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ISSN:0365-6217    

DOI:10.1039/AR93936FP001

出版商:RSC    

年代:1939

数据来源: RSC

摘要:

ANNUAL REPORTSON THEPROGRESS OF CHEMISTRY.RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.I&-oduction and Summary.AMONG the advances made in nuclear physics during the currentyear, the oustanding feature is the discovery and investigationof a new type of nuclear reaction for which the name ‘(nuclearfission ” has been fairly generally adopted ((‘ nuclear cleavage ”is used sometimes). In this reaction the nucleus does not merelyemit light particles (like protons, neutrons, or a-particles) butbreaks up into two fragments of roughly half the original mass,with the liberation of an energy of about 200 m.v., which is verymuch larger than the energies (up to 27 m.v.) liberated in ordinarynuclear reactions. Both fission fragments contain too large anumber of neutrons to be stable and readjust themselves by theemission of one or several electrons (p-particles), giving rise toradioactive chains similar to the well-known natural radioactivefamilies.A large number of different radioactive substances thusoriginating from nuclear fission have been identified and the listis probably still far from complete. Special interest has beenfocused on the observation that neutrons are emitted in the actof fission. These neutrons can, under suitable conditions, causefurther fission processes, and consequently the possibility seemsto exist that one neutron should start an ever-increasing avalancheof neutrons, a “nuclear chain reaction,” with the consequentliberation of nuclear energy on a large scale.Another important achievement is the discovery of a methodfor the chemical separation of isomeric nuclei.This method hasproved very helpful in clarifying nuclear isomerism in bromine andtellurium. An excited, metastable (isomeric) state of the stablenucleus 1I5In has been found to be the explanation of a long-known4-hours activity of indium, produced by neutron bombardment,and several other ways of exciting this level have been discovered.Further items dealt with in this Report are : nuclear reactionsin the interior of stars; a new radioactive element (2 = 87) in th8 EADIOACTIVITY AND SUB-ATOMIC PHENOMENA.actinium family; and the discovery of stable 3He. I n addition, adetailed account is given of the present state of the theory ofnuclear forces.Nuclear Fission.HistoricaL-Although the discovery of nuclear fission was brieflyannounced in last year’s Report, the events leading up t o it areworthy of record. Ever since the discovery of the production ofartificial radioactivity by neutrons,l the case of the two heaviestelements thorium and uranium has aroused special interest.2 Inthe case of uranium some of the active bodies produced werebelieved to have atomic numbers greater than 92, and attemptswere made to assign definite atomic numbers to them by comparingtheir chemical properties with those to be expected from an extrapol-ation of the Periodic Table, combined with EL study of their geneticrelations and of the particles emitted in their transformations.The investigation of these products was rendered extremely difficultby their surprisingly large number.In the beginning of 1938, tendifferent active bodies with half-lives ranging from 10 secondsto 60 days had been ascertained, mainly through the efforts of0. Hahn, L. Meitner, and F. Stras~rnann.~ Seven of them showedproperties compatible with ‘‘ transuranic ” elements but not withany element between uranium (2 = 92) and polonium (2 = 84).The production of still lower elements seemed t o be excluded byall experimental evidence of nuclear physics, since no reactionwas known in which more than two elementary charges (the chargeof an a-particle) were given off.It was therefore a great surprise to ( f i e . ) I. Curie and P.Savitch when they discovered yet another disintegration productof uranium (of 3.5 hours half-life) which behaved chemically likea rare-earth element, for none of the transuranic elements could beexpected to show such a behaviour.The authors suggested anumber of alternative explanations for their curious observationbut their publications did not mention the possibility of theproduction of nuclei much lighter than uranium. Also 0. Hahnand F. Stra~srnann,~ who found two more rare-earth activities andthree alkaline-earth activities, thought at first that they weredealing with isotopes of actinium and radium, respectively. How-ever, when they used fractional crystallisation they found that1 E. Fermi, F. Amsldi, 0. d’Agostino, F. Rasetti, and E. S e e , Proo. Roy.SOC., 1934, A , 146, 483.2 E.Fermi, Nature, 1934, 133, 898.3 Ber., 1937, 70, 1374; Naturwks., 1938, 26, 475.4 Compt. rend., 1938, 206, 906, 1643; J . Phys. Radium, 1938, 9, 355.Ibid., 1939, 27, 11. Natum*s8., 1938, 26, 755FRISCH : NUCLEAR FISSION. 9their " radium " could not be separated from barium but was easilyseparated from radio-thorium (a radium isotope) in the samecrystallisation experiment. With some hesitation they suggestedthat the uranium nucleus breaks up into two parts of comparablesize, a barium nucleus (2 = 56) and a krypton nucleus (2 = 36)(36 + 56 = 92).The physical interpretation of these findings was given by L.Meitner and 0. R. Frisch,' who pointed out that the mutualrepulsion of charges in a heavy nucleus reduces the form stabilityof the nucleus, in the same way as the stability of a liquid drop(due to its surface tension) is decreased when the drop is given ahigh electric charge.A relatively small disturbance such as theaddition of a neutron may then cause so large a deformation that thenucleus does not recover its spherical shape but breaks up into twosmaller nuclei. After this the electrical repulsion of the two frag-ments makes them fly apart with considerable speed; it wasestimated that they must get a kinetic energy of about 100 m.v.each. On the other hand, it was shown that an energy liberation ofabout 208 m.v. must, in fact, be expected, on account of the estimatedmass defects (packing fractions) of the fission fragments and theuranium nucleus.Physical evidence (as opposed to the chemical evidence of Hahnand Strassmann) for the existence of this new reaction was obtainedvery soon and almost simultaneously in a number of laboratories.I n one type of experiment * the heavily ionising fission fragmentswere discovered by means of an ionisation chamber connected to alinear amplifier.Another type of experiment9 was based on thecollection of the fission fragments, which are able, on account oftheir large velocity, to emerge from a uranium layer and even topenetrate additional layers of material ; the successful collection offission fragments was demonstrated by their radioactivity. Tracksof the fission fragments, recognisable through their dense ionisation,were made visible by means of the cloud chamber lo and in theemulsion of photographic plates l1 covered with uranium andexposed to neutrons.The number of ions Energy and range of the Jission fragments.Nature, 1939, 143, 239.0.R. Frisch, Nature, 1939, 