.” The differencein iodine colour observed in different degradation products is relatedto a molecular association. The action of a-amylase involves amarked alteration in iodine colour and this is thought to be due toa preliminary disruption of molecular associations, followed bydestruction of “ colouring groups,” achroic dextrins being finallyformed.With p-amylase, however, there is progressive reductionin “ colouring groups,” whilst maltose fragments are broken off at theend of the chain. The failure to break down the molecular associ-ations of the residual dextrins is reflected in the relative constancyof the absorption characteristics of the iodine compounds formed.It is a well known fact that the action of amylases on starchresults in the production amongst other products of the so-calledstable or limit dextrins. At the same time, none of the structuresso far suggested, largely on chemical grounds, for the starch moleculesatisfactorily explains the inability of the usual enzymes to degradethe dextrin further, or shows exactly why the hydrolytic actionceases a t a certain point.Amongst many investigations on thissubject may be mentioned those of K. Myrback, B. Ortenblad andK. Ahlborg,6* who suggest that the formation of such dextrins is5 Proc. Roy. Soc., 1938, B, 125, 387.6 Compt. rend. Trav. Lab. Carhberg, Ser. chim., 1938,22, 357.7 Bwchem. Z., 1938,297, 160, 172, 179NORRIS : PLANT. 361due to the non-uniform character of the starch molecule; whilstaccepting the Haworth conception of chains of maltose as the basisof the starch molecule, they consider that there may also be branchedchains or abnormal types of linkage, and that the proportion of themolecule represented by such an arrangement would be resistantto enzyme action. They have obtained the limit dextrin (or a-amylodextrin) by the action of p-amylase on starch, and by alcoholprecipitation have obtained a number of fractions which appear tohave widely differing molecular weights and phosphorus contents.The latter varied from 0.3% to 0.8% and the authors consider thatthe whole of the phosphorus of the original starch remains in thelimit dextrin, provided that phosphatase is absent.The suggestionis made that the presence of a phosphoric acid group in the molecule,or at certain points in the chain, protects the associated residuesfrom amylase action. The dextrins produced by fi-amylase were ofhigh molecular weight, whereas those produced by a-amylase were oflow, consisting apparently often of only from three to six glucoseresidues.The increase in amylase activity observed during the germinationof the cereal grains has given rise to much speculation.Earlysuggestions that the increase was due to the actual synthesis ofenzymes have been shown to be erroneous and more modern theoriesinvolve the presence of an activator-the amylo-kinase of E .Waldschmidt-Leitz and A. Purr *-formed as germination pro-ceeded; but this possibility has not found general acceptance.T. Chrzaszcz and J. Janicki9 proposed the exact opposite of thiswhen they suggested that an inhibitor-sisto-amylase-was presentand that the protein breakdown products formed during germinationcounteracted the effects of the inhibitor, whereby the amylase wasrestored to maximum activity.Eluto-substances such as peptoneand sodium chloride had the same effect, namely, increase in amylaseactivity. It was later shown that the amylase might be inactivatedby adsorption on protein and that the addition of peptone had aprotective effect on the amylase. The possibility of an inactiveprotein-amylase complex was indicated by J. S. Ford and J. M.Guthrie as long ago as 1908,10 when it was shown that an addition ofpapain to barley extracts caused a large increase in amylase activity.More recently K. Myrback and S. Myrbackll differentiate betweenthe free amylase in an aqueous extract of barley and the boundamylase which is only liberated after papain digestion.The greatincrease in p-amylase activity was assumed to be due to the proteo-ti Z.physi01. Chem., 1931, 203, 117.Biochem. Z., 1933,263, 250; 264, 192; 265, 260.lo J . Inst. Brew., 1908, 14, 61. l1 Biochem. Z., 1933, 258, 158362 BIOCHEMISTRY.lytic release of insoluble amylase bound in some manner withprotein, and such a view is now confirmed by T. Chrzaszcz and J.Sawicki,12 who find that papain and other proteolytic enzymes, andhydrogen sulphide, liberate bound amylase, which is chiefly of thep-amylase type, since the saccharifying power of such treatedextracts is much increased. C. H. Hills and C. H. Bailey 13 reviewthe present position and have failed to confirm the presence ofamylokinase in green malt extracts of barley; they regard theincrease of the p-amylase activity after papain digestion as a proteo-lytic breakdown of a protein complex, and consider that this processprovides a satisfactory means of determining total p-amylaseactivity.Peptone did not affect the p-amylase activity, butincreased a-amylase activity by about 25%, in the case of green maltextract and of purified or-amylase solutions. No explanation ofthe increase in a-amylase activity by peptone is yet advanced.A minor point of controversy in the constitution of starch hasbeen settled by the outcome of experiments on the yield of carbondioxide obtained by an improved decarboxylation technique appliedto polysaccharides and sugars. It has been observed by severalworkers in the past that small yields of carbon dioxide were obtain-able from starch and cellulose, and the question arose as to whetheruronic acid residues in small amount were present in the poly-saccharide molecule, or whether such existed in an adventitiousimpurity.The result of the most recent determinations by W. G .Campbell, E. L. Hirst, and G. T. Young,14 employing a modifiedapparatus of the type suggested by A. D. Dickson, H. Otterson,and K. P. Link l5 and conducting the determination in an atmos-phere of nitrogen, shows that starch, cellulose and the naturallyoccurring sugars such as maltose, glucose, galactose, sucrose, etc.,all yield amounts of carbon dioxide, averaging about O-Syo, which isobviously not due to the original presence of uronic acids and in thecase of the above polysaccharides has no structural significance.In polysaccharides where uronic acids are definitely known to bepresent, it is obvious that these findings must in future be taken intoaccount, although the correction may be difficult to apply accurately.For the same reason, many of the published figures for uronic acidcontent must be somewhat too high.Pectin.-The nature and constitution of pectin and its congenersstill remain matters for further experiment and speculation.Theolder views of Ehrlich, involving a ring structure of four carbo-hydrate residues, were never in keeping with present views onpolysaccharide structure, which have developed almost concurrentlyl2 Enzymologk, 1937, 4, 79.l4 Eature, 1938, 142, 913.l3 Cereal Chem., 1938, 15, 273.15 J .Amer. Chem. SOC., 1930, 52, 775NORRIS : PLANT. 363with the work of Ehrlich on pectin. Such views are giving waynow before the results of more recent work, which tends to bringpectin much more in line with other polysaccharides. The work ofLink et a2.16* l7 from 1934 onwards, based on the results of methyl-ation of pectin derivatives similar to those investigated by Ehrlich,and on viscometric and X-ray measurements, indicated that chainformation of galacturonic acid units provides a t least the basis ofpectic substances. Further support for the uronic acid chain hasbeen forthcoming as a result of the experiments of G. Schneider I * andco-workers, who approached the problem from a slightly newer angle.They prepared nitro-pectin and found that the product containedtwo nitro-groups for each galacturonic acid unit; in its physicalproperties-formation of thin films, viscosity, etc.-it resembledcellulose nitrate.The molecular weight, based on viscosity meamre-ments, varied between 20,000 and 50,000 according to the originof the product and its method of preparation. From a similarexamination of the pectin esters these authors conclude that theessential pectin molecule is built up of a chain of galacturonic acidresidues, the carboxyl groups being free, a large proportion beingesterified with methyl alcohol. Galactose and arabinose areregarded as impurities and not essential constituents of themolecule.Whilst arabinose as araban is a recognised concomitant impurityassociated with most pectins as prepared in the laboratory, theposition of galactose is not quite so clear.F. W. Norris and C. E.Reach l9 have prepared pectins from a number of plant sources,including the flower of the hop, and it is by no means clear from theresults of analyses of the products whether galactose may be regardedas an essential constituent or not. The substance known as pecticacid, which corresponds to a completely demethylated pectin, wasformerly thought to be a chemical entity, but it is now shown thatit is a mixture which under certain conditions of preparationapproaches constant composition. By suitable methods of prepar-ation, the araban content of pectin may be reduced to negligibleamounts, but so far as is known it is not possible to separate thegalactan fraction, nor is the precise nature of this portion known.Even assuming that the basal molecule of pectin is a galacturonicacid chain, the substance isolated in the laboratory is a much morecomplex product than this, and many of the properties of pectinsubstances depend on the presence or absence of groups or unitswhich may or may not be part of the molecule.An accuratel6 J . Biol. Ghem., 1934, 105, 15.1s Bwchem. J., 1937, 31, 1945.l7 Ibid., 1935, 109, 293.Ber., 1936, 89, 309, 323, 2537, 2541; 1937, 70, 1611, 1817364 BIOCHEMISTRY.definition of the term pectin is lacking at present; if the power toform jellies in acid-sugar mixtures is to be accepted as a criterion,then many so-called pectins must be excluded from the class, sincethey will be found not to give such jellies.Indeed, beet pectin,which was employed as a typical pectin by Ehrlich, will not formjellies. Schneider correlates jellying power with chain length :pectins from vegetable sources in general are assumed to have shortchains and low jellying power ; pectins from fruits, especially citrusfruits, have a long chain and corresponding high jellying power.It will be seen, then, that according to this theory jellying power isassociated with high molecular weight.Confirmation of the high molecular weight of citrus pectins inparticular, and of fruit pectins in general, is forthcoming from theapplication of ultracentrifugal methods.T. Svedberg and N.Gralen20 point out that cellulose, starch and glycogen give poly-disperse systems in solution which do not possess well-definedmolecular weights, and the semi-solid proteins behave similarly.On the other hand the proteins of the body fluids show well-definedmolecular weights and it is argued from this that it is to be expectedthat the carbohydrates of plant juices would behave similarly.The largest proportion of carbohydrate in plant juices is pectin ;in bulb and tuber juices regular polysaccharides predominantlyoccur. Solutions of pectin from fruits were not monodisperse, butwere better defined than starch or cellulose solutions. By sedimenta-tion methods, orange pectin was found to have the highestmolecular weight (40,000-50,000), and that of apples, pears andplums ranged from 25,000 to 35,000.There is thus substantialagreement on the probable molecular weight whether obtainedby sedimentation methods or by the methods adopted bySchneider.The carbohydrates of bulb and tuber juices proved to be morenearly monodisperse in sedimentation and diffusion. The carbo-hydrate from the Lilium bulb had a molecular weight of 16,000. Itwas also observed, with potatoes, that the changes undergone bythe plant as it develops are reflected in the sedimentation curves.Two well-defined components of high molecular weight may bedistinguished even in the early stages of sprouting, and, as growthactivity increases, the presence of these components becomesincreasingly well marked.It is thought that this is an indicationthat the reserve carbohydrate passes through two intermediatestages before products of low molecular weight are formed.I n the present uncertain state of knowledge of the precise natureof pectin it is not surprising that definite information with regard2o Nature, 1938, 142, 261NORRIS : PLANT. 365to the enzymes responsible for pectin breakdown is not yet available.Much work has been done, and a number of enzymes have beenindicated as taking part in the stepwise degradation of pectin to itssimpler components. One of these is to be regarded as effectingthe removal of methoxyl groups from the pectin, and Z. I. Kertesz 21gives details for measuring this pectin-methoxylase activity. Theextent of demethylation in slightly alkaline solution increases withthe amount of enzyme added, and decreases with increasingconcent,rations of pectin.The above author has also provided a review22 of the presentstate of knowledge of the pectic enzymes.Cultures of B.carotovorus have been largely used as a sourceof the hydrolytic enzyme pectinase and the effect of variations inthe medium on pectinase production has been studied by M.Fernando.23 The optimum pB. at which the enzyme acts is alteredaccording to whether the medium is acid or not; where acidity ofthe medium obtains, the optimum pH changes to the acid side.By growth comparison it was shown that active pectinase is producedmore freely in alkaline than in acid conditions, and good enzymeproduction is effected under conditions which favour the rapidmultiplication of the organism.HemiceEZuZoses, etc.-The hemicellulose from cottonseed hulls wasfound by E.Anderson and S. IGmman 24 to contain glycuronic acid,xylose and an unknown substance which they called “body X,”now thought to be a dark-coloured condensation product of ligninand furfuraldehyde-an artefact o€ hydrolysis. The subject hasbeen re-investigated by E. Anderson, J. Hechtman, and M. Seele~,~5who separate two hemicelluloses from the alkaline extract of thehulls by differential precipitation with acid and alcohol, and removethe contaminating body X by successive chlorinations, or preferablybrominations, whereby the hemicelluloses are obtained as whitepowders.The hemicelluloses are mixtures containing only xyloseand glycuronic acid in proportions of 1 molecule of acid to 10 to 16molecules of the sugar.Hemicelluloses of a somewhat similar type, but containing glucosein addition to xylose and glycuronic acid, were described by S.Angel1 and F. W. Norris,26 who extracted them from the flower ofthe hop. This is believed to be the first description of hemicellulosesof floral organs, and it was rather surprising to find that the hemi-celluloses were of the xylan type usually associated with highly21 J. Bid. Chern., 1937,121,589.22 Ergebn. Enzymforsch., 1936,5, 233.23 Ann. Bot., 1937, 1, 727.25 Ibid., 1938,126, 175.24 J . Biol. Chem., 1931, 94, 39.ee Biochem. J., 1936, 30, 2159366 BIOCHEMISTRY.lignified tissues ; in the case of hops, however, considerable amountsof lignin are present. The carbohydrates of the bark of trees havenot been studied so much as those of the wood, and differences inconstituents are indicated by results obtained by H.W. Bustonand H. S. Hopf 27 for the bark of ash (Fraxinus ezcebior). Thecontent of pectic substance was higher than that usually encounteredin woods, where it is normally present to but a slight extent, and inthis case was about 7%. The content of hemicellulose was of theorder of 20%, but the nature of this constituent recalled rather thehemicelluloses of leaves than of wood, since galactose was thepredominant product of hydrolysis together with galacturonicacid and smaller amounts of mannose and arabinose.Thehemicellulose of the bark presented a striking contrast to that othe wood, which contained some 60% of xylan.The carbohydrate and other constituents of the pericarp of thehazel nut (Corylus avellam) have been examined by J. G. Boswe11,28who compares his results with those of I). F. J. Lynch and M. J.Goss 29 for the hull of the peanut (Arachis hypogea) and his own forthe shell of the Brazil nut (Bertholletia e~celsa;).~~ Fractions solublein benzene, alcohol, water and 4% sodium hydroxide solution wereexamined, and the contents of cellulose and lignin determined. I naddition to chlorophyll the benzene-soluble fraction probablycontained a wax; and a phlobatannin was probably present in thealcohol-soluble portion. The water-soluble substances werenegligible, but the alkaline extract contained three fractions ofhemicellulose-like nature together with lignin.The predominanthydrolysis product was xylose with smaller quantities of uronic acidand methoxyl. The results with hazel nut and peanut showed asimilarity in keeping with their morphological identity, and bothdiffer from those obtained for the brazil nut shell, which is a seedcoat. It is suggested that, although lignification follows the samegeneral plan in both types of tissue, different processes or factorsare at work in the case of the lignified seed coat.Proteins.-A review of the abstracted literature for the last yearshows an apparent lack of great activity where plant proteins areconcerned. Amongst publications which may be mentioned is oneby N.F. Burk,3l who continues, in the case of gliadin, investigationswhich have been proceeding for some years on the osmotic pressure,molecular weight and stability of plant proteins. The authorrecalls that Sorensen suggested that gliaclin amongst many otherproteins is composed of reversibly dissociated systems of components.27 Biochem. J . , 1938, 32, 44.OD I n d . Eng. Chem., 1930, 22, 903.28 Ibid., p. 986.Biochem. J . , 1936, 30, 971. 31 J . Bwl. Chem., 1938,124, 49NORRIS : PLANT. 367N. F. Burk and D. M. Greenberg32 had already shown that ureasolution involved the dissociation of some proteins into definiteunits of lower molecular weight, and N. F. Burk 33 has more recentlyshown that excelsin has a molecular weight of about 212,000 inaqueous salt solution, which is reduced to 35,700 in urea solution.In the case of gliadin osmotic measurements on five preparations inurea solution showed more or less regular variations according toprecipitation temperature, and thus demonstrated the non-homogeneous character of the protein.Gliadin is, however, morestable in urea solution than excelsin and certain other proteins, asthere mas little difference in molecular weight of the protein whetherin alcohol or urea solution. It was found that, if the gliadin hadbeen coagulated to some extent by alcohol, such coagulated prepar-ations did give a lower molecular weight in urea solution, and thediffering molecular weights indicated for the five preparations aboveare probably due to the presence in them of varying amounts ofcoagulated protein.It is also considered that gliadin is denaturedby urea, disulphide linkages being present in urea solution, butthiol groups are absent.The black bean, a variety of Phaseolus vulgaris, has an interestin addition to the purely chemical, in that together with maize itcomprises almost the entire diet of the Mayas. The proteinsof the bean have been recently studied by D. Breese Jones, C. E. F.Gersdorff and S. Phillip~,3~ who find that the chief proteins are ana- and a p-globulin. They contain relatively large amounts oflysine, tryptophan, histidine and cystine, are closely similar incomposition to proteins of other varieties of Phaseolus, and withregard to the dietary indicated above are ideal in that theamino-acid composition is supplemental to that of the maizeproteins.The enzyme papain, a representative of plant proteolytic enzymes,continues to attract the attention of investigators.The presenceof natural activators in unpurified preparations of the enzyme isgenerally recognised and their source lies in the latex of Caricapapaya, wherein the presence of glutathione and other thiolcompounds is reported by C. V. Ganapathy and B. N. Sa~tri.3~The suggestion that glutathione is an activator is contrary to theviews, amongst others, of W. Grassmann,36 who postulates aphytokinase which is not glutathione but a dipeptide of cyst(e)ineand glutamic acid. In a later communication C.V. Ganapathyand B. N. Sastri37 endeavoured to establish the activation as a32 J . Biol. Chem., 1930, 87, 197.3& Ibid., 1938, 122, 745.36 Biochem. Z., 1935, 279, 131.33 Ibid., 1937, 120, 63.35 Current Sci., 1938, 6, 330.37 Nature, 1938,142, 539368 BIOCHEMISTRY.function of the form of sulphur present by treating fresh latex withhydrogen peroxide to oxidise all -SH groups to the -S*S- form, andprepared the product in a dry state. The substance was inactivetowards peptone, but retained its action on gelatin; it was in factas active in this respect as when activated by hydrogen cyanide orglutathione. It was most active a t about pH 3, that is, in far moreacid medium than usually reported for papain; maleic acid hadlittle effect on activity, but iodoacetic acid produced an irreversibleinactivation.These results would suggest that the presence of-SH groups is unnecessary for gelatinase activity, but essential forpeptonase activity, and it is argued that possibly the hydrolysis ofprotein by papain takes place in two stages : fbst to peptone andthen to amino-acids, the activation mechanism being specific forthe two stages.The nature of the activation mechanism has also been studiedby M. Bergmann and J. S. F r ~ t o n , ~ ~ who find that, although phenyl-hydrazine will activate unpurified preparations of papain whichcontain the natural activators, it is without action on purifiedspecimens. Substrates such as benzoylarginineamide, albuminand peptone were used and in each case the activating action ofphenylhydrazine was restored by addition of hydrocyanic acid tothe purified preparations.A study of the papain-amylase complex by S.Akabori and K.Kasimoto 39 has led to the preparation of more highly active papainpreparations than the original product used. From the complexin acetate buffer solution, the amylase is removed by alumina,leaving the papain some 10-20 times more active. It was foundby S. Okomura,4° however, that the preparation on these linescoagulated readily and a more satisfactory preparation was obtainedby him after alumina adsorption, by saturating the solution withammonium sulphate, dialysing , and precipitating with acetone.Thiol groups were absent from the preparation, which hydrolysedgelatin more rapidly in presence than in absence of hydrocyanic acid.Pigments.-The flowers of Gamnia rigens provide a rarity in thatmost of the carotenoids present belong to the y-carotene series.Inthe fifth contribution to a series of papers on the carotenoids,K. Schon 41 describes a new xanthophyll, gazaniaxanthin, whichcontains one atom of oxygen and is of probable formula C40H540 orC40H560. The new xanthophyll was obtained by chromatographicanalysis of the saponified lipoid extracts of the flowers. There is anupper zone of rubixanthin and a large colourless zone separatings 8 Science, 1937, 86, 496.39 Bull. Chem. SOC. Japan, 1938, 13, 453.4* Ibid., p. 634. *l Biochem. J., 1938, 32, 1566NORRIS: PLANT. 