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CHAMBERS, LM.,38 Soh0 Square, London, W.lTelegrams: BELLAMY, PHONE, LONDONTelephone: EAST 1892JOHNBELLAMYLTD.43 BYNG STREET,MILLWALL, E. 14Makers of TANKS, MIXERS,AUTOCLAVES, etc., i n Mildand Stainless Steel to suitthe special requirements ofthe CHEMICAL MANU-FACTURERSSPECIAL ATTENTION TOINDIVIDUAL DESIGNPURIFICATIONOFWATERFOR ALL PURPOSESBOILER FEEDPROCESS WORKTEXTILE PURPOSESTOWN SUPPLY, Etc.IS THE SPECIALITY OFL 'EN N I COT'WATER SOFTENERWO LV E RHA M PTO NCO., LTD.Established 40 YearsPLACE YOUR WATER PROBLEMSBEFORE US AND AVAIL YOUR-SELF OF OURUnrivalled ExperienceManufacturers of Domestic Water SoftenersTo face title page. xi

ISSN:0365-6217    

DOI:10.1039/AR93633FP001

出版商:RSC    

年代:1936

数据来源: RSC

摘要:

ANNUAL REPORTSON THEPROGRESS OF CHEMISTRY.RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.DTJEING the year no entirely new line of nuclear research has beenopened. The study of nuclear reactions has now reached the stagewhere it is important to collect a large quantity of precise data,and the energy changes involved have been particularly examined.The existence of a pebuliar selective absorption of very slow neutronsin atomic nuclei has led to the production of new theoretical ideasabout nuclear structure. Bohr has suggested that energy suppliedto a nucleus may be extensively distributed over its components(see p. 30), and the theory of Breit and Wigner involves similar ideasof the energy levels of the nucleus as a whole.A theoretical survey of a large part of nuclear physics has ap-peared.1 The problems of the behaviour of the cosmic radiation,though not of its origin, are gradually assuming more definite form.ISOTOPIC CONSTITUTION OF THE ELEMENTS.A good deal of work has been done during the year with massspectrographs.New instruments of this type have been describedby A. J. Dempster,2 K. T. Bainbridge and E. B. Jordan 3 and byM. B. Sampson and W. Bleakney.* New sources of ions are alsode~cribed.~*~*~ F. W. Aston has made. some improvements in hisdesign of mass spectrograph, and has applied it mainly to the precisedetermination of atomic masses. These instruments have boen usedin the discovery of new isotopes, the determination of isotopeabundance ratios, and the precise determination of nuclear masses.An isotope 5Li 7 was discovered in the emission from a, platinum1 H.A. Bethe and W. Bacher, Rev. Mod. Physics, 1936, 82, 8.3 Phyaical Rev., 1936, 50, 282.4 Ibid., p. 456.5 J. P. Blewett arid E. J. Jones, ibicl., p. 464; S. L. Ch'u, ibid., p. 212.6 Nature, 1936,137, 357.7 A. K. Brewer, Phg&aZ Rev., 1936, 49,636.Proc. Amer. Phil. Soc., 1935, 75, 76516 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.filament impregnated with lithium, but this was not coilfirmed byother worker^.^ A special search was made for 8Be,8 since thisnucleus appears as a product in the current interpretations of manynuclear reaction^,^ often recoiling intact with considerable energy.On the basis of nuclear mass considerations 8Be appears to be astrongly bound element.1° It was not found in the mass spectro-graph analysis, with a detection limit of 1 part in 104.Theappearance of induced radioactivity under neutron bombardmenthas led to a search for new isotopes of several elements, since theknown isotopes were not considered sufficient to explain the differenttypes of radioactivity observed. No third isotope was found for79p81Br,11 which shows three decay periods when activated with slowneutrons. The limits of detection varied from -& for 78, 82 upto much larger values. No third isotope was found for 1 1 5 9 1131n.12*4In the case of 59C0 an isotope 57C0 has been found.13 Bainbridgeand Jordan have applied their mass spectrograph to the problemof the existence of isobaric pairs of stable elements, differing by oneunit in atomic number.According to some theories of nuclearstability, such pairs should not exist.14 Previous mass-spectrographwork has often been complicated by the existence of hydrides, butin Bainbridge and Jordan's work hydrogen-free conditions wereobtained and la;In was found isobaric with 'iiCd, l:XIn with l;6,Sn,5XTe isobaric with l::Sb. The theoretical consequences of this arediscussed. Other isotopes found by the mass spectrograph during130*132Ba,18 136* 13*Ce.18 A number of determinations of abundanceratios have been made with the mass spectrograph and in the caseof oxygen20 some variation has been found between various sources.The new atomic masses observed by Aston6 are in good accordthe year include 22Na,15 58Fe,16,17 64NiJ17 84Sr,12, 4 102M0,lS 134Ba,4,198 W.Bleakney, J.P. Blewett, R. Sherr, and R. Smoluchowski, Physical Rev.,9 See this report, p. 20.10 M. L. Oliphant, Nature, 1936, 137, 396; cf. N. K. Saha, Proc. IndianI1 J. P. Blewett, Phpical Rev., 1936, 49, 900.12 J. P. Blewett and M. B. Sampson, ibid., p. 778.13 M. B. Sampson, L. N. Ridenour, and W. Bleakney, ibid., 50, 383.1 4 Cf. K. Sitte, 2. Physik, 1935, 96, 512.l6 A. K. Brewer, Physical Rev., 1936,49,866 ; but see ref. (4).1* J. de Gier and P. Zeeman, Proc. K . Akad. Wetenach. Amsterdam, 1935,1' A. J. Dempster, Physical €Lev., 1936, 50, 98.1936, 60, 646.Acad. Sci., 1936, 6, 110.38,969.J. de Gier and P. Zeeman, Proc. K . Akad. Wetensch. Amsterdam, 1936,39, 327.ID A.J. Dempster, Physical Rev., 1936, 49, 047.2o W. Bleakney and J. A. Hipple, ibid., 1935, 47, 800BRADDICK. 17with the values obtained from nuclear transformations.10 It isinteresting to note that mass differences of the heavy elements cannow be obtained sufficiently accurately to reveal the mass equivalentof the energy emitted in their radioactive transformations.21Spectroscopic Methods.-The method of hyperfine structure ofspectral lines has been used to check the abundances of the lead 22and the platinum 23 isotopes, and the cadmium isotopes have beenexamined in the band spectrum of CdH, CdD.24 The elaboratecorrections necessary to obtain isotopic mass ratios from bandspectra have been worked out by W. W. Watson 25 and applied to theratios :H/:H, the value obtained agreeing with that of Aston.The hyperfine structure data on nuclear spin have been usedz6 toformulate a set of rules for the building up of atomic nuclei, whichagree with the isotope abundance data.NUCLEAR TRANSMUTATIONS.The work in this field has been directed largely to the measure-ment of the energies involved in nuclear reactions and the excitationfunctions, i.e., the probability of reaction considered as a functionof the energy of the bombarding particle. The energies have beenlargely used in the determination of differences in nuclear mass, and aconsiderable amount of data, has been acquired on the energy levelsof lighter nuclei.a-Particles.-Detailed investigations have been made of thetransmutations of several nuclei under a- particle bombardment.The reactions are of the (a ; p ) type 27 first investigated by Ruther-ford, in which the product nucleus is stable.The maximum energy of the protons may be calculated from theconservation of energy and momentum, a quantity of energyequivalent to the mass difference between initial and product nucleiappearing in the reaction.The proton may, however, carry awayless than the full energy of the transformation, the product nucleusbeing left in an excited state, which subsequently emits aThe investigation of the energies of the proton groups gives,therefore, mass differences between nuclei and the energies of nuclear21 A. J. Dempster, Nature, 1936, 138, 120, 201.22 J. L. Rose and R. K. Stranathan, Physical Rev., 1936, 4g, 916.23 S.Tohnsky and E. Lee, Nature, 1936, 137, 908.24 A. Heiner amd E. Hulthen, Naturwiss., 1936, 24, 377.46 Physical Rev., 1936, 49, 70.2s H. Schiiler and H. Korsching, 2. Yhysik, 1936, 102, 373.27 Thie notation is used to denote a change in which an a-particle is capturedA similar notation is used for proton, deuteron, neutron and a protonernitted.reactions; cf. Ann. Reports, 1935.38 H. J. von Baeyer, 2. Physik, 1935, 95, 41718 RhDlOAUTIVITY AND SW-ATOMC PHENOMENA.exoited state^. 0. Haxel 29 found that the reactions Mg (a; p ) Al,Si ( a ; p) P, S ( a ; p ) C1 gave very simiIar proton spectra consistingin each ewe of three groups. The excited atates are given in Table I.A. N. &y and R. Vaidymathan 30 find that the reactions 3' (a; p )Ne, Na (cc ; p ) Mg, P (a ; p) S each give four proton groups correspond-ing with three excited levels differing by about 1 M.E.V.C. J.Brasefield and E, Pollard 31 find for S (a ; p ) C1 three groups generallysimilar t o those of Haxel, while for K (a ; p ) Ca, C1 ( a ; p ) A, P ( E ; p ) Sthey find excited levels differing by about 1-5 M.E.V. Prom thefull energy proton group of S ( a ; p ) C1 they calculated the ma~s of325 from Bainbridge's 36Cl value. The evidence, then, points to theexistence of homologous series of nuclei differing by four units ininase and two in atamic number. These may be correlated withthe existence of a-particles as such in the nuolei (Hrtxel) or withthe formation of successive shells of neutrons and protons.Thehomologous series 27Al, 31P, 36Cl does not appear to extend to 1lBand "N, which have different level systems.32TABLE I.E'nepgy of a-particle r e c d o m : excitation levels of lzuclei fromtransitions. A (a ; p ) + B (+ Q).Reaction.Energy change,Q(M.E.V.). - 1 4 - -- 2-28 - 2.4 + 1-4 + 1.94- 2.1+ 0-0 + 0.1 - 1.0IEnergy of ex-Product. cited levelsnucleus. (M.E.V.).1.40.8, 1.7A = 31p 0.8, 1.6 i" 0-6, 1.254n + 3 8KC1 0.65, 1.62ike 1.5, 3.5, 4.62.3, 4.0, 5.039S 1.2, 2.6, 4.63sA -, 2.6, 4-342Ca -, 1-3, 2-641% $. 2The transmutation function in the case of S (K ; p ) C1 appears toconsist of an increase of transmutation probability with a-particleenergy corresponding to the Gamow theory €or penetration of apotential barrier.May and Vaidyanathan point out that the exist-ence of preferred velocities for a-particle entry to the nucleus29 Physileal. Z., 1936, 38, 804.30 Proc. Roy. SOC., 1936, A , 155, 519; cf. R. F. Paton, 2. Physik, 1934, 90,3l Physical Rev., 1936, 50, 296, 890.Y2 J. D. Cockroft and W. B. Lewis, f r o c . Roy. Soc., 1936, A , 154, 246, 261.33 G. Stetter, 2. Physik, 1936,100, 052.34 W. E. Duncanson and H. Miller, Pmc. Boy. SOC., 1934,146, 396.586BRADDICE. 19(resonance penetration) may give rise to groups in the protonspectrum when an inhomogeneous soiirce of or-particles or a thicktarget is used. An extra group in the reaction P (a ; p ) S is probablyaccounted for in this way.Protom.-The transmutation of some of the light elements byproton bombardment has been studied in detail. The excitationfunction for the reaction7Li + :H + 2*Hehas been determined from 23 k ~ ., 3 ~ 40-225 k ~ . , ~ ~ and up to 110038 The curve rose monotonically with energy ; no speciallypreferred energy values (resonance) were detected. A new wave-mechanical treatment of the problem of a nucleus with a potential wellunder proton bombardment 3g has been given. The simpler treatmentof the problem as penetration through a potential barrier is not ade-quate; the depth and width of the well have a marked effect on theefficiency curve. The calculation gives the position of the stationaryproton levels and the mass of the 8Be nucleus, and the potential wellhas to be adjusted to give consistent values for these data as well asfitting the excitation curve. A further calculation using '' exchangeforces" which vary with the velocity of the proton gives betterresults.4°The angular distribution of the a-particles produced in this re-action has been shown to be r&ndom,dl and the variation of rangewith angle is in agreement with the conservation of energy andmomentum.42 If 8Be is formed as an intermediate step, the factthat it does not lose e3ergy by collision shows that its life is lessthan 3 x 10-14 sec.The y-ray emission from lithium, showing resonance at about 450kv. and a rise at higher voltage^,^' has been confirmed and shown toarise from 7Li.43 The y-ray emission process is independent of thatwhich produces the x-rays; it may consist of the excitation of *Beto a state which is debarred from disintegration by a selection rule,or to the production of an excited and a normal a-particle.A y-ray emission from fluorine bombarded with protons 37 showsa6 H.D. Doolittle, Physical Rev., 1936, 49, 779.36 N. P. Heydenburg, C. T. Zahn, andL. D. P. Khg, a i d . , p. 100.37 L. R. Hafstad, N. P. Heydenburg, and M. A. Tuve, ibid., 50, 504;38 L. R. Hdstad and M. A. Tuve, ibid., p. 306.38 M. Ostrofsky, G. Breit, and D. P. Johnson, ibid., 1926, 49, 22.40 M. Ostrofaky, W. 33. Bleick, and G. Breit, ibid., p. 362.4 1 J. Giarratana and C . G. Brennecke, ibid., p. 35.42 A. Roberts, T. Zrcndstra, R. Cortell, and F. E. Myers, ibid., p. 783.43 L. H. Rumbaugh and L.R. Hefstad, {bid., 50, 681.R. G. Herb, D. B. Parkinson, and D. W. Kent, ibid., 1835,48,11820 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.resonances at 328, 892, and 942 kv. and probably some weak mul-tiple structure between 500 and 700 kv., but the reaction involvedis uncertain.The reactionIiB + iH --+ 3iHehas been confirmed and e~arnined.4~ The products of disintegrationhave been studied by the Wilson chamber.45 The distribution ofenergy among the a-particles is continuous, with a small homo-geneous group superposed. The symmetrical emission of threea-particles, formerly regarded as a preferred process, is now shownto be rare, and the mechanism suggested is the formation of an ex-cited 8Be nucleus ( p ; a change) and its subsequent splitting into twoa-particles. The life of the excited 8Be lies between 1O-l' andsec., and it is suggested that according to the uncertainty principlethe excitation energy is rather indefinite and the particles emittedin the ( p ; a) reaction have a velocity spread.On these assumptionsthe continuous distribution may be explained, the total energyreleased in the transmutation being 8-7 M.E.V. in accordance with therevised nuclear masses.l0 The small homogeneous group may thencorrespond to the reactionl;B + ;tH ,j :Be + $He (& = + 8.7 M.E.V.)with the mass of SBe very nearly equal to that of two a-particles. Asimilar argument to that above may be used to explain the deuteronreaction46lgOB + ;H-+ 3$HeThe excitation function for the two proton-boron processes showsa marked diff eren~e,~' the continuous distribution rising steadilywith increase of bombarding voltage while the longer range groupshows evidence of resonance.W. H.Wells and E. L. Hill 48 have attempted to avoid the neces-sity for the nucleus !Be in this and similar reactions by postulatingthat some of the nuclear particles are coupled in sub-groups.Deuterons.-Several new nuclear transmutations have been ob-tained by deuteron bombardment, and some of the formerly-knownreactions have been studied in more detail. A number of excitationfunctions have been determined, and the energy of the productparticles has been the subject of special attention. By intercompari-44 J. D. Cockroft and W. B. Lewis, Proc. Roy. Soc., 1936, A, 154, 246.46 P.I. Dee and C. W. Gilbert, ibid., p. 279.46 Cf. M. L. E. Oliphant, A. E. Kempton, and (Lord) Rutherford, ibid.,4 7 J. H. Williams and W. H. Wells, Physical Rev., 1936, 50, 186.da Ibid.? 49, 858.1935, A, 150, 24121 BRADDICK.son of the energy liberated in the reactions with the atomic massscale, the latter has been corrected and further various proposednuclear reactions have been checked. This check is important, sincethe reactions produced by deuteron bombardment of the lighternuclei are in general complicated.The excitation function for the reaction;H + ;H-+ :He + inhas been investigated by T. W. Bonner and W. M. Br~batker.~~The probability of transmutation rises rather slowly with the energyof the deuterons, while the yield of neutrons from the reaction:Be + ;H 4 I;B + inwhich was also studied, rises much more steeply.The neutronsproduced are nearly homogeneous in energy,50 2.55 M.E.V., andthe energy released in the reaction is 3.2 M.E.V. No yradiationcould be dete~ted.~lThe reactionl;B + :H+ l;C + ingives two groups of neutrons, the lower one corresponding with theproduction of an excited I2C nucleus. The excited level of 12C atabout 4 M.E.V. has also been detected by J. D. Cockroft andW. B. Lewis52 in the reactionl$N + :I3 --+ l;C + :Heand by Chadwick, Bothe, and others in the reaction:Be + ;He 4 l;C + tnAn investigation 53 of the neutrons from the bombardment of beryl-lium, boron, and carbon, which are believed to be produced by thereactions:Be + fH --+ IiB + inl;B + ?H -+ liC + inIiB + ;H -+ 3;He + in + ;H + + inl;C + TH ---+ $N + tnl;C + fH ---+ l;N + inhas led to energy values for these reactions and to a revised atomic-mass scale.In addition to the neutrons of maximum energy,neutron groups of lower energy were emitted, the nuclei being left inan excited state. No satisfactory correlation has been made with the49 Physical Rev., 1936, 49, 19.50 Cf. P. I. Dee and C. W. Gilbert, Pro(:. Roy. Soe., 1935, A , 149, 200.51 K. D. Alexopoulous, Naturwiss., 1935, 23, 817.52 Proc. Roy. SOC., 1936, A, 154,246, 261.53 T. W. Bonner and W. M. Brubaker, Physical Rev., 1936, 50, 30822 RADIOAC!MVITY AND SUB-ATOMIC PHENOMENA.y-rays which accompany the bombardment .a The transmutationof boron, carbon, nitrogen, and oxygen by deuterons has also beenstudied by J.D. Cockroft and W. B. Lewis.5% In this work theranges of the a- and H-particles were measured. With boron,homogeneous groups of a-particles were attributed to'iB + ;H+ !Be + $He':B + :H _I, :Be + :Hewhile proton groups were attributed toand a continuous distribution of a-particles toloB + 2H --+ 34Heand with less certainty tollB + 2H + 34He + inThe energy values of several reactions with carbon, nitrogen, andoxygen were determined and used to amend the mass scale.A new group of a-particles from carbon probably arises from13C + 2H +- 11B + "e, though the energy balance with otherreactions is not satisfactory.During the experiments on boron, an attempt was made to detectthe recoil of SBe, a nucleus which rather frequently appears in pro-posed transmutation reactions.The energy data lead to the con-clusion that the mass of sBe should be slight'lygreater than that oftwo a-particles :8Be + Z4Me + 0.3 M.E.V. (cf. p. 20)The production of P-radioactive elements of short life fromlithium, boron, and fluorine 55 has been further in~estigated.~~The radio-elements are now believed to be ?Li, 12B, and 2oF, formedby ( d ; p ) processes. The corresponding proton emission has beenfound for lithium and fluorine and the energy balances calculated.The protons from boron have not been definitely identified, buttheir energy is < 2.5 M.E.V. These radioactive elements are allbelieved to have atomic weights given by 2 2 + 2, containing twomore neutrons than protons. The positron-emitting elements 13N[12C ( d ; 12)13N], 150 [14N ( d ; 12) 150], 16N [15N ( d ; p ) 16N], 11C[1OB ( d ; n) W] were also examined.No evidence was obtained forpositron emission from l0Be or 14C-these nuclei are either stableor are not formed by 9Be ( d ; p ) and I3C ( d ; p ) . For all these radio-64 H. I&. Crane, L. A. Delsasso, W. A. Fowler, and C. C. Lauritsen, PhysicalRev., 1935, 47, 782.56 Crane, Delsasso, Fowler, and Lamitsen, ibid., pp. 971, 887 ; 48, 848.86. Idem, ibid,, 1936, 49, 501.'EB + !H -> 'kB + :BRADDICK . 23element& the positron or electron spectra were determined, Thereis some evidence 57 for a radioactive substance I0Be with a, very longlife (> 10 years) and a I4C with a, half-life of about 3 months.The deuteron bombardment of heavier elements has led to severalinteresting transmutations.Magnesium gives a composite p-radio-activity attributed to the processes 58The transmutation function for the latter process follows a Gamowrelation ; that for the former reaction agrees with the theory of J. R.Oppenheimer and M. Phillips 59 based on the idea that the deuteronsplits into a proton and a neutron, only the neutron penetrating thenuclear potential barrier. S. N. Van Voorhis 6* finds two radioactivesubstances from copper, which he aacribes to ( d ; p) reactions withthe two stable isotopes. He considers that B4Cu may decay either toWZn with emission of an electron or to HNi with emission of a posi-tron, since the half-life of positron and electron activities was thesame (12.8 hrs.).gives an electron-emitting radioactive substance of half-life 110 minutes.This is almost certainly *lA formed by a ( d ; p )reaction. It behaves chemically like argon. The excitation functionagrees with the theory of Oppenheimer and Phillips. A weak activityof the same type was excited in argon by intense neutron bombard-ment. The ps2- and emission from 41A has been investigated.The former seems to consist of two groups with upper energy limitsa t about 1.5 M.E.V. and 5 M.E.V., and the latter consists of a singleline with energy 1.4 M.E.V. Copper, zinc, antimony, ruthenium,bismuth, and tin give radioactive products when bombarded withdeuterons of 6 M.E.V.64 Copper gives 64Cu, as observed by E.Permiby neutron bombardment,65 and some other activities of obscureorigin. Zinc, antimoiiy, and ruthenium give complex activitieswhioh cannot yet be assigned with certainty to particular nuclei.Bismuth gives radium-E (210Bi) by it (d ; p ) (Oppenheimer-Phillips)Argon6 7 E. McMillan, Physical Rev., 1936, 49, 876.5 8 M. C. Henderson, ibid., 1935, 48, 855.59 Ibid., p. 500; see Ann. Reports, 1935, 32, 23.60 Physical Rev., 1936, 49, 876; 50, 895; cf. E. 0. Lawrence, E. McMillan,and R. L. Thornton, ibid., 1935,48,493.6f A. H. Snell, ibid., 1936, 49, 555.62 F. N. D. Kurie, J. R. Richardson, and H. C. Paxton, ibid., p. 368.63 J. R. Richardson, ibid., p. 203.434 J.J. Livingood, ibid., 50, 428; J. J. LiVingood and. G. Seaborg, ibitl.,8 6 Ann. Reports, 1936. p. 43524 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.reaction. This represents the first artificial production of a natur-ally occurring radio-element. Radium-E decays to the a-emitterXa-P (polonium) with a half-life of 5 days. The cc-particle emissionfrom this substance was det'ected, and the identity of the range of theparticles with polonium a-particles was verified. The complexactivities observed from zinc, antimony, and ruthenium indicatethat the Oppenheimer-Phillips process is not the only method ofattack of deuterons on the heavy nucleus. The alternative is pre-sumably a resonance process, but excitation functions have not yetbeen determined.Tin also shows a complex activity, and a chemicalseparation showed the presence of active isotopes of indium, tin,and antimony. The antimony fraction emits both positrons andelectrons, and there is some evidence that this is a branched trans-formation and not due merely to the presence of two different radio-elements. Platinum 66 bombarded with 5 M.E.V. deuterons gives acomposite activity with emission of both positrons and electrons.A chemical separation reveals isotopes of platinum and iridium.The reactions involved possibly include'iiPt + :H -> ':iPt + iH 193Pt + 1931r + e+ (49 mins.)1;6gPt + :H --+ l:;Pt + ;H lg7Pt I_, 19'Au + e- (14.5 hrs.)'P;Pt + :H + lP;Ir + :He 194Ir --+ 194Pt + e-The transmutation functions in this case definitely show the maximaexpected for a resonance process, and there is evidence that theresonance is involved in the production of iridium isotopes, theplatinum isotopes being formed by an Oppenheimer-Phillips processrising monotonically with the energy of bombardment.Neutrons.-The reaction of slow neutrons with boron18B + iLi + $Hehas been investigated by D.R ~ a f , ~ ~ using boron trifluoride in anexpansion chamber, and the energy released in the reaction is foundto be 0-61 M.E.V. A new value for the mass of loB was obtained.The helium obtained by bombarding boron (methyl borate) withslow neutrons has been separated and observed spectroscopically.This is the first time a product of artificial transmutation has beenobserved by such methods.6BThe disintegration of nitrogen by neutrons has again been investi-gated in the expansion chamber.69 The reactions observed weresupposed to be6 6 J.M. Cork and E. 0. Lawrence, Physical Rev., 1936, 49, 788.67 Proc. Roy. SOC., 1936, A , 153, 568.6 8 F. A. Paneth and H. Loleit, Nature, 1935, 136, 950.69 T. W. Bonner and W. M. Briibalcer, Physical Rev., 1936, 49,223, 778; 50,781BRADDICK. 25';N + in --+ l;B + :He'$N' + in ~ _ f 23€e + iLiand the first of these reactions was supposed to be exothermic and totake place with slow neutrons. A closer consideration of the energybalance as compared with other known reactions of the nuclei in-volved showed that this conclusion was wrong, the reaction beingendothermic (& = - 0.3 M.E.V.).The reaction which does occurwith slow neutrons is the (n ; p ) change leading to 14C. The radiationof energy during the capture of fast neutrons 7o by nitrogen is notsupported by these experiments.Some additions have been made to the results on the productionof radioactive nuclei by neutron bombardment; these are given inTable III.Beryllium bombarded with neutrons and examined after a veryshort interval showed a strong activity of period 0.9 sec.71 Theradioactive substaiice was identified as a helium isotope, probably 726He formed by a (12 : a) process. It is not produced by very slowneutrons, but is formed by neutrons of 1.5 M.E.V.73 It emits @-rayswith maximum energy about 3-7 M.E.V.Lithium 74 bombarded with slow neutrons gives a @-emittingsubstance, probably sLi, with half-period 0.7 sec., and identical withthe substance produced from lithium by a (a; p ) reaction.75 Thediscrepancies in the results obtained on the rare earths, due to thedifficulties of separation, have led to a re-examination of theseelements by G.Hevesy and H. L e ~ i . 7 ~ Their results will be found inTable 111. They investigated in addition the absorption of slowneutrons by the rare-earth elements and found very large absorptioncross-sections for europium, dysprosium, gadolinium, and samarium.In the cases of the last two and possibly some other elements, theinduced radioactivity is very small compared with the absorptioncross-section, and the product nucleus is presumably stable. Thecomplicated system of reactions observed when uranium is bom-barded with neutrons has been further investigated.7' In additionto previously-known activities with half -lives 10 sees., 40 sees.,13 mins., 100 mins., and 3 days, an activity of 12 hours' half-life has70 F.N. D. Kurie, Physical Rev., 1935, 47, 97; Ann. Reports, 1935, 32, 24.71 T. Bjerge, Nature, 1936, 137, 865.72 Idem, ibid., p. 400.73 M. L. Olipliant, quoted in ref. 72.74 K. S. Knol and J. Veldkamp, Physica, 1936, 3, 145.7 5 Crane, Delsasso, Fowler, and Lamitsen, PhysicaE Rev., 1935, 47, 971;76 Nature, 1936, 137, 185.77 (Frl.) L. Meitner and 0. Hahn, Naturwiss., 1936, $24, 158.',4N + :?z -> 'tC +see, however, ref. 5626 RADIOACTWITY AND SUB-ATOMIC PHENOMENA.been assigned to eka-oamium(as'eka-0s).Evidence is obtained forthe following reactions :(1) ":U + n + ';6,Th + o! + 235Pa --+ 235U --+235eka-Re --+The reaction goes with slow neutrons and 239U may be formed by a(12; -) reaction and behave as an a-emitter of very short life.B B BB I::eka-Os a Q,9ieka-IrThe reaction requires fast neutrons, and may be of a new type inwhich a neutron is absorbed and two neutrons are emitted :The reaction of neutrons with thorium has been investigated ;78 thethorium salt used had been chemically kept free from its isotopicradioactive products of moderate life. The processes suggested are2!iTh + n .+ =%Ra + a ; ";Ra + "8",4Ac __+ 2i:Th --+ B B BB ":Pa a:iAc _I, YgThThe two isotopes of actinium have half-lives of 3.5 and 42 hoiirs, andan isotope of thorium a half-life of 25 mins.y-Rap.-The disintegration of nuclei by y-rays (nuclearphiliceffect 79) has been further investigated in beryllium and deuterium.80No other reactions of this type have been discovered, and from thepresent nuclear masses it appears that no other reactions among thelight elements are energetically possible using 2-3 M.E.V.y-rays.*lIn the case of 2H the threshold value for the reactionZH + h v + lH + nis found to be 2.26 M.E.V.82 The mass of the neutron may be cal-culated from this result to be 1.009.The threshold for 9Be + hv --+ *Be + n is found to be 1.6&LE.V.83 The efficiency of the process (yield per quantum) falls78 E. Rona and E. Neuninger, Naturwiss., 1936,24, 491.70 Nuclear photo-effect.80 D.P. Mitchell, F. Rasetti, G. A. Fink, and G. B. Pegram, PIiysicoZ Rev.,1936, 50,189; S. Nishida, Japan. J . Physics, 1936,11, 9.81 N. Feather, '' Nuclear Physics," Cambridge, 1936.82 J. Chadwick, N. Feather, and Bretscher, quoted in ref. 81.83 J. Chadwick and M. Goldhaber, Pvoc. Roy. Soc., 1935, A , 151, 479; cf.G. Iairig and M. Helde, Nature, 1936, 137, 273BRADDICK. 27TABLE 11.Energies of some nuclear reactiom (in lo6 electron-volts) .(Note : 1 M.E.V. corresponds with 0-00106 unit of atomic mass.)For the calculation of masses from data of this type, see, e.g., refs. 51, 53.with increasing y-ray energy rather like that of the photoelectriceffect in the extra-nuclear54 R. Fleischmann and W. Gentner, 2. Physik, 1936, 100, 440.85 P.I. Dee and C. W. Gilbert, Proc. Roy. SOC., 1935, A , 149,200.86 J. Chedwick and M. Goldhaber, Proc. Camb. Phil. SOC., 1935, 31, 612 ;87 P. I. Dee, Proc. Roy. SOC., 1935, A, 148, 623.88 M. L. Oliphant, B. B. ICinsey, and (Lord) Rutherford, ibid., 1936, A ,see also ref. 81.149,40628 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.82ow Neutrons.-A great deal of work has been done on the mech-anism by which neutrons are slowed down by passage through matterand on the capture of slow neutrons by nuclei. Experiments showthat the efficiency of neutrons in causing transmutation and thecross-section for absorption of slow neutrons were in some casesincreased by cooling the paraffin or other hydrogen-rich materialin which the neutrons were slowed down.5 The interpretation of the4 Be9 F11 Na15 P17 C127 Co28 Ni35 Br39 Y46 Pd50 SnTABLE 111.New activities produced by neutrons.12 5.15 d.96 60 Nd 1 h.80 d. 97 62 Sm 40m.,long.72 h. 98 63 Eu 9.2 h.IY 1 yr. 1 3 64 Gd 8 h.3 h. 9s 65 Tb 3.9 h.24 h. 66 Dy 2.5 h.70 h. 76 67 Ho 35 h.12 h., 3 m., 60 h. 68 Er 12h., 7 m.0-8 m. 1, 18 m. ? Og* 70 Yb 3.5 h.71 Lu 6 d., 4h.80 Hg 205Hg 40 h.81 T1 T197 m., 4m.g6 :g :h )seep. 26.0-9s 'It95 57 La 1.9 d. 7658 Ce - 95195 59 Pr 19h., 5 m .experiments is complicated by geometrical considerations and bybut it is clear that some of the neutrons are slowed down89 J. D. Cockcroft and E. T. S. Walton, Proc. Roy. Soc., 1934, A, 144, 704.90 M. L. Oliphant, A. E. Kempton, and (Lord) Rutherford, ibid., 1935, A,91 T.W. Bonner and W. M. Brubaker, Physical Rev., 1935,4$, 742.92 Oliphant, Kempton, and Rutheriord, Proc. Roy. b'oc., 1935, A, 150, 240.93 H. Miller, W. E. Duncanson, and A. N. May, Proc. Comb. Phil. SOC., 1934,94 J. Chadwick, N. Feather, and W. T. Davies, ibid., 1935, 31, 357; see95 31. E. Nahmias and R. J. Walen, Compt. rend., 1936, 203, 71.96 P. Preiswerk and H. von Halban, ibid., 1935, 201, 722.97 E. 13. Andorsen, 2. physikal. Chem., 1936, B, 32, 237.9 8 Idem, Nature, 1936, 138, 76,99 R. Naidu, ibid., 137, 578.1 C. H. Johnson and F. T. Hamblin, ibid., 138, 504.2 I. V. Kurtschatov, G. D. Lutischev, L. M. Nemenov, and I. P. Selinov,3 M. E. Nahmias, Compt. rend., 1936, 202, 1050.4 E. B. Andersen, Nature, 1936, 137, 457.5 Proc.Roy. Soc., 1936, A, 153, 476.6 P. B. Moon, Proc. Physical SOC., 193G, 48, 648; J. R. Tillman, ibid., p.642 ; P. Lukirsky and T. Zarewa, Nature, 1936, 136, 681 ; W. F. Libby andE. A. Long, Physical Rev., 1936, 50, 575.149, 406.30, 549.also ref. 81.Physilcal. Z. Sovietunion, 1936, 8, 589BRADDICK. 29to thermal values. This is confirmed by direct experi~nents.~ Evid-ence has been obtained for the diffraction of slow neutrons at crystals,in accordance with the de Broglie wave-length of the neutrons.8 Anenormous mass of experimental material has been obtained on thescattering and absorption of the slow neutron^.^ The scatteringof neutrons by protons has been studied in order to check a theor-etical formula of Wigner, but the results are not entirely consistent.1°TABLE IV.Properties of slow neutrons.( a ) Groups of neutrons according to Fermi.laStrongly Stronglyabsorbed by Activates absorbed by ActivatesC Cd B Ag (moderately) AgD Rh, In Rh, InA Ag Ag, Ir I I I(b) Resonance energies for slow neutrons (from Rasetti, " Elements of NuclearElement and Resonance Element and ResonancePhysics," 1936, Blackie, London).period. energy (volts).period. energy (volts).Rh 44s. 1.1 In 54m. 1.3Rh 4 m . - 1 Ir 19 h. * 1.6Ag 22 8. 2.5, 4-6 Au 2.7 d. 2.5In 16s. - 2The fist theory of the capture of neutrons by nuclei 11 shows thatin the absence of resonance the capture cross-section varies inverselywith the neutron velocity. The experiments of P.B. Moon andG. A. Fink, J. R. Dunning, G. B. Pegram, and D. P. Mitchell, PhysicalRev., 1936,49, 103.D. P. Mitchell and P. N. Powers, Physical Rev., ibid., 50, 486; H. vonHalban and P. Preiswerk, Compt. rend., 1936, 203, 73.@ C. H. Collie, Nature, 1936, 137, 614; C. H. Collie and J. H. E. GrifEths,Proc. Roy. SOC., 1936, A , 155, 434; C. T. Zahn, E. L. Harrington, and S.Goudsmit, Physical Rev., 1936, 50, 570; D. P. Mitchell, ibid., 49, 453; G. A.Fink, J. R. Dunning, and G. B. Pegram, ibid., 49,340; F. Rasetti, E. SegrB,G. A. Fink, J. R. Dunning, and G. B. Pegram, ibid., p. 104; C. Y . Chao andC. Y. Fu, Sci. Rep. Not. Tsing Hua Univ., 1936, 3, 451; I. Kara, L. Rosen-kevitsch, C. Sinebrikov, and A. Walther, PhysikaL 2. Sovietunion, 1935, 8,219; V.Fomin, I?. G. Houtermans, J. V. Kurtschatov, A. I. Leipunski, L.Schubnikov, and G. Schtschepkin, Nature, 1936, 138, 326; H. von Halbanand P. Preiswerk, ibid., 137, 905; N. Dobrotin, Compt. rend. Acad. Sci.U.R.S.S., 1936,2, 235; V. Fomin, F. G. Houtermans, A. I. Leipunski, L. B.Rusinov, and L. V. Schubnikov, Nature, 1936, 138, 505; 0. R. Frisch, G.Hevesy, and H. A. C. McKay, ibid., 13'7, 149; A. C. G. Mitchell, E. J. Murphy,and M. D. Whitaker, Physical Rev., 1936,50,133,10 M. A. Tuve and L. R. Hafstad, ibid., p. 490 ; M. Goldhaber, NGture, 1936,127, 824.11 H. A. Bethe, Physical Rev., 1936, 48, 265; for other references, seeAnn. Reports, 1936,82,2'730 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.J, R. Tillmans and of E, Fermi and E. Ama1dil2 show a seleotiveeffect, and Fermi divides neutrons into groups as in Table IV.The neutrons of the C-group seem to have “thermal” ve10cities~~J~with energies of the order 0-03-1.0 volt.The energies correepondingto the other bands have been determined 13* 14* 15 by assuming, ontheoretical and experimental grounds,14 that the capture of neutronsin boron and lithium (12; a transformation) follows the l / v law. Itbeing assumed that the capture process in cadmium takes placewith maximum probability at about 0.03 volt, the energy for anyother band can be determined from the absorption in boron orlithium. It appears that the resonances of rhodium, silver (224.period), indium, iridium, and gold lie in the range 1-5 volts, whilemanganese, copper, arsenic, bromine, silver (2.3 m.), iodine andrhenium are activated by higher-energy neutrons of 30-85 volts.These phenomena have led to very interesting theoretical con-clusions.N. Bohr l7 has given reasons for the existence of closelyspaced energy levels in excited heavy nuclei, and he and G. Breit andE. Wiper 1* have shown that the assumption of such levels leads to a,satisfactory explanation of slow neutron capture. The neutronentering the nucleus forms an excited compound nucleus, whichbreaks up with re-emission of a neutron scattering, or of anotherparticle (n; p or n ; cc process), or goes into a lower state (capture).The existence of a number of closely spaced levels gives a possibilityof resonance capture of a neutron at low energies. H.A. Bethe l9calculates by it statistical argument that the spacing of the levelsis of the order 50-500 V. for elements of medium atomic weight,while the excitation energy of the compound nucleus is of the order10 M.E.V. The theory accounts for the fact 2o that good absorbersfor slow neutrons are not always strong scatterers, the procesaesof capture and scattering being alternatives after the absorption hasonce taken place. Bohr l7 produces interesting arguments of ageneral kind to explain various features of the process. He suggeststhat the energy of capture is diffused inside the compound nucleusla Ric. Sci., 1935, 2, 344, 443; 1936, 1, 66, 233, 310; L. Szilard, Nature,1s H. H. Goldsmith and F. Resetti, PhylskE Rev., 1936, 60, 328.14 0.R. Frisch and G. Placzek, Nature, 1936, 187, 357.15 D. F. Weekea, M. 8. Livingston, and H. A. Bethe, Phpicul Rev., 1936,16 F. Resetti, D. P. Mitchell, G. A. Fink, and Q. B. Pegram, aid., p. 777.l7 Nature, 1936, 137, 344.18 Phyeicd Rev., 1936,49, 519.lo Ibid., 50, 332.20 A. C, Gt. Mitohell and E. J. Murphy, ibid., 1935,47,881; 48, 653; 1936,1935, 136, 950.49,471.49,400,401 ; 60,133 ; see also ref. 76BRADDICK. 31and finally becomes concentrated on an escaping particle. G.Gamow 2l has predicted resonances for the oapture of fast neutronsby lighter nuclei to which the Bohr and the BreitFWigner theoryare inapplicable, but these have not yet been observed.The production of y-radiation attending the capture of slow neu-trons has been studied by various workers,22 and represents amethod of studying nuclear excitation energies. S.Kikuchi, K.Husimi, and H. Hoki 23 find that the maximum y-energy for a, givenelement is connected with the atomic number by one of two smoothcurves.The p-Disintegration.-The conclusion that the upper limit of thecontinuous energy spectrum of P-particles repesents the energyliberated in the nuclear reaction24 has been strengthened by ob-servations on the artificial p-ray emitters lzB 56 and 13N.25 In boththese cases the energy emitted in the @-ray change can be calculatedindependently, the energies of other reactions being used.The @-rayand positronenergy distributions from the radio-elements13N, 17F, 24Na, "Si, 32P, C1, 4lA, d2K26 and from indium, silver,rhodium, manganese, and dysprosium activated by neutrons2' havebeen determined.The Konopinski-UHenbeck theory of the disinte-gration has been used in these experiments t o provide an extrapoh-tion formula for the observed energy distribution curves. The justi-fication for this procedure is empirical. The relation between themaximum @-ray energy and the decay period of these lighter radio-active nuclei does not, apparently, show the regularity associatedwith the natural radio-elements (Sargcnt rules). The continuousP-spectra of some of the heavy radio-elements have been re-examined,28 and the end-points determined with the aid of the Kono-pinski-Uhlenbeck formula. The values obtained for radium-E amnot very concordant, but lie rather above the accepted value bmedon simple examination of distribution curves.The cornpaxison of81 Physical Rev., 1936, 50, 946.2' R. Fleischmmn, 2. Phyeik, 1935, 97, 242, 266; F. Rasetti, ibid., p. 64;C. Rammy, Compt. rend., 1936,203, 173; H. Hersxfhkiel and L. Wortenstein,Naure, 1936,137, 106.23 Ibid., pg. 186, 745, 992; see also ibid., pp. 30, 398; cf. R. Fleischmann,Natumoias., 1936, 24, 77.Ann, Repork, 1935, 32, 32.86 W. A. Fowler, L. A. Delsasso, and C. C. Lamitsen, Phy8kd Rev., 1936,26 F. N. D. Kurie, J. R. Richardson, and H. C. Paxton, ;bid., p. 369.27 E. R. Gaerthner, 3. J. Turin, and H. R. Crane, ibid., p. 793.28 F. A. Soott, Wd., 1936, 48, 391; F. C. Champion and N. 5. Alexander,Nature, 1936, 137, 744; P. C. Ho and H. Wang, C h k e J.P h y k , 1936,2, 1; M. Lecoin, Compt. rend., 1936, 202, 1067; L. Goldstein and M. Leooin,ibid., p. 1169.49, 66132 RADIOACTIVITY AXD SUB-ATOMIC PHENOMENA.the form of the continuous p-spectrum of radium-E with that of3OP29 shows a considerable difference in the shapes of the curves,which is presumably connected with the difference between heavyand light nuclei.There has been little development in the theory of the p-raychange. The current ideas of the continuous spectrum involve anon-ionising particle (neutrino) to carry away the energy differencebetween the energy of the nuclear reaction and that of the @-raysctually emitted from a particular nucleus. An attempt has beenmade to detect the neutrino by measuring the energy distributionof the nuclei recoiling after a 8-ray change.3O A light element, llC,was used so that the recoil velocity might be as high as possible.The experiment is difficult and the results rather indefinite, but theydo favour the neutrino hypothesis.0. Gamow and E. Teller31have modified the Fermi theory as it refers to selection rules for thep-disintegration by taking into account the spin of the heavy particlesin the nucleus. Their new selection rule is consistent with the ob-served lives of the different atoms of the thorium series. C. Mdler 32considers the possibility of the simultaneous creation of an electron-positron pair, together with the proton-electron pair of the Fermitheory. He uses this process to explain the positron emission ob-served by Alichanow, Alichanian, and Kosodaew from Th-C + llC.A theoretical calculation on the basis of the Fermi theory= showsthat a weak continuous y-ray spectrum should accompany the (3-decay, especially in light elements.There is as yet no experimentalevidence for this.THE PASSAGE OF ENERGETIC 8- AND ?-RAYS THROUGHMATTER.The scattering of fast @-particles by nitrogen nuclei has beenexamined by F, C. Champion,= who finds general agreement withN. F. Mott’s theoretical treatment, no losses of energy by radiationbeing found. D. Skobeltzyn and E. Stephanowa 35 find with p-rays ofenergy between 1.5 and 3 M.E.V. that there are sudden losses ofenergy when 8-particles pass through nitrogen, which they ascribet o a special intranuclear effect.Similar collisions have been observed2* A. I. Alichanow, A. I. Alichanian, and B. Z. Dgelepov, Nature, 1936,137, 314.8O A. I. Leipunski, Proc. Camb. Phil. Soc., 1936, 32, 301.31 Phy8iwl Reu., 1936, 49, 895.32 Nature, 1936, 137, 314.33 Ibid., 1935, 136,475, 719; F. Bloch, Physicd Rev., 1936, 50, 272; J. K.sc Proc. Roy. SOC., 1936, A, lS3, 353.8 5 Nature, 1936, 137, 234, 466.Knipp and G. E. Uhlenbeck, Phy8iCa, 1936,3,42533 BRADDICK.in argon.36 Skobeltzyn and Stepanowa have also found evidenceof electron-positron pair production by @-rays.37 These develop-ments must still be regarded as under investigation. Theoreticalinvestigations of pair production by @-rays and protons have beenmade, which give a much lower order of magnitude for this effect.3*The production of pairs by y-rays has been investigated theor-etically 39 and experimentally.40THE PENETRATING RADIATION.The origin of the cosmic radiation remains obscure.Some furtherevidence has appeared against the reported increase in the radiationdue to super-nova stars.41 A. Ehmert 42 has reported that there is adiurnal change in the cosmic ray intensity. On account of the com-plicated paths followed by the particles in the earth’s magneticfield, barometric changes which cause the rays to be filtered by moreor less air have an effect on the phase of the diurnal variations whichobscures the latter over long periods unless allowed for. Thisconclusion must for the present be accepted rather tentatively. Theproblems attacked by cosmic ray workers have been the nature of theprimary particles and their behaviour in the earth’s atmosphere andin other absorbers. The showers are especially interesting, bothfrom the point of view of sub-atomic physics and in that they contri-bute to the radiation observed in the lower atmosphere.G. Pfotzer 43has made balloon flights nearly to the top of the atmosphere withself -registering triple-coincidence sets of Geiger-Muller counters, andvery recently R. A. Milliban, H. V. Neher, and S. K. Haynes 44 havesent electroscopes to comparable heights. Pfotzer’s curve has as itsmain features a rise in the vertical intensity of the rays with altitude,a maximum a t a barometric pressure of about 70 mm. of mercury,and a rapid fall at the top of the atmosphere.There is also a, smallsubsidiary hump at about 300 mm. Pfotzer45 has attempted arather complete analysis of this curve, using the idea due to W. P. G.36 L. Leprince-Ringuet, Compt. rend., 1935,201, 712.37 Nature, 1936, 13’9, 272.38 H. J. Bhabha, Proc. Roy. SOC., 1935, A , 152, 559; Y . Nishina, S. Tomo-naga, and M. Kobayasi, Sci. Papers Inst. Phys. Chern. Res. Tokyo, 1935,27, 137.39 J. C. Jaeger and H. R. Hulme, Proc. Roy. Soc., 1936, A , 153,443.40 M. N. S. Immelman, Naturwiss., 1936, 24, 61; W. Bothe and H. Klar-mann, 2. Phyeik, 1936, 101, 489.4 1 J. Barn6thy and M . Forrb, Nature, 1936, 138, 544.4 2 2. Physik, 1936,101, 260.43 Ibid., 102, 23.44 Physical Rev., 1936,50, 992 ; cf. E. Regener and G. Pfotzer, Phyailcal. Z.,45 2.Physib, 1936, 102, 41.1934, 35, 782.REP.-VOL. XXXIII. 34 IEADIOACTLVITY AND SUB-ATOMIC PHENOMENA.Swann46 that primary particles come through a large part of theatmosphere, producing secondaries by the shower process with anefficiency increasing with the primary energy. The majority of theparticles in the lower part of the atmosphere are secondary. Thehump is due to the fact that below a certain altitude primary par-ticles are being progressively rernovcd as they come to the end oftheir range, while particles which would end above tho criticalaltitude have been filtered out by the action of the earth’s magneticfield. Yfotzer finds it necessary to postulate, in addition, a hardcomponent which is absorbed exponentially and which he considersmay be pr0tons.4~ W.F. G . Swam 48 has produced independently amore complete and general but essentially similar theory. He findsit possible that the ‘‘ hard component ” is not affected by the earth’smagnetic field, and may be due to photons. An unpublished argu-ment by P. M. S. Blackett, based on a balance-sheet for the cosmicray intensity entering the atmosphere, leads to the view that thenumber of particles entering the atmosphere is small compared withthe number of secondaries formed and leaves place for an appreciablephoton component. The existence of protons in the cosmic rays hasbeen the subject of several investigation^,^^ and it has been foundthat a few per cent. of the particles a t sea level may be protons.Ifthe hard component of the cosmic rays consists of protons, they mustact as producers of secondaries.I?. M. S. Rlackett and R. B. Brode 50 have obtained an energydistribution for the cosmic ray particles at sea, level by measuring thecurvature of their Wilson chamber tracks in the field of a largeelcctro-magnet. The spectrum is approximately of the formg(E) = lIE2for energies between 2 x 109 and 2 x 1010 E. V. There isan irregularity in the spectrum at about 2-5 x lo9 E.V., which isprobably significant and indicates a selective absorption action onparticles of this energy, or possibly a singularity in the primarydistributic~n.~~Several absorption measurements of the primary rays have been4 6 Physical Rev., 1936, 48, 641 ; i l n i z .Reports, 1935, 32, 37; cf. B. Cross,* 7 Cf. A. H. Compton, Guthrie Lecture, PTOC. Physical SOL, 1936, 47,4 8 Phy8ical Rev., 1936, 50, 1103.49 C. G. Montgomery, D. D. Montgomery, W. E. Ramsey, and W. F. G.Swrtnn, ibid., p. 403; R. B. Brode, H. G. MacPherson, and M. A. Starr, ibid.,p. 383; W. F. G. Swarm, ibid., 49,478; q’. 1%. Wilkins and H. St. Helens, ibicl.,p. 403 ; L. H. Kurnbaugh ant1 G. L. Locher, iDitE., p. 885.50 Proc. Roy. rSoc., 1936, A, 154, 564, 673 ; cf. L. Lepsirice-Ringuet, Cyompt.rend., 1935, 201, 1184.5 1 I?. M. S. Blackett, unpublished.l’hysikal. Z., 1936, 37, 12.747BRADDICK. 35made, showing hard and soft components.b2 The cosmic rays havebeen detected in a deep mine under the equivalent of 700 m.of water.53 Evidence was found for the existence of showers atthis depth. At a depth of 30 m. under London clay (68 m. waterequivalent), D. H. Pollett and J. D. Urawshaw 54 found thatthe proportion of showers to vertical rays was much the same asat sea level. The production of “ showers” and “ bursts” hasbeen investigated with counter arrangements and with ionisationchambers. The experiments of H. CarmicEiael 55 show that evenlarge bursts contain thinly ionising particles and are essentiallyidentical with showers observed in the Wilson chamber or withcounters. Thc producfion of very large bursts may occasionallybe observed with a comparatively thin-walled steel chamber, so it isprobabIe that showers start either in a single act or as a result of acascade process with an enormous efficiency. The production ofshowers by eIectrons has been observed in the cloud chamber.56 Theevidence available shows that a ratlicr large proportion of showersis initiated in this way.56* 57 The efficiency of shower production,measured in thin layers of different elements, varies with thc squareof the atomic number.5s This relation holds also a t an altitude of4000 m.59 The average size o€ showers aiid bursts, as well as theirfrequency , increases with a1 t i t ude .Go13. J. J. RRADDICK.52 J. Clay, Pkys;cn, 1936,3, 332 ; P. Bugor and A. Itosenberg, Compt. rmd.,53 J. Barn6thy and M. Forri), Nature, 1936, 138, 325, 399.64 Proc. Roy. SOC., 1936, A , 155, 546.b 5 Ibid., 154, 224; cf. T.V. Ehrenberg, ibid., 155, 532.5 6 E. C. Stevenson and J. C. Street, Plzysical Kev., 1926, 49, 425.6 7 J. Clay and A. Van Gemert, Physica, 193G, 8, 763.68 C. G. Montgomery and D. D. Montgomery, Physical Rev., 1936, 50, 490;59 Hu Chim Shan, unpublished.6o C. D. Anderson and S. Neddermeyer, Physical Eev., 1936, 50, 263;1936, 202, 1923.J. E. Morgan and W. M. Nielsen, ibid., p. 852.1L. T. Young, ibicl., p. 638

ISSN:0365-6217    

DOI:10.1039/AR9363300015

出版商:RSC    

年代:1936

数据来源: RSC

摘要:

GENERAL AND PHYSICAL CHEMISTRY.I. INTRODUCTION.IN the present Report an attempt has been made to review some ofthe subjects which, on account of shortage of space, and for otherreasons, were omitted from the previous Report. The application ofquantum mechanics to the study of molecular structure and relatedproblems has given important results but it has not been previouslydiscussed adequately in the Annual Reports : this is no doubt to beattributed to the inherent difficulty of reviewing a subject of suchcomplexity in the short space available. It may be noted, however,that a valuable survey of the quantum theory of valency has beenmade by J. H. Van Vleck and A. Sherman.1 Spectroscopic methodscontinue to provide valuable information concerning moleculardimensions and valency force constants, and the article on spectro-scopy in the present Report is a continuation of the previous onedealing with polyatomic molecules.The second volume of (Frl.)H. Sponer’s book on Molecular Spectra which was published during1936, deals with a number of topics of special interest to chemists.Mention may also be made of the appearance of a Comprehensivearticle on Raman spectra of organic compounds by J. H. HibbenY3and of a compilation of data of the Raman effect, covering the years1931 to 1934, made by M. Magat.4 Although the method of investi-gating molecular structure and inter-atomic distances by means ofelection diffraction in gases and vapours has been mentioned previ-ously in these Reports, the subject has not been treated fully.Animportant review has appeared during the year by L. 0. BrockwayY5one of the chief workers in the field : this deals more particularly withthe experimental method, and includes a comprehensive tabulationof the results obtained, with complete references, but the implicationsof the results are considered only briefly. In the present Report theemphasis is mainly on the significance of the measurements, althoughthe principles involved in the interpretation of electron-diffractionphotographs are also considered,1 Rev. Nod. Physics, 1935, 7, 167.2 ‘‘ Molekulspektren,” Vol. 11, Springer, Leipzig, 1936.a Chem. Reviews, 1936, 18, 1.4 ‘‘ Annual Tables of Constants and Numerical Data-The Raman Effect,1931-4,” Gauthier-Villms, Paris, 1930.5 Rev.Mod. Physim, 1936, 8,231PENNEY AND KYNCH: QUANTUM MECHANICS OF MOLECULES. 37Fundamental advances still continue to be made in the field ofchemical kinetics, and the importance of the possibility of calculatingthe velocity of a chemical reaction from purely theoretical consider-ations of the molecules involved cannot be over-emphasised. It isinevitable, therefore, that there should again be a report on chemicalkinetics.In the Report for 1935 certain aspects of surface chemistry werediscussed, and in the present Report two further aspects, vix., colloidalelectrolytes and unimolecular surface films, are reviewed. Duringthe year the collected papers of Sir William B. Hardy have beenpublished, and a number of useful short monographs dealing withvarious topics in colloid and surface chemistry have been issued.'A very large number of measurements of dipole moments in solutionhave been described in recent years, and it is of importance to knowhow the values so obtained are related to the true values obtainedirom the temperature variation of the polarisation of the substanceas vapour.Important progress has been made in this connexion anda report on the subject should not be out of place.It will be observed that there is no special report on deuteriumthis year : there are several reasons for this omission, the chief beingthat the main interests of deuterium, namely, in spectroscopy andkinetics, are considered in the reports on these subjects. It is hoped,however, to review in a subsequent Report such properties ofdeuterium and of other isotopes as are not covered in this manner.Finally, it may be recorded that a report on photochemistry, forwhich the time is undoubtedly ripe, is in preparation and it is hopedto publish it next year.S. G.2. THE QUANTUM MECHANICS OF MOLECULES.The interpretation of chemical binding offered by quantummechanics has not been previously discussed in the AnnmE Reports,although J. H. Van Vleck and A. Sherman1 have published acomprehensive review of the subject, including work to June 1935.The present Report is an attempt to combine a very brief surveyof the whole field with an account of the main developments sincethis date.The Report may be conveniently divided into sections, classifiedas follows :(1) Variation methods for accurate calculations.(2) Structural problems by approximate methods.6 Collected Scientific Papers, Cambridge University Press, 1936.7 Actualitks Scientifiqzres, Hermann, Paris.1 Rev.Mod. Physics, 1935, 7, 16738 GENERAL AND PHYSICAL CHEMISTRY.(3) Resonance and related properties.(4) Interaction of atoms with solid surfaces.(5) Miscellaneous.Discussions on lattices and on activation energies and reactionrates are omitted, since the former topic has been dealt with verythoroughly in a recent book by N. F. Mott and HI. JonesY2 and thelatter is dealt with later in this vol~irne.~(1) Accurate Cidczclations by Vuyiational Methods.Although quantum mechanics defines quite clearly a mathe-matical process by which the energy of formation of a moleculefrom atoms may be calculated, computational difficulties haveprevented much progress from being made in all but the simplestcases.Two methods of approximation have been tried. The fistis a generalisation of the Heitler-London theory of the hydrogenmolecule. Molecular wave functions are constructed as the sum ofproducts of atomic orbitals of the separate atoms, and the energyof formation of the molecule is evaluated as a first-order perturb-ation. This type of calculation has given many results of im-portance, but attempts to improve the numerical accuracy have ledto many difficulties. The more obvious corrections, of which thereare many, are relatively enormous, and it seems clear that themethod cannot claim to havc much more than qualitative sig-nificance.In spite of thirj, the application of the theory in itssimplest form to the calculation of activation energie~,~ one reactionbeing calibrated in terms of another, has been remarkably successful.Because of this, the method is usually accepted as “ semi-empirical.”The second possibility €or calculating the energy of formation ofa molecule makes use of the Ritz variation prin~iple.~ A promisingform is selected for the approximate wave function of the groundstate of the molecule, but the exact expression is left arbitrary tothe extent of involving a, number of parameters. The numericalvalues of these parameters are chosen in such a way that a certainintegral, which is an approximation to the energy of the molecule,has its least value.The strength of this method lies in the factthat a first-order variation of the wave function from its truecharacter causes only a second-order increase in the energy. Themethod therehre always gives a lower limit for the energy offormation.2 “ Properties of Metals,” Oxford, 1936.3 P. 56.4 See, e.g., ref. (l), or L. Pa.ulhig and E. B. Wilson, “ Introduction to&nantum Mechanics,” McGraw-IIIill, 1935, Chapter XIIPENNEY AND KYNCH: QUANTUM MECHANICS OF MOLECULES. 39At least half -a-dozen attempts have been made to calculate theenergy of formation of the hydrogen molecule by a variationmethod.* Each succeeding author irisertcd more and more para-meters into the wave function, thereby increasing the accuracy, buta t the same time making the calculations much longer.Even so,the results were very disappointing until H. M. James and A. S.Coolidge made a classical improvement. These authors demon-strated that it is absolutely essential to introduce the inter-electronicdistance rI2 explicitly into the wave function; otherwise, it isimpossible to make proper allowance for the repulsion between theelectrons. They assumed a 13-term expansion for the wave func-tion, and adjusted each of the coefficients to give a minimumenergy of formation. Their final result for the energy of dis-sociation, allowance being made €or the residual energy,6 was4.454 0.013 e.v., the accuracy being about the same as thatobtainable by spectroscopic methods.H. M. James, A. S. Coolidge,and R. D. Present have also considered the energy of the repulsivestate of H, which dissociates into two normal hydrogen atoms.The same authors then investigated the validity of the Franck-Condon principle by calculating the intensity throughout thecontinuous spectrum arising from transitions from an upper stablotriplet level to the repulsive state. d t appears that this principleleads to results incompatible with the experimental data. Whichof the two is in error is not yet clear. has made a13-term expansion of the wave function of the ground state oflithium hydride, and has also considered thc binding of the LiH-ion. Both systems are stable, and in the case of the former thecalculated energy is in fair agreement with experiment.The ionhas so far not been observed experimentally. J. P. Beach 10 hasmade a variation calculation on the ion He€€+, and finds a dis-sociation energy of about 2.0 e.v. The doubly charged ion HeHf+is shown to be unstable. J. Hirschfelder, H. Eyring, and N. Rosen 11have made a variation calculation on the energy of the linear H3molecule. They obtain 27 kg.-cals./mol. for the activation energyof the ortho-para hydrogen conversion, compared with theexperimental value 7 kg.-cals./mol.12J. K. Knipp6 J . Chem. Physics, 1933, 1, 825.6 C. G. Darwin (Nature, 1936, 138, 908) makes the excellent suggestion7 J . Chem. Physics, 1936, 4, 187.8 Ibid., p. 193.Ibid., p. 300.11 Ibid., p.121.12 See, e.g., A. Farbs, “ Ortho-Hydrogen, Para-Hydrogen and Heavythat residual energy should be used instead of xero-pint eneTgy.lo Ibid., p. 353.Hydrogen,” Cambridge University Press, 193640 GBNERAL AND PHYSICAL CHEMISTRY.(2) Structural Problems by Approximate Methods.Suppose that the energy of a molecule for all possible geometricalconfigurations can be calculated, Then the most stable arrange-ment is that where the energy function has its least value. Unfor-tunately, as explained in the previous section, a t present it isimpossible to make accurate calculations of the energy of formationof molecules other than the very simplest. Approximate methodsmust therefore in general be employed, and in practice there are twopossibilities, known as the orbital method and the pair method.Both must be considered as limiting cases, and neither can claimalways to be a better approximation than the other.The orbital method attempts to solve separately the motion ofeach electron in the time-average potential field of the other par-ticles of the system. Since an electron moves freely through thecharge-density distribution representing the other electrons, theorbital method gives a finite probability that any two electrons willbe at the same place at the same time.This is the main weaknessof the orbital method, since, of course, the electrostatic repulsione2/rij between any two electrons i and j effectively prevents theirever simultaneously occupying the same spot.The pair method attributes chemical binding to a number ofbonds, each of which arises from the interaction of a pair of electronson different atoms.Each bond is assumed similar in type to theHeitler-London bond of the hydrogen molecule. From the theoryit appears that a necessary condition for a bond to be formed is thateach electron entering into a bond should be in a singly occupiedorbit of its atom (compare H + H and H + He; in the latter casethere are two electrons in the same orbit, giving rise to anti-bondingor repulsion). The total energy of a molecule is the sum of theenergies of the bonds, together with the sum of the interactions ofelectrons in different bonds. To make the energies of the bonds aslarge as possible, directed wave functions are employed, and it isfrom the mathematical construction of these wave functions thatthe spatial arrangement of the molecule is revealed.The structures of a number of molecules and ions have been con-sidered either by the pair method or by the orbital method. Oftheae we may mention water, methane, ethylene, ethane, hydrogenperoxide, hydrazine, benzene, and related systems, and [Ni( CN),]2-and other complex ions.Details will be found in the review articleof 5. H. Van Vleck and A. Sherman,l where references to the originalpapers are also given. As an illustration, however, we compare theview-points of the two methods on the ion [Fe(CN),]4-.The neutral iron atom has 26 electrons, of which all except two,the 3d electrons, are in closed shells. According to the pair theoryPENNEY AND KYNCH: QUANTUM MECI-TANICS OF MOLECULES.42therefore, iron is at most bivalent. To possess a valency of six, theatom must acquire four more electrons, and these are provided inthe ion. As shown by L. Pauling,13 in order to construct sixequivalent orbits, pointing to the corners of a regular octahedron,the six valency electrons of the central atom must have the aggregateconfiguration d2sp3. Moreover, only d orbitals of the symmetrytype dE (of which there are three), and not orbitals of the symmetrytype dy (of which there are two), must be used. The orbital theoryalso predicts the regular octahedral configuration, and uses onlydc, p , and s orbitals of the central atom. To this extent there isagreement between the two methods, but clearly the pair theoryover-emphasises the capacity of the iron atom for absorbing elec-trons. On the other hand, the conventional structure E’e++(CN-),goes too far in the other direction.Since, in the orbital theory thereis no location of electrons on particular atoms, the “ ionicity ” 14can assume a state intermediate between that of the pair model andthat of the conventional model. For this reason the orbital methodmay be considered to give a better approximation than does thepair method for compounds involving iron-group atoms.There has so far always been agreement between the predictionsof the pair theory and those of the orbital theory for the forms ofvarious specific molecdes. Hitherto, this has been consideredmerely a fortunate circumstance, because it was felt that theapproximations in the two methods were so drastic, and different,that sooner or later an example would be found where the methodsseriously diverged.This rather worrying situation has to someextent been cleared up by J. H. Van Vleck.15 His conclusions areso important that it is worth while suminarising his arguments.Consider a multivalent atom surrounded by a number of univalentatoms. According to the orbital theory, one constructs molecularorbitals of the formwhere #(C) is an atomic orbital of the central atom conforming tothe symmetry of the whole molecule, #a is the atomic orbital of theattached atom i, and ai is a constant yet to be determined. Now,in general, there will be orbitals of the central atom whose symmetrytypes cannot be matched by linear combinations of the atomic13 J .Arner. Chern. SOC., 1931, 53, 1367.l* For want of a better word, w0 use “ ionicity ” ; Mulliken uses “ ionicness ”and Van Vleck *‘ ionic cliaracter.” Distinguish between ionic and polar.Part of the bonding in H, is ionic because the molecule may have the instan-taneous character H 8- + H-, but the molecule is not polar because the ioniccharacter averages out t o zero.+ = +(Q) + &ai+i,l5 J . Chem. Physics, 1935, 3, 80342 GENERAL AND PHYSICAL CIIEMISTRY.orbitals of the surrounding atoms, even though they obey thesymmetry properties of the moleculc. When this is so, the over-lapping of the orbital of the central atom with that of the attachedatoms will not be perfect, and anti-bonding, or a t best weak bonding,results.Thus, in iron-group compounds with six univalent groupsarranged octahedrally, the ds orbitals are bonding and the dy arcnot. Let us now consider the situation according to the pair theory.Here the object is to construct combinations of atomic orbitals ofthe central atom in such a way that each of the resulting wavefunctions is directed tow:irds a particular attached atom. Hencethese central directed wave functions have the same transformationproperties as do those of the orbitals Cpit.ji of the attached atoms inthe orbital theory. As we have already explained, the orbitalmethod requires only those orbitals of the central atom which areof the same symmetry types as linear combinations of orbitals ofattached atoms. Therefore, the same atomic orbitals for the centralatom must be used in the pair theory and in the orbital theory.Fromgroup-theory symmetry arguments he shows that if six atoms areattached either octahedrally or at the corners of a trigonal prism,only s, p , and d orbitals of the central atom are needed.Sincethese are commonly available, an immediate explanation of thefrequent appearance of co-ordination numbers six is obtained. Onthe other hand, if eight atoms are attached to the central atom theirfull bonding power is not used unless f wave functions of the centralatom are included. As a rule f orbits are considerably higher inenergy than d, p , or s orbitls, but this is no longer true for veryheavy elements.Prior to Van Vleck’s paper, J. E. Lennard-Jones l6 had suggested that only very heavy elements could have avalency of eight, and quoted OsO, as an example. The atoms in theneighbourhood OP osmium in the periodic table are the first wherethe outermost electrons can be easily changed from s to f orbits.MuWiken’s Papers.-R. S. Mulliken,l7 in a formidable series ofpapers extending over several years, has made an intensive studyof thc molecular orbitals, ionisation potentials, dipole moments, andelectron affinities of a number of triatomic, tetra-atomic, and evenmore complicated molecules. Pdost of his papers are mainly con-cerned with the spectroscopy of polyatomic molecules and aretherefore hardly appropriate for review here.Paper VIIJ deals with the effect of dipoles in the molecule on theVan Vleck’s paper contains further results of importance.16 J .SOC. Chem. Ind., 1934, 53, 249.17 VIII, J. Chem. Physics, 1935, 3, 514; IX, ibid., p. 51s; X, ibid., p. 564;XI, ibid., p. 579; XII, ibid., p. 586; XIPI, ibid., p. 635; XIV, ibid.,p. 720PENNEY AND KYNCH: QUANTUM MECHANICS OF MOLECULES. 43ionisation potential. W. C . Price l8 has shown experimentally thatan effect of this type is present in methyl iodide.Paper IX enumerates the one-electron molecular orbitals ofmethane, ethane, ethylene, and acetylene. By considering theultra-violet absorption spectra and the ionisation potentials ofthese molecules, fairly precise estimates of the bonding powers ofthe various orbitals are obtained.Similar considerations foraldehydes, ketones, and related molecules are given in Paper X .Papers XI and XI1 consider the molecular orbitals of moleculeswhich are appreciably polar, and supply a rough theoretical justi-fication of L. Pauling’s electronegative scale for atoms.lg FromPauling’s values, the polarity of molecules can be estimated; forexample, Mulliken finds, very roughly, C-072(H018)4 for methaneand C@60( Cl-O’15), for carbon tetrachloride.Theexperimental fact that this compound is diamagnetic at room tem-peratures 2O requires a singlet for the ground state. Previously, itwas thought that a triplet state might be lowest.21I. Lmgmuir 22 intro-duced this term to denote molecules having the same number ofelectrons and the same electronic structure as judged by theirproperties ; e.g., nitrogen and carbon monoxide, nitrous oxide andcarbon dioxide. Mullilren considers 15 isosteres of the lest anddiscusses their molecular orbitals, “ ionicity,” ionisation potentials,and ultra-violet spectra.As a rule, molecules containing the samenumber of electrons, and whose nuclei correspond closely in nuclearcharge, have the same shape and similar physical properties. Thisrule has been verified by W. G. Penney and G. B. B. M. Sutherland 23in the case of a number of triatomic systems.Valemy Xtcctes of Carbon.-A type of calculation where the pairmethod has so far proved more fruitful than the orbital method isin estimating the energy of valency states of atoms. By far themost inkeresting case from a practical point of view is, of course,carbon. The first explicit calculation of the energy of the valencystate of carbon was given by J.H. Van Vleck 24 on the assumptionof an aggregate sp3 configuration. For any particular arrangementof the four bonds, the valency state involves to a varying extentthe various states of the free atom in the sp3 configuration (vix.,Paper XIII deals with the molecular orbitals in diborane.Paper XIV is concerned with “ isosteres.”19 J. Chern. Physics, 1936, 4, 539.XI J. Amer. C‘hem. SOC., 1932, 54, 3570.20 L. Farkas and H. Sachsse, Tram. Paraday SOC., 1934, 30, 331.2 1 R. S. Mulliken, Physical Aev., 1933, 43, 765.29 J . Amer. Chem. SOC., 1919, 41, 868, 1543.23 Proc.Roy. SOC., 1936, A, 156, 654.24 J . Chern. Physics, 1934, 2, 20, 29744 GENERAL AND PHYSICAL CHEMISTRY.5*3X, 3*1.D, 3*1P), and the energy of the valency state is easilyevaluated by the pair method in terms of these states. The resultswere 163 kg.-cals./mol. for the energy in the tetrahedral arrange-ment (e.g., as in methane, ethane, etc.), and 167 kg.-cals./mol. forthe trigonal arrangement (e.g., as in ethylene, benzene, etc.). Thedifference is practically without significance.He assumesthat the valency state is a mixture of sp3 and s2p2, and adjusts the‘( coefficient of mixing ” in such a way that the energy of methaneas calculated by the pair method is a minimum. He concludes thatthe valency configuration is mainly sp3 and that the energy of thevalency state is about 106 kg.-cals./mol., a figure appreciably lowerthan Van Vleck’s estimate.However, the gross bonding energy isalso affected, and the net calculated heat of formation of methaneis increased by only 28 kg.-cals.jmo1.Voge assumes from the experimental evidence that the heat offormation of methane from atoms is 390 kg.-cals./mol. Thisenables him to fix certain parameters which are then used to calculatethe heats of formation of CH, CH,, and CB3. We finds 92, 194,and 278 kg.-cals./mol. respectively. There is no indication thatCH, occupies a favourable position with respect to the others. Themost stable arrangement of CH, is planar, in agreement with earliercalculations.26 No att’empt was made to calculate the energy offormation of CH5.H.H. Voge 26 has improved on the above estimate.(3) Resonunce .The word resonance is being used in many different senses in thetheory of the structure of molecules. We shall follow Pauling andhis collaborators2‘ and say that “resonance” is present in anysystem which cannot be adequately described in terms of s singlebond diagram. The choice of the term is hardly a happy onebecause the connexion between “ resonance ” in the present senseand resonance in the ordinary mechanical sense is rather remote.The word, however, was introduced before the precise nature of theeffect was understood, and the mechanical analogy did at leastoffer a plausible interpretation of the experimental facts. In anycase, the word is now so commonly used that it would be a mistaketo attempt to substitute another.A better word, ‘‘ mesomerism,”has indeed been suggested by C. K. Ingold,28 and this fits in well withz 5 J. Chem. Physics, 1936, 4, 581.z6 J. H. Van Vleck, ibid., 1934, 2, 20; W. G. Penney, Trans. Pa~uday SOC.,97 L. Pauling and G. W. Wheland, J . Chem. Physics, 1933,1,362, and many28 Nature, 1934, 133, 946.1935, 31, 734.subsequent papersPENNEY AND HYNCH: QUANTUM MECHANICS OF MOLECULES. 45all the other “ merisms ” of chemistry. &om the construction ofthe word mesomerism, a situation is implied where the actual con-ditions are intermediate between various extremes.The mathematical calculations of the theory of resonance haveachieved two results of importance.These are best illustrated byreference to benzene. The main result is that all of the bondsbetween neighbouring carbon atoms are similar, and are inter-mediate between single and double bonds. Hence all carbon atomsare equivalent, and the chemical stability (Le., reactions with acids,etc.) is greater than would be expected if the molecule containedthree locslised double bonds. The second result is that the effectof resonance is to increase the mechanical stability (i.e., the energyof formation from atoms) beyond that expected on the hypothesisof a, single bond structure. The increase is not very much com-pared with the energy of formation of the molecule (in benzene, forexample, about 2 e.v. in 60 e.v.), but it is quite enough to be detectedin the ordinary calculations of heats of formation in terms of bondenergies.It is noteworthy that the first of these results cannot be upset byimproving the accuracy of the calculations, but that the secondmay be.This, it seems to us, is an important point not explicitlymentioned before. One of the most surprising features of the longseries of calculations made by Pauling and his collaborators on theincrease of mechanical stability of a molecule due to resonance isthat the results are so remarkably consistent. No doubt it is anexample of a simple theory which concentrates on an essential pointgiving results with an accuracy very difficult to obtain by morecomplicated theories, because in these the second, third, and higherapproximations, although all large, practically b &lance out to zero.Effect of Resomnce on Internuclear Distances.-It is well knownthat internuclear distances in molecules are affected by resonance.For example, the carbon-carbon distance in benzene is 1.39 A.,29intermediate between the single-bond value 1.54 A.30 and the double-bond value 1.33 A.31 L.Pauling, L. 0. Brockway, and J. Y. Beach 32have suggested a method of estimating internuclear distancesaffected by resonance. We may illustrate their suggestion by con-sidering the benzene molecule. Here the resonance is mainlybetween the two Kekulh structures. Since neighbouring carbon29 L. Pauling and L. 0. Brockway, J. C‘hem. Physics, 1934, 2, 867.3O See, e.g., Sidgwick, “ The Electronic Theory of Valency,” Oxford, 1927.31 Pauling, Brockway, and Beach use 1-37 A.As will be shown by oneof the Reporters in an article soon to appear in the Proc. Roy. SOC., the value1.33 is probably the correct one.32 J . Amer. Chem. SOC., 1036, 57, 270646 GENERAL AND PHYSICAL CHEMISTBY.atoms linked by a single bond in one structure are linked by a doublebond in the other, the carbon-carbon linkage may be said to be oforder 3/2. Considerations of a similar sort 33 show the linkage ingraphite to be of order 4/3, while the internuclear distance is knownaccurately to be 1-41 A.34 Thus four simultaneous pairs of valuesof internuclear distance and bond order are known. By plottingorder against distance a smooth cuhe results. This curve may beused to predict distanccs in molecules where it is possible to estimatethe bond order.To find the order of the linkages in any molecule,Pauling, Brockway, and Beach proceed as follows. The resonanceproblem is solved by the pair method, and the wave function of theground state is obtained in the formwhere kj is a numerical constant, and $j is the wave function corre-sponding to the canonical structure j . The order of the linkage pbetween neighbouring carbon at'oms is then defined aswhere g3 is unity if the canonical structurej has a, bond between thetwo atoms, and is zero otherwise.By substituting for naphthalene the values of the coefficients kjas calculated by L. Pauling and J. it is found that thelinkages are not all equivalent.Variations of some 0.06 A. aboutthe mean 1.41 A. are to be expected. J. M. Robertson36 finds amean internuclear distance 1.41 A,, in exact agreement with khis.No attempt has so far been made to measure deviations from themean.Pauling, Brockway, and Beach suggest that the curve relatinginternuclear distance with bond order which they obtain for carboncompounds may be used for molecules containing other elementsprovided a suitable change of scale and end-points is made. Al-ternatively, if an internuclear distance is known from experimentaldata, then, by using Pauling's values of single-, double-, and triple-bond ionic radii,37 the order of the linkage may be calculated. Inthis way, e.g., the carbon-chlorine bond in carbonyl chloride iscalculated 5s 83% single and 17% double bond.Many otherexamples are considered.33 5. E. Lennard-Jones, Trans. Faraday SOC., 1834,30, 58; G. W. Wheland,31 G. I. Finch and H. Wilman, Proc. Roy. Xoc., 1936, A , 155, 345.35 J . Chm. Phpica, 1933, 1, 679; {bid., 1934, 2, 488.36 Proc. Roy. Soc., 1933, A, 142, 674.37 Proc. Nat. Acad. Sci., 1932, 18, 293.J . Chem. Phys$cS, 1934, 2, 474(4) Interaction of Atoms with Solid Xurfaces.Leniiard- Jones and his collaborators 38 have made an extrerriclypromising start a t a detailed theory of Dhe interaction of atoms andmolecules with the surfaces of crystals. The type of system whichthey consider is one where the absorbed atom is held only looselyby the crystal, probably by forces of a van der Waals character.The atom can exist in one of a small number of vibrational levels or,if its energy is great enough, can leave the surface altogether.Questions which are studied are the spacing of the energy levels,transitions between them, and between them and the continuum,caused by the thermal agitation of the surface, the migration of theatom over the surface, and the scattering of a homogeneous beamof the atoms by the crystal.The fundamental approximation of the theory is that the energyof interaction of the absorbed atom and the crystal may be repre-sented by a Morse function.39 Let the x axis be drawn through theabsorbed atom, perpendicular to the surface of the crystal.Write2 for the displacement at a particular instant of the surface atomsof the crystal in the neighbourhood of the absorbed atom from theirmean position 2 = 0, and x for the displacement of the absorbedatom from 2 = 0 a t the same instant.Let b be the equilibriumdistance of the absorbed atom from the surface a t the absolutezero of temperature. Then the interaction energy of the absorbedatom with the crystal is writtenThe first of these terms represents the short-range repulsive field,and the second the long-range attractive field. The constant D isthe energy required to take the atom off the surface a t absolutezero, and K is a parameter controlling the breadth of the potentialtrough holding the atom on the surface.The motion of the surface atoms of the crystal is small comparedwith the range of the potential field V .Hence V may be expandedin a power series in 2, and terms after the second rejected. We thenobtainI V = vo + yl == [ & - 2 K k - - b ) - 2De-/d.~--b)] + 2~-Zl]e-Z/ck-b) - e-di-b)The first term gives the interaction onergy of the atom and crystal38 I, J. E. Lennard-Jones and C. Strachan, Proc. Roy. SOC., 1935, A , 150,44,"; 11, C. Strachan, ibid., p. 456; 111, J. E. Lennard-Jones and A. li'.Devonshire, ibid., 1936, A , 156, 6 ; IV, 'idem, ibid., p. 29; V, A. F. Devon-shire, ibid., p. 37 ; J. E. Lennard-Jones and A. P. Devonshire, A'atuw, 1936,39 See, e.g., L. Pauling and E. B. Wilson, L c Introductian to Quantum137, 1969.Mechanics," McGraw-Hill, 1935, p. 27148 GENERAL AND PHYSICAL CHEMISTRY.at absolute zero, and the second gives the coupling between thevibrations of the attached atom in the field of the stationary surface,and the thermal vibrations of the lattice.The effect of Vl is tocause a surge of energy to and fro between the crystal and theattached atom.An important step has now been made. The perturbing potentialVl and the complete wave functions of the system are all in productform, one factor of each depending only on the lattice, and the otherdepending only on the attached atom. Straightforward perturb-ation technique may be applied, and there results the probabilitythat the lattice loses to the atom just the right amount of energyneeded to cause excitation to a higher vibrational level. Thisprocess may occur in many ways, because of the large number ofdegrees of freedom of the lattice.An averaging process over allthe normal modes present at any temperature must therefore bemade, and a t this point temperature appears explicitly in theformula. The final result of paper I is the life-time of the attachedatom in a vibrational level on the surface. For argon on potassiumchloride a t low temperatures, the atom vibrates many times inthe ground state before being activated to the first excited state,while a t room temperatures thc intcrval is of the same order as thevibration period.Paper I1 extends the above calculations to transitions of theabsorbed atom from a discrete state to the continuum. By inte-grating over the continuum, an expression is obtained for theprobability of evaporation from the surface.The average lengthof time spent by an absorbed atom on a surface may thus beestimated as a function of temperature.Formula? arefound for the probability that an impinging particle will condenseon a solid surface. The constants which occur in Langmuir’sisotherm are thus for the first time explicitly calculated in termsof the physical properties of the solid and its surface field. Evapor-ation processes are also considered. It is found that evaporationmay, even at low temperatures, take place in two or more stages,the atom being first excited to a higher vibrational level and then,while in that excited state, receiving another quantum of energysufficient to cause evaporation. The theory is illustrated by con-sidering the condensation and evaporation of H,, HD, and D, onthe same solid surface.Thistime the potential holding the atom on the surface is dssumed tohave central symmetry about the point of attachment.Paper V gives an interpretation of the experiments of R.FrischPaper I11 extends the calculations of paper 11.Paper IV covers roughly the same ground as paper 111PENNEY AND KYNCH: QUANTUM MECHANICS OF MOLECULES. 49and 0. Stern 40 on the scattering of beams of helium by crystals oflithium fluoride and sodium fluoride. The theory shows that whenthe components of momenta of the incident beam satisfy certainrelations, involving the energy intervals of the vibration spectrumof the atom on the crystal, absorption without loss of energy canoccur, thus accounting for minima in the reflected and refractedbeams.Excellent agreement with experiment is obtained if it isassumed that helium on lithium fluoride can exist in two vibrationallevels, given by - 129 cals./mol. and - 57 cals./mol. severally.Similar values hold for helium on sodium fluoride, but here the exactfigures are somewhat doubtful because the experiments were not socomplete.( 5 ) Miscellaneous.A number of papers have recently appeared dealing with thetheory of various physical properties of molecules and crystals.For want of space, these are grouped together under this heading.Restricted Rotutiolz.-To account for the temperature variation ofthe specific heat of certain crystals (e.g., oxygen, nitrogen, iodine,methane, carbon dioxide, etc.), L.Pauling suggested in a classicalpaper 41 that above a critical temperature, depending on the crystal,the molecules rotate more or less freely, but that at lower tem-peratures rotation is inhibited and only oscillation occurs. Eachmolecule is supposed to be influenced by an inhomogeneous potentialfield due to the surrounding molecules. When the mean thermalenergy, as measured by kT, is small compared with the restrictingpotential, most of the molecules have not enough energy to turnover, and their motion is therefore mainly oscillatory. At hightemperatures, however, the mean thermal energy is more thanenough to overcome the restricting potential, and rotation iscommon throughout the crystal. According to these ideas, thespecific heat of the crystal should show a maximum a t temperatureswhere IcT is about equal in magnitude to the restricting potential.By observing where the maximum occurs, a rough estimate of therestricting potential may be obtained.The above theory is unable to account for a maximum in thespecific heat-temperature curve of anything like the magnitude andsharpness of that observed. R.H. Fowler42 has explained thereason. It is because the restricting potential acting on one moleculedepends on whether the other molecules near it are also rotating.By making the magnitude of the restricting potential a function ofthe amount of rotation already present in the crystal, the specific4O 2. Physik, 1933, 84, 430.41 PhYSiCcGl Rev., 1930, 36, 430.42 Proc.Boy. SOC., 1935, A , 151, 1heat curve can be made to follow the experimental results veryclosely. Similar calculations on the dielectric constants along thethree principal axes of susceptibility of certain crystals also givegood agreement with the somewhat peculiar observed results.43Suppose that the restricting potential on one molecule due to therest of the crystal is expanded in a Taylor's series about the centreof the molecule. Apart from an additive constant which does notaffcct the freedom of rotation, the potential V may be writtenSincc V is a potential in a region due to outside charge distributions,the terms of each order in V must satisfy Laplace's equation.Assume now that the molecules are arranged in the lattice withcubic symmetry.Then the first non-vanishing terms in B are thoseof fourth order, and they may be writtenV = (AX2 + By2 + CX2) + (Dx3 + . . .) + . . . . . (1)V = E(3r4 - 5(x4 + y4 + z~)). . . . (2)A. P. Devonshire 44 has investigated the effect of the potentialfield [equation (a)] on the energy levels of the dumb-bell rotator.The way in which the various rotational levels, characterised by therotational quantum number J , split up under the influence of thefield had already been worked out by H. Bethe 45 from the methodsof group theory. The levels belong to five different symmetrytypes (irreducible representations), and therefore the infinitesecular equation giving the energy levels of the system factorisesinto five equations, each of which is infinite and refers to one of therepresentations.Devonshire confined his attention to the f i s t fewrows and oolumns of each determinant, and obtained the approxi-mate roots with the aid of an electrical calculating machine.46The calculations were straightforward for the levels up to aboutJ = 5 and ]kl not too large. Special considerations were neededfor ]k1 large, and the asymptotic behaviour of the levels was con-sidered. Curves showing the behaviour of the energy levels askcranges from - 60 to + 60 are given in the papeF. The notationused to describe the levels is that suggested by R. S. Mulliken.47Whether there is any molecular crystal to which the theory workedout by Devonshire would apply has not yet been considered. Theinterpretation of the experimental results will in any case be verydifficult, because the crystalline forces will probably break downmost of Che ordinary selection rules, and levels considerably higherthan J = 6 will be present even at low temperatures.43 h.13. Fowler, Proc. Roy. SOC., 1935, A , 149, 1.44 Ibid., 1936, A , 153, 601.46 R. R. M. Mallock, Proc. Roy. Soc., 1932, A , 140, 457.4 7 Pkgsical Rev., 1933, 43, 278.46 Ann. Physik, 1933, 3, 133PENNEY AND KYNCW: QUANTUM MECIEANICS OF MOLECULES. 51Paramagnetic Properties of Crystals.-There is a very close formalconnexion between the calculations of the previous section and thosegiving the paramagnetic properties of crystals of iron-group andrare-earth salts. The paramagnetism arises from the presence inthe metallic ion of electrons in incomplete shells to a large extentunaffected by the crystalline forces. For this reason, the crystallinepotential acting on an ion may be expanded in a Taylor’s seriessimilar to (1).If the atoms surrounding the ion have cubic sym-metry, then once again we have the potential (2). Now very oftenthe atoms surrounding the ion are arranged with cubic symmetry,and therefore the study of the effect of the field ( 2 ) on the energylevels of paramagnetic ions is of real practical importance. Thetheory in the case of hydrated crystals has already been carried tothe point of accurate quantitative agreement with e~perirnent,~~but in the case of certain complex salts, notably ferro- and ferri-cyanides, and cobaltammines, the theory is not so well developed.These salts are diamagnetic if they involve a complex ion containingan even number of electrons, e.g., [2’e(CN>,l4-, and have a suscep-tibility of order of magnitude corresponding to one free spin if thisnumber is odd, e.g., [Fe(CN),I3-.L. PaulingI3 was the first toaccount for this behaviour, but his explanation was not entirelyaatisfactory because it was based on directed wave fmctions andperfect electron pairing. J. H. Van Vleck 49 has now put the matteron a much wider foundation. He shows that the method of crystal-line fields, as obtlined above, the method of electron pairs, and themethod of molecular orbitals all formally predict similar results.The crystalline forces are so strong that the Russell-Saunderscoupling is broken down and the state of lowest energy is one oflowest possible spin for the whole complex ion, rather than one inwhich the central metallic ion has its greatest allowed spin.I nother words, the complex ion must be considered as a unit in whichthe interactions between electrons in orbits of the metallic ion areof subsidiary importance to interactions between these electronsand the electrons of the surrounding co-ordinated systems.has made detailed numerical calculations on theprincipal magnetic susceptibilities of potassium ferricyanide by themethod of crystalline potentials. His results confum the abovetheory of Pauling and Van Vleck.Diamagnetic Anisotropy of Aromatic Molecules.-When thestructure 01 a molecule may be represented by a single bond diagram,48 See, e.g., a review article by R.Schlapp and W. G. Penney, “Reportson Progress in Physics,” 11, 1935, Physical Society, p. 60.49 J . Chem. Phy8iC8, 1935, 3, 807.J. 13. Howard50 Ibid., p. 81352 GENERAL AND PHYSICAL CHEWSTRY.the diamagnetic susceptibility may be calculated by adding togetherthe susceptibilities of the separate atoms of the molecule.51 Thisis because the susceptibility of a free atom is proportional to Z?where ? is the mean square radius of an electron’s orbit, and thesum is over all the electrons of the atom. If resonance occurs in themolecule, however, the situation is different. Consider the benzenemolecule, for example. Here, the electrons concerned in bonds inthe plane of the ring, i.e., those whose atomic orbitals are symmetricalabout the plane of the ring, are regular, and for these the additiveprinciple applies.The resonance electrons have a chttrge dis-tribution which is practically cylindrically symmetrical about theaxis of the molecule, and is large only in two anchor-ring regions,one above and one below the carbon hexagon. When the magneticfield is parallel to the plane of the molecule, the contribution to thesusceptibility is normal, because the mean square distance of theanchor rings above or below the central plane is about the same asr2 for a p orbit of carbon. When the magnetic field is perpendicularto the plane of the molecule, 011 the other hand, the contribution tothe susceptibility is not normal, as it is proportional to R2, where Ris the radius of either anchor-ring region, and is also approximatelythe C-C distance in the ring (since the side of a regular hexagonequals the radius of the circumscribing circle).Now, R2 is severaltimes larger than for a p orbit of carbon, and the susceptibilityof benzene in a direction perpendicular to the plane of the moleculeis therefore much greater than that in a direction parallel to thisplane.L. Pauling 52 has estimated the principal diamagnetic suscep-tibilities of a number of aromatic molecules, using the above ideasas a basis. He finds almost exact agreement with experiment inthe cme of benzene. More complex molecules he calibrates veryingeniously in terms of benzene, and for these, too, obtains excellentagreement with experiment.The method of calibration is to replaceany pair of neighbouring electrons in the resonance problem by aconstant electrical resistance. A conducting network is thenobtained, and the currents induced in this network when a time-varying magnetic field acts in a direction perpendicular to the planeof the network, and hence the magnetic moment of the network,are found in terms of those corresponding to benzene. The contri-butions of the resonance electrons of the molecules to the magneticsusceptibility are linearly proportional to the magnetic momentsof the networks. For naphthalene and anthracene the calculatedand the observed values do not agree so well as do those of other5 1 See, e.g., E. Stoner, “ Magnetism and Matter,” Methuen, 1934, p.469.52 J . Chem. Physics, 1936, 4, 673.SUTHERLAND : SPECTROSCOPY. 53molecules. Pauling therefore considers that the experimentalresults for these molecules are probably in error.Vibrational and Rotational Levels of Polyatomic Molecules.-Thecalculation of the vibrational and rotational levels, and theirstatistical weights, has an important bearing on specific heats.However, the subject is more appropriately dealt with in the theoryof infra-red spectra and will therefore not be considered here. Anadequate review of the subject, treated by the methods of grouptheory, has rcceiitly been given by J. E. Rosenthal and G. M.3Xiirphy.53W. G. P.G. J. K.3. SPECTROSCOPY.In this section of last year’s Reports a general review was givenof the various types of vibration spectra associated with polyatomicmolecules ; the information derivable from them was indicated, andits limitations considered, but little attention was paid to particularinstances.This year it is proposed to exemplify the more importantresults by a small compilation. We shall follow the classificationof molecules given in last year’s Reports, oix., linear molecules,spherical molecules, symmetrical-top molecules, and asymmetrical-top molecules. The examples we have taken in each class are theonly ones for which the moments of inertia have been determinedwith any degree of certainty from the rotational fine structure of thebands. The methods of finding molecular dimensions from vibra-tional frequencies alone cannot yet be regarded as giving precisionvalues : these methods will be discussed later in this Report.It willbe observed that several molecules have been listed containing thedeuterium isotope ; in all of these cases it has been assumed that thedimensions are exactly the same as for the molecule containingthe corresponding hydrogen atom; in fact, this assumption hasoccasionally made it possible to determine the dimensions. Theinaccuracy from this cause cannot be more than about 0.001 A. in aninternuclear distance. The values of the fundamental frequencies ofthe molecules have only been given to within lOcm.-l, since correctionshave not been made for anharmonicity, and accordingly these valuesmay be in error by approximately that amount.The figure inparentheses after certain of the frequencies indicates the degree ofdegeneracy for frequencies which are isotropic in two (2) or in three(3) dimensions. Data which are not connected to a specific referencenumber have been taken from H. Sponer’s compilation.1 Paren-53 Rev. Jlod. Ph7JSiC8, 1936, 8, 317.1 “ Molckulspektrcn,” Springer, 193554 QENXRAL AND PHYSICAL CHEMISTRY.theses placed round a frequency indicate that the value is a cal-culated one, inchded. €or completeness, and probably correct towithin 30 crn.--lMolecule.ocoscsNNOHCNDCNHCiCHHCjCDDCtCDTABLE I.Linear Molecules.Internuclear Moment of inertia, Fundamental fre-distance, A. g.-em. x 1040.quencies, em.-l.CO 1.16 70.6 23601320670 (2)CS 1-52 a 247 1620660400 (2)- 66 22201290590 (2)CH 1.06 18-7 3290CN 1.15 2090CD 1-06 3CN 1-15CH 1.057 cc 1.204CH 1.057CD 1.057CC 1.204CD 1.067CC 1-204712 (2)22.9 2630190023.5 329033701980570 (2)730 (2)610 (2)27.9 2590 4 p33801880680 (2)520 (2)(2410) 4~27001760540 (2)500 (2)I n addition to those in Table I, the followiiig molecules and ionshave been shown to be linear and have had their vibration frequen-cies determined ; their actual dimensions, although not determinedapectroscopically, are known in many cases from studies on X-rayor electron-diffraction (see p. 65) : carboriyl sulphide,l cyanogenchloride,l cyanogen bromide,l cyanogen iodidc,l cyanogen,6 C,lH,,lq-, 7 s CN -.2 J.A. Sanderson, PhysicaZ Rev., 1936, 50, 200.3 P. F. Bartunek and E. F. Barker, ibid., 1935, 48, 516.4 G. Herzberg, F. Patat, and J. VET. T. Spinks, 2. PhpiE, 1934, 92, 87;G. Herzberg, F. Patat, and H. Verleger, ibid., 1936, 102, 1.6 W. F. Colby, Physical Rev., 1935, 4'7, 388 ; G. Glockler and C. E. Morrell,ibid., p. 569.S. C. Woo, T. K. Liu, and T. C. Chu, J . C'hinese Ghem. Soc., 1935, 3, 301.7 'tV. G. Penney and G. B. B. M. Sutherland, Proc. Roy. Xuc., 1936, A, 156,654SUTHERLAND : SPECTROSCOPY. 55In the ease of carbon dioxide the value given for one of the fre-quencies as 1320 cm.-l requires further explanation. Actually,one observes no frequency of this magnitude, but a pair of frequenciesa t 1286 crn.-l and 1388 cm.-l.This arises because the overtone of thefrequency a t 670 cm.-l falls very closo to this fundamental, so causinga " resonance " splitting.8 The value given is therefore an estimateof the unperturbed frequency and is sufficieptly good for most cnl-culations. The frequency at 660 cm.-l for carbon disulphide isprobably slightly erroneous for the same reason.In addition to those in Table 11, the following molecules and ionshave been shown to be spherical; their vibration frequencies m eTABLE 11.Spherical Molecules.CH, CH 1-09 9 5.298 9 FLH 1.78.5 5.47 105.27 11CCl, CCI 1.755 l 7ClCl 2.877.08.92920:H)W ( 3 )1300 ( 3 )2260 ( 3 )990 ( 3 )2110 ( 3 )930 (J)2180 ( 3 )980 ( 2 )$110 ( 3 )y o (!)f20so 13, 14(1070)($)19'30S? (?)21904 ti0760 (3)31CJ ( 3 )220 (?)known and thcir dimensions have been deduced in many cases fromdata on X-ray and electron diffraction (see p.65) : carbon tet'ra-bromide,l silicon tetrLzchloride,l titanic chloride,l stannic chloride,lstannic bromide,l SO,",l* CIO,'ls. It will be noticed that three dries8 Cf. this section in last year's Reports.9 N. Ginsburg and E. P. Barker, J. C'hern. Physics, 1933, 3, 668.10 Physical Rev., 1935, 48, 868.11 W. H. J. Childs, Proc. Roy. Xoc., 1936, A, 153, 555.12 A. H. Nielsen and H. H. Nielsen, Physicul Rev., in the press.13 D. M. Dennison and M. J. Johnston, ibid., 1935, 47, 93.14 G. E. MacWood and H. C. Urey, J . Chem. Physics, 1936, 4, 402.15 A.H. Nielsen and H. H. Nielsen, Physical Rev., 1935, 48, 861.16 W. B. Steward and H. H. Nielson, ibid., 1935, 47, 828; F. B. Stitt and17 Electron-diffraction values. Cf. L. 0. Brockway, Rev. 3f od. Physics,18 J. E. Rosenthal, Physical Rev., 1934, 46, 730.n. M. Yost, J. Ckem. Physics, 1936, 4, 82.1936, 8, 23156 GENERAL AND PTIYSTCAL CHEMISTXY.have been given for the moment of inertia of methane. The firstone is that deduced from the investigation of the deuteromethanemolecule and is presumably the most accurate value. The other.values have been deduced from the CH, bands only, by the method ofM. Johnston and D. M. Dennison,lo and are the ones which shouldbe compared with that given for CD,, the latter having been obtainedby a similar method from observations solely on CD,.In addition to those in Table 111, the following molecules and ionsare known to belong to this class and have had their vibration fre-TABLE 111.Xyrnrnetr ical- t op Molecules.NH 1.016 l9 I* 2.782 loHH 1.64511 0.36 I c 4.497ND 1.016 l g I A 5.397DD 1.645h 0.36 I c 8-985CH 1.093 I A 7.16GHH 1.785 I ( ; 5.298CD 1.093CH 1.09 -CD 1.09DD 1.8CF 1.6 In 38.6CH 1.1HH 1.8 I c 5.61CC1 1.6 I A 50.0CH 1.2HH 2.8 Ic 5.43330 9O(3450)( 2)1630 (2)9502420 2O(2560) (2)1160 (2)7502980221013103030 (2)1480 (2)1160 (2)(2100)(990)(2220)(2)(1290)(2)f 1020)( 2)(2990)2970148010502990 (2)1480 (2)1200 (2)297013507323050 (2)1460 (2)1020 ( 2 )qizencies determined with a reasonable degree of certainty : PH3,20n 21PD3,22 AsH~,~O PF,,l PC13,1 PBr3,23 AsF3,1 AsC13,1 SbCl,,l BiC1,,2319 M.V. Migeotte and E. F. Barker, Physical Rev., 1936, 50, 418.20 5. l3. Howard, J. Chem. Physics, 1935, 3, 207.2 1 L. W. Fung and E. 17. Barker, Physicql Rez:., 1934, 45, 238.22 M. de I-Iemptinne and J. M. Delfossc, Bull. Acad. TOY. Belg., 1935, 21,793; G. B. B. M. Sutherland and G. K. T. Conn, Nature, 1936, 138, 641.33 J. B. Howard and E. B. Wilson, J. Ghem. Physics, 1934, 2, 630SUTHERLAND : SPECTROSCOPY. 57BF3,25 BCI 3, 249 26 BBr3,25 N03',SG C0,",26 CH,Br,l CH31,1 CHCl,,lCHBr,,l POC1,,1 and C2H6.27 A certain amount of knowledge isavailable about their dimensions both from spectroscopic and fromdiffraction sources, but it is not sufi?ciently complete to warrant itsinclusion here without more discussion than space permits.Besides those in Table IV, the following molecules may be said tohave had their fundamental frequencies assigned beyond reasonabledoubt : sulphur d i ~ x i d e , ~ nitrogen d i ~ x i d e , ~ and chlorine dioxide1TABLE IV.As ymmetrical-top Molecules.OH 0-955 I* 1.009a 105" I B 1.901.7c 2.908a 105" -3 3 2 0D,O OD 0.955 -HOD As above -SH 1-36 I* 2.68a 92' I B 3.08As above -332sD2SI c 5.85-HSD As above -CH,O CH 1.04 I* 24.3CQ 1.2 J B 21.4HH 1.88 I c 2.9CH2D, '3 l3 CH 1.09- CD 1.093650 28376016002670 29278011802720 29372014002616265012651900 3019409001910 302620108029702900174014601040920(2 140)( 1420)(2230) 1240(2970) 1040(1320)(3010) 1090The references cited should be consulted for the state of currentknowledge regarding their exact dimensions.In the following casesthere is still a certain doubt about the assignment of one, or at most24 A. B. D. Cassie, Proc. Roy. Soc., 1935, A, 148, 87.25 T. F. Anderson, E. N. Lassettre, and D. M. Yost, J . Chem. PhysiC8,26 A. C . Menzies, Proc. Roy. SOC., 1931, A , 134, 265.37 E. Bartholomi, and H. Sachsse, 2. physikal. Chem., 1935, B, 30, 40.28 D. Bender, Physical Rev., 1935, 47, 252.29 E. F. Barker and W. W. Sleator, J. Chem. Physics, 1935, 3, 660; E.30 C. R. Bailey, J. W. Thompson, and J. B. Hale, J . Chem. Phl~si~.~, 1936,1936, 4, 703.Bartholorn6 and K.Clusius, 2. EZektrochem., 1934, 40, 530.4, 625; A. H. Nielsen and H. H. Nielson, ibid., p. 22958 GENERAL AND PHYSICAL CEEMISTRY.two, of the fundamentals : ozone,? oxygen fluoride,' chlorine mon-oxide," 31 ethylene,32* nitrosyl chloride,l formic oxalic a ~ i d , ~ 5acetic acid.36 Although enormous numbers of complex moleculeshave been investigated, the analysis of their vibration spectrahas only been partial (certain groups being recognised by theircharacteristic frequencies), and here we can only refer to a few of t hmore important contributions to structural problems.Particular XtructuyaZ Problerns.-The molecule which continues toreceive most attention is that of benzene, and the past year isremarkable for the number of important papers concerning it.Themost outstanding come from a group of workers 37 in University Col-lege who have made a very thorough study of the infra-red, Raman,and fluorescence spectra of benzene and hexadeuterobenzene. Theimportance of their work lies in the fact that until this was done thecoincidences between infra-red and Raman frequencies in the spec-trum of benzene made it appear as though the molecule did not possessthat hexagonal symmetry which modern resonance theories demand.They have been able to show that these coincidences are either acci-dental or else are due to a breakdown of the strict selection rules inthe liquid state. They have also been able to identify many of the20 fundninental frequencies. 0. Redlich and TV. Stricks 38 fromobservations on the Raman spectra of mono-, di-, and tetra-deutero-bcnzene have also been able to correlate the frequencies of benzeneand to correct earlier provisional assignments by E.B. Wilson.39C. Maimebaeh48 has made an analysis of the data on the isotopicmolecules to evaluate many of the constants of a very general poten-tial function for the force field in benzene. He has shown that appre-ciable interaction occurs betwcen non-adjacent carbon atoms.The other important development is the use of infra-red andRaman spectra for the detection of hydrogen bonds, particularlyin molecules containing hydroxyl groups. It is manifested eitherby a shift in the position of the frequency characteristic of the31 R. Pohlmann and W. J. Schumacher, Z .Physik, 1936, 102, 678.32 E. Teller and B. Topley, J . , 1935, 885.33 L. G. Bonner, J . Amer. Chem. Soc., 1936, 58, 34.34 G. Herzberg and 11. Verleger, PhysihZ. Z., 1936, 37, 444; J. Gnpta,Indian J . Physics, 1936, 10, 117, 313; C. S. Venkateswaran, Proc. IndinnAcad. Sci., 1936, 2, A , 615; Current Sci., 1936, 4, 736; P. B. Sarkar andB. C. Ray, Nature, 1936, 137, 495.35 J. H. Hibben, J. Chem. Physics, 1935, 3, 676; W. R. Angus and A. H.Leckie, ibid., 1936, 4, 83, 324.96 W. R. Angus, A. H. Leckie, and C. L. Wilson, Nature, 1935, 135, 913.37 W. R. Angus, C. R. Bailey, J. B. Hale, C. K. Ingold, A. H. Leckic,38 Molzatsh., 1936, 68, 374; J . Chem. P?qsics, 1935, 3, 834.39 Physical Rev., 1934, 46, 146.C. G. Raisin, J. W. Thompson, and C.L. Wilson, J., 1936, 912-971SUTHERLAND SP:ECTROSCOPY. 59013 vibration or by its non-appearance. The particular applicationsof this 40 would take t;oo much spacc: to be summarised adequatelyhere, particularly as many of them are still rather controversialsub j ect s .Intramolecular Forces.Next in importance to the dimensional coiistants of a moleculecome those characterising the forces requircd to alter the distancesbetween the constituent atoms, since they presumably bear a fairlydirect relation to the strengths of the corresponding chemical bonds.The magnitudes of the vibration frequencies of a molecule dependsolely on the inasses of the various atoms and on the forces broughtinto play when the latter are displaced from their equilibrium posi-tions.A proper analysis of the vibration spectra of a moleculeshould $heref w e give information coiicerning this interatomic forcefield. The early steps in this direction have already been reviewedin these Report>s,*1 but much progress has been made in the past twoyears. We sh:tll accordingly treat this problem from a more generalstandpoint and endeavour to show how the various methods arerelated to one another.It is well known that in a system executing simple harmonicmotion the potential energy may be expressed as $Ex2, where x is theco-ordinate which varies harmonically, and Ex is the restoring forcecalled into play when the system is displaced from its equilibriumposition in which x is zero. For example, in a diatbmic molecule, xdescribes the variation in the internuclear distance during the vibra-tion, the frequency of which is given by 2;72/lc(ml $- m,)/mp2, ml andm2 being the masses of the atoms.The force constant E may there-€ore be directly determined from the vibration Irequency. In thecase of a polyatomic molecule consisting of n atoms, the matter is notso simple. The 3n - 6 internal degrees of freedom may each be char-acterised by a co-ordinate xT ; the corresponding general expressionfor the potential energy is____--Using the methods of classical medianics, one obtains expressionsfor the 3n - G frstqixencies of the form v = f(kl . . . k13 . . . ml . . .).In other words there are only 3'1~ - G equations from which to deter-mine all the force constants E,, k,, .. . El, . . . etc. Clearly thisis impossible, unless some assumption is made which reduces the40 L. Pauling, J . Amer. Chern. SOC., 1935, 57, 2680; 1936, 58, 94; L.Onsager, ibid., p. 1486; R. H. Gillette and A. Sherman, ibid., p. 1135; R. H.Gillette and F. Daniels, ibid., p. 1139; W. Gordy, J . Ghem. Physics, 1936,4, 750.4 1 Ann. Reports, 1934, 31, 2160 GENERAL AND PHYSICAL CHEMISTRY.number of arbitary constants in (1) to not more than 3n - 6. Alltheories of the intramolecular force field are directed towards sur-mounting this difficulty by making some specific assumption regard-ing the nature of the field which will effect the required reduction.It is, of course, desirable that the number of constants to be deter-mined should be less than 3n - 6, for there must then exist certainrelations be€ween tlie frequencies and hhe atomic masses which areindependent of the force constants.The cxactness with which theserelations are fulfilled forms a test of the validity of the assumptions.We shall consider briefly the types of assumption which have beentricd, and how these are related to the chemical conceptions of thebonds in a molecule.The VaEency Force Field.-The assumption which is based mostdirectly on chemical ideas is that of the valency force field.42 Hereeach chemical bond in the molecule has associated with it a forceconstant, Ic (analagous to that for a diatomic molecule), while theangles between neighbouring bonds each have a characteristicconstant, 0, measuring their resistance to deforniation.This meansthat the vibrations of the molecule are described in terms of thechanges in the lengths of the bonds (a), and of the angles between thebonds ( E ) , the potential energy being writtenV = &(kld: + k,d$ + . . . + 0,c4 + O2E; + . . . 1The number of arbitrary constants is obviously considerably re-duced, since all interaction terms of tlie type 2E1,x1x2 have beenomitted. The valency force field is liherefore essentially an inade-quai;e representation, in that one assumes that the only forces actingon the atoms are those rcsishing simple stretching and deformationof the bonds, and (what is more important) that these stretchingsand deformations are quite independent of one another. Neverthe-less, it has been applied not uiiprofitably to a great number of mole-cules by many different workers over a number of years, and it isonly rccently that its limitations and value have been criticallyexamined.For the symmetrical triatomic molecule XYX, only two constantsare required to describe this field, one giving the force needed toalter the length of the UX bond, the other giving that needed toalter the XYX angle.This means that a relation must exist betweenthe three frequencies of the molecule, the masses of the atoms, andthe angle CI between the YX bonds. W. G. Penney and G. B. B. 3%.Sutherland have tested this relation for the molecules sulphurdioxide, water, deuterium oxide, sulphur dioxide, nitrogen dioxide,42 R. C. Yates, Physical Rev., 1930, 38, 555; R.Meckc, 2. physikal. Chem.,1931, B, 16, 409, 421; 1032, 17, 1SUTHERLAND : SPECTROSCOPY. 61carbon dioxide, carbon disulphide, and the CH, group. They foundthat for all except carbon dioxide and disulphide the discrepancieswere less than 5%. On the other hand, the converse process ofemploying the valency force field to determine the angle a of themolecule cannot be relied on to give a result with an error of less than20’. For pyramidal molecules of the type YX, again only two con-stants are needed to correlate the four frequencies, so the adequacyof the representation may also be tested here. This has been donefor NH,, ND,, PK, and As€€, by Howard20 and for PP,, PCl,, PBr,,Ass,, AsCl,, SbCI,, and BiC1, by Howard and Wilson.23 The resultsindicate that as a first approximation the valency force field is reason-ably satisfactory, but that interaction forces (particularly in the lattergroup of molecules) are by no means negligible.For regular tetra.hedral molecules of the form YX,Rosenthal l8 has made a very carefulinvestigation of CH,, CCl,, SiCl,, TiCI,, SnCl,, CBr,, SnBr,, SO4”,CIO,”, and finds that methane is the only one for which the valencyforce field is a reasonably good approximation. This field has beenwidely applied by K. W. H. Kohlrausch43 to many more complexsystems. His results may be regarded as a useful confirmation of thegeneral correctness of the assignment of fundamental frequencies ;the actual values given for the force constants should not be regardedas more than a first rough approximation to a description of themolecule.Central Force Field-Another simple type of force field whichwas tried out44 but which has not been so successful is basedon the assumption that the only forces which act are directed solelyalong the lines joining the atoms.Thus if r,,, r23 . . . denote thedistances between the centres of the atoms then the potential energyis writtenAlthough this is possibly a better approximation than the valencyforce field for certain tetrahedral molecules such as carbon tetra-chloride and for some symmetrical plane ions such as CO,’ and NO,’,yet it cannot be said to be very suitable either from a chemical or froma physical point of view. Attempts to improve it by bringing inadditional forces have been made by H.C. Urey and C. A. Bradley 45and by A. Eucken and IF’. S a ~ t e r . ~ ~43 Monatah., 1936, 68, 349; 2. physikal. Chem., 1935, B, 30, 298. Theseare only two typical examples from a very large number. They are chosenhero because they are referred to in Table V.44 N. Bjerrum, Verhandl. deut. physikal. Qea., 1914, 16, 737; D. M. &Mi-son, Phil. Mag., 1926, l, 195.45 Physical Rev., 1931, 38, 1969.46 2. physikal. Chem., 1934, B, 26, 46362 GENERAL AND PHYSICAL CHEMISTRY.Hore General Types of Force. Field.-A more general method ofapproaching the problem has been pursued by J. E. F t ~ s e n t h a l ~ ~C. Manneba~h,~~ G. B. €3. M. Sutherlancl and D. &I. Dennison 49 andothers. Assuming that the potential function possesses the samegeometric symmetry as docs the molecule itself, they investigatethe miniinurn num'ncr of arbitrary coixstants required in the generalpotential function (1).Thus for the isosceles triangular moleculeYX, it is 4, for tho regular pryarnidal YX,, 6, for the regula8r tPetm-hedral PX,, 6, for axially symmetrical ZYX3,50 9, for ethylene,sl 15,and for bcan~cne,*~, 34. The corresponding number of fundamentalfrequencies in such molecules being respectively 3,4,4,6, 12, and 20,some further reduction is still nccessary. This has been attempted intwo ways, either by introducing some generalised type of valencyforce field which does take account 01 the more importantinteractions,239 257 33,489 51 or a!Gcriiativelg, by assuming that certaingroups in the molecule are practically indcpeiident of the rest of themolecule.The latter assuniption is suficiently justified by a mass ofempirical data showing that whenever certain groups are prcsentin a molecule certain characteristic frequen cics appear in its vibrationspectra. It was first applied to the CI-I, and the CH, groups in somesimple compounds by Sutherland and Dennison ; 49 its generalisedextension to the series of molectrles methane, methyl chloride,chloroform, and carbon tetrachloiide by €I. H. Voge and J. E.nosentha152 has proved it to be a reliable method of computing thefrequencies of a molecule from a knowledge of the force constants ofits constituent groups. It should Fc emphasised that the values ofthe potential constants in this method may not always be capable of adirect physical interpretation ; yet ccrtain combinations of them canbe shown to be equivalent to the " bond strengths " ( k l , E, .. . ) ofthe valency forco field.There are, however, two i ~ ~ t h o d s (each applicable t o a, limitedclass of molecule) whereby all the constants of the Rosenthal-Mannebach generalised function may be found. The first is from theisotope effect ; if the molecule coiicerned coiitsins one or morc hydro-gen atoms, thcn when thcse am replaced by dcuteriuni the frequen-cies are altered while the potential constants remain Dhe same. Onelias consequently two or more sets of frequencies from which todetermine the same set of constants.This has been done for47 Physic*at Rev., 1934, 45, 835; 46, 730; 1935, 47, 235; 1936, 49, 535.48 A m . SOC. sci. Rruxelles, 1935, B, 55, 5, 129, 237; Van den Boasche andt!. Mannebach, ibid., 1934, 54, 230.4 9 PTOC. ROY. SOC., 1935, A, 148, 250.611 J. E. Rosenthal and H. H. Voge, J . Chem. Phgsics, 1936, 4, 131.5 1 J. M. Delfosse, Ann. SOC. sci. Bruxelles, 1935, 55, 114.J . G%em. Physics, 1036, 4, 137SU'I'HKRLAND : SPEUTBOSCOPY . 63smnxxria 19 and methane and will doubtless soon be extended. Theother nieChod depends on the interpretation of the anomalous spacingof the rotation lines in the degenerate vibrations of symmetrical-topand spherical molecules. This has becn accomplished by Johnstonand Dcnnison,10 who have extended the earlier work of E.Teller 53on this subject, vix., thc interaction between vibration and rotation,and have applied it t o the calculation of the five potential constantsof mcthane.I n all of the above methods no account has been taken of possiblecubic terms in the potential function, i.e., of the anharmonicity of thcvibrations. The frequencies cmp1oyt:d in the calculations shouldtherefore not be the observed ones but the frequencies €or infinitesi-mally small amplitude of vibration. The latter can be deduced fromthe observational data provided a number of the overtone frequenciesare known. The errors introduced from this cause are probablynot more than a few units yo. Anothcr common feature of all of themethods is that cerhain constants or combinations of them (in par-ticular, the bond constants or" the valency force field) differ very litthno matter which approach is employed ; it, is the interaction constantswhich differ very greatly on tihe various theories.Fortunately, thebond constant, i.e., the force required to stretch a definite bond agiven distance, is 01 more chemical interest than the latter at themoment. Accordingly we have gathered together in Table V a,number of the values now available for some of the commoner bonds.I n this connection it is important to note the work of R. M. Badger 54and C. If. D. Clark 55 on the relation between the force constant andthe internuclear distance in a bond. Originally given for diatomicmolecules as an extension o€ Morse's relation r30, = const., it hassince been modified by several workers 5G in attempts to correlate itwith the position of the two atoms in the periodic table and to makeit applicable to polyatomic molecules.The most; convenient form inwhich to state it is possibly that used by Badger himself, viz.,where re is the equilibrium internuclear distance, k, is the bond forceconstant, Qij and dij are constants the values of which depend on thopositions of the constituent atoms in the periodic table. If a forceconstant for a particular bond is evaluated by the methods we have53 '' Hand- und Jahrbuch der Chemischsn Physik," 1934, Band 9/11.54 J . Chew%. Physics, 1934, 2, 128.6 6 1%. M. Badger, ,7. ( ' J i ( m . Phy&s, 1935, 3, 710; C . H. D. Clark, Phil.Jlq., 1935, 19, 470; PlLysicnl Rev., 1935, 47, 338; Trans.Fnraduy Sac.,1935, 31, 1017; Proc. Lee& Phil. Soc., 1936, 3, 218, 221; 13. S. Allen aiidA. K. Longair, Phil. Mag., 1935, 19, 1032; W. Lotmar, Z. Physik, 1935, 93,528; M. L. Huggins, J . Chem. Phys'k8, 1935, 3, 473; 1936, 4, 309.66 Phil. Mag., 1934, 18, 45964 GENERAL AND PHYSICAL CHEMISTRY.been considering, this relation enables the corresponding internucleardistance to be computed. This has been done for several mole-cules,23* 251 331 4*#51 and the results are in surprisingly good agreementwith the distances deduced from X-ray and electron-diffraction data.Regarding the values listed in Table V, it is interesting to noticethat those below 7 x lo5 dynes/cm. are associated with single bonds,TABLE V.Force Constants Characteristic of Bonds in PolyatomicMolecules.Forceconstant,Type of dynes/ Moleculebond.cm. x or group. Ref.c=cC E NN=Nc-cc-0N=OS-0 c=sO-H15.717.916-716.916.717.514.615.022.09.59.88.68.213.414-215.319.09.113-710.07.68.07.0C,H2 - HCNClCNBrCNICNC,N,NNON-N,c2CZI-1439OZH, ocs ococoNO,NNOso2cs, ocsH2O497777677494951534977497777757-Forceconstant,Type of dynes/bond. em. x low6.N-H 6.4S-H 4.0C-H 5.95.85.04.95.04.85-0 c-c 5.04-87.6c--0 4.5C-S 3.0 c-I? 5-8C-C1 3.63-45.2C-Br 2.94-2c-I 2-33.0Ref.2074974952337434964343434940527497497those between 7 and 15 x lo5 dynes/cm.with double bonds (in theconventional sense), and those over 15 x lo5 dynes/cm. with triplebonds. This is important when one remembers that the agreementbetween various methods is within 10% on any particular molecule.One therefore finds pleasing confirmation that the C-0 bond incarbon monoxide and dioxide is nearer triple than single in accord-ance with the theory of resonance (see p. 45). Similarly the C-Cbond in benzene is half-way between a single and a double bond.These examples might be multiplied, but sufficient has been said toindicate the great possibilities of this method of putting a quantitativeestimate to the shades of difference between the many types of bind-ing which we are realising exist in chemistry.G.B. B. M. S.57 J. H. Van Vleck and I?. C. Cross, J . Chem. Physks, 1933, 1, 357GLASSTONE : ELECTRON DIFFRACTION. 654. ELECTRON DIFFBACTION AND m E STRUCTURES OFGASEOUS MOLECULES.Theoretical.-In 1915 P. Debye 1 and P. Ehrenfest 2 independentlydeveloped equations giving the angular distribution of the intensityof X-rays when scattered by non-crystalline substances ; these areparticularly applicable to scattering by a gas or vapour, since themolecules are sufficiently far apart to make intermolecular effectsnegligible in comparison with the total scattered radiation. Theobserved effects then virtually result only from scattering byatoms within the individual molecule, and the random movementsof the latter do not affect the interference of X-rays.Electronwaves, the existence of which can now be regarded as definitelyestablished, behave like X-rays in so far as they are scattered byindividual atoms in a given molecule, and M. Mark and R. W i dfound that the intensity of the coherent (elastic) scattering forhigh-velocity electrons could be represented by an equation similarto that of Debye and Ehrenfest; thus, a t an angle e between theprimary and the scattered electron beam, the intensity -Ic,,. of thelatter is given by(1)where E is a constant, $ is the scattering factor of the particularatom for electrons, andxij = ( 4 x / ~ ) . Zij sin e/a . . . . * ( 2 )the term Zzj being the distance between the atoms designated byi and j.The equivalent wa.ve-length of the electrons, A, is deter-mined by the relationshipx 10-scm. . . 1where V is the potential in volts applied to accelerate the electrons.In this equation, the first term is the equivalent of the de Broglieequation, A = himu, and the second term is the relativitycorrection.In determining the total coherent scattering by means of equation(l), it is necessary to sum the terms for all possible pairs of atoms inthe molecule; the scattering due to individual atoms must beincluded, and this is given for each atom by the corresponding $2,since now i = j and consequently xi.i is zero and (sin xij)/xij is unity.Ann. Physik, 1915, 40, 809.Vera. K . Akad. Amsterdam, 1915, 32, 1132.Natzcrwiss., 1930,18, 205, 778 ; Z.Physik, 1930, 60,741 ; 2. Elektrochem.,REP.-VOL. XXXIII. C1930, 36, 675; R. Wierl, Physikal. Z., 1930, 31, 366, 102866 GENERAL AND PHYSICAL CHEMISTRY.If free rotation is possible within the molecule, then the distance Zijbetween a given pair of atoms may not remain constant, and allow-ance for this variation must be made in the calculations.4Strictly speaking, the factor Q varies with the scattering angle 0,and for the ith atom is given by the formula. . (4).Zi being the atomic number of the atom and Fi its scattering, or" form," factor for X-rays.5 The form factors, which decrease as(sinO/2)/~ increases, have been calculated by Rl. W. James and0. W. Brindley,6 and by L. Pauling and 5. the valuesof the latter authors being, apparently, in better agreement withexperiment.I n addition t o the coherent scattering already considered, allow-ance must be made for incoherent scattering, consisting of electronswhich have undergone change of wave-length.According t oL. Bewilogua,O this is given by the relation( 5 )ill whichf(v,) is a function of tii, andvi = 4~(0.176/Zi2/3)(sin8/~)/~ . . . . (6)The values of j ( v i ) for various values of vi are quoted by Bewiloguu.It appears from his calculations that for electron diffraction theintensity of the incoherent scattering, which is added to the coherentamount so as to give the total scattering, falls off rapidly as(sin ~/Z)/X increases and becomes quite small a t appreciable scatteringangles, especially if the atomic number is large.The coherent scattering may be divided into two parts : first," atomic " scattering due to individual atoms, and secondly," molecular " scattering in which two atoms are concerned.Theformer, as shown above, is given by $2 for each atom and hencefalls off continuously as the scattering angle increases, but theexpression for the latter contains the (sin x)/x terms of equation (l),R. Wierl, Physikal Z . , 1930,31, 266; Ann. Physik, 1933, 13, 453; L. E.Sutton and L. 0. Brockway, J . Amer. Chem. SOC., 1935, 57, 473; see also,S. H. Bauer, J . Ghem. Physics, 1936, 4, 406.H. Bethe, Ann. Physik, 1928, 87, 55; 1930, 5, 325; N. F. Mott, Proc.Roy. SOC., 1930, A , 127, 658.Phil. Mag., 1931, 12, 81, 739 (correction).7 Z. Krist., 1932, 81, 1.See R.W. G. Wyckoff, &id., 1930, 75, 632; cf. V. 33. Cosslett, Trtrtw.Faraday SOC., 1934, 30, 987.Physilcal. Z . , 1931, 32, 740; 1932, 33, 688GLASSTOFIX : ELECTRON DIFFRACTION. 67and hence passes through a series of maxima and minima as 8increases. If a beam of high-velocity electrons after traversing agas in an appropriate manner falls on a photographic plate, and thisis examined photometrically after development, the record showsa steadily decreasing background intensity, due mainly to atomic,and at small scattering angles also to incoherent, scattering, withoccasional inflexions corresponding to the maxima in the coherentscattering. Visual examination of the plate appears to show, how-ever, a central spot, caused by the unscattered electron beam,surrounded by a series of concentric diffraction rings, apparentlyalternately light and dark, suggesting a series of maxima andminima of scattering without a falling background.This is never-theless a purely psychological effect, since photometric investigationgives an intensity curve of the type anticipated from theoreticalconsiderations, the positions of apparent maximum density in thediffra ctioii rings corresponding approximately to the inflexions inthe curve.Experimental Methods and Interpretation of Results.-The experi-mental method in general use is bascd on that devised by €3. JVierl,loalthough important modifications ha've been made.ll A fine boamof electrons, accelerated by a potential of about 50,000 volts, ismade to pass at right angles through a narrow stream of the gas orvapour under investigation, and then falls on a photographic plate.The electrons are produced either by a heated cathode in it high-vacuum type of discharge tube, or by gas-discharge, in either airor hydrogen, using a cold cathode.Although some authors haveused the latter, a t the California Institute of Technology, wherethe most important recent work on electron-diffraction of vapourshas been done, the hot cathode is preferred.12 The electron-accelerating voltage is measured either by an electrostatic (or other)voltmeter, or else by a milliammeter in series wit'h it suitableresistance; the instrument is calibrated with the aid of electron-diffraction photographs obtained through thin gold foil, for whichthe space-lattice dimensions are accurately or by the useof ammonium ch10ride.l~ A method for studying electron diffrac-tion by gases in which a relatively low voltage, vix., 6,400 volts, isemployed has been described recently l5 ; it is not capable, however,of giving such accurate results as the high-voltage method.lo Ann.Physik, 1931, 8, 521.11 V. E. Cosslett, Zoc. cit., ref. (S), p. 981; H. cle Laszlo, Proc. Roy. Xoc.,12 L. 0. Brockway, Zoc. cit., p. 240.l a E. A. Owen and J. Iball, Phil. Nag., 1932, 13, 1020; M. C. Neuborger,1 5 P. G. Ackermann and J. E. Mayer, J . Chem. Physics, 1936, 4, 377.1934, A , 143, 672; L. 0. Brockway, Rev. Mod. Physics, 1936, €?, 231.2. Krist., 1936, 93, 1. lP IT. Boersch, Monatsh., 1936, 65, 33 I 68 GENERAL AND PHYSICAL CHEMISTRY.Since the quantity xij in equation ( 2 ) depends on the correspondinginteratomic distance ZiJ, it is evident that the positions of thediffraction rings, or the discontinuities in the photometric curve,will be related to the various atomic separations within the mole-cule, and it was shown by Mark and Wierl that the electron-diffrac-tion patterns could be used to determine int,eratomic distances ina molecule.The principle of the method is analogous t o thatpreviously used in connexion with the scattering of X-rays bygases : certain definite configurations are assumed for the atomswithin the given molecule, a i d the theoretical scattering curves arecalculated and compared with the experimental results.Theconfiguration for which the best agreement is obtained is regardedas being correct, and from this the interatomic distances aredetermined. When the molecule is relatively complex, the calcul-ations may become laborious, although certain simplifications(see below) can be made without involving serious error.Prom equation (4) it may be seen that it is possible to write + = Z+, wherei$ = (1 - F/Z)/[(sin8/3)/~]2 . . . ' (7)and consequently, as a first approximation, since P, which is alwaysless than 2, decreases as the scattering angle increases (p. 66),equation (1) can be put in the formFor a simple molecule, e.g. , carbon tetrachloride, the configurationof which can be taken with confidence as tetrahedral, thisapproximate equation for the coherent scattering can readily bewritten in terms of one parameter, e.g., xc-cI, and of the atomicnumbers of carbon and chlorine.By taking a series of arbitrarynumerical values of x, the corresponding values of .Ico. can be calcul-ated and the resulting hypothetical scattering curve, showing aseries of maxima and minima, plotted. From the electron-diffrac-tion photograph, or from the photometric curve obtained therefrom,the actual positions of the maxima and minima of scattering aredetermined and expressed in terms of (sine/2)/h, since 8 can becalculated from the corresponding displacement of these positionson the plate and the dimensions of the apparatus, and A from fireaccelerating voltage (equation 3). A comparison of the x valuesfor the calculated maxima and minima with the observed (sin 0 / 2 ) / hvalues gives an approximate relationship between these twoquantities which can be used t o calculate the atom-form correction4 (equation 7) in terms of x.The approximate -Ico. values, forvarious distances x, are now multiplied by the corresponding 4 a GLASSTONE : ELECTRON DIFFRACTION. 69each point to give the correct coherent scattering intensities, whichcan now be plotted against x ; the new values of the latter for themaxima and minima are then compared with the correspondingobserved (sin 0/2)/1 values, and the distance between the atoms,e.g., Zcc-cI, calculated by means of equation (2). If the configurationchosen for the molecule is the correct one, all the maxima andminima should give approximately the same value for the inter-atomic distance ; should this not be the case, however, the configur-ation is probably incorrect and a new one must be sought whichgives more satisfactory constancy.The correctness of any configur-ation can usually be determined by a general comparison of thediffraction rings and the calculated scattering curve for thatconfiguration. A further correction for incoherent scattering shouldbe made before the final comparison of observed and calculatedpositions of maxima and minima, but as this quantity diminishessteadily and has to be added to Ice., the positions of the inflexionsin the curve are not appreciably affected. The main objection tothe inclusion of .linco.is that its rapidly falling value tends to suppressthe maxima in the scattering intensity curves and makes theiridentification difficult : this has been overcome to some extent byplotting the total intensity multiplied by [(sin o/2)/hj2 against x,when definite maxima and minima appear in the curves.16When the configuration of a molecule can only be expressed interms of two parameters, e.g., for compounds of the type Y/- -"Y,then it is convenient t o chose these as the distance lx-y and thevalency angle a. The values of Ipo. are then plotted against x fordifferent probable values of a, and the general shape of the curveis compared either with the actual diffraction pattern or with itsphotometer record ; the value of a giving a calculated curve showingthe best agreement, as far as the positions and intensities ofmaxima and minima are concerned, is assumed t o be the correctone, and from the corresponding curve the distance Zx-y is cal-culated. Frequently it is not possible to be quite certain as towhich curve gives the best agreement, and then the molecular con-figuration is in doubt ;l7 this weakness of the method will certainlybe overcome in time, as the experimental technique is improved.When more than two parameters are required to define thedimensions and configuration of a molecule, e.g., in benzenederivatives, a large number of calculated intensity curves may have16 L.R. Maxwell, S. R. Hendricks, and V. M. Mosley, J . Chem. Physics,1935, 3, 699.17 See, e.g., L.R. Maxwell, V. M. Mosley, and L. S . Deming, ibid., 1934, 2,331.x70 GENERAL AND PHYSICAL CHEMISTRY.to be plotted. If something is known about the molecule, as isgenerally the case, then the calculations are limited to the mostprobable configurations in the fist place. A number of approxi-mations can also be made which do not seriously affect the accuracyof the final results but greatly simplify the calculations; some ofthese simplifications are mentioned below. l8One of the main sources of error in the application of the electron-diffraction method to the determination of interatomic distanceslies in the identification of the points on the photometric recordcorresponding to the maxima and minima of coherent scattering in-tensity.Since the continuously falling background tends to flattenout the photometric maxima and makes their accurate identificationdifficult, it is desirable to compensate for the background intensity ofthe photographic plate. One means of achieving this end is to printthe original plate by allowing the incident light to pass through aspecial revolving sector so designed as to compensate for fhe steepfalling off, from the centre outwards, in background blackening ofthe plate :I9 this method has the disadvantage that the relativeintensities of the various maxima and minima are altered, whereasa knowledge of such intensities is often of importance in determiningthe correct molecular configuration. An alternative method 20is to make a special compensating cell having the same shape asthe photometric background-scattering curve.This cell is filledwith a dark coloured liquid and light is allowed to pass through itand to fall on a photographic plate: the plate will, therefore,hecome fogged and the density of fogging will be almost the exactreverse of the background blackening of the original plate. Thelatter and the compensating plate are then placed together andprinted on to a third plate, giving a series of sharp dark and lightbands ; a photometer record of this shows clear maxima and minimaof coherent scattering. The compensation process described isparticularly valuable for giving accurate measurements of thepositions of the first few maxima, but its use is limited to thisregion; a t greater scattering angles the fall in the background andthe prominence of the maxima above it become so small that it isalmost impossible to construct a compensation cell that will permitof the separation of one from another with any accuracy. It is aremarkable fact, however, that the eye is more sensitive than anymechanical photometer, and it is possible by direct visual examin-For full discussion, see L.Pauling and L. 0. Brockway, J. Chern. Phylsics,lB F. Trendelenburg, Naturwiss., 1933, 21, 173; F. Trendelenburg and*O V. E. Cosslett, bc. cit., ref. (11).1934, 2, 867.E. Franz, W k . Veriff. Siemens-Konz., 1934, 18, 48GLASSTONE : ELECTRON DIFFRACTION. 71ation of the plates to detect ten or more diffraction maxima, afiwell as several minima.Owing to the intenbe blackening of thec*sntral spot, caused by unscattered electrons, however, the positionsof the maxima in the first one or %wo diffraction rings cannotgenerally be estimated correctly : this is mainly due to the St. Johneffect,Z1 a physiological phenomenon which militates against theaccurate estimate of the position of maximum density of a photo-graphic plate when the rate of decline of the background intensityis different on both sides of the maximum. The effect is alsooperative when two diffraction rings are close together ; under theseconditions the photometer and the calculated intensity curves haveSL “ shelf.” 22 Measurements liable t o be in error because of theSt. John effect should not be used in the final calculations, althoughthe approximate positions of the diffraction maxima may be usedfor purposes of qualitative comparison with the positions in thecalculated intensity curves, in order t o determine which of theserepresents the correct molecular configuration.Approximation Methods.-In applying the correction for theatom-form factor (equation 7), it is found that the value of 4approaches a constant as the scattering angle increases, so thatfor the higher orders of maxima and minima # may be replacedby 2, the atomic number, without appreciable error ; consequently,under conditiions such that visual identification of the positions ofmaxima and minima is satisf sctory, the approximate equation (8)can be used with reasonable accuracy.This simplification wasintroduced by and it has been subsequently confirmedthat the use of 2 instead of does not introduce any appreciableerror in the calculation of interatomic distances.Although someauthors use the simple form of the acattering-intensity equation inconjunction with the photometric method of identifying the positionsof inflexions, it has been shown by L. Pauling and L. 0. Brockway,lsin a very comprehensive study of the visual method of observingthe maxims and minima in diffraction photographs, that there isreason for supposing that because of the nature of the backgroundthe eye automatically corrects, a t least approximately, for thedifference between 2 and 4. Quite accurate results should, there-fore, be obtained by supposing the scattering factor of an atom tobe proportional to its atomic number, and finding the positions ofapparent maxima and minima of scattering, other than the firstone or two, by visual examination : under these conditionsincoherent scattering can be neglected in calculating the intensityvalues, The conclusion is borne out by the fact that, using this21 E.C. St. John and L. W. Ware, Astrophya. J . , 1916, 44, 35.22 I,, 0. Brockway and F. T. Wall, J . Anzer. Chem. SOC,, 1934, 56, 237372 GENERAL AND PHYSICAL CHEMISTRY.method, Pauling and Brockway found the C-C1 distance in carbontetrachloride to be *1*76A., whereas the careful work of V. E.Cosslett,l'$ 23 who applied corrections for the atom-form factor andfor incoherent scattering, and also compensated for backgroundscattering in determining the positions of the first few maximaand minima, led to a value of 1.74 -+ 0.02 A.The accuracy ofinteratomic distances obtained by electron-diffraction methods isgenerally stated to be 4 1%.A further approximation made by some workers, in order tosimplify the calculations for molecules containing both light andheavy atoms, is to ignore the scattering due to the lightest atoms,e.g., hydrogen; this is justified by the fact that the scatteringfactor of an atom is approximately proportional t o its atomicnumber. I n halogenobenzenes, for example, the intensity of thescattering caused by halogen-carbon and by halogen-halogen is solarge compared with that due to carbon-carbon, hydrogen-carbon,or hydrogen-hydrogen, that the corresponding scattering terms ofthese latter in the intensity equation (8) may be neglected withoutserious error.Using this simplified procedure and the visualmethod of examining the diffraction photographs, H. de Laszlo 24obtained 2-05 jI 0.01 A. for the C-I distance in p-di-iodobenzene,based on the positions of twelve scattering maxima, whereasS. B. Hendricks and his co-workers,25 who studied the photometricrecords of the plates, applied corrections for atom-form factors,and took into consideration the scattering from all the atoms,gave 2.00 A. (probably, a t least, 3 0.05). It may be concluded,therefore, that until there is a marked improvement in the technique:which permits of more accurate identification than is a t presentpossible of the positions of maxima and minima in the electron-diffraction photographs, the application of the approximationsdescribed can be generally justified.26Analytic Method-An analytical procedure which facilitates theaccurate interpretation of electron-diffraction photographs has beenproposed by S.H. Bauer 27 : the first step involves the differentiationof equation (8) so that the positions of maxima and minima of scat-tering are given by23 See also V. 12. Cosslett and H. de Laszlo, Na,ture, 1934,2 1 PTOC. Roy. SOC., 1934, A , 146, 690.2 5 S. B. Hendricks, L. R. Maxwell, V. L. Mosley, and26 See, however, L. R. Maxwell et nE., Zoc. cit. ref. (16).2' LOC. cit., ref. (4).J . Chem. Physics, 1933, 1, 649.134, 63.M.E. JeffersonGLASSTONE : ELECTRON DIFFRACTION. 73As before, a probable configuration is choscn with definite values ofI,; these are inserted in equation (9) together with a value of( ~ T c / A ) sin el2 representing the position of an observed inaximuinor minimum, and if the parameters chosen are correct, the sum ofthe terms will reduce to zero for every maximum and minimum.As it is improbable that the first model tried will be the right one,the equations will, in general, lead to a set of residuals, and Bauerhas shown how by a process of successive approximation it is possibleto obtain a set of Zij values which satisfy equation (9). These onlyrepresent the true inter-atomic distances, however, if the valueschosen arbitrarily a t the commencement of the calculation are closeto the correct ones, Only the positions of sharp, well-defined ringsmay be used in the calculation, and maxima associated with a“ shelf’’ or a low “trough” should be ignored.Although themethod may be useful in certain cases, the limitations are such as toprevent it from being generally applicable until improvements intechnique permit more complete diffraction patterns to be obtained.Radial Distribution Method.-L. Pauling and L. 0. Brockway 28have described a procedure, known as the “ radial distributionmethod,” for the examination of electron-diffraction rings which isrelated t o that used for the interpretation of X-ray diffractionpatterns obtained with It has the advantage of not re-quiring any assumption or previous knowledge concerning the con-figuration of the molecule or of inter-atomic distances.A distribu-tion function for scattering power is calculated representing, in termsof 1, the product of the scattering powers in volume elements,instead of by atoms, at a distance I apart. Since the electrons arescattered mainly by atomic nuclei, a maximum in the functionrepresents an inter-nuclear distance in the molecule equal to thecorresponding value of I ; thus the inter-atomic distance is deter-mined. The theoretical intensity equation (1) is based on theassumption that discrete atoms act as scatterers, but if the scatteringpower is regarded as spread over the molecule as a whole, thenintegration replaces summation, thusf , ~ o m 12D(1) sin sl dl .. . . I = k -~s4 * slwhere s is used for (4x11) sin 012, so that sl is identical with x. I nthis equation l20(1) represents the product of the scattering powersin all volume elements a t a distance I apart. Equation (10) beingwrittjen in the form&51 = kftLw ID(,!). sin 81. dl . . . . (11)28 J . Amer. Chem. SOC., 1035, 57, 2684.29 P. Zernike and J. A. Prins, 2. Physik, 1927, 41, 18474 GENERAL AND PHYSICAL CHEMISTRY.it mn be inverted, thusmorsind ds . . . . (13)For practical purposes the integral may be replaced very approxi-mately by a sumsin s,l D(Z) = XIn-- . . . . . (14)n 41in which one term appears for every ring in the diffraction pattern ;s, is the s value for the nth ring and In is its intensity.The latterquantity is estimated visually for each diffraction ring, and s iscalculated from its position determined by the visual method : it isthus possible to evaluate D(Z) for a series of I values, generally atintervals of 0.1 A. between 0 and 4 A. The positions of the maximain the curve of D(Z) against I give the distances apart of importantscattering centres in the molecule. The method can only be used,a t present, for the complete analysis of simple molecules in whichthere are few important inter-atomic distances involved, and itfails when two of these distances are close togother, so that the twoseparate maxima ,%re fused into one broad one.Applicatim.-Bond distances. The interest of electron-diffrac-tion measurements of gaseous molecules lies mainly in two directions:first, for the determination of interatomic distances with the objectof testing the Pauhg-Sidgwick rule 30 of the additivity of covalentbond distances and the possibility of throwing light on the type oflinkage in a given molecule; and secondly, for the investigation ofmolecular configuration and the evaluation of valency angles,With simple molecules, for which atomic radii obtained from theirband spectra are available, it is found that the electron-difbactionmethod gives results in good agreement with those expected, asmay be seen from the following data for the interatomic distancesin chlorine,l8 bromine,la iodine,26 and iodine monochloride.18Interatomic distances, A.f Molecule.Electron diffraction.Band spect>a.c1-Cl 2.0 1 1.99Br-Br 2-29 2.281-1 2.64 2-66I-CI 2-30 2.3 1so N. V. Sidgwick and E. J. Bowen, Ann. Reporb, 1931, 28, 385; N. V.Sidgwick, “The Covalent Link in Chemistry,” 1933, p. 64; L. Pauling,Proc. Nat. A c d . Sci., 1932,18,293 ; see also W. H. Rodebush, [I’mnR. FnmdaySoc., 1934, 30, 778; C. H. D. Clark, {bid., 1935, 31, 1017GLASSTONE : ELECTRON DIFFRACTION. 75Tho I-Cl distance calculated from the C1-C1 and the 1-1 value, onthe assumption of additivity, is 2-325A., which differs from theobserved results by no more than the experimental error.Until recently, the C-Cl distance in aliphatic compounds was 25.31accepted as 1.81-1433 A., approximately the same value beingfound in carbon tetrachloride, aa- and ap-dichloroethane, cis- andtrans-dichloroethylene, tri- and tetra-chloroethylene, and in carbonyland acetyl chlorides ; later work 18?20*23,32 has indicated that thebond distance is actually somewhat less, zlix., 1.76 &- 0.02 A., thisvalue having been obtained in all four chlor0methanes.~3 Furtherinvestigation of the six chloroethylenes has shown that in thesesubstances the 6 4 1 distance is less than in the chloromethanesand varies from one compound to another : the following distancesare given by L.0. Brockway, J. Y. Beach, and L. Pauling 34 :vinyl chloride, 1.69 A. ; ax-dichloro-, 1.69 A. ; cis-dichloro-, 1.67A. ; trans-dichloro-, 1-69 A. ; trichloro-, 1.71 A. ; and tetrachloro-ethylene, 1.73 A. These results have been interpreted 35 as im-plying resonance involving two states of the type >C--d-Cl and> & b d l , so that the G-Cl distance tends to approach that for adouble bond; in vinyl chloride the shortening should be greatest,since there is only one chlorine atom to take part, but in tetra-chloroethylene the effect of the double bond is divided amongst fourchlorine atoms and the bond distance should approach the normalsingle bond value.It may be noted that H. de Laszlo,36 in apreliminary communication, has given the C-C1 distance in bothtrans-dichloro- and tetrachloro-ethylene as 1.74 A. ; this authorhas also reported the length of the C-Br bond as 1.93 A. incarbon tetrabromide, 1.91 A. in trans-dibromoethylene and intetrabromoethylene, and 1.84 A. in dibromoacetylene ; beforethis, an almost constant distance of 2-05 -+ 0.05 A.had beenrecorded for the four brornomethanes, tert.-butyl bromide, cis-and t m?zs - dibr omoe t hy lene s , t ri br omoet h y lene , and c arb ony 1 andacetyl bromides.10~37 Similarly, the constant value of 2-283 1 R. Wierl, Zocc. cit., refs. (4) and (10); J. Hengstenberg and L. Brfi,Anal. Pis. Quim., 1932, 30, 341; S. B. Hendricks et al., Zoc. cit., ref. (25);R. W. Dornte, J. dmer. Chern. SOC., 1933, 55, 4126; J . Chem. Pkylsics, 1933,1, 566.32 H. Braune and S. Knoke, 2. physikd. Chem., 1933, B, 21,297 ; C. Degard,J. Pierard, and W. van der Grinten, Nature, 1935, 136, 142; C. Degard,Compt. rend., 1935, 201, 951; Bull. SOC. chim. Belg., 1936, 45, 15.33 L. E. Sutton and L.0. Brockway, Zoc. cit., ref. (4).34 J . Arner. Chem. SOC., 1935, 57, 2693.56 L. Pauling, L. 0. Brockway, and J. Y. Beach, ibid., p. 2705.36 Nature, 1935, 135, 474.97 R, W, Dornte, J. Chem. Physics, 1933, 1, 03076 GENERAL AND PHYSICAL CHEMISTRY.0.05A. for the C-I distance in methyl and ethyl iodides, and formethylene iodide, 3'9 38 has now been replaced by 2-12 A. in iodoform,2.10 A. in tram-di-iodo- and tetraiodo-ethylene, and 2.03 A. indi-iodoacetylene. It is clear from these results that further accurateinvestigation on the halogeno-ethylenes a,nd -acetylenes will haveto be undertaken before the suggestion of resonance involvingdouble-bonded halogen can be regarded as proved or disproved :it is important to bear in mind that the tendency to form thedouble bond might be expected to increase in the series C1, Br, I ,but there is hitherto no evidence that this is the case.In aromatic compounds the carbon-halogen distances are lessthan in the halogenomethanes, as the following results (in A.) show :-Ca1.--X.3 6 v 39 >Car,-X. 24$ 2 5 Additive. x = c1 1.76 1-69 1.76Rr 1.93, 1.91 1.88 1.91I 2.12 2-05, 2.00 2.10The observed values for the aliphatic compounds are in goodagreement with those calculated on the assumption of additivity ofcovalent bond distances by using the best data in the literature,aObut with the aromatic compounds a distinct shortening of thebond distance is evident. Here again resonance between two states,>C,,-X and >Car.rX, has been suggested35*41 to account for thedifference; resonance of this type, however, not only appears to beout of harmony with chemical reactivity and other properties ofaromatic halogen derivative^,^^ but the results seem to be capableof another interpretation.It may be noted in the first place thatthe > C,,.-Cl distance recorded is for hexachlorobenzene, in whichthe double-bond character can be divided amongst six atoms :the actual shortening should thus be very small. Further, the same>C,,,-Br distances have been found in di-, tri-, and hexa-bromo-benzenes, whereas a steady increase might have been anticipated.Prom general considerations, the difference between additive andobserved bond distances might be expected to increase through theseries C1, Br, I, but there is no evidence that it does so.It is notimpossible that the conjugated resonating system of single anddouble linkages in the benzene nucleus can bring about a " tighteningup " of external bonds, and so produce a small discrepancy from the38 L. Brh, Anal. Pis. Quirn., 1933, 31, 115.39 Unpublished, see L. 0. Brockway, Zoc. cit., ref. ( l l ) , pp. 260-261.40 Data from N. V. Sidgwick and E. J. Bowen, lor. cit., ref. (30), pp. 401,402; N. V. Sidgwick, op. cit., ref. (30), Chap. 111; L. Pauling, Zoc. cit., ref. (30) ;I;. Pauling and M. L. Ruggins, 2. Krist., 1934, 8'9, 205.*l See, e.g., H. P. Klug, J. Chem. Physics, 1935, 3, 747; N. V. Sidgwick, J.,1936, 533 (537).42 G. Baddelcy, G. M. Bennett, S. Glasstone, and B. Jones, J., 1935, 1827GLASSTONE : ELECTRON DIPFXACTION.77additive carbon-halogen distance ; there would then be no necessityto postulate resonance and double-bond formation. Some evidencefor this view is to be found in the fact that the Cal.-Car. distance,obtained from X-ray observations on crystals of durene and di-berm~yl,*~ are 1-47 A. compared with the value of 1.54 A. for theCal.-Ca,. bond. The electron-diffraction method gives the Cal.-Car.distance as 1-50 A. in di-, tri- and hexa-methyl benzene^,^^ whichis again less than the normal value. The suggestion might be madethat this was due to resonance 45 involving the structures >C-CH,and >C=GH,H, but if this were so, some difference in the C-Cdistance might be expected according to the number of methylgroups substituted in the nucleus.The C-F distance in methyl fluoride 46 is 1.42 A., in excellentagreement with the spectroscopic value (1.43 A.) and that based onadditivity (1.41 A.), but in carbon tetrafluoride 14* 22 the bond lengthis 1-36 A., similar values being found in dichlorofluoromethane anddich10rodiAuoroniethane.~~ It was a t one time suggested 22 thatthe shortening of the bond was due to the partially ionic characterof the C-F link resulting from the difference in the electronegativityof the two elements.It should be noted, however, that the ionicdistance Cj-F- is about 1.53 A., which is actually greater than thecorresponding covalent distance ; further, the dimensions of the ionsare such as to make the structure C4t(F-)4 irnpr~bable.~' Analternative view has been proposed by L.Pa~ling,~* who considersthat, in addition to the single-bonded structure of carbon tetra-fluoride, the molecule resonates among structures having an F- ionbound electrostatically to a CF3+ ion in which there is a double.. bond, as shown in the inset, so that a shortening of: F : the C-F bond distance, determined by the double-bond character which should be shared by all four 'F"C' :jl:- . bonds, would be observed. This resonance would:P: .. not be possible in methyl fluoride, since only onefluorine atom is present. If this explanation for thelength of the C-F bond in tetrafluoromethane is correct, then, it mustbe pointed out, the shortening of the distance is unexpectedly large.This fact is brought out more clearly by considering the bond dis-.... .. . ..43 J. AX. Robertson, Proc. Roy. SOC., 1933, A , 141, 594; 1934, A, 146, 473.44 P. L. F. Jones, Trans. li'araday SOC., 1935, 31, 1036.4 5 Compare J. W. Baker and W. S. Nathan, J . , 1935, 1844.46 Unpublished, see L. 0. Brockway, Zoc. cit., ref. ( l l ) , pp. 260, 261.4 7 N. V. Sidgwick, Ann. Reports, 1933, 30, 118; see also M. L. Huggins,Quoted by L. 0. Brockway and H. 0. Jenkins, J . Amer. Ghem. SOC.,Chem. Rez&zus, 1932, 10, 427.1936, 58, 2036 (2043)78 GENERAL AND PHYSICAL CHEMISTRY.tances in SiF4,22 PF3,22 and A S F ~ , ~ ~ which are as follows, the additivefigures being given below each measured value :Si-F 1.54 P-F 1.52 As-F 1.72Additive 1.81 1.74 1-85The maximum decrease due to the complete formation of doublebonds, ie., 10% of the single bond distances, would be 0.18,0-17, and0.18 respectively, whereas the actual differences are 0.27, 0.22, and0.13.The subject evidently requires further consideration. It hasbeen mentioned in a previous Report 49 that the discrepanciesbetween observed and additive distances in the hexafluorides ofsulphur, selenium, and tellurium 5 0 p 51 have been interpreted asimplying a tendency towards ionic linkage in all these bonds, but insulphur hexafluoride, at least, it is not possible to accommodatesix fluorine ions (radius 1.33 A.) about the S6+ ion (radius 0-3 A.) 5 2 ;even if the latter were extended to 0-55 A., so that the bond distancewas equal to the measured value, 1-88 A., this would still not bepossible.Resonance of the type postulated above, involving theelectrostatically bound structure SF5+F-, with one fluorine atomdoubly bound, might account for the results, but again the effects arevery large.With chlorides there appears to be no tendency for ionisation ofthe chlorine, since the GC1 distance in carbon tetrachloride isexactly equal to the additive value; hence the shortening of thebond in SiC1, (0-16 A.),10p22* 51 GeCl, (0.13 A.),lO> 53 SnCI, (0.09 A.),Io1 22PCl, (0.09 A.),22 and AsC1, (0.04 A.),22 must be explained in anothermanner. It was originally suggested 22 that this might be due to thedifference in the electronegativity of the two atoms forming thebond, but this view was disposed of by the fact that in the methylderivatives of silicon, germanium, tin, nitrogen, and sulphur thedistance between each of these atoms and the carbon atom is almostexactly equal to the additive value, in spite of the difference ofele~tronegativity.~~ An alternative explanation is that double-bond formation can occur between the halogen and the centralatom, as a result of the latter holding five, or more, pairs ofelectrons.22p54 There is no reason to believe that this increase canoccur in the flrst row of the periodic classification, and for theseelements the decrease is not found.In fact a discrepancy in theopposite direction appears to exist between the observed and the48 Ann. Reports, 1933, 30, 93.6o L. 0. Brockway and L.Pauling, Proc. Nut. Acad. Sci., 1933, 19, 68.51 H. Braune and S. Knoke, Zoc. cit., ref. (32).52 For data, see N. V. Sidgwick, Zoc. cit., ref. (47); M. L. Huggins, Zoc. cit.,53 L. 0. Brockway, J . Amer. Chena. Soc., 1935, 57, 958.5* L. 0. Brockway and H. 0. Jenkins, Zoc. cit., ref. (48).ref. (47)GLASSTONE : ELECTRON DIFFRACTION. 79additive distances for the 0-F and the 0-C1 bonds in oxygenfluoride and chlorine rnono~ide,6~ respectively ; the values are asfollows :0-F . 0-c1.Observed, A. . , . . , . 1.36 f 0.10 ; 65 1.41 f 0.05 l4 1.7 1 & 0.02 55 ; 1.68 f 0.03 66Additive, A. ...... 1.30 1.66The difference in the case of the fluoride may be due to experimentalerror, but it is believed not to be so for the 0-C1 bond; L. E.Sutton and L.0. Brockway 55 have suggested tentatively that theaccepted value for the radius of the singly-linked oxygen atom,0*66A., may actually be low by 0*06A., but it is neverthelessconcluded that the rule of additivity of atomic radii is only approx-imate. It is of interest to note here that the G O distance invarious compounds 551 5' has been found to be between 1.42 and1.45 A.,? in good agreement with the additive value 1.43 A. :this result lends support to the accepted oxygen radius. TheC1-0 distance in chlorine dioxide 58 is 1.53 A., a value not verydifferent from that to be expected for a double bond betweenchlorine and oxygen, vix., 1.48 A. The measurements have beenused to suggest a structure for chlorine dioxide involving tworesonance states, vix., : 0 C1: 0 : and : 0 : C1: 0 : ; the argumentsare based on the probable assumption that the 0 : C1 distance liesbetween those for a single and a double bond, since the three-electron linkage is generally equivalent to a single-electron bond.The distance between singly linked carbon atoms in aliphaticcompounds has been found 59 to be 1.60-165 A,, whereasbetween adjacent atoms in the benzene nucleus it is 1-39-1.42249 25* 44 The C=C double-bond distance in ethylene deriv-atives is apparently 1-38 34, 60, 61 in agreement with expectation(see, however, p.45). The C-C distance in acetylene lo anddiacetylene 62 is given as 1.20-1-22 A., the latter figure being. . . . . *** . .. . . . . . . . . . . . ...5 5 L. E. Sutton and L. 0.Brockway, Zoc. cit., ref. ( 4 ) .6 6 L. Pauling and L. 0. Brochvay, Zoc. cit., ref. (28), recalculated by tho57 D. C. Carpenter and L. 0. Brockway, J. Amer. C'hem. Xoc., 1936, 58,5 8 L. 0. Brockway, Proc. Nat. Acad. Sci., 1933, 19, 303, 874.59 R. Wierl, Ann. Physik, 1932, 13, 453; R. W. Dornte, loc. cit., ref. (31);80 L. 0. Brockway and P. C. Cross, Zoc. cit., ref. (57).61 R. W. Dornte, J. Chena. Physico, 1933, 1, 666.62 L. 0. Brockway, Proc. Nat. Acad. Sci., 1933, 19, 868.f The observed distance 1-34 &- 0.07 A. proposed for dimethyl and diethylradial distribution method.1270; L. 0. Brockway and P. C. Cross, ibid., p. 2406.L. 0. Brockway, Zoc. cit., ref. (46).ethers (L. Brh, Anal. Pis. Quirn., 1932, 30, 486) is probably in error80 GENERAL AND PHYSICAL CHEMISTRY.identical with the length generally attributed to this linkage; theobsemed value for the E N linkage in cyanogen 49 G2 and in aceto-nitrile,63 1-16-1.18 A., is also in excellent agreement with theadditive distance 1-16 A.The use of additive values for the carbon-nitrogen and the nitrogen-nitrogen bond in methyl azide 6* givescalculated electron-scattering curves in harmony with the experi-mental maxima and minima, and the C-N and N-0 distances innitromethane and in a-methylhydroxylarnine, respectively, con-firm the concept of a d d i t i ~ i t y . ~ ~It has been mentioned that the measured length of the singly-linked C-0 bond is very close to the additive value, but the measure-ments on the C=O bond were at one time confusing, since distancesof about 1.13 A.were reported in carbonyl and acetyl chloride andbromide 65 and in formaldehyde,66 as compared with the expectedvalue of 1-28 A. New measurements on carbonyl chloride,34however, give the C=O distance as 1-28 A., and a similar result isreported from observations on the dimeric form of formic acid.66Distances of the same order, 1-25-1-29 A., have been obtained bythe X-ray study of crystals of carbonates, oxalic acid, urea, and basicberyllium acetate G7 : it is somewhat surprising, however, to finda distance of 1.14 A. reported for the C=O bond in solid benzo-quinone,G8 The carbon-oxygen distance in carbon dioxide lo andin carbon oxysulphide14~ 65369 is 1.13 A., according t o electron-diffraction measurements, a result in agreement with the value cal-culated from Raman spectra and from X-ray scattering of theformer compound.The marked difference between this distanceand the additive C=O bond value of 1-28 A. has been attributed 7Oto resonance between the normal state O=C=O and the twoexcited states -O-CEO+ and + 0 3 Y O - , for then the carbon-oxygen distance would approach that for the CEO bond, namely,1.13 A. Similar resonating states apparently take part in thestructure of carbon oxysulphide and of carbon disulphide,68although there is less tendency for the formation of the - C 3 3bond, than for the corresponding oxygen link.-a3 L. 0. Brockway, J. Amer. Ghem. Soc., 1936, 58, 2516.64 L. 0. Brockway and L. Pauling, Proc. Nnt.Acad. Sci., 1933, 19, 860;see also N. V. Sidgwick, Trans. Paraday Soc., 1934, 30, 801.66 R. W. Dornte, J. Anaer. Ghem. Soc., 1933, 55, 4126.6 6 L. Pauling and L. 0. Brockway, Yroc. Nu,t. Acad. Sci., 1934, 20, 336:the results differ from those given by L. Hmgst,enberg and L. Brb, Zoc. cit.,ref. (31).6 7 For summary, see H. P. Klug, Zoc. cit., ref. (41), p. 750.6 8 J. M. Robertson, Proc. Roy. SOC., 1935, A, 150, 106.69 P. C. Cross and L. 0. Brockway, J . Cihern. Physics, 1935, 3, 821.' 0 L. Pauling, Zoc. cit., ref. (30)GLASSTONE ELECTRON DlFFRACTION. 81The length of the C-H bond as used by different authors variesfrom 1.06 to 1.10 A. in aliphatic 4137955*64 and from 1.06 to 1-14 A. inaromatic substances ; 18a25* 64 the additive distance is at least 1-06 A.,and agreement between the results is as good as could be expected,especially as the electron scattering of the hydrogen atom is sosmall that it is frequently neglected (p.72).Nolecular conjiqurutions. Electron-diffraction measurementshave been applied in a number of different ways to throw light onthe structures of various molecules. The diffraction pattern ofmethyl azide vapour is quite incompatible with IL ring structurefor the azide group, and a linear structure is indicated : 64 theconfiguration and distances in A. favoured may be represented by1.26 1.10 $/ N ~ N - N * This structure is taken to imply resonanceHaC 135°&150.between the forms -N=&=N and -N-kN, for the twonitrogen-nitrogen bond distances would then approach the values forN=N, i.e., 1-26 A., and N 3 , i.e., l-lOA., respectively.Thenitrogen valency angle of 135" & 15" is in reasonable agreementwith the value of 126" to be expected €or a tetrahedral nitrogenatom. Striking confirmation of the proposed structure for theazide group has been obtained from X-ray measurements oncrystalline cyanuric azide;71 the azide group is found to be linear,as in alkali azides, the bond distances between successive nitrogenatoms being 1.26 A. and 1.11 A. respectively. The nitrogen bondangle is, however, stated to be 114", and the C-N distance is givenas 1-38, compared with 1.47 A. indicated by bond additivity.The commonly written ring structure for diazomethane is rejectedfrom an examination of the electron-diffraction pattern given bythe vapour ; l4 the carbon-nitrogen and ni trogen-nitrogen distancesof 1.34 and 1.13 A.suggest resonance between the structuresH2C=kN and H26-kN. As might be expected, azomethaneis a conventional azo-compo~nd,~* CH,*N=N*CH,, the methylgroups being in the trans-position ; this formulation is compatiblewith the small dipole moment of pp'-dibromoazobenzene. Thecis- and trans-forms of other substances, e . g . , A2-butenes andpy-epoxybutanes,6° have been distinguished by means of electron-diffraction measurements.The carbon-oxygen and carboil-carbon distances in carbonsuboxide 149 64 have been given as 1-18-1-20 A, and 1.27-1.30 A.respectively, whereas the normal formula 0:C:C:C:O would requirethe double-bond values of 1-28 and 1-38 A.This result is interpreted7 1 (Miss) I. E. Knaggs, PTOC. Roy. SOC., 1935, A , 150, 576$2 GENERAL AND YHYSICAL CHEMISTItY.as implying resonance between the normal state and two excitedstructures kC-C=C-6 and O-C33-C=bJ so that all thebond distances would approach the values for trebly-bound atoms.Early work 72 on cyanogen and dincetylene indicated a non-linearstructure for these molecules, but later study62 has shown thisconclusion to be incorrect, a result in harmony with ordinarystereochemical considerations. The diffraction pattern forcyanogen agrees with a carbon-nitrogen distance of 1.16 A., thesame as the accepted additive value for the CEN bond, but thecarbon-carbon distance is only 1.43 A., which is somewhat closerto that for C=C than for cl-C.This suggests that the normalstate of cyanogen, N33--CE-N, which is the most important, isin resonance with other states, e.g., %=C=C=N and &=C=C=N,containing doubly-bound carbon atoms. It is of interest to recordhere that the terminal carbon-nitrogen distances in methyl cyanideand isocyanide have been found to be almost identical 63 (1.16 A.),thus providing strong evidence for the view that the form R*N=Cis an important contributor to the structure of isocyanides. Thestructure of diacetylene is believed to be analogous to that ofcyanogen: the carbon-carbon distances at the two ends of themolecule are 1.21A., as expected for the CEC bond.62 The dis-tance between the central carbon atoms is, as with cyanogen,1-43A., a result implying resonance, to some extent, of thenormal structure H*CEEC-C33H with the excited statesH&=C=C=C*H and H&C=C&H.Electron-diff raction results are incapable of distinguishing 73between the structures of NNO and NON for nitrous oxide, becauseof the small difference in the scattering powers of oxygen andnitrogen atoms, but the first of these formulae is generally favouredas being in harmony with the chemical properties, spectrum, anddipole moment.The extreme nitrogen-oxygen distance is found 73to be 2.38 5 0.06 A., which is in fair agreement with the sum ofthe bond distances for NEN, i.e., 1.10 A., and N=O, i.e., 1.22 A.,and also corresponds with the known moment of inertia of themolecule. The interpretation 709 74 of this result is that in nitrousoxide there is resonance between N=N=O and FTFl-0.Thethird possible state N-NGO is definitely excluded since thiswould reduce the shorter nitrogen-oxygen distance to 1.07 A., ar,dthe extreme distance would be 0.21 A. less than actually observed.f _--- + +7% R. Wierl, Zoc. cit., ref. (59).73 L. R. Maxwell et aZ., Eoc. cit., ref. (17).74 L. Pauling, Proc. Nat. Acad. Sci., 1932, 18, 498GLASSTONE : ELECTRON DIZ'FRACTION. 83The electron-diffraction patterns of nitrogen dioxide, tetroxide, andpentoxide have also been examined, but the results are notsufficiently precise to permit of an unequivocal interpretation : 73it is certain, however, that the linear model for nitrogen dioxide isnot correct, the nitrogen valency angle being between 90" and 120".The evidence for the planar configuration of benzene is so over-whelming that there is little need for further confirmation : it issatisfactory to note, however, that the scattering of electrons bybenzene derivatives can only be accounted for on this ba~is.l0*18*~4~4*The compound B,N,H,, known as boron amide, gives an electron-diffraction pattern similar to that of benzene, and the molecule isevidently a flat, regular hexagon with alternate boron and nitrogenatoms round the ring.75 The boron-nitrogen distance is uniformly1.47- & 0.07 A,, which is much smaller than that required for thesingly-linked B-N bond, vix., 1-59A., but reasonably close to theB=N value, 1.43A.; it is probable that in boron amide, as inbenzene, there is resonance between two alternative structures ofthe Kekul6 type, so that all the boron-nitrogen bonds are effectivelydouble.Mention may be made of the fact that X-ray diffractionmeasurements of crystalline cyanuric triazide 54 indicate that inthe cyanuric ring alternate carbon-nitrogen distances are 1.38and 1.31 A., corresponding approximately to the C-N and C=Nbond values, 1.47 and 1.32 A., respectively ; in spite of the apparentsimilarity to benzene and to boron amide, there is in this caseevidently no resonance, the single and double bonds occupyingfixed positions. Electron-diffraction measurements have beenused to determine the structure of pentaborane, B,H9 7 6 ; itappears to consist of a square four-membered ring, made up ofthree BH, groups and a boron atom, the fifth boron group, as BH,,being attached to the latter, almost coplanar with the ring.The structure of nickel carbonyl, Ni(CO),, presents an interestingproblem which has now been solved by means of electron diffraction.The dipole moment of this compound is zero, so that it is not cyclic,as had been suggested, but the four CO groups must either be a t thecorners of a square, that is planar, or else arranged tetrahedrally.The diffraction pattern definitely favours the latter structure, 77in agreement with Pauling's views.The carbon-oxygen distanceis 1-15 A., which is close to the value in carbon monoxide and to thatexpected for the C Z O bond; hence the triply linked carbonylstructure probably predominates in nickel carbonyl, as it appearsto do in carbon monoxide.Paraldehyde has been shown to con-7 6 A. Stock and R. W i d , 2. anorg. Cltem., 1931, 203, 228.76 S. H. Bauer and L. Pauling, J . Arner. Chm. SOC., 1936, 68, 2406.7 7 L. 0. Brockway and P. C. Cross, J . Chem. Physics, 1935, 3, 82984 GENERAL AND PHYSICAL CHEMISTRY.sist of a staggered six-membered ring of alternate oxygen andcarbon atoms : the angles are all approximately tetrahedral.15~ 78Valency angles. Measurements with carbonyl chloride andbromide 65 are in harmony with an angle of 110" & 5" between thetwo carbon-halogen bonds in each case; the same result was foundfor the angle between the carbon-carbon and carbon-halogenbonds in acetyl chloride and bromide.65 The experimental valueis close enough to 109" to confirm the tetrahedral configuration ofthe carbon atom concerned; the value of 125" & 10" found for theangle between the C-0 and the other bonds also provides supportfor this The angles between the C-C1 bonds inmethylene chloride and in chloroform were at one time believed tobe markedly in excess of the tetrahedral value :lo* 79 more recentwork 55 has shown these results to be in error, and it now appearsthat the angles are 111" & 2".The oxygen bond angle in chlorine monoxide 55 is 111" & 2", andin oxygen fluoride 55 it is somewhat less, 105" & 5" or 100 & 3" ;in dimethyl ether 55t the oxygen angle is 111" & 4", allowing forfree rotation of both methyl groups about the C-0 bonds, and aclosely similar result has been obtained with a-methylhydroxyl-amine.3* These results might a t first sight be taken as supporting thetetrahedral value as the natural oxygen valency angle, but this con-clusion may not be justified.The distance between the chlorineatoms in chlorine monoxide, 2.82 A., is appreciably less than the nor-mal distance of closest approach of two non-bonded chlorine atoms,Blvir,., 3.7 A. ; similarly in dimethyl ether the carbon atoms areonly 2-39A. apart, although the minimum distance of approach ofnon-bonded atoms s2 is normally 3.4A. It is evident that in boththese compounds there must be considerable repulsion between thechlorine atoms and the methyl groups, respectively, so that theobserved valency angles may well be greater than the "natural"value.It may be noted that the approach of the methyl groups indimethyl ether is not sufficient to interfere with free rotation, evenafter allowing an envelope 0.5 A. thick 83 round each hydrogenatom. 5", andthe same factor of repulsion of the groups attached to the oxygenatom arises here as with the compounds just considered. TheThe oxygen angle in dioxan is stated t o be 110"7 8 D. C. Carpenter and L. 0. Brockway, Zoc. cit., ref. (57).79 L. Bewilogua, PhysikaZ. Z., 1931, 32, 865.80 The value given by L. Br6, Anal. Pis. Quirn., 1932, 30, 486, is probably81 R. (2. Dickinson aiid C. Billiukc, J. Ainer. Chern. Xoc., 1928, 50, 764;82 S. B. Hendrieks, ibid., 1931, 7, 430.a3 N.V. Sidgwick, Ann. Reports, 1932, 29, 70.incorrect.M. L. Huggins, Chern. Reviews, 1932, 10, 447GLASSTONE : ELECTRON DIFFRACTION. 