143, 276; G. K. Green and L. W. Alvarez,Physical Rev., 1939, 55, 417; R. D. Fowler and R. W. Dodson, ibid., p. 417;R. B. Roberts, R. C. Meyers, and L. R. Hafstad, ibid., p. 416.F. Joliot, Cornpt. rend., 1939, 208, 341 ; E. McMillan, Physical Rev., 1939,55, 510; L. Meitner and 0. R. Frisch, Nature, 1939, 143, 471.lo D. R. Corson and R. L. Thornton, Physical Rev., 1939,55, 609; F. Joliot,Cornpt. rend., 1939, 208, 647.l1 L. Myssowsky and A. Idanoff, Nuture, 1939, 143, 79410 RADIOACTIVITY AND SUB-ATOIEIC PHENOMENA.formed by one fission fragment is a convenient measure of its energy.By using a very thin uranium layer and an ionisation chamberdesigned to allow nearly complete collection of the ions formed,W.Jentschke and F. Prank1 l2 showed that the energy distributionof the fission fragments was not uniform but consisted of two well-separated energy groups of about equal intensity. The ratio of thetwo energies was given as 1.6, and the phenomenon was interpretedas indicating that the uranium nucleus undergoes fission in anunsymmetrical way such that the two fragments have a mass ratioof 1.6. (on account of the conservation of momentum, the energiesof the two fragments must be in the inverse ratio of their masses).G. von Droste l3 believed that he had found indications of a sub-division of these groups, but this was not confirmed in the experi-ments of E.T. Booth, J. R. Dunning, and F. G. Slack l4 and ofL. Simons (not yet published), who find two energy groups of about72 and 100 m.v. respectively, corresponding to a mass ratio of 1.4.The total energy of the fission fragments has recently beenchecked by an entirely independent method,l5 'uix., the measure-ment of the heat produced in a sample of uranium exposed to anintense beam of neutrons. The result, 175 m.v. with a probableerror of lo%, is seen to agree well with the sum of the two energiesfound in the ionisation experiments, but it must be rememberedthat an appreciable fraction of the heat produced was due to thesubsequent p-disintegrations of the fission fragments rather thanto their kinetic energy.The accuracy of both types of experimentsis, however, not sufficient for any definite conclusions to be drawnfrom them.For the maximum range of the fission fragments in air, figuresbetween 1 and 3 cm. have been published. The most reliableexperiments l6 indicate that the two energy groups have ranges of1.5 and 2.2 cm. respectively. I n these experiments the particleswere detected by means of their ionisation. It was suggested l7 thatthe higher value of 3 cm. found by J ~ l i o t , ~ who detected the fissionfragments by their radioactivity, might be explained by assumingthat the fragments can travel a short way after losing their chargeand thereby their ionising power. The value of 2-2 cm. for themaximum range was, however, also found by McMillan9 who, likeJoliot, used the radioactivity of the fragments to detect theirpresence.12 Naturwiss., 1939, 27, 134.1 4 Physical Rev., 1939, 55, 981.1 5 M.C. Henderson, ibid., 56, 703.l6 E. T. Booth, J. R. Dunning, and F. G. Slack, ibid., 55, 982.l7 G. Beck and P. Havas, Cornpt. rend., 1939, 208, 1643.l3 Ibid., p. 198FRISCH : NUCLEaR FISSION. 11“ Transuranic Elements.”-When nuclear fission was discoveredit was immediately realised that the arguments for the formation ofelements beyond uranium were no longer conclusive. Some ofthem were identified very soon as isotopes of tellurium and iodine,18but others have not so far been identified. It was shown, however,by L. Meitner and 0. R.Frisch that they certainly originate froma fission of the uranium nucleus, so they cannot be “ transuranic ”elements. The authors collected the fission fragments emergingfrom a uranium layer, by placing a dish of water 1 mm. below theuranium layer. The water was then subjegted to the chemicalprocedure which had been developed3 for the isolation of thetransuranic substances, i.e., precipitation of platinum sulphide fromthe 2~-hydrochloric solution. All the “ transuranic ” ‘periods werefound to be present (except the longest one, of 60 days, for whichthe time of irradiation was far too short). Since then, one more ofthese substances has been identified as m01ybdenum.l~ The wholeof the chemical evidence is discussed in the next section.Capture of neutrons in uranium without subsequent fission does,however, occur, and results in the formation of a uranium isotopeof 25 minutes half-life.Since this isotope emits negative electrons,it must transform itself into an element of atomic number 93. Thesearch for any radiations which might be emitted from this elementhas, however, been so far unsuccessful,2o which points to either a veryshort or, more likely, a very long period. A method of concentratingthe 25-minutes uranium, based on a change of valency causedby the energy liberation due to the neutron capture, has beenreported by J. W. Irvine.21The production of this isotope is a typical case of “resonancecapture,” 22 i.e., of the selective capture of neutrons within a narrowenergy region.On account of the high value (about 10-21 cm.2)of the capture cross-section, the process must be attributed to theabundant isotope 23*U. On the other hand, the resonance neutronsdo not seem to cause fission to a measurable extent, although fissionis observed with the still slower neutrons of thermal energy, as wellas with fast ones. It was pointed out by N. Bohr23 that thisapparently erratic behaviour of the fission probability can beexplained by ascribing the fission observed with slow neutrons tothe rare isotope 236U (actino-uranium, abundance 007%). Thel8 P. Abelson, PhyeiccsZ Rev., 1939, 55, 418; N. Feather and E. Bretscher,Nature, 1939, 143, 516.l9 0. Hahn and F. Strassmann, Naturwk., 1939, 27, 451.2o E. SegrB, Physical Rem, 1939, 55, 1104.21 Ibid., p.1105.22 L. Meitner, 0. Hahn, and F. Stragsmann, 2. Physik, 1937, 106, 249.23 Physical Rev,, 1939, 65, 41812 RADIOACTIVITY AND SUB- ATOMIC PHENOMENA.main isotope =SU is assumed to undergo fission with fast neutronsonly, the fission probability decreasing rapidly 24 for neutron energiesbelow 1 m.v. The arguments for this view are strong, but directproof will have to wait for at least a partial separation of the uraniumisotopes.Identification of Fission Products.-Of the substances originallybelieved to be “ transuranic elements,” the first to be identifiedwere a 3 days activity and its 2.4-hours daughter substance,which were found to be tellurium and iodine respectively. It wasfound by Abelson and independently by Feather and Bretscher 18that these bodies emitted a soft y-radiation which, by absorptionexperiments with suitable elements, could be identified as thecharacteristic X-rays of iodine and xenon, respectively.