369this from the second coloured zone, which contains thegazaniaxanthin, accompanied by another unknown and difficultlyseparable carotene. Finally, there is a small zone of y-carotene.The structure of gazaniaxanthin is not yet known; it yields anacetyl derivative on treatment with acetic anhydride in pyridinesolution, whereby the presence of one alcoholic hydroxyl group isinferred.It is tentatively suggested that it may be an isomeride ofrubixanthin, the hydroxyl being in the aliphatic side chain as inlycoxanthin and lycophyll. An interesting consequence of such asuggestion is that the substance, unlike rubixanthin, would then beactive as a provitamin A, and biological tests would thereforedecide this structural consideration.A new xanthophyll is also reported by H. H. Strain,42 who findsthat in ester form it is the principal pigment present in the petalsof the Californian poppy.He calls the pigment eschscholtzxanthinafter the botanical name of the plant and, as obtained by saponific-ation of the esters, it has the empirical formula C,,H,, * 202. Themolecule is highly unsaturated, containing twelve double bonds,possibly in a single conjugated system, and two hydroxyl groups.The pigment and its esters are more unstable than the commoncarotenoids, a fact which causes difficulties in the preparation ; thus,they are easily affected by heat, as indicated by changes in thespectral absorption properties. Similarly, they take up oxygenmuch more readily from the air; the rate of oxidation in differentsolvents varies but is not increased in the presence of hamin, as hasbeen reported in the case of lycopene.Apparently the large green-yellow fruit of Machra pornifera Raf.known as the Osage orange, growing widely in parts of Oklahoma,and Texas, has largely escaped the attention of the chemist.Theyellow pigment has, however, been isolated recently by E. D.Walter, M. L. Wolfrom, and W. W. He~s,4~ who have obtained asmuch as 6% on the dry weight of the fruit. The pigment is solublein organic solvents in general, but not in light petroleum, a factwhich is made use of in its preparation. The dried and powderedfruit is extracted exhaustively with light petroleum and then withethyl ether, from which solvent the pigment may be recovered andthen recrystallised from xylene and alcohol.Evidence of structureis not yet complete, but the product appears to be an o-dihydricphenol and a lactone structure is indicated. It gives a mono-and a di-acetate, the second acetyl group being saponified only withdifficulty; the name osajin has been suggested and the provisionalformula in accordance with present findings is C24H,20(CO*O)(OH)2.J . Amer. Chem. SOC., 1938, 60, 574.42 J . Biol. Chem., 1938, 123, 426370 BIOCZ3EMISTRY.A new colouring matter belonging to the naphthalene group isthe subject of a preliminary communication of J. R. Price andR. Robinson.44 The name dunnione issuggested for the pigment, which occurs as//-A) deposits on the leaves of Streptocurpus Dunnii ( 11 (, (I.) Mast. and appears to be a derivative of \qN wg2z p-naphthaquinone of empirical formula0-c C,,H,,O,.The third oxygen atom is a* H/ \CH, member of a coumaran ring, and the general<cH,* may be attached chemical and physical properties and itsthat it is 2 : 3 : 3-trimethyl-6 : 7-benzo-coumaran-4 : 5-quinone (I). This colouring matter is differentfrom, but possibly related to, colouring matters described byS. Siddiq~i:~ which were obtained from the reddish dust on leavesof Didymocarpus pedicellata.The red pigment of the beet, which was first isolated byG. Schude146 and has since been examined by A. D. Ainly andR. R~binson,~' is the subject of a communication by G. W. Pucher,L. C. Curtis, and H. B. Vi~kery,~8 who describe in the first instancea method of preparation of the unstable pigment.The method isbased on the fact that most of the pigment may be obtained in theprecipitate formed when the dried tissue is extracted with acidalcohol, and the extract subsequently neutralised with lithiumhydroxide. The dried concentrate contains 16% of pigment andthe latter may be obtained, after lead treatment, in ill-definedcrystalline form, which has a constant extinction coefficient (Zeissspectrophotometer) . Although formulation is not possible on theevidence so far obtained, betanin is undoubtedly a glycoside of anitrogenous nucleus, which appears to be closely related to theanthocyanidins. The form in which the nitrogen is present is notknown yet with certainty ; aliphatic amino-groups are unlikely,aromatic amino- or ring nitrogen is possible.The authors alsodescribe a method of determination of betanin based on a know-ledge of the extinction coefficient of the pure substance a t definiteconcentration when viewed through the S 53 Nter of the Zeissinstrument.The survey of anthocyanins, commenced by R. Robinson et aZ.(1931 onwards), is taken up by J. R. Price and V. C. SturgessFg whohave examined 200 species in 110 genera with respect to the nature46 J . Indian Chem. Soc., 1937, 14, 703.47 J . , 1937, 446.8* degradative reactions lead to the conclusion CH,* at 0.44 Nature, 1938, 142, 147.4 6 Dissert., Zurich, 1918.4 8 J . Biol. Chem., 1938, 123, 61, 71.19 Biochern. J., 1938, 32, 1658NORRIS : PLANT. 37 1of the anthocyanins of the young leaves.The anthocyanin color-ation of young leaves which disappears on reaching maturity isprobably a more general phenomenon than the more obviousfamiliar autumnal coloration, and a wide range of plants has beenexamined. The great majority-93%-of the pigments werecyanidin saccharides, and half of these were pentose glycosides,about 30% in each case were monoglycosides and 3-biosides, witha small remainder of 3 : 5-dimonosides.In a later communication on the same subject, W. J. C. Lawrence,J. R. Price, G. M. Robinson, and R. Robinson 50 indicate new pointsin the technique of examination designed to overcome the difficultiesin determining glycoside type involved in the presence of a numberof substances such as tannins and anthoxanthins. As in the youngleaves, the autumn leaves showed a great preponderance of cyanidinsaccharides, but owing to the interference of foreign substances ofthe type indicated the results with regard to sugar type are not soconclusive as in the case of young leaves, where interfering sub-stances gave less trouble.Finally, J.R. Price, V. C. Sturgess, R. Robinson, and G. M.Robinson 61 have summarised the results of recent surveys ofanthocyanins, and forecast interesting future possibilities. Theanthocyanins of angiosperms show an overwhelming predominanceof pigments based on pelargonidin, cyanidin and delphinidin andmethyl ethers of the last two. New types are exemplified by thenitrogenous pigment of the beet already discussed and by gesnerinfrom the flowers of Gemera fulgens; the yellow pigment of theIceland poppy is also nitrogenous. The new types of anthocyaninhave been found in the Pteridophyta ; they consist of monoglycosidesand diglycosides, and the corresponding anthocyanidins do notcorrespond to the common types already established; they areprobably based on 6-hydroxypelargonidin and 6-hydroxycyanidin.An interesting point is raised by D.Erikson, A. E. Oxford, andR. Robinson,52 who discuss the occurrence of anthocyanins inbacteria, and draw the conclusion that this has not so far beenestablished despite the numerous references to such in the literatureand in text-books. It is pointed out that the evidence for theirexistence is not satisfactory or complete, since there is no exampleof the isolation and complete characterisation of an anthocyaninfrom such a source. Many classes of basic d y e s t h e oxazines,thiazines and azines-contain a heterocyclic nucleus associated withhydroxylated benzene rings and would simulate the indicatorreactions of anthocyanins.Moreover, the flavylium nucleus will6o Biochem. J . , 1938, 32, 1661.61 Nature, 1938, 142, 356. 62 Ibid., p. 211372 BIOCHEMISTRY.not withstand treatment with boiling aqueous alkali, whereas apigment from Actinomyces Waksmanii, described as an anthocyaninby A. E. K r i ~ s , ~ ~ gives a stable royal-blue colour after such treat-ment. The latter pigment thus probably belongs to one of the morestable types suggested above.Chemical Aspects of Some Micro-organisms.Aspergillus.-In papers dealing with the intake of nitrogen asnitrates by A .niger, D. Itzerrott 54 and E. Bunning 55 are in agreementthat the effect of the pa of the substrate does not lie in its influenceon the charge on the colloids of the plasma or on the permeabilityof the cell membrane to nitrate molecules. Accumulation of nitrateions occurs when the substrate is more acid than pH 3, but the nitrateis not utilised under these conditions. With decrease in acidity,part of the accumulated nitrate disappears. Assimilation ofnitrogen as ammonium ions also increases with increasing alkalinity,but is not entirely inhibited by acid conditions as in the case ofnitrate. The latter author also discusses the intake of dyes by theorganism and finds that the rate of intake is conditioned by theconcentration of dyes within the cell.Such concentration dependson the adsorptive power of the sap colloids, and this is controlledby the pH of the substrate. Increasingly acid substrates tend toincrease the concentration of basic dyes and to decrease that of theacid dyes.The utilisation of various forms of nitrogen by A . niger withspecial reference to the supply of essential metallic salts has beeninvestigated by R. A. Steh~berg,~~ who finds that ammonium andnitrate ions and the nitrogen of urea and asparagine are equallyutilised, provided that such metallic salts are present. In particular,zinc, copper, manganese and molybdenum in suitable amount arenecessary for satisfactory nitrogen uptake and the importance of thelast element is stressed.It was found that more molybdenumwas necessary when nitrogen was presented as nitrate than for otherforms, and it is suggested that molybdenum is required in respectof the activity of the nitrate-reducing enzyme system.The influence of certain heavy-metal salts on the compositionof A . niger has been shown by G. Schulz 57 to vary with the strainand age of the culture. The formation of higher carbohydrates isfavoured, and that of lignin and its congeners inhibited by thepresence of manganese, cadmium, iron and zinc. Fat formationalso is influenced by the metals indicated, manganese and iron63 Compt. rend. Acad. Sci. U.R.S.S., 1936, 4, 283.64 Flora, 1936, 31, 60. 6 5 Ibd., p. 87.6 6 J.Agric. Res., 1937, 55, 891. 6 7 Plan@ 1937,27, 196NORRIS : PLANT. 373stimulating, and zinc and cadmium retarding production. Saltsof all four metals increase the production of metabolites, but showconsiderable differences individually in the extent of stimulationwhich they induce.In the twelfth part of a series of investigations on the chemistryof mould tissue, D. W. Woolley a.nd W. H. Peterson 68 identifyhistidine, lysine a.nd arginine in the mycelium of A . sydowi. Thefirst two are isolated from the autolysate, but arginine undergoesdestruction during autolysis and is probably present in combinedform. It may, however, be obtained in the aqueous extracts of thefresh tissue. The minimum amounts of the acids found are small,representing little more than 5% of the total nitrogen of themycelium.In the next communication 59 of the series, some 17% of thenitrogen of the mycelium had been accounted for as definitecompounds. The amino-acids of the autolysate now includepredominantly leucine and serine, and dicarboxylic acids, proline,tryptophan, tyrosine, isoleucine and valine are also present.Theauthors were unable to detect alanine, glycine, phenylalanine andhydroxyproline.Finally, in the latest communication 6o to date, an acetoneextract of the fat-free mycelium or the usual autolysate has beenfound to contain cyclic choline sulphate.The zymase system of enzymes which is responsible for normalalcoholic fermentation is shown to occur in various species ofAspergillus and Penicillium by T.G. TomlinsonYG1 who finds, forexample, that A. niger cultured in peptone is able to convert sugarinto alcohol under anaerobic conditions. Two penicillia, P.divaricatum and P. sanguijluus, produce, in presence of calciumcarbonate, citric acid and alcohol, but the former is produced morerapidly than the latter, and there appears to be no relation betweencitric acid production and the presence of zymase.An increase in the production of citric acid from sugar, and ofoxalic acid from acetic acid, is claimed by V. S. Butkevitsch andE. I. Trofimova G2 when the mycelium of A . niger is removed from thenormal nutrient medium and placed for 24 hours in aqueousmagnesium sulphate solution.New NetaboZites.-In a continuation of studies on the biochemistryof micro-organisms, J.N. Ashley and H. Raistrick 63 describe twonew metabolic products isolated from the mycelium of Helmintho-5 8 J . Biol. Chem., 1937, 118, 363.6o Ibid., 1938, 122, 213.62 Compt. rend. Acad. Sci. U.R.S.S., 1937, 17, 221.63 Biochem. J., 1938, 32, 449.59 Ibid., 1937, 121, 507.hTew Phytol., 1937, 36, 418374 BIOCHEMISTRY.sporium Zeersii. These are present in considerable quantity andare chemically similar, the names luteoleersin and alboleersin beingsuggested. As the names imply, the former is a yellow substance,the latter white; they have both been obtained in crystalline formand bear the chemical relationship of a substituted quinone orsemiquinone and its corresponding phenol. Thus, luteoleersin isreadily reduced to alboleersin, and the opposite change is effectedby simple oxidation.Derivatives were not obtained in crystallineform, since a number of attempts t o methylate, acetylate andbenzoylate the substances yielded products of a gummy or glass-like nature. The simple relationship between the two substancessuggests that they may comprise an oxidation-reduction systemin the life-process of the organism.Another pair of metabolic products, which also probably comprisean oxidation-reduction system in A . fuwigatus, is described byW. K. Anslow and H. Raistrick.64 The metabolism solution of thisfungus was observed to change in colour from yellowish-brown topurple when made alkaline, and the substance responsible was shownto be a new product, fumigatin.This was found to be 3-hydroxy-4-methoxy-2 : 5-toluquinone (I), and it was readily interconvertiblewith its reduction product, 3-hydroxy-4-methoxytoluquinol (11).A further interest attaches to these products in that it has now beenpossible to convert fumigatin in vitro into a metabolic product ofPenicillium spindosum, now named spinulosin (111). The latternow appears as 3 : 6-dihydroxy-4-methoxy-2 : 5-toluquinone, or6-hydroxy-fumigatin. The formula of these compounds recallseveral naturally occurring derivatives of 2 : 5-dihydroxy-1 : 4-such as embelin (IV ; R‘ = H, R” = n-lauryl) and(IV ; R’ = R” = phenyl).benzoquinone,polyporic acidAs this Report goes to press a further communication by W. K.Anslow and H. Raistrick 65 appears, in which they report theisolation of spinulosin from cultures of a strain of A .fumigatus.This is in contrast with the previous finding that from anotherstrain of the same organism fumigatin ody was produced. Thus,two strains of the same species give rise to different metabolites,and, further, since spinulosin was originally obtained from64 Biochem. J . , 1938, 32, 687. 65 Ibid., p. 2288NORRIS : PLANT. 375P. spinulosum, yet another example o f the same metabolite from twodifferent genera is afforded.Proteolytic Enzymes of Bacteria.-Of recent investigations onbacterial proteinases may be mentioned those of G. Gorbach, whowith E. Pirch 66 has shown that B. fluorescens and B. pyocyaneusexcrete into the culture medium a proteinase whose optimum pH is7.A peptidase operating at pH 8-4 was shown to be present inthe cells. The proteinase was later shown to be a product of theautolysis of dead bacteria.67 G. Gorbach 68 was also able toseparate from cultures of Caseiococcus and Gastrococcus a proteinaseof the papain type which had an optimum pH of 4.7, as distinctfrom the common bacterial proteinase, whose optimum pH, asabove, was 7. The separation was effected by dialysis with di-ammonium hydrogen phosphate.The view that bacterial proteinases belong t o neither the papainnor the tryptase group, but constitute an intermediate group, isadvanced by E. Ma~chmann,~~ who has examined the proteolyticactivity of culture filtrates of a number of strains of B. prodigiosus,pyocyaneus and fluorescens liquefaciens.Act'ivators, such ascysteine, reduced glutathione, hydrocyanic acid, ascorbic acid,chloroacetic acid and potassium ferrocyanide , are without activatingaction on the filtrates, nor do they activate the proteinase solutionsfree from peptidase prepared from them. The proteinases preparedfrom the different culture filtrates were probably identical, and wereeffective in hydrolysis of gelatin and clupeine a t pn 7.However, activating agents are effective with some bacterialproteinases, as shown in an investigation of the proteinase ofClostridium histolyticum by L. Weil and W. K~cholaty,~O whoemployed the bacteria-free filtrates from anaerobic cultures. Theenzyme was extracellular and operated best a t pH 7.0.Thiolcompounds activated the enzyme and the activation was itselfcatalysed by heavy-metal ions. In the presence of cysteine andferrous ions, the activation was maximal under anaerobic conditions.As the growth of the cultures increased, proteinase activity alsoincreased up to a maximum in 24 hours, followed by progressivedecrease after that period. Moreover, somewhat similar resultswere later obtained by E. Ma~chmann,~~ using Bacillus perfrigens,VVibrio septicus and B. botulinus. It was found that the first-namedorganism yielded small amounts of di- and aminopoly-peptidase,and larger amounts of an enzyme which hydrolysed gelatin, andanother enzyme which on activation by thiol compounds such as6 6 Enzymologia, 1936, 1, 191.6 8 Ibid., 1937, 3, 65.70 Bwchem. J., 1937, 31, 1255.67 Ibid., 1937, 2, 92.Bwchem.Z., 1937, 294, 1.71 Biochem. Z., 1937, 295, 1376 BIOCHEMISTRY.cysteine and reduced glutathione or, to a less extent, by hydrocyanicacid, hydrolysed clupeine. Vibrio septicus yielded a closely similarmixture of enzymes, as also did B. botulinus, but in the latter case theprotease was able to hydrolyse native protein such as caseinogen andfibrin in addition to gelatin.The subject of bacterial proteinases has also been taken up byJ. Berger, M. J. Johnson, and W. H. Peterson,', who communicatethe fist of a series of papers in which the peptidases of Leuconostocmesenteroides are described. In some cases the presence ofacidopeptidases from bacterial autolysates has been demonstrated.The complex of peptidases obtained appears to consist of at leastsix enzymes , including two dipeptidases, three polypeptidases andan acylase; but no carboxypeptidase was found.Both opticalcomponents of a number of racemic peptides were hydrolysed byLeuconostoc peptidases, such peptides including leucylglycine ,alanylglycine, and the diglycyl peptides of alanine and leucine. Anumber of metallic ions were capable of producing an activatingeffect in some of these hydrolyses.The conversion of E-aspartic acid into B-alanine has been shownby A. I. Virtanen and T. Laine 73 to be accomplished by simpledecarboxylation by living legume bacteria :HO,C*CH2*CH(NH2)*CO2H = HO,C*CH,*CH,*NH, + CO,In collaboration with P. Rintala 74 they have now shown thatsuch a decarboxylation takes place when a bacterial suspension intoluene is used at pH 7. A similar decarboxylation takes place withZ-glutamic acid, y-aminobutyric acid being formed, and in bothreactions the change is quantitative.It seems doubtful, however,whether the same e n z p e is acting in both reactions, since it hasbeen shown that some plant tissues contain an enzyme which willdecarboxylate glutamic acid but not aspartic acid. Hence it issuggested that the legume bacteria may produce two de-carboxylating enzymes : glutamic decarboxylase and asparticdecarboxylase.The deamination of aspartic acid has also been investigatedby A. I. Virtanen and J. Erkama,75 who precipitate a substancehaving aspartase and asparaginase action, but not fumarase action,from the cell-free solution of B.JEuorescens liquefaciens. Thefollowing experimental facts were observed with this fumarase-free preparation : malic acid was formed from fumaric acid in thepresence of ammonia, in absence or presence of toluene; on72 J . BWZ. Chem., 1938,124, 395.73 Sumnen Kem., 1937, B, 10, 2; Enzymologia, 1937,3,266.74 Nature, 1938, 142, 674. 75 Ibid., p. 954NORRIS : PLANT. 377prolonged action, aspartic acid, malic acid and ammonia only werepresent in the solution; with aspartic acid as substrate, fumaricacid, malic acid and ammonia were formed. Hence it is concludedthat two distinct enzymes are present in the preparation, whichcatalyse the two reactions below, the first being a true aspartaseaction :(1) H0,C*CH2*CH(NH2)*C02H H02C*CH:CH*C02H + NH,(2) H02C*CH2*CH(NH,)*C02H + H20 =H0,C*CH2*CH(OH)*C02H + NH3It is claimed that the latter reaction is probably the first demon-stration of a hydrolytic deamination.It is further pointed outthat this work represents an advance on that of E. I?. Gale 76 inthat, although he separated two deaminases from the aspartaseof B. coli, both of his preparations contained fumarase, which thusmasked the true nature of the mechanism of action.Bacteria and Carbohydrates.-The fist of a series of studies oncellulose-decomposing organisms is published by E . Walker andF. L. Warren,77 who have used Cytophaga Hutchinsoni, an aerobicorganism which is specific for cellulose in the sense that no othercarbohydrate is decomposed by it. The products of its action arecomplex, and under fully oxygenated conditions one half of thecellulose may be decomposed in about eight days. Amongst thenon-gaseous products formed is predominantly a mucilaginoussubstance which appears to be an oxycelhilose of acidic type, non-reducing, and yielding xylose amongst other hydrolysis products.About one third of the products is accounted for by this mucilage,together with a yellow pigment-possibly of the nature of analiphatic acid of rather low molecular weight-a higher fatty acid,and a carbohydrate soluble in 75% alcohol. The remaining two-thirds of the cellulose is accounted for as carbon dioxide, and it issuggested that this large production of carbon dioxide from cellulosicmaterial plays an important part in the return of cellulose to thecarbon cycle. It is also suggested that the mucilaginous oxycellulosemay possibly represent one of the so-called organic colloids of thesoil; it is resistant to bacteria, but sometimes succumbs to theattack of fungi, and its general properties, mode of formation andcapacity to hold large volumes of water render it particularlysuitable as a humic substance. Decomposition up to 80% of addedcellulose is claimed for certain strains of Sorungium and Archangiumby H. and S. Krzemieniewski.78 The best source of carbohydrateis cellulose, and normal growth takes place with this sole source,76 Biochern. J., 1938, 32, 1583.’8 Bull. Acad. polonaise, 1937, B, I , 11, 33.7 7 Ibid., p. 31378 BIOCHEMISTRY.although certain other carbohydrates may be substituted for it.As sources of nitrogen, nitrates are utilised, being reduced, andammonium salts also; organic nitrogen is not utilised. Theproducts of cellulose degradation appear to be similar in generalcharacter to those described in the previous reference ; mucila,ginoussubstances are formed, together with fat'ty substances and pigments.The action of a number of common pathogenic and non-pathogenicbacteria on sugars and their derivatives has been studied by L.Sternfeld and F. Sa~nders.'~ As a general rule it was found that thederivative of a sugar was less likely to be decomposed by any givenorganism than the sugar itself. Hexoses and pentoses werefermented in most cases, but fewer organisms attacked the latter,and heptoses and octoses were unattacked. Glucononose wasattacked by only two bacteria and one yeast which was includedin the survey.Several studies on enzyme formation and polysaccharide synthesisby bacteria have been published recently by E. A. Cooper andhis associates. Polysaccharides are formed by B. mesentericus,B. megaterium, and Ps. pruni from sucrose, and Ac. xylinum producespolysaccharides from sorbitol; but the synthesis in all cases isinhibited by mannose and arabinose, owing, it is thought, to a toxicaction on the cell rather than to inhibition of enzyme action. Inmost cases, the supply of nitrogen is obtained by use of a peptonemedium, but this is not essential, as it has been shown that asparaginemay be used as sole source of nitrogen. The bacteria which arepathogenic to plants synthesise polysaccharides from sucrose, andsuch polysaccharides have been shown to be of fructosan type, noevidence of dextrans or pentosans having been obtained (E. A.Cooper and J. F. Preston).**In the next paper of the series, A. Carruthers and E. A. Cooper 81find that a fructosan is formed by B. Zactis from sucrose only. When,however, Leucolzostoc dextranicum was incubated with sucrose, adextran was formed, the solution containing fructose ; incubationwith glucose, however, gave little or no dextran. An accelerationof growth, over and above that due to added nitrogen, was evincedon addition of alcoholic extracts of molasses ; dextran formation waslikewise increased.The synthesis of polysaccharides from nitrogen- fixing organismsis the subject of the next paper by E. A. Cooper and J. F. Preston.82A large number of substances yield a gum-like substance, built ofglucose and glycuronic acid, when supplied to Rhixobium radicicolum.79 J. Amer. Chem. SOC., 1937, 59, 2663.80 Biochem. J., 1935, 29, 2267.89 J. SOC. Chem. Ind., 1937, 56, 1 ~ .Ibid., 1936, 30, 1001NORRIS : PLANT. 379These include mono-, di- and poly-saccharides, polyhydric alcoholsof 3, 5 and 6 carbon atoms, and the sodium salts of such acids aslactic and succinic. Similar results were obtained with Axotobacterchroococcum, but organisms of this type will not synthesise poly-saccharides in media containing high concentrations of sugars, incontrast to those of the preceding papers above.Pinally, to date, E. A. Cooper, W. D. Daker, and M. Stacey 83describe media for the large-scale preparation of polysaccharidesfrom Rhizobium and Axotobacter and suggest that these poly-saccharides are of the same class as the specific polysaccharides ofpneumococcus types I1 and 111.F. W. NORRIS.88 Bwchem. J., 1938,32, 2752