85observations with dioxan show that in the vapour state, a t least,the Z, or trans-, form predominates; this configuration agreeswith the zero dipole moment of the liquid. In pp'-di-iododiphenylether the oxygen valency angle,l6 according to elect,ron-diffractionresults, is 118" j, 3"; as previously indicated,g4 a larger anglethan in aliphatic ethers is not unreasonable. The ordinary methodfor interpreting electron-diffraction data does not permit of adetermination of the configuration of sulphur dioxide with suffi-cient certainty to give the sulphur valency a11gle,~9 but by meansof the radial distribution method the distance between the twooxygen atoms, as well as between sulphur and oxygen, can beevaluated, a t least approximately.The results indicate an angleof 124" &- 15°728 in agreement with the value obtained from Ramanand infra-red spectra. This angle and the sulphur-oxygen distancesuggest that in sulphur dioxide there are a t least two resonatingstructures, vix., 6-6=0 and O=$-O. In sulphur vapour itself,containing complex molecules, the sulphur angle is about 100".85Apart from the uncertain interpretation of the observations onmethyl azide (p. 81) and on azomethane, which suggest a valuegreater than the tetrahedral, there is no definite quantitative evidencefrom electron scattering concerning the valency angle of tervalentnitrogen J in PCl,, PF,, and AsCl,, however, the angles are 100" & 2",99" 5 4" and 101" j, 4", respectively.22 According to calculationsby wave mechanics,*6 the bond angles in nitrogen and its congenersin the tervalent state should lie between 90" and 109" 28', theformer value being approached as the atomic weight increases ; theresults quoted above are in general agreement with this expectation,since there is reason to believe that the nitrogen angle is close tothe tetrahedral value.*' I n nitroniethane the valency angle hasbeen found to be 127" & 3" ; 34 this is in harmony with the structure-Nq0 as one of the resonating forms of the nibro-group, the + Onitrogen, in the quadrivalent state, being tetrahedral.S. G.8* Ann.Reports, 1935, 32, 132.8 5 L. R. Maxwell, V. M. Mosley, and S. B. Hondricks, PhysicaZ Rev., 1936,8 6 L. Pauling, J . Amcr. Chem. SOC., 1931, 53, 1367.87 See, e.g., R. €3. Barnes, W. S. Beiiedict, and C. M. Lewis, Physiccd Rev.,50, 41.1934, 45, 34786 GENERAL AND PHYSICAL CKELWSTR;Y.5. CHEMICAL KINETICS.Though numerous ideas in the subject of chemical kinetics havebeen profitably pursued again during the current year, we mustrestrict attention in the present report to the major developments inthe study of thermal reactions in homogeneous systems. The yearhas witnessed important advances in theory and an increased rateof accumulation of experimental material.The Quanta1 Theory of Chemical Change.lThe quantal theory of chemical change, which was briefly out-lined in last year’s report,2 has been in itself refined and elaboratedby thermodynamic 3,4 and statistical 5 ~ 6 methods, and has beenapplied with marked success to a number of diversified problems,including diabatic unimolecular transformations,! ternary atomiccollisionsYs calculation of the energy ol triatomic s y s t e m ~ , ~ ~ re-actions between hydrogen atoms and moleculcs,lo* reactionsbetween hydrogen and the halogens,ll the ortho-para conversionof hydrogen under the influence of cx-particles,l2 the radiochemicalsynthesis of hydrogen brornide,l3 reactions involving four atoms,14and the addition of atomic and molecular halogens to ethylene andits derivatives.15 That the theory is capable of accommodatingsuch diversity without distortion of its general features is in itselfsignificant.The object of the quantal theory of chemical change is anambitious one, namely, to predict the absolute magnitude of thevelocity of chemical reactions of all kinetic orders in homogeneousand heterogeneous systems.Though still in its infancy, it may besaid to have succeeded, at least as far as elementary chemicalchanges are concerned. Its present protases will doubtless be1 We adopt the words “ quantal ” and “ quantally,” following the sug-gestions of C. G. Darwin (Nature, 1936, 138, 908), instead of the cumbrous‘ ‘ quantum-mechanical,’ ’ etc.E. A. Moelyn-Hughes, Ann. Reports, 1935, 32, 89.M. G. Evans and M. Polanyi, l‘rams. Paraday SOC., 1936, 32, 1333.4 W.H. Rodebush, J. Chem. Physics, 1936, 4, 744.L. Farkas and E. Wigner, Trans. Faraday SOC., 1936, 32, 708.H. Eyring and numerous collaborators (vide infra).A. E. Stearn and H. Eyring, J . Chem. Physics, 1936,3, 778.J. Hirschfelder, H. Eyring, and N. Rosen, ibid., 1936, 4, 121.* 13. Eyring, H. Gershinowitz, and C. E. Sun, ibid., p. 786.l o J . Hirschfelder, 13. Eyring, and B. Topley, ibid,, p. 170.11 A. Wheeler, B. Topley, and H. Eyring, ibid., p. 178.l a H. Eyring, J. 0. Hirschfelder, and H. S. Taylor, ibid., p. 479.l4 W. Altar and H. Eyring, ibid., p. 661.l6 A. Sherman, 0. T. Quimby, and R. 0. Sutherland, ibid., p. 732,Idem, ibid., p. 570MOELWYN-HUGHES : CHEMICAL KINETICS. 87replaced by others less drastic, but there can be no doubt that itsfundamental conception constitutes a permanent acquisition tothe science of chemical dynamics.The theory treats the approachof reactant molecules, their interaction during chemical change,and their separation thereafter as (z continuous process, depicted bythe movement, in phase space, of the representative point for thesystem. Occurrence of chemical change coincides with the passageof tillis point over an energy barrier, the height of which corresponds,roughly, with the energy of activation. Experiment demandsthat the velocity of chemical change shall generally be expressibleas the product of two terms [equation (I)], of which the first, ifnot absolutely independent of temperature, is far less dependentupon it than is the second term :(1) k* = A .e - E A / f < y ’ . . . .The problem thus resolves itself into a determination of the twoquantities, A and EA, which, although not strictly separable, mayconveniently be treated as if they were. Ea must be evaluatedquantally, A either quantally or classically according to circum-stances. A is determined by the average velocity with which therepresentative point surmounts the col.The quanta1 theory of reaction velocity has been applied in detailto reactions between two atoms, reactions between atoms anddiatomic molecules, and to reactions between two diatomic mole-cules. In order t o illustrate the principles involved, we shallselect for discussion a reaction of intermediate complexity, namely,that occurring between an atom, a, and a diatomic molecule, bc :@ + @-@ _3 @****@****@ 4 @-@ + @f*Tab Tbc”f---3f---,Tab TbcThe method of determining the height, E,, of the pass was outlinedin last year’s report.2 It is due to H.Eyring and M. Polanyi,16whose treatment we have now to reconsider, paying attention tosome of its finer points. For generality, rectangular co-ordinatesmust be replaced by co-ordinates inclined at an angle +, such thatsin 4 = - (mamb/(ma + mb)(mb + mc)}* * . (2)The resulting model enables us to represent the potential energyof the triatornic system, pictorially at least, as a function of a specialspatial co-ordinate, which is usually termed the reaction path(see figure). Now the height (Zm) of the summit is the differencebetween the potential energies of the reactants (at the point x)and the activated complex (at the point y), both being, of course,16 5.physikal. Chew., 1031, B, 12, 27088 GENERAL AND PHYSICAL CHEMISTRY.static values. According to the quanta1 theory, both systemspossess residual energies, which, at; the absolute zero of temperature,are S&, and Z-ihv* respectively. I f , therefore, we choose to defineour energy of activation (E,) as the difference between the actualDecomposition co- ordinate.energies of reactant and activated systems a t T = 0, we have therelationOf the quantities in this equation, v, and E, are known experimentallyfrom spectroscopic and kinetic data respectively; Em and v* maybe calculated from the theory under discussion.Since activated complexes usually contain an odd number ofelectrons and are not molecules in the ordinary sense, the vibrationfrequencies which characterise their internal motions are notamenable to direct measurement, but must be obtained by indirectmeans.is a directapplication of the classical equations of motion to the movementof a point particle in the neighbourhood of the co1, where the forcefield is assumed to be expressible by a function of the formE, = Em - (C$hv0 - X-$hv*) . . . - (3)The method commonly adopted 16* 17* l 8 1 8* l 1 pI n this equation) 8 denotes the small difference produced in thepotential energy (v), in the interatomic separations (rab and Tbc)and in the deformation angle (a) for systems displaced very slightlyfrom the equilibrium system, for which = Em; Tab = r*ab;rbc = r*bc; The desired frequencies may be calculatedfrom a knowledge of the masses and of the force constants (f).An important distinction is afforded by this analysis between thebehaviour of normal triatomic molecules and activated triatomiccomplexes, since one of the f values for the latter is negative, with1 7 H.Pelzer and E. Wigner, ibid., 1932, B, 15,445.18 Cf. the treatment of stable triatomic systems, discussed by W. G. Penney0: = 0.alld G. B. B. If. Sutherland, Proc, Roy. SOC., 1936, A , 156, 654MOELWYN-HUGHES : CHEMICAL KINETICS. 89the result that one of the frequencies of transverse vibration (whichwe shall call v-) has an imaginary value. The frequency ofdeformation (va) and the frequency of the other transverse motion(vT) have real values for complexes as for normal molecules.I n order t o illustrate the principles involved, we shall considerthe specific example discussed in last year's Report,2 attempting,a t the same time, to show the relation of the new theory to the old,and of both to the facts.The Kinetics of the Reaction Br + H, --j BrH + H.-(1)Experimental facts.The results of M. Bodenstein and S. C. Lind l9yield the following values for the constants of equation (1) :-B = 1.20 x 10-lo C.C. per molecule-second; EA == 17,640 cals./g.-mol. Extending the temperature region, and employing a totallydifferent technique, F. Bach, K. F. Bonhoeffer, and E. A. Moelwyn-Hughes 2o found A = 1-17 x 10-lo and EA = 17,740, thus fullysubstantiating the earlier work.I n round figures, therefore, andfor the temperature region T = 576' 2 75'Abs., A has a value of1.2 x 1 V 0 and Ea of 17,700 in these units.According to the collision theoryin its simplest form, the rate of reaction is equated to the fractionof the total number of collisions for which the energy exceeds acritical value E, the theoretical expression for the velocity constantbeing k* = (ra + rbc)2(8X~T/EL)le-~'~~. It follows that Ea = E- $RT;hence the kinetic value of (ra + rbc) is 1.57 A. In this manner,M. Trautz 21 found values of the same reasonable order of magnitudefor the present reaction and for many others, thus establishing theclassical collision theory for gases. If we regard the energy of activ-ation as a critical value of the component of the relative kineticenergy referred to the line of centres,22 we may proceed one stagefurther along classical lines.The above theoretical expressionmust now be multiplied by the factor (1 + EIRT), so that, towithin less than 3%, E = EA + ART. Solving for (ra + rbc)now gives us the value 0-38 A., showing that the greater the imposedrestriction on the direction of approach, the sma'ller becomes thetarget area derived from kinetic measurements. Hence the classicalinterpretation is consistent, though inadequate.(3) Quanta1 interpretation. With a constant resonance factorof 0-14, we have seen that Em = 22,100 cals. For the sake ofsimplicity, we now assume a strictly linear structure for the threeatoms throughout the chemical change, i.e., we take fa of equation(2) Classical interpretation.l9 Z.physikal. Chem., 1906, 57, 168.a. Ibid., 1934, B, 27, 71.21 2. anorg. Chem., 1916, 96, 1.23 It. C, Tolman, " Statistical Mechanics," New York, 192790 GENERAL AND PHYSICAL CHEMISTRY.(4) as zero. We then find -&hv,. = 2,730 and - iihv- = 160; &hvbci s known t o be 6,180 cals./g.-mol. Henoto, by equation (3), Eo ==18,650 cals., which, though not directly comparable with E d , liesvery near to it. From the imaginary frequency v-, we may estimatethe value of E. Wigner’s factor,23 for quanta1 transits (“ tunnelling ”),which is [l - 4 ( $ h ~ - / k T ) ~ ] = 1.0052. The correction thusamounts in the present case to about 0-5%, and can be ignored.The application lo.l1 of H. Eyring’s general formula 24 to thepresent case gives results in agreement with previous treatments,l7~and proceeds as follows. The formula for the velocity constant isThe transmission coefficient ( K ) is the average value of the absolut’eprobability that the representative point, having reached the 001,shall pass over i t ; its, maximum value, according to classicaltheory, is 112. Leakage through the potential barrier may increaseK by an amount given approximately by the Wigner factor. c isa, symmetry term, which is integral for both reactant and activatedsystems. I n the following account, we shall include all these factorsin the term K*, which must be of the order of magnitude of unity.v* is the average velocity of transit over the barrier, and will begiven the classical value of dSk’P/rp*.The partition function,Pa, for the atom, a, is due entirely to translation, and is therefore(2.xmaET)3’2/h3. The corresponding function for the molecule ,bc, includes additional terms to account for rotation and qiiantisedvibrations ; Fbe is accordingly-___IThe nine degrees of freedom for the reactive complex, taken inorder, are three for translation of the complex as a whole, two forrotations, one for the symmetrical transverse vibration, two forthe degenerate deformation, and one for the relative translatorymotion of the component parts of the decomposing complex,referred to the ordinate of decomposition. These motions, con-sidered as separable, enable us to write23 Z.physiknl. Chem., 1932, B, 19, 303,z4 J . Chenz. Phyeica, 3935, 3, 107MOELWYN-HUGHES : CHEMICAL KINETICS. 91Substituting in equation (5), and combining the result with equation( 3 ) , we have the theoretical expression for the velocity constantp is hI2ET.relationEm, of the niountsin pass (No being the Avogadro number) :Comparison with equation (1) leads to the followingbetween the Arrhenius constant, Ea, and the height,Ea = Em - &RT - *iVohVbe coth pubc + $Nohv+ coth PV I- +Nohv,coth pu, . . (7)Introducing the numerical values quoted above, we obtain thefollowing theoretical results : Ed = 18,090 cals./g.-mol., andA = 1.11 x 1W0 C.C. per molecule-second. Both are in goodagreement with experiment.A.Wheeler, B. Topley, and H. Eyring l1 have made calculationson the same reaction, assuming the resonance factor to be 0.20,and making allowance for the deformation of the triatomic system.The theoretical value of A [equation (l)] so obtained is 1.06 x 10-lo,so that the quanta1 theory, like its classical predecessor, guaranteesa fairly reasonable value for the collision frequency. The reasonin both cases is to be traced to the high magnitude of interatomicrepulsive forccs a t low separations. On the other hand, it is nowfound that E,rA = 25,100 and that IN, = 1,309 cals./g.-mol. Sub-stituting into equation (7) , the calculated value of tho Arrheniusactivation energy, ELI, becomes 23,630. Thus the present methodof evaluating the energy of activation is sensitive to the proportionof the total potential energy which is ascribed to the Coulombicterms-which raises the following questions.Is the Londonprocedure for estimating the potential energy of triatomic con-figurations in itself a sufficiently good approximation ? Can we, asone of the authors asks, regard the existence of a dip round the col(shown by the dotted line wqx in the figure, p. 88) as a virtue or adefect in the Eyring-Polanyi theory? If the activated complexsiiffers marked bending, how far are we justified in constructingan energy surface in terms of oizly two spatial co-ordinates ? Whilethese and similar questions must await authoritative answers, themethod may confidently be applied as a self-consistent, semi-empirical procedure, justified a posteriori.Reactions in the Gaseous Phase.Increasing attention is being paid to simple processes, especiallythose involving Eree atoms, and to the elucidation of the detaile92 GENERAL AND PHYSICAL CHEMISTRY.simultaneous mechanisms which together are responsible for thenet observed velocity of the decomposition of polyatomic molecules.A.Parkas 25 has studied the exchange of hydrogen and deuteriumatoms between the corresponding molecules and ammonia. Therate-determining step is D $- NH, __z NH,D -t H, for whichEd = 11,000, and the absolute rate is about 35 times as slow asthat of the reaction D + H, --+ DH + 13. The exchange re-actions of water and of methane have similarly been investigatedby A.Farkas and H. W. Melville.26 W. Heller and M. P~lanyi,~'measuring the rate of reaction between sodium atoms and numerousinorganic halides, find an instructive parallelism between the velocityand the restoring force-constant as estimated from the Ramanfrequency of the halide molecule. En has a value of about 6,000for the reaction 28 0 + 0, -+ 20,. Atomic mechanisms are verycommon in photochemical reactions, as for example, in the chlorine-sensitised oxidation of chloromethane, where the step C1 + CH2C1,--+ HC1 + CHC1, has been detected.29The reaction D, + HC1--+ DH + DCl proceeds as a homogeneousbimolecular with En = 27,000. Equally simple examplesare afforded by the rate of formation31 and decomposition31aof deuterium iodide, D, + I, 2DI.The data for these reactionsare summarised in Table I.M. Bodenstein and W. Kraus have made a complete study ofthe reaction of nitric oxide with oxygen, chlorine, and brominemolecules.32 Essentially t,ermolecular mechanisms control thereactions between nitric oxide and hydrogen,33 and between oxygenatoms and molecules.28 I<. H. Geib's conclusion (1924) that mostof the reactions undergone by the hydroxyl radical are termolecularhas been confirmed by A. A. Frost and 0. Ol~lenberg.~~The chain theory has again been applied to EL number of reactions,including the oxidation of methane,35 ~entane,,~ a~etylene,~'25 J., 1936, 26.27 Trans. Paraday SOC., 1936, 32,633.28 A. Eucken and F. Patat, 2. physikal. Chern., 1936, B, 33, 459.29 W.Brenschede and H. J. Schumacher, ibid., 1936, A , 177, 245.30 P. Gross and H. Steiner, J . Chern. Physics, 1936, 4, 165.31 K. H. Geib and A. Lendle, 2. physikal. Ckern., 1936, B, 32, 463.31a J. C. L. Blagg and G. M. Murphy, J . Chern. Physics, 1936, 4, 631.32 2. physikal. Chem., 1936, A , 1'75, 294.33 C. N. Hinshelwood and J. W. Mitchell, J., 1936, 378.34 J . Chem. Physics, 1936, 4, 642.3 5 H. Sachsse, 2. physikal. Chem., 1936, B, 33, 229; W. A. Bona and J. B.Gardner, Proc. Roy. SOC., 1936, A , 154, 297; R. G. W. Norrish and S. G.Foord, ibid., 1936, A, 157, 503.2 G Proc. Roy. SOC., 1936, A , 157, 625.36 A. Aivazov and M. Neumrtnn, 2. physikal. Chem., 1936, By 33, 319.37 E. W. R. Steacie and R. 0. Macdonald, J . Chern. Physics, 1936, 4, 75MOELWYN-HUGHES : CHEMICAL KINETICS.93TABLE I.*EA for IZT*In E* for R'*In -theH 5 1. theH 5Reaction. reaction. k~ \ pD' Reaction. reaction. ku *pz'H + H2 5,500A 1,050 H + N20 13,800D 0'D + D,D + D2Br + D,Na +- HC1 6,100C 300 H2 + H2 + NO 45,00033 0Na + DCl D, + D2 + NO42,5OO3l 580 H + H + H OG 0 H2 + I2D2 + I 2D + N2OH + ND,D + PJ3,n + H2 4,850A 1,160 D + NH, 10,80026 1,230Br + H, 17,70020 1,440 H + PH, 14,400E 60043, lOOF 1,490 c1+ H2 ca. 6,000B 1,400 H, + C2H,c1+ D2 D2 + C2H4D + D + D40,000 31a 1,240 HI f HIDI + DI* After H. W. Melville, Science Progress, 1936, No. 123, p. 499.A. A. Farkas and L. Farkas, Proc. Roy. Xoc., 1935, A , 152, 124.B. G. K. Rollefson, J . Chem. Physics, 1934, 2, 144.C. C. E. H. Bawn and A. G.Evans, Trans. Paraday SOC., 1935, 31, 1932.D. H. W. Melville, J., 1934, 1243.E. H. W. Melville and I. L. Bolland, Proc. Roy. SOC., in press.F. R. A. Pease and A. Wheeler, J . Amer. Chem. SOC., 1936, 58, 1665.G. I. Amdur, ibid., 1935, 57, 856.benzeneF8 rneth~lamine,~~ and silane,4°g 41, 42 and the decompositionof alkali azides 43 and divinylPolymerisation processes formed the topic of a discussion organisedby the Paraday Society. The kinetic aspects of the general treat-ment have been discussed by A. Abkin and s. Medvedev ; C. E. H.Bawn, J. E. Carruthers, and R. G. W. Norrish; H. Dostal and H.Mark; K. Freudenberg; G. Gee; M. W. Melville and S. C. Gray;E. A. Moelwyn-Hughes; M. W. Perrin; E. K. Rideal; G. Salomonand W. F. K. Wynne-J~nes.~~ The earlier theory of polymerisationreactions has been generally developed, and modified 46 to allowfor the specific influence of promoters and inhibitors.The decompositions of azomethane?' ethylene oxideY4* ethyl-38 3%.M. Griffith and S. G. Hill, Trans. Ir'araduy Xoc., 1936, 32, 829.39 H. J. Emelhus and L. J. Jolly, J . , 1936, 1524,*O P. S. Schantarowitsch, Acta Physicochim., U.R.S.S., 1935, 2, 673.41 H. Gutschmidt and K. Clusius, 2. p h y s i b l . Chem., 1935, B, 30, 265.4 2 H. J. Emelbus and K. Stewart, J., 1935, 677.43 W. E. Garner and D. J. B. Marks, J . , 1936, 657.4 4 H. A. Taylor, J. Chem. Physics, 1936, 4, 116.45. Trans. Paraday SOC., 1936, 32, pp. 1-412.46 G. Gee and E. K. Rideal, ibid., p. 666; Proc. Roy. SOC., 1936, A, 153,4 7 D.V. Sickman and 0. K. Rice, J. Chem. Physics, 1936, 4, 236.4 8 C. J. M. Fletcher and G. K. Rollefson, J. Amer. Chem. SOC., 1936, 58,2129; R. V. Seddon and M. W. Travers, Proc. Roy. SOC., 1936, A, 156, 273;H. W. Thompson and M. Meissner, Trans. Paraday SOC., 1936, 32, 1451.11694 GENERAL AND PHYSICAL CHEMISTRY.amine 49 and diethyl ether have all been carefully rc-examinedunder wide ranges of conditions. I n connexion with the lastreaction, L. A. K. Staveley and C. N. Hinshelwood 51 have deter-mined the conditions under which nitric oxide may act either as acatalyst or as an inhibitor. The reaction B,O, -> F, + 0,proceeds by a simple unimolecular mechanism.52 The kineticsof the decomposition of benzylideneazine and o-azotoluene 53yield values of EA which are consistent with the greater stabilityof the azo-nitrogen bond, compared with the azine bond.Thehomogeneous unimolecular deconlposition of silane 53a is moreconsistent with the mechanism SiH,+ SiH, + H,, proposedby Kassel (1933), than with the mechanism SiH, ---+ SiH, + Hanticipated by analogy from nice and Dooley’s work (1934). Acommon energy of activation has been found for the homogeneousunimolecular decomposition of tert.-butyl and tert. +my1 ~hlorides.~~bTwo further examples may be added to the not very abundantinformation available j 4 3 on the direct experimental comparisonbetween the kinetics of reactions in the gas phase and in solution.The unimolecular racemisation of 2 : 2’-diamino-6 : 6’-dimethyl-diphenyl has roughly the same velocity and the same Ed valuein the homogeneous gas phase as in solution in diphenyl ether:Me Me <2H52 -+ cx3 NH, MeThe same observation applies to the bimolecular addition ofacraldehyde to cyclopentadiene in the gas phase 56 and in benzenesolution.Reactions in Solution.The greater difficulties in the way of interpreting the kineticsof reactions in solution are to some extent offset by the greater49 H.A. Taylor and J. G. Ditman, J . Clzem. Physics, 1936, 4, 212.60 E. W. R. Steacie, W. H. Thatcher, and S. Rosenberg, ibid., p. 220;5 1 Proc. Roy. SOC., 1936, A , 154, 335; J., 1936, 812.52 P. Frisch and H. J. Schumacher, 2. physikal. Chem., 1936, B, 34, 322.53 G. Williams and A. S. C. Lawrence, Proc.Roy. Xoc., 1936, A , 156, 444.5 3 ~ T. R. Hogness, T. L. Wilson, and W. C. Johnson, J . Amer. C‘lzem. Xoc.,53b D. Brearly and G. 13. Kistiakowsky, ibid., p. 43.54 E. A. Moelwyn-Iluglies, “Kinetics of Reactions in Solution,” Oxford, 1933.6 5 G. B. Kistiakowsky and W. R. Smith, J. Amer. Chem. SOC., 1936, 58,1042; cf. C. C. Li and R. Adams, ibid., 1935, 57, 1565; VV. H. Itodebush,J . Chem. Physics, 1936, 4, 744.56 CX. B. Kistiakowsky and T. R. Lachor, J . Amw. C‘hem. Soc., 1936,58, 123.57 A. Wassermann, J., 1936, 1027.C. J. M. Fletcher and G. K. Rollofson, Zoc. cit., ref. (48). .1936, 58, 108NOELWYN-HUGHES : CHEMICAL KINETICS. 96wealth of experimental material. Unless we adopt a quasi-thermo-dynamic approachy2> 3* 4p 58 we must be content with making step-wiseprogress, by examining, for example, reactions in groups, selectedso as to reveal the effect of a single variable factor.When dealingwith fairly complicated molecules, the homologous groups of organicchemistry are eminently suitable. On the other hand, a classific-ation of chemical reactions based on the nature of the interatomicforces concerned s9 offers certain advantages.I n some respects, the simplest known reactions in solution arethe bimolecular reactions between ions and polar molecules, mostof which have normal velocities.2* 54 Ogg and Polanyi’s method forevaluating their energies of activation was described in the lastreport.2 Further instances of great interest have been studiedby E. D. Hughes, F. Juliusberger, A.D. Scott;, B. Topley, and J.Weiss,60 by E. Bergrnann, M. Polanyi, and A. L. Szabo,61 by D. P.Evans,62 and by A. R. Olson and collaborator^,^^ who have attemptedan interpretation of the slight differences in P values for reactionsinvolving halide ions in terms of their entropieq of solution. J. W.Baker and W. S. Nathan have, independently, given a, statisticalexplanation of the relative reactivities of halide and nitrate ionsin terms of their shapes (spherical and planar, respectively), andof their absolute dimension^.^^ C. K. Ingold and W. S. Nathan,65in a study of the hydrolysis of esters, have chosen a series of re-actions in such a way as to eliminate the direct electrostatic inter-action between the hydroxyl ion and the carboxylic group, and toisolate the induced polar effects.For a series of p-substitutedderivatives of ethyl benzoate, the P factor remains constant, whilethe absolute velocity varies by a factor of about 5,000, which isreflected in a change of Ed values amounting to 5,500 calories.The results are in good agreement with Nathan and Watson’srule.66 The problem of hydrolysis has also been studied by W. B. S.Newling and C. N. Hin~helwood,~~ chiefly from the point of viewof discovering the comparative behaviour of esters towards acidand basic attack. They find that a 10,000-fold change in k is to6 8 E. A, Moelwyn-Hughes, Trans. E’uraday SOL, 1936, 32, 1723.69 E. A. Moelwyn-Hughes and A. Sherman, J., 1936, 101.60 Ibid., p. 1173.6 1 Trans. Paraday SOC., 1936, 32, 843.62 J., 1936, 785.63 A.R. Olson and F. A. Long, J . Amer. <!hem. SOC., 1936, 58, 383; M. J.64 J . , 19’36, 230.Young and A. R. Olson, ibid., p. 1157.c 5 Ibid., p. 222.Cf. C. N. Hinshalwood, Ann. Reports, 1933, 30, 43.6 7 J . , 1936, 135796 GENERAL AND PHYSICAL CHEMISTRY.be attributed almost entirely to a change in EA. It is noteworthythat (Ex+ - EOH-) in aqueous acetone seems to be about 1,000calories less than in .pure water.6s Another interesting series ofreactions which have been measured and discussed, by G. N.Burkhardt and collaborator^,^^ is the hydrogen-ion catalysis ofthe hydrolysis of alkyl hydrogen sulphates. An isolated exampleof an unusual kind is afforded by Yun-Pu Liu and Tien-Chi Wei'sstudy 70 of the rate of hydration of methylethylethylene underthe influence of acids. A theory of reactions between ions and polarmolecules has been advanceda7lContinued attention is being paid to the kinetics of reactionsbetween two polar molecules.A. W. Chapman and I!. A. Yidler 72conclude, from a, study of the effects of substituents on the Beck-mann transformation of picryl ethers in carbon tetrachloride solu-tion, that the change is an intramolecular conversion of a complexformed from the reactant and the catalyst. Cyclisation reactionshave been studied in great detail by G. Sal~rnorr,~~ who resolvesthe semi-empirical term, P, into two factors, one of which is quantit-atively related to the surface energy. This, in turn, is calculatedfrom Langmuir's formula for capillary forces, which differ accordingto the geometric configuration of the halogeno-amine.Furtherexamples of the Menschutkin reaction have also been examined byJ. W. Baker,'* by N. J. T. Pickles and C. N. Hinshel~ood,~~ and byA. Singh and D. H. Peacock,76 while the kindred change involvedin sulphonium-salt formation has been studied by N. H e l l ~ t r o m . ~ ~The theory of reactions between ions in solution has been furtherdeveloped,78 yielding the following relations for the factor P and€or the variation of E A with temperature and with ionic strength :(3LT - 1). X*X*E2L Z*X*&2 lnP=------+- kDr 2DkT(LT - 1)(1 - 3 K r )E * = E - A E L N Z Z E 2Dr6 8 Cf. Moelwyn-Hughes, op. cit., p. 253.O9 G . N. Burkhardt, W. G.N. Ford, and E. Singleton, J., 1936, 17; G. N,Burkhardt, A. G. Evans, and E. Warhurst, ibid., p. 25; G. N. Burkhardt,C. Horrex, and (Miss) D. I. Jenkins, ibid., p. 1649.70 J . Chinese Chern. SOC., 1936, 4, 297.71 E. A. Moelwyn-Hughes, Proc. Roy. Xoc., 1936, A , 157, 667.72 J., 1936, 448.7 3 Trans. Paraday SOC., 1936, 32, 153 ; Helv. Chirrb. Acta, 1936, 19, 743.74 J., 1936, 1448.7 5 Ibid., p. 1353.7 6 J . Physical Chern., 1936, 40, 669.7 7 Z. physikal. C'lbern., 1936, A , 177, 337.7 8 E. A. Moelwyn-Hughes, Proc. Roy. SOC., 1936, A , 155, 308MOELWYN-HUGHES : CIZENICAL KINETICS, 97Both equations are in substantial agreement with experiment,the former being capable of accounting for the extremely highvalues of P found when the charges of thereacting ions are unlike and like respectively.The principles and method of the technique for measuring rapidreactions have been described in detail by F.J. W. Roughton andG. A. iUillikan,79 and have been applied by G. A. Millikan todetermine the rates of combination and dissociation of musclehzmoglobin with oxygen and with carbon monoxide. H. vonHalban and H. Eisner have continued their investigation ofinorganic reactions by the same method.H. M. Dawson has extended his well-known work on individualcatalytic coefficients to include the influence of temperature onthe hydrolysis of aqueous solutions of monochloroacetate.82Different values of EA have been found for the three simultaneousmodes of decomposition of isopropyll bromide in alkaline solution,which, according to Ingold’s theory, are denoted by the symbolsSN2 (bimolecular substitution), E 2 (bimolecular elimination) andSK1 (unimolecular dissociation). 83 A composite mechanism seemsprobable also in the acidolysis of numerous phenolic ethers, whichhave been studied by R.P. Ghaswalls arid 3’. G. D ~ n n a n , ~ ~particularly in view of their discovery that the Arrhenius equationis not applicable to the pseudo-unimolecular constants obtained.Two modes of decomposition of the ether-hydrogen halide complexare thus postulated.M. Buboux and R. Farre 85 have supplied further confirmationof Bredig and Fraenkel’s standard work on the hydrogen-ioncatalysis of diazoacetic ester. C. A. Marlies and V. K. LaMer 86have added to our knowledge of the catalytic decomposition ofnitroamine.Catalyses by hydrosulphide ions 87 and in sulphuricacid solution 88 have also been the subject of investigation. Amongmore complicated systems must be noted the reaction betweenferric ions and the oxy-acids of nitrogen,sg and between bromineand ally1 alcohol.go E. F. Caldin and J. H. Wolfenden 91 have madeand low?* E. A. Moelwyn-Hughes, Proc. Roy. Soc., 1936, A , 155, 258.81 Helv. Chim. Acta, 1936, 19, 916.82 H. M. Dawson and E. R. Pycock, J., 1936,153.83 E. D. Hughes, C. K. Ingold, and U. G. Shapiro, J . , 1936, 225.s4 Ibid., p. 1341.s6 J . Amer. Chem. SOC., 1935, 57, 1812.s7 E. Friedmann, J . p r . Chem., 1936,146,179.8 8 H. C. S. Snethlage, Rec. trav. chim., 1936, 55, 712, 874.89 E.Schroer, Akademische Verlagsgesellschaft, Lcipzig, 1936.QO M. Schar and L. C. Riesch, J . Amer. Cheni. SOC., 1936, 58, 667.91 J . , 1936, 1239.Ibid., 1936, By 120, 366.8 s Helv. Chim. Acta, 1936, 19, 1177.ItEEP.-VOL. XXXIII. 913 UENERAL AND PEYSICAL CHEMISTRY.an interesting study of the cyclisation of a charged molecule.R. Livingston and E. A. Schoeldgz have confirmed the work ofLivingston and Bray (1923) on the reaction between bromine andhydrogen peroxide, and have demonstrated the absence of a chainmechanism.The Influence of Pressure on the Velocity of Reactions in Solution.The quasi-thermodynamic treatment of reaction velocity wasgiven first by 5. H. vaii’t NofK93 Within the restricted limitsimposed by the suppositions underlying the treatment, it can beshown that, just as the increase (AE.) in heat content betweenpassive and active molecules may be found from the temperaturevariation of E, so may the increase (AV) in volume betwecn passiveand active molecules be found from the pressure variation of k.The values of the term A V given in the table have been calculateddirectly by means of the equation dlnkldp = - AV/RT, fromReaction. Solvent.c.c./g.-mol.A v,Hydrolysis of methyl acetate, catalysed byReaction between acetic anhydride and ethylN-HC1 ................................................ Water - 9.0alcohol ................................................ Ethyl alcohol - 16.5Hydrolysis of sucrose, catalyscd by AT-HC1 ... Water + 2.79 9 9 9 9 , 9 ,7, 9 , Y , 9 ,Toluene - 12.5Hexane - 4.16the early data quoted by van’t Hoff , and from the recent and moreextensive data obtained by E.G. Williams, M. W. Perrin, and R. 0.Gibson .94Beactions imolving Deuterixm in Solution.T. M. . L ~ w r y ~ ~ proposed the name “prototropy” to describechemical changes which may be represented by the migration ofa proton. Hydrolytic reactions in general Come under this category,as do also catalyses by acids and bases. Hydrolyses are amongthe most studied and least undersbood oi chemical changes. Thediscovery of deuterium quickened general interest in the problem,and, although relatively little quantitative work has yet been carriedout on deuterolysis,96 it is quite clear that the new isotope is to be92 J .Amer. Chern. SOC., 1936, 58, 1244.93 ‘‘ Vorlesungen uber theoretische und physikalische Chemie,” Vol. 1,94 Proc. Roy. Soc., 1936, A, 154, 684.95 Chem. Reviewa, 1927, 4, 231.96 Yellowing K. F. Bonhoeffer (see below), wc shall adopt the termsprotolysis and cleuterolysis for roac tions ii lioroiii tho molocdes H,O andD,O, respectively, are participating.p. 236, Braunschweig, 1901; cf. refs. 2, 6, snd 68MOELWYN-HUGHES : CHSMICGL KINETICS. 99regarded more as a useful tool than as a golden key. We shalltherefore refer only to some of the established experimental facts.When aliphatic compounds are dissolved in heavy water, thereoccurs a ready exchange between the deiaterium atoms o€ the solventand hydrogen atoms of the solute.M. Harada and T. Titani 97have confirmed the findings of Bonhoeffer and Brown (1933) onthe exchange of deuterium atoms between D,O and certain hexoses.After establishment of equilibrium, the distribution coefficientof deuterium atoms between solute and solvent is 0 . 8 7 4 . 7 0 inthe case of acetone,98 0.88 for acetylacetone,9!3 and 0.78 for nitro-methane.l The hydroxyl ion is often found $0 induce, or at leastto accelerate, the exchange. Thus K. Wirtz arid K. F. Bonhoefferfind that the hydrogen atoms in the hydrogen molecule exchangewith the deuterium atoms of heavy water in tlze prcsence of alkaliat 100". They formulate the following mechanism, in conformitywith the Lowry-Bronsted definition of bases as proton-acceptors :!D-6z--+--@-;JX + D:OD -j DON: + H-D + OD-Were all the deuterium atoms replaced by protium atoms, thechange would be described as the alkaline hydrolysis of the hydrogenmolecule.Other solutes for which exchange bas been eitherattempted or effected are chloroform: the dihydroxybenzenes:and formaldehyde .The ionic product of D,O in the neighbourhood of %Go has beendetermined electrornetrically by W. I?. I!. Wynne- Jones,6 wlioseresults, which confirm the earlier value given by E. Abel, E. Rratu,and 0. Redlich at 21", are given in the following form :(H20) ; - loglo K = 14.00 - 0.0331 (to - 25) -+ 0-00017(t0 - 25)2I.----------'! -------- _----- I.- --------AH = 13,460 - 42.5 (to - 25)(D2O) ; - loglo K == 14-71 - 0.0354 (to - 25) + 0*00017 (to -- 26)'AH = 14,420 - 42.8 (to - 25)The quantity AHl - AH2 is thus 970 calories.Ka,o = [H+][OH-] = 1-00 x l W 4 ;At 2 5 O , we haveKn,,, = [D'-][OD-] == 1.95 xJ.0. Halford, L. C:.Anderson, J. R. Bates, and R. D. Swisher, J. Amer. Chew. SOC., 1935, 57,1663.97 33ukl. Chem. SOC. Japan, 1936, 11, 65.9 8 1%. Klar, 2. physiknl. Chein., 1934, By 26, 335;99 R. Klar, Zoc. cit., ref. (98).1 0. Reitz, 2. physikal. Chem., 1936, A , 176, 363.3 J. Horiuti and Y. Sakamoto, Bull. Chem. SOC. J a p n , 1936, 11, 627.4 F. K. Miinzberg, 2. physik02. Chem., 1936, B, 33, 39.6 K. Wirtz and K. F. Bonhoeffer, ibid., 32, 108.6 [I'raw. Faradccy SOC., 1936, 32, 1397.7 Z. physikul. Chem., 1936, A , 173, 363.!4 IbicE., 177, 1100 GENERAL AND PHYSICAL CEEMISTRY.10-15 (mols./l.)2. The equilibrium constant X = [EtOD][HOH]/[EtOH][HOD] has the value 1.11 a t 25", and the rate a t whichthe equilibrium is reached has also been determined.*The principal kinetic data on reactions in deuterium oxide referto the following changes.(1) Mutarotation of glucose, uncatalysed.E. Pacsu publishedthe first datum on the velocity of chemical change in pure heavywater. It referred to an 18% solution of glucose at 20°, and,although the corresponding velocity in ordinary water under theseconditions has not been measured, a sufficiently close estimatemay be obtained by interpolation from the classical work of Hudsonand Dale. The comparison yields a ratio kD,OlkHaO 0.328. I nmore dilute solutions of glucose in heavy water, a slightly lower valueof 0.317 was found by E.A. Moelwyn-Hughes, R. Klar, and K. F.Bonhoeffer lo to hold, within the limits of error, over a temperaturerange of 30". Hence, there is no difference in the two EA values.If , however, collisions between solute and solvent molecules deter-mine the rate, both EA values must be corrected for the temperaturecoefficient of the collision frequency, which has a different valuefor the two solvents. On the simplest basis, EDao - EHaO becomes750 calories. These figures refer, of course, to velocities of mutarot-ation in the two pure media. For solvents of intermediate com-position, it seems reasonable to ascribe catalytic efficiency to themolecule HOD also. To do so requires a knowledge of theequilibrium constant K = [HQD]2/[HOH][DBD], the values forwhich have been estimated by B.Topley and H. Eyring.11 I nthis way, W. H. Hammill and V. K. LaMer l2 find itHoD to have avalue intermediate between those for kHoH and kDOD, while the ratioof the latter is concluded to be 1/0.263 at 25'.(2) Hutarotation of glucose, catalysed by protons and deuterons.With hydrochloric acid as catalyst, the following values have beenobtained for the ratio of the catalytic coefficients at varioustemperatures : l3t ........................ 9-00' 14.80' 20.69' 25.19' 30.39" 35-24'k D s ~ + / k ~ 8 ~ + ......... 0.53 0.56 0.63 0.64 0.68 0.77(3) Inversion of sucrose, catalysed by acids. A ratio kD30+/kHao+greater than unity holds for this reaction, and for a number ofothers, discussed below. With sulphuric acid as the source ofW.J. C. Orr, Trans. Paraday SOC., 1936, 32, 1033.Q J . Amer. Chew&. SOC., 1934, 56, 745.10 2. physikal. Chem., 1934, A , 169, 113.l1 J. Chem. Physics, 1934, 2, 381.l3 E. A. Moelwyli-Hughes, 2. phy8ikaZ. Chem., 1934, By 26, 272.l a Ibid., p. 891MOELWYN-HUGHES CHEMT.CAL KINETICS. 101protons the ratio 1-66 was obtained l4 for kD,,+/E,,,+ at 40°, andan approximate value of 1.67 at 30.7". B. Gross, H. Suess, andH. Steiner,15 studying the same system, obtain a value nearer 2.The discrepancy may be due, as they note, to the difference inconcentration of catalyst employed in the two cases. The di-basicity of the acid introduces complications which may be avoidedby using HCl and DC1.With these catalysts,13 the followingfigures are found :t ........................... ... 18.71" 24.27" 30.02" 37-13'a = I C ~ ~ O f / k x ~ o f ......... 1.80 1.77 ' 1.75 1.55(4) Hydrolysie of esters, catalysed by acids. K. Schwarz l6 foundthat methyl and ethyl acetates were hydrolysed by acids about50% more rapidly in heavy than in ordinary water. J. C. Horneland J. A. V. Butler,17 using sulphuric acid as catalyst, have foundthe ratios for the rates of deuterolysis and protolysis of methylacetate to be a = 1.85 a t 15' and a = 1.68 a t 2 5 O , in striking agree-ment with the data, for the inversion of sucrose, and indicatingthat the term AE is mainly responsible for the difference in rates.(5) Decomposition of diazoacelic ester, catalysed by acids.Againthe heavy isotope has the faster velocity,18 a being about 3.( 6 ) Neutralisation of nitroethane. A ratio of 1.5 holds forkOD-JjkOH-- in the case of the reaction between the two ions andnitroethane, and a ratio of 10 for the relative rates of reaction ofthe common ion OD- with %-nitro- and with a-nitro-aa-dideutero-ethane. l9According to Pedersen (1932),the rate of substitution of bromine in nitromethane is governedby the rate of conversion from the keto- $0 the enol form. Bromineand chlorine are introduced at the same rate, which is independentof their concentration and is proportional to that of any basiccatalyst. The rate-determining step may thus be regarded as therate of transference of a proton from the substrate to the base.0.Reitz20 finds that, in water a t 25", nitromethane passes on itsfirst proton to the acetate ion 6.5 times as rapidly as its trideutero-analogue passes on its first deuteron to the same base. Smallervalues of the same ratio are found when the proton- or deuteron-acceptor is the water molecule or the monochloroacetate ion.14 E. A. Moelwyn-Hughes and K. F. Bonhoeffer, Naturwiss., 1934, 11, 174.1 5 Ibid., p. 662; Trans. Paraday SOC., 1936,'32, 883.16 Anzeiger Alcad. W&3. Wien, 1934, 26, 4.17 J., 1936, 1361.18 P. Gross, H. Stoiner, and F. Krauss, Trans. Faraday Xoc., 1936, 32,19 W, F. K. Wynne-Jones, J . Chem. Physics, 1934., 2, 381.20 Z . physikd. Chem., 1936, A , 176, 363.(7) Enolisation of nityomethane.877102 GENERAL AND PHYSICAL CHEMISTRY.(8) Hydrolysis of the monochloroacetate ion.The ratio kDZO/kHzOappears to be 1.2 in both ordinary and heavy waLer as media, butaccurate analysis of the complete reaction presents c~rtaindifficulties.21(9) Hydrolysis of acetal and of ethyl orthoformate, catalysed byacids. Hornel arid Butler l7 find, for the two reactions respectively,the ratios kD30+/kx30+ = 2.66 and 2.05, both being independentof the nature of the buffer.Interesting information is accruingon the rate of growth of moulds in culture media containing D,Q,bui; we must be content with merely citing the references.2zHypothetical energy differences which may be held responsiblefor the die'erence in rates are shown in the following table :(lo) BiochemimZ processes.Catalysed reaction.RZ' . In kH/kD (cals./g.-mol.).a t 15" ............... + 325Mutarotation of glucose ............... + 255at 35" ............... + 180j at 15" ...... - 360.................. - 340.................. - 270at 18" Hydrolysis of sucrose ( at 3,0...... - 280 Hydrolysis of methyl acetate at 250Neutralisation of nitroethane .................. - 240Hydrolysis of acetal ..............................Hydrolysis of ethyl orthoformate ............- 570- 430It may be noted that, if Ic were regarded as proportional t o theviscosity of the medium, the energy terms would be small positivevalues, increasing with temperature a t such a rate as to be com-parable with the energy terms found for reactions in the gaseousphase at high temperatures.The mechanism of proton transfer rea,ctions has been discussedtheoretically from very differciit standpoi:ita.23 I n all discussions,however, the importance of Bronsted's empirical relation betweencatalytic coefficient and dissociation constant is fully appreciated.The Frequency of Collisions in Liquid Systems.I n view of the forthcoming discussion which is being arranged b:ythe Fara,day Society on the kinetics of reaction in solution, it will21 0.Reitz, 2. physikal. Chem., 1936, A, 177, 85.22 A. Farkas, L. Farkas, and J. Yudkin, Proc. Roy. Soc., 1934, B, 115, 373;B. Cavanagh, J. Noriuti, and M. Polanyi, Nature, 1934, 133, 797; K. H.Geib and K. F. Bonhooffer, 2. physikal. Chem., 1936, A, 175, 459; 0.Reitz,ibid., p. 257; F. Salzer and K. F. Bonhoeffer, ibid., 176, 202,z3 J. Horiuti and M. Polanyi, Acta Physicochim. U.R.S.S., 1935, 2, 505;R. P. Bell, Proc. Roy. Soc., 1936, A, 154, 414; E. A. Moelwyn-Hughes, ActaPhysicochim. U.R.S.S., 1936, 4, 173; J. C. Hornel and J. A. V. Butler, Zoc.cit., ref. (17)ADAM : SURFACE CHEME3TRP AND COUOIDS. 103serve no useful purpose to eirter into any detail on this highlycomplicated problem. Mcntion must be niade, however, of thecontinued attention which has been paid to it during the prcscntyear,2* and to the desirability, well exemplified by the work ofW. A. of applying as many of the formuh as are extantto the new experimental results. E. A. M.-H.6. SURFACE CHEMISTICY AND C:OLLOID.S.The vast range of these two subjects has rendered it impossibleto touch on more than a fraction of the work being published;instead of attempting to cover mnch ground, two restricted fieldshave been selected for this year’s Report,, and an attempt made topresent a readable account of thc more important advances duringthe last few years in these fields.The reporter is only too wellaware that even in these fields much has been deliberately, andperhaps much more inadvertently, omibted.Great advances have been made during recent, years in our know-ledge of aqueous solutions of substances containing, a t the endof a long hydrocarbon chain, a water-soluble and electrolyticallydissociated group. Besides the soaps, this class of substance includesmany with strongly dissociated, non-hydrolysable end groups, givingions such as R-XO,’, R*O*SO,’, R-NMe,’. These substances havelately come into great prominence industridly on account of theirpowerlul wetting mnd detergent action, cornpounds with manydifferent end groups having been synthesised 2nd patented, a d not afew placed on the market.The whole class, inchding soaps, hasrecently been called by G. S. Ilartley the “paraffin-chain salts,”a name perhaps preferable to the alternative “ long-chain salts,yyas the latter would be applicable to numerous classes of highlypolymerised compounds containing long chains with oxygen ornitrogen atoms coderring considerable water-attracting power onthe chains. The peculiar properties of these substances, whichrender them so active as depressants of surface or interfacial tension,are due to their unsymmetrical structure, with the very stronglyhydrophilic group at one end of a great length of hydrophobicchain.24 B.I. Sve6niBov, Compt. rend. Acad. Sci. U.R.S.S., 1936, 3, 61; T. S.Wheeler, Proc. Indian Acad. Sci., 1936, 4, 291 ; K. S. G. DOSS, ibid., p. 23;E. Rabinowitch and W. C. Wood, Tmm. Paraday SOC., 1936, 32, 1381.25 J., 1936, 1014; “ Physical Aspects of Organic Choinistry,” JEoutledge,1935104 GENERAL AND PHYSICAL CHEMISTRY.F. Krafft’s early studies 1 showed that the soaps have such lowosmotic activity as to be rightly called colloids in aqueous solution.J. W. McRain’s recognibion 2 in 1913 t’hat their simultaneous highelectrical conductivity and low osmotic act>ivity require the presenceof large electrical charges on the “ micelles ” or colloidal particleswas the commencement of his well-known researches with manycollaborators 3 on soap solutions, which have established the ionicmicelle as perhaps the most characteristic feature of these solutions.In the same year A.Reychler4 independently concluded thatcetanesulphonic acid forms charged aggregates with the paraffinchains in the centre and the sulphonic groups outside, from consider-ations of the water-attracting power of the different parts of themolecules, and in 1921. N. K. Ada= assigned the same structureto the. ionic micelle from considerations of the forces which orientmolecules of this general constitution a t surfaces.In a series of papers,g-lon and one short monograph,ll G.S. Hartleyand others have established beyond doubt that the ionic micelle isformed from the paraan-chain ions, a t dilutions much greater thanthose formerly associated with the ionic micelle, and that its form-ation is fairly sudden, as the concentration increases, and is accom-panied by (a) a marked decrease (not an increase, as had previouslybeen supposed) in the t’otal equivalent conductivity l2 of the solution,( b ) an increase in the mobility of the parafin-chain ions, (c) anenormous increase in the solubility of the whole salt in water, andcertain other changes. A good deal Q€ light has also been shed onthe structure of the ionic micelles, on the way in which the smallions (called the “gegenions”) of opposite charge to the paraffin-Ber., 1894, 27, 1747; 1895, 28, 2566; 1896, 29, 1328, 1344.Cf.J., 1919,115,1279; 1922,121,2325; 1923,123,2417; J . Amer. Chern.SOC., 1920,42,426 ; 1928, 58,1636; 1933,55,545, 2250, 2762 ; 1935,57, 1905,1909, 1913, 1916; Proc. Roy. SOL, 1920, A, 97, 44; 1933, A , 139, 26.2 Trans. Paraday SOC., 1913, 9, 99.KOllOid-Z., 1913, 12, 283.5 Proc. Roy. SOC., 1921, A, 99, 348.J. Mdsch and G. S. Hartley, 2. physikal. Chern., 1934, A, 170, 321.7 33. C. Murray and G. S. Hartley, T’ram. Paraday SOC., 1935, 31, 183.J. L. Moillet, B. Collie, C. Eobinson, and G. S. Hartley, ibid., p. 120.G. S. Hartley, ibid., p. 31.lo G. S. Hartley, B. Collie, and C. S. Samis, ibid., 1936, 32, 795.10a G. 8. Hartley, J .Amer. Chern. Soc., 1935, 58, 2347.11 G. S. Hartley, “ Aqueous Solution of Paraffin Chain Salts,” Actua1iti.sScientifiques et Industrielles, Paris, 1936.12 The expression “ total equivalent conductivity ” is here used instead ofthe more usual “ equivalent conductivity,” t o distinguish it from tho “ equi-valent conductivity of the paraffin-chain ions,” zc term which Hartley hasused in place of “ mobility ” as it is more informative; the last two will beused interchangeably hereADAM : SURFACE CHEMISTRY AND COLLOIDS. 10 5chain ions adhere to the micelles, partially neutralising their charge,and on the solvent properties of the interior of the ionic micelles,whic;;h appear to be a,lrnost the same as those of liquid para’ffmsin bulk, and account, for tlie curious solvent properties of solution8of soaps.It has also been shown that there is no need to postulate‘‘ neutral micelles ” as well as “ ionic micelles ” to account fort,he properties of these solutions.The total equivalent conductivity of a paraffin-chain salt changeswith increasing concentration in the manner of curve I of the--figure. The curve given is for cetylpyridinium bromide ; similarcurves were first obtained with all the important details on the alkylsodium sulphates by A. Lottermoser and E”. Piischel; l3 the cetane-sulphonates, trimethylcetylammonium salts, and some otherparaffin-chain salts with 16 carbon atoms in the chain show closelysimilar curves.The main features are : below about N/1000, the curve (plottedagainst the square root of the concentration) is the ordinary linearone of a uni-univalent electrolyte ; beyond this concentration ( A ) ,the conductivity falls very sharply ; with increasing concentration,the fall becomes gradually less steep and finally ceases.At stilll3 KolZOid-Z., 1933, 63, 175206 GENERAL AND PHYSICAL CHEMISTRY.higher concentrations (from N/20 to N12 usually), the total equivalentconductivity increases more often than not ; in the partictilarcase shown, and in some others, however, there is almost no rise.This rise in the conductivity curves att higher concentrations isalways gradual, and is much smaller than the fall commencing at A .Salts with longer or shorter chains give similar curves, but theconcenhrations at which the various features, particularly the suddenfor a 12-carbon chain A occurs at about; N/100, instead of N/1000for a 16-carbon chain.The specific nature of the end groupsmakes minor differences only; the " critical concentration " A issome 30% lower for *O-SO,K than for -80,K; l5 it is intermediatefor *NMe,Br. Rise of temperature increases the critical concentra-tion somewhat.l3* l4 Bivalent positive gegenions (e.g., in thezinc alkyl sulphafes) give a decidedly lower critical concentrationthan univalent .I3 Addition of ordinary uni-univalent salts to thesolution lowers the critical concentration, but little quantitat'iveevidence is available yet on the amount of this lowering.With solutions of soaps, hydrolysis of the end groups complicatesmatters in very dilute solutions, so that the curve rises above thelinear one for uni-univalent salts at dilutions considerably belowthe critical.The most careful measurements show the presence ofthe discontinuity a t A , however.16G. S. Hartley brings ample evidence that the discontinuityat A is associated with t'he start of aggregation of the paraffin-chain ions into ionic micellcs. There are three main consequencesof this aggregation : (1) a diminished viscous resistance to flowof a given number of these ions through the water, by Stokes'slaw, as McBain pointed out in 1913 ; (2) a much increased " braking "effect of the Debye-Hiickel atmospheres of oppositely chargedgegenions, and (3) a considerable diminution of the total chargeon the aggregated ions through the adherence of gegenions suffi-ciently closely to travel with the niicelles, in the opposite directionto that which they would take if free.Under ordinary conditions,(2) and (3) predominate over (l), so the equivalent conductivityfalls when micelles are formed.If, however, the conductivity is measured at extremely high fieldstrengths, as in curve 11: (200 kV./cni.), the conductivity risesinstead of falling at A.6 M. Wien has shown that at these highfield strengths the effects of ionic atmospheres are very much reduced,14 0. R. Howell and €1. G. B. Robinson, Proc. Roy. Soc., 1936, A , 155, 386.z.fall at A , take plaoe are lower the longer the chain ; 11* l 3 ~ l4 e4.YG. 8. Hartley, op. cit., p. 36.P. K.Ekwall, Acta Acad. h o e n s i s (17lath. Phys.), 1927, 4, 40;physikal. Chem., 1932, A, 161, 195ADAM : SURFACE CHEMISTRY AND COLLOIDS. 107because the ions move so rapidly that the atmospheres have nottime to form pr0per1y.l~ This diminishes (2); and owing to thediminished concentration of gegenions near the micelle, the equili-brium between adherent and free gegenions is probably so alteredthat many of the adherent gegenions leave the micelle, so that effect(3) is also much diminished. Consequently the effect (l), the diminu-tion of resistance t o motion resulting from aggregation, now pre-dominates, and the conductivity rises a t the eoncentration wheremicelles begin to form. The later fall of the curve is due to themuch increased stability of the ionic atmospheres as the concen-tration increases, sothat theeffects (2) and (3) againpredominate, evenunder the maximum field strength attainable short of actual sparking.The total equivalent conductivity, including effects due to thegegenions equally with those due to the paraiiin-chain ions, is notthe best quantity to employ for detecting changes in aggregationof the latter.Curve 111 shows Olio mobility, or equivalent con-ductivity, of the paraffin-chain ions, obtained as usual from measure-ments of conductivity and transport number ; the latter weremeasured by an interesting new method, the “ balanced boundary ’’method.18 I n all cases yet examined lo* l1 the mobility of theparaffin-chain ions increases suddenly a t the critical concentration.At the same time, the mobility of the gegenions decreases even moremarkedly than the total equivalent conductivity, and soon becomesnegative.The change of sign of the mobility of the gegenions canonly mean that a large proportion of them adhere to the pamffin-chain micelles and travel with them in the opposite direction tothat which they would take if free.The effects due to the ionic atmospheres have been estimated,but only semi-q~antitatively,~- lo on account of hhe difficultieswhich the Debye-Huckel theory presents when applied to ions of thevery high valency of the micelles. The braking effect is certainlymuch greater than would be found with uni- or bi-valent ions.Whether or not these is any sharp distinction between the gegenionsin the atmospheres and those adhering sufficiently closely tomove with the micelles is not certain, so perhaps the effects (2)and (3) above are not sharply distinguishable; but that adherenceoccurs and that the effective charge on the micelles and theircurrent-carrying capacity are very much diminished is beyonddoubt, on account of the transport-number measurements.17 J.Malsch and M. Wien, Ann. Physilc, 1927, 83, 305; M. Wien, ibid.,p. 327; 1928, 85, 795; 1929, 1, 400; Physikal.Z., 1027, 28, 834; 1929, 30,196; cf. G. Joos, Physikal. Z., 1928, 29, 765; M. Blumentritt, Ann. Physik,1928, 85, 812.18 G. S. Hartley, B. Collie, and E. Drew, Trans. Ir’araday SOC., 1934, 30, 648108 GENERAL AND PHYSICAL CHEMISTRY.The number of paraffin-chain ions and gegenions which go tomake up an ionic micelle can only be provisionally estimated atpresent.The most probable size of the micelle, i.e., the numberof paraffin-chain ions, may be estimated from considerations of thedimensions of the single ions.l0u l1 A 46-carbon chain is about18 A. long; 3 A. being added for the end group, the length of thewhole ion is about 21 A. The attraction between the end groupsand water is so much greater than that between the latter and thechains that it is very unlikely the micelles will contain hydrophilicend groups in their interior ; the largest micelles of 16-carbon-chainions must be 42 A. in diameter, if a sphere; this implies about 50paraffin-chain ions. If the micelles are not spherical, but elongated,they may be longer than this when they have reached their maximumsize, and contain more paraffin-chain ions.G. S. Hartley has calcul-ated that the surface energy of the various parts of these ions ismore than sufficient to bring this number together against the re-pulsive electrostatic forces which arise from bringing together thecharged end groups on the surface of the micelles.The number of adherent gegenions could be found from themobilities, if the effects of the Debye-Hiickel atmospheres couldbe exactly calculated; an approximate estimate lo gives, for thefraction of the gegenions adhering, in the dilute solutions in whichthey are first formed, about 0.74; this gives as the net charge on amicelle of 50 paraffin-chain ions, about 13 units, no fewer than about37 gegenions being dragged along with the micelle.had observed some of the curious changesin transport number with increasing concentration, and concludedfrom these and other observations that there is present, in additionto the ionic micelle, neutral colloid.Their theory involved, origin-ally, the presence of a certain proportion of uncharged colloid andionic micelle car‘sying the full number of charges associated withthe number of single paraffin-chain ions in the micelle. It was,unfortunately, worked out without full consideration of the ionicatmospheres; and many diagrams oE the constitution of soapsolutions with the proportions of uncharged colloid and entirelyun-neutralised ionic micelle required by this theory have appeared.20G.S. Hartley lo* 21 has shown that these diagrams can be replacedby much simpler ones, in which there is no ‘‘ neutral colloid,” butthe ionic micelle is partially neutralised by the adherent gegenions,whose number varies somewhat with variation in concentration ofthe solutions. This appears far more probable than that two sharply10 Cf. particularly J. W. McBain and R. C. Bowdon, J., 1923, 123, 2417;20 Cf. “ International Critical Tables,” 1929, 5, 448. 21 O p . cit., p. 56.McBain and othersMcBain, J . Amer. Chem. SOC., 1928, 50, 1636ADAM : SURFACE CHEMISTRY AND COLLOIDS. 109distinguished types of colloidal micelle exist simultaneously, oneuncharged and the other bearing the full charge of all its paraffin-chain ions.The suddenness of the discontinuity a t the critical concentrationfor micelle formation indicates that the proportion of micellesincreases very rapidly as the concentration increases; this is evenmore striking if the " differential equivalent conductivity " dK/dc,or A + c .dh/dc, where K is the specific and A the equivalent con-ductivity, is plotted against concentration (curve V). Considerationof the mass-action equilibrium between the single ions and micellescontaining a large number of single ions shows that there is reasonto expect 7, 22 a very sudden change from infinitesimal micelleconcentration to a solution consisting almost entirely of micellts,if as many as 50 ions unite to form one micelle. If there were aninfinite number of single ions in the micelles, the change would beentirely abrupt, as with any other phase change.G. S. Hareleyconsiders that the discontinuity is not quite so abrupt as if nothingbut 50-ion micellcs were formed from the start, and suggests thata proportion of smaller micelles, containing perhaps about 10 ions,is formed at first. When the concentration has reached from twoto five times the critical, it is thought that practically the wholeof the salt is in the form of ionic micelles, with about 50 ions.Fairly sudden changes in other properties of the solution, besidesthose associated with the transport of electricity, would be expectedwhen micelle formation commences. Perhaps the most remarkableof these is in the solubility of the paraffin-chain salts, which changeswith temperature in a characteristic and very unusual manner.Below a certain temperature, which depends both on the lengthof the chains and on the nature of the end group, the solubilityincreases with temperature in a normal manner.Above thistemperature, the solubility increases extremely rapidly, so much sothat only 5" or 7" above a temperature at which the solubility is buta small fraction of 1%, the paraffin-chain salt may be almostindefinitely soluble, solutions of 50 yo and upwards being easilyobtainable. This is explained by the ionic micelle's being extremelysoluble, whereas the single ions are but slightly soluble; as thetemperature rises, the solution becomes gradually richer in singleions, until a critical concentration is reached a t which the equilibriumshifts quickly over to the side of ionic micelles, so that there is noimpediment; to very high solubilities.G. S. Hartley and R. C.Murray 7 show theoretically that the rate of increase of solubilitywith temperature should be rather less abrupt than the actualtransition between single ions and micelles.22 Op. cit., pp. 23 ff110 GBNERAL AND PHYSICAL CBXMISTRY.C. a. Bury has found appreciable changes in the density and thepartial specific volume of paraffin-chain salta as the critical con-centration is passed ; 23 this work includes observations on the octo-atecr and the laurates, Some tendency to micelle formation isfound even iii butyric acid solutions.24Another effect of ionic micelle formation is a displacing effeaton the equilibrium point of various acidimetric indicators.25 Ifparaffin-chain salts are gradually added to buffered solutions con-taining indicators, there is little colour change until the concentrationis sufficient for micelles to form, whereupon it may change by asmuch as corresponds to 1 or 2 units of pR.The sign of the chargeson the ionic niicelle and the indicator ions determines whether ornot the equilibrium is displaced; and G, S. Hartley has givenrules for the choice of indicators not subject to displacement fromthis cause, which leads to oonsiderable errors in pH determinationby colorimetric methods.The activity and osmotic coefficients of the solutions are verymuch lowered, naturally, by micelle formation.26 The aggregationreduces the osmotic activity of the paraffin-chain ion to practicallynil ; and that of the gegenions must also be lowered very considerablyby the Debye-Hiickel effeot and the adherence of gegonions tothe rni~lles.~' J.W. &IcBain and M. 14. Retz2* bave demon-strated the very great decrease in the activity of the hydrogen ionin solutions of various paraffin-chain sulphonic acids, its the con-centration rises above the critical; but it should be mentioned thathere the sharp discontinuity a t the critical concentration has beenmiwed. No one appears a8 yet to have obtained sufficientlyaccurate osmotic measurements in dilute solution to detect thediscontinuity due to incipient micelle formation, sxcept perhapswith potassium o ~ t o a t e .~ ~It remains to account for the changes in conductivity and mo-bility at ooncentrations sbove those at which the formation of theionicz micelle is complete, according to the theory given above.With the 16-carbon chains, the total equivalent conductivity mayrise a little above 8/20; this rise was, at one stage of McBain'stheories, attributed to ionic micelle formation in addition to alarge amount of neutral colloid. The mobility of the pmaffin-chainp3 D. G. Davies mid C. R. Bury, J., 1030,2263 ; C. R. Bury- and G. A. Parry,24 J. Grindley and C. R. Bwy, J., 1929, 679.25 G. S. Hartley, Tram. Paraclay Soc., 1934, 3Q, 444.e 6 Cf. McBain et al., ref. (3).27 G. S. Hartley, B. Collie, and C. S . Samis, ref.(lo), p. 812.2g J . Amer. Chem. SOC., 1935, 57, 1913.J., 1935, 626.J. W. McBain, M. E. Laing, and A. F. Tifley, J . , 1919, 115, 1291ADAM : SIJRB’ACE CHICXIYTRY AND COI&OIDS. 111ions begins to decrease (see figure) a t about 0.005N, and simul-taneously that of the gegenions begins to increase, and these changesgo on steadily up to above N/10. Increase of concentration wouldbe expected, if no other changes occurred in the solution, to decreasethe mobility of all the charged particles, owing to the increasedbraking effects of the ionic atmospheres. The observed increase inmobility or equivalent conductivity of the gegenions indicates thatsome of the adherent gegenions corn(: off the micelles as they becomemore crowded in the solution.Albhough conditions in such con-centrated solutions are so complex that exact calculation seemsimpossible, some effect of this kind seems very probable. AtX / l O , the micelles occupy some 3% of the total volume, so that closeapproach must occur frequently; and when this takes place, thecharges on the surface of one micelle will tend to pull off the gegenionsadhering to the other.Soap solutions have, in addition to their emulsifying power,considerable solvent power for organic compounds in soluble, or veryslightly soluble, in water. S. U. Piekering 30 and E. Lester Smith 31have called attention to this, which indeed can scarcely be overlookedby anyone conducting organic preparations in the course of whichany quantity of soap is formed.6. S. IPartley makes the mostinteresting suggestion32 that this solvent property is due to thcsolute’s going into the interior of the ionic micelles, which is almostprecisely sirnila’r to a liquid paraffin in nature. It has been shownthat the amount of azobenzene which will go into a solution of aparaffin-chain salt consisting mainly of micelles is proportionalto the amount of the salt present. As this substance, and manyothers which dissolve similarly in solutions containing ionic micelles,are very soluble in Liquid paraffins, but insoluble or very slightlysoluble in water, and also do not form solid solutions with para,ffins,it is concluded that the interior of the ionic rnicelles is a chaoticarrangement of hydrocarbon chaks possessing all the propertiesof a liquid.The very pronounced elastic properties of many paraffin-clnaiiisalt solutions are ascribed by H a r t l e ~ , ~ ~ following a suggestion ofA.S. C. to adhesion between micelles; as this adh3 monis by the exterior of the micelles, the nature of the end groups isof great importance. Adhesion such as this may perhaps havesomething to do with the explanation of the results of ultrafiltration30 J . , 1917, 111, 86.31 J . Physa’cal Chem., 1932, 36, 1401, 1672.s2 Op. cit., pp. 41 ff,34 Trans. If’arudcty Soc., 1935, 31, 189.33 Im., pp. 5s fn”112 GENERAL AND PHYSICAL CHEMISTRY.measurements of soap solutions carried out by J. W. McBain andothers .35Recent Work on Unimolecular Pilrns.The structure of the ‘‘ liquid-expanded ” type of unimolecularfilm of long-chain fatty substances on water has been explainedat last by I.L a n g r n ~ i r , ~ ~ who uses the very bold conception thatthe upper, hydrocarbon parts of the molecules adhering to the waterby their lower, soluble, end groups form a liquid layer with sufficientof the properties of a phase in bulk to have both an upper and a lowersurface tension; the upper surface is supposed to have the sametension as that of a paraffin in bulk; the lower is similar to aninterface between a paraffin oil and water, containing a few fatty-acid molecules in addition to the paraffin. Such films form, accord-ing to Langmuir, the limiting case of an oil caused to spread on waterthrough the presence of water-attracting groups in the water-oilinterface.These films had proved exceedingly difficult of inter-pretation; the work of N. K. Adam and G. J e s ~ o p , ~ ~ in particular,having shown that they have an area and a compressibility inter-mediate between that of the condensed films, in which the moleculesstand nearly upright and are closely packed, and that of moleculeslying flat. It was obvious that there was some considerable degreeof tilt in the molecules; it was supposed that the thermal agitationproduced a state of chaotic agitation in the hydrocarbon chains,but there seemed no reason why the film should cohere, instead ofspreading to unlimited areas, like the “ gaseous ” type of film,or why the area should so often be about 2; times that of the mole-cules standing upright.Langmuir points out that the relationbetween the outward spreading force or ‘‘ surface pressure ” of theseliquid-expanded films is identical with the spreading force of a thinlayer of a hydrocarbon oil on water, when a certain number of fattyacid molecules are present in the interface between the oil and thewater. The theory appears to meet all the facts, and provides anexplanation for the failure to spread indefinitely in the cohesionof the “ liquid ” layer formed by the hydrocarbon portions of themolecules, a, liquid layer only some four-fifths of a molecule thick !If a layer of this thickness only can possess the properties of a liquid,there can be no objection to the interior of the ionic micelle possessingthem also, as suggested a t the end of the preceding section.35 J.W. McBain and W. J. Jenkins, J., 1922,121, 2325; J. W. McBain, Y.Kawakami, and H. P. Lucas, J. Amer. Chem. SOC., 1933, 55, 2762.313 J . Chem. Physics, 1933, 1, 756; cf. also 3rd Colloid Symposium Mono-graph, 1925, 71 ; Alexander, “ Colloid Chemistry,” 1926, vol. 1, 625.37 Proc. Roy. SOC., 1926, A, 112, 362; cf. also N. K. Adam, IfT. A. Berry,and H. A. Turner, ibid., 1928, 11’7, 532; N. K. Adam, ibicl., 1930, 128, 366ADAM. : SURE’ACX CHEMISTRY AND COLLOIDS. 113The transition between liquid-oxpanded and condensed filmspresents some curious features, resembling in some ways, but notexactly, a phase change in the surface; Langmuir considers that itindicates a condensation of the molecules into surface “ micelles ”of from five to thirteen single molecules-the numbers cannot beestimated with great accuracy, though they are probably not thesame for all different types of end group in the molecules-and thatthese micelles have a constant surface vapour pressure, but themselvesbehave as the units in a ‘‘ gaseous ’’ type of film.This part ofthe theory is more difficult to test experimentally than that dealingwith the expanded films alone, hut appears to fit the surface-pressure measurements.The transition region between the expanded and the condensedfilms appears, however, from measurements of the surface potentialtaken at different parts of the surface, to consist often of at leasttwo types of film in patches large enough to give a fluctuatingpotential as the exploring air electrode moves over the surface.It will be remembered that the surface potential, or the changein contact potential between the water and the air caused by thepresence of a unimolecular film a t the surface, is measured with ametallic wire just above the water, the end of the wire being coatedwith a little radioactive material 60 render the air condu~ting.~~A film consisting of patches appears inhomogeneous to a movingair electrode.J. H. Schulman and A. H. Hughes39 found smallfluctuations with films of myrisfic acid, and N. K. Adam and J. B.Harding 4O found fairly large oncs with margaronitrile, in the tran-sition region. Such patches must be of the order of millimetresacross, as the air electrode is usually about 1 mm.above the surface,and can scarcely be accounted for by micelles consisting of a fewmolecules only. The transition region appears to require furtherinvestigation, in order t o account for this patchy struckure. Apartfrom this obscure point, the structure of unimolecular surfacefilms of long-chain fatty substances on water now appears to befairly well understood.A beginning has been-made with the investigation, by F. A.Askew and 5. P. Danielli,41 by methods analogous to those used forinsoluble films at water-air surfaces, of films a t the interface betweenan aqueous and a non-aqueous, immiscible, liquid. Preliminary38 Cf. J. Guyot, Ann. Phgsique, 1924, 18, 506; A. Frumkin, 2. physikal.Ghem., 1925, 116, 486; J.H. Schulmari and E. K. Rideal, PYOC. Roy. SOC.,1931, A,‘130, 259; N. K. Adam and J. B. Harding, ibid., 1932, 138, 411;l’raw. Faraday Soc., 1933, 29, 837.Proc. Roy. Soc., 1932, A, 138, 443.40 Ibid., 1933, A , 143, 107. Ibid., 1936, A , 165, 696I14 GENERAL AND PHYSICAL CHEmSTRY.results at the interface between bromobenzene and water indicatethat, for long-chain aliphatic compounds, the lateral adhesionin the films, due to hydrocarbon chains, is much less when these areimmersed in a non-polar or slightly polar liquid than at the water-air interface. This is because the chains are moved about amongthe molecules of the liquid ; their surface energy does not have to besatisfied, as in the case of a water-rtir surface, by close adhesion tothe hydrocarbon chains of other molecules in the film, but is satisfiedby adhesion to the molecules of the non-aqueous liquid, which are inconstant translatory motion.As a general rule: mere presence at a liquid surface does not appearto alter the intrinsic reactivity or energy of activation of a molecule.In fhis respect liquid surfaces differ, of course, from solid.Never-theless, it has been shown that the rate of reaction of a substanceat a liquid surface may be influenced by the special conditions gre-vailing at; the surface, through change in the accessibility of the re-acting groups in the molecules at the surface to reagents in thesubstrate or underlying liquid. A striking instance of this wasfound by A. M. Hughes and E. K. Ridea142 in the oxidation ofacids containing a double bond in the middle of the hydrocarbonchain, such as oleic or petrsselinic acid, by permanganste in theunderlying water.The rate of oxidation is nearly ten times asgreat when the film is under low compression, so thaf the moleculesfrequently lie nearly flat, as when the film is highly compressed andthe double bonds in the molecules have less chance of reaching thewater. These films are of the expanded type, i.e., the moleculesare oscillating in a chaotic manner, so that probably all parts of thehydrocarbon chain come into contact with the water a t one time oranot'her ; but the chance of the upper and middle parts of the chainsreaching the water is much greater if the film is not too highlycompressed.Similar results have been obtained on the morehighly unsaturated addition compouiid of elaeostearin and maleicanhydride by G. Gee and E. K. Rideal; 43 A. H. Hughes44 findsthat snake venoms in the substrate hydrolyse the oleyl chains offlecithin in a unimolecular film on the surface more easily if thelecithin film is not highly compressed; Le., if the double bonds inthe oleyl chains can easily reach the water.In ell such work, as indeed in all work on surface films, there is arisk of changes in the surface being due, not to actual chemicalchanges in the substance originally spread in the film, but to thearrival, often accidental, of other substances at the surface from the42 Proc. Roy. soC.7 1933, A , 140, 233; cf. dso A. €I. Hughes, J b , 1933, 338,48 PTOC.Roy. SOC., 1935, A , 153, 116.4b Bwchpm. J., 1935, 29, 437ADAM : SURFACE CHEMISTRY AXD COLLOIDS. 116solution. In this connexion the veyy slow rates of adsorption ofdilute solutions of certain paraffin-chain salts may be of interest :N. K. Adam and H. L. S h ~ t e , ~ ~ also R. C. Brown 46 by a differentmethod, found that the final surface tension in extremely dilutesolutions may not be reached for days, A curious fact is that, if theconcentration is high enough for ionic micelles to be present, thefinal tension is reached almost a t once. Incidentally, R. C. Brownfinds that the (‘ ripple ” method for determining surface tensiongives values as low as the usual static methods, proving that whenripples pass over the surface of an aqueous solution there is no dis-placement of the solute from the surface.It has been shown byJ. H. Schulrnan and A. H. Hughes 47 that some soluble but stronglysurface-active substances, especially soaps and other paraffin-chain salts, will displace such substances as tripalmitin from aunimolecular film on the surface, by reason of their own tendencyto pass from the interior of the solution to its surface. Proteinfilms also may be displaced.Besides the long-chain fatty substances, the sterols,48 and manyallied complex ring structures,4g* 50* 51 form very stable unimolecularfilms, which have been investigated €or several years by N. M.Adam, F. A. Askew, J. F. Danielli, and others. Very frequentlythe principal or the only water-soluble group is found at the extremeend of the molecule, any aliphatic side chain, if present, being at theopposite end; and usually surface films of such substances have themolecules standing upright in the surface, closely packed and form-ing very coherent films.Exceptions do, however, occur, the mostnotable being with coprostenone, the ketone formed by oxidation ofthe sterol cholesterol. The change cuf the CN(0MI) group into COYwithout any change of position, results in the molecules becomingvery much tilted to the vertical, and the area increasing by nearly50%. Some other substances, particularly ketonic derivatives of46 Trans. Paraday SOC., 1936, 31, 204.46 Ibid., p. 206; Proc. Physical SOC., 1936, 48, 312.47 Biochem. J., 1935, 29, 1236, 1243.48 Sterols : N.K. Adam, Proc. Roy. Soo., 1928, A , 120, 473; N. K. Adamand 0. Rosenheim, ibid., 1929, A, 126, 25 j 1929, B, 105, 422; J. F. DanielliandN. K. Adam, Biochem. J., 1934,28, 1583; N. K. Adam, F. A. Askew, andJ. F. Danielli, ibid., 1935, 29, 1786.49 Oestrin derivatives: N. K. Adam, J. F. Danielli, G. A. D. Haslewood,and G. F. Marrian, ibid., 1932, 26, 1233; Danielli, Marrian, and Haslewood,ibid., 1933, 27, 311.60 Sapogenins: F. A. Askew, S. N. Farmer, and G. A. R. Kon, J., 1936,1399.s1 Resinols : F. A. Askew, ibid., p. 1595; W. D. Harkins, H. E. Ries, andE. F. Carun, J. Amer. Chem. Xoc., 1935, 57, 2224; 1936, 58, 1377; J .Chem. Physics, 1936, 4, 228116 GENERAL AND PHYSICAL CHEMISTRY.sterols, show the same effect in lesser degree.Irradiation of ergo-sterol produces the same effect. The cause remains a completemystery, and the fact, with the possibility of tilt of the moleculesoccurring even when there is only one water-soluble group at theextreme end of the molecule, renders it much more difficult to makedeductions as to the constitution of new members of this class ofcompound from surface-film measurements than had been hoped.The oestrin group has proved interesting, in so far as derivativesof the same parent substance, differing only in the number andposition of certain water-soluble groups, stand on one or the otherend of the ring system, in the surface films; and may also, withappropriate distribution of water-soluble groups, lie flat in the surface.These results are quite simply interpreted in the light of the coii-stitution of the molecules.49The surface-film measurements give a measurement of the sizeof organic molecules in certain packings and orientations on thewater surfaces, and have been used as an aid in determining theconstitution of various substances; the size and properties of thesurface films to be expected for a given constitution can often beforetold from measurements on nearly related compounds, or evenon models of the molecules.It was shown by B. C . J. G. Knight,52for instance, that batyl alcohol, known to be an ether of glycerolwith one molecule of octadecyl alcohol, has the long chain on oneof the terminal hydroxyls in the glycerol, not on the centre one,by a comparison of surface films of this substance with those ofa-monopalmitin ; the films are very closely similar, but quite differentfrom those to be expected if the long chain were attached to thecentral hydroxyl group.This conclusion, disputed a t first, wasafterwards confirmed by more ordinary 1nethods.~3 Surface-film measurements on the sterols are quite inconsistent with theolder formulae, but consistent with the new and now universallyadopted formulae of 0. Rosenheim and H. King.Cellulose derivatives ,54 proteins J55* 56 and highly polymerisedsynthetic substances containing numerous hydroxyl groups in the62 Biochem. J., 1930, 24, 257; cf. N. K. Adam, J., 1933, 164.53 W. H. Davies, I. M. Heilbron, and W. E. Jones, J., 1933, 165; 1934,1232.ti4 N.K. Adam, Trans. Fwraday Soc., 1933, 29, 90; N. K. Adam and J. El.Harding, ibid., p. 837.55 E. Gorter and others, Proc. A’. AEwd. Wetensch. Amsterdam, 1925, 28,371 ; 1926, 29, 1262 ; 1929, 32, 770; 1932,35, 838; 1933,36, 922 ; 1934, 3’7,20, 355, 788; J . Gen. Physiol., 1935, 18, 431 ; Biochem. J., 1935, 29, 38, 48.li6 A. H. Hughes and E. K. Rideal, Proc. Roy. Soc., 1932, A , 137,62; A. H.Hughes, Tram. Paraday SOC., 1933, 29, 214; J. H. Schulman and A. H.Hughes, Biochem. J., 1935, 29, 1236GLASSTONE : SOLVENT AND MEASUREMENT OF DIPOLE MOMENTS. 117chains 57 generally lie flat. in the surface, if they can be spread a t all.Complete spreading is decidedly difficult to obtain, and practicallyno spreading is obtained if the protein is first denatured.5* Whenspread, the protein films, and the cellulose films, may be compressedor expanded somewhat without collapsing ; in the case of the proteinfilms this is considered by A.H. Hughes and E. K. Rideal to be afolding of the chains without leaving the surface, similar to thosecaused by stretching protein fibres. N. I<. Adam 54 considers thatthe compressibility of cellulose derivatives is due to a tilt of theunit glucose rings slightly away from the surface on lateral com-pression.Finally, some interesting work on the transference of orientedfilms 01 Iong-chain molecules from water surfaces to solids must bementioned.59 By repeatedly dipping r2 clean glass, or polishedmetal, plate into water covered by unimolecular films, layers may bedeposited one by one.Generally, the first layer has the polargroups oriented towards the glass or metal, the next has themoutwards, and so on alternately. The structure is very similarto that of crystals of these paraffin-chain compounds. If the outerlayer has the hydrocarbon ends of the molecules outwards, thesurface is not easily wetted by water ; but if it has the water-attract-ing groups outwards, it is perfectly wetted. I n certain circum-stances successive layers can be deposited all with the hydrocarbonchains pointing outwards.Even one of these layers, as 1. Langmuir showed in 192OY6O hasa considerable lubricating effect on the solid.N. K. A.7. THE EFFECT OF THE SOLVENT IN THE MEASUREMENT OFDIPOLE MOMENTS.Although it was realised before 1932 that, when determined insolution, the dielectric polarisation of a compound possessing a result-an6 dipole moment varied somewhat with the nature of the solvent,even when the results were extrapolated to infinite dilution, it wasgenerally believed that the differences were not considerable and thatthe dipole moments calculated from data obtained in this manner5 7 W.D. Harkins, E. F. Carman, and H. E. Ries, J . Chern. Physics, 1935,3, 692.5 8 H. Neurath, J . Physical Chem., 193G, 40, 361.be K. B. Blodgett, J. ,4?ner. Chern. SOC., 1934, 56, 495; 1935, 57, 1007; I.Langmuir and V. J. Schaefer, ibid., 1936, 58, 254; G. L. Clark, R. R. Sterrett,and P. W. Leppb, ibid., 1935, 57, 330.60 Trans. Furadny SOC., 1020, 15, 68118 GENEBAL AND PHYSICAL CHEMISTRY.were in good agreement with those derived from measurements onthe vapour.The results of F. H. Miiller f on the polarisation ofchlorobenzene in a number of solvents called attention, however, tothe possibility that the solvent influence might be appreciable, andthat dipole moments estimated from measurements in dilute solutionmight require reconsideration. I n the past three years manystudies of the solvent influence on dielectric polarisation have beenmade, from both theoretical and experimental points of view, andMiiller’s results have been substantiated and extended. One of theobjects of this work has been to discover a, relationship between themoment determined in solution and the true value, it being assumedthat the latter is given by the vapour-temperature method based onthe well-known Mosotti-Clausius-Debye equation.The treatmentmay be divided very roughly into three sections: (a) empiricalmethods for correcting for the solvent influence, (b) theoretical con-sideration of factors not included in the Debye equation, (c) funda-mental modifications of this equation. It will be assumed, for thepresent, that the deviation from ideal behaviour is to be ascribedto electrical interaction between solvent and solute, and that nochemical action occurs.(a) Empirical Corrections for the Solvent Influence.--In order toaccount for the results with a number of substances, F. H. Miiller 2proposed the relationshipwhere P, and R represent the total polarisation and molecularrefractivity respectively of the solute and E is the dielectric constantof the solvent.The value of cQ P, in solution is obtained by extra-polation to infinite dilution. If the atom polarisation is negligible,then equation (1) can be written, to a first approximation, in theform- (2) = 1 - 0.038 (E - 1)’ . . . tR*h a p .This equation implies that the dipole moment measured in solution isless than the vapour value, the discrepancy increasing with increasingdielectric constant of the solvent. To obtain the true momentit is necessary to extrapolate the results in solution to the valuefor a medium of dielectric constant unity. The facts were explainedqualitatively by supposing that the intense electrical field of a dipolemolecule produced saturation of the dielectric in its vicinity, so that2 Ibid., 1933, 34, 659; Trans.Faraday Soc., 1934, 80, 729.PJ.,ysilcccl. Z., 1932, 88, 732GLASSTONE : SOLVENT AND MEASUREMENT OF DIPOLE MOMENTS. 119the polarisability of the non-polar solvent is decreased below itsvalue in the pure state. The decrease in polarisation of the solution,which is evident as an apparent decrease of moment of the solute, is,according t o Miillcr, due t o the solvent. By adapting the methodemployed for the interpretation of dielectric phenomena in electro-lytic solutions, an expression was deduced for the expected change inpolarisation of the solvent. It has been pointed however, thatthe almost exact additivity of refractivities in solution argues againstthe postulate of dielectric saturation.The empirical equation (1)is satisfactory for calculating pmp, in certain instances, but it failsin other^,^ and in any case it can only have limited applicability,since it is now evident that, although for the majority of compoundsthe apparent dipole moment decreases with increasing dielectricoonstant of the solvent, yet for some substances, e.g., alcohols, themoment is almost independent of the medium, whereas for others,e.g., chloroform, the moment in solution is greater than that of thevapour .6suggested that ,nPz in various media is a linearfunction of 1 /E, thuswhere A and B are constants. By altering the sign in front of theB/c term, equation (3) could be used to represent both positive andnegative solvent effects.This empirical relationship has the advan-tage of covering a wider range of dielectric constants than equation(1) and appears to be applicable to nitrobenzene, chlorobenzene, aridp-nitroaniline in a number of solvents, both polar and non-polar,It fails, however, in certain instances to give the correct value for thepolarisation when the results are extrapolated to E = 1. In itssimplest form the relationship proposed by S. Sugdeq8 that Pd 0 1s * izlinear function of the volume polarisation, may be writtenH. 0. Jenkinsa P , = A &B/E . . . . . . (3)P z = A & B ( & - 1 ) / ( & + 2 ) . . . . (4)so that it covers both types of solvent influence: as will be seenshortly, an equation of this type has a theoretical basis.It has beenfound to be of the correct form to represent the variation of polarisa-tion with dielectric constant of the medium for a number of dipolarsolutes, but it is doubtful if the significance originally attached to d ,H. Sack, Phyeikat. Z., 1927, 28, 199.C. P. Smyth et nl., J . Chem. Physics, 1935, 3, 55, 347, 557; E. G. CowloyK. Higesi, Bull. Inst. Phys. Chent. Re. Tokyo, 1934, 13, 1167.4 F. C. Frank, Proc. Roy. SOC., 1935, A, 152, 171 (172).and J. R. Partington, J., 1936, 1184; 1937, 130.7 Nature, 1934, 133, 106; J., 1934, 480.8 Natirre, 1934, 133, 415; 12‘mn.s. Paradcsy Soc., 1934, 30, 720120 GENERAL AND FZIYSICAL CHEMISTRY.as the sum of e p - and a small constant, and to B , as the orienta-tion polarisation (Po) of the solute, can be substantiated either theor-etically (see below) or from actual measurements.By Sugden'sequation the plot of P, against (E - 1)/(& 4- 2 ) for various solvents, orfor different concentrations in the same solvent, should be a straight,line, which on extrapolation to (E - l ) / ( ~ + 2) = 0, that is E = 1,should give e p . , but this procedure does not always yield satis-factory result^.^ F. Fairbrother lo has tested equation (4) by plot-ting 9, against (& - l ) / ( ~ + 2) for nitrobenzene in solution a t severaltemperatures, and found, as required, that straight lines convergingto a common point for ( E - l ) / ( ~ + 2) = 1 are obtained. Promthe slope of the lines, assumed equal to Po, the moment was foundto be 4-24 D, in excellent agreement with the vapour value.A com-prehensive test of equation (4), however, has led H. 0. Jenkins andL. E. Sutton to conclude that it is only approximately correct : thevalue of B is often very different from Po, and the agreement ob-served by Fairbrother for nitrobenzene is regarded as fortuitous.Another type of semi-empirical equation is that of R. J. W. LeF&vre,ll vix.,PJP; = I<(&' -1 2)/(&' + 2) . . . . (5)where Po and Pi represent the orientation polarisations for a givensolute in two media of dielectric constant E' and E' ' , respectively, andK is a constant approximately equal to unity for a number of sub-stances. If one of the solvents is regarded as a vacuum (E" = I),then it follows that- (6) p",ol. f p 6 p .- X3/(& + 2) . . .The use of this equation is restricted by the uncertainty in the valueof K , and also because it only applies to negative solvent effects,that is, when polarisation decreases with increasing dielectric con-stant. In spite of their limitations, and the fact that they cannot beusedfor accurate extrapolation to E = 1 , one or other of the equationsgiven above may be employed for interpolation purposes, for ex-ample, when it is required to compare polarisations of differentsubstances under analogous conditions, e .g. , in media of the samedielectric constant. Por this purpose a function of E giving a linearrelationship against P, is to be preferred : the volume polarisation(E - l)/(& + a), or its square, appears to be best for this purpose.l29 H.0. Jenkins and L. E. Sutton, J., 1935, 609; E. G. Cowley and J. R.10 J . , 1934, 1846.11 J., 1935, 773.12 D. P. Earp and S. Ghsstone, ibid., pp. 1709, 1720.Partington, low. cit., ref. ( 5 ) GLASSTONE : SOLVENT AND MEASUREMENT OF DIPOLE MOMENTS. 121(b) Theoreticnl Consideration of Factors not included in the DebyeEquntimz.--Soon alter the publication of &fiiller’s work on the polari-sation of chlorobenzene, an attempt) ~;lras made by J. Weigle l 3 toexplain the results theoretically. Two factors not included in theDebye treatment of dipolar molec~tles were considered, namely,(i) the polarisation of the medium by the dipolar molecules of solute,and (ii) the orienfation of optically anisotropic solvent moleculessurrounding the dipole.The second of these factors should producea moment Apt, acting in the same direction as the primary moment,given bywhere A is a numerical constant, p is the moment of the dipolarmolecule, assumed to be spherical, and a is its radius ; a’ and a” arethe polarisabilities along the two chief axes of the anisotropic solvcntmolecule, assumed to be an ellipsoid of revolution. Since a’ - a”is involved, Ap’ is evidently small, and for most solvents it is pro-bably of the order of 1 yo of the primary moment. The main influ-ence of the solvent is attributed to the polarisation of its moleculesby the dipoles. If the molecules are spherical, Weigle finds themoments induced by the solut’e in surrounding molecules shouldcancel one another, so t,hat the resultant effect is zero.For non-spherical solvent molecules, however, the resultant induced momentis generally not zero : its value and sign depend on the actual shapeof the molecules. Weigle considered only the case of a moleculeconsisting of a cone terminating at its point in a spherical surface,and found the resultant induced moment Ap, in the direction of theprimary moment, to be given by the following equation, in whichsmall terms have been ignored, viz.,Ap‘ = A ( p 3 / t 6 ) ( ~ ’ - E”)~//cT . . . . ( 7 )Ap = Bp(a‘ + 2 ~ ” ) . . . . ’ (8)where the magnitude and sign of B dt:pend on the shape of the solutemolecule and a’ and a” are the polarisabilities of the solvent.‘Thisis virtually the form in which Weigle left his deductions, but furtherconsiderationshows that it can be written in another way so as t obring out more explicitly the influence of the dielectric constant ofthe medium. If the difference in a‘ and a” is not great, equation (8)reduces to Ap = SBpcc, where a represents the mean polarisabilityof the solvent molecules, and for a non-polar substance this is givenN(& - l)/d(& + 2) = 4 / 3 X i V E . . . . (9)bYso thatAp = ~ C ( E - 1)/(& + 2)or ~sol./pvap. = 1 + C(E - I)/(& + 2 ) . .la Helv. Physlsica Acta, 1933, 6, 68122 UiENERAL AND PHYSICAL CHEMISTRY.where C is a constant, dependent on the shape of the solute molecule.The relationship between this and Sugden’s equation (4) is evident.K.Higasi has shown that Weigle’s theory predicts a negativesolvent effect for molecules elongated along the dipole axis, and apositive effect for molecules having their elongation perpendicularto this axis. The latter type of molecule should have negativeKerr constants, and it was in fact found thak with such substances,only a limited number of which are known, the dipole moment insolution is greater than in the vapour.The calculation of the moment induced in the solvent by the di-polar solute has been extended by P. C. Prank,l* who has given LLvery complete discussion of the solvent effect in the measurement ofdipole moment, and independently by K. Higasi.15 Frank makesuse of the relationship I = E(& - 1)/4~e for the induced moment perunit volume, where B is the field strength in the given volumeelement : the field strength at any point in the vicinity of the dipole,assumed t o have no finite length, can be readily calculated.I norder to obtain the resultant induced moment it is convenient todivide the space round the dipole into elementary shells of uniformfield, aiid each of these is further divided into elementary rings inwhich the uniform field is uniformly inclined t o the dipolar axis,The induced moment is calculated to beAp = LIE/,(€ - l ) / ~ . . . . . (11)or E-L.sol./~vap. == 1 -t- - l>/& ’ - - * (12)where A is a quantity determined by the shape of the molecule andthe position of the dipole within it : the value of A may be positiveor negative and is evalu:$ted by a process of graphical integration.Actual dipolar molecules may be divided roughly into four cate-gories according to their geomstry, with characteristic solventeffects.(i) Small molecules with no large group attached, e.g., HC1,H20, for which A is about + 0.1, so that the solvent effect should bepositive. (ii) Molecules with a radical on the dipole axis, e.g., CH,Cl,C6H5*N0,, C,H,Cl; nearly all the substances considered by F. H.Miiller fall into this category. The solvent effect is negative, andFrank’s calculations give results in approximate agreement withMuller’s rule (equation 2). (iii) Molecules with a single radical noton the dipole axis, e.g., CH,*OH; with such substances the effectdepends largely on the angle 0 representing the polar co-ordinate ofthe radical with respccb to the dipole axis, the position of the dipolebeing the origin.If 8 is less than 55”, Ap is negative and of appreci-14 LOC. cit., ref. (4), p. 171.l5 Sci. Papers Inst. Phys. Chm. Res. Tokyo, 1936, 28, 884GLASSTONE : SOLVENT AXD MEASUREMEST OF DIPOLE MOMENTS. 123able magnitude, but if 0 is greater than 55" then Ap tends to becomepositive although it, is oidy appreciable when 0 is about 90°. Foralcohols, the solvent effect might be expectcd to be small. (iv) Mole-cules with radicals off the dipole axis but possessing axial symmetry,e.g., CH,*O*CH,, (CHE,),N, (CM,),CO ; the induced moment in thesolvent is, as in case (iii), negative or positive according as 8 is lessor greater than 65". For dimethyl ether it should be small, for tri-methylamine it shonld be positive, whereas for acetone it should benegative but not large.The anticipations are in general agreementwith experimental observations. It is of interest to record that3'. H. Muller and P. Mortier,16 as a result of measurements with anumber of compounds, have divided molecules into groups corres-ponding closely to those proposed by Frank from theoretical con-siderations : the former authors also emphasise the importanceof the position of the dipole in the molecule, which is determined byFrank's angle 8. Since equation (12) may be writtenp.soI./pvap. = 1 + L4~vap. - A ~ v a p . / c * (13)it follows that the plot of peal. against 1 / E should be linear, and whenextrapolated to E = 1 the result should give the true moment, in thevapour state.As far as the available data are concerned theseanticipations are only realiscd very approximately, the extrapolatedvalue of pvap being higher than that 0bserved.l' Although it isapparcnt that the main solvent effect is to be attributed to inducedpolarisation in the solvent molecules, other factors, e.g., distortionof the field surrounding the dipole, various forms of interaction be-tween the molecules of solvent and the solute, and orientation of thesolvent molecules on account of their anisotropy, must be taken intoconsideration. It may be no-ted that since Po is proportional top2, equation (13) reduces to one similar to that ol Jenkins [equation(3) 1, if the term involving 1/z2 is neglected.The treatment of K.Higasi l5 is based on the relationship A p =aE, where cc is the polarisability of the solvent molecule, as given byequation (!I), and E is the field strength. The value of Ap is cal-culated asorwhich is identical in form with that obtainable from Weigle's treat-ment : this is to be expected, as Hipsi's method is a direct extensionof that of Weigle. The sign and value of A depend on the shape ofthe solute molecule, and a number of cases are considered. (I) Ifl6 Physikal. Z., 1935, 36, 371.1 7 See, however, E. G. Cowley and J. R. Partington, J., 1936, 1184 (1189).Ap = ~A(E - l ) / ( ~ -1- 2) . . . * (14)P80l./P.,,P. = 1 + -4. - + 2) - * * (15224 GENERAL AND PHYSICAL CHEMISTRY.the molecule is spherical, then A is zero and ps.l.= p,,,.. (11) Thedipolar molecule has the shape of an ellipsoid of rotation with adipole at its centre along its axis of symmetry : if a is the radius alongthe dipolar axis and c the value at right angles, then there are twopossibilities, according as (a) a > c (Fig. 1A) or ( h ) a < c (Fig. 1B).For case (a) , the value of A is given bywhere li: is equal to alc, the ratio of the radii, which is greater thanunity : the value of A,,, is a'lways negative, so that for moleculesof this type the solvent effect should always be negative. For case( 6 ) it is calculated thatwhere k is now less than unity, and AIIb is always positive, as also isthe solvent influence. (111) The solute molecule is an ellipsoid ofrotation but the dipole is not a t its centre (Fig.2) : several cases are00FIG. 1. FIG. 2.possible.A, and A,, where(a) I€ a, > c and a2 > c, then A,,,, is the sum of two termsand A, has an analogous value with a2 replacing a1 : both A, and A ,are always negative. ( b ) If a, > c and a2 < c, then AIIIb is thesum of A,, as above, and B,, wherGLASSTONE : SOLVENT AND MEASURICMENT OF DIPOLE MOMENTS. 125which is always positive. The actual solvent effect will therefore beeither negative or positive according as A, is greater or less than B,.(c) If a1 < c and a2 < c, thenAuIC=Bl+B2 . . . . a (20)where B, is as already given and B, is the corresponding value whenal replaces a2 : both terms are positive.< c and az > c,thenwhich may be negative or positive, according t o the relative values ofA, and Bl. Provided the dipole is not situated far from the centreof the molecule, the results of Higasi may be summarised, in general,by the statement(d) IfA1m=Bjl+Az . . . . * (21)> <psol. 7 pvap. according as a cwhere a and c are measured along the dipolar axis and perpendicularto it, respectively. The main difficulty in the application of theequations given above to determine pvap. from measurements insolution lies in the determination of the shape of the molecule and theposition oEthe dipole in it. This is done approximately from theknown atomic dimensions and from stereochemical considerations,the molecule being assumed to be equivalent in shape to an ellipsoidof rotation. Where the necessary data are available, Higasi hasshown the calculated values of Ap to be in good agreement withps,,l.- pvap., and the same conclusion has been reached by E. G.Cowley and J. R. ParfingtonY5 who have made measurements onbenzonitrile, propionitrile, bromobenzene, and ethyl bromide in sixnon-polar solvents. The theory of the electro-optical Kerr effect l8indicates that positive Kerr constants are, in general, to be expectedfor molecules in which the dipole lies in the direction of the longeraxis, so that they should show negative solvent effects : most com-pounds have positive Kerr constants, and hence the dipole momentsin solution are usually smaller than the vapour values.When theKerr constant is negative, e.g., for chloroform, the solvent effect ispositive : for such substances the dipole is perpendicular to the longeraxis of the molecule.6 Before proceeding, attention may be calledto a difference between the equation of Frank and those of Weigleand of Higasi : both the last two involve (E - I)/(& + 2), but thefirst gives Ap as a function of (E - l)/e. Since E for most non-polarsolvents is about 2, the general results are not very different, but thediscrepancy requires further investigation.An entirely different approach has been outlined by P. Debye,lSSee, e.g., H. A. Stuart, “ Molekciilstruktur,” 1934, p. 197 et seq,l@ Physilcal. Z., 1935, 36, 100; Chem. Reviews, 1936, 19, 171126 GENERAL AND PH'YSICAL CHEMISTRY.based on the theory of quasi-crystalline structure of liquids : theaxis of the dipolar molecule is supposed to rotate relatively slowly, sothat an additional term is to be added to that of thermal agitationhindering the orientation of dipoles in an external field.The expres-sion for the orientation polarisation per molecule should then bewrittenwhere F(y) is a fuxtion of y = E/k[i', E being regarded as the coup-ling energy between solvent and solute molecules which preventsrapid rotation. The treatment so far has been qualitative; itaccounts only for negative solvent effects but does not explain itsvariation with dielectric constant. It has been suggested that thetheory may prove more useful lor polar than for non-polar solvent^.^(c) Fundamental Modijcations of the Debye Eqmtion.-TJnless a,molecule is optically isotropic, i.e., equally polarisable in all direc-tions, neither the Mosotti-Clausius equation nor its extension byDebyc to polar molecules can be strictly applicable.(Sir) C. V.Raman and K. S. I(rishnan20 have pointed out that there is muchevidence to show that actual molecules are not isotropic ; they haveconsidered the general case of a pure liquid consisting of anisotropicmolecules and have derived the equationPo r= (47q491cT). F(y) . . * . . (22)E - 1 E - 4 r N p + g ) + E - l N ( y+-- &) * (23)& + 2 ' d -3 3 312 E + 2where Zx = a' + a" + a"', the polarisabilities along three axes, andY and 0 give the effects of anisotropy on the induced and the orient-ation polarisation, respectively, which can be determined, approxi-mately at least, from mea.surements ol light scattering and from thegeometry of the molecule.21 The equation has been extended toliquid mixtures,22 then becomingwhere the subscripts 1 and 2 stand for solvent and solute respectively.M. A.Govinda Rau 23 has considered the special case when one of thef O Proc. Roy. Soc., 1928, A , 117, 689.2 1 See (Sir) C . V. Raman and K. S. Krishnan, Phil. Mag., 1928, 5, 498;K. S. Krishnan and S. R. Rao, Indian J . Physics, 1929-30,4,39; M. Raman-adham, Proc. Indian Acad. Sci., 1934, 1, A , 281; H. 0. Jenkins and 8. H.Bauer, J . Amer. Chm. Soc., 1936, 58, 2435.22 D. S. Subbaramaiys, Proc. Indim Acad. ScL, 1934, 1, A , 355.23 [bid., 1935, 1, A , 498; see also H.0. Jenkins and S. li. Eauer, koc. tit.,ref. (21)GLASSTONE : SOLVENT AND MEASUREMENT OF DIPOLE MOMENTS.components, i.e., the solvent, is non-polar, that is pl = 0 and 0,so that127= 0,The molar polarisation of the non-polar solvent in tho gaseous statcis - n i ~ ~ l , and according to equation (23) this can bc put equal to 4x3 3-___ --___ -c 1 + 2 ' d ~ 1 + 2 NY1; further, {,'he molar polarisatioii of the &1- 1 nf4 x 2 \N (z? + -k), so that 31cT solute in thc vapour state is equal 60substitution in equation (25) givesthe fir& term on the right-hand side being .*I.. I n very dilutesolutions it may be assumed that the dielectric constant and thedensity vary in a linear manner with the concentration, thusE = E 1 ( 1 + &> and dl,2 = q a + bf2)It can then be showii 24 that in the limit as infinite dilution isapproached, when the first term in equation (26) becomes ,P2, the33& second term becomes A'\k:, -1 and iii the third E bocomes thevalue for the solvent, i.e., so that(El + a2In fhis equation the quantity 'r, applies to the pure solvent, butY2 and 0 are those applicable tQ the solute molecule in a state ofin$nite dilution in the solvent, and not those for the pure homogeneoussolute.Of the correction terms in -the square bracket of equation(27) the first two are generally small and negative, but the third,which is the most important, can be negative or positive accordingas the dipole moment of the solute molecule lies along the axis ofgreatest polarisability or not : that if;, according as the solute has apositive or negative Kerr constant, the sign of which is oppositc to24 G.Hedestrand, Z . phyeikal. Cyhena., 192!4 €3, 2, 428128 GENERAL AND PHYSICAL CHEMISTRY.that of 0.25 This result is, therefore, in qualitative agreement withexperiment and with Higasi’s treatment. By assuming the soluteto be represented by an ellipsoidal cavity of the same shape as ben-zene, M. A. Govinda Rau 23 was able to apply equation (27) tomeasurements 26 on nitrobenzene in various solvents, and therebyobtained a value of P, in good agreement with that observed for thevapour : for dioxan as solvent, however, there was an appreciabledifference. have tested theequation with measurements on benzonitrile, bromobenzene, andethyl bromide ; the calculated G P .values are of the correct order,and almost constant for data from different solvents, but they differsomewhat from the experimeatal vapour values. It is importantto note that for carbon disulphide as solvent, the molecules of whichare anisotropic, the discrepancies are considerable. The funda-mental diEculty in the exact application of equation (27) lies in theevaluation of the important quantity 0 for the solute : not only isthe basis of its calculation from optical and other data uncertain,but the result so obtained is for the pure solute, whereas, as emphas-ised above, it is the value at infinite dilution in the particular solventwhich is required.By using experimental Ppp- data 0 can becalculated, and the results so obtained are different from thoseevaluated for the pure solute ; 27 further, the 0 values vary appreci-ably from one solvent to anothcr.28 The fundamental arguments ofRaman and Krishnan, upon whose treatment Govinda Rau’sequation is based, have also been subjected to criticism.29(Mrs.) C. G. Le FBvre and R. J. W. Le Fb~re,~O following F. R.G o s s , ~ ~ have shown that the relationshipE. G. Cowley and J. R. Partington. (28)may be derived from the Raman and Krishnan equation for a pureliquid, and there is reason to suppose that a similar equation willapply if Pp is replaced by Pi’. determined from measurements25 M. A. Govinda Rau, Zoc. cit., ref. (23), p. 505; (Mrs.) C.G . Le FBvre26 M. A. Govinda Rau and B. N. Narayanaswamy, PTOC. Indian Acad.27 M. A. G. Rau, Zoc. cit., ref. (23), p. 507; F. C. Frank, Chem. and Ind.,2 8 R. J. W. Le FBvre and P. Russell, ibid., 1936, 491 (492); H. 0. Jenkins29 H. 0. Jenkins and 2. E. Sutton, J., 1935, 609 (614); H. Miiller, Physical3o J., 1935, 1747.81 J . , 1934, 696.and R. J. W. Le FBvre, J., 1035, 1747 (1748).Sci., 1935, 1, A, 489.1936, 55, 37; E. G. Cowley and J. R. Partington, J., 1937, 130.and S. H. Bauer, Zoc. cit., ref. (21).Rev., 1936, 50, 547; H. 0. Jenkins and S. H. Bauer, Zoc. cit., ref. (21)QLASSTONE : SOLVENT AND MEASUREMENT OF DIPOLE MOMENTS. 129in solution after extrapolation to infinite dilution. It must bepointed out, however, that the argument is not exact, since 0, p, andE in equation (28) for the pure liquid refer to the same substance;when the equation is applied to a solution, however, 0 and p refert o the solute and E to the solvent.By making use of the equationPrp* = 45;Np2/9kT, it is seen that the relationship of Le FBae andLe FBvre is identical with equation (27) with the first two terms in thesquare bracket omitted : it can only be regarded, therefore, asapproximate. If 0 is assumed to bt: equal to - 4xp2/3, then equa-tion (28) becomes identical with the empirical relationship, equation(6), with K equal to unity (p. 120). By making the same assumption,M. A. Govinda Rau 32 has shown that equation (27) may be reducedto the form of equation (4) with A and B having the significanceattributed to them by Sugden (see p.119). It has been emphasised,however, by F. R. Goss 31 that it is very unlikely that 0 should bcequal to - 4xp2/3 ; this only occurs when p is zero. Further, at thecritical point 0 vanishes, whereas p retains its normal value. Men-tion may be made of the fact that, even before Rau had applied theRaman-Krishnan equation to dilute solutions, F. R. G O S S ~ ~ hadused it to calculate vapour dipole moments from measurements insolution : the treatment is, however, not entirely justifiable, since thesame equation was assumed to apply to dilute solutions as well as topure liquids. It should be noted that Goss, Rau, and Le Fbvre haveall obtained relationships which can be written in the form ofSugden’s equation (4), and by utilising the fact that p is proportionalto no they all reduce to the same type as equations (10) and (15)of Weigle and of Higasi, respectively, provided small terms are neg-lected : the constant factor preceding (E - l)/(s + 2) is in each caserelated to the shape of the molecule.Apart from the modifications of the Mosotti-Clausius-Debyeequation described above, attention must be called to a, number oftheoretical investigations; some of these have not yet reached thestage of being of practical value, but they may have an importantinfluence on future developments.Amongst other factors, theDebye treatment neglects the force on a polar molecule due to thesurrounding molecules being polarised by the molecule considered.M. Kub0,34 E.A. G~ggenheim,~~ and L. Onsager 36 have independ-ently attempted to take into consideration what is called by Onsagerthe ‘‘ reaction field,” as distinct from the “ cavity field ” treated by32 LOC. cd., ref. (23), p. 508.38 LOC. cit., J., 1935, 502, 727; see also F. Fairbrother, J., 1934, 1846.34 S&. Papers Inst. Phye. Chem. Rea. Tokyo, 1935, 27, 295.85 Nature, 1936, 137, 459.36 J . Amer. Chent. SOC., 1936, 58, 1486.REP.-VOL. XXXIII. 130 GENERAL AND PHYSICAL CHEMISTRY.&bye, following Mosotti and Clausius. Kubo has applied hisargument to gases only, and finds. . (29) E - 1 &! 4 X 2xctp2vE+2' d= VN [a + &(I + mdlwhere v is the number of molecules per c.c., a is the polarisability,and p is the radius of the " sphere of action " of the molecules.In apreliminary report, Guggenheim gives the result of a treatmentbased on the use of a model for polar solutions similar to that em-ployed by Debye and Huckel for electrolytes : the solvent molecule isassumed to be spherical and the solvent is regarded as a continuousmedium. It is deduced that[ ( E - &J2 - (no" - n2)]/c0 = 4xp%,/3i%T . . (30)where E and n are the dielectric constant a'nd refractive index of thesolution, and c0 and no are the values for the solvent ; v, is the num-ber of solute molecules per C.C. of solution, and p is here defined asthe total electric moment between the plates of a, large parallelcondenser filled with the solvent containing one single molecule ofsolute with its polar axis normal to the plates.The values of pobtained from equation (30) are somewhat lower than those given bythe Debye formula, but the results are independent of concentration,so that the decrease of polarisation often observed with increasingconcentration cannot be due to association, as has been frequentlysuggested (see below). According to Guggenheim, the variationof p with solvent should be given byp(a0 + &i) = constant . . . * (31)where ( E ~ - 1)/4x is the polarisability per unit kolume of the solutcsphere. The treatment is preliminary and is only applicable tospherical molecules, for which the solvent correction should, accord-ing to the views described above, be zero. Onsager has given asomewhat fuller report of his deductions : he finds for a pure dipolarliquidE - 1 n 2 - I E ( n 2 + 2 ) 4 d p O 2E + 2 n2 + 2 - ( 2 ~ + n2)(& + 2) * 3Ll'where the symbols have their usual significance, and vo is the dipolemoment as vapour.For a dilute solution of a polar solute in anon-polar solvent the relationship deduced isP . (32) ----where E and n refer to the solution, and the subscripts 1 and 2 to thGLASSTONE : SOLVENT AND MEASUREMENT OF DXPOLE MONENTS. 131solvent and solute respectively. Further, the relationship betweenpsol. as measured and pvap. is given byAccording to this equation, the solvent effect for a spherical molecule-the deductions so far only apply to such molecules-should benegative. It may be pointed out that the treatments of Guggen-heim and of Onsager should lead to the same equations, and it is notyet evident why the discrepancy e ~ i s t s . 3 ~ J. G. K i r k w o ~ d ~ ~ hasinvestigated the polarisation of a non-polar dielectric in a homo-geneous field from the molecular point of view, and has shown thatthe Mosotti-Clausius equation can hold only if every molecule hasthe same induced moment throughout all phases of its thermalmotion. Statistical calculations show that the fluctuations fromthe mean value of this moment lead to deviations from ideal be-haviour, and it is possible to deduce the equation(E - 1)M/3d P[1 + (1 + y $- ~)Pd/lcf + . . . 1. . (36)wlicro P is the polarisation, y is approximately equal to P/4vm,v, being the volume of a single molecule, and (I is a correction foranisotropy. This may be compared with the ordinary Mosotti-Clausius equation written in the form(C - 1)M/3d PL1 + PdIM . . . 3 (36)The treatment has not so far been extended to polar molecules.Temperature and Concentration EfSeects.-?Xow that it is realised thepolarisation of a solute frequently depends on the dielectric constantof the medium, it is possible to account for the fact that the tempera-ture method, used for determining the dipole moment of a gas orvapour, has not been found applicable to solutions.39 Since thedielcctric constant of the solvent changes with temperature, an addi-tional factor is introduced, and it has been found that the productPOT, which should be constant if there were no solvent effect, oftenfalls off steadily with increasing ternperat~re.~~ Further, the markeddecrease in polarisation sometimes observed with increasing con-centration of a polar solute in a non-polar solvent, e.g. , nitrobenzenein benzene, and which had been attributed to association of the37 Private communication from Mr. E. A. Guggenheim.38 J. Chem. Physics, 1936, 4, 592.39 Cf. C. P. Smyth, ibid., 1933, 1, 247; C. P. Smyth and IS;. B. McAlpine,40 F. H. Miiller, Physilcal. Z., 1934, 35, 346; E. a. Cowley and J. R.ibid., 1935, 3, 347 ; H. 0. Jenkins, Trans. Paraday Soc., 1934, 30, 739.Partington, Zocc. cit., ref. ( 5 ) 132 GENERAL AND PHYSICAL CHEMISTRY.solute,4l is probably to be attributed almost entirely to an increasein dielectric constant. A. E. van Arkel and J. L. Snoek 42 have shownthat, apart from other considerations, the Debye equation can onlyapply to solutions if vsp2<kT, where v, is the number of dipolemolecules per C.C. ; for substances having high moments this occursonly in very dilute solution, and so it is proposed to apply an em-pirical correction to the Debye equation, thuswhere c is a constant. It can be shown43 that this equation isvirtually identical with equation (4) for the variation of polarisationwith the dielectric constant of the medium. It should be noted thatthe remarks made above concerning association do not apply to allsubstances : with the alcohols, for example, it is certain that thevariation of association with concentration is an important factor.44A brtorml Solvent EfSects .-The exceptionally high dipole momentsobtained for aluminium and boron trichlorides in certain solvents 45are undoubtedly due to the formation of compounds containingsemi-polar links, and the results obtained with mixtures of halogeno-methanes or -ethanes and ether, acetone, or quinoline are probablyto be ascribed to some kind of association between the two constitu-e n t ~ . ~ ~ It is a striking fact that the dipole moment of ethylenedichloride is almost the same in a number of solvents, in spite of thepossibility of free rotation, but in benzene the value is exceptionallyhigh.47 This may also be due to a type of attraction between soluteand solvent in which other than van der Waals forces are involved.Another type of abnormality has been found in connection with thehydrogen halides ; 48 the moments in solution are invariably higher41 Cf. J. Rolinski, Physikal. Z., 1028, 29, 658; L. G. Davy and N. V.S i d s c k , J . , 1933, 281.42 Tram. Paraday SOC., 1934, 30, 707.48 J. L. Snoek, ibid., p. 721.44 See, e.g., K. L. Wolf and W. Harold, 2. physikal. Chem., 1934, B, 27,58; C. Hennings, ibid., 1936, B, 28, 267.46 H. Ulich, ibid., 1931, Bodenstein Festband, p. 423; H. Ulich and W.Nespital; 2. Elektrochenz., 1931, 37, 659; W. Nespital, 2. physikal. Chem.,1932, B, 16, 153.46 0. Hassel and A. H. Uhl, ibid., 1930, B, 8, 187; F. H. Miiller, loc. cit.,ref. (2); M. Kubo, Bull. I n s t . Phys. Chem. Res. Japan, 1934,13, 1221; D. P.Earp and S . Glasstone, Zoc. cit., ref. (12).47 A. E. Stearn and C. P. Smyth, J . Amer. Chem. Soc., 1934, 58, 1667; cf.also M. A. G. Rau and B. N. Narayanaswamy, Proc. Indian, Acad. Sci., 1934,1, A , 14; M. Kubo, loc. cit., ref. (46).4s F. Fairbrother, J., 1932, 43; 1933, 1541; Trans. Paraday SOC., 1934,30, 862 ; S. Mizushima, K. Suenaga, and K. Kozima, BulI. Chem. SOC. Japan,1936, 10, 167GLASSTONE : SOLVENT AND MEASUREMENT OF DIPOLE MOMENTS. 133than for the gas. This has been explained by postulating that thesolvent brings about a change towards an ionic linkage,*S or byassuming that there is a small displacement of the protonY5O but F. C.Frank 51 has expressed the view that the observations are adequatelyaccounted for by reflex induced polarisation in the hydrogen halidemolecules brought about by the induced moments in the solvent.These will always act in the same direction as, and so will enhance,the primary moment. The normal solvent effect for an almost spheri-cal molecule of hydrogen halide is in any case probably positive.The marked increase of moment of iodine chloride in solution hasalso been attributed to an increase in the ionic contribution to thelinkage,52 but normal solvent effects have not been entirely excluded.A number of compounds containing symmetrically situated polargroups, e.g., p-nitrobenzene, have appreciable moments in certainsolvents : this has been explained 53 by assuming that, as a result ofsolvent-solute forces, the moment of each group is not constant butfluctuates, independently of the other, about a most probable value.The resultant moment is then not zero, and by postulating a Gaussiandistribution la6 54 an expression for the effective moment of theniolecule, in terms of the most probable value of the group moment,can be derived. This explanation requires the period of fluctuationto be long in comparison with the time of relaxation of tlie solutemolecule in tlie electrical field, but some preliminary calculations byL. E. Sutton and F. C. Frank 55 indicate that this may not be thecase. A possibility being considered by these authors is that thedistribution of the solvent around the dipole is affected by the appliedelectrical field in such a way as to influence the measured moment.Polar Solvents.-In the theoretical discussion of solvent effects,only non-polar solvents were considered : when the solvent is polaronly a qualitative Oreatment is possible.56 There are a number ofresults in the literature 5 7 which suggest that certain polar solventsmay be used in the measurement of dipole moments, provided acorrection is made for the dielectric constant of the medium, gener-49 F. Fairbrother, Zocc. cit.51 LOC. cit., ref. (4), p. 183.52 F. Fairbrother, J., 1936, 847.63 H. 0. Jenkins, ibid., p. 862.54 See S. H. Bauer, J . Chern. Physics, 1936, 4, 459.5 5 Private communication from Dr. L. E. Sutton.68 See, e.g., F. C. Frank, Zoc. cit., ref. (2), p. 190.51 H. Higasi, Sci. Papers Inst. Phys. Chern. Res. Tokyo, 1934, 24, 57;H. 0. Jenkins, J., 1034, 480; 1936, 862; R. J. W. Le FBvre et d., ibid.,1935, 957; 1936, 491, 496; D. P. Eerp and S. Glasstone, loc. eit., ref. (12),p. 1719; A. E. Stearn and C. P. Smyth, Eoc. cit., ref. (47).J. D. Bernal, Trans. Paraday SOC., 1934, 30, 872.134 GENERAL AND PRYSICAL CHEMISTRY.ally by an empirical procedure. It is not certain, however, that thegeneral use of polar solvents is permissible. (Mrs.) C. G. Le FQvrcand R. J. W. Le FBvre 5* have measured the polarisations ofsome non-polar compounds in polar solvents, and have obtainedvalues of considerable magnitude, e.g., a moment of 1.5 D is indicstedfor benzene in nitrobenzene solution. The observations have beeninterpreted in terms of induced polarisations brought about by thepolar molecule of solvent, but the results must be accepted withcaution until due allowance can be made in the calculations for therelatively large change in the dielectric constant of the polar solventresulting from the addition of the non-polar solute.59 An interestingqualitative discussion of the influence of polar solvent moleculeson a polar solute is given by R. J. W. Le FBvre : 60 if molecules maybe divided approximately into two types, similar to those consideredby Higasi (p. 124), according as the principal moment lies along theaxis of maximum polarisability (A) or perpendicular to it (B), thenit is considered that a solvent of type A will be more effective inreducing the polarisation of a solute of its own type.than in increas-ing that of a type B molecule, and a solvent of type B will cause asmaller diminution of polarisation of an A molecule than it will in-crease the polarisation of one of the B type. The actual effects willdepend on the polarisabilities and moments of solute and solvent,on the distance apart of the molecules in the solution, and often oninternal distances between dipoles. S. G.N. K. ADAM.G. J. KYNCH.E. A. MOELWYN-HITGEES.W. G. PENNEY.8. GLASSTONE.G. R. B. M. SUTHERLAND.68 J., 1936, 487.69 See D. P. Earp and X. Glasstone, Zoc. cit., ref. (12)) p. 1721.60 J., 1935, 1747; 1936, 491