(TheX-rays are emitted after the P-disintegration and must thereforebe characteristic of the daughter element.) This “ physical ”identihation was supported by chemical tests. Hahn andStrassmann19 confirmed the iodine but found that the 3-daysactivity is a mixture of two substances with nearly identicalperiods but different chemical properties, one being tellurium(which transforms itself into the 2.4-hours iodine) and the othermolybdenum. The latter is perhaps the same isotope as the onestudied by G. T. Seaborg and E. Segr8,25 who obtained it bybombarding molybdenum with deuterons or neutrons.In three further publications P.Abelson26 reported a numberof new activities. Three had the chemical properties of iodine,six of tellurium, and three of antimony. Their periods, geneticrelations, and supposed atomic weights are given in the table onp. 14.Little is known about the formation of active bromine isotopesfrom uranium. Various periods have been observed27 but onlyone of them28 (of about 40 mins.) by more than one author.Bromine isotopes with periods of 2.5 hours and 22 hours have beenreported 29 to be formed by the fission of thorium.An interesting line of attack has been opened by 0. Hahn andF. Strassmann.30 It is based upon the fact that any noble gasesformed (either as primary products or by subsequent P-decay) canbe continuously removed by bubbling air through a uranium (orthorium) solution during the irradiation.The air is then passed34 R. B. Roberts, R. C. Meyers, and L. R. Hafstad, ibid., p. 416.2 K Ibid., p. 808. Ibid., pp. 670, 876; 56, 1.27 J. Thibaud and A. Moussa, Cornpt. rend., 1939, 208, 652, 744.28 R. W. Dodson and R. D. Fowler, PhyahZ Rev., 1939, 55, 880.29 E. Bretscher and L. G. Cook, Nature, 1939, 143, 559.30 Natuwbs., 1939, 27, 89, 163FRISCH : NUCLEAR FISSION. 13through a wash-bottle or (better) absorption coal ; the productscollected can be subjected to various chemical separations. Severalisotopes of cesium, barium, lanthanum, rubidium, and strontiumhave been found by F. A. Heyn, A.H. W. Aten, jun., and C. J.Bakker,31 and by 0. Hahn and 3’. Stra~smann,~~ and their periodsand genetic relations have been determined. By varying the speedof the air, estimates of the periods of the corresponding noble-gasisotopes have been obtained. The same cesium, etc., isotopes, anda few more, have also been obtained from the irradiated uraniumsolution directly ;6* 33 the absence of some of these periods amongthe substances collected by the “ bubbling ” method indicates eitherthat they are primary fragments of the fission or, more probably,that they originate from a noble gas with a period less than a fewseconds (the time required for the gas to reach the collecting bottle).A rubidium isotope of 17 minutes half-life 34 is probably identicalwith s*Rb which can be obtained from rubidium by slow-neutronb~mbardment.~~ The same isotope was found to grow from akrypton of 3 hours half-life, which is formed, together with severalother noble-gas activities of longer period, in the fission of th0rium.3~Some investigators have carried out chemical tests on the activeproducts collected by the “ recoil method,” that is, on a surface(filter-paper, glass, or water) placed a t a small distance from auranium (or thorium) layer irradiated with neutrons.L. Meitner 36found periods of about 40 minutes and 13.5 hours, with the chemicalproperties of “ transuranics,” among the fission products fromthorium. G. N. Glasoe and J. Steigman3’ attempted to dis-criminate between lighter and heavier fission products by placinga screen of cellophane, of thickness equivalent to the range (1.5 cm.)of the less penetrating fragments, between the uranium layer andthe collecting surface.Unfortunately, in this kind of experimentthe activities obtainable are very weak.It has been possible to assign definite atomic weights to some ofthe periods. For example,31 the barium activity of 86 minuteshalf-life obtained from uranium or thorium agrees with respect toboth the period and the hardness of the P-rays with a barium isotopewhich is obtained from ordinary barium by bombardment withslow neutrons and must therefore be 139Ba (all the barium isotopesfrom 134 to 138 are stable, and the isotopes 130 and 132, whichmight form active isotopes by capturing a neutron, are very rare).31 Nature, 1939, 143, 516, 679.33 C.Lieber, Naturwiss., 1939, 27, 421.3* (Mme.) I. Curie and P. Savitch, Compt. rend., 1939, 208, 343.35 A. Langsdorf, jun., Physical Rem., 1939, 56, 205.36 Nature, 1939, 143, 637.3a Naturwiss., 1939, 27, 529,37 Physical Rev., 1939, 55, 98214 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.The following table includes only those activities, resulting fromthe fission of uranium, which the Reporter believes to be fairly wellestablished. A number of them have also been observed among thefission products of thorium; they are marked with an asterisk.Papers dealing with thorium fission products are given in refs. (28),(291, (31), (34), (35), and (38).Table of chemically identi3ed products of the Jission of uranium andt hori urn.Ref., no.28, 3231, 32, 34, 3530, 3319, 3818, 19, 26, 32, 38262626, 3226, 3226, 326, 29, 31, 32, 386, 29, 31, 32, 386, 34Atomicweight.88{ (89)(99 or 101)131139(140)Br, 35-40 mins.Kr,* 3 hours+Rb,* 17 mins.Sr, 7 mins.Sr, 6 hours --+ Y, 3.5 hours.Sr, 54 days.Mo,* 67 hours.Sb, 5 mins.(+) Te,* 77 hours--+ I,* 2.4hours.Sb, 80 hours-Te, 10 hours.Sb, 4.2 hours-Te, 70 mins.Te, 43 rnins. -+- I, 54 mins.Te. 60 mins. _I, I. 22 hours. . ,Te; 30 hours (isomers) --+ I, 8 days. Te, 25 mins.}Xe,* few sees. --+ Cs,* 33 mins. --+- Ba,* 86m i n S .12 days.40 hours.Xe,* ca. 15 mins. --+ Cs,* 33 mins. + Ba,*Ba, 14 mins. -+ La,* 2-5-3.5 hours --+- La,** Results also from the fission of thorium.It is seen that the active isotopes identified so far form, roughlyspeaking, two groups, one around krypton and with atomic weightsof about 90 or 100, and one around xenon and with atomic weightsin the neighbourhood of 140.This supports the conclusion drawnfrom the presence of two energy groups among the fission fragmentsthat for some (probably energetic) reason 39 the fission into two partsof equal size does not occur or is, a t least, much less probable thanthe fission into two parts with a mass ratio of about 5 : 7.The Emission of Neutrons in the Fission Process.-On account ofthe large energy liberation in nuclear fission (about 170 m.v.) it wasto be expected that a fraction of this energy might be used up in" evaporating " one or several neutrons from the nascent nuclei(the energy required to remove a neutron from such a nucleus isprobably only about 4 m.v.).The problem of discovering andcounting the neutrons emitted on top of the background of the38 0. Hahn, F. Strassmann, and S. Flugge, Naturwiss., 1939, 27, 544.39 G. Beck and P. Havas, Compt. rend., 1939, 208, 1084&RlSCH : NUCLEAR FISSION. 