ISSN:0365-6217    

DOI:10.1039/AR9383500330

出版商:RSC    

年代:1938

数据来源: RSC

摘要:

ANALYTICAL CHEMISTRY.1. INTRODUCTION.THE majority of the problems presented to the analyst are not new,and they can usually be solved by standard routine methods.The existence of such methods does not mean, however, that in allcases the answer obtained is adequate. A large proportion ofthe recent work in Analytical Chemistry has very properly beendevoted to modifying current procedure and devising new methods,along classical analytical lines, to give results which more nearlyapproximate to the truth. The development in this field is now oneof detail : the problem, the manipulative technique, even thereactions involved, are often familiar; it is the conditions or theprecipitants or the application of a particular reaction that may benew. E. S. Larsen’s observation that the analysis of samples ofsilicates by a number of commercial analysts showed differences of2.5% in the determination of silica, titania, and alumina and ofmore than 4% in lime shows that such development is essential andthe field by no means exhausted.I n addition to the problems which classical analysis presents,a new series has arisen.The use of small quantities of rare earthsin non-ferrous alloys (e.g., cerium or niobium in aluminium), and ofthin films of corrosion-resistant materials, the importance of cobaltand copper in ruminant nutrition, the physiologically essential traceelements, vitamins, hormones-these exemplify the growingcomplexity which calls for improved methods of attack. The needfor increased speed in the analysis of large numbers of routinesamples, e.g., metals and soils, has also encouraged progress.New applications of the evident facts that any property which ischaracteristic of a material may in principle be used as a qualitativetest, and that a quantitative method may be founded on the measure-ment of any quantity the value of which is dependent upon theamount of material present, have formed the bases of recentdevelopments.Such properties as crystal structure, dielectricconstant, or reduction potential, or emission, absorption,fluorescence, and Raman spectra fall within this category.Progress along these and similar lines has encouraged and incertain cases been dependent upon the development of newtechniques, some of which we shall describe. X-Ray, polarographic,Amer.J . Sci., 1938,3!5, 94GRIFFITHS, GULL, AND WH.A.LLEY. 381and absorption-spectra methods have received only brief commentin earlier Reports and these are given due treatment. Electron-diffraction analysis has previously not been mentioned. Problemsin the analysis of alkaloids and other drugs, sugars, vitamins, andrecent attempts to solve them are recorded. The continued growthof micro-analysis, and the realisation that a micro-method, even iflarge amounts of material are available for analysis, may often bemore accurate than macro-analysis, give added importance to thissubject.Limitations of space have restricted the number of subjects dealtwith, and even in the treatment of particular themes direct referenceto much work of merit has of necessity been omitted.2.APPLICATIONS OF X-RAYS.To Moseley the use of X-rays as an analytical weapon was nomore than a possibility. Sixteen years ago that possibility wasfirst realised by A. HaddingY2 and since that time X-ray methodshave gradually emerged from the tentative stage to the position ofrecognised practical value which they enjoy to-day.That the frequencies of X-rays emitted by a target on bombard-ment with cathode rays are characteristic of the element composingthe target is a fundamental property which forms the basis of oneanalytical method. A second depends upon the fact that primaryX-rays from one source may on striking another target give rise tocharacteristic secondary rays.Absorption of X-rays serves as athird method, and the extensive work on X-ray diffraction hasprofitably been adapted to give a fourth means of solving analyticalproblems.The measurement of the primary spectral emission lines, in whichthe unknown material served as the target, enabled D. Coster andG. von Hevesy to confirm the existence of hafnium and played apredominant part in the discovery of maswium, rhenium, andillinium. Its quantitative possibilities were soon realised, and vonHevesy and his collaborators used the method for the quantitativeestimation of hafnium in zirconium, and tantalum in niobium.C. E. Eddy, T. H. Laby, and A. H. Turner * developed the technique,and were able to detect one part of iron in 300,030 parts of zinc.G.R. FondaY5 who used cathode rays which had passed out of thevacuum tube through a window on to the specimen, obtained an2. anorg. Chem., 1922, 122, 195.Proc. Roy. SOC., 1929, A, 124, 249; 1930, 127, 20.J . Arner. Chem. SOC., 1932, 54, 116; G. R. Fonda and G. B. Collins, ibid.,Nature, 1923, 111, 79.1931, BS, 113382 ANALYTICAL CHEMISTRY.accuracy of 2% in the determination of tantalum and niobium inmolybdenum. By comparing line intensities of the elements soughtfor with those of another element (e.g., cerium) present in knownamount, I<. Kiimra has determined lanthanum, neodymium, andgadolinium in the presence of other rare earths.The method is attractive in that the spectra obtained, particularlythe K-series, are simple in comparison with optical emission spectraand, unlike these, are independent of electrical conditions.Thatthey are equally independent of the chemical combination of theelements and their environment is in general true, though Guntherand his co-workers observed that a mixture of chromium andcopper in the ratio 46 : 54 gave an apparent ratio of 60 : 40 owingto the chromium being excited by the rays emitted by the copper.Dilution of the mixture with ground quartz removed this inter-ference. The danger of the distortion of results due to the effect ofan absorption edge on emission lines must also be recognised. Ifin a mixture one element has a characteristic absorption edge oflonger wave-length than the emission wave-length of the constituent,then selective absorption occurs.Inaccuracies in the Erst method may also arise from the heatingof the anticathode affecting the surface concentration.G. vonHevesy avoided this difficulty by the use of secondary rays. Thechoice of the exciting radiation is important. Characteristic primaryrays give fluorescent secondaries many times more intense thanthose obtained with continuous spectra, and the greatest intensityis obtained when the characteristic rays of the target metal are0.15-0.20 A. shorter than the absorption bands of the elementsundergoing analysis.have given tables of comparison elements which may be added ascalibrating media for the determination of any particular element.The absorption of X-rays by a screen of the material underinvestigation has been shown by R.Glocker and W. Frohnmayer l oto be governed by the equation I J I , = e-cp, where I2 is the intensityof radiation leaving the screen on the short wave-length side of theabsorption discontinuity, Il that on the long wave-length side, cis a constant experimentally determined, and p the amount of theelement present. V. Caglioti and P. Agostini l1 employed themeasurement of characteristic absorption edges in the analysis ofG. von Hevesy, J. Bohm, and A. Faessler6 Bull. Chem. SOC. Japan, 1938, 13, 10.P. Giinther and I. N. Xtranski, 2. physikal. Chem., 1925, 118, 257;‘‘ Chemical AnaIysis by X-Rays and Its Applications ” (1932).P. Gunther and G. Wilcke, ibid., 1926,119, 219.a 2. Physik, 1930, 63, 74. lo Ann. Phyaik, 1926, 76, 309.l1 Atti R.Accad. Lincei, 1931, 14, 301GRIFFITHS, GULL, AND WHALLEY. 383mixtures of alumina containing 0+-4% of nickel oxide. F.Voges 12 has discussed improvements in the accuracy Obtainable.N. H. Moxnes 13 used X-ray line absorption. 10-6 G. of nickel inzinc was detected by P. de la Cierva and L. Rivoir l4 by employingthe coefficient of weakening through successive films of theblackening due to X-rays to determine the constant in Glocker'sformula.Since the atoms in a crystal are arranged in a regular manner, it isevident that, within the crystal, planes exist which contain largenumbers of atoms. If the perpendicular separation for one seriesof planes is d, then for X-rays striking this series a t an angle 0 anddiffracted a t the same angle, equality of phase and thereforereinforcement will occur when 2d sin 0 = nh, I, being the wave-length of the incident beam and n an integer.From this funda-mental formula the interplanar spacings and hence the structure ofthe crystal may be calculated. If the diffracting beams are photo-graphically detected, a series of points will be obtained on the plate.A number of partly oriented crystals give spots, then arcs, andfinally, when the orientation is completely chaotic, rings areobtained.X-Ray diffraction methods may be used when the materialunder investigation is either a single crystal or in the powderedstate, but since few substances are conveniently obtainable as singlecrystals the powder method of Debye and Scherrer and of Hull ismore generally employed.An essential condition of the method isthat an entirely chaotic orientation of the particles should beobtained, so that enough particles are inclined a t the required angleto the monochromatic incident beam to give a strong reflexion fromone set of parallel planes, reflexion from another set being producedby other particles inclined a t a different angle to the incident beam.Even with powder ground to pass a 200-mesh sieve, it is generallydifficult to obtain a sufficiently chaotic arrangement of the crystalsof any constituent present to an extent less than 1% by volume,whereas for crystals of low symmetry (e.g., triclinic) a finer state ofsubdivision may be necessary.It is inherent in the method that the diffraction patterns producedare dependent on the state of chemical combination of the elementswhich form the crystal lattice : for example, sodium chloride andpotassium bromide can be distinguished from sodium bromide andpotassium chloride, a feature the analytical value of which is evident.Both the breadth of the method and its limitations are illustratedl2 2.Physik, 1933, 80, 542.13 2. physikal. Chem., 1929, A, 144, 134; 1931, A, 152, 380.14 Anal. Fis. Quim., 1936, 34, 770384 ANALYTICAL CHEMISTRY.by the observation l5 that of X ,000 substances from a typical chemicalstores only 50 gave no pattern, some were identifiable a t less than1%, others at less than lo%, and others at less than 50%. Theexistence of this limit of sensitivity and its numerical value, which incertain cases can be quite high, are determining factors in assessingthe utility of the diffraction method for a particular problem.From the X-ray diffraction pattern of a single material theinterplanar spacings may be calculated and the relative intensitiesof the diffracted beams measured by an ionisation chamber, aGeiger-Muller counter, or more usually, by obtaining a photo-graphic record.Inspection alone enables orders of blackness to beestimated, and this is often sufficient. When greater precision isrequired, recourse can be made to microphotometric methodsfor determining the blackening of the image, and hence, from aknowledge of the characteristics of the film used (ie., the relationbetween intensity of incident radiation and the blackness produced),the intensities of the diffracted beams calculated. The data soobtaJined, i.e., interplanar spacings and intensities of diffractionbeams, are characteristic of the material examined, and anysubstance which yields precisely the sa-me data is definitely identifiedas one and the same material.The utility of the method therefore depends upon diffraction dataof many substances being on record (e.g., “ International CriticalTables”; I.E. Knaggs, B. Karlik, and C. F. Elam “ Tables ofCubic Crystal Structure,” Hilger, 1932) and preferably classified toassist rapid identification. Hanawalt’s card catalogue system,l5 inwhich the three strongest lines are given for over 1,000 substances,greatly facilitates identification.A striking example of the ability of the diffraction method to givea result where standard chemical methods are impotent is that ofthe detection of crystalline silica in lung tissue.16 A chemicalattack of this problem would not differentiate between free andcombined, crystalline or amorphous silica in the lung, since whendifferentiation is attempted the silica may react with the alkalineconstituents of the ash at the temperature necessary to eliminatecarbon. Quartz was detected in tissue containing only 0.26% of silica.A second example is found in the work on the effect of sodiumfluoride and parathormone on the incisors and tibiz of rats,l’ in16 J.D. Hanawalt and H. W. Rim, I d . Eng. Chem. (Anal.), 1936, 8, 244;J. D.Hanawalt, H. W. Rim, and L. K. Frevel, Ind. Eng. Chem., 1938,30,457.1s R. Klaas, H. C. Sweany, J. N. Mrgudich, and G. L. Clark, Science, 1937,86, 544.17 L. Reynolds, K. E. Corrigan, H. S. Haydn, I. G. Macy, and H. A.Hunscher, Amer. J . Roentgenol., 1938, 39, 103GRIFFITHS, GULL, AND WHALLEY. 385which X-ray patterns showed that the brittleness of the teeth wasdue to lack of orientation, increased crystal size, and heterogeneityof the material.As a positive test the diffraction method is unequivocal, but as anegative test it must be accepted with caution. If the patternof the substance sought for is obtained, then that substance ispresent : but the possibility of some other crystalline material oflow sensitivity mixed with it, or the presence of some substancein solid solution that has not appreciably altered the lattice cannotbe excluded.If no pattern is obtained, an upper limit, which maybe high, can be set to the amount present. A pattern different fromthat expected does not necessarily mean that the material is absent,for traces of impurity in solid solution can change the interplanarspacings. For example, K. N. Ivanov and 0. K. Kundralsobserved that the lattice parameters of copper, cadmium, cuprousoxide, and zinc oxide and the powder-like cathode precipitatesobtained from aqueous solution at high current density wereincreased up to 100% by the absorption of hydrogen. This apparentdisadvantage can in some cases be turned to good use, and the extentof solid solubility may be determined by the change in the latticeparameters of the solvent.Within these limitations, the method can be extended to theidentification of mixtures, which requires two or more patternsto be found which give an exact match with that of the unknownmaterial.Once the components are identified, quantitativeestimation is possible by comparison of the diffraction pattern of thesample with those of prepared standard mixtures. T. N. Agafona,lgusing a photometric method, determined the variation in therelative intensity ratio of suitable pairs of lines of binary (A-B)mixtures, including apatite-alumina and Mn0,-Mn,O,, withpercentage composition. By adding a known percentage of standardB (e.g., iron, aluminium, or sodium chloride) to a mixture containingan unknown amount of A, and determining the intensity ratios,the amount of A present was read off the intensity ratio-percentagecomposition curve.In certain cases the error was less than 1%.A similar method in which an added known material served as aninternal standard was used by G. L. Clark and D. H. Reynolds 20 inthe analysis of mine dusts. K. Schafer,21 using a photometricmethod for the determination of the intensities of selected reflexionsfrom certain 1 : 1 binary mixtures and alloys, obtained resultsaccurate to 3%.18 J . Phys. Chem. Russia, 1935, 6, 469.l9 Compt. rend. Acad. Xci. U.R.X.S., 1937, 16, 367.20 Id. Eng. Chem. (And.), 1936, 8, 36. 21 2. Krist., 1938, 99, 142.REP.-VOL. XXXV. 386 ANALYTICAL CHEMISTRY.Though microscopy and thermal anaIysis are the usual tools forexploring the composition and structure of phase systems, thediffraction method must now rank with them.To summarise thevast quantity of work of this type is virtually impossible, and theinvestigations on tin bronzes,22 on the binary systems Ti0,-MgO,Zr0,-MgO, Zr0,-TiO, and the correlation of information soobtained with the ceramic properties of certain theequilibrium diagrams of ternary alloys,24 the Mg-Ca,25 Au-Hg,26Al-Mg,27 Co-Sn28 systems are quoted only as examples of recentadditions to the subject.Thedifferentiation of the micas,29 the analysis of Estonian blue clay,l0and the presence of crystobalite in glass 31 illustrate ratherthan define the catholicity of its powers.X-Ray diffraction hasshown that a chemical compound is formed when litharge andtitania are calcined in equimolecular pr0portions.3~ The reactionsoccurring in lead-acid storage batteries, which have been thesubject of study for the past 50 years, have been elucidated byevidence in support of the double sulphate theory.33 Though manyexamples may be chosen in which X-ray methods have given thenecessary and sufEicient analyses unaided by other physical orchemical methods, it should be recognised that in their value as anauxiliary weapon-auxiliary as the five senses are auxiliary one toanother-lies their general utility in the analytical laboratory.Just as in the analysis of a, single material, gravimetric, volumetric,electrolytic , colorimetric, spectrographic , and microscopic met hods(to name a few) are frequently used, each cross-checking and supple-menting the other, so X-ray methods may dovetail with these togive a clearer answer to analytical problems.The method has also been extensively used in other fields.22 T.Isawa, Mem. Ryqjun CoU. Eng., 1937, 10, 53.23 W. Biissem, C. Schusterius, and A. Ungewies, Ber. deut. keram. Ges., 1937,24 A. J. Bradley, H. J. Goldschmidt, H. Lipson, and A. Taylor, Nature, 1937,25 K. Riederer, 2. Mehllk., 1937, 29, 423.z 6 I. N. Plaskin, Ann. Sect. Anal. Phys. Chim., 1938, 10, 129.27 F. Laves and K. Moeller, 2. Metallk., 1938, 30, 232.28 0. Nial, 8. anorg. Chem., 1938, 288, 287.29 G. Nagelschmidt, 2. Krist., 1937, 97, 541.30 W. Pralow, Chem. Erde, 1938, 11, 480.51 A.A. Lebedev, BuU. Acad. Sci. U.R.S.S., 1937, Ser. Phys., 381; B. E.Warren and J. Biscoe, J . Arner. Ceramic Soc., 1938,21, 49.32 D. G. Nicholson, Ind. Emg. Chem., 1937, 29, 716.33 C. S. Barrett, ibid., 1933, 25, 297.18, 433.140, 543GRIFFITHS, GULL, AND WHALLEY. 3873. APPLICATIONS OF ELE~TRON DIFFRAUTION.It is little more than ten years ago that L. de Broglie’s suggestionthat electrons were associated with wave systems was experimentallyverified by C. J. Davisson and C. H. Kunsman34 and by G. P.Thomson and A. Reid.35 The wave-length h corresponding toan electron velocity v is given by the equation1 = -- h or = hJ-LFL/Jl+ 6oom,c2 ePmv ePm,where h is Planck’s constant, P is tho potential difference throughwhich electrons are accelerated, e the charge and m, the rest massof the electron.For example, electrons accelerated through apotential difference of 30-70 kv. have an associated wave systemof wave-length 0.07-0.05 A. It is interesting to compare thesevalues with the shortest X-rays regularly used, namely, the K ,radiation of tungsten, which has a wave-length of more than 0.2 A.An electron beam on striking a crystalline surface is subjected,just as are X-rays, to diffraction governed by the Bragg equation,and the applicability of electron diffraction to analysis is comparableto that of X-rays, with the difference that the low penetrability ofelectrons is turned to advantage in the examination of surfacefilms. Whereas X-rays pass through the surface atoms withoutbeing much affected and penetrate to great depth, electrons, beingcharged and easily deflected by the intense fields of the atomicnuclei, are diffracted strongly by the outermost layer.Hence, to besuitable for examination by a transmitted electron beam, films shouldbe not more than a few hundred A. thick; the same film examinedby transmitted X-rays would scatter into the pattern only a negligibleproportion of the incident beam. Relatively bulky specimens maybe examined by reflexion, the incident electron beam a t grazingincidence being used, the half-pattern so produced being character-istic of the crystalline state of the surface layer. X-Rays diffractedin the same manner give a pattern in which the influence of aninvisibly thin surface layer is overwhelmed by the effect of theunderlying layers.When the bulk sample is of the same composi-tion, structure, grain size, state of strain, and orientation as theouter inch layer, then this difference will not operate to thedisadvantage of the X-ray method, but for the examination of verythin films produced, e.g., by electro-deposition, sputtering, precipit-ation from colloidal suspension, condensation of vapours, oxidationand other chemical reactions a t metal surfaces, the use of theelectron beam presents the only method of attack. That exposures34 Science, 1921, 54, 522. 86 Nature, 1927, 119, 890388 ANALYTICAL CHEMISTRY.of only fractions of a second are required compared with the hoursthat are usual in X-ray work is an incidental but not inconsiderableadvantage.It is of primary importance that, in general, the electrons have noeffect on the specimen, yet the possibility of a positive influencein exceptional cases cannot be ignored.The fading of the patternof gold leaf, observed by J. J. Trillat and S. Oketa11i,~6 was not inagreement with the results of G. I. Finch, A. G. Quarrell, and H.Wilman,37 who have suggested that the observed phenomenon wasdue to condensation on the specimen of metal evaporated from thehot filament used as an electron source. The observation of thedecomposition of silver bromide and iodide into their constituentelements 38 has not been contraverted. Finch, however, findsthat silver chloride is unaffected. Since the diffraction pattern inany case is determined by the surface of the specimen, it is evidentthat great care must be exercised to exclude all sources ofcontamination.The electron-diffraction pattern of platinum sputtered in oxygenshowed the presence of an oxide, though the film had all theappearance of platinum,39 and the bloom which formed on silverused as a catalyst for the oxidation of methanol and was suspectedof being a compound, was shown to be only the metal.40The composition of certain oxide films and their relation toprotection against corrosion has been the subject of investigationby electron diffraction.Recent work in this field includes theobservation that iron heated in air a t 800-900" gave a film ofrelatively large crystals of a-ferric oxide in the (100) orientationwhich has low corrosion re~istance,~~ whereas " blued " (nitre)steel has a fairly resistive crystalline surface layer of y-Fe,03 orFe304, the crystals being much smal1er.aThe film from iron made passive with potassium chromate hasbeen examined by transmitted electrons, and that from iron madepassive by nitric acid or potassium chromate by the reflexionmethod; the protective film was deduced to be Y - F ~ , O , .~ ~ Themethod has also been used for the study of the grain boundaries inir0n:3 and the presence of Fe,C and either iron or iron oxide atthe grain boundaries inferred.36 Compt. rend., 1936, 202, 1332.37 Trans. Faraday SOC., 1935, 31, 1051.R. Merigoux, J . Phys. Radium, 1936, 7, 497.J. J.Trillat and H. Motz, J . Physique, 1936, 2, 89; J. J. Trillat and39 G. I. Finch, Proc. Roy. SOC., 1933, 141, 414. 40 Idem, unpublished.41 G. D. Preston and L. L. Bircumshaw, Trans. Pczmday SOC., 1935,31,1051.42 T. Imori, Bull. Chem. SOC. Japan, 1938, 13, 152.43 R. Morgan, 8. Steckler, and B. L. Miller, J . Chem. Physics, 1937, 5, 953GRIFFITRS, GULL, AND WHALLEY. 389Gold leaf in oxygen a t 450" gives a pattern which disappearson heating a t 400" in a vacuum, and has been interpreted as beingprobably due to the formation of an oxide; 44 gold foil containingcopper, when heated in air, gives a pattern interpretable as beingdue to the formation of cupric oxide.454. POLAROGRAPHIC ANALYSIS.Polarographic methods of analysis, due initially to Heyrovskfand his co-workers, were last dealt with in the Reports for 1933,where the opinion was expressed that the method should find widerapplications.Further work has elucidated the various physicalphenomena encountered, and Heyrovskf has compiled anextensive bibliography of the work of his school on the determinationof various ions and molecules in solution, both separately andtogether. It is only during the last two years, however, that themethod has found any extended use by other workers, and severalrecent papers have described successful applications of the methodto routine analysis, where the speed with which a number ofdeterminations of exactly the same type can be carried out wellrepays the time spent in working out the optimum conditions ofanalysis.With the technique most generally employed now, a solution ofthe material to be examined is made the electrolyte of a cell in whichthe anode is a pool of mercury and the cathode is a dropping-mercury electrode.A potential, slowly increasing from 0 to 2 or4 volts, is applied to the cell by means of a rotating potentiometer,which is directly geared to a recording drum. A strip of photo-graphic paper is wrapped around the drum, and the current passingthrough the cell is automatically recorded by means of a beam oflight reflected from the mirror of a galvanometer in the circuit. Inthis way current-voltage curves are recorded for the cell. Theelectrical resistance of the electrolyte in the cell is made negligibleby the addition of a salt such as lithium or tetramethylammoniumchloride, in which the cation has a high deposition potential.Sincethe area of the anode is large relative to that of the droppingelectrode, and therefore unpolarisable, the resistance of the wholecell is determined solely by the processes occurring at the cathodicmercury-water interface. As the E.M.F. across the cell is raisedgradually from zero, the current passed by the dropping electroderemains negligible until the deposition or reduction potential ofone of the ions or molecules present in the electrolyte is reached.44 G. L. Clark and E. Wolthus J . Appl. Physics, 1937, 630.4 5 J. J. Trillat, S. Oketani, and S. Miyak6, J . Phys. Radium, 1937, 8, 353.1 J. Heyrovskjr and J, Klumpar, Coll, Czech, Chem, Comm., 1938, 10, 153390 ANALYTICAL CHEMISTRY.At this point a sudden but limited increase in current occurs andconcentration polarisation sets in.The cathodic interface becomesdenuded of cations with that deposition or reduction potential,and further electrolysis is limited by the rate at which fresh materialcan diffuse to the interface from the bulk of the solution. Furtherincrease in the applied voltage produces no increase in the diffusioncurrent until the next deposition or reduction potential is reached.Currentvoltage curves obtained in this way consist of steps orwaves; the voltage a t which the wave occurs is a qualitativeindication of the material responsible, and the height of the wave isa measure of its concentration.The apparatus itself has been improved.For instance, byimposing a small A.C. voltage on the ordinary D.C. voltage appliedto the cell, any desired portion of the current-voltage curve can beviewed continuously on a cathode ray oscillograph. No recordingis required, and interpretation is similar to that employed in theclassical method.2 The photographic method of recording hasbeen replaced by a recording pen actuated through an amplifier,whereby advantages in speed and ease of manipulation are ~btained.