ISSN:0365-6217    

DOI:10.1039/AR9363300036

出版商:RSC    

年代:1936

数据来源: RSC

摘要:

INORGANIC CHEMISTRY.1. ATOMIC WEIGHTS.THE period which has elapsed since this subject was last reviewedfor the Annual Reports has seen the redetermination of a numberof atomic weights by chemical methods. Hiinigschmid and hiscolleagues have published papers on radium,l cadmi~in,~germanium,~tantalum,* m~lybdenum,~ tungsten,6 and raniu urn,^ as well as on theratio AgNO, : AgCl,* and American workers have made importantcontributions to this subject dealing with potas~ium,~ rubidium,lOgallium,ll carbon,12 arsenic,13 gadolinium,14 and eur0piurn.1~ I naddition, investigations have appeared on radiogenic lead,16, l7erbium,ls, terbium,lg protoactinium,m and neon.22 Asurvey of some of this new work has appeared in the fifth 23 and t,h&0. Honigschmid and R.Sachtleben, 2. anorg. Chem., 1934, 221, 66.0. Honigschmid and R. Schlee, ibid., 1936, 227, 184.0. Honigschmid, K. Wintersberger, and F. Wittner, ibid., 1935,225,Sl;0. Honigschmid and R. Schlee, ibid., 1935, 225, 64; 1934, 221, 129.0. Honigschmid and G. Wittmann, ibid., 1936, 229, 65.0. Honigschmid and F. Wittner, ibid., 1936, 226, 289.0. Honigschmid and R. Schlee, Angew. Chern., 1936, 49, 464.C. R. Johnson, J . Physical Chem., 1935, 39, 781.0. Honigschmicl and K. Wintersberger, ibid., 1936, 227, 17.cJ 0. Hiinigschmid and W. Menn, ibid., p. 49.lo E. H. Archibaldand J. G. Hooley, J. Amer. Chem. Xoc., 1936,58,70, 618;E. H. Archibald, J. G. Hooley, and N. W, F. Phillips, Tran8. Roy. SOC. Canada,1935, [iii], 29, 111, 155.l1 G. E. F. Lwidell and J.L. Hoffmann, J . Res. Nat. Bur. Stand., 1935, 15,409.l2 G. P. Raxter and A. H. Hale, J. Amer. Chew&. SOC., 1936, 58, 510.l3 G. P. Baxter and L. D. Frizzell, ibid., 1935, 57, 851.l4 C. R. Naeser and B. S . Hopkins, ibid., p. 2183.l5 E. L. Meyer and B. S. Hopkins, ibid., p. 241.l6 G. P. Baxter and C. M. Alter, ibid., p. 467.l7 F. Hecht and E. Kroupa, 2. anorg. C'hem., 1036,226,248.18 0. H6nigschmid, Natumiss., 1936, 24, 619.19 J. K. Marsh, J., 1935, 772.2o A. V. Grosse, J . Amer. Chem. SOC., 1934, 56, 2501; Proc. Roy. Soc.,21 F. G. Ntiiiez, Anal. Fis. Qu,irn., 1935, 33, 633.22 A. von Antropoff, Ber., 1935,68, B, 2389.33 G. I?. Baxter, 0. Hiinigschmid, P. Lebeau, and R. J. Meyer, Bet-., 1935,1935, A, 150, 363.68, -4, 73-84136 INORGANIC CHEMISTRY.sixth24 report of the Committee on Atomic Weights of the Inter-national Union of Chemistry, and in the forthcoming seventh reportthe more recent investigations will be described.In these the readerwill find a complete account of the chemical methods and the data,obtained in each investigation, as well as the table of approvedatomic weight values for the year. It is therefore unnecessary toattempt here a complete summary, and attention will be directedonly to those points which appear to be of special interest andimportance.Some of these new researches are an extension of work mentionedalready25 and lead by different ratios to the same atomic weight.Por example, the ratio TeCl, : 4Ag : 4AgC1 26 gives Te = 127-63, a resultonly slightly higher than that from the corresponding bromide ratioswhich is identical with the figure Te = 127.61 obtained from thesynthesis of silver telluride.2' Similarly, the new work on tantalumchloride 4 confirms the previous value for this element, i.e., Ta =180.88, obtained by the analysis of the bromide, which is more than0.5 unit lower than the old value of 181.4.28 This and similar workon niobium brings the chemical into close agreement with massspectrograph values.The same may now be said of germanium.39 52The work of Honigschmid and Menn on tungsten and Hhigschmidand Wittmann on molybdenum presents many points of interest onaccount of the difficulties which had to be surmounted before anhy-drous specimens of WCI, and MoCI, could be prepared in a highlypurified state and a satisfactory procedure devised for titration withsilver ion.This is the first time that a direct nephelometric com-parison with silver has been used in determining the atomic weightsof these two elements and the values W = 183.92 and Mo = 95.95obtained both from chemical evidence and from the close agreementwith Aston's values are probably very close to the truth.Another interesting revision is that of the atomic weight of radiumcarried out by Honigschmid and Sachtleben,l using as startingmaterial 5 g. of radium bromide containing 1.17% of barium bromidelent for the purpose by the Union Minibre du Haut Katanga ofBrussels. The accepted value for this element was based on the ratiosRaC1, : 2Ag : 2AgC1 and RaBr, : 2Ag : 2AgBr determined by Honig-schmid in 1912 29 with about 1 g.of the chloride supplied by theVienna Radium Institute. The much larger amount made possible a24 G. P. Baxter, 0. Honigschmid, and P. Lobeau, J. Amer. Chem. SOC., 1936,3 5 Ann. Reports, 1934, 31, 95.26 0. Hanigschmid and H. Baudrexler, 2. nnorg. Cirem., 1935, 2%, 91.27 Ann. Reports, 1933, 30, 83.28 Ibid., p. 82; 1934, 31, 96.29 Monntsh., 1912, 33,253; 1913, 34, 283.58, 541-548WHYTLAW-GRAY : ATOMTC WETGHTS. 137more elaborate purification and recrystallisation. The final material,ttfher an extensive series of recrystallisdiions as chloride, was testedspectroscopically by W. Gerlsch and E. Riedl and found to contJniria trace only of barium, estimated at ~.O02-@0O3%.Of this purifiedmaterial 3-5 g. were obtained. Quantities varying from 2 to 3.4 g.were dried and converted into the anhydrous salt by heating ingaseous hydrogen bromide charged with bromine up to a temperatureof 750°, the gas being displaced by nitrogen, and this in turn by air.After weighing, the bromide was converted into the chloride bysimilar treatment with hydrogen chloride and chlorine, followed bynitrogen and air-a method essentially similar to that used first byR. Whytlaw-Gray and (Sir) W. R,amsay 31 when attempting todetermine the atomic weight of radium with very small amounts ofmaterial.Difficulties were experienced in weighing the anhydrous radiumsalts on account of the heat evolution. The final value found for theatomic weight was 226.05, slightly higher than the older value225.97.Success with this element has led Honigschmid andWittner to revise earlier work carried out in Munich on the atomicweight of the parent element uranium, and in a comprehensiveinvestigation recently published they describe the preparation ofanhydrous UC1, and UBr,-every precaution being taken to obtainperfectly homogeneous materials of definite stoicheiometric composi-tion-and their subsequent analysis in terms of silver by standardmethods.The mean values for the nephelometric titrations gave U =238.073 from the chloride and U = 238.076 from the bromide ratios,The halides prepared from minerals from different districts andof varied geological age gave identical values for the atomic weight.Although a number of determinations were also made in which theprecipitated silver halides were collected and weighed, giving valuesof 238.066 from the ratio UC1, : 4AgC1 and 238.088 from UBr, : LiAgBr,yet these were not considered so reliable and were rejected in cal-culating the final mean.Some indication was also obtained thatfusion of the uranium halides before weighing led to a slight dis-sociation and so raised the atomic weight. ,411 the sources of errorindicated by a careful study of the data being taken into account,U = 238.07 is advanced as the most probable value, appreciablylower than the international figure 238.14.At the end of the paper the authors discuss the bearing of theirresults on the uranium-radium series and the origin of actinium andare able to show that they accord satisfactorily with physical data,30 2.anorg. Clwm., 1934, 221, 103.31 Proc. Roy. SOC., 1912, A , 86, 270138 INORGANIC CHEMISTRY.Starting from uranium-lead from Morogoro, the atomic weight ofwhich 0. Honigschmid, R. Xachtleben and H. Baudrexler foundsome years ago to be 206-03,32 and which G. P. Baxter and C. M.Hilton= have since confimed, they point out that this value isidentical with the mass-spectrograph figure for uranium-lead 34 fromthe same source when the latter is corrected to the chemical standard.Aston showed that this lead contained only the isotopes m6Pb(Ra-G)and m7Pb(Ac-D) in the ratio of 93.1 to 6.9. The atomic weight ofradium-@ is hence 206965, from which, by taking into account theenergy changes and the a-particles lost in passing from uranium toradium and from radium to radium-G, they find the calculated atomicweights of uranium and radium to be 238.044 and 226418, insatisfactory agreement with the experimentally found values of238.07 and 226.05.That uranium consists mainly of 238U and contains no higherisotope but only something less than 1% (0.4% estimated fromradioactivity measurements) of 235U, the parent of protoactinium,seems certain from the work of A.J. Demp~ter,~~ who has recentlycompared in his mass spectrograph the doubly-charged ions ofuranium and thorium with the two tin isotopes llGSn and lI9Sn.Reducing the values to the chemical scale and taking into accountthe small amount of 235U, he finds U = 238-028 and Th = 2320024.No indication of a higher isotope was obtained.Thus Aston'sconclusion that 231 is the atomic weight of protoactinium is againconfirmed. This is in accordance with a direct measurement ofthe atomic weight made by A. V. Grosse36 by the conversion ofK,YaF, into Pa20, by evaporation with sulphuric acid, followed byprecipitation with ammonia and subsequent ignition. Though thequantity of material was small (about 50 mg. of oxide), it showed noimpurities when examined in an X-ray spectrograph, but the value230.6 &0.5 might well be checked later on by a standard method.Pa = 231 appears this year for the first time in the internationaltable.Important work on fundamental ratios has appeared during 1936from the Munich laboratories.It has been found possible to carryout the conversion of silver nitrate into silver chloride with gaseoushydrogen chloride with the high accuracy required in this class ofinvestigation.It is obviously an advantage if solution, precipitation, filtration,32 2. anorg. Chem., 1933,214,104; s0e Ann. Reports, 1933,30,34.33 J . Amer. Chem. SOC., 1935, 57, 469.34 3'. W. Aston, Proc. Roy. SOC., 1933, A , 140, 535.35 Nature, 1936, 138, 120, 201.36 Proc. Roy. Soc., 1936,150, 363; Ann. Reports, 1935, 32, 146WYTLAW-GRAY : ATOMIC WEIGHTS. 139transference, and the evaporation of la,rge volumes of liquid can beavoided, and the reaction carried out in the same vessel with gaseousreagents. Dry reactions are, however, subject to errors due to avariety of effects such as adsorption and sublimation, but it is inter-esting to note their increasing use in modern work as exemplified bythe synthesis of silver ~lrlphide,~' ~ e l e n i d e , ~ ~ and telluride,3Q thereduction of silver nitrate to silver by hydrogenY4* the conversion ofbarium perchlorate into barium chloride 41 by hydrogen chloride gas,of silver iodide into silver chloride,42 and of radium and bariumbromides into the chlorides Making use of atechnique similar t o that employed in the reduction of silver nitrate,0.Honigschmid and R. Schlee * obtained for this ratio from eightclosely concordant experiments a mean value of 1.185241 with amaximum divergence of 7 in the last decimal place.Internationalatomic weights being used, the calculated ratio is 10185235. Com-bining the new ratio with the well-established ratios AgNO, : Ag =167479 and AgCl : C1= 4-042592, the following values were obtained:Ag = 107.881, C1 = 35.456, N = 14.009, which, taking into accountthe indirect method of calculation, the authors regard as a confirma-tion of the accepted values rig = 107.880, C1 = 35.457, N = 14.008,which are based on more direct ratios.Another example of stoicheiometric work on a standard ratiois that by C . R. Johnson on the atomic mass of potassium in whichthe experience gained in previous work on sodium 43 has now beenapplied to this element. The investigation on the ratios NaCl : Agand NaCl : AgCl mentioned in the 1934 Report presented a numberof new features, among others the checking of the equal opalescencemethod of nephelometric titration by potentiometric analyses.Inthe latest work, five samples of highly purified potassium chloride,prepared from material from American, German, and Norwegiansources, were referred to three independently purified samples ofsilver, and the fifteen determinations gave values for the KCl : Agratio ranging from 0.691 103 to 0.691 112, giving mean of 0.691 108 &0.0000005, which, with international values for Ag and C1, gaveK = 39.100. This lies midway between the international value37 0. Hilnigsclimid and R. Sachtleben, 2. anorg. Chem., 1931,195,207.88 0. Honigschmid and W. Kapfenberger, ibid., 1933, 212, 198 (see Ann,39 0.Honigschmid and I<. Wintersberger, ibid., p. 242 (see Ann. Reports,40 0. HBnigschmid, E. Zintl, and P. Thilo, ibid., 1927, 163, 66.4 1 0. Honigschmid and R. Sachtleben, ibid., 1929, 178, 1.42 0. Honigschmid and H. Striebel, 2. physikaZ. C7zem., Bodenatein Fest-43 J. Physical Chem., 1933, 37, 923 ; Ann. Reprta, 1934, 31, 96.in a similar way.Reports, 1933, 30, 82, 83).loc. cit.).band, 1936, 283140 INORGANIC CHEMISTRY.K = 39.096, based on the work of G. P. Baxter and W. M. Mac-Nevin *4 and of Honigschmid and Sa~htleben,~~ and the high valueK = 39.104, found previously by Honigschmid and J. G o u b e a ~ , ~ ~and is identical with the value for potassium appearing in the inter-national table prior to 1934. No satisfactory reason for the cause ofthese small differences has so far been given, but a suggestive investi-gation on the ratio of the two main isotopes of this element 39K and41K by A.K. Brewer 47 shows the importance of a knowledge of iso-topic composition in stoicheiometric work of high accuracy. Brewer,using a mass spectrograph of considerable resolving power, hasmeasured the 39K/41K ratio in potassium from a lasge number ofsamples of sea water and found a hardly detectable variation from themean value 14-20 ; minerals exhibited a slightly greater variation(39K/41K = 14-25), whilst in the ashes of plants a change of 15% inthe 41K content was found. Kelp contained the largest amount of41K. The atomic weight of potassium calculated from the sea-waterratio, probable values being assumed for the packing fraction and forthe change to the chemical scale, was 39.094.To account for a difference of 0-01 unit in the atomic weight ofpotassium would require the displacement of the abundance ratio of1.1 units, which is well within the variation found in potassium ofvegetable origin, but the author, after discussing the available data,rejects this explanation.Brewer's results seem well foundedand are in agreement with the values for the same ratio found byA. 0. Nier,48 who finds 39K/41K = 13.96 and an atomic weight of39-096. It may be noted that the rare isotope 40K discoveredrecently by Nier48sa and confirmed by Brewer49 is probably thesource of the p-radiation of potassium. The suggested degradationof 41K to *Wa has been negatived by recent work of F.W. Aston,5*who was unable to detect this isotope even in calcium separated fromvery old potassium minerals and which was reported to have a, highatomic weight : 40K is only present in small amount, and the ratio39K/40K is estimated at about 840011 and would have no detectableeffect on the chemical atomic weight. The atomic weight of the44 J . Amer. Chem. Soc., 1933, 55, 3185.4 5 8. anorg. Chem., 1933, 213, 365 (see Ann. Reports, 1933, 30, 85).46 Ibid., 1927,163, 93 (see Ann. Reports, {bid.).4 7 J. Amer. Chern. SOC., 1936, 58, 370, 365.48 Physical Rev., 1935, 48, 283.48a Ibid., 1936,50, 104; see also G. von Hevesy and M. Logstrup, 2. anorg.49 Physical Rev., 1935, 48, 640; see dso 0. Klemperer, Proc.Roy. SOC., 1935,5O Proc. Roy. Soc., 1935, A , 149, 399; F. H. Newman and H. J. Walke,Chem., 1928, 1'71, 1.A, 148, 638; andH. J. Walke, Nature, 1935,136,755.Phil. Mag., 1935, 19, 767WHYTLAW-GRAY : ATOMIC WEIGHTS. 141closely related element rubidium has been redetermined with modernrefinements by E. H. Archibald and J. G . Hooley and found to be85.481.Until recently it has been assumed that the variation in isotopiccomposition of the elements in chemical and physical processes is,with the exception of hydrogen, too small to influence even the mostaccurate of atomic-weight values. Recent physical considerations,however, show that on account of isotopic exchange occurring duringchemical reactions this view may require modification.H. C . Ureyand L. J. Greiff 51 have calculated from spectroscopic data the equili-brium constants and enrichment factors of several exchange reactionsinvolving isotopes of the lighter elements, and claim that in somecases the theoretical limit to precision in atomic-weight determina-tions has already been reached. They conclude that “ the atomicweights of many common elements as determined by known chemicalmethods are not fundamental constants of nature to more than a,limited precision.” For instance, in a mixture of chlorine andhydrogen chloride, when equilibrium is established the chlorine willbecome richer and the hydrogen chloride poorer in the 37Cl isotopeto an extent which would alter the atomic weight by 0.001 unit.So far, enrichment factors have been calculated only for a fewreactions, but for some of these, experimental confirmation has beenobtained, as, e.g., the concentration of l80 in carbon dioxide inequilibrium with water,52 and 13C from exchange between bicarbon-ate ion and carbon dioxide.53Since oxygen is the standard of afomic weights, the question maywell be asked : What isotopic composition is to be regarded as nor-mal? Oxygen in air has been proved to be heavier than oxygencombined in water.M. Dole54 finds a difference of 6 parts per millionin the densities of the water made by combining these two oxygenswith the sadme sample of hydrogen, whilst N. Morita and T. Titani 55find 7 p.p.m.; that is, if water oxygen is taken as standard, airoxygen has an atomic weight of 16-00012 ; this difference is, however,very small, and unless chemical reactions involve a greater isotopicseparation than has so far been found, it can exert no appreciableinfluence on atomic weights for chemical use.5GNier computes the atomic weight a t 85.45.5 1 J .Amer. Chem. SOC., 1935,57, 321.52 L. H. Webster, M. H. Wahl, and H. C. Urey, J . Chem. Physics, 1935, 3,53 H. C. Urey, A. H. W. Aten, jun.? and A. S. Keston, ibid., 1936, 4, 623.54 Ibid., pp. 268, 778.65 BuU. Chem. Soc. Japan, 1936, 11, 414; see also C. H. Greene and R. J.Voskuyl, J . Amer. Chem. Soc., 1936, 58, 693.66 See also W. Bleakney and J. A. Hipple, jun.? PhySiCd Rev., 1936, @],129.47, 800142 INORGANIC CHEMISTRY.It does, however, seem important to have an invariable standardfor chemical work, if only to be able to detect any considerable iso-topic exchanges which may occur in chemical operations and alsoto check atomic weights from physical data.It is obviouslydesirable, too, that fundamental chemical ratios should be deter-mined with material of known isotopic composition. Since thepreparation and purification of chemical substances are usuallycarried out in aqueous solution, the isotopic ratio of oxygen in freshwater, which appears from numerous measurements from differentlocalities to be remarkably constant, might well be taken as normal.Turning now from chemical to physical methods, progress hasbeen rapid in the determination of the exact masses of isotopes andthe computation of atomic weights from the abundance ratios.Since the survey of the rare earths which revealed some remarkablediscrepancies in the chemical values that have in some cases beenexplained by revision on the chemical side (terbium,lg erbium,l*gadolinium 14), F.W. Aston 57 has applied his methods to titanium,zirconium, calcium, gallium, silver, nickel, iron, hafnium, indium,cadmium, carbon, thorium, and rhodium. Good agreement withchemical values was obtained for the first seven elements, the silvervalue agreeing within the limits of error of the instrument withthe chemical. With hafnium, indium, and cadmium the agreementwas not so good, and for the last element has led to a revision bychemical methods which has confirmed the international value112.41 and exceeds the physical figure by 1 part in 557.Thoriumand rhodium were found to be simple elements. Recently, A. 0.Nier 48a has studied cadmium with a mass spectrograph of highresolving power, and has found somewhat different values for theproportions of the nine isotopes, leading to 112-37 for the atomicweight. Gold, one OI the four elements which has withstood allAston’s attempts at analysis, has recently been resolved by A. 5.D e m p ~ t e r . ~ ~ He finds it to consist of only one.species of atom 197,and its chemical atomic weight 197.2 is very probably too high.One section of last year’6 Report 59 drew the attention of chemiststo the remarkable developments in nuclear physics which enable themasses of atoms to be calculated with a surprising degree of accuracyfrom a knowledge of the energy changes accompanying nucleartransformations. It described how a study of the mass equivalentsof the energy released when light atoms are disintegrated by protonand deuteron bombardment has brought to light an error in the mass-spectrograph value for helium which was subsequently corrected.Since then Aston,60 using his third mass spectrograph, has obtained67 LOC.cit., p. 396.69 Ann. Reporta, 1936,233, 17, 18.6 8 Nature, 1935, 136, 65.6o Nature, 1936, 137, 357, 613WHYTLAW-GRAY : ATOMIC WEIGHTS. 143iiew and more accurate values for a number of isotopes, and thestudy of nuclear energy changes is extending with such rapidity thatexact values for a large number of atomic masses will soon be avail-able. Already a number of computations of values for the lighteratoms have been either from nuclear transformationsalone or from a combination of the two methods. The values soobtained show a close concordance.The great significance of the new work in the interpretation ofnuclear stability and structure is dealt with in another section.These advances promise to furnish chemistry with a table of atomicweights of an accuracy as great as, if not greater than, that attainedso far in a few of the fundamental ratios.At present, however,atomic-weight values of high accuracy can be calculated only (a> forsimple elements, (b) for elements whose isotopic composition has beenmeasured with sufficient pre~ision.~ For example, although theatomic masses of 35Cl and 37Cl 66* 67 are now known with a probableerr'or of & 0.0008 unit, the estimated uncertainty in the latest valuefor the 35C1/37C1 ratio 68 gives an error ten times as great in the atomicweight, i.e., -+ 0.008 unit.In addition, the change from the scale1 6 0 t o that of chemical oxygen involves a slight uncertainty, foreven with this element the limit of accuracy of the 160/180 ratiois still an open question. Recent work in America 69 points to aslightly higher figure for the conversion factor (1-000275) than theusually accepted value of R. Mecke and W. H. J. Childs 70 (1.00022).The difference, however, is only about 1 part in 20,000. At themoment, on account of these uncertainties, and also because the mostaccurate of the chemical values are not those of the lighter elements,a comparison except in a few cases is valueless. I n the appendedtable values for the atomic weights of helium, oxygen, deuterium,carbon, and nitrogen are given and compared with the internationalvalues. They are taken from Aston's latest measurements 60 andfrom H. A.Wilson's values 63 deduced from nuclear reaction energiesalone without the use of mass-spectrograph results. For the mixed61 M. L. Oliphant, A. E. Kempton, and (Lord) Rutherford, Proc. Roy. SOC.,1935, A , 150,241.62 H. Bethe, Physical Bev., 1935, 47, 633.63 H. A. Wilson, Proc. Roy. Soc., 1936, A , 154, 660; see also L. Isakov,Corn@. rend. Acad. Sci. U.R.S.S., 1935, 3, 301.64 T. W. Bonner and W.hl. Brubaker, Physical Rev., 1936, 50, 308.65 0. Hahn, Ber., 1936, 69, 6.66 F . W. Aston, Nature, 1936, 138, 109.1.67 K. T. Bainbridge, Physicul Rev., 1933, 43, 348.6 s A. 0. Nier and E. E. Hanson, ibid., 1936,50,722.69 S. H. Manian, If. C. Urey, and W. lSleakney, J . Amer. C'hem. Soc., 1934,70 2. Physit, 1931, 68, 362.56, 2610144 INORGANIC CHEMISTRY.elements hydrogen, carbon, and nitrogen the isotopic ratios chosenare those which appear to be the most reliable. Mecke and Childs’sconversion factor has been used.Element.Protium, ‘H ............Hydrogen ...............Helium .....................Carbon ..................Nitrogen ..................Fluorine ..................Deuterium, D(2H) ......Atomic Weights.Mass spectrum.1.00790 f 0*000042.01426 f 0.000071.008084.00303 f 0.0001612*011814-008019.0003 & 0.0006Nuclearenergy.1-007692.013721.007874.0025412-01 1814.0081-Internationalvalue.I -1.00784.00212-0014.00819.000H. A.Wilson’s values for lH, D, and He appear to be on the lowside. Probably the most reliable values for the atomic masses arethose recently advanced by M. L. Oliphant 71 and by E. Pollard andC. J. Brasefield 72 by combining both methods. The values found byA. L. Vaughan, J. H. Williams, and J. T. Tate for the isotopicratios with a mass spectrograph were used in computing the values ofnitrogen and carbon.For the proportion of deuterium in normal hydrogen, a mean valuetaken from the recent researches of H.L. Johnston,T4 of N. F. Halland T. 0. and of N. Morita and T. Titani 76 was used, whichgave H/D = 5550/1. The higher value for lH explains to a greatextent the discrepancy between the chemical and the mass-spectro-graph atomic weights mentioned in the 1934 Report.77 The inter-national value is based on results obtained with electrolytic hydrogen,and hence of low deuterium content-probably about 1 part in25,000.78~ 56It has been recognised for some years that the chemical value forcarbon approximates to 12.01. The new physical values confirmthis, and are in close agreement with W. Cawood and H. S. Patter-son’s determinations of the limiting density of ethylene and of carbondioxide, which lead to 12.0108. A full account of this work, whichgives as well as carbon, nitrogen = 14.007 and fluorine = 18.996,has now appeared.79 It may be noted that the value for carbon7 1 Nature, 1936, 137, 396.72 Ibid., p.943.73 Phy8icd Rev., 1934, [GI, 46, 327.74 J . Arner. Chem. Soc., 1935, 57, 404.75 Ibid., 1936, 58, 1915.76 Bull. Chem. SOC. Japan, 1936,11,404.7 7 Ann. Reports, 1934, 31, 98.78 W. Bleakney and A. J. Gould, Phy8icd Reu., 1933, 44, 365; see also7D Phil. !L’ra128., 1936, A, 236, 77.E. Moles, Anal. Fb. Quint., 1935, 33, 721CARTER AND WARDLAW : BLUOMNNE AND ITS COMPOUNDS. 145becomes 12.008 if Aston's value of 14011 is taken for the 12C/13C ratioinstead of the value 91.6/1 of Vaughan, Williams, and Tahe.E. Moles 8o and his collaborators contend that C = 12.009 is acloser approximation, and some very interesting though preliminarywork by G.P. Baxter and A. H. Hale on combustions in oxygenof the aromatic hydrocarbons chrysene , pyrene, triphenylbenzene,and anthracene supports this figure.R. W A .2. FLUORINE AND ITS COMPOUNDS.When Moissan isolated fluorine in 1896 he opened a new chapter ininorganic chemistry, for the new element had many curious propertiesand above all, an amazing reactivity unique amongst the chemicalelements. Moreover, it was soon realised that this new substancecould produce compounds of the highest theoretical value. :Forforty years this element has continued to excite the liveliest interest,and quite recently A. Damieiis 1 and 0. Ruff,2 distinguished workersin the field of fluorine chemistry, have each told the fascinating storyof fluorine and its compounds as it stands to-day.Although inprevious Reports references have been made to isolated discoveriesas they have arisen, the Reporters consider that no apology isneeded for bringing together now, as a connected account, some ofthe important facts about fluorine and its derivatives.The demand for the element itself has led to the elaboration of newmethods of preparation, with the result that the original method ofMoissan is now very little used. Nevertheless, in surveying thesenew methods it will be noticed that they are all based on Moissan'sfundamental idea of making hydrogen fluoride electrolyticallyconducting by the addition of an appropriate metallic fluoride, anddiffer from it only in the proportions and nature of the fluorideadded.It will be recalled that Moissan's process required a platinumor copper vessel with platinum electrodes and a solution containing1 g.-mol. of potassium fluoride to 12 or more g.-mols. of hydrogenfluoride cooled to - 30". Nowadays two main processes are inuse. The first employs the molten acid fluoride, KHF, (m.p. 227"),in an apparatus of copper: g r a ~ h i t e , ~ ~ i l v e r , ~ magnesium,6 or MonelEo Moncttel~,'l936, 69, 342.1 Bull. SOC. chim., 1936, [v], 3, 1.a W. L. Argo, F. C. Mathers, B. Humiston, and C. 0. Anderson, J . PhysicalChew., 1919, 23, 348; K. C. Denbigh and R. Whytlaw-Gray, J. SOC. C'hem.l r d , 1934, 53, 139.4 F. Meyer and W. Sandow, Ber., 1921, 54, 760; 3'.Fichter and K.Humpert, Helv. Chim. Acta, 1926, 9, 467.6 K. Fredenhagen, D.R.-P., 1928, 493,873.(i N. C. Jones, J. Phyaical Cltem., 1929, 33, 801.Ber., 1936, 69, [A], 181146 INORGANIC CHElVfJ.S‘J%Y.A789101112131uetalY7 using a graphite anode, as first proposed by Mathers and hiscollaborators in America.3 The second process, due to P. Lebeauand A. Damiens,* uses the salt KF,3HF (1n.p. 65O) as electrolyte ina copper apparatus wit,h an anode of iron or preferably nickel.Pi. Fredenhageng advocates the use of an electrolyte containing1 g.-mol. of potassium fluoride to about 1.8 g.-mols. of hydrogenfluoride, whilst E’. C. Mathers and P. T. Stroup lo have found asystem approximating to CsF,ZHP (m.p. 19”) as a satisfactoryelectrolyte in a magnesium cell.There is a marked differencebetween the type of cell employed by some workers and that used byMoissan. For example, Moissan’s U -shaped copper or platinumvessel is replaced in Lebeau’s 8 process by a cylindrical vessel ofcopper, magnesium or Monel metal with a copper or magnesiumdiaphragm. Mathers’s process,3 likewise, uses a cylindrical vesselof graphite, copper or magnesium with a diaphragm. In theelectrolysis the fluorine never separates from the anode without somealteration of the anode surface. When platinum was employed asanode in Moissan’s apparatus, a layer of platinous fluoride wasformed, and over it the platinic salt. The latter dissolved in thefluoride bath, with formation of the difficultly soluble K,PtF,, sothat appreciable quantities of platinum were lost in this way (about5-6 g.of platinum for 1 g. of fluorine produced2). I n Lebeau’sapparatus a layer of nickel fluoride forms on the nickel anode, butthis is so thin that a P.D. of 6 volts may be employed. Here again,in fluorine liberation an intermediate formation of a higher fluoride,possibly Nip3, may take part. When graphite is employed as ananode, fluorine is absorbed on the surface and causes an expansionof the crystal lattice of the graphite.11 As a result, the P.D. inspecial circumstances may increase from 8 to 110 volts. Therebythe anode temperature rises until finally an almost explosive decom-position of the surface layers again frees the surface. W. T. Millerand L.A. Bigelow,12 using a heavy nickel U-tube and graphiteelectrodes, with potassium bifluoride as electrolyte, have recentlyshown that fluorine of 94-9974 purity can be obtained.Amongst the remarkable compounds which fluorine forms withother elements those with the halogens are of considerable interest.N. V. Sidgwick has discussed these interhalogen compounds in asrevious Report,13 and it will be found that if the halogen combiningW. C. Schumb and E. L. Gamble, J . Amer. Chem. Soc., 1930, 52, 4302.Compt. rend., 1925, 181, 917.K. Fredenhagen and 0. T. Krefft, 2. Elektrochem., 1929, 35, 670.T’rana. Electrochem. Xoc., 1934, 66, 113.See ref. 30.J . Amer. Chem. Xoc., 1936, 58, 1685.Ann. Reports, 1933, 30, 128CAWTER AND WARDLAW : F L U O J ~ E AND ITS COMPOUNDS.147with fluorine is its neighbour, then this halogen has covalenciea ofone and three (ClF, CIF,). If, however, one member of the seriesseparates the combining halogens, covalencies of 1, 3 and 5 areshown (BrF, BrP,, ErF,), and finally when two members intervenea covalency of seven is attained (IF7). Much of the data relating tothese substances is based on the masterly researches of 0. Ruff andhis collaborators.In recent years three oxygen fluorides OF2,14 02F2,15 and OF15have been prepared and their properties described, but the questionwhether oxy-acids of fluorine exist or not is still under discussion.It is noteworthy that although OF, is very slightly soluble in water,yet it fails to produce hypofluorous acid.It must not be inferredfrom this, however, that the acid cannot exist. It should be remem-bered that hyponitrous acid (H,N20,) is well known, yet it cannotbe synthesised from water and nitrous oxide. The reaction of OFwith water has not been fully investigated, and as 02F2 is onlystable below - 64", a consideration of its action with water does notarise. L. M. Dennis and E. G. Rochow16 have examined theaction of fluorine on a concentrated solution of sodium hydroxide at- 20" and obtained a solution which is relatively stable, liberatesiodine from potassium iodide, and has a high oxidising power whichis not due to potassium ozonate, ozone, hydrogen peroxide, or theoxygen fluoride OF,. They express the opinion that it containseither hypofluorous acid or more probably fluoric acid.Moreover,these workers state that by the electrolysis of a molten mixture ofpotassium hydroxide and fluoride in a silver crucible with a carbonanode, they have isolated a silver salt which has the formula AgFO,.However, G. H. Cady l7 does not accept the interpretation whichDennis and Rochow place upon their experiments, and suggests analternative explanation which does not involve the existence of anyoxy-acids of fluorine. Ruff considers that the silver salt may bethe complex compound AgQF,.The literature contains references to a number of sulphur fluorides :SF,, SF,, SF,, S,F,, S,Fl,. That SF, exists is incontestable, forit has been prepared and its properties examined by a number ofinvestigators since H.Moissan and P. Lebeau l8 obtained it from thereaction between sulphur and fluorine. Moreover, there is no doubtthat S2F10 is another product of this reaction.19 This is proved by itsmolecular weight of 256. In the case of the other fluorides, how-14 P. Lebeau and A. Damiens, Compt. rend., 1927,135, 652.15 0. Ruff and W. Menzel, 2. anorg. Chem., 1933, 211, 204.16 J . Amer. Chem. SOC., 1933, 55, 2431.l7 Ibid., 1934, 56, 1647.18 Compt. rend., 1900, 130, 865.10 K. G. Denbigh and R. Whytlaw-Gray, J . , 1934, 1347148 fNORGAN1C CHEMISTRY.ever, the published data are very confusing. Ruff and his collabor-ators in 1905 attempted to prepare lower fluorides of sulphur bythe reaction between sulphur nitride, N4S4, and hydrogen fluoride,but without success, and they were also unsuccessful when they triedto decompose sulphur chlorides with certain fluorides.Twentyyears later, however, 0. Ruff and E. Ascher observed the formationof a gas froin cobaltic fluoride and sulphur, and a detailed investig-ation led J. Fischer and W. Jaenckner 2o to the conclusion that theliberated gas was SF,. Their analysis gave S : F = 1 : 3.8 or 3-9,and a molecular weight 107 (SF, reqiiires 108). Unfortunately, thisresult was not reproducible, but a very recent re-examination of thereaction by W. Luchsinger 2 l has clarified the matter. He hasshown that pure SF, is not liberated, and that in all reactions ofmetallic fluorides and sulphur, the fluorides SF,, SF,, S,F,, and oftenalso SP, result in varying proportions according to the kind and.amount of the metallic fluoride and the velocity of the reaction.The lower fluorides S2P, and SF, can be removed from the reactionproducts by shaking with mercury, the SF, can then be fractionatedout, and the gas which remains is practically pure SF,.Thisconstitutes the evidence for SF4. What data are available for thelower fluorides ? In 1923 M. Centnerszwer and C . Strenk 22 obtaineda colourless gas from the reaction between silver fluoride andsulphur. It had a varying molecular weight (93-98) depending onthe temperature of the reaction, and it contained S, 64; F, 35(S2F, requires S, 62.8; P, 37.2y0). Although, as the authors say,‘‘ the agreement is not ideal,” yet they conclude that their substanceis disulphur difiuoride.Recently, M. Trautz and K. Ehrmann23have repeated this work and isolated a gas with a molecular weight of98.8 and containing S, 60.98; F, 39.54%. They consider that theirproduct is a mixture of two fluorides : S,F2, 90%, and SF,, 10%.Up to the present, therefore, the experimental evidence shows thatno one has handled either pure S,F, or pure SF2. Ruff states thathe and his collaborators have obtained a gas containing 90-95% ofS,F2, but it is decomposed by light with the separation of sulphurand the formation of SF,. Moreover, the exceptional reactivity ofboth these fluorides, even with the quartz of the walls of the con-taining vessels, rendered isolation of the pure gases impossible.Ruff is of opinion that pure S2F2 and pure SF, will be obtained ifthe experimental work is conducted exclusively in platinum vessels.2o 2.artgew. Chem., 1929, 42, 810.z1 Diss., Breslau, 1936.22 Ber., 1923, 56, 2249; 1925, 58, 914.23 J. pr. Chem., 1935, [ii], 142, 79CARTER AND WARDLAW : ~ U O R ~ I N E AND ITS COMPOUNDS. 149Many attempts have been made to bring about direct combinationof fluorine and nitrogen, but so far without success. Nevertheless,in 1928 0. Ruff, J. Fischer, and F. Luft 24 succeeded in isolating NF,as a colourless gas (b.p. - 120") by the indirect method of electro-lysing NH4HF,. The yield of NF, was small and it was accompaniedby small quantities of NH,F, some NHF,, and possibly a secondnitrogen fluoride NF,. These compounds, when associated withNF,, apparently bestow on the trifluoride explosive properties, forif the crude gas is led over manganese dioxide the explosive com-pounds are destroyed and the NF3 is quite stable. In this respectNF, offers a marked contrast to the highly explosive NC1,. When-ever NF, or NHF, was present under a pressure higher than ca,350 mm.it exploded, and Ruff emphasises that these substanceshave not yet been obtained pure in spite of prolonged research.He also states that the claims of 0. T. Krefft 25 to have preparedpure NH2F cannot be admitted. Nitrogen trifluoride is veryreactive and when sparked with hydrogen a shattering explosiontakes place,ZNF, + 3H, = N, + 6HF + 336K,and with water vapour a flame travels through the reaction vessel,filling it with deep brown fumes,2NY3 + 3H20 = GHF + Nz03.In 1890 Moissan described several fluorides of carbon, obtained bythe direct union of the elements, but it is only in the last decade thatpure compounds have been isolated.26.,7 On passing fluorine overcarbon, spontaneous combination takes place with considerabledevelopment of heat. The gaseous products of the reaction arecooled in liquid air and subsequently fractionated, whereby thefollowing have been obtained : CF4, C,P,, C3F8, and otherhomologues up to C,F,,. These carbon fluorides are extremelystable to heat and most chemical reagents. Even moderatelyheated sodium does not decompose them. An ethylene analogue,C,F,, has also been identified in the reaction products; and thisis also formed when carbon tetrafluoride is repeatedly subjected to anelectric arc discharge between carbon electrodes.It forms C,F4Br,with bromine-water ; but, apart from such reactions, which dependupon its unsaturated character, it is very indifferent to most reagents.A solid compound, carbon monofl~oride,~~ CP, is also formed during24 2. anorg. Chem., 1928,172, 417.25 D.R.P., 1932, 448,929.26 P. Lebeau and A. Damiens, Conapt. rend., 1926,182, 1340.27 0. Ruff and R. Keim, 2. anorg. Chem., 1930, 192, 249.28 0. Ruff and 0. Bretsohneider, ibid., 1933, 210, 173.28 F. Ebert, see idem, ibid., 1934, 217, 1150 INORGANIC CHIGMISTRY.the interaction of fluorine and carbon, particularly at low pressuresand high temperatures, e.g., carbon in the form of norit at 420" and25 mm.or of graphite a t 420" and 760 mm. The maximum yield inrelation to the other fluorides is about 3% of the carbon converted.Carbon monofluoride is a grey solid, insoluble in ordinary solventsand indifferent to most reagents. It can, however, be reduced byzinc dust and acetic acid, yielding the original form of carbon fromwhich it was derived.- % 7 2 3 4 5 6 7 8 9 70 77 72FIG. 1.The X-ray analysis 29 (Fig. 1) shows that the introduction of thefluorine atoms takes place without any appreciable alteration in thedistance of the carbon atoms in the basic planes of the graphitelattice. The insertion of the fluorine atoms, however, occurs be-tween the basic planes and expands the carbon lattice in a per-pendicular direction from 3-40 A.to 8.17 A. On regeneration, itshrinks to its original size. This enormous distortion of the latticCARTER AND WARDLAW: FLUOR~NE AND ITS C O ~ O U N D S . 151is sometimes the cause of an explosion in the formation of CP, andthe authors have investigated the conditions for its avoidance. Itis not surprising, therefore, that carbon monofluoride i s formedwhen carbon electrodes are used as anodes in the electrolysis offluorides, and considerable expansion is usually observed.30 Thespecific electrical resistance of CF is over 3000 ohms as comparedwith 0.03 ohm for graphite, and considerable passivity effects arethereby set up. 0. Ruff 31 considers that the structure of carbonmonofluoride closely resembles that of graphite oxide, described byU.HofmannF2 in which oxygen atoms are inserted between thecarbon basic planes of graphite.Amongst interesting new metallic fluorides the isolation of ReF,has already been mentioned in an earlier ReportF3 but attentionshould be directed to an investigation undertaken with the object ofisolating a higher fluoride of copper and silver.34 No fluoride ofcopper higher than CuF, could be prepared, but the existence ofAgF, is now well e~tablished.~~ This compound has been preparedby the action of fluorine at 150-200" on a silver halide, or molecularsilver prepared by reducing silver oxide with formaldehyde, or onfine silver gauze. It is a dark brown powder which with water givesoxygen containing ozone. The fluorine is relatively firmly bound,for only at 440" does the dissociation pressure of argentic fluoridereach 1 atmosphere.This fluoride is strongly paramagnetic, as isto be expected from its electronic structure. It is an excellentfluorinating agent and in many cases can act as a substitute forfluorine.Some extraordinary mistakes by earlier observers are disclosed inrecent publications on the acid fluorides of the metals. I n 1905,E. Bohm 36 recorded the preparation of acid fluorides of cobalt,nickel, and copper of the general formula MF2,5HP,5 or 6H,O.Sixteen years later, F. H. Edminster and H. C . Cooper 37 publishedtheir conclusions from a reinvestigation of these substances. Theystated that the correct formula was MF2,5HP,6H,O, where M couldbe Coy Ni, Cu, or Mn, but added that " It was a surprise to obtainthe acid fluoride by recrystallisation from water." However, rz30 Seeref.11.32 Ber., 1932, 65, 1821 ; U. Hofmann, A. Frenzel, and E. CsalBn, Annnlen,33 Ann. Ileprts, 1933, 30, 91.34 0. Ruff and M. Giese, 2. anorg. Chem., 1934, 219, 143.35 Idem, ibid.; M. S. Ebert, E. L. Rodowskaa, and J. C. W. Frazor, J.Amer. Chern. SOC., 1933, 55, 3056; Naturiuiss., 1934, 22, 561.36 2. anorg. Chem., 1905, 43, 326.57 J . Amer. Chern. Soc., 1920, 42, 2419.Angew. Chern., 1933, 47, 739.1934, 570, 1152 TNORGANIC! CHEMISTRY.recent, investigation by A. Ifurtenacker, W. Finger, and F. Hey 38leads to a very different conclusion. They find that the so-calledacid fluorides of the type MF,,5HF,xH20 do not exist, but that theyare really fluosilicates and must be eliminated from the literature.The story, however, does not end here.According to an earlyinvestigator, 1. E. Willm,39 an acid fluoride HTIF, exists, but in1920 J. Barlot 40 re-examined the compound and concluded that itwas H2T1F,. 0. Hassel and H. Kringstad 41 then took up the matterin 1932 and proved that the formula was really H,T1F3,0.5H,0,and that the substance was isomorplious with a compoundM,(NH,)P,,O-5H2O which they prepared. This year C. Finbak and0. Hassel 42 published an account of a reinvestigation of a numberof so-called acid fluorides. They agree with Kurtenacker and hiscollaborators that the recorded acid fluorides of nickel, cobalt,manganese, and copper are really fluosilicates and, what is par-ticularly interesting, find that the acid fluorides of fhallium also donot exist but are actually fluosilicates.Moreover, a mercurouscompound Hg,F,,4HF,4Hz0, described by E. Bohm36 in 1905, isfound to be Hg,SiF6,2H20. It is obvious that the greatest care isnecessary in investigations where hydrofluoric acid is employed.It is noteworthy that quite recently J. Meyer and W. Taube43state that they have prepared RbHl?, and RbH,F3, but that thesesubstances are commonly contaminated with fluosilicates.Attention should be directed to an ingenious method for deter-mining critical temperatures which has been applied with success toanhydrous hydrogen fluoride by P. A. Bond and D. A. Williams.44A tube of Monel metal is charged with the pure hydrogen fluorideand heated in an air-bath above its critical temperature.Thistube, in an inclined position, is mounted on knife edges and con-nected a t one end by a fine platinum wire to the beam of a balance.The system is then cooled slowly and the critical temperature isclearly indicated by a sudden change in the balance-beam when thecontinuous phase passes to a system of vapour and liquid, withconsequent displacement of the centre of gravity. The criticaltemperature thus determined is 230.2".S. R. C.w. w.38 2. anorg. Chem., 1933, 211, 83.39 Ann. C?&n. Phys., 1865, [iv], 5, 6 .4 0 Cornpt. rend., 1920, 171, 1143.2. anorg. Chem., 1932, 208, 382.*? Ibid., 1936, 226, 175.Ibid., 1936, 227, 337.44 J . Arner.Chem. SOC., 1932, 54, 129CARTER AND WARDLAW : METALLIC CBRBIDES. 1533. METALLIC CARBIDES.Results of great value have been obtained during recent years bythe application of X-ray methods to the structure of the carbides.These substances have long presented a problem in molecularstructure of the very highest interest, for the attention of chemistshas always been arrested by the extraordinary differences inbehaviour exhibited by the metallic carbides in their reactions bothwith water and with acids. In certain cases the reaction productsare of unexpected complexity, and many explanations have beenadvanced to account for these results.There is evidently some connection between the behaviour of acarbide and its position in the periodic table.Those of the first andsecond groups, with the exception of beryllium carbide, give withwater, acetylene only. Beryllium carbide, Be&, and aluminiumcarbide, AI,C,, yield pure methane, but manganese carbide, Mn,C,gives a mixture of methane and hydrogen in equal volumes. Car-bides of yttrium, lanthanum, cerium, and the other rare earths, alsothose of uranium and thorium., are attacked by waher and yield acomplex mixture of gaseous, liquid, and sometimes solid hydro-carbons.In seeking an explanation of these results some early workers onthe carbides did not hesitate to represent them by graphic formule,but others, more cautious, endeavoured to reconcile the formulzeof the carbides with the valency of the constituent elements. Duringrecent years, as a result of the work of M. von Stackelberg and hiscollaborators, the constitution of a number of metal carbides hasbeen disclosed by the use of X-ray methods, and the relationshipbetween chemical reaction and structure made clear for the firsttime.The well-known reaction of calcium carbide with bromine, andfurther, its decomposition with water, have convinced chemists thatin this carbide the two atoms of carbon must be joined :In 1930 von Stackelberg studied the acetylides of the alkali metals,and the carbides of the alkaline-earth metals and the rare-earthmetals. The structure which he finally assigned to CaC,, UC,,Lac,, PrC,, and NdC, is most conveniently described as a face-centred cubic lattice or sodium chloride lattice made up of metalatoms amnd C, groups.1 Z.physsikal. Chern., 1930, B, 9, 437154 INORGANIC CHEMISTRY.As Pig. 2 shows, thc C, groups are all arranged parallel to one edgeof the cube, which is thereby extended in this direction. The disfor-tion may be expressed by an axial ratioc/a of 1*15-1.20. It is not surprising,therefore, that acetylene is liberatedas a primary product from the decom-position with water, for already inthe crystal lattice a C*C bond is present.Prom the fact that acetylene is thesole gaseous product in the case ofcalcium carbide, it must be concludedthat the energy conditions are favour-able for the evolution of this gas. Withthe carbides of uranium and of therare earths, acetylene is evolved butit is accompanied by saturated andunsaturated hydrocarbons of greatcomplexity. The composition (%) ofthe gases evolved from some of these carbides is given by H.Moissan 2 as follows :o=ca @=CFIG.2.La. Ce. Pr. Nd. Sm. Y. Th.C,H, ............... 71 75.5 67.9 66.3 70.6 71.7 47.7C,H, ............... 1.5 4.3 3.0 6.3 7.9 4.6 5.8CH, .................. 27.9 20.3 29.1 27.6 21.5 18.9 29.4H, .................. - - - - 4.7 17.1Later investigations,3 whilst not confirming these analytical resultsin detail, have only served to emphasise the complexity of thegaseous mixtures. In a recent communication N. G. Schmahl*has put forward a theory of carbide hydrolysis based on theseresults of Moissan. Schmahl considers that the following reactionoccurs in the decomposition of the rare-earth metal carbides bywater :4XC2 $- 6H,O = 2X20, (hydrated) + 3C,H2 + CH, + CH,According to Schmahl this CH, radical is changed into ethylene andpropylenc or t o methane and ethane, depending on the heat of thereaction.J. Schmidt has examined this suggestion, and pointedout that Schmahl’s theory demands the formation of acetylene andmethane in a ratio 3 : 1, which would be lowered in those cases wherethe CH, radical is reduced to methane. Actually, if the figuresA. Damiens, Compt. rend., 1913, 157, 214; P. Leboaii and A. Damiens,2 Ann. Chim. Phys., 1896, [vii], 9, 302.ibid., 156, 1987.4 2. h’lektrochem., 1934, 40, 68.Ihid., p. 170CARTER AND WARDLAW : METALLIC CARBIDES. 155given by Moissan are examined, it will be seen that the ratioC,H, : CH, is sometimes greater than 3 and sometimes less.Aboveall, however, Schmahl’s theory fails to recognise that in the crystallattice a C-C bond is already present. In Schmidt’s view thesuggestion of Schmahl is untenable, and there appear sound groundsfor this conclusion. Instead, Schmidt considers that the differencein the reaction products from calcium carbide and the rare-earthmetal carbides is due to the different valencies of the metal atoms.If the metal atom, My is bivalent, as in calcium carbide, then thecarbon is bound as acetylene and the metal as the hydroxideM(OH),. If, however, the metal is in the tervalent state, hydrogenis liberated, and i t is the further reactions between the acetylene andthis hydrogen which produce the complicated mixture of hydro-FIG.3.carbons. Schmidt is of opinion that methane itself is a side productof such reactions. He considers that his views are supported bythe carbides of the tervalent elements aluminium and cerium.Carbides of these elements can be prepared of the general formulaX,(C E C), in which the metal atom has a valency of Onhydrolysis, acetylene alone is liberated, because the metal atonisconcerned do not undergo a valency change but are stable asAl(OH), and Ce(OH),. Reference to the preceding table will showthat the composition of the gaseous products from the hydrolysisof thorium carbide, ThC,, offers a striking contrast to that from theother carbides included. It might be anticipated, therefore, thatthis difference in chemical behaviour would be reflected in thestructures of these carbides, and it is interesting to find that this isso.The structure of ThC, (Fig. 3), although similar to that of the6 J. F. Durand, Bull. SOC. cl~im., 1924, 38, 1141; L. Damiens, tibid., 1914,15. 370156 INORGANIC CIIEMISTRY.CaC, type, has the C, groups all parallel to a cube face but with theiraxes in two mutually perpendicular directions. The distortionproduced gives rise to a tetragonal lattice with an axial ratioc : a = 0.903.Particularly interesting are the detailed structures which havebeen evolved for the carbides of aluminium and beryllium, Al,C,and Be,C, for they explain in a most convincing way why methaneis the sole hydrocarbon produced by hydrolysis. Beryllium car-bide, Be2C,7 has been shown t o have an antifluorite structure, inwhich each beryllium atom is surrounded by four carbon atoms andeach carbon atom has eight beryllium atoms as neighbours.TheC-C distance is 3.06 A., and Be-C is 1.9 A. This separation of thecarbon atoms in the crystal lattice, combined with the bivalency ofthe beryllium atoms, explains most effectively why methane resultsfrom the hydrolysis.is complicated, and is best understood by reference to the diagramsin the original publication. However, it can be described as a layerlattice in which three layers of carbon atoms are interleaved withfour layers of aluminium atoms so that each unit has the composition(Al4C3lW and is, in itself, saturated with regard to valency.Eachaluminium atom is siirrounded by four carbon atoms at a distanceof 1.9-2-0 A., while the carbon atoms have either 5 or 6 aluminiumatoms as neighbours. With such a structure the formation ofmethane, by hydrolysis of the carbide, would be expected. It iswell established that hydrogen and a number of hydrocarbons areproduced when either Ni,C or Fe,C is treated with hydrochloric acid.To explain this result, J. Schmidt assumes that the CH, group isformed initially, and it then undergoes hydrogenation to methaneor polymerisation to ethylene. This ethylene can then be furtherchanged by hydrogenation or renewed polymerisation or reactionwith a new CK, group. I n the decomposition of Fe3C, polymeris-ation must occur to a marked degree, for in addition to gaseoushydrocarbons, liquid and solid hydrocarbons may be f ~ r m e d .~H. A. Bahr and T. Bczhr lo state that they observed the formationof liquid hydrocarbons in the decomposition of Ni,C with hydro-chloric acid, but J. Schmidt could not confirm this. Incidentally,the decomposition of Fe,C is complicated by the separation ofelementary carbon, which is accelerated by ferrous ions.11 A carbonseparation can also take place when Ni,C is decomposed, but it hasThe detailed structure of aluminium carbide7 M. von Stackelberg and F. Quatram, 2. physikal. Chem., 1934, B, 27,50.8 M. von Stackelbsrg and E. Schnorrenberg, ibid., p. 37.9 E. D. Campbell, Amer. Chem. J., 1896, 18, 836.lo Ber., 1928, 61, 2177.11 R.Schenck and R. Stenkhoff, Z. anorg. Chem., 1927,161, 287WARDLAW : CO-ORDINATION COMPOUNDS. 157not yet been demonstrated that it can be influenced by concentrationof nickel ions.5An X-ray investigation of these carbides does appear to throwsome light on their behaviour with acids, for it indicates that theindividual carbon atoms in the lattice of Fe,C and Ni3C l2 are separ-ated from one another, and this implies the possibility of theformation of a primary CH, group. This is especially so in Fe,C,for its method of preparation and its existence in equilibrium withiron (ferrite) indicate that the metal in the carbide is in the lowerstate of oxidation, i.e., bivalent. By analogy one might assume asimilar method of decomposition for Mi@ but, as is well known,methane and hydrogen are the only products.The crystal structureof Mn,C is not known accurately, but evidently it must be funda-mentally different from that of Fe3C. F. Fischer and I?. Bangert 13have prepared a manganese carbide of a different type by thereaction of manganese oxide and methane. When it was decomposedwith water, the evolved gas contained 2.5% of unsaturated hydro-carbons, 45% of saturated hydrocarbons, and 52.5 % of hydrogen.The unsaturated hydrocarbons contained on an average at leastfour carbon atoms. This carbide agrees with the formula (Mn,C,),.A. Westgren l4 has recently examined the crystal structure of amanganese carbide to which he assigns the composition Mn,C3.A magnesium carbide, Mg,C,, is known to give pure allyleneCH, - C = CH on hydrolysis but its crystal structure is unknown.15The fact that only one hydrocarbon is formed suggests, by analogywith the carbides of the CaC, type, that the C-C-C bond is alreadypresent in the crystal lattice.S.R. C. w. w.4. CO-ORDINATION COMPOUNDS.The old idea that the term co-ordination compound is restrictedto the well-known cobalt, chromium, and platinum ammines isundoubtedly disappearing, and it is being realised that these complexsalts represent only a special section of an exceedingly wide anddiverse class of substances. In an introduction to the symposiumon complex inorganic compounds arranged by the AmericanChemical Society, L. F. Audrieth l pointed out how recent develop-la B. Jacobsen and A.Westgren, 2. physikal. Chern., 1933, B, 20, 361:J. Schmidt, 2. anorg. Chem., 1933, 216, 85.l3 Breninsto$-Chem., 1929,10, 261.11 Jernk. Arm., 1935, 118, 231.1 Chem. Reviewe, 1936, 19, 65.l5 See N. GI-. Schmahl, ref. (4)158 INORGANIC CHEMISTRY.nients in theoretical chemistry and in research technique had givennew prominence to this field of investigation. The Bronsted conceptof acid-base equilibria has directed attention to complex ions in thedevelopment of acidic and basic properties in solution, whilst thecver-changing theories of atomic structure have demanded investiga-tion of the physical and chemical properties of compounds char-acterised by the covalent link. Interest in the modern theories ofoptical activity has stimulated investigations of the optical propertiesof complex inorganic compounds, whilst improved apparatus andthe development of new research technique, such as are available inX-ray and electron-diffraction methods and in measurements ofdipole moments, have thrown a flood of light on the detailedstructure of co-ordination compounds.A few years ago it was quite true to say that the available evidenceindicated that the arrangement of the valencies of 4-covalent atomswas almost always tetrahedral.This was the general conclusionarrived a t by the classical methods of stereochemistry and it wassupported by a substantial mass of physical data. I n the discussionon modern stereochemistry, held by the Chemical Society, S. Sugden2reviewed recent work on 4-covalent complexes of bivalent nickel,palladium, platinum, and copper, and showed that in the case ofthese elements there is definite evidence for the frequent occurrenceof a planar configuration.Sugdcn pointed out that there are nowthree main lines of evidence which lead to this conclusion in the casesof n i ~ k e l , ~ palladium: and p l a t i n ~ m . ~ Erst, there is the occurrenceof cis-trans-isomerides when two unsymmetrical chelate groups area.ttachcd to the metallic atoms. Examples of this are found in theisomcric nickel derivatives of benzylmethylglyoxime andisomeric glycine derivatives of palladium and platinum (I) andScconclly, there is the evidence provided by the resolution4-covalent compound of bivalent platinum. This work of W.H.Mills and T. H. €1. Quibell was discussed in the Report last year.Finally, there are the X-ray studies by E. G. Cox, W. Wardlaw, andcollaborators who, in the last two years, have demonstrated aa Nature, 1936, 137, 543.4 F. W. Pinkard, E. Sharratt, W. Wardlaw, and E. G. Cox, J . , 1934, 1012.5 A. A. Grunberg and B. W. Ptizyn, J . pr. Ohm., 1933, [ii], 136, 143.6 cJ., 1935, 830.7 See E. G. Cox, F. W. Pinkard, W. Wardlaw, and K. C. Webster, J . ,S . Sugden, J., 1932, 246.1‘338, 459; E. G . Cox, W. Wardlaw, and K. C. Webster, J., 1936, 1476WARDLAW : CO-ORDINATION COMPOUNDS. 159planar configuration in no less than 14 derivatives of nickel, palla-dium, and platinum. Thus there is, in Sugden's view, abundantevidence for planar structures in co-ordination compounds of4-covalent nickel, palladium, and platinum.Obviously there must be a theoretical explanation why in certaincases the structure is tetrahedral, and in others planar, and thereader will probably recall that in 1931 L.Pauling * put forward atheory to explain this. In connection with this theory it should benoted that the electrons in an octet are divided into two sub-groupsof 2 and 6, and those of an 18 group into three sub-groups of 2, 6,and 10. The values of the second quantum number for these sub-groups are II: = 1, 2, 3, and the spectroscopic designations of thethree are s, p , and d respectively. Pauling accepts the idea that abond involves two electrons, and he lays down that when the linksare tetrahedrally distributed these bonds are compounded ofclectrons in s and p levels.GeneraJly, it might be said that thelinks are of the form sfi3. When however onc d level is used and thelinks are of the type spad, Pauling predicts an arrangement of fourbonds at 90" in one plane. Such vacant d levels, with energiescomparable with s and $3 levels, are found in the atoms of thetransition elements. Moreover, since the d electrons are chieflyresponsible for the magnetic moment of the atom, sharing of themshould reduce this property so that bivalent nickel, which is para-magnetic in its simple salts, should becomc diamagnetic in its4-covalent planar compounds. It is interesting to find that therecorded magnetic evidence for nickel agrees with Pauling's theory,for all the planar compounds investigated have proved to bediamagnetic.With palladium and platinum, the magnetic evidencedoes not appear to be so significant, for all simple and complex saltsof these elements are diamagnetic, but the diamagnetism of theplanar compounds is in accord with Pau1ing:'s views. Sugdenindicates, however, that SL real discrepancy arises with certain cupriccompounds. E. G. Cox and K. C. Webster ti have found from X-raystudies that the cupric derivatives of p-diketones have a planarconfiguration. These compounds are paramagnetic, and there isnot a vacant 3 d level in the cupric ion. This is readily seen from theelectron distributions for nickel and copper atoms, which show thatthe difference between nickel and copper is not merely the additionof an electron in the nickel atom but a change in the number ofelectrons in the d level :Ni (At.no. 28) ...... Is2 282 2p6 388 3p6 3d8 48'(At. no. 29) ...... 28* 2p6 h2 3p6 3d1° 48l8 J . Amer. Chm. Soc., 1931, 58, 1367.J . , 1936, 731160 INORGANIC CHEMISTRY.The planar configuration for 4-covalent cupric compounds is nowfirmly established. J. M. Robertson 10 found that in the phthalo-cyanines of nickel, platinum, and copper the metal atom and thefour surrounding nitrogens lie in one plane. Again, an X-rayinvestigation of the crystal structure of cupric chloride dihydrate,CuC12,2H20, by D. Harker,ll shows that each copper atom isattached to two chlorine and two oxygen atoms by covalent linkingsdirected to the corners of a square.To illustrate how X-ray resultscan give evidence of this planar structure in simple derivatives of4-covalent copper, details of a recent investigation l2 of CuC12py2may be given. This substance, which crystallises well frommethyl alcohol, was prepared under a variety of experimentalconditions with the object of discovering the theoretically possiblenWFIG. 1.cis- and trans-isomerides. Under all conditions it was found tocrystallise in the same trans-planar form. It is evident that 4-covalent copper compounds of cis- configuration, like those ofpalladium, are generally unstable when chelate groups are absent.That CuC12py2 has a trans-planar configuration follows from aconsideration of its cell dimensions as determined by X-ray methods.The short length of the c axis (3.84 A.) shows that the pyridine ringsmust be coplanar (or very nearly so), since this value is of the sameorder as the distance of approach of =CH- groups in differentorganic molecules (m.3-7 A.). Reference to a model shows thatthis can only be so in a molecule of trans-planar configuration (Fig. 2)for with it cis-planar configuration the parallel arrangement of thepyridine rings shown in Fig. 1 is impossiblo on account of thelo J., 1935, 613.18 E. G. Cox, E. Sharratt, W. Wardlaw, and K. C. Webster, J., 1936, 129.l1 2. K h t . , 1936, 93, 136WARDLAW : CO-ORDINATION COMPOUNDS. 161proximity of the two rings (minimum distance 1.9 A. instead of3.7 A.). In order to obtain the requisite clearance between therings in a cis-planar structure they must be rotated about theN-Cu bonds through approximately 40°, thus increasing the thick-ness of the molecule and necessitating a c-axis of at least 4-5 A.FIG.2.This is impossible in view of the experimental datum that c is 3-84 A.On the same grounds, a molecule in which the distribution of coppervalencies is tetrahedral is excluded. Since the j ~ yMe:NO\] distribution of valencies in nickel and copper>M 4-covalent compounds may be planar, and themetal atoms are not greatly different in radius, it ’\ (111.) is to be expected that corresponding nickel andcopper compounds will sometimes be iso-morphous. This has proved to be the case with the methylethyl-glyoxime derivatives (III).12 In view of Sugden’s findings 13 thatthe nickel derivatives of unsymmetrical glyoximes are planar, thisresult idds additional weight to the conclusion that 4-covalentcopper may be planar in its cupric compounds.In a paper on the stereochemistry of the metallic phthalocyanines,R. P.Linstead and J. M. Robertson l4 have shown that bivalent4-co-ordinate beryllium, manganese, iron, and cobalt, like nickel,copper, and platinum, all exhibit planar symmetry in the crystalsof their phthalocyanine derivatives (see Pig. 3). The fact thatcobalt is tetrahedral l5 in the group CoC1,” makes the result with thcphthalocyanine derivatives particularly interesting, and providesthe first example of this metal exhibiting planar symmetry. Themost remarkable of these results, however, is provided by beryllium,for which a tetrahedral symmetry is well established by bothchemical and physical considerations.Beryllium is tetrahedral1s H. J. CavellmdS. Sugden, J., 1935, 621.14 J . , 1936, 1736.16 H. M. Powell and A. F. Wells, J., 1935, 359.1 CEt*N,OH j2REP.-VOL. XxxIU. B162 INORGANIC CHEMXSTRY.in its bcnzoylpyruvic acid derivative l6 and in basic berylliumacetate,17 and BaBeF, is isomorphous with BaS04.1S That theFIG. 3.very simple atom beryllium, which normally contains no d electrons,should adopt a planar distribution of valencies, appears inexplicableon Pauling’s theory. Linstead and Robertson point out that thetheoretical difficulty can be avoided by the assumption that inberyllium phthalocyanine the metal is combined with only twonitrogen atoms, but there seems no justification for arbitrarilydifferentiating between this cornpoiind and the other covalentmetallic phthalocyanines which resemble it so closely in crystallineform.The general conclusions from these facts are : (1) that in themetallic phthalocyanines, and probably also the correspondingporphyrins, the rigid planar organic portion of the molecule imposesits steric requirements upon the metal, and (2) that there is moretolerance in the distribution of valencies about 4 co-ordinate-metalatoms than has hitherto been realised.The work already surveyed has shown that many 4-hovelentcomplexes of copper, nickel, palladium, and platinum actuallypossess a planar configuration, and that this configuration ismaintained even when considerable changes are macle in the natureof the co-ordinate groups.On the other hand there is definiteevidence that a change in the principal valency of the metal maylead to a change in the spatial distribution of the bonds. Forexample, trimethylplatinic chloride, Pt (CH,),Cl, in which platinumis 4-covalent but also quadrivalent, has been shown l9 to be non-planar and is most probably tetrahedral. Again, nickel carbonyl,Ni(CO),,20 in which the nickel has no principal valency, possesses a16 W. H. Mills and R. A. Gotts, J., 1926, 3121.17 (Sir) W. Bragg and G . T. Morgan, Proc. Roy. SOC., 1923, A , 104, 437.18 N. N. Ray, 2. anorg. Chem., 1931, 201, 259.19 E. G. Cox and K. C. Webster, Z.Krist., 1936, A, 90, 561.20 L. 0. Brockway and P. C. Cross, J . Chem. P~Q&cL?, 1935, 3, 825WARDLAW : CO-ORDINATION COMFOUNDS. 163tetrahedral structure. Eecenf investigations have provided addi-tional examples of this change of structure with change in theprincipal valency of the central element. For instance, in strikingcontrast to the planar 4-covalent dcrivahives of bivalent copper, ithas been proved that some 4-covalent cuprous compounds aretetrahedral. Similarly, silver has been found to be planar whenbivalent and tetrahedral when univalent. Prior to this year, theonly evidence on the configuration of either 4-covalent cuprous orargentous derivatives mas that of F. Hein and H. Regler, who, in apreliminary note,21 claimed to have effected a partial resolutionof an argentous derivative of S-hydroxyquinoline. Since then,these authors 22 have described their work in detail, and state thatby the use of bromocamphorsulphonate they have obtainedevidence that their silver compound is optically active and musttherefore have a tetrahedral disposition for the valency bonds of thesilver atom.They were unable however to retain the activitywhen the optically active acid was removed.+ I-INO, eE. G. Cox, W. Wardlaw, and I<. C. Webstter 23 imve examined byX-ray methods potassium cuprocyanide, K&u( CN),], and theisomorphous substances t etrakis - t hioacetamide cuprous andaxgentoua chlorides [as (IV)]. In eaeh of these substances a tetra-hedral valency distribution bas been found, and it will be noted thatin every case the effective atomic number of the metallic atom isthat of an inert gas.It is also noteworthy that the complex ionCu(C"),"' has exactly the same number of electrons, and pre-sumably the same electronic distribution, as tho neutral complexNi(CO),, which liz~s been shown to be tetrahedral. This tetrahedraldistribution of valencies in a co-ordinated cuprous complex has alsobeen found by F. G. Mann, D. Purdie, and A. P. Wells 24 in themolecule [Et3As->CuI),. Silver, with SL principal valency of two21 Nntzcrwiss., 1935, 23, 320.82 Ber., 1936, 69, 1692.a3 J., 1936, 775.14 Ibid., p. 1503164 INORGANIC CHEMISTRY.and a covalency of four, has proved 23 to be planar as a result of anX-ray examination of the argentic derivative of picolinic acid.Thiso=c M c=oPV.)result is based on the high birefringence of the compoundisomorphism with the corresponding copper derivative, which hasbeen shown to be trans-planar as in (V). Further, E. G. Cox andK. C. Webster 25 have demonstrated that potassium auribromide,K[AuBr4],2H20, in which gold is tervalent, possesses the ion AuBr4‘with a planar configuration. The X-ray evidence shows that thewater in the auribromide is held mainly as water of crystallisation,and that the substance does not contain the sexacovalent complex[AuBr,,2H20]’. This appears to be the first example of a tervalentmetal with a planar distribution for its four valency bonds. Itwill be realised that a definite advance in the stereochemistry ofthese so-called currency metals has been made.Some years agoR. Dickinson 26 investigated the complex cyanides of potassiumwith zinc, cadmium, and mercury of the type K,[X(CN),], and foundthat the co-ordinated cyanogen groups had a tetrahedral arrange-ment around the central metal atom. W. H. Mills and R. E. D.Clark 27 have prepared compounds of the type (VI), where M = Hg,Cd, and Zn, in order to investigate the stereochemistry of thesemetals in the 4-covalent state. Various alkaloid salts were in-vestigated, but in no case could direct evidence of their opticalresolution be obtained. Nevertheless, other results of great interestwere recorded, but as these cannot be satisfactorily summarised,the original papers must be consulted.Outside the range of the transition elements, the stereochemistryof 4-covalent tin and lead has been considered.A tetrahedraldistribution for the four valencies of stannic tin is fimly establishedby chemical and physical methods. An optically active compoundof tin was prepared by W. J. Pope and S. J. Peachey 28 in 1900, and2s J., 1936, 1636.26 J. Amer. Chem. SOC., 1922, 44, 774.a7 J., 1936, 175.28 P., 1900, 16, 42, 116WARDLAW : CO-ORDINATION COMPOUNDS. 165this tetrahedral configuration was also revealed in the four atoms ofiodine which surround the metal in stannic iodide.29 Until recently,however, no attempt had been made to determine whether thistetrahedral distribution also holds for 4-covalent compounds ofstannous tin.The preliminary results of an investigation ofK2[SnC1,],2H,0 have been published,30 and they show that incontrast to SnI, the complex ion SnC1,” is planar. The X-rayresults plainly prove that the tin is 4-covalent, an\d not sexacovalentas the presence of the two molecules of water might suggest. Otherstannous compounds lead to a similar conclusion. Further, lead,which is tetrahedral in the 4-covalent and quadrivalent leadcompound, Pl~Ph,,~l proves to be planar in its bivalent and 4-coval-ent derivatives such as lead benzoylacetonate, lead salicylate, andPbC12,2CS(NH,)2.30 This short summary indicates that investig-ations on 4-covalent compounds are yielding results of considerableinterest and valuc.Although the structure of compounds of the type AB, has notyet been determined, suggestions have been made as to possibleconfigurations.Iron pentacarbonyl, Fe( CO),, is a substance ofthis type, and two possible structures have been advocated. Thefirst is a tetragonal pyramid in which the apical carbon monoxidemolecule is further removed from the central atom than the otherfour ; such is the structure advanced by W. Graff under and G. Hey-mann 32 to explain the small dipole moment. Thc second, whichJ. S. Anderson 33 considers more probable, is a trigonal bi-pyramid.It provides the closest packing possible in a 5-covalent arrangement,and affords a satisfactory explanation of the ready formation ofFe,(CO), as formulated by N. V. Sidgwick and R. W. Bailey 34 anddescribed in a previous Report.35Anomalies in the parachor of co-ordination compounds wereobserved by S.S ~ g d o n , ~ ~ who found that beryllium in the basicpropionate Be,O( C,H,*CO,), and t’he acetylacetonate appearedto have a variable negative parachor. Co-ordination compounds ofthallium and aluminium displayed a similar anomaly, and in lastyear’s Report attention was directed to some results of F. G. Mannarid D. P~rdie,~’ who found that in certain series of organic metallic29 It. G. Dickinson, J . Amer. Chem. Soc., 1923, 45, 958.30 E. G. Cox, A. J. Shorter, and W. Wardlaw, Nature, 1937, 139, 72.31 W. H. George, Proc. Roy. SOC., 1927, A, 113, 585.32 2. physikal. Chem., 1932, B, 15, 377.33 J , , 1936, 1283.34 Proc. R o g . SOC., 1934, A, 144, 521.36 “ Parachor and Valoncy,” London, 1930, p.145.37 ?7., 1935, 1549.Awn. Reports, 1934, 31, 1041.66 INORGANIC CIIEMISTRY.compounds, both simple and complex, the metal atom showed anapparent parachor which fell steadily as the homologous series wasascended. For example, in the homologous series PdC1,,2R2S theparachor of palladium fell from 36 for the methyl to - 7 for then-amyl compound. Sugden sought to obviate the anomaly in thecompounds of beryllium, thallium, and aluminium by a singlet-linktheory of co-ordination ; in the case of palladium derivatives,however, the deficit cannot be explained by substituting a singletlinkage for the co-ordinate linkage, but must be regarded as a realeffect. Mann and Purdie suggested that the effect might beexplained, in part a t least, as due to the molecular shape, since thetrans-planar arrangement of groups about +,he palladium conEers amolecular configuration which might well be associated withanomalous packing effects.This explanation may account in somemeasure for the results of the parachor in the homologous seriesconsidered by Mann and Purdie, but it cannot be regarded ascomplete in view of some new results by J. S. Anderson 33 on theparachors of metal carbonyl compounds. These compact, non-planar molecules show a large anomaly in their parachors. Nickelcarbonyl, which is tetrahedral,20 and has a close-packed structure,gives a parachor which is a few units greater than four times theobserved parachor of carbon monoxide. For iron pentacarbonyl theobserved total parachor is less than four times that of carbon mon-oxide, I n the ca'rbonyls the available evidence indicates thatthe carbon-oxygen linkage differs very little from that in carbonmonoxide, BO that the assumption that the parachor of co-ordinatedGO is the same as that of free carbon monoxide should give anapproximate value for the parachor of the metal atom.Theparachors of the tricarbonylnitrosylcobalt, Co( CO),(NO), anddicarbonyldinitrosyliron, Fe(CO),(NO),, have also been determined.The assumption is made that as NO must be closely related to COin the nitrosocarbonyls, it is therefore reasonable to calculate theparachor on the relation PNO - 2'00 = PN - Pa. The parachoraof the metals calculated in this way are given in the followingtable :Ni(CO),.Co(CO),NO. Fe(CO),(NO),. Pe(CO),. CO.249.8 252.5 300.6 61.6 P ... ... ... ... ... ... ... ... 255.3Apparent P of metal 8.9 - 8.9 - 18.5 - 7.4From Sugden's atomic number-parachor curve, iron, cobalt, andnickel should have nearly equal atomic parachors of about 50(Cr = 54-3, Cu = 46). It is plain that all four substances show alarge deficit, just as do the co-ordination compounds of beryllium orpalladium. No adequate explanation of this anomaly has yet beenadvancedWARDLAW : CO-ORDINATION COMPOUNDS. 167I n $1) c most stable derivatives of cuprous copper the co-ordinationnumber appears to be four, als, e . ~ . , in K,[Cu(CN),]. It is interestingto find, therefore, that cuprous and silver iodides form compounds 24with tertiary phosphines and arsines analogous to the well-knownnon-ionic aurous chloride derivatives, R,P(As)+ AuCI, and thatmany members of this series possess considerable stability in spiteof the fact that the metal atom has apparently a co-ordinationnumber of 2.Actually, one would have expected the stable com-pounds to be of the type (PR,),CuI, where copper would have anatomic number of 36 and thereby attain the electronic structure ofkrypton. X-Ray analysis 24 of the arsine compound shows that thetrue molecule is not R,As+CuI, but that it really consists of foursimple units (Et,As+CuI),, and this is in accordance with molecular-weight determinations by the cryoscopic method. The phosphinederivative Et3P+ Cul is strictly isomorphous with the triethyl-arsine compound and has therefore the same structure. The detailedstructure shows that the four cuprous atoms are arranged at theapices of a regular tetrahedron and the four iodine atoms lie eacha t the centre, but above the plane, of one face of the tetrahedron.Beyond each cuprous atom is an arsenic atom lying on the elongationof the axis joining the centre of the tetrahedron to the copper.The three ethyl groups are then joined to each arsenic atom, so thatthe tetrahedral angle is subtended both a t the arsenic and at thefirst carbon atom of the ethyl groups.The stability is conferred byeach iodine atom, in addition to being covalently linked to itsoriginal copper atom, also being joined by two co-ordinate links tothe other two copper atoms of the same tetrahedral face.Eachcopper atom acquires seven electrons and is identical, therefore, inboth co-ordination number and electronic structure, with that inBenzoinoxime, as is well known, i s one of &number of organicreagents employed in the detection and estimation of metals. Thecopper derivative, discovered by F. Feig1,38 is a deep green amorphouscompound, insoluble in water and organic solvents, to which formula(VII) was assigned. Until recently, however, this structure couldnot be regarded as fully established. It is unusual to find thehydrogen atom of the secondary alcoholic group replaced bycopper; moreover, benzoinoxime is a reducing agent, and onewould expect it to reduce a proportion of the cupric salt to thecuprous state.From the analytical data, structure (VIII), whichis that of a cuprous compound, is a possible alternative to (VII).Convincing evidence that the structure is' (VII) has been obtainedby treating Feigl's compound with alcoholic hydrogen chloride. A3a Ber., 1823, 56, 2083,K3CCu(CN) 4168 INORGANIC CHEMISTRY.green crystalline salt (IX) then separates with a molecule of alcoholof crystallisation. With hot water, two molecules of hydrogenchloride are eliminated from (IX) and the original compound (VII)is produced. A compound of formula (VITI) on treatment withH HI /cu CPh=N<o>Cl CPh=N\(VII.) (VIII. ) PX.)CHPh-Q CBPh-O\ CHPh-0 c1 I I %CU’ \cuC P h = N dHCHPh-O> CPh=N\QH I ,cuc1 [g::$J(X.1 2 (XI.)alcoholic hydrogen chloride would give the derivative (X) .WhilstFeigl’s compound must therefore have structure (VII), there is, atpresent, no direct evidence whether the ring is five- or six-membered.It) has also been shown 39 that nickel, palladium, and platinum givecovalent compounds of the type (XI), where iU = Ni, Pd, or Pt,and it has also been demonstrated that in the case of nickel theoxime may function as a chelate group attached by two co-ordinatelinks. It will therefore be seen that benzoinoxime forms co-ordination compounds with a number of metals and can act as achelate group in three ways. In Feigl’s compound it may beattached to a copper atom by two principal valencies; with otherbivalent metals it may be associated either by one principal valencyand one co-ordinate link as in (XI), or by two co-ordinate links.When anhydrous cuprie chloride reacts with a glyoxime, such asdimethyl- or benzylmethyl-glyoxime, in ethyl-alcoholic solution,green crystalline co-ordination compounds (XII) are produced of atype different from the more familiar nickel derivatives.I n these(XII) + EtOH -1 &Oz = HZO -j-copper compounds the oxime is functioning as a chelate groupattached by two co-ordinate links. When methylglyoxime isemployed, not only is a co-ordination compound of type (XII)obtained, but a second product of entirely different constitution39 J. S. Jennings, E. Sharratt, and W. Wardlaw, J., 1936, 818WARDLAW : CO-ORDINATION COMPOUNDS. 169(XTII) may be produced.A new chelate group is formed40 in thereaction. This methylalkoxyglyoxirne may readily be distinguishedfrom the familiar dialkylglyoximes by the colour of its nickel deriva-tive. For example, the dimethylglyoxime of nickel is crimson, hutthe methylethoxyglyoxime (XIV) is orange.Although gold may be tervalent, there is no evidence that atervalent gold ion can exist. However, when suitably co-ordinrtted,this metal can form part of a tervalent cation as in (Auen2)Br3,where gold has a covalency of i o ~ r . ~ l This covalency of four isalso exhibited in the dialkyl compounds of tervalent gold, whichhave been shown to have the symmetrical constitution (XV),and tribromogold is similarly forrn~lated.~~ When these dialkylcompounds are treated with ethylenediamine there is an interestingdifference between the behaviour of the diethyl and the di-n-propylderivative. Diethylbromogold 43 yields directly the co-ordinationcompound (XVI), but the di-n-propyl compound 44 gives the inter-mediate derivative (XVII) , which in chloroform slowly yields amixture of the original di-n-propylbromogold and the di-n-propylanalogue of (XVI).When diethyl- or di-n-propyl-bromogold isBr BrjEt,*&NH2*yH2] Br Pr-**tNH,.C2H4*NH2-t~~~-~r II PrEt' 'NH,*CH2 I (XVI.) Pr (XVII.)heated with silver cyanide,45 the corresponding cyano-compoundis obtained as a colourless crystalline non-electrolyte which provesto be tetrameric in freezing bromoform. Reactions with ethylene-diamine lead to crystalline salts R,Au*CN*en*CNAuR,.In theReport for 1933 it was stated that C. S. Gibson 46 had announced thepreparation of two auric derivatives of unusual type (XVIII)40 E. Sharratt and W. Wardlaw, J., 1936, 563.4 1 C. S. Gibson and VC'. M. Colles, J., 1931, 2410.42 A. Burawoy and C. S. Gibson, J., 1935, 217.43 C. S. Gibson and J. L. Simonsen, J . , 1930, 2531.44 A. Burawoy and C. S. Gibson, J., 1935, 219.45 A. Burawoy, C. S. Gibson, and S. Holt, ibid., p. 1024.4G Nature, 1933, 131, 130170 INORQANIC CHEMISTRY.and (XIX). He now states *' that in the light of further experi-mental work the constitutions of these compounds must bc correctedto (XX) and (XXT) respcctively.1 (XIX.)BrIt will be recalled that a few years ago H. Carl~ohn,~* by a simplebut ingenious reaction, prepared a nitrate of iodine, co-ordinated withone or two molecules of pyridine.A solution of iodine in chloroformwas added to silver nitrate dissolved in a chlorof orm-pyridinemixture ; silver iodide was precipitated and dipyridinc iodinenitrate INO,,Zpy crystallised from the filtrate. A molecule ofpyridine was lost when the compound was left in a desiccator oversulphuric acid. More recently,49 the bromine analogue has beenprepared by a similar method. H. Carlsohn obtained it as a hygro-scopic substance by adding bromine in chloroform to silver nitratein a chloroform-pyridine mixture, removing the silver bromide, andadding the filtrate to ether containing a little pyridine. A dipyridinebromine perchlorate has also been isolated.Apparently co-ordina-tisn with pyridine is necessary for the isolation of these interestingsubstances.The fundamental principles of Werner's theory are now so firmlyestablished that it can be asserted with confidence that when asubstance is formulated at variance with these principles then theformulation is incorrect. In the course of his researches onruthenium, A. Joly Ii0 prepared its trichloride, RuC13, and noted thatit would absorb ammonia with the formation of an ammine, whichwas stated to be Ru,C1,,7NH3. By the action of water it yielded anintense violet-red solution from which was obtained a crystallinehydroxy-compound, to which the formula Ru,Cl4(OH),,7NH3,3H,Owas assigned. This hydroxy-compound, also obtained by the action47 J., 1936, 324.48 Habilitat.Schrift., 1932 (S. Hirzel, Leipzig).49 M. I. Uschakov and T7. 0. Tchiatov, Ber., 1935, 68, 824; H. Carlsohn,6o Compt. rend., 1892, 114, 391; 115, 2399.ibid., p. 2209WARDLAW : CO-ORDINATION COMPOUNDS. 171of ruthenium trichloride on aqueous ammonia, is known as“ruthenium red” and dyes animal fibres in red shades. Bothformuke seem unlikely in the light of modern ideas on molecularstructure, and an investigat’ion by G. T. Morgan and F. H. Burstall 51has shown that the Ru,C1,,7NH3 is not a simple substance but amixture of arnrninated chlorides, probably including the hexammine[Ru(NM,),]Cl,. Moreover, ‘( ruthenium red ” proves to be theco-ordination compound [Ru( OH)C1(NH3),]CI,€I,O, in whichruthenium has the usual co-ordination number six.With hydro-chloric acid it gives the yellow salt [RuCI~(NH,)~]C~,~H,O. It isinteresting to find that when the ammonia molecules are replacedby ethylenediamine, ethylamine, or pyridine, the tinctorial poweris greatly reduced. Morgan? and Eurstall suggest that a possibleexplanation lies in the fact that ammonia may induce a differentdistribution of the hydroxy- and chloro-groups from that of theseother ammines. It is obvious in the octahedral arrangement shownby ‘( ruthenium red ” and its analogues that the hydroxy- and chloro-groups may occupy cis- or trans-positions relative to one another.F. H. Burstall52 has recently described a series of very stable redco-ordination compounds [Ru 3dipy]X,,yH,O which have beenobtained by the action of 2 : 2‘-dipyridyl on ruthenium salts.Bythe inbraction of this diamine and ruthenium trichloride at 250°,an almost quantitative yield of the complex chloride[nu 3dipy]C12,6H,0may be isolated from the reaction products :2RuC1, + 8CIoHgN2 = 2[Ru Sdipy]Cl, + C20H,4N4 + 2HUThe stability of these tris-2 : 2’-dipyridylruthenous salts is remark-able; they can be boded with concentrated (50%) potassiumhydroxide solution without destruction of the complex cation. Asthe base, dipyridyl, forms a chelate ring in the same way as ethylene-(1.1 (11.) (111.)diamine [cf. (I)] these trisdipyridylruthenous salts should be capableof resolution. With the aid of d- and Z-ammonium tartrates, thecomplex [Ru 3dipy-j has been resolved into optically active forms(11) and (111), and the optically active bromides isolated. These51 J., 1036, 41..53 Ibid., p. 173172 INORGANIC CHEMISTRY.gave [OL];& + 860" and - 815". I n 1931 R. Charonnat 53 obtainedd- and I-forms of the complex salt R[Ru(NO)(C5H5N)(C,0,),],where R is NI-1, or C,H,N. Here the ruthenium is present as acomplex anion. H. Gleu and K. Rehm 54 record that they haveobtained luteo- and purpureo-salts of ruthenium. The former arethe stable hexammines, [Ru(NH3),],(S0,),,5H,0 and[WNH, 1 6 I H (8 0 4 1 2,[Ru(NH,)5Cl]Cl,.and the latter are the pentammines [Ru(NH,),Br]Br2 andThese compounds are analogous wit'h the corresponding well-knowncobalt and chromium ammines, but the hexammines of rutheniumare colourless like those of rhodium.All the compounds areparamagnetic, with a moment of 2 Bohr magnetons at 20".The heats of formation and solution of some isomeric coba1ta.m-mines have been determined by T. C. J. Ovenston and H. Terre~.~5The method adopted was to decompose the ammine with an excessof M-sodium sulphide. The reaction can be represented for thetetrammine salts by the equation2[Co(NH3),C1,] C1+ 3Na,S = CO&, + 8NH, + GNaC1-I- 2Q cals.If the heats of formation, in solution, of sodium sulphide andchloride and ammonia (or other amine) and the heat of formnt' ionof solid cobaltic sulphide are substituted in the equation, then therequired heat of formation can be calculated from &. The resultsare summarised below :Heat of formation, Weat of solution,cals .cals.trans-[Co(NH,),C1,161 .................. 214,880 - 8290trans- [ Co en,CI,]Cl ..................... 171,920 - 5340css- 7 7 Y Y .................. 214,170 -9510......................... C'LS- 172,830 -8010Although much work has been done on the vapour tensions ofammines, mention should be made of a very interesting seriesof results obtained by G. Spacu and P. Voiche~cu.~~ I n a study ofcertain ammoniates of the thiocyanate, formate, acetate, chromate,glycdate and other salts of the ion Cu2+, the strength of the bondbetween the metal ion and ammonia was found to be inverselyproportional to the base strength of the anion of the salt, underotherwise comparable conditions.In his papers reporting the discovery of unusually stable com-53 Ann.Chim., 1931, 16, 126.54 2. csnorg. Chem., 1936, 22'9, 237.5 5 J., 1936, 1660.56 Z. anorg. Chern., 1936, 226, 273WARDLAW : CO-ORDINATION COMPOUNDS. 173plexes with o-phenanthroline (IV), I?. Blau 57 draws attention to theexistence of two different ferric complexes. The blue one isobtained only by oxidation of the ferrous complex whose formulationis well established as [Fe(CI2HSN2),l2 + ; analysis of its chloroplatinateshowed it to be [Fe(C,2HsN2),]3+. By contrast, direct reaction ofo-phenanthroline and ferric salts led to the formation of brownsolutions from which Blau isolated no solid compounds. A. Gaines,L. P. Hammett, and G. H. Walden 58 have now obtained from thesebrown solutions an interesting crystalline salt of definite compositionwhose properties correspond to the formula of a tetraphenanthroline-dioldiferric chloride (V) .The iron atoms have acovalency of 6H 1and the unusually low magnetic susceptibility of the new complexsuggests the partial neutralisation of the magnetic moments of thetwo atoms, and is additional evidence of a polynuclear structure.There is nothing repugnant in this formulation. The ease offormation and stability of the double “ 01 ” bridge are well estab-lished for cobaltic and chromic ammines and are basic features ofthe theories of colloidal oxides which E. Steasni 59 and A. W.Thomas 60 have developed.Many facts have come to light from a study of the rotatory powerof complex inorganic compounds, with a covalency of six.Studiesof such compounds have been made by F. M. Jaeger,61 J. Lifschitz,62C. H. Johnson,G3 R. Samuel,G4 and many others. A. Werner,65 itwill be remembered, carried out many transformations involvingoptically active compounds in his efforts to find a relationshipbetween configuration and direction of rotation. Typical of theseinvestigations are the following :Z-[Co en,Cl,]Cl+ K,CO, -+ d-[Co en2C0,]C1 + 2KC1Z-[Co en,Cl(SCN)]Cl + NaNO, -+ d-[Co en,(NO,)(SCN)]Cl + NaClZ-[Co en2C1(NO,)]C1 + KCNS -+ Z-[Co en,(N02)SCN]C1 + KCl57 Monatsh., 1898, 19, 647.5 8 J. Amer. Chem. SOC., 1930, 58, 1668.59 Collegium, 1932, No. 751, 902.60 J . Amer. Chem. Soc., 1934, 56, 794.61 “ Optical Activity and High Temperature Measurements,”,NewYork, 1930.62 2.physihl. Chem., 1923, 105, 27; 1925, 114, 485; Rec. trav. chim.,63 Trans. Paraday Soc., 1932, 28, 845; 1933, 29, 626.64 ibid., 1935, 81, 423.1922, [iv], 41, 13.6 5 Ber., 1912, 45, 1228174 INORGANIC CHEMISTRY.He assumed that no change in configuration took place during thesereactions and formulated the structures in accordance with thisassumption. The complex salts [Co en2C1( SCN)]Cl, [Co en2C1(N0,)]C1,and [Co en2(N02)( SCN)]Cl were then resolved as bromocamphor-sulphonates. Werner now assumed that the complex ions of thesame configuration form, in each caBe, the less soluble salt with theactive acid. The experimental results obtained agreed with thosebased on his first assumption, for the Z-[Co en,Cl(SCN)]+,d- [Co en2C1(N02)]+ ,and d-[Co en,(NO,)(SCN)I+ ions crystallised as bromocamphor-sulphonates in the &st fractions.Werner's views have beencriticised by F. M. Jaeger,c6 who states that these rules are quiteillusory and that a much better criterion of analogous spatialconfigurations is based on a comparison of the crystal form. J. P.Mathieu,e7 on the other hand, from studies of the optical absorptionand rotation of many optically active complex salts, finds somesupport for Werner's rule relating configuration and solubility of thediastereoisomerides. W. Kuhn and K. Bein 68 have deducedabsolute configurations of inorganic compounds from the theory ofthe origin of optical rotation. J. C. Bailar and R. W. Auten G9 haverecently shown that Werner's assumption that atoms or groups inthe complex ion are always displaced by others without change ofconfiguration cannot be maintained.They proved that whensilver carbonate reacts with Z-[Co en,C12]@l it gives E-[Co en,CB,]Cl,whereas potassium carbonate gives the dextrorotatory product.A more recent study 70 has demonstrated that an excess of silvercarbonate gives the l ~ v o - and a deficiency the dextro-rotatory salt.Potassium carbonate always gives a dextrorotatory product. Ofthe mechanisms suggested for the Walden inversion, on the basis ofthe reactions of organic molecules, is one 71 which states thatinversion accompanies every reaction. This means that everyreaction which involves a single step in the substitution of one groupby another on a tetrahedral atom should lead to inversion.Accord-ingly if the over-all reaction takes place in an odd number of stepsthe product should be the enantiomorph of the original material.The object of 8ome recent work by J. C. Bailar, J. H. Haslam, andE. M. Jones 72 was to see if this theory might be applied to &covalent6 6 Ref. 61, pp. 93, 139.Compt. rend., 1934, 199, 278; 1935, 201, 1183.68 2. anorg. Chem., 1934, 218, 321.69 J . Arner. Chem. SOG., 1934, 56, 774.' 0 J. C. Bailar, F. G. Jonelis, and E. H. Huffman, ibid., 1936, 58, 2224.71 A. R. Olson, J . Chem. Physics, 1933, 1, 418; E. Borgmann, M. Polanyi,and A. Szabo, 2. physikat. Chem., 1933, By 20, 161.J . Arner. C h m . SOC., 1936, 58, 2226WARDLAW : CO-ORDINATION COMPOUNDS.175inorganic compounds. The case selected was the reaction ofammonia with E-[Co &n2Cl2]C1. At - 77" or - 33" with liquidammonia, the product was Z-[Co en,(NH,),]Cl,, but a t 25" andhigher it was the d-form. These investigators argue that the twochlorine atoms in the complex ion must be attached to the cobaltatom in exactly the same way, and occupy like positions in themolecule. They assume, therefore, that the same mechanismfunctions in their displacement from the complex. If this is correct,then the conversion of the dichloro-salt into the diammino-derivativemust take place in an even number of steps, and the theory men-tioned would allow no inversion. Actuadly, the reaction does leadto an inversion, for the product a t low temperatures is laevo- andthat a t higher temperatures is dextro-rotatory.The authors 72point out, however, that it is possible for the displacement in thecomplex of a chlorine atom by a molecule of ammonia to producesuch a profound change in the complex ion that the second step ofthe reaction does not follow the samc mechanism. E. Bergmann 7Zahas recently stated that the theory mentioned above 7 1 is concernedexpressly with substitations of ions for polar bonds and the reactionstudied by Bailar is not of this type.R. Tsuchida, M. Kobayashi, and A. Nakamura 73 have reportedthat when solutions of certain racemic complex compounds areshaken with powdered quartz, it preferentially adsorbs one antipode,compounds of the same configuration being preferentially adsorbed byquartz of a given sign of rotation.As an example, when a solutionof chloroamminobisdimethylglyoxime cobalt [Co(dm),Cl(NP-I,)],Wdm being dimethylglyoxime, is shaken with the quartz powder thesupernatant liquid is optically active. This method, it is claimed,may be used to determine whether a given compound is cis- or trans-.I n the case just cited, the complex compound must be of cis-configuration, for the trans- woulci be incapable of resolution.Y, Shibata 74 and his colleagues have studied the catalytic oxidationof certain racemic amino-acids in the presence of optically activecomplex compounds, and state that one isomeride of the amino-acid is oxidised faster than the other. They explain this as beingdue to an " enzyme-like action " of the inorganic complex.J. C.Bailar 75 suggests as an alternative explanation that one form of theamino-acid becomes part of the complex while the other does not,120 J . Afmer. C k e m Xoc., 2937, 59, 423.J . Ch,ern. SOC. Japan, 1935, 56, 1339; Bull. C'kem. SOC. Japan, 1936,74 Y. Shibats and R. Tsuchida, i b i d . , 1929,4, 142; Y . Shibata, Y. Tanah,75 Chem. Reviews, 1936, 19, 82.11, 38.and S. Gocla, ibid., 1931, 6, 210176 INORGANIC CHElklISTRY.and subsequent oxidation might destroy one or the other. C. E. M.Pugh's results 76 are not in entire accord with those of Shibata.An interesting account by N. F. Hall 77 of the acid-base propertiesof complex ions has appeared. He summarises the results on theacid strength of various ammino-cations from the work of Lamb,Werner, and Bronsted.As would be expected, those cations withthe greatest tendency to liberate ammonia should be the weakestacids, and this is, in general, the case. It is also interesting tonotice from Werner's work 78 on 6-covalent-metal cations that thecentral atom confers acid strength in the diminishing orderIn connection with complex anions, A. Hantzsch remarked thatamong the oxygen acids those with the most oxygen were in generalthe strongest, and that, as a rule, complex anions tend to be weakbases. In two recent papers, 1. M. Kolthoff and W. J. Tomsicek 79have brought forward the striking fact that, although [Fe(CN),]3-and [Mo(CN),I4- are weak bases, yet [Fe(CN)J4- is about as stronga base as the benzoate ion.An important extension to the chemistry of the metal carbonylshas been made by W.Manchot and W. J. Manchot.80 They haveisolated Ru(CO), as a very volatile crystalline compound (m. p.- 22") by the action o f carbon monoxide on finely divided rutheniumat 180" and a pressure of 200 atmospheres. Moreover, by the actionof light, or better, by heating its benzene solution, they have pre-pared from the pentacarbonyl another derivative, Ru2(CO),, asorange-yellow crystals which in the absence of air only decompose a t200". By the action of the halogens on this enneacarbonyl, theyhave formed compounds of the type RuX,(CO), and have alsoobtained a nitrosyl compound, Ru(NO), or RU(NO)~, from theinteraction of nitric oxide and Ru,(CO),.These results emphasisethe periodic relationship which is found between iron and ruthenium.The three carbonyls c"r(CO),, Mo(CO),, and W(CO), have been thesubject of an extensive investigation by W. Hieber, E. Romberg,and F. Miihlbauer.81 These carbonyls prove to be isomorphous, allforming colourless, strongly refracting, volatile, orthorhombiccrystals, readily soluble in inert organic solvents. Compared withother metal carbonyls they are very stable, the vapour decomposingslowly only above 120". The boilingpints (abs./l atm.) are Cr(CO),Pt4+, Ru4+, Cr3+, Coat.76 Biochem. J., 1933, 2'4, 480.7 7 Chem. Reviews, 1936, 19, 89.7 8 " New Ideas on Inorganic Chemistry," London, 1911, p. 201.7O J . PhysicaE Chem., 1935, 39, 945.8O 2.anorg. Chem., 1936, 226, 385.81 lbid., 1935, 221, 321, 332, 337, 349WARDLAW : CO-ORDINATION COMPOUNDS. 177420*5", Mo(CO), 429-4", W(CO), 448.0". As in the cases of thenickel, cobalt, and iron carbonyls, it is possible to replace the co-ordinated CO group by suitable organic units. For example, bythe use of pyridine, the derivatives Cr(CO), 3py, Mo(CO), 3py, andW(CO), 3py have been prepared. Derivatives of similar type havebeen obtained by the use of such chelate groups as ethylenediamine,o- phenanthroline, or cccc ' -dipyrid yl .There is no doubt that at present most chemists consider that theelectron-pair theory of the co-ordinate link offers the best explan-ation of the many properties of co-ordination compounds. Theformation of complex compounds of the olefins with metallic saltssupplies an interesting test of the application of the lone-pair bondtheory.The first compound of this series was obtained in 1831 byZeise,82 who isolated a substance with the empirical formulaK[PtC13,C2H,],H20 from a reaction mixture of chloroplatinic acidand alcohol. Later, K. Birnbaum 83 prepared similar compoundswith propylene and amylene, and C. Chojnacdki 84 obtainedK[PtBr,,C,H,]. This series of substances is obviously derivedfrom a platinous derivative of the general type PtX,Y, where X isa halogen atom and Y a molecule of a hydrocarbon. Substances ofthis type are bimolecular, but it seems most unlikely that Zeise'ssalt is other than unimolecular, for it has the covalency of 4 which isnormally associated with bivalent platinum.Now if the ethylenemolecule is associated in the usual way with the central metal atom,il "lone pair " of electrons must be available. These are notapparent in the usual formulation for ethylene and allied molecules.One possible mechanism 85 supposes that the lone pair is producedby an elect'romeric change, R.CH=CKR R-6H-EHR. Thisinvolves (a) an opening of the double bond, and ( b ) leaving one ofthe carbon atoms-that which bears the residual positive charge-with a sextet of electrons. Discussing this possibility in the forma-tion of K[PtCl,,C,H,], J. S. Anderson 86 states that it is not alto-gether free from objection on physical grounds. The hypotheticalpolarised state of the bond concerned, supposing as it does thecomplete transfer of one electron, represents an excited state of theinolecule and could be represented at room temperature by only a\very lowsupposedplatinumprobability of occurrence.Alternatively, it might bethat rearrangement takes place in the field of the adjacentatom which possesses a high electron affinity. In either82 Pogg. Ann., 1831, 21, 497.S3 Annalen, 1868, 145, 67.84 Jahresber., 1870, 23, 510.8 5 G. M. Bennett and G. H. Willis, J., 1929, 256.86 J., 1936, 1042178 INORGANIC CHBMISTRY~.case the reactions concerned should involve a high energy ofactivation. There are no data available as to the energy of activ-ation either for the reactions of the type involving formation ofcomplex compounds of olefins with metallic salts or for addition-compound formation by aromatic hydrocarbons, but reactions ofboth kinds proceed either very rapidly or fairly rapidly at roomtemperature.Anderson concludes that, on the evidence so faravailable, any attempt to formulate compoundssuch as Zeise's salt in terms of the electron-pairbond theory possesses a certain artificiality. T. KR A. Ashford and M. S. Kharasch 87 have proposed I R for compounds of the type PtC1,,C,H4 a structure c < ~ which embodies the idea of the electron-pair bond h . 7 but appears t o imply a change in the valency ofcl/p\cl the platinum from two to four. This is difficultto reconcile with their stat,ement that it is wellestablished that these compounds are derivatives of platinousplatinum.It should be mentioned that R. F. Hunter and R.Samuel 88 believe that the conception of the lone pair of electrons asan agent for true chemical linkage is in direct contradiction to theresults of band spectroscopy.Much work of value has been omitted from this report owing tolimitations of space, but the Reporter has attempted to deal with ava'riety of topics in the hope that this course will make the reportof wider interest.\pt/C1c11% ..( '\ R R>y g>cw. w.5. THE RARE EARTHS.As a general rule, chemists now recognise that the elementsof the rare earths are not a confused collection of metals but sub-stances of the highest scientific interest. It is, of course, quitetrue that there are members of the group so scarce and so difficultto separate that they are little more than names in the list of knownchemical elements.Nevertheless, it is not always realised that thegroup as a whole is as plentiful in nature as lead, zinc, or cobalt,and that cerium, the masb abundant member, is more plentiful thansilver, gold, or platinum. The following table gives the estimatedoccurrence of the elements in the earth's crust :Element La Ce Pr Nd Sm Eu Gd Tb D y Ho Er Tin Yb LuAt.No. 67 58 50 60 62 63 64 65 66 67 68 69 70 71"/o x 10'' 7 31 6 18 7 0.2 7 1 7 1.2 6 1 7 1.5$ 7 J. Amer. Gh,em. Xoc., 1936, 58, 1733.1 V. M. Goldschmidt and L. Thomassen, VVidensEa(ps.-Slc~~fte~, I, Matemat.-88 Nature, 1936, 133, 411.Naturu. K h s e (Krbthnia), 1924, No. 5, p. 49CARTER AND WARDLAW : THE RARE EARTHS.179It shows that the elements of even atomic number are always moreabundant than their neighbours of odd atomic number, and thissuggests that their stability is closely related to their detailed atomicstructures.At one time the metals of the rare earths were supposed to havean invariable valency of three, so that cerium, being quadrivalent,was considered an intruder. Although it is still correct to saythat the characteristic valency of the group is three, yet it is nowfirmly established that both higher and lower valencies are possible.Por inshnce, cerium, praseodymium, and terbium can be quad-rivalent, and samarium, europium, and ytterbium may be inducedto show a valency of two. G. Jantsch and W. Klemmy2 prominentworkers on these anomalous valencies, have published a diagramwhich shows the results of recent investigations. In this diagram(see figure) lines above the central horizontal line represent quadri-valency, and lines below show bivalency.The length of the line[Cp = Lu (at. no. 71) and Tu = Tm] Igives an approximate measure of the stability, and the size of thepoint denotes the relative stability of the electronic configurationof the Me3+ ion. There is evidence in the cases of lanthanum,gadolinium, thulium, and lutecium that the lower-valency compoundsexist, but these have not yet been obtained in a form capable ofdetailed study. Lanthanum was stated3 to form an oxide of thequadrivaleiit element, but this could not be confirmed by G.Jantsch and E.Wie~enberger.~These variable valencies are proving most useful in makingpossible new methods of separation. Cerium, for example, haslong been separated from its neighbours by boiling an oxidisedsolution containing thein, whereby ceric salts are readily hydrolysedand precipitated as basic compounds. The new processes, however,utilise a valuable observation first made by Jantsch and his col-laborator~,~ that when the rare-earth metals become bivalent,2 Z . anorg. Chin., 1933, 216, 80.3 I. M. Kolthoff and 1%. Elmquist, J . Amer. Chem. SOC., 1831, 53, 1230.4 Monatsh., 1932, 60, 1.5 G. Jantsch, H. Alber, and H. Grubitsch, iKom~%h., 1929, 53-64, 305180 INOELGBNIC CHEMISTRY.the solubilities of their sulphates resemble those of barium andstrontium.This fact led L.F. Yntema 6 to explore the possibility of separ-ating europium from other rare earths by electrolytic reductionin the presence of the sulphate ion. He dissolved a mixture ofthe oxides of samarium, europium, and gadolinium in hydrochloricacid, added a small amount of dilute sulphuric acid, and electrolysedthis solution in a two-compartment cell with a mercury cathodeand platinum anode. As the electrolysis proceeded, colourlesseuropous sulphate, EuSO,, separated. A spectrographic examin-ation of this material showed only a trace of samarium. Thismethod successfully accomplishes one of the most difficult separ-ations in the field of analytical chemistry. states thatif the material contains less than 2% Eu,O, there is a greaterdifficulty in effecting a separation, but co-precipitation with theisomorphous strontium sulphate is helpful.He confirms that theelectrolytic method gives good yields of europous sulphate of highpurity. have shown that bivalentytterbium sulphate may similarly be precipitated from an acidsolution by electrolytic reduction in the presence of the sulphateion, In this way ytterbium may be separated from yttrium,erbium, and thulium. The precipitate has the variable compositionYbSO,,xH,O and is a very light green crystalline compound. W.Prandt19 has used this method to prepare pure ytterbium, butstates that it is not always successful. D. W. Pearce,lo however,has found it satisfactory for the separation of ytterbium fromthulium and from lutecium fractions.33. N. McCoy l1 has shownthat reduction by zinc, in a modified Jones reductor, changesEuCl, into the dichloride. Investigators 9* 11 on. the sulphates ofytterbium have all commented on the reaction of the yellowish-green YbSO, with the dilute acid as soon as the current is stopped :ZYbSO, + 2H' = 2Yb"' + 250,'' + H,It appears that the order of decreasing stability amongst the sul-phates of the bivalent rare-earth metals is europium, ytterbium,samarium,During recent years several attempts have been made to evolvemethods of separation depending on partial thermal decompositionof rare-earth metal sulphates. For example, H. H. Willard andA. BruhlR. W. Bell and L. F. YntemaJ . Amer. C'hem. SOC., 1930, 52, 2782.Aiagew.Ckena., 1936, 49, 159.J . Arner. Chem. Sac., 1930, 52, 4264.@ 2. anorg. Chem., 1932, 209, 13.lo Thesis, Illinois, 1934.l1 J . Amer. Chem. SOC., 1936, 58, 1677CARTER AND WARDLAW : THE RARE EARTHS. 181R. D. Fowler l2 determined the products formed in such decom-positions and also the dissociation pressures of the pure anhydroussulphates at definite temperatures. They then attempted tomaintain the partial pressure of sulphur trioxide above the heatedisomorphous sulphates a t a value intermediate between thoseof the constituents, and thus bring about complete decompositionof one compound to the insoluble oxide without affecting theothers, By adopting these principles, a separation of cerium fromother earths was achieved. Cerous sulphate ignited readily toceric oxide, whilst the associated rare-earth metals remainedas the sulphates.It was found that the separation of praseodymiumfrom lanthanum was not completely successful, because the sulphateof the former ignited only partially to the higher-valency oxide,and the success of the separation requires the formation of thishigher oxide of praseodymium. Similar work has been carriedout recently by L. Wohler and K. F1i~k.l~ Attempts to separaterare earths which did not oxidise on ignition were unsuccessful,because the decomposition products formed solid solutions with noappreciable soiubility differences between the constituents. D. W.Pearce l4 mentions that he and Knlischer have determined thetemperatures at which certain nitrates of tho rare-earth metalslose some or all of their water of crystallisation. When certainmixtures of carefully heated, partly dehydrated nitrates are ex-tracted with anhydrous ether a t low temperatures separationsare obtained.The magnetic susceptibilities of the rare-earth metals, withanomalous valencies, afford an interesting approach to the studyof the electronic structures of the rare-earth metal ions.The largeparamagnetism of these metals and their salts is well known.Susceptibility determinations of praseodymium and cerium inthe quadrivalent state were described in 1925,15 and later investiga-tors l6 have examined compounds of bivalent samarium, tervalentgadolinium, and both bi- and ter-valent europium and ytterbium.The results from the various researches bear out the law thatthe susceptibility of a quadrivalent rare-earth metal ion approachesthat of the ion of a metal with atomic number one less, but havinga valency of three.Also the susceptibility of a bivalent rare-earth metal ion approaches that of the ion of a metal with atomic12 J . Amer. Chem. SOC., 1932,54,496.l3 Ber., 1934, 67, 1679.l4 Chem. Reviews, 1935,16, 121.It S. Meyer, Phy8ikd. Z., 1925, 26, 51, 479.l6 W. Klemm and J. Rockstroh, 2. anorg, Chem., 1928,176,181 ; W. Klemmand W. Schuth, ibid., 1929,184,352 ; P. W. Selwood, J . Amer. Cham. ~SOC., 1933,55,4869; 1934,56, 2392; G. Hughos and D. W. Percrce, ibid., 1933,55,3277182 INORGANIC CHEMISTRY.number greater by one, but with a valency of three.These factsmust mean that, on reduction, the third electron-the one not inuse for valency purposes--is suppressed and becomes associat'edwith the 4, orbital groups. On oxidation this inner group thengives up the electron as a valency unit. For example, the diEerencebetween ytterbium (at. no. 78) in the bivalent and in the tervalentstate is expressed by the electronic distribution :I<. 1;. M . N . 0.Yb3+ .................. 2 8 18 18 + 13 8Yb2+ .................. 2 8 18 18 + 14 8I n view of the fact that the rare-earth metals differ, as far as theorbital electrons are concerned, only in the distribution in the fourthquantum group, it might be expected that the colour of their saltswould be due mainly to the degree of incompleteness of this shell.Thereby colour relations might be thought to be periodic, but thisidea is not substantiated by the facts, as the following table shows.Colours of tervalent ions.57 La 71 Lu Colourless58 Ce 70 Yb ? 958 Pr 69 Tm Green60 Nd 68 Er Red62 Sa 66 Dy Yellow63 Eu 65 Tb Faint rose64 Gd colourlossThis intleresting colour sequence has been discussed by variouswriters, e.g., L.F. Yntema and J. D. Main Smith,18 but it cannotyet be considered as fully explained. There is, incidentally, aninteresting resemblance in colour in the cases of certain bi- andter-valent ions :At. No. ..................... 63 63 69 70Colour ........................ Palo yellow Colourless Green GreenIt should be mentioned that magnetic susceptibilities, when care-fully measured, afford a most accurate means of analysis, becausethe magnetic susceptibilities of mixtures of rare-earth compoundsare additive.The strengths of the rare earths as bases have very frequentlybeen determined, and the results show that there are considerabledifferences in this property among the various members of thegroup.B. S. Mopkins l9 has produced a table which gives theIon ........................... Sm3t EU2+ Tm3 + 133%-l7 J. Amer. Chem. SOC., 1926, 48, 1598.la Nature, 1927, 120, 583.lS J . Chem. Educ., 1936, 13, 363CARTER AND WARJ3LAW : THE RARE EARTIIS. 183relative atrengkh of any rare earth, where the strength of P(OH),is hken its unity.At. No. .................. 39 57 t 9 60 62 G4 66Element ...............Y La I'r Nd Sm Gd DyRel. basicity ............ 1 1300 80 47 8 3.4 0.5It is safe to say that lanthanum hydroxide is the strongest tervalentbase known. It is also important to notice that lanthanum is eleventimes as basic as praseodymium, while neodymium is nearly sixtimes as basic as samarium. The order of decreasing basicitybecomes a matter of importance, because some of the most usefulmethods of separation are based upon the differences in this property.The latest investigations of G. EndresZ0 and of B. 5. 130pkins~~and his collaborators lead with great certainty to the results thatthe order of decreasing basicity throughout the rare-earth groupis exactly the order of increasing atomic number. If yttrium (at. no.39) were included in the rare-earth group it would form an exception,for Hopkins l9 states that in basicity it falls between illinium(at. no.61) and samarium (at. no. 62), and G. Endres 2o places itbetween gadolinium (64) and dysprosium (66).J. Newton Friend 22 has carried out a series of solubility investiga-tions on the selenates, nitrates , and double magnesium nitratesof lanthanum , praseodymium , and neodymium , largely withthe object of facilitating the separation of these rare-earth metals.Finally, mention should be made of the interesting results obtainedby G. Jantsch and his c~llaborators,~~~ 24 who have prepared thealmost complete series of the chlorides , bromides , and iodides ,and determined their melting points. It will be seen from thefigure given by Jantschz4 that the melting points are arrangedvery regularly, and it is noteworthy that in the first half of theseries the chlorides possess the highest melting points, and in thesecond half the iodides.W. Klemm 25 suggests that this is due tothe fact that in the second half of the group another lattice typeoccurs.Prom this short summary of modern work on the rare earthsit will be clear that the study of this group'is far from exhausted.i h c h still remains to be done on the chemistry of anomalous valenciesin spite of the work of investigators in different parts of the world,20 2. anorg. Ci~em., 1932, 205, 321.21 J . Arner. Chem. SOC., 1933, 55, 3117, 3121.22 J . , 1928, 1820; 1930, 1633, 1903; 1931, 1802; 1932, 707, 1083; 1035,83 2.anorg. Chem., 1929,185, 49; 1931,2ol, 207.24 Ibid., 1932, 207, 357.Angew. Chem., 1934,47, 21.356, 824, 1430184 INORGANIC CHEMISTRY.and the group of elements as a whole presents many fresh problemsto the (=ourageous and resourceful investigator,S. R. C. w. w.6. SOME ELEMENTS AND COMPOUNDS.There has been a considerable output of interesting and importantwork, although in the main the year's work has followed closelyalong established lines. Again, full use has been made of thefacilities provided by modern chemical equipment and methods.P. W. Schenli and H. Platz 1 have announced the preparation of ahitherto unknown peroxide of phosphorus. On passing a mixtureof the vapour of phosphoric oxide (P205) and oxygen a t a pressure ofca.1 mm. of mercury through a hot discharge tube, a bluish-violetproduct separated behind the discharge zone and was stable for aday at room temperature, if moisture was excluded. Its aqueoussolution was colourless, and slowly liberated iodine from potassiumiodide. The product is considered to contain about 2% of a newperoxide of phosphorus of the empirical formula PO,.The hydrides of phosphorus have recently been subjected torenewed investigation and some important facts have been disclosed,To the liquid hydrogen phosphide which accompanies gaseous phos-phine when phosphorus is acted on by aqueous potassium hydroxide,the formula P2H, (H.W. 66) has been generally ascribed, althoughthe molecular weights of 74.4-77.0, found by L. Gattermann andW.Hausknecht,2 are by no means in good agreement with it. Thediscrepancy has usually been attributed to the presence of higherhomologues. Liquid hydrogen phosphide has now been carefullyprepared by P. Royen and K. Hill3 in a pure state, and densitydeterminations are in satisfactory agreement with the formulaY,H,. Moreover, a careful search for other homologues has demon-strated their absence. A solid yellow hydride of phosphorus is alsoproduced during the action of aqueous potassium hydroxide onphosphorus. The empirical formula, P,H, has 'long been ascribed tothis substance, as the result of the work of P. Th4nard,4 and ofGattermann and Mausknecht,z who regarded its formation as due toa breaking up of the P,H, molecule :5P2H4 = 6PH, + 2P2H* ,Xafurwiss., 1936, 94, 651.Ber., 1890, 23, 1179.Z .anorg. Chem., 1936, 229, 97.Ann. Chim. Phys., 1845, [iii], 14, 6 ; Annalen, 1845, 55, 27CARTER AND WARDLAW SOME ELEMENTS AND COMPOUNDS. 185A cryoscopic determination of molecular weight by R. Schenckand E. Buch raised the formula Y,H to I?,,€€,. Direct estimationsof phosphorus and hydrogen in the solid hydride, made by R.Schenck and by A , Stock,' indicated a composition varying betweenP,,H,.,, and P12H6.4, the difference being due, presumably, toexperimental errors. P. Royen and K. Hilly3 however, have nowreinvestigated this substance and consider that the yellow hycirideis not a definite compound, but that it arises from adsorption of PH,on amorphous yellow phosphorus, these products having been formedby the decomposition of liquid hydrogen phosphide :3P2H4 = 2P + 4PH3It is pointed out that the analytical methods employed for thedeterminations of phosphorus and hydrogen are very exact (accuracyfor hydrogen, -+0.03%) and the variations found are due simply tothe different amounts of phosphine adsorbed according to theexperimental conditions.Royen and Hill * consider that they have substantiated theirsorption theory by the artificial production of a similar substance bybringing phosphine into contact with amorphous phosphor us, althougha product of composition higher than Pi&l4.12 was not obtained.Very little is known about the modifications of phosphoric oxide,or phosphorus pentoxide, as it is frequently called.Reference toany standard text-book reveals the conflicting nature of the availabledata. It seems agreed, however, that there is a form without arecognisable crystalline structure, and a vitreous form. Otherforms, of more or less doubtful existence, are a crystalline form (a),produced by distillation at comparatively low temperatures, say350", and a second crystalline form ( b ) , stated to be produced fromthe vitreous modification by prolonged heating and having a meltingpoint of 569". A third crystalline form ( c ) , stable above 570", isthought to exist in the absence of the lower-melting form. A. N.Campbell and A. J. R. Campbell have investigated the amorphous,the vitreous, and the low-temperature crystalline form (a), producedfrom the amorphous form a t any temperature between 350" and 600°,provided the heating be not prolonged.These workers have deter-mined densities, solution tensions, and solubility in chloroform, andconclude that, of the three modifications, the only homogeneous formis the vitreous. This is the most stable, since it has the lowestBer., 1904, 37, 915.Ibid., 1903, 36, 991, 4202.Ibid., 1909, 42, 2849.2. anorg. Chem., 1936, 229, 369.it l ' r m s . Faraday Xoc., 1935, 31, 1567186 INORUANIC CHEMISTRY.solubility aiicl the highest density. It is suggested that, as thevitreous form is produced from the amorphous modification, a truesolution of amorphous in vitreous is formed as an intermediateproduct. It is also pointed out that, if the two allotropes aresufficiently stable to form a true solution, their structural units mustbe very different.The nitrides of the non-metals are very diverse in character andinclude a group distinguished by the most extraordinary stability.Prominent in this group are the nitrides of phosphorus, and althoughin the past much research has been done on these and allied sub-stances, they still continue to excite the marked interest of manyinvestigators.Published work dealing with the nitrides of phos-phorus has appeared in recent years from H. Moureu l o and hiscollaborators, P. Renard,ll V. F. Postnikov and L. L. Kuzmin.12Phosphorus pentanitride, P3N5, can be obtained in good yield byA. Stock's method l3 from ammonia gas and P,S5, but H. Moureuand P.Rocquet l4 have described another method which uses thechloronitride of phosphorus, discovered by Liebig and prepared fromphosphorus pentachloride and ammonium chloride. The simplereaction may be expressed thus :CI,PC13 + H3N = (C1,PN) + 3HC1but the chloronitride is really the polymer (PNCl,),. By the actionof liquid ammonia, the chloronitride is changed into phospham,probably by the reactionWhen phospham is heated in a vacuum a t 380" it yields PN,H by thereaction PN(NH,), = PN2H + NH,, and if the temperature nowrises above 400°, pure P N is obtained from the decomposition3PN,H = P,N5 + NH,. 'Tie pentanitride is a light amorphouspowder, insoluble in cold water and the usual solvents. It isattacked only very slowly by concentrated sulphuric acid, but it isquantitatively converted into orthophosphoric acid and ammoniaby sulphuric acid a t the boiling point :It is therefore conveniently analysed by the Kjeldahl method.12When heated to 730" in a vacuum, P3N5 yields PN, which sublimes.PNC1, + 2NH3 = PN(NH,), + 2HCl2P$?, f- 5H2SO4 + 24M,O= 6H3PO4 + S(NH,),SO,10 H.Moureu and A. M. de Ficquelmont, Compt. rend., 1934, 198, 1417;11 Ibid., p. 1159; B2cE.Z. SOC. chim., 1933, [iv], 53, 692; Ann. C?~im., 1835,11 J . AppL. Chem. Russia, 1935, 8, 429.l3 A. Stock and B. Hoffmann, Ber., 1903, 36, 314.l4 Cwrnpt. rend., 1934, 198, 1691.also refs. (14), (15), and (16).xi], 3, 443CARTER AND WARDLAW : SOME ELEMENTS AND COMPOUNDS. 187This, according 10 W. Jfoiireii a,nd l?. Rocquet,*j can exist in twoforms.The more stable red form reduces warm concentratedsulphuric acid, but this reachion is very slow in the cold. The otherform obtained from P3N5 at temperatures in the neighbourhood of720" is yellow, and is readily soluble in sulphuric acid, reducing iteven a t room temperature. Neither form shows crystal structurewhen examined by X-rays. H. Moureu and G. Wetroff 1 6 haveadded a new nitride to the list. When the products of the reactionof phosphorus trichloride on liquid ammonia are heated in a vacuuma t 550", a white, insoluble, non-volatile substance is obtained, spon-taneously inflammable in air. This nitride, P4NG, heated above750" in a vacuum, gives PN, which condenses in a pure state.Until recently, the heats of formation of the metallic nitrideshave been derived indirectly.Now B. Neumann, C. Kroger,and their collaborators l7 have evolved a method whereby thesemeasurements can be made from the direct union of the metal andthe gas, and their work has disclosed some very interesting factsabout this chemical reaction. Certain of the metals studied wouldunite with nitrogen under a pressure of 5-25 atmospheres and atemperature of 500-1000" with sufficient velocity to give a measur-able rise of temperature within one or two minutes. Manganese,chromium, and lithium would do this, but aluminium, beryllium,and magnesium required a catalyst, of which sodium fluorideproved to be the best. The reactions of a number of metals such asnickel, cobalt , aluminium, and beryllium were catalysed by lithiumnitride.It was found that thorium must be very pure to react withnitrogen and, curiously, its reactivity was not improved by sodiumfluoride. A relation-ship has been established between the heats of formation of thenitrides and the atomic numbers of the metallic elements, and onthe basis of this the authors have deduced values for the nitrides ofother elements such as scandium, vanadium, and tungsten. As theease with which a metal takes up nitrogen varies very much with itscondition, this has been studied for molybdenum-iron alloys andfor molyLdenum by A. Sieverts and his collaborators.18In 1909, A. Hantzsch l9 determined the molecular weight ofchamber crystals (HO*SO,*ONO) cryoscopically in sulphuric acidand obtained values varying from 70.8 to 72.5, compared with theIn all cases the nitrogen must be oxygen-free.15 Bull.SOC. chim., 1936, [v], 3, 1801.16 Compt. rend., 1935, 201, 1381.1 7 %. nnorg. Chela., 1931,196, 65; 1932, 204,81; 207, 133, 145; 1934, 218,18 A. Sievarts and K. Briining, Arch. Eisenhiittenw., 1933-34, '7, 641;10 2. physikal. Chem., 1909, 65, 57.379.A. Sieverts and G. Zapf, 2. anorg. Chem., 1936, 229, 161188 INORGANIC CHEMISTRY.calculated value of 127 for HNS05. He concluded, therefore, thatthis substance behaves as an electrolyte, and suggested that dissocia-tion into NO+ and HS0,- ions took place. Twenty-one yearslater, from an examination of the conductivity of nitrosyl perchloratein nitromethane, Hantzsch and K.Berger 2o deduced that nitrosylperchlorate, like nitrosyl sulphate, exists as a salt-like compound[NO]-'[X]-, where X = C10, or SO,. A recent investigation byW. R. Angus and A. H. Leckie of the Ramnn spectrum of nitrosylsulphate (chamber crystals) ,21 and nitrosyl perchlorate 22 has givenresults which can be interpreted only on the assumption that thesesubstances have an ionic structure.I n order to substantiate the deductions from Ramanmeasurements,electrolytic experiments 23 were undertaken. A qualitative demon-stration that nitrosyl sulphate has an ionic structure was made byelectrolysing a solution of nitrosyl sulphate in sulphuric acid betweena platinum anode and an iron cathode. The lower portion of aglass IJ -tube was filled with a concentrated solution of nitrosylsulphate in sulphuric acid, and the upper portion of each limb filledup with more sulphuric acid; the electrodes were clipping into theacid.The iron cathode provided a source of ferrous sulphate in thecathode limb where NO+ would be discharged. After the currenthad passed for some time, an intense brown colour developed in thecathode limb, which suggests that NO+ ions are discharged a t thecathode to give the well-known brown PeSO,,NO. The authorsconclude that, although, unfortknately , quantitative conductivitymeasurements have not yielded results of high accuracy, they haveindicated that nitrosyl sulphate and nitrosyl perchlorate are electro-lytes. No salts of nitrosylsulphuric acid could be isolated in spiteof several attempts.This fact supports the view that the substanccis a salt, and actually the salt-like configuration is the ionised formof the structure hitherto accepted by most chemists, SO,(OH)*ONO.The authors also discuss the theoretical possibility of the existenceof such a radical as NO+. The most important criterion is theease with which a neutral molecule can lose an electron and becomepositively charged. To bring this about, a certain ionisation poten-tial is required, and it follows that the lower the ionisation potentialthe greater the probability of the existence of that particular ion.For nitric oxide the ionisation potential is 9.5 v0lts.~4 The ionisa-tion potential of N, --+ N,+ is very considerably higher, and that20 2.anorg. Chem., 1930, 190, 321.21 Proc. Roy. Soc., 1935, A , 149, 327.22 Ibid., 1935, A , 150, 615.23 W. R. Angus and A. H. Leckie, T'mns. Paraday Xoc., 1935, 31, 958.24 J. T. Tate and P. T. Smith, Physical Rev., 1932, 39, 270CARTER AND WARDLAW : SOME ELEMENTS AND COMPOUNDS. 189for 0, -+ O,+ also very much higher than that for NO -+ NO+.The value for the ionisation potential of 0, is given by R. S. Mullikenand D. S. Stevens 25 as 12.2 volts. It is clear that for the nitric oxidemolecule the ionisation potential is decidedly low, as in general fordiatomic molecules the value is above 10 volts. This may arise fromthe fact that nitric oxide is an odd-electron molecule, having 15 extra-nuclear electrons. When it becomes ionised it is isoelectronic withcarbon monoxide and nitrogen.Since isoelectronic structuresexhibit many similar properties, it is possible that the NO+ radicalis a relatively stable one.Although nitrosoamine, NH,*NO, is probably not stable a t roomtemperature, there is good evidence to show that R. Schwarz andH. Giese 26 have obtained this compound by the interaction of solidanhydrous ammonia and solid dinitrogen trioxide, N,O,, a t lowtemperatures. The reaction was conducted at the melting point ofanhydrous ammonia, and the experiments exhibit some novelfeatures. Liquid anhydrous ammonia (m. 60 c.c.) was poured intoa quantity of liquid air contained in a large porcelain dish, which wascovered with a loosely fitting wooden lid. The ammonia soon solidi-fied, and after the workers’ hands had been suitably protected withgloves, the ammonia and liquid air were ground with a pestle into athin paste.Dinitrogen trioxide in a smaller amount (1-2 g.) wassimilarly crushed in liquid air, and the two reagents were transferredto a wide-necked flask which was rapidly connected, through aground joint, t o a pump, and the excess of liquid air removed. Thereaction mixture was shaken and allowed to warm somewhat, where-upon the light blue colour of the mass changed into the orange-redcolour characteristic of the nitrosoamine. After the whole of theammonia had melted, a clear red solution remained. (Some nitrogenwas evolved, and this was swept out by ammonia gas and collectedin an azotorneter containing dilute acid.) The ammonia was care-fully distilled off , and the solution gradually assumed a deep purple-red colour. This is probably the real colour of the nitrosoamine, andthe orange-red appearing in its preparation with dinitrogen trioxidemay be due to admixture with nitric oxide, which has a yellowcolour when dissolved in liquid ammonia. The authors representthe formation and decomposition of nitrosoamine thus :N,O, + ZNH, = (NH,)NO, + H,N*NO2H2N*N0 = (NH4)N02 + N2Nitrosoamine cannot be obtained in any solvent other than liquidanhydrous ammonia, for it at once breaks up into ammonium nittrite25 Physical Rev., 1934, 44, 720.46 Ber., 1934, 67, 1108190 INORGANIC CI-IBMISTRY.and nitrogen.The nitrosoamine was also formed when the dinitrogentrioxide was replaced by nitrosylsulphuric acid, mO]HSQ,,nitrosyl perchlorate, [NO]ClO,, or nitrosyl chloride, NOC1. Theproposed formulation of the nitrososmine is further supportedby the fact that methylaniline and dinitrogen trioxide at- 5" yield N-nitrosomethylaniline, NPhMe*NQ ; also that nitricoxide under pressure acts on potassium amide in solid ammonia togive the nitrosoamine :KNH, + 2NO = 9CNO -+ NH,*NOThe authors suggest two possible structures for the nitrosoamine,H,N--N--O and H-N=-N-OH, of which the latter is in accordancewith its deep colour, whilst the former is more consistent with itsmode of formation.Probably the two forms are in tautomericrelation to one another.In their study of the decomposition products of carbon suboxide(C,O,), ,4.Klcmenc, R. 'Mreclrsberg, and C. LVagner 27 hare made thefascinating observation that carbon may probably exist in a gaseousform, a s dicarbon C,. The reaction is consideredto be C , O , ~ C O , +C, and these authors state that at 200" the equilibrium constant E =P,, .Pc,/Pc,,2 is ca. 10-7. The equilibriuni is constantly disturbedby the polymerisation process, C,(gas) + graphite. Dicarbon is acarmine-red gas, soluble in water. It rapidly polymerises to apurplish-red, finely divided carbon, which gives an X-ray diagramidentical with that of graphite. In the early stages of the decom-position of the suboxide C,Q,, the head of the Swan band at 4737 A.is clearly visible, and this is known to be characteristic of C,.Theformation of dicarbon may be an intermediate stage in the oxidationof carbon. H. G. Grimm 28 has calculated that the change fromdicarbon gas to solid carbon, as diamond, is strongly exothermic,and is 100,000 cals. The absorption spectrum of gaseous carbonsuboxide bas been recently studied in detail by IH. W. Thompsonand N. K e a l e ~ . ~ ~In a paper on the cbemicd nature of graphite, A. E. Balfour, H. L.Riley, and R. XI. Robinson bring forward scversl coizsiderationswhich, in their opinion, show the aromatic character of the carbonhexagon planes in pure graphite. N. M. Adam 31 pointed out sometime ago that, if one of the carbon atoms in a hexagon plane of tfhegraphite lattice is selected, then the three valency bonds lead to27 %.&:lektrochcm., 1934, 40, 488; 2. physikal. Qhem,, 1934, 170, A, 97." 8 Z. Elektrochem., 1934, 40, 461.2s Proc. Roy. Soc., 1936, A , 167, 331.30 J., 1936, 456.31 !,!'rams. Paraday Xoc,, 1931, 30, 57CAETER AND WARDLAW : SOME ELEMENTS AND. COMPOUNDS. 191three aromatic hexagons, suggesting a similarity, “ though thismay be only superficial,” between the structure of graphite andtriphenylmethyl. Riley and his co-workers believe that thisformal similarity is reflected in a very fundamental way in thechemical properties of these two substances. A. Frenzel and U.Hofmann 32 prepared graphite bisulphate in which the carbonhexagon planes remained intact, the hydrogen sulphate iona havingpenetrated between them, increasing their distance apart. Graphitemonofluoride (see p.149) is a similar type of compound, thoughmuch more stable. In these compounds, Riley states, the hexagonplanes are playing the part of macro-positive radicals. The analogybetween graphite and triphenylmethyl is emphasised from the factthat in liquid sulphur dioxide triphenylmethyl chloride is an electro-lyte, and contains the ions Ph,C+ and Cl-. On the other hand,K. Fredenhagen and G. Cadenbach 33 and K. Fredenhagen and H.Suck 34 have prepared the compounds C,K and C,,K, and A. Schleedeand M. Wellmann 35 have shown that in these compounds the alkali-metal atoms have penetrated, and formed layers between, the hexa-gon carbon planes. These compounds, according to Riley, areobviously analogous to the alkali-metal triphenylmethyls, and thehexagon planes are acting as macro-negative radicals.Otherarguments are brought forward to support this interesting idea.In the literature many methods are given for the preparation ofcuprous oxide, but the colour of the product varies widely : it maybe yellow, orange-yellow, orange, red, and even dark reddish-brown.There are marked differences of opinion as to whether the pre-parations with yellow and red colours should be considered asidentical. In many older and also in some newer text-books, thered product is regarded as the oxide Cu,O and the yellow and orangecompounds as cuprous hydroxide. F. Gebhardt, R. Kohler, andE. Korner 36 have shown that the yellow compound obtained byreduction of Felrlirmg’s solution with glucose, gelatin, or sugar, atboiling heat, is identical with the red crystalline oxide. In order tosettle the question, M.Straumanis and A. Cirulis 37 have preparedcuprous oxide by a, wide range of methods and a t various temper-atures, and submitted the products to an X-ray investigation. Thered product was obtained in a high state of purity by reduction of asolution of cupric hydroxide in concentrated ammonia with hydrazine32 Z. Elektrocimn., 1933, 40, 511.33 Z . anorg. Chem., 1927, 158, 249.34 Ibid., 1929, 178, 353.35 2. physikal. Chem., 1932, B, 18, 1.37 2. amrg. Chem., 193s. W, 107.36 Kolloid-Z., 1933,639 267192 INORGANIC CHEMISTRY.hydratein a hydrogen atmosphere. The yellow product was isolatedfrom the reaction between cupric nitrate in ammoniacal solutionand hydrazine and 2N-potassium hydroxidein a nitrogen atmosphere.The yellow product was also obtained by other methods.Theidentity of the red and the yellow oxide was established from thefact that they had identical lattice dimensions. The yellowpasses into the red modification on growth of crystallites, e.g., onignition, as is shown by the increase in sharpness and number ofdiffracted Rontgen lines with the redness of the material.Lead monoxide, as is well known, occurs naturally in two crystal-line forms, yellow and red. These can also be prepared in thelaboratory by artificial means. The difference between the formshas been attributed to polymorphism, the red being regarded as themore stable form at the ordinary temperature and at all temperaturesup to the transition point.Some years ago the existence of thesetwo forms was in dispute, but M. P. Applebey and R. ID. Reidasisolated the varieties in well-crystallised forms and brought forwardevidence derived from solubility measurements and examinationof crystalline structure which showed clearly that the two modi-fications were polymorphic forms. E. Rencher and M. Bassibre 3*now report the results of an X-ray investigation of two forms of themonoxide E- and p-PbO. The cc-form was obtained as an orange-yellow compound by the dehydration of lead hydroxide (producedfrom a lead salt and alkali) at 130°, and also by heatling lead carbon-ate to 260". An investigation of this modification in a dilatometergave a sharp contraction at 530°, indicating a transition into a newform, a lemon-yellow power, which they designate p.These twoforms gave distinctive X-ray diagrams. When the p-form wasmelted and allowed to solidify, the X-ray diagram showed that it wasstill p, so presumably a p-+ a transition did not occur. The thermaldecomposition of lead dioxide or red lead always led to a-lead oxide,provided that the temperature was below 530". If a sodium hydr-oxide solution of concentration above 30% acted on lead hydroxideat 20" a grecnish-yellow p-lead oxide was formed. After longstanding, this p-form slowly changed into a carmine-red a-form.S. S. Bhatnagar and G. S. Ba140consider that pure nickeloxide,NiO, is green, and that black samples owe their colour to adsorbedoxygen. They also state that their magnetic-susceptibility deter-minations, made at 25-366", show that the high values of % forNiO recorded in the literature are due to traces of nickel formed byreduction during its preparation.On the other hand, W. Klemm38 J., 1922, 121, 2129.3D C m p t . rend., 1936, 202, 765.J. Indian Ghem. SOC., 1934, 11, 603CARTER AND WARDLAW: SOME ELEMENTS AND COMPOUNDS. 193and K. Haas 41 express the view that the variable values for themagnetic susceptibility of nickel oxide, NiO, are due to partialsplitting up into nickel and a higher oxide at temperatures above400". In an earlier Report, attention was directed to some work by(Miss) W. R. A. Hollens and J. F. Spencer 42 on the supposed sub-halide of cadmium, Cd,Cl,, and the so-called cadmous hydroxide andoxide, Cd,O.The cadmium atom (at. no. 48) has the electronicstructure 2, 2.6, 2.6.10, 2.6.10.0, 2, from which it is seen that theatom has two s-electrons in the Ol shell and the bivalent cadmiumion a complete N,,, shell. Both cadmium and the Cd++ ion must bediamagnetic, but the Cd+ ion with one odd electron will be para-magnetic. Thus if solutions of cadmium in molten cadmium chloridecontain cadmous chloride, CdC1, in appreciable amount the systemwill be paramagnetic. Measurements of the solid systems, made byHollens and Spencer, show these to be diamagnetic ; hence the existenceof a sub-chloride, CdC1, has to be excluded. This result has been con-firmed by J. Farquharson and E.He~mann.4~ These authors pointout, however, that the measurements do not exclude the existence ofa birnolecular sub- chloride, Cd,Cl,, because such a substance wouldbe diamagnetic. A definite verdict on this matter is given by thework of R. E. Hedges and H. Terrey,*4 who have examined by X-raymethods the so-called sub-halide, Cd,Cl,, prepared by solution ofcadmium in molten cadmium chloride, and find that the structure isidentical with that givenby the normal chloride, CdCl,, and themetal.Powder photographs of the so-called cadmous oxide, Cd,O, preparedfrom Cd,Cl, by decomposition with water, were taken, and com-pared with those from the normal oxide. It was then quite evidentthat thq so-called sub-oxide is merely a mixture of the normaloxide with very finely divided metal.These findings are in har-mony with the results obtained from other physical measurementson the solid product, e.g., density, heats of solution, etc., and it mustbe concluded that the sub-halides and sub-oxides of cadmium areincapable of existence as solid phases.It has always been questionable whether the formula for the higheroxides of the alkali metals M,O, is not better halved. F. Ephraim 4 ~ iexpresses the opinion that there is little to be said against theformulation MO,. Nevertheless, the double formula is possiblyeasier to construct from the usual valency considerations. L.Pauling has recently raised the question whether the potassium41 2. anorg. Chern., 1934, 219, 82.42 J., 1934, 1062.43 Trans. Paraday Soc., 1935, 31, 1004.44 Ibid., 1936, 32, 1614.45 " Inorganic Chemistry," Gurney and Jackson, London, 1926, p. 341.REP.-VOL. XXXIII. 194 INORGANIC CHIElVlISTRY.oxide should not be KO, instead of K20,. E. W. Neurna~m,~~ atthe suggestion of L. Pauling, studied the magnetism of this peroxide,found the paramagnetism of the expected magnitude for the simplermolecule, and concluded therefore that KQ, was really present.W. Klemm47 has discussed the exact measurements, and statesthat here is a case where such measurements cannot decide betweenthe two €ormula and that we must await further investigations,especially those of the lattice structure, before a final opinion can begiven. This year the structure of potassium tetroxide has beendetermined by X-ray methods, by V. Kassatochkin and V. K o ~ o v , ~ ~and they state that the formula KOz is supported.J. F. Spencer and (Miss) G. T. Bddie 49 have successfully preparedlithium alum, despite the fact that the probability of its existencehas been denied. To prepare the alum, molecular proportions oflithium sulphate monohydrate and the octadecahydrate of alumin-ium sulphate were dissolved in the minimum quantity of cold water.The solution was concentrated considerably by evaporation on asand-bath, and cooled in a freezing mixture of ice and salt withvigorous stirring, whereupon it crystallised suddenly and depositeda mass of small crystals. The mother-liquor after a further slightconcentration deposited small transparent crystals on keepingin the freezing mixture. Both crops of crystals contain H20, 49.0[Li2S04,N2(S04)3,24H20 requires H20, 48.93%]. The crystals areisotropic, a combination of cube and octahedron. M. Mousseronand P. Gravier 5O conclude from solubility, density, viscosity, anddilatometric measurements that sodium alum is stable only between1.1" and 39". The heat of formation of A12(S04),,18H,0 andNa,SO4,10H,O is -3980 g.-cals., and the heat of dissolutionin water-8500 g.-cals. A stable hydrate containing 4H20 has also beenobtained at 15" in a vacuum. In the literature it is generally statedthat two alums are known containing tervalent titanium,Rb,S04,Ti2(S0,),,24H,0 and the cesium analogue. J. Meyer andH. Meissner 51 have recently attempted to extend the series, buttheir attempts to prepare titanium-potassium, -ammonium, and-thallous alums failed. They state that pure RbTi( S04),,12H,0could not be obtained.In a continuation of the studies of the phosphates, H. Bassett,W. L. Bedwell, and J. B. Hutchinson s2 have examined the p p o -46 J . Chem. Phyasics, 1934, 2, 31.47 Angew. Chem., 1935, 48, 617.48 J . Chem. Physics, 1936, 4, 458.2iy Nature, 1936, 138, 169.j0 Bull. SOC. chim., 1932, [iv], 51, 1382,61 J . pr. Chern., 1936, [ii], 143, 70.J., 1936, 1412UARTER AND WARDLAW : SOME ELEMENTS AND COMPOUNDS. 195phosphates of some bivalent metals, and have noted that there is amarked tendency for the formation of solid solutions containingsodium, although definite double salts also occur. They make theimportant suggestions ( a ) that the water molecules are distributedso as to give cations with even co-ordination numbers, and (b) thatreplacement of [M(H,O),]" by ~a2(H20),]** or [M(H20),]"* by 2Na'occurs owing to approximate equality of molecular volumes. Insupport of this view it is mentioned that the Na,P2O7,10R2O whichseparates in large transparent crystals from solutions containingmagnesium, cobalt, nickel, or zinc pyrophosphate contains a smallamount of these in solid solution. This is explicable on the basis ofthe above theory and indicates that Na,P,O,,ZQH,O is probablyAlthough indium is present in minute amounts in a number ofminerals, it is one of the rarest of metals, and its scarcity hasrestrictedthe investigation of its chemistry. In an arc-spectrographic deter-mination of indium in minerals, F. 1cT. Brewer and (Miss) E. Baker 53have made the valuable observation that indium is present in un-usually large amounts in the mineral cylindrite. This mineral,obtained from the Santa Cruz mine, Poopo, Bolivia, is a sulphide oflead, antimony, and tin, and has been shown to have an indiumcontent estimated a t @1-1%. Brewer and Baker 54 have alsofound that indium is present in large traces in some chalcopyritesand as a general impurity in metallic tin, and they have described itsextraction and concentration from these sources.The subject of the nomenclature and classification of inorganiccompounds is one of great and ever-increasing difficulty, and fornearly twenty years chemists of many countries have been tryingto devise a systematic international nomenclature. In his lecture,delivered before the Chemical Society this year, C. Smith 5 5 gavcan account of the agreement that has been reached, and as modernchemical nomenclature is a subject of the deepest concern to allchemists, this address deserves the closest study.Finally, attention should be directed to the recent publication by(Sir) G. T. Morgan and F. H. B ~ r s t a l l , ~ ~ which gives a survey ofmodern developments in inorganic chemistry."a(H20)sl;. "a~(H~O>,1'"P~0,1"".s. It. c.w. w.S. It. CARTER.W. WARD LAW.R . WHYTLAW- GRAY.$3 J . , 1936, 1286.56 " Inorganic Chemistry," Heff er, Cambridge, 1936.64 Ibid., p. 1290. 5 5 Ibid., p. 1067

ISSN:0365-6217    

DOI:10.1039/AR9363300135

出版商:RSC    

年代:1936

数据来源: RSC

摘要:

CRY STALLOCRAPHYTHE change from biennial to annual publication of the report onCrystallography occurs a,ppropriately at a time when attention hasbeen focused on the subject by Sir William Bragg’s presidentialaddress to the Royal Society summarising many of the recentadvances in crystal analysis. The past history of structure deter-mination has also been brought nearly up to date this year by theappearance of the long-awaited second volume and part of the thirdvolume of the “ Strukturbericht,” the first volume of which hasmeanwhile become a classic. The main lines of Vol. I have beenfollowed, and the results so far available include all inorganicstructures, but not alloys, organic compounds, and fibres.As it is impossible t o cover all phases of crystallography adequatelyin this survey, some subjects which appear to be more suitable forbiennial treatment have been left over for consideration in laterReports. This applies particularly to metals, which have beendiscussed at length in the two preceding Reports.1.THE TECHNIQUE OP STRUCTURE ANALYSIS.For all kinds of crystal structure work, more powerful X-ray tubesare highly desirable, and a nokble advance in the design of rotatinganode tubes has now been made by V. Linnitzki and V. G~rski.~They have combined the anode with a molecular pump so that therotation of the anticathode, which formerly introduced manydifficulties in construction and maintenance, is now turned topositive advantage. As far as the recording of the X-ray reflectionsis concerned, there are three main types of instrument that can beconsidered.G;. Kellstrom’s 4 new value for the viscosity of air maybe taken to show, inter aEia, the reliability of the X-ray method forthe measurement of e, and there is therefore the more justificationfor continued work on precision measurements of lattice spacings,1 Proc. Roy. Soc., 1936, A , 157, 697.2 Akademische Verlagsgesellschaft m.b.H., Leipzig, 1936 : Vol. I1 (1928-32) by C. Hermann, 0. Lohrmann, and H. Philip; Vol. I11 (1932-35) byC. Gottfried and F. Schossberger.8 Tech. Php. U.S.S.R., 1936, 3, 220.4 PhysicaE Rev., 1936, [S], 50, 190COX AND CROWFOOT: TECIENIQU’E OF STRUCTURE ANALYSIS. 197particularly by powder method^.^ M. 5. Buerger’s new Weissenberggoniorneter is likely to prove useful for the more general examin-ation of a crystalline species, and other cameras have also beendevisedy7 including some for work at high and low temperatures *and low pressure^.^ It does not appear to be generally recognised,however, that many of the advantages of a vacuum can be attainedmore simply by filling the X-ray camera with hydrogen.Finally,for the exact measurement of intensities a new automatic ionisationspectrometer has been designed by W. A. Wooster and A. J. P.Martin.lo The use of electrometer triodes (in conjunction with anionisation chamber) is well established ; a further advance whiehbas been proposed l1 is the replacement of the ionisation chamberor photographic plate by a Geiger-nlluller counter.The introduction of the Patterson method of synthesis was de-scribed in last year’s Report and it is already taking a definite placeits a first stage in the determination of many crystal structures.One example of its use is that of silver uranyl acetate.12 D.Harker 13has pointed out that improvements may be introduced by makingfull use of the symmetry of the crystal under investigation. In thegeneral case the Patterson series is of the formP(xyz) = ChC&JIF(hlcZ)J2 cos (hx + Icy + Z X ) . . . . (1)the maxima in the function P representing interatomic distances.To be manageable, however, this must be reduced t o a two-dimensional series&(xx) = C ~ C ~ ] l ? ( h O Z ) ~ ~ cos (hx + Z X ) . . . . . . . (3in which, since the P’s of one zone only axe used, the resolutionof the peaks is not very good.If, however, the b axis is a two-fold axis of symmetry, two equivalent atoms have co-ordinates(xyx) and (~yx’) and the vector between them has components (2xy0,2x)5 3. W. M. du Mond and V. L. Bollmann, ibid., pp. 383, 524; W. Kossel,Ann. Physik, 1936, [v], 26, 533; M. Straumanis and A. Ievins, 2. Physik,1936, 98, 461 ; E. R. Jette and F. Foote, J. Chem. Physics, 1935,3,605; M. U,Cohen, 2. Krist., 1936, 94, 288, 306.6 Ibid., p. 87.7 M. J. Buerger, Amer. Min., 1936, 21, 11; E. Sauter, 2. Krist., 1936, 93,* R. L. McFarlan, Rev. Sci. Instr., 1936, [ii], 7, 82.9 E. Franke, 2. physikal. Chem., 1936, B, 31, 454.10 Proc. Roy. SOC., 1936, A , 155, 150.11 W. Van der Grinten and H.Brasseur, Nature, 1936, 137, 657; D. P.Ie Galley, Rev. Sci. Instr., 1935, 6, 279 ; M. Pahl and A. Faessler, 2. Physik,1936,102, 562.93; 0. Kratky and G. Krebs, ibid., 95, 253.12 I. Fankuchen, 2. Krist., 1936,94,212.13 J. Chem. Phpics, 1936, 4, 381198 URY STALLOQRAPHY.and is represented by a maximum value of P in the plane y = 0.Evidently, in such a case, the x and the y co-ordinates of all theatoms can be determined by measurements of P for y = 0 only;(1) then becomesP(x0x) = ChCl COS (hx + ZZ) . (&p(hkz)l2) . . . . , (3)a two-dimensional Fourier series which can readily be computed.This series (3) has two advantages over (2) : it gives greater reaolu-tion because all the 3”s are used, and it shows only interatomicvectors perpendicular to the symmetry axis, so the risk of over-lapping is reduced.Similar improvements can be introduced wherethe crystal has other elements of symmetry, and in one of thesecases the method has been applied by D. Harker to determine thecrystal structure of proustite and pyrargyrite.These methods render it necessary to carry out Fourier synthesesin the very first stages of the analysis instead of once at the end;but by means of calculating devices, such as those of J. M. Robert-son l4 and A. L. Patterson l5 and the sine and cosine strips nowmade available by C. A. Bcevers and H. Lipson,16 a two-dimensionalFourier synthesis can be carried out in little more than a day.Robertson l7 has also described simplifications of the calculationsnecessary in the case of non-centrosymmetrical projections andsucccssf6lly used them on the s6ructure of rcsorcinol.A furthervaluable contribution to the literature of crystallography is (‘ Struc-ture Factor Tables ” by (Mrs.) ]EL Lonsdale.ls In these, thenecessary data for Fourier synthesis and for the calculation of thestructure factors have been presented for each of the 230 spacegroups in the form in which they can most readily be applied inactual practice. The most laborious part of structure analysis(after the experimental data have been obtained) is still the calcu-lahion of structure factors, both to derive an approximate structureby ‘( trial and error ” and to determine the phases of the coefficientsin a Pourier series ; the labour involved can be considerably lightenedby the adoption of W.L. Bragg’s proposal l9 to’use contoured graphsfrom which phase factors can be read off directly when the co-ordinates of the atoms are given. Since it is usual to investigateonly special planes of the type (hEO), the total number of graphsl4 Phil. Mug., 1936, 21, [vii], 176.15 Ibid., 1936, 22, 753.lG Proc. PhysicccE SOC., 1936, 48, 772; Nuture, 1036, 157, 825.18 “ Simplified Structure Factor and Electron Density Formula for tho 230I* Natu.re, 1936, 1318, 382; W. L. Bragg and H. Lipson, 2. Kri.Pt., 1937,95,Ibid., 138, 683.Space Groups of Mathematical Crystallography,” Bell and Sons, 1936.383COX AND CROWFOOT : TECHNIQUE OB STRUCTURE ANALYSIS. 199required is not very great, about twelve (for all values of h and kup to h + k = 8, say) for each of the seventeen plane groups beingsufficient;.Fig. 1 shows the graph for the plane (230) in any spacegroup of the tetragonal classes &2m, 4mm, 42, and 41mmm. Thecontour8 give the value of the functionS = cos 4-nx . cos 6x2~ +- cos 6nx . cos 47r~for all values of x and y between 0 and 1; the heavy lines arecontours with S = 0, and negative contours are dotted. ThusFIG. 1.0 X. 1.0Contours of S = cos 47rx. cos Giry + cos 6nx . COB 4ny.the quantity S (multiplied by a power of 2 according to the spacegroup) read off for the co-ordinates (x, 9) is the contribution of anatom in the general position (xyz) and of all the atoms in the cellrelated to it by the symmetry elements of the space group to the phasefactor of that particular plane.The contribution to the structurefactor is then simply ZnSfe. One very valuable feature of the methodis that it is possible to determine by inspection of the appropriategraph how the co-ordinates of an atom or atoms must be altered toobtain a desired change in the phase factor for any plane; thisshortens considerably the time necessary for trial and error analyses200 CRYSTALLOURAPHY.A complete set of graphs is being prepared and subjected to practicaltests in various laboratories.Several workers 2o have directed their attention to the determin-ation of the exact form of thef-curves for various atoms, vix., nickel,copper, zinc, cadmium, aluminium, silver, palladium, and sulphur.In the case of the hexagonal metals, cadmium and zinc, the atomicscattering factor has a low or high valuc according as the plane fromwhich reflection occurs is nearly parallel or perpendicular to thebasal.plane. This is interpreted by G . IV. Brindiey 21 as being dueto asymmetry of lattice vibrstions-a view which, though contestedby H. Hermann,22 receives support from the work of C . Zener.23Zener has investigahed the dependence of the Debye-Waller temper-ature coefficient e-M upon reflection plane orientation for the caseof metals of hexagonal symmetry, and finds tha6 the ratio of M forvibrations perpendicular to and parallel t o the c-axis is 1430 and1-73 for zinc and cadmium respectively. Other work on zinc,24while showing that the anomalous f-values are chiefly due to theanisotropy in the thermal vibrations, suggests that Hermann’s viewthat the atoms themselves are anisotropic may be partly correct.Other supposed cases of anisotropic thermal vibrations are men-tioned elsewhere in the Report.A critical test of atomic symmetrymight be possible through the use of polarised X-rays as developedby W. H. George.25Optical and magnetic methods have now definitely establishedthemselves as aids to structure determination, particularly in thefield of aromatic compounds, and in favourable cases it appearspossible t o fix the direction cosines of the plane of the molecules inthe lattice t o within lo. Somewhat uncritical use has, however,sometimes been made of magnetic data, and a detailed discussionby (Mrs.) K.Eonsdale and K. S. Krishnan 26 of the precise relation-ships existing between molecular susceptibilities and those of thecrystal as a whole is welcome. L. Pauling 27 has also discussed the4o J. Laval, Compt. rend., 1935, 200, 1605; E. Niihring, 2. Physilc, 1935, 93,197; C. M. Kotin and T. Losada, Anal. Pis. Quim., 1935, 33, 597; P. de laCierva and J. Palacios, ibid., p. 34; G. W. Brindley, Phil. Mag., 1936, [vii],21, 778: G. W. Brindley and F. W. Spiers, ibid., 20, 865.21 Proc. Leeds Phil. Soc., 1936, 3, 200; Phil. Mag., 1936, [vii], 21, 790;Nature, 1936, 138, 290.22 Ibid., p. 290.23 Physical Rev., 1938, [ii], 49, 122; C. Zener and 8. Bilinsky, ibid., 1936, 50,24 G. E. M. Jauncey and W. A. Bruco, ibid., pp.408, 413; R. D. Miller and2s Proc. Roy. Soc., 1936, A , 156, 96.26 Ibid., p. 597.27 J. Chem. Physics, 1936, 4, 673.489; see also idem, ibid., p. 101.E. S. Foster, ibid., p. 417COX AND CROWFOOT : TECHNIQUE OF STRUCTURE ANALYSIS. 201diamagnetism of aromatic molecules, and the relation betweenoptical anisotropy and structure has been treated by M. Ramanad-ham28 and K. S. S~ndararajan.~~ Although it is unlikely, in viewof the greater accessibility of other properties, that thermal con-ductivity will be used as an aid to structure determination, yet it isof great importance that the relationship of this property to crystalstructure should be understood; first step in this direction hasbeen made by W. A. Wooster,m who has collected the availabledata and attempted a correlation of thermal anisotropy withstructure.The possibilities and advantages of orienting moleculesor particles of markedly anisotropic form by streaming or similarmethods have long been realised ; an interesting example is affordedby the orientation of tobacco mosaic virus “molecules ” in quitedilute solutions by flow through a Lindemann glass capillary tube,31and a new procedure, vix., sedimentation from an aqueous solutionin an alternating electric field, has been applied successfully inobtaining highly oriented preparations of wool ~ells.~2 Suchmethods are capable of extension to many other imperfectlycrystalline substances.Two other applications of X-rays not concerned with structureanalysis may be mentioned.One is the determination of particlesize, which has been carried out particularly on graphite33 fromdifferent sources and also applied to the colloid chemical behaviourof vanadium pentoxide 34 and gold By measurements oncounted layers of fatty acid films on water, G. L. Clark and P. IN.Leppla 36 have been able to obtain a direct test of the Laue equationconnecting the broadening of X-ray lines with film thickness. Theagreement is very satisfactory down to distances corresponding toonly three or four fatty acid layers.Several papers have dealt with the systematic application ofmorphological crystallography to the identification of chemicalindi~iduals.~’ X-Ray methods provide both a simpler and a more28 Proc. Indian Acad. Sci., 1936, 3, A , 43.2D 2.Krist., 1936, 93, 238.31 J. D. Bernal and I. Fankuchen, Nature, 1936,138, 1051.33 H. J. Woods, Proc. Leeds Phil. Soc., 1935-6, 3, 132.33 U. Hofmann, D. Wilm, and E. Csalhn, 2. Elelctrochem., 1936, 42, 504;G. R. Levi and A. Baroni, 2. Krist., 1936, 93, 156; P. Corrier, Compt. rend.,1936, 202, 59; N. Ganguli, Phil. Mag., 1936, [vii], 21, 355; cf. G. I. Finch andH. Wilman, Nature, 1936, 137, 271; Proc. Roy. Xoc., 1936, A , 155, 345.30 Ibid., 95, 138.34 J. A. A. Ketelaar, Nature, 1936,137, 317.35 J. B. Haley, K. Soltner, and H. Terrey, Trans. Paraday Soc., 1936,32,1304.36 J . Amer. Chem. Soc., 1936,58, 2199.37 A. K. Boldirev and V. V. Dolivo-Dubrovolaki, 2. Krkt., 1936, 93, 321;C. Weygand, Angew. Chon., 1936, 49, 243; B. N. Delone, Ann.Sec. Anal,Phys. (;him., 1936, 8, 92 ; A. F. Kapustinski, ibid., p. 103202 CRYSTALLOGRAPHY.delicate means, and several attempts have been made to classifycertain groups of compounds by means o€ powder photographs.One such “ finger-print system ,” developed mainly for industrialincludes 4000 patterns from over 1800 inorganic sub-stances, and there are several examples of its use.39 Among organiccompounds, only the method of direct, ad hoc comparison of twocompounds suspected of being the same has been employed to anyextent, as in the identification of tetrahydroartimisia ketone,4O thebarium saltis of the pterins2l the hydrocarbon ‘f CZ1Hl6 ” from cholicncid,42 the phrenosiiiic acids,43 and 0thers.4~E. G. C.D. M. C.2. CRYSTAL CHEMISTRY.Metals.-Precision measurements of the lattice constants ofberylli~m,~~ cadmium, osmium, and ruthenium 47and of tantalum and vanadium 48 have been made.In addition t ohis usual annual survey 49 of lattice constants and other propertiesof the elements, M. C. Neuburger 50 has published “ Die Allotropieder chemischen Elemente uiid die Ergebnisse der Rontgenographie.”This monograph contains a critical discussion of the allotropy of allthe chemical elements and is notable for a list of over 1000 references.During the past year new results have accumulated regarding theallotropy of titanium, calcium, and boron. Titanium, like zir-conium, might be expected to occur in an a- and a p-form, hFxagonalclose-packed and cubic body-centred respectiveIy ; no convincingevidence for this had previously been obtained, however, the88 J.D. Hanawalt and H. W. Rinn, Ind. Eng. C‘hem. (Alzcal.), 1936, 8, 244.39 A. TV. Waldo, Amer. Min., 1935, 20, 575; J. N. Antipov-Karataev and40 L. Ruzicka, T. Reichstein, and R. Pulver, Helv. Ghim. Acta, 1936, 19,4 1 C. Schbpf and E. Becker, Annalen, 1936, 524, 49.4% W. E. Bachmenn, J. W. Cook, C. L. Hewitt, and J. Iball, J., 1936, 54.43 A. C. Chibnall, S. H. Piper, and E. F. Williams, Biochem. J., 1936, 30,100 ; (Miss) D. M. Crowfoot, J., 1936, 716.44 H. J. Backer, J. Strating, and A. J. Zuithoff, Rec. tmv. chim., 1936, 55,761 ; M. P. Wolarowitsch, G. 13. Rawihch, andK. F. Gussjew, KoZZoid-Z., 1936,76, 338.B. K. Brunowski, Kolloid-Z., 1936, 75, 325.646.45 A.Ievins and M. Straumanis, 2. physilcal. Chem., 1936, B, 33, 265.46 E. A. Owen and T. L. Richards, PhLiZ. Mag., 1936, [vii], 22, 304.47 E. A. Owen and E. W. Roberts, {bid., p. 290.48 M. C. Neuburger, %. Krist., 1936, 93, 312, 314.4D Ibid., p. 1. ,60 Sammlung chemischei- und chemische techniacher Vortriige, F. Erlke,S tuttgar t COX : CRYSTAL CHEMSTRY. 203irregularities in the resistance-temperaturo curve for $he metalbeing attributed to impurity taken up at high temperatures. J. H.de Boer, W. G. Burgers, and J. D. Fast 51 have now shown thatimpurities are indeed taken up, but that the effect of these is to maskthe transition which occurs (quite sharply in the absence of air) a tnearly the same temperature as for zirconium ($82’).X-Rayexamination confirms that @-titanium has an A2 structure witha = 3-32 A.Calcium is known t o occur in three forms, with transitions O! --+ pa t 300’ and p --+ y at 450°, the c(- and the y-structure being cubicand hexagonal close-packed respectively. The p-form was formerlyconsidered to be of lower symmetry, but tho measurements ofA. Schulze 52 indicate that it may possess an A2 lattice. Thediamond-like and the graphitic form of so-called crystalline boronformerly described have probably been aluminium boride or boro-carbide ; 8. von Naray-S~abo,~~ however, now reports an adamantinetetragonal boron with a = 12.55 and c = 10.18 A., and a graphiticor orthorhombic form with a = 17.64, b = 25.0, and c = 10.26 A.No outstanding advances have been made in the study of alloysor in the theory of metallic structures generally; a number ofbinary and ternary systems have been studied and further work hasbeen done on order-disorder transformations and related topics,but the results are deferred for more comprehensive discussion insubsequent reports.An excellent and very full account of thequantum thcory of metals, covering conduction, cohesion, magneticand optical properties, and crystal structure is given by N. F. Mottand H. Jones in “ The Theory of the Properties of Metals andAlloys,” 54 and W. Hume-Rothery 55 has written a most lucid reviewof the subject from a more descriptive point of view which shouldbe of the utmost value to chemists and metallurgists.0rides.-i. A. A. Ketelaar 56 has determined the structure ofvanadium pentoxide.The structure contains chains of oxygentetrahedra linked by shared corners, accounting for the formationof elongated micelles in solution.Structures of the spinel type have been the subject of severalinvestigations. A. E. van Arkel, E. J. W. T’erwey, and M. G. vanBruggen 57 have shown that various ferrites (AfO,Fe,O,) are able to5 1 ,€‘roc. K . Alzad. Wetensch. Amsterdam, 1936, 39, 515; ?V. G, Burgers andF. M. Jaeger, 2. Krist., 1936,94,299.53 Z. Metallk., 1936, 28, 55.53 Naturwiss., 1936, 24, 77.54 International Monographs on Physics, Clarendon Press, Oxford, 1936.55 “ The Structure of Metals and Alloys,” Institute of Metals, 1936,55 2. Krist., 1936, 95, 28.57 12ec. trav. chim., 1936, 55, 331, 340204 CRYSTALLOGRAPHY.dissolve excess Fe203 without change .of (spinel) structure.This isexplained by the stability of the anion framework, which is thesame for y-Fe,O, as for the ferrites, the former having on the average28 vacant cation positions per unit cell. I n a solid solution ofFe203 in ferrite the number of vacant positions diminishes, withconsequent stabilisation of the y-Fe203 structure. These workersshow that the maximum in the magnetisation curve correspondsto the maximum solubility; the dissolved Fe,03 takes up the ferro-magnetic y-lattice, but when the solubility limit is transcended, thesystem becomes a two-phase conglomerate containing non-magnetica-Fe203 so that the total magnetisation of the mixture is lowered.The coincidence of the solubility limit in certain cases with thecomposition 2M0,3Fe20, is probably accidental, and is apparentlynot due, as has been suggested,58 to the formation of a new type offerrite.Trimanganese tetroxide, Mn304, and ferric oxide, Fe203, form(above 800°) a continuous series of solid solutions from 100% to14% of the former with a gradual change of structure from thetetragonal (distorted spinel) structure of Mn,Q4 to ‘the true spinellattice; at lower temperatures solid solution still occurs but withthe structure of Rln203 (C-modification of the sesquioxides).Thesolubilities in ferric oxide of oxides with the sodium chloridestructure were also studied ; FeO-Fe,O, mixtures have only a verylimited range of homogeneity, but NiO and MgO appear to formsolutions over a wider range.Some fersites have rhombohedra1symmetry ; 59 they may possibly possess structures of the hEmatitetype. The dominating influence of the anion arrangement isillustrated by some observations of R. Mehl and E. L. McCandless 60on the orientation of oxide films on iron. Pe30, films formed bythe decomposition of ferrous oxide have identical orientation withthe parent crystal; the same relation holds when ferrous oxideis obtained on the surface of the magnetite crystals by reduction.suggest that, whereas Mn,O,and Co,O, have true spinel structures M1W$I04 (the former beingdistorted tetragonally on account of the lower symmetry of thehalf the tervalent cations occupying tetrahedral positions in thespinel structure, and the other half sharing the octahedral positionsa t random with the ferrous ions.Bond distances and X-ray5 8 R. S. Hilpert and R. Scheveinhagen, 2. physikal. Chem., 1935, B, 31, 1.59 W. Soller and A. J. Thompson, Physical Rev., 1935, [ii], 47, 644; A.Krause, A. Ernst, S. Gawrych, and W. Kocay, 8. anorg. Chem., 1936,228,353.60 Nature, 1936, 137, 702.61 Rec. trav. chim., 1936, 55, 531,E. J. W. Verwey and J. €I. de BoerMnIVion), yet Fe,04 is a solid solution J?eO,Fe,O, or FeIII(FeIIE”eII104COX : CRYSTAL CHEMISTRY. 205reflection intensities are considered to support these views, althoughit seems doubtful whether either can be relied upon to distinguishunequivocally between the very closely similar structures in question.With the proposed distribution of ions in magnetite, an electronpassing from Fe++ to Pe+++ is in the same energy state finally asinitially, and the probability OE a transition is therefore reasonablyhigh, in agreement with the high conductivity of Fe,O, as comparedwith Co,O, or Mn30,.It is of interest to enquire whether theseconsiderations can be applied quantitatively to other compounds,e.g., nickelous and ferrous oxides and ferrous, cobaltous, and cuproussulphides, in which there is normally a cation deficiency, and there-fore presumably a proportion of cations in higher valency states.Although experiments 62 suggest that there is a close relation be-tween cation deficiency and conductivity, the results for Pe304 andCo304 are very similar, and the conductivity of the latter is appar-ent,ly not so greatly inferior to that of magnetite as Verwey andde Boer have supposed; moreover, the necessity of assumingquadrivalent cobalt ions is a weakness in their hypothesis.Morequantitative measurements of conductivity (and also of magneticsusceptibility) in relation to composition, radius ratios, and otherfactors appear to be necessary before the structures of these oxidescan be regarded as fully elucidated.Oxides of tungsten [W,O,,, W,O,,(OH),, and W1,03,(OH)2] inwhich the metal appears to be present with a lower valemy thansix have been obtained by F. Ebert and 1%. Flasch 63; it is difficult,however, to exclude the possibility of the presence of hydrogen ionsin these compounds.Their cell dimensions show that they are veryclosely related to W 0,.It has been suggestedG4 that quartz assumes a new crystallineform below -183.6", but other workers 65 have not confirmed this.-Further work also appears to be necessary before the statementsthat the lattice of a-quartz is deformed to the extent of 2-30/, inagate and finely ground sand can be accepted. B. E. Warren and hisco-~orkers,67 continuing their studies of oxide glasses, have obtainedmuch more precise results by the application of a generalised Fourier62 C. Wagner, 2. tech. Physik, 1936, 16, 327; C. Wagner and E. Koch, 2.63 2. anorg. Chem., 1935, 226, 65.64 H. Osterberg, Physical Rew., 1936, [ii], 49, 552.65 H. Dobberstoin, Naturwiss., 1936, 24, 414; L.Balamuth, F. Rose, and65 N. A. Schischakow, Cornpt. rend. Acad. Sci. U.R.S.S., 1936,1,19.67 B. E. Warren and 0. Morningstar, Phy8icaE Rev., 1935, [C], 47, 808;B. E. Warren, H. Krutter, a i d 0. Morningstar, J . Amer. Cerarn. SOC., 1930,19,202.physikal. Ghem., 1936, B, 32, 439.S. L. Quimbg, Physical Rev., 1936, [ii], 49, 703206 CBYSTALLOGRAPHY.method; the existence of tetrahedral networks in silica withSi-0 = 1.60 A. is definitely confirmed, and vitreous boric oxide isshown to consist of a network in which each boron is surrounded bythree oxygens at 1.39 A. as in crystalline borates. In both casesthe oxygen atoms are shared between only two cations, thus con-ferring a considerable degree of flexibility upon the network, so thatthe irregular glass structure has a configuration almost as stable asthe crystalline arrangement.N. A. Schischakow 66 and N. Valenksfand E. Porai-Koschitz 68 have studied the transition from vitreoussilica to cristobalite.8iEicutes.Further work has been done on clay minerals; thestructures previously assigned to dickite and kaolinite have beenconfirmed by C. J. Ksanda and T. W. Barth 69 and by S. B. Hen-dricks 70 respectively, and the latter has also studied anausite.J. W. Gruner 71 has shown that glauconite has a mica-type ofstructure with a higher Si : A1 ratio ; some silicon may possiblyoccupy 6-co-ordinated cation positions. P. A. Bannister andM. H. Hey 72 have continued their studies of zeolites with measure-ments on scolecite, metascolecite, and ettringite ; the first is shownto be iso-structural with nairolite and its transition to meta-scolecite has been investigated.The cubic mineral pollucite(Cs2Si4Al,01,,H,0) appears to be related to the zeolites.73E. Podschus, V. Hofmann, and K. Leschewski 74 have made adetailed study of ultramarine-blue and several related substances.The highly symmetrical structure proposed for the ultramarinesby F. M. Jaeger,v5 although undoubtedly correct in essentials, wasnot entirely satisfactory from the point of view sf interatomicdistances or of X-ray reflection intensities. The structure nowdetermined is analogous to that of hauyne and nosean 76 and is lesssymmetrical and less rigid than that suggested by Jaeger, account-ing in a satisfactory manner for the variation in cell dimension whenthe sodium of ultramarine-blue is replaced by other alkalis.Leschewski and his co-workers consider it unnecessary to assumethat the sodium ions and sulphur atoms are mobile ; €or the sodium,they emphasisc that careful analyses never show more than eightions per unit cell, and these can be located definitely on cight three-Nature, 1936, 137, 273; cf.G. Peyronol, Z. Krist., 1936, 95, 274.Amer. Min., 1935, 20, 631.70 2. Krist., 1936, 95, 247.71 Amer. Mipz., 1935, 20, 699.72 Min. May., 1936, 24, 324; idern,ibid., p. 227.73 H. Strunz, 2. Krist., 1936,95, 1.74 2. anorg. Chem., 1936,228,305.76 F. Machatschki, Centr. Min., A, 1934, 5, 136.76 T m 8 . & b d t t Y SOC., 1929,=, 320COX : CRYSTAL CHEMISTRY. 207fold positions in the lattice.The sulphur is best accounted for (inagreement with the chemical evidence) by dividing it into (a)sulphur ions and ( b ) S, molecules, distributed statistically over thetwelve-fold positions; a sharp distinction between the two is notpossible. There is some evidence from these compounds that thethermal vibrations of the alkali ions may have the symmetry oftheir environment .7' The colour of ultramarine-blue is attributedto the S, groups.SuZphides.-That close crystallo-chemical relationships existbetween germanium and silicon is well known; 78 attention wasdrawn in last year's Report (p. 209) to the new type of fibrousstructure exhibited by SiS,, and the determination of the structureof GeS, by W.H. Zachariasen 79 is therefore of considerable interest.As in SiS,, each cation is surrounded by four sulphur atoms in aslightly distorted tetrahedron, the Ge-S distance being 2.19 A.(cf. 2.26 from sum of tetrahedral radii, and 2.47 in th& monosulphide),but the linking of tetrahedra is three-dimensional, giving rise to astructure which is much more like that of SiO, than t'hat of SiS,.The sulphur bond angle is 103".The high-temperature modifications of the cuprous and argentoussulphides, selenides, and tellurides have one of two structures,BOaccording as the catiorm/anion radius ratio is greater or less than 0.6.In the former category are a-Ag2S and a-Ag,Se, in which the silverions are distributed statistically in the interstices of a cubic body-centred arrangement of anions, whereas in the unit cells of a-Ag,Te,cr-Cii,Se, and a-Cu,S four anions and four metal ions form a zinc-blende structure, with the remaining cations distributed statistically.cc-Cuprous telluride is not cubic, and cuprous sulphide is deficientin copper, its formula being spproximately Cu,S,.Similarlycobaltous sulphide (nickel arsenide type) is said 81 to be stable onlywhen slightly deficient in cobalt; in both these cases it is note-worthy that the radius ratio is very near the limiting value for thcstructure concerned. Two other sulphides of cobalt, Co,S, andCoSSs, are reported; both are based on a cubic close-packing ofsulphur, and have similar cell dimensions. Photographs of Co,S,itre alrnos t identical with those of pentlandite,*2 suggesting theformula (Ni,Fe),S, for the latter, in better accord with the observeddensity.The transition from 7-NiS (millerite) to p-NiS (nickel7 7 See p. 200.78 E.g., W. Schiitz, Z. physikal. Cliertb., 1936, B, 31, 292.79 J . C h m . Physics, 1936, 4, 618.83 P. Rahlfs, 8. physikal. Chem., 1936, B, 31, 157.81 H. Hiilsmann, F. Weibke, and K. Meisel, 2. worg. Ckem., 1936,227, 113.8% M. Lindqvist, D. Lunclqvist, and A. Westgren, S v m b Kern. Tidskr., 1936,48, 156208 CRYSTALLOGRAPHY.arsenide type) has been studied by G. R. Levi and A. Baroiii,83and by W. Biltz et ~ 1 . 8 ~ ; the transition temperature is 396". W.Biltz and J. Laar 85 have confirmed the existence of Pd4S, Pd5S2,and PdS,, and a study of hauerite 86 (MnS,) has been made.M. J.Buerger 8' has discussed the arsenopyrite structure in detail, andshows how it may be regarded as a superstructure based on themarcasite type ; several new examples of this structure are recorded.D. Harker has applied his modified Patterson's method ofanalysis 88 to proustite, Ag3AsS3, and pyrargyrite, Ag,SbS,. Thetwo structures, which are almost identical, contain continuous(AgS), groups in the form of trigonal spirals, the bond angles forsulphur and silver being 83" and 165" respectively, while the lengthof the Ag-S bond is 2.40 A. Each arsenic (or antimony) is bonded tothree sulphur atoms in a flattened pyramid. W. V. Medlin 89 hasused B. E. Warren and E. Gingrich's method90 to find the radialdistribution of atoms in realgar, ASS, and orpiment, As,S,.Theresults, which are remarkably similar for the two compounds, areinteresting as showing the possibilities and limitations of resultsbased on visual estimation oE intensities in powder photographs ;for these two substances the first two or three peaks in the distribu-tion curve can be related to the appropriate atomic distances withoutdifficulty, but in other cases (e.g., CaHgBr,) interpretation is moredifficult.A study of berthierite, FeSb,S,, has been made.g1HaZides.-By means of a modified Debye-Scherrer methodM. Straumanis and A. Ievins 9, have determined the cell dimensionsof NaCl and rock-salt with, it is claimed, greater accuracy than anyyet attained. The value for rock-salt (5.6276, 0.00005 A.)differs by 0.00032 A. from that obtained by Siegbahn.Radium fluoride has the fluorite structure 93; the radius of theradium ion (C.N.= 6) is 1-62 A. On the other hand, thallousfluoride94 has a new type of (orthorhombic) structure which maybe regarded as a deformed sodium chloride lattice, and the iodide 95s3 2. Krist., 1936, 92, 210.84 2. anorg. Chem., 1936, 228, 275.86 W. Biltz and F. Wiechmann, ibid., p. 268.8 7 Z . Krist., 1936, 95, 114.a8 Seep. 197.Rg J . Amer. Chem. SOC., 1936,58, 1590.90 Physicd Rev., 1934, 46, 368.9 1 M. J. Buerger, Amer. Min., 1936, 21, 442.ga Z. Phyeik, 1936, 102, 353.aa G. E. R. Schulze, 2. physikal. Chern., 1936, B, 32, 430.g4 J. A. A. Ketelaar, 2. Krkt., 1935, 92, 30.g 5 L.Helmholz, ibid., 1936, 95, 129.8 5 Ibia., p. 257COX : CRYSTAL CHEMISTRY. 209is also orthorhombic with a semi-layer lattice in which each ionhas five near neighbours.G. Wagner and L. Lippert 96 have studied transformationsbetween the sodium chloride and the cmium chloride lattice;rubidium chloride when condensed from vapour on a surface a t-190O has the latter type, reverting to the normal former type atroom temperature. A thermodynamic study of the transformationof ammonium bromide at -39" has been made,97 and J. Weigle andH. Sainigs have shown how its tetragonal structure below thistemperature is obtained by slight deformation of the normal cubicstructure. The energy relations of super-lattices in mixed crystalshave been discussed by H.O'Daniel99 with special reference toalkali halides ; he concludes that both NsC1-AgCl and TlC1-CsC1should give rise to super-lattice structures, but the experimentalresults are not in agreement with the theory.Hydrous Oxides and Salts.-Although there is a tendency in somequarters to ignore the distinction between the true hydrogen bondand the less symmetrical hydroxyl bond, the significance of theselinkages is now generally appreciated, and examples of both inhydrated compounds continue to accumulate. A wave-mechanicaltreatment of the problem shows that both symmetrical andunsymmetrical states of the system 0-H-0 must exist.Manganite, Mn(OH)O, as anticipated, has a structure of thediaspore type, but the lattice now determined is monoclinic, witha larger cell than that formerly proposed.As in diaspore, the closeapproach of oxygen atoms (2.65 A.) indicates the existence ofhydroxyl bonds, which, however, link the structure together insheets, giving rise to (010) cleavage. The octahedron of oxygensaround each cation is so much distorted that the manganese hassquare co-ordination rather than octahedral. Unfortunately, it isdifficult to judge the accuracy of the parameters in this interestingstructure from the published qualitative comparison of intensities.Sb,O,, Sb,Ol,, and Sb,O, are all known to possess structureswhich are essentially that of senarmontite, and it is therefore notsurprising to find that Sb205,H,0 has the same space group andsimilar cell dimensions t o Sb203.3 It is noteworthy that the higher96 2.physikal. Chem., 1936, B, 31, 263; 33, 297.9 7 A. Smits, J. A. A. Ketelmr, and G. T. Miiller, ibid., 1936, A, 175, 359.as Helv. Physicas Acta;, 1936, 9, 516.8. Rh&!., 1935, 92, 221.1 R. H. Gillette and A. Sherman, J . Anter. Chew&. SOC., 1936, 58, 1135; cf.M, J. Buerger, 2. K&t,, 1936, 95, 163; cf. J. Garrido, Bu,Zl. SOC. fmw.M. L. Huggins, J . Physical Chem., 1936,40,723.Min., 1935, 58, 224.8 G. Natta and M. Baccaredda, Gazxettu, 1936, 66,3082 10 CRYSTAUOURAPHY .oxides of antimony as usually prepared contain a considerableamount of water, which probably plays a part in stabilising theoxygen-rich senarmontite structures by making possible the form-ation of hydroxyl bonds.The dihydrate of boron fluoride has almost identical cell dimen-sions with ammonium perchlorate, from which it is concluded 4 thatits structure is ( OH3)+ (BF,OH)- ; also, from the resemblance of thepowder diagrams of nitric acid monohydrate and phosphoric acid itis inferred 5 that the former may be orthonitric acid, H3N04.Substances of the type M(Hal),,3M(OH), (M = Co or Ni) hn17csimple layer lattices in which there is a statistical distribution ofhalogen and hydroxyl.6 Space groups of three hydrates of sodiumpyroborate, Na2B,D? , have been determined.V.Kassatochkin and V. Kotov 8report that “ potassium tetroxide,” KO,, has the same structure asstrontium and barium peroxides (CaC, type). This substance isthus definitely not K,O, but contains the singly charged 0; ion ; the0-0 separation is given as 1.28 A., a value which appears slightlyhigh by comparison with the distance 1-31 A.in the peroxides, since0; is presumably a resonance structure between O=O and -0-0-.A preliminary note 9 on the structure of NH4C1BrI suggests that itis closely similar to that of ammonium di-iodide ; the BrICl- ion islinear, with the iodine at its centre. L. K. Frevel lo has madequantitative studies of several azides, and finds that the N-Ndistances in the potassiuin, sodium, and ammonium salts are 1-145,1.150, and 1.166 A., respectively. These distances are in agreementwith the accepted formulation of the linear azide ion ; if it is assumedthat the empirical function of L. Pauling, L. 0. Brockway andJ.Y. Beach li can be applied to variations between N=N andNSN, 1-15 A. corresponds to about 30% of triple-bond function,and 1-165 A. to about 24%. It is noteworthy that although theradius of NH,+ is considerablygreater than that of K+, each ammoniumion in ammonium azide is surrounded tetrahedrally by four azidenitrogens at exactly the same distance (2.96 A.) as the shortest K-Ndistance in the potassium salt; this relative shortening of thecation-nitrogen distance indicates the formation of hydrogen, orComplex Ions.-Lznear ions.4 L. J. Klinkenberg and J. A. A. Ketelaar, Ree. trav. chim,, 1938, 54, 959.6 E. Zintl and W. Hauoke, 2. physikal. Chem., 1935,174,312.W. Feitknecht, Helv. C h h . Acta, 1936, 19, 467; W. Feitknecht and A.W. Mhder, Z.K ~ k t . , 1936, 92, 301.Collet, ibid., p. 831.a J. Chem. Phy8ic8, 1936, 4, 458.* R. C. L. Mooney, Phyaical Rev., 1935, [ii], 47, 807.lo J . Amer. Chem. Soc., 1936, 58, 779.11 Jbid., 1935, 57, 2705. See this vol., p. 45COX : CRYSTAL CHEMISTRY. 21 1rather “ imino,” bonds. Silver azide coutains linear azide ions withAX, Ions. The cell dimensions l3 of potassium hydrogen car-bonate suggest that its structure is related to that of the sodiumsalt, but the proposed orientation of the carbonate ions is verydifferent, and earlier magnetic measurements 1* show that the CO,groups arc considerably inclined to each other. Sodium carbonatemonohydrate has also been studied l5 by the Patterson method;the oxygen-water separation is giver1 as 2.69-2.72 A.The cell dimensions OE the anhydrous and the mono-hydrated snlphates of the magnesium series have been determinedfrom powder photographs by pr’.Rammel,l6 and the first case ofisomorphism between tellurates and sulphates (potassium salts) hasbeen rec0rded.l’ W. Schiitz 18 has demonstrated the isomorphismof the ions [Ge0,]4- and [GcF6I2- with [Si04]4- and [SiP6]2-respectively.The structure of silver phosphate, &,PO,, has been determinedin greater detail by L. Melrnh~lz,~~ who finds the P-0 distance tobe 1-61 A. This is greater than in dipotassium hydrogen phosphatea,nd is attributed to the formation of covalent bonds between oxygenand silver (Ago = 2.34 A.). In order to obtain satisfactory agree-ment between observed and calculated intensities, it was necessaryto assume the thermal vibrations of the silver atoms to have betra-gonal symmetry, and the ratio of the amplitudes along and per-pendicular to the tekragonal axis mas calculated (cf.the work ofBrindley and others, p. 200).Strong forces between anion and catioil are suggested also in thestructure of hydrated cadmium sulphate, 3CdS04,8H20,1Qa wherethe oxygen-oxygen linkages on the whole are weak.C. Finbalr and 0. Walssel 2o have studied the cubic high-tempera-ture forms of the alkali perchlorates and borduorides. By\ asmm-iiig rotation of the [C104]- and [BF,]- ions, they deduce a structurefor which both the interatomic distances (Cl-0 = 1-55 and B-33 =1.48 A,) and the agreement between observed and the calculatedintensities are more satisfactory than for the structures previouslyN-I4 = 1.18 rfr 0.04 A.12AX4 Ions.12 M.BassiArc, Bull. SOC. frarq. Jfh, 1935, 58, 333; Compt. r e d . , 1935,13 J. Dhar, Current Xci., 1936, 4, 867.14 A. Mookherjee, Physical Rev., 1934, [ii], 45, 844.1 5 J. P. Harper, 2. Krist., 1936, 95, 266.16 Qompt. rend., 1936, 202, 57, 2147.18 2. physikal. Chem., 1936, B, 31,292.10 J . Chem. Physics, 1936, 4, 316.1 9 5 H. Lipson, Proc. Roy. SOC., 1936, A , 156, 462.20 8. physisifcal. Chem., 1936, €3, 32, 130, 433.201, 735.l7 M. Patry, ibid., p. 16162 12 CRYSTALLOGRAPHY.proposed. They conclude that rotation of the anions also occursin the cubic hexafluorophosphates.The hydrates of calcium sulphate have been the subject of severalinvestigations during the past year.The structure of gypsum hasbeen worked out in detail by W. A. Wooster; 21 it is built up oflayers of sulphate alnd calcium ions parallel to the cleavage plane(OIO), linked together by layers of water molecules. Each watermolecule forms two hydroxyl bonds (length 2-70 A.) with oxygenatoms of sulphate groups in successive layers and one ionic linkwith a calcium atom (2.44 A.). A structure proposed for calciumsulphate hemihydrate 22 is based on cell dimensions and symmetrydifferent from those previously found,23 and is not in agreementwith the work of H. B. Weiser, W. 0. Milligan, and W. C. Eckholm,24who found hhat the water is not zeolitic, and that the dehydrationproduct has a lattice which, although closely similar to, is notidentical with that of the hemihydrate.It appears still to beuncertain whether the '' soluble anhydrite " first prepared byvan't Hoff by the action of nitric acid on gypsum is identical withthe dehydrated hemihydrate.[AX,] Ions. J. Beintema,25 from a study of the antimonates ofmagnesium, nickel, and barium, concludes that part of the waterwith which these compounds crystallise goes to form theoctahedral complex [Sb(OH),]-. A. I?. Wells26 has shown thatin Ag[Co(NH,),(N0.J4], contrary to the chemical evidence, thecomplex ion has a trans-configuration. The structure is a dis-torted cubic close-packing of the octahedral complexes as in trans-[PtCl,(NH,),] 27 with the cations in the interstices.As a result of the approximately spherical form of the large[RX,] ion, most structures involving it are based on cubic close-packing.Thus in many substances of the type A,M[RX,] (A =alkali metal ; n = 0, 1, or 2) the metals M and R occupy the positions(000) and (500) of sodium and chlorine in a rock-salt lattice, thealkali ions being at the centres ($a*) of small cubes formed by 4Mand 4R. Recent examples of this are afforded by complex nitrites(e.g., K,Pb[Ni(NO,),]) 2* and by Prussian-blue and related sub-21 2. Kriat., 1936, 94, 375.22 W. A. Caspari, Proc. Roy. SOC., 1936, A , 155, 41.23 P. Gallitelli and W. Riissem, Per. Min., 1933, 4, 1.z4 J . Amer. Ckem. SOC., 1936,58,1261; cf. P. Gaubert, Bull. Soc. f r a q . &!in.,p5 Proc. K . Akad. Wetemch. Amsterdam, 1936, 39,241, 652.ws 2.Krist., 1936, 95, 74.28 L. Cainbi and A. Ferrari, Gazzetta, 1935, 65, 1162; M. van Driel andH. J.1934, 57, 252.E. G. Cox and G. H. Preston, J., 1933, 1089.Verweel, 2. Krist., 1936,137, 677COX : CRYSTAL CHEMISTRY. 213stances.29 In the latter case the rock-salt structure of theFe[Fe(CN),] system appears to be particularly stable ; ferrousalkali ferrocyanides, A,FeI1[Pe1I( CN) J, readily lose half their alkali,and with very little change of the remainder of the lattice are oxidisedto Prussian-blue, AFe[Fe(CN)6], which again can be oxidised LoBerlin-blue, Pe1x1[Fe1x1(CN)6], without serious alteration in thestructure other than loss of alkali. Analogous compounds in whichruthenium or copper replaces part of the iron have been preparedand have similar structures.It should perhaps be pointed out thatthe X-ray evidence available does not distinguish between the€ormulz AFeI1CFe1I1(CN),] and AFe1IX[Fe1I( CN) ,] ; a further pointof interest is that, in the ferrous ferrocyanide and Berlin-blue, all theiron atoms appear to be equivalent. This might be taken toindicate that individual hexacovalent ferro- or ferri-cyanide groupsdo not exist in the crystal as such, and that a continuous three-dimensional network -Fe-CN-Pe- extends through the lattice,This view, while attractive in many respects, is not without itsdifficulties (e.g., the same crystallographic equivalence of atoms isobserved in the mercury atoms of K,Hg[Hg(No,),]), and the moredetailed analysis of these interesting compounds must be awaitedbefore any certain conclusions can be drawn.Co-ordination comjdexes.I n many cases the analysis of co-ordination compounds has been carried far enough to determinethe configuration of a central metal atom only; in others, completestructure determinations have been made. It is probable, however,that the study of such compounds will in future be more frequentlypursued to completeness, not only for stereochemical reasons, butalso in order to determine the structure of organic molecules, owingto the technical advantages resulting from the presence of asymmetrically placed metal atom.Much additional information on the distribution of the valenciesof quadricovalent metal atoms has been obtained and there isincreasing evidence in favour of the view that bond distribution andprincipal valency are closely connected, the configuration of thebonds in many cases changing from tetrahedral to planar as thestate of oxidation of the atom alters. The implications of thiswould seem to merit attention from a theoretical point of view.In addition to the complete structure determinations by J. M.Robertson on metal derivatives of phthalocyanins (see p.215),several reasonably detailed analyses have been carried out.D. Harker 30 has shown that cupric chloride dihydrate, CuC1,,2H20,29 J. F. Keggin and F. D. Miles, Nature, 1936, 187, 577,30 2, Krist., 1936, 93, 136,\/ \//', / 214 ORY STALL0GRAPH.Y .is a true quadricovalent compound in which, in agreement, withearlier work, the copper valencies are coplanar.From a, com-parison of interatomic distances, Harker was led to suggest thatthe CuC1,,2H20 complex occurs in K2CuCl4,2H,O, which shouldtherefore be written K2[CuC1,,2H,0]C1,. An analysis 3l of( NIX4),CnC14,2H,0 gives interatomic distances which confirm this,On the other hand, the water molecules in K[AuBr4],2€I,0 are notco-ordinated to the metalH. Brasseur and A. de Rassenfos~e,3~~ continllring their investiga-tions of complex cyanides and related compounds, have shownthat barium cadmichloride tetrahydrate, BaCdC1,,4H2O, and thecorresponding cadmibromide have cell dimensions very closelysimilar to those of barium platinocyanide tetrahydrate. Theirinference that the ion [CdCl,]” has nearly the same form anddimensions as [Pt(CN),]” must await confirmation by more detailedstudies, since it is quite possible that the anions in these compoundsare of the form [MX4(H20),]”.The higher hydrate of 12-phosphotungstic acid, H3BW,,0,,,29H,0,33is of special interest.The anions (PW,,04,)-3 (which are identicalwith those found by J. F. Keggin in the pentahydrah) are heldtogether almost entirely by water molecules ; anions and groupsof 29H,O lie on interpenetrating diamond lattices. A noteworthyfeature is the constancy of both the I-1,Q-0 and the H,O-H,Odistance, which scarcely vary by more than the experimental errorfrom the value 2.88 A. This is the more remarkable since a watermolecule may be attached by three, four, or seven such bonds toneighbouring oxygen atoms or water molecules.Other co-ordination compounds are discussed in the Report onInorganic Chemistry .34E.G. C.3. MOLECULAR CRYSTALS.Until this last year exact X-ray analyses of organic compoundshave always depended on some preliminary knowledge of thestructure of the molecules concerned. J. M. Robertson has ncwachieved in his work on the phthalocyanines the first absolutelydirect analysis of an organic molecule, and one which does notinvolve even the assumption of the presence of discrete atoms.31 A. Silberetsin, Compt. rend., 1936, 202, 1196.351 See this vol., p. 164.32a 8. Krist., 1936, 95, 474 ; Bull. SOC. roy. Sci. Li2ge, 1936, No. 5, 125 ;s8 A. J. Bradley and J. W. Illingworth, Proc.Roy. SOC., 1936, -4, 15’9, 113.a4 See this vol., p. 157.Nos. 8-10,199.1 J., 1936, 1195CROWFOOT : MOLECULAR CRYSTALS. 2115The success of this analysis depends upon the fulfilment of two con-ditions. I n the first place the phthalocyanines crystallise in a,molecular arrangement having cent'res of symmetry at which, bychemical meaizs, different metal atoms can be inserted withoutappreciably disturbing the crystal structure. The P values directlycalculated from the intensities of the X-ray reflections observed withthe metal-free compound and nickel phthalocyanine were conse-quently known to differ only by the contribution of the nickel atom,which geometrically had to be equal to the structure factor furFIG. 2.Projection along the b cczi8, showing one complete phthwlocyanine molaule. Theplane of the molecule is steeply indined to the plane of the projection, the Mdirection making an.angle 04 46" with the b axis, and the L direction 2.3".Each contour represents a density increment of one electron per A,a, the one-electron line being dotted. .nickel a t the angle of reflection. A plot of the sums and differencesof the observed P values for the two compounds against sin e/xshowed a congregation of certain valuea about the theoretical curveof the nickel scattering factor. These values fixed the phase con-stants of the reflected rays, and therefore a Fourier synthesis couldbe formed directly from the measured P values.The Fourier synthesis of the (h01) terms gave a projection of thestructure on (010) which shows clearly resolved a pattern of atomsjoined in six-membered and five-membered rings unitcd together(sec Fig.2). This pattern may be said to provide the first purel216 CRYSTALLOGRAPHY.physical demonstration of the truth of organic chemistry. It illus-trates also the second condition necessaq- for the success of thisdetermination of chemical structure-that the projection obtainableshculd be one in which little overlapping of atoms occurs, so that$an unambiguous view may be obtained of the pattern as a whole.For example, the projection of the phthalocyanine structure alongthe c axis shows no clem resolution and could alone give no direct,chemical information.The method of direct determination of the phase constants of theFourier terms by isomorphous replacement of metal atoms hasalready been used by J.M. Cork 2 and C. A. Beevers and H. Lipsonin their investigations of the alums. Owing to the peculiarlyf avourable chemical and crystal structure of the phthalocyaninesthe results are here much more striking, and it would seem worthwhile to explore further in the field of organic chemistry for othercompounds which may possess this particular combination ofcharacteristics. For most structures it will be necessary, of course,still to use the trial and error method--with the renewed confidencenow given for its results.The exact X-ray analyses discussed last year proved that themethod was capable of giving purely chemical information of twokinds : (1) the actual determination of the mutual orientation ofthe atoms in the molecule, and here Robertson's analysis providesus with a notable advance; (2) the diagnosis of the nature of thechemical bonds present from the measured interatomic distances.In this both theory and experiment are still far from complete, butthe function described by E.Bauling, L. 0. Brockway, and J. Y.Beach of the relation between bond length and single-bond-double-bond resonance does a t least provide us with a new empiricalstandard with which t o compare the experimental values.Simple Holecular Compounds.The crystal structures of most of the simplest quasi-sphericaldiatomic and triatomic molecules have already been measured, andthe remaining types are likely to prove more complicated.E.Pohland ti has found, for example, that solid hydrogen cyanide, nitricoxide, and sulphur dioxide are all doubly refracting. More compli-cated types of X-ray goniometer are needed for further work in thelow-temperature region,6 and with one of these W. H. Keesom and2 Phil. Mag., 1927, 4, 688.B Proc. Roy. SOC., 1936, A, 148, 664.4 J . Amer. Chem. SOC., 1935, 5'7, 2705.Angew. Clwm., 1936, 49, 482.W. H. Keasom and IS;. W. Taconis, Physica, 1035, 2, 463; R. L, MeFsrlan,Re,,. S a i . Instr., 1936, [ii], 7, 89CROWFOOT : MOLECULAR CRYSTALS. 2 17K. W. Taconis have studied y-oxygen and chlorine.* y-Oxygenis cubic in agreement with the work of L. Vegard,g and chlorinecrystallises at - 185' in the tetragonal system with eight (non-rotating) molecules in the unit cell.The C1-Cl distance calculatedIrom the rather limited X-ray intensities available is 1-99 in eachmolecule, and 2.79 A. between molecules. The lattice constant andX-ray intensities of solid hydrogen sizlphide do no& appear to changethrough a wide temperature range, though transitions, probably ofrotation and orientation of the molecules, are indicated by otherdata, e.g., dielectric constnnt.l* That some orientation of themolecules does exist at liquid-air temperatures has been suggestedto account for the Raman spectrum of the solid.11In a number of crystals of this class, where rotating forms com-monly occur, entropy calculations suggest that equilibrium isfrequently not established a6 low temperatures. Tetramethyl-methane has a zero-point entropy of 8 e.u.which may be due torandom orientation,12 and the residual entropy of ethane cansimilarly be correlated with a form of incomplete r0tati0n.l~ Thestructure of ice is perhaps the most important example, since thedifficulties of placing the hydrogen atoms in all varieties of ice sofar measured have led many authors to describe the structures asi0nic.14 The Bernal-Fowler model l5 requires definite orientation ofthe hydrogen atoms between the water molecules forming hydrogenbonds, each hydrogen atom remaining still most closely associatedwith one oxygen, and although it is possible to form such a structurein a regular way, yet there is no evidence of any superstructure inthe X-ray results.L. Pauling calculates that if the orientation israndom, the residual entropy would be 0.805 e.u., compared withthe observed value of 0.87 e.u.16The structure of the different polymorphic forms of ice should beof particular interest for a further test of these theories. Fromtime to time in the literature measurements have been reportedsuggesting that ordinary ice, ice-I, is rhombohedral, which mightbe due to a correctly oriented form of the Bernal-Fowler type.N. Seljakow l7 has, however, now shown that if distilled water isPhysica, 1936, 3, 141.* 2. Physik, 1935, 98, 1.10 E. Justi and H. Nitka, Physikal. Z., 1936, 37, 435.11 S. C. Sirkar and J. Gupta, Indian J. Phgsics, 1936, 10, 227.l2 J. G. Aston and G. H. Mesaerly, J.C h m . Physic8, 1936, 4, 391.14 CP. W. H. Barnes, Tyam. Roy. SOC. Canada, 1935, [iii], 29, 111, 53.15 J . Chern. Physics, 1933,1, 515.17 Compt. rend. Acad. Sci. U.R.S.S., 1936,1, 293; 2, 227.Ibid., p. 237.J. D. Kemp and K. S. Pitzer, ibid., p. 749.1% J . ~ m e r . mm. SO^., i935,57, 2680218 CRYSTALLOGRAPHY.frozen from the surface in the open air, two quite different modi-fications may be obtained. Ordinary ice-I, a-ice, appears when thetemperature of crystallisation is between 0" and - 8' and gives thcusual hexagonal Laue photograph. Below - 8O, i.e., with somedegree of supercooling, fhe is formed, which shows a quite differentrhombohedra1 Laue pattern and appears to be pseudo-cubic ( c I ~ = 1-33).The high-pressure forms of ice, ice-11 l8 and i ~ e - 1 1 1 , ~ ~ according toR.L. McFarlan, have orthorhombic structures of some complication.Both the molecular arrangements suggested show oxygen atomssurrounded by four nearest neighbours at 2.71 A., very little differentfrom the distance in ice-I, 2.74 A. The higher densities imposedby the higher pressure, 1.2 in ice-11, 1.105 in ice-111, are attained inboth by different distortions from the regular tetrahedral arrange-ment of nearest neighbours showd by ice-I, which permits thenext neighbour distance to decrease from 4-47A. in ice-I to about 3.4 A. in ice-I1 and ice-111.It does not seem necessary to correlate thisdistortion with a truly ionic structure, sincesuch alterations of the valency angle mayoccur under strain even with homopolarbonds such as those in diphenyl ether-I~o$' 9776" where the C-0-C angle is about 128°.20 I nmany hydrates the water molecules are sur-rounded by similarly distorted tetrahedra of* G m h oox5'P oxygen atoms, and the most significantfeature seems a t present to be, not the dis-tortion, but the even approximately tetrahedral nature of thcco-ordination.FIG 3.Dimensions of the OxalicAc;dMolecule.7'24 1 u123-j0Aliphatic Compounds.To the complete structure determinations in the aliphatic serieswe may now add that of oxalic acid dihydrate by J .M. Robertson.21The approximate structure found by W. H. Zachariasen showed thetwo oxygen atoms to be differently situated with respect to thewater molecules and suggested therefore that these were different incharacter. The results now obtained by the use of absoluteintensities and double Fourier syntheses fully conflrm and extendthis.The two C-0 distances are found to be different, 1.24 and1.30 A., and though neither corresponds to pure double-bond orsingle-bond distances, they may be correlated with links mainlyl8 J. Chem. Phy8leic8, 1930, 4, 60.le Ibid., p. 253.2o L. E. Sutton and G . C. Hampson, Tram. Paraday Soc., 1935, 31, 945.a1 J., 1936, 1817CROWFOOT : MOLECULAR URYSTALS. 218C=O and C-OH respectively. The C-C distance as measured isconsiderably shorter than that first proposed, vix., 1.43-1-45 A.,which corresponds to 30-25% double-bond quality. According tocalculations of J. E. Lennard-Jones,22 such a shortening is to beexpected in a singlo link between two doubly-bound carbon atoms,as, e.g., in a conjugated chain.Here, it seems that it could takeplace through the co-operation of the water molecules forminghydrogen and hydroxyl bond chains through the structure asxnggested by J. I). Bernal and (Niss) H. D. Megaw 23 (Type B).Exactly opposite effects appear to occur with the oxalate ion,particularly in ammonium oxalate monohyclrate .a* Here the dis-tance between the central carbon atoms is 1.58 A,, longer than thatexpected for a normal single link. The lengthening might be dueto repulsion between the negative parts of the CO, ions, and therecertainly seems no allowance for a partial double-bond character ofthe central link. Also, the two CO, groups are found to be no longercoplanar, but inclined at an angle of about 28' to one another, aresult which seems most reasonable if there is a pure single linka t the centre, about which free rotation should be possible.Inmoat other oxalates studied, e.g., those of potassium, sodium, andrubidium, the ion is planar within a probable experimental error of& lOO.25 The difference in ammonium oxalate may partly be dueto a new system set up by possible hydrogen-bond formationbetween the ammonium ions and oxygen atoms of tihe oxalate ion.The interatomic distances in ammonium and potassium oxalatesshow relations similar to those of animonium azidc compared withpotassium azide26 (see p. 210). Calcium oxalate dihydrate istetragonal, and it is interesting that this occurs with calcium citratein deposits a t the bottom of the WeddellInvestigations have begun on a number of the homologues ofoxalic acid.28 These crystallise commonly in two different poly-morphic modifications, cc and p, the cc being the stable form for acidsof more than nine carbon atoms, the p for those of less.The changeis probably associated with the differential effective interaction ofthe carboxyl groups : below C, the crystals are hard and shining;above, platy and waxy. Of several tartaric acid derivatives de-~cribed,2~ tartramide seems most promising for further exact2% Private communication to 5. M. Robertson.23 PTOC. Roy. SOC., 1938, A , 151, 384.24 S. B. Hendricks and M. E. Jefferson, J . Chem.Physics, 1936, 4, 102.25 S. B. Hendricks, Z . K r i s t . , 1935, 91, 48.38 L. K. Frevel, J. Amer. ('hem. SOC., 1936, 58, 770; 2. Krist., 1936,94, 197.27 F. A. Bannister, Discovery Reports, 1936, XIII, 60.28 P. de la, Tour, C'ompt. rend., 1936, 202, 1935.2s J. Wyart and Y. Hi-Heng, ibid., 203, 96220 CRYSTALLOGRAPHY.information. A number of measurements are recorded on long-chain acids and salts,3O and also the ac-monoglycerides,31 which haveinteresting liquid-crystal properties. The choleic acids are some-what of a mysbery, since the same X-ray photographs are obtainedwith considerable variation in fatty acid present .32The measurements on oxalic acid and oxalates provide us with aseries of G O distances which can be described as due to varyingsinglc-bond-double-bond mixtures.That in metaldehyde probablyrepresents the pure single link and is given as 1.43 & 0.02 Met-aldehyde crystallises in the tetragonal system, each molecule having afourfold axis of symmetry. The molecule consists of a puckeredeight-membered ring of alternate oxygen and carbon atoms, similarFIG. 4.Metaldehyde.FIG. 6.Resorcilzol.@Carbon 0 Oxygent o the six-membered ring of paraldeh~de,~~ the methyl groups herelying npproxinmtely in the plane of the ring (Fig. 4). A Fourierprojection along the four-fold axis has been obtained, but theparameters at right angles to this are not so accurately fixed.The whole series of C-0 distances hitherto found in organiccompounds, including that in resorcinol (p.221), are shown in thetable.InteratomicMain bond type. Compound. distance, A.C-0-C Metaldehyde 1.43*C-OH Resorcinol 1.36*GOH Oxalic ac;d dihydrate 1.30GO- Ammonium oxalate monohydrate 1.25 *c= 0 Urea 35 1-25 *c= 0 Oxalic acid dihydrate 1.24 c=o Benzoquinone 36 1.14 * Probably most accurate values.--30 P. A. Thiessen and J. Stad, 2. phyalsikd. Chem., 1936, 176, 397; with81 T. Malkin and N. R. el Shurbagy, J., 1936, 1628.W. Wittstadt, Alzgew. Chem., 1936, 49, 641 ; R. Brill, ibid., p. 643CROWFOOT : MOLECULAR URYSTALS. 221Aromatic Compounds.The exact structure of the molecule of resorcinol 37 is shown inFig. 5 . The most interesting feature of this crystal structure is thespiral method of packing, which is able to bring the hydroxyl groupswithin that distance of each other, W ~ Z .2.66-2-74 A., associatedwith hydroxyl-bond formation without placing the carbon atomsnearer than the customary 3-5 A. Both theory and experimentnow show that in the type of hydrogen- and hydroxyl-bond form-ation common in organic compounds there is not usually completedegeneracy, hydroxyl and keto-groups still preserving individualcharacteristics. This is true in oxalic acid (above) and also,apparently, in quinhydrone, where more exact work shows that thesymmetry first found is a pseudo-symmetry, and that the benzo-quinone and the quinol molecules can actually be distinguished inthe crystal cell.38 Their mutual arrangement is necessarily almostexactly the same as that first put forward, and the lines of attractionbetween them are still those of the C:O .. . HO bonds running throughthe whole structure. In iaatin, the question of a difference of thiskind is bound up with the old problem of a distinction between thelactim and the lactam st.ructure. E. G. Cox, T. H. Goodwin, and(Miss) A. I. Wagstaff 39 find an orientation of the molecules in thecrystal unit which indicates a hydrogen bond between the nitrogenatom and the carbonyl group of neighbouring molecules; butwhether this is to be written mainly as of the type NH . . . 0:C(lactam) or =N . . . HOC (Ilactim), only a complete analysis candecide. The present work implies that to a certain degree thestructure is intermediate between the two.I n the 'phthalocyanine molecule there appears to be the firstexample of an internal hydrogen bond.The exact molecularstructure found (see p. 215) is illustrated in Fig. 6. The directPourier projection first obtained showed that the ring system issomewhat inclined to the plane of projection, but the regularity ofthe pattern proves that the molecule is essentially planar. Theangle of inclination adopted agrees with the observed intensities.32 Y . Go and 0. Kratky, 2. K~ist., 1936, 92, 310.33 L. Fading and D. C. Carpenter, J . Amer. Clhem. SOC., 1936, 58, 1274.34 D. C. Carpenter and L. 0. Brockway, ibid., p. 1270; P. G. Ackermann35 R. W. G. Wyckoff and It. B. Corey, 2. Krist., 1934, 89, 462.36 J. M. Robertson, Proc. Roy. Soc., 1936, A, 150, 106.37 Idem, ibid., 1936, A , 157, 79; cf.(Mrs.) K. Lonsdale, Nature, 1936,a8 J. Palacios and 0. R. Foz, Anal. Fis. Qui,m., 1935, 33, 627; J. Bijvoet,39 Proc. Roy. SOC., 1936, A, 167, 399.and J. E. Mayer, J . Chem. Physics, 1936, 4, 377.137, 826.private communication222 ORYSTALLOGRAPHY.Chemically thc structure is that assigned by R. P. Lin~tead,~O butthe interatomic distances indicate the additional regularity of acomplete resonance system. There are no systematic differences,e.g., in the C-C distances of the benzene ring that might indicateeither o-quinonoid forms or fixation of one of the Kelculh modes bythe fusion of the five-membered sing; but the molecule as a wholeshows a slight departure from tetragonal symmetry, the centralnitrogen atoms being drawn more closely together dong two out ofthc four possible lines.The distance between them, vix., 2-85 A,FIG. 6.Dinwasions of the PhthaZocyanine Molecule.suggests that this is due to hydrogen-bond formation and thehypothesis is being tested by further examination of the metallicderivatives ?1It is comparatively rarely that the full symmetry of a molecule isshown in that of the crystal if the symmetry is at all high. In thephthalocyanines this is due to the molecules being packed with theplanes of neighbouring ring systems slanting at a considerable angleto one another; and this behaviour appears to be common amongthe many aromatic compounds o€ which preliminary measuremcnt,s40 See Ann. Reports, 1935, 32, 360.41 J. M. Robertson, J . , 1936, 1736UROWPOOT : MOLECULAR ORYSTALS.223arc recorded this year 42 and also in reduced ring systems such asthose of the sex One exccption is hexabromomethyl-benzene which crystallises in a very simple rhombohedra1 structurewith one molecule in the unit cell.44 This molecule must crystallo-graphically possess a thrce-fold axis of symmetry, and the nearidentity of the intensities of equatorial and layer-line reflectionsshows that all the atoms fall nearly into a single plane. A planarcharacter is shown also in the crystal structure of hesaethylbenzene,45which is, however, triclinic like hexamethylbenzene. Molecularcentres of symmetry can more readily appear than axes, e.g., indiben~anthracene,~G r~brene,~7 and q~aterphenyl.~~ In the optic-ally active substitutcd diphenyls 48 the crystal centre of symmetrydisappears, as would be expected.The exact analyses described show several examples of slightdistortions of the external valency angles of the benzene carbonatoms, towards substituent atoms.7!hat in resorcinol is very smalland may not be real, and that in the phthalocyanines is forced bythe fusion of the five-membered ring. Both these distortions arein the plane of the ring, but in two other structures examined,p - toluidine 49 and flu or en^,^^ preliminary calculations of intensitiessuggest that deviations also occur a t right angles to this plane. Influorene, however, where such a distortion would seem mostplausible, the dipole moment of the solution indicates a planarstructure,51 and it is evident that further work is necessary toestablish with certainty the correct configuration in the solid.42 J.Iball, Z. Krist., 1936, 92, 293; 93, 47; 94, 7; 95, 282; J. Dhar andA. C. Guha, ibid., 1935, 91, 123; M. Milone, ibid., 1936, 93, 113; M. Prasadand J. Shanker, J. Indian Chem. Soc., 1936, 13, 123; with M. P. Lakhani,ibid., p. 519; R. Hultgren, J. Chem. Physics, 1936, 4, 84; E. Hertel andH. W. Bergk, 2. physilcal. Chem., 1936, B, 33, 319; L. Rivoir and R. Salvia,Anal. Pis. Quim., 1935, 33, 314; B. K. Blount and (Miss) D. Crowfoot, J.,1936, 414; J. 35. Robertson, M. Prasad, and (Miss) I. Woodward, Proc. Roy.SOC., 1936, A, 154, 187.43 J. D. Bornal and (Miss) D. Crowfoot, 2. K h t . , 1936, 93, 464.44 H. S . Backer, Rec.trav. chim., 1935, 54, 745; J. Beintema, P. TorpsLre,45 H. K. Pal and A. C. Guha, 2. Krist., 1036, 92, 392; N. Ganguli, ibid.,46 J. Iball, Nature, 1936, 137, 361.47 M7. H. Taylor, 2. Krist., 1936, 93, 151; cf. E. Bergmann and E. Her-linger, J. Chem. Physics, 1936, 4, 532.48 L. W. Pickett, J. AmeT. Chem. Soc., 1936, 58, 2299.49 J. Wyart, Bull. SOC. f m q . Min., 1936, 58, 281.50 J. Iball, I;. Krist., 1936, 94, 397; J . W. Cook and J. Iball, Chem. and61 E. D. Hughes, (Mrs.) C. G. Le FBvre, and R. J. W. Le FBvre, ibid.,and W. J. van Weeden, ibid., p. 962.93, 42.Ind., 1936, 467.pp. 646, 581224 CRYSTALLOGRAPHY.Fibre Structures.The most important contribution of the first application of X-raycrystallography to the problem of fibre structures was the demon-stration that the patterns obtained corresponded to units withinthe molecule many times smaller than the estimated molecular size.52Most subsequent work has concentrated on the examination of thescsmall repeating units, and with the introduction of such methods ofanalysis of fibre diagrams as that proposed by E.Sauter thisyear,53 it is to be hoped that still more accurate information will bemade available along this line. With synthetic polymers, however,such as the polyoxyrnethylenes, two types of X-ray interferencecan be obtained, one due to the fibre repeat unit and the other tosmall angle reflections corresponding to the molecular length.54Most natural polymers have very much larger molecules than these,and long spacings due to regularity in chain length would be muchmore difficult to observe; but the constant reports of long spacingsin the litcrature-particularly on proteins 55-suggest that a morecomprehensive search should be made in the region of small anglescattering.This has been now initiated by R. W. G. Wyckoff andR. 13. Gorey, using for their first attempt apparatus capable ofshowing spacings up to 150 A.55a They find that, on the basis ofthe scattering visible a t small angles, the compounds examined fallinto three classes, of which rubber, cellulose, and the proteins maybe taken as typical.For stretched rubber, Wyckoff finds no scattering a t all a t smallangles, which is not surprising since, even if chains of a single lengthwere present, it would be unlikely that the orientation producedby stretching would be sufficient to demonstrate them.However,in p-rubber, in which a rather different collfigura'tion of the chainappears, a spacing of 115 A., 24 times 6he simple identity period,has been observed.56 This may, of course, represent no more thana purely crystallographic superstructure. The exact configurationof the residues in ordinary, " crystalline," a-rubber has beenreinvestigated by K. H. Meyer and W. LotmarY5' who find amonoclinic cell in which the chains themselves have a twofold52 Cf. J. R. Katz, Tram. Paraday Soc., 1936, 32, 77.53 8. KriRt., 1936, 93, 93.54 H. Staudinger, H. Johner, R. Signer, G. Mie and J. Hengstenberg, 2.55 See Ann. Reports, 1935, 32, 241 ; W.T. Astbury, Nature, 1936, 13'4, 803.55a J . Biol. Chem., 1936, 114, 407.56 G. W. Pankow, Helu. Chim. Acts, 1936,19, 221.67 Sitzungsber. A M . Wiser. Wien, 1936, IIb, 145, 721; Arch. Sci. &YS.pkyerikal. Chem., 1927, 128, 425.nd., 1936, [v], 18, Suppl., 61CROWFOOT : MOLECULAR CRYSTALS. 225screw axis of symmetry, the crystal being essentially a racemate ofright- and left-screwed molecules. The density found is still ratherlower than that calculated for the measured unit, but it seemsprobable that this is due to holes between the rubber crystallites.The same discrepancy appears with the “ inorganic ” rubber,phosphonitrile chloride.58 In this, too, the crystal structuresuggests long chains formed on a screw-axis pattern, the spacegroup here being orthorhombic.Both rubber and phosphonitrilechloride give very similar X-ray scattering curves in the amorphousstate. That of rubber has now been submitted to a Fourier analysis,and the radial density found is in good agreement with the con-figuration of the rubber chain suggested for a - r ~ b b e r . ~ ~ Thestrongest peak at 5 A. corresponds to distances between neigh-bouring chains and moves out to 6-15 A. in phosphonitrile chloride.In thin rubber films the a-rubber structure again appears, but maybe rather differently oriented on stretchingCellulose, according to Wyckoff, shows diffuse scattering at smallangles but no definite line pattern. This is contrary to manyprevious reports of long spacings, but some at least of these havebeen proved by W.A. Sisson, G. L. Clark, and E. A. Parker 61 tobe actually not diffraction lines but absorption edges, and resultsmight differ with cellulose from different sources. 0. L. Clark andA. F. Smith 62 have also investigated chitin and various deriv-atives such as its nitrate and chitosan, with which, again, longspacings seem to appear. For the repeat structure of chitin, theirresults agree with those of K. H. Meyer and G. W. Pank0w,6~ theunit cell being similar in dimensions to that of cellulose, and largerthan that put forward by A. N. J. Heyn; 64 but the latter’s workdoes show the orientation of the chitin chains in the sporangiophoreof the fungus phycomyces. It is interesting that plant and animalchitin appear identical,65 whereas among the starches from thesetwo sources there are marked differences.Glycogen has been madeto give only a single amorphous ring, and the patterns from severalvegetable starches show a number of Debye lines and differ from5 B K. H. Meyer, W. Lotmar, and G. W. Pankow, Helv. Chim. Acta, 1936,19, 930; K. H. Meyer and G. W. Pankow, Arch. Sci. phys. nat., 1935, [v],17, 139-59 G. L. S h a r d and B. E. Warren, J . Amer. Chem. Soc., 1936, 58, 507.60 K. I. Krilov, Physikal. 2. Sowietunhn, 1935, 8, 136.61 J . Amer. Chem. Soc., 1936, 58, 1635.62 J . Physical Chem., 1936, 40, 863.63 Nelv. C h h Acta, 1935, 18, 589.64 Proc. K . Akad. Wetensch. Amsterdam, 1936, 39, 132.66 K. EL Meyer and W. Lotmar, Arch. Sci. phy8. not., 1935, [v], 17, 287;with G.van Iterson, Rec. trav. c h h . , 1936, 55, 61.REP.-VOL. XXxm. 226 CRY STALLOGIRAPHY.plant to plant.66 The actual laying down of these fibres in plants isa fawinating problem.67 In Valonia, protoplasm streams can beobserved running nearly at right angles to the primary cellulosefibre axis,68 and these probably determine the orientation of thesecondary axis as found by X-ray studies. Perhaps the time is notfar off when X-ray cinematographs will be taken of this process.They have already been successfully made by M. Mathieu for thenitration of cellulose,69 and could obviously be applied widely,especially in the many other cellulose reactions awaiting elu~idation.~~In the nitration of cellulose with gaseous nitrogen pentoxide, thewhole process can be observed in the course of one hour from thefirst disappearance of regularity in the direction of the cellulosefibre atxis to the final appearance of the new fibre period, 25.1 A., oftrinitrocellulose.In the third group, the proteins, more and mare evidence appearsof a surprising degree of natural orientation and complexity ofstructure.71 The only natural protein fibre to show an almostamorphous state appears to be " byssus " or silk of oysters, whichmay be a mixture of different ~haiiis.7~ In most cases the a-keratinoriented state appears even in the actual arrangement of the proteinin cell walls,73 e.g., of wool cells, 74 and the structures present maybe much more complicated than this, as the patterns obtained fromtendon, collagen, quill, and feather keratin In all these,spacings over 100 A.long have been observed, and the real fibrerepeat of tendon is probably at least 330 A. Truly crystallineDebye-Scherrer patterns are given by both the Bence Jones protein 75and chymotrypsinogeii 55 suspended in water, but the most interest-ing results of all have been obtained on the tobacco mosaio virus.The preparation of biologically active crystals was first effected by66 F. May and L. Graf, 2. Biol., 1936, 97, 167.87 W. Wergin, Angew. Chem., 1936, 49, 843; W. A. Sisson, J . PhysicalChern., 1936, 40, 343; W. K. Farr, Paper Trade J., 1935,101, T.A.P.P. 1.Sect. 183; F. Worschitz, Afagyar Chem. Pol., 1934, 40, 60; T. Pujiwara andY. Imanaka, J. Sci. Hiroshina Univ., 1936, A, 6, 237.68 G. van Iterson, Nature, 1936, 138, 365. 68 Ibid., p. 824.70 M. Mathieu and (Mdlle.) T. Petitpas, Corn@. rend., 1936, 203, 46; A. J.Barry, F. C. Peterson, and A. J. King, J . Amer. Chem. SOC., 1936, 58, 333;K. Hess and C. Trogus, 2. Elektrochem., 1936, 42, 696, 705, 710; J. B.Calkin, J. Phy8iCal Chem., 1936, 40, 27; G. N a t h and M. Baccaredda, AttiR . Accad. Lincei, 1936, [vi], 23, 444; M . Iaihara, J . SOC. Chem. Id. Japan,1936, 39, 62, 65, 68, 70; A. Frey-Wyssling, Hdv. Chim. Ada, 1936, 19, 901.71 Cf. W. T. Astbury, Nature, 1936, 157, 803.72 G. Centola, Gazxetta, 1936, 66, 71.73 A. Giroud and a. Champetier, Bull. SOC. C h h . biol., 1936, 18, 666.7 4 H. J. Woods, Proc. L e d Phil. Soc., 1036-36, 5, 132.75 A. Magnus-Levy, K. H. Meyer, and W. Lotmar, Nature, 1936, 187, 616CROWFOOT : MOLECULAR CRYSTALS. 227W. M. Stanley,76 and the Debye-Scherrer pattern obta,ined from asuspension of these by R. W. G. Wyckoff 77 and 1%. B. Corey issimilar to, though somewhat more complicated than, those of othercrystalline proteins. This is true both of preparations obtained bythe usual methods of protein fractionation and of “ crystalline ”pellets isolated directly by centrifuging clear juice pressed fromvirus-infected plants.78 The most remarkable effects are shownby the highly purified protein solutions prepared by F. C. Bawdenand N. W. Pi15e.~~ Therme separate on standing into two layers;the lower layer, which may be waher-clear, is liquid-crystalline,whereas tho upper layer shows to a high degree the phenomenon ofanisotropy of flow. On drying, at f i r s t a “ wet gel ” is formed witha much higher birefringence than the liquid but this graduallyshrinks by about 50% to form a “ d r y ” gel. J. D. Bernal andI. Fankuchen 79 have obtained X-ray patterns both from the wetand the dry gel, and from the liquid down to 13% concentrakionoriented by flow. All Hhow approximately the same large anglescattering, which oan be correlated with that given by the crystdls--a protein pattern of some complexity with a repeat unit of3 x 22-2 A. This must be due to the internal structure of theprotein molecule. There is also an inner pattern corresponding toa hexagonal paclsing of long rods; and the unit of the long spacinghere varies from 131.8 A. in the dried gel to 398 A. in the liquid,and corresponds to distances between the protein moleculc~,. Therelations between the various patterns permit Bernal and Fanlrucbcnto deduce Che presence of rods 100 A, across roughly triangular insection. Both the sharpness of the X-ray reflections and the shapeof the lenticols formed in the liquids suggest a length for thGse P&of a t least 1000 A., which would agree with Svedberg’s molecularweight of about 17,000,000 ; but there is no X-ray evidence atpresent against the rods being quite indefinite in length. Crystalo-graphically, the gel and the liquid structures may be awigned f oC. Herrnann’s liquid-crystal class R I1) BD,81 there being regularitywithin the long rods and in theiz arrangements normal to theirlength without accurate co-ordination between the $wo; but, theobservation of such regularities is indeed an achievement in amolecule of such a high molecular weight and with at least a, suspicionof life. D. M. C.E. G. Cox.D. M. CROWFOOT.76 Science, 1935, 81, 644; J. Biol. Chem., 1936, 115, 673.7 7 Ibid., 116, 61.78 Science, 1936, 84, 513.80 J . Arner. Uhern. SOC., 1936, 58, 1863.2;a€ure, €936, 3.38, 1051,81 2. Krist., 1931, 78, 186