15'neutron bombardment required to produce a sufficient number offissions is by no means simple. H. von Halban, jun., F. Joliot, andL. Kowarski 4O used a large container filled with a solution of uranylnitrate, with a neutron source at the centre. Neutron detectorsplaced at various distances from the source served to determine thedensity distribution of neutrons within the tank.The experimentwas then repeated, a solution of ammonium nitrate of the samemolar concentration being used (this amounts very nearly toremoving the uranium nuclei while leaving the concentrations of allthe other nuclei unchanged). I n spite of the fact that the uraniumabsorbs neutrons, the average neutron density within the tankwas found to be even slightly larger in the presence of the uraniumnuclei. From a quantitative consideration of all the nuclearprocesses taking place in the two solutions, the authors concludedthat between three and four neutrons, on an average, are emittedin every fission process. A somewhat smaller figure, 2.3, wasobtained by L. Szilard and W. H. Zinn,41 who avoided the " back-ground" of primary neutrons by using a neutron source whichemits fairly slow neutrons, and a neutron detector which does notrespond t o neutrons of such a low energy.The interpretationof this experiment is on the whole more complicated and impliesa number of corrections but their result is confirmed by some recentexperiments by H. von Halban, jun., F. Joliot, L. Kowarski, and F.Perrin,42 from which the same figure of 2.3 can be deduced. Otherinvestigators43 have found figures between 1.5 and 6 neutrons perfission, but their experimental arrangements were such that it isdifficult to compare their results.Nuclear Fission as a Possible Basis for a Chain Reaction.-Theemission of more than one neutron, on an average, in the fissionprocess is a very important fact in so far as it suggests, for thefirst time, the possibility of a nuclear chain reaction.A neutron,placed within a large mass of uranium, would hit a uranium nucleusand cause fission, thereby liberating, let us say, two neutrons;these in turn would cause fission of two further uranium nuclei andliberate four neutrons, and so on. Since the energy release in thisreaction would be about lo* times larger than in ordinary chemicalreactions there has been considerable concern about the catastrophicconsequences of such an experiment, and it has been feared that it40 Nature, 1939, 143, 471, 680.41 Physical Rev., 1939, 55, 799.42 J . Phys. Radium, 1939, 10, 428.43 H. L. Anderson, E. Fermi, and H. B. Hanstein, Physical Rev., 1939, 55,707; J.L. Michiels, G. Parry, and G. P. Thomson, Nature, 1939, 143, 760;G. von Droste and H. Reddemann, Naturwiss., 1939,27,371; H. L. Anderson,E. Fermi, and L. Szilard, Physical Rev., 1939, 56, 28416 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.might form the basis for the construction of a super-bomb exceedingthe action of ordinary bombs by a factor of lo6 or more.Fortunately, our progressing knowledge of the fission process hastended to dissipate these fears, and there are now a number of strongarguments to the effect that the construction of such a super-bombwould be, if not impossible, then at least prohibitively expensive,and that furthermore the bomb would not be so effective as wasthought at first.Let us begin with the simplest arrangement : a solid sphere ofuranium or uranium oxide.The mean free path of a fast neutronin U,O, is about 10 cm., but the mean path covered by a neutronbefore causing a fission is much longer, since only one collision inabout 100 causes fission of the uranium nucleus hit. I n con-sequence, the sphere must be fairly large, otherwise too manyneutrons would escape from it without causing fission. Accordingto a calculation by F. P e ~ ~ i n , ~ ~ the sphere must have a diameter ofabout 9 feet and contain 40 tons of U,O,.I n this calculation it is implicitly assumed that those collisionswhich do not lead to fission are ‘‘ elastic,” leaving the energy of theneutron nearly unchanged. It is however known, fiom experimentswith other heavy nuclei, that most collisions are inelastic ; thereforethe energy of a neutron will be reduced, after a few collisions, tosomething like 0.1 m.v., which is too small to cause fission.Onemight think of using a still larger block of uranium which wouldallow the neutrons to undergo a very large number of collisions andultimately to get down to thermal energy when they can causefission again (this time of the 235U nuclei), but then practicallyall the neutrons would be captured in one of the resonance levelson the way down, without causing fission.If one wants to utilise the fission caused by slow neutrons, theobvious thing to do is to mix the uranium with a hydrogenoussubstance, such as water. Collisions with hydrogen nuclei rapidlycarry the neutrons down to thermal energy, and the number ofneutrons captured by the uranium on the way down will becomesmaller with increasing hydrogen concentration. At the same time,however, the number captured by the hydrogen itself will increase.Experiments by the Paris group42 indicate that the optimummixture contains about four atoms of hydrogen to one atom ofuranium, but even in this mixture the production of neutrons is toosmall to replace those which are absorbed.The possibility of producing a nuclear chain reaction seems todepend upon the separation of the uranium isotopes.No completeseparation is required; if several kg. of uranium with about ten4 4 Compt. rend., 1939, 208, 1394PRISCH : NUCLEAR FISSION. 17times the normal concentration of 235U could be produced, thecapture of neutrons in the uranium would probably be sufficientlyreduced to permit a chain reaction to develop.Methods for theseparation of isotopes have recently been greatly improved and itdoes not seem unlikely that such an experiment may be carriedout before long. It would not, however, form an effective basis forthe construction of a super-bomb, a t any rate according to presentknowledge, because the reaction is not fast enough. The timerequired for a neutron to become thermal is about see. ; EL furtherlo* sec. is lost, on an average, before the neutron hits a uraniumnucleus. So the ‘‘ reproduction cycle ” takes about loA sec., andthe time required to double the “ population ” of neutrons is probablyseveral times longer.As soon as the temperature has reachedseveral thousand degrees the container will be broken, and in a timeof lo4 sec. the parts of the bomb will be well separated. Theneutrons will then be able to escape and the reaction will stop.Consequently, the energy liberated will only be about sufficient tobreak the container or, in other words, of the same order as withordinary explosives.The question then arises whether it would be possible to controlthe reaction in such a way that it does not result in an explosion butproceeds a t a moderate speed so as to permit the utilisation of theenergy liberated. It was pointed out by F. Adler and H. von Halban,j ~ n . , ~ ~ and independently by F. Perri11,~6 that this can be achievedby simply adding a suitable amount of a cadmium compound to theabove-mentioned mixture of uranium and water.The effect of thecadmium would be to make the reaction strongly temperature-dependent with a negative temperature coefficient. The captureprobability of neutrons in cadmium increases with increasing neutronvelocity and, therefore, with increasing temperature, whereas foruranium and hydrogen it remains constant. Consequently, withincreasing temperature an increasing fraction of neutrons iscaptured by the cadmium rather than causing fission of the uranium,and above a certain temperature the chain reaction will no longer beself-sustained. The reaction vessel will adjust itself at a temper-ature just below the critical value; any attempt to cool it will causeonly a temporary drop in temperature with consequent increase ofthe reaction rate and return to the critical temperature.Thereaction can be interrupted by simply heating the reaction vessel.It is seen that the behaviour of this reaction, surprising as it mayseem, would be very convenient indeed. On account of the highcost of isotopically separated uranium it would probably not bea serious competitor with other sources of energy, but it might45 Nature, 1939, 143, 793. 