~Further modification is described in connexion with the determin-ation of copper in bl00d.4The construction of capillary tubes suitable for the droppingelectrode requires care, since the internal and external diameters ofthe drawn-out tip and other dimensions all influence the droppingtime of the electrode and, therefore, the polarograms obtainedwith it.Dislocation of routine work caused by breakage of acapillary in the middle of a series of analyses may be avoided by theproduction of standard capillary electrodes from thermometertubing.5 It is claimed that results with these electrodes varybut little from one electrode to another.The theory underlying the polarographic method has beenexamined in relation to the diffusion currents (which are thequantitative factor in a polarogram) and their variation in thepresence of a large excess of an indifferent electrolyte.has derived the relationshipD. Ilkoviki,, = @63nRCD,m%*where 32 is the valency of the ion undergoing electrolysis, C itsa R.H. Miiller, R. L. Garman, M. E. Droz, and J. Petras, Ind. Eng. Chem.(AmZ.), 1938, 10, 339.* H. C. Gull, J . SOC. Chem. Ind., 1937, 56, 1 7 7 ~ .4 A. Roncato and B. Bassani, Arch. Sci. bioZ., 1936, 19, 541 ; Chem. Zentr.,5 H. Siebert and T. Langer, Chm. Tab., 1938, 11, 141.1938, i, 4772.J . Chim. phydqw, 1938, 35, 129GRIFFTTHS, GULL, AND WHALLEY. 391concentration, D its diffusion coefficient in solution, F Faraday'sconstant, m the mass of mercury flowing from the dropping electrodeper second, and t the drop time in seconds. He has also foundthe temperature coefficient of the diffusion current to be about1.63% per degree for most ions.' J. Maas * has confirmed theseresults experimentally and shown that with cadmium sulphate in0.1N-potassium chloride the diffusion current varies directly withthe concentration of cadmium sulphate unless the dropping time ofthe capillary is below 3.8 seconds and an unusually high pressureof mercury is employed in the capillary.Under these conditionshe has found that the diEusion current tends to increase withincreasing applied voltage instead of remaining constant. Otherworkers have investigated the theoretical aspects of diffusioncurrents with and without an excess of indifferent electrolytepresent: and also with stationary and with growing mercuryOther factors affecting the quantitative aspect of polarographyhave been investigated. The height of the wave obtained withferrous sulphate and cadmium acetate varies directly with theirconcentration, but with zinc, stannous, and nickel chlorides therelationship is not linear.The presence of other ions in the solutionalso depresses the wave height.ll In this connexion the presenceof univalent polymerised ions in one-third basic aluminium acetatesolution l2 is noteworthy, since such a solution would give a muchsmaller wave than would be expected from an equivalentconcentration of unpolymerised tervalent aluminium.The concentration of cyanide ions affects the deposition potentialand the wave heights associated with nickel in solutions of potassiumnickelocyanide,13 and wave heights obtained with solutions ofvarious ions are lessened by the addition of primary alcohols, dioxan,trimethylene glycol, and glycerol, the curves being poorly definedfor the more viscous s01utions.l~Since the outline and sharpness of waves vary considerably,some standard method must be adopted to obtain consistent resultsin measuring wave heights for quantitative work.Heyrovskfdrew tangents at 45" to the axes, touching the curves at the topand the bottom of the wave. The height of the wave was thendrops.10Coll. Czech. Chem. Comm., 1938, 10, 249.Ibid., p. 42.D. MacGillavry and E. K. Rideal, Rec. TTCLV. chim., 1937,56, 1013, 1039.lo Idem, aid., 1938, 57, 33.11 P. N. Pavlov, J . Gen. Chem. Russia, 1937, 7, 2246.12 C. Rohmann and W. Mirus, Arch. Pharm., 1937, 975, 641.1s J. P. Gochschtein, J . Gem. Chem. Russia, 1937, 7, 2486.14 E. S. Peracchio and V. W. Meloche, J . Amer.Chem. ~Soc., 1938, 80, 1770392 ANALYTICAL CHEMISTRY.taken as the vertical distance between the points of contact. Otherprocedures are discussed in a paper dealing with the determinationof ketones by this method.15Large and sharply defined maxima sometimes occur a t the topof an ordinary wave in a polarogram. These are generally ascribedto adsorption effects l6 but their appearance is frequently confusing.They may be suppressed by adding colloidal material such asgelatin to the solution, and for the production of clear and distinctpolarograms, H. Hohn l7 recommends a series of standard electro-lysing solutions (“ Grundlosung ”) containing colloidal material,complex-forming reagents, and indifferent electrolytes suitable forspecific analyses.Certain features of the somewhat similar maximaobtained when nitro-compounds are reduced at the droppingelectrode are not explained by existing theory.l8 The maximavary with p H , and it is suggested that the accumulation of reductionproducts at the interface is responsible for the observed phenomena.When solutions to be analysed contain two or more ions withdeposition potentials so close that only one wave results andseparation for purposes of measurement is impossible, addition of areagent to form a complex with one or both of the ions may effecteither a shift of the deposition potential or a total suppression of thewave associated with one of the ions. Sometimes adjustment ofthe pH will achieve this result. The deposition potentials of nickeland zinc present together in neutral or slightly acid solution aretoo close for separation.Addition of ammonium acetate andadjustment of the pH to 8.5 with aqueous ammonia produces aseparation of 0.3 v01t,19 and addition of gelatin and ammoniaseparates them by 0.4 volt.20 In this way two distinct andmeasurable waves are obtained. Similar methods are adopted whenexamining plant ash for zinc in the presence of nickel, cobalt,cadmium, lead, copper, and bismuth.21Adaptation of the polarograph has been described for the routineanalyses of copper 22 or of copper, nickel, and cobalt present16 G. T. Borcherdt, V. W. Meloche, and H. Adkins, J. Amer. Chem. SOC.,1936,59,2171.16 See, e.g., J. Heyrovskf and E. Vascautzanu, Coll. Czech. Chem.Comm.,1931, 3, 418; N. V. Emelianova and J. Heyrovskf, Trans. Paraday Soc., 1928,24, 257.1’ ‘‘ Chemische Analysen mit dem Polarographen,” Julius Springer, Berlin,1937, pp. 41-44.A. Winkel and H. Siebert, 2. Elektrochem., 1938, 44, 402.1s P. R. Stout and J. Levy, Coll. Czech. Chern. Comm., 1938,10, 136.‘ 0 P. N. Pavlov and G. S. Pavlenko, J. Gem Chem. Russia, 1937, 7 , 2259.21 P. R. Stout, J. Levy, and L. C. Williams, COX Czech. Chem. Comm., 1938,22 J. I. Usatenko and J. S. Lialikov, Zauod. Lab., 1937, 6, 1394.10, 129GRIFFITHS, GULL, AND WHALLEY. 393together23 in steel, and of aluminium, manganese, zinc, and leadwithin certain limits of concentration in magnesium alloys.24 Thelimitations of the method when applied to the analysis of brasseshave been examined,25 and the polarograph has been found satis-factory for the determination of the total alkali metals, after removalof calcium and magnesium, in mineral waters and natural plantashes where the concentration is of the order of O - O O ~ N .~ ~ Thedetermination of traces (>O-00001 yo) of lead and arsenic in reagentphosphoric acid presents some unusual feature^.^' The two ions,present together, are determined in the presence of concentratedphosphoric acid with the addition of hydrochloric acid after reductionof quinque- to ter-valent arsenic by boiling with hydrazine.An examination of the behaviour of aconitic acid undergoingreduction a t the interface of the dropping electrode 28 has led toa method for the analysis of mixtures of the cis- and the tr~ns-acid.~~The behaviour of quinoline and quinine30 and of camphor andbilirubin31 has also been examined.General applications of themethod to inorganic, organic, and microanalysis have been discussedby A. Winkel and G. P r o ~ k e . ~ ~In the biological sphere, the polarograph has found severalapplications by reason of the small quantities of material thatcan be examined successfully. The determination of lead in bloodrequires but 2 C.C. of material,33 and a method for copper in bloodis also given.34 Vitamin-C may be determined in the absence of airin concentrations as low as 10-5~,35 and 1 pg. in 1 C.C. of watercan be detected. Constituents other than vitamin-C, present inextracts from animal tissues, hinder the electrode reaction.No summary of progress in polarographic analysis would becomplete without reference to the work of R.Brdicka on thedetermination of proteins especially in regard to the detectionof carcinoma, of which a summary has been given recently byH e y r ~ v s k f . ~ ~ Addition of protein to a solution containing24 H. C . Gull, Zoc. cat., ref. (3). 23 Angew. Chem., 1937, 21, 375.25 E. Mnich, 2. Elektrochem., 1938, 44, 132.26 N. V. Komar, Zavod. Lab., 1937, 6, 1074.27 T. A. Kriukova, ibid., p. 1385.2 8 G. Semerano and G. Bettinelli, Mem. R. Accad. Ital., 1937, 8, 243, 255.2n G. Semerano and L. Sartori, Mikrochem., 1938, 24, 130.30 I. Tachi and H. Kabai, J. Electrochem. Assoc. Japan, 1935, 3, 250.s1 I. Tachi, Mem. Coll.Agric. Kyoto, 1938, No. 42, 2.32 Angew. Chem., 1937, 50, 18-25.33 J. Teisinger, 2. ges. exp. Med., 1936, 98, 520.34 A. Roncato and B. Bassani, Zoc. cit., ref. ( 4 ) .35 E. KodiEek and K. Wenig, Nature, 1938, 142, 35.36 Ifbid., p. 317; see also 0. M. Henriques and C, G. Wolffbrandt, ibid.,p. 212; and E. C. Dodds, Lancet, 1938, 835, 351394 ANALYTICAL CHEMISTRY.ammonium and cobalt salts gives a polmogram having a series ofmaxima between 0.8 and 1.8 volts.37 These correspond to theevolution of hydrogen, which occurs a t a lower overpotential in thepresence of protein. The effect of the protein is catalytic, and isassociated with the presence of thiol radicals, the activity of whichis decreased by the incidence of carcinoma. Protein derived fromcarcinomatic sera, therefore, gives lower maxima.An alternativemethod involves a somewhat similar determination of the albuminosecontent of the serum which, in cases of carcinoma and also in certaincases of fever or inflammation, is unusually high. The determin-ations can be carried out on as little as 0.2 C.C. of blood.5. APPLICATIONS OF RAMAN AND ABSORPTION SPECTRA.Light incident on a molecule suffers one of several fates, dependingupon its wave-length and the nature of the molecule : it may betransmitted, scattered, or absorbed.Ramn Spectra.-Of the incident light scattered, a small pro-portion may be found differing in wave-lengths from the incidentlight. These changes of wave-length, or frequency, produced byscattering, constitute the Raman effect.1 In general, each differentlinkage and structure has characteristic Raman frequencies, whichmay be modified slightly by the rest of the molecule, but are generallyunaffected by the presence of foreign molecules.In principle,therefore, the Raman spectrum may be used to identify a compoundin terms of its structure, and to determine the proportion present in amixture, since the intensity of each line is proportional to theconcentration of the entity concerned. The dust-free sample(solid, liquid, or gas) is irradiated by means of strong monochromaticlight, usually from a mercury arc, and the spectrum of the scatteredlight is recorded by exposing a photographic plate for severalhours in a wide-aperture spectrograph. Alternatively, the intensityof the lines may be determined by replacing the plate with a secondslit and a photoelectric counter.2 Any fluorescence of the sampleis minimised, e.g., by adding an inhibitor such as nitrobenzene.3The Raman-spectrum method is especially valuable in the analysisof unstable substances in equilibria which cannot be " frozen," as inthe identification and determination dinitrogen pentoxide innitric-sulphuric acid mixture^.^ The method has succeeded withmixtures of very similar and difficulty separable substances.a7 R.Brdicka, J . Chim. phym&ue, 1938, 35, 89.1 Ann. Reports, 1934, 31, 22.2 V. Kudrjavzeva, Acta Physicochim. U.R.S.S., 1935, 3, 613.4 J. Chbdin, Ann. Chim., 1937, [xi], 8, 243.J. H. Hibben, I n d . Eng. Chem., 1934, 26, 646GRIFFITHS, GULL, AND WHALLET. 395Hydrolysates fiom proteins containing a limited number of amino-acids can be analysed, but with more complex mixtures, seriousoverlap of the lines interfere^.^ Valuable results have been obtainedin identifying the constituents of essential oils and products fromterpenes,6 and simple mixtures of similar hydrocarbons have beenanalysed by several authors.J. Goubeau has analysed mixtures ofbenzene, toluene, and the xylenes by measuring the persistence ofthe Raman lines through a series of standardised exposures decreasingin geometrical progression, and comparing them with the intensitiesderived from the pure substances, but quantitative results areunreliable with lines of low intensity. L. Piaux identified A=-pentene and cis- and trans-A!-pentene in the dehydration productof p-pentanol by means of small specific differences between theet h ylenic frequencies.Absorption Spectra-In general terms, radiations absorbed inthe far infra-red part of the spectrum correspond with changesin the rotational energy of the absorbing molecules, those absorbedin the near infra-red correspond with changes in the vibration androtation, and those absorbed in the visible and ultra-violet correspondwith electronic transitions accompanied by vibrational and rota-tional changes.In recent years, electronic absorption spectra havereceived extensive analytical applications, as in vitamin investiga-tions, and it is now apparent that infra-red absorption spectroscopyhas its own largely undeveloped field of utility.These can be used to identify asubstance by observing exact coincidences of a large number ofbands in the unknown with those in the absorption spectrum of agiven compound.Thus, a large proportion of methane has beenfound in the atmospheres of the major planets by means of photo-graphs of the absorption spectra at wave-lengths less than 1 p.9Radiation of wave-length greater than about 1.2 p is determined by athermopile-galvanometer system, and with the increase in re-solving power and precision of infra-red spectrometers,10 the recogni-tion that absorption bands near certain wave-lengths are due to thevibrations of particular groupings of atoms renders it possible toidentify substances in terms of the actual wave-lengths and characterof the absorption bands and to determine the proportions of theingredients in mixtures. For example, the concentrations of* E.g., G.Dupont, V. Desreux, and R. Dulou, BUZZ. SOC. chim., 1937, [v],(i) Infra-red absorption spectra.N. Wright and W. C. Lee, Nature, 1937, 139, 551.4, 2016.2. anal. Chem., 1936,105,161.Chim. et Ind., 1935, 34, 507.A. Adel and V. M. Slipher, PhyaicaZ Rev., 1934, [ii], 46, 902.lo E.g., J. J. Fox and A. E. Martin, Proc. Roy. SOC., 1937, A, 162, 419396 ANALYTICAL CHEMISTRY.imino-, amino-, and hydroxy-groups in carbon tetrachloride solutionsof organic substances were determined by absorption observationsin the region 1.65-1.35 p,ll and constituents of petroleum fractionswere identified by means of their absorption spectra in the range7-20 p.12 Absorption maxima due to a particular group in mole-cules, very similar chemically, may differ in character and wave-length, and such differences, although small, can be utilisedanalytically ; for instance, traces of 2- and 4-hydroxydiphenyl wereidentified and determined in samples of synthetic phenol by removingthe phenol in a vacuum and using the observation that, in carbontetrachloride, 2-hydroxydiphenyl has a double hydroxyl absorptionband of which the weaker limb is at 2-77 p, whereas phenol and 3-and 4-hydroxydiphenyl have a single sharp band at 2-77 1.1.Bandsnear 3.27 p due to CH are affected by small changes in the molecule,and phenol and 4-hydroxydiphenyl have sharp absorption peaksat 3.283 p and 3.295 p, respectively, easily distinguished from the lessprominent, corresponding, peaks of 2- and 3-hydroxydiphenyl.13In little more thana decade, colorimetric and absorption spectrometric methods havebeen developed extensively for detecting and determining smallquantities of substances which cannot be isolated conveniently orquantitatively.The recent Report on colorimetry 1* includestopics germane to absorption spectrophotometry also, and thesematters will not be detailed here. Few tests in chemistry are“ specific ” in the sense recently defined,15 but inasmuch as colours,different spectroscopically, may be indistinguishable visually, so isthe spectrometric method more “ selective ” than the colorimetric.However, an absorption band with a maximum at a particularwave-length is not necessarily proof of the presence of a particularsubstance, but it may be characteristic of a particular group of atomsin the molecule. For instance, each of the ergot alkaloids has amaximum at 318 mp and a minimum at 270 rnp,l6 and the thera-peutically more important ergometrine can be distinguished fromergotoxine and ergotamine since these, unlike ergometrine, do notdevelop a transient absorption maximum at 289 mp during photo-decomposition. l7Providing Beer’s law is obeyed, i.e., the light absorbed at wave-length h by a substance is proportional to its concentration C , thel1 0.R. Wulf and U. Liddel, J . Amer. Chem. SOC., 1935,57, 1464.12 P.Lambert and J. Lecomte, Compt. rend., 1938,206, 1174.l3 Journal, Brit. Ass., 1938, p. 26, and unpublished work.l4 Ann. Reports, 1936, 33, 456.l5 Ibid., 1937, 34, 489.l6 S. Smith and G. M. Timmis, J., 1937, 396.l7 I. Bennekou and S. A. Schou, Dansk Tidsskr. P a m . , 1936,10, 105.(ii) Visible and ultra-violet absorption spectraGRIFFITHS, GULL, AND WHALLEY. 397absorption density is related to the thickness I of the homogeneousmedium and the molecular extinction coefficientlog l o / I = absorption density = qCZwhere I , is the intensity of the incident and I that of the trans-mitted light. It follows that the accuracy of absorption-densitymeasurements controls that of the concentration deduced. It isimportant to remember that the above relationship applies strictlyonly for monochromatic light, although it is near the truth for aregion of absorption in which E changes little with wave-length.For determining a substance, such as benzene, from the absorptiondensity a t a wave-length corresponding with a sharp absorptionpeak, observations with light of a single wave-length alone affordtrustworthy results.18Technique has been advanced, in particular by replacing the eyeas a colour or density matching instrument by photo-cell arrange-ments, thereby increasing accuracy and rapidity of observation.The fraction of incident monochromatised light transmitted by thehomogeneous medium may be determined photoelectrically.Forexample, gaseous chlorine can be determined by using 365mpmercury light,lg or if there is no such convenient source of appro-priate monochromatic light, spectrally continuous light anda monochromator may be employed.A recent photoelectricspectrophotometer provides and uses bands only 1-11 A. broad a tany wave-length between 2200 and 7000 ~ . , 1 8 and such an instrumentcan also be employed for determining the absorption curve of asubstance to be characterised by its spectrum. A self-recordinginstrument 2o has been used for investigating optimum conditions forcolorimetric determinations.21 In other methods, spectroscopicallyundispersed light is incident on the medium, and the portion trans-mitted is spectrally resolved and either determined photometrically,e.g., in the visibls by matching ,with a similar part of the‘‘ unabsorbed ” light beam which is diminished to a determinableor recorded photographically, the blackening of the platea t a point corresponding with a particular wave-length being ameasure of that light transmitted.The general contour of the~ - - h relationship, i.e., the absorption spectrum, is obtained by usingbyT. R. Hogness, F. P. Zscheile, and A. E. Sidwell, junr., J . Physical Chem.,1937, 41, 379.l9 M. Ritchie and R. G. W. Norrish, Proc. Roy. Soc., 1933, A , 140, 99.2o J. L. Michaelson and H. A. Liebhafsky, Gen. Electric Rev., 1936, 39,21 J. P. Mehlig, Ind. Eng. Chem. (And.), 1938, 30, 136.22 As, e.g., in the Hilger-Nutting spectrophotometer (for improvements, ,see445.J. H. Dowell, J. S c i . Instr., 1931, 8, 382)398 ANALYTICAL CHEMISTRY.an arc source emitting very many spectral lines and observing on theplate the wave-length of points of equal density in pairs of spectra,one from the solution under investigation and the other from thesolvent, the density from the latter having been reduced in a knownratio.23 Sufficient spectra can now be photographed simultaneouslywith a notched echelon cell, thereby minimising any effects ofchanging absorption or photo-decomposition.2*When details of an absorption spectrum are required, a spec-trally-continuous source, such as a hydrogen lamp for the ultra-violet and a filament lamp for the visible, is used, and in a quanti-tative method, one photographic exposure suffices for the solution,and the solvent is then submitted to a series of exposures of predeter-mined decreasing duration, thereby providing on the derivedmicrophotographic record of the absorption spectrum a series ofstandard absorption densities.25 As illustrative of progress in theapplication of these methods, traces of strongly absorbing substancescan be detected and determined in media optically transparent inthe appropriate spectral region; e.g., as little as 0.1 mg.of benzeneextracted by 10 ml. of alcohol from air or viscera can be identifiedby means of four sharp absorption bands with maxima at characteris-tic wave-lengths.26 The concentrations of two substances, withoverlapping known absorption spectra, can generally be determinedby absorption-density measurements at only two wave-lengths.In this way, tyrosine and tryptophan can be determined in as littleas 5 mg.of This principle has been extended to theanalysis of ternary and quaternary mixtures of carotenoid andchlorophyll pigments .28In spectrophotometric analysis, possible effects of temperatureand solvent on the wave-length of the absorption maximum and themolecular extinction coefficient cannot be ignored, and it is importantto eliminate or allow for irrelevant absorption. On the other hand,sources of error can be detected by comparing, spectrophotometrically,absorption and colorimetric results obtained from the same substance.Some of these points are illustrated in recent determinations ofvitamin A.29F. Twymm arid C. B. Allsopp give details on this and other topics in‘ ‘Absorption Spec tropho tometry, ’ ’ Hilger , 1 9 3 4.24 F.Twyman, Proc. Physical SOC., 1933, 45, 1.Z K H. C. Gull and A. E. Martin, J. Sci. Instr., 1935, 12, 379.z 6 P. Laurin, J. Pharm. Chim., 1938,27, 561.27 E. R. Holiday, Biochem. J., 1936, 30, 1795.28 E. S. Miller, Cereal Chem., 1938,15, 310.28 R. A. Morton, “ Practical Aspects of Absorption Spectrophotometry,”Institute of Chemistry, 1938; A. E. Gill- and M. S. El Ridi, Biuchem. J . ,1938, 32, 820GRIFFITHS, GULL, AND WHALLEY. 3996. VITAMINS.When correlation between a chemical or physicochemical propertyof a material and its vitamin activity is well established, thechemical methods devised generally have advantages of speed,accuracy, and cheapness when compared with biological assays.l(i) Vitamin A in marine fish-liver oil, for example, affords atransient blue colour when antimony trichloride is added to a chloro-formic solution of the oil or its unsaponifiable fraction. The colourcorresponds with absorption bands having maxima at 620 mp and583 mp, but these are at 603 mp and 572 mp in oils of low potency.The maximum at 603 mp and the blue colour are frequently not fullydeveloped owing to inhibitory substances, but small quantities ofbromine in the reagent result in greater absorption a t 603 mp and inratios of Eso3/E,,2 approaching the corresponding value for the purevitamin.2 Personal errors are eliminated by means of a photo-electric colorimeter, and the contribution to the blue colour by anycarotene present is determined by measuring the absorption of theoriginal solution at 440mp and multiplying by the appropriatefactor derived from experiments with pure carotene.3The unsaponifiable fraction of fresh-water fish-liver oils gives agreen colour, owing to the presence of a factor (or vitamin) A, whichaffords a maximum absorption at 693 mp.The ratio of the absorp-tions at 620 and 693mp does not, however, correspond with theratio of vitamins A, and A,, since the latter affords some absorptionat 6 2 0 m ~ . ~ Oils containing vitamin A, in chloroform, give withperchloric acid, guaiacol, and phenol, it violet colour changing tobright red, which appears to be specific for the vitamin, and is notgiven by inactive ~arotene.~Vitamin A in alcoholic solutions has a broad absorption band inthe ultra-violet with a maximum a t 328 mp.In the case of oils oflow potency, substances other than the vitamin contribute markedlyto the gross absorption; hence the unsaponifiable fraction of theoil is employed for the measurement, and allowance is made for anycarotene present, as in butter, by means of absorption measure-ments at 455mp. Oils with high content of vitamin A, affordabsorption maxima a t 280 and 350mp instead of 3 2 8 m ~ . ~ Thedecrease of absorption at 325 mp produced by irradiating an alcoholic1 R. A. Morton, “Absorption Spectra of Vitamins and Hormones,”Hilger, 1935, describes absorption spectra methods as late as 1934.0. Notevarp and H. W. Weedon, Biochem. J., 1938,32, 1054.W.J. Dann and I(. A. Evelyn, ibid., p. 1008.E. Lederer and F. H. Rathmann, ibid., p. 1252.6 A. E. Pacini and M. H. Taras, J. Amer. Pharm. ASSOC., 1937, 26,721.6 A. E. Gillam, Biochem. J., 1938,32, 1496400 ANALYTICAL CHEMISTRY.solution of a marine fish-liver oil with mercury light of 365 mp,which destroys vitamin A, is said to be an accurate measure ofthe vitamin.?(ii) In addition to investigations of the methods of analysis forvitamin B, (aneurin) reported last yearr8 the sensitivity of theformaldehyde-azo-reaction has been in~reased.