ISSN:0365-6217    

DOI:10.1039/AR9363300196

出版商:RSC    

年代:1936

数据来源: RSC

摘要:

ORGANIC CHEMISTRY.1. STEREOCHEMISTRY.Deutero-compounds.-A number of attempts have been made toascertain if a compound CHDRR' could exhibit optical activityowing to the difference between hydrogen and deuterium. H.Erlenmeyer and H. Gartner I. failed to resolve a partly deuteratedP-phenylpropionic acid, C6H2,,8D,.82'C2H,6,D,,8.C0,H, and laterphenylpentadeuterophenylacetic acid, C6D5*CHPh*C02H. E. Bid-man, K. A. Jensen, and E. Knuth at first concluded that decomposi-tion of Z-bornylmagnesium chloride with deuterium oxide gave aslightly active 2-deuterocamphane, but repetition of this workshowed that water and deuterium oxide gave products which werestereochemically indistinguishable. M. T. Leffler and R. Adamsreduced Z-bornylene with hydrogen and with deuterium, and foundthat, although 2 : 3-dideuterocamphane had a higher density thancamphane, it had the same optical rotation as the latter.The sameauthors also reduced ethyl maleate and ethyl fumarate catalyticallywith deuterium, and obtained from both the same ethyl aa'-dideutero-succinate, and this was found to be saponified to a single acid, thealkaloid salts of which showed no mutarotation. Similarly, J. B. M.Coppock and S. M. Partridge reduced y-phenyl-a-methylallylalcohol with hydrogen and with deuterium, and failed to observeany optical difference between the products. All the above authorsconcluded, therefore, that the formally " asymmetric '' carbonatom in CHDRR' does not give rise to optical activity.8On the other hand, G. R.Clemo and A. McQuillen have claimedthe resolution of pentadeuterobenzhydrylamine, C6D5*CHPh*NH2,prepared by reducing the oxime of pentadeuterobenzophenone,obtained by a Friedel-Crafts reaction from hexadeuterobenzene.etc. etc.48 ORQANIC CHEMISTRY.The reduction of the double bond in the side chain of ergosterolwithout disturbance of the nuclear system was accomplished in anelegant manner by A. Windaus and R. Langer.40 The adduct ofergosteryl acetate and maleic anhydride mas reduced to the dihydro-compou?d,4l which underwent thermal dissociation to give theacetate of 22-dihydroergosterol (XXI). Reduction of (XXI) withsodium and alcohol gives y-ergostenol (XXII), which is isomerisedby a palladium or platinum catalyst to the well-known a-ergostenol,containing an '( inert " double bond.42 Formula (XXIII) is nowfavoured for a-ergostenol 43 and on the basis of selenium dioxideoxidation experiments R.K. Callow 4.4 has derived an analogousstructure for the stereoisomeric a- and p-apocholic acids.HOp-Ergostenol, which arises by isomerisation of a-ergostenol withhydrochloric acid,45 has now been shown to have the structure(XXIV). P-Ergostenyl acetate was ozonised, and the ozonidesubmitted to reductive fission, followed by thermal decomposition.In this way 4G opening of ring IV was followed by splitting off of theside chain as an unsaturated aldehyde, C,,H,,O, with the productionof the acetate of a keto-alcohol, the structure of which (XXV)follows from its dehydrogenation with selenium to %methyl-p henant hrene .4340 Annalen, 1934, 688, 106.4 1 H.€3. Inhoffen, ibid., p. 81.4 2 Compare F. Reindel and E. Walter, ibid., 1928, 460, 214; S. v. Reichel,2. physiol. Chem., 1934, 226, 146.4 3 F. Laucht, ibid., 1935, 237, 236.44 J., 1936, 462; compare H. Wieland, E. Dietz, and H. Ottawa, 2. physiol.45 I. M. Heilbron and D. 0. Willrinson, J., 1932, 1708; compare I?. Reindel,46 Th. Achtermann, 2. physiol. Chem., 1934, 285, 141.Chem., 1936, 244, 194.E. Walter, and H. Rauch, Annalen, 1927, 452, 34COOK: NATURAL PRODUCTS OE* THE STEROL GBOUP. 349The Vitamin D Problem.There have been developments of outstanding importance in thisfield, and although it is evident that the problem is more complexthan was formerly suspected, we now have fairly precise knowledgeof the chemistry of at least some of the natural antirachitic vitamins.The main outlines of the chemistry of the photoisomerides ofergosterol have been established ; the structure of calciferol has beenelucidated ; new vitamins and provitamins have been preparedartificially from sterols, and the isolation of natural vitamins andprovitamins has been accomplished.Lumisterol, the first of the series of ultra-violet irradiation pro-ducts of ergosterol, appears to be stereoisomeric with ergoster01.~‘It contains intact the tetracyclic sterol ring system, as it is dehydro-genated to 3’-methyl- 1 : 2-cy~Zopentenophenanthrene~~ but unlikeergosterol it gives no insoluble precipitate with digitonin, althoughby epimerisation of their hydroxyl groups isolumisterol, dihydro-lurnisterol, and lumistanol are converted into isomerides which areprecipitated by digitonin.49 Dehydrolumisterol, obtained by milddehydrogenation of lumisterol with mercuric acetate,4’ was shownby K. Dimroth 5O to give it perhydro-derivative which differs fromlumistanol and also from ergostanol, but is identical with perhydro-pyrocalcif erol (p.35 I). If dehydrolumisterol (like dehydroergosterol)is correctly represented by formula (XXVII), the difference betweenthese two perhydro-compounds lies solely in the configuration of C,,and the experimental results are consistent with Dimroth’s con-clusion that the conversion of ergosterol into lumisterol (XXVI)consists solely in the inversion of con5guration of Clo.H.Lettrh’s s1 observation that calciferol (vitamin D,) gives no3’-methyl-l : 2-cyclopentenophenanthrene when dehydrogenatedwith selenium led him 60 a further study of tachysterol, which isintermediate between lumisterol and calciferol in the series ofirradiation products of ergosterol. This was shown to contain not4 7 I. M. Heilbron, F. S. Spring, and P. A. Stewart, J., 1935, 1221.dB K. Dimroth, Ber., 1935, 68, 539.49 A. Windaus, K. Dithmar, and E. Fernholz, Anmlen, 1932, 493, 259;60 Ber., 1936, 69, 1123.61 Anmlem, 1934, fill, 280.G. Ahrens, E. Fernholz, and W. StoU, ibid., 1932, 500, 109350 ORQANIC OHEMISTRY.three, but four double bonds (three of them conjugated). Hencetachysterol is tricyclic, which means that ring fiasion has occurred,and Lettr6 suggested that its structure is (XXVIII) or (XXIX).The essential accuracy of this conception has been demonstratedby investigations which have established the structure (XXX) forcalciferol (vitamin D2), the succeeding member in the photochemicalseries.I. M. Heilbron, K. M. Samant, and F. S. Spring 52 obtained,by oxidation of calciferol with chromic acid, an unsaturated aldehydeC21H380 (XXXI), the formation of which can only be interpretedby the assumption that fission of ring I1 has occurred in the con-version of ergosterol (XII) into calciferol. The location of thedouble bonds was elegantly shown by A. Windaus and W. Thiele,53who dehydrogenated the adduct of calciferol with maleic anhydride(XXXII), and obtained p-naphthoic acid with palladised charcoal,and 2 : 3-dimethylnaphthalene with selenium.Further, a saturatedketone, C,,H,,O (XXXIII), was obtained by ozonisation of thedihydro-derivative of this maleic anhydride adduct :52 Nature, 1935, 135, 1072.(xxxrI1.)63 Ammlm, 1935,521, 160COOK: NATURAL PRODUCTS OF THE STEROL GROUP. 351Pinally, Heilbron and his collaborators 54 and A. Windaus and W.Grundmann 55 isolated a keto-acid, C13H2003 (XXXIV), from theproducts of direct ozonolysis of calciferol (XXX). The chemicalevidence appears conclusive, although J. D. Bernal and D. Crow-foot 56 find difficulty in reconciling the X-ray crystallographic datawith this formdation.In connexion with these investigations the degree of unsaturationof calciferol and its derivatives has been re-examined. Althoughonly three double bonds could be detected in calciferol by perbenzoicacid titration ,s7 microhydrogenation has demonstrated 58 thepresence of the four double bonds required by the tricyclic structure(XXX) of the vitamin. Furthermore, dihydrocalciferol,69 whichmay also be obtained by reduction of tnchysterol,60 has been shownto contain three double bonds by perbenzoic acid titration 61 andby refractometric measurements.60 In the thermal transformationof calciferol to pyrocalciferol and " isopyrovitamin " 621 63 thetetracyclic sterol system is re-formed (compare p.349), 3'-methyl-1 : 2-cyclopentenophenanthrene being formed by subsequentselenium dehydrogenation.60 The epimerides of di- and hexa-hydropyrocalciferol are precipitated by d i g i t ~ n i n .~ ~ Suprasterols Iand 11, which arise by further irradiation of calciferol, are alsotetracyclic, but give no crystalline products on dehydrogenation.60In the meantime, it became apparent on biological grounds thatcalciferol is not the only antirachitic vitamin. For instance,J. Waddell 64 showed that irradiated cholesterol and cod-liver oilare more effective in curing rachitic chicks than irradiatedergosterol, compared on the basis of the same number of rat units.65905.64 I. M. Heilbron, R. N. Jones, K. M. Samant, and F. S. Spring, J., 1936,s5 Annulen, 1936, 524, 295.66 Chem. and Ind., 1935, 54, 701.67 A. Windaus, 0. Linsert, A. Luttringhaus, and G. Weidlich, Annrclen,6 8 R.Kuhn and E. F. MCiller, Angew. Chem., 1934,47, 145.69 E. Fernholz, Annalen, 1932, 499, 198.60 M. Miiller, 2. physiol. Chena., 1935, 233, 223.61 S. v. Reichel and M. Deppe, ibid., 1936, 239, 143.68 F. A. Askew, R. B. Bowdillon, H. M. Bruce, R. K. Callow, J. St. L.6s P. Busse, 2. physiol. Cherra., 1933, 214, 211.64 J . Biol. Chem., 1934,105, 711 ; for a discussion of " The Multiple Natureof Vitamin D " see C. E. Bills, Cold Spring Harbor Symposia on QuantitativeBiology, 1935, 3, 328.65 See also 0. N. Massengale and M. Nussmeier, J . Bid. C'hem., 1930, 87,415, 423; A. F. Hesa and G. C. Supplee, Proc. SOC. Exp. Biol. Med., 1930,27,S a m , Amer. J . Pharm., 1936,108,237.1932,492, 226.Philpot, and T. A. Webster, Proc. Roy. SOC., 1932, B, 109,488.609; M.J. L. Doh, 2. V'itMninf~t~h., 1936, 5, 161; A. Black a d €€. L352 ORGAN10 CHEMISTRY.The double bond in the side chain of calciferol is evidently notessential for activity, for 22-dihydroergosterol (p. 348) acquiresantirachitic properties on irradiati~n.~o This led to the suggestion 66that the analogous derivative of cholesterol, without the additionalmethyl group of the side chain, might be the provitamin normallypresent in cholesterol. This compound (XXXVI), for which theterm 7-dehydrocholesterol was suggested by C. E. Bills,64 wasprepared from cholesterol by A. Windaus, H. Lettr6, and Fr.Schenk O7 by oxidation of cholesteryl acetate to the 7-keto-compound(XXXV), followed by reduction with aluminium isopropoxide, andpyrolysis of the dibenzoate of the resulting A5-cholestene-3 : 7-diol.In a similar manner sitosterol and stigmasterol 69 have beenconverted into 7-dehydro-derivatives. In its absorption spectrum,07its photochemical oxidation and dehydrogenation, and its con-version into a series of dihydro-compounds, y-, a-, and ~-cholesten~ls,~~7-dehydrocholesterol shows a very close resemblance to ergosteroland 22-dihydroergosterol, and it acquires powerful antirachiticproperties on irradiation.The vitamin so formed has been isolatedin the pure state by A. Windeus, Fr. Schenk, and F. v. Werder 71and has been termed vitamin D,. Moreover, the irradiation pro-ducts of both 22-dihydroergosterol and 7-dehydrocholesterol arejust as effective in curing rachitic chickens, on the basis of thenumber of rat units which they contain, as the vitamin D of cod-liver oil and irradiated crude cholesterol.72 Irradiated 7-dehydro-sitosterol has antirachitic properties, but is less active than irradiatedergosterol, and it is remarkable that the antirachitic activity ofirradiated 7-dehydrostigmasterol is either feeble or nil ; for thissterol differs from ergosterol only by the presence of an additionalmethyl group in the side chain.The isolation from natural sources of the provitamin 7-dehydro-cholesterol (XXXVI), and also its irradiation product vitamin D,,6 6 R.K. Callow, Sei. J . Roy. Co2l. Science, 1934, 4, 41.6 7 Annalen, 1935, 5f10, 98.6 * W. Wunderlich, 2. phylsiol. Chem., 1936, 241, 116.69 0.Linsert, ibid., p. 125.70 Fr. Schenk, K. Buchholz, and 0. Wiese, Ber., 1936, 69, 2696.7 1 2. phy8iOE. Chem., 1936, 2 4 , 100.72 W. Grab, ibid., 1936, 243, 84COOK: NATURAL PRODUCTS OF !EIE STEROL GROUP. 353has now been achieved. Using the method of chromatographicadsorption on alumina and working with a cholesterol of unspecifiedorigin, containing as much as 4.5% of provitamin D, estimated fromthe intensity of its characteristic ultra-violet absorption, A. G. Boer,E. H. Reerink, A. van Wijk, and J. van Niekerk 73 isolated pure7-dehydrocholesterol. Actiniasterol, a sterol isolated in the previousyear by E. Klenk and W. Diebold 74 from the fat of the sea anemone,shows very close resemblance in its recorded properties to 7-dehydro-cholesterol, except that the optical rotations, measured in differentsolvents, show considerable divergence.Vitamin D,, which hasalmost the same absorption spectrum as calciferol (XXX) andpresumably has an analogous structure, was isolated from tunny-liver oil by H. Bro~krnann.?~ This is clearly not the only naturalvitamin, however, as A. Windaus and 0. Stange 76 have nowisolated ergosterol from cholesterol prepared from egg-yolk, althoughthese authors point out that ergosterol is not necessarily synthesisedby the hen, as there is e~idence,~7 which they could corroborate,that ergosterol, fed to hens in small quantities, is gradually absorbedand appears again in the eggs. There is evidence of the existenceof other antirachitic vitamins of a type chemically distinct fromcalciferol and vitamin D,.78Bile Acids.The stereochemical relationships of the bile acids have been tosome extent elucidated. Both lithocholic acid 79 and hyodeoxy-cholic acid 80 have been shown to belong to the epicoprosterol series(hydroxy-group at C, in the trans-position with respect to the methylgroup a t C,, ; cis-fusion of rings I and 11). Presumably this is alsotrue of the other bile acids. By analogy with the varying capacitiesof lactonisation shown by stereoisomeric hydroxycyclohexanecar-boxylic acids H. Lettri: 81 concluded that the hydroxyl group at C7of cholic and chenodeoxycholic (= anthropodeoxycholic) acids is inthe trans-position to the methyl group at Clo. The validity of this73 Proc. K. Akad. Wetensch.Amsterdam, 1936, 39, 622.74 8. physiol. Chem., 1935, 236, 141.75 Ibid., 1936,241,104; see also E. J. H. Shons and T. F. Zucker, J. Amer.76 2. physiol. Chem., 1936, 244, 218.7 7 R. Schoenheimer and H. Dam, ibid., 1932, 211,241 ; W. Menschick and78 0. Rygh, Nature, 1935, 136, 552.7B I,. Ruzicka and M. W. Goldberg, Hdv. Chim. Acta, 1935,18, 668.80 0. Dalmer, F. v. Werder, H. Honigaann, and K. Heyns, Ber., 1935, 68,81 Ibid., p. 766.Chem. Xoc., 1936, 58, 2655.I. H. Page, ibid., p. 246.1814.REP.-VOL. XXXIII. 354 ORGANIU CHEMISTRY.(XXXVII.)Me I(XXXVIII. )E02C PTy i iI co-0argument is supported by recent work on ursodeoxycholic acid,which is shown to be stereoisomeric with chenodeoxycholic acid,differing from it in the configuration of the hydroxyl group at C7.82Hypobrornite oxidation of chenodeoxycholic acid (XXXVII) givesa hydroxy-tricarboxylic acid which readily passes into a lactonicacid,s8 but the hydroxy-tricarboxylio acid similarly formed fromursodooxycholic acid (XXXVIII) shows no tendency to Iacfonise :P 3Me ~-CH,--CH,--CO,HThe isolation of new bile acids has been recorded,s4 and by aconvenient new method 3'.Cortese and L. Bauman 85 have preparedthe naturally occurring conjugated bile acids, glycocholic andglycodeoxycholic acids. Recognition that the hydroxyl group atC, of the bile acids has the opposite configuration from that in thesterols has led to speculation concerning the possible mode of bio-logicd conversion of cholesterol into the bile acids.The fact thatoholestenone is hydrogenated to coprostanone and then, in neutralsolution, to epicoprosterol 86 supports the view that these ketones,which have not been isolated from natural sources, are concernedin cholesterol rnetaboli~m.~~ In attempting to secure evidence onthis point R. Schoenheimer and his collaborators have adopted theinteresting device of " labelling " the molecule by introducingdeuterium. Cholestenone (V) was reduced with deuterium, and82 T. Iwasaki, Z. phpiol. Chem., 1936, 244, 181.83 A. Windaus and A. van Schoor, ibid., 1926, 167, 181.84 H. Wieland and S. Kishi, ibid., 1933, 214, 47; W. Gumlich, d6a'd., 1933,215, 18; E. Pernholz, ibid., 1935, 232, 202; S. Kishi, dbid., 1936, 238, 210.85 J . Amer. CRern. SOC., 1935, 57, 1393; J .Bid. Chem., 1936,113, 779.86 L. Ruzicb, H. Briingger, E. Eichenberger, and J. Meyer, Hdv. C'hin~.87 Compare 0. Rosenheim and T. A. Webster, Nature, 1935, 136, 474.Actct, 1934,17, 1407.CO,COOK: NATURAL PRODUCTS OJT TEE STEROL GROUP. 356when the resulting coprostanone-4 : 5-d, was fed to animals theyexcreted coprosterol containing deuferium,B* in confirmation of theview that chole~tenons and coproatanone are intermediates in thetransformation of cholesterol into coprosterol. However, when thesame coprostanone-4 : 5-d, was injected into dogs with bile fistulas,the Cholic acid subsequently recovered from the bile contained nodeuterium, so coprostanone had passed through the liver withoutthe formation of cholic acid.8Q Naturally, this negative evidencedoes not prove that the bile acids are not formed in the body fromcholesterol, with oxidative removal of three carbon atoms from theside chain.Of interest in this connexion is scymnol, present inthe bile of sharks, for which formula (XXXIX) is probable?* Ifthe hydroxyl group at C, is carrectly placed, a poinf which has notbeen established with certainty, this alcohol would appear torepreBent an arrested stage in the transition from cholesterol to thebile acids. A compound of somewhat similar type, containing anoxidised ergosterol side chain, is trihydroxybufosterocholenic acid(XL) isolated from the winter bile of toads; this acid was ozonisedto 3 : 7 : 12-trihydroxybisnorcholanic acid,91 which was also obtainedby “ Wieland degradation” of cholic acid.K. Wieland andG. HankeQ2 have commenced a study of the weak acids of ox-bileand have isolated an acid of the probable formula C,,H,,03, whichthey term sapocholic acid. The properties of this interesting acidare very similar to those of pyroquiiiovaic particularly inrespect to the reaction with bromine, which is characteristic of the88 R. Schoenheimer, D. Rittenberg, and M. Graff, J . Biol. Chem., 1935,111,183.89 R. Schoenheimer, D. Rithnberg, B. N. Berg, and L. Rousselot, ibid.,1936,115,635.90 A. Windaus, W. Bergmann, and G. Khig, 2. physiol. Chem., 1930, 189,91 T. Shimiza and T. Oda, ibid., 1934, 237, 74; T. S k i m and T. Kazuno,9% lbid., 1936, 241, 93.93 H. Wieland, A. Hartmann, and H. Dietrich, AnnaZm, 1936, 528, 191.148; R.Tschesche, {bid., 1931, 203,263.&id., 1936, 244, 167356 ORGANIC CHEMISTRY.triterpene sapogenins such as hederagenin and oleanolic acid. Itmay be that the triterpenes have a closer structural and biogeneticrelationship to the sterol group than has hitherto been demonstrated.Sex Hormones.It is now recognised that the terms '' male and female hormones "are unfortunate, as both groups of hormones are present in both sexes,and the biological effects of a hormone are not restricted to thereproductive organs of one sex. Moreover, the same compoundmay give rise t o the characteristic biological effects of both male andfemale hormones. In general, however, the male hormones areunderstood to be those compounds of which the essential functionis to promote growth of the secondary male organs, e.g,, the combin the capon or the seminal vesicles of castrated male rats, and thefemale hormones are those which are highly potent in promotingthe normal activities of the female reproductive organs, e.g., oestrusand uterine enlargement in rodents, An extraordinarily largenumber of physiologically active compounds have been preparedby the methods made available by the work of Ruzicka,g4 and manyinteresting studies have been made of the effect of changes ofstructure and configuration on the biological activity.95 The resultshere reported must be restricted largely to an outline of the structuralfeatures of the natural hormones.The oxidation of epicholestanol to androsterone was followed bythe oxidation of sitosterol,96 ch~lesterol,~~~t o the dehydroandrosterone which Butenandt 99 had isolated frommale urine.During oxidation of the sterols the hydroxyl group wasprotected by acetylation, and the double bond by addition ofbromine. These degradations showed that dehydroandrosterone(XLI), unlike androsterone, has the cis-configuration of the hydroxylgroup with respect to the methyl a t Cloy a conclusion already drawnby W. Schoeller, A. Serini, and M. Gehrkel from the fact thatdehydroandrosterone, but not androsterone, gives an insolublecompound with digitonin. Hence androsterone cannot be formedin the body by direct reduction of dehydroandrosterone. epiDehy-g p Ann. Reports, 1934, 31, 207.96 See, for example, E.Tschopp, Arch. internat. €'harm. Thdrap., 1936, 52,9 6 R. V. Oppenauer, Nature, 1935,135,1039.97 L. Ruzicka and A. Wettstein, Helv. Chim. Acta, 1935, 18, 986; E. S.Wallis and E. Fernhole, J . Amer. Chem. SOC., 1935, 67, 1379, 1504; I. A.Remesov, Compt. rend. Acad. Sci. U.R.S.S., 1936,1, 261.9s L. Ruzicka, W. Fisoher, and J. Meyer, Helv. Chim. Acta, 1935, 18, 1483.O9 A. Butenandt and H. Dannenbaum, 8. phyeiol. Chem., 1934, 229, 192.and stigmasterol 9 8 ~381 ; R. Deanesly and A. S. Parkes, Biochem. J., 1936,30,291.Naturui.s8., 1936, 23, 337COOK: NATURAL PRODUCfTS OF THE STEROL GROUP. 357droandrosterone has recently been obtained by L. Ruzicka andM. W. Goldberg2 as a product of partial hydrogenation with anickel catalyst of A5-androstenedione (compare formula VII) .(XLII.)The unsaturated chloro-ketone which is formed from dehydroandro-sterone by the action of hydrochloric acid used in the course ofisolation 99* 3 has also been prepared from cholesteryl chloride 4and directly from dehydroandr~sterone.~Certain biological and cheinical discrepancies rendered it uiilikelythat the hormone present in testicular extracts was either andro-sterone or dehydroandrosterone.The biological evidence dependedupon differences of activity towards capons and rats and was of asimilar nature to that which led to the conclusion that calciferol wasnot the vitamin D of irradiated crude cholesterol (p. 351). Moreover,T. F. Gallagher and F. C. Koch 7 showed that the active principle ofthe testis is destroyed by boiling alkali.This suggested an ap-un-saturated ketone and led to the preparation of androstene-3 : 17-dione (XLII),8 which had the expected high activity in rats. When,shortly afterwards, the testicular hormone (testosterone) was isolatedin the crystalline state and shown not to be androstenedione,”the alternative structure of A4-androsten-17-ol-3-one (XLIV) cameinto consideration; it was known already that reduction of the17-keto-group of androsterone results in a three-fold increase inbiological activity.1° This structure was rapidly confirmed by the2 Helv, Chim. AcM, 1936, 19, 1407.3 A. Butenandt, H. Dannenbaum, G. Hnisch, and €I. Kudszus, 8. phy&ol.4 R. E. Marker, F. C. Whitmore;O. Kamm, T. S.Oakwood, and J. M.6 A. Butenandt and W. Grosse, Ber., 1936,69,2776.6 See, for example, E. Dingemanse, J. Freud, and E. Laqueur, Nature,7 Endccrimology, 1934, 18, 107; J. Bwl. Chem.., 1924, 104, 611.8 L. Ruzicka and A. Wettsteiiij Helv. China. Acta, 1935,18,986; A. Buten-andt and G. Hanisch, Ber., 1935, 68, 1859; E. S. Wallis and E. Fernholz,J . Amer. Chem. SOC., 1935,57, 1511.9 K. David, E. Dirigemanse, J. Freud, and E. Lrzquour, 2. physwl. C’hem.,1935, 233, 281.10 L. Ruzicka, M. W. Goldberg, and J. Meyer, Helv. Chirn. Actct, 1935, 18,210.Chem., 1935,237, 57.Blatterman, J. Amer. Chern. SOC., 1936, 88,338.1935,135, 184358 ORGIANIO OHEMISTRY.oxidation of testosterone to androstene-3 : 17-dione (XLII) 11 andby the preparation of testosterone from dehydroandrosterone, inaccordance with the following scheme l2 :CrO, ondibromlde, ‘followed bydebrominationaod hydrolysisThe yields were subsequently much improved by the use of mixedesters of A5-androstene-3 : 17-dio1 (XLIII).r3 This diol was shownby A.Butenandt l4 to have pronounced oestrogenic activity as wellas male-hormone action; thus a, single molecule has two types ofbiological activity which are in some respects mutually antagonistic.Even more striking is the influence of the position of a double bondon the activity of androstenedione, for, whereas the A4-compound(XLII) has powerful male-hormone activity but no oestrogenicactivity, the isomeric Al-compound (XLV) is fairly strongly oestro-genic but has no male hormone action.15(XLV.)A Ogata and S.Hirano l6 isolated from testicuIar extracts acrystalline male hormone which differs in its properties from testo-sterone. L. Ruzicka and A. Wettstein l2 have suggested that this11 K. David, Acta Brew. Nierl., 1935, 5, 85.12 A. Butenandt and G. Hrtniach, Ber., 1935, 68, 1869; L. Ruzicka andA. Wettstein, Helv. Chim. Acta, 1936,18, 1204.13 L. Ruzicka, A. Wettstein, and H. Kagi, &bid., p. 1478.l4 Nuturwhe., 1936, 24, 15.16 A. Butenandt and H. Dannenberg, Ber., 1936, 60,1158.16 J . Pham. SOC. Japan, 1934, 54, 199UOOK: NATURAL PRODUCTS OF THE STEROL GROUP. 359ia androstane-3 : 17-dione (XLVI), which can be prepared by oxid-ation of androrsterone.lO* 17The most active natural male hormone is testosterone (XLIV),which shows high activity both in capons and in rats. It was shownby Laqueur and his collaborators that testosterone displays itsmaximum biological activity only in the presence of an “X-sub-stance ” present in testicular extracts, and consequent upon investiga-tions in which it was shown that many fatty acids can replace this“ X-substance ” l8 it was shown that by esterification of testosteroneits activity may be much enhanced and also considerably prolonged.This is especially so with the esters of the lower fatty acids and themost active of these esters is the propionate,lg which is now availablefor clinical use under the name of “ perandren.” It is evident thatthe function of the fatty acid or the “ X-substance ” is to promoteabsorption of the testosterone, the optimum effect being shown byan ester of testosterone which is slowly hydrolysed with constantproduction of biologically effective quantities of the hormone.Thisview is confirmed by the observation that, although 17-methyl-testosterone is highly active, its acetate, which contains a verydifficultly hydrolysable tertiary ester group, is completelyinactive.20In attempts to isolate cortin, the hormone of the adrenal cortexnecessary for the maintenance of life, E. C. Kendall, T. Reichstein,and 0. Wintersteiner, and their respective associates 21 haveisolated several crystalline compounds, some of which are apparentlyrelated to the pregnane (C2J group of sterol derivatives. One ofReichstein’s compounds, adrenostcrone, was an ap-unsaturateddiketone, CIBHB4O3 or Cl9H2,O3, having comb-growth promotingactivity.Reichstein also showed that three of his other compoundscould be degraded to the same saturated diketone, C19H2,0, orC19H2803, which had strong male hormone action in the capon test.This diketone, for which a structure of type (XLVII) is suggested,was reduced to 17-androstanone (XLVIII) and androstanc.1’ A. Butenandt and K. Tscherning, 2. physwl. Chem., 1934, 229, 185.1* K. Miescher, A. Wettstein, and E. Tschopp, Schweiz. med. Woch., 1936,66,310; Biochem. J., 1936,30, 1970.1Q L. Ruzicka and A. Wettstein, Helv. Chim. Acta, 1936, 19, 1141; K.Miescher, A. Wettstein, and E. Tsohopp, Biochem. J . , 1936, 30, 1977; A. S.Parkes, Lancet, 1936, 231, 674.20 Statement by Dr.K. Miescher at the meeting of the Biochemical Societyon December llth, 1936.2 l H. L. Mason, C. S. Myers, and E. C. Kendall, J. Biol. Chem., 1936, 114,613; 116, 267; T. Reiohstein, Helv. Chim. Acta, 1936, 19, 29, 223, 402, 979,1107 ; T. Reichstein and A. Goldachmidt, ibid., p. 401 ; 0. Wintersheher andJ. J. PWner, J . Biol. C‘hem., 1935, 111, 599; 1938, 116, 291360 ORGANIC CHEMISTRY.A compound, C21H2805, isolated by both Kendall and Winter-steiner, 'was stated to have qualitatively the biological action ofcortin by Kendall, who degraded it to a ketone, C19H2403, havingmale hormone activity. This and other observations support theview that cortin belongs to the pregnane-androstane group." Ofinterest in this connexion is the isolation from the urine of a manwith an adrenal tumour of relatively large amounts of an unsaturatedketone, C19H260, which was hydrogenated to 17-androstanone(XLVIII).23 The unsaturated ketone has since been shown (un-published experiments) to be A3: 5-androstadien-17-one.Thiscompound could be formed, during the acid hydrolysis used in itsisolation, by dehydration of epidehydroandrosterone (comparep. 342).I n view of the confusion introduced into the earlier literaturedealing with the oestrogenic hormones by the use of many names forthe same substance it is satisfactory that the European repre-sentatives a t the Second Conference on Standardisation of SexHormones agreed 23 to adopt the following nomenclature for thesehormones : hydroxy-ketonic form = oestrone ; trihydroxy-form =oestriol ; dihydroxy-form = oestradiol.The structures of thesehormones, and also of equilin and equilenin, have been establishedin every When, for instance, the methyl ether of oestradiol22 H. Burrows, J. W. Cook, and F. L. Warren, Chem. and Ind., 1936, 55,1031.23 Quart. Bull. Hlth. Org., League of Nations, 1035, 4, 625 ; see also J . Amer.x e d . Assoc., 1936,107, 1221.24 A. Cohen, J. W. Cook, and C. L. Hewett, J., 1935,445; W. Dirscherl andF. Hanusch, 2. physiol. Chem., 1935, 233, 13; 230, 131; J. W. Cook andE. Roe, Chem. and Ind., 1935, 54, 501. * One of Reichstein's compounds (" substance H ") was stated to be anap-unsaturated ketone, C18H2101 or C2,H,,0, (Helv. Chim. Acta, 1936, 19,1107).This has now been freed from a small amount of higher-meltingcontaminant, and the pure ketone, m. p. 180-182°, was found to have in avery high degree the biological activity of the cortical hormone (P. de Fremery,E. Laqueur, T. Reichstein, R. W. Spanhoff, and I. E. Uyldert, Nature, 1937,139, 26). It is stated in this important paper that the constitution of thehormone has been elucidated except for a few details, and it is evident fromthe name, corticosterone, which these authors give to the compound, that theyare satisfied that it is a ketone of the sterol groupCOOK : NATURAL PRODUCTS OF THE STEROL GROUP. 361(XLIX) was dehydrated, and the product dehydrogenated, therewas formed 7-methoxy-3'-met hyl- 1 : 2 - cyclopentenophenant hrene(L), identical with a synthetic specimen.By these and similar reactions in which dehydration of carbinolsof type (XLIX) is accompanied by methyl migration it was shownthat the earbonyl group of oestrone, equilin, and equilenin must be atC1,, and the quaternary methyl group a t CIS.The other structuralfeatures had been proved alreadyYz5 with the exception of theposition of the ethylenic linkage of equilin, which is now placed atC7 : (compare formula XLIX).The degradation of ergosterol (XII) to oestrone (LII) has beenaccomplished by R. E. Marker, 0. Kamm, T. S. Oakwood, andJ. F. Laucius,2G who reduced Honigmann's dehydroneoergosterol(XIV) to a tetrahydro-compound (LI) in which the phenolic hydroxylgroup is still present, so that, contrary to all analogies, ringbeen reduced.7-I1 has(LIT.)Oestrone (LTI) was isolated after oxidation of the acetate of (LI)with chromic acid.These reactions demonstrate only a partialstereochemical correspondence between the sterols and the oestro-genic hormones, for it is possible (though unlikely) that the con-figurations of the carbon atoms 8 and 9 of (LII) are different fromthose found in the original ergosterol.Both stereoisomeric oestradiols (XLIX), 111.p.'~ 172" and 209",which are formed by reduction of oestrone (LIQY2' have been isolatedfrom mares' urine.28 One of these (the principal reduction product,25 Ann. 12eports, 1934, 31, 214.26 J . Amer. Chem. Soc., 1936, 58, 1503 ; see, however, A. Windaus and M.27 E. Schwenk and F.Hildebrandt, Naturwiss., 1933, 21, 177.28 0. Wintersteiner, E. Schwenk, and B. Whitman, Proc. Xoc. Exp. Bid.Med., 1935, 82, 1087; see also 0. Wintersteiner, E. Schwenk, H. Hirschmann,and B. Whitman, J . Amer. Chem. Soc., 1936, 58, 2652.Deppe, Ber., 1937, 70, 76362 ORQANIU OHEMISTRY.m.p. 172") has been isolated from the ZiquorfoZZicuZi of sows' ovaries 29and is evidently the true follicular hormone. Its oestrogenic activityis several times that of oestrone.It is unlikely that the sex hormones are present in urine in thefree state, and the water-soluble complex of oestriol has beenisolated and shown to be probably a monoglucuronic acid 30; theglucuronic acid of pregnandiol 31 has also been isolated from humanpregnancy urine.32An unexpected development in the field of oestrogenic hormoneswas the isolation from ovarian tissue by R.H. Andrew and F.Fenger 33 of a crystalline nitrogenous compound which gave adelayed but prolonged oestrous response in rats in doses of 10-5 mg.( i e . , about 1/50 of the dose of oestrone necessary for oestrogenicaction). If the formula C,,H,102N suggested by analysis is correct,this compound cannot be a tetracyclic sterol derivative.Cardiac Aglycones.The chemistry of these substances was reviewed in these Reportsin terms of the modern structures in 1934, and more recent work,mainly by R. Tschesche, has amply confrmed the main structuralfeatures, and has filled in many of the details.Digoxigenin, a digitalis aglycone containing one tertiary and twosecondary hydroxyl groups, has not been correlated with the othermembers of the group, but resembles digitoxigenin very closely.Structure (1,111) is favoured for digoxigenin, the secondary hydroxylCH,*CO\O$!=zCH'(LIII.) H 2 e p i f q H*$lvHgroup being placed at C, mainly because no other position can bereadily reconciled with the chemical proper tie^.^^R. Tschesche 35 has shown that thevetigenin differs from uzarigenin29 D.W. MacCorquodale, S. A. Thayer, and E. A. Doisy, Proc. SOC. EXP.30 S. L. Cohen and G. F. Marrian, Biochem. J., 1936, 30, 57; S. L. Cohen,31 See Ann. Reports, 1931, 28, 237.32 E. M. Venning and J. S. E. Browne, Proc. SOC. Expo Biol. Med., 1936, 34,33 Science, 1936, 84, 18; Endrocrinology, 1936, 20, 563.34 S. Smith, J., 1935, 1305; R.Tschesche and K. Bohle, Bw., 1936, 09, 793,36 Hw., 1936, 69, 2368.Biol. Med., 1935, 32, 1182; J . Biol. Chem., 1936, 115, 435.G. F. Marrian, and A. D. Odell, ibid., p. 2250.792COOK : NATURAL PRODUCTS OF THE STEROL QROUP. 363(LIV) only in the configuration of C5 ; in thevetigenin there is acis-fusion, and in uzarigenin a tram-fusion of rings I and 11, and inboth genins the hydroxyl group at C, occupies the cis-position withrespect to the methyl at Clo. Digitoxigenin differs from them inthe latter respect; the C, hydroxyl group is trans to the methyla t Cl0, and there is a, cis-locking of rings I and 11. These stereo-chemical relationships suggested that the low biological activityof uzarin is due to the trans-fusion of rings 1 and 11, and as W.A.Jacobs and R. C. Elderfield 36 had suggested a similar confiaurationfor strophanthidine and probably also periplogenin, the latterquestion was reconsidered by R. Tschesche and K. B0hle.~7 Bysubmitting di h ydrostrophant hidine to the c yanoh ydrin synthesis ,W. A. Jacobs and R. C . EIderfield38 had obtained a hydroxy-acidwhich readily undergoes lactonisation involving the hydroxyl a tC,. Tschesche and Bohle infer from models that such a lactone (LV)can only be formed if there is a cis-fusion of rings I and 11.I 4-0,(LVII.)It is concluded that both strophanthidine and periplogenin havecis-fusions of rings I and 11, and that this configuration is presentin all the highly active heart poisons of the digitalis group.Sarrnent~genin,~~ a genin from the seeds of Stroplimnthus sar-mentosus, and other species of Strophanthus which have not beenidentified with certainty, has been converted by R.Tschesche andK. Bohle40 into a saturated lactone identical with that similarlyobtained from digitoxigenin by A. Windaus and G. Stein.41 Assarmentogenin gives no precipitate with digitonin, the hydroxylgroup assumed to be a t C, should be trans to the methyl group atClo. The corresponding diketone, sarmentogenone , like digoxi-genone, contains a non-reactive carbonyl group, which is likewise36 J . BioZ. Chem., 1935, 108, 506.37 Ber., 1936, 69, 2443.38 J . Biol. Chem., 1936, 113, 625.39 W. A. Jacobs and M. Heidelberger, ibid., 1929, 81, 765; R. Tschesche,40 Ber., 1936, 69, 2497.Ber., 1935, 68, 423.41 Ber., 1928,61, 2436364 ORGANIC CHEMISTRY.placed at Cll, and it is inferred that sarmentogenin is a stereo-isomeride of digoxigenin (LIII), differing only in the configurationabout C,.It is considered likely that in digoxigenin the con-figuration of C, is that of the sterols, since the genins of the glycosidesdigitoxin and gitoxin, from the same plant, have this configuration,and that sarmentogenin has the opposite configuration. If thisconception be correct, sarmentogenin is unique among the naturalproducts related to the sterols, in that rings I1 and I11 would belocked in the cis-position.The anomalous position of scillaridin-A has been partly removedby the demonstration 42 that this aglycone contains 84 carbonatoms in its molecule and not 25 as previously supposed, and thata-scillanic acid is identical with aZZocholanic acid.43Correlation of the toad poisons with the plant heart poisons hasbeen established by the dehydrogenation of cinobufagin to 3'-methyl-1 : 2-cycZ0pentenophenanthrene.~~ Nolecular weight determinationsof cinobufagin and two derivatives, employing X-ray crystallo-graphic measurements, have shown45 tha-t, this genin has theformula C26H3406, in close relationship to bufotalin C26H3606.46Chrysene has been obtained by selenium dehydrogenation ofb ~ f o t a l i n , ~ ~ and a provisional structure (LVI or LVII) has beenassigned to bufotalin by H.Wieland, G. Hesse, and R. Huttel,4?who discuss its relationship to the other toad poisons.Essentiallythe same formulation has been proposed for cinobufagin by R.Tschesche and H. A. Offe,48 who leave open the position of theacetoxy-group and the additional double bond.Xaponins.These are glycosides of plant origin which have the property offorming colloidal aqueous solutions which foam on shaking. I naddition, they are able to effect hBmolysis of the red blood cells,even in high dilution. Few of them are known in the pure state,but the sepogenins which result from their hydrolysis have beenwell characterised. These fall into two groups, of which onecontains such triterpenes as hederagenin and oleanolic acid ; theseare dehydrogenated by selenium to mixtures of naphthalene and42 A. Stoll, A. Hofmann, and 3.Peyer, Helv. Chim. Acta, 1935, 18, 1247.43 A. Stoll, A. Hofmann, and A. Helhstein, ibid., p. 644.4 4 €I. Jensen, J. Amer. Chem. SOC., 1935, 57, 2733; R. Tschesche arid45 ID. Crowfoot, Chem. and Ilzd., 1935,54,568; D. Crowfoot and H. Jensen,46 H. Wieland and G. Hesse, Alznalen, 1935, 517, 22.4 7 Ibid., 1936, 524, 203.48 Ber., 1936, 69, 2361.13. Offe, Ber., 1935, 68, 1998.J . Amer. Chent. SOC., 1936, 58, 2018COOK : NATURAL PRODUCTS OF THE STEROL GROUP. 365picene homologues, and do not come within the purview of thisreport. The other group contains sapogenins which are relatedin structure to the cardiac aglycones and sterols; some of thecorresponding saponins occur with the cardiac glycosides in theleaves of Digitalis purpurea. The most important genins fromdigitalis are digitogenin, C,,H4405, gitogenin, c&&&,, and tigo-genin, C2,Hd403, derived from digitonin, gitonin, and tigonin,respecti~ely.4~ Sarsasapogenin, C327H4403,49 from sarsaparilla root,has also been extensively investigated. An isomeric compound,smilagenin, has recently been de~cribed.~O It is surprising that thesegenins should be related to the characteristic animal sterol,cholesterol (C,,H,,O), rather than to the phytosterols, which contain29 carbon atoms in their molecules.W.A. Jacobs and J. C. E. Simpson showed that both sarsasapo-genin 51 and gitogenin 52 give, on dehydrogenation with selenium,3’-methyl-1 : 2-cyclopentenophenanthrene and a ketone, C,H,,O,not methyl isohexyl ketone, which evidently represents a side chaincommon to these genins.The close structural relationship betweenthe three digitalis genins was shown by R. Ts~hesche,~~ who foundthat chromic acid oxidation of both gitogenin and tigogenin leads,by opening of ring I, to gitogenic acid, which was also obtained byWolff-Kishner reduction of the keto-dicarboxylic acid arising fromthe oxidation of digitogenin. Digitogenin, gitogenin, and tigo-genin confain respectively three, two, and one secondary hydroxylgroups, the remaining two oxygen atoms being present in oxiderings.54The relationship of the genins of the digitalis group to the sterolswas completely demonstrated by R. Tschesche and A. Hagedorn,55who degraded the side chain of tigogenin (LVIII) and reduced thehydroxyl group in ring I (assumed to be at C,) with the formationof aetioctZZobilianic acid (LIX).F. A. Askew, S. N. Farmer, andG. A. R. Kon 50 conclude, on the basis of surface film measurements,that the hydroxyl group of sarsasapogenin is also at C,, and not a tC,, as originally suggested by J. C. E. Simpson and W. A. Jacobs,5649 For revision of empirical formulae, see J. C. E. Simpson and W. A. Jacobs,J . Biol. Chem., 1935, 109, 573; R. Tschesche and A. Hagedorn, Ber., 1935,68, 1412.50 F. A. Askew, S. N. Farmer, and G. A. R. Kon, J . , 1936, 1399.5 1 J. Biol. Chem., 1934, 105, 501.52 J . Amer. Chem. Xoc., 1934, 56, 1424.63 Ber., 1935,68,1090; see also W. A. Jacobs and J. C. E. Simpson, J . Biol.64 compare W. A. Jacobs and E. E.Fleck, ibid., 1930,88,545; A. Windaus,56 Ber., 1935, 68, 1412.66 J . Biol. Chem., 1935, 109, 673.Chem., 1935, 110,429.2. phyeiol. Chem., 1925, 150, 205; Nach. Ge%. Wiss. Gcittingen, 1935, 89366 ORGANIC CHEMISTRY.a conclusion since supported by ohemical e~idence.~' Using themethod of Tschesohe and Hagedorn, Kon and Farmer5* havedegraded sarsasapogenin to etiobilianic acid, a result which provesthat sarsasapogenin is a ooproshne derivative, and indioates that itis stereoisomeric with tigogenin (LVIII), differing from it in theconfiguration with respeat to C,.HW(LVIII.) (LIX.)The oxidation of gitogenin to gitogenic acid shows that the secondhydroxyl group of this geain is at C, or C,, and a6 the same acid i sformed by oxidation of tigogenin (LVIII) belonging to the cholestaneseries, opening of the ring should occur between C, and C, (seep.345). This and other evidence leads to the conclusion that thesecond hydroxyl group of gitogenin is a t C,. Both tigogenin50and sarsasapogenin 5O are precipitated by digitonin, 80 that thehydroxyl group a t C, has the same configuration (cis to methyl atCI,) as in the aterols. Incidentally it is of interest that neither ofthe epimeric 4-choleaterola gives an insoluble compound withdigitonin. 59The third hydroxyl group of digitogenin is placed at C,. Theearlier work on the degradation of this genin i s reviewed by R.Tscbesche and A. HagedorrQO who interpret the reactions in termsof formula (LX). Thus tho keto-dioarboxylic acid, digitogenic acid(LXI), resulting from the chromic acid oxidation of digitogenin 61may be further oxidised by permanganate to keto-triearbozsylicacid (LXXI) in which ring I1 is opened.This is a P-keto-acid whichreadily eliminetea a molecule of carban dioxide, and by thermaldecomposition loses a secgnd molecule of carbon dioxide. Thesechanges are expressed by the following partial formulae, analogiesfor the later stages being given by the experiments of H. Lettr6,6267 Private communication from Dr. Kon.6 8 Chern. and Ind., 1936, 55, 925.59 R. Tschesche and A. Hagedorn, Ber., 1935, 68, 2247,6o Ber., 1936, 69, 797.61 See, for example, €1. KUei, Rer., 1916, 49, 701; 1918, 51, 1613; A.Windau ctnd K. Wed, Z. p h y 8 W Chem., 1922, 121, 62; -4. Windaus aridU. Willerding, ibid., 1925, 143, 33.g* Ibid., 1933, 218, 67; 221, 73TURNER : HETEROCYCLIC COl@OtTNDS.367who, for example, obtained an unsaturated hydrocarbon bypyrolysis of a keto-acid of type (LXIII) formed by oxidation ofA5- cholestene :(LXI.)(LXIII.)The evidence for the structure of the side chain present in this groupof sapogenins (see formula LVIII) has been summarked by L. F.Pieser 1 (p. 341), in which connexion reference should also be madeto the critical discussion by Tschesche and Hagedorn.60By no means the least interesting development in the chemistryof the sterol group is the recognition that there is a class of alkaloidscontaining the sterol ring system, the side chain a t C,, being utilisedin the formation of heterocyclic systems containing nitrogen.'Reference to these compounds is made in another section of thisReport.J.W. C.8. HETEROCYCLIC COMPOUNDS.Large Oxygen Rings.-Large rings containing oxygen have beenprepared for the first time by M. Stoll and W. Scherrer.1 The mono-sodium derivative of tetradecane-1 : 14-diol was treated with oneequivalent of benzenesulphonyl chloride, and the resulting ester (1)was treated with sodium in boiling benzene (the sodium, to be effec-tive in this reaction, must be very finely divided, and the authorsprepared it by passing strictly dry ammonia into a mixture of sodiumand toluene, cooled in ether and solid. carbon dioxide. When themetal had dissolved, the ammonia was allowed t o evaporate; thesodium slowly formed very reactive, minute crystals).Under theseconditions, the benzenesulphonyl derivative passes into its sodiumderivative (II), which partly cycfises to 1 : 14-0~idotetradecane(oxacyclopentadecane) (111). Since (11) can only be formed S ~ O W ~ J T ,Helv. Chim. Acta, 1936, 19, 735368 OR(3 ANIC CHEMISTRY'.(I) has plenty of time to undergo side reactions, e.g., to give (IT).As a result, the yield of (111) is poor.OH*[CH,],4*ONa + Ph*S02C1 + OH~[CH,],,*O*SO,Ph (1.)Ph*SO,Na + ICH2]1z<~3>0 (In.)1 NaO [ CH,],,*O*SO,PhNaO*[CH,],,*O*[CH,],,*O~SO,Ph (IV.) 4 (11.12OH*[CH,],,~O*SOzPh G+=OH*[CH2],,*OH + Ph*S0z*O*~CH,]l,*O~S02Pl~ -+ (1V)A second method was to begin as follows :OH*[CH,],*O*[CH2]10~C0,Me --+ C1[CH,],~O~[CK,]10*C02Me --+(CO,Et),CH*[ CH,],*O*[CH2]lo*C0,Me -+Distillation of the cerium salt of the acid (V) gave 1 : 15-oxidopenta-decan-&one (VI), and this was reduced by the Wolff-Kishner processC02H*[CH,],*O'[CH,],o.Co,H (v.)to 1 : 15-oxidopentadecane (oxacycZohexadecane) (VII).The twooxacyclocompounds are low-melting solids, with a very feeble musk-like odour ; the oxide-ketone (VI), which is isomeric with " exalto-lide " (5-hydroxypentadecoic acid lactone),, has a powerful odour ofmusk, although of a modified type.G. Salomon3 has considered the kinetics of the formation of largerings of the cyclic imine and lactone series.Naturally Occurring Oxygen Ring Compounds.-Psoralene, fromthe oil of Phoralea cory-lijolia seeds, is (VIII), since the usual degrada-tive methods (methylation ; oxidation ; methylation), lead to methyl4 : 6-dimethoxyisophthalate (IX) . A substance, ficusin, apparentlyidentical with psoralene, has been extracted by K.Okahara fromthe leaves of Picus carica.(VIII.) (IX. 1 (X.1Xanthotoxin, isolated from Fagara xanthoxgloides and variousRzctaceae, is the methoxy-derivative (X) of psoralene (ficusin) .62 L. Ruzicka, and M. Stoll, HeZv. Chim. Acta, 1928, 11, 1159.4 E. Spiith, B. L. Manjunath, M. Pailer, and H. S. Job, Bey., 1936, 69,6 BuU. Chem. SOC. Japan, 1936,11, 389.Ibid., 1936, 19, 743.1087.E. Spiith and M. Pailer, Ber., 1936, 69, 767TURNER : HETEBOCYCLIC COMPOUNDS. 369H. Raistrick, R. Robinson, and D. E. White 7 have investigated ayellow pigment, ravenelin, produced during the metabolism of theplant Helminthsporium Waoendii, Curtis, and of H .Turcicum,Passerini. The pigment is shown to be 1 : 4 : 8-trihydroxy-3-methylxanthone (XI), and is the third hydroxyxanthone to be isol-ated from natural sources, euxanthorie and gentisin being the othertwo representatives of this class.Phenuxthionin.-It has been shown * that bromination, sul-phonation, and condensation with acyl chlorides (Friedel-Crafts)occurs in the 2-position in phenoxthionin (XII), the orienting effectof the oxygen thus outweighing that of the sulphur.Reduced Dipyridinobenxenes.-Some interesting results have beenobtained by P. Ruggli and A. Staub.9 When m-phenylenediacrylicacid is nitrated, 4-nitration occurs (contrast cinnamic acid).Re-duction of the nitro-compound (XIII) is unaccompanied by cyclis-ation, suggesting that the amino-acid (XIV) has the trans-configur-ation. Methyl m-phenylenediacrylate also gives only onenitro-derivative (as XIII), which, catalytically reduced, (a) in thecold, gives the methyl ester of (XIV), and ( 6 ) in the warm, givesmethyl 2-ketotetrahydroquinoline-6-propionate (XV), ring closureoccurring spontaneously .C O,H*CH: CH()!C$:CH*C 02H C 0,H CH : CH():CH&CH* C 0 $12(XiII.) (XIV.)CH,(XVI.)CO,Me*CH,-CH,(xv.) NHIn order to introduce a second nitro-group at the outset, it was foundnecessary to reduce the m-diacrylic ester to the m-dipropionic ester.The latter was readily dinitrated to give (XVI). Reduction of thisester, curiously enough, produced (XVII), and in order to effect7 Biochem.J., 1936,30, 1303.8 C. M. Suter, J. P. McKenzie, and C. E. Maxwell, J. Amer. Chem. Soc.,9 Helv. Chim. Acta, 1936, 19, 439.1936, 58, 717370 ORGANIC CHEMISTRY.ring closure in the 6 : 7-positions it was necessary to heat (XVII) to260°, or to treat it with boiling hydrochloric acid for some time. Theproduct (XVIII) was unaffected by distillation with zinc dust, andCH, CH,C02Me*CH2*CH2 @c3 H2?A(x>c" coNH2 oc\ NH NH NH( XVII . ) (XVIII. )(XIX.)the well-known method of reduction, starting with NHGO _jN:CCl, could not be applied. Recourse was made to the classicalreduction with phosphorus and hydriodic acid under pressure,but even this reaction only gave good results within a very narrowtemperature range.The reduced dipyridinobenzene (XIX) obtained' is a-crystalline solid.E. E. T.9. ALKALOIDS.Peganine ( Vasicine) .-The optical resolution of peganinc wasoffected by E. Spath, F. Kuffner, and N. Platzer,l who thought thealkaloid probably existed in the active condition in PeganumIzarmZa, but did not succeed in isolating it as such. A. D. Rosenfeldand D. G. Kolesnikov found that the active alkaloid can be ex-tracted from the plant, and in their later paper regard their productas probably identical with the Z-peganine isolated by E. Spath andP, Kesztler from Adhatoda vasim, Nees.A simple synthesis of peganine (I) has been described : 4The interesting work of Schopf and his co-workers on synthesesunder physiological conditions " has been extended to vasicine.5It is found that o-aminobenzaldehyde, allylamine, and formaldehyde,1 Ber., 1935, 68, 1384.2 Sixth Mendele'eff Congress, 1932 ; Ber., 1936, 69, 2022.a Ber., 1936, 69, 384.4 E.Spiith and N. Platzer, ibid., p. 255.6 C. Schopf and F. Oechler, Annalen, 1936, 523, 1TURNER : A L W f D S . 371c( )+c~H~*cH:cH~NHwhen left together in aqueous solution for three days at 2 5 O , condenseas in the annexed scheme, the product (11) behg ieolated in 73%yield as the picrate :r CH*OH 1+J RCOH(11.1'S.CH2* CH:CH2a : H a NHN€I,-GE,-CH:UHt and H.CO,H ~ (y~m*cH2nca:cH2The synthesis begins at pH 4.8 and ends at pE 5.2, and proceedssimilarly in phosphate-buffered solution at pE 7. The constitution of(11) is proved by the oxidation of its picrate to the picrate of 3-allyl-4-quinazolone, prepared independently from isatoic anhydride :R.CJOIE $hen heat co 1Moreover, the oxidation of /'H2 to vbH can be effected\I3under physiological conditions, by using potassium f erricyanideand a phosphate buffer at pE 7 at the ordinary temperature.It is concluded that the actual bioksynthesis of vasicine probablyoccurs between o-aminobenzaldehyde and y-amino-a-hydroxybut-aldehyde :CHaOHCH-OHf372 ORGANIC CHEMISTRY.Since the aminohydroxybutaldehyde is unknown, the authors carriedout the analogous synthesis (citrate buffer, 4 days, p3 5) :and obtained (111) in 75-78y0 yield, as the picrate.Its constitutionwas established by its oxidation to the known compound (IV).Further, if a condensation mixture containing (111) was shaken withpalladium and hydrogen, the originally yellow solution was decolor-ised and deoxyvasicine (V) could be isolated in 18% yield, suggestingthat biogenetic synthesis probably proceeds along these lines.Theauthors think it likely that the precursor in the plant of the o-amino-benzaldehyde is tryptophan, and that of the y-amino-a-hydroxybut-aldehyde is hydroxyornithine :1c /CHO*CH( OH)*CH2*CH2*NH2 CHO*CH( OH)*CH,*CO,HC. Schopf and G. Lehmann' had already suggested that thehydroxytropine (VI) isolated by 0. Wolfes and H. Hromatka 8 fromcocaleaves owed its biogenetic synthesis to malic dialdehyde, and this,and the aminohydroxybutaldehyde, would both come from hydroxy-ornithine.This may be compared with the derivation of hygrineand cuskhygrine from ornithine.Lupin AZkaloids.-in 1931, G. R. Clemo and G. R. Ramage9synthesised octahydropyridocoline (VIII) by performing a Dieck-mann condensation on (VII). The product was not identical withnorlupinane (A) obtained from lupinine.l* Later,ll however,6 R. C. Momis, W. E. Hanford, and R. Adams, J . Amer. Chem. Soc., 1935,67, 961.Annulen, 1935, 518, 1.J., 437 ; Ann. Reports, 1931, 174.8 Mercks Jahresber., 1934, 47, 45.lo G. R. Clemo, G. R. Ramage, andR. Raper, J . , 1931, 437, 3190.l1 Idem, J., 1932, 2959TURNER : ALKALOIDS. 373qHz vH*CO,EtCH, NCH,*CH,*CH,*CO,Et (VII.)\ /CH,norlupinane (A) was obtained by cyclisation of (IX) and morerecently 12 as follows :@\CH,*CW2*CQ,Et(X-1 I ll~*c~z*C()2E~ CH, N-CH,*CO,Et \/- BrCH, CH,p 2 QH-QH2CH, N CH, HC1 CH, N CO (XI.) ( V J q +zcg 9H2 ’\’ QH )H2\ / \ / CH, CH,\ / \ /CH, CHMeThis dismisses the possibility that norlupinane (A) is (XI), and sub-stantiates the &-trans relationship of the two octahydropyridoco-lines (VIII) obtained from (VII) and froin (IX) or (X). It has beenestablished by synthesis l3 that dl-oxysparteine is (XII).K. Winterfeld and H.E. ROnsberg,l4 by oxidising a-didehydro-sparteine with chromic anhydride, have isolated p-aminopropionicacid, which is regarded as indicating the presence (see XIII) of a4 : 5-ethylenic linkage in the norlupinane ring of sparteine. Whendidehydrosparteine is treated with benzoyl chloride and alkali, anunstable benzoyl derivative is formed, suggesting tKat the secondethylenic linkage is in the ccp-position to a nitrogen atom, and isjoined t o a tertiary carbon atom.This corresponds with unsatur-ation at C9-Cll or Cll-C12.12 G. R. Clemo, W. McG. Morgan, and R. Raper, J., 1935, 1743.l3 Idem, J., 1936, 1025.1 4 Arch. Pharm., 1936, 274, 48374 ORGANIC CHEMISTRY,Ergot Alkaloids (continued from Ann. Reports, 1935, 345).-In anexamination of their proposed constitution of lysergic acid, W. A.Jacobs and L. C. Craig l5 synthesised 3 : 4 : 5 : 6-tetrahydro-4-carboline-5-carboxylic acid and 3-phenyl-4-methyltetrahydro-4-carboline-5-carboxylic acid. These substances did not respond totests characteristic of lysergic acid.Later,16 a new formula wassuggested for this substance, since the tribasic acid, Cl,H,OsN,previously described l7 gave quinoline when it was distilled withsoda-lime. The same authors have confirmed their previousconclusion that ergotamine, and therefore ergotaminine, are de-rived from ergine, proline, phenylalanine and pyruvic acid. Theyhave also isolated d-proline (as its methyl ester) by hydrolysis notonly of ergotamine but also of ergotoxine. Ergoclavine is given thenew formula C,6H,o04N4. It is possible that this alkaloid is built upfrom ergine, I-leucine and pyruvic acid, but very little is really known,S. Smith and G. M. TimmisZ0 have shown that ergometrinine,like ergometrine, is lysergic acid hydroxyisopropylamide. The sameauthors 21 have obtained from ergot a new alkaloid, ergosinine,l5 Science, 1935, 82, 421.l6 Ibid., 1936, 83, 38.l7 J.Biol. Chem., 1932, 97, 739.I* J. Org. Chem., 1936, 1, 245.8o J., 1936, 1166.Science, 1936, 81, 256.Nature, 1936, 187, 111, 1075TURNER : ALKALOIDS. 375C&0HQ505N5, which is converted by acids into the isomericergosine.R. L. Grant and S. Smith 22 have found that ergometrine exists intwo physical forms.G . W. Holden and G. R. Diver 23 have isolated from ergot yetanother alkaloid, ergomonamine, C,9Hl,0,N, and an acid (citergic),which may be ccccpy-tetrahydroxypropane-a&-tricarboxylic acid.It is now agreed 24 that ergometrine, ergotocine, ergobasine andcrgostetrine are identical.S. Smith and G. M. Tirnmisz5 have used conditions (hot alcoholicphosphoric acid) under which ergotinine changes into ergotoxinefor the conversion of ergine ([0(]5461 + 635", in pyridine) into the newisomeric base, isoergine + 2 5 O ) , and conclude that the physio-logically active (lavorotatory) alkaloids ergotoxine, ergotamine,and ergometrine contain the isoergine structure. They furthershowed that alkalis rapidly isomerise ergine and isoergine to anequilibrium mixture.Again, using the conditions (action of pyrid-ine, or hot methyl alcohol, or hot ethyl alcohol, or sodium hydroxide)effecting the change of ergotoxine into ergotinine, or, better, by theaction of hot water, the authors have succeeded in converting lysergicacid into an isomeride, isolysergic acid. The latter has [a]5461 +365", as compared with [a15461 + 49" for lysergic acid.Possiblepartial formulae are suggested for lysergic acid, based on one putforward, but since rejected, by W. A. Jacobs and L. C. Craig.26W. A. Jacobs and L. C. Craig 27 altjo point out that the existenceof the pairs of ergot alkaloids depends on the ethylenic linkage inlysergic acid, since, while methyl lysergate mutarotates in warmmethyl-alcoholic solution, its dihydro-derivative does not. A freshmethod of attacking the problem is described by these authors, whohave obtained one and the same lysergic acid by hydrolysing anyof the alkaloids, whether of the dextro- or of the Iavo-rotatory class,On the other hand, reduction (2H) of the lavorotatory alkaloidsergotoxine, ergotamine, and ergometrine, followed by hydrolysis,gave a laevoro tatory acid, called a-diliydrolysergic acid ; similartreatment of the dextrorotatory alkaloids ergotinine and ergota-minine and also of ergine gave a dextrorotatory acid, .y-.dihydroly.sergic acid.Lysergic acid is not a mixture, but when it is reduced,23 Nature, 1936, 137, 154.23 Quart. J . Pharm., 1936, 9, 230.24 M. S. Kharasch, H. King, A. Stoll, and M..R. Thompson, Nature, 1936,2 5 J., 1936, 1440.26 J . Bid. Chem., 1936, 113, 771.2 7 Ibid., 115, 227.137, 403; Science, 1936, 83, 206; Ann. Reports, 1935, 349376 ORGANIC CHEMISTRY.it gives a mixture of the above t(- and y-dihydro-derivatives. Theauthors conclude that in this reduction new centres of asymmetryare produced, and suggest that lysergic acid isCH2*CH*Co2H (XIV), since this best accounts for the pro-stability of lysergic acid in presence of alkali.The above a-dihydro-acid (from ergotoxine))=Jm2 was identical with that previously obtainedby reducing lysergic acid with sodium andamyl alcohol; its methyl ester, on reductionwith sodium and butyl alcohol, gave a-di-hydrolysergol ; but methyl y-dihydrolysergate, similarly reduced,gave a new substance, y-dihydrolysergo1, different from thep-dihydrolysergol obtained previously from ergotinine.Neithermethyl a- nor y-dihydrolysergates gave p-dihydrolysergol onreduction.Aconitine.-Some advance hats been made in the chemistry of thisdifficult alkaloid. A. Lawsoii 28 has oxidised aconitine with chromicanhydride in acetone solution, and obtained a new substance,aconitoline, C,,H,,O(NMe)(OH)(OMe),(OAc)(OBz).The author'sresults support the formula C,2H,,01,N of E. Spiith and F. Galinov-sky 29 for oxonitin. W. Freudenberg and E. F. Rogers 3O showedthat dry distillation of aconitine hydrochloride with barium hydr-oxide gave hydrocarbons, methylamine, and Z-ephedrine, the struc-ture of the last therefore probably being present in aconitine. Ithas usually been assumed that aconitine contains the NMe group,but it is now found 31 that when aconitine hydrochloride is fused withpotassium or barium hydroxide, ethylamine is formed, and whenaconitine is heated with hydriodic acid ethyl as well as methyl iodideis obtained. It is thought that the NEt group is affected when aconi-tine is oxidised to oxonitin.This would fit in with the observedformation of acetaldehyde during this oxidation. W. Freudenberg 32has also identified ethylamine among the products of distillingaconitine with barium hydroxide, and gives the alkaloid the formulaVeratrurn Alkaloids.-B. K. Blount 33 showed that the verine ofC. R. A. Wright and A. P. Luff 34 was identical with cevine (veratrid-ine being veratroylcevine) , and that cevine, when dehydrogenateddH2 \ NMe duction of two dihydro-derivatives, and for the/=\ / / \-\ / NHCl~H19(NEt)(oH)3(oMe),(BAc)(oBz)'2B J., 1936, 80.30 J . Amr. Chem. Xoc., 1936, 58, 533.31 W. A. Jacobs and R. C. Elderfield, ibid., p. 105.9.32 Ber., 1936, 69, 1962.s3 J., 1935, 122.s4 J , , 1875, 33, 341.Ber., 1930, 63, 2994; 1931, 64, 2201TURNER : ALKALOIDS. 377with selenium, ga've a base, cevanthridine, possibly a phenanthridinederivative. I n conjunction with (Miss) D.Crowfoot 36 the sameauthor isolated cevanthrol, a phenol, from the dehydrogenationmixture, and concludes further, fro& X-ray crystallographicalexamination, that cevanthridine contains a benzphenanthrenc (XV)or benzanthracene (XVI) structure. The authors regard the con-ditions employed in the dehydrogenation as insufKciently drastic tobe conducivc to ring enlargement, that is, they appear t o have con-sidered, but rejected, the idea that cevanthridine might contain amet hylcyclopentenophenanthrene skeleton.Veratrzcm album (white hellebore) contains the alkaloid jervine,NH:CaF;H,,(OH)(CR,O,:), and amorphous materials of various kindsfrom which both angelic and tiglic acids have been is0lated.~6Heliotropium and Senecio AZkaEoids.-G.Menschikov 37 isolatedfrom HeZiotropium Zasiocarpum an alkaloid heliotrine, C,,H,,O,N,which by the action of barium hydroxide gave heliotric acid,OH*C,H,,( OMe)( CO,H) (a saturated aliphatic acid), and heliotridine,C,H1,O,N. The latter 38 contains two hydroxyl groups, replace-able (thionyl chloride) by two chlorine atoms. The (unstable)dichloro-compound was converted by a series of simple reactionsinto heliotridan, C,H1,N. Later work showed that heliotrine wasreducible to hydroxyheliotridan, which was probably a tertiarya,l~ohol,3~ and that heliotridan contained a pyrrolidine ring.40 Thesame author, with V.Rubinstein$l has also isolated from Tri-chodesma incanum the alkaloid trichodesmine, C18H,,Q,hT. Thiswith alkali gave methyl isobutyl ketone, dl-lactic acid, and a sub-stance, C,W130,N, trichodesmidine, which was not identical withheliotridine, but was convertible by simple reactions into helio-tridan. Heliotridine and trichodesmidine therefore differ in theposition of the hydroxyl group and possibly also that of the ethyleniclinkage. Later 42 it was found that lasiocarpine, a second alkaloid35 J., 1936, 414.38 K. Saito, H. Suginome, and M. Takaoka, Bulb. Cizern. SOC. Japan, 1934,9, 15; K. Saito and H. Suginome, ibid., 1936, 11, 168; K. Raito and M.Takaoka, ibid., p. 172.3 7 Ber., 1932, 65, 974.38 G.Menschikov, Ber., 1933, 66, 875.39 Ber., 1935, 68, 1081.40 Ibid., p, 1555.42 G. Menschikov and J. Schdanowitsch, Ber., 1936, 69, 1110.*l Ibid., p. 2039378 ORQANIO CHEMISTRY.from Heliotropiurn lasiomrpum, was hydrolysed by alkali to angelicacid and heliotridine. I n heliotrine, only one hydroxyl group ofheliotridine is esterified (with heliotric acid) , whereas in lasiocarpineone hydroxyl group of heliotridine is esterified with angelic acid andthe other with lasiocarpic acid, C8H,,05 : this is an unsaturated acidcontaining two hydroxyl and two methoxyl groups.Xenecio pZatyphyZlus contains two alkaloids, platyphylline,C18H2,05N, and ~eneciphylline.~~ Platyphylline on alkaline hydro-lysis gave platynecic acid, OH*C,H,,0*C02H, and platynecine,C8Hl,N(OH),. The two hydroxyl groups can under certain con-ditions be replaced by chlorine, and by simple reactions the authorsconverted the dichloro-compound into heliotr idan.Apparentlyseneciphylline is also derived from this substance. The Boraginucece(Heliotropium) and Senecio alkaloids therefore contain the sameC8H15N skeleton and differ in their degree of unsaturation, theposition of the hydroxyl groups, and the nature of the attachedacids.Solanum Alkaloids.-Solanidine-t (from the potato, Solanurntuberosum), when heated with selenium, gives phenanthrcne, chry-sene, and pyridine, together with other c0rnpounds.4~ A. Soltys andI<. Wallenfels 45 have shown that solaneine, described as occurringwith solanine, solanidine, and solanthrene in S.tuberosum, is amixture of solanidine and solanine. Having found that solanidinegives a flocculent precipitate with digitonin in alcoholic solution, areaction characteristic of sterols, they further found that seleniumdehydrogenation of solanidiene (obtained by elimination of waterfrom solanidine) gave methylcyclopentenophenanthrene. Fromthis, it follows that solanidine-t is (XVII), and the authors thinkthat a possible formula for the .alkaloid is (XVIII).OH( / g q ? 1 5 N /\yjjg)O I I C XVIII . ) ( XVII . ) O I I V J (XVIII.)Solanidine-s, from S. sodomaurn, contains structure (XIX),46 afact which explains the formation of ‘‘ tetra-acetylsolanidine ” when43 A. Or&hov, Ber., 1935, 68, 650; A.Or6khov and R. Konovalowa,ibid., p. 1186; R. Konovalowa and A. OrBfiov, Ber., 1936, 69, 1908.44 H. Dieter10 and H. Rochelmeyer, Arch. Pibarn., 1935, 273, 532.4 5 Ber., 1936, 69, 811.48 cf. Oddo and G. Caronna, {bid., p. 283TURNER : ALKALOIDS. 379the alkaloid is treated with a mixture of glacial acetic acid, aceticanhydride, and concentrated sulphuric acid :CXHc,,F126<~H*0H 4 c , AcQH.(XIX.)Eblanum pseudocapsicurn (winter cherry) may, 1 ike other Xolanums,contain a gluco-alkaloid, but this is not settled. The new alkaloids,solanocapsine, C25H4,O2N2 or C,,€I,,O,N,, and solanocapsidine,probably C2BH4204N2, have been isolated from it, and the former hasbeen i~ivestigated.~’ Solanocapsine contains NH, NH,, and OH(probably as iC*OH), the second oxygen probably being a member ofa heterocyclic ring.With nitrous acid, the NH is nitrosated, thearnino-group becomes h ydroxyl, one hydroxyl group, probably theone originally present, is eliminated as water, and an ethyleniclinkage is formed. Selenium dehydrogenation of solanocapsinegives hydrocarbons, pyridine bases, and methylcyclopentenophen-anthrene. This suggests that the struetiire of the alkaloid is Lzppros-imately expressed by formula (XX).The position of the ring oxygen atom recalls the oxygen bridge incertain saponins of Solangustidine, c27H4302N,49 differsfrom solanidine-t in having an extra oxygen atom, and in solano-capsine this difference is increased by an additional nitrogen atom(amino-group).I. Z. Saiyed and D.D. Kanga 50 have isolated from Solanurnxanthocarpum a sterol, C,,H5,0 (carpesterol) , an alkaloid, solan-carpidine, C26H,,0,N, and aC44H77019N, which, on hydrolysis,rhamnose, and (probably) galactose.gluco-alkaloid, solancarpine,gives solancarpidine, glucose,I d o l e Derivatives.-A base, gramine, was isolated from a chloro-phyll-defective strain of barley by H. voii Euler and H. Hellstrom.514 7 G. Barger and H. L. Fraenkel-Conrat, J . , 1936, 1537.48 Cf. J. C. E. Simpson and W. A. Jacobs, J . Biol. Chem., 1935, 109, 573;4s F. Tutin and H. W. B. Clewer, J., 1914, 105, 559.60 Proc. Indian Acad. Sci., 1936, 4, 283.61 Z . physiol. Chem., 1933, $217, 23.n. Tschesche and A. Hagedorn, Ber., 1935, 68, 1412; 1936, $9, 797380 ORUANIC CHEMISTRY.It was later thought to be identical with donaxine, isolated 52 fromArundo donax, and regarded as (XXI), but no proof of constitutionwas put forward. T. Wieland and C. Y. Hsing 53 have synthesised5-me thoxy- 3-dimethy laminome t hylindole (XXII) , which appears tobe identical with gramine, although the methiodide has a muchhigher melting point than that of the natural substance :+ CNC13,*NRle2 -+ CN*MgINHOMe(&CH2*NMe, (XXII.)-tNHTobacco Allca1oid.-Myosmine (XXIII), one of the tobacco a&a-loids, has been synthesised s4 as follows :NHN(XXIII.)isoQuinoliiae Alkaloids.-A synthesis has been recorded 55 of dl-bicuculline (XXIV), the d-form of which was isolated by R. H. F.Manske 56 from Dicentra cuczdlaria, Adlumia fungosa, Corydalissempervirens, and C . aurea.(XXVI.)O-CH,(XXIV.) (XXV.)52 A. Or6khov and S. Norkina, Ber., 1935,68, 436.53 Annalen, 1936, 528, 188.54 E. Sp&th and L. Mamoli, Ber., 1936, 69, 757.55 P. W. G. Groenewoud and R. Robimon, J., 1936, 199.56 Carutd.ian J . Res., 1932, 7, 258, 265; 1933, 8, 142TURNER: VITAMIN B1 (ANEURIN) AND THIOCHROME. 381It has been stated 57 tha6 the compound obtained " under physio-logical conditions " by G. Hahn and 0. Schales 58 is not (XXV) but(XXVI). The last-named authors 59 have, however, repliedsatisfactorily to the criticism.Tropinone Derivative.-Although there are many recorded casesin which Claisen coiidensations between carbonic esters and ketonesor ketonic esters have given very indifferent yields, it has now beenfound 6o that tropinone reacts vigorously with methyl or ethylcarbonate in presence of sodium or potassium, preferably when benz-ene or xylene is used as a medium. It thus becomes possible toprepare tropinonecarboxylic esters quickly and in good yields.E. E. T.10. VITAMIN B, (ANEURIN) AND THIOCHROME.Vitamin B, (I) has been synthesised by R. R. Williams and J. K.Cline1, according to the scheme :E G O E tC02Et*CH2*CH2* OEt --A COZEt *CH (CHO)*CH,*OEtNN hle0NtidJlr N CH,BrSSJ N AThe chloride was identical with the natural substance in ultra-violetabsorption and antineuritic potency, but had a melting point of232-234", whereas the natural product melts at 246". Possiblythe latter is a mixture of stereoisomeridea.6 7 E. Spath, F. Kuffner, and F. Kesztler, Ber., 1936, 69, 378.68 Ber., 1936, 68, 24. 68 Ber., 1936, 69, 622.80 N. A. Preobrashenski, M. N. Schtschukina, and R. A. Lapina, ibid.,J . Amer. Chem. Soc., 1936, 58, 1504. p. 1616382 ORUANIU CHEMISTRY.A. R. Todd and F. Bergel proposed formula (11) for thiochrome(obtained by the action of alkaline ferricyanide3 or of alkali aloneon aneuria) and later, with H. L. Frrtenkel-Conrat and Miss A.Jacob,5 effected its synthesis :60 XO,Et M0gE2*C0,Eti -~,,kX2*C0*N3NH, H*CH2*C0,EtNNH/CHONS CH,*C02*CH,*CH2Rr + CH,*CO*CHNa*CO,Et - .1 A NH,*sH fi*CH,*CH2*OHE-CMeCH,*C0,*CH2*CH2*CH( C02E t)*CO*CH,OH*CH,*CH,*CHCl.CO*CH,The encl-product of the synthesis was in all respects identical withthiochrome as obtained from vitamin B,.E. E. T.W. BAKER.J. w. COOK.R. D. HAWORTK.E. L. HIRST.R. P. LINSTEAD.S. PEAT.E. E. TURNER.2 J., 1936, 1559.3 G. Barger, F. Bergel, and A. R. Todd, Ber., 1935, 68, 2257.* R. Kuhn and H. Vetter, {bid., p. 2376. * J., 1936, 1601

ISSN:0365-6217    

DOI:10.1039/AR9363300228

出版商:RSC    

年代:1936

数据来源: RSC

摘要:

BIOCHEM.ISTRU.THIS year has scen further definite progress in the isolation ofsubstances belonging to the groups of hormones and vitamins.The constitution of vitamin B, has been established beyond doubt ;for the first time a substance with anti-rachitic properties has beenisolated from natural sources ; a cyclic alcohol, apparently pure,with the activity associated with vitamin E has been isolated;and of a number of sterol-like substances obtained from the adrenals,one is highly active in the manner characteristic of the corticalhormone. The anti-anEmic factor in liver has not yet, apparently,been obtained pure, though considerable progress has been madetowards its isolation.Attention is directed to the attempts now being made to elucidatethe arrangement of amino-acids within the protein molecules,attempts which seem likely to prove of increasing importance andvalue as methods continue to improve for characterising andestimating specific amino-acids and for synthesising more complexpeptides.The nature of the researches involved in chemotherapy makesmaterial progress slow in this field.Nevertheless, results areemerging from prolonged systematic investigations and are makingdefinite contributions to our knowledge of the mode of action, andof the relative efficiencies of both natural and synthetic therapeuticagents.In the Plant Biochemistry section considerable space has beendevoted this year to questions relating to photosynthesis in plants.Recent additions to our knowledge of the pure chemiatry of chloro-phylll may contribute much to our understanding of the morephysiological aspects of the photosynthetic process.The manyramifications of this problem and the divergence of opinion amongauthorities on this subject, coupled with the fact that nine yearshave elapsed since the matter was dealt with in these Reports,seem to afford sufficient justification for a general review of someof the more important researches and theories on this fundamentalprocess of plant chemistry.1 Ann. Reports, 1936, 83, 362384 BIOCHEMISTRY.1. ANIMAL BIOCHEMISTRY.The Vitamins.Vitamin B,.-The constitution of vitamin B, originally suggestedhas been modified2 to that shown-in (11) by R. R. Williams (I)and the new formula has been confirmed by ~ynthesis.~The excretion of vitamin B, in human urine has been measuredby the bradycardia r n e t h ~ d , ~ the vitamin being first adsorbed onactive clay, which is then fed to B,-deficient rats for observation ofits effect on the heart rate.Normally 12-35 international units(approximately 30-90 7 ) are excreted per day, i.e., about 543%of the daily intake. In human beri-beri the excretion of vitamin Blmay almost cease, and a daily excretion of less than 12 units is held toindicate some deficiency of the vitamin in the diet. W. H. Schopferhas estimated vitamin B, by measuring the amount of growth inthe mould Phycomyces Blakesleanus on a vitamin-free syntheticmedium after addition of vitamin concentrates ; the method has,so far, however, only been applied successfully to fairly purepreparations.On the grounds that many diseases showing anorexia, cedema(with consequent heart symptoms) and peripheral nerve degener-ation (characteristic signs of experimental B1-deficiency) may bedue to a deficiency of the vitamin, and that in such cases the absorp-tion of the vitamin from the intestine may be unsatisfactory, theparenteral administration of pure vitamin B, has been advocatedby a number of workers.has obtained goodresults by this method in cases of chronic progressive neuritis,alcoholic neuritis, subacute combined degeneration of the spinalcord, etc., although in some of them oral administration had littleor no effect.W. R. Russelll a Ann. Reports, 1935, 32, 402.2 R.R. Williams, J . Amer. Chew. Soc., 1936, 58, 1063.4 L. J. Harris and P. C. Leong, Lancet, 1936, 230, 886.6 2. Vitaminforsch., 1936, 5, 67.6 E d k . Med. J., P936, 43, 315.This vol., p. 381STEWART AND STEWART. 385Vitamin B, Complex.-Although i t has been suggested that theterm B, should be restricted to lactoflavin,' there is still no uni-formity in nomenclature, and since there evidently exist morethan the two factors which led to the differentiation of the complexinto B, (flavin) and B, (curative of rat dermatitis) the tendency isto refer to the factors by their effects rather than by specific names.T. W. Birch, P. Gyorgy, and L. J. Harris distinguish a t least twoand possibly four factors in addition to flavin. They find that thefactor curative of dermatitis in rats (erroneously described as rat-pellagra) is present in considerable amounts in maize, and inmolasses, so that rats fed on typical human-pellagra-producingdiets remained free from dermatitis, and such diets cured ratssuffering from dermatitis.They conclude that this factor (= B,)is different from the factor curative of human pellagra. This, the'' P-P " or pellagra-preventing factor, is found especially in liverextract, autolysed yeast, etc., and is apparently not required bythe rat. It is not lactoflavin (which is required by the rat, ofcourse, for growth). Dogs fed on a human-pellagra-producing dietdid not develop pellagra, but " black tongue " (a condition un-affected, evidently, by B6), which was cured by a diet rich in P-Pfactor but not by lactoflavin. Xhe dog, however, needs B, as wellas lactoflavin and the " anti-black tongue " factor, as was shownby experiments with " synthetic '' diets. It seems that the blacktongue and the P-P factor may be identical, though the evidence isnot conclusive.Finally the factor curative of chicken pellagra isdifferentiated from B,, though its relation to the P-P or the blacktongue factor was not decided.S. Lepkowsky and T. H. Jukes9 found that the factor curingdermatitis in chickens could be concentrated from aqueous ricebran extracts, since inert matter, but not the vitamin, was absorbedby fullers' earth. Their experiments suggested that the factor (B6)curative of rat dermatitis was absorbed by the earth, and laterexperiments lo confirmed this.T. H.Jukes and S. Lepkowsky l1 investigated the distributionof the anti-chicken-dermatitis factor in foodstuffs. They found,for example, that wheat germ, kale, and maize contained approxim-ately equal amounts, and since wheat germ and kale contain muchmore of the P-P factor than does maize, they conclude that thetwo are different. They thus confirm the differentiation of therat-dermatitis and the chick-dermatitis factor and show that the7 Ann. Reporte, 1935, 32, 404.9 J. BioZ. Chert,., 1936, 114, 109.10 S. Lepkowsky, T. H. Jukes, and M. E. Krause, ibid., 1936, 115, 557.l1 Ibid., 1936, 114, 117.REP.-VOL. XXXIII. NBiochem. J., 1935, 29, 3830386 BIOCHEMISTRY.latter is different from the P-9 factor.The vitamin B, complex,therefore, consists of, at least, four factors, including lactoflavin.Concerning vitamin B, itself (i.e., the flavin growth factor)R. Kuhn, H. Rudy, and F. Weygand l2 have now reported thesynthesis, by a method which fixes the position of the phosphoricacid residue, of 6 : 7-dimethyl-9-d-riboflavin-6‘-phosphoric acid,which is identical with the natural lactoflavin phosphoric acid insolubility of its salts, absorption spectrum, oxidation-reductionpotential, and in growth-promoting activity (rats) whether givenorally or intra-peritoneally. R. Kuhn and H. Rudy l3 have shownfurther that the synthetic can replace the natural substance inthe “yellow enzyme.” R. Kuhn, H. Rudy, and F. Weygand14have also synthesised the E-arabinose analogue, and have shownthat it too can combine with the colloidal carrier derived from theyellow enzyme to form a chromoprotein whose catalytic activity ishigh, though less than that of the natural enzyme.Vitamin B,.-The existence of vitamin B,, originally describedby V. Reader,15 has more recently been doubted, and thc opinionexpressed that vitamin 33, deficiency (so-called) is merely a chronicdeficiency of vitamin B,, and can be cured by a sufficiently largedose of that substance.8B l6 states, however, thatin his laboratory M.Malmberg was unable to restore growth in ratsby addition to the diet of vitamin B, and lactoflavin. J. A. Keenan,0. L. Kline, C. A. Elvehjem, and E. B. Hart l8 found in 1933 thatconcentrates of the alleged vitamin B, were able to prevent thedevelopment of certain paralytic symptoms in the chick, the dietalready containing adequate amounts of vitamin B,.This workwas later confirmed and extended.19 NOW,,* it has been shownthat by the use of specially purified diets, crystalline vitamin B,,and highly potent liver concentrates as source of the vitamin B,complex, it is possible to reproduce in rats the syndrome describedby Reader and to restore growth by vitamin B, concentrates (e.g.,from peanuts) but not by crystallinc vitamin B,. These workersH. von Euler12 Ber., 1936, 69, 1643.13 Ibid., p. 1974.14 Ibid., p. 2034.16 Biochem. J., 1929, 23, 689; 1930, 24, 77, 1837.16 J. R. O’Brien, Chem. and Ind., 1934, 53, 452; L. J. Harris, Ann. Rev.Biochern., 1935, 4, 331; H.W. Kinnersley, J. R. O’Brien, and R. A. Peters,Biochem. J., 1935, 29, 701.1 7 Ann. Rev. Biochem., 1936, 5, 364.18 J . Biol. Chem., 1933, 103, 671.19 0. 1;. Kline, 0. D. Bird, C. A. Elvehjem, and E. B. Hart, J . Nutrifion,20 0. L. Kline, C. A. Elvehjem, and E. €3. IIart, Biochem. J . , 1936, 30,1936.780STEWART AND STEWART. 387consider, therefore, that vitamin B, is a real entity with demon-strable functions in at least two species of animals.Vitamin (?.-With the definite identification of vitamin C asascorbic acid, interest has shifted to such questions as its synthesisin vivo, its excretion under various conditions, the form in whichi t occurs in the tissues, the changes it undergoes there, and itsfunctions. The published results bearing on these questions are,in many ca,scs, contradictory, largely in all probability because bheusual methods for estimating ascorbic acid (titration with 2 : 6-dichlorophenolindophenol is the commonest) are by no meansspecific.Many of the published conclusions can, therefore, beaccepted only with reserve.The report of B. C. Guha and A. R. Ghosh,21 that rat tissueswere able to synthesise ascorbic acid in vitro from mannose, hasbeen contradicted by R. Ammon and G. Grave 22 and by M. Laportaand E. Rinaldi.23 On the other hand, in vivo synthesis of ascorbicacid by rats is suggested by the experiments of K. M. Daoud andM. A. S. El Ayadi2* and evidence has been adduced in supportof the view that the human foetusZ5 and the human sucMing,26but not the guinea pig foetus or suckling,27 can synthesise the vitaminto some extent.It has also been suggested by H. K. Muller 28that the eye lens is capable of synthesising ascorbic acid, butS. W. Johnston 29 finds that, although in scorbutic guinea pigs theindophenol-reducing power of the lens is merely reduced, theascorbic acid determined spectrographically has completely dis-appeared from lens and humourg, the rate of disappearance (andof re-appearance when the vitamin is administered) running parallelwith that of the other tissues. On the other hand, it has beenclaimed 30 that the indophenol-reducing substance of the lens andeye humours is ascorbic acid, since it is completely oxidised by theascorbic acid oxidising enzyme-a conclusion which is obviouslynot justified until more is known of the specificity of the enzyme.Other indophenol-reducing substances (besides those which, like21 Ann.Reports, 1935, 32, 404.sa 2. Vitaminforsch., 1936, 5, 185.23 Boll. SOC. ital. BioZ. aperim., 1935, 10, 319.24 Bioclzenz. J . , 1936, 30, 1280.25 R. Rohmer, N. Bezssonoff, and E. Storr, Compt. rend. SOC. B i d , 1936,26 Idem, Bull. Acad. Me'd., 1935, 113, 669; Compt. Tend. Soc. BioZ., 1936,2 7 G. Mouriquancl, A. Ceur, and P. Viennois, Gompt. rend. Xoc. BioZ., 1936,2 8 Klin. Tl'och., 1935, 14, 1498.2s Biochem. J., 1936, 30, 1430.30 L. Eosner and J. Bellows, Proc. SOC. E x p . BhZ. filed., 1936, 34, 493.121, 987.121, 988.121, 1005388 BIOCHEMISTRY.cysteine, reduce it slowly) do exist in nature, for one containingnitrogen, and possibly phosphorus, has been obtained from supra-renals by E.Ott, K. Kramer, and W. F a ~ s t . ~ lA similar confusion exists on the question of the state in whichascorbic acid exists in the tissues. Thus B. C. Guha and J. C. Pal,32having found that some plant extracts (e.g., cabbage) yielded moreascorbic acid on heating, concluded that ascorbic acid was presentto some extent in a combined form, whereas G. L. Mack33 andM. van Eekelen 34 attribute the phenomenon to heat-inactivationof the ascorbic acid oxidase. Van Eekelen considers that ananalogous phenomenon occurs in blood, ascorbic acid being oxidisedby the erythrocytes, but A. E. Kellie and S. S. Zilva3j deny thatintact erythrocytes are capable of oxidising ascorbic acid.Byspectrographic measurement they conclude that plasma containsno dehydroascorbic acid.A large number of papers deal with the urinary excretion ofascorbic acid, and many are concerned with the unsatisfactorynature of the available methods. M. A. Abbasy, L. J. Harris,S. N. Ray, and J. R. Marrack,36 using the method described byL. J. Harris and S. N. Ray,37 state that the urinary excretion ofascorbic acid is, in general, proportional to the intake, and fornormal adults (in England) receiving small allowances of fruit, etc.,is about 20 mg. per day. A diet is deficient in vitamin C whenthe urinary output falls below 10-15 mg. per day (per 10 stonebody weight) or when a dose of 700 mg.of ascorbic acid producesno increased excretion on the second day. The increased indo-phenol-reducing power of the urine after ascorbic acid administra-tion, and the decrease during the feeding of a scurvy-producingdiet, which has been observed by others as well as Harris and hisco-workers, certainly suggest that the reducing substance of urineis ascorbic acid or a t least a closely related substance. B. Ahmad 38found that a high meat diet caused a very considerable increase inthe excretion of indophenol-reducing substance, and concluded thatthis was probably ascorbic acid from a study of its heat stability.A failure to detect ascorbic acid by biological assay he ascribedto the presence of toxic substances in urine. Wieters39 also hasfailed to demonstrate ascorbic acid in urine by biological methods.Although these failures can be discounted to some extent byaccepting Ahmad’s explanation, it is more difficult to ignore the31 Z.phyeiol. Chem., 1935, 243, 199.33 Ibid., 1936, 138, 505.36 Biochem. J., 1936, 30, 361.3 7 Ibid., p. 71.3D Mercks Jahresber., 1935.32 Nature, 1936, 137, 946.34 Acda Brev. Ne’erl., 1935, 5, 78.as Lancet, 1935, 229, 1399.3a Biochern. J., 1936, 30, 11STEWART AND STEWART. 389chemical results reported by K. Hinsberg and R. Arnm~n.~O Theywere able to separate from urine ascorbic acid added to the extentof 1 mg. per 100 c.c., using the fact that its derivative with 2 : 4-dinitrophenylhydrazine is insoluble in cold alcohol or in ethyl hydro-gen oxalate but soluble in ethyl oxalate.From normal urine(containing more than this amount of indophenol-reducing ssb-stance) they failed to extract any of the vitamin C derivative,and from a study of the limits of their methods conclude thatnormal urine cannot contain more than 0.3 mg. of ascorbic acidper 100 C.C.The fact that ascorbic acid exists in the tissues largely, if notentirely, in the reduced form has been ascribed by several authorsto the presence of glutathione,*l which has also been shown toprotect ascorbic acid from autoxidation in vitro, provided that it ispresent in relatively large amountsj2 It is claimed that in highconcentration, glutathione can even reduce dehydroascorbic acid,provided the pH is not too F. G. Hopkins and E.J. Morgan 44have studied the relationship between ascorbic acid and glutathione,alone and in the presence of the enzyme (from cauliflower, cabbage,etc.) which A. Szent-Gyorgi45 found to oxidise ascorbic acid andnamed “ hexoxidnse.” They find that a mixture of pure ascorbicacid with pure glutathione may be quite inert, neither being oxidised(e.g., at pH 6) ; if, however, a trace of copper is present and the pHis such as to allow oxidation of the glutathione (e.g., 7.4), theformer is protected while the latter is oxidised exactly as if noascorbic acid was present. They are, therefore, inclined to ascribethe protective action of glutathione under these conditions to itsformation of a stable compound with the metal catalyst. In thepresence of the enzyme the conditions are quite different.The reactionsDehydroascorbic acid + 2GSH --+ ascorbic acid + G*S*S*GAscorbic acid -> dehydroascorbic acidare both catalysed by the enzyme, and, the second of these beingthe more rapid, ascorbic acid remains practically fully reduceduntil all the glutathione is oxidised.Hopkins and Morgan pointout that so far no enzyme capable of oxidising either ascorbic acidor glutathione has been discovered in animal tissues. Nevertheless,40 Biochem. Z., 1936, 288. 102.4 1 L. de Caro and M. Giani, 2. physiol. Chem., 1934, 228, 13; C. A. Mawson,48 Bersin, Koster, and Zmatz, 2. physiol. Chern., 1935, 235, 12.4 3 H. Borsook and C. E. I?. Jeffreys, Science, 1936, 83, 397.44 Biochem. J . , 1936, 30, 1446.45 Ibid., 1928, 22, 1387.Biochem.J., 1935, 29, 569390 BIOCHEMISTRY,their experiments in which these substances were aerated withhepatic tissue yielded some suggestion that here too glut'athioneaffords some protection to the vitamin. Other substances besidesglutathione may well be concerned in preserving ascorbic acid fromoxidation; for instance, M. Yamomoto 46 has shown adrenalin tohave this effect in vitro.S. Rusznyak and A. Szent-Gy6rgi47 report that Hungarian redpepper and lemon juice contain a substance which is closely alliedto vitamin C, curing pathological fragility and permeability of thecapillary walls to plasma proteins. They name it vitamin P, andstate that it appears to be Aavone or flavonol glucoside.Vitamin D.-The fact that antirachitic activity is the propertyof more than one compound was mentioned in these Reports lastyear.48 During the year under review the number of active sub-stances has been increased, and for the first time one has beenisolated from natural sources.The evidence leading to the acceptedconstitution of these compounds is reviewed elsewhere : it isbelieved that all the active substances so far obtained have incommon the three-ring structure with the three conjugated doublebonds of calciferol (111) .50A. Windaus 48* 51 found, over a year ago, that 7-dehydrochole-sterol, differing from ergosterol in having no double bond at C,2-C,,and no methyl group at C2*, but with the same ring structure,yielded an antirachitic substance on irradiation.He has now, withP. Schenk and F. von VVerde~-,~~ succeeded in isolating the irradi-ation product (vitamin D3) by chromatographic absorption onalumina. It has an activity of 24,000 international units per mg.(i.e., rather more than half that of calciferol). H. Brockmann 53has isolated a compound identical with vitamin D,, from funnyliver oil, and various experiments on the relative effects of different46 8. physiol. Chem., 1935, 243, 266.4 7 Nature, 1936, 138, 27.48 Ann. Reporta, 1935, 32, 405.49 This vol., p. 349.60 I. M. Heilbron, R. N. Jones, K. M. Samant, and F. S. Spring, J . , 1936,5 1 A. Windaus, H. Lettrit, and F. Schenk, Annalen, 1935, 520, 98.sa 2. physiol. Chem., 1936, 241, 100,w Ibid., p. 104.905STEWART AND STEWART.39 1liver oils in curing avian rickets suggest that it is present in otherfish liver oils (e.g., those of cod and halibut) as weIL5* G. A. D.Haslewood and J. C. Drummond 55 also have obtained a highlyactive concentrate from tunny liver oil (10,000-20,000 inter-national units per mg.), but believe it to be different from thevitamin D3 of Brockmann and Windaus.That calciferol is much less effective in curing avian rickets thanan amount of cod liver oil containing an equal number of inter-national (rat) units of vitamin D has been mentioned in theseReports before.48 It has also been found that purified cholesterol,apparently free from ergosterol, still possesses provitamin Dproperties. Cholesterol purified through the dibromide is onlyslightly active, but its activity (or rather activatability) is greatlyincreased if it is heated in presence of a little 0xygen.~~*~7 Theirradiation products of crude cholesterol and of purified heatedcholesterol resemble cod liver oil in their efficacy in avian ri~kets.~7A.G. Boer, E. H. Reerink, A. Van Wijk, and J. van Niekerk 58have isolated the provitamin from crude cholesterol, confirmed theactivity of its irradiation product as resembling that of cod liveroil with respect to avian rickets, and identified it as 7-dehydro-cholesterol. The suggestion arises, therefore, that purified chole-sterol may, under the conditions used by M. L. Hathaway andD. E. Lobb,57 undergo dehydrogenation to a small extent. Sinceirradiated plant products (cottonseed oil, wheat middlings, lucerneleafmeal, yeast, fungus mycelium) resemble calciferol in being muchmore efficacious in rat than in avian rickets, it has been suggestedthat plant and animal fats contain differeht vitamin D precursor^.^^The similarity in this respect between the unsaponifiable matterfrom lucerne oil and calciferol is confirmed by A.Black and H. L.Xa~aman,~~ who extend the similarity to irradiated “ phytosterol.”It is possible, of course, that crude phytosterols, like crude chole-sterol, may contain small amounts of dchydro-derivatives, for0. Linsert 6O has prepared 7-dehydrostigmasterol, which on irradi-ation shows definite antirachitic activity, as does 7-dehydrosito-54 M. J. L. Dols, 2. Vitnrninforsch., 1936, 5, 161; A. Black and H.L.65 Chem. and Ind., 1936, 598.66 C. E. Bills, E. M. Honeywell, and W. A. MacNair, J . Biol. Chenz., 1928,33, 251; J. Waddell, ibid., 1934, 105, 711; M. L. Hathaway and 3’. C. Koch,ibid., 1935, 108, 773.Sassaman, AnEer. J . Pharm., 1936, 108, 237.6 7 Ibid., 1936, 118, 105.68 Proc. R. Alcnd. Wetensch. Amsterdam,, 1936, 39, 662.69 R. M. Bethke, P. R. Record, and 0. H. M. Wilder, J , Biol, Chem., 1935,80 8. phy8ioE. Chem., 1936, 241, 125,112, 231392 BIOCHEMISTRY.sterol, which has been prepared by W. Wunderlich.61 The irradi-ation products of thefie substances have not yet been isolated, sotheir activity has not been measured quantitatively. It is inter-esting to note that, again, the power of acquiring antiracliitic activityis associated with the ring structure found in cholesterol, but thatagain the side chain is of little importance, for whereas stigmasterolhas the unsaturated side chain of ergosterol with, however, an ethylgroup at C24, sitosterol has the ethyl group at C,, but a saturatedside chain.The relative unimpor-tance of the side chain is furthershown by the fact that 22-di-hydroergosterol becomes antirachiticon irradiation.*** 62 The presenceof two conjugated double bonds inthe ring structure is important, andthat they must be in the ring itself is suggested by the inactivityafter irradiation of 7-methylenecholesterol (IV) prepared by B.Bann, I. M. Heilbron, and F. S. Spring.63Vitamin E.-From the unsaponifisble fraction of wheat germ oil,H.M. Evans, 0. 11. Emerson, and G. A. Emerson 64 have isolated asubstance believed to be the allophanate of P-amyrin, the allo-phanate of an alcohol, C29H50Q2, and the allophanate of " a-toco-pherol," C,,H,,O,. The alcohol from the first of these is inactive,the second shows some vitamin E activity, but a single 3 mg. doseof the regenerated a-tocopherol regularly enables vitamin E deficientrats to bear young. A dose of 1 mg., however, was insufficient toallow the regular production of litters. a-Tocopherol (tolos, child-birth, and phero, to bear) is an apparently homogeneous, oily alcohol,optically inactive, with a strong absorption band maximal a t2980 A. The relatively inactive alcohol has similar absorption,which appears to explain the observation of H.S. Qlcott 65 thatcertain concentrates with good absorption a t 2940 A. showed littleor no vita'min activity. Treatment of a-tocopherol with silvernitrate in methyl alcohol caused the disappearance of the absorp-tion band a t 2980 A., with appearance of two new bands at 2710and 2620 A., the biological activity being reduced but not lost.(Drummond et aZ.66 have stressed the presence of absorption a t2670 A. as well as 2940 A. in their active concentrates.) OllcottMePV.1 * ,-C&Ho /\/- (q3L:61 2. phySi0l. Chern., 1936, 241, 116.68 A. Windaus and R. Langer, AnmEen, 1933, 508, 105; F. G. McDonald,I'roc. Amer. SOC. Biol. Chem. ( J . Biol. Chem.), 1936, 114, lxv.63 J., 1936, 1274.64 J . Biol. Chem., 1936, 113, 319.6 5 Ibid., 1935, 110, 695.Biochem.J., 1935, 29, 2510STEWART AXD STEWART. 393(Eoc. cit.) had observed the similar persistence of activity with dis-appearance of the absorption band a t 2940 A. when his concen-trates were treated with methyl-alcoholic silver nitrate, but con-cluded that the substance responsible for the absorption Waf;,therefore, not the vitamin. A siniilar conclusion has been reachedby J. C. Drummond, E. Singer, and R. J. MacWalter,GG who foundcertain preparations to be less active than was expected from theabsorption intensity, although they had earlier G7 believed absorp-tion and activity to be parallel. They point out, however, that theband at 2940 A. may really be characteristic of the vitamin, butChat certain molecular changes may affect potency without affectingthe absorption spectrum. Evans and his collaborators, however,consider that the effect of silver nitrate merely shows provitamin Eactivity to be possessed by more than one substance, since (on thebasis of its conversion into a p-nitrophenylurethane derivative andregeneration unchanged, as well as the failure to effect any fraction-ation by solvents or adsorption on a calcium carbonate column)they consider a-tocopherol to be a chemical individual.The most potent preparations of Drummond gave analyticaldata, for both the free alcohol and its acetate, in good agreementwith those for a-tocopherol.R. H. Kimm6* also has obtained ahighly active substance which, from analysis of its P-naphthoate,appears to have the formula C,gH,,O.This is, of course, theformula of tocopherol minus H,O, but the published chemical dataare too scanty to permit reasoned suggestions as to the relationshipof the two substances. All that is known is that tocopherol is analcohol, yielding a monoallophanate and a mono-p-nitrophenyl-urethane, that it does not react with ketone reagents, that itprobably contains a condensed cyclic nuclcus, and that it containsreactive ethylenic linkages.The suggestion that vitamin E is required for growth as well asfertility is negatived by experiments 69 in which the growth of ratswas measured from weaning on a diet free from E but otherwiseadequate. The growth was as good as that of rats on a stockcolony diet and was accelerated only very slightly in males (butnot in females) when vitamin E concentrates were used to supple-ment the basic diet.Small supplements of wheat germ oil, sufficientt o ensure fertility, were without effect on growth. The inclusionof lard, however (the fat in the basic diet consisted of the ethylesters of fatty acids from hydrogenated cotton seed oil), produced67 Biochem. J . , 1935, 29, 456.6s Sci. Papers Inst. Phys. Chem. Res. Tokyo, 1935, 28, 74.60 H. S. Olcott and H. A. Mattill, Proc. Amer. Soc. Biol. Chem. ( J . Biol.Chem.), 1936, 114, lxxvii394 BIOCHEMISTRY.a significant increase in the growth rate, a fact of some interest inview of the suggestion that certain unsaturated fatty acids arecssential dictary constituents.VitcGrnin K.-H.Dam and P. Schsnheydcr 70 described, in 1934,a deficiency disease in chicks, characterised by a tendency tohemorrhage, anamia, pathological changes in the gizzard, and aprolonged blood clotting time. This was later 71 ascribed to lackof a specific fat-soluble, thermostable vitamin (K) and the sugges-tion was confirmed independently by H. J. Almquist and E. L. R.S t ~ k s t a d . ~ ~ The vitamin occurs in hog’s liver fat (one of the firstsources) and to a smaller extent in dog, chick, and cod liver ; greenvegetables are a particularly rich source.73 The vitamin is destroyedby alkali.73* 74 H. Dam and P. Schmheyder 73 have achieved apartial purification from alfalfa by extraction with various solvents,followed by adsorption on calcium carbonate or cane sugar, theirmost active preparation containing 600 to 1000 units per mg.(Aunit is defined 75 as the smallest daily dose per g. body weightwhich, given for three days, will restore the clotting time to normal.Thus a chick weighing 400 g. would require 1200 units.) H. J.Almq~ist,~* also by solvent fractionation from alfalfa, obtained aconcentrate of which 2 mg. were adequate when added to 1 kg.of vitamin-free diet ; later 76 by fractional distillation in a vacuumhe obtained a yellow viscous oil of which 0-5 mg. per kg. of dietwas adequate. Exact comparison of the degree of concentrationachieved by the two workers is not possible in the absence of dataas to weight of chicks and food consumption in Almquist’s experi-ments, though it seems likely that his preparation is the moreactive.As to the mode of action of vitamin K, P. Schmheyder 77has suggested, and H. Dam, F. Schmheyder, and E. Tage-Hansen 78support the view, that the low clotting power in the blood of chickslacking the vitamin is due to a reduced pro-thrombin content.Treatment of the serum from normal chicks by the methods ofHowell or Mellanby gives precipitates with pro-thrombin activity,though serum from K-avitaminous chicks, treated similarly, givesinactive precipitates. Vitamin K concentrates themselves, how-ever, do not accelerate clotting in vitro, but pro-thrombin from‘O Biochern. J., 1934, 28, 1935.7 1 Nature, 1935, 135, 653; Biochem. J., 1936, 29, 1273.72 J . Biol. Chern., 1935, 111, 105.73 Biochem.J . , 1936, 30, 897.74 J . Biol. Chem., 1936, 114, 241.7 5 Biochem. J., 1936, 30, 890.7 6 J . Biol. Chem., 1936, 115, 589.7 7 Nature, 1935, 135, 652.7 8 Biochem. J . , 1936, 30, 1075STEWART AND STEWART. 395normal chick serum, extracted with acetone and ether to removelipoids, itself exhibits vitamin K activity. It is possible that thevitamin may be present in pro-thrombin as a prosthetic group indefinite chemical combination with the rest of the molecule.Hormones.Adrenal Cortex.-Recent work has shown the nucleus of the sexhormones, of the sterols, the bile acids, the cardiac aglucones, andthe antirachitic vitamin to be present in ye6 another substance ofbiological importance.The necessity for life of a substance produced by the adrenalcortex was shown in the case of adrenalectomised dogs by J.M.Rogoff and G. N. Stewart,79 who later 8o found that their extractswere of some benefit in cases of Addison’s disease. Similar resultswere obtained by W. W. Swingle and J. J. PfiffnerY8l and byF. A. Hartman.82 The hormone preparations used by these workerswere very impure, but in 1934 the isolation of a crystalline substancehaving the activity of the cortical hormone was announced fromthe Mayo Clinic.83 The crystals were later found to be a rnixt~re,8~but recently H. L. Mason, C. S. Myers, and E. C. Kendall 85 haveseparated from a number of somewhat similar compounds one whichhas definite, though small, activity when tested on the rat. It isdescribed as a strongly dextrorotatory, unsaturated ketonic alcohol,C21H30Q5, m.p. 201-20S0.The fact that this preparation is less active than was expectedsuggested that it is still impure, and certainly its description doesnot tally with that of an active substance obtained by Reichstein.Early in 1936 T. Reichstein g6 reported the ready concentration ofthe cortical hormone by means of ketonic reagents after preliminarytreatment with pentane and 20% methyl alcohol. From theseactive concentrates (and in part from inactive by-products) heobtained nine crystalline substances, all apparently closely related.One of these substances, p-adrenosterone, has one-fifth of the activityof androsterone by the capon test, three more are oxidisable tosubstances with slight androsterone-like activity, a fifth is oxidised79 Amer.J . Physiol., 1928, 84, 660.80 J . Amer. Med. ASSOC., 1929, 92, 1569.81 Science, 1930, 71, 321.s2 Endocrinology, 1930, 14, 229.s3 E. C. Kendall, H. L. Mason, B. F. McKenzie, C. S. Myers, and G. A.s4 E. C. Kendall, J . Amer. Med. Assoc., 1935, 105, 1486.8 5 J . Biol. Chern., 1936, 114, 613.58 He&. Chim, Acta, 1936, 19, 29, 223, 402, 979, 1107.Koelsche, Proc. StafS Meetings, Mayo Clinic, 1934, 2, 245396 BIOCHEMISTRY.to adrenosterone and is considered, though without cortical activity,to be identical with the active substance of Kendall et al. If thisidentification is correct, it follows that the preparation obtainedby Kendall and his collaborators is a mixture containing a smallamount of the hormone.Of the nine substances obtained byReichstein, eight were devoid of cortical activity when tested onrats by the Everse-de Fremeny 87 method in doses of 0.5-2 mg.The ninth has recently 8s been found to be active, and to yield onfurther fractionation a pure crystalline compound, m. p. 180-182*,which ‘( shows to a large extent the biological activity of the rawmaterial,” and is named corticosterone. By the method of Everseand de Fremeny, 0.5-1 mg. represents the approximate rat unit;tested on dogs, 0.25-0.5 mg. of corticosterone was found to beequivalent to 1 C.C. of standard ‘( cortin ” solution. It is claimedthat the chemical formula, with the exception of a few details, hasbeen elucidated. It has not yet been reported, but the impuresubstance of which corticosterone is the main coiistituent wasdescribed as an ap-unsaturated ketone.Reichstein and his co-workers point out that the isolation of corticosterone does notexclude the possibility that other active or activating substancesmay be present in the gland.InszLZin.-From the results of electrometric titration of crystallineinsulin, C. R. Harington and A. Neuberger 89 have deduced that theinsulin mo!ecule contains 43 & 2 acid-binding groups and 60-70base-binding groups. A study of iodinated insulin suggests thatin iodination only the tyrosine groups are affected (substituted inthe 3 : 5-positions) and on this assumption it appears that theinsulin molecule contains 24 tyrosine molecules. Titration of theiodinated protein suggests that the phenolic groups are free ininsulin.Since iodiiiated insulin is almost inactive physiologicallyand activity is (nearly) proportionately restored by partial remov a1of the iodine, it seems that the phenolic groups of insulin are im-portant in relation to its physiological activity. Combining theseresults with an estimate of the amide nitrogen of insulin (34 groupsper mol.), C. R. Harington and T. H. Mead9* have shown thatinsulin contains about 38% of glutamic acid. In view of inactiv-ation which follows release of the labile axnide nitrogen or thelabile sulphur from insulin and of the suggestion that insulin maycontain a ‘( prosthetic group ” just as thyreoglobulin owes its87 J. W. Everse and P. ds Fremeny, Acta Brev.Nkerl., 1932, 2, 152.8 8 p. de Fremeny, E. Laqueur, T. Reichstein, R. W. Spanhoff, and I. E.Uyldert, Nature, 1937, 139, 26.89 Biochem. J., 1936, SO, 809.90 Ibid., p. 1598STEWART AND STEWART. 397activity to thyroxin, Harington and Mead have synthesised cysteyl-glutamine (V) and glutaminyl-cysteine (VI).QH,=SH QH,*CO*NH,QH-NH, QHz(V.) CO-NH*$X*CO-OH (?H*NH, CH,*SH 0'1.)CH,*CH,*CO*NH, CO-NH-QHCOOOHBoth of these peptides were, however, without hypoglycaemic effectin the disulphide as well as the sulphydryl form. The lability oftheir amide nitrogen was not far removed from that of insulin;their sulphur, however, was far less labile.An interesting development in the therapeutic use of insulin isdue to H. C. Hagedorn, B. N. Jensen, N. M.Krarup, and I. Wud-s t r ~ p , ~ l who find that insulin combines with protamines to formcomplexes which have isoelectric points at about pK 7.3, a t whichthey are only slightly soluble in water though rather more so inserum. Their low solubility results, after their subcutaneous injec-tion, in the slow absorption of insulin into the body fluids. Inconsequence, the hypoglyczmic effect of an injection of protamineinsulinate lasts about twice as long as that of the same amountof free insulin. These results have been confirmed r e p e a t e d l ~ , ~ ~and it has been shown that (in rabbits) protamine insulinate couldbe detected in the lymphatics five hours after injection, whereasordinary insulin had disappeared in 45 minutes.93 The publisheddata, however, indicate that there is, as yet, no general agreementas to the best way of using the new modification of insulin therapy.Indeed, it seems likely that not only will different types of dietdemand rather different ways of using standard insulin along withprotamine insulinate, but that by using, e.g., different protamines itmay be possible to produce complexes suited to particularpurposes.The Xex Normones.-The chemical relationships of the numerousactive substances which have recently been obtained are discussedelsewhere in thisD.W. McCorquodale, S. A. Thayer, and E. A. Doisyg5 haveisolated dihydrotheelin (= oestradiol) from sow ovaries and havefound it to be identical in melting point and biological assay with91 J .Arner. Med. ASSOC., 1936, 106, 177.92 E.g., H. W. Boolt et aZ., {bid., p. 180; R. D. Lawrence and N. Archer,Brit. N e d . J., 1936, i, 747; I. M. Rabinowitch et ul., Cctnudian Med. Assoc. J.,1936, 35, 124.93 H. K. Beecher and A. Krogh, Nuture, 1936, 13'7, 458.94 P. 356.9 5 Proc. SOC. E x p . Biol. Med., 1935, 32, 1182398 BIOCHEMISTRY.the substance obtained by catalytic hydrogenation of oestrone.An improved method of isolation from the aspirated liquor folliculi-as the di-a-naphthoate-leads to the conclusion 96 that at least 52%of the oestrogenic activity of the starting material is due to dihydro-theelin, which, therefore, is the chief active principle of the sow’sovary (though others may be present). The amount present isabout 0-015 rng.per kg. of ovary. Two isomeric dihydrotheelinshave been isolated from the urine of pregnant mares.97 The twoisomers should both be obtained by chemical reduction of oestrone,and McCorquodale’s material, there€ore, is a mixture or the twoisomers have equal activities.R. H. Andrew and F. Fenger98*99 have reported the isolationfrom ovaries of a substance, probably C,,H,,O,N, of which 0.00001mg. produces oestrus in rats after 96 hours. This would appear tobe the most active oestrogenic substance yet obtained.The existence in pregnancy urine of bound oestrogenic materialliberated by boiling with hydrochloric acid has been confirmed byG. van S. Smith and 0. W. Smith.1 S. L. Cohen and G. P. Marrian2have obtained from pregnancy urine a water-soluble, ether-insoluble,amorphous substance containing about 50 yo of its weight of oestriol.Its composition and reactions suggest that it is a compound ofoestriol and glycuronic acid, a suggestion which has been confirmedby later work.3Testosterone remains the most active male hormone from naturalBources, though its 17-methyl ether is stated to be more active inthe capon test and also, incidentally, to possess progesteroneactivity 4 (the two conipounds are R-O-Me and R-CO-Me, respect-ively). The activity of testosterone is said to be increased byincrease in the amount of the oily medium in which it is adminis-tered 5 or by esterification with acetic or propionic acid.6 Possiblyby these means it is protected from destruction in the animal body.Like some of the artificial male hormones (particularly those con-taining ethylenic linkages), both androsterone and testosterone aredescribed as possessing certain of the properties of the ovarian96 J .Biol. Chern., 1936, 115, 435.9 7 Proc. SOC. E x p . Biol. Med., 1935, 32, 1187.D8 Science, 1936, 84, 18.On Endocrinology, 1936, 20, 563.Arncr. J . Physiol., 1935, 112, 340.S. L. Cohen, G. F. Marrian, and A. D. Odell, Biochem. J., 1936, 30,L. Ruzicka and H. R . Roseenberg, Helu. C h k . ActCG, 1936, 19, 357.A. S . Parkes, ibid., 1936, 321, 674.2 Biochem. J . , 1936, 30, 57.2250.5 R. Deanesly and A. S. Parkes, Lancet, 1936, 230, 837STEWART AN11 STEWART. 399llor~r-~ones.~ V. Korenchevsky, M. Dennison, and S. L. Simpson *have found in prolonged experiments that large doses of andro-stcrone (or better androstanediol) caused a partial recovery of theatrophied uterus and vagina in sprayed rats.The administrationof androsterone together with oestrone was more effective (especiallyin the recovery of the uterus) than either male or female hormonealone. A similar, though smaller, co-operation between andro-sterone and ocstrone was shown in the ratc of involution of thethymus, but the two substances appeared to antagonise each otherin their effects on the adrenals (in which androsterone normallycauses reduction of weight to normal) and on the body weight.A similar co-operative effect of the two hormones was also shownin the recovery of the sexual organs (and thymus) of males.Asthc authors point out, the mutual interaction of the male andfemale hormoncs is of considerahle importance, since it is wellestablished that both are found in normal urine from males andfeiiiales. These cxperirnents have been extended to testosteroneand oc~tradiol.~ Testosterone shows the same co-operative a i dantagonistic effects with the ovarian hormones as does androsterone,the action again being much more marked in females than in males.Testosterone (and also androstanediol), i t is remarked, differs fromandrosterone in bringing about a quantitative2y normal developmentof the male sexual organs, and these substances also produce someof the changes associated with progesterone. If, therefore, theyare injected simultaneously with ocstrone, the effects in femalessimulate some of those seen dining pregnancy.Although incastrated male rats the effect of androsterone is increased byoestrone, the increase is not nearly so great as that produced bythe " X " substance of Laqueur et aE., a substance, itself inert,obtained (impure) in extracts of plant or animal tissues.1°Proteins and Amino-acids.Protein Structures.-Steady improvement in the methods avail-able for the determination of individual amino-acids in proteinhydrolysates is beginning to reveal stoicheiometrical relationships.Thus M. Bergmann l1 has extendcd his work on gelatin reported7 E. Wolff and A. Ginglinger, Compt. rend. SOC. Biol., 1936, 121, 1470;E. Wolf€, ibid., p. 1474, V. Korenchevsky, Nature, 1936, 137, 494; A.Butenandt, Nteturwius., 1936, 24, 16.8 Biochern.J . , 1935, 29, 2634.9 V. Korenchevsky, M. Dennison, and I. Brovsin, ibid., 103G, 30, 558.1" Acta Breu. Nker., 1935, 5, 84; J. Freud, ibid., p. 97; L. Ruziclra,M. W. Goldberg, and H. R. Rosenberg, HeZv. Chim. Acta, 1935, 18, 1487.11 M. Bergman and C. Niemann, J. Biol. Chem., 1936, 115, 77400 BIOCHEMISTRY.last year .12 He finds that glycine, proline, hydroxyprolinc, arginine,alanine, leucine-isoleucine, and lysine occur in the molecular pro-portions 24 : 12 : 8 : 4 : 8 : 4 : 3. On the assumption of a regulararrangement of the amino-acids in a polypeptide chain this gives aperiodicity (in the same order) of 3, 6, 9, 18, 9, 18, 24 and it ispointed out that these numbers are all multiples of 3.This period-icity of the amino-acids would be satisfied by either of the arrarrge-ments :G-P-X-G -X-X-G-P-X-G- or G-X-P-G-X-X-G-X-P-G-W. Grassmann and K. Riederle l3 have isolated Iysylprolylglycinefrom gelatin, and since the first of Bergmann's suggested arrange-ments demands the presence only of glycylproline peptides, thissupports the second. A similarly extensive stoicheiometricalrelationship has been found among the amino-acids of blood fibrin(cattle) , where glutamic acid, lysine, arginine, aspartic aid, proline,tryptophan, histidine, methionine, and cysteine (total 54.57, ofthe protein) are found to be in the molecular proportions72 : 48 : 32 : 32 : 32 : 18 : 12 : 12 : 9, with corresponding periodicities8, 12, 18, 18, 18, 32, 48, 48, 64.Similarly, R.Block and H. Vickery l4 showed some years agothat the keratins form a group of proteins with histidine : lysine :arginine molecular ratios of 1 : 4 : 12. More recently, R. Block 15has found that hzmoglobins exhibit another characteristic arrange-ment with iron : arginine : histidine : lysine in the ratios 1 : 3 : 8 : 9.Another example of attempts to gain an insight into the structureof protein is supplied by H. Bauer and E. Strauss,16 who, from astudy of iodination of globin and various derivatives, have reachedthe conclusion that globin is a complex of six units, each of molecularweight 11,680, the units being linked through the glyoxaline groupsof histidine.Canavanine and Ca.nmline.-R". Kitagawa and A. Takani l7 have con-firmed the structure of canaline as NH,-O*CH2*CH2*CI-I(NH2)*C0,H.By treatment of or-benzoylcanaline with methylisocarbamide theyobtained M- benzoylcanavanine, which yielded canavanine on hydro-lysis.NH,*C( :NH) -NH*O*CH,*CH,*CH(NH,)*CO,H,the two amino-acids having the same relationship to each other asornithine and arginine in conformity with the demonstration thatCanavanine is, thereforc, confirmed as12 Ann.Reports, 1935, 32, 418.3 4 J . Biol. Chem., 1931, 93, 113.16 Biochem. Z., 1936, 284, 107, 231.17 J . Agric. Chent. SOC. Japaiz, 1935, 11, 1077; J . Biochern. J C Z ~ C L ~ Z , 1936,l3 Binchem. Z., 1936, 284, 177.l5 Lbid., 1934, 105, 663.23, 181STEWART AND STEWART. 401they can share in the synthesis of urea.18 Incubation of canavaninewith a pig liver extract a t 37" yields canaline and y-ethylidene-canaline, which can be hydrogenated to an cc-amino-y- hydroxy-acid,C,H,O,N, and can be obtained from canaliiie and acetaldehyde.19The growth-promoting action of canavanine, shown by &I.Ogawa,20 is denied by M.Kitagawa and M. Wada.21 M. Ogawa 22now states that canavanine is not essential for growth in the laterpart of the growing period and that it is beneficial to the health ofpregnant animals though not essential for pregnancy.23a-Amino- P-hydroxybutyric Acid.-In the course of feeding experi-ments with pure amino-acids, W. C. Rose 24 found that young ratsfailed to maintain themselves when supplied with a mixture ofnineteen amino-acids instead of protein.Growth, however, occurredif the mixture was supplemented by a concentrate of the monamino-fraction of a protein hydrolysate. M. Womack and W. C. Rose 25found that the supplementary concentrate supplied two factors,one of which was identified as isoleucine (which was present in theartificial mixture, but, evidently, in insufficient amount). Thesecond essential factor has been isolated26 from fibrin and shownto be cc-amino-p-hydroxybutyric acid, since on reduction it givescc-aminobutyric acid, and since (unlike a-amino-y-hydroxybutyricacid) it does not yield a lactone when warmed in acid solution.Moreover, a-amino-y-hydroxybutyric acid (synthetic) was unableto replace the natural acid in growth experiments. H. E. Carter 27prepared a-amino-p-hydroxybutyric acid by the method of E.Abder-halden and I<. Heyns,28 but the product was without effect in growthexperiments. The synthetic material, obtained from crotonic acid,contained two of the four possible isomers. Carter, therefore, con-verted it into a mixture of the two epimers by preparing the formylderivative, heating this with sodium hydroxide and acetic anhydride,and hydrolysiiig the product with hydrobromic acid. This treat-ment yielded a mixture which supported growth, with about afifth of the activity shown by the natural acid. Attempts to con-1 8 M. Kitagawa and T. Tomita, Proc. Imp. Acad. Il'okyo, 1929, 5, 380.19 M. Kitagawa, I<. Sawada, and Y. Hosoki, J. Agric. Chem. Xoc. Japan,20 Ibid., p. 558.3 1 J .Agric. C'hem. SOC. Japan, 1935, 11, 1083.22 Ibid., 1936, 12, 256.z 3 ]bid., p. 828.24 J . Biol. Chenz., 1931-3, 94, 155; C. T. Caldwell and W. C. Rose, ibid.,25 Ibid., 1935, 112, 275.26 R. H. McCoy, C. E. Meyer, and W. C. Rose, ibid., p. 383.27 Ibid., p. 769.a8 Ber., 1934, 67, 530.1935, 11, 539.1934, 10'9, 57402 BIOCHEMISTRY.centrate the active isomer by fractional crystallisation have not yetbeen successful. A more detailed study29 of the amino-acid fromnatural sources involving its reduction to d-a-aminobutyric acid(which belongs to the L series) and its oxidation to Z-lactic acid(which belongs to the D series) indicates that it corresponds inspatial structure to d(-)-threose (VII). It therefore has theconfiguration represented in (VIII).It is proposed to name itd( -)-threonnine.TO*OHH p F * I I YHO H0.Q.H( V W H*T*OH HOPOH (VIII).CH,*OH CH3&'. Kimop, B'. Ditt, W. Heckstcdcn, J. Maier, W. Merz, and 1%.Hurlc 30 have synthesised a-amino- p-hydroxy-y-phenylbutyric acidand a-amino-p-hydroxy-6-phonyl-n-valeric acid. Their study ofthese indicates that a-amino- p-hydroxy-acids are not degraded inthe same way as simple amino-acids, but that they undergo p-oxid-ation and yield nitrogen-free acids. Presumably a-ainino- P-keto-acids are formed, and these, they say, have a much greater redoxpotential than ascorbic acid.Sulphur-containing rl mino-acids .-Dj enkolic acid 31 has beensynthesised 32 by the action of methylene dichloride on the sodiumderivative of cysteine in liquid ammonia, and its constitution con-firmed as CH,[S*CH,*CH(NH,yCO,a],.From the same laboratory %comes a synthesis of glutathione with improved yields, the methodemployed differing from that of C . R. Harington and T. H. Mead31in that the SH group of the cysteine is protected by benzylation sothat S-benzylcysteinylglycine is condensed with the a-monomethylester of N-carbobenzyloxyglutamic acid, and the final reduction isachieved by means of sodium in liquid ammonia.34 A new synthesisof methionine has been published by E. M. Hill and W. Robson,35who treat ethyl y-chloro-a-benzamidobutyrate (prepared froma-benzamido-y-butyrolactone) with sodium methyl mercaptide,followed by alkaline hydrolysis, and hydrolyse the resulting benzoyl-methionine with acid.It has been known for some time36 thatmethionine is capable of replacing cystine in a cystine-deficient29 C. E. Meyer, and W. C. Rose, J . Biol. Chem., 1935, 115, 721.3O 2. physwl. Chem., 1936, 239, 30.31 Ann. Reports, 1935, 33, 418.32 V. du Vigneaud and W. I. Patterson, J . Biol. Ch~m., 1930, 114, 633.33 V. du Vigneaud and Miller, ibid., 1936, 118, 469.34 Cf. H. S. Loring and V. du Vigneaud, ibid., 1935, 111, 38s.3b Bwchem. J., 1936, 30, 248.36 Ann. Reports, 1934, 31, 340STEWART AND STEWART. 403diet; now, however, it is suggested that the converse is not true,and that methionine is itself an “ essential ” amino-acid.37Chemotherapy.Trypanosomiasis and Sypitilis.-G. T . Morgan and E. Walton 38have studied compounds of the general formula (X)-for values ofn ranging from 1 to 8 and in which R and R’ are either hydrogen,alkyl or aryl groups-in relation to arsacetin (IX) and tryparsamide(XI), which in all probability is the most widely used of the quin-quevalent arsenical drugs.There does not appear to be any0 3 H N a As0,HNa(XI. )NH*CO*CH, NII*CO*[CH,];CO*NRR’ NH*CH,*CO-NH,well-defined relationship between the chemical constitution and thetherapeutic activity of these compounds. They exhibit varyingdegrees of curative action on experimental trypanosomiasis in mice,many of them having a therapeutic activity in trypanosome-infected mice which is at least equal to, if not greater than, thatof tryparsamide. Branching of the carbon chain tends to diminishthe activity and as the value of n in the straight chain approaches8 there is considerable rise in toxicity.W. Yorke, F. M~rgatroyd,3~and their collaborators reporb very favourably on extensive trialsof sodium succinanilomethylamidc-p-arsonate (Neocryl) (X ; n = 2 ;R - H, R’ = CH,), which is the most readily available of thesederivatives, and they regard this compound as being more activethan is tryparsarnide on trypanosomiasis in laboratory animals.They record instances of its having effected definite clinical im-provement in Nigerian sleeping sickness, in some cases with restor-ation of the cerebrospinal Auid to its normal state. They havefound too that it differs from tryparsamide in its ability toexert a definite action in primary, secondary and tertiary syphilis,as distinct from neuro-syphilis.The latter group OE workers 40 have long interested themselves inthe important problem of arsenic-resistant strains of trypanosomes,their more recent investigations of the mechanism of the action ofarsenicals on trypanosomes 40-recently summarised by W.Yorko0 (X. 137 W. C. Rose et nl., J . Biol. Chem., 1936, 114, lxxxv.38 J., 1931, 615, 1743; 1932, 2764; 1933, 91, 1064; 1935, 390; 1936, 902.39 Brit. Med. J., 1936, 1042.40 Awn. Trop. Med. and Pamsit., 1930, 24, 449; 1931, 25, 313, 351, 521;1932, 26, 215, 577; 1933, 2’9, 157; Brit. Med. J., 1933, 176404 BIOCHEMISTRY.and I?. Murgatroyd 41-being aided very materially by their funda-mental discovery 42 of a satisfactory method whereby the pathogenictrypanosomes could be maintained in vitro for twenty-four hours at37' in undiminished numbers and in a condition of unloweredvitality. Confirmation and extension of their findings are nowaccumulating from various sources.L. Launoy, M. Prieur, andA. hcelot 43 have produced an arsenic-resistant strain of T. anna-mense in the guinea pig by repeated tryparsamide treatment andhave found that, like the similarly produced arsenic-resistant2'. rhodesiense of W . Yorke and his collaborators, it is therebyrendered resistant to the quinquevalent arsenicals and to a thio-arsinite. C. H. Browning and R. Gulbransen 44 record experimentsindica$ing that the immunity which develops after treatment witha curative drug depends on the particular strain of trypanosomeand on the species of host.After studying the mode of action ofa number of organic arsenicals on rats infected with T. Zewisi andon rats infected with 2'. equiperdum, M. L. Kuhs, C. C. Pfeiffer,mid A. L. conclude that a specific relationship appearsto exist between the type of arsenical and the type of trypanosome.The same authors 46 have made the interesting observation thatinfections of T. Zewisi in rats which are easily cured by arseno-phenylglycine provided that treatment is begun within 3 4 daysof inoculation lose their arsenic susceptibility if there is furtherdelay in commencing this treatment. T. Naito and S. Oka 47 haveproduced a strain of trypanosomes resistant to orsanine (3-acet-amido-4-hydroxyphenylarsonic acid) and to the tervalent arsenicalsiieosalvarsan and neosilversalvarsan, and studied its sensitivity toother arsenical and non-arsenicaldrugs.F.R. W. K. Allen *s has treated nine cases of syphilis in Indiawith a Merck preparation Modenol, a salicylate of arsenic andmercury, and eight of these cases have shown considerable im-provement. A. B. Cannon and J. Robertson,Pg who set out todetermine the relative values of bismuth and mercury preparationswith arsphenamine in the treatment of early syphilis, have con-cluded that it is difficult to assay the relative values of bismuthand mercury, both of which are important in syphilis therapy. A41 Tram. Roy. SOC. Trop. Med. Hyg., 1935, 28, 435; Ty. Yorke. Riv.Malarial., 1935, 14, Suppl.4a Ann.Z'mp. Ned. and Parasit., 1929, 23, 501.48 Bull. SOC. Path. mot., 1935, 25, 857; 1936, 29, 769.44 J . Path. Bat., 1936, 43, 478.45 J . P b m . Exp. Ther., 1936, 57, 144.*t3 Amer. J . Nyg., 1936, 23, 10.47 2. Bakt., 1936, 137, 401.(@ J . Amer. Ned. Aaaoc., 1936, 106, 2133.48 I n d i m Med. Qaz., 1936, 329STEWART AND STEWART. 405leading article in a recent issue of the Lancet expresses the opinionthat bismuth preparations are replacing mercurials in antisyphilitictreatment and makes special reference to the very favourableresults of the tests by F. M. Thurmon 51 on some two hundredpatients in his clinic over a period of eighteen months with a fat-soluble preparation, bismuth ethyl camphorate, either alone or inconjunction with arsphenamine.In these trials it comparedfavourably both as regards local pain or discomfort and moregeneral toxic effects with the standard bismuth preparation-bismuth salicylate suspended in oil-which was in routine use onother patients in the clinic, and stress is laid on one particularlyvaluable feature of its activity, the efficiency of its mode of actionin serological tests. W. &I. Lauter and H. A. Braun 52 have pre-pared a series of bismuth trialkyl camphorates by allowing bismuthnitrate to react in aqueons glycerol with the appropriate sodiumalkyl camphorate and have determined their toxicity on intra-muscular injection into rats.Malaria.-Preliminary reports 53 on the treatment of malariawith atebrin musonate (atebrin methyl sulphonate) have beenpromising.In recent months much evidence has been publishedwhich serves to substantiate the claims of atebrin and its musonatefor wider clinical application. A. T. W. Simeons 54 has obtainedvery satisfactory results in the mass treatment of all persons in anendemic area with two injections of atebrin musonate at twenty-four-hour intervals. With atebrin, as with all synthetic prepar-ations, claims on the grounds of therapeutic efficiency are con-sidered together with cost of production. Thus J. A. Carman andR. P. Cormack 55 record the comparison of a number of cases ofmalaria in Kenya treated with atebrin musonate with an equalnumber of controls given quinine and plasmoquine. They considerthat the results were as good as those of quinine treatment, with aprobable lower relapse rate and without toxic symptoms, but theyconsider that the drug is uneconomical for use on natives.Incontradistinction to this conclusion a large-scale trial of atebrin asa prophylactic in malarial regions of the Southern States, havingshown that the drug is superior to quinine, producing completedestruction-not merely inhibition-of the parasites, has caused60 1936, 1163.5 1 New Eng. J . Med., 1936, 315.52 J . Amer. Phnm. A ~ ~ o c . , 1936, 2!j, 394; cf. M. Picon, Bull. SOC. chirn.,53 Ann. Reports, 1935, 32, 422; S. Somasundram, Tram. Roy. SOC. Trop.54 Indian Med. Gaz., 1936, 71, 132.55 Trans. Roy. SOC. Trop. Med. Hyg., 1936, 29, 381.1936, 3, 176.Med. Hyg., 1935, 29, 103; E.C. Vardy, Malayan Med. J., 1935, 10, 67406 BIOCHEMISTRY.W. W. Bispham 56 to consider such treatment not only superiorto quinine but actually cheaper in spite of the greater cost of thedrug, for the simple reason that a smaller quantity suffices toeffect a cure.For all comparative work of this nature it is well to note theobservation of F. Mietszch, H. Mauss, and G. Hecht 57 that aqueoussolutions of atebrin decompose slowly on keeping with the form-ation of an acridone and falling off of toxicity, and the conclusionwhich S. F. Seelig and W. Singh 58 have drawn from a comparisonof three methods of atebrin musonate treatment with or withoutadrenaline as to the most satisfactory method of administering thedrug. They obtained the best and quickest results by givingadrenaline, followed by an intramuscular dose of atebrin musonate,and allowing twenty-four hours to elapse before commencingregular doses of atebrin tablets.C.Ragiot and I?. Moreau 59 have used quinacrine 60 with successin cases of hematuria due to quinine. 0. J. Magidson and hiscollaborators 61 have continued to study the therapeutic activitywith acridine derivatives closely allied to atebrin in relation tovariations in chemical structure. From observations of malariain children R. Sherman 62 considers that acriquine (6-chloro-9-diethylaminobutylamino-2-methoxyacridine) has a high therapeuticvalue. B. N. Rubenstein 63p64 has found this same drug verysuccessful for the treatment of induced malaria in paralytics andregards it as having a prophylactic action on experimental malariain man.I n the study of monkey malaria anomalies in the behaviour ofquinine and the various synthetic antimalarials have been noticedfrom time to time.Working with PI. Knowlesi infections in apes,E. G. Nauck and B. Malamos 65 have furnished evidence in favourof the conception that atebrin and quinine are alike in one respect,that they exert a, direct action on the malarial parasites, but thatthey differ in their mode of action in that the morphological changeswhich the parasites undergo are quite different for the two drugsand different from the changes in the controls.66 Amer. J . Trop. Med., 1936, 16, 547; cf. H. Flack, D. C. Majumder, andK. Goldsmith, Indian J. Med. Res., 1936, 71, 373.67 Indian Ned.Caz., 1936, 71, 521.58 Records Mal. Survey Ind., 1936, 6, 171.69 Bull. SOC. Path. mot., 1936, 29, 496.60 Identical in chemical constitution with atebrin.6 1 Ber., 1936, 69, 396, 537.62 Med. Parasit. and Parasit. DiS., 1935, 4, 446.68 Arch. Schiff. Trop. Hyg., 1936, 40, 167.64 Med. Parasit. and Parasit. Dis., 1936, 5, 256.65 Klin. Woch.. 1936, 888STEWART AND STEWART. 407Antiseptics.-Noteworthy contributions have been made duringthe year under review to the problems of antisepsis. Investigationsof the means of combating infection of the urinary tract discussedin an earlier report G. H. Newns and R. Wilson 67have found that mmdelic acid in the form of its ammonium saltis an effective remedy for B.coli pyelitis in children. P. Ganguli 68has employed the sodium salt. H. 3'. Helmholz and A. E. Oster-berg 69 have studied both the urinary excretion of sodium mandelateand the bactericidal effect of this salt in various concentrations ona, number of organisms, while in continuation of his pioneer workon the subject N. L. Rosenheim 70 has given an account of thetreatment of almost one hundred cases of various types of urinaryinfection with ammonium mandelate.The Prontosil group of antiseptics, derived from paminobenzene-sulphonamide, of which Prontosil (XII) 71 and Prontosil X (XIII) 72still continue.OHare at present the most efficacious, has come into prominence andis receiving considerable attention for the treatment of strepto-coccal and staphylococcal infection^.^^ E.Fourneau, J. Tr6fouE1,F. Nitti, and D. Bovet 74 have observed that p-aminobenzene-sulphonamide has an inhibitory effect on the growth of mouldswhich is not seen in prontosil, and P. Nitti and D. B o ~ e t , ~ ~ review-ing the present position of our knowledge of prontosil and itsderivatives, note that guinea pigs cim be sensitised to prontosil but66 Ann. Reports, 1936, 32, 425.67 Lancet, 1936, 230, 1087.6 8 Indian Med. Gaz., 1936, 71, 517.69 Proc. Mayo Clinic, 1936,11,373 ; J . Amer. Med. Assoc., 1936, 107, 1794;cf. L. P. Dolan, ibid., p. 1800.70 Lancet, 1936, 230, 1083.7 1 Angew. Chem., 1935, 657.72 Ibid., p. 661.73 K. Imhauser, Klin. TYoch., 1938, 282; L. Ley, Munch. rned. Woc?~.,1936, 1092; A.Roth, Deut. med. JT70ch., 1935, 1734; C. Levaditi and A.Vaisman, Compt. rend. Soc. biol., 1035, 119, 946; 1936, 121,803; L. Colebrookand M. Kenny, Lancet, 1936, 1279, 131!1; H. Rorloin, Pror. Roy. Xoc. Med.,1936, 29, 313.74 Compt. rend. Xoc. biol., 1936, 122, 6.52.7 6 Revue d'Imrnun., 1936, 2, 450, 461408 BIOCHEMISTnY.not to thc parent substance. Prontosil and the more solubleprontosil S , administered intravenously or better orally, are graduallyestablishing themselves as successful means of combating ery-sipelas.76 H. Floch 77 has administered prontosil orally withsuccess in the treatment of elephantiasis. Numerous derivativesof p-aminobenzenesulphonamide 78 have been prepared, but thereis as yet insufficient evidence on which to base a discussion oftheir therapeutic activity.The observation of R. Hilgermann 79that alkali-metal salts of the bile acids, suitably protected by acolloid, can cure streptococcal infections opens up interestingpossibilities. c. P. s.J. S.PLANT BIOCHEMISTRY.Metabolism and Biochemical Activity of Certain Bacteria.Axotobacter.l-The production of free ammonia by these organismshas been the subject of much controversy. Earlier workers haddisagreed not only on the question of whether or not the organismdid actually produce free ammonia, but also as to whether thisammonia should be regarded as the first product of nitrogen fixationwith subsequent elaboration into bacterial protein. S. Winogradsky,2working on silica-gel to avoid secondary reactions, confirmed hisearlier adherence to the view that the nitrogen exchange of theorganisms takes the course N, --+ NH, -+ cellular protein, andthat in very alkaline media a surplus of NH, appeared in the nutrientsubstrate.S. Kostytchev and 0. Schelo~rnova,~ following upprevious investigations with A . vinelandii, added further supportto Winogradsky's theories and also demonstrated that free ammoniawas produced only in the presence of an adequate carbohydratesupply. Fixed nitrogen supplied to the organism was reduced to7 6 L. Gmelin, Munch. med. Woch., 1935, 221; W. Kramer, ibid., 1936,608; G. Scherber, W i e n . med. Woch., 1935, 284, 346, 376; E. Wehren,Schweiz. med. Woch., 1936, 06, 665 ; V. Anghelescu and collaborators, Deut.med. Woch., 1936, 1639; K.Hartl, ibid., 1936, 1641; J. Frankl, K l i n . Woch.,1936, 15, 1562.77 Bull. Boc. Path. exot., 1936, 29, 165.7 8 P. Goissedet and collaborators, Compt. rend. SOC. bid., 1936, 121, 1082 ;E. Fourneau, J. Trkfouel, F. Nitti, and D. Bovet, ibid., 1936, 122, 258:G. A. H. Buttle, W. H. Gray, and D. Stephenson, Lancet, 1936, 1286; F.Nitt,i and D. Bovet, Compt. rend., 1936, 202, 1221.79 Deut. med. Woch., 1936, 883.1 See Ann. Reports, 1933, 306.2 Ann. Inst. Pasteur, 1932, 48, 269.8 8. physiol. Chen,., 1931, 198, 105POLLARD. 409ammonia and subsequently u tilised in protein synthesis. Hefurther showed that in the absence of a suitable carbon source cellularprotein was itself deaminated with the formation of ammonia.A. Isakova,4 working with A .vinelandii and A . chroowccurn,obtained similar results and demonstrated the production ofammonia in neutral or only very slightly alkaline media in whichglucose, mannitol, or even salts of organic acids (sodium acetate,benzoate) formed the source of carbon. M. Roberg5 and alsoD. M. Novogrudski examined filtrates from Azotobacter cultureswhich were shown to contain nitrogen compounds utilisable by othermicro-organisms (notably those utilising amino-acids or ammonia).Free ammonia, however, did not appear in the filtrates until theenergy source had been exhausted by the bacteria. These resultsfall into line with an earlier suggestion of Kostytchev that ammoniafound in culture media was largely derived from bacterial protein.Presumably any ammonia derived directly from nitrogen would beutilised by actively growing organisms as fast as it is formed.Onthe other hand A. N. Bach et al. reported the production of ammoniafrom nitrogen by the expressed juice of Axotobacter cells, thus support-ing the conception of the enzymic formation of ammonia as the firststep in the nitrogen fixation process. In a series of detailed andcarefully controlled experiments D. Burk and C. K. Horner,8continuing earlier investigations, showed that the extra-cellularproduction of ammonia by both A . winelandii and A . clwoococcumprobably results almost entirely from the decomposition of cellularprotein and not to any appreciable extent from free nitrogen. Underoptimum agrobic conditions (px 7-8 and 3 0 4 0 " ) as much as 50%of the microbial nitrogen was liberated as ammonia.The presenceof nitrogen was found to be quite unnecessary for ammonia produc-tion. The course of liberation of ammonia was closely paralleledby that of oxidation of cell constituents and was inhibited by re-agents which normally check biological oxidations as well as by thepresence of even small amounts of oxidisable organic matter. It issuggested that ammonia may not even be a necessary step in thesynthesis of bacterial protein from nitrogen and that amides may beconcerned here. In this connexion G. Endres9 indicates the pro-duction of oximes in culture media of Azotobacter and suggests hydr-oxylamine as an intermediate stage in the fixation process. Burk4 Bull.Acad. Sei. U.R.S.S., 1933,9, 1493.5 Jahrb. wigs. Bot., 1935,82, 1, 65.Microbial. U.S.S.R., 1933, 2, 237.A. N. Bach, Z. V. Yermolieva, and M. P. Stepanion, Cornpt. rend. Acad.Sci. U.R.S.S., 1934,1, 22.8 Soil Sci., 1936,41, 81.@ Naturwiss., 1934, 22, 662 ; Annalen, 1935, 518, 109410 BIOOHEMISTRY.and Horner propound the following scheme of nitrogen exchangebeing most in accord with experimental data :aslllc8 stable cellular rlcnminatioliN, + organic matter -e--tz compounds of F---+ NH,.reduced N growthProm this point of view extracellular ammonia is liberated onlyunder conditions in which growth is insufficiently rapid to permit thecomplete utilisation of the ammonia produced by the oxidativedecomposition of the cellular constituents.The authors, however,point out that the data cannot be interpreted as definitely ruling outthe possibility that some ammonia may be formed in the fixationprocess.An examination of the cellular proteins of Axotobacter by R. A.Greene lo indicates that these consist largely of globulins, glutelins,and albumins. The amino-acid distribution (Van Slyke) showeddifferences among the species, but in general arginine and lysinepredominated and smaller proportions of tyrosine, tryptophan,cystine, and histidine together with approximately 40% of the non-basic fraction were found. The presence of glutathione was alsoindicated.Another aspect of the activity of Axotobacter is presented by N. R.Dhar and colleagues,ll who have shown that the fixation of nitrogenby these bacteria in tropical soils is optimum a t 35", as comparedwith 28" in temperate soils, and in both cases is negligible at 10".It would seem, therefore, that the value of Axotobacter in maintainingthe nitrogen supply in soil has been somewhat over-estimated.Theaddition of molasses to soil for the purpose of increasing fixationresulted in a rapid iiicrease in the number of organisms, but theamount of nitrogen fixed did not increase proportionally. Rapidfixation is associated with more or less stationary nunibers ofAxotobacter. The improved nitrogen-status of molasses-treatedsoils, formerly attributed to increased bacterial fixation, is repre-sented as being partly due, at least in tropical soils, to photochemicaleffects.Among investigations of the influence of different carbon sourceson the activity of Axotobacter may be cited that of S.WinogradsBy,l2in which it is shown that in addition to sugars, certain alcohols andsimpler fatty acids (2-4 C) may be utilised. T. R. Bhaskaran andV. Subrahmanian,13 working with mixed soil organisms in glucosel1 N. R. Dhar and S. P. Tandon, Proc. Nat. Acnd. Sci. India, 1936, 6,35; N. R. Dhar and E. V. Seshacharyulu, ibid., p. 99; N. R. Dhar and S. K.Mukerji, J . Indian Chem. Xoc., 1936, 13, 155.10 Soit? S&., 1935, 39, 327.l2 Compt. rend., 1936, 203, 10. Is Current Sci., 1935, 4, 234POLLARD. 41 1media, noted an initial period of activity, in which carbon dioxideand organic acids were formed from glucose, but the amount ofnitrogen fixed was much less than that to be expected.Moreovermuch of this nitrogen was in a soluble form. Subsequently theorganic acids were decomposed and apparently normal fixationproceeded. In a later paper l4 fixation of nitrogen by the mixedflora was shown to be facilitated by addition of organic acidsobtained in the nnagrobic decomposition of sugar. Utilising purecultures of A . chroowccum, Bha.skaran l5 found no relationshipbetween the presence of these sugar-decomposition products andthe fixation of nitrogen, the course of which differed from thatoccurring with mixed soil cultures. It appears possible, however,that the acids contributed largely to the production of cellularconstituents or perhaps served as energy sources.In young culturesthe accumulation of carbon in the slime and bacterial cells was muchmore rapid than that of nitrogen. Later the ratio narrowed some-what. G. Guittonneau and R. Chevalier l6 record that pure culturesof Axotobacter can utilise sodium sslicylate and continue the fixationprocess .Carbon Metabolism of, and Nitrogen Fixation by, Rhizobia.The close relationship between the carbon metabolism and nitro-gen exchange of these organisms referred to in a previous Report 17continues to receive considerable attention at the hands of variousresearch workers. Interesting data relating t o the effect of nutri-tional factors on the respiratory quotient of cultures have now beenobtained. have examined theoxygen consumption of R. meliloti on glucose media, and have shownthat the carbon dioxide produced corresponds to approximatelyone-third of the carbon in glucose, the amount being somewhatgreater when ammonia than when nitrate forms the nitrogen source.The pH optimum for growth of R. meliloti and R.japonicum appearsto be less than that for re~pirati0n.l~ In a further publication 0. R.Neal and R. H. Walker 2O record that the oxygen consumption ofR. meliloti was substantially the same on glucose, mannitol, andsucrose media, but was very much greater on arabinose-nitratemedia. Galactose was more effectively utilised than was glucose onboth ammonia and nitrate media, whereas maltose, lactose, inositol,Thus 0. R. Neal and R. H. Walker14 Proc. Indian. Acad, SCi., 1936, 4, B, 163.l5 Ibid., p.67.l6 Compt. rend., 1936, 203, 211.l7 Ann. Reprta, 1934, 347.19 D. W. Thorne and R. H. Walker, J . Ract., 1935, 30, 33.20 Ibid., p. 173.Proc. Iowa Acnd. Sci., 1934, 41, 1674 12 BIOCHEMISTRY.dulcitol, and sorbitol with both forms of nitrogen, and raffinose anderythritol in ammonia media, proved inferior energy sources.For this species ammoniacal nitrogen was in general more readilyutilised than was nitrate. The reverse was true of R. japonicurn,which also exhibited characteristic differences in its ability to utilisecarbohydrates. Arabinose proved the best energy source, followedby glucose, galactose, and xylose, which were equally effective.Maltose, lactose, sucrose, mannitol, and erythritol were of little orno value in this respect.Subsequently Thorne, Neal, and Walker 21determined changes in respiratory quotient with time for five speciesof Rhixobia, using different sources of nitrogen, and found character-istic species-differences in this case also. Comparing 24- hour cul-tures, the mean quotients for four nitrogen SOiirces for R. Qaponicumand R. leguminosarum were definitely lower for R. rneliloti, R. trifolii,and R. phuseoli in glucose media. In the absence of the sugar thesedifferences disappeared. The mean quotients of the five specieswere similar on nitrate and on ammonia media with glucose, butwere lower when yeast or asparagin was used to supply nitrogen.In the absence of glucose respiration in nitrate and ammonia mediawas largely endogenous and the quotient approached the theoreticalvalue for protein, wix., 0.13.Asparagin and yeast provided somecarbon supplies and the quotients were lower in these cases, especiallywith yeast.The much-discussed dependence of the nodulation of leguminousplants on the carbon : nitrogen balance of the plants themselves hasbeen further examined by P. W. Wilson,22 who traces characteristiceffects of differences in C : N balance on the size and distri'uution ofnodules, the amount and rate of nitrogen fixation, and the influencethereon of external conditions. On the basis of these effects a systemof classification of plants in respect of their carbohydrate : nitrogenratio is developed. An interesting review of the significanceof the carbohydrate supply of the plant in the symbiotic relationshipis given by F.E. Allison 23 who emphasises that, provided soil con-ditions are suitable, the activity of organisms within nodules isprimarily controlled by the availability of carbohydrates, and thatit is only when these become inadequate that the bacteria may makea direct attack on plant tissue. C. E. Georgi,a in examining thewell-known effect of a supply of fixed nitrogen in reducing nodulation,showed that this condition is reflected in a temporary increase in theamount of carbohydrates and a decrease in that of nitrogenousal Arch. Mikrobiol., 1936, 7 , 477.22 Wisconsin Agric. Exp. Sta. Res. Bull., 1935, No. 129, 40 pp.s3 Soil Sci., 1935, 39, 123.24 J . Agric. R e . , 1935, 51, 597POLLARD.413matter in the sap of red clover. The inhibitory action is diminishedby further increasing tho carbohydrate supply, e.g., by increasing thesupply of carbon dioxide to the leaves. Similar conclusions arereached by E. W. Hopkins 25 in the case of soya-bean organisms,the carbohydrate : nitrogen balance in this case being altered byvarying the period of exposure and light, by partial shading, and byalteration of the nitrate supply of the plants. Whatever com-bination of external factors was adopted, the general conclusion isdrawn that accumulation of soluble nitrogen in the plants restrictedand that of carbohydrates favoured nodule formation. F. S.Orcutt and P. W. Wilson,26 also working with soya bean to whichvarying supplies of nitrate were given, record similar results.Stressis laid, however, on the indirect effect of nitrates on nodulation, thecarbohydrate level in the plant sap varying with the nitrate concen-tration in a manner similar to the intensity of nodulation. It isinferred that nodule formation is directly related to the carbohydratesupply and is affected by other conditions only to the extent to whichthese conditions influence the carbohydrate concentration in theplant. There is evidence that a definite rate of nitrate supply to theplant can be associated with the cessation of nitrogen fixation by thebacteria. Below the limiting value, the nitrate concentration in-creases or decreases nodulation according to whether photosynthesisor nitrogen supply becomes the limiting factor in protein formation,i.e., whether there is a surplus of carbohydrate in the sap or a surplusof nitrogen, which is necessarily accompanied by a very low level ofcarbohydrate.H. G. Thornton and H. Nicol27 support this view byshowing that in sand-cultured lucerne the yield and nitrogen contentof lucerne were not affected by varying (within limits) the amountof nitrate supplied. Presumably the limiting factor here was thecarbohydrate produced by photosynthesis, and the nitrogen supplywas derived from nitrate or from nodule organisms to meet require-ments. Above certain concentrations of nitrate in the nutrient thenumber and size of nodules diminished. In other concentrationsnitrates actually prevented the infection of growing roots by noduleorganisms.This was to some extent counteracted by addition ofglucose to the media.28 In the latter paper Thornton recorded astimulation of growth and an increase in the number of root hairs dueto secretions from the nodule bacteria.In many instances stimulation either of nodulation or of growth ornitrogen fixation by free cultures of nodule organisms has beenobserved following the addition of various substances. Thus S.26 Soil Sci., 1935, 39, 297.27 J . Agric. Sci., 1936,26, 173.B8 H. G. Thornton, Proc. Roy. SOC., 1936, B, 119, 474.26 lbid., p. 289414 BIOCHEMISTRY.Winogradsky 29 found the addition of simple nitrogen compounds,e.g., ammonia, amines, amides, t o otherwise nitrogen-free culturesimproved the development and sugar consumption but caused nomarked increase in the amount of nitrogen fixed.Addition of moresubstances such as extracts of yeast or of plant organs further in-creased development and initiated a normal rate of fixation of nitro-gen. Similar results were obtained by A. Itano and A. M a t s ~ u r a , ~ ~the activity of extracts being in the order seedlings > germinated> ungerminated seed, and among corresponding extracts of differentspecies in the order, nodulc-bearing legumes > non-legumes > non-nodule-bearing legumes. In a later paper 31 the same authors foundthe actual principle from bean nodules to pass into the cathodechamber on electrodialysis. In this respect it differed from yeastextract, in which the accessory substance showed no tendency tomigrate.No relation was apparent between the activity of acoessorysubstances and their nitrogen contents. Their action was that of atrue growth-promoting substance rather than that of a nutrient.P. E. Allison and S. R. Hoover 32 attribute the increased growth ofRhixobia by natural, but not by synthetic, huniic acid to the presenceof co-enzyme R. This is the reverse of the view previously expressedby D. W. Thorne and R. H. Walker,33 who ascribed the stimulatoryeffects of plant and yeast extracts to nutrient matter present anddiscredited the intervention of any co-enzyme in the activity of theorganisms. A somewhat different view of this question was pre-sented by C. A. Ludwig and F. E. Allis0n,3~ who observed increasednodulation of soya bean and lucerne when grown in sand cultures inthe presence of other plants, e.q., wheat or maize.Additions of sugaror small amounts of nitrogen compounds sometimes producedsimilar effects under these conditions, but extracts of the sand inwhich the plants had been growing were inactive. The excretionof stirnulatory agents by the plant roots seems therefore excludedfrom consideration. The authors suggest that the presence of otherplant roots induces in the rhizosphere conditions conducive to thedevelopment of the bacteria, possibly including the formation of abacterial growth-promoting substance. Thorne, Neal, and Walker(Zoc. cit.) support the view that yeast extracts exert a stimulatoryaction on the growth and respiration of Rhizobia, which can bedifferentiated from that attributable to the carbonaceous and nitro-genous nutrients which they contain.The action of yeast is, how-29 Ann. Tmt. Pasteur, 1936, 56, 221.3O Ber. O h r a Irzst. larzdw. Forsch., 1936, '7, 185.31 J . Ayric. C h e m SOC. Japan, 1936, 12, 457.33 Proc. Iowa Acccd. Sci., 1934, 41, 63.34 J. Arner. SOC. Agronomy, 1935, 27, 895.'2 Soil Sci., 1936, 41, 333POLLARD. 415ever, ascribed to its ability to act as an effective hydrogen-donatorto the organisms. This is in agreement with the observation ofW. P. Allyn and I. L. Baldwin35 that yeast, unlike potassiumnitrate, when used as a nitrogen source for Rhixobia cultures, tendsto maintain in the media an oxidation-reduction potential which isvery favourable to the growth of the organisms.In a recent paper 36Thorne and Walker record that reducing agents, e.g., cysteine andthioglycollic acid, increased the growth and oxygen consumption ofRhixobia.The nitrogen exchange of nodule organisms, especially in relationto the mechanism of the fixation process, and to the observed excre-tion of nitrogenous substances, has formed the subject of manyinvestigations. According to A. I. Virtanen and M. Tornianen 37the nodular proteins yield tryptophan, arginine, tyrosine, asparticacid, and some diamino-acids. In culture media, following thegrowth of the inoculated legumes there are prescnt aspartic acid,lysine, and smaller amounts of simpler compounds, e.g., nitrite,nitrate, hydroxylamine or ammonia.Excretion of these compoundsis dependent on appropriate supplies of air to the root^,^^,^^ andceases when these are immersed in stagnant liquid media. Thevitality of the organisms is not destroyed, however, since on re-aera-tion nitrogen fixation and excretion of fixed nitrogen continue.Virtanen concludes that the aspartic acid and probably the lysineexcreted are not derived from nodular protein (the proteolyticactivity of the organisms is apparently small 40), but represent prim-ary products of nitrogen fixation.41* 42 It is suggested that asparticacid may be formed from hydroxylainine and oxalacetic acid.43S. Winogradsky (Eoc. cit.) observed the elimination of ammoniafrom cultures to occur only during fixation of nitrogen.G.Bondt4 in an examination of the nitrogen exchange in soyabean, established that a very considerable proportion of the totalnitrogen fixed by nodule organism (in some cases probably SO--SO%)diffuses into the cytoplasm of the host plant and is translocatedinto the plant system. In a discussion of the fixation process theauthor considers this to resemble a type of respiratory activityrather than a stage in the synthesis of bacterial protein.3 5 J . Bact., 1932, 23, 369.37 Sumen Kern., 1936,9, B, 13.38 A. I. Virtanen, J. Agric. Sci., 1935, 25, 278, 290.39 A. I. Virtanen and S. von Hausen, ibid., 1936, 26, 281.40 A. I. Vistanen and T. Laine, Biochem. J . , 1930, 30, 377.4 1 Idem, Suomen Kern., 1936, 9. B, 12.42 A. I. Virtanen and M. Tornianen, Zoc.cit., ref. (37).43 A. I. Virtanen and T. Laine, Suomen Kern., 1936, 9, B, 5.44 Ann. Bot., 1936, 50, 659.36 Soil Sci., 1936, 42, 231416 BIOCHEMISTRY.Photosynthesis in Plants.InflzLence of External Factors.-The complex problem of the effectsof the quality and intensity of light, of the carbon dioxide concen-tration of the surrounding atmosphere, and of temperature on therate of carbon assimilation of plants forms the subject of a greatnumber of publications of the last few years. Much of this workfollows along lines which are not altogether new in general principlebut either develop an improved technique, expand the detail ofexperimental data, or, in the light of advancing knowledge, leadto new interpretations of already accepted facts.The applicationof the theory of limiting factors either as put forward by Blackmanas a development of the “ law of minimum,” or with the modification(introduced by Harder) of the idea of relative minimum, servedfor a number of years as a working basis for much experimentalwork. More recent research tends to explore the limits of applicabil-ity of these theories. No attempt can be made in the space of thisReport to give a comprehensive review of this field of enquiry, butsome indication of the general trend of recent work seems desirable,especially in view of its ultimate bearing on the more purely chemicalconsideration of the mechanism of the photosynthetic process.W. H. Hoover, E. S. Johnston, and F. S. Brackett 45 record dataagreeing within limits with Blackman’s law, and show that in wheatplants carbon assimilation exhibits a straight-line relationship withcarbon dioxide concentration in an excess of light, and with lightintensity in the presence of an excess of carbon dioxide.Theyindicate, however, a range of conditions between zones in which eachlimiting factor becomes dominant and conclude that this intermedi-ate range is wider for higher plants than for algz. 13. N. Singh andK. N. La1,46 using wheat, linseed, and sugar cane plants, compare theresults of much experimental work with the theories of Blackmanand of Harder. The form of carbon dioxide concentration-assimil-ation curves obtained shows no sharp change of direction at a criticalconcentration such as would be anticipated if assinilation werecontrolled entirely by the level of supply of the factor in minimum(Blackman).The gradual and regular change of direction ismore in accord with the view that factors other than that inminimum influence to a definite though relatively smaller extentthe rate of carbon assimilation (Harder). The principal observationsemerging are that under conditions of low carbon dioxide concen-tration and low light intensity the rate of assimilation is controlledby carbon dioxide. With high light intensity, however, irrespective45 8mithsonian Misc. CoEI., 1933, 87, No. 16.46 Plant Physwl., 1935, 10, 245; Proc. Indian Acad. Sci., 1935, 1, B, 909,754POLLARD. 417of the level of carbon dioxide present, light controls assimilation.The influence of temperature on assimilation rates is also examined 47and relationships are found to assume the same general nature.The temperature range over which assimilation takes place in radishleaves is recorded as 12.647.4", with maximum values at 30".It isconcluded that under no conditions is assimilation determined by anyone factor alone, but that, on the other hand, the theory of " relativeminimum " is only of limited application. It is held that withoutconsideration of the internal cellular mechanism of photosynthesis,no relationship between environmental factors can be applied as ageneral principle under all conditions.The extent to which light of different wave-lengths can be utilisedby plants varies somewhat with the species examined. Differencesin the colour and thickness of leaves are partly concerned here(see further, under nutritional factors).G. R. Burns 48 shows thatwhite pine and spruce utilise all the visible spectrum except theviolet and part of the blue. Other plants, however, utilise the blue-violet range, and with this as sole illumination, assimilation is pro-portional to its intensity.4s In general, however, rates of photo-synthesis are highest in the red-orange region and decrease steadilytoward the 51 As is to be expected, the percentage utilis-ation of light by different plants shows considerable variation. Aninstance of this is shown by recent work of Gabrielsen (Zoc. cit.), thealga ChZoreZZa exhibiting a notably greater efficiency in this respectthan mustard.The influence of the quality, as distinct from in-tensity, of light on the assimilation process has obvious practicalbearings on greenhouse practice, and is frequently of prime import-ance in research work under conditions in which light of constantintensity must be obtained from artificial sources. In this connexionR. H. Dastur and K. M. Samant 62 have examined the relative ratesof carbohydrate formation in leaves exposed to different sourcesof light. Their investigations suggest that in addition to the actualphotosynthetic process the subsequent elaboration of carbohydratesmay also be affected. Thus the amount of starch produced in arti-ficial light was approximately 30% of that produced in daylight,whereas sucrose production was similar with both light sources.In diffused daylight the total carbohydrate production was doublethat obtained in artificiallight.In plants producing no starch, e.g.,4 7 B. N. Singh and K. Kumar, Proc. Indian Acad. Sci., 1935, 1, B, 736.48 Plartt Physiol., 1933, 8, 247; 1934, 9, 645.4s R. H. Dastur end R. J. Mehta, Ann. Bot., 1935, 49, 809.50 LOC. cit.5 1 E. K. Gabrielsen, Planta, 1935, 23, 474.52 Ann. Bot., 1933, 47, 295.REP.-\'OL. XXXIII. 418 BIOCHEMISTRY.AlZium cepu, sugar production in diffused daylight was approximatelythree times that in artificial light. In these varied effects of differentlight sources, quality, rather than intensity, appears to be the domin-ant factor. On somewhat similar lines J. M.Arthur and W. D.Stewart 65 compared the efficiency of various artificial light sourceson the basis of dry matter production in buckwheat plants. It isnoted that the order of efficiency thus obtained differs from thatshown by calculations on a basis of equal energy radiated within thevisible spectrum. The efficiency of dry matter production in theplants did not appear to depend upon any relationship between theemission bands of the lamps and the absorption bands of chlorophyllpigments. Gaseous-discharge lamps (sodium, mercury, neon) bycomparison with ordinary filament bulbs produced greener leaves andplants having lower stem : leaf ratios.The ill-effect of ultra-violet light on the photosynthetic processunder certain conditions is examined by W.Arnold 54 in the case ofChlOreZh pyrenoidma, and is ascribed to its action in rendering in-active an unidentified unit in the mechanism of photosynthesis.Neither the chlorophyll nor the respiratory process is affected.0. Jirovec,55 as a result of experiments with green and colourlessstrains of Euglena grmilis, concludes that chlorophyll normallyaffords partial protection against ultra-violet rays.Plane-polarised light appears to cause no abnormality in the carbo-hydrate content of leaves.56The influence of external factors on the relative ratio of carbonassimilation and of respiration becomes a matter of considerableimportance in the investigation of photosynthesis. Not only do thetwo processes take place simultaneously with the same end-products,but also the " compensation point " in a closed system, Le., thecondition in which respired carbon dioxide is quantitatively utilisedin photosynthesis, is often regarded as an index value in studies ofthe influence of light or temperature on carbon assimilation.F. vander Paauw 67 showed that temperature produced parallel effects onrespiration and assimilation in the green alga Stichococcus bacillarisand also, a t temperatures less than 22", in Oocystis. At highertemperatures in the latter and at lower temperatures in Chlamy-domoru;cs respiration responded more than assimilation to changes oftemperature, With many other plants there was very close parallel-ism between rates of assimilation and respiration over the range63 Contr.Boyce l'hompon Inst., 1935, 7, 119.64 J . Ben. Phy8wl., 1933, 17, 135.55 Protophrna, 1934, 21, 617.66 R. H. Dastur and R. D. Asans, Ann. Bot., 1932, 46, 879.67 Plan@, 1934, 22, 396POLLARD. 41910-30*. Moreover mild stimulation or retardation of both processescould be effected by appropriate treatment with potassium cyanide.68Somewhat similar results were obtained by E. S. Miller and G. 0.Burr,59 who determined the compensation point for a number ofplants, using a special apparatus in which the upper portions of theplants were subjected to light of high intensity but the roots werekept relatively cool. Plants of various species quickly reduced theconcentration of carbon dioxide in the circulating air to a levelof O-Ol% (vol.), which was maintained for periods of 24 hours.Thisvalue did not change with temperature in the range 5-35". Sincethe respiration rate is known to increase by as much as 15 timesover this range, and under the conditions of the experiment light wasalways in excess, it is concluded that the limiting factor in assimil-ation is not the primary process of light absorption but the intermedi-ate reaction which is controlled by the carbon dioxide concentration ;also that the temperature coefficient of this reaction is identical withthat of respiration. The utilisation of the increased products ofrespiration without increase in carbon dioxide concentration isascribed to the assimilation of an intermediate product of respirationbefore any carbon dioxide is liberated from it, a possibility whichwas suggested previously by Warburg. At 35-37' the above rela-tions appear to break down rapidly and the gas exchange of differentspecies shows wide variations.The dependence of the rate of photosynthesis on the water contentof the leaf is examined by a number of workers.60.62 I n general amore or less direct relationship is established up to a critical watercontent, beyond which assimilation tends to decline. Dastur(h. cit.) determines the " assimilation number " of various plants(ie., H,O content/C02 assimilated) and finds this to increase withrising water content to an optimum value and subsequently todecrease. Comparison with Willstiitter's " assimilation number "(i.e., chlorophyll content-CO, assimilated) shows a much closerrelationship of assimilation with the water than with the chlorophyllcontent.The lack of proportionality between chlorophyll content of leavesand assimilation observed in many cases by Willstatter and by sub-sequent workers does not apparently obtain in the case of ChZoreZh,in which a direct ratio is established by W.E. Fleischer,63 even whenthe chlorophyll content is artificially varied by controlling the supply58 F. van der Paauw, Rec. Trav. bob. nterl., 1932, 29, 497.5s Plant Phpiol., 1935, 10, 93.60 R. Melville, Ann. Re@. Exp. Stcb. Cheshunt, 1933, 87.61 B. N. Singh and K. N. Lal, Ann. Bot., 1935,49, 291.62 R. H. Dastur and B. L. Desai, ibid., 1933, 47, 69.63 J . Gen. Physwl., 1935,18, 573420 BIOCHEMISTRY.of iron. R.Emerson,64 with somewhat different experimental con-ditions, had made similar observations, and further recorded thatlight conditions giving optimum assimilation rates in leaves rich inchlorophyll were also optimum for those poor in chlorophyll.Possibly this case resembles that of Elodea densa, examined by E. vonEuler, B. Bergman, and H. H e l l ~ t r o r n , ~ ~ in which the chlorophyllcontent per chloroplast and the number of chloroplasts per cell weresubstantial 1 y constant.Mechanism of Photosynthesis.-The complexity of the effects ofenvironmental conditions and of internal plant factors on carbonassimilation observed directly by plant physiologists has beenparalleled by the more purely chemical investigations of thecomplexity of chlorophyll.Recent years have brought a much more complete understandingof the chemistry of chlorophyll 66 and related compounds, but themeans by which chlorophyll brings about the conversion of carbondioxide into carbohydrate is still the subject of controversy.It isvery generally accepted that formaldehyde represents an intermedi-ate stage in the conversion and that the change CO, + H,O -+CH,O + 0, is effected (probably in the absence of light) with the aidof light energy previously absorbed by the chlorophyll. Theories ofthe mechanism of photosynthesis differ considerably in detail, butare centred round considerations of whether the fundamental energyexchange involves carbon dioxide, water, oxygen, or the chlorophyllitself.Warburg originally supposed that the chlorophyll (andcarotene) in leaves was transformed into an isomeric substance duringexposure to light and in the subsequent (dark) reaction the isomer,a reducing agent, caused the transformation of carbonic acid intoformaldehyde and water. By contrast among the earlier theories,that of Thuiiberg supposed the absorbed light energy to act on thewater associated with chlorophyll rather than on carbon dioxide, thechain of reactions being :2H,O + chlorophyll + light --+ H, + H,02co, + H, + 5 2 0 2 -4- 0, + H4CO2(1 methyleneglycol)H,CO, + CH,O + H,OAs will be shown, these and other early theories of assimilation havereappeared in recent years, modified or extended to bring them intoaccord with newly observed facts.E.C. C. B a l ~ , ~ ' after prolonged investigation of relevant catalytic6* J . Gen. Physiol., 1929, 12, 609; Proc. Nat. Acad. Sci., 1929, 15, 281.e5 Ber. deut. bot. Ges., 1934, 52, 458.G6 Ann. Reports, 1935, 362.67 Proc. Roy. SOC., 1936, B, 117, 218POLLARD. 42 1actions, has now formulated the primary photosynthetic reactionas depending in the absorption of carbon dioxide by chlorophyll-a,the photosensitised complex changing to chlorophyll-b and formalde-hyde. The cycle is completed by reduction in the dark (Blackmanreaction) of chlorophyll-b to chlorophyll-a, the reducing agentsuggested being carotene. Thus :C,,H720,N4Mg-C0,,H20 light C55H7006N4Mg,H20 + CH20chlorophyll-a-CO, complex. chlorophyll-b.C,5H7006N4Mg~H20 + c40135G C55H7205N4Mg + C40HijG02ch loroph y ll- b.carotene. chlorophyll -a. xanthophyll.The kinetics of these reactions are shown to be in accord with pub-lished experimental data relating to the carbon assimilation ofChlorella,By mathematical consideration of the effects of temperature andlight intensity on carbon assimilation G. E. Briggs 68 indicates asystem involving the formation of a chlorophyll-CO, complex whichin light undergoes molecular rearrangement to a peroxidised sub-stance. This is decomposed through the agency of plant catalysts,yielding carbohydrate and oxygen, or, in part, decomposes aninhibitor (present in the cell) which inactivates the catalyst. Theclassic researches of Willstatter and StoH had previously led tosimilar views.More recently there has appeared some divergencebetween the theories of Willstatter and of Stoll, the differencescentring on the position of oxygen as a necessary agent in the firststages of the assimilatory process. A. Stoll 69 assumes that chloro-phyll-a and -b contain a ‘‘ supernumerary ” double linking outsidethe conjugated system, which permits catalytic hydrogenation with-out significant change in the absorption spectrum.70 The dihydro-derivative is easily dehydrogenated and serves as reducing agent forthe chlorophyll-CO, complex , yielding formaldehyde. Rehydro-genation of the chlorophyll results from the fission of water closelyassociated with it,H2O + H + OH (-+ HZOz),the hydrogen peroxide being subsequently decomposed by the cata-lase of the leaf.I n a later publication 71 Stoll brings his scheme moreclosely into line with recent developments in the elucidation of thestructure of chlorophyll. The catalytic hydrogenation of chloro-phyll is now known to yield a dihydro-derivative by addition at the68 Proc. Roy. SOC., 1933, B, 113, 1.69 Nnturwiss., 1932, 20, 965.70 LOC. tit. ; also R. Kuhn and A. Winterstein, Ber. deut. bot. Ges., 1932, 65,71 Naturwias., 1936, 24, 53.1737422 BIOCHEMISTRY.double bond of the vinyl group, a position in which mobility or theeasy interaction with carbon dioxide co-ordinatively attached to thecentral magnesium atom seems unlikely, Accepting Fischer’sformula for chlorophyll (I), Stoll now associates photoactivity withthe mobility of the hydrogen atom in position 10 (Fischer havingnow introduced the two ‘i extra” hydrogen atoms into thestructure).An enolisationis indicated as related to the brown phase in the chlorophyll cycle.The hydrogen attached to the carbon C,, in (11) may be replaced byhydroxyl and in this substance the hydrogen on C,, becomes mobilein daylight (but not in darkness) provided atmospheric oxygen isexcluded.Stoll, therefore, although reconstructing his earliermechanism, still retains his primary conception that oxygen is not animmediately active agent in photosynthesis, which is more accur-ately represented as involving a photolysis of water as a result of theprincipal energy exchange.On somewhat similar lines K. Shibata and E. Yakushiji T2 assumethe co-ordination of four water molecules with the central magnesiumatom of the chlorophyll.These become activated by the absorbedlight in such a manner that the reaction,is facilitated. Here again oxygen is not immediately concerned andthe associated water molecules are the vehicle of the energy exchange,72 hTaturwk., 1933, 21, 267.HZCO, + 4(H . . . OH) = 2H20 + CH,O + 40H( = 2H,O,POLLARD. 423four quanta being involved. The Blackman (dark) reaction isrepresented by the decomposition of hydrogen peroxide by catslase,this being the sole source of oxygen in the system.H. Gaffron 73 supports the conception that the assimilation processdoes not necessitate the intervention of an activated or metastableoxygen atom.By contrast to the above Willstatter’s later work 74 leads him toassume the necessity of a t least a small amount of oxygen to initiatethe activity of chlorophyll. He also differs from Stoll in supposingthe photosynthetic cycle to involve the formation of dehydrogenatedchlorophyll derivatives.The formation of actively reducing hydro-gen atoms is represented schematically by an initial reaction of chloro-phyll with oxygen, yielding monodehydrochlorophyll :chlorophyll + 0, ---+ (0,H) -t monodehydrochlorophyll.The wandering of a hydrogen atom into the Mg-CO, complex yieldsdehydrochlorophyll. Then follows,dehydrochlorophyll + H,O -> OH -+ monodehydrochloropl~ylland againmonodehydrochlorophyll _I, dehydrochlorophyll + H,the H going to the Mg-CO, complex. This cycle is completed fourtimes, yielding the necessary four hydrogen atoms for the reductionof one molecule of carbon dioxide.The process is assumed toproceed in stepwise manner, each hydrogen atom reacting singly.Regeneration of chlorophyll in light is effected thus,dehydrochlorophyll + H,O --j OH + monodehydrochlorophyllmonodehydrochlorophyll + H,O + OH + chlorophyll.The radicals 0,H and OH formed intermedially either take part in afurther hydrogenation cycle or yield H,O, 0, and H,O, accordingto the environmental conditions which regulate the intensity of thevarious stages of the reaction.J. Franck 75 supports WillstBtter’s view of the necessity of oxygenfor the process, but considers that photochemical reactions in solu-tion are more likely to occur by means of reactions of activatedmolecules than through the formation of radicals 76 as indicated byWillstSCtter.With this in view and with the purpose of adjustingthe cycle of changes to accord more satisfactorily with calculatedenergy relationships, Franck modifies Willstgtter’s system by assum-ing a somewhat different series of intermediates, and, adopting73 Biochem. Z., 1935, 280, 337; 1936, 287, 130.74 R. Willstiitter, NatWr~i88., 1933, 21, 262.7 5 Naturwiss., 1935, 23, 226.719 J. Franck and E. Rabinowitsch, Trans. Paraday Soc., 1934, 153, No. 30424 3IOCHEMISTRY.Fischer’s views, includes in the chlorophyll molecule the two looselybound hydrogen atoms. To make the comparison with Willstiitter’sscheme more evident, he designates ordinary chlorophyll as HH-chlorophyll, monodehydrochlorophyll as H-chlorophyll, dehydro-chlorophyll as “ chlorophyll,” and dehydrochlorophyll, t o which ahydroxyl group is loosely attached, as OH-chlorophyll.The pre-liminary (light) reaction involves dissociation of one of the twoloosely bound hydrogen atoms,HH-chlorophyll + hv --+ H-chlorophyll + Hthe hydrogen atom being taken up in a series of changes with waterand oxygen (as in Willstatter’s scheme) with the ultimate formationof hydrogen peroxide, and H-chlorophyll combining with carbonicacid. The actual assimilation process is represented as :OH (i) H-Chlorophyll . . . OH>C=O + hv --+OH-chlorophyll . . . og>CxO(ii) OH-chlorophyll . . . ‘g>C=O + H,O + hv -+H-chlorophyll . .. O:>C=O + H20,(iii) H-chlorophyll . . . O:>C=O + hv -+H OH-chlorophyll + H>C-O(iv) OH-chlorophyll + H,O + hv ---+ H-chlorophyll + H,O,By assuming differences in the energy of combination of hydrogenand of hydroxyl in themselves, and in relation to position in theco-ordinated magnesium complex or the chlorophyll residue,Franck brings the above cycle of reactions into line with the acceptedenergy balance of the complete assimilation process.Evidence of a vital part played by oxygen in the photosyntheticprocess is put forward by H. Kautsky and colleagues and is based onphenomena of an entirely different character. Following an exten-sive study of photosensitised surface reactions, including those con-cerned in fluorescent conditions, Kautsky concluded that in manysurface oxidations the presence of an activated or metastable oxygenatom is essential to effect the energy transfer.A green leaf whichhas been placed in the dark for a period and afterwards exposed toultra-violet light exhibits a temporarily increased fluorescence,followed by a steady decline to a low level which is substantiallyconstant in unchanged external conditions. The process, lasting a POLLARD. 425most a few minutes, may be repeated indefinitely by alternate ex-posure of the leaf to darkness and to light.In examining these changes H. Kautsky, A. Hirsch, and F.Davidshofer 77 associate the fluorescence with changing intensitiesof different stages of the photosynthetic process. The photosensit-ised chlorophyll is able to transfer it!s energy only to a molecule ofdefinite type.Of those present in the leaf system, only oxygenfulfils this requirement, and the presence of activated or metastableoxygen in the leaf plastids is assumed.78 The transference of energyto oxygen lowers the intensity of fluorescence. The energised oxygeneffects the building up of the chlorophyll-carbon dioxide-peroxidecomplex,79 resulting ultimately in the production of carbohydrateand oxygen. The increase in the oxygen supply brought about inthis way results in a still further decrease in fluorescent intensity(declining portion of curve) until a balanced condition is reachedbetween light absorption, fluorescence, and oxygen transfer, which ischaracteristic of the normal condition of assimilation.The rate ofinitial increase in fluorescence under these conditions is controlled bythe intensity of irradiation, but is unaffected by temperature.80 Thesecond stage of the assimilation process (reactions involving thechlorophyll-CO, complex and the final production of carbohydrate)is definitely restricted by decreased temperature and also by treat-ment with hydrocyanic acid or toluene, and such restriction,by lowering the supply of photosynthetically derived oxygen, causesa prolongation or an increased intensity of the fluorescence.81 Anartificially increased concentration of carbon dioxide in the atmo-sphere (to 1%) has no influence on the course of fluorescence, butvariations in the oxygen concentration cause corresponding changesin intensity, A critical point is apparently reached with 0.5% ofoxygen, below which fluorescence does not increase with the intensityof irradiation.82 I n an atmosphere free from oxygen leaves fluorescewith high and constant intensity until liberation of oxygen causes adiminution to the normal equilibrium In a later and moredetailed examination of fluorescence curves Kautsky 84 traces thecourse of activation of the chloroph-yll-0, complex and finds it tobe of a unimolecular type.I n the light of this and previous observ-77 Ber., 1932, 65, 1762.7 8 H. Kautsky, H. de Bruijn, R. Neuwirth, and W. Baumeister, Ber., 1933,79 H. Kautsky and A. Hirsch, Naturuliss., 1931, 19, 964.80 H. Kautsky and H.Spohn, Biochem. Z . , 1934, 274, 435.8 1 H. Kautsky and A. Hirsch, ibid., 1935, 277, 260.82 H. Kautsky and W. Flesch, ibid., 1936, 284, 412.83 H. Kautsky and A. Hirsch, ibid., 1935, 278, 373.84 H. Kautsky and A. Marx, Naturwiss., 1936, 24, 317.66, 1588426 BIOCHEMISTRY.ations he considers that in the darkened leaf the equilibrium, chloro-phyll + 0, =+= chlorophyll-0, complex, [ChIO,, in the plastids isnormally balanced almost completely to the right, The complex isdissociable but non-fluorescent. On irradiation [ChIO, undergoesrearrangement to form a new non-dissociable but fluorescent complex[ChO,], probably a peroxidised form. This unimolecular changecorresponds with the initial increase in the fluorescence curve.J. Franck 86 doubts the physical soundness of Kautsky's views of theproperties of a metastable oxygen molecule, and considers the fluores-cent changes are more in agreement with the existence of mobilehydrogen atoms bound to the chlorophyll molecule.The risingpart of Kautsky's fluorescence curves may well be represented by thechangeHH- chlorophyll -+ H- chlorophyll.II. Gaffron a6 also criticises Kautsky's interpretation of the experi-mental data, and advances evidence, based on the carbon assimil-ation of Chlorella, in support of his view that neither free nor looselybound oxygen is necessary for the initiation of the assimilationprocess.recently reports the isolation of two crystallinefluorescentl substances from leaves, both of which actively absorbultra-violet light, especially in the shorter wave-lengths.Bothresist saponification, but gradually lose their characteristic propertieson exposure to air. The fluorescent spectra indicate the absence ofester, carboxyl or hydroxyl groups. The fact that one or both of thesesubstances occurred in leaves of all plants examined suggests thatthey may have an interesting bearing on Kautsky's observations.From considerations of the photobleaching of fluorescent dyes inan oxygen-free atmosphere by the action of ferrous salts J. Weiss 88suggests the reactionFe" + HOH + hv = Fe"' + OH' + Hmay explain the vital change taking place in the case of chlorophyllas with the photosensitised dyes, and recalls the observation of K.Noack a9 that chloroplasts in leaves contain appreciable proportionsof ferrous iron.An interesting discussion of the energy relationships in the varionstheories of the photosynthetic mechanism is given by H.Gaffron andH. H. StrainK. w0hi.908 5 O p . cit.; also J . Franck and H. Levi, Naturwiss., 1935, 23, 229.8 6 Biochem. Z . , 1933, 264, 270; Naturwiss., 1935, 23, 528.8 7 Nature, 1936, 137, 946.88 Ibid., 1936, 136, 794.89 2. Bot., 1930, 23, 957. Naturwiss., 1936, 24, 18, 103POLLARD. 427Condition of Chhophyll in the Plant.It has long been assumed that in the leaf chlorophyll exists in acolloidal condition. The fact that chlorophyll cannot be extractedfrom dried leaves by certain organic solvents until water has beenadded, has suggested that in the chloroplast chlorophyll occurs insome form of labile combination or elaborate physical state €romwhich it is released or dissociated by means of water.Moreover it has been shown91*92*93 that in the assimilationprocess some 1500-2000 molecules of chlorophyll (Emerson andArnold’s “ photosynthetic unit ”) must be present to effect the trans-fer of the four light quanta (necessary for reduction) to one moleculeof carbon dioxide.This contributes to the view that some diEerenti-ation between the chlorophyll molecules is likely in respect of theirphysical or chemical condition.Recent observations, among which may be cited those of W.M e n ~ k e , ~ ~ L. G . M. Baas-Becking and H. C. K ~ n i n g , ~ ~ and J. G.Wakkie,96 lend further support to the conception that the physicalcondition of chlorophyll in leaves is a somewhat complex one.Acolloidal state seems unlikely and the absorption and fluorescencespectra indicate that chlorophyll cannot be present in simple solution.Mencke, suggests that two phases are present: one, a lipoid phasein which the chlorophyll is dissolved in the lipoid constituents of theplastid, and an aqueous phase in which the lipoid solution is dis-persed. B. Hubert 97 indicates that if chlorophyll is in solution itmust be in a medium of very high refractive index, and concludesthat a condition of adsorption is probable.Discussing Mencke’s views, J. Weiss 98 points out that, if a lipoidsolution of chlorophyll is dispersed in an aqueous phase in the chloro-plast, a considerable portion of the absorbed light may be stored bymolecules of chlorophyll in the interior of the lipoid phase as a formof electronic excitation energy, and may be passed from moleculeto molecule by a “ resonance ” effect.Only those molecules a t thelipoid-aqueous interface react with carbon dioxide, but in time thewhole of the energy stored by the “ internal ” molecules may reachthe “ surface” molecules and bring about the formation of thechlorophyll-C0, complex. I n weakly assimilating leaves, energyreaching the surface may not be entirely utilised and will appear as91 R. Emerson and W. A. Arnold, J . Gen. Physiol., 1932, 16, 191.92 W. A. Arnold and H. I. Kohn, ibid., 1934, 18, 109.99 H. 1. Kohn, Nature, 1936, 13’7, 706.94 Protoplatma, 1934, 21, 279.95 Ibid., 1935, 38, 1082.97 Ibid., 1934, 37, 694.Proc.K . Akad. Wetenach. Ameterdam, 1934, 37, 674.Nature, 1936, 137, 997428 BIOCHEMISTRY.fluorescence. This accords with Kautsky’s observation that fluores-cence in some cases bears an inverse relation to the rate of assimil-ation. The “ photosynthetic unit ” may also be regarded as directlyrelated t o the ratio of ‘‘ surface ” : “ internal ” molecules, in whichcase some 400-500 molecules of chlorophyll are present in the in-terior of the lipoid phase for each actively assimilating “ surface ’’molecule.The possibility of labile compounds of chlorophyll and protein isexamined by R. S. Hilpert and K. H e i d r i ~ h , ~ ~ who show that a de-finite portion of “ mobile ” protein, different from the general proteinof the leaf, can be associated with chlorophyll in all organs of theplant and in all stages.A.Stoll discuss a further development of the chlorophyll-proteincomplex theory. I n the light of Willstatter’s explanation of theactivity of lactoflavin, wiz., the formation of a “ Symplex,” lacto-flavin-phosphoric acid-colloid carrier, Stoll suggests the presence inthe plastids of a symplex (“ chloroplastin ”), chlorophyll-colloidcarrier [ ? protein]. The symplex may be assumed to dissociate inthe presence of water containing dissolved electrolytes from the leaf.The insolubility of chlorophyll from dried leaves in certain organicsolvents is thereby explained. The point of attachment of the col-loid is possibly the double bond of the vinyl side chain.On thisbasis the actual absorption of light and its transformation intopotential chemical energy is associated with the chlorophyll moleculeand is independent of temperature. The subsequent production offormaldehyde (temperature sensitive) may be regarded as anenzymic reaction since the symplex has an enzyme-like structure.The chlorophyll-colloid (protein) combination may thus be regardedas a specific assimilating enzyme.Chlorophyll Formation in Plants and Nutritional Factors affecting it.Nitrogen.-In addition to the environmental influences alreadydiscussed, genetic,2 nutritional and physiological factors areconcerned in the production of chlorophyll in plants. Recent workhas in many cases thrown further light on the manner in which theseindirect and often less obvious factors affect the photosyntheticactivity of plants.An adequate supply of nitrogen to plants is obviously necessary99 Ber., 1934, 67, 1077.1 Naturwiss., 1936, 24, 53.2 H.von Euler et al., Svensk Kem. Tidskr., 1934, 46, 301; 2. physiol.Cheqn., 1935, 233, 81 ; 234, 151.3 W. Mevius, Jahrb. wiss. Bot., 1935, 81, 327.4 B. N. Singh and K. N. Lal, Ann. Bot., 1935,49, 291; W. E. Loomis andK. €3. Burnett, Proc. Iowa Acad. Sci., 1931, 38, 150POLLARD. 429for the actual elaboration of the chlorophyll molecule. It is alsogenerally recognised that conditions favouring rapid vegetativegrowth are in general those which favour chlorophyll production. Agenerous nitrogen supply is a prominent factor in this.It mighttherefore be anticipated that a deficient nitrogen supply couldoperate as a limiting factor in chlorophyll production on much thesame lines as it does in gross dry-matter formation in the growingplant. A relationship of this kind is indicated by the work of R. K.Tamm and 0. C. Magi~tad.~ In pineapple leaves the chlorophyllcontent tended to increase uniformly with the amount of nitrogenousfertiliser applied, up to a limiting amount. Very large applicationsresulted in a decrease in chlorophyll production. F. M. Schertz,Gexamining chlorotic mottling in leaves, found this could be correctedby treatment with sodium nitrate. Moreover the customary cor-rectives, iron and manganese, for chlorosis were ineffective if thenitrogen supply was inadequate.It was later shown that the levelof nitrogen supply could be correlated directly with pigment form-ation in the chloroplast. J. D. Guthrie ' also records that nitrogendeficiency had little influence on the chlorophyll content of plants inwinter (when factors other than nitrogen limit growth), but duringrapid spring growth chlorophyll production was restricted by apartial deficiency of nitrogen. The form in which nitrogen is sup-plied to the plant affects the .nitrogen-chlorophyll as well as thenitrogen-growth relationship. G. B. Ulvin,* working with sugar-cane, found that nitrate-fed plants produced more chlorophyll thandid those supplied with ammonium salts.The observation by G. Gassner and G. Goeze of a direct relation-ship between the protein and the chlorophyll content of cereal plantsseems to add further confirmation of the significance of nitrogennutrition in the formation of chlorophyll.Potassium.-The close relation between potassium and theassimilatory process in plants is very generally recognised.It isusually considered that potassium acts in this respect by regulatingenzyme activity rather than through any direct influence on thechlorophyll itself. Such an influence is, moreover, difficult to estab-lish experimentally owing to the varied ways in which potassiuminfluences the functional activities of the plant.LundegBrdh 10 observed that at moderately high temperatures(20-30") assimilation in potassium-deficient leaves was greater than6 Plant Physiol., 1935, 10, 159.6 Bot.Gaz., 1921, '91, 81; Plant Physiol., 1929, 4, 269.7 Arner. J . Bot., 1929, 16, 716.8 Plant Physiol., 1934, 9, 59.9 Ber. deut. bot. Ges., 1934, 52, 321.1" " Die Nahrstoff aufnahme der Pflanzen," 1932430 BIOCHEMISTRY.in those adequately supplied and that this difference was related tothe higher chlorophyll content of the deficient leaves. I n olderleaves from which much of the normal potassium content had beeneliminated, assimilation was restricted. Gassner and Goeze l1associate (( moderate ” potassium deficiency with a maximumchlorophyll content in wheat leaves, and simultaneously with maxi-mum assimilation and respiration. Amore severe deficiency of potass-ium has a definite inhibitory effect on all factors. It seems possible,therefore, that the potassium supply may influence the amount ofchlorophyll formed as well as its activity, although the apparentlyreciprocal effects of potassium and nitrogen on chlorophyll pro-duction12 tend to introduce an element of doubt in this respect.D. Miiller and P. Larsen l3 regard the lowered ratio of assimilationof potassium-deficient plants as being due to ‘( protoplasmic ” factorsrather than to direct effects on chlorophyll.In a review of the effects of potassium deficiency on carbon assimil-ation in plants G. Rohde l4 points out that deficient leaves aresmaller, thicker, and more bluish-green than those which are ade-quately nourished, and that these factors influence the intensity ofabsorption of light by chlorophyll in regard to total absorption andto the proportional absorption of light of different wave-lengths inthe visible spectrum. Willstatter’s earlier observations show that inyellow-green leaves (low chlorophyll content) much more carbondioxide is assimilated per unit chlorophyll than in blue-green(chlorophyll-rich) leaves. I n the former, assimilation is probablylimited by the proportion of chlorophyll present and in the latter byenzymic activity. Hence, although the importance of potassium inthe assimilation process is manifestly great, its apparent directinfluence on chlorophyll may in some cases be attributable tosecondary effects.Iron, Manganese, and Magnesium.--It has long been recognisedthat deficiency of any of these elements may result in chloroticconditions in plant leaves. Iron and manganese are not constituentsof the chlorophyll molecule, but are doubtless concerned in its form-ation, probably by acting as oxidation-reduction catalysts. I nmany respects iron and manganese have been shown to differ in theireffects on chlorophyll formation.15 I n general, iron has by far thegreater stimulative action, although the work of G. B. Ulvin16suggests that manganese to some extent supplements the effect of iron.Rohde l7 suggests that the observed effects of manganese in increas-l3 Ann. Reports, 1936, 438.l4 2. Pfianz. Diing., 1936, A , 44, 1.l6 Plant Physdol., 1934, g, 69.l1 LOC. cit. ; also 2. Bot., 1934,27,257.l3 Planta, 1935, 23, 501.l5 Ann. Reports, 1934, 355.17 LOC. citPOLLARD. 43 1ing carbon assimilation depend very frequently on the stimulationof the later enzymic stages of the process, although there is littledoubt that this element can affect the chlorophyll content of leaves,and probably also its photo-oxidative properties.l8Deficiencyof iron leads to chlorosis, but chlorotic plants, the condition of whichmay be remedied by treatment with iron, do not always show anotably low iron content. Evidently iron may exist in the plantand yet be unable to play its normal part in chlorophyll production.J. Oserkowsky19 in an attempt to determine the “active ” ironfinds a general correlation between the chlorophyll content of leavesand the amount of iron extracted by N-hydrochloric acid. A smallbut definite amount of ‘‘ inactive ” iron probably dissolves in theacid. No relationship is apparent between the total and the‘‘ active ” iron contents or between total iron and chlorophyll con-tents. Moreover the active iron within the leaf is not all in a water-soluble condition. Prolonged iron deficiency is shown to lead toserious breakdown in the chloroplasts, thus explaining the frequentfailure of iron treatment to cure chlorosis when applied late in theseason. There is evidence that iron is concerned in the formationof pyrrole compounds, utilised in synthesising the central pyrrole-niagnesium nucleus of the chlorophyll molecule. G. Polacci,20working with ChZoreZZa, observes that the presence of magnesiumpyrrole-2-carboxylate in the nutrient medium obviates the necessityof supplying iron. Magnesium supplied as sulphate in an iron-freemedium cannot induce chlorophyll production. The apparentlycatalytic effect of iron on pyrrole ring-formation is not produced ifmanganese or titanium 21 is used in its place.The action of iron is much more definitely established.A. G. P.A. G. POLLARD.C. P. STEWART.J. STEWART.li. Noaok, Naturwiss., 1926, 14, 383.Is Plant Physiol., 1933, 8, 449.2u Ber. deut. bot. Ges., 1935, 53, 540; C. Polacci, B. Oddo, and M. Gallotti,Boll. SOC. itd. Biol. sperin~, 1935, 10, 665.21 0. L. Inman, G. Barclay, and M . Hubbard, Plant Physiol., 1936, 10, 821

ISSN:0365-6217    

DOI:10.1039/AR9363300383

出版商:RSC    

年代:1936

数据来源: RSC

摘要:

ANALYTICAL CHEMISTRY.THE number of papers with a bearing on analysis which haveappeared during the period under review has not diminished and thetask of selection is no easier. In surveying the literature, however,it has again been noticed that certain papers appear to be devoted tothe rediscovery of well-established facts or of methods which are byno means new. It is true that such contributions make a Reporter’stask somewhat easier, but with the literature in its over-burdenedcondition they are surely superfluous.In this Report a separate section has been devoted to Colorimetry,a, branch of analysis which, in recent years, appears t o be coming intoits own, with a wider future before it. Hence the time seems ripefor a separate treatment of the subject in its quantitative aspect,with especial reference to the instrumental side.L.S. T.MACNETO-OPTIC METHOD OF CHEMICAL ANALYSIS.has grown round this much-debatedmethod of analysis since it was first launched by Allison in 1930.2Subsequently, the method has been the subject of much contro-versy. Some investigators have claimed success with it, whilstothers have reported a complete failure, and not only has the inter-pretation of the results been in dispute, but also the very existenceOF the minima has been called in question.Recently, F. G. Slack has reported a critical investigation of themethod, and although minima were observed he regards them as atype of N-ray phenonienon, and as such, subject to physiologicaland psychological effects. Further, with J.A. Peoples, jun.,4 hereports that attempts to reproduce time-lag measurements and1 Bibliographies which cover the field will be found in the articles bySlack, ref. (3), and by Cooper, ref. (9). Tho method has been mentioned in theseReports from time to t h e , see Ann. Reports, 1931, 28, 181; 1932, 29, 300;1933, 30, 349 ; 1934, 31, 372 ; 1935,32, 142, a detailed description being givenin Ann. Reports, 1930, 27, 203.2 F. Allison and E. J. Murphy, J . Apner. Chern. SOC., 1930, 52, 3796; thefirst papers on the time-lag in the Faraday effect by Allison appeared in 1927;see J. W. Beams and-F. Allison, Physical Rev., 1927, 29, 161; Phil. Mag.,1927, [vii], 3, 1199.3 J . Franklin In&., 1934, 218, 445; cf. also H. W. Farwell and J.B.Hawkes, Physical Rev., 1935, [ii], 47, 78.4 Ibid., 1934, [ii], 45, 126.An extensive literaturTHEOBALD : INORGANIC ANALYSIS. 433chemical analyses have failed. Working independently, H. G.MacPherson finds himself in substantial agreement with Slackand Farwell and Hawkes, and is unable to confirm sharp minimacharacteristic of the substance under investigation. More evidenceof a similar nature comes from M. A. Jepperson and R. M.On the other hand, G. Hughes and R. Goslin seem to have madea pertinent reply to many of these doubts and misgivings by demon-strating the reality and reproducibiIity of the minima photographic-ally, and they claim that these objective tests are characteristicof the inorganic acids and salts which they have examined.Further-more, G. M. Wissink and J. W. Woodrow * have such confidence inthe method that they use it to detect vitamin-A, to the presence ofwhich they attribute the characteristic minimum given by manyanimal and vegetable products.Finally, we have a recent series of articles by S. S. Cooper andT. R. Ball9 who, after a somewhat enthusiastic introduction, inwhich they describe the magneto-optic apparatus as “ perhaps themost important tool for chemical research developed in the pastdecade ” and extol the advantages of this method of analysis, pro-ceed in the first paper to deal with the history and present status ofthe method. From their review they believe conclusively that theminima do exist and that they are characteristic of the substance orsubstances under investigation.The second paper discusses insome detail the construction, arrangement, and adjustment of theapparatus, and describes a successful test of the method in solving aseries of unknowns, whilst the last paper gives the actual procedureused in locating the minima for a specific example, vix., salicylic acid.The authors’ concluding remarks are illuminating and make it clearthat the technique is difficult, whilst a long and very specialisedtraining is necessary before success in the use of the method canhope to be achieved. It would seem, therefore, that for the presentat least the practising analyst will still have to rely on the morepurely chemical methods which are at his disposal for the identifica-tion and determination of small concentrations of unknowns.L.s. T.INORGANIC ANALYSIS.Quantitative.Standards for Volumetric Analysis.-In last year’s Report (p. 452)The stabilisation of5 Physical Rew., 1935, [ii], 47, 310.6 Ibid., p. 546.8 Ibid., 1934, Lii], 45, 126.9 J. Chew,. Educ., 1936,18, 210, 278, 3%; cf. also T. €3. Ball, Physical Bev.,this subject was dealt with in some detail.Ibid., p. 317.1936, Lii], 47, 548434 ANALYTICAL CHEMISTRY.Q.1N-sodium thiosulphate solutions by the addition of borax wasmentioned. Now it is pointed out lo that such solutions give, inneutral solution, iodine values which are too low even when onlyone-twelfth of the usual amount of crystalline borax is added.Experimental work indicating the suitability of borax as an acidi-metric standard appears from time to time, but the methods adoptedfor drying the hydrated salt have probably prevented its more ex-tended use.Drying by alcohol and ether is now shown to be aneasy and satisfactory procedure which eliminates this disadvantage.llFurther, loss of water by exposure to air is not a serious source oferror over periods of less than a week or ten days.I. M. Kolthoff and J. J. Lingane l2 have shown that potassiumthiocyanate is a suitable standard for work of ordinary accuracy(& O.lyo), and when stored in the dark the pure, melted salt is stableindefinitely ; deliquescence, moreover, is harmless a t a relative humid-ity of less than 45%. When protected from light, aqueous solutionsgave no detectable change in titre after eleven months’ st0rage.1~In spite of their high precision or reproducibility, potentiornetrictitrations of silver with thiocyanate are not suited to work of ahighly exact nature, owing to side reactions which have been foundto take place, and the relatively good results obtainable with theVolhard method are due, as is often the case in an analytical process,to a compensation of errors.12G. I?.Smith, V. R. Sullivan, and G. Frank l4 have proposed thesalt (NH4),Ce(N03)6, which, incidentally, is indicated to be the com-plex ammonium hexanitratocerate, as a reference substance inceriometry. They have worked out an easy method of preparationin a degree of purity sufficient for this purpose and have shown thatthe stability of the salt in hot, dilute sulphuric acid‘is satisfactory.Many desirable properties are claimed for the new standard, and itsuse may well prove to be a definite advance in volumetric work.I.ndicators.-There is now available a wide range of indicatorssuitable for the titration of acids and bases, but in those of the neweroxidation-reduction type there is still room for improvement and awidening in scope.As time goes on this extension is graduallybeing made, and one of the latest additions offering promise of wideuse is phenylanthranilic acid which has now been recommended 18for many of the usual oxidation processes of volumetric analysis,10 P. Horkheimer, Pharm. Z t g . , 1935, 80, 1330.11 I?. Hurley, jun., I n d . Eng. Chem.(Anal.), 1936, 8, 220.12 J . Amer. Chem. SOC., 1935, 57, 2126.13 Cf., however, E. N. Taran, J . Ben. Chem. Russia, 1935, 5, 602.1 4 I n d . Eng. Chem. (Anal.), 1936, 8, 449.1 5 A. Kirssanov and V. Tscherkassov, BUZZ. SOC. chi?n., 1936, [v], 3, 817;W. S. Syrokomsky and V. V. Stiepin, J . Amer. Chem. SOC., 1936, 58, 928THEOBALD : INORGANIC ANALYSIS. 435especially for titratioiis with ceric sulphate. It gives, it is claimed,a sharp, reversible colour change and is more stable in the presenceof excesB of oxidant than diphenylamine and its derivatives; theoxidation potential is + 1.08 volts and the indicator error is negli-gible. In iron titrations the addition of phosphoric acid is nolonger necessary, and the ease with which it can be preparedgives it a decided advantage over the costly o-phenanthrolinecompound.A 1 yo solution of brucine in 3N-sulphuric acid is another indicatorof this type which presents possibilities, and has been described asa suitable internal indicator for iron in dichromate titrations.16The colour change from green to red is said to be more distinct thanthat of diphenylamine and to be unaffected by ferric ions in largeexcess, by mercury, and by stannic ions; here again, phosphoricacid is unnecessary, and permanganate can be used as the titrant withhydrochloric acid present, This indicator has been employed withadvantage in the analysis of chromiurn-iron alloys, or of ores wherethe concentration of ferric iron is high.Sodium diphenylbenzidinemonosulphonate and the diphenylaminederivatives, NHPh*C,H,*SO,Na and NHPh*C,H,Me*SO,Na, havealso been described l7 as oxidation-reduction indicators for dichro-mate titrations.The details for the successful and accurate use of diphenylcarb-azide as an internal indicator in the volumetric determination ofiron have been fully worked out,18 but the close attention to pro-cedure which is demanded, the indicator correction which has to befound, and the careful control which is necessary in the titration itselfmay restrict the popularity of the method.The same substance has been satisfactorily applied l9 also todetermine the end-point in titrating chloride ion with mercuricnitrate solution.Benzopurpurin-B and -4B have been put forward as indicatorsfor the bromometric titration of tin and antimony.20The advantages to be gained from the recently-introduced fluores-cence indicators are discussed by &I. DBrib6r4, who recommendsumbelliferone, p-methylumbelliferone, and uraiiyl salts (in theabsence of halogens) as suitable for strong acids and bases, @-naphtholor eosin-BN for weak acids, and axxulin or fluorescein for weak16 D. S.Narayanmurthi and T. R. Seshadri, Proc. Indian Acad. Sci., 1936,17 S. Cohen [with R. E. Oesper], Ind. Eng. Chem. (And.), 1936, 8, 364.18 H. E. Crossley, Analyst, 1936, 61, 164.1s 1. Roberts, Ind. Eng. Chem. ( A w l . ) , 1936, 8, 366.20 Z . Raichinschtein, J . Appl. Chern. Rueeia, 1935, 8, 1470.3, A, 38; $3. Miyagi, J. SOC. Chern. Znd. Japan, 1933, 36, 146436 ANALYTICAL CHEMISTRY.bases.21 l-Naphthol-4-sulphonic acid (Nevile and Winther’s acid)shows a sharp change from no fluorescence to an intense blue atp , 6-66,22 and naphthionic acid and Schaeffer’s salt give, re-spectively, changes in fluorescence from pH 3 to 12 and 5 to > 11, bywhich pH can be measured to 0.5 unit.23In connexion with adsorption indicators, A.J. Berry 24 describesthe conditions under which phenosafranine, tartrazine, and rose-Bengal are best adapted to systems such as silver-halogen25 andthallous-thallic halides, and by titrating nitric or acetic acid withsodium hydroxide in the presence of lead nitrate and fluorescein oreosin, S. N. Roy 26 extends their application to acidimetry. Otherindicators worthy of note are a universal indicator for the pH range1-2-12.7,27 and 4-nitrocatechol,28 and oximinothiocamphor, pHrange 8.6-9.0,29 for acidimetry.The theories of Bjerrum and Brmsted have been applied to thetitration of weak acids and bases in water-ethyl alcohol mixtures,and it is found that the titration of weak bases is less practicable thanin water, but the salts of weak bases, e.g., alkaloid hydrochlorides,may be titrated with much enhanced accuracy in concentratedaqueous-alcoholic solutions.30Finally, I.M. Kolthoff 31 has discussed possibilities for the furtherdevelopment of acid-base indicators for the measurement of hydro-gen-ion activity and concentration, as well of adsorption, oxidation-reduction, and specific indicators for volumetric purposes .32Reagents.-No new reagent * comparable with 8-hydroxyquinoline21 Ann.Chim. analyt., 1936, [iii], 18, 37.22 Idem, ibid., p. 120.24 Analyst, 1936, 61, 315.26 Cf. also R. Ripan-Tilici, 2. anal. Chem., 1936, 104, 16, for axgentometrictitration of halide, thiocyanate, selenocyanate, and cyanate with fluoresceinas adsorption indicator.23 Idem, ibid., p. 173.26 J . Indicm Chem. Xoc., 1936, 13, 486; cf. idem, ibid., 1935, 12, 584.27 F. &ha and K. KBmen, Chem. his&, 1936,30, 22, 129.t 8 S. R. Cooper and V. J. Tulane, I n d . Eq. Chem. (Anal.), 1936,8, 210.29 D. C. Sen, J . Indian Ghem. Xoc., 1935,12, 751.30 H. Baggesgaard-Rasmussen, 2. and. Chem., 1936,105, 269.31 I n d . Eng. Chem. (Anal.), 1936, 8, 237.32 For a useful general article see “ Universal and Other Indicators,” byT.G. Pearson in Thorp’s “ Dictionary of Applied Chemistry,” 1935, Supple-ment, Vol. 2, p. 617.* Styryl dyes (P. Krumholz and E. Krumholz, Mikrochem., 1935, 19, 47),8-hydroxy-5-methylquIuinoline (C. E. Giete and A. SB, Anal. Asoc. Qzcim.Argentina, 1935, 23, 45), a mercaptan-like substance named “ thiocarbin ”(A. Steigmann, Phot. Ind., 1936, 34, 499), and what is probably ethyl 5-keto-2-thionhexah~drop~rimidine-4-carbox~late (S. E. Sheppard and H. R. Brigham,J . Amer. Chem. Soc., 1936, 58, 1046) are newly-described reagents for certainmetalsTHEOBALD : INORGANIC ANALYSIS. 437or thionalide has recently come to the fore, but a review which hasjust been published 33 of the use of organic reagents in both qualita-tive and quantitative analysis and their increasing significance willbe of much interest to all engaged in analytical work.Gravimetric and Volumetric Methods for the Determination, of theElements.-In a report of this nature it is impossible to do more thanmention a comparatively small number of the many papers whichhave been concerned with the determination of the elements duringthe period under review, and although all new analytical methodsshould be approached with an open mind tempered by a criticaloutlook, any criticisms of the present work would be presumptiveand premature, for the true value of a method can be assessed onlyin relation to the purpose for which it is designed, and after it hasbeen put to the test of practical experience.Group I .The accuracy of the potentiometric iodide-silver titra-tion as distinct from its precision or reproducibility has been recentlyin~estigated.~~ In the slow titration of silver with iodide, errors areproduced by the adsorption of iodide ions by the silver iodide formed,but the magnitude of the error can be reduced to a small value(0.017% or 0.028%) by titrating a t go", or by digesting the precipi-tate a t 90" in presence of a slight excess of silver prior to completionof the titration a t the ordinary temperature. Silver can also besuccessfully titrated with potassium iodide, even in the presence ofcupric or ferric ions, by using ceric ammonium sulphate and starch asinternal indicators, since oxidation of the iodide ion to iodine byCe"" is not permanent until the end-point is reached.35 Havingfound that, using the iodine monochloride end-point, the titrationof thaEZous salts with either potassium permanganate or ceric sulphateis unreliable, E.H. Swift and C. S. Garner 36 recommend titrationwith potassium iodate instead.The method previously described 37 for the removal of tungstenfrom tin by means of 8-hydroxyquinoline in an oxalate medium giveshigh results for tungsten owing to retention of tin, and a modificationnow put forward 38 is designed to overcome this.Group I I . Further details 39 have now been supplied 40 concerning33 F. Feigl, I n d . Eng. Chem. (Anal.), 1936, 8, 401.34 I, M. Kolthoff and J. J. Lingane, J . Amer. Chem. SOC., 1936, 58, 1524;See idem, ibid., 1935,57, 2126, 2377, for similar studies cf.idem, ibid., p. 1528.of the systems silver-thiocyanate and mercury-thiocyanate.2.5 A. Bloom and W. M. McNabb, I n d . Eng. Chem. (Anal.), 1936,8, 167.36 J . Amer. Chem. Soc., 1936, 58, 113.3 7 A. Jilek and A. RyBhek, Coll. Czech. Chem. Comm., 1933, 5, 136.313 Idem, ibid., 1936, 8, 246.39 Cf. Ann. Reports, 1935, 32, 457.40 G. Spacu and M. Kurag, 2. and. Chem., 1936,104, 88438 ANALYTICAL CHEMISTRY.the gravimetric determination of lead, thallium, bismuth, and gold,which are precipitated by thiolbenzthiazole as C7H,NS2PbOH,C7H,NS,T1, (C7H4NS2)3Bi, and (C7H,NS2)3Au, respectively ; andlead has been separated as carbonate, from copper, or cobalt andnickel, by the passage of carbon dioxide into a solution of the nitratesin presence of ~ y r i d i n e .~ ~ After a critical review of the determinationof lead as sulphate, and of antimony as sulphide by the method ofVortmann and Metz1,42 modifications of procedure have beenrecommended for these metals and their alloys.43 The chromatemethod for lead has receiyed further in~estigation,~~ and the B.P.(1932) method has been criticised as inaccurate owing to the non-quantitative liberation of oxalic acid from the lead oxalate precipi-tate; more accurate results are obtained, it is stated, by determin-ation of the excess of oxalic acid in the filtrateeq5In the gravimetric determination of mercury, mercuric sulphide isremoved from the weighed sulphide-sulphur precipitate by dis-solution in cold, concentrated hydriodic acid and the residual sulphuris weighed.The procedure can conveniently be applied to the rapidevaluation of technical grades of the ~ulphide.*~ An indirectvolumetric method, based on a critical study of the dichrornate-pyridine method of G. Spacu and J. Diekt7 consists of titrating thedichromate ion in the precipitated fHg py,]Cr,O, by one of the con-ventional methods, whilst substitution of acetone, in which thecomplex is less soluble than in alcohol, simplifies and improvesthe washing technique originally advocated by Spacu andDick.A critical comparison of a number of methods by an independentworker often serves a useful purpose in assessing the true value ofproposed methods and helps to clarify the position for those seekingan alternative to the older methods available. Several such reviewshave been published during the year.Various separations ofbismuth from lead, vix. , bromide-bromate hydrolysis,48 the pyro-gallol preci~itation,4~ and the cupferron methodY5O have now been4 1 A. Jilek, J. Kot’a, and J. Vfegt’al, Chem. Liaty, 1935, 29, 299.42 F. P. Treadwell and W. T. Hall, “ Analytical Chemistry,” 1935, Vol. 11,43 H. Vdoviszevski, 2. anal. Chem., 1936, 104, 94.44 Idem, ibid.; L. Guzelj, ibid., p. 107; Z. Karaoglanov and M. Jblichov,ibid., 1935, 103, 113.45 S. Wetherell, Quart. J . Pham., 1935, 8, 453.48 E. R. Caley and M. G. Burford, Ind. Eng. Chem. (Anal.), 1936,8,43.4 7 2. anal. Chem., 1929, 76, 273.O 8 L. Moser and W. Maxymowicz, 2.anal. Chem., 1925, 67, 248.49 F. Feigl and H. Ordelt, ibid., 65, 448.60 A, Pinkus and J. Dernies, Bull. SOC. cham. Belg., 1928, 37, 267.p. 220THEOBALD : INORQBNIC ANALYSIS. 439checked,51 but the hydrolysis in formic acid solution 52 leads toirregular results. Bismuth can also be separated from copper by amodification of the cyanide method of Fresenius and Haidlen,53but for both the bismuth-lead and the bismuth-copper separationsthe bromide-bromate procedure of Mosdr and Maxymovicz is pre-ferred. L. ICielt and G. C. Chandlee 64 find that precipitation withgallic acid at 70" serves to separate bismuth from lead, copper,cadmium, and many other metals, but not from mercury, antimony,tin, or silver. The phosphate method has also been re-examined 55and found to be inaccurate when lead is present.F. Hecht and R.Reissner 56 report that the micro-determination of bismuth asoxyiodide 57 is inexact, and that the macro-determination asC,H,N*OH,HBiI, 58 is unsatisfactory owing, inter alia, to the partialdecomposition of the precipitate during washing.59 Good results onboth the macro- and the micro-scale can be obtained, however, underthe exact conditions prescribed, by precipitation with 8-hydroxy-quinoline.The well-known Haen-Low volumetric method for copper isaccurate but long, and a shortening of the time required is much tobe desired. B. Park's procedure 6o which aims at effecting this hasnow been modified ; 61 potassium hydrogen phthalate has no materialeffect on the pH of the solution and can be omitted, but in order toensure complete oxidation of an ore containing sulphide, iron, andarsenic, a double treatment with nitric and hydrochloric acids, or asingle treatment with the two acids followed by one with saturatedbromine-water, is found to be essential.H. W. Foote and J. E.Vance 62 apply their modified iodometric method,63 with controlledpE, to determine copper in the presence of AsV and not more thanapproximately 20 rng. of antimony, interference by iron being pre-vented by the now common device of adding sodium fluoride.*61 E. A. Ostroumov, 2. (Mzal. Chm., 1936,106, 36.58 A. L. Benkert and E. F. Smith, J . Amer. Chem. Soc., 1898, 18, 1065.59 See Treadwell and Hall, op. d., p. 206.54 Ind. Eng.Chem. (AnaZ.), 1936, 8, 392.55 W. C. Blasdale and W. C. Parle, ibid., p. 352.56 Mikmchem., 1935, 18, 283.67 R. Strebinger and W. Zins, Mikrochem., 1927, 5, 166; 2. awl. Chem.,58 R. Berg and 0. Wurm, Ber., 1927, 80, 1664.59 F. Hecht and R. Reissner, 2. anal. Chem., 1935,103, 261 ; see also, idem,60 Ind. Eng. Chem. (Anal.), 1931, 3, 7 7 .6 1 W. R. Crowell, T. E. Hillis, S. C. Rittenberg, and R. F. Evenson, ibid.,68 Ibid., p. 119. * See K. Heller and F. Machek (Mikrochm., 1936,19, 147), for a review of1927,72, 417.ibid., pp. 88, 186.1936, 8, 9.63 Ann. Reports, 1935,32, 459, ref. (73).the literature on the determination and detection of cadmium440 ANALYTICAL CHEMISTRY.The complete precipitation of molybdenum by hydrogen sulphideis generally a matter of difficulty in an analysis, and it is noteworthythat the trisulphide can be precipitated quantitatively in the presenceof formic acid by initial reaction with a solution of hydrogen sulphidesaturated a t 0°,63a a finding which supports previous claims of asimilar nature ; 64 separation from tungsten is accomplished byadjusting the p , to 2.9 by means of a suitable buffer.There is littleto be gained, in general, by conducting the precipitation of the molyb-denum under pressure-anot her point which has been much disputedin the past, According to H. G o ~ o , ~ ~ molybdenum is completelyprecipitated by 8-hydroxyquinoline in the range pH 3.3-7.6, andvanadium a t pH 2.7-6.1 : and the conditions under which the formercan be determined volumetrically by oxidation of MoV to MoVI with0-1N-ammonium vanadate have been investigated by R.Lang andS. Gottlieb; G6 iron, vanadium, and large amounts of copper renderthe method impracticable. N. H. Furman and W. M. Murray,j ~ n . , ~ 7 reduce MoVI quantitatively to MoV by shaking with mercuryin a solution which is 2-3.5N with respect to hydrochloric acid,and titrate the quinquivalent molybdenum with ceric sulphate atthe ordinary temperature using the o-phenanthroline-ferrous com-plex indicator. They state that the presence of considerablequantities of phosphate, arsenate, or of ammonium salts is withouteffect on the accuracy of the molybdenum determination.A fractional distillation method has been worked out at theBureau of Standards for the separation of arsenic, antimony, and tinfrom one another and from elements having non-volatile chlorides ;germanium and rhenium, but not bismuth, interfere.68 The op-timum conditions of acidity for the volumetric determination ofantimony and arsenic by Andrews's iodine monochloride method 69have been fully in~estigated,'~ and a critical examination of variousmethods for arsenic in iron, steels, and iron ores has shown that thebest results are obtained by dissolution in nitric acid or bromine-water (bromine and hydrochloric acid for ores) followed by distilla-tion of the arsenic as chloride.71 Published methods for the Gutzeitreaction carried out on paper strips have also been critically re-viewed.7863a H. Yrtgoda and H. A.Fales, J . Amer. Chem. SOC., 1936,58, 1494.64 Cf. I. Koppel, Chem.-Ztg., 1924, 48, 801; J. fit6rba-Bohm and J. Vos-6 5 J . Chern. SOC. Japan, 1935, 56, 314. O6 8. awl. Chem., 1936, 104, 1.67 J . Amer. Chem. SOC., 1936, 58, 1689.6s J. A. Schemer, J . Res. Nat. Bur. Stand., 1936, 16, 253.69 J . Amer. Chem. Soc., 1903, 25, 756.70 A. Mutschin, 8. anal. Chem., 1936, 106, 1.71 A. Stadeler, Arch. Eisenhuttenw., 1935-36, 9, 423.72 W. Mddsteph, Z. anal. Chem., 1936, 104, 333.tfebal, 8. anorg. Chern., 1920, 110, 81THEOBALD : INORGANIC ANALYSIS. 441Dry distillation in oxygen serves to separate O ~ l - O - O O 1 ~ o ofselenium from sulphur and sulphur-containing materials.73 Arsenicand tellurium present in an amount equivalent to the selenium donot interfere.74Volumetric methods for tin have long been a source of tribulationt o the analyst, and two papers which have recently been publishedmay help to clear the situation.According to F. L. Okell and J.L ~ m s d e n , ~ ~ low results in tin titrations are due to oxygen dissolvedin the iodine solution and not necessarily to incomplete exclusion ofair in the flask, and the interfering action of titanium experienced inthe analysis of tin ores is eliminated when oxygen-free iodine is usedfor titration. Reduction with aluminium turnings is recommendedin ore analysis.76 For alloys of tin and lead with less than 2% ofantimony, the tin and lead are best dissolved directly in concentratedhydrochloric acid in absence of oxygen, and the antimony removedby filtration before titration with potassium iodate.Removal ofantimony is essential since cold stannic chloride reacts with freshly-precipitated antimony too rapidly to permit accurate titration ofSn" in its presence.77 The titration of Sn" has also been carriedout with ceric sulphate, diphenylamine being the indicator.78When heated a t 400-500" with excess of ammonium iodide, tindioxide is quantitatively volatilised as stannic iodide and advantagecan be taken of this to ascertain the purity of the ignited metastannicacid obtained in the usual course of an analysis.79R. Gilchrist and E. Wichers have made an important contributionto the analysis of the phtinum metals in which a new procedurefor the separation of osmium, ruthenium, platinum, palladium,rhodium, and iridium from one another, and their gravimetricdetermination, have been described ; no specialised equipment orreagents are necessary and an accuracy comparable with that of thebest analytical procedures for the common metals is claimed fortheir methods.Goup 111. For the determination of small amounts of iron,aluminium, and titanium in admixture, 8-hydroxyquinoline and its5 : 7-dibromo-derivative, which precipitates titanium in acid andaluminium in alkaline solution, have been utilised.*l J.Dewar and73 See G. G. Marvin with W. C. Schumb, I n d . Eng. Chem. (Anal,), 1936, 8,109, for determination of selenium in 18 : 8 stainless steels.74 Idem, ibid., 1935, '7, 423.7 5 Analyst, 1935, 60, 803.76 See also L. Deutsch, Ann.Chim. analyt., 1936, [iii], 18, 10.7 7 H. F. Hourigan, Analyst, 1936, 61, 328.7 8 N. A. Rudnev, Trans. Butlerov Inst. (.'hem. Tech. Kazan, 1934, No. 2, 51,79 E. R. Caley and M. G. Burford, I n d . E n g . Chem. (Anal.), 1936, 8, 114.80 J . Arner. Chem. Soc., 1935, 67, 2565.81 A. M. Zanko and A. J. Bursuk, J . Appl. Ckem. Russia, 1936, 9, 895442 ANALYTICAL CHEMISTRY.P. A. Gardiner 83 find that, contrary to the adverse criticism of L.Moser and M. Nie~sner,*~ a slight modification of H. Britton'smethod 8* (hydrolysis of the alkali beryllate) furnishes an accurateseparation of aluminium and beryllium when the former is not greatlyin excess of the latter. For the case of aluminium and zinc, F. H.Fish and J. M. Smith, jun., adopt the aluminate method,85 in whichaluminium is weighed as 2Li,O ,5A1,0,, zinc being determined in thefiltrate as the pyrophosphate, whilst T.K8zu 86 separates aluminiumfrom manganese, cobalt, and nickel, but not zinc, by precipitationwith a saturated, aqueous solution of aniline, the aluminium beingweighed as the oxide.This use of organic bases in preference to ammonia is e~tending,~'and 20% pyridine is now employed to precipitate iron, chromium,and aluminium as hydroxides from dilute nitric or hydrochloric acidsolution in the presence of the corresponding ammonium salts. Asingle precipitation is said to give a separation, which is practicallycomplete, from manganese, cobalt, and nickel, but not zinc, and themethod has been applied to pyroluaite and to cobalt ores.88 Uran-ium, also, is precipitated, as HzUzO,, from solutions of uranyl salts,thus providing a quantitative separation from the alkaline earths.89For the removal of gullium from beryllium, titanium, zirconium,and thorium, S.Ato 90 has recourse to the ether-extraction methodfrom hydrochloric acid solution, and finally precipitates the galliumwith sodium camphorate ; and for the determination of this metal inaluminium, J. A. Scherrer 91 adopts the same device but precipitatesthe gallium with cupferron and then ignites it to the oxide, afterremoval of any iron, tin, etc., which has accompanied the galliuminto the ether extract. An alternative method, obviating an extrac-tion and based on precipitation with cupferron in sulphuric acidsolution, is also given.In view of the use which is made in some laboratories of perchloricacid as an oxidising agent for chromium, it is of interest to learn thatthe incomplete oxidation which results when this acid alone is usedis due to the production of it small amount of hydrogen peroxide;82 Analyst, 1936, 61, 536.84 Analyst, 1921, 46, 361, 437 ; 1922, 47, 50.85 Ind.Eng. Chem. (Anal.), 1936, 8, 349; see J. T. Dobbins and J. P.86 J . Chem. SOC. Japan, 1935, 56, 562, 683.88 E. A. Ostroumov, 2. anal. Chem., 1936, 106, 170.89 Idem, ibid., p. 244.90 Sci. Papers I m t . Phys. Chem. Res. Tokyo, 1936,29, 71 ; cf. 1:ba'd., 1931, 24,91 J . Rerr. Nat. BUT. Stand., 1935, 15, 585.83 ~?lonatsh., 1927, 48, 113.Sanders, J . Amer.Chem. SOC., 1932, 54, 178.See Ann. Reprt8, 1935, 32, 462, ref. (10); 460, ref. (86).270; 1931, IS, 289THEOBALD : INORGANIC ANALYSIS. 443quantitative results, however, are obtained with a mixture of per-chloric and sulphuric acids in certain proportion^.^^Analytical methods for the determination of zirconium and thecomplete analysis of zirconium minerals have been re~iewed.9~W. R. Schoeller and his collaborators have now completed theirinvestigations into the analytical chemistry of tantalum, niobium,and their mineral associates : the four papers recently published com-plete the series. I n the first of theseYg4 the fate of beryllium in themore important, operations advocated for the separation of the vari-ous earths and the analysis of minerals containing them is dealt with ;the secondg5 is concerned with the determination of tungsten inearth-acid minerals,g6 and the third with the separation of phosphorusand vanadiuimg7 The last paper 98 contains a general summarywhich is intended as a key to facilitate the study of the whole series.Not the least striking feature of these remarkable investigations isthe simplicity of the apparatus and reagents whereby the resultshave been achieved; and, as is pointed out in the final paper, “ thesimple classic processes of mineral analysis have proved adequatefor the solution of some of its most difficult problems.” The mono-graph based on these researches, which is to be published under theaegis of the Society of Public Analysts, will be awaited with greatinterest by allwhosework takes them into the field of mineral analysis.Anthranilic acid has been confirmed as a suitable, althoughrestricted, reagent for the determination of zinc, cadmium, cobalt,nickel, and copper; the conditions specified by 13. Funk and M.Dittg9 are satisfactory except in the case of nickel, and are notimproved by the addition of ammonium or sodium acetate, orsodium tartrate.9ga This acid, in the form of its sodium salt, hasalso been employed for the micro-determination of zinc.1The post -precipitation of zinc sulphide with mercuric sulphidehas been studied in its theoretical and practical aspects by I.M.Kolthoff and R. Moltzau ; and J. R. Caldwell and H. V. Moyer3 find92 G. F. Smith, L. D. McVickers, and V.R. Sullivan, J . SOC. Chern. Ind.,1935, 54, 3 6 9 ~ .93 G. A. Ampt, J . Proc. Austral. Chem. I m t . , 1935, 2, 321.94 W. R. Schoeller and H. W. Webb, Analyst, 1936, 61, 235.9 5 W. R. Schoeller and E. F. Waterhouse, ibicl., p. 449.96 Cf. Ann. Reports, 1935, 32, 462, ref. (21).97 W. R. Schoeller and H. W. Webb, ilna,lyst, 1936, 61, 585.98 W. R. Schoeller, ibid., p. 806.99 Z . anal. Chem., 1933, 93, 241.9% R. J. Shennan, J. H. F. Smith, and A. M. Ward, AnaZyst, 1936,61, 395.1 C. Cimerman and P. Wenger, Arch. Sci. phys. na,t., 1935, [v], 17, Suppl.,2 J . Physical Chem., 1936, 40, 779.9 J . Amer. Chem. SOC., 1935, 57, 2372.94-98444 ANALYTICAL CHEMISTRY.that the addition of small amounts of gelatin or agar producesimmediate and complete flocculation of zinc sulphide suspensionsand permits filtration 15 minutes after precipitation.Satisfactoryseparations from nickel, manganese, aluminium, or chromiumcan $hus be ~btained,~ and when a small amount of acraldehydeis also added, a good separation from cobalt can be effected witha single pre~ipitation.~Precipitation is generally preferable to extractionfrom solids in quantitative work, and one such method has beenworked out 6 for the nitrates of the alkaline-earth metals. Strontiumnitrate is completely precipitated in a dense, crystalline form andseparated from numerous other metals by the addition of lOOyonitric acid until the resultant solution contains not less than 79% ofnitric acid. Barium and lead can be obtained free from othermetals in a similar way.The solubility of calcium nitrate decreasesrapidly with increasing acid concentration, and caZcium and stron-tium nitrates are separated from each other when the content ofnitric acid lies between 79 and 81% : the method seems preferableto that of S. G. Rawson.7 Attempts to separate these two metalsby precipitation of strontium nitrate with nitric acid in variousorganic media were not encouraging.Rosolic acid has been used as indicator for the direct titration ofbarium with potassium chromate by the method of K. Jellinek andJ. Czerwinski,g and this furnishes an indirect method for the deter-mination of sulphate and of sulphur in pyrites and slags.9Group V . The determination of potassium on the micro-scaleforms the subject of a detailed examination by P.Wenger, C.Cimerman, and C. J. Rzymowska,lo who find that Emich's chloro-platinate method gives good results for this element alone, but not inthe presence of more than four times as much sodium. By an adapt-ation of the macro-method of F. G. Smith and J. L. Gring,ll in whichpotassium is converted into its perchlorate before treatment withchloroplatinic acid, they have been able to determine gravimetricallyamounts of potassium of the order of 0-5 mg. in the presence of tenGroup I V .4 Idem, J . Amer. Chem. Soc., 1935,57, 2372.5 Idem, ibid., p. 2375.6 13. H. Willard and E. W. Goodspeed, I n d . Eng. Chem. (Anal.), 1936, 8,7 J. SOC. Chem. Ind., 1897,16, 113; cf. W. Noll, 2. alzorg. C'hem., 1931,199,414.193.2.anorg. Chern., 1923, 130, 253.9 A. V. Vinogradov, Ann. Chirn. analyt., 1935, [iii], 17, 285.10 MiErochem., 1936, 20, 1 ; Arch. Sci. phys. nat., 1935, [v], 17, Suppl.,11 J . Amer. Chem. SOC., 1933, 55, 3957.p. 89THEOBALD : INORGANIC ANALYSIS. 445times as much sodium. A volumetric ending, which is particularlysuitable in the determination of potassium in biological media, hasalso been worked out by these authors, and depends on the conversionof the K,PtCl, into K,PtI, by treatment with potassium iodide, andtitration of the iodoplatinate with thiosulphate.12C. H. Greene l3 has examined the sensitivity of the magnesiumuranyl acetate reagent to sodium and potassium, and his data showthat addition of alcohol increases the sensitivity of the reagent to-wards sodium more than towards potassium-a desirable result.The distinction between these two metals also improves as the ratioof the volume of the reagent to that of the test solution is increased.Errors arising from the micro-determination of sodium by means ofan aqueous-alcoholic solution of this reagent have also been discussedby A.Krassilchik,14 who puts forward an improved technique.Disturbing discrepancies have often come to light in the valuesobtained for the alkalis by independent analysts using the LawrenceSmith method on the same material, and incomplete attack in thefusion may often be the explanation of the disagreement. This andother sources of error are discussed by M. 0. Lamar, W.M. Hazel,and W. J. O’Leary,15 who suggest remedies and improvements parti-cularly for substances known to be refractory. For aluminiumrefractories, other workers l6 fuse with ammonium fluoride as amethod of attack, and then, after expulsion of hydrogen fluoride,precipitate the sodium with zinc uranyl acetate, reduce the uraniumin the precipitate by a coil of aluminium, and titrate back withpermanganate. For amounts of sodium ( ? Na,O) from 0.6 to 4.574,test results show goodagreement with those obtained by the LawrenceSmith method.Anions. There remain to be mentioned in this section some in-vestigations concerned with the determination of the anions.According to G. L. Jenkins and C. F. Bruening,17 the official(National Formulary) methods are suitable for ferric but notfor ammonium, calcium, sodium, potassium, and manganesehypophosphites,18 and improvements are suggested.H. Terlet andl2 For a “ Semmelreferat ” of methods for the micro-determination ofpotassium, see C. Cimerman and C. J. Rzymowska, Mikrochem., 1936, 20,129.13 Ind. Eng. Chem. (AnaE.), 1936, 8, 399.14 Compt. rend., 1936, 203, 78.15 Ind. Eng. Chem. (AnaE.), 1935, 7, 429.16 H. V. Churchill, R. W. Bridges, arid A. L. Miller, ibid., 1936, 8, 348.17 J. Amer. Pharrn. Aasoc., 1936, 25, 19.18 For these last five salts the methods are based on oxidation t o phosphatewith nitric acid, precipitation of phosphate with excess of silver nitrate,m d a back-titration with ammonium thiocyanate446 ANALYTICAL CHEMISTRY.A.Briau l9 report that for phosphoric acid Scheffer's method,awhich consists in the titration of ammonium phosphomolybdatewith sodium hydroxide in the presence of formaldehyde, is trust-worthy and accurate when steps are taken to remove co-precipitatedinolybdic acid. They outline procedures for the examination ofnatural and artificial phosphates of various kinds.21The conditions necessary for the precipitation of benzidine sul-phate (pH 2-3),22 the titration of sulphnte with lead nitrate with eosinas incticat~r,~~ and indirect methods with sodium rhodizonate 24and rosolic acid as indicators 25 have also been communicated.Much of the work recently done on the determination of $wineis concerned with H. I€. Willard and 0. B. Winter's distillationmethod 26 and suggested modifications of it,27 and a150 with Sanchis'Owing to the marked adsorption properties of lanthanumfluoride, determination of fluorine by precipitation in this form 29is found to be impra~t~icable.~~ Precipitation as PbFBr 31 or asK2SiF6 32 forms the basis of gravimetric or volumetric methods ; andfor the determination of fluorine in minerals, calcium fluoride pro-tected as a colloid with gelatin forms the basis of a nephelometricmethod.33 A review of various procedures for silica in the presenceof fluorine has also been made.34When iodine monochloride solution is treated with saturatedpotassium bromide, iodine is a t first liberated, but on addition ofmore bromide this disappears, iodine bromide being re-formed.19 Ann.Faiaif., 1935, 28, 546.20 J. OfficieZ, 1934, Aug. 30th.21 See H. Trapp, J. pr. Chem., 1935, [iif, 144, 93, for calcium phosphates.23 E. C. Owen, Biochem. J., 1936, 30, 352.23 J. E. Ricci, Ind. Eng. Chem. (Anal.), 1936, 8, 130.24 R. Strebinger and L. von Zombory, with L. PollBk, Z. a d . C'hem., 1936,25 A. V. Vinogradov, loc. cit., ref. (Q), p. 444.26 Ind. Eng. Chern. (Anal.), 1933, 5, 7.27 D. Dahle and H. J. Wichmann, J. Assoc. 03. Agric. C'hem., 1936,19, 313,320; D. S. Reynolds, J. B. Kershaw, and K. D. Jacob, ibid., p. 156; W. K.Gilkey, H. L. Rohs, and H. V. Hansen, Ind. Eng. Chenz. (Anal.), 1936, 8, 150;W. D. Armstrong, ibid., p. 384 (micro-method).28 E. H. Ducloux, Anal. Aaoc. Quim. Argentina, 1935,23,63; J . M. Muiioz,Rev.Xoc. Argentin. Biol., 1934, 10, 395; A. H. de Carvalho, Rev. C'him. puraappl., 1936, [iii], 11, 99.105, 346.20 Cf. R. J. Meyer and W. Schulz, Z. angew. Chem., 1925,38,203.30 J. Fischer, with E. Muller and H. Knothe, 2. and. Chem., 1936,104, 344.31 A. A. Vesiliev, J . Appl. Chem. Ru88&3, 1936, 9, 747; see also, ideln, ibid.,3% A. A. Vasiliev, with N. N. Martianov, 2. anal. Chem., 1935, 103, 107.33 R. E. Stevens, Ind. Eng. Chem. (Arttrl.), 1936,8, 248.34 S. S. Korol and V. M. Ka,lushskajja, J. Appl. Chem. Russia, 1936, 9, 148.p. 943, for the determination of fluorine in the presence of berylliumTHEOBALD : INOR(3ANIC ANALYSIS. 447To apply the iodine bromide process tjo the determination of iodineor iodide, the sample is treated with a large excess of potassium bro-mide, and concentrated hydrochloric acid.After dilution and addi-tion of carbon tetrachloride, the solution is titrated with potassiumiodate-other oxidising agents such as ceric sulphate, potassiumperiodate, permanganate , or dichromate can be used-until thecarbon tetrachloride is decolorised. Antimony in the presence ofa hydrochloric acid concentration too great for the iodine mono-chloride process to be satisfactory can also be determined by this~ i i e a n t i . ~ ~Iodides can be titrated with ceric sulphate to a visual end-point inthe presence of acetone and sulphuric acid, o-phenanthroiine-ferrousion being used as indicator : moderate amounts of chloride have noadverse effect, and interference due t,o bromide can be largely elimi-nated by appropriate d i l u t i o i ~ .~ ~ Other methods for bromide andchloride,37 and bromine and iodine in the presence of each 0ther,~8have also been given.The use of mercury 39 or amalgams seems to be increasing in popu-larity in analytical work, and advantage has been taken40 of thereduction of chlorates, brornates, and iodates by zinc amalgam or byWood’s alloy for their determination.Vanadous sulphate serves for the quantitative reduction of chlor-ates, nitrates, and persulphates in an inert atmosphere, -the excessVS04 being titrated with potassium ~ermanganate.~~ M. B. Donaldreports that the optimum conditions for the reduction of nitratesare very different from those originally specified by Devarda, muchless sodium hydroxide being required.42A routine method, based on the ‘‘ partition ” of boric acid betwcenwater and ether in the presence of hydrochloric acid and ethylalcohol, has been developed for the determination of boron in gla~s.4~Boric oxide contents varying from 0.7 to 16% can be rapidly deter-mined with no material sacrifice of accuracy; zinc interferes seri-ously, but barium, fluorine, and abnormal amounts of iron onlyslightly.Phosphoric acid (40%) has been recommended for the expulsiona5 R.Lang, 2. unal. Chem., 1936, 100, 12.36 D. Lewis, Ind. Eng. Chern. (Anal.), 1936, 8, 199.37 G. G. Longihescu and E. I. Prundeanu, Bull. Acad. Sci. Rotmaiiw, 1935,38 L. Spitzer, Ind. Eng. Chern. (Anal.), 1936, 8, 466.39 Cf. N. H. Purman and W.M. Murray, jun., Zoc. cit., ref. (67), p. 440.40 P. G. Popov, Ukrain. Chem. J . , 1936, 10, 413.41 P. C. Banerjee, J . lndkn Chem. Soc., 1936, 13, 301.42 A w l y e t , 1936, 61, 240.43 F. W. Glaze and A. N. Finn, J . Rm. Nat. BUT. Stand., 1936,16,421.17, 47448 ANALYTICAL CHEMISTRY.of carbon dioxide from carbonate^.^^ This is by no means new,for the use of this acid was advocated over 30 years ago by G. T.Morgan,45 and since that time many hundreds of determinationsof carbon dioxide in dolomite and rocks, for which it is particularlysuitable, have been carried out by this means in the laboratory towhich the Reporter is attached. It is surprising that the method isnot more widely adopted, for it has many advantages, chief amongwhich are the elimination of the condenser and absorption tubenecessitated by the volatility of hydrochloric acid, and the verysmall “ blank ” which it affords.The preparation of a solution of manganic sul-phate as a reagent for volumetric work has been recently described.46When protected from light the solution showed no change in titreover a period of nine days, and it rapidly oxidises nitrites, oxalates,ferrous iron in presence of chloride, and VII to V V .The reactionsare stoicheiometric, and the end-points well-defined, thus affordingresults superior to titrations with permanganate.There are many signs in the literature that more attention is beingpaid to the statistical evaluation of the possible errors to which ananalysis is subject. In the past, this has generally been taken intoaccount in the determination of atomic weights, but it has beensomewhat neglected in ordinary analytical work, and this interestwhich is being displayed in the theoretical aspect of the reliabilityof an analytical measurement is all to the good.It is also desirablethat there should be a clear recognition of the meaning of the termserror, precision, and accuracy, which have often been too vaguelyused. An interesting chapter on this subject is to be found in I. M.Kolthoff and E. B. Sandell’s recently published book on analysis:’and an article which should be of much interest to analysts has beenwritten by A. A. Benedetti-Pichler 48 who discusses the statisticalaspects of chemical measurements applicable to analytical data.MiscelZaneous.Qualitative.Methods for the -Detection of Anions and Cations.-During the periodunder review several new schemes for the systematic separation ofanions have been put as well as methods for the commoner44 F. Vojif, Chem.Listy, 1935, 29, 185.4 5 J . , 1904, 85, 1004.46 A. R. J. P. Ubbelohde, J., 1935, 1605.4 7 “ Text-book of Quantitative Inorganic AnalyEiis,” Macmillan, New Yo&,48 Ind. Eng. Chem. (Anal.), 1936, 8, 373.49 E. Umblia, Keem. Teated, 1935, 2, 79; J. T. Dobbins and H. A. Ljung,J . Chem. Educ., 1935, 12, 586; E. W. Flosdorf and C. Henry, ibid., 1936, 13,274; F. Pozna and E. Migray, Ann. Chim. appl., 1936, 26, 81.1936, Chapter XV, p. 250THEOBALD : 1NORG.ANIC ANALYSIS. 449cations which dispense with the use of hydrogen ~ulphide.~O Asimplified method for Group I1 51 has also been recommended.E. R.Caley and M. G. Burford 52 find that concentrated hydriodicacid is a valuable reagent for the detection and separation of com-pounds such as lead sulphate, stannic oxide, silver halides, calciumfluoride and fluorspar, and certain chromium compounds, whichhelp to form the " insolubles " of qualitative analysis. Reactionsare often distinctive and frequently more rapid and convenient than afusion, and some of the separations are quantitative. L. C. Hurd 53shows that rhenium concentrates with arsenic in the Prescott-Johnson system 54 of analysis. He points out that sublimationmethods for the detection of rhenium in minerals may fail, and re-commends opening up by a fusion when the mineral is insoluble inhydrochloric or nitric acid.He adds that rhenium is probably bestdetected 55 by the thiocyanate reaction after molybdenum has beenremoved as a xanthic acid complex soluble in chloroform.Antipyrine is chosen from a number of organic bases as the bestreagent for antimony, with which it yields a yellowish-orange pre-cipitate in the presence of potassium iodide; tin gives a white pre-cipitate, but here the reaction is less sensitive. The reaction isapplied after digestion of the arsenic, antimony, and tin sulphides ofGroup IIb with hydrochloric acid56For the detection of platinum in small amount in minerals, alloys,and the like, the alkaline solution is treated with potassium iodideand acetic acid and a reddish-brown or rose colour appears if Pt'**'is present.When precipitated from sodium tellurite by sulphurdioxide, tellurium separates platinum, gold, selenium, molybdenum,and mercury from other metals and so concentrates the platinum.57The formation of red compounds with 4-methyl-1 : 2- and 4-chloro-1 : 2-dithiolbenzene (" dithiol ") is used as a test for tin by R. E. D.Clark.58 These reagents, it is said, can be employed in the presenceof all other metals when the colour of the mercaptides which they mayform is not intense enough to mask the red colour due to tin, but50 A. B. Levin, 2. anal. Chern., 1936,105,328; M. B. Schtschigol and N. M.Doubinski, Ann. Chim. analyt., 1936, [iii], 18, 257; V. J. Petraschenj, 2.anal.Chem., 1936, 106, 330.61 E. ChirnoagB, ibid., 1936, 104, 356.62 I n d . Eng. Chem. (Anal.), 1936, 8, 63; E. R. Caley, J. Arner. Chem. SOC.,53 I n d . E q . Chem. (Anal.), 1936, 8, 11.54 R. K. McAlpine and B. A. Soule, '' Qualitative Chemical Analysis," 1933.66 See L. C. Hurd and B. J. Babler, fnd. Eng. Chem. (Anal.), 1936,8, 112, for66 J. A. Gautier, J . Pham. Chim., 1936, [viii], 23, 283.67 S. K. Hagen, Mikrochem., 1936, 20, 180.68 A d y 8 t , 1936, 61, 242.1932, 54, 4112.determination of rhenium.REP.-VOL. XXXIII. 450 ANALYTIOAL CHEMISTRY.the only metals likely to interfere me copper, bismuth, and nickel.Udortunately, like many reagents recommended for colour reactions,these thiolbenzenes are unstable and must be freshly prepred orstored in hydrogen.The test will undoubtedly be useful, but itseems that the ideal reagent for tin has yet to be f0und.~9The white precipitate which Sn"" in hydrochloric or sulphuricacid forms with nitrophenylarsinic acid on boiling provides anotherselective test for this element which can be applied to its detectionin alloys since the majority of metals likely to be present in such acase do not interfere. The material under investigation is firsttreated with concentrated nitric acid and the test made on the hydro-chloric acid solution of the metastannic acid thus produced.60In the absence of mercury, silver, and thallium, copper can bedetected (and determined) in the presence of relatively large amountsof bismuth, cadmium, lead, and zinc by means of the yellow ammineCu[Cr(CNS),(NH,),], which is precipjtated by the addition ofReinecke's salt to Cu" ions reduced to Cu' by K,SnCI4,2H2O in hydro-chloric acid solution,61 and since cupric ions give no precipitate,the same reagent serves for the sensitive detection (and determina-tion) of mercury, as Hg[Cr(CNS),(NH,),],, in the presence of manyother metals.62 After removal of copper by means of potassiumthiocyanate, cadmium can be detected by 2 : 7-diaminofluorene,which is preferred to hydrogen sulphide for this purpose.@In view of the utility of ammonium mercuric thiocyanate as aconfirmatory test for zinc, determinations of the solubilities of zincmercuric thiocyanate in alkali-salt solutipns are of interest, as is theconclusion that zinc should be in the form of nitrate when this testis applied.64According to H.Ditz and R. Helleb~and,~~ the sensitivity of theammonium thiocyanate-acetone reaction for cobalt is much reducedif accompanying iron is removed either by sodium carbonate or bythe formation of a complex fluoride. Removal by calcium carbon-ate, however, leaves the sensitivity unchanged and then 1.5 mg. ofcobalt per litre can be detected in the presence of no less than 15 g. ofiron. F. P. Dwyer 66 has also examined this reaction and finds that69 Ann. Repork?, 1935, 32,459; cf. also this Report, p. 463.60 B. Tougarinoff, Bull. SOC. chim. Be@, 1936, 45, 542.61 C. Mahr, 2. anorg. Chem., 1935, 225, 386.62 Idem, 2. a d . Chem., 1936,104, 241.63 E.L. NSO and F. Calvert, A&. ma. Q U ~ P ~ . , 1934,353,698; cf. &ISO A. w.Scott and E. G. Adam, J . Amer. Chm. SOC., 1935,57,2541.Ellso B. V. J. Cuvelier, 2. anal. Chem., 1935,102, 16.64 B. V. J. Cuvelier and F. Bosch, Natuwwetenach. Tijds., 1936, 18, 9; see6s 2. m r g . Chm., 1936, 225, 73; 888 dso idem, &id., 1934,2U, 97.e6 J . Proc. Austral. Cht?rn. Inat., 1936, 3, 239TREOBBLD : INORQAIYIU ANALYSIS. 451the addition of ammonium acetate and tartaric acid to preventinterference from iron also leads to a serious loss of sensitivity,and he prefers to add potassium ammonium fluoride or, better still,sodium ammonium hydrogen phosphate, for this purpose.I n view of the peculiar behaviour of precipitated nickel and cobaltsulphides towards mineral acids, which is utilised in so many schemesof analysis and for which a satisfactory explanation has yet to beestablished, it is of interest to note that, according to A.M. Middletonand A. M. Ward,67 the precipitates which are usually obtained inqualitative analysis are oxygenated and not the normal sulphides.A mixture of potassium ferrocyanide and Cu(NH3),S04,H,0 isstated to give a sky-blue precipitate with calcium ions,@ whilst newand more sensitive reagents described for magnesium 69 are p-nitro-benzenediazoamino-4-nitronaphthalene, p-nitrobenzenediazoamino-benzene, and 4-nitro-4'-amino-l: 1 '-azonaphthalene. It is claimedthat no other metal hydroxide, even those of beryllium or therare earths, gives a blue colour with the last reagent.Several papers have been concerned with the removal of phosphateions in qualitative analysis, and of these S.Ishimaru's contributions 70are by far the most comprehensive. He finds that (i) POL" can becompletely removed from a solution just acid to methyl-orange byaddition of ferric nitrate, and this is more convenient than the leadmethod which can be applied satisfactorily only after removal ofGroup IIIa and manganese, (ii) precipitation with BY' leads to lessocclusion and adsorption of other ions by the precipitate than theiron method, but is less satisfactory in the presence of a high ironconcentration, (iii) the zirconium method equals that of the ironin merit, (iv) precipitation with tin leads to loss of iron and chromium,but can be adopted after removal of the aluminium group and man-ganese, Reynoso's procedure 71 being the best, and (v) T.B. Smith'sformate method 72 is the most suitable of all the methods advancedfor elimination of the effects of phosphate ions based on the additionof excess of phosphate or oxalate. It is finally concluded that, in sofar as accuracy is concerned, the bismuth method, except in the caseof a high iron content, is the best of the many methods which havebeen examined in considerable detail in this series of investigations.L. J. Curtman and T. B. Greenslade 73 also find that with the tinand the ferric chloride method loss of cations is serious. Both these67 J., 1935, 1459.68 8. A. Celsi, Anal. Fam. Bwquh., 1934, 5, 85.69 F.P. Dwyer, J . Proc. Awrtmt. C h m . Imt., 1936, 3, 184, 224.70 Sci. Rep. TbhoXru, 1935,24,426, 439, 448, 461, 473.7 1 An%. Chim. Phy8., 1862, 84, 320.72 J., 1933, 253.73 J . Chm. Educ., 1936,18,238452 ANALYTICAL CHEMISTRY.and the zirconyl chloride method are all efficient in removing phos-phate, but they consider that the last is the most rapid, effective, andconvenient. C. N. Potschinok 74 eliminates this ion as aluminiumphosphate, and S. Augusti 75 uses lead acetate in acetic acid solutionto remove oxalate, fluoride, silicate, and silicofluoride ions as well.V. J. Petraschenj 76 has outlined a scheme for cations of the thirdand the fourth analytical group in the presence of phosphate, andW. Fischer, W. Dietz, K. Brunger, and H. Grieneisen ‘7 have in-vestigated the same subject in considerable detail, putting forwardnew schemes for these groups.The sensitivity of the phospho-molybdate reaction is said to be enhanced by the addition of a suit-ably-prepared glycerol-gelatin solution.78In order to detect very small percentages of non-metallic impuritiesin metals, the sample of metal is made the cathode in the electrolysisof dilute sulphuric acid or dilute sodium hydroxide plus potassiumcyanide. Phosphorus, arsenic, antimony, sulphur, selenium, andtellurium, combined or in solid solution, are reduced to their hydrides,which are identified by filter-paper impregnated with suitable re-agents ; 0.001 yo of phosphorus, for example, can thus be dete~ted.7~Small amounts of bromide in sodium chloride can be identified by amodification of the colour reaction with fuchsin,sO and bromates aredetected in the presence of potassium chlorate and bromide by agreenish-yellow colour which develops with fluorescein.In 4N-hydrochloric acid solution, bromates rapidly decolorise methyl-orange, and this forms the basis of a test in the presence of otheroxidising agents such as chlorates, iodates, nitrates, persulphates,dichromates, ferricyanides, and nitrites. The same reaction canalso be used to detect small amounts of bromate in a large excess ofchloride or bromide. 82Methods for dealing with insoluble ferricyanides and the detectionof the ferricyanide ion with leuco-malachite green or benzidine aredescribed by L. K ~ h l b e r g .~ ~ According to J. Plank,m freshly-prepared ceric sulphate plus potassium carbonate will detect 1 part ofhydrogen, peroxide in 160,000 parts of solution.74 J . Appl. Chem. Rumia, 1936, 9, 140.v 5 Ann. Chim. appl., 1935, 25, 448.76 Z. anal. Chem., 1936, 106, 241.A. Steigmann, Chem.-Ztg., 1936, 60, 129.79 K. W. Frohlich, Angew. Chem., 1935, 48, 624.8o R. C. Lbpez, Farm. moderna, 1935,. 46, 55; see also F. Feigl, “ Qualit-81 F. L. Hahn, Mikrochem., 1936, 20, 236.a2 I. M. Korenman, 2. anal. Chem., 1935, 103, 269.83 Ibid., 1936, 106, 30.84 Magyar Chem. Pol., 1934, 40, 105.7 7 Angew. Chem., 1936, 49, 719.ative Analyse mit Hilfe von Tiipfelreaktionen,” 1935, p. 278THEOBALD : INORGANIC ANALYSIS. 453Drop Remtions.-The output this year of papers dealing with thesetests, conveniently but unfortunately spoken of as “ spot ” tests, issomewhat less than in previous years, but the importance and inter-est of the subject make it desirable again 85 to sumrnarise the workwhich has been done.The tendency too readily to regard thesetests as specific still exists in some quarters, although the series ofcritical investigations which are being undertaken by certain workersmay help to correct this erroneous view.* For example, havingshown that the cacothelin test for tin is by no means specific,s6J. B. Ficklen, I. L. Newell, and N. R. Pike87 have turned theirattention to the cinchonine-potassium iodide reagent for bismuth,which likewise is not truly specific, and to p-nitrobenzeneazoresor-cinol for magnesium, which should be used only when ions of GroupsI, 11, and 111, and ammonium have been removed.88The use of drop reactions in the identification of substances solublewith difficulty in acids, such as the silver halides, insoluble sulphatesand fluorides, ignited oxides, silica, etc., is described by P.Feigl,*9and A. A. Benedetti-Pichler and W. F. Spikes have presented a schemefor the separation, identification, and estimation of mixtures ofthallium, Zead, and siZver using 0.5--P mg. of solid material.gO Thisis the first of a series of papers on qualitative separations on themicro-scale, and those who, like the Reporter, hold the view thatgroup separations are still essential for the analysis of any but thesimplest materials, and that the future of qualitative analysis liesin the judicious combination of these separations and drop reactions,will look forward with considerable interest to the contributions85 Cf.Ann. Reports, 1935, 32, 471.86 Cf. ibid., p. 472, ref: (36).87 8. anal. Chem., 1936, 104, 30.8 8 I. L. Newell, N. R. Pike, and J. B. Ficlrlen, 2. worg. Chem., 1935, 225,89 Nikrochem., 1936, 20, 198.90 Ibid., 1936,19, 239.* Part of the misapprehension which has arisen as t o the true selectivity oforganic reagents now employed in drop reactions may be due t o a confusionof terms. Feigl, who has done so much to advance this branch of analysis-and, presumably, German-speaking authors have followed him-uses theterm “ specific ” in a wider sense than is customary with English-speakingpeople, but he is careful both in his book ( o p .cit., p. 10) and in his latestarticle [ I n d . Eng. Chem. (Anal.), 1936, 8, 4011 t o differentiate between‘6 specific ” reagents and those he calls ‘‘ special ” reagents, few of which, as hepoints out, are known at the present time. ‘‘ Special ” reactions or “ Sonder-reaktionen” are, in the ideal case, limited solely to one substance and arenot subject to interference by the presence of any other, and it is these(‘ special ” reactions and reagents which we regard as “ specific,” since withus this term implies a property characteristic of and peculiar t o one substancealone.281454 ANALYTICAL CHEMISTRY.which are to follow, based, aa they are to be, on the thorough andexhaustive investigations of Noyes and fiis school.Q1A new test for siEver with what is probably ethyl 5-keto-2-thion-hexahydropyrimidine-4-carboxylate is said Q2 to be more selectivethan, and about as sensitive as, the rhodaqine base used by F.Feigl.93Lead can be detected in the presence of a, large excess of barium,copper, iron, manganese, nickel, etc., by applying the triple nitritetest to the ammonium acetate solution of the precipitated sulphste,"and tervalent thallium can be recogniaed by the intense green colourwhich it gives with leuco-o-nitrodiamant green.95 The action ofcupric salts on benzidine has been discussed, and a reagent consistingof o-tolidine (which gives tolidine-blue) and ammonium tbiocyanatein acetone is preferred Q6 as a more sensitive test.After conversionof the iron into [FeF6]***, it is claimed that O~OOOIS~o of copper iniron salts can be detected. F. Feigl and R. Uzel Q7 utilise as a dropreaction for copper the yellow to red c0lour,9~ due to tervalent copper,which is formed with potassium tellurate or periodate in alkalinesolution and in the presence of an oxidising agent such as potassiumpersulphate, A reversal of the test serves to detect either tellurium,for which drop reactions are all too few, or periodic acid which canthen be sought in the presence of other oxidising anions: Periodicacid, and tellurium in the presence of a very large excess of selenium,can both be identifiedQ' by their inhibiting action on the catalyticeffect of copper in the oxidation of manganese to manganate ionsby sodium hypobromite.Drop methods for bismuth have also beenadapted fkom well-known macro-reacti0ns.lInduced precipitation is well known as a device for collectingtraces of an element from a very dilute solution, and it is nowemployed for the detection of small quantities of titanium and zir-conium.2 Zirconium is added to the suspected titanium solution andprecipitated by means of arsenic acid ; coprecipitated titanium isconfirmed in the usual way with hydrogen peroxide. In effect, thesensitivity of the hydrogen peroxide test thus becomes muchincreased. The procedure detailed is particularly useful whenmuch iron, vanadium, etc., which interfere in the ordinary way91 See A. A. Noyee and W.C. Bray, " A System of Qualitative Analysis92 S. E. Sheppard and H. R. Brigham, J . Amer. Chem. SOC., 1936,68, 1046.Ss Z. w a l . Chem., 1928, 74, 380.94 I. M. Korenman and S . S . Messonshnik, Mikrochm., 1936,20, 189.95 L. Kuhlberg, ibid., 1936, 19, 183.95 Idem, aid., 1936, 20, 153.9* B. Brauner and B. Kuzma, Ber., 1907,40, 3362.for the Rare Elements," 1927.O7 Ibid., 1930, 19, 132.2 N. A. Tsnanrtev and A. V. Tananaeva, J . AppZ. Chm. Ruesia, 1936, 8,S F. Feigl and E. Rajmann, lkZikro&em., 1936,19, 60.1457THEOBdLD : INORQANIO ANALYSIS. 455with this test, are present. By a reversal of the process, smallamounts of zirconium can be gathered with titanium amenate andconfirmed with azoarsinic acid.In addition to providing a serviceable test for aluminium, morincan also be used for gallium, but unlike the case of alumhiurn, thefluorescence which it gives is not suppressed when sodium fluorideis added.3 In daylight the fluorescence of these two elements withmorin appears to be specific, but in ultra-violet light other elementsalso fluoresce.This fluorescence with morin has served to detectgallium in minerals such as zinc blende and arsenopyrite.8 Othercolour reactions for gallium, vix., a bright red lake with alizarin inpresence of ammonia and ammonium chloride, and a reddish-browncoloration or precipitate with potassium ferrocyanide, manganesechloride and potassium bromate, applicable when aluminium andindium are present, have also been described and applied to minerals.*Drop methods for cerium with leuco-malachite-green,5 berylliumwith alkannin and naphthazarinY6 cobalt with Na,[Fe(CN),NO] andpiperidine in acetic acid s~lution,~ and ammonium with Nessler's re-agent 8 have been worked out.The sensitivity of the benzidine-bluetest for dichrornate is increased by the addition of hydrogen peroxide,according to L. Kuhlberg: who adds that greater sensitivity isattained when o-tolidine replaces benzidine. The formation ofoctahedral crystals of a triple nitrite with praseodymium nitrate andsodium nitrite provides a sensitive test for cmium which is notaffected by the presence of potassium or rubidium.lOThe ferrous sulphate test for hydroxylamine has been put on amicro-basis by F. Feigl and R. Uze1,l1 the ammonia evolved beingidentified by its action on silver nitrate and manganese su1phate;Pi0.1 y of hydroxylamine, it is claimed, can thus be detected, and 0-5 yin the presence of a 3000-fold excess of hydrazine.A selection of the Behrens tests l3 considered to be the most satis-factory in the actual practice of determinative mineralogy," is de-8 G.Beck, Mikrochem., 1936, 20, 194.4 N. S. Poluektov, ibid., 1936, 19, 248.5 L. Kuhlberg, J . Appl. Chem. Russb, 1935, 8, 1452.6 J. Dubskf and E. Krametz, Mikrochern., 1936, 20, 57.7 F. Feigl and R. Uzel, ibid., 1936, 10, 132.8 N. A. Tananam and A. A. Budkevitsch, J . Appl. Chem. RzWreia, 1936,0,362.Mikrochem., 1936, 20,244.10 H. C. Goswami and P. B. Sarhr, J . Indian Chem. Soc., 1935,12, 608.11 Mikrochem., 1936,19, 132.18 F.Feigl, op. cit., p. 271. 18 See Ann. Reports, 1936,32,474. * For the dehtion in rocks and minerals of molybdenum, lead, and cobaltby means of their colour reactions with calcium xanthate, benzidine, andaJkali thiocyanates, respectively, 8ee H. Leitmeier and F. Feigl, Tach. Nin.Par. ilia., 1936,47, 313456 ANALYTICAL CECEMISTRY.scribed and illustrated byL. W. Staples,l* who has also given details 15of a microchemical test for siZicon.16 This depends on the formationof sodium silicofluoride from silicon tetrafluoride and its recognitionunder the microscope, and is claimed to be better than the meta-phosphate bead, the rubidium silicornolybdate, or the benzidinetest.Electro-capillary methods of drop analysis have also been dis-cussed by various authors l7 during the past year.In the drop reactions mentioned in this section, the limitingamount of an element or ion which can be detected is of the order of10-6 g.or less, but attention must always be paid to the possiblepresence of other constituents which frequently necessitate a modifiedprocedure with a resultant loss of sensitivity.I;. S. T.QUANTITATIVE COLORIMETRIC ANALYSIS.During the past few years publications relating to colorimetricmethods of analysis have been so numerous that for the presentReport it has been possible to refer only to a selection which con-veniently illustrates the progress that has been made.The essentials of colorimetric analysis are : (1) preparation of asolution of a suitable coloured derivative, (2) evaluation of thissolution by measurement of its light absorptive power.It is desir-able to consider (2) in some detail, since it is the factor common to allcolorimetric analyses.‘ ‘ Colour ” Measwement or Comparison.-Measurements areessentially relative, ultimately in terms of similar solutions of thesame substance in known concentration. For convenience, artificialstandards are sometimes used, e.g., Lovibond glasses, liquids such asferric chloride solutions,l aqueous picric acid, and aqueous potassiumchromate? The disadvantage of this method is that the spectralabsorption curves of the test solutions and the sub-standard glassesor solutions may be far from identi~al.~ Errors due to this cause are14 Amer.Min., 1936, 21, 613.16 Ibid., p. 379.16 See W. R. Schoeller and E. F. Waterhouse, Analyst, 1936, 61, 454, con-17 S. I. Dijatschkovski, J. Gen. Chem. Russia, 1935, 5, 728; A. F. Orlenko,1 M. G. Mellon and C. T. Kasline, Ind. Eng. Chem. (Anal.), 1935, 7, 187;2 R. Strohecker, R. Vaubel, and K. Breitwieser, 2. anal. Chern., 1935,3 Cf. J. P. Mehlig and M. G. Mellon, J . Physical Chem., 1931, 35, 3397;cerning the inadequacy of certain tests for tungsten.{bid., 1936, 5, 1091 ; H. Fritz, Mikrochem., 1935, 19, 6.cf. also ibid., 1936, 8, 463.103, 1.A. L. Bacharach and E. Lester Smith, AnaZyst, 1934,59, 70STRAFFORD : QUANTITATNE COLORIMETRIC ANALYSIS. 457greatly magnified in the case of observers suffering from partialcolour-blindne~s.~ Better results may be anticipated in the rarecases where it is possible to prepare a sub-standard which hasabsorption curves practically identical with those of the test solu-tion.5Instruments.In the simplest form of measurement using comparison tubes of theNessler-cylinder type, the probable error is rarely less than & 3%,and in some cases may be as high as & 8%. The accuracy obtain-able with colorimebers of the Duboscq type is not much greater.6It appears to be now generally recognised, however, that in aninstrument using white light, Beer’s law cannot apply rigidly, withthe result that empirical correction curves are necessary.’ More-over, owing to the diluting effect of the white light, the sensitivityis less than that of spectrophotometric methods.The use of suitablecoloured filters appreciably increases the accuracy of the Duboscqtype of instrument .8Measurement of Absorption Density .-In modern instruments, therelative absorption density of the coloured solution, for light of wave-length approximating to that for which the solution shows a maxi-mum selective absorption, is measured. The obvious advantagesare (1) maximum sensitivity, and (2) a rectilinear (logarithmic)calibration curve, in accordance with Beer’s law. A further impor-tant advantage is that, once a calibration curve has been constructed,there is no necessity to prepare the colour standards each time ananalysis is made.Undoubtedly the best method of measuring the absorption densityis by means of the spectrophotometer, whereby measurements maybe made over a very narrow range (ca. 50 A.) a t any desired wave-length in the visible spectrum.By measurement at two suitablewave-lengths, it is often possible to determine two coloured substancesin admixture.* By use of the quartz spectrograph, measurement canbe extended to the ultra-violet, opening up an important field, e.g.,the determination of vitamin A by measurement of the absorptiondensity at 3280A.Possibly from considerations of cost, references to the employmentF. Twyman and G. F. Lothian, Proc. Physical SOC., 1933, 45, 643.H. W. Swank and M. G. Mellon, Ind. Eng. Chem. (Anal.), 1934, 6, 348;A. Thiel, Ber., 1935, 68, 1015; 2. anal. Chem., 1936, 106, 281.W. D. McFarlane, ibid., 1936, 8, 124.7 J. H.Yoe, “ Photometric Chemical Analysis,” Vol. 1, Colorimetry; cf.A. P. Mussakin, 2. anal. G‘lzem., 1936, 105, 351.8 W. D. Armstrong, Ind. Eng. C’hem. (Anal.), 1933,5,300; A. Thiel, loc. cit.,ref. (6); R. J. Robinson and H. E. Wirth, Ind. Eng. Chem. (Anal.), 1935, 7,147458 ANALYTICAL CHEXISTRY.of the spectrophotometer for colorimetric chemical analysis axerelatively few, but it has undoubtedly proved of value in initialresearch on individual colorimetric methods for the determinationof the full spectral absorption curve of the coloured solution. Thisis exemplified in the studies of H. W. Swank and M. G. Mellon 5 oncolorimetric standards for silica, and in the determination of17ibmin-D.~In the Pulfrich step photometer, colour filters are employed;consequently, the absorption densities determined are for light ofcomparatively broad wave-length range, and have relative ratherthan absolute significance. As with the spectrophotometer, theinstrument enables a permanent calibration curve to be constructed,As an alternative to the mechanical (variable shutter) photometricdevice of the Pulfrich, use is made of a neutral grey solution of vari-able thickness for reducing the intensity of the direct beam in the6c absolute ” colorimeter.l*Photo-electric Instruments.-These should be described as spectro-photometers or absorptiometers, rather than colorimeters. Thephoto-electric cells, which may be of the photo-emission or the semi-conducting type, can be used (1) as a null-point instrument to replacethe eye in a spectrophotometer with polarising photometer 11 orDuboscq colorimeter,12 (2) to afford a direct measure of light in-tensity and hence of absorption density.Instruments in thesecond class may be divided into two groups depending upon thenumber of photo-cells employed.The solution to be measured is interposedbetween the cell and the source of light, and the absorption of lightby the solution is measured directly by determining the currentoutput of the photo-electric cell in relation to the value obtainedwith the pure s01vent.l~ In instruments of this type it is of para-mount importance to use a light source of constant intensity; thismay be realised by incorporating a Barretter (current-regulating)lamp in a circuit buffered ” by an acc~mulator.~~ In the case of9 H.BrockmRnn and Y. H. Chen, 2. p h y h l . ChMn., 1936,241,129.10 A. Thiel, 2. amZ. Chm., 1933, 94, 170; A. Thiel and W. Thiel, Chern.p&., 1932, 409; A. Thiel, ibid., 1934, 7, 383.11 M. G. Mellon and C. T. Kasline, Zoc. &t., ref. (1); A. G. Winn, Tmns.Fcaraday Soc., 1933, 29, 689.1% G. Bernheim and G. Revillon, Ann. Faleiif., 1936, 29, 6; cf. &O A.G o u d d t and W. H. Summerson, J . Biol. Chem., 1935,111, 421; E. W. H.Selwyn, J . Sci. Inetr., 1933, 10,116.I* J. H. Yoe and T. B. Crumpler, Ind. Eng. Chem. (AmZ.), 1935, 7, 281;N. StraiTord, Analyst, 1936, 61, 170; R. S. W. Thorne and L. R. Bishop,J . In&. Brew., 1936, 42, 15; L. E. Howlett, Canadian J. Res., 1936, 14, A ,38; R.A. O h m , J . A880C. Off. AQ&. Chm., 1934,17, 136.(a) One-cell type.14 N. Stra$ord, Zoc. cit., ref. (13)STRAFFORD : QUANTITATIVE OOLORIMETRIC ANALYSIS. 459cells showing a fatigue ” effect it is necessary to allow the photo-cellto attain its equilibrium current after each change of light intensity.15(b) Two-cell type. Two photo-electric cells illuminated by thesame source of light are balanced against each other through a,galvanometer. The test solution is placed before one cell, the puresolvent before the other, and the current output difference measureddirectly.ls Variations due to small fluctuations of the light sourceare automatically cancelled in an instrument of this type.Photo-emission cells with different characteristic response curvesare available, permitting the choice of one having maximum responseto the coloured light under measurement.17&loured light in most instruments is obtained by atering whitelight by colour filters, as in the Pulfrich photometer.More nearlymonochromatic light is obtained by filtering the light from metal-vapour discharge lamps, e.g., mercury or sodium.lsWhen a monochromator of the spectroscope type is used, the lightis of such relatively low intensity that valve amplification of thephoto-electric current is necessary.Since most colour filters are comparatively transparent to infra-redrays, to which the photo-electric cells are responsive, an additionalfilter must be used (“ minus-infra-red ”) in order to obtain maximumabsorption-density readings.lQ Weston Electrical Instrument Co.provide a “ Viscor ” filter which fulfils this purpose.20Accuracy of Photometric Colorimetric Analysis.-Even with thebest instruments, careful choice of operating conditions is necessaryto ensure the highest accuracy.According to I?. Twyman andG. F. Lothian,21 the percentage error is a t a minimum at an absorp-tion density of between 1.5 and 2.0 in the case of a visual spectro-photometer, and of 0.43 in objective (photo-electric) instruments.Theseauthors also consider that, although theoretically photo-electricmethods give much greater sensitivity of discrimination than the eye,yet visual methods are more trustworthy as far as absolute measure-ments are concerned.In the Reporter’s opinion, a simple and16 J. H. Yoe and T. B. Crumpler, loc. cit., ref. (13); N. Strafford, Zoo. cit.,ref. (13).16 C. Zinzadze, Id. Eng. Chem. (Awl.), 1935, 7 , 280; R. B. Withrow,C. L. Shrewsbury, and H. R. Kraybill, ibid., 1936, 8, 214; B. Lange, Chem.Fabr., 1934, 7 , 45.17 R. B. Withrow, C. L. Shrewsbury, and H. R. Kraybill, loc. cit., ref. (16).18 R. Sewig and F. Miiller, Chem. Fabr., 1934, 7, 26; H. Alterthum andM. Reger, ibid., 1933, 6,283.19 E. R. Bolton and K. A. Williams, Analyst, 1936, 60,447; N. Strafford,too. cit., ref. (13); cf. also R. Fonteyne and P, de Smet, Mikrochern., 1933,13,289.a0 J . Sci. Imtr., 1936, 13, 338.21 LOC. cit., ref. (4)460 ANALYTICAL CHEMISTRY.relatively inexpensive photo-electric instrument,22 properly used, isas accurate as a spectrophotometer for the relative measurementsrequired by colorimetric analysis.Nephelometry .There is no sharp division between colorimetry and nephelo-metry.Some of the organometallic derivatives, such as copperdiethyldithiocarbamate in aqueous media, and sulphides such aslead sulphide may be described as being in colloidal “ solution’’in colorimetric tests. Particular care in preparation of the standardand test solutions is necessary in order to obtain reproducible resultsand compliance with Beer’s law. The use of protective colloids isof value in this connection.23Photo-electric measurements have shown that transmission oflight by two similarly prepared colloidal lead sulphide ‘‘ solutions ”apparently equal in shade to the eye may be appreciably different.=For true nephelometric determinations, e.g., of zinc as ferrocyanide,the photo-electric absorptiometer affords an appreciably greateraccuracy than visual c~mparison.~~ K.W. Franke, R. Burris,and R. S. Hutton 26 describe a novel procedure by which colouredprecipitates of colloidal fineness, e.g., selenium, are filtered on toa mat of barium sulphate. Permanent colour standards are thusprepared.Colorimetric Determination of the Elements.Although so far almost exclusively used for determination ofminor amounts of an element, in the Reporter’s opinion there areadequate reasons (mainly saving of time) why much wider useshould be made of colorimetric methods for determination ofelements present as major constituents.* At the same time, theopinion is recorded that, for micro-analysis, colorimetric methodsare at least as accurate as, and usually simpler and more convenientthan, alternative methods ; in many cases, moreover, alternativemethods of adequate sensitivity do not exist.Cf. N.Strafford, Zoc. cit., ref. (13).83 L. de Brouckbre and S. Solowiejczyk, Bull. SOC. chim. Belg., 1934, 43,597; C. Zinzadze, Ind. Eng. Chem. (Anal.), 1935, 7 , 227.e4 Second Report of the Sub-Committee on the Determination of Arsenic,Lead and other Poisonous Metals in Food Colouring Materials to the AnalyticalMethods Committee of the Society of Public Analysts : 11, The Determinationof Lead; Analyst, 1935, 60, 541.26 N. Strafford, loc, cit., ref. (13).26 I d .Eng. Chern. (Anal.), 1936, 8, 435.* As an example, J. P. Mehlig [Id. Eng. Chem. (Anal.), 1935,7,387] claimsthat the copper content of ores (up to 22%) may be determined with a photo-electric spectrophotometer to an accuracy of * 0.1%STRAFFORD : QUANTITATIVE COLORIMETRIC ANALYSIS. 461The first task of the analyst is to devise conditions ensuring speci-ficity, and in spite of the availability of numerous organic reagents,cases in technical analysis where a preliminary separation is notnecessary are the exception rather than the rule. The most impor-tant advance in recent years is in the application of organic reagentsin organic solvents €or separation of interfering elements, as well asfor the formation of a coloured derivative.The following will serveas examples of modern technique in the inorganic field.Lead.-A general method for the determination of lead in the pre-sence of other metals involves isolation of the lead, first as sulphideand then as sulphate, followed by the application of the colloidalsulphide method, the limitations of which are disc~ssed.~4The use of dithizone is rccommended both for the separation of leadfrom most other metalsY2' and from bismuth,28 a.nd also for theactual colorimetric measurement. The latter may be applied tothe red lead dithizone or to the regenerated greendithizone .30P. A. Clifford and H. J. Wichmann 31 show, from considerationsof distribution between aqueous and organic media, that both thesemethods €ail to give complete recovery of the lead, and they recom-mend a " mixed colour " photometric method in which completeextraction of lead is ensured by use of an excess of dithizone appliedto a solution of optimum pE value (9.0).They also criticise themethods €or removal of bismuth referred to above, and suggestmethods €or preventing interference from tin.It is of particular importance to employ a purified reagent freefrom oxidation products,30 and to avoid the presence of oxidisingreagents .32In certain cases, the extraction of lead from aqueous solutionscontaining insoluble matter by means of a solution of dithizone is notcomplete owing to occlusion of lead by the insoluble matter.24Dithizone is, however, used for extracting insoluble lead compoundsfrom spray residues.3327 N.L. Allport and G. H. Skrirnshire, Analyst, 1932, 57, 440; P h a m . J.,1932,129, 248; G. Rocho Lynch, R. H. Slater, and T. G. Osler, Analyst, 1934,59, 787.28 S. L. Tompsett, ibid., 1936, 61, 591; C. E. Willoughby, E. S. Wilkins,jun., and E. 0. Kraemer, Ind. Eng. Chem. (Anal.), 1935, 7, 285.29 J. R. Ross and C. C. Lucas, J . Biol. Chem., 1935,111,285; 0. B. Winter,H. M. Robinson, F. W. Lamb, and E. J. Miller, Ind. Eng. Chem. (Anal.), 1935,7, 265.30 H. Fischer and G. Leopoldi, Angew. Chem., 1934, 47, 90; F. Morton,Analyst, 1936, 61, 465.31 J . A880c. 08. Agric. Chem., 1936,19, 130.32 S. L. Tompaett, Zoc. cit., ref. (28).33 W. E. White, Ind. Eng. Chem. (And.), 1936, 8, 231462 AXALYTICAL CHEMIS!L%Y.Hercury.-For the determination of mercury, N.Strafford andP. F. Wyatt 34 recommend the reaction with p-dimethylamino-benzylidenerhodanine, which is less subject to interference than thatwith diphenylcarbazide or diphenylcarbazone. Preliminary separa-tion of the mercury from most other metals is essential. H. Fischerand G. Leopoldi 35 and W. 0. Winbler 36 separate and determinemercury as the dithizone complex.Tin.-Since previous methods for tin depend merely on the reduc-ing action of stannous salts, the appearance of a reagent which formsa coloured derivative with tin is welc0me.3~ It must be noted,however, from the author’s own findings, that the reaction is notspecific for tin (see p. 449), a number of other metals, particularlycopper, bismuth, and nickel, giving coloured derivatives.Zinc.-W. Deckert 38 determines zinc, after removal of copperas sulphide, as the coloured complex obtained with dithizonein alkaline solution.Dithizone is also recommended by H. E’ischerand G. Le~poldi.~~ A novel method for zinc consists in precipitatingthe metal, again after a preliminary separation and removal ofcopper as sulphide, as its complex with 8-hydroxyquinoline.The absorption density of the 8-hydroxyquinoline is then de-termined, after decomposition of the complex, in ultra-violetlight .40Caper.-Numerous papers continue to appear, most of themdescribing variations of well-known methods. C. A. Goethals 41discusses the sensitivity of several colour reactions. General opinionseems to favour the dithiocarbamate methodF2 although it is recog-nised that preliminary separation of other metals is often necessary.&G. Bertrand and L.de Saint Rat 44 recommend urobilin as a selectivereagent. H. Fischer and G. Leopoldi45 determine copper as thedithizone complex in an organic solvent. E. Stolze46 points outa4 Analyst, 1936, 61, 628.a6 J . Aesoc, Off. AgTic. Chena., 1935, 18, 638.87 R. E. D. Clark, Am?y8t, 1936,61,242.38 2. anal. Chem., 1935, 100, 305.39 Ibid., 1936, 107, 241.40 J. D9browski and L. Marchlewski, Biochem. Z., 1935,282,387.4 1 2. anal. Citem., 1936,104,170.** T. Callan and J. A. R. Henderson, Andgat, 1929,54,650.2. anal. Chem., 1935,103,241.L. W. Cow, A. H. Johnson, H. A. Trebler, and V. Karpenko, Ind.Eng.Chem. (Anal.), 1935, 7, 15; N. D. Sylvester and L. H. Lampitt, Analyst* 1935,60, 376; E. Lasausse and L. Frocain, J . PJmm. China., 1936, [viii], 23, 77;B. Eisler, K. G. Rosdahl, and H. Theorell, Biochem. Z., 1936, 285, 76.44 Compt. rend., 1936, 2U3, 140.4O Alzgew. Chem., 1934,47, 90.40 Bodenk. Pflamenernlihr., 1936,l, 115STBAFFORD : Q U B N T I T A ~ COLORIBIETRIC ANALYSIS. 463that it is necessary to reduce any ferric mlts before applying thismethod. N, Straf€ord4‘ suggests the use of salicylaldoxime as asensitive and specific nephelometric reagent.Iron.-Attention continues to be paid to improvement of thethiocyanate 48 and the sulphosalicylic acid 49 method. [Incident-ally, calcium (as oxalate) may be determined by its bleaching actionon the iron-sulphosalicylic acid c01our.l~ ad-Dipyridyl is recom-mended as a colorimetric reagent.61Aluminium.-Calcium salts and other interfering substancescause fictitiously high values in determinations with ali~arin.5~Interference from iron is prevented by its removal as thiocyanate inamylGermanium.-N.S. Poluektof describes the determinationof small quantities of germanium, the method depending onthe blue colour formed by the reduction of germanomolybdicacid.Titanizm.-Titanium is determined by hydrogen peroxide 55 or bysalicylic acid.56AZkaZi Metals.-Existing methods for the colorimetric determin-ation of potassium, involving the precipitation as cobaltinitrite, arereviewed, and a modified procedure is described by R. J. Robinsonand G.L. P~tnarn.~’Sodium is determined as an aqueous yellow solution of its tripleacetate with uranium and magnesium.58PhoslpF,orus and XiZicon.-Considerable attention has been given47 ‘ ‘ m e Detection and Determination of Small Amounts of InorganicSubstances by Colorimetric Methods,” Institute of Chemistry Publication,1933, p. 27; cf. also F. Alten, B. Wandrowsky, and E. Knippenberg, MiEm-chem., 1936, 20, 77.48 K. Steinhauser and H. Ginsberg, 2. anal. Chem., 1936, 104, 385; G. E.Farrer, jun., J . Biol. Ohm., 1935,110,685.40 F. Alten, H. Weiland, and E. )Iille, 2. w r g . Chem., 1933, 215, 81; A.!Chiel and 0. Peter, 2. anat!. Chm., 1935, 103, 161.60 L. Jendrassik and F. Takhs, Bwchem. Z., 1934, 274, 200.61 G. Bode, Woch. Brau., 1933,50, 321; L.L. Engel, J . Dent. Rea., 1934,14,273 : W. D. McFarlane, Zoc. cit., ref. ( 5 ) ; F. B. Shorland and E. N. Wall,Biochem. J., 1936,30,1049; H. I. Coombs, ibid., p. 1688.62 D. F. Eveleth and V. V. Myers, J . Biol. Chm., 1936, 113, 449.68 A. P. Mussakin, J . A@. Chem. R u s k , 1936,9, 1340.54 Z . m l . Chem., 1936,105,23.55 H. Ginsberg, 2. amrg. Chern., 1933, 211, 401; 1935, 226, 67; G. P.Lutschinski and A. I. Lichrttscheva, 2. a d . Chm., 1936, 103, 196; H. A.Liebhafsky, ibid., 105,113; L. Maillard and J. Ettori, C m p t . rend., 1936, $302,594.56 M. Schenk, Hdv. Chh. A&, 1936,19,1127.57 Ind. Eng. Chm. (Anal.), 1936,8,211.68 A. EUas, A d . Aaoc. Qub. A r g d h z , 1936,23,1464 ANALYTICAL ClIEMISTRY.to the important determinations of phosphorus 59 and of silicon 60by the molybdenum-blue reaction.Determinution of pH Value.According to E.A. Guggenheim and T. D. Schindler,61 resultsof colorimetric pa determinations by means of a Gillespie com-parator are reproducible within 1%. M. Kilpatrick, E. F. Chase,and L. C. Riesch 62 maintain that the experimental error of thecolorimeter method is about 5%, and of the electrometric methodabout 2.5%. A. G. de Almeida 63 plots dominant hue, expressedas a wave-length, against pH for a series of indicators, and claimsthat it is possible to determine the pH of an unknown solution moreaccurately than by electrometric methods.Textile assistants such as sulphonated oils, sulphated and sul-phonated fatty alcohols, sodium alkylnaphthalenesulphonates, etc.,exert a specific effect on most indicators which is frequently a sourceof considerable error, even up to 1.0 unit, in the colorimetric deter-mination of pH.64 This is discussed elsewhere in these Reports(p. 110).Photometric Titrations.Photometric methods may be employed for the accurate objectivedetermination of the end-point in a colorimetric or turbidimetrictitration. E.T. Bartholomew and E. C. Raby 65 determine alka'licyanides by titration with silver nitrate to the incipient developmentof turbidity, detected by a system of balanced photo-electric cells.S. Hirano 66 titrates mercuric chloride or nitrate with 0.01 or 0-001N-sodium sulphide in presence of gum-arabic as protective colloid, theend-point being indicated when the turbidity reaches a maximumvalue.In a similar manner he determines silver by titration withsodium chloride, in presence of starch.67 He also describes methodsfor determining soluble sulphides,68 gold,69 and halides.'O69 K. C. Scheel, 2. mal. Chem., 1936,105,256; R. Amrnon and K. Hinsberg,Z. phy8si0l. Chem., 1936,239,207; C . Zinzadze, Ind. E n g . Chem. (Anal.), 1935,7, 227; K. Boratyiiski, 2. awl. Chem., 1935, 102,421; H. Etienne, Bull. SOC.chirn. Belg., 1936,45,516; H . L. Brose and E. B. Jones, Nature, 1936,138,644.60 F. De Eds and C. W. Eddy, J . Biol. Chem., 1936, 114, 667; R. Stro-hecker, R. Vaubel, and R. Breitwieser, 2. anal. Chern., 1935, 103, 1.6r J . Physical Chem., 1934, 38, 543.64 J. E. Smith and H.L. Jones, J . Physical Chern., 1934, 38, 243; H. L.66 I n d . Emg. Chem. (Anal.), 1935, 7, 63.66 J . SOC. Chem. I n d . Japan, 1935, 38, 646.67 Ibid., 1934, 37, 75413.gg Ibid., 1935, 38, 5 9 8 ~ .6D Ibid., 1934, 37, 1 7 8 ~ , 5 6 1 ~ .J . Arner. Chem. SOC., 1934, 56, 2051. 63 Diss., Lisbon, 1935.Jones and J. E. Smith, Amer. Dyleatu, Rep., 1934, 23, 423.'O Ibid., p. 1 7 7 ~ ; 1935, 38, 175WEST : ORGANIC ANALYSIS. 465F. Muller reviews the use of photo-electric cells in automatictitrati~ns.'~CoZorirnetric Oxidation-reduction Reactions.-W. P. Lundgren 72describes a modified Duboscq colorimeter used for following fadingcurves in oxidation-reduction reactions.N. S.ORGANIC ANALYSIS.Elements.-Difficulties experienced in the determination ofsulphur, oxygen, and nitrogen by the ter Meulen method have nowbeen overcome,2 and it is claimed that satisfactory results for theestimation of nitrogen in compounds of high halogen content areobtained if soda-lime is placed both in front of and behind the cata-l y ~ t .~ Ultimate analysis of an organic substance may be based onpressure measurements after combustion in a bomb calorimeter .*Sulphur may also be satisfactorily determined by the bomb methodY5and chlorine may be determined accurately by the rapid lampmethod.6 Convenient wet oxidation methods have been describedfor the determination of (a) sulphur and copper,' and (b) carbon andnitrogen. 8Qualitative.-When treated with nascent chlorine, i.e., potassiumpermanganate in dilute hydrochloric acid, ketoximes give a bluish-green coloration, whilst aldoximes yield a solution which gives ared colour with ferric chloride : certain aromatic aldoximes do notgive this reaction. The reaction with hydroxylamine hydro-chloride has been the basis of a somewhat elaborate scheme for therecognition of aldehydes, ketones, acids, acid chlorides, anhydrides,amides, esters, and lactones.1°The following reagents have been investigated for the identific-ation of aldehydes and ketones : p-bromo-,ll m-chloro-,12 and m-7 1 2.Elektmchem., 1934, 40, 46.73 Science, 1934, 80, 209.1 5. Gauthier, Bull. Soc. chim., 1935, [v], 2, 506.3 If. ter Meulen and H. J. Ravenswaay, Chem. Weekblad, 1936, 33, 248.4 P. J. Merkus and A. H. White, Proc. Amer.Gas ASSOC., 1934, 991.5 H. C, Chiang and C. L. Tseng, Sci. Kep. Nat. Univ. Peking, 1936,1, 19.6 W. N. Malisoff, Ind. Eng. Chem. (Anal.), 1935, 7 , 428.7 N. N. Melnikov, J. Gen. Chem. Russia, 1935, 5, 839.8 C. N. Acharya, Biochem. J., 1936,30, 241.9 E. Graf, Anal. $'is. Quh., 1936, 34, 91.10 Idem, ibid., p. 95.11 8. M. Wang, Cheng-Heng Kao, Chung-Hsi Kao, and P. P. T. Sah, Sci.19 P. P. T. Sah and C. S. Wu, ibid., 1936, 3, 443.H. ter Meulen, ibid., p. 1692.Rep. Nat. Tsing Huct Univ., 1935, A , 3, 279466 ANALYTICAL CHEMISTRY.bromo- benzhydrazide,lS m- tolylhydrazine,14 which in conjunctionwith the o- and p-isomerides is suggested as a reagent for the ident-ification of sugars, l5 p-naphthoylhydrazide,l6 and m-tolylsemi-carbazide.l' It has been shown that the melting points of manyof the recorded 2 : 4-dinitrophenylhydrazones are incorrect ; the useof isopropyl instead of ethyl alcohol in Brady's method gives purercompounds.lS3-Nitrobenzazid<lg p-bromobenzazide,20 and m-nitrobenzoylthio-carbimide 21 have been investigated as reagents for the identificationof amines , and benzylamine and a-phenylethylaminc salts 22 andl-chloro-2 : 4-dinitrobenzene 23 are recommended for use in theidentification of acids and phenols respectively.Japanese acid clay is a powerful adsorbent for diamino-acidsobtained in the hydrolysis of proteins, arginine being adsorbed to theextent of 86*8% compared with 8.45% for g l y ~ i n e .~ ~ A process isdescribed for the removal of the adsorbed amino-acids and for thcregeneration of the clay.25It has been found that most ethers form peroxides on storage andtend t o explode on dry distillation, and the use of certain reagentsas peroxide destroyers and oxidation inhibitors has been investi-gated.26 Phenolic ethers may be identified through their picrates,although some of the compounds are unstable in air.27A simplified copper solution for use in sugar analysis is made up of100 C.C.of %.970 sodium hydroxide solution, 1 g. of copper sulphate,and 10 C.C. of water.a8Quulztitative.-Accurai;e determination of .the hydroxyl groupsmay be rapidly effected by heating the substance with pyridine-13 Chung-Hsi Kao, T. Tao, Cheng-Heng Kao, and P. P. T. Sah, J . Chinese14 P. P. T. Sah and C.Z. Tseu, SCi. Rep. Nat. Tsing Hua Univ., 1936, A,X 5 Idem, &bid., p. 409.16 H. Chen and P. P. T. Sah, J . Chinese Chem. SOC., 1936,4,62.1' P. P. T. Sah, S. M. Wang, and C. H. Kao, ibid., p. 187.19 K. Meng and P. P. T . Sah, J . Chinese Chem. Soc., 1936, 4, 75.2* P. P. T. Sah, C. H. Kao, and S . M. Wang, ibid., p. 193.81 W. L. Tung, Cheng-Heng Kao, Chung-Hsi Kao, and P. P. T. Sah, Sci.c'hem. SOC., 1936, 4, 69.3,403.N. R. Campbell, Analyst, 1936, 61, 391.Rep. Nat. T8iny H m Univ., 1935, A, 3, 285.2181.C. A. Buehler, L. Carson, and R. Edds, J . Amer. Chem. SOC., 1935, 57,2s R. W. Bost and F. Nicholson, ibid., p. 2368.z4 M. Mashino and N. Shikazono, J . SOC. C'hern. I n d . Japan, 1936, 39, 5413,25 Idem, ibid., p. 1 3 6 ~ . 26 E. C.Williams, C h m . and I&., 1936,580.27 0. L. Baril and G. A, Megrdichian, J . Amer. Chem. SOC., 1930, 68, 1416.88B.E. J. Mueller, J . Pham. Cltim., 1936, [V;ii], 24, 18WEST : ORGANIC ANALYSIS. 487acetic anhydride, decomposing the product with water, and titratingthe excess acetic The method is not valid with tert.-alcoholsand gives low results with sugar alcohols. Small quantities of ethylalcohol may be determined by an oxidation method.30Reducing sugars may be determined by direct potassium ferri-cyanide titrationF1 or by back titration with ceric sulphate.32Quantitative differentiation of fructose and mannose in glucose-fructose-mannose mixtures is possible by the use of micro-organ-isrnsg3 and sucrose inversions may be followed by means of the glassbut not the quinhydrone ele~trode.~* Accuracy is claimed formethods of determining the acetyl 35 and the nitrate 86 group incarbohydrate derivatives.Errors in the titration of the amino-groups in amino-acids, etc., areminimised if glacial acetic acid is used as the solvent.37Convenient methods are described for the determination of :toluidines in aqueous solution:* xylidine isomerides,3Q camphor bythe titration of the hydrogen chloride liberated from hydroxylaminehydrochloride after oxime formationto phenol and cresols in thepresence of each other,4l and pyridine in the presence of nicotine.42The methods available for the titration of alkaloids in anhydrousmedia, have been critically reviewed.&Colorimetry .-Carbamide, urethanes, and carbazides give a cerisecoloration on heating with vanillin in concentrated hydrochloric acidafter pre-heating with phenylhydrazine hydrochloride.44 Colourreactions are described for certain o-nitro-compounds,45 cyclopentadi-ene,46 and tartaric, citric, and aconitic acidsP7a9 M.Freed and A. M. Wynne, Ind. Ertg. Chem. ( A d . ) , 1936,8, 278.30 T. E. Friedemann and R. Klass, J . BioZ. Chem., 1936,115, 47.31 G. I. Solomos, BuW. SOC. Chim. bioZ., 1935,17, 1465.32 W. Z. Hassid, Id. Eng. Chm. (And.), 1936,8, 138.33 T. F. Nicholson, Biochem. J., 1936,30,1804.34 H. P. Cady and J. D. Ingle, J . Phy8icaZ Chm., 1936, 40, 837.35 A. Friedrich and H. Sternberg, Biochm. Z., 1936, 286, 20.36 J. Dewar and G. W. Brough, J. SOC. Chem. Ind., 1936,55,207.37 L. J. Harris, Biochem. J., 1935,29,2820; G. F. Nadeau and L. E. Bran-38 D. Cismaru, BuZ. SOC. Chim. Rorrz&nia, 1934, 16, A , 37.39 B. P. Fedorov and A. A. Spriskov, 2. anal. Chem., 1936,105,412.40 R. Vandoni and G. Desseigne, Bull. SOC. chim., 1935, [v], 2, 1686.41 V. Mikhschevskaja, Chim. Tverd. Tog., 1934,5, 553.42 R. L. Fratkin, L. P. Juravleva, and A. G. Blankachtein, Sborn. Robot43 G. N. Thomis, J . Pham. Chim., 1936, [vs], 24, 162.4 1 J. A. Sanchez, Ann. Chim. curacclyt., 1936, [c], 18, 66.45 P. K. Bose and S. Ram, J. Indian Chm. Soc., 1935,12,687.46 B. N. Afanasiev, Ind. Eng. Chem. ( A d . ) , 1936, 8, 16.47 R. Casares, A w l . Pis. Qdm., 1936,34,694; 0. Fiirth and H. Herrmann,chen, J . Amer. Chem. Soc., 1935,57,1363.Chim. OtdeEa, 1935, 88.Bwchem. Z., 1936,280,448468 ANALYTICAL CHEMISTRY.The colours formed in the bromide-resorcinol reaction are tracedto the intermediate formation of glyoxylic acid, and a solution of thisacid is recommended as a reagent for the characterisation of phenols,phenolic acids, and the chief opium alkaloids.48Spot tests are described for the detection of phenol,4s oxalicacidYS0 and of benzidine and tolidine in the presence of each other.51fMicro-metho~~.-Methods for the determination of various organicgroups have been reviewed,52 and the technique detailed for thedetermination of carbon, hydrogen, nitrogen, halogen, and methoxylas applied to samples of 0-001-0.01 g.53The necessary data are given for the characterisation, by theexamination of crystals under the microscope, of : alkaloids aspic rate^,^* d- and Z-cocaine after treatment with potassium perman-ganate,55 and amino-acids as their phosphotungstates, phospho-molybdates, picrates, and Aa~ianates.~~ Berberine gives character-istic micro-crystalline precipitates with a number of compounds ofpharmacological importance. 57Accurate methods are described for the determination of : acetylgroups,58 acetone, 59 oxalic acid, the permanganate titration in hotsolution bcing shown to be untrustworthy,m glucose by the ferri-cyanide-ceric sulphate metl.lod,61 and protein nitrogen in thepresence of ammonium salts.62Apparatus.-Improved apparatus is described for the micro-hydrogenation of organic comp0unds,~3 and for avoiding loss byspurting during ashing with nitric acid.64An electrically-heated melting-point apparatus gives an accuracyof 0.5°,65 and a method for the determination of setting pointsenables metastable forms fusing within 1" of each other to be de-4 8 M. Pesez, Bull. SOC. chim., 1936, [v], 3, 676.40 Y. Kondo, Mikrochem., 1936, 19, 214.F. Feigl and 0. Frehden, ibid., 1935, 18, 272.s1 L. Kulberg, J . Gen. Chem. Russia, 1935, 5, 1754.s2 A. Lacourt, Bull. Soc. china. Belg., 1936, 45, 313.63 C. Weygand and H. Hennig, Chem. Pabr., 1936,9, 8.64 A. Ionesco-Matiu and E. Iliesco, J . Pham. Chim., 1936, [viii], 23, 117.s5 R. Ceeconi, Ann. Chim. appl., 1936, 26, 218.66 B. Bullock and P. L. Kirk, Mikrochem., 1935,18, 129 ; B. L. Crosby and67 C. van Zijp, Pharm. Weekblad, 1936, 73, 764.E8 A. Elek and It. A. Harte, Ind. Ena. Cherq. (Anal.), 1936, 8, 267.56 A. Lindenberg, Compt. r e d . SOC. Biol., 1936, 122, 317.6 o J. Reneudin, J. Pham. Chim., 1936, [viii], 23, 447.61 R. Vanossi and R. Ferramola, Anal. Asoc. Quim. Argentina, 1935, 23, 162.62 A. Roche and F. Marquet, Bull. SOC. Chim. biol., 1935,17, 1630.63 H. Jackson and R. N. Jones, J., 1936, 895.64 H. Kaunitz, Mikrochem., 1936, 20, 104.B G E. Dowzard and M. J. Russo, Ind. Eng. Chcm. (AnaZ.), 1936, 8, 74.P. L. Kirk, ibid., p. 137WEST : ORGANIC ANALYSIS. 469tected.66 A differential mercury manometer 67 is used for measuringboiling points with only a few drops of liquid.Modern resistance glass enables simple all-glass water stills to beconstructed, which compare favourably with metal stills for effici-ency.6* R. W. W.N. STRAFFORD.L. S. THEOBALD.R. W. WEST.66 F. Francis and F. J. E. Collins, J., 1936, 137.6 7 R. Dolique, Bull. SOC. chim., 1935, [v], 2, 1832.68 B. Siede, Chem.-Ztg., 1935, 59, 925

ISSN:0365-6217    

DOI:10.1039/AR9363300432

出版商:RSC    

年代:1936

数据来源: RSC

摘要:

INDEX OF AUTHORS’ NAMESABBASY, M. A,, 388.Abderhalden, E., 40 1.Abel, E., 99.Abkin, A., 93.Acharya, C. N., 465.Achtermann, T., 348.Ackermann, P. G., 67, 221.Adam, N. K., 104,112,113,115,116,117, 190.Adams, E. G., 480.Adams, R., 94,228,231,236,330,372.Adler, E., 328.Afanasiov, B. N., 467.Ahmad, B., 388.Ahrens, G., 349.Aivazov, A., 92.Akabori, S., 308.Alber, H., 179.Alder, K., 238, 328.Alexander, N. S., 31.Alexopoulos, K. D., 21.Alichanian, A. I., 32.Alichanow, A. I., 32.Allen, F. R. W. K., 404.Allen, H. S., 63.Allen, W. M., 344.Allison, F., 432.Allison, F. E., 412, 414.Allport, N. L., 461.Allyn, W. P., 415.Almquist, H. J., 394.Altar, W., 86.Alten, F., 463.Alter, C. %I., 135.Alterthum, H., 459.Amaldi, E., 30.Amdur, I., 93.Ammon, R., 387, 389, 464.Ampt, G.A,, 443.Ancelot, A., 404.Andersen, E. B., 28.Anderson, C. D., 35.Anderson, C. O., 145.Anderson, J. S., 165, 166, 177.Anderson, L. C., 99.Anderson, T. F., 57.Ando, T., 343.An&&, M., 249.Andrew, R. H., 362, 398.Andrews, D. H., 291.Angelescu, V., 408.Angus, W. R., 58, 188, 279.Ankersmit, P. J., 268.Antipov-Karataev, J. N., 203.Antropoff, A. von, 135.Apfelbaum, P. M.,, 298, 320.Applebey, M. P., 192.Archer, N., 397.Archibald, E. H., 135.Argo, W. L., 145.Arkel, A. E. van, 132, 203.Armstrong, W. D., 446, 457.Arnold, W., 418, 427.Arthur, J. M., 418.Asam, R. D., 418.Ascher, E., 148.Ashford, T. A,, 178.Askew, F. A., 113,115,351,365.W. T., 224, 226.2i;z. W., 16,138,140,142,143.Aston, J. G., 217.Aten, A. H. W., jun., 141.Ato, S., 442.Audrieth, L. F., 157.Auger, P., 35.Awterweil, G., 295.Auten, R. W,, 174.Auwers, I(. von, 316, 331.Avery, 0. T., 261, 262, 265.BBRBBB€3BBBBBBBI3BBBBI3I3laas-Becking, L. G. M., 427.,abler, B. J., 449.Iaccaredda, M., 209, 226.hch, A. N., 409.lach, F., 89.lecharach, A. L., 456.lacher, W., 16.; a c h n n , W. E., 202, 324, 339.lacker, H. J., 202.iacker, H. S., 223.laddeley, G., 76.iadger, R. M., 63.aer, E., 246.Iaeyer, A. von, 294.IWyer, H. J. von, 17.lrcggesgmrd-Rasmussen, H., 436.lrchr, T., 166.‘ailar, J. C, 174, 176.,ailey, C. R., 57, 58, 279.,dey, R. W., 166.H. A*, 156.47472 INDEX OF AUTHORS’ NAMES.Bainbridge, K.T., 15, 18, 143.Bak, B., 228.Baker, (Miss) E., 195.Baker, J. W., 77, 95, 96.Baker, W., 283, 284, 286.Bal, G. S., 192.Balamuth, L., 205.Balas, F., 298.Baldwin, I. L., 415.Balfour, A. E., 190.Ball, T. R., 433.Baly, E. C. C., 420.Banerjee, P. C., 447.Banerji, S. K., 341.Bangert, F., 167.Bann, B., 392.Bannister, F. A., 206, 219.Barclay, G., 43 1.Bardhan, J. C., 304, 319, 320, 321,327, 332, 341.Bardhan, T. B., 258.Barger, G., 379, 382.Baril, 0. L., 466.Barker, E. F., 54, 55, 56, 57.Barlot, 152.Barnes, R. B., 85.Barnes, W. H., 217.Barnett, E. de B., 330, 339.Barnbthy, J., 33, 35.Baroni, A., 201, 208.Barrett, J. W., 300, 311, 331, 333.Barry, A. J., 226.Barsha, J., 260.Barth, T.W., 206.Bartholome, E., 57.Bartholomew, E. T., 464.Bartunek, P. F., 54.Bassett, H., 194.Bassiare, M., 192, 211.Bates, J. R., 99.Baudrexler, H., 136, 138.Bauer, H., 400.Bauer, S. H., 66, 72, 83, 126, 128, 133.Bauman, L., 354.Baumeister, W., 426.Bawden, F. C., 227.Bawn, C. E. H., 93.Baxter, G. P., 135, 136, 138, 140, 145.Beach, J. Y., 39, 45, 75, 210, 216.Beams, J. W., 432.Beck, G., 455.Becker, B., 247, 254.Becker, E., 202.Beckmann, S., 242.Bedwell, W. L., 194.Bee, J., 271.Beecher, H. K., 397.Beevers, C. A., 198, 216.Bein, K., 174.Beintema, J., 212, 223.Bell, R. M., 433.Bell, R. P., 102.Bell, R. W., 180.Bellows, J., 387.Bender, D., 57.Benedetti-Pichler, A. A., 448, 453.Benedict, W. S., 85, 291.Bengtsson, B.E., 345.Benkert, A. L., 439.Bennett, G. M., 76, 177.Berg, B. N., 355.Berg, F., 254.Berg, R., 439.Bergdolt, B., 307.Bergel, F., 382.Berger, H., 299.Berger, K., 188.Bergk, H. W., 223.Bergman, B., 420.Bergrnann, E., 95, 174, 175, 223, 288,Bergmann, M., 399.Bergmann, W., 345, 355.Bernal, J. D., 133, 201, 219, 223, 227,Bernheim, G., 458.Berry, A. J., 436.Berry, W. A., 112.Bersin, 389.Bertram, S. H., 277.Bertrand, G., 462.Beschke, E., 337.Bestian, H., 289.Bethe, H., 50, 66, 143.Bethe, 13. A,, 15, 29, 30.Bethke, R. M., 391.Betz, M. D., 110.Bewilogua, L., 66, 84.Beynon, J. H., 342.Bezssonoff, N., 387.Bhabha, H. J., 33.Bhaskaran, T. R., 410, 411.Bhatnagar, S. S., 192.Bigelow, L. A., 146.Biilmann, E., 228.Bijvoet, J., 221.Bilinsky, S., 200.Billicke, C., 84.Bills, C.E., 351, 352, 391.Biltz, W., 208, 257.Bingham, H. R,., 436.Binz, A., 231.Birch, T. W., 385.Bird, 0. D., 386.Birnbaum, K., 177.Bishop, L. R., 458.Bispham, W. NT., 406.Bjerge, T., 25.Bjerrum, N., 61.Black, A., 351, 391.Blackett, P. M. S., 34.Blagg, J. C. L., 92.Blankschtein, A. G., 467.Blasdale, W. C., 439.Blatterman, J. M., 357.Blau, F., 173.319.351INDEX OF AUTHORS’ NAMES. 473Bleakney, W., 15, 16, 141, 143, 144.Bleick, W. E., 19.Blewett, J. P., 16, 16.Bloch, F., 32.Block, R., 400.Blodgett, K. B., 117.Blomquist, A. T., 318.Blomquist, G., 259.Bloom, A., 437.Blount, B. K., 223, 376.Blum-Bergmann, (Mrs.) O., 319.Blumentritt, M., 107.Bode, G., 463.Bodenstein, M., 89, 92.Bodroux, M.D., 296.Boeseken, J., 277, 308Bohm, E., 151, 152.Bohme, R., 252.Boer, A. G., 353, 391.Boersch, H., 67.Bogert, M. T., 268, 298, 318, 320, 321,Bohle, K., 362, 363.Bohr, N., 30.Boldirev, A, K., 201.Bolland, I. L., 93.Bollmann, V. L., 197.Bolton, E. R., 459.Bond, G., 415.Bond, P. A., 152.Bone, W. A., 92.Bonhoeffer, K. F., 89, 99, 100, 101,Bonner, L. G., 58.Bonner, T. W., 21, 24, 28, 143.Bonstedt, K., 343.Boolt, H. W., 397.Boratynski, K., 464.Borissov, P. P., 306.Borsook, M., 389.Bosch, F., 450.Bose, P. K., 467.Bosshard, W., 343.Bost, R. W., 466.Bothe, W., 33.Bougault, J., 331.Bourdillon, R. B., 351.Bovet, D., 407, 408.Bowden, R.C., 108.Bowen, E. J., 74.Bowman, P. I,, 291.Brackett, F. S., 416.Bradfield, A. E., 341.Bradley, A. J., 214.Bradley, C. A., 61.Brady, 0. L., 231.Bragg, (Sir) W., 162, 196.Bragg, W. L., 198.Branchen, L. E., 467.Brandt, C. W., 269.Brasefield, C. J., 18, 144.Brasseur, H., 197, 214.Bratu, E., 99.322.102.Braun, H. A., 405.Braun, J. von, 295, 296, 301, 337.Braune, H., 75.Brauner, B., 454.Bray, W. C., 454.Brearly, D., 94.Bredereck, H., 254.Breit, G., 19, 30.Breitweiser, K., 456, 464.Brennecke, C. G., 19.Brenschede, W., 92.Bretscher, 26.Bretschneider, O., 149.Breuning, C. F., 445.Brewer, A. K., 15, 16, 140.Brewer, F. M., 196.Briau, A., 446.Bridges, R. W., 445.Briggs, G. E., 421.Briggs, L. H., 271, 273, 274.Brigham, H.R., 454.Brigl, P., 255.Brindley, G. W., 66, 200.Britton, M., 442.Brockmann, H., 353, 390, 458.Brockway, L. O., 36, 45, 55, 66, 67,70, 71, 73, 75, 77, 78, 79, 80, 83,162, 210, 216, 221.Brode, R. B., 34.Brose, H. L., 464.Brough, G. W., 467.Brovsin, I., 399.Brown, R. C., 115.Browne, J. 8. L., 362.Browning, C. H., 404.Br6, L., 75, 76, 79, 84.Brubaker, W. M., 21, 24, 28, 143.Bruce, H. M., 351.Bruce, W. A., 200.Bruce, W. F., 286.Briihl, A,, 180.Briinger, K., 452.Briingger, H., 343, 354.Briining, K., 187.Bruggen, M. G. van, 203.Brunowski, B. H., 202.Buboux, M., 97.Buch, E., 185.Buchholz, K., 352.Budkevitsch, A. A., 455.Buehler, C. A., 466.Buerger, M. J., 197, 205, 209.Biissem, W., 212.Bullock, B., 468.Burawoy, A., 169.Burford, M.G., 438, 441, 449.Burger, A., 315.Burgers, W. G., 203.Burk, D., 409.Burkhardt, G. N., 96.Burnett, K. H., 428.Burns, G. R., 417.Burr, G. O., 419474 INDEX OF AUTHORS’ NAMES.Burris, R., 460.Burrows, H., 360.Burstall, F. H., 171, 195.Bursuk, A. J., 441.Bury, C. R., 110.Bwe, P., 351.Butenandt, A., 338, 343, 344,357, 358, 359, 399.Butler, J. A. V., 101.Buttle, G. A. H., 408.Cadenbach, G., 191.Cady, G. H., 147.Cady, H. P., 467.Caldin, E. F., 97.Caldwell, C. T., 401.Caldwell, J. R., 443.Caley, E. R., 438, 441, 449.Calkin, J. B., 226.Callan, T., 462.Callow, R. K., 348, 381, 362.Calvert, F., 450.Cambi, L., 212.Campbell, A. J. R., 1.85.Campbell, A. N., 185.Campbell, E.D., 156.Campbell, N. R., 466.Cannon, A. B., 404.Capato, E., 316.Carlsohn, H., 170.Carman, E. F., 115, 117.Carman, J. A., 405.Carmichael, H., 35.Crtronna, G., 378.Carpenter, D. C., 79, 321.Carruthers, J. E., 93.Carson, L., 466.Carter, H. E., 401.Carter, S. R., 258.Casares, R., 467.Caspari, W. A., 212.Cassie, A. B. D., 67.Cavanagh, B., 102.Cavell, H. J., 161.Cecconi, R., 468.Celsi, S. A., 451.Centnerszwer, M., 148.Centola, G., 226.Cerkovnikov, E., 237.Chadwick, J., 26, 27, 28.Challinor, S. W., 262.Champetier, G., 226.Cham ion, F. C., 31, 32.Chamhe, G. C., 439.Chao, C. Y., 29.Chapman, A. W., 96.Chamux, C., 255.Chargaff, E., 262.Charonnat, R., 172.Chase, E. F., 464.Chatterjce, N. N., 297, 359.Chen, H., 466.356,Chen, Y.H., 468.Cheng-Heng Kao, 466, 466.Chevalier, R., 411.Chiang, H. C., 465.Chibnall, A. C., 202.Childs, W. H. J., 65, 143.Chirnoagh, E., 449.Chocklova, E. G., 308.Chojnacdki, C., 177.Chou, L. H., 231.Chowdhury, J. K., 258.Christman, C. C., 252.Ch’u, S. L., 15.Chu, T. C., 64.Chuang, C. K., 302, 328, 331, 334,340, 341.Chung-ICsi Kao, 465, 466.Churchill, H. V., 445.Cimerman, C., 443,444,4445.Ciorinescu, E., 309.cirulis, A., 191.Cismaru, D., 467.Clark, C. H. D., 63, 74.Clark, G. L., 117, 201, 225.Clark, R. E. D., 164, 232, 449, 462.Clay, J., 35.Clemo, G. R., 228, 291, 302, 303, 308,331, 372, 373.Clewer, H. W. El., 379.Clifford, P. A., 461.Cline, J. K., 381.Clusius, K., 57, 93.Cockcroft, J.D., 18, 20, 21, 22, 28.Coeur, A., 387.Coffey, D. H., 346.Cohen, A., 301, 303, 317, 324, 328,330, 333, 338, 360.Cohen, M. U., 197.Cohen, S., 435.Cohen, S. L., 362, 398.Cohen, W. D., 277.Colby, W. P., 54.Colebrook, L., 407.Colles, W. M., 169.Collet, A., 210.Collie, B., 104, 107, 110.Collie, C. XI., 29.Collins, F. J. E., 469.Compton, A. H., 34.Compton, J., 255.Conn, G. K. T., 66.Conn, L. W., 462.Cook, A. H., 300, 331, 333.Cook, J. W., 202, 223, 296, 300, 301,302, 303, 304, 307, 309, 312, 317,318, 321, 322, 324, 325, 328, 332,338, 339, 340, 343, 360.Coolidge, A. S., 39.Coombs, H. I., 463.Cooper, H. C., 151.Cooper, S. R., 436.Cooper, 8. S., 433.Coppock, J. B. M., 22INDEX OF AUTHORS’ NAMES.476Corey, R. B., 221, 224, 227.Cork, J. M., 24, 216.Cormack, R. P., 405.Corner, G. W., 344.Cornier, P., 201.Cortell, R,., 19.Cortese, F., 354.Cosslett, V. E., 66, 70, 72.Cowley, E. G., 119, 123,125,128, 131.Cox, E. G., 158, 159, 160, 162, 163,164, 165, 212, 221.Craciunescu, E., 250.Craig, L. C., 374, 375.Crane, H. It., 22, 25, 31.Crawshaw, J. D., 35.Crooks, H. M., 342.Crosby, B. L., 468.Cross, P. C., 64, 79, 80, 83, 162.Crossley, H. E., 435.Crowell, W. R., 439.Crowfoot, (Miss) D. M., 202, 223, 335,Crumpler, T. B., 458, 459.CsalAn, E., 151, 201.Curie, P., 295.Curtman, L. J., 451.&ta, F., 436.Cuvelier, B. V. J., 450.Czerwinski, J., 444.351, 364, 377.Dabrowski, J., 462.Dahle, D., 446.Dallimore, W., 273.Dalmer, O., 353.Dam, I-I., 353, 394.Damiens, A., 145, 146, 147, 149, 154.Dane, E., 343, 345.Danielli, J.F., 113, 115.Daniels, F., 59.Dannenbaum, H., 356, 357.Dannenberg, H., 344, 358.Dan& A., 318, 332.Daoud, K. M., 387.Darwin, C. G., 39, 86.Darzens, G., 29G, 297, 304, 319, 326,Dastur, R. H., 417, 418, 419.David, K., 357, 358.Davidshofer, F., 425.Drtvidson, D., 298, 318, 320, 321.Davies, D. G., 110.Davies, W. H., 116.Davies, W. T., 28.Davy, L. G., 132.Dawson, H. M., 97.De Almeida, A. G., 464.Deanesly, R., 356, 398.De Boer, J. H., 203, 204.De Brouckbre, L., 460.De Bruijn, H., 425.Debye, P., 65, 125.De Caro, L., 389.327.De Carvalho, A. H., 446.Deckert, W., 462.Dee, P. I., 20, 21, 27.De Eds, F., 464.De Ficquelmont, A.M., 186.De Fremory, P., 360, 396.Dogard, C., 75.De Gier, J., 16.De Hemptinne, I&, 50.De la Cierva, P., 200.De Laszlo, H., 67, 72, 76.De la Tour, F., 219.Delfosse, J. M., 56, 62.Dolone, B. N., 201.Delsasso, L. A., 22, 25, 31.Derning, L. S., 69.Dempster, A. J., 15, 16, 17, 138, 142.Denbigh, K. G., 145, 148.Denissenko, J. I., 311.Dennis, L. M., 147.Dennison, D. M., 55, 56, 61, 62.Dennison, M., 399.Deppe, M., 351, 361.De Ras~enfosse, A., 214.Dernies, J., 438.Desai, B. L., 419.De Saint Rat, L., 462.De Smet, P., 469.Desseigne, G., 467.Deutsch, L., 441.Devonshire, A. F., 47, 50.Dewar, J., 441, 467.Dhar, J., 211, 223.Dhar, N. R., 410.Diamant, E., 278.Dick, J., 438.Dickenson, H.G., 302, 308, 331.Diokinson, R., 164, 165.Dickinson, R. G., 84.Diebold, W., 353.Diels, O., 299, 302, 309, 323, 324, 328.Dieferle, H., 378.Dietrich, H., 355.Dietz, E., 348.Dietz, W., 452.Dijatschkovski, S. I., 450.Dimroth, K., 347, 349.Dingemanse, E., 357.Dirscherl, W., 345, 360.Dithmar, K., 349.Ditman, J. G., 94.Ditt, F., 402.Ditt, M., 443.Ditz, H., 450.Diver, G. R., 375.Dobberstein, H., 205.Dobbins, J. T., 442, 448.Dobrotin, N., 29.Dochez, A. R., 261.Doisy, E. A., 362, 397.Dolan, L. P., 407.Dole, M., 141.Dolique, R., 469476 INDEX OF AUTHORS’ NAMES.Dolivo-Dubrovolski, V. V., 201.Dols, M. J. L., 351, 391.Donald, M. B., 447.Donnan, F. G., 97.Doolittle, H. D., 19.Dorbe, C., 301, 305, 346.Dornte, R.W., 75, 79, 80.DOSS, K. S. G., 103.Dostal, H., 93.Doubinski, N. M., 449.Dowzard, E., 468.Dreher, E., 259, 267.Drew, E., 107.Dreyfuss, P., 275, 276.Driel, M. van, 212.Drummond, J. C., 346, 391, 392, 393.Dubsky, J., 455.Ducloux, E. H., 446.Dudley, H. W., 262.Du Mond, J. W. M., 197.Duncanson, W. E., 18, 28.Dunn, F. P., 231.Dunn, J. L., 347.Dunning, J. R., 29.Durand, J. F., 155.Du Vigneaud, V., 402.Dwyer, F. P., 450, 451.Dkelepov, B. Z., 32.Earp, D. P., 120, 132, 133, 134.Easterfield, T. II 271.Ebert, F., 149, 2015.Ebert, M. S., 151.Eckholm, W. C., 212.Edds, R., 466.Eddy, C. W., 464..Edminster, F. H., 151.Eekelen, M. van, 388.Ehmann, L., 301, 303, 312, 332.Ehmert, A., 33.Ehrenberg, W., 35.Ehrenfest, P., 65.Ehrmann, K., 148.Eichel, H., 265.Eichenberger, E., 343, 345, 364.Eilers, H., 256.Eisler, B., 462.Eisner, H., 97.Ekenstein, A.von, 258.Ekaall, P. K., 106.El Ayadi, M. A. S., 387.Elderfield, R. C., 363, 376.Elek, A., 468.Elias, A,, 463.Elmquist, R., 179.E l Shurbagy, M. R., 220.Elvehjem, C. A,, 386.Emde, H., 274.Emelhus, H. J., 93.Emerson, G. A., 346, 392.Emerson, 0. H., 346, 392.Emerson R., 420, 427.Endres, G., 153, 409.Engel, L. L., 463.Ephraim, F., 193.Epprecht, A., 229, 291, 292, 293, 294.Erdtman, H., 274, 277.Erlenmeyer, H., 228, 229, 291, 292,293, 294.Ernst, A., 204.Errera, J., 285.Etienne, H., 464.Ettori, J., 463.Eucken, A., 61, 92.Euler, E. von, 249, 254, 420.Euler, H. von, 247, 325, 379, 386,Evans, A.G., 93, 96.Evans, D. P., 95.Evans, E. A., 341, 343.Evans, H. M., 346, 392.Evans, M. G., 86.Eveleth, D. F., 463.Evenson, R. F., 439.Eventova, M. S., 311.Everse, J. W., 396.Eyring, H., 39, 86, 87, 90, 91, 100.428.Faessler, A., 197.Fairbrother, F., 120, 129, 132, 133.Fales, H. A., 440.Fankuchen, I., 197, 201, 227.Farkas, A., 39, 92, 93, 102.Farkas, L., 43, 86, 93, 102.Farmer, S. N., 115, 365, 366.Farquharson, J., 193.Farr, W. K., 226.Farre, R., 97.Farrer, G. E., jun., 463.Farrow, F. D., 259.Farwell, H. W., 432.Fast, J. D., 203.Fatajev, L., 310.Faust, W., 388.Feather, N., 26, 28.Fedorov, B. P., 467.Feigl, F., 167, 437, 438, 452, 453, 454,Feitknecht, W., 210.Fenger, F., 362, 398.Fermi, E., 23, 30.Fernholz, E., 343, 349, 351, 364, 356,Ferramola, R., 468.Ferrccri, A., 212.Fichter, F., 145.Ficklen, J.B., 453.Fidler, F. A., 96.Fieser, L. F., 282, 287, 290, 296, 297,304, 328, 329, 333, 341, 367.Fieser, (Mrs.) M., 297, 328, 329.Finbak, C., 152, 211.Finch, G. I., 46, 201.Finger, W., 152.455, 468.357INDEX OF AUTHORS’ NAMES. 477Fink, G. A., 26, 29, 30.Finn, A. N., 447.Fischer, F., 157.Fischer, H., 461, 462.Fischer, H. 0. L., 246.Fischer, J., 148, 149, 446.Fischer, K., 278.Fischer, W., 356, 452.Fischer, W. H., 343.Fish, F. H., 442.Fisher, C. H., 283.Flack, H., 406.Flasch, H., 205.Fleck, E. E., 365.Fleischer, W. E., 419.Fleischmann, R., 27, 31.Flesch, W., 425.Fletcher, C. J. M., 93.Flick, K., 181.Floch, H., 408.Flosdorf, E.W., 448.Follett, D. H., 35.Fomin, V., 29.Fonteyne, R., 459.Foord, S. G., 92.Foote, F., 197.Foote, H. W., 439.Ford, W. G. N., 96.Forrb, M., 33, 35.Foster, E. S., 200.Fourneau, E., 407, 408.Fowler, R. D., 181.Fowler, R. H., 49, 50.Fowler, W. A., 22, 25, 31.Foz, 0. R., 221.Fraenkel-Conrat, H. L., 379, 382.Francis, F., 369.Franck, J., 423, 426.Frank, B., 268.Frank, F. C., 119, 122, 128, 133.Frank, G., 434.Franke, E., 197.Franke, K. W., 460.Franke, M., 315.Frankl, J., 408.Franz, E., 70.Fratkin, It. L., 467.Frazer, J. C. W., 151.Fredenhagen, K., 145, 146, 191.Freed, M., 467.Frehden, O., 468.Frei, J., 301, 303 307.Frei, P., 254.Frenzel, A., 151, 191.Freud, J., 357, 399.Freudenberg, K., 93, 256, 259, 266,Freudenberg, W., 376.Frevel, L.K., 210, 219.Frey-Wyssling, A., 226.Friedemann, T. E., 467.Friedmann, E., 97.Friedrich, A,, 467.267.Friemann, M. G., 310.Friend, J. N., 183.Fries, K., 289.Frisch, 0. R., 29, 30.Frisch, P., 94.Frisch, R., 48.Fritz, H., 456.Frizzell, L. D., 135.Frocain, L., 462.Frohlich, K. W., 452.Frost, A. A., 92.Frumkin, A,, 113.Fu, C. Y., 29.Fuchs, J., 307.Furth, O., 467.Fujise, S., 231.Fujiwara, T., 226.Fulton, J. D., 299, 325.Fung, L. W., 56.Funk, H., 443.Furlong, R. W., 283.Furman, N. H., 440, 447.Gabrielsen, E. K., 417.Gadke, W., 299, 309.Giirtner, H., 228, 229, 291, 292, 293.Gaerttner, E. R., 31.Gaffron, H., 423, 426.Gaines, A,, 173.Galinovski, F., 376.Gallagher, T.F., 357.Gallitelli, P., 212.Gallotti, M., 431.Gamble, D. J. C., 323.Gamble, E. L., 146.Gamow, G., 31, 32.Ganguli, N., 201, 223.Ganguli, P., 407.Gardiner, P. A., 442.Gardner, J. B., 92.Garner, C. S., 437.Garner, W. E., 93.Garrido, J., 209.Gassner, G., 429, 430.Gattermann, L., 154.Gaubert, P., 212.Gauthier, J., 465.Gautier, J. A., 449.Gaverdovskaja, N. V., 311.Gawrych, S., 204.Gazowczyk, F., 290.Gebhardt, F., 191.Gee, G., 93, 114.Gehrke, M., 366.Geib, K. H., 92, 102.Gentner, W., 27.George, W. H., 165, 200.Georges, L. W., 250, 262.Georgi, C. E., 411.Gerecs, A., 249, 255.Gerlach, W., 137.Gershinowitz, H., 86418 INDEX OF AUTHORS’ NAMES.Ghaswalla, R. P., 97.Ghosh, A.R., 387.Giani, M., 389.Giarratana, J., 19.Gibson, C. S., 169, 170.Gibson, R. O., 98.Giese, H., 189.Giese, M., 151.Gietz, C. E., 436.Gilbert, C. W., 20, 31, 27.Gilchrist, R., 441.Gilkey, W. K., 446.Gillette, R. H., 59, 209.Ginglinger, A,, 399.Gingrich, E., 208.Ginsberg, H., 463.Ginsburg, N., 55.Girard, A., 324.Giroud, A., 226.Glasstone, S., 76, 120, 132, 133, 134.Glaze, F. W., 447.Gleu, H., 172.Glinka, N., 306, 307.Glockler, G., 54.Gmelin, L., 408.Go, Y., 221.Goda, S., 175.Godchot, 316.Goebel, W. F., 262, 264, 265.Goethals, C. A., 462.Goeze, G., 429, 430.Goissedet, P., 408.Goldberg, M. W., 302, 312, 332, 363,Goldhaber, M., 26, 27, 29.Goldschmidt, A., 359.Goldschmidt, V. M., 178.Goldsmith, H.H., 30.Goldsmith, K., 406.Goldstein, L., 31.Goodspeed, E. W., 444.Goodway, N. F., 339.Goodwin, T. H., 221.Gordy, W., 59.Gorski, V., 196.Gortm, E., 116.Ooslin, R., 433.GOSS, F. R., 129.Goswami, H. C., 455.Goto, H., 440.Gottfried, C., 196.Gottfried, S. P., 340.Gottlieb, S., 440.Gotts, R. A., 162.Goubeau, J., 140.Goudsmit, A., 458.Goudsmit, S., 29.Gould, A. J., 144.Grab, W., 352.Graf, E., 465.Graf, L., 226.Graff, M., 355.Graffunder, W., 105.357, 399.Grant, M., 283.Grant, R. L., 375.Grassmann, W., 400.Grave, G., 387.Gravier, P., 194.Gray, S. C., 93.Gray, W. H., 408.Green, J. W., 251.Greene, C. H., 141, 445.Greene, R. A., 410.Greenslade, T. B., 451.Greiff, L. J., 141.Grieneisen, H., 452.Griffith, R.H., 93.Griffiths, J. H. E., 29.Grimberg, A., 262.Grimm, H. G., 190.Grindley, J., 110.Gring, J. L., 444.Grinten, W. van der, 75, 197.Groenewoud, P. W. G., 380.Gross, B., 34.Gross, P., 92, 101.Grosse, A. von, 135, 138.Grosse, W., 357.Gruber, E. E., 330.Grubitsch, H., 179.Griinberg, A. A., 158.Grundmann, W., 381.Gruner, J. W,, 206.Guggonheim, E. A., 129, 131,464.Guha, A. C., 223.Guha, B. C., 387, 388.Guiterm, A., 345.G.uittonneau, G., 41 1.Gulbransen, R., 404.Gulland, J. M., 253.Gumlich, W., 354.Gupta, J., 58, 217.Gussjev, K. F., 202.Guthrie, J. D., 429.Gutschmidt, 93.Guyot, J., 113.Gueelj, L., 438.Gyisrgy, I?., 385.14I3I3HHHI3I3HHHHHHBHLaas, K., 193.[aberland, G., 297.Laenny, C., 31.[afstad, L.R., 19, 29.[agedorn, A., 366, 366, 367, 359.[agedorn, H. C., 397.Lagen, S. K., 449.[ahn, F. L., 452.[ah, G., 381.[ah, O., 25, 143.[alban, H. von, 28, 29, 97.[ale, A. H., 136, 145.[ale, J. B., 57, 58, 279.raley, J. B., 201.[alford, J. O., 99.[all, N. F., 144, 176INDEX OF AUTHORS’ NAMES. 479Hall, W. T., 438, 439.Hamblin, F. T., 28.Hammel, F., 211.Hammett, L. P., 173.Hammill, W. H., 100.Hampson, G. C., 218, 237, 289.Han, C. T., 328.Hanawalt, J. D., 202.Hanford, W. E., 372.Hanisch, G., 344, 357, 358.Hanke, G., 355. ,Hansen, H. V., 446.Hanson, E. E., 143.Hantzsch, A., 176, 187, 188.Hanusch, F., 360.Harada, M., 99, 292, 293.Harding, J. B., 113, 116.Hardy, (Sir) W.B., 37.Harington, C. R., 396, 402.Harker, D., 160, 197, 208, 213.Hmkins, W. D., 115, 117.Harper, J. P., 211.Harper, S. H., 323.Harries, C. D., 316.Harrington, E. L., 29.Harris, L. J., 384, 385, 386, 388,Harris, P. L., 287.Hart, E. B., 386.Harte, R. A., 468.Hartl, K., 408.Hartley, G. S., 104, 107, 110, 111.Hartman, F. A., 395.Hartmann, A., 356.Hahina, H., 260.Haslam, J. H., 174.Haslewood, G. A. D., 116, 301, 307,Hessel, O., 132, 152, 211.Hasselstrom, T., 268.Hassid, W. Z., 261, 467.Hatbway, M. L., 391.Haucke, W., 210.Hausen, S. von, 415.Hausknecht, W., 184.Hawkes, J. B., 432,Haworth, R. D., 270, 271, 272, 273,Haworth, W. N., 257, 261, 262.Hawthorne, J. R., 335.Haxel, O., 18.Haynes, S. K., 33.Hazel, W.M., 445.Healey, N., 190.Hecht, F., 135, 439.Hecht, G., 406.Heckel, W., 307.Heckstedon, W., 402.Hedestrand, G., 127.Hedges, R. E., 193.Heidelberger, M., 261, 262, 263, 2%Heidrich, K., 428.467.309, 332, 339, 343, 347, 392.274, 275, 300, 328, 337.265, 363.Heilbron, I. M., 116, 316, 342, 345,347,348,349,350,351,390,392.Hein, F., 163, 232.Heiner, A,, 17.Heinz, A., 326.Helde, M., 26.Helfenstein, A., 364.Hellebrand, R., 460.Heller, G., 231.Heller, K., 439.Heller, W., 92.Hellstrbm, H., 379, 420.Hellstrbm, N., 96.Helmholz, H. F., 407.Helmholz, L., 208, 211.Henderson, G. G., 298.Henderson, J. A. R., 462.Henderson, M. C., 23.Hendricks, S. B., 69, 72, 84, 85, 206,219, 284, 285, 286, 287.Hengstenberg, J., 75, 224.Hennig, H., 468.Hennings, C., 132.Henry, C., 448.Herb, R.G., 19.Herlinger, E., 223.Hermann, C., 196, 227.Hermann, H., 200.Herold, W., 132.Herrmann, H., 467.Hershberg, E. B., 296, 297, 329,33Herszfmkiel, H., 31.IIertel, E., 223.Herzberg, G., 54, 58.Hem, A. F., 351.Hess, K., 226.Hesse, G., 364.Hevesy, G. von, 25, 29, 140.Kewett, C. L., 202,300, 301, 303,304,307, 312, 317, 321, 322, 324, 325,332, 333, 334, 338, 339, 360.Hey, F., 152.Hey, RI. H., 206.Heydenburg, N. P., 19.Heymann, E., 193.Heymann, G., 165.Ileyn, A. N. J., 225.Reyns, K., 353, 401.Hibben, J. H., 36, 58.Hibbert, G. E., 255.Hibbert, H., 260.Hibbit, D. C., 316, 317.Hieber, W., 176.Higasi, K., 119, 121, 123, 133.Higginbotham, R.S., 269.Higginbottom, (Miss) A., 304, 340.Hilbert, G. E., 284, 285, 286.Hildebrandt, F., 361.Hilgermcmnn, R., 408.Ilill, E. L., 20.Hill, E. M., 402.Hill, K., 184, 185.Hill, P., 304, 340480 INDEX OF AUTHORS’ NAMES.Hill, S. G., 93.Hills, E., 463.Hillemann, H., 323, 339.Hillis, T. E., 439.Hills, H. W. J., 234.Hilpert, R. S., 204, 428.Hilton, C. M., 138.Hinsberg, K., 389, 464.Hinshelwood, C. N., 02, 94, 95, 96.Hipple, J. A., jun., 16, 141.Hirano, S., 358, 464.Hirsch, A., 425.Hirschfelder, J., 30, 86.Hirschmann, H., 361.Hirshberg, J., 288.Hirst, E. L., 262.Ho, P. C., 31.Honigschmid, O., 135, 136, 138, 139,Horlein, H., 407.Hosli, H., 268, 301,312,324,332,337.Hoff, J. H. vctn’t, 98.Hoffmann, B., 186.Hoffmann, J.L., 135.Hofmann, A., 364.Hofmann, K., 301, 303, 307, 312,Hofmann, U., 151, 191, 201.Hofmann, V., 206.Hogness, T. R., 94.Hoki, H., 31.Holden, G. W., 375.Holiday, E. R., 253.Hollens, (Miss) W. R. A,, 193.Holmberg, B., 274.Holmes, H. L., 207, 304, 329, 333.Holscher, F., 293.Holt, S., 169.Honeywell, E. M., 391.Honigmann, H., 312, 346, 353.Hooley, J. G., 135.Hoops, L., 278.Hoover, S. R., 414.Hoover, W. H., 416.Hopkins, B. S., 136, 182, 183.Hopkins, E. W., 413.Hopkins, F. G., 389.Horiuti, J., 99, 102, 292.Horkheimer, P., 434.Hornel, J. C., 101.Horner, C. K., 409.Horrex, C., 96.Hosking, J. R., 269.Hosoki, Y., 401.Hotchkiss, R. D., 264.Hourigan, H. F., 441.Houtermans, F. G., 29.Howard, J. B., 51, 56.Howell, 0.R., 106.Howlett, L. E., 458.Hromatka, H., 372.Hsing, C. Y., 236, 380.Hsu, E. I, F., 237.140.337.Hsu, T. T., 237.Hu Chien Shan, 35.Huang, J. V. S., 314, 337.Huang, Y. T., 334, 341.Hubbard, M., 431.Hubert, B., 427.Huckel, W., 314, 340.Hudson, C. S., 246.Hulsmann, H., 207.Hiirle, R., 402.Hiittel, R., 364.Hdlrnan, E. H., 174.Huggins, M. L., 63, 76, 77, 84, 209.Hughes, A. H., 113, 114, 115, 116.Hughes, E. D., 95, 97, 223.Hughes, G., 181, 433.Hughesdon, R. S., 308.Hulme, H. R., 33.Hultgren, R., 223.Hulthen, E., 17.Hume-Rothery, W., 203.Humiston, B., 145.Humpert, K., 145.Hund, F., 229.Hunter, R. F., 178.Hurd, L. C., 449.Hurley, F., jun., 434.Husimi, K., 31.Hutchinson, J. B., 194.Hutton, R.S., 460.Iball, J., 67, 202, 223, 324, 332.Ievins, A., 197, 202, 208.Iliesco, E., 468.Illingworth, J. MT., 214.Imanakct, Y., 226.Imhauser, K., 407.Immelman, M. N. S., 33.Ingle, J. D., 467.Ingold, C. K., 44, 58, 95, 97, 229, 232,Inhoffen, H. H., 341, 343, 346, 347,Inman, 0. L., 431.Ionesco-Matiu, A., 468.Ipatiev, V. N., 305.Irineu, D., 270, 336.Irmisch, G., 296, 301, 337.Isakov, L., 143.Isakova, A., 409.Ishiguro, T., 270, 273, 274.Ishimaru, S., 451.Isihara, M., 226.Ising, G., 26.Itano, A., 414.Iterson, G. van, 226, 226.Iwasaki, T., 354.233,234, 236, 279, 291,292.348.Jackson, E. L., 246.Jackson, H., 468.Jacob, (Miss) A., 382INDEX OF AUTHORS' NAMES. 481Jacob, K- D., 446.Jacobs, W. A., 363,365,374,375,376,Jacobsen, B., 157.Jaeger, F.M., 173, 174, 203, 206.Jaeger, J. C., 33.Jaenckner, W., 148.James, H. M., 39.James, R. W,, 66.Janot, M., 269.Jansen, E. F., 255.Jantsch, G., 179, 183.Jauncey, G. E. M., 200.Jefferson, M. E., 72, 219.Jeffreya, C. E, P., 389.Jellinek, K., 444.Jendrassik, L., 463.Jenkins, (Miw) D. I., 96.Jenkins, G. L., 445.Jenkins, H. O., 77, 119, 120, 126, 128.Jenkins, W. J., 112.Jennings, J. S., 168.Jensen, 8. N., 397.Jensen, H., 364.Jensen, K. A., 228.Jepperson, M. A., 433.Jessop, G., 112.Jette, E. R., 197.Jilek, A., 437, 438.dirovec, O., 418.Johner, H., 224.Johnson, A. H., 462.Johnson, C. H., 28, 173.Johnson, C. R., 135, 139.Johnson, D. P., 19.Johnson, W. C., 94.Johnsfon, E.S., 416.Johnston, H. L., 144.Johnston, M. J., 55, 56.Johnston, 6 . W., 387.Jois, H. S., 368.Jolly, L. J., 93.Joly, A., 170.Jonelis, F. G., 174.Jones, B., 76.Jones, E. B., 464.Jones, E. J., 15,Jones, E. M., 174.Jones, E. R., 341.Jones, H., 38, 203.Jones, H. L., 464.Jones, N. c., 145.Jones, P. L. F., 77.Jones, R. N., 351, 390, 468.Jones, T. O., 144.Jones, W. E., 116.Joos, G., 107.Jordan, E. B., 15.Josephson, K . O., 328.Jukes, T. H., 385.Julianelle, L. A., 262.Juliusberger, F., 95.379.131, 133.RF4P.-VOL. xxxm.Jwavleva, L. Pa, 467.Justi, E., 217.Kagi, H., 358.Kaffer, H., 307.Kaku, T., 277.Kalushskaja, V. M., 446.Karnai, G., 237.Kamen, K., 436.Kamm, E. O., 316.Kamm, O., 342, 357, 361.Kamp, J.van de, 315, 322.Kanga, D. D., 379.Kapfenberger, W., 139.Kapustinski, A. P., 201.Kara, I., 29.Karaoglanov, Z., 438.Karpenko, V., 462.Karrer, P., 246, 247, 254.Xarry, C. von, 249.Karstens, (Frl.) R., 299, 302.Kcasline, C. T., 466, 458.Kassatochkin, V., 194, 210.Katz, J. R., 224.Kaufler, F., 241.Kaunitz, H., 468.Kitutsky, H., 425.Xawagoe, M., 273.Kawakami, Y., 112.Kawamura, J., 274.Kwmnski, B. A., 311.Kazuno, T., 355.Keenan, J. A., 386.Keesom, W. H., 216, 217.Keggin, J. F., 213.Keim, R., 149.Keimatsu, S., 270, 273.Kelbe, W., 295.Kellie, A. E., 388.Kellstrom, G., 196.Kelly, W., 271, 273, 274.Kemp, J. D., 217.Kernpton, A. E., 20, 28, 143.Kendall, E. C., 359, 395.Kondall, F. E., 263, 264.Keuner, J., 237.Kenny, M., 407.Kent, D.W., 19.Kenyon, J., 234, 235.Kershaw, J. B., 446.Keston, A. S., 141.KesztIer, F., 370, 381.Ketelaar, J. A. A., 201, 203, 208, 209,Kharasch, M. S., 178, 375.Ki-Heng, Y., 219.Kielt, L., 439.Kikuchi, S., 31.Kilictni, H., 366.Kilpatrick, M., 464.Kimball, R. H., 234.Kimm, R. H., 393.210.482 INDEX OF AUTHORS’ NAMES.King, A., 375.King, A. J., 226.King, H. I?., 76.King, L. D. P., 19.Kinnersley, H. W., 3%.Kinsey, B. B., 27.Kip, C. J., 277.Kirchner, E., 347.Kirk, P. L., 468.Kirkwood, J. G., 131.Kirschbaum, G., 296.Iiirssanov, A., 434.Kishi, S., 354.Kistiakowsky, G. B., 04, 280.Kitagawa, M., 400, 401.Klages, I?., 260.IClar, E., 99, 100.Klare, H., 302.Xlannann, H., 33.Klass, R., 467.Klauditz, W., 289.Klemenc, A., 190.Klemm, W., 179, 181, 183, 192,Klemperer, O., 140.Klenk, E., 353.Icline, 0.L., 386.Eilinkenberg, L. J., 210.Xlit, A., 291.Iinaggs, (Miss) I. E., 81.Icnauf, A. E., 231.Knight, B. C. J. G., l l G .Knipp, J. K., 32, 39.Knippenberg, E., 463.Knoevenagel, E., 307.Knoke, S., 75.Knol, K. S., 25.Knoop, F., 402.Knothe, H., 446.Knuth, E., 228.Kobayashi, M., 33, 175.Kocay, W., 204.Koch, E., 205.Koch, F. C., 357, 391.KBhler, R., 191.Koelsche, G. A., 395.Kiinig, G., 355.KBrcling, P., 299.Kiirner, E., 191.Kohler, E. P., 286, 319.Kohlrausch, K. W. I?., 61, 269.Kohn, H. I., 427.Kolesnikov, D. G., 370.Kolthoff, I. M., 176, 179, 434, 436,437, 443, 448.Komrtrevski, V.I., 305.Komppa, G., 242.Kon, G. A. R., 115, 302, 304, 321,323, 331, 365, 366.Kondo, Y., 468.Koning, H. C., 427.Iionovalovrt, R., 378.Koolhaas, D. R., 331.194.Koppel, I., 440-KorenchevSky, V., 399.Korenmnan, I. M., 452, 454.Korol, S. S., 446.Korsching, H., 17.Kossel, W., 197.Koster, 389.Kostytchev, S., 408.I-Cot’a, J., 438.Kotin, C. M., 200.Kotov, V., 194, 210.Kozima, M., 132.K ~ z u , T., 442.Kraemer, E. O., 461.Krafft, F., 104.Kramer, K., 388.Kramer, W., 408.Kramete, E., 455.Krarup, N. M., 397.Krassilchik, A., 445.Kratky, O., 197, 221.ICraus, W., 92.Krause, A., 204.Krause, M. E., 386.Krauss, F., 101.Kraybill, H. R., 459.Krebs, G., 197.Krefft, 0. T., 146, 140.Krilov, K. I., 225.Kringstad, H., 152.Krishnccn, K.S., 126, 200.Kroger, C., 187.Krogh, A., 397.Krollpfeiffer, F., 315, 336.Kroupa, E., 135.Kriiger, P., 316.Krumholz, E., 436.Krumholz, P., 436.Krutter, H., 205.Ksanda, C. J., 206.Kubo, M., 129, 132.Kuclszus, H., 343, 357.Kuflner, F., 370, 381.Kuhlberg, L., 452, 454, 455, 468.Kuhn, R., 254, 351, 382, 386, 421.Kuhn, W., 174.ICuhs, M. L., 404.Kumar, K., 417.Kunz, K., 278.KuraS, M., 437.ICurie, F. N. D., 23, 25, 31.Kurtenacker, A,, 152.Kurtschatov, I. V., 28, 29.Kusin, A., 245.Kutani, N., 277.Kuzma, B., 454.Kwzmin, L. L., 186.Laar., J., 208.Lacher, T. R., 04.Lacourt, A., 468.Laidlaw, P. P., 262INDEX OF AUTHORS’ NAMES. 483Laine, T., 4J5.Laing, M. E., 110.Lakhani, M. P., 223.Lal, K.N., 416, 419, 428.Lamar, 31. O., 445.Lamb, F. W., 461.La Mer, V. K., 97, 100.Lampitt, L. H., 462.Lancefield, 262.Lang, R., 440, 447.Lango, B., 459.Langer, R., 348, 392.Langmuir, I., 43, 112, 117.Langseth, A., 291.Lannar, K., 278.Lantz, R., 290.Lapina, R. A., 381,Laporta, M., 387.Laqueur, E., 357, 360, 396.Larsen, P., 430.Lasaussa, E., 462.Lassettra, E. N., 57.Latischev, G. D., 28.Laucht, F., 348.Laucius, J. F., 342, 361.Launoy, L., 404.Lauritsen, C. C., 22, 25, 31.Lauter, W. M., 405.Laval, J., 200.Lawrenee, A. S. C., 94, 111.Lawrence, C. A., 296, 300, 312, 322,325, 330, 339, 340.Lawrence, E. O., 23, 24.Lawrence, R. D., 397.Lawson, A., 376.Lebeau, P., 135, 136, 146, 147, 149,Leckie, A. H., 58, 188, 279.Lecoin, M., 31.Leder-Packendorff, L., 306.Lee, E., 17.Le Fbvre, (Mrs.) C.G., 128, 134, 223.La Fevre, R. J. W., 120,128,133,223.Leffler, N. T., 228.Le Galley, D. P., 197.Lehmam, G., 372.Leipunski, A. I., 29, 32.Eeitmoier, H., 456.Lendle, A., 92.Lennard-Jones, J. E., 42, 46, 47, 219.Leong, P. C., 384.Leopoldi, G., 461, 462.Lepkowsky, S., 385.Leppla, P. ?V., 117, 201.Leprince-Ringuet, L., 33, 34.Leschewski, K., 206.Lesslie, (Miss) M. S., 230.Lettr6, H., 341, 349, 352, 353, 366,Leuchs, H., 233.Levaditi, C., 407.Levene, P. A,, 255.Levi, G. It., 201, 208.154.390.Levi, W., 25, 486.Levin, A. B., 449.Levina, R. J., 308, 309.LB-vy, A., 304, 326, 327.LOvy, G., 296, 297.Lewis, C. M., 85.Lewis, W., 447.Lewis, $1.J., 338.Lewis, I?/. B., 18, 20, 21, 22.Ley, L., 407.L1, C. c., 94.Libby, MT. F., 28.Lichatsclzeva, A, I., 463.Lichtenstadt, L., 270, 336.Liddol, U., 284,285, 286, 257.Liebhafsky, W. A., 463,Lifschitz, J., 173.Lind, S. C., 89.Lindenberg, A., 468.Lindqvist, !&I., 207.Lindsay, J. B., 274.Lingano, J. J., 434, 437.Linnitzlri, V., 196.Linssrt, O., 351, 452, 391.Linsteatl, R. P., 161, 222, 300, 311,316, 317, 327, 331, 333.Lintrier, J., 278.Linton, R. W., 262, 265.Lippert, L., 209.Lipson, €I., 198, 211, 21G.Liu, T . K., 54.Livingood, J. J., 23.Livingston, 92. S., 30.Livingston, R., 9,3.Ljung, K. A., 448.Lobb, D. E., 391.Lobcck, El., 229, 291, 392, 293, 294,Locher, G. L., 34.Lob, A., 249.Logstrup, M., 140.Loew, O., 306.Lohrmann, O., 196.Lolsit, I%, 24.Long, E.A., 28.Long, F. A., 95.Longair, A. K., 83.Loiiginescu, G. G., 447.Lonsdale, (Mrs.) K., 198, 200, 221.Loomis, W. E., 428.Lbpcz, 1%. C., 452.Loring, H. S., 402.Losada, T., 200.Lothian, G. F., 457, 459.Lothian, (Miss) 0. M., 284.Lothrop, W. C., 282, 287, 290.Lotmar, W., 63, 224, 226, 226.Lottcrmoser, A., 105.Lucas, C. C., 461.Lucas, H. P., 112.Luchsinger, W., 148.Ludwig, C. A., 414.Liittringheus, A., 351.Lowry, T. M., 98, 234484 INDEX OF AUTHORS’ NAMES.Luft, F., 149.Lukirsky, P., 28.Lumsden, J., 441.Lundegkdh, 429.Lundell, G. E. F., 135.Lundgren, H. P., 465.Lundqvist, D., 207.Lutschinski, G. P., 463.Lynch, G. Roche, 461.Ma, C. M., 302, 331, 340.McAlpine, K.B., 131.McAlpine, R. K., 449.McBain, J. W., 104, 108, 110, 112.McCandless, E. L., 204.MacCorquodale, D. W., 362, 397.McCoy, H. N., 180.McCoy, R. H., 401.McCrone, R. 0. O., 298.McDonald, F. G., 392.Macdonald, R. O., 92.McFarlan, R. L., 197, 216, 218.McFarlane, W. D., 457, 463.Machatschki, F., 206.Machek, F., 439.Mack, G. L., 388.McKay, H. A. C., 29.McKenzie, A., 236.McKenzie, B. F., 395.McKenzie, J. P., 369.McMillan, E., 23.M’Nab, W., 298.McNabb, W. M., 437.MacNair, W. A., 391.MacNevin, W. M., 140.MacPherson, H. G., 34, 433.McQuillen, A,, 228, 291.McVickers, L. D., 443.Macwalter, R. J., 346, 393.MacWood, G. E., 55.Madelung, W., 256.Magat, M., 36.Magidson, 0. J., 406.Magistad, 0.C., 429.Magnus-Levy, A., 226.Mahr, C., 450.Maiden, J. H., 276.Maier, J., 402.Maillard, L., 463.Xaitland, P., 229.Majumder, D. C., 406.Malamos, B., 406.Malerczyk, W., 249.Malisoff, W. N., 465.Malkin, T., 220.Mallock, R. R. M., 50.Malmberg, M., 254.Malsch, J., 104, 107.Mameli, E., 273.Mamoli, L., 344, 380.Mmchot, W., 176.Manchot, W. J., 176.Manian, S. H., 143.Manjunath, B. L., 368.Mann, F. G., 163, 165.Rlannebach, C., 58, 62.Manske, R. H. F., 380.Manz, G., 337.Marchlewski, L., 462.Mark, H., 65, 93.Marke, D. J. B., 93.Marker, R. E., 342, 357, 361.Markovnikov, V. B., 295.Marlies, C. A., 97.Marquet, F., 468.Marrack, J. R., 388.Marrian, G. F., 115, 362, 398.Marsh, J. K., 136.Martens, W., 249.Martianov, N.N., 446.Martin, A. J. P., 197.Martin, E. L., 334.Martius, C., 345.Marvel, C. S., 300, 315.Marvin, G. G., 441.Marx, A., 425.Mashino, M., 466.Mason, H. L., 359, 395.Massengale, 0. N., 351.Mathers, F. C., 145, 146.Mathieu, J. P., 174.Mathieu, M., 226.Matsuura, A,, 414.Mattill, H. A., 393.Maurer, K., 252.Mauss, H., 406.Mavin, C. R., 270, 300, 328.Mawson, C. A,, 389.Maxwell, C. E., 369.Maxwell, L. R., 69, 72, 85.Maxymowicz, W., 438.May, A. N., 18, 28.May, F., 226.Mayer, E. W., 279.Mayer, F., 301, 337.Mayer, J. E., 67, 221.Mayneord, W. V., 303, 325, 332.Mead, T. H., 396, 402.Mecke, R., 143.Medlin, W. V., 208.Medvedev, S., 93.Megaw, (Miss) H. D., 219.Megrdichian, G. A,, 466.Mehl, R., 204.Mehlig, J.P., 456, 460.Mehta, R. J., 417.Meier, P. T., 268.Meisel, K., 207.Meissner, H., 194.Meissner, M., 93.Meitner, (Frl.) L., 25.Mellon, M. G., 456, 457, 458.Melnikov, N. N., 465.Melville, H. W., 92, 93.Melville, R., 419INDEX OF AETRORS' NAMES. 485Mencke, W., 427.Mong, K., 466.Menn, W., 135.Menon, E. V., 237.Menschick, W., 353.Menschikov, G., 237, 377.Menzel, W ., 147.Menzies, A. C., 57.Morkus, P. J., 465.Merz, V., 290.Merz, W., 402.Messerly, G. H., 217.Messonshnik, S. S., 454.Mevius, W., 428.Moyor, C. E., 401, 402.Meyer, E. L., 135.Meyer, F., 146.Meyer, Jules, 295, 343, 354, 356, 357.Meyer, Julius, 152, 194.Meyer, R. H., 224, 225, 226.Meyer, R. J., 135, 446.Meyer, S., 181.Micheel, F., 250, 251.Michlina, S.E., 311.Michov, 15., 438.Middleton, A, If., 451.Nie, G., 224.Miescher, K., 359.Mietzsch, F., 406.Migeotte, M. V., 56.Migray, E., 448.Miklaschevskaja, V., 467.Miles, F. D., 213.Miller, A. L., 445.Miller, E. J., 461.Miller, E. S., 419.Miller, G. L., 402.Miller, H., 18, 28.Miller, R. D., 200.Miller, VC'. T., 146.Millidge, A. F., 317, 331.Milligan, W. O., 212.Millikan, G. A., 97.Millikan, R. S., 33.Mills, IV. H., 158, 162, 164, 229, 232,Milone, M., 223.Blinder, W., 210.Mingaxzini, &I., 295.Mitchell, A. C. t., 29, 30.Mitchell, D. P., ~ 6 , 29, 30.Mitchell, D. T., 318.Mitchell, J. W., 92.Mitra, B. N., 265.Miyagi, S., 435.Mizushima, S., 132.M0ller, C., 32.Moller, E. F., 351.Moller, K., 331.Iaoelwyn-Hughes, E.A., 86, 89, 93,Morgeli, E., 312.Moillst, J. L., 104.281.94, 95, 96, 97, 108, 101, 102.Moissan, II., 147, 154.Moles, R., 144, 145.Mollet, P., 285.Moltzau, R., 443.Montgomery, C. G., 34, 35.Montgomery, D. D., 34, 35.Mooklierjee, A., 211.Moon, P. B., 28, 29.Mooney, R. C. I,., 210.Moreau, P., 406.Morgan, E. J., 389.Morgan, (Sir) G. T., 162, 171, 195,Morgan, J. F., 35.Morgan, W. %I., 373.Morgan, W. T. J., 262, 265.Morita, N., 141, 144, 294.Morningstar, O., 205.Morrell, C. E., 54.Morris, It. C., 372.Pllorrison, A. L., 347.Morticr, P., 123.Morton, F., 461,Mosor, L., 438, 442.Mosettig, E., 315, 322.Mosley, V. N., 69, 72, 85.Mott, N. F., 32, 38, 66, 203.Moureu, H., 186, 187.Mouriquand, G., 387.Mousseror-, M., 194.Moyer, €3.V., 443.Midilbauer, F., 176.W;ihlsteph, W., 440.Miiller, D., 430.Miiller, E., 446.Mneller, E. if., 466.Miillor, I?., 459.Miiller, F. H., 118, 123, 131, 132.Miiller, G. T., 209.Muellsr, R., 128.Muller, H., 314, 337.Muller, H. I<., 387.Mueller, J. H., 262.Miiller, M., 351.Miinzberg, F. IC., 99, 292.Mukerji, S. K., 410.Xuller, F., 465.Mdliken, R. S., 42, 43, 50, 189.Munro, J., 249.Murgatroyd, F., 403, 404.Murphy, E. J., 29, 30, 432.Murphy, G. N., 53, 92.Murray, J. W., 291.Murray, R. C., 104.Murray, W. M., jun., 440, 447.Muskat, I. E., 256.Muasakin, A. P., 457, 463.Mutermilch, S. , 262.Mutschin, A., 440.Myers, C. S., 359, 395.Myers, P. E., 19.Myers, V.V., 463.403, 448.nfuCioz, J. M., 446486 INDEX OF AUTHORS’ NAMES.Naab, H., 340.Nadeau, G. P., 467,Nahring, E., 200.Eaeser, C. R., 135.Nagasaki, A,, 231.Nahmias, M. E., 28.Naidu, R., 28.Naito, T., 404.Nakamura, A,, 176.Nakatsuka, Y., 232,Naray-Szabo, S. von, 203.Narayanamurthi, 13. S., 435.Narayanaswamy, B. N., 128,Nathan, W. S., 77, 95,Natta, G., 209, 226.Nauck, E. G., 406.Neal, 0. R., 411, 412.Neddermeyer, S., 35.Neher, H. V., 33.Nemenov, L. M., 28.Nenitzoscu, C. D., 309.Nespital, W., 132.Nesty, G. A., 300, 315.Neter, E., 265.Neuberger, A., 396.Neubusger, IM. C., 67, 202.Neumann, B., 187.Neumam, E. W., 194.Neumann, M., 92.Neunhger, E., 26.Neurad, K., 278.Neurnth, H., 117.Neuwirth, R., 425.Nswell, I.L., 453.Nowling, W. 33. S., 95.Newman, P. H., 140.Newman, M. S., 297,Newns, G. H., 407.Nicholson, F., 466.Nicholson, T. F., 467.Nicol, H., 413.NiederlZinder, K., 343.Niekerk, J. van, 353, 391.Nielsen, A. H., 55, 57.Nielsen, H. H., 55, 57.Nielsen, W. M., 35.Niemann, C., 399.Niemann, R., 260.Nier, A. O., 140, 142, 143.Niessner, M., 442.Niiio, E. L., 450.Nishida, K., 260.Nishida, S., 26.Nishina, Y., 33.Nitka, H., 217.XTitti, F., 407, 408.Nixon, I. G., 281.Noack, K., 426, 431.Norkina, S., 380.Norrish, K. G. W., 92, 93.Novogrudski, D. M., 489.Noyes, A. A., 454.Noll, w., 444.138.Nhfiez, F. G., 135.Nussmeier, M., 351.Oakley, H. B., 258.Oakwood, T. S., 342, 357, 361.O’Brien, J. R., 386.Oda, T., 355.O’Daniel, H., 209.Oddie, (Miss) G.T., 194.Oddo, B., 431.Oddo, G., 378.Odd, A. D., 362, 308.Oechler, F., 370.Oespor, R. E., 435.Offc, H. A., 364.Ogata, A,, 368.Ogawa, M., 401.Ohle, H., 248, 249.Oka, S., 404.Okahara, K., 368.Ukcll, F. L., 441.Olcott, H. S., 392, 303.Oldenberg, O., 92.O’Leary, W. J., 445.Oliphant, M. L., 16, 20, 25, 27, 28,Olson, A. R., 95, 174.Onsager, L., 59, 129.Oommen, (Miss) M., 338.Oppenauer, R. V., 356.Oppenheimer, J. R., 23.Orcutt, F. S., 413.Qrdelt, If., 438.OrBkhov, A., 319, 378, 380.Qrlenko, A. F., 456.Ormston, J., 303.Orr, W. J. C., 100.Osborn, R. A., 458.Oserkowsky, J., 431.Osler, T. GI-., 461.Osterberg, A., 407.Osterberg, H., 205.Ostrofsky, &I., 19.Ostroumov, E.A., 439, 442.Ott, E., 388.Ottawa, H., 348.Ovenston, T. C. J., 172.Owen, E. A., 67, 203.Owen, E. C., 446.Owens, W. M., 316.143, 144.Paauw, F. van, 418, 419.Packendorff, K., 306, 308.Pacsu, E., 100, 249, 351.Page, I. H., 353.Pahl, M., 197.Pailer, M., 368.Pal, H. K., 223.Pal, J. C., 388.Palacios, J., 200, 221.Paneth, F. A., 24INDEX OF AUTHORS' NAMES. 487Pankow, G. W., 224, 225.Park, B., 439.Parker, E. A., 226.Parkes, A. S., 356, 359, 398.Parkinson, D. B., 19.Parle, W. C., 439.Parry, G. A., 110,Partington, J. R., 119, 123, 125, 128,Partridge, S. M., 228, 235.Patat, F., 54, 92.Paton, R. F., 18.Patry, M., 2 j l .Patterson, A. L., 198.Patterson, T. S., 231.Patt'erson, W. I., 402.Pauling, L., 38, 41, 43, 44, 45, 46, 47,49, 51, 52, 59, 66, 70, 73, 74, 75, 76,77, 78, 79, 80, 82, 83, 85, 169, 200,210, 216, 221, 237, 282, 287.131.Pavlov, N., 306, 308.Paxton, H.C., 23, 31.Peachey, S. J., 164.Peacock, D. H., 96, 237.Peak, D. A., 271, 274, 306, 335, 336.Pearce, D. W., 180, 181.Pearson, T. G., 436.Pease, R. A., 93.Pegram, G. B., 26, 29, 30.Pelzer, H., 88.Penfaillit, L., 295.Penney, W. G., 43, 44, 51, 54, 60, 88.Peoples, J. A., jun,, 432.Percival, E. G. V., 249.Perlman, D., 321.Perrin, M. W., 93, 98.Pesez, BI., 468.Peter, Q., 463.Peters, R. A., 386.Peterson, F. C., 226.Petitpas, (Mlle.) T., 226.Petraschenj, V. J., 449, 452.Petrow, V. A., 301, 305, 346.Petru, F., 278.Peyer, E., 301, 309.Poyer, J., 364.Peyronel, G., 206.Pfaehler, K., 246, 247.Pfeiffer, C.C., 404.Pfiffner, J. J., 359, 395.Pfotzer, G., 33, 3-2.Philip, H., 196.Phillips, H., 234.Phillips, M., 23, 267.Phillips, N. W. F., 135.Philpot, J. St. L., 361.Phipers, R. F., 345, 347.Pickard, R. H., 347.Pickering, S. U., 11 1.Pickett, L. W., 223.Pickles, N. J. T., 96.Picon, M., 405.Pihrard, J., 75.Pieth, P., 303.Pike, N. It., 453.Pinkard, F. W., 158.Pinkney, P. S., 300, 315.Pinkus, A., 438.Piper, S. K., 202.Pirie, N. W., 227, 250, 251.Pitsch, W., 252.Pitzer, K. S., 217.Piwonka, R., 259.Plaezek, G., 30.Plank, J., 452.Plate, A. F., 311.Plattner, P., 310.Platz, H., 184.Platzer, N., 370.Potlschus, E., 206.Poliland, E., 216.Pohlmann, R., 58.Polomi, G., 431.PoLtnyi,M., 86,87,92,95,102,174,292.Poll& L., 446.Pollard, E., 18, 144.Polucktov, N.S., 455, 463.Pope, W. J., 164.Pord-Koschitz, E., 306.Posner, I., 231.Postornsk, T., 259.Postnikov, V. F., 186.Potschinok, C. N., 462.Powell, H. M., 161.Powers, P. N., 29.Pozna, F., 448.Prandtl, W., 180.Prawd, M., 223.Preiswerk, P., 28, 20.Prelog, V., 237.Preobrashenski, N. A, 381.Present, R. D., 39.Preston, G. &I., 212.Price, W. C., 43.Prieur, M., 404.Prim, J. A., 73.Prundeanu, E. I., 447.Ptizyn, B. W., 158.Puschel, F., 105.Pugh, C. E. &I., 176.PulaTer, R., 202.lhrtlie, D., 163, 165.Putnam, G. L., 463.Pycock, E. R., 97.Popov, P. G., 447.Quatram, F., 156.Qudrat-i-Khuda, BI., 331.Quilmll, T.R. H., 158.Quirnby, 8. T., 86.Quiinby, S. L., 205.Rabe, P., 321, 331.Rabinovitsch, E., 103, 423488 INDEX OF AUTHORS’ NAMES.Rabinovitsch, I. M., 397.Raby, E. C., 464.Radulescu, D., 233.Ragiot, C., 406.Rahlfs, P., 207.Raichinschtein, Z., 435.Raisin, C. G., 58, 229, 279, 291, 292.Raistrick, H., 261, 262, 369.Rajmann, E., 454.Rake, G., 262.Ram, S., 467.Ramage, G. R., 337, 338, 372.Rainan, (Sir) C. V., 126.Ramanadham, M., 126, 201.Ramsay, (Sir) W., 137.Ramsey, W. E., 34.Rao, S. R., 126.Raper, R., 372, 373.Rapson, W. S., 335, 340.Rasetti, F., 26, 29, 30, 31.Rau, M. A. G., 126, 127,129, 132.Rauch, H., 348.Raudnitz, W., 278.Ravonswaay, H. J., 465.Ravitsch, G. B., 202.Rawson, X. G., 444.Ray, B.C., 58.R&y, N. N., 162.Ray, S. N., 388.Raymond, A. L., 248.Read, J., 308.Reader, V., 386.Record, B. R., 258.Record, P. R., 391.Redlich, O., 58, 99, 294.Redos, M., 249.Reerink, E. H., 353, 391.Regener, E., 33.Reger, M., 459.Regler, H., 163, 232.Rehm, K., 172.Rehorst, K., 263.Reichsl, S. von, 347, 348, 351.Reichstein, T., 202, 247, 303, 359,360, 395, 396.Reid, R. D., 192.Reindel, I?., 343, 348.Reinemund, K., 254.Reissner, R., 439.Reitz, O., 99, 101, 102.Remesov, I. A., 356.Remy, E., 262.Renard, P., 186.Renaudin, J., 468.Rencher, E., 192.Revillon, G., 458.Reychler, A., 104.Reynolds, D. S., 446.Ricci, J. E., 446.Rice, 0. K., 93.Richards, T. L., 202.Richardson, J. R., 23, 31.Richardson, T., 270, 271, 275.Richardson, W.A,, 259.Richter, G., 254.Ridoal, E. K., 93, 113, 114, 116.Ridenour, L. N., 16.Riederle, K., 400.Riedl. E., 137.Ries, H. E., 115, 117.Riesch, L. C., 117, 464.Riley, H. L., 190.Rinaldi, E., 387.Rim, €1. W., 202.Ripan-Tilici, R., 436.Rittenberg, D., 355.Rittenberg, S. C., 439.Ritter, H., 268.Rivoir, L., 223.Roaf, D., 24.Roberg, M., 409.Roberts, A., 19.Roberts, E. W., 202.Roberts, I., 435.Robertson, G. J., 308.Robertson, J., 404.Robertson, J. M., 46, 77, 80, 160, 161,198, 214, 218, 221, 222, 223, 298.Robinson, (Mrs.) A. M., 309, 332.Robinson, C., 104.Robinson, H. G. B., 106.Robinson, H. M., 461.Robinson, R., 266, 276, 299, 305, 325,328, 334, 335, 336, 337, 338, 339,340, 369, 380.Robinson, R.J., 457, 463.Robinson, R. M., 190.Roblin, R . O., 320.Robson, W., 402.Roche, A., 468.Rochelmeyer, H., 378.Itochow, €2. G., 147.Rockstroh, J., 181.Rocquet, P., 186, 187.Rodebush, W. H., 74, 86, 94.Rodowskas, E. L., 151.Roe, (Miss) E., 303, 325, 332, 347,Ronsberg, H. E., 373.Rogers, E. I?., 376.RogoB, J. M., 395.Rohds, G., 430.Rohrner, R., 387.Rohs, H. L., 446.Rolinski, J., 132.Rollefson, G. K., 93.Romberg, E., 176.Romeyn, H., 280.Rona, E., 26.Rosdahl, I<. G., 462.Rose, F., 205.Rose, J. L., 17.Rose, W. C., 401, 402, 403.Rosen, N., 39, 86.Rosenberg, A., 36.Rosenberg, H. R., 398, 399.360INDEX OF A'ZJTHORS' NAMES. 489Rosenberg, S., 94.Rosenfeld, A. D., 370.Rosenhcim, M. L., 407.Rosenheim, O., 115, 354.Rosenkevitsch, L., 29.Rosenmund, K.W., 30G.Rosenthal, J. E., 53, 55, 62.Rosner, L., 387.Ross, J. R., 461.Roth, A., 407.Roughton, F. J. W., 97.Rousselot, I,., 355.Roy, S. N., 436.Royen, P., 184, 185.Rubenstein, B. N., 406.Rubinstein, V., 377.Rudnev, N. A,, 441.Rudolph, E. A., 295, 297, 298.Rudy, H., 386.Ruff, O., 145, 147, 148, 149, 151.Ruggli, P., 369.Ruhkopf, H., 250.Ruhoff, J. R., 280.Rumbaugh, L. H., 19, 34.Rusinov, L. B., 29.Russell, P., 128.Russell, W. R., 384.RUSSO, M. J., 468.Rusznyak, S., 390.Rutherford, (Lord), 20, 27, 28, 143.Ruzicka, F. C. J., 304, 323.Ruzicka, L., 202, 268, 295, 296, 297,298, 299, 300, 301, 302, 303, 304,,305, 306, 307, 309, 310, 312, 316,324, 331, 332, 337, 343, 344, 345,353, 354, 356, 357, 358, 359, 368,398, 399.Rydon, H.N., 327.Rygh, L., 353.Rykinek, A,, 437.Rzymowska, C. J., 444, 445.Sa, A., 436.Sabatier, P., 306.Sachsse, H., 43, 57, 92.Sachtleben, R., 135, 138, 139, 140.Sack, H., 119.Sah, P. P. T., 465, 466.Saha, N. K., 16.Saini, H., 209.St. Helens, H., 34.St. John, E. C., 71.St. Pfau, A., 310.Saito, K., 377.Saiyed, I. Z., 379.Sakamoto, Y., 99.Salomon, G., 93, 96, 368.Salvia, R., 223.Salzer, F., 102.Samant, K. M., 347, 350, 351, 390,Samis, C. S., 104, 110.417.Sampson, M. B., 15, 16.Samuel, R., 173, 178.Sanchez, J. A., 467.Sandell, E. B., 448.Sandermann, W., 269.Sanders, J. P., 442.Sanderson, J. A., 54.Sandow, W., 145.Sarkar, P. B., 58, 455.Sassaman, H.L., 351, 391.Saunders, B., 323.Sauter, E., 197, 224.Sauter, F., 61.Sawada, K., 401.Schtidel, K., 231.Schaefer, V. J., 117.Schaefer, W., 262, 336.Schales, O., 381.Schantarowitsch, P. S., 03.Schar, M., 97.Schartner, H., 274.Schdanowitsch, J., 377.Scheel, K. C., 464.Scheffer, 446.Schellenberg, H., 303.Scheloumova, 0 ., 40 8.Schenck, R., 156, 185.Schenk, F., 352, 390.Schenk, M., 463.Schenk, P. W., 184.Schenkel, H., 229.Scherber, G., 408.Scherp, H. W., 262, 263.Scherrer, J. A., 440, 442.Scherrer, W., 367.Schertz, F. M., 429.ScMner, R., 301.Schindler, T. D., 464.Schinz, H., 298.Schischakov, N., 205, 206.Schlapp, R., 51.Schlee, R., 135, 139.Schleede, A., 191.Schlenk, W., 319.Schlittler, E., 334.Schmahl, N.G., 154, 157.Schmidt, H., 308.Schmidt, J., 154, 156, 157, 344.Schmidt-ThomB, J., 344.Schnorrenberg, E., 156.Schoeld, E. A., 98.Schoeller, W., 356.Schoeller, W. R., 443, 456.Schon, K., 296, 339.Schoenheimer, R., 228, 341, 343, 344,Sch~nheyder, F., 394.Schiipf, C., 202, 370, 372.Schtipp, K., 254.Scholz, H., 253.Schoor, A. van, 354.Schopfer, W. H., 384.Schossberger, I?., 196.353, 354, 355490 INDEX OF AUTHORS' NAMES.Schramm, G., 338, 343.Schroer, H. C. S., 97.Schroeter, G., 270, 314, 315, 336, 337.Schtschepkin, G., 29.Schtschigol, M. B., 449.Schtschukina, M. N., 381.Schubnikov, L. V., 29.Schuler, H., 17.Schuth, TV., 181.Schutz, W., 207, 211.Schulman, 5. H., 113, 115, 116.Schulte, W., 343.Schulz, W., 446.Schulze, A., 203.Schulze, G .E. R., 208.Schulze, If., 346.Schumachnr, H. J., 58, 92, 94.Schumb, W. C., 146, 441.Schuppli, O., 279.Schwarz, K., 901.Schwarz, R., 189.Schweinhagen, R., 204.Schwenk, E., 301.Scott, A. D., 95.Scott, A. W., 450.Seaborg, G., 23.Seddon, R. V., 93.Seelig, 5. F., 406.Segr6, E., 29.Seidel, C. F., 295, 300, 310.Seligman, A. M., 329.Selinov, I. B., 25.Seljakov, N., 217.Selwood, P. W., 181.Selwyn, E. W. H., 468.Semmler, F. TV., 315, 316.Sen, D. C., 436.Sen-Gupta, S. C., 304, 319, 320, 381,Senger, N., 245.Serini, A., 356.Seshacharyulu, E. V., 410.Seshadri, T. R., 435.Sevag, %I. G., 263.Sewig, R., 459.Shankar, J., 223.Shapiro, iJ. G., 97.Sharratt, E., 158, 160, 168, 169.Sheldrick, G., 270, 271, 272, 300, 328.Shennan, R.J., 443.Sheppard, S. E., 436,454.Sherman, A., 36, 37, 40, 59, 86, 95,Sherman, J., 46, 66.Sherman, R., 406.Sherr, R., 16.Sherwood, I. R., 297, 339.Shibata, K., 422.Shibata, Y., 175.Shilrazono, N., 466.Shildneck, P. R., 231.Shimizu, T., 355.Shinoda, J., 273.327.209.Shoppee, C. W., 234.Shorland, F. B., 463.Short, W. F., 297, 399, 304, 339, 340.Shorter, A. J., 168.Shrowsbury, C. L., 459.Shriner, R. C., 236.Shrivastava, D. L., 265.Shute, H. L., 115.Sickman, D. V., 93.Sidgwick, N. V., 74, 76, 77, 80, 84,Siebert, C., 319.Siede, B., 469.Sioverts, A., 187.Signer, R., 224.Silberstein, A., 214.Silvester, W. A., 287.Simard, G. L., 225.Simeons, A. T.W., 405.Simon, A. F. J., 278.Simons, E. J. H., 353.Simonsen, 5. L., 169, 341.Simpson, J. C. E., 347, 365, 379.Simpson, S. L., 399.Sinelnikov, C., 29.Singer. E.. 346. 393.132, 146, 165, 282, 284.Sinih,'A.,'96. 'Singh, B. N., 416, 417, 419, 428.Singh, TV., 406.Singleton. E., 96.SirEar, S.- C.,-217.Sisson, W. A., 225, 226.Sitte, K., 16.Skobeltzyn, D., 32, 33.Shimshire, G. W., 461.Slack, F. G., 432.Slater, R. H., 461.Sleator, W. W., 67.Slotta, K. H., 344.Small, P. A., 292.Smith, A. F., 225.Smith, C., 195.Smit>h, E. F., 439.Smith, E. L., 111, 456.Smith, F. G., 444.Smith, G. F., 434, 443.Smith, G. van S., 395.Smith, H. A,, 280.Smith, €3. G., 276.Smith, J. C., 281.Smith, J. D. M., 182.Smith, J.E., 464.Smith, J. H. F., 443.Smith, J. M., jun., 442.Smith, 0. W., 398.Smith, P. T., 188.Smith, S., 362, 374, 376.Smith, T. B., 451.Smith, W. R., 94.Smits, A., 209.Smyth, C. P., 119, 131, 132,133.Smoluchowski, R,., 16.Snell, A. H., 23INDEX OF AUTHORS' NAMES. 491Snethlage, H. C. S., 97.Snoek, J. L., 132.Sobotka, R., 265.Soff, K., 256, 259.Soller, W., 204.Solornos, G. I., 467.Solowiejczyk, S., 460.Soltner, K., 201.Soltys, A., 378.Soltzberg, S., 252.Somasundram, S., 405.Soule, B. A., 449.Spacu, G., 172, 437, 438.Spady, J., 295.Spath, E., 278, 368, 370, 376, 380,Spahedda, A., 262.Spanhoff, R. W., 360, 396.Spencer, J. F., 193, 194.Spiers, F. W., 200.Spikes, W. F., 453.Spinks, J. W. T., 54.Spitzer, L., 447.Spohn, H., 425.Sponer, (Frl.) H., 36, 53.Spring, F.S., 342, 345, 347, 349, 350,351, 390, 392.Springall, H. D., 282.Spriskov, A. A,, 467.Squire, C. F., 291.Stacey, M., 261.Stackelberg, M. von, 153, 166.Stadeler, A., 440.Stamm, G., 337.Sfange, O., 353.Stanley, W. M., 227.Staples, L. W., 456.Starr,M. A., 34.Statham, F. S., 237.Staub, A., 369.Staudinger, H., 224, 256, 259, 267.Stauff, J., 220.Staveley, L. A. K., 94.Steacie, E. W. R., 92, 94.Steam, A. E., 86, 132, 133, 134.Steiger, M., 247.Steigmann, A., 436, 452.Stein, G., 238, 363.Steiner, H., 92, 101.Steinhauser, K., 463.Stenkhoff, R., 156.Stepanion, M. P., 409.Stephan, I., 233.Stephanowa, E., 32, 33.Stephenson, D., 408.StGrba-Bohm, J., 440.Stern, O., 49.Sternberg, H., 467.Sterrett, R.R., 117.Stetter, G., 18.Stcur, J. P. K. van der, 277.Stevens, D. S., 189.Stevens, R. E., 446.381.Stevenson, A., 336.Stmwnson, E. C., 35.Steward, W. B., 55.Stewart, G. N., 395.Stewart, K., 93.Stewart, P. A., 349.St,ewart, W. D., 418.Stiasny, E., 173.Stiepin, V. V., 434.Stitt, 3'. B., 55.Stobbe, H., 335.Stock, A., 83, 185, 186.Stokstad, E. L. R., 394.Stoll, A,, 364, 375, 421, 428.Stoll, M., 295, 298, 306, 367, 368.St,oll, w., 349.Stolze, E., 462.Stoner, E., 52.Storr, E., 387.Strachan, C., 47.Strafford, N., 458. 459, 460, 462, 463.Strain, H. H., 426.Stranathan, R. K., 17.Strating, J., 203.Straumanis, M., 191, 197, 202, 208.Stmmss, E., 400.Strebinger, R., 439, 446.Street, 5.C., 35.Stzenk, C., 148.Stricks, W., 58, 294.Striebel, H., 139.Strobele, R., 254.Strohecker, R., 456, 464.Stromberg, H., 299, 304, 340.Stroup, P. T., 146.Strunz, H., 206.Stuart, H. A., 125.Subbaramaiya, D. S., 126.Subrahmanyan, V., 410.Slick, H., 191.Suckful, F., 250.Suenaga, K., 132.Suess, H., 101.Sugden, S., 119, 158, 161, 165.Suginomo, M., 377.Sullivan, V. R., 434, 443.Summerson, I f J . €I., 458.Sun, C. E., 86.Sundararajan, I<. S., 201.Supplee, G. C., 351.Susko, J., 290.Suter, C. M., 369.Sutherland, G. B. B. M., 43, 54, 56,Sutherland, R. O., 86.Sutton, I;. E., 66, 75, 79, 120, 128,133, 218, 282.Suzuki, T., 308.Svegnikov, B. I., 103.Swank, H. W., 457, 458.Swarm, W.F. G., 34.Swift, E. H., 437.Swingle, W. W., 395.68, 62, 88492 INDEX OF AUTHORS’ NAMES.Swisher, 11. D., 99.Sylvester, N. D., 462.Syroliomsky, W. S., 434.Szabo, A. L., 95, 174.Szent-Gyorgyi, A., 389, 390.Szilard, L., 30.Szongott, H., 262.Taconis, K. W., 216, 217.Tage-Hansen, E., 394.Takhcs, I?,, 463.Takahashi, J., 277.Takanj, A., 400.Takaoka, M., 377.Tamm, R. I<., 429.Tanaka, Y., 175.Tananaev, N. A., 454, 455.Tananaeva, A. V., 454.Tanasescu, I., 250.Tandon, S. P., 410.Tao, T., 466.Taran, E. N., 434.Tate, J. T., 144, 188.Tatum, A. L., 404.Taubadel, H., 319.Taube, W., 152.Taylor, H. A., 93, 94.Taylor, H. S., 86, 291.Taylor, W. H., 223.Tchistov, V. O., 170.Teller, E., 32, 58, 63.Terlet, H., 445.Ter Meulen, H., 465.Terpstrrt, P., 223.Terrey, H., 172, 193, 201.Thatcher, W.H., 94.Thayer, S. A., 362, 397.Theilacker, W., 231.ThBnard, P., 184.Theorell, H., 462.Thiel, A., 457, 458, 463.Thiel, W., 458.Thiele, W., 305, 380.Thiessen, P. A., 220.Thilo, P., 139.Thomann, G., 302.Thomas, A. W., 173.Thomassen, L., 178.Thomis, G. N., 467.Thompson, A. J., 204.Thompson, H., 338.Thompson, Harold W., 93, 190.Thompson, Henry W., 334.Thompson, J. W., 57, 58, 279.Thompson, M. R., 375.Thorne, D. W., 411, 412, 414.Thorne, R. S. W., 458.Thornton, H. G., 413.Thornton, R. L., 23.Thorpe, J. F., 234, 336.Thurmon, F. M., 405.Thurston, J. T., 236.Tiemann, F., 315, 316.Tien, V. L., 302.Tien, Y. L., 331, 340, 341.Tien-Chi Wei, 96.Tiffeneau, M., 319.Tillman, J.R., 28, 30.Timmis, G. M., 374, 375.Titani, T., 99, 141, 144, 292, 293, 294.Titley, A. F., 110, 337.Titz, I. N., 307, 310, 312.Todd, A. R., 382.Tolansky, S., 17.Tollens, B., 274.Tolman, R. C., 89.Tomcsik, J., 262.Tomita, T., 401.Tomonaga, S., 33.Tompsett, S. L., 461.Tomsicek, W. J., 176.Topley, B., 58, 86, 91, 95, 100,Topley, W. W. C., 262.Tornianen, M., 415.Tougarinoff, B., 450.Trachtenberg, D. M., 308.Trapp, H., 446.Trautmann, G., 305, 347.Trautz, M., 89, 148.Travers, M. W., 93.Treadwell, F. P., 438, 439.Trebler, H. A., 462.TrBfouel, J., 407, 408.Treibs, W., 308.Trendelenburg, F., 70.Trogus, C., 226.Tscherkassov, V., 434.Tscherning, K., 359.Tschesche, R., 346, 355, 362, 363, 364,365, 366, 367, 379.Tschopp, E., 356, 359.Tseng, C.L., 465.Tseu, C. Z., 466.Tsuchida, R., 175.Tuan, H. C., 237.Tulene, V. J., 436.Tung, W. L., 466.Turin, J. J., 31.Turner, E. E., 230.Turner, H. A,, 112.Turova-Pollak, M. B., 305.Tutin, F., 379.Tuve, M. A., 19, 29.Twyman, F., 457, 459.279.Ubbelohde, A. R. J. P., 448.Ufimzev, V. N., 288.Uhl, A. H., 132.Uhlenbeck, G. E., 32.Uhlenhuth, P., 262.Ulich, H., 132.Ulvin, G. B., 429, 430.Umblia, E., 448INDEX OF AUTHORS’ NAMES. 493Urey, H. C., 55, 61, 141, 143.Urushibara, Y., 343.Uschakov, M. I., 170.Uyldert, I. E., 360, 396.Uzel, R., 454, 455.Vaidyanathan, R., 18.Vaisman, A., 407.Valenkof, N., 206.Vance, J. E., 439.Van den Bossche, 62.Vandoni, R., 467.Van Gemert, A., 35.Vanossi, R., 468.Van Vleck, J.H., 36, 37, 40, 41, 43,Van Voorhis, S. N., 23.Vanzetti, B. L., 275, 276.Vardy, E. C., 405.Vargha, L. von, 248.Vasiliev, A. A., 446.Vaubel, R., 456, 464.Vaughan, A. L., 144.Vaughan, W. E., 280.Vdoviszevski, H., 438.Veen, A. G. van, 298, 299, 307.Vegrtrd, L., 217.Veldkamp, J., 25.Venkateswaran, C. S., 58.Venning, E. M., 362.Verleger, H., 54, 58.Verweel, H. J., 212.Verwey, E. J. W., 203, 204.Vesterberg, A., 295.Vetter, H., 296, 304, 339, 382.Vickery, H., 400.Viennois, P., 387.Villiger, V., 294.Vinogradov, A. V., 444, 446.Virtanen, A. I., 415.Vocke, F., 268, 341.Voge, H. H., 44, 62.Vogel, A. I., 338.Voichescu, P., 172.VojU, F., 448.Volarovitsch, M.P., 202.Vorliinder, D., 319.Voskuyl, R. J., 141.Vostfebal, J., 440.VfeLt’al, J., 438.44, 51, 64.Wada, M., 401.Waddell, J., 351, 391.Wagner, C., 205.Wagner, G., 190, 209.Wagner-Jauregg, T., 343.Wagstaff, (Miss) A. I., 221.Wahl, M. H., 141.Wakkie, J. G., 427.Walden, G. H., 173.Waldmann, H., 268, 304, 309.Waldo, A. W., 202.VC’alen, R. J., 28.Walke, H. J., 140.Walker, J., 328, 334, 336, 340.Walker, R. H., 411, 412, 414.Wall, E. M., 463.Wall, F. T., 71.Wallach, O., 315, 319.Wallenfels, K., 378.Wallis, E. S., 356, 357.Walter, E., 348.Walther, A., 29.Walton, E., 403.Walton, E. T. S., 28.Wandrowsky, B., 463.Wang, H., 31.Wang, S. M., 465, 466.Wang, Y . , 343.Ward, A. M., 443, 451.Wardlaw, W., 158, 160, 163, 165, 168,Ware, L.W., 71.Warhurst, E., 96.Warren, B. E., 205, 208, 225.Warren, F. L., 360.Wassermann, A., 94.Waterhouse, E. F., 443, 456.Waterman, M. I., 277.Waters, W. A., 103.Watson, W. W., 17.Watters, A. J., 308.Webb, H. W., 443.Webster, K. C., 168, 159, 160, 162,Webster, L. E., 141.Webster, T. A,, 351, 354.Wechsberg, R., 190.Weeden, W. J. van, 223.Weekes, D. F., 30.Weevers, T., 267.Wehren, E., 408.Weibke, F., 207.Weidle, H., 278.Weidlich, G., 351.Weidlich, H. A,, 338.Weigle, J., 121, 209.Weil, K., 366.Weil, R., 316.Woiser, H. B., 212.Weiss, H., 319.Woiss, J., 95, 426, 427.Weiss, R., 296.Woissberger, A., 237, 289.Weith, W., 290.Woldon, L. H. P., 294.Wellmann, M., 191.Wells, A.F., 161, 163, 212.Wells, W. H., 20.Wonger, P., 443, 444.Werdar, F. von, 352, 353, 390.Wergin, W., 226.Werner, A., 173, 1’76.Werner, L., 343.169.163, 164494 INDEX OF AUTRORS' NAMES.Wertenstein, L., 31.Westgren, A,, 157, 207.Westphal, U., 344.Westphalen, T., 347.Wetherell, S., 438.Wetroff, G., €87.Wettstein, A., 344, 356, 357, 358, 359.Weygand, C., 201, 468.Weygand, F., 254, 386.Wheeler, A., 86, 91, 93.Wheeler, T. S., 103.Wheland, G. W., 44, 46.M7hitaker, 3%. D., 29.White, A. H., 465.White, D. E., 369.Whit,e, W. E., 461.Whitman, B., 361.Whitmore, F. C., 357.Whytlaw-Gray, R., 137, 145, 148.Wichers, E., 441.Wichmann, H. J., 446, 461.Widmaier, O., 255.Wiechmann, F., 208.Wicghard, C. W., 262.Wieland, H., 293, 306, 307, 345,Wien, M., 107.Wienhaus, H., 268.TiVierl, R., 65, 66, 67, 79, 82, S3.Wiese, O., 352.Wiesenberger, E., 179.Wieters, 388.Wiper, E., 30, 86, 88, 90.Wijk, A. van, 353, 391.Wilder, 0. H. M., 391.Wiles, A. E., 299, 304, 340.Wiley, R. H., 300, 315.Wilkins, E. S., jun., 461.Wilkins, T. R., 34.Wilkinson, D. G., 348.Willard, H. H., 180, 444, 446.Willerding, U., 366.Williams, D. A., 152.Williams, E. C., 466.Williams, E. F., 202.Williams, E. G., 98.Williams, G., 94.Williams, J. H., 20, 144.Williams, K. A., 459.Williams, R. R., 381, 384.Willis, G. H., 177.Willm, I. E., 152.Willoughby, C. E., 461.IVillstiitter, R., 279, 423.Wilm, D., 201.Wilman, H., 46, 201.Wilson, C. L., 58, 229, 232, 233, 236,279, 291, 292, 294.Wilson, E. B., 38, 47, 56, 58.Wilson, H. A., 143.Wilson, Y.'W., 412, 413.Wilson, R., 407.Wilson, T. L., 94.348, 354, 355, 364, 380, 463.Wind, A. EL, 331.Windaus, A., 305, 346, 347, 348, 349,350, 351, 352, 353, 354, 355, 361,363, 365, 36G, 390, 392.Winkler, W. O., 462.Winn, A. G., 458.Winogradsky, S., 408, 410, 414, 415.Winter, 0. B., 446, 461.Wintorfeld, K., 373.Wintersberger, K., 135, 139.Winterstein, A., 286, 304, 339, 421.Wintersteiner, O., 359, 361.Wirth, H. E., 457.Wirtz, K., 99.Wirz, H., 343.Wissink, G. M., 433.Witebsky, E., 265.Withrow, R. B., 459.Wittmann, G., 135.Wittner, F., 135.Wittstadt, W., 220.Wohler, L., 181.Wohl, K., 426.Woidich, K., 296.Wolf, K. L., 132.Wolfenden, J. H., 97, 292.Wolfes, O., 372.Woltf, A., 343, 344.WOE, E., 309.Wolfrom, 31. L., 250, 251, 252.Womack, M., 4-01.woo, s. c., 54.Wood, W. C., 103.Woodcock, J., 297, 339.~Voodrow, J. w., 433.Vfoods, H. J., 201, 226.Woodward, (Miss) I., 223.Woolloxall, J. L. D., 271.Wooster, W. A., 197, 201, 212.Worschitz, F., 226.Wright, H. R., 345.WU, c. s., 465.Wudstrup, I., 397.Wulf, 0. R., 284, 285, 286, 287.Wunclerlich, W., 362, 392.Wurm, O., 439.Wutke, J., 233.Wyart, J., 219, 223.Wyatt, P. F., 462.Wyckoff, R. W. G., 66, 222, 224,Wynne, A. AT., 467.Wynne, W. Y., 287.Wynne-Jones, W. I?. K., 93, 99, 101.227.Yagoda, H., 440.Yakushiji, S., 422.Yamamoto, M., 390.Yates, J., 347.Yates, R. C., 60.Yermolieva, 2. V., 409.Yntema, L. F., 180, 182INDEX OF AUTBORS’ NAMES. 495Yoo, J. H., 457, 458, 459.Yorke, W., 403.Yoshiki, Y . , 270, 273.Yost, D. M., 65, 57.Young, F. G., 258.Young, M. J., 95.Young, R. T., 35.Yudkin, J., 102.Yun-Pu Li, 96.Young, P. c., 339.Zacliariasen, W. H., 207.Zahn, C. T., 19, 20.Zajic, E., 278.Zandstra, T., 19.Zanks, A. M., 441.Zepf, G., 187.Zarewa, T., 28.Zeeman, P., 16.Zeis~, 177.Zeitschel, O., 233.Zelinski, N. D., 305, 306, 307, 306,309, 310, 311, 312.ZemplBn, G., 249, 255.Zener, C., 200.Zernike, P., 73.Zi’p, C. van, 468.Ziiva, S. S., 388.Zins, W., 439.Zintl, E., 139, 219.Zinzadze, C., 459, 460, 464.Zombory, L. von, 446.Zucker, T. I?., 353.Zuithoff, A. J., 202.Zusatz, 389

ISSN:0365-6217    

DOI:10.1039/AR9363300471

出版商:RSC    

年代:1936

数据来源: RSC

摘要:

INDEX OF SUBJECTS.Abietic acid, dehydrogenation of, 298,Absorption, infra-red. See underSpectra.Absorption density, measurement of,457.Acetal, hydrolysis of, in deuteriumoxide, 102.Acetic acid, lead tetra-salt, use of, insugar group reactions, 247.silver uranyl salt, crystal structureof, 197.Acetic acid, chloro-, hydrolysis of,in deuterium oxide, 102.esters, hydrolysis of aqueoussolutions of, 97.Acetobromoglucose, 251.action of, on 4 : 6-benzylidene-a-methylglucoside, 256.Acetone, determination of, 468.Ace tophenones, o - hydroxy -, fixationof double bonds in, 284.Acetyl groups, determination of, 468.Acetylene, molecular orbital of, 43.Acids, from naphthalenes a.nd tetra-lins, synthesis of, 326.Aconitic acid, detection of, 467.Aconitine, 376.Aconit oline, 37 6.Acraldehyde, addition of, to cyclo-Acriquine in malaria therapy, 406.Acrylic acid, addition of, to cydo-Actiniasterol, 353.Adenosine, absorption spectrum of,Adhatoda vasica, Z-peganine from, 370.Adrenal cortex, hormones of, 395.Adrenos t erone, 359.B-Adrenosterone, 395.2EtioaZZobilianic acid, 365.Agar, galactose from hydrolysis of,Aglycones, cardiac, 362.Alantolactone, degradation of, 303.Alcohols, aromatic, cyclo-dehydrationolefinic, cyclo-dehydration of, 316.unsaturated, cyclo-dehydration of,309.structure of, 268.oxidation of, 92.unsaturated, lactonisation of, 327.pentadiene, 94, 240.pentadiene, 240.253.251.of, 318.315.Aldehydes, detection of, 465.Aldehydo-d-mannose pentaacetate,Aldehydo-sugars, 250.Algze, sterols of, 346.Aliphatic compounds, structure of,Alkali azides, decomposition of, 93.borofluorides, structure of, 211.perchlorates, structure of, 211.halides, super-lattices in mixedcrystals of, 209.containing sterol ring system, 367.detection of, 468.lysis of, 96.ation of, 308.250.benzoyl derivatives, 252.218.Alkaloids, 370.Alkyl hydrogen sulphates, hydro-Allyl-A l-cycbhexene, dehydrogen-Alums, 194.Aluminium, determination of, 463.determination and separation of,lattice constants of, 202.Aluminium carbide, structure of, 156.Amides, optically active, rates ofAmines, detection of, 466.Amino-acids from nodular proteins,441, 442.racemisation of, 236.415.from protein hydrolysates, 399.sulphur -cont aining, 402.Ammonia, exchanw of deuteriumwith hydrogenbh, 92.production of, by Azotobacter, 408.Ammonium, detection of, 455.Ammonium azide, structure of, 210.bromide, crystallography of trans-chlorobromoiodide, structure of,hexanitratocerate as standard information of, 209.210.ceriometry, 434.94.Ammoresinol, 278.tert.-Amy1 chloride, decomposition of,Analysis, reagents for, 436.colorimetric, 456, 459, 467.instruments for, 457.organic, 467.inorganic, 433.qualitative, 448.quantitative, 433.magneto-optical, 432.nephelometric, 460.49INDEX OF SUBJECTS. 497Analysis, organic, 465.apparatus for, 468.qualitative, 465.quantitative, 466.volumetric, 433.Anawite, crystal structure of, 206.da : 6-Androstadien-17-one, 360.Androstene-3 : 17-dione, preparationd 5-Androsten-17-ol-3-one, 344.Aneurin, synthesis of, 381.5 : 6-Anhydroglucose 1 : 2-acetone,Aniline hydrochloride, equilibriuma- and fl-Anisaldoximes, equilibriumAnisotropy, diamagnetic, of aromaticAnthracene, hydrogenation of, 315.Antimony, detection of, 449.of, 357.249.of, with deuterium oxide, 293.of, 232.molecules, 5 1.structure of, 290.determination of, 438.determination and separation of,440.Antimony oxides, and their hydrates,crystal structure of, 209.Antimonates, structure of, 212.Antirachitic substances, 3 90.Antiseptics, 407.1-Arctigenin, 272.Arctium lappa, Z-arctigenin in seedsof, 272.Argon, bombardment of, withdeuterons, 23.Aromatic compounds, 279.Arsacetin, 403.Arsenic, determination and separa-tervalent, stereochemistry of, 237.Arsenicals, 403.Arundo donas, donaxine from, 380.l-Asarinin, 277.Asarum sieboldii, 1-asarinin from,Ascorbic acid, synthesis of, in w h o ,Asymmetric synthesis, 234.Atebrin, and its musonate, in malariatherapy, 405.Atoms, action of, with solid surfaces,47.determination of distances be-tween, from electron diffraction,70, 74.Atomic weights, 135.calculation of, from energy changesin nuclear transformations, 142.d-Atrolactic acid, replacement ofhydrogen by deuterium in, 229.bicyclo-[1 : 2 : 2]-Azaheptene, 237.Azides, structure of, 210.tion of, 440.277.387.urinary excretion of, 388.Azomethane, decomposition of, 93.Azotobacter, 408.w-Azotoluene, decomposition of, 94.structure of, 81.Bacillus dysente.lim, polysaccharideBacteria, metabolism and activity of,Barium, determination of, 444.Barium cadmi-bromide and -chloridetetrahydrates, structure of, 214.Eatyl alcohol, structure of, fromsurface films, 116.Benzaldehyde, o-nitro-, condensationof, with glycosides and sugars,249.a- and p-Benzaldoximes, 2 : 6-di-chloro -3-nitro-, equilibrium of,231.Benzene, diamagnetic susceptibilityof, 52.dipole moment of, in nitrobenzene,134.exchange of hydrogen for deuteriumin, 291.oxidation of, 93.structure of, 58, 83, 279.Benzene, bromo-, dipole moment of,in non-polar solvents, 125.chloro-, polarisation of, in varioussolvents, 118.Benzenesulphonamide, p-amino-,antiseptic action of, 407.BBnzidine, detection of, in presenceof tolidine, 468.Benz-1 : 3 : 3-bicycZo-d2-nonene, 325.Benzoic acid, sodium mlt, bromin-ation of, 287.Benzoinoxime, co-ordination com-pounds of, with metals, 167.Benzonitrile, dipole moment of, innon-polar solvents, 125.Benzonitrile, o-hydroxy-, structureof, 285.Benzophenone oximes, 2-hydroxy-,and their acetates, configurationof, 286.Benzopurpurin-B and -4B as indica-tors, 435.Benzpyrene, hydroxy-, 297.1 : 2-Benzpyrene, synthesis of, 339.2-Benzyldecalin, dehydrogenation of,307.1 -Benzylcyclohexanol, dehydration of,325.Bemylideneazine, decomposition of,94.4 : 6-Benzylidene-a-methylglucoside,action of acetobromoglucoseon, 256.from, 265.408.isotopes, 16498 INDEX OF SUBJECTS.Benzylmenthol, cyclisation of, 319.2 -Benz yl- tram-oc t a h ,ation of, 300.Berberine, detection of, 468.Berlin blue, structure of, 213.Berthierite, crystal structure of, 208.Beryllium, bombardment of, by deu-dehydrogen-terons, 21.by neutrons, 25.by y-rays, 26.detection of, 465.lattice constants of, 202.nucleus, mass of, 22.parachor of, in co-ordination com-Beryllium carbide, structure of, 156.dl-Bicuculline, synthesis of, 380.Bile, shark’s, scymnol from, 355.toad’s, trihydroxybufosterochol-enic acid from, 355.Bile acids, 353.dehydrogenation of, 303.Bilianic acids, 345.Biochemistry, 383.animal, 384.plant, 408.a-Bisabolol, 316.Bismuth, detection of, 453, 454.determination of, 438.determination and separation of,formation of radium-E from, 23.Bismuthials in syphilis therapy, 404.Bisnorcholanic acid, 3 : 7 : 12-tri-hydroxy-, 355.Black tongue in dogs, 385.Bond distances, 74.n- and iso-Borneols, relationship of,Boron, allotropy of, 203.bombardment of, by deuterons, 21.by neutrons, 24.by protons, 20.determination of, 447.fluoride dihydrate, structure of,pounds, 165.438.241.Boron amide, structure of, 83.Bromates. See under Bromine.Bromides.See under Bromine.Bromine, determination of, inpresence of iodine, 447.interatomic distance in, 74.kinetics of reaction of, withhydrogen, 89.Bromides, detection of, 462.determination of, 447.Brornates, detection of, 452.determination of, 447.Bruoine in sulphuric acid as indicator,435.Buckwheat plants, effect of artificiallight sources on dry matterproduction in, 418.210.Bufosterocholenic acid, trihydroxy-,from bile of toads, 355.Bufotalin, structure of, 364.Burdock.See Arctiurn Eappa.tert.-Butyl chloride, decomposition of,94.1.1-Butylcyclopentane, hydrogenationof. 311.Butyric acid, a-amino-/?-hydroxy-,growth-promoting action of, 401.“ BYSSUS,” structure of, 226.Cadalene, 295, 298.Cadmium, at. wt. of, 142.detection of, 450, 455.isotopes, 17.lattice constants of, 202.Cadmium halides and oxides, 193.sulphate hydrate, structure of, 211.Calciferol, 349.antirachitic value of, 391.structure of, 390.Calcium, allotropy of, 203.detection of, 451.,determination of, 444.Calcium sulphate hydrates, structureCamphor, determination of, 467.Camphoric acid, bismuth ethyl ester,in syphilis therapy, 406.Canaline, 400.Canavanine, 400.Carane, dehydrogenation of, 309.Carbamide, detection of, 467.Carbazides, detection of, 467.Carbides, structure of, 153.Carbohydrates, 245.Carbon, at. wt. of, 144.of, 212.bombardment of, by deuterons, 21.bonds, single, double, and treble,determination of, in organic com-gaseous, 190.valency angles of, 84.valency states of, 43.bital of, 43.fluorides, 149.suboxide, structure of, 81.dioxide, determination of, 448.distances of, 79.pounds, 465.Carbon tetrachloride, molecular or-isosteres of, and their properties,43.Carbon-bromine distance, 75.Carbon-chlorine distance, 75.Carbon-fluorine distance, 77.Carbon-iodinq distance, 76.Carbon-nitrogen distance, 80.Carbon-oxygen distance, 80.Carbonyl chloride, carbon-chlorineCarbonyls, metallic, 176.bond in, 46INDEX OP2 -0-car box ybenz ylindan- 1 -one, brom-ination and racemisation of, 233.Carpesterol, 379.Catalysts, dehydrogenation, 294.Catalytic dehydrogenation, 294.with metals, 305.with selenium, 299.with sulphur, 295.Catechol.Bee Pyrocatechol.Cellobiose oxime nonuacetate andsemicarbazoiie, structure of, 261.Cellulose, cotton and wood, 260.derivatives, films of, 116.nitration of, 226.structure of, 225.structure and particle weights of,Central force field, 61.Cerium, detection of, 455.258.isotopes, 16.magnetic susceptibility of, 181.separation of, 181.Getylpyridinium bromide, conductiv-Cevanthridine, 3 77.Cevanthrol, 377.Chelate compounds, 283.Chemotherapy, 403.Chenodeoxycholic acid, 353.Cherry, w-inter.See Solanum peudo-Chicks, deficiency disease in, due t oChitin, structure of, 225.Chlamydomonas, effect of temperatureon respiration and assimilationin, 418.Chlorates. See under Chlorine.Chiorella pyrenoidom, effect of ultra-violet light on photosynthesis in,418.Chlorine, at. wt. of, 139.interatomic distance in, 74.structure of, 217.Chlorine dioxide, structure of, 79.Hydrochloric acid, exohnge ofdeuterium with hydrogen in, 92.Chloratcs, determination of, 447.Perchloric acid as oxidising agentfor chromium, 442.Chlorophyll, chemistry of, 420.condition of, in plants, 427.effect of nutrition on formation of,in plants, 428.formula for, 422.Chlorophyll-a and -b, 421.“ Chloroplastin,” 428.Cholanthrene, preparation of, 332.synthesis of, 339.Cholera vibrio, polysaccharide from,Cholestenols, 352.d4- and A 5-Cholestenones, 344.ity curve of, 105.capmum.lack of vitamin-K, 394.265.SUBJECTS.499Cholesterol, dehydrogenation of, 305,irradiated, antirachitic value of,isomerides of, 341.309.391.p-Cholesterol, 343.alloCholes terol, 342.epiCholestero1, 342.epialZoCholestero1, 342.Cholic acid, 353.dehydrogenation of, 302.a- and ,!3-apoCholic acids, 348.Chromium, determination and separa-Chromium hemcarbonyl, 176.Dichromates, detection of, 455.Chrysene, from sterols, 302.synthesis of, 324.Chrysenes, dime syntheses with, 329.Chrysofluorene, 323.Chymotrypsinogen, structure of, 226.Cinobufagin, structure of, 364.Citergic acid, 375.Citric acid, detection of, 467.Cobalt, detection of, 450, 455.isotopes, 16.Cobalt ammines, heats oi formationand solution of, 172.chloromnm%nobisdime thylgly oxime,effect of powdered qwrtz onoptical activity of, 175.compounds, complex, rotation andconfiguration of, 173.nitrosyltricarbonyl, parachor of,166.sulphides, crystal structure of, 207.tion of, 442.d- and Z-Cocaines, detection of, 468.Co-enzyme R, 414.Colloids, 103.electrolytic, with long hydrocarbonchains, 103.Colorimeters, 457.Colorimetric analysis, organic, 467.photometric, accuracy of, 459.quantitative, 456.Colour, measurement, of, 466.Conidendrin, 274.Co-ordination compounds, 157.complex, 213.Copaene, dehydrogenation of, 298.Copper, bombardment of, with deu-terons, 23.detection of, 454.detection and determination of,determination of, 439, 462.Copper phthalocyanine, 100.Lbpric chloride &hydrate, structurechloride &hydrate and pyridineP-diketones, 169.450.in organic3 compounds, 406.of, 213.derivative, 160500 INDEX OF SUBJECTS.Copper :-Cuprous iodide, co-ordination com-pounds of, with arsines andphosphines, 167.oxide, red and yellow, 291.salts, ammoniates of, 172.aelenide, sulphide, and telluride,crystal structure of, 207.Oorticosterone, 360, 396.Cortin, 359.Crotonaldehyde, addition of, to cydo-pentadiene, 240.trans-Crotonyl chloride, addition of,to cyclopentadiene, 240.Crystals, action of atoms and mole-cules with surfaces of, 47.molecular, 214.paramagnetism of, 51.structure analysis of, 196.structure factor tables for, 198.Crystallography, 196.Cubebin, 273.Cupressus obtusa.See Cypress,Japanese.Cupric and Cuprous compounds.See under Copper.Cyanides. See under Cyanogen.Cyanogen, structure of, 82.Cyanides, determination of, 464.Cyanuric triazide, structure of, 81, 83.Cylindrite, indium in, 195.p-Cymene from terpenes, 296.Cypress, Japanese, l-hinokinin fromhinokiol from resin of, 270.Cysteylglutamine, 397.resin of, 273.Dacrydium biforme, manool from,Dacrydium colensoi, manoyl oxideDecalin, dehydrogenation of, 307.trans-Decalin, dehydrogenation of,trans-/3-Decalone, dehydrogenation of,Dehydroandrosterone, configurationepiDehydroandrosterone, 357.7-Dehydrocholesterol, 352.irradiated, antirachitic propertiesDehydroneoergosterol, preparationDehydrogenation, 2 9 4.Dehydrolumisterol, 349.7-Dehydrositosterol, irradiated, anti-7-Dehydrostigmasterol, irradiated,dLDemethoxymatteucino1, resolution269.from, 269.300.305.of, 356.of, 390.of, 312.rachitic value of, 392.antirachitic properties of, 391.of, 231.Dermatitis, in chickens and in rats,385.Deuterium (heawy hydrogen) atoms,exchange of, with hydrogenatoms, 92, 99.bombardment of, by y-rays, 26." labelling " molecules by intro-duction of, 354.proportion of, in hydrogen, 144.reactions with, in solution, 98.Deuterium compounds, aromatic, 291.oxide (heawy water), exchange re-actions of, with polyphenols,293.ionic product of, 99.kinetics of reactions in, 100.Deut ero -compounds, s tereochemis tryof, 228.Deuterolysis, 98.Deuterons, bombardment of nucleiby, 20.Diacetylene, structure of, 82.2 : 4- and 4 : 6-Diacetylresorcinols,structure and properties of, 283.Dialk y lnaphthalenes , dihydroxy - ,properties and configuration of,288.Diamino-acids from proteins, adsorp-tion of, by Japanese acid clay,466.Diazoacetic acid, ethyl ester, effectof deuterium oxide on decom-positionof, 101.hydrogen-ion catalysis of, 97.Diazomethane, structure of, 81.Dibenzanthracene, crystal structureof, 223.Dibenzoylkojic acid, 253.Diborane, molecular orbitals in, 43.Dicarbon, 190.Dichromates. See under Chromium.Dickite, crystal structure of, 206.Dicyclic compounds, synthepis of,from olefins, 316.Dienes, condensation of, with quin-ones, 328.heats of hydrogenation of, and ofbenzene, 280.syntheses with, 328.Diethylbromogold, 169.1 : 2-Diethylcyclohexene, dehydrogen-ation of, 303.Digitalis purpurea, saponins from,365.Digitogenin, 365.Digoxigenin, 362.22-Dihydroergosterol, irradiation of,352.irradiated, antirachitic value of,392.a-Dihydrofucosterol, identity of, withsitosterol of wheat germ oil, 345.structure of, 365INDEX OF SUBJECTS.501a- and y-Dihydrolysergic acids, 375.Dihydronaphthalene, dehydrogen-ation of, 307.Dihydronaphthoic acids, substitutedesters, preparation of, 333.Dihydrophenanthrene - o- dicarboxylicanhydrides, 333.42 : 6-Dihydroterephthalic acid, di-met h y 1 ester , dehydrogenationof, 307.Dihydrotheelin. See CEstradiol.1 : 3-Diketodecalin, preparation of,Diketohexahydrochrysenes, 337.Diketones, cyclo-dehydration of, 333.1 : 5-Diketones, cyclisation of, 333.( - )ay-Dimethylallyl alcohol, asym-metric synthesis with, 234.6 : 6’-Dimethyldiphenyl, 2 : 2’-di-amino-, racemisation of, 94.1 : 2-Dimethylphenanthrene, syn-thesis of, 338.6 : 7-Dime thyl-9-d-riboflavin- 5’-phos-phoric acid, 386.Dicyclopentyl, dehydrogenation of,310.Diphenic acids, reduced, pyrolysis of,341.Diphenyl, 2 : 2‘- and 3 : 3’-dichloro-,electric moments of, 237.Diphcnyl-2-acetic acid, cyclo-dehydr-ation of, 339.Diphenylbenzidinesulphonic acid,sodium salt, as oxidation-reduc-tion indicator, 435.Diphenylcarbazide as indicator, 435.Diphenyldinaphthylallene, resolutionof, 230.as-Diphenylethylene, polymerides of,319.Dipole moments, influence of sol-vents on, 117, 132.measurement of, in polar solvents,134.Di-n-propylbromogold, 169.Dipyridine iodine nitrate, 170.Dipyridinobenzenes, reduced, 369.Disaccharides, 245.Diterpenes, 267.Di-o-tolyl, dehydrogenation of, 299.o-Divinylbenzene, properties andDivinyl ether, decomposition of, 93.Djenkolic acid, 402.Dodecahydrobenzanthracene, de-hydrogenation of, 301.Dodecahydrochrysene, dehydrogen-ation of, 296, 301.Dodecahydrophenanthrone, 335.Donaxine, 380.Dwema ammoniacum, ammoresholfrom, 278.Drop reactions, 453.331.structure of, 289.Earth, rare-earth elements in crust ofthe, 178.Earths, rare, 178.colours of salts of, 182.separation of, 179.strength of, as bases, 182.Eka-osmium, formation of, 26.Electrons, diffraction of, 65.analytic interpretation of, 72.radial distribution method ofexamination of, 73.Elements, isotopes of, 15.Equation, Debye, modifications of,126.Equilenin, 360.Equilin, 360.isoErgine, 375.Ergobasine, 375.Ergoclavinc, structure of, 374.Ergomonamine, 375.Ergometrine, 375.Ergometrinine, structure of, 374.Ergosinine, 374.Ergostane-3 : 6-dione, 347.Ergostanetriol, 347.Ergostenedione, 347.a-, 8-, and y-Ergostenols, 348.Ergosterol, degradation of, 361.structure of, 346.neoErgostero1, 343.dehydrogenation of, 346.Ergostetrine, 375.Ergot alkaloids, 374.Ergotamine, 374.Ergotaminine, 374.Ergotocine, 375.Esters, hydrolysis of, 95.effect of deuterium oxide on, 101.ketonic, cyclo-dehydration of, 330.Ethane, molecular orbital of, 43.Ethane, nitro-, effect of deuteriumoxide on neutralisation of, 101.Ethyl bromide, dipole moment of, innon-polar solvents, 125.ether, decomposition of, 94.Ethylamine, decomposition of, 93.Ethylene, molecular orbital of, 43.dichloride, dipole moment of, 132.oxide, decomposition of, 93.platinous chloride, structure of, 178./3 -E t h ylgalac t o furanoside , 2 5 1,Ettringite, crystal structure of, 206.Eucalyptus oil, E-eudesmin from, 276.Eudalene, 295, 297, 327.1-Eudesmin, 276.Eudesmol, dehydrogenation of, 297.Euglena gracilis, effect of ultra-violetEuropium, separation of, 180.light on photosynthesis by, 418.Fagara xanthoxyloides, xanthotoxinfrom, 368502 INDEX OF SUBJECTS.Farnesene, 3 16.Farnesol, dehydration of, 316.Ferric salts.See under Iron.Ferricyanides, detection of, 452.Ferrocyanogeii ions, structure of, 40.Fibre structures, 224.Fibrin, blood, amino-acids from, 400.Fichtelite, dehydrogenation of, 298,309.Yicus carica, ficusin from, 368.Ficusin, 368.Films, thickness of, in relation toX-ray broadening, 201.transference of, from water surfacesto golids, 117.unimolecular, 112.Flavanone, 7-hydroxy-, resolution of,Flavine, structure of, 254.Fluorene, formation of, by dehydro-genation, 31 1.structure of, 223.Fluorene, 2-bromo-, asymmetric syn-thesis with, 236.Fluorescence in relation to photo-synthesis, 425.Fluorine, at.wt. of, 144.bombardment of, by protons, 19.determination of, 446.preparation of, 145.y-rays from, 19.halides, 146.dioxide, decomposition of, 94.oxides, 147.Hydrofluoric acid, anhydrous, criti-cal temperature of, 152.Fluorides, acid, 151.Foods, anti-chicken-dermatitis factorin, 385.Force constants of molecular bonds,64.Force fields, 60.d-Fructose, synthesis of, 245.fi-Fructosediacetone, oxidation of,Fucostanol, 345.Fucosterol, 345.Furanose derivatives from galactose,251.Furtondicarboxylic acid, and its iso-propylidene derivative, 248.231.Fluorine compounds, 146.247.Galactans, 261.dl-Galactose heptaacetate, 250.Gallium, detection of, 455.determination and separation of,Gas reactions, 91.Gases, molecular structure of, fromGegenions, 104.442.electron diffraction, 65.Gelatin, amino-acids from, 399.Gentiobioss, synthesis of, 256.Geraniol, cyclisation of, 3 16.Geraniolens, cyclo-dehydration of,Germanium, at.wt. of, 136.determination of, 463.Germanium disulphide, crystal struc-ture of, 207.Gitogenin, structure of, 365.Glass, oxide, 205.Glauconite, crystal structure of, 206.Globin, structure of, 400.1 dGlucopyranosidocy tosine, 255.Glucose, determination of, 468.mutarotation of, 100.315.effect of deuterium oxide on4-phosphate, 248.reactions of, with bases, 245.Glucose, g-thio-, 249.l-P-Glucosidofructose, synthesis of,2 -/3 -Glucosido - a-glucose, 25 6.Glucosone, and its tetrabenzoyl de-6- Glucosylpiperidine, 249.Glucoxazoline, p-hydroxy-, and p-Glutaminylcysteine, 3 97.Glutathione, relation of, to ascorbicsynthesis of, 402.Glycocholic acid, 354.Glycodeoxycholic acid, 354.Glycogen, structure of, 225.Glycosides, 245.Glyoximes, copper co-ordination com-pounds with, 168.Gold, at.wt. of, 142.determination of, 438.sols, particle size of, 201.valency of, and its co-ordinationcompounds, 169.Goniometer, Weissenberg, 197.Gramine, 379.Graphite, chemistry of, 190.particle size of, 201.Guaiacunz oficinale, guaimetic acidfrom resin of, 270.Guaiaretic acid, 270.Guanine-uridylic acid, 254.Gum arabic, aldobionic acid from,255.rivative, 252.thiol-, 249.acid, 389.262.Phmoglobin, muscle, combination of,with oxygen and carbon mon-oxide, 97.Hkmoglobins, 400.Hauerite, crystal structure of, 208.Heat of hydrogenation, 380.Heliotric acid, 377.Heliotridan, and hydroxy-, 377503 INDEX OF SUBJECTS.Heliotridine, 377.Heliotrine, 377.HeZiotropium lasiocarpum, alkaloidsHelium, scattering of, by lithium andHelminthosporium, ravenelin from,Hemlock, Japanese, tsugaresinolHepta - acetylgentiobiuronic acid,Heterocyclic compounds, 367.Hexadeuterobenzene, preparation of,Raman spectrum and structure of,structure of, from spectra, 58.Hexae t hylbenzene, crys t a1 s true tureHexahydrobenzylbenzoic acids,Hexahydrochrysenes, 338.Hexahydrofluorene, dehydrogenationHexahydrohydrindene, dehydrogen-Hexahydrozingiberene, dehydro -Hexamethylbenzene, hezabromo -,cycZoHexane, dehydrogenation of,cycZoHexanone, dehydrogenation of,cycloHexenones, synthesis of, 336.Hexoxidase, 389.cycZoHexylmethylcyclopentane, de-hydrogenation of, 3 10.2-cycZoHexylnaphthalene, dehydro-genation of, 296, 300.cycZoHexylcycZopentane, dehydro-genation of, 310.dl- and Z-Hinokinins, 273.Hinokiol, 270.Hormones, 395.from, 377.sodium fluorides, 49.369.from, 274.methyl ester, 264.291.280.of, 223.cyclisation of, 339,of, 300, 307.ation of, 307.genation of, 307.crystal structure of, 223.306.297.in naphthalene, 296.nomenclature of, 360.mals, from testicular extracts, 358.cest rogenic nitrogenous, 362.sex, 356, 397.derivatives, 281.Hydrindene, configuration of, 281.Hydrindenes, bromo-, dipole momentsof, 282.Hydroaromatic compounds, poly-cyclic, synthesis of, 312.Hydrocarbons, aromatic, formationof, by cyclo-dehydrogenation ofaliphatic hydrocarbons, 3 11.Hydrochloric acid.See underChlorine.tetracyclic, synthesis of, 323.Hydrofluoric acid. See u&rHydrogen bonds, conditions for form.detection of, by spectra, 58.exchange of, with deuterium, 92.ions, determination of, 464.kinetics of reaction of, withmolecules, Heitler-London theoryHydrogen chloride.See Hydrochloricfluoride. See Hydrofluorio acidperoxide, detection of, 452.sulphide, solid, lattice constant andHydrophenanthrene derivatives, syn-Hydrophenanthrenes, diene syn-Hydroxyl groups, determination of,Hydroxylamine, detection of, 455.Hyodeoxycholic acid, 353.Hypophosphites. See under Phos-Fluorine.ation of, 285.bromine, 89.of, 38.acid under Chlorine.under Fluorine.optical properties of, 217.theses of, 327.theses in, 328.synthesis of, 319.infra-red absorption of, 285.466.phorus.Ice, structure of, 217.Imino-groups, infra-red absorptionof, 285.Immuno-polysaccharides, 261.Indicators, 434.effect of ionic micelle formationadsorption, 436.fluorescence, 435.on equilibrium point of, 110.Indigotin, isomeric change of, onfibre of dyed materials, 231.Indium, determination of, in minerals,195.Indole derivatives, 379.Inorganic analysis, qualitative, 448.quantitative, 433.Inosine, absorption spectrum of, 253.Insulin, structure of, 396.Iodates.See under Iodine.Iodides. See under Iodine.Iodine, determination of, 447.interatomic distance in, 74.Iodine nitrate, co-ordination com-pound of, with pyridine, 170.Iodides, determination of, 447. 'Iodates, determination of, 447.Periodic acid, detection of, 454.Ions, complex, acid-base propertiestherapy with, 397.of, 176.structure of, 210504 INDEX OFIonene, dehydrogenation of, 298,302.Ionisation potential, effect of mole-cular dipoles on, 42.Iridium as catalyst, 305.Iron, determination of, 463.determination and separation of,in relation t o assimilation in plants,isotopes, 16.Iron carbide, decomposition of, 156.pemtmarbonyl, parachor of, 166.dinitrosyldicarbonyl, parachor of,Ferric salts, compounds of, with441, 442.430.structure of, 165.166.o-phenanthroline, 17 3.Isatin, structure of, 221.Isomerism, geometrical, 231.Isosteres, 43.Isotopes, 15.Ivory nut, mannans in, 260.Jervine, 3 7 7.Kaempherol-Z-rhamnoside, 255.Kaolinite, crystal structure of, 206.Keratin, structure of, from variousKeratins, 400.Ket ohydrochrysenes, 335.l-Keto-7-hydroxy-1 : 2 : 3 : 4-tetra-hydrophenanthrene, synthesis of,338.3-Ketomanoyl oxide, 269.Ketones, dehydrogenation of, 297.detection of, 465.cyclic, formation of, 336, 341.Kinetics, chemical, 86.sources, 226.Lanosterol, 346.Lanthanum nitrates and selenste,Larch. See Larix decidua.Lariciresinol, 278.Larix decidua, lariciresinol from resinof, 278.Lasiocarpine, 377.Lead, detection of, 454.ation of, 453.438.183.de tee tion, determination, and separ -determination of, 461.determination and separation of,isotopes, 17.Lead compounds, stereochemistry of,monoxide, red and yellow, 192.sulphides, crystal structure of, 208.164.UBJECTS.Leaves, fluorescent substances from,426.photosynthesis in relation to chloro-phyll and water content of, 419.Lemon juice, vitamin-P from, 390.Light of varying wave-lengths, utilis-ation of, by plants, 417.ultra-violet, effect of, on photo-synthesis, 418.Lignanes, 270.Lignin, structure of, 267.Limonene, dehydrogenation of, 308.Linalool, cyclisation of, 316.Liquids, frequency of collisions in,Lithium, bombardment of, by neu-102.trons, 25.by protons, 19.isotopes, 15.y-rays from, 19.Lithium alum, preparation of, 194.isoLithobilianic acid, 345.Lithocholic acid, 353.Lucerne, effect of nitrates on nitrogenfixation and nodule formation by,413.Lumist erol , 349.Lupin alkaloids, 372.Lysergic acid, structure of, 374, 375.isoLysergic acid, 378.Magnesium, bombardment of, bydetection of, 451, 453.in relation to assimilation inMagnesium carbide, 157.Magneto-optical analysis, 432.Malaria in monkeys, atebrin andMaleic anhydride, addition of, t oto cyclopentadiene and its deri-Maltose semicarbazone, structure of,Mandelic acid, ammonium salt,, anti-Z-Mandelic acid, replacement ofManganese in relation t o assimilationManganese carbides, 157.Manganic sulphate as reagent inManganite, crystal structure of, 209.Mannans, 260.Mannosaccharodilactone, structureManool, 269.Manoyl oxide, 269.deuterons, 23.plants, 430.quinine therapy in, 406.therapy in, 405.abietic acid, 268.vatives, 240.251.septic action of, 407.hydrogen by deuterium in, 229.in plants, 430.volumetric analysis, 448.and properties of, 253505 INDEX OF SUBJECTS.Matai.See Podocarpus spicatus.Z-Matairesinol, 271.dl- and Z-Matairesinol dimethyl ethers,Melting-point apparatus, 468.Mercurials in syphilis therapy, 404.Mercury, detection and deterniin-determination of, 438, 462.Mercuric salts, determination of,Mesomerism, 44.Metals, detection of non-metallicquantum theory of, 203.catalytic, dehydrogenation with,noble, as catalysts, 306.272.ation of, 450.464.impurities in, 452.305.Metaldehyde, structure of, 220.l\fetascolecite, crystal structure of,Methane, molecular orbital of, 43.Methane, nitro-, enolisation of, indeuterium oxide, 101.Methionine, synthesis of, 402.5-Methoxy- 3-dimethylaminomethyl-indole, synthesis of, 380.7-Methoxy-1 : 2-cyclopentenophenan-threne, synthesis of, 324.y-Methoxy- up- isopropylidenedioxy-p-carbomethoxy-n-butyric acid,methyl ester, 248.206.oxidation of, 92.Methyl azide, structure of, 81.Methylamine, oxidation of, 93.2 -Methyl- 1 - A 7-but enyl- 3 : 4-dihydro -phenanthrene, cyclisation of, 317.1 - Methyl - 2 - dr - butenylcyclo -hexanol, cyclisation of, 317.9-Methyl-l-decalone, synthesis of, 341.7-Methylenecholesterol, irradiated,inactivity of, 392.2 : 5 - endoMethylene - ,41:3 - dihydro -benzoic acid, catalytic reductionof, 244.3 : 6 - endoMethylene - A1:* - dihydro -phthalic acid, catalytic reductionof, 244.(endo) 2 : 5-endoMethylenehexahydro-benzoic acid, 242.trans-3 : 6-endoMethylene - 4 - keto-hexahydrophthalic acid, cataly-tic reduction of, 244.eX0-Cis-3 : 6-edoMethylene - 4 - keto-hexahydrophthalic anhydride,catalytic reduction of, 244.trans-2 : 5-endoMethylene - 6 - methyl-(ezo)tetrahydrobenzoic acid(endo), 241.2 : 6-endoMethylene - d3 - tetrahydro-benzoic acid, 240.trans-3 : 6-endoMethylene - A4 -tetra-hydrophthalic acid, 241.Me thyle thyle thylene, hydration of,under influence of acids, 96.Methylethylglyoximes, copper andnickel, 161.a-Methylglucopyranoside, action of,with lead tetra-acetate, 247.oxidation of, 246.5-Methylglucose, 248.Methylglycogen, particle weights of,in benzene and in calciumchloride, 258.1 - Methyl - dl - cycZohexen - 3 - one,dehydrogenation of, 305.a-Methylhydrindene, dehydrogen-ation of, 309.a- and p-Methylhydrindenes, de-hydrogenation of, 302.8 - Methyl - 1 - hydrindenone, prepar-ation of, 340.a-Methylmannopyranoside, oxidationof, 246.a-Methylmannoside, oxidation of,246.Met h y lme t hox y phenan t hrenes , pre -paration of, 340.9-Methyloctalin, dehydrogenation of,302.3 - Methylcyclopentenophenanthrene,302.2 -Methylpyrrolizidine, 23 7.&Methyl Z-rhamnofuranose, 255.4-Me t hyl Z-rhamnopyranose, 2 55.a-Methylstyrene, polymerides of, 319.1 -Me thylte tralin, formation of, 3 18.l-Methyltetralin-4-carboxylic acid,dehydrogenation of, 296.,!?-Methyl- a- te tralone, preparation of ,336.7 -Met h y 1 - 1 - t e t ralone , dehy drogen -ation of, 312.Micelles, ionic, structure of, 104.Micro - organisms, forma tion of poly-saccharides by, 261.Modenol, antisyphilitic action of, 404.Molecules, energy of formation of,by variational methods, 38.surface, in films, 113.forces between-59.quantum mechanics of, 37.structure of, from electron diffrac-from spectroscopy, 53.aromatic, diamagnetic anisotropyof, 51.polyatomic, vibrational and rota-tional levels of, 53.dipolar, polarisation of medium by,121.linear, 54.polar, velocity of reaction between,spherical, 55.symmetrical-top, 56, 57.tion, 81.96506 INDEX OF SUBJECTS.Molluscs, sterols of, 346.Molybdenum, at.wt. of, 136.determination of, 440.isotopes, 16.Molybdenum hexacarbonyl, 176.Monosaccharides, 245.Moulds, growth of, in deuteriumoxide, 102.Myosmine, 380.Naphtha( 1’ : 2’ : 2 : 3)fluorcne, pre-Naphthalene, preparation of, froinparation of, 332.tetralin, 295.hydrogenation of, 314.structure of, 287.sulphonation of, 290.Naphthalene, chloro-derivatives, di-Naphthalene-1 : 5-disulphinylacetic1 -( 1’-Naphthyl)cycZohexoue, dehydro-Neodymium nitrates and solenate,Nephelome t ry, 4GQ.Nerolidol, dehydration of, 316.Nervous diseases, administration ofNeutrons, bombardment of nuclei by,slow, properties of, ant1 theirpole moments of, 289.acid, preparation of, 289.genation of, 296.183.vitamin-B, in, 384.24.capture, 28.Nickel as catalyst, 305.isotopes, 16.Nickel benzylmetliylglyoximes, 158.carbide, decomposition of, 156.carbonyl, structure of, 83,” 162.structure and parachor of, 166.oxide, colour of, 192.phthalocyanine, 160.sulphides, crystal structure of,Niobium, analysis of, 443.Nitrates.See uruler Nitrogen.Nitrides, metallic, heats of formationNitroarnine, catalytic decompositionNitrogen, at, wt. of, 139, 144.207.at. wt. of, 136.of, 187.of, 97.bombardment of, by neutrons, 24.determination of, in organic com-fixation of, by Azotobacter, 410.nucleus, scattering of fast jl-supply of, t o plants in relation totervalent, stereochemistry of, 337.pounds, 465.by Rhizobia, 411.particles by, 32.chlorophyll, 428.valency angle of, 85.Nitrogen fluorides, 149.monoxide (nitrous oxide), structureof, 82.dioxide (nitric oxide), reactions of,with bromine, chlorine, hydro-gen, arid oxygen, 92.Nitric acid monoliydrate, structureof, 210.Nitrates, determination of, 447.Nitrogen-oxygen distance, 80.Nitrosoamine, preparation and struc-Ni trosyl perchlora te and sulpha te,exoNorbornylamine, 242.Norlupinane, 373.Nuclei, effect of resonance on dis-tances between, 45.tmnsmutations of, 17.ture of, 189.188.Nucleosides, natural and synthetic,Nutrition, effect of, on formation of253.chlorophyll in plants, 428.Octahydrodibenzanthrone, synthesisas.- Octahydrophenanthrene, syn-Octahydro-9-phenanthrol, dehydro-Octahyclropyridocoline, synthesis of,d* : 1°-a-Octdone, preparation of, 340.cyclo Octane, dehydrogenation of, 3 10.CEstmdiol, 360, 397.(Xstresstanol, 345.(Estreasterol, 346.C1Estrio1, 360.Uhtrone, 360.Olea europea, Z-olivil from resin of,275.Olefins, complex compounds of, withmetallic salts, 177.Olive.See Olea europea.n- and iso-Olivils, 275.Opium alkaloids, detection of, 468.Optical activity and tautomerism,Orcinol, exchange of hydrogen withOrganic analysis, 465.Organo-metallic compounds, com-plex, optically active, 232.Orpiment, crystal structure of, 208.Orsanine, trypanosomes resistant to,404.Orthoformic acid, ethyl ester, hydro-lysis of, in deuterium oxide, 102.Osmium, lattice constants of, 202.Oxalic acid, detection of, 468.of, 339.thesis of, 321.genation of, 312.372.232.deuterium in, 293.determination of, 468.dihydrate, structure of, 218INDEX OF SUBJECTS. 507Oxalic acid, ammonium salt, mono-calciuni salt, dihydrate, structure0 xidation-reduction reactions, colori-Oxides, crystal structure of, 203.1 : 15-Oxidopentadecane, 368.1 : 14-Oxidotetradecane, 367.Oximes, configuration of, 286.a- and fl-Oximes, equilibrium ofOximinothiocamphor as indicator,Oxonitin, structure of, 376.Oxygen, determination of, in organichydrate, structure of, 219.of, 219.metric, 466.interconversion of, 231.436.compounds, 465.isotopic composition of, 141.valency angles of, 84.y-Oxygen, structure of, 217.Oxygen-chlorine distance, 79.Oxygen-fluorine distance, 79.Oxygenated compounds, seleniumdehydrogenation of, 304.dZ-Oxysparteine, structure of, 373.Palladium as catalyst, 305.Palladium glycines, lb8.I’arachor of co-ordination com-pounds, 165.Paraldehyde, structure of, 83.Particles, determination of size of,by X-rays, 201.a-Particles, bombardment of nucleiby, 17.Peganine, 370.Peganum harmala, peganine from,370.Pellagra, chicken and human, 385.Pentaborane, structure of, 83.Pentadeuterobenzhydrylamine ,Pentadeuterobenzoic acid, 293.cycZoPentadiene, additions to, 240.resolution of, 228.adduct of, with maleic anhydride,detection of, 467.polymerisation of, 238.239.cyclopentadiene-l-carboxylic acid,methyl ester, adduct of, withmaleic anhydride, 240.Pentane, oxidation of, 92.cycZoPentane, hydrogenation and de -hydrogenation of, 311.cycZoPent anoperhydrophenanthrene,natural products from, 341.cycZoPentanot e trahydrophenan-threne, 322.1 : 2-cycZoPentenophenanthrene series,cyclisation of, 339.1 -cycZoPentylhydrindene, dehydro -genation of, 299.:Pepper, red Hungarian, vitamin-PPerandren, 359.Perchloric acid. See under Chlorine.Periodic acid.See under Iodine.Periplogenin, 363.Persulphates. See under Sulphur.Petroleum naphthencs, dehydrogen-ation of, 307.Phcnanthrene, formation of, bydehydrogenation, 31 1.from, 390.hydrogenation of, 314.preparation of, 299.o-Yhenanthroline, compounds of, withferric salts, 173.Phenol, detection of, 468,determination of, in presence ofPhenol, o-chloro-, configuration of,Phenols, detection of, 466, 468.Phenol ethers, aciclolysis of, 97.Phenosafranine as indicator, 436.Phenoxarsines, dissymmetry of, 230.Phenoxthionin, 369.a-Phenylacet oacet ic acid, 1 -menthy1ester, enolisation and racemis-ation of, 234.Phenylanthranilic acid as indicator,434.a-Phenylbutyric acid, a-amino+-hydroxy-, synthesis of, 402./I -Phen yle t hy lcyc lo pent y lcarbinol ,325.2 -PhenylcycZohexylacet ic acids,preparation of, 339.3 - Phenyl - 4 - methyltetrahydro - 4 -carboline - 5-carboxylic acid, 3 74.10 - Phenylphenoxarsine - 2 - carboxy-lie acid, optical activity of,230.8-Phenyl-n-valeric acid, a-amino-j3-hydroxy-, synthesis of, 402.Phosphates.See under Phosphorus.Phosphonitrile chloride, structure of,225.Phosphorus, determination of, 463.Phosphorus hydrides, 184.cresols, 467.287.nitrides, 186.peroxide, 184.pentoxide, 185.Phosphates, removal of, in quali-Hypophosphitos, determination of,Pyrophosphates, 195.12-Phosphotungstic acid, hydrated,structure of, 214.Photometric titrations, 464.Photosynthesis in plants, 416.mechanism of, 420.Phrenosinic acids, detection of, 202.Phthalocyanine, structure of, 221.tative analysis, 451.445508 INDEX OFPhthalocyanines, structure of, 215.metallic, 160.stereochemistry of, 161.structure of, 213.Picea d i e s , d-pinoresinol from resinPicene, synthesis of, 324.Picolinic acid, copper and silverderivatives, 184.d- and 1-Pimaric acids, 267.Pinane, dehydrogenation of, 3 10.Pine, pink.See Dacrydium biformc.silver. See Dacrydium colensoi.Pinene, dehydrogenation of, 308.d-Pinoresinol, 27 7.Pinus nigra, d-pinoresinol from resinPiper cubeba, cubebin from fruit of,Piperit one, dehydrogenation of, 308.Plants, carbon assimilation of, 416.of, 277.of, 277.273.effect of nutrition on chlorophyllformation in, 428.photosynthesis in, 416.leguminous, nodulation of, in rela-tion to carbon-nitrogen balance,412.Platinum as catalyst, 305.bombardment of, by deuterons, 24.detection of, 449.isotopes, 17.Platinum glycines, 158.metals, analysis of, 441.phthalocyanine, 160.Platyphylline, 378.Pneumococcus, polysaccharides from,261.Podocarpus spicatzu, 1-matairesinolfrom, 271.Podophyllot osin, 27 5 .Poisons, toad, 364.Pollucite, crystal structure of, 206.Polymerisation, 93.Polyphenols, exchange reactions of,with deuterium oxide, 293.Polysaccharides, formation of, bymicro -organisms, 2 62.osmotic pressure of acetyl andmethyl derivatives of, 258.Pneumococcus, 263.determination of, 444, 463.in relation to assimilation inPotassium mribromido, structure of,cuprocyanide, structure of, 163.ferricyanide, magnetic suscepti-hydrogen carbonate, structure of,tetroxide, structure of, 194, 210.Potassium, at.wt. of, 140.plants, 429.164, 214.bilities of, 51.211.Potato. See Solanum tuberosum.SUBJECTS.Praseodymium, magnetic suscepti-Praseodymium nitrates and selenate,A 5-Pregnene-3 : 20-dione, 344.Proabietic acid, 268.Progesterone, 344.d-Proline from ergot alkaloids, 374.Prontosil, 407.Prontosil 5, 407.Propionitrile, dipole moment of, inisoPropy1 bromide, decompositionProtein,Bence Jones,structureof, 226.Proteins, 399.bility of, 181.183.non-polar solvents, 125.of, in alkaline solution, 97.films of, 116.structure of, 224, 226.Protoactinium, at.wt. of, 138.Protons, bombardment of nuclei by,Proustite, crystal structure of, 208.Prussian blue, structure of, 213.Psoralea corylifolia, psoralene from,Psoraleno, 368.Pterins, detection of barium salts of,Pyrargyite, crystal structure of, 208.Pyridine, determination of, in pres-Pyrocatechol, infra-rod absorptionPyrocatechol, C-nitro-, as indicator,Pyrogallol, exchange of hydrogenPyrophosphates. See under Phos-Fyroyuinovaic acid, 355.Pyrrole, stereochemistry of, 237.19.368.202.ence of nicotine, 467.and structure of, 287,436.wit'h deuterium in, 293.phorus.Quantum mechanics of molecules, 37.Quartz, crystal structure of, 285.Quaterphenyl, crystal stmcture of,Quinacrine in malaria therapy, 406.Quinol, exchange of hydrogen withdeuterium in, 293.isoQuinoline alkaloids, 380.223.Racemic compounds, effect of pow-Radioactive elements from boron,Radioactivity , 15.Radium, at.wt. of, 136.Radium fluoride, crystal structure of,Radium-E, formation of, from bis-dered quartz on, 175,fluorine, and lithium, 22.208.muth, 24INDEX OF SUBJECTS. 509Radium-#, at. wt. of, 138.Ravenelin, 369.Rays, cosmic, 33.@-Rays,. emission of, in nuclearpassage of, through matter, 32.y-Rays, bombardment of nuclei by,passage of, through matter, 32.X-Rays, tubes for, 196.use of, in crystal structure deter-minations, 196.Reactions in solutions, 94.addition and substitution, stericcourse of, 238.chemical, quanta1 theory of, 86.dry, use of, 139.gaseous, 91.Realgar, crystal structure of, 208.Resins, natural, 266.Resonance, 44.Resorcinol, exchange of hydrogenstructure of, 221.Resorcinol, 2-nitro-, structure of, 285.Rhenium, detection of, 449.Rhenium fluoride, 151.Rhizobia, carbon metabolism andnitrogen fixation by, 411.Rhodium as catalyst, 305.Rings, aromatic, reduction of, 314.large, containing oxygen, 367.Rose-Bengal as indicator, 436.Rotation, relation of, to configura-tion, 173.Robinobiose, 255.Rock-salt, crystal structure of, 208.Rubber, structure of, 224.Rubidium, at.wt. of, 141.Rubidium chloride, crystallographyof transformation of, 209.Rubrene, crystal structure of, 223.Ruthenium, lattice constants of, 202.Ruthenium ammines, 172.Ruthenium red, constitution of, 171.disintegration, 31.26.with deuterium in, 293.restricted, 49, 236.chloroammine, 170.Saccharodilactone, preparation of,Salicylaldoxime acetate, configurationSapietic acid, 268.Sapocholic acid, 355.Saponins, 364.Sapotalin from triterpenes, 303.Sarmentogenin, 363.Sarmentogenone, 363.Sarsaparilla root, saponins from, 365.Sarsasapogenin, 365.Scillaridin-A, 364.Sclareol, 269.253.of, 286.Scolecite, crystal structure of, 206.Scymnol in bile of sharks, 355.Selenium as dehydrogenation cata-separation of, from sulphur, 441.Selinene, dehydrogenation of, 297.Senecio plutgphyllus, alkaloids from,Seneciphylline, 378.Sesame oil, d-sesamin from, 277.d-Sesamin, 277.Sesquiterpenes, dicyclic, dehydro-genation of, 295.Silane, decomposition of, 94.oxidation of, 93.Silicon, detection of, 456.determination of, 463.Silicon dioxide, determination of, indisulphide, crystal structure of,Silicates, crystal structure $, 206.Silk of oysters.See " Byssus.Silver, at. wt. of, 139.detection of, 454.detection, determination, and sep-aration of, 453.determination of, 437, 464.Silver fluoride, 15 1.organic compounds, complex op-tically active, 232.phosphate, structure of, 211.selenide, sulphide, and telluride,crystal structure of, 207.lyst, 299.378.presence of fluorine, 446.207.Sitostanol, 345.Sitosterol, 345.Sleeping sickness, Nigerian, chemo-Smilagenin, 365.Soaps, colloid character of, 104.Soap solutions, solvent power of, andSodium, determination of, 445, 463.isotopes, 16.Sodium borate as standard solution,carbonate monohydrate, structurepyroborates, hydrated, spacetherapy in, 403.structure, 11 1.434.of, 211.groups of, 210.Solancarpidine, 379.Solancarpine, 379.Solaneine, 378.Solangustidine, 379.Solanidiene, dehydrogenation of, 378.Solanidine-s, 378.Solanidine-t, 378.Solanocapsidine, 379.Solanocapsine, 379.Solanum pseudocapsicum, alkaloidssolanum sodommum, solanidhe-8of, 379.from, 378510 INDEX OF IUBJECTS.Solanum tuberosum, alkaloids from,Solanurn xanthocarpum, allraloidsSolids, action of atoms with surfacesSolvents, effect of, on dipolemoments,117, 118.orientation of anisotropic mole-cules of, round dipoles, 121.polar, 133.d-Sorbose, synthesis of, 245.Soya beans, nodule formation andSpectra, infra-red absorption, ofmolecular vibration, in relation t oquartz, 467.378.from, 379.of, 47.nitrogen fixation by, 413.organic compounds, 285.interatomic force, 59.Spectrographs, mass, 15.Spectrometer, automatic ioniuation,Spectrophotometers, 457, 45 8.Spectroscopy, 53.Spinels, structure of, 203.Spruce.See Picea abies.Starch, constitution of, 256.particle weight of, in zinc chloridedispersions, 258.phosphoric acid in, 259.Starch dextrins, osmotic pressure andviscosity of, 257.Step photometers, Pulfrich, 468.S t ereochemistry, 22 8.Sterols, dehydrogenation of, 302.197.synthesis of substances related to,unirnolecular films of, 115.332.Sterols, brominated, 343.Sterol group, natural products of, 341.Stichococczcs bacillaris, effect of tem-perature on respiration andassimilation in, 418.Stigmastanol, 345.St igmast erol, 345.configuration of, 347.Strontium, determination of, 444.isotopes, 16.S trophanthidin, 3 63.Strophuntlaus, sarmentogenin fromStructure, determination of, by ap-proximate methods, 40.by dehydrogenation, 294.Succinanilomethylamide - p - arsonicacid, sodium salt, in trypanoso-miasis, 403.Sucrose, effect of deuterium oxide oninversion of, 100.Sugars, copper solution for analysisof, 466.reducing, determhation of, 467.Sulphates.See under Sulphur.seeds of, 363.Sulphit e -liquors lact one, 2 74.Sulphur as dehydrogenation catalyst ,determination of, in organic com-dioxide, structure of, 85.Sulphates, determination of, 446.isomorphism of, with tellurates,211.Persulphates, determination of , 447.Suprasterols, 351.Surface chemistry, 103.Syphilis, treatment of, in India, 404.295.pounds, 465.Sulphur fluoridos, 147.Tachysterol, 349.Tantalum, analysis of, 443.at.wt. of, 136.lattice constants of, 202.Tar oils, dehydrogenation of, 307.Tartaric acid, detection of, 467.Tartramide, structure of, 219.Tartrazine as indicator, 436.Tautomerism and optical activity,Tellurium, at. wt. of, 136.232.detection of, 454.Tellurates, isomorphism of, withsulphates, 211.Temperature, critical, determinationof, 152.Terpenes, dehydrogenation of, 295.Testosterone, 357, 398.Tetracyclic con~pounds, preparationof, 322.Tetrahydroartemisia, ketone, detec-tion of, 202.Tetrahydrobenzpyrene, dehydrogen-ation of, in quinoline, 296.Tetrahy drocadinene, 2 95.3 : 4 : 5 : 6-Tetrahydro-4-carboline-5-carboxylic acid, 374.Tetrakis-thioacetamide cuprous andsilver chlorides, 163.Tetralin, configuration of, 281.dehydrogenation of, 295.formation of, 318.Tetralins, bromo-, dipole moments of,n-Tetralone, dehydrogenation of, 297.a-Tetralones, synthesis of, 336.Tetramethylmethane, zero point en-Tetraphenanthrolinedioldiferric chlor-Thallium, detection, determination,282.tropy of, 217.ide, 173.and separation of, 453.determination of, 438.tervalent, detection of, 454.thallous, determination of, 437.Thallous fluoride, crystal structureof, 208INDEX OF SUBJECTS.51 1T heophylline 6-me thyl-2-rhamno -furanoside, synthesis of, 255.Thevetigenin, 3 62.Thiochrome, structure and synthesisof, 382.Thiocyanic acid, potassium salt, asvolumetric standardsolution, 434.Thorium, at. wt. of, 138.bombardment of, by neutrons, 26.Thorium carbide, gases from hydro-lysis of, 155.d( - )-Threonine, 402.d-Threose, preparation of, 247.Thujane, dehydrogenation of, 310.Tigogenin, structure of, 365.Tin, detection of, 449.determination of, 441, 462.determination and separation of,stannic, valencies of, 164.Tin compounds, stereochemistry of,Titanium, allotropy of, 202.detection of, 454.determination of, 463.determination and separation of,Tobacco, alkaloid of, 380.Tobacco mosaic virus, crystalstructure of, 226.orientation of molecules of, insolutions, 201.a-Tocopherol, 392.Tolidine, detection of, in presence ofbenzidine, 468.Toluene, 2 : 3-dichloro-, nitration andsulphonation of, 287.p-Toluidine, structure of, 223.Toluidines, determination of, 467.Transmutation, nuclear, 17.2 : 3 : 4 - Tribenzoyl 5 - triphenyl-methyl Z-arabinose dicthyl-mercaptal, 252.Trichodesma incanum, alkaloid from,377.Trichodesmidine, 3 7 7.Trichodesmine, 377.1 : 1 : 3 - Trimethyl - 2 - n - butylcyclo-hexane, dehydrogenation of, 303.2 : 3 : 6-TrimethylgalacDose, 261.1 : 1 : 2-TrimethylcycZoheptane, de-hydrogenation of, 310.Trimethylplatinic chloride, structureof, 162.Trisdipyridylruthenous salts, 17 1.Tropinone, action of, with allrylcarbonates, 381.Trypanosomes, arsenic-resistant, 403.Trypanosomiasis, 403.Tryparsamido, 403.Tsuga sieboldii.See Hemlock, Japa-Teugaresinol, 2 74.440.164.441.nese.Tubera aalep, mannan from, 260.Tungsten, at. mt. of, 136.Tungsten hexacarbonyl, 176.Tunny-liver oil, vitamin-D, from,determination of, in presence of tin,oxides, 205.353, 390.437.Ultramarines, crystal structure of,Unsaturated compounds, heat ofUranium, at. wt. of, 137, 138.bombardment of, by neutrons, 25.Uranium-lead, at. wt. of, 138.Urethanes, detection of, 467.Urine, specific polysaccharides from,human, excretion of vitamin-12, in,pregnancy, ccstrogenic hormones206.hydrogenation of, 250.265.384.from, 398.Ursodeoxycholic acid, 334.Uzarigenin, 362.Uzarin, 363.Valency angles, 84.Valency force field, 60.Valonia, fibre formation in, 226.Vanadium, lattice constants of, 202.Vanadium pentoxide, crystal atruc-sols, particle size of, 201.Varianose, 261.Variation principle, Ritz, 38.Vasicine, 370.Veratridine, 3 76.Veratrum album, constituents of, 377.Veratrum alkaloids, 376.Velocity of reaction in solution, 94.effect of pressure on, 95.quanta1 theory of, 87.Verine, 376.Vitamin-A, detection of, 433.Vitamin-B,, 384.Vitamin-B,, complex iiat ure 01, 383.Vitamin-B,, 386.Vitamin-U,, 385.Vitamin-C, 387.Vitamin-D, 349, 390.Vitamin-D,, aihydro-deriva tive ofmaleic anhydride adduct of,dehydrogenation of, 306.Vitamin-D,, 352, 390.Vitamin-E, 392.Vitamin-K, 394.Vitamin-P, 390.ture of, 203.synthesis of, 381.alcohol from wheat germ oil withactivity of, 346512 INDEX OF SUBJECTS.433.Wheat gem oil, constituents of, 392.Wool, orientation of cells of, 201.Xanthotoxin, 368.o-Xylem, configuration of, 282.Xylidines, determination of, 467.Zeolites, crystal structureZinc, detection of, 450.Zingiberene, dehydrogenation ofdetermination of, 443, 462.298.180.of, 206.Zirconium, detection of, 454.determination of, 443

ISSN:0365-6217    

DOI:10.1039/AR9363300496

出版商:RSC    

年代:1936

数据来源: RSC