4 6 Compt. rend., 1939, 208, 157318 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.gain great importance for large-scale production of artificial radio.activity .Delayed Neutron Emission.-Even before the discovery of neutronemission in the fission process itself, it was found4' that uraniumand thorium emit neutrons for a short time after bombardmentwith neutrons. The decay of this radiation was analysed48 intotwo components of 10-15 secs. and 45 secs., and later a further twocomponent^,^^ of about 3 and 0.3 sec., were found, attempts to findstill shorter components 50 being unsuccessful. These neutronsare obviously not connected with the fission process itself but areemitted from some of the fission products.The emission of hardp-particles, with a decay similar to that of the " delayed neutrons,"has been observed,50a and the simultaneous emission of a P-particleand a neutron must be expected to happen occasionally if the@-disintegration energy is sufficient for such a process. The theoryof this phenomenon was given by N.Bohr and J. A. Wheeler,51together with that of many other aspects of nuclear fission.In the fission process itself there is no appreciable delay. G. K.Green and L. W. Alvarez 52 bombarded uranium with a periodicallyinterrupted beam of neutrons; no fissions were observed duringthe intervals, and the authors concluded that the delay, if any,must be less than 0.003 sec. A still more sensitive test was madeby N. Feather.53 It is based on the fact that by the impact of afast neutron a uranium nucleus is given a certain velocity, whichit loses again within about 10-13 sec., on account of collisions withsurrounding atoms. Feather collected fission fragments from athin uranium layer and found that the number and penetratingpower of those emerging in a forward direction (with respect to theincoming neutrons) was slightly greater than of those emerging in abackward direction.This difference can only be explained if thenucleus undergoes fission while still in motion, i e . , within about10-13 sec.Other Cases of Nuclear Fission.-Fission of protoactinium (2 =91) under neutron bombardment has been reported by A. von Grosse,E. T. Booth, and J. R. Dunning.54 The typical bursts of ionisationdue to the fission fragments were observed by means of a linear47 R. B. Roberts, L. R. Hafstad, R. C. Meyers, and P. Wang, Physical Rev.,1939, 55, 510, 664.4 8 E. T. Booth, J. R. Dunning, and F. G. Slack, ibid., p. 876.49 K. J. Brostram, J. Koch, and T. Lauritsen, Nature, 1939, 144, 830.50 D.F. Gibbs and G. P. Thomson, ibid., p. 202.50a H. H. Barschall, W. T. Harris, M. H. Kanner, and L. A. Turner,Physical Rev., 1939, 55, 989; see also refs. (2) and (22).51 Physical Rev., 1939, 56, 426.63 Nature, 1939, 143, 597.52 Ibid., 55, 417.54 Physical Rev., 1939, 56, 382. FRIYCH : NUCLEAR ISOMERISM. 19amplifier, and fission products were collected by the recoil method.Chemical separations showed the presence of a rubidium with 17mins. and a caesium with about 30 mins. period, which are probablyidentical with those resulting from uranium and thorium fission.Slow neutrons do not cause fission of protoactinium, and the energythreshold seems to be about 1 m.v.A few cases of fission. of elements below thorium have beenrep0rted,5~ but other investigators have not confirmed these results.Fission of uranium under bombardment with 9-m.v.deuteronsfrom the Cambridge cyclotron has been reported by D. H. T. GanL5(jThe yield of this process is small and falls of3 rapidly with decreasingdeuteron energy.No fission of either thorium or uranium was observed2* underirradiation with y-rays of 17 m.v. energy, obtained by the bombard-ment of lithium with protons. This result is in agreement withtheory 51 which predicts a very small yield for this reaction.The spontaneous fission of uranium or thorium is energeticallypossible but, according to theory,51 exceedingly improbable. W. F.Libby,57 using several very sensitive tests, found no indication of it,and concluded that the average life of a uranium or thorium nucleuswould be a t least 1014 years if it were limited only by the spontaneousfission.Nuclear Isomerism.An interesting case of isomerism, exhibited by the nucleus l151n,has been the subject of considerable study.It has been known for along time that a period of 4.1 hours is produced in indium by neutronbombardment, and that this period follows the chemical reactionsof indium. This activity has been thoroughly investigated byM. Goldhaber, R. D. Hill, and L. S~ilard,~* who found that itcan be produced by neutrons of 2-5 m.v. but not by slow neutrons.The latter fhding shows that it is not the result of neutron capture(which occurs always most easily with slow neutrons). On theother hand, it cannot be produced by a neutron-loss reactioneither, for 2-5 m.v.is far too small an energy to knock off aneutron from the nucleus. In view of the chemical evidence whichexcludes the emission of charged particles, the only remainingexplanation seems to be that the activity is due to an excited stateof the stable nucleus 1151n (the other stable isotope 1131n is too rareto account for the observed yield). This state, for which the symboll151n* has been used, is metastable ; Le., the return, by emission ofradiation, into the ground state (which in general takes place within5 5 C. Magnan, Cornpt. rend., 1939, 205, 742. 56 Nature, 1939, 144, 707.5 7 Physical Rev., 1939, 55, 1269. 5 8 Ibid., p. 4720 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.a very small fraction of a second) is greatly delayed, so that the half-life of the state has the observed value of 4-1 hours.The correctiiess of this explanation has been proved in the mostdirect way, by showing 59 that l151n* nuclei can be produced byirradiating indium with X-rays.By varying the voltage of theX-ray tube, the energy threshold was found 60 to be about 1.3 m.v.This is considerably more than the excitation energy of 115In* (theenergy difference between l151n* and 1I5In), which is probablyabout 0.6 m.v., to judge from the energy of the electrons which areemitted when l151n* returns into the ground state. The mechanismof the excitation process is obviously such that the indium nucleiare first raised into a level at about 1.3 m.v. ; some of them will goback into the ground state but some will be “trapped ” in themetastable level at 0.6 m.v.Direct excitation of this level byX-rays of 0.6 m.v. is not possible, since a “ forbidden ” transitionis always forbidden both ways.The energy necessary for the excitation of the nucleus can alsobe provided by the impact of charged particles. Both protons 61and a-particles 62 have been found to produce the 4-l-hours activityin indium.Chemical Separation of Nuclear Isomers.