~ 2 : 4-Dichloro-benzenediazonium chloride affords a colorimetric determination,other coupled compounds being easily separable .I*(iii) Nicotinic acid and amide act as anti-pellagra vitamins, andcolorimetric determinations of these substances, in the absence ofother pyridine derivatives, are based on : (1) the red colour producedwhen the product of gentle fusion with 1 -chloro-2 : 4-dinitrobenzeneis made alkaline,ll and (2) the yellow colour produced by rupturingthe pyridine ring with cyanogen bromide and treating the productwith an aromatic amine.12(iv) Vitamin C (ascorbic acid) is determined by means of reactionsbased chiefly on its reducing properties, but it exists in some materialspartly as a complex with proteins from which it is released, beforedetermination, by hydrolysis with hydrochloric acid.13 The acidin extracts may be partly in a reversibly oxidised state and is reducedby preliminary treatment with hydrogen sulphide.A very selectivedetermination of (reduced) ascorbic acid depends on the reductionof methylene-blue by the acid in the presence of light.By carefulcontrol of pH and light intensity, 0.0045 mg. of ascorbic acid insodium citrate-bicarbonate buffer, containing thiosulphate to preventoxidation of the leuco-dye, can be determined titrimetrically. l4I n the absence of buffer at pH 2, 0.02 mg. of ascorbic per 100 g. maybe estimated in deproteinised serum by determining photometricallythe residual unreduced dye.15 In the titration of ascorbic acid with2 : 6-dichlorophenol-indophenol, it is said that adventitious oxid-ation is avoided by extracting vegetable matter with 5--15%sulphuric acid in place of acetic or trichloroacetic acids, therebyeliminating the preliminary hydrogen sulphide treatment.Theinactivating effect of any copper is avoided by adding metaphos-phoric acid.16 The method has been adapted so that 1 mg. of the7 A. Chevallier, 2. Vituminforschung, 1938, 7, 10.9 H. W. Kinnersley and R. A. Peters, Biochem. J., 1938, 32, 1516.10 H. Willstaedt and F. B&r&ny, Enzymologiu, 1938,2,316.11 P. Karrer and H. Keller, Helv. Chim. Acta, 1938, 21, 1170.12 H. Kringstad and T. Naess, Naturwiss., 1938, 26, 709.l3 E. J. Reedman and E. W. McHenry, Biochem. J., 1938, 32, 85.14 A. A. Policard, M. Ferrand, and E. Arnold, Bull. SOC. Chim. bioZ., 1938,16 H. Wahren, Klin. Woch., 1937,16, 1496.l6 G. L. Mack and D. K. Tressler, J . BioZ. Chem., 1937, 118, 735.Ann. Reports, 1937, 34, 401.20, 165GRIFFITHS, GULL, AND WHALLEY.401vitamin per 100 g. of plasma is determined in 0-1 ml. by observingwith a photo-electric colorimeter the decrease in concentrationof the dye. The pH is carefully controlled, and cysteine and gluta-thione then have negligible effect.1' Ascorbic acid extracted fromtissue by aqueous metaphosphoric acid reduces phosphotungsticacid at pH 3, and the colour produced is measured photometrically.Other reducing substances are inactivated by iodoacetic acid, andthe selectivity is greater than that of other methods.18 Otherreactions have been proposed. For instance, as little as 0.0001mg. of ascorbic acid gives a lilac colour with hydrochloric acid andca~othelin.1~ The reduction by vitamin C of potassium ferri-cyanide to ferrocyanide, which gives a red-brown colour or precipitatewith an ammonium molybdate reagent, is the basis of a veryselective colorimetric determination and a " spot " test by which0-5 pg.of ascorbic acid in 5 c.mm. can be detected.20 Ascorbic acidreduces, non-reversibly, diazotised sulphanilamide in acid media,and the excess of diazonium ion is determined colorimetrically bycoupling with dimet hyl- a-naphth ylamine.(v) Vitamin D, and D, are colorimetrically determined in theabsence of tachysterol and large amounts of other sterols or vitaminA by means of the orange colour reaction (maximum absorption at500 mp) with antimony trichloride in chloroform.22 Measurementsat the absorption maximum (265 mp) of the vitamins are employedin the specification of these substances, but at present, thereappear to be no satisfactory alternatives to biological assays.23(vi) Vitamin E (tocopherols), the antisterility factor, is in theunsaponifiable fraction of the benzene extract of the natural material,and is titrated potentiometrically in 80% ethyl alcohol with auricchloride, but carotenoids interfere.The tocopherols have differentbiological activities and may occur in different ratios in differentmaterials, so only approximate correlation between the titrationand the biological activity may be expected.24 a-Tocopherolreduces ferric chloride, and th? ferrous iron produced by 0-01-0-4mg. of tocopherol is determined colorimetrically as the ferrousma'-dipyridyl complex.25l7 R.L. Mindlin and A. M. Butler, J . Biol. Chem., 1938, 122, 673.l8 A. Fujita and T. Ebihara, Biochem. Z., 1937,290,182.I@ L. Rosenthaler, 2. Vitaminforschung, 1938, 7, 126.2o K. V. Giri, Milcrochem., 1937--8,23, 283.21 J. V. Scudi and H. D. Ratish, I n d . Eng. Chem. (And.), 1938, 10,2 2 H. Brockmann and Y. H. Chen, 2. physiol. Chem., 1936,241,129.23 Cf. R. A. Morton, ibid., p. 12.Z 4 P. Karrer and H. Keller, Helv. Chim. Acta, 1938, 21, 1161.z6 V. Emmerie and C. Engel, Nature, 1938, 142, 873.420402 ANALYTICAL CHEMISTRY.7. ALKALOIDS AND OTHER DRUGIS.The importance of drugs in medicine and forensic work is reflectedin advances in methods of isolation, identification, and deter-mination, particularly in biological material. Methods of separatingdrugs from animal matter have generally been based on the Stas-Ottoprocess (1856).This consisted essentially in extracting the activeprinciples with a dilute aqueous alcoholic solution of a weak organicacid and evaporating the filtered extract to low bulk. Proteins,etc., were precipitated and eliminated by a succession of extractionsand evaporations with absolute alcohol. The drugs were finallyextracted from aqueous solution by immiscible solvents. C. G.Daubney and L. C. Nickolls showed that only 40% of the morphineand quinine injected into rats is recovered by this rather tediousprocess owing to inefficient extraction and inevitable losses. Theyobtained good and rapid recovery of six’alkaloids by mincing theanimal matter while frozen solid, which facilitates fine comminutionand cell rupture, and precipitated the protein by warm dilute aceticacid and saturated ammonium sulphate. The alkaloids were theneasily extracted from the protein by acidified water, and wererecovered by immiscible solvents from the combined acid extracts.C. P.Stewart, S. K. Chatterji, and S. Smith treated the mincedviscera with 10% trichloroacetic acid, adsorbed the alkaloids fromthe protein- and fat-free filtrate on kaolin, then adsorbed any veronalon charcoal, and subsequently eluted the alkaloids with hot chloro-form, and the veronal with ether. F. Bamford claims success with amodified Stas-Otto process in which the protein is precipitated withacid or basic lead acetate according as alkaloids or barbituric acidderivatives are sought.(i) Cocaine, extracted from preparations in the usual manner bymeans of ammonia and immiscible solvents, is usually contaminatedwith any other bases present; but, utilising the observation thatcocaine is extracted by light petroleum from aqueous solutions ofits salts in presence of sodium bicarbonate, while many other basesare not, J.R. Nicholls4 has isolated and determined cocaine incoca leaves and mixtures with synthetic local anzesthetics and otheralkaloids, traces of the latter being destroyed by oxidation withacid potassium permanganate, which does not oxidise cocaine underthe conditions employed.(ii) Ecgonine, the alkaloid to which cocaine is easily hydrolysed,is neither extractable from water by immiscible solvents nor easilyidentified, but gives with platinic chloride and saturated sodiumAnalyst, 1937,62,851; 1938,63,560.Brit. Med. J., 1937, 790.Analyst, 1938, 63, 645. Ibid., 1936, 61, 155GRIFFITHS, GULL, AND WHAUEY. 403iodide a characteristic microcrystalline precipitate distinguishablefrom that afforded by betaine.6(iii) The flow of fresh colour reactions for morphine and relatedalkaloids continues, and W. Deckert 6 has described a nephelometricdetermination of morphine, dilaudide, and heroin based on theobservation that, of a large number of alkaloids, these have a muchlower solubility in vanadomolybdic acid than in molybdic acid.Although there are accurate methods for determining morphine inpure salts, such as by forming an insoluble ether with l-chloro-2 : 4-dinitrobenzene,' determination of morphine in opium has not beenunequivocal owing to the presence of similarly reacting phenolicalkaloids.* R.Eder and E. WackerlinQ review this century-oldproblem and claim to have solved it by elaborating the classicalextraction with calcium hydroxide and re-extraction with immisciblesolvents, so that the morphine is completely extracted and theuncertainty of the correction for that remaining in the mother-liquors after precipitation is abolished.(iv) Ouabain, a glycoside and probable active ingredient ofcertain arrow poisons, warmed with naphtharesorcinol and con-centrated hydrochloric acid, and diluted, gives an amyl-alcoholicextract which, unlike that of strophanthin, has a green fluorescence.Ouabain and strophanthin are determined colorimetrically by thered colour produced with o-nitrobemaldehyde and sodiumhydroxide.10(v) Malonylurea (barbituric acid) derivatives have been identifiedhitherto chiefly by m. p. determinations of the drugs and derivatives,and observations of the microcrystalline form. The blue complexesformed with cobalt salts in alkaline organic solution have beenextensively investigated. Thus, with aqueous cobalt nitrate-calcium chloride, the barbiturate in methyl alcohol gives a blueprecipitate from which the drug is liberated by dilute acid andextracted with ether for identification.ll The colour is due to oneor two, but not more, imino-groups, and that due to one such groupis stable only in a narrow pH range.12 0-05 G.of a barbiturate inchloroform is determined colorimetrically by means of cobaltacetate and lithium hydroxide in absolute methyl alcohol.13 OfF. Amelink, Phrm. Weekblad, 1938,75, 861.2. anal. Chem., 1938, 112, 241.C. Mannich, K. Hendke, and G. Baumgarten, Arch. Pharm., 1935,273,97.J . R. Nicholls, Analyst, 1937, 62, 440.Quart. J . Pharm., 1937, 10, 680.lo W. D. Raymond, Analyst, 1938, 63, 478.l1 M. Pesez, J . Pharm. Chim., 1938, 28, 69.l2 F. L. Kozelka md H. J. Tatum, J. P h m . Exp. Ther., 1937, 59, 54.l 3 H. Oettel, Arch. Pharm., 1936, 2'74, 1404 ANALYTICAL CHEMISTRY.chloroform-soluble substances, only theobromine, theophylline,thymine, and lecithin interfere,l* and some of these can be separated,and so can certain acids, since alkali barbiturates are decomposed bycarbonic acid to give crystalline acids when extracted by ether.15Sulphuric acid and formaldehyde give with ally1 derivatives a yellowcolour and green fluorescence, and with certain phenyl derivatives anintense red.0.1 Mg. of diallylbarbituric acid (" Dial ") gives aspecific reaction with a salicylaldehyde reagent. Phenyl derivativesgive colours when the products of nitration are treated with acetone. l6Ten barbiturates have been identified by the different precipitationreactions given with a special Millon's reagent (mercurous-mercuricnitrate).l7(vi) Sulphanilamide is determined colorimetrically by diazotisingthe amino-group and coupling the product with dimethyl-x-naphthylamine ; 1 part in 20 million parts of water can be detected.18Microcrystalline tests have been described.lg8. CARBOHYDRATES.The reducing properties of carbohydrates are the basis of mostreaction methods of determining these substances.The methodsare largely empirical, and progress includes new and improvedmethods and, in particular, their application to mixtures.Pentoses.-Interest in the pentose content of plant tissues has ledto improvements of the classical distillation of pentoses withhydrochloric acid and determination of the evolved furfuraldehydeas the phloroglucinol derivative. The relation between the latterand furfuraldehyde-yielding substances singly and in admixture hasbeen determined, together with the effects of hexoses,l and, as is notinfrequent in analysing carbohydrate mixtures, the sum of the yieldsfrom single ingredients differs from the yield from the mixture, andtherefore corrections are applied. Inconsistencies attributed to theclassical method are due to departures from the prescribed technique,and added salt is essential to stabilise the acidity when convertingmethyl pentoses into methylfurfuraldehyde, which may be pre-cipitated with either phloroglucinol or thiobarbituric acid.2ASSOC., 1934, 23, 1074.l4 T.Koppanyi, J. M. Dille, W. S. Murphy, and S. Krop, J . Amer. €'ham.l5 E. Schulek and P. Rozsa, 2. anal. Chem., 1938,112, 404.Is M. Pesez, J. Pharm. Chim., 1938, [viii], 27, 247.l7 M. Paget and F. Tilly, ibid., 1937, [viii], 25, 222.la E.g., E.K. Marshall, junr., J . Biol. Chem., 1938, 122, 263.l9 E.g., F. Amelink, Pharm. Weekblad, 1938, 75, 851.S. Angell, F. W. Norris, and C. E. Resch, Bwchem. J., 1936, 30, 2146.C. R. Marshall and F. W. Norris, ibid., 1937, 31, 1053, 1939GRIFFITHS, GULL, AND WIIALLEY. 405Hexoses and Disaccharides.-In sugar analysis, trustworthy deter-minations of total reducing sugars are of value, and a modified Pellet'ssolution, consisting of a 1 : 4 mixture of (343-5 g. of CuS04,5H20 +34.35 g. of NH,C1 per 1.) and (216.25 g. of Rochelle salt + 283.5 g.of Na2C03 per 1 .), determines glucose, fructose, maltose, and lactoseand their mixtures and, unlike Fehling's solution, without anyinterference by sucrose except in the case of lactose mixed withmuch sucrose.3 A new, but empirical, gravimetric determination offructose and sucrose alone and in sugar mixtures is based on thefact that they reduce selenious acid to selenium in hot sulphuricacid solutions whereas glucose, galactose, lactose, and maltose haveonly slight effects.4 Reducing sugars convert alkaline potassiumferricyanide into ferrocyanide, and glucose is determined by titratingthe ferrocyanide with potassium dichromate in acid solution withdiphenylamine as indi~ator,~ or the change in ferricyanide con-centration is determined by the ferri-ferrocyanide electrode.6Advances continue to be made in the complete analysis of sugarmixtures.In binary mixtures, glucose is determined by oxidationwith sodium hypoiodite, and fructose is subsequently determinedby a micro-copper-iodide method.' In a method of the latter type,sodium sulphate prevents atmospheric oxidation of the precipitatedcuprous oxide,* which is determined iodometrically, thereby per-mitting 0.01 mg.of glucose to be determined accurately, and im-parting to copper reagents the advantages of the (less selective)potassium ferricyanide reagents. The selective destruction ofcarbohydrates by five micro-organisms, and acid hydrolysis a tappropriate stages, together with determinations of reducingvalues before and after each stage, permit glucose, fructose, mannose,galactose, sucrose, maltose, and lactose to be determined in mixturesof these sugar^.^Distinction is made between ketoses, aldoses, and correspondingalcohols by oxidation with potassium periodate, since one mol.ofketose with n carbon atoms consumes n, - 2 mols. of periodatecompared with n - 1 mols. by aldoses and alcohols. Oxidation of1 mol. of alcohol or ketose yields 2 mols. of formaldehyde and n -2 mols. of formic acid compared with 1 mol. of formaldehyde andn - 1 mols. of formic acid from 1 mol. of a1dose.loC. Y. Chang and H. A. Shuette, Trans. Wisconsin Acad. Sci., 1935,29,381.G. Reif, Z . Unters. Lebenm., 1937, 73, 20.S. M. Strepkov, Biochem. Z . , 1937, 290, 91.P. A. Shaffer and R. D. Williams, J . Biol. Chem., 1935,111, 707.C. R. Marshall and A. G. Norman, Analyst, 1938,63,315.M. Somogyi, J . Biol. Chem., 1937, 117, 771.T. F. Nicholson, Biochem. J . , 1936, 30, 1804.10 F. Rappaport and I.Reifer, Mikrochirn. Acta, 1938, 2, 273406 ANALYTICAL CHEMISTRY.Fructose, but not glucose, sucrose, maltose, or lactose, gives ablack colour when heated with sulphur and glycerol containing leadacetate,ll and the purple colour produced by warming fructose withskatole and hydrochloric acid l2 affords a selective colorimetricdetermination.Starch.-This has been determined hitherto by iodine methodsof limited application, or by applying reduction or other methodsto the products of hydrolysis. In a rapid iodine method, for whichhigh selectivity and general applicability are claimed, a dilutealkaline solution of the starch is neutralised, and the starch-iodinecomplex, precipitated by potassium acetate or alcohol underspecified conditions, is weighed.13 In a modification, starch can beseparated almost quantitatively from de~trin.1~9.MICRO- ANALY $IS.The development of micro-methods in organic and inorganicanalysis during the past year has proceeded over such a wide fieldthat any attempt to cover the subject within the space availablein this Report is impossible. Attention will be directed thereforeto subjects thought to be of general interest. Foremost in thissense are developments in technique.The development of qualitative analysis for the rarer elements onthe micro-gram scale mentioned in the last Report has been con-tinued,l the methods of A. A. Noyes and W. C. Bray serving as abasis for the work. Most of the operations are carried out in micro-cones of 0.5 c.mm.capacity under observation with a low-powermicroscope. A screw clamp for closing the cones allows pressuredigestions to be performed without loss, and the settling andcoagulation of precipitates are accelerated by means of a buzzerclamped firmly to the stand holding the cones. In 1 mg. ofmaterial, 5 pg. of arsenic, germanium, or selenium can be detected inthe presence of 500 pg. of the other two elements, whilst 10 pg. of anyalkali ion may be detected and determined in the presence of notmore than 500 pg. of the others. Osmium and ruthenium can bedetected separately in mixtures having ratios 0 s : Ru varying froml1 E. V. Zmaczynski, J. Qen. Chem. Russia, 1937, 7, 2861.12 R. C. Jordan and I. Pryde, Biochem. J . , 1938,32,272.lS J.J. Chinoy, F. W. Edwards, and H. R. Nanji, Analyst, 1934, 59, 673.l4 F. W. Edwards, H. R. Nanji, and W. R. Chanmugam, ibid., 1938, 63,A. A. .Benedetti-Pichler et al., Ind. Eng. Chem. (Anal.), 1937, 9, 483,2 “ A System of Qualitative Analysis of the Rare Elements,”Macmiilan and697.589; ibid., 1938,10, 107; Mikrochern., 1938,24, 16.Co., New York, 1927GRIFFITHS, GULL, AND WHALLEY. 4071 : 100 to 100 : 1. Suitable confirmatory tests for these elements havealso been devised.The detection and determination of the precious metals in verysmall quantities have received attention. A micro-titration methodfor platinum in silver cupellation beads containing also gold and otherplatinum metals and, possibly, lead and copper, involves solution ofthe metals as chlorides followed by reduction with stannous bromide.Precipitated gold is filtered off and the bivalent platinum titratedwith standard sodium diethyldithiocarbamate solution in the pre-sence of benzene.The end-point is indicated by discharge of colourin the aqueous phase. The benzene solution of the compound ofbromine, platinum, and diethyldithiocarbamate left after titrationchanges in colour from orange to olive-green in direct sunlight, areaction characteristic of platin~rn.~Another interesting method for the recovery of 0.01 mg. of goldor 1.0 mg. of silver from 40 1. of water is de~cribed.~ Mercuricchloride solution is added to a large volume of the gold-silversolution, and a fine cloud of mercury and mercurous chloride isproduced by reduction with magnesium and sulphuric acid.Thecloud settles and takes with it all the gold and silver in solution orcolloidally dispersed ; these two metals are then recovered from theprecipitate by a cupellation process. Sea water, mine water, andore-leach solutions have been thus tested.Methods for the analysis of 1 mg. samples, suitable for investig-ations on the heterogeneity of alloys, metallic diffusion, and com-position of surface layers have been de~ised.~ A. Glazunov hasemployed anodic dissolution6 in a chemical examination of themacro-structure of alloys. A piece of filter-paper soaked in a suitablereagent is placed between the metal to be examined and analuminium cathode. When the metal is connected to the anode, asmall quantity passes into solution in the reagent and is identifiedby the characteristic colour produced.A method for the colorimetric determination of zinc (0.05-2 mg.)in soils depends on separation of zinc from interfering elementsas sulphide, which is then dissolved in hydrochloric acid andprecipitated with 5-nitroquinaldinic acid.Dissolution of theprecipitate in stannous chloride and hydrochloric acid gives amorange-coloured solution suitable for photo-electric comparison.W. B. Pollard, Bull. Inet. Min. Met., 1938, Nos. 400 and 406.W. E. Caldwell and K. N. McLeod, Ind. Eng. Chern. (Anal.), 1937, 9,A. Portevin and A. Leroy, Compt. rend., 1938,206, 518.Osterr. Chern.-Ztg., 1938,41,217.530.7 W. L. Lott, Ind. Eng. Chem. (AnaZ.), 1938,10, 335408 ANALYTICAL CHEMISTRY.The micro-analytical determination of elements present in smallquantities in rocks (0-01--0-02%) has been reviewed at length.8Numerous workers have extended and refined the use of manyknown reagents.Among the new reagents reported is the complexsalt [Fe11(2 : 2'-dipyridyl),]SO,, which gives characteristic micro-crystalline precipitates with many anions : e.g., I' (1 pg.), CNS'(0.2 pg.), VO,', Cr207", MOO,", e t ~ . ~In organic elementary analysis attention has been directed toimprovements in the design of automatic combustion furnaces, l oand to purification of the gas supplied to the combustion tube bypassage through a pre-heater made of copper tubing.11 Modific-ations in the tube filling for carbon and hydrogen determinationshave been suggested ; copper oxide containing copper, lead, chro-mium, manganese, and silver in the atomic ratios 12 : 3 : 3 : 1 : 1is recommended as an oxidation catalyst,12 and silver depositedelectrolytically in the form of closely woven clusters of crystals ispreferred to silver wire in the ordinary Pregl method.13 Othermodifications designed for the more convenient and exact combustionof volatile and easily sublimed substances have also been described.l*After combustion, the carbon dioxide may be determined bytitration with standard baryta,15 or the water formed may be ab-sorbed in cinnamoyl chloride a t 65", and the liberated hydrogenchloride caught in water and titrated with O-O2~-borax.l6The direct determination of oxygen by the ter Meulen destructivehydrogenation process has undergone extensive improvement.It can now be applied with reasonable accuracy to most organiccompounds, with the possible exception of sugars which have a highoxygen content and produce a voluminous deposit of carbon in thecombustion tube : results with these substances are often l0w.l'Various hydrogenation catalysts have been used ; the best appearto be nickel chromite and nickel-thoria.Both of these are un-affected by sulphur, and it is suggested that the former could bemade resistant to halogens also.18 Before hydrogenation with thelatter, the vaporised substance may be cracked over platinised silica, l9F. Hecht, 2. anal. Chem., 1937,110,385.N. S. Poluektov and V. A.Nazarenko, J . AppZ. Chem. Russia, 1937,10,2105.lo L. T. Hallett, Ind. Eng. Chern. (Anal.), 1938,10, 101.11 W. MacNevin and H. S. Clark, ibid., p. 338.la H. Reihlen, Mikrochem., 1938,23, 285.l3 W. MacNevin, Ind. Eng. Chem. (Anal.), 1938, 10, 341.l4 A. Elek, ibid., p. 51.1 5 R. B. Schmidt and J. B. Niederl, Mikrochem., 1938,24, 59.l6 C. J. van Nieuwenburg, Mikrochim. Acta, 1937, 1, 71.1' W. R. Kirner, Ind. Eng. Chem. (Anal.), 1937, 9,535.lQ J. Unterzaucher and K. Biirger, Ber., 1937,70, 1392.P. Goodloe and J. C . W. Frazer, ibid., p. 223GRIFFITHS, GULL, AND WHXLLEY. 409and halogens removed by passage over heated silver and lime.20After hydrogenation, the water formed may be absorbed in anhydrouscalcium sulphate 17 and weighed, or else absorbed in naphthyl-phosphoryl 21 or cinnamoyl22 chloride and the liberated hydrogenchloride titrated. If the substance contains nitrogen, the gasesleaving the tube often contain ammonia, in which case the watermust be absorbed in anhydrous lime.20Attention is directed to the possibility of errors arising in themicro-Dumas determination of nitrogen through contamination ofthe final volume of nitrogen with methane,23 and it is suggested thatresults by this method should be checked by an alternative procedure.The combustion of volatile substances is simplified by using a U-shaped capillary tube to hold the weighed material. This is cen-trifuged after filling and before sealing, and avoids the necessity forusing potassium chlorate in the Pregl straight weighing tube.24Acceleration of oxidation in the Kjeldahl digestion with hotconcentrated sulphuric acid has been examined.25 Most rapidoxidation is achieved by passage of chlorine through the liquid in thepresence of selenium dioxide.A modification of the Pregl combustion tube for the determinationof halogens has been described.26 The necessity for drying the tubebefore analysis, and waiting for it to cool before the combustionproducts are washed out after analysis, may be avoided. A veryrapid halogen determination may be carried out on materialscontaining no nitr~gen.~' Hydrogenation over a nickel-chromiumcatalyst liberates the halogen as the corresponding hydride, whichmay then be absorbed in water and titrated directly with sodiumhydroxide or borate, methyl-red or methyl-orange being theindicator.For the determination of sulphur, the combustion or other de-structive oxidation of the material may be followed by titration of thesulphate ion with 0-Oh-barium chloride under carefully controlledconditions with sodium rhodizonate as indicator.28 In the Preglmethod, transference of the barium aulphate from the precipitationvessel, and the difficulty of removing adherent precipitate may beavoided if precipitation is carried out in a small weighed crucible.2o J. Unterzaucher and I(. Burger, Ber., 1938,71, 429.21 J. Lindner and H. E. Wirth, Ber., 1937, 70, 1035.22 A. Lacourt, Bull. SOC. chim. Belg., 1937, 46, 428.23 H. J. Ravenswaay and A. Schweizer, Rec. Trav. chim., 1938, 57, 688.24 V. A. Aluise, Ind. Eng. Chem. (Anal.), 1938,10, 56.25 J. Milbauer, Chem. Obzor, 1937, 12, 17.z6 L. T. Hallett, Ind. Eng. Chem. (Anal.), 1938,10, 111.27 A. Lacourt, Mikrochem., 1938,23, 308.28 E. Abrahamczik and F. Bliimel, Mikrochim. Acta, 1937, 1, 354410 ANALYTICAL CHEMISTRY.After precipitation is complete, the mother-liquor is removed througha small, weighed filter stick, the precipitate washed, and the washliquid removed in the same manner. Crucible, filter stick, andprecipitate can then be dried and weighed.29J. G. A. GRIFFITHS.H. C. GULL.H. K. WHALLEY.2g W. Saschek, Ind. Eng. Chem. (Anal.), 1937,9,491

ISSN:0365-6217    

DOI:10.1039/AR9383500380

出版商:RSC    

年代:1938

数据来源: RSC

摘要:

INDEX O F AUTHORS’ NAMES.ABBASY, M. A., 333.Abderhalden, E., 293.Abelson, P., 10, 351.Abrahamczik, E., 409.Adam, N. K., 105, 113,255, 258.Adamson, P. S., 274.Addis, H. W., 248.Adel, A., 49, 395.Adkins, H., 229, 392.Adriani, J. H., 259.Aeschbacher, R., 286.Agafona, T. N., 385.Agar, J. N., 92, 94, 99.Agostini, P., 382.Ahlborg, K., 360.Ahmad, B., 333.Ainly, A. D., 370.Akabori, S., 368.Alexander, W. O., 180.Allchorne, E., 340.Allen, H. S., 46, 47.Allers, W. D., 295.Allison, S. K., 13.Allsopp, C. B., 398.Almquist, H. J., 340, 341.Alport, A. C., 336.Aluiae, V. A., 409.Alvarez, L., 11, 26, 34, 35.Amelink, F., 403, 404.Andersen, A. G. H., 182.Anderson, C. D., 17.Anderson, E., 365.Anderson, F. W., 304.Anderson, J. S., 168.Angell, S., 365, 404.Anschutz, L., 307.Anslow, W.K., 374.Anwyl-Davies, T., 354.Appelbaum, P. M., 280.Archer, N., 345.Archibald, E. H., 130.Arcus, C. L., 234, 235.Argument, C., 116.Arley, N., 21.Armstrong, G., 101.Arnold, E., 400.Arnulf, A., 115.Asahina, Y., 268, 270, 315.Ashford, T. A., 168.Ashley, J. N., 373.Ashton, R., 252.Astbury, W. T., 198, 199, 200, 201,Aston, F. W., 125, 127, 128,134.Aten, A. H. W., 109, 146.Austin, C. R., 184.Austin, H. E., 255.Austin, J. B., 265.Auwers, K. von, 269, 304.Avery, W. H., 52.Ayling, E. E., 248, 249, 250.202.Baars, E., 96.Bacharach, A. L., 304, 337, 338, 340.Bacher, R. F., 19, 33.Baddeley, G., 242.Badger, R. M., 38, 41, 42, 46, 48, 49,Bailey, C. H., 362.Bailey, C.R., 49, 50, 51, 52.Bailey, K., 201.Bainbridge, K. T., 125, 128.Bak, A., 359.Baker, J. W., 240, 243, 349, 250.Baker, W., 243.Baker, W. O., 194, 255.Bakker, C. J., 22.Baldinger, E., 22.Bamberger, E., 288.Bamford, F., 402.Banerjee, K., 176.Banerji, G. G., 335.Bannister, F. A., 188.Bar, F., 318.Bbdny, F., 400.Baren, I?. A. van, 191.Barendregt, F., 351.Barger, G., 326, 328.Barker, E. F., 42, 50.Barmore, M., 264.Barnes, R. B., 74.Barnett, J., 297.Baroni, A., 118.Bm, T., 286.Barrer, R. M., 77.Barnett, C. S., 386.Barrett, H. M., 349.Barrie, M. M. O., 340.Bartlett, P. D., 228, 229, 232.Barwich, H., 139.Bassani, B., 390, 393.51.41412 INDEX OF AUTHORS’ NAMES.Bassibre, M., 185.Batchelor, R.C. L., 354.Bateman, L. C., 215,216,218.Bath, J., 174.Bauer, L. N., 307.Bauer, S. H., 38, 40, 41, 42, 51.Baumgarten, G., 403.Baumgarten, P., 120.Baur, E., 267.Bavin, E. M., 345.Bawden, F. C., 202.Baxter, G. P., 127, 128, 129, 130, 134.Beach, J. Y., 50.Bcall, D., 295, 311.Beams, J. W., 140.Bean, W. B., 336.Beck, G., 123.Beckmann, S., 270.Beebe, R. A., 77.Beevers, C. A., 164.Bell, F. O., 200, 201, 202.Bell, R. P., 228.Bellamy, J. C., 24.Benedetti-Pichler, A. A., 406.Benedict, W. S., 74, 75, 76.Benford, G. A.. 242.Bennekou, I., 396.Bennett, C. W., 14.Bennett, G. M., 241, 242, 245, 249,Benz, F., 322.Berg, B. N., 348.Bergel, F., 309, 310, 338,339.Berger, J., 376.Bergmann, E., 222.Bergmann, M., 200, 308, 368.Bergmann, W., 306.Bernal, J.D., 197, 201, 202, 855.Bernet, E. J., 8.Bernstein, H. J., 48.Best, A. P., 243.Best, C. H., 345, 346, 349, 350.Bethe, H. A., 8, 15, 19, 24, 26, 126,Bettinelli, G., 393.Beutter, G., 234.Beynon, J. H., 284.Bhabha, H. J., 17, 21.Bhatt, L. A., 253.Biach, O., 268.Biassotti, A., 345.Bijvoet, J. M., 175, 185.Binkley, S. B., 341.Birch, H. F., 315.Bircumshaw, L. L., 388.Bird, (Miss) M. L., 242, 243.Biscoe, J., 386.Bjerge, T., 23.Blabolil, M., 118.Blackett, P. 3%. S., 8, 17, 18.Blackie, J. J., 328.Blanchard, E., 333.Blankenhorn, M. A., 336.250.128.Blatt, A. H., 243.Bleakney, W., 12, 78, 127, 141.Bliss, E. A., 352, 354.Blodgett, K. M., 201.Blokker, P. C., 109.Blom, J., 359.Bliimel, F., 409.Boam, J. J., 313.Bock, F., 303.Boeseken, J., 307.Bohm, J., 382.Boehm, R., 313.Boettger, B., 319.Bogatzki, D.P., 118.Bogert, M. T., 280.Bohle, K., 297.Bonhoeffer, K. F., 55.Bonner, L. G., 45.Bonner, T. W., 12, 22.Borcherdt, G. T., 229, 392.Borchman, H., 103.Borden, A., 42, 50.Borghello, N., 117.Boris, G., 76.Borissova, T., 11 1.Borsche, W., 321.Borsook, H., 351.Bosschieter, G., 50.Boswell, J. G., 366.Bosworth, R. C. L., 61,67,68.Bothe, W., 9.Bowden, F. P., 91, 92, 95, 96, 97, 99,101, 102, 104, 112.Bowen, A. R., 263.Bower, J. C., 27.Bowie, F. J. T., 354.Boylston, A. C., 130.Braae, B., 359.Bradfield, A. E., 237, 273, 274, 275,Bradley, A. J., 181, 182, 386.Bradley, R. S., 147.Bradley,W.F., 188,191,192.Bragg, (Sir) W. H., 191, 193.Bragg, W. L., 176.Braine, G. I. H., 354.Bramley, A., 14, 130.Brammall, A., 188, 191.Branch, G. E. K., 238,243.Brandenberger, E., 175.Brandes, H., 1 1 1.Bratton, A. C., 353.Bratzler, K., 142.Bray, R. H., 188.3ray, W. C., 406.3rdicka, R., 394.3reese-Jones, D., 367.3renschede, W., 116.3retscher, E., 9, 27.3reue1, W., 160.3rewer, A. K., 14, 15, 127, 130.3rickwedde, F. G., 24,3right, N. F. H., 84.279413>ampbell. W. R., 345. Brill, R., 178.Brindley, G. W., 176.Brislee, F. J., 109.Brocker, W., 307.Brocklesby, H. N., 263.Brockmann, H., 303, 313, 401.Brockway, L. O., 50, 115.Bronsted, J. N., 105.Broom, W. A., 345.Brosi, A. R., 128.Brosset, C., 186.Briill, W., 259.Briingger, H., 281.Brun, J., 131, 142.Brundage, P.S., 134.Brunner, E., 92.Bryan, W. L., 340.Bryce, G., 64, 65, 67.Buchholz, K., 305.Buckley, T. A., 313.Bucknall, E. H., 184.Biiming, E., 372.Burger, K., 408,409.Bussem, W., 386.Bull, B. A., 232.Burawoy, A., 149, 150, 305.Burcham, W. E., 32.Burdon, R. S., 56.Burk, N. F., 366, 367.Burkhardt, G. N., 238, 239, 249.Burnham, J., 41.Burnop, V. C. E., 264.Burrows, G. J., 157, 159, 160.Bursian, K., 326.Burstall, F. H., 161, 163, 317.Burton, H., 233, 234.Bury, A. B., 121.Bury, C. R., 263.Busch, G., 174.Busse, A., 303.Buston, H. W., 366.Buswell. A.. 38.Butenandt,’A., 284, 285, 286, 289,Butkevitsch, V. S., 373.Butler, A. M., 401.Butler, C. L., 307.Butler, G.C., 300, 357.Butler, J. A. V., 95, 97, 101, 105, 108.Butterworth, E. C., 210.Buttle, G. A. H., 352.291, 298, 301, 302, 303, 306.Caglioti, V., 185, 186, 382.Cahn, R. S., 313.Caldin, E. F., 228.Caldwell, W. E., 407.Callow, (Mrs.) N. H., 300.Callow, R. K., 243,245,283,284,300.Calvin, M., 108.Campbell, E. C., 11.Campbell, J., 346,350.Campbell, W. G., 362.kpion, P., 140.=arey, (Miss) P. C., 252,257, 259.2arlson, G. H., 228.>arlson, J. F., 17.krruthers, A., 378.>aspari, W. A., 255, 267.>aspersson, T., 203.Zattle, M., 360.kuchois, (Mlle.) Y., 124.Zavanagh, R., 348.Zavassilas , D . , 1 1 5.?awood, W., 133.“haikoff, I. L., 351.Zhakravorty, P. N., 285,288.Challinor, S. W., 357.Champetier, G., 52, 135, 142, 199.Chang, C.Y., 405.Chang, F., 102.Chang, T. S., 68.Chanmugam, W. R., 406.Channon, H. J., 350.Chapin, H. C., 127.Chaplin, E. J., 172.Chaplin, H. O., 244,245.Chapman, D. L., 110.Chase, M. W., 356, 357.Chatt, J., 153, 155.Chattaway, F. W., 164, 167.Chatterjee, N. N., 276.Chatterji, S. K., 402.ChBdin, J., 394.Chen, Y. H., 401.Chevallier, A., 400.Chibnall, A. C., 252, 253, 257, 260.Chick, H., 336.Childs, W. H. J., 48, 50, 131.Chinoy, J. J., 406.Choong, S. P., 14.Christ, R., 307.Christeleit, W., 171.Christie, J. M., 354.Chrzaszcz, T., 361, 362.Churgin, J., 8.Clark, C. H. D., 46.Clark, G. L., 118, 191, 192, 194, 384,385, 389.Clark, H. S.. 408.Clark, R. 0. J., 357.Clarkson, C. E., 268.Clemmensen, E., 252.Clemo, G.R., 320, 321, 323.Clough, G. W., 219.Clusius, K., 140.Clutton, R. F., 356.Coehn, A,, 109.Cohn, W. E., 351.Collins, F. J. E., 195, 252, 253, 257.Collins, G. B., 381.Collip, J. B., 346, 357.Conant, J. B., 228.Conn, G. K. T., 45, 46, 52, 75.Cook, 8. F., 351414 INDEX OF AUTHORS’ NAMES.Coop, I. E., 42.Cooper, C., 336.Cooper, E. A,, 378, 379.Cooper, J. A., 85.Cooper, K. A., 214, 227.Coops, J., 268.Cope, O., 347.Copping, A. M., 309, 339.Corey, R. B., 196, 202.Cork, J. M., 32.Cornish, R. E., 144.Cornog, J., 117.Corrigan, K. E., 384.Coster, D., 381.Cover, W. L., 355.Coward, K. H., 333.Cowdrey, W. A., 220, 222, 224.Cowley, E. G., 249.Cox, E. G., 162,167,106,197.Crawford, B. L., 51.Craxford, S.R., 111.Cremer, E., 77.Cristeleit, W., 165.Critcher, L. N., 307.Critchfhld, C. L., 15.Crittenden, E. D., 33,141.Crooks, H. M., 300, 301.Cross, P. C., 41, 51.Crowfoot, (Miss) D., 151, 201.Crowther, B. M., 136.Cruz, A. O., 252.Cullinane, N. M., 261.Cuntze, W., 160.Curd, F. H., 315.Curie, (Mme.) I., 13.Curtis, L. C., 370.Cutting, W. c., 355.Dahlke, W., 43.Daker, W. D., 379.Dam, H., 340,341,342.Daniels, F., 39.Daniels, J., 272.Dam, W. J., 336,337, 399.Dannenberg, H., 302.Dannohl, W., 182.Das, S. R., 120.Datta, S. C., 145.Daubney, C. G., 402.Davidson, N. R., 42.Davies, G. R., 166.Davies, M. M., 38, 39, 40.Davies, W. C., 248, 249, 251.Davisson, C. J., 387.Dawson, L. R., 122.Day, J. N.E., 145.De Boer, G. M., 256.Deborin, G., 101.De Bruyn, C. A. L., 213.Debye, P., 179.Deckert, W., 403,De Fremery, P., 295.De Groot, W., 22.De Hemptinne, M., 61,140.Deitz, V., 38.Dejardin, G., 115.De Koch, A. C., 259.De la, Cierva, P., 383.De Lapparent, J., 191.Delfosse, J. M., 45, 51, 140.Delwaulle, (Mlle.) M. L., 118.Demole, V., 339.Dempster, A. J., 14, 26, 125, 127.Dengel, F., 324.Den Hertog, H. J., 317.Dennison, D. M., 40, 45, 47, 51.Deppe, M., 288, 303.Derksen, J. C., 199.De Salas, E., 229.Desreux, V., 395.DeVault, D., 50.Deville, H. St. C., 149.De Visser, L. E. O., 252, 254.Devonshire, A. F., 53, 69.De Wilde, J. H., 185.Diamond, H., 72.Dickel, G., 140.Dickinson, S., 199, 201.Dickson, A. D., 362.Diebner, K., 34.Diemair, W., 253.Dietzel, E., 309, 310.Dihlstrom, K., 119.Dijk, H.van, 144.Dille, J. M., 404.Dimroth, K., 305.Dippy, 5. F. J., 239, 240, 241, 246,247, 248, 250, 251.Dirscherl, W., 288, 302.Dodds, E. C., 330, 393.Doisy, E. A., 341.Dole, M., 131.Doh, M. J. L., 351.Dowell, J. H., 397.Downing, A. E., 27.Dresler, D. von, 303.Drew, H. D. K., 164, 165, 167, 169.Drossbach, P., 110.Droz, 31. E., 390.Drummond, J. C., 332,337,340.Dube, G. P., 68.Du Bridge, L. A., 15.Duchesne, J., 44.Dulou, R., 272, 395.Dunning, J. R., 24.Dupont, G., 272, 395.Dvorkovitz, V., 165.Dyas, H., 108.Dyke, S. C., 354.Ebers, E. S., 48,51.Ebihara, T., 401.Eckart, C., 48.Eckhardt, H. J., 306INDEX OF AUTHORS’ NAMES.415Eddy, C. E., 381.Eddy, C. R., 50.Eder, R., 403.Edgar, C. E., 336.Edgar, J. L., 114.Edisbury, J. R., 331.Edwards, E. G., 232.Edwards, F. W., 406.Ehmert, A., 18.Eichenberger, E., 281.Eisenlohr, E., 264.Elek, A., 408.Elema, B., 323.Eley, D. D., 108.Elkins, (Miss) M., 171.Elliott, N., 157, 187.Ellis, C. D., 27.Ellis, J. W., 39, 174.El Ridi, M. S., 398.El Sadr, M. M., 336.El Shurbagy, R., 268.Elvehjem, C. A., 334, 336, 337.Emelhus, H. J., 121.Emelianova, N. V., 392.Emerson, G. A., 339, 340.Emerson, K., 355.Emerson, 0. H., 310,339,340.Emmerie, V., 401.Emte, W., 310.Engel, C., 401.Engelhardt, W. von, 191.Engler, W., 49.Erbe, H., 120.Ercoli, A., 290.Erdey-Gdz, T., 99, 102, 103, 104,Erikson, D., 371.Erkama, J., 376.Erlbach, H., 317.Errera, J., 38, 39.Erschler, B., 101.Erskine, D., 354.Escher, R., 310.Escribano, A., 131, 133.Eucken, A., 142.Euler, H., 16, 225.Euler, H.von, 331, 332, 334.Euw, J. v., 288, 295.Evans, D. P., 231, 232, 237,238, 245,246, 248,260.Evans, E. A., 283, 343.Evans, G. M., 354.Evans, H. M., 339, 340, 345.Evans, M. G., 249.Eva-, P. B., 307.Evans, R. C., 174.Evans, U. R., 95.Evans, W. J., 165.Evelyn, K. A., 399.Ewald, P. P., 178.Ewell, R. H., 264.Eyring, H., 76, 106.Eyster, E., 52.111.Faessler, A., 382.him, L., 313.igirclough, R. A., 237.kjans, E., 76.pang, S., 185.Tduchen, I., 190, 201, 202.Tarinacci, N. T., 217.Tarkas, A., 55, 71, 72, 73, 74, 76, 79,?arkas, L., 72, 73, 74, 76, 79, 101.?ad, J.H., jun., 134.?aw&Fremiet, E., 199.?ay, J. W. J., 35.Teather, N., 9.Fellner, C., 156.Fenton, (Miss) T. M., 264.Fernando, M., 365.Fernholz, E., 284, 309, 338.Ferrand, M., 400.Fertel, G. E. F., 26.Fieser, L. F., 283.Filinov, F. M., 167.Finbak, C., 195.Finch, G. I., 388.Findlay, A., 124.Findlay, G. M., 353.Fink, C. G., 109.Finn, A. E., 151, 153.Fischer, W., 149.Fischer, W., H., 282, 285.Fishbeck, K., 119.Fisher, A. M., 344, 345.Fleischer, G., 285, 298.Fleming, A., 354.Fletcher, A. A., 345.Flynn, D. G., 315.Foerster, F., 92.Follis, R. H., 352.Fonda, G. R., 381.Ford, E. G., 284.Ford, J. S., 361.Ford, W. G. K., 239.Foshag, W. F., 191.Foster, G. L., 349, 350.Fouts, P.J., 336.Fowler, R. H., 68, 97, 104.Fox, J. J., 38, 41, 45, 47, 395.Fox, M., 135, 146, 350.Frahms, H., 307.France, H., 210.Francis, E. M., 279.Francis, F., 195, 252, 253, 257.Franqois, F., 118.Frank, F. C., 174.Frankenburger, W., 55.Frankl, E., 102.Frankland, P. F., 219, 221, 225.Frazer, J. C. W., 408.Freudenberg, K., 219, 343.Frevel, L. K., 384.Freymann, R., 38.Friend, J. N., 123.Fries, B. A., 351.80, 101416 INDEX OF AUTHORS’ NAMES.Frisch, 0. R., 13, 24.Frischmuth, G., 166.Fritzsche, H., 309, 310, 338, 339.Frohlich, H., 21.Frohnmayer, W., 382.Frumkin, A., 94, 96, 101, 105, 106:110, 111, 112, 113.Fruton, J. S., 368.Fujita, A., 401.Furter, M., 283.Fuson, R. C., 232, 273.Gabbard, J. L., 131.Gatzi, K., 284, 295, 299.Gaisford, W.F., 354.Gale, E. F., 377.Gamertsfelder, C., 173.Gamow, G., 15.Ganapathy, C. V., 367.Garman, R. L., 390.Garner, C. S., 115.Garner, W. E., 82, 83, 84, 85, 256,264, 266, 267.Garrod, L. P., 352.Gascard, A., 256.Gattiker, D. C., 151.Gatty, O., 110, 111, 113.Gauthier, 37.Geiger, A., 332.Gelmann, A. D., 169.Gephart, F. T., 284.Gersdorf€, C. E. F., 367.Ghalioungui, P., 336.Giacomello, G., 185, 186.Giauque, W. F., 66.Gibbs, R. E., 266.Gibson, C. S., 149, 150.Gilbert, C. W., 27.Gilchrist, (Miss) H., 253.Gillam, A. E., 273, 331, 332, 398, 399.Gillette, R. H., 39, 41.Gingrich, N. S., 173.Ginsburg, N., 51.Girard, A., 295.Girardet, A., 326.Giri, K. V., 401.Giroud, A., 199.Glaser, H., 165.Glasstone, S., 93, 96, 102, 241, 242.Glavind, J., 341, 342.Glazunov, A., 407.Gleave, J.L., 212.Gleu, K., 134, 160.Glocker, R., 382.Glockler, G., 49.Gluckauf, E., 13, 35.Glynn, H. E., 340.Gochschtein, J. P., 391.Godward, L. W. N., 161.Goergens, C., 298.Goetz, A., 173.Goldberg, M. W., 281, 283, 299.Goldhaber, M., 32.Goldschmidt, H. J., 386.Goldwasser, S., 77.Goodloe, P., 408.Goodwin, E. T., 69.Goodwin, T. H., 196, 197.Gorbach, G., 375.Gordon, J. J., 237, 245, 246, 248, 250.Gordon, R. R., 51.Gordy, W., 38, 39.Gorham, J. E., 146.Gorodetzkaja, A., 112.GOSS, M. J., 366.Goubeau, J., 395.Gould, A. J., 78, 147.Gouter, E., 201.Gouy, G., 110, 111.Graff, M., 348.Graham, G., 345.Grahame, D. C., 25.Gralen, N., 364.Granick, S., 323.Grant, G.H., 213.Grant, J. M., 337.Grasshof, H., 297.Grassmann, E., 34.Grassmann, W., 367.Gratton, G., 272.Graves, E. R., 13.Greenberg, D. M., 351, 367.Grdgoire, 34.Greiff, L. J., 135, 145.Grew, K. E., 96, 112.Grewe, R., 327.Gridgeman, N. T., 333.Grieve, W. S. M., 210.Griffith, H. D., 333.Griffiths, D. C., 241.GrBths, H. N., 263.Grim, R. E., 188, 191, 192.Grimm, H. G., 178,261.Grindley, E. N., 254.Groenewoud, I). W. G., 325.Gr6h, J., 80.Gross, S. T., 194.Gross, W., 317.Grosse, W., 285.Groves, L. G., 241,242,248,249.Griintzig, W., 256.Grunberg, A. A., 167.Grundmann, W., 305.Gruner, J. W., 190, 193.Giinther, M., 261.Giinther, P., 382.Guggenheim, E. A., 68, 111.Guha, P.C., 269.Gull, H. C., 390, 393, 398.Gunther, P., 309, 310.Gurney, R. W., 85, 104.Guthier, A., 156.Guthrie, J. M., 361.Guy, J. B., 254, 263.Gyorgy, P., 337INDEX OF AUTHORS’ NAMES. 417Hadding, A,, 381.Hafstad, L. R., 11, 137.Hagedorn, H. C., 344, 345.Hahn, L. A., 351.Hahn, O., 13, 14, 35, 127, 130, 148.Hailes, H. R., 84.Halban, H. von, 24, 25.Hale, A. H., 129.Hale, J. B., 50, 52.Halford, R. S., 217.Hall, D. A., 123.Hall, N. F., 131, 241.Hall, W. H., 142.Hallett, I,. T., 408, 409.Hamill, W. H., 349, 350.Hamilton, (Miss) J. E., 185.Hamilton, J. G., 351.Hammarsten, E., 203.Hammett, L. P., 99, 217, 222, 239,Hammick, D. L., 241.Hampson, G. S., 160.Hanawalt, J. D., 384.Handke, K., 403.Hanes, C. S., 360.Hanhart, W., 226.Hanisch, F., 288.Hann, A.C. O., 230.Hanna, G., 336.Hanson, D., 184.Harbord, E. H., 119.Hardy, R., 196.Harington, C. R., 343,356.Harkins, W. D., 128.Harmsen, E. J., 185.Harmsen, H., 138.Harper, S. H., 313.Harris, L. J., 331, 333, 334, 335, 336,Harris, P. L., 263.Harris, R. M., 259.Hartley, G. A. R., 116.Hartman, H., 268.Haslewood, G. A. D., 300,303,311.Hassan, A., 336.Haughton, J. L., 184.Hauk, V., 127.Hausman, E., 303.Haxby, R. D., 12.Haydn, H. S., 384.Hazlewood, E. A., 186.Hebb, M. H., 10, 33.Hecht, F., 408.Hechtman, J., 365.Hegde, B. H., 273.Heidelberger, M., 356,357.Heilbron, I. M., 210, 284, 285, 286,Heisenborg, W., 16.Heitler, W., 17, 21.Hellstrom, N., 275.Helmer, 0. M., 336.Helmholtz, H.von, 110, 111.241.337.305, 331.REP.-VOL. XXXV.Hemmendinger, A., 130,137.Hemmings, A. W., 355.Hendershot, 0. P., 173.Hendricks, S. B., 38, 189, 192, 193.Heme, A. L., 115.Hennion, G. F., 290.Henriques, 0. M., 393.Henriquex, P. C., 307.Henry, T. H., 116.Henson, A. F., 67.Herb, R. G., 8,24.Heringa, G. C., 199.Heritsch, H., 186.Herman, R. C., 40,61.Hermann, C., 178.Herrmann, R., 319.Herschel, H., 311.Hertz, G., 138, 139.Herzberg, G., 49.Herzfeld, K. F., 57.Herzog, R., 128.Hess, K., 307.Hem, W. W., 369.Hesse, T., 171.Hettner, G., 43.Heusner, A., 301.Hevesy, G., 14, 16, 80, 347, 381, 382.Hevesy, G. C., 351.Hey, D. H., 209,210.Heydenbwg, N. P., 34.Heyningen, W. E. van, 348.Heyrasymenko, P., 96.Heyrovskf, J., 96, 98, 104, 110, 389,Hibben, J.H., 394.Hickling, A., 93.Hickman, K. C. D., 253.Hilbert, G. E., 38.Hilditch, T. P., 263.Hill, D. W., 343.Hill, R. D., 32.Hillemann, H., 320, 322.Hills, C. H., 362.Hills, G. M., 252.Hills, H. W. J., 234.Hilsch, R., 87.Himsworth, F., 101.Himsworth, H. P., 347.Hinshelwood, C. N., 213, 236, 237,Hintikka, S. V., 271, 272.Hinton, H. D., 290.Hipple, J. A., 141, 145.Hirota, K., 104.Hirst, E. L., 362.Hoar, T. P., 102.Hoard, J. L., 197.Hodges, J., 285.Hodler, A., 55.Hoehn, W. M., 295,297, 298.Hoekstra, J., 103.Honigschmid, O., 127, 129, 134.Hoerlin, J., 271.0392, 393.238, 239, 245418 INDEX OF AUTHORS’ NAMES.Hoffman, A., 313.Hoffman, J. G., 27.Hoffiann, J.I., 134.Hofmann, K., 289, 290, 292, 299.Hofmann, U., 188, 192.Hofstadter, R., 40, 51.Hoge, H. J., 24.Hogness, T. R., 397.Hohlweg, W., 290.Hohn, H., 392.Holiday, E. R., 398.Holleck, L., 142.Holmberg, B., 221, 222.Holmes, F. T., 44.Holst, J. J., 351.Holzner, J., 187, 189.Hooley, J. G., 130.Hopf, H. S., 366.Hopkins, B. S., 123, 127.Hopkins, S. J . , 252.Horiuti, J., 74, 98, 104, 105, 107,Horrabin, H. W., 117.Horrex, C., 238,249.Houssa, A. J. H., 220.Hornsay, B. A., 345.Howard, J. B., 42,48.Howitt, F. O., 343.Hrynakowski, K., 264.Hsii, S. K., 229.Huang-Minlon, 286.Huber, K., 278.Huber, P., 22.Hudson, C. M., 24.Hudspeth, E., 12.Huffman, H. M., 264.Huffman, J. R., 135, 144, 145, 146.Hughes, D., 300.Hughes, E.D., 211, 212, 214, 215,216, 218, 219, 220, 222, 223, 224,227, 233, 234, 237.Hulubei, H., 124.Hume-Rothery, W., 173, 180, 184.Hunscher, H. A,, 384.Hunt, B., 103.Hunter, L., 171, 244, 245.Hurley, F. H., jun., 129.Husemann, E., 358.Hutton, C. O., 190.108.Ichiba, A., 337.Ilkovic, D., 111, 390.Imori, T., 388.Ingold, C. K., 145, 209, 210, 211, 212,215, 217, 218, 222, 223, 224, 226,227, 228, 229, 232, 233, 237, 240,242, 243, 248.Ingold, (Mrs.) E. H., 209.Inhoffen, H. H., 285, 286, 290.Irimescu, I., 265.Irvine, J. W., 120.Isaacs, B. L., 333.Isawa, T., 386.Ishidate, M., 270.Itzerrott, D., 372.Ivanov, K. N., 385.Ives, D. J. G., 229, 231.Ivy, A. C., 333.Jackson, H., 286.Jackson, 0. B., 173.Jacob, A., 338,339.Jacob, (Miss) A., 309, 310.Jacob, C.W., 184.Jacobs, R. B., 121, 173.Jagelki, W., 271.Jahn, H. A., 48,50.Jakowlew, K. P., 136.Jakubowicz, B., 283.Jampolskaja, R., 102.Janicki, J., 361.Jansen, B. C. P., 351.Jantzen, E., 253, 259.Jeans, P. C., 333.Jefferson, M. E., 189, 192.Jeghers, H., 333.Jenkins, C. H. AT., 184.Jenkins, (Miss) D. I., 238,249.Jenkins, F. A., 128, 139.Jenkins, 0. N., 350.Jenkins, H. O., 263.Jensen, B. N., 344.Jensen, H., 124, 343.Jensen, K. A., 171, 310.Jentsch, W., 24.Jersild, T., 342.Jeske, J., 264.Jette, E. R., 182.Jorgensen, S. RI., 166.John, W., 309, 310, 338.Johnson, A. G., 354.Johnson, M. C., 67.Johnson, M. J., 376.Johnson, R. P., 56.Johnston, H. L., 141, 142.Johnston, M., 47, 49.Joliot, F., 12.Jones, B., 237, 242, 245, 249.Jones, D.M., 301.Jones, E. R., 274.Jones, E. R. H., 286.Jones, G. G., 76.Jones, T. O., 131.Jones, W. E., 331.Jones, W. O., 237.Jordan, E. B., 125, 128.Jordan, R. C., 406.Joseph, M., 351.Jost, D. M., 351.Jost, W., 79.Jukes, T. H., 336.Juliusberger, F., 220.Jung, F. T., 333.J u g , H., 188INDEX OF AUTHORS’ NAMES. 419Jungers, J. C., 51, 71, 76, 77.Jusa, W., 102.Kabai, H., 393.Kabanov, B., 96, 108, 112.Kachler, J., 271.Kading, H., 88.Kagi, H., 281,285,299.Kahovec, L., 243.Kalbfell, D. C., 10.Kallman, H., 82.Kamm, O., 284, 288, 297, 298, 300,Kanda, E., 115.Kandiah, A., 229.Kandler, L., 99.Kanner, M. H., 22.Kapfenberger, W., 128.Kardos, R., 102.Karges, R.A., 117.Karlik, (Miss) B., 253.Karpatschev, S., 109.Karrer, P., 309, 310, 322, 331, 332,338, 339, 400, 401.Karweil, J., 42.Kasimoto, K., 368.Kathol, J., 290.Kautsky, H., 89.Kayser, C., 96.Keenan, H. W., 102.Keesom, W. H., 132, 144.Keffler, L., 253.Keifer, J. M., 307.Keighley, G., 351.Keimatsu, I., 327.Keller, H., 310,400,401.Kelley, W. M., 134.Kemmer, N., 21.Kendall, E. C., 293, 295.Kendall, J., 141, 142, 143.Kennedy, T., 286,305.Kenyon, H. F., 95, 97.Kenyon, J., 220, 221, 222, 225, 233,Keresztesy, J. C., 337.Kerr, R. B., 345.Kertesz, Z. I., 365.Keston, A. S., 146, 349, 350.Kharasch, M. S., 168, 169.Kimball, R. H., 230.Kimura, K., 382.King, A., 119.King, (Miss) A. M., 252, 264.King, G.W., 45.King, H. J. S., 168.Kinnersley, H. W., 334, 400.Kinsey, E. L., 39.Kinsman, S., 365.Kirchner, F., 13.Kirner, W. R., 408.Kistiakowsky, G. B., 42.Kitschelt, M., 288.301.234, 235.Klaas, R., 384.Klami, A., 269,270.Klar, R., 77,144.Klem, A., 253.Klemm, W., 166.Klenk, E., 253.Klose, A. A., 341.Klumpar, J., 110,389.Knorr, C. A., 99,109.Kobayashi, R., 265.Koch, J., 24.Kocholaty, W., 375.KoEnar, M., 134.KodfEek, E., 393.Koebner, A., 306.Konig, F., 269.Koenig, O., 111.Koenigs, W., 271.Koster, W., 182, 184.Kogl, F., 320.Kohler, E. P., 232.Kohlhaas, R., 255.Kohbrausch, K. W. F., 49, 243.Kokkoros, P., 186.Kolkmeijer, N. H., 175.Kolpak, H., 200.Kolthoff, I. M., 241.Komar, N. V., 393.Komppa, G., 269, 270, 271, 272,Komppa, O., 272.Kondo, H., 327.Konovalova, L., 328.Konovalova, R.A., 328.Kopfemann, H., 139.Koppanyi, T., 404.Korolkov, I. I., 265.Kowarski, L., 25.Kozelka, T. L., 403.Krarup, N. B., 344.Krauas, A., 144.KEepelka, J. H., 118,134.Kringstad, H., 400.Krishnamurthy, S., 269.Iiriss, A. E., 372.Kriukova, T. A., 393.Krogh, A., 348,350,351.Kromrey, G., 111.Krop, S., 404.Kriiger, F., 11 1.Kriiger, H., 139, 140.Kriiger, P., 280.Kruger, P. G., 22.Krzemieniewski, H., 377.Krzemieniewski, S., 377.Kuck, J. A., 323.Kudrjavzeva, V., 394.Kudszus, H., 286, 306.Kuhn, R., 318,322,337.Kuhn, W., 148.Kuna, M., 222.Kundra, 0. K., 385.Kunsman, C. H., 387.280420 INDEX OF AUTHORS’ NAMXS.Kuwada, S., 289,291.Kynch, G.J., 198.Laaff, O., 13.Lacher, J. R., 42.Lacourt, A., 409.Ladenburg, R., 22.Ladigina, L. V., 249.Lahy, T. H., 381.Laidler, K. J., 237, 238.Laine, T., 376.Lajos, S., 342.Lake, D. B., 109.Lambert, P., 396.LaMer, V. K., 237.Lande, L. M. F., 317.Landquist, J. K., 169.Landateiner, K., 356, 357.Lane, J. F., 234.Langedijk, S. L., 263.Langer, L. M., 10.Langer, T., 390.Langmuir, I., 61, 63, 67, 176, 177,Lapworth, A,, 230,242,248,251,263.Laqueur, E., 295.Larsen, E. S., 380.Larson, W. D., 241.Lassettre, E. N., 50,243.Latcham, W. E., 82.Laucht, 305.Laucius, J. F., 284,288, 300.Laue, G., 99.Lauffer, M. A., 202.Laurie, L. L., 231.Lamin, P., 398.Laves, F., 183,386.Lawrence, J.H., 16.Lawrence, R. D., 345.Lawrence, W. J. C., 371.Lawson, E. J., 284, 297, 300, 301.Lebedev, A. A., 386.Lecomte, J., 396.Lederer, E., 331, 332, 399.Lee, E., 43, 49, 50.Lee, W. C., 395.Leech, J. G. C., 188,191.Lees, R., 354.Legmd, A. R., 237, 238,246.Leighton, P. A., 41.Lennard-Jones, J. E., 68, 69.Leong, P. C., 335.Lepkovsky, S., 336.Leroy, A., 407.Le Sueur, H. R., 252.Levaditi, C., 352,353,354.Levene, P. A., 222,253.Levy, J., 392.Lewina, S., 96,97,99.Lewis, G. N., 97, 143, 144, 221.Lewis, J. R., 271.Lewis, L., 341.201.Lewis, R. H., 240,246,247.Leyton, O., 345.Lialikov, J. S., 392.Liddel, U., 38,396.Lidwell, 0. M., 228.Liebhafsky, H. A., 397.Linderstr~m-Lang, K., 203.Lindner, J., 409.Lingane, J.J., 241.Link, K. P., 362.Linnett, J. W., 44, 45, 46, 49, 52.Linsert, O., 306.Linstead, R. P., 229.Lipmann, F., 322.Lipp, P., 272.Lippmann, E. von, 308.Lippmann, G., 111.Lipschitz, M. A,, 334.Lipscomb, A. G., 225.Lipson, H., 164, 181, 182,386.LitcMeld, J. T., 353, 355.Livingood, J. J., 34, 35.Livingston, M. S., 27, 126, 128.Llewellyn, F. J., 195.Lloyd, V. E., 354.Loach, J. V., 350.Locher, G. L., 34.Lockwood, J. S., 354.Logemann, W., 290, 292, 299.Lohmann, K., 334.Lomax, R., 199.London, F., 211.Long, C. N. H., 346.Long, F. A., 222.Long, P. H., 352, 354, 355.Longair, A. K., 46, 47.Loon, M. von, 317.Lord, R. C., 49.Loring, H. S., 202.Lott, W. L., 407.Lotze, H., 342.Lovern, J. A., 331.Lowry, T. M., 105, 221.Lucas, H.J., 169.Lundell, G. E. F., 134.Lundsgaard, E. C., 351.Luther, R., 109.Lux, A., 219.Lynch, D. F. J., 366.MMMMMMMMMMMMhas, J., 391.hcCdhr~, F. O., 353.:acClement, W. D., 202.hcCorquodale, D. W., 341.IacDonald, R. T., 97, 143.IacDougall, D, P., 48.hcGillavry, C. H., 185, 196.;acGillavry, D., 139, 391.:cGookm, A., 313.IcGrew, R. V., 301.:achatski, F., 187, 193.:cHenry, E. W., 335, 400INDEX OF AUTHORS’ NAMES. 