-The energy liberatedin the transition between two isomeric states of a nucleus doesnot, in general, appear as radiation but is used to eject one of theelectrons of the K or L shell (“ internal conversion ”). I n thesubsequent re-establishment of the shell, the characteristic X-raysare emitted.By investigating these X-rays, it has in some casesbeen possible to check the atomic number of the resulting nucleus.For example, L. I. Roussinow and A. A. Yusephovich 63 placedradioactive bromine ( 80Br, periods of 18 mins. and 4.4 hours) betweenthe pole pieces of a magnet in order to prevent the p-particles fromreaching the counter. The radiation then recorded by the counterwas found to contain a soft component which, from its absorptionin selenium, arsenic, mercury, and lead, was identified with thecharacteristic X-rays of bromine. The radiation showed a simpledecay with 4.4 hours period and must therefore be emitted in thetransition from the 4-4-hours state of 80Br into a lower state of thesame nucleus.That this lower state is identical with the isomer of 18 mins.periodwas shown conclusively by E. Segrb, R. S. Halford, and G. T. Seaborg 64L 9 B. Pontecorvo and A. Lazard, Compt. Tend., 1939, 208, 99.G. B. Collins, B. Waldman, E. M. Stubblefield, and M. Goldhaber,Ph,ysical Rev., 1939, 55, 507.61 S. W. Barnes and P. W. Aradine, ibid., p. 50.E2 K. Lark-Horovitz, J. R. Risser, and R. N. Smith, ibid:, p. 878.c3 md., p. 979. Ibid., p. 321FRISCH : NUCLEAR ISOMERISM. 21who succeeded in isolating, by a chemical method, the nucleiwhich result from the isomeric transition, and found that theydecayed with a period of 18 mins. The separation method isin principle the same as in the classical experiment of L. Szilardand T. A. Chalmer~,~~ and is based on the recoil of the brominenuclei which is caused by the ejection of an electron in the isomerictransition. The recoil energy is sufficient to remove the bromineatom from the molecule to which it belongs, or at least to activatethe molecule so that it can undergo some chemical reaction.Segri:et al. prepared tert.-butyl bromide containing S%r and introducedit into aqueous methyl alcohol at O", where it underwent chemicalreaction resulting in the liberation of hydrogen bromide. Thisreaction requires an activation energy which may be supplied by theisomeric transition. After the reaction had gone on for some time,silver bromide was precipitated from the solution (after extractionof the butyl bromide with benzene). The precipitate was found todecay with a period of 1s mins., even if the separation was carriedout many hours after the preparation of the 8oBr when the 18-mins.period had apparently died off.If the precipitation was repeatedwith intervals of several hours, the same lot of butyl bromide beingused, the initial activity of the precipitate decreased with a periodof 4.4 hours, the period of the upper state of 80Br, as expected.Don C. DeVault and W. F. Libby 66 also separated the bromineisomers, by preparing a bromate solution containing soBr andprecipitating silver bromide from it. Immediately after precipit-ation the solution was found to be nearly inactive, and the authorsthink it probable that the upper state does not emit p-rays a t allbut that the apparent 4.4-hours P-decay of aoBr is due to the equi-librium between the upper state and its shorter-lived p-activedaughter substance.Three pairs of isomers of tellurium isotopes have been recognisedthrough the work of G.T. Seaborg, J. J. Livingood, and J. W.Kennedy,G7 and separation experiments showed that in all threecases the shorter period grows from the longer one. The isotopesare : 12'Te (90 days-10 hours), 129Te (30 days-70 mins.), and131Te (30 hours-25 mins.).It is becoming increasingly clear that nuclear isomerism, whichwas at first believed to be a peculiarity of a few nuclei only, is infact a very common phenomenon, the possibility of which must beconstantly kept in mind when assignments of radioactive periodsto definite isotopes are attempted. In particular, the occurrence66 Nature, 1934, 134, 462.6 6 Physical Rev., 1939, 55, 322.6 7 Ibid., pp.410, 79422 RADIOACTIVITY AND SUB- ATOMIC PHENOMENA.of active isomers of stable nuclei (as in the case of indium) increasesthe number of possible assignments in a disturbing manner.There are fortunately several ways in which the transition betweenisomeric states can be distinguished from a true p-transition(emission of an electron from the nucleus itself). Two have alreadybeen mentioned, vix., the study of the characteristic X-rays and therecoil separation. A further important criterion is the energydistribution of the electrons emitted in the transformation. Theinternal-conversion electrons, ejected from the K or the L shell as aconsequence of the transition between two states of the samenucleus, have a line spectrum, i.e., they are concentrated in one or afew narrow energy bands, whereas the electrons emitted from thenucleus itself in a p-transformation have the well-known continuous(bell-shaped) distribution. The use of a p-spectrograph permitsimmediate decision, but is not essential since even simple absorptionexperiments will show the difference: the absorption of a true,continuous p-spectrum is approximately exponential or, in otherwords, the logarithm of the transmitted intensity plotted againstthe thickness of the absorber gives nearly a straight line, but in thecase of an isomeric transition the plot bends downwards [see, e.g.,ref.(25)l.Nuclear Reactions in the Interior of Xtars.An important contribution to the problem of energy productionin stars has been given in a paper by H.A. Bethe.68 His conclusionsare based on a very careful and exhaustive discussion of all thosenuclear reactions which may be expected to occur in stars. Thetemperature in the interior of a star can be calculated, accordingto Sir A. Eddington, without making special assumptions as to thenature of the energy source, and is, e.g., a t the centre of the sun1-9 x lU7". On account of the presence of large amounts of hydrogenand helium, any nucleus present will be subjected to an intensebombardment by protons and a-particles possessing a Maxwellianenergy distribution, with energies of the order of 20,000 volts.Bethe shows that under these conditions most light nuclei arequickly broken up into protons and a-particles, so they cannot forma permanent energy source.This does not hold, however, for thefollowing cycle of reactions :E2C + H --+ 13N 13C + H --+ 14N1*N + H -+ l5O 15N + M + 12C + HeDuring the cycle, four protons are absorbed and two positronsemitted and the end result is a helium nucleus and the original 12C68 Physical Rev., 1939, 55, 434.13N --+ 13C + e+150 --+ l5N + eFRISCH : NATURAL RADIOACTIVITY. 