42 1Mcnwain, H., 320, 321, 323.Mack, a. L., 400.McKay, H. A. C., 81.McKenzie, B. F., 295.McKibben, J. L., 8.MacLean, D. L., 350.McLean, J. H., 253.McLeod, K. N., 407.McMillan, E., 351.MacNevin, W., 408.MacNulty, B. J., 214, 227.McQuillin, F. J., 274.Macrae, T. F., 336.Macy, I.G., 384.Madden, F. C., 264.Madden, R. J., 336, 337.Madelung, W., 308.Maegdefrau, E., 188,192.Magat, M., 41.Maier, K., 313.Maitra, M. K., 333.Makin, F. B., 210.Makuc, J., 261.Malkin, T., 255, 256, 258,267, 268.Mamoli, L., 290, 298.Manley, J. H., 24.Mann, F. G., 150, 151, 153, 155, 157,158, 159, 172.Mannebach, C., 45.Mannich, C., 403.Manske, R. H. F., 248,251, 324, 325,Manteuffel, R., 321.Marble, A., 345.Marble, J. P., 134.Marke, D. J. B., 83.Marker, R. E., 284, 288, 297, 298,300, 301, 302.Marks, H. P., 347.Marrack, J. R., 356.Marrian, G. F., 300, 301, 311, 357.Mmiott, J. A., 171.Marsden, R. J. B., 241,248.Marshall, C. R., 404, 405.Marshall, E. K., jun., 353,355,404.Martin, A. E., 38,41,45,47,395,398.Martin, A.J. P., 336.Martin, C. J., 336.Martin, H., 148.Martin, J. J., 313.Marwick, T. C., 199.Mmchmann, E., 375.Masing, G., 99.Masket, A. V., 140.Mason, H. L., 295,297,298.Mason, K. E., 340.Masson, J. I. O., 116.Masterman, S., 220, 222, 223, 224.Matheson, H., 131.Mathews, A. P., 336.Mathews, R. S., 336.Mattauch, J., 126, 127, 128, 130, 131.Mattill, H. A., 340,328.Maurer, K., 318,319.Mayeda, S., 315.Mayer, E. W., 276.Mayo, F. R., 169.Mead, T. H., 333, 343, 356.Mecchi, E., 341.Mecke, R., 47, 49, 131.Medwedowsky, W., 101.Meer, N., 221, 222.Meerwein, H., 287.Megaw, H. D., 174.Mehlig, J. P., 397.Mehmel, M., 188, 194.Meier, a. , 264.Meinerts, U., 303.Meisenheimer, A., 22 1.Meisenheimer, J., 234.Meitner, L., 13.Meldahl, H.F., 289, 290, 299.Meldrum, F. R., 82.Mellor, D. P., 159.Mellor, G. A., 184.Meloche, V. W., 391, 392.Melville, H. W., 76, 77.MOM, W., 129.Menschikov, G. P., 328, 329.Menzel, D. N., 115.Menzies, A. C., 43.Merigoux, R., 388.Merriam, E. S., 93.Meyer, J., 281.Meyer, (Miss) J. D., 256.Meyer, K., 345.Meyer, K. H., 267.Michaelis, L., 322, 323.Michaelson, J. L., 397.Michi, K., 337.Mickelsen, O., 337.Miekeley, A., 308.Miescher, K., 282, 285, 292, 293, 299.Milbauer, J., 409.Miller, B. L., 388.Miller, E. S., 398.Miller, J. J., 186.Miller, (Miss) M. L., 237.Miller, N., 121.Miller, W. L., 93, 110.Miller, W. O., 333.Mills, H. R., 43.Milner, 85.Milward, (Mrs.) J. L., 166.Mindlin, R.L., 401.MiPUB, W., 391.Miser, H. D., 187.Mitchell, A. C. G., 10.Miyak6, S., 389.Miyasaka, M., 291.Mizushirna, S., 43.Mnich, E., 393.Moller, G., 112.Moeller, K., 386.Morgeh, E,, 289,MoelwJ?1-HughW, A*, 41422 INDEX OF AUTHORS’ NAMES.Moermm, N. F., 197.Moffet, G. L., 305.Mohammed, A., 340.Mohr, S., 123.Moles, E., 128, 131, 133.Moll, T., 310, 342.Mollet, P., 38.Moon, C. H., 82.Moon, P. B., 26.Mooney, (Miss) R. C. L., 185, 186.Moore, C. J., 130.Morand, M., 136.Morawietz, W., 117.Morgan, (Sir) G. T., 161, 163, 166,Morgan, R., 388.Morgan, V. G., 231, 238.Morgan, W. T. J., 357.Morikawa, K., 74, 75, 76.Morino, Y., 43.Morita, N., 131, 142.Morral, F. R., 182.Morris, B. S., 159.Morris, T.N., 109.Morton, A. A., 217.Morton, R. A., 331, 398, 399,401.Moschel, W., 263.Moss, A. R., 340.Mosses, A. N., 250.Mott, N. F., 85.Mottram, E. N., 263.Motz, H., 388.Moullin, E. B., 265.Moxnes, N. H., 383.Mrgudich, J. N., 384.Muller, A., 194, 254, 255, 256, 259.Muller, E., 103.Muller, G., 284.Muller, 0. H., 98.Muller, P., 289.Muller, R. H., 390.Mulliken, R. S., 140.M d o r d , S. A., 252, 256, 257.Murphy, W. S., 404.Murrell, M., 354.Murtazajew, A., 112.Mutch, J. R., 333.Myers, C. S., 295.Myrback, K., 360,361.263, 317.Naeser, C. R., 127.Naess, T., 400.Nagelschmidt, G., 188, 192, 193, 386.Nakagawa, S., 27.Nanji, H. R., 406.Narang, K. S., 313.N&ray-Szabb, S. von. 186.Nath, B., 269.Nathan, W. S., 231, 237, 240, 249.Nazamnko, V.A., 408.Neddermeyer, S. H., 17.Nenizescu, C, P., 265,Nernst, w., 93.Neuberger, A., 343.Neuert, H., 13.Nevell, T. P., 220.Neville, E. H., 176, 201.Newbery, E., 109.Newing, R. A., 47.Newling, W. B. S., 238.Newton, E. F., 191.Nial, O., 386.NichoJls, J. R., 402, 403.Nicholson, D. G., 386.Nicholson, T. F., 405.Nickolls, L. C., 402.Nicol, J., 78.Niederl, J. B., 408.Nielsen, H. H., 47, 48, 49, 51.Niemann, C., 200.Nieuwenburg, C. J. van, 408.Nieuwland, J. A., 290.Nikiforov, V. K., 265.Nilsen, K. W., 99.Nishikawa, S., 27.Nitta, I., 195.Nixon, A. C., 238.Norman, A. G., 405.Norris, F. W., 363, 365, 404.Norris, J. F., 217.Norrish, R. G. W., 397.Novak, J., 98.Nowacki, W., 123,174.Noyes, A.A,, 93, 406.Nyman, G. A., 272, 280.Notevarp, o., 399.Oakwood, T. S., 284, 288, 297, 298,300, 301.Oberwegner, M. E., 308.Ochoa, S., 334.O’Connor, E. A., 95, 112.Odell, A. D., 301.Ortenblad, B., 360.Oettel, H., 403.Ogawa, E., 147.Ogden, G., 74.Ohle, H., 317.Okamoto, G., 98, 104, 106.Oketani, S., 388, 389.Okomura, S., 368.Oldenberg, O., 34.Oldham, J. W. H., 195.Oliphant, M. L., 136.Oliver, W. A., 364.Olivier, S. C. J., 214, 245.Olson, A. R., 211,217,221,222.Oppenauer, R. V., 287.Oppenheimer, J. K., 17.Orekhof, A. P., 328.Ormondt, 3. van, 201.Ormont, B., 118.Omstein, L. S., 128.OSf, Kv, 259INDEX OF AUTHORS’ NAMES. 423Ott, E., 258.Otterson, H., 362.Owen, E. A., 180.Owen, J., 269.Oxford, A.E., 243, 371.Pace, J., 77.Pacini, A. E., 399.Packer, J., 117.Page, J. E., 240, 250.Paget, M., 404.Pahl, M., 14.Paland, J., 303.Palmer, C. E., 333.Palmer, K. S., 157.Paneth, F. A., 13, 35, 114, 351.Parish, H. J., 352.Parker, R. H., 160.Parkinson, D. B., 8,24.Parks, G. S., 264.Parnell, T., 78.Parsons, L. G., 337.Partington, J. R., 249.Partridge, S. M., 233, 234, 235.Patat, F., 49.Patterson, H. S., 133.Pauling, L., 43, 50, 187, 255.Pavlenko, G. S., 392.Pavlov, P. N., 391, 392.Peacock, D. H., 245.Pearce, J. N., 122.Pearson, J. D., 95, 101.Pearson, (Mrs.) L. K., 263.Pease, R. N., 76.Pedersen, K. J., 230,232.Pegram, G. B., 144.Peierls, R., 68, 68.Pell-Walpole, W. T., 184.Penfold, A. E., 275, 279.Penney, W.G., 51, 198.Penning, F. M., 22.Pennington, W. D., 343.Peracchio, E. S., 391.PercivaI, A. B., 313.Perkins, G. A., 252.Perlman, G., 322.Perlman, I., 351.Perrin, M. W., 237.Persson, E., 182.Perutz, M., 201.Pesez, M., 403, 404.Peters, C., 178.Peters, D., 289.Peters, R. A., 334, 400.Peterson, W. H., 373, 376.Petras, J., 390.Petrov, B. A., 118.Pfeiffer, P., 149, 165, 171.Pf3lher, J. J., 295.Pfitzner, H., 171.Pfleiderer, G., 109.Patzug, w., 109.Pfluger, H. L., 239.Phillips, E. O., 269.Phillips, H., 220, 221, 222, 225, 233,Phillips, J. W. C., 252, 256, 257.Phillips, S., 367.Philpot, J. St. L., 111.Phipers, R. F., 313.Piaux, L., 395.Pickup, E., 11, 18.Pike, H. V., 84,Pinkard, F. W., 167.Piper, S.H., 195, 252, 254, 255, 257.Pirch, E., 375.Pirie, N. W., 202.Pbskin, I. N., 386.Platt, B. S., 334.Plattner, P. A., 286.Plotnikov, V. A., 125.Plummer, C. A. J., 261.Pohl, R. W., 87.Pohlman, R., 43.Polanyi, M., 74, 77, 105, 108, 221,Policard, A. A., 400.Pollard, A., 252.Pollard, W. B., 407.Polonskaja, L., 109.Poltoratskaja, O., 109.Poluektov, N. S., 408.Ponndorf, W., 287.Pontecorvo, B., 10, 32.Pool, M. L., 10, 11, 23, 26.Pope, W. J., 149.Porter, C. R., 155, 164.Portevin, A., 407.Postowsky, J. J., 320.Potter, V. R., 334.Powell, H. M., 150, 162.Pralow, W., 386.Prandtl, W., 123.Pratt, N. H., 165.Preston, G. D., 388.Preston, J. F., 378.Pr&ost, C., 234.Price, J. R., 370, 371.Price, L. E., 99.Prichard, W.W., 309, 339.Prim, A., 259.Pritchard, R. R., 273.Proske, G., 393.Proskurnin, M., 101, 111, 112.Pryde, I., 406.Pucher, G. W., 370.Pulver, R., 268.Purdie, D., 150, 157, 158,159.Purr, A., 361.PGin, N. A., 261.234, 235.222, 235.Qurtrrell, A. G., 388.Quill, L. L., 10,26,124.Quirke, T. T., 118424 INDEX OF AUTHORS' NAMES.Raeder, M. G., 99.Rahlfs, P., 183.Raisin, C. G., 243.Raistrick, H., 330, 357, 373, 374.Ramage, G. R., 269, 276, 277, 278,Randall, F. C., 256, 264, 267.Randall, H. M., 51.Randall, J. T., 85.Ranganathan, S. K., 269.Ranke-Madsen, E., 171.Ransley, C. E., 78.Rao, B. S., 119, 273.Raper, H. S., 348.Rappaport, F., 405.Rasniussen, K. E., 203.Rathmann, F. H., 332, 399.Ratish, H. D., 401.Ratner, S., 350.Rrtvenswaay, H.J., 409.Ray, B. S., 313.Rayleigh, (Lord), 115.Raymond, W. D., 403.Raynor, G. V., 184.Read, J., 222.Reach, O., 44.Reed, F. P., 313.Reedman, E. J., 400.Regener, V. H., 114.Regnaut, P., 142.Rehm, K., 134, 160.Reichert, F. L., 345.Reichstein, T., 268, 284, 287, 288,293, 295, 297, 299.Reid, A., 387.Reid, E. E., 256.Reid, G. C. K., 354.Reif, G., 405.Reifer, I., 405.Reihlen, H., 408.Reimann, A. L., 61, 89.Remesov, I. A., 289.Rempel, S., 109.Renninger, M., 178.Resch, C. E., 363, 404.Reynolds, D. H., 191, 385.Reynolds, F. M., 249.Reynolds, G. D., 93.Reynolds, L., 384.Reynolds, P. W., 173, 180.Riber, R. K., 323.Rich, A. R., 352.Richardson, K. C., 346.Richardson, 0. W., 78.Rideal, E.K., 61, 68, 73, 76, 77, 95,Ridley, P., 176.Ridout, J. H., 349, 350.Riecken, F. F., 191.Rieder, G., 123.Riederer, K., 184, 386.Riehl, N., 88.Riley, D., 201, 202.279.391.Rimington, C., 355.Ringier, B. H., 309, 310, 339.Rinn, H. W., 384.Rintah, P., 376.Ritchie, M., 130, 397.Rittenberg, D., 347, 348, 349, 350.Ritter, D. M., 121.Rivett, A. C. D., 117.Rivoir, L., 383.Roberts, I., 235.Roberts, J. K., 52, 56, 58, 60, 61, 65,Roberts, R. B., 11, 22, 34.Robertson, A., 313, 315.Robertson, J. M., 187, 194, 195, 198.Robertson, P. W., 263.Robinson, G. M.. 251, 252, 371.Robinson, (Sir) R., 240,243,252,274,306, 325, 370, 371.Rodebush, W., 38.Rordam, H. N. K., 220.Roginski, S. Z., 83.Rohmann, C., 391.Rohrmann, E., 300, 301.Roiter, W., 102.Roncato, A., 390, 392.Root, H.F., 345.Roozeboom, H. W. B., 259.Roquero, C., 131.Rose, M. E., 8.Rosebrugh, T. R., 93, 110.Rosenberg, C., 333.Rosenthaler, L., 401.ROSS, C. S., 192.Rothen, A., 222.Rothschild, Lord, 110.Rothstein, E., 242.Rousselot, L., 348.Rowlands, E. N., 335.Rozsa, P., 404.Ruben, S., 351.Rudall, K. M., 199.Riiegger, A., 332.Ruffin, J. M., 336.Rumbaugh, L. H., 11, 136, 137.Rushbrooke, 0. S., 68.Rushbrooke, J. E., 264, 266.Russell, H. A., 115.Rusznybk, S., 342.Ruzicka, L., 268, 276, 277, 278, 280,281, 283, 285, 286, 289, 290, 292,299.Rydon, H. N., 269, 276, 278.67, 68.Sabinina, L., 109.Saek, H., 39.Sakata, S., 19, 33.Salazar, T., 131.Salomon, H., 309, 310, 338, 339.Sampson, M.B., 127.Sancho, J., 131.Saad, U. J. S., 110INDEX OF AUTHORS’ NAMES. 426Sandro, J., 133.Sandulesco, G., 295.Sanford, E. P., 159.Sankaran, D. K., 269.Sardonnini, C., 117.Sarinsky, V., 95, 96, 97.Sartori, L., 393.Saschek, W., 410.Sastri, B. N., 367.Sasvari, K., 186.Saunders, F., 378.Saville, W. B., 254,256.Savitch, P., 13.Sawicki, J., 362.Scarborough, H., 342.Schafer, K., 385.Schaefer, V. J., 201.Scharwachter, W., 179.Schenck, F., 303.Scherr, R., 139.Schiedt, B., 318.Schieltz, N. C., 118.Schiff, L. I., 9.Schilbert, M. P., 323.Schinz, H., 280.Schittler, E., 326.Schlesinger, H. I., 121.SchIogl-Petzival, G., 311.Schmeil, M., 310.Schmidt, R., 287.Schmidt, R. B., 408.Schmidt, W., 253.Schmidt, W. J., 203.Schmidt-Thom6, J., 291.Schneider, G., 363.Schock, E.D., 343.Schoeller, W., 291.Schon, K., 368.Schoenheimer, R., 283, 347, 348,349,Schofield, H. Z., 193.Scholl, W., 171.Schoh, C., 285.Schoon, T., 256.Schopfer, W. I€., 335.Schossberger, F., 173.Schou, S. A., 396.Schramm, G., 286.Schrankler, W., 82.Schroeter, H., 318.Schuck, C., 333.Schudel, G., 370.Schutze, W., 138, 139.Schulek, E., 404.Schulz, G., 372.Schumacher, H. J., 116.Schumm, P., 270.Schuster, P., 334.Schusterius, C., 386.Schwartz, E., 99, 109.Schweizer, A., 409.Schwenk, E., 285,286,Schwitzer, C., 99.350.Scott, A. D., 215, 220, 222, 223, 227.Scott, A. F., 129.Scott, D. A., 343, 344, 345.Scott, D. B. M., 347.Scott, K.G., 351.Scudi, J. V., 401.Seaborg, G. T., 10,25, 34, 35.Seeley, M., 365.SegrB, E., 10.Seidel, C. F., 280.Seith, W., 80, 81.Seitz, F., 87.Selke, W., 256.Selwood, P. W., 141.Semerano, G., 393.Semmler, F. W., 276.Senter, G., 224, 225.Serini, A., 290, 292, 299.Seshadri, T. R., 328.Seyler, R. C., 169.Shaffer, P. A., 405.Shapiro, U. G., 214,223,227,231.Shaw, (Miss) F. R., 242.Shearer, G., 254.Shearin, P., 43.Shen, Y., 49.Shepherd, W. G., 12.Sherman, A., 76.Sherman, J., 41.Sherr, R., 12.Sherrill, (Miss) M. L., 263.Shire, E. S., 136.Shoppee, C. W., 232.Shorter, A. J., 162.Shouff, W. E., 22.Shuette, H. A., 405.Shutt, G. R., 220.Sibgatullin, N. C., 249.Sidgwick, N. V., 240, 243, 245, 254.Sidwell, A.E., jun., 397.Siebert, H., 390, 392.Sieverts, A., 79.Signer, R., 202.Silberfarb, M., 99.Simonsen, J. L., 268, 269, 271, 272,273, 274, 275, 276, 217, 278, 279.Simpkins, G. W., 331.Simpson, J. C. E., 276.Simpson, M. E., 345.Sinclair, H. M., 335.Singh, A., 245.Singleton, E., 239.Sizoo, G. J., 34, 351.Skaggs, L. S., 13.Skau, E. L., 306.Skinner, H. A., 42.Slipher, V. M., 395.Slygin, A., 101.Smiles, S., 165.Smith, D. T., 336.Smith, E. L., 304.Smith, E. R., 131, 144, 300,Smith, G. F., 237426 INDEX OF AUWORS' NAMES.Smith, G. S., 171.Smith, J. A. B., 252, 350.Smith, J. C., 252, 253, 254, 256, 267,259, 263.Smith, J. W., f24.Smith, K. M., 202.Smith, L., 12.Smith, L. I., 309, 339.Smith, P. E., 293, 357.Smith, S., 396, 402.Smith, S.G., 336.Smith, W. M., 13.Smithells, C. J., 78.Smithuysen, W. C. B., 263.Smyth, C. P., 194, 255.Smythe, W. R., 128, 130, 131, 136,Snitter, P., 271.Snoddy, L. B., 140.Solmssen, U., 331, 332.Soltan, A., 25.Somogyi, M., 405.Sonnichsen, H. M., 232.Soremba, K. H., 255.Southon, W., 84.Spath, E., 325.Spanhoff, R. W., 295.Speakman, J. B., 199.Specht, W., 109.Spencer, F., 237.Spengler, H., 119.Spies, 2'. D., 336, 337.Spooner, E. C. R., 110, 111, 113.Sprague, A. D., 51.SprFg, F. S., 284, 285, 286, 305.Sprinkle, M. R., 241.Stacey, M., 357, 379.Stallman, P. W., 22.Stanley, W. M., 202.Stare, F. J., 322.Staub, H., 12, 22.Staudinger, H., 358.Stauffer, C. H., 228, 229.Staveley, H.E., 306.Steckler, S., 388.Stedman, D. F., 144, 145.Steger, A., 213.Steiger, M., 287, 295, 297.Steigmctn, J., 35, 217, 222.Steinberg, R. A., 372.Steinheil, M., 134.Stekol, J. A., 349, 350.Stenhagen, E., 200.Stephens, W. E., 12,22.Stern, K. G., 343.Stern, O., 106, 110.Sternfeld, L., 378.Stetter, G., 24.Stevens, J. R., 337.Stevens, R. E., 187.Steward, W. B., 49.Stewart, C. P., 342, 402.Stewart, G. W., 255.137, 139.Stitt, F., 42.Stoddart, E. M., 124.Stokinger, H. E., 357.Stokstad, E. L. R., 340,341.Stoll, W., 284.Stone, R. E., 336.Stotz, E. H., 345.Stout, H. P., 99.Stout, P. R., 392.Stoves, J. L., 46.Strack, E., 320.Strain, H. H., 369.Stranski I. N. 382.Strassen, H. zur, 73.Strassmann, F., 13, 130.Strepkov, S.M., 405.Strobele, R., 322.Strong, F. M., 336, 337.Strunz, A., 186.Sturgess, V. C., 370, 371.Subbarow, Y., 336,337.Suess, H., 14.Sugden, S., 241, 242, 248, 249.Summerbell, R. K., 307.Sumoto, I., 27.Surugue, J., 14.Suter, C. M., 307.Sutherland, G. B. B. M., 37, 38, 39,Sutton, L. E., 42, 241, 248.Svedberg, T., 364.Swain, G., 286,305.Sweany, H. C., 384.Szabo, A. L., 222, 235.Szent-Gyorgyi, A., 342.40, 43, 45, 46, 47, 49, 50, 51.Tachi, I., 393.Taebel, W. A., 123.Tafel, J., 91.Tage-Hansen, E., 341.Takagi, S., 268.Takamoto, T., 270.Taketani, M., 19.Tammann, G., 267.Taras, M. H., 399.Tate, J. T., 128.Tattersfield, F., 313.Tatum, H. J., 403.Tauber, H., 334.Tavastsherna, N. I., 288.Taylor, A., 182, 386.Taylor, F.A., 253.Taylor, F. M. H., 220.Taylor, H. S., 71, 72, 74, 75,78, 140, 141, 147.Taylor, T. I., 142, 143, 146.Taylor, T. W. J., 198.Taylor, W., 226.Tchang, Y., 45.Teal, G. K., 97.Teisinger, J., 393.Tellegen, F., 307.76, 77INDEX OF AU!CHORS’ NAMES, 427Teller, E., 47.Telling, M., 354.Tendick, F. H., 298.Thayer, S. A., 341.Thielert, H., 171.Thiessen, P. A., 256.Thode, H. G., 135, 146.Thomas, C. C., 356.Thomas, L. H., 9.Thomas, S. B., 264.Thompson, H. W., 42, 44, 45, 46,Thompson, J. W., 50.Thomson, G. P., 26, 387.Thon, N., 102.Thorbjarnmson, T., 332.Thornton, R. C., 32.Thorpe, J. F., 232.Tiedcke, C., 253.Tiede, E., 88.Tiemann, F., 270, 280.Tilly, F., 404.Timm, B., 49.Timm, E.W., 236,238.Timmis, G. M., 396.Tisza, L., 47.Titani, T., 131.Titeica, S., 265.Tittus, H., 261.Todd, A. R., 309,310,338,339.Tomlinson, T. G., 373.Tommila, E., 239.Tompa, H., 44.Tonnis, B., 320.Topley, B., 105, 220.Topley, W. W. C., 357.Toral, T., 131, 133.Traud, W., 97.Trautmann, G., 303.Trautz, M., 263.Treibs, W., 279.Tress, H., 167.Tressler, D. K., 400.Trillat, J. J., 388, 389.Tristram, G. R., 350.Trofimova, E. I., 373.Trombe, F., 123.Tronov, B. V., 249.Tromtad, L., 131, 142.Troost, L., 149.Tscherniaev, I. I., 169.Tscherning, K., 302.Tschesche, R., 297.Tschopp, E., 285.Tucholski, T., 76.Tuemmler, F. D., 128, 134.Tufts, E. V., 351.Tullock, C. W., 273.Turley, H. G., 220.Turner, A. H., 381.Tutin, F., 269.Twigg, G.H., 75.Twyman, F., 398.49.Ubbelohde, A. R., 194, 195, 267.Uhlenbeck, G. E., 33.Underhill, S. W. F., 333.Ungewiss, A., 386.Ungley, C. C., 335.Ungnade, H. E., 309, 339.Unterzaucher, J., 408, 409.Urey, H. C., 97, 109, 135, 141, 142,143, 144, 145, 146, 235.Usatenko, J. I., 392.Ussing, H. H., 350.Uyldert, I. E., 295.Vaisman, A., 354.Van Bibber, (Miss) K., 264.Van Cleave, A. B., 56, 62.Vascautzanu, E., 392.Vaughan, A. L., 128.Vavon, G., 283.Vedder, E. B., 333.Verkade, P. E., 268.Verleger, H., 49.Verleysen, A., 45.Verweel, H. J., 185, 196.Vestin, R., 334.Vick, F. A., 67.Vickery, H. B., 370.Villars, D. S., 67.Vilter, S. P., 336.Vincent, J. R., 228.Virtanen, A. I., 376.Vitek, V., 102.Voge, H.H., 211, 222.Volmer,M., 99,100,102,103,104,108.Vorlander, D., 256, 259.Wackerlin, E., 403.Wagner, C., 97.Wagner-Jauregg, T., 284.Wagstaff, (Miss) A. I., 197.Wahl, M. H., 144, 146.Waken, H., 400.Waisman, H. A., 337.Walbig, E., 14.Walcher, W., 130, 137.Waldschmidt-Leitz, E., 36 1.Walker, E., 377.Walker, J., 222.Wall, F. T., 49, 50.Wallagh, G., 317.Walling, E., 130.Wallis, E. S., 284, 285, 288, 289.Walter, E. D., 369.Walton, H. F., 98.Wang, J. S., 59, 68, 79.Ward, A. M., 214.Ward, D., 242.Wardlaw, W., 161, 162, 166, 167.Warren, B. E., 184, 255, 386.Warren, F. L., 377.Washburn, E. W., 97, 141, 253428 INDEX OF AUTHORS’ NAMES.Watanab6, T., 195.Waters, W. A., 209, 210.Watson, H. B., 228,231,232,237,238,239, 240, 241, 245, 246, 247, 248.Watson, H.E., 145, 263.Watson, R. E., 22.Watt, H. E., 328.Way, W. J. R., 162, 166.Weatherill, P. F., 134.Weber, A. P., 214.Weber, L. R., 51.Webster, L. A., 145.Weeded, V., 319.Weedon, H. W., 399.Wegner, H., 319.Weidenhagen, R., 319.Weider, F., 310.Weidinger, A., 199.Weigert, F., 93.Weil, L., 375.Weinberg, A., 48.Weiss, J., 220.Weizsacker,C. F. von, 9,15,28,34,130.Wells, A. F., 151, 153, 166, 158, 169,162, 186, 187.Wells, W. H., 8.Wendt, G., 337.Wenig, K., 393.Werner, L., 284.Werner, S., 183.Wessely, F., 311.West, J., 176.West, S. S., 136.Westgren, A., 119.Weatphal, U., 285.Wetter, F., 303.Wettatein, A., 285, 292, 299.Weygand, C., 256, 268.Wheeler, A., 76.Whitby, G. S., 258.Whitby, L. E. H., 352, 353, 354.White, A., 343.White, P., 345.Whitman, B., 285, 286.Whitney, W. R., 93.Whytlaw-Gray, R., 116, 133.Wiardi, P. W., 337.Wibaut, J. P., 317.Wick, H., 99, 100, 102, 108.Widman, O., 308, 315.Widmann, A., 79.Wiebenga, E. H., 197.Wienhaus, H., 270.Wilcke, G., 382.Wildner, E. L., 77.Wilkinr, F. J., 60.Wilkins, T. R., 14.Wilkinson, H., 333.Wilkinson, J. F., 335.Wilkinson, R., 210.Wilks, G. C., 229.Williams, E. F., 252, 267,Williams, E, G., 237.Williams, E. J., 11, 18.Willisme, F. R., 240.Williams, J. H., 12, 128.Williams, L. C., 392.Williams, R. B., 241.Williams, R. D., 405.Williams, R. R., 334.Williamson, A. T., 237.Willis, G. H., 245.Willis, J. A. V., 252.Willstaedt, H., 400.Wilman, H., 388.Wilson, C. L., 220, 229, 243.Wilson, D. A., 258.Wilson, E. B., 48.Wilson, J., 357.Wilson, J. G., 16.Wilson, R. E., 93.Wilson, R. R., 8, 9.Wind, A. H., 276.Windaus, A., 288, 303, 305, 306.Winkel, A., 392, 393.Winkler, C. A., 237, 238.Winstein, S., 169.Wintersteiner, O., 293, 295, 298, 299,343, 357.Wirth, H. E., 409.Wirtz, K., 99.Win, H., 281.Withers, J. C., 252.Witte, H., 183, 184.Wittle, E. L., 284, 297, 300, 301.Wittner, F., 127.Wodstrup, I., 344.Wolfenden, J. H., 98.Wolffbrandt, C. G., 393.Wolfrom, M. L., 369.Wolthus, E., 389.woo, s. c., 49.Woodford, A. O., 191.Woodward, L. A., 37.Wooldridge, D. E., 139.Woolley, D. W., 336, 337, 373.Wooster, N., 161.Wooster, W. A., 173.Wooten, L. A., 241.Work, T. S., 309, 310, 338, 339.Wrede, F., 320, 325.Wright. J.. 228.Wriiht; N:, 49, 395.Wrinch, D. M., 176, 177, 201.Wu, C. -K., 43,-50, 62.Wu, T., 49.Wulf, 0. R., 38, 396.Wunderlich; W., 303.Wyckoff, R. W. G., 196, 202.Wyk, A. van der, 267.Wynn-Williams, C. E., 26.Yabroff, D. L., 243.Yabuta, T., 328.Yago, M., 289INDEX OF AUTHORS’ NAMES.Yamashita, Y., 327.Yanganita, M., 315.Yarnall, W. A., 289.Yates, E. D., 232.Yates, E. L., 137, 180.Yoshitomi, E., 268.Yost, D. M., 50, 115.Young, F. G., 283, 284, 346, 347.Young, G. T., 362.Young, R. C., 120.Young, W. G., 234.Youtz, M. A., 93.Yuill, M. E., 356.Yukawa, H., 19, 33.Zachariasen, W. H., 185.Zentmire, Z., 333.Zieren, M., 109.Zilva, S. S., 338, 342.Zimmermann, W., 278.Zintl, E., 117.Zlotowski, I., 12.Zmaczynski, E. V., 406.Zscheile, F. P., 397.Zschiesche, E., 337.Zuber, K., 148.Ziihlsdorff, G., 306.Zumwalt, L. R., 48.Zunino, J., 43.42

ISSN:0365-6217    

DOI:10.1039/AR9383500411

出版商:RSC    

年代:1938

数据来源: RSC

摘要:

INDEX OFAcetaldehyde-ammonia, structure of,197.Acetic acid, potassium salt, reactionof, with cinnamyl chloride, 234.Acetoacetic acid, ethyl ester, bromin-ation of, 232.Acetones, halogenated, electro-metric study of aqueous solu-tions of, 232.Acetophenones, nuclear-substituted,prototropy of, 231.Acids, aliphatic, dissociation con-stants of, 251.carboxylic, and their esters, poly-dissociation constants of, 240.infra-red spectra and structurepolymorphism of, 256.dicarboxylic, crystal structure of,267.fatty, compound formation with,desaturation of, in liver, 349.heat of crystallisation of, 265.melting of, 265.polymorphism of, 256.preparation and synthesis of,purification of, 252.cis- and trans-Aconitic acids, analysisof mixtures of, 393.Actinomyces Waksmanii, pigmentfrom, 372.Adermin, 337.Adlumidine, 325.Adlumina, alkaloids from, 324.Adlumine, 325.Adrenal cortex, steroids of, 293.Adsorption of gases on metal surfaces,Btiocholane-3(~)-17-diol from men’sd 5-2Etiocholenic acid, 3(P)-hydroxy-,morphism of, 257.of, 39.263.251.52.theory of, 68.urine, 302.292.preparation of, 287.3(/3) : 17-dihydroxy-, 290, 292.Alboleersin, 374.Albumin, egg, structure of, 201.wxmm-, antigenic complexes of,356.4SUBJECTS.Alcohols, bond distances in, 40.polymorphism of, 258.Aldimines, metallic, 171.Aliphatic compounds, X-ray analysisof films of, 254.substitution in, 210.Alkali metals, determination of, inplant ashandmineral waters, 393.isotopes, separation of, 146.Alkaloids, 323.analysis of, 402.Alkyl groups, influence of, on re-activity, 248.halides, hydrolysis of, 2 13.Allene, spectrum of, 52.Alloys, analysis of, 407.X-ray analysis of, 385.ternary, 179.theory of, 184.X-rrty analysiS Of, 386.Aluminium, a t wt.of, 134.Aluminium alloys with cadmiumand magnesium, 184.with carbon and iron, 182.with copper and manganese, 182.with copper and nickel, 180, 182.with iron and nickel, 182.with magnesium and zinc, 184.Aluminium chloride, structure of,halides, structure of, 157.Amalgams, dental, 180.Amino-acids, metabolism of, 350.Amino-groups, determination of, 396.Ammonia, density of, 133.exchange of deuterium with, 71.spectrum of, 50.Ammonium chlorobromoiodide,crystal structure of, 185.dichromate, ignition of, 119.halides, Raman spectra of, 43.149.tert.-Amy1 halides, elimination andAmylases, activity of, 359.decomposition of starch by, 359.Amylokinase, 361.Analysis, electron-diffraction, 387.microchemical, 406.organic, elementary, 408.polarographic, 389.X-ray, 381.spectroscopic, 394.substitution in, 227.INDEX OF SUBJECTS.43 1Anauxite, 193.d 6:7-Androstadiene-3(/3) : 17-&01,303.Androstane series, transition of, topregnane series, 289.Aneurin, 3 3 3.Anilines, benzoylation of, 237.Anionotropy, 233.Anolobine, 325.Anthocyanins, 370.bacterial, 37 1.Anthracene, catalytic combustion of,in oxygen, 129.Antigens, bac t er ial, 3 5 7.specificity of, 356.Antihormones, 357.Antimonic acid, effect of heat on,Arachis hypogea.See Peanuts.Archangiurn, cellulose decomposi-tion by, 377.Argon in atmosphere, 115.Arsenic, at. wt. of, 134.119.isotopes, separation of, 139.detection of, in presence of germ-anium or selenium, 406.determination of, in phosphoricacid, 393.Arsines, tertiary, palladium andplatinum compounds with, 150.Arsinimines, 172.Artemesia ketone, 268.Arylsulphuric acids, hydrolysis of,Ascorbic acid, 337.Ash. See Fraxinus excelsior.Asirnina triloba, anolobine from, 325.E-Aspartic acid, conversion of, intoAspartic decarboxylase, 376.Aspergillus, chemistry of, 372.Aspergillus fumigatus, metabolic pro-ducts of, 374.Aspergillus niger, nitrogen utilisationby, 372.Atmosphere, argon and neon in, 11 5.ozone in, 11 4.Atomic weights, 125.Aurotensine, 324.Axerophthol, 331.Azides, detonation of, 83.Azobenzene, 2-hydroxy-, copper lakeof, 169.2 : 2’-dihydroxy-, copper salt,170.Azobenzene-o-carboxylic acid, cop-per salts, 170.Azotobacter.Dolvsaccharide svnthesis238.determination of, 400.p-alanine by bacteria, 376.by, 379.&p-Azoxvanisole. equilibrium of,kith p-&zoxy-&enetole, 259.with p-methoxycinnamic acid,259.p-Azoxyphenetole, equilibrium of,with p-azoxyanisole, 259.Bacillua botulinus, enzymes of, 376.Bacillus chlororaphis, yellow pig-Bacillus jluorescens, enzymes of, 375.Bacillus jluorescens liquefaciens,Bacillus pyocyaneus, blue pigment of,Bacteria, anthocyanins in, 371.ment of, 319.enzymes of, 376.320.enzymes of, 375.carbohydrate-decomposing, 377.legume, enzymes of, 376.nitrogen-fixing, polysaccharidepolysaccharide synthesis by, 378.proteolytic enzymes of, 375.Barbituric acid derivatives, doter-Barley extracts, amylase activity of,Batteries, storage, lead, reactions in,Beans, black, proteins of, 367.Beer’s law, 396.Beet pectin, 364.Beetroots, red pigment of, 370.Bentonites, 191.Benzene, exchange of deuteriumwith, 74.nucleus, effect of halogens linkedto, 242.Benzenes, halogeno-, velocity ofnitration of, 242.substituted, mesomeric momentsof, 241.Benzoic acid, esters, hydrolysis of,237, 238.ethyl ester, velocity of nitrationof, 242.Benzoic acid, o-nitro-, esterificetionof, 245.Benzoic acids, o-substituted, dis-sociation constants of, 247.Benzoyl chloride, alcoholysis of, 238.Benzyl chloride, hydrolysis of, 214.a -Benz y le t h yl alcohol, configurationBertholletia exceka.See Brazil nuts.Beryllium, disintegration of, by y-synthesis by, 378.mination of, 403.after papain addition, 361.386.of derivatives of, 220.rays, 35.isotopes, 12.neutrons from, 23.Betanin, determination of, 370.Betulenols, 278.Betulenolic acid, 278.Bicucine, 325.Bicuculline, 325.Biochemistry, animal, 330.plant, 358432 INDEX OB SUBJECTS.Biology, nuclear physics in, 15.Biotite, decomposition of, 188.Birch-bud oil, betulenols from, 278.Black-tongue, cure of, 336.Blood, coagulation of, effect oivitamin-R on, 340.determination in, of copper, 390,of lead, 393.vitamin-B, in, 335.and vitamin-P, 342.in, 351.137.393.Blood capillaries, permeability of,Bond length and force constants, 46.Bone, exchange of phosphorus atomsBoron, isotopes of, separation of,Boron trifluoride, spectrum of, 60.Brass, analysis of, 393.Brazil nuts, shells, constituents of,Bridged compounds, 149.Bromine dioxide, decomposition of,Bulbocapnine, 325.tert.-Butyl halides, elimination and366.116.substitution in, 227.hydrolysis of, 216.Cadmium alloys with aluminiumand magnesium, 184.Cadmium bromide, compounds of,with trialkyl-mines andCaesium chromate, crystal structureof, 186.Calciferol, structure of, 304.Calcium sulphide, luminescent, 87.Camphedene, structure of, 271.Camphenilone, synthesis of, 272.Camphenilyl chloride, structure of,272.a-Campholenic acid, oxidation of,270.a- and ,%Camphylic acids, structureof, 271.Capauridine, 325.Capaurine, 325.Capnoidine, 325.Carme, synthesis of, 269.Carbohydrates, determination of, 404.Carbon, at wt.of, 128.determination of, 408.isotopes, separation of, 138.Carbon tetrachloride, Raman spec-suboxide, force constants of, 44.dioxide, spectrum of, 49.dkulphide, spectrum of, 49.Carbonyl chloride, spectrum of, 52.Carcinoma, detection of, by protein-phosphinM, 157.trum of, 60.determination, 393.Car& papaya latex, papain activ-Caryophyllenes, 276.Catalysis, heterogeneous, 70.Catalysts, hydrogenation, 408.Cathodes, mercury, electrodepositionof hydrogen with, 95.Cellulose, decomposition of, bybacteria, 377.structure of, 194.Cepharanthin, 327.Cereah, germinating, amylase activ-ity in, 361.Cetyl iodide, polymorphism of, 256.dZ-Chaulmoogrio acid, synthesis of,252.Chelation in o-substitution, 244.Chemotherapy, 352.Chiolite, crystal structure of, 186.Chlorine, determination of, 397.isotopes, separation of, 140, 148.Chlorites, 189.Chlororaphine, structure of, 323.Ae:‘-Cholestadiene, irradiation of, 306.d 6:7-Cholestadien-3-ol in pig’s skind s:8-Cholestadien-3-ol, irradiation of,A 1~4-Cholesadieen33-one, 286.i-€%olesterol, 284.Cholesteryl ethers, “ abnorma1,” 284.Chromium alloys with iron andsilicon, 182.Chrmobacteriurn wdinum, purple pig-ment of, 320.Chryyne, catalytic combustion of,111 oxygen, 129.Cinnamyl chloride, reaction of, withpotassium acetate, 234.Citric acid, formation of, by moulds,373.Citrin, effect of, on capillary per-meability, 342.Citrus pectins, 364.Clays, 190.Estonian blue, analysis of, 386.minerals of, 187.Clostridium histolytkurn, proteinasefrom, 375.Cobalt chloride, compounds of, withpyridine, 162.salts, colour change in solutions of,122.Cocaine, determination of, 402.Co-carboxylase and vitamin-B,, 334.Colchicoine, structure of, 326.Colchiche, structure of, 326.Colloids, addition of, to solutions forpolarographic analysis, 392.Combustion tube, Pregl, 409.Condensation, mechanism of, 68.Zookeite, 189.Go-ordination compounds, 160.ators in, 367.and whelks, 303.305INDEX OF SUBJECTS.433Copper, analysis of, 392.determination of, in blood, 390,radioactive, concentration of, 35.Copper alloys with aluminium andmanganese, 182.with aluminium and nickel, 180,182.Copper halides, compounds of, withtrialkyl-mines and -phosphines,158.393.sulphate, structure of, 164.A Woprostenone, 286.Cordrasthe, 325.Corlumidine, 325.Corlumine, 325.Corrosion and oxide films, 388.Corticosterone, conversion of, toCorydaliS, corypalline from, 324.Corydine, 324.Corylus avellana. See Hazel nuts.Corypalline, 324.Corypalmines, 324.Corytuberine, 324.Cottonseed hulls, hemicellulose from,Cottonseed oil, tocopherols from, 338.Cristobalite, detection of, in glass,Cronstedtite, 189.Cryolite, crystal structure of, 186.Crystals, chemistry of, 184.of long-chain substances, 266.physics of, 173.Crystallography, 173.technique in, 174.Cucumber virus, structure of, 202.Cularidine, 326.Cularine, 325.Cyanogen, force constants of, 44.Cyanuric acid, structure of, 197.Cyanuric triazide, structure of, 197.Cyclotron, 8.Cyperones, 273.Cyperus rotundus, cyperone from, 273.Cytophaga Hutchinsonii, cellulose de-electrochemistry of, 113.allopregnane, 296.365.386.Cryptopines, 324.composition by, 377.Decarbousnic acid, 3 15.Decarbousnol, 316.2-Dehydrorotenone, 31 1.N-Demethylcularine, 325.Density of gases, 131.Dental amalgams, 180.Deoxycorticosterone, 287.Dermatitis from 2 : 4-dinitrochloro-benzene, 357.pig’s, effect of nicotinic acid on,336.Derris root, constituents of, 311.Detonators, 81.Deuterides, exchange of, withhydrides, 74.Deuterium, adsorption of, and ofhydrogen, 77.diffUsion of, through metals, 79.exchange of, for hydrogen, 71,229, 243.in water, 131.neutrons from, 22.separation of, from hydrogen, 134.spectra of, 52.use of, in metabolism studies, 347.velocity of reaction of, and ofDeuterium oxide, determination of,Deuteromethyl deuteralcohol, spec-Diabetes, effect of hypophysectomyDiacetylene, spectrum and structureDiallylbarbituric acid, detection of,1 : 4-Dibenzylphenazine, 321.Diborane diammoniate, 121.Dicentra, alkaloids from, 324.Dicentrine, 324.Dickite, 193.Didymocarpus pedicellata, leaves,Diethylbromogold, structure of, 149.Diffraction, X-ray, data for, 384.Diffusion, gravitational, isotopeisotope separation by, 138.thermal, isotope separation by,degradation of, 298.structure of, 271.hydrogen, 76.350.trum of, 50.on, 345.of, 49.treatment of, 344.404.colouring matters on, 370.separation by, 140.140.Digoxigenin, 297.GoDihy dro - 8- camph ylic acid, br orno -,Dihydroequilenins, reduction of, 288.Dihydrousnic acid, 3 16.2 : 5-Diketopiperazine, structure of,196.ay -Dimethylally1 hydrogen phthalate,optical activity and substitutionin, 234.1 : 3 -Dime t hyl- 7 - wopropylnaphth-alene, preparation of, 274.Di-l-naphthylmethane, di-2-hydr-oxy-, alkali salts, 165.Di- l-naphthyl selenide and sulphide,di-2-hydroxy-, alkali salts, 165.Dioxan, preparation and propertiesof, and its derivatives, 307.Diphenyl, 2- and 4-hydroxy-, de-tection and determination of,in phenol, 396434 INDEX OF SUBJECTS.a y -Diphenylmethyleneazomethines,prototropy of, 232.ay-Diphenylpropenes, prototropy of,232./3/3-DiphenylpropionyImesitylene, a-bromo-, prototropy of, 232.Dipole moments, mesomeric, 241.Di-n-propylcyanogold, structure of,149.Dissociation constants of aliphaticacids, 251.Distillation, fractional, isotope separ-ation by, 143.Double layer and electro-capillarity,110.Drugs, separation of, from biologicalmaterial, 402.Dunnione, 370.Durangite, crystal structure of, 186.Durene, structure of, 198.Dyes, absorption and emission ofradiation by, 89.mordant, metallic lakes of, 169.of carboxylic acids, 240.Earths, rare, oxides and salts of, 123.Ecgonine, determination of, 402.Elastin, structure of, 200.Elastoidin, 199.Electro-capillarity and the doublelayer, 1 10.Electrodes, dropping, 390.mercury, 95, 110.Electrolysis, isotope separation by,141.Electrons, diffraction of, analysis bymeans of, 387.K-Electrons, capture of, by nuclei, 33.in radioactive decay, 11.Electron-acceptors, 245.Electrophilic reagents, 209.Elements, no.43, 10, 124.nos. 61, 87, and 93, 124.rare, detection of, 406.trans-uranium, 13.Embelin, 374.Enzymes, bacterial, 375.pectic, 365.Equilenjn, reduction of, 288.isoEquilin, 286.Equol, 311.Erbium, at. wt.of, 127.Eremophilone, and hydroxy-, 274.Ergosterol, degradation of, 288.in wheat-germ oil, 303.Ergot alkaloids, analysis of, 396.Eschscholtzxanthin, 369.Ethane, hydrogenation of, 70.Ethanes, exchange of, with deu-irreversible processes at, 90.rotation of, 42.terium, 74.17-Ethinyl-dS-androstene-3(/3) : 17-17-Ethinylcestratriene-3 : 17-diol,291.E t hin yl tes tos terone, 2 90.Ethyldibromogold, structure of, 149.Ethylene, exchange of, with deu-heavy and light, spectra of, 51.hydrogenation of, 73.molecules, potential function for,Ethylene, tetrachloro - , force constantsEthylenediaminecupric salts, 164.17-Ethylax1tradiol, 17 -a/3-dihydroxy-,Europium, at. wt. of, 128.Evaporation, mechanism of, 68.Excelsin, mol.wt. of, 367.Exchange reactions, isotope separ-ation by means of, 145.diol, 290.terium, 75.45.and spectrum of, 44.291.isolation of, 123.with deuterium, 71, 229, 243.dl-Fenchone, synthesis of, 270.Fermentation, alcoholic, enzymes of,in moulds, 373.Ferrostilpnomelane, 190.Filaments, heat of adsorption on, 56.Films, adsorbed, formation and re-moval of, on tungsten, 67.immobile, holes and gaps in, 61.mobile and immobile, 67.X-ray analysis of, 254.Fish, freshwater, vitamin-A, in, 331.Fluorescence, 86.Fluorine, at. wt. of, 134.properties of, 115.Force constants, 44.and bond length, 46.Formaldehyde, rotation and vibrationspectrum of, 51.Formic acid, dimer, bond distances in,moments of inertia of, 51.rotation of, 42.loses of, 366.in, 47.40.Fraxinus excelsior bark, hemicellu-Fructose, determination of, 405.Fumigatin, 374.Furnaces, combustion, 408.Gadolinium, at.wt. of, 127.determination of, 382.Gallium, double layer capacity for,radioactive, concentration of, 35.Gas reactions, heterogeneous, 70.Gases, adsorption of, on metal112.surfaces, 52INDEX OF SUBJECTS. 435Gases, density of, 131.diffusion of, through metals, 77.Gazania rigens, flowers, pigments of,Gazaniaxanthin, 368.Gelatin, antigenic coupling of, 356.Germane, spectrum and structure of,49.Germanium, detection of, in presenceof arsenic or selenium, 406.Gesnera fulgens, flowers, pigment of,371.Gesnerin, 37 1.Glass, detection of cristobdite in,386.Glaucentrine, 325.Glaucine, 324.Glauconite, 188.Gliadin, 366.Globulin, serum-, antigenic com-Glucazidone, 317.Glucose, determination of, 405.Glutamic decarboxylase, 376.Glyoxalines, 3 19.Gold, diffusion coefficient of, 81.diffusion of, in lead, 80.foil, electron-diffraction patternsof, 389.leaf, electron-diffraction patternsof, 389.recovery of, from water, 407.Gold halides, compounds of, withtrialkyl-arsines and -phosphines,159.368.plexes of, 356.structure of, 149.Gonorrhea, treatment of, 354.Granite, argon and neon in, 115.Groups, effect of, on reactivity, 236.polar effects of, 240.Hafnium, determination of, in zir-Halloysite, 193.Halogens, determination of, 409.Hazel nuts, pericarp, constituents of,Heat of adsorption on filaments, 56.Heliotridan, 328.Heliotrine, 328.Heliotropium alkaloids, 328.Helium, accommodation coefficientof, on tungsten, 52.isotopes, mass 5, 12.particles, range of, 27.products from, 373.permeability, 342.conium, 381.366.Helminthosporium leersii, metabolicHemicelluloses, 365.Hesperidin, effect of, on capillaryHeterocholestenone, 285.Heterocyclic compounds, 307.Hexadecane, polymorphism of, 286,Hexahydroequilenin, 289.Hexahydrophenazine, 32 1.Hexamethylbenzene, structure of,198.Hexamethylenetetramine, structureof, 196.Hexapyridyl, 3 17.Hexatetracontanoic acid, synthesisof, 252.Hexoses, analysis of, 405.Holmium, atomic weight of, 127.Homocaryophyllenic acid, 276.Hop flowers, hemicelluloses from,Hormones, sex, configuration of, 298.steroidal, metabolism of, in thebody, 302.synthesis of, from biIe acids andsterols, 287.Hydrocarbons, analysis of mixturesof, by Raman spectra, 395.Hydrochloric acid, infra-red spectrumand rotation of, 43.Hydrogen, adsorption of, and ofdeuterium, 77.on mercury, 56.on tungsten, 55.atomic, conversion of, to molecularhydrogen, 80.formation of, by hot tungsten,63.determination of, 408.diffiwion of, through metals, 79.electrodeposition of, 95.exchange of, for deuterium, 71,heat of adsorption of, on tungstenisotope, mass 3, 12.isotopes, overpotential of, 97.overpotential of, on metals, 99.velocity of reaction of, and ofHydrogen bond, association and, 38.internal formation of, 244.Hydrogen peroxide, spectrum and365.229, 243.filaments, 56.separation of, 134.theories of, 103.deuterium, 76.structure of, 51.spectrum of, 51.sulphide, density of, 133.Hydromuscovite, 188.Hydroxy-groups, determination of,replacement of, by halogens, 225.Hypophysectomy, effect of, on dia-Hypovitaminosis-C in diseases, 338.396.betes, 345.Illite, 188.Imino-groups, determination of, 396436 INDEX OF SUBJEUTS.Immunity, chemical aspects of, 355.Immunology, ascorbic acid in, 338.Insulin, antigenic coupling of, 356.Intermetallic compounds, 183.Iodine monochloride, electrolysis of,and its reactions with salts, 117.Iodous sulphate, 11 6.Ions, high-speed, formation of, 8.Irene, 280.Iron, detection of, in zinc, 381.diffusion of gases through, 78.oxide films on, 388.passivity of, 388.Iron alloys with aluminium andcarbon, 182.with aluminium and nickel, 182.with chromium and silicon, 182.chemistry of, 343.structure of, 201.Irone, 280.Isotopes, 126.abundance ratios of, 125.radioactive, use of, in biology ahdmedicine, 15.separation of, 134.use of, in metabolism studies, 347.Isotopic weights, 126.Jacobine, 328.Kamala, rottlerin from, 313.Kaolinite, 193.Keratins, structure of, 199.Keto-mi&, synthesis of, 252.12-Ketocholanic acids, ll-hydroxy-,2 - Ke to -N-meth y lphenazine, 3 2 1.Ketones, bromination, deuterium ex-change, and racemisation of,229.297.d4-3-Ketones, preparation of, 286.17-Ket0-d~:5:7:~-0estratetraene, 288.l*I-Ket~-d~:~:~-~stratriene, 289.d-p-Keto-a-phenyl-n-butyric acid,Z-menthyl ester, optical activityand tautomerism of, 230.d4-3-Keto-steroi&, en01 esters of,285.Kinetic equation, 236.Kinetics, chemical, 69.Labels on molecules, 348.Lactic acid, ethyl ester, configur-ation of, 220.Lanceol, 279.Lanthanum, determination of, 382.Laaiocaxpine, 328.Lead, at.wt. of, 134.determination of, in blood, 393.in phosphoric acid, 393.Lead, isotopes of, 126.self-diffusion of, 80.Lead azide, detonation of, 82.oxides, 118.Leaves, young, anthocyanins of,Ledol, 280.Lepidolite, 187.Leuco-malachite-green, oxidation by,89.Leuconost oc dextranicus, dex tranformation from sucrose by, 378.Lezcconostoc mesenteriodes, peptidasesof, 376.Lichens, usnic acid in, 314.Liliurn bulbs, carbohydrate from,364.Lithium isotopes, separation of, 136,142, 146.371.neutrons from, 22.particles, range of, 27.Luminescence of solids, 87.Lumisterol, structure of, 304.Lumisterol-3, 303.Lungs, detection of silica in, 384.Lutecium, at.wt. of, 134.Luteoleersin, 374.M. & B. 693, 353.Maclura pornitera. See Oranges,Magnesium alloys, analysis of, 393.with aluminium and cadmium, 184.with aluminium and zinc, 184.with silver and zinc, 184.Manganese alloys with aluminiumMedicine, nuclear physics in, 15.Melting, theory of, 265.Melting points of homologous series,Meningitis, treatment of, 354.Menthone, acid-catalysed prototropyof, 228.Mercuric halides, compounds of,with trialkyl-arsines and-phosphines, 167.Mercury, adsorption of hydrogen on,56.Mercury alloys with silver and tin,Mesotrons, 7, 16.Metabolism, study of, by means ofisotopes, 347.Metahalloysite, 193.Metals, adsorption of gases on, 52.diffusion of gases through, 77.overpotential of, 102.overpotential of hydrogen on, 99.precious, analysis of, 407.therapy with, 352.Osage.and copper, 182.267.isotopes, separation of, 148.180INDEX OF SUBJECTS.437Metallic compounds, four-covaIent,halides, bridged structure of, 149.Methane, detection of, in planets,exchange of, with deuterium, 74.p-Methoxycinnamic acid, equili-brium of, with p-azoxyanisole,259.Methyl alcohol, rotation of, 42.Methyl deuteralcohol, spectrum of,Methyl groups, influence of, onhalides, spectra and structure of,iodide, reaction of, with dirnethyl-Methylacetylene, spectrum and struc-Methylamine, rotation of, 42.Methyldisilylamine, 12 1.Methyleneazomethines, deuteriumexchange and racemisation in,229.3-Methyl-4 : 5-phenanthrolin0, com-plex salts, 165.y-Methyl-a-n-propylallyl alcohol,optical activity and substitutionin, 235.Mica, 187.X-ray diffraction analysis of, 386.Micro-organisms, chemistry of, 372.Mine dusts, analysis of, 385.Minerals, age of, 14.Mixtures, identification of, by X-rayMolecules, asymmetrical-top, 51.162.polynuclear, 148.395.spectrum and structure of, 50.50.reactivity , 2 49.50.anilines, 237.ture of, 49.clay, 187.patterns, 385.linear, 49.spherical, 49.polyatomic, rotation and vibrationin, 47.symmetrical-top, 50.Molybdenum, bombardment of, bydeuterons, 10.Montmorillonite, 191.Morphine, determination of, 403.Moulds, chemistry of, 373.Muscovite, 188.Myosin, structure of, 199.Narcotoline, 325.Neodymium, determination of, 382.isotopes, 127.Neon, accommodation coefficient of,on tungsten, 53.in atmosphere, 115.isotopes, separation of, 134, 138,144.Neutrons, 21.collisions of, with nuclei, 24.detection of, 23.free, production of, 21.magnetic moment of, 24.mass of, 24.spin of, 24.Nickel, detection of, in zinc, 383.Nickel alloys with aluminium andcopper, 180, 182.catalyst, 408.catalyst, 408.with aluminium and iron, 182.Nickel chromite as hydrogenationoxides, 118.Nickel-thoria as hydrogenationNicotinic acid, 336.determination of, 400." Night-blindness," 333.Niobium, determination of, inmolybdenum, 382.orthoNitrates, 11 8.Nitrates, unsaturated, deuterium ex-change in, 229.orthoNitrites, 118.Nitrogen, at.wt. of, 134.determination of, 409.isotopes, separation of, 139, 146.Nitrogen triiodide, detonation of, 82.dioxide, compound of, withphosphorus pentoxide, 124.Nitrosopentamminocobalt wltlts, 166.Nonacosane, crystal structure of,255.Nonacosanone, synthesis of, 252.2-Norequilenin methyl ether, syn-Nuclear forces, theory of, 19.Nuclei, collisions of neutrons with, 24.K-electron capture by, 33.isomerism of, 9.spontaneous change of, 28.transmutations of, by fast neutrons,by slow neutrons, 26.Nucleophilic reagents, 209.thesis of, 306.25.Octadecane, polymorphism of, 256.Octahydrophenazine, 321.Octammino-p-dihydroxydicobaltictetrabromide, 148.p-n-Octyl alcohol, configuration ofderivatives of, 220.,8-n-Octyl halides, elimination andsubstitution in, 227.a-CEhtradiol, configuration of, 299.Olivenite, crystal structure of, 186.Opium, determination in, of morphine,Optical activity, losa of, in sub-hydrolysis of, 223.403.stitution, 234438 INDEX OPOptical inversion, Walden’s, 218.Orange pectin, 364.Orangos, Osage, yellow pigment of,Organic chemistry, 204.Organic compounds, crystal structureof, 194.Osajin, 369.Osmium, detection of, in mixtureswith ruthenium, 406.Ouabain, determination of, 403.Overpotential, activation, 90.concentration, 92, 109.of hydrogen on metals, 99.of oxygen, 101.resistance, 94.Oxide films, analysis of, 388.Oxides, classification of, 117.mixed, X-ray analysis of, 386.Uxychlororaphine, 31 9.structure of, 323.Oxygen, at.wt. of, in air and inwater, 131.density of, 132.determination of, 408.electrodeposition of, from fusedsodium hydroxide, 109.films, formation and removal of,on tungsten, 67.heat of adsorption of, on tungsten,62.isotopes, 13 1.separation of, 141.overpotential of, 101.Ozone in atmosphere, 114.369.Palladium, diffusion of deuteriumand hydrogen through, 79.Palladium dichloride, structure of,166, 187.compounds with hydrocarbons,169.with tertiary arsines and phos-phines, 160.Palmitic acid, cetyl ester, crystalstructure of, 255.ethyl and wobutyl esters, poly-morphism of, 266.ethyl ester, mixed crystals of,with ethyl stearate, 260.Papain, 367.effect of, on amylme activity, 361.Papaver somniferum, alkaloids of,325.Paraffins from plant waxes, 260.liquid, X-ray structure of, 255.polymorphism of, 258.specific heats of, 267.Parsettemite, 190.Peanuts, hulls, constituents of, 366.Pectic acid, 363.Pectin, constitution of, 362.SUBJECTS.Pectins, mol.wts. of, 364.Pectin-methoxylase, 366.Pectinase, 365.Pellagra, cure of, 336.PeniciUium, citric acid productionPenicillzum &nulosum, metabolicPentaerythritol, structure of, 195.Pentaerythritol tetraacetate, struc-Pentapyridyl, 317.Pentenes, identification of, by RamanPentoses, determination of, 404.Pepsin, structure of, 201.Petroleum, analysis of, 396.Pbeolzcs vulgaria. See Beans, black.Phentuhydrins, 323.Phenazines, 319.reduction of, 322.Phenol, synthetic, detection anddetermination of hydroxydi-phenyls in, 396.Phenols, o - subs ti t ut ed, hydrogenbond in, 243.Phenolic ethers, chlorination of, 237.Phenyl alkyl ketones, acid-catalysedprototropy of, 250.cyanohydrins, dissociation con-stants of, 251.22-Phenylbehenic acid, synthesis of,252.Phenylisobutylacetophenone, acid-catalysed racemisation of, 228.Phenyldimethylarsine, compoundsof, with metallic halides, 157.a-Phenylethyl alcohol, configurationby,.373.product of, 374.ture of, 196.spectra, 395.of,- 220. -a-Phenylethyl chloride, alcoholysisof. 215.elimLtion and substitution in,227.halides, hydrolysis and alcoholysisof, 223.Phenylmethylacetophenone, acid-catalysed racemisation of, 228.15-Phenylpentadecoic acid, synthesisof, 252.p-Phenylpropionic acid, p-hydroxy-,ethyl ester, corkiguration of, 220.Phlogopite, 188.Phosphines, tertiary, palladium andplatinum compounds with, 150.Phosphinimines, 172,Phosphors, 8 8.Phosphorescence, 86.Phosphorus, allotropes of, 121.at. wt. of, 129.radioactive, use of, in metabolismstudies, 351.Phosphorus oxychloride, analysis of,129INDEX OFPhotochemistry, isotope separationPhthalocyanines, metallic, 163.Physics, nuclear, in biology andmedicine, 15.Pigments, carotenoid and chlorophyll,analysis of, 398.Pinane, synthesis of, 269.a-Pinene, synthesis of, 269.Z-Piperityltrimethylammonium hydr-oxide, inversion and substitutionin, 222.Pituitary, anterior, diabetogenic andin relation to carbohydrateby means of, 147.of solids, 85.glycotropic factors of, 346.metabolism, 345.Plants, hemicelluloses in, 365.pectins in, 362.pigments in, 368.proteins in, 366.Plant ash, analysis of, 392, 393.Plant products, 358.Plant viruses, structure of, 202.Platinum, detection and determin-ation of, 407.electro-capillary curve for, 112.sputtered, electron-diffraction pat-tern of, 388.Platinum compounds with olefhs,168.with tertiary arsines and phos-phines, 150.Platinum diammines, 167.Platinumphthalocyanine, crystalstructure of, 187.Platyphylline, 328.Pneumonia, treatment of, 354.Polymorphism, 256.Polyneuritis from vitamin-B, de-ficiency, 335.Polyporic acid, 374.Polypyridyls, 317.ruthemum compounds with, 161.Polysaccharides, synthesis of, bybacteria, 378.Poppies, Californian, pigment in, 369.Iceland, yellow pigment of, 371.Porphyrins, metallic derivatives, 163.Potassium isotopes, 130.separation of, 137.radioactive, 14.Potassium pentaborate, crystal struc-ture of, 185.chloride phosphors, 88.tetrachloroiodide, crystal structureof, 186.hydrofluoride, crystal structureof, 185.stannous chloride, structure of, 162.A4:*-Pregnadiene-17:21-diol-3 : 11 : 20-trione as precursor of sex-hormones and steroids, 302.SUBJECTS .439d5:1e-Pregnadien-3-ol-20-one, 292.aZEoPregnane, formation of, fromPregnanediol, 301.aEloPregnane-3: 17:20:21-tetrol, 292.Pregnanetriol-B, 300.A 6-Pregnene-3:17:20:2 1 -tetrol, 292.A4-Pregnene-17:20:21-triol-3-one, 292.Progesterone, biological reduction of,Progesterone, 17-hydroxy-, 290.Prolopine, 324.Prontosil, therapy with, 352.Propionic acid, a-bromo-, and itsmethyl ester, hydrolysis andalcoholysis of, 224.1 -isoPropylcycEopropane- 1 :Z-dicarb-oxylic acids, synthesis of, 269.Protamine-insulin, 344.Protamine-zinc -insulin, 344.Proteins, coupling of, t o form anti-determination of, 393.fibrous, classification of, 198.globular, structure of, 200.metabolism of, 350.plant, 366.structure of, 198.corticosterone, 296.natural and synthetic, 299.302.en01 esters of, 285.gens, 356.Proteinases, bacterial, 375.Protons, bombardment by, trans-formations produced by, 15.Prototropy, 228.base-catalyeed, theory of, 231.Provitamin-D, 303.Pyridines, halogeno-, 316.Pyrocalciferols, irradiation of, 305.Pyocyanine, 320.Pyrophyllite, 188.Pyrroles, metallic comploxos of,Pyruvic acid, ethyl ester, bromin-oxidation of, in relation to vitamin-171.ation of, 232.B,, 334.isoQuinoline alkaloids, 323.Quinoxalines, 3 17.Radioactive disintegration by K -elements, use of, in metabolismnuclei, half-periods and mass-natural, 14.electron capture, 11.studies, 350.numbers of, 30.Radioactivity, artscial, 27.Radio-iridium, isomerism of, 11.Radio-phosphorus in biology andmedicine, 16440 INDEX OF SUBJECTS.Radio-sodium in biology and me&.cine, 16.Raman effect, 394.Rays, cosmic, mesotrons in, 7.X-Rays, analysis by means of, 381.cameras for, 180.ditrraction of, applied to analysis,powder method with, for ternaryin solids, 81.mechanism of, 208.383.alloys, 179.Reactions, elimination, 2 2 6.Reactivity, influence of groups on,Reagents, classification of, 208.Resorcinol, structure of, 195.Retrorsine, 328.Rhenium cyanides, complex, 166.oxides, 120.Rhizobium, polysaccharide synthesisby, 379.Rhizobium radicicolum, polysaccharidesynthesis by, 378.Rhodium isotopes, 32.Riboflavin, 336.Rice-germ oil, tocopherols from,Rocks, analysis of, 408.Rotation, fxee, 42.Rotators, asymmetrical, envelope-shapes of absorption bands of,48.2-Rotenone, structure of, 31 1.Z-isoRotenone, 311.d-epiRotenone, 312.Rottlerin, 313.GoRottlerin, 313.Rottlerone, 313.Rubidium, at.wt. and isotopes of,isotopes, separation of, 137.Ruthenium, at. wt. of, 134.detection of, in mixtures withRuthenium ammines, 160.Ruthenium organic compounds withpolypyridyls, 161.236.microchemical, 408.338.130.osmium, 406.Salicylaldehyde, Raman spectrum of,Salicylic acid, ethyl ester, alkalineSalicylidene-o-aminophenol, copperSalicylideneaniline, copper lake of,Salmiridin, 344.Sahlidine, 324.Salt hydrates, dehydration Qf, 84.243.hydrolysis of, 246.Raman spectrum of, 243.derivative, 170.169.Salts, fused, overpotential in, 109.Samarium, radioactive, 14.Santalum hmolutum, lance01 from,Sarmentogenin, 297.Scandium isotopes, 32.Scombrine, 344.Scoulerine, 324.Scurvy, vitamin-P in relation to, 342.Selenium, detection of, in presenceof arsenic or germanium, 406.Semicarbazides, metallic derivatives,171.Senecio alkaloids, 328.Senecionine, 328.Seneciphylline, 328.Sericite, 188.Serum, vitamin-B, in, 335.Sesquiterpenes, 273.Silane, density of, 133.spectrum and structure of, 49.Silicon, at.wt. of, 133, 134.Silicon tetrafluoride, density of, 133.dioxide, crystalline, detection of,Silver, nuclear isomerism of, 11.recovery of, from water, 407.Silver alloys with magnesium andzinc, 184.with mercury and tin, 180.Silver iodide, compounds of, withtrialkyl-wines and -phosphines,159.pemanganate, crystal structure of,186.Silyl chloride, 122.derivatives, 121.Sisto-amylase, 361.Sodium, at. wt.of, 129.films on tungsten, 61.Sodium metaborate, crystal structurebromate, crystal structure of, 185.isocyanate, crystal structure of,cyanide, crystal structure of, 185.peTiodate, crystal structure of, 186.go&, determination in, of clayminerals, 191.of zinc, 407.Solids, interdiffusion of, 80.photochemistry of, 85.reactions in, 81.rotation in, 43.279.in lungs, 384.of, 185.185.hangium, cellulose decompositionby, 377.gpectra, absorption, 85.infra-red, analysis by means of,395.ultra-violet and visible, analysisby means of, 396.infra-red and Raman, of poly-atomic molecules, 37INDEX OF SUBJECTS.441Spectra, infra-red, of hydrogen bonds,mass, isotope separation by meansRaman, analysis by means of, 394.Spectrograph, mass, 137.Spectrophotometer, photoelectric,Spectroscopy, 37.Spinulosin, 374.Starch, constitution of, 358.determination of, and its separ-ation from dextrin, 406.Stars, atom building in, 15.Stearic acid, conversion of, intopalmitic acid, 349.ethyl and isobutyl esters, poly-morphism of, 256.ethyl ester, mixed crystals of,with ethyl palmitate, 260.Steel, analysis of, 393.oxide films on, 388.Stephunia cepharantha, alkaloid of,Stereoisomerism of steroids, 281.Sterility in women, treated withSteroids, 281.38.of, 136.397.327.vitamin-E, 340.adrenal, 293.table of, 294.irradiation of, 305.synthesis of, 306.urinary, 300.Sterol derivatives, bromination of,Stilpnomelane, 190.Streptocarpus Dunnii, pigment of,Strontium, at.wt. and isotopes of,Strophanthin, determination of, 403.Substitution, aliphatic, 210.Succinic acid, structure of, 196.Sugars, action of bacteria on, 378.Sulphdamide, determination of,Sulphilimines, 172.Sulphites, oxidation of solutions of,Sdphocamphylic acid, structure of,Sulphonamides, toxicity of, 355.Sulphur, allotropes of, 120.at. wt. of, 133, 134.determination of, 409.Sulphur suboxide, 119.dioxide, density of, 133.Superchatwe, 359.Sutton’s rule, 241,286.370.131.electrophilic, 2 10.nucleophilic, 2 1 1.analysis of, 405.therapy with, 352.404.120.270.Systems, binary, polymorphism of,259.T.693, 353.Tachysterol, structure of, 305.Tachysterol-3, 303.Taeniolite, 187.Talc, 188.Tantalum, determination of, inin niobium, 381.Teeth, exchange of phosphorus atomsin, 351.X-ray patterns of, after adminis-tration of fluoride and para-thormone, 385.molybdenum, 382.Tellurium tetrafluoride, 1 16,Terpenes, 268.Testosterone, en01 esters of, 285.Tetracosanoic acid, synthesis of, 252.Tetradeuteroethylene, spectrum of,46.Tetradeuteromethane, spectrum andstructure of, 49.Tetrahydroartemisia ketone, 2 6 8.Tetrahydrobenzoglyoxalines, 319.Tetrahydropalmatine, 324.Tetrahydrorottlerone, 3 13.Tetrakis( iodotriethylrtrsinecopper),158.Te trame th ylme thane, bond constantsof, 50.Te trame t h ylp yrrome thene -4 : 4’-d i -carboxylic acid, ethyl ester,metallic compounds, 164.Tetramethylsilane, bond constantsof, 60.Tetrapyridyl, 31 7.Tetratriacontanoic acid, 252.Thallium compounds with thiourea,halides, activation of alkali halidesstructure of, 162.by, 87.Thiamin, 333.Thujane, synthesis of, 269.Thymonucleic acid, structure of, andits derivatives, 203.Tin alloys with mercury and silver,180.Tin bronzes, analysis of, 386.Tin tetraiodide, structure of, 162.Tobacco mosaic virus, structure of,a-Tocopherol, structure of, 339./3-Tocopherol, structure of, 339.Tocopherols, 308, 338.determination of, 401.Tolan, structure of, 198.Toluene, velocity of nitration of, 242.o-Toluidine, reactions of, with benzylchloride and 2 : 4-dinjtrochlo~o.beweno, 245,202442 INDEX OFU- and p-Toxicarols, 312.Transmission coefficient, 239.Triacontane, crystal structure of,255.n-Triacontanoic acid, synthesis of,252.Trialkylsulphonium hydroxides, hy-drolysis of, 212,Triazens, hydroxy-, metallic salts,171.Trichodesmine, 328.Tricosanoic acid, synthesis of, 252.Trideuteroarsine, spectrum of, 50.Trideuterophosphine, spectrum of,50.s-Trimethylbenzoic acid, esterific-ation of, 245.Trimethylcarbohydrazidomethyl-ammonium chloride, separationof natural compounds by, 293.Trimethylstibine dihalides, crystalstructure of, 186.Trimethylsulphonium hydroxide, 2 12.Triphenylbenzene, catalytic com-bustion of, in oxygen, 129.Tripyridyl, 3 17.Tryptophan, determination of, inproteins, 398.Tungsten, adsorption of gases on, 52.formation and removal of adsorbedfilms on, 67.hot, formation of atomic hydrogenby, 63.Tyrosine, determination of, in pro-teins, 398.E-TOxicaXOl, 313.Unsaturated compounds, exchange ofUranetriol, 297, 301.Uranium, crystal structure of, 184.Uranyl salts, spectra of, 62.Urine, bull’s, steroids from, 301.deuterium with, 73.disintegration of, 9.elements beyond, 13.mare’s pregnancy, steroids from,steroids in, 300.women’s, steroids from, 302.women’s pregnancy, steroids from,300.vita~&l-Bl in, 335.301.Usnetic acid, 315.Usnetol, 316.Usnic acid, 314.Usnolic acid, 316.Usnonic acid, 316.Velocity of nitration, 242.Verbanone, synthesis of, 269.Vermiculites, 189.3UB JECTS .Vibrio septicus, enzymes of, 376.17-Vinylandrostane, 3(13) : 17-di-Vinyltestosterone, 290.Vitamins, 330.Vitamin-A, 331.hydroxy-, 292.analysis of, 399.chick antidermatitis, 336, 337..deficiency of, in man, 333.detection and determination of,determination of, 398.potency of, in relation to p-caro-storage of, in liver, 332.Vitamin-A,, 331.Vitamin-B,, 333.and co-carboxylase, 334.determination of, 400.Vitamin-B,, complex, 335.Vitamin-B,, 336.Vitamin-C, 337.Vitamin-D, 303.Vitamin-D, and -D3, determinationof, 401.Vitamin-D, in halibut- and tunny-liver oils, 303.Vitamin-D,, 303.Vitamin-E, 338.399.tene, 333.determination of, 393, 400.activity of, in tocopherols, 308.determination of, 401.Vitamin-K, 340.Vitamin-P, 342.Walden inversion, 2 18.Water, deuterium content of, 131.exchange of deuterium with, 72.heavy oxygen, electrolytic pro-mineral, determination of alkalimolecules, potential function for,recovery of gold and silver from,spectra of, 41, 61.Wheat-germ oil, tocopherols from,duction of, 144.metals in, 393.45.407.338.Zeise salts, stereochemistry of, 168.Zinc, determination of, in plant ash,Zinc alloys with aluminium andwith magnesium and silver, 184.Zinc salts, effect of, on insulin action,sulphide, luminescent, 87.392.in soils, 407.magnesium, 184.345.phosphors, 88

ISSN:0365-6217    

DOI:10.1039/AR9383500430

出版商:RSC    

年代:1938

数据来源: RSC