23nucleus. I n other words, the carbon acts as a catalyst for thereaction 4H+ He + 2e+, which is accompanied by an energyevolution of about 30 m.v. Possible side reactions are discussed,and it is found that they are too weak to destroy the catalyst, evenin the course of astronomical times.From the nuclear reactions discussed, no other cycle can beconstructed which does not result in the quick destruction of thecatalyst.Elements below carbon do not permit the accumulationof four protons, but break up with emission of an a-particle beforethe last proton can be added. Elements higher than 15N have tooslow a reaction rate (because of their high charge which repels theprotons) to be of any importance in the energy production. Actually,the C-N cycle gives just the right amount of energy, in the sunand several other stars for which it was checked, to replace theenergy lost by radiation.One important conclusion drawn by Bethe is that a t presentheavy elements are not being built up to any appreciable extent,in the sun or other stable stars.It is probable that the buildingup of the heavy elements has taken place in the remote past, underextreme conditions of pressure and temperature (stellar or cosmicexplosions). Some stimulating speculations on this subject arecontained in a paper by C. F. von Weiz~acker.~~Natural Radioactivity.The discovery of a new natural radio-element has been announcedby M. Perey.'O The element-which has been given the nameactinium-K-originates from actinium by the emission of an a-particle. These a-particles had been known for a long time but hadbeen ascribed to impurities; Perey showed that they are presenteven if all the relevant impurities are removed. If measured on ap-ray electroscope, freshly purified actinium is practically inactiveand it takes days before the activity due to actinium-B and -Gbegins to develop.Perey found that a sniall fraction (0.5%) of thefinal activity develops within the first hour after purification, beingapparently due to a body of 21 minutes half-life growing directlyfrom the actinium. This active body was separated chemically andfound to follow the reactions of an alkaline element. On account ofthis chemical evidence, and on the assumption that it originatesfrom actinium through the emission of an a-particle, the newelement must have the atomic number 87. This seemsto be thefirst definite proof of the existence of an element with this atomicnumber.69 Physikal. Z., 1938, 39, 633.70 Compt. rend., 1939, 208, 97; J .Phys. Radium, 1939, 10, 43524 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.It is also noteworthy that, according to these observations, thedecay of actinium is a branching reaction similar to the decay ofradium-C, thorium-C, and actinium-C. The ct-p branching ratiois about 1 : 100, i.e., about one out of a hundred actinium nucleidecays with the emission of an a-particle.The Existence of Stable 3He.Using the Berkeley cyclotron as a mass spectrograph of very highintensity, L. W. Alvarez and R. Cornog 71 discovered the presenceof small quantities of 3He in ordinary helium. On adjusting themagnetic field so as to give resonance for doubly charged ions of mass3, they observed a weak beam with a range of 54 cm. in air, the rangeexpected for 3He nuclei of the energy determined by the field.Atmospheric helium was found to contain about ten times more3He than helium from gas wells.3He is by far the rarest stableisotope yet discovered ; a its " abundance " in atmospheric heliumis only about lo-'. The authors looked also for a possible beam of5PIe nuclei but without result.If 3He is stable, 3H should be unstable, decaying into 3He with theemission of P-particles. Alvarez and Cornog found that a long-lived activity which can be passed through hot palladium is producedon bombarding deuterium with deuterons and believe that thisactivity is due to the 3H which is known to be formed in the reaction2D + 'D -+ 3H + 'H.0. R. F.The Theory of Nuclear Forces.I n the year under review, progress of our knowledge of the nuclearforces has largely been negative, in that the discovery of the quadripolemoment of the deuteron by Rabi and his collaborators 1 has provedthe inadequacy of certain assumptions which had so far been thebasis of most discussions.The meson * theory of nuclear forceshas made further progress, but important diiEculties remain.Since the subject has not been specifically discussed in theseReports, it seems advisable not to limit the discussion to the currentyear, but to include a summary of the earlier development.It is now practically certain that nuclei consist of protons andneutrons. The Coulomb forces between the protons are repulsiveand do not affect the neutrons a t all. Magnetic forces (due to spin)7 1 Physical Rev., 1939, 56, 379, 613.1 J.H. B. Kellogg, I. I. Rabi, N. F. Ramsay, and J. R. Zacharias, PhysicalRev., 1939, 55, 318. * This term is now used instead of " mesotron.PEIERLS : THE THEORY OF NUCLEAR FORCES. 25between these particles might in certain circumstances produceattraction, but would be too weak to account for the observedstability of nuclei. It is therefore necessary to postulate forces ofa new type, “nuclear forces,” which hold the parts of a nucleustogether .However, if they were alwaysattractive, and acted between any two particles in the nucleus, thebinding energy of a nucleus would increase roughly as the numberof pairs of particles in the nucleus, Le., roughly proportionally tothe square of the mass number; the size of the nucleus would beindependent of the number of particles in it, since they would allcluster closely together.2 I n fact, however, both the bindingenergy and the volume (as estimated from scattering experiments,or from the Gamow barrier of radioactive nuclei,2 or from theenergy differences of light isobars 3, are roughly proportionalto the mass number.The reason for this might be that, as in aliquefied gas, the forces between the particles become repulsive atvery close approach. However, we are here dealing with shortdistances in which the quantum effect of penetration throughpotential barriers is of importance, and a repulsive force will not beable to keep the particles away from each other unless it is ofenormous strength. For this reason the explanation has notfound much favour.An alternative is to assume that the forces are attractive betweensome pairs of particles and repulsive between others.This wouldbe in analogy with the forces acting in homopolar molecules, whichmay be attractive or repulsive according to whether there is avalency bond between the atoms in question or not. Whether thisis the case depends in quantum theory on the symmetry of the wavefunction of the molecule with respect to the interchange of anelectron between the two atoms. Similarly W. Heisenberg4 andE. Majorana suggested that the nuclear forces between twoparticles might be exchange forces, i.e., that they might depend onthe symmetry of the wave function with respect to the two particles.A symmetric state would then give a different interaction from anantisymmetric state.Such forces are known as “ exchange forces.”This would give the required saturation of the forces sinceaccording to Pauli’s principle the wave function of a large nucleuscannot be symmetric in too many particles. I n fact, accordingThese forces must be attractive.H. A. Bethe and R. F. Bachor, Rev. illod. Physics, 1936, 8, 82.H. A. Bethe, Physical Rev., 1938, 54, 436; J. G. Fox, E. C. Creutz, M. G.White, and L. A. Ddsasso, ibid., 1939, 55, 1106; H. Brown and D. R. Inglis,ihid., p. 1182.2. Physik, 1932, 77, 1. Ibid., 1933, 82, 13726 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.to Heisenberg’s original scheme a neutron in the nucleus would beunivalent, forming a bond only with one proton, whereas onMajorana’s scheme it would be tervalent, forming bonds with twoprotons and a second neutron. (When considering this analogybetween nuclei and molecules it should, however, be realised that,owing to the high zero-point energy of the particles inside a nucleus,no definite positions can be allocated to them, and hence a geo-metrical localisation of the bonds or the use of structural formulzeis impossible.Nevertheless, it will still be true that each particlewill, on the average, be closer to those to which it is linked by“ bonds ” than to the others.)We may therefore expect that the force between two particlesdepends (a) on whether the wave function is symmetric or anti-symmetric (abbreviated to + and -), ( b ) on whether the spinsof the particles are parallel ( f f ) or opposite (J.+), ( c ) on the natureof the particles, i.e., whether neutron-neutron, proton-proton, orneutron-proton, ( d ) on the distance between the particles, and ( e )on their orientation, i.e., on the direction of the line joining themrelative to the direction of their resultant spin.Factors (a) and (b) give rise to four different arrangements :of which, however, in the case 6f like particles the last two are ruledout by Pauli’s principle.6 As regards ( c ) , it seems highly probablefrom the symmetry of the table of stable and radioactive isotopesthat the force between two protons is the same as that between twoneutrons, except for the electrostatic repulsion between the protons,which is responsible for the excess of neutrons over protons in allheavier nuclei.This leaves four possible cases of interactionbetween unlike particles and two between like particles.As regards (d), the force must in the main represent attractionand, if one introduces the exchange forces in order to account forthe saturation, there is no need to assume that attraction changesinto repulsion a t close approach. The potential is then of the typeof a potential well, which is characterised by its width ( i e . , therange of the force) and its depth (Le., the mean potential energy forclose approach). Lastly, as regards the dependence on direction( e ) , this possibility was not taken into account until experimentalevidence made it unavoidable, and so it has been considered incomparatively little work.6 The forces are customarily represented as a combination of four terms,of which the “ Wigner force ” is the same in all four cases, “ Majorana’s ” isattractive for the symmetric states and repulsive for the others, “Heisen-berg’s ” attractive for (+++) and (-J.-f) and “ Bartlett’s ” for parallel spin.We shall return to this point laterPEIERLS THE THEORY OF NUCLEAR FORCES. 27The most reliable evidence on the interaction potentials comesfrom the direct observation of the interaction between two particles.The angular momentum about the common centre of gravity is thena constant, and in quantum theory equal to a multiple of h / 2 x . Ifthe angular momentum is 1 units, centrifugal force makes it unlikelythat the particles approach more closely than to about 1 timesthe wave-length.Hence if the wave-length is much larger than therange of the interaction forces, only pairs of particles without orbitalangular momentum (1 = 0) are able to interact. From the angulardistribution of the neutrons and protons scattered by hydrogen, it isindeed possible t o verify that, up to energies of several m.v. (ie.,wave-lengths down to 3 x 10-13 cm.) only particles with zeroangular momentum are scattered '), so that the range of the forces iscertainly less than about 3 x 10J3 cm. Further, in the case of theneutron-proton interaction, the amount of scattering is theoreticallygiven by a constant which, for a given shape of the potential well,depends on its depth B and width a only in the combination Ba2,although it depends, of course, to a certain extent on the detailedshape of the well. It is found that by a suitable choice of thisconstant one can represent the data on the scattering, provided oneadmits two different values of the constant for pairs with paralleland with opposite spin.2 The bound state of the deuteron must alsobe expected to have no orbital angular momentum.Moreover, thebinding energy can again be shown to depend only on the combin-ation Ba2, and can therefore be compared with one of the twoconstants from scattering. The agreement seems satisfactoryY2- *The one unit of angular momentum which the deuteron is knownto possess must then be due to the spin of the particles, and thenormal state has therefore parallel spins.Moreover, a generaltheorem of wave mechanics states that even orbital momentumalways belongs to a symmetric state.We have thus obtained some information about the forces betweenunlike particles in a symmetric state with parallel spin. The secondconstant which is derived from the scattering law, together withcertain experiments on the phase of the scattered waveYg gives thesame information about the case of opposite spin, in which theinteraction is much weaker.I n the case of the proton-proton scattering, the situation is' P. I. Dee and C. W. Gilbert, Proc. Roy. SOC., 1937, A , 163,265.* M. A. Tuve and L. R. Hafstad, Physical Rev., 1936, 50, 308; cf., how-ever, M.Goldhaber, Nature, 1936, 137, 824; E. Amaldi, D. Bocciarelli, F.Rasetti, and G. C. Trabacchi, Physical Rev., 1939, 56, 881 ; T. Goloborodkoand A. Leipunski, ibid., p. 891.F. G. Brickwedde, J. R. Dunning, H. J. Hoge, and J. H. Manley, ibid.,1938, 54, 266; E. Teller, ibid., 1936, 49, 42028 RADIOACTMTY AND SUB-ATOMIC PHENOMENA.similar in that we have again a case in which the wave-lengthgreatly exceeds the range of the force, and in which therefore onlycollisions with no orbital angular momentum are affected by thenuclear forces. The mathematical treatment of the collision processis more complicated than for neutron-proton scattering, owing tothe simultaneous presence of the Coulomb repulsion.l0 As a resultof the higher experimental accuracy obtainable with protons,measurements of the scattering at a number of angles and energiesmake it possible to determine not only a combination of width anddepth of the potential well, but both the width and the depthseparately.In principle, such data would be suflicient to determinethe whole potential function (i.e., the shape of the well), and evenwith the data at present available, some shapes give a better fit thanothers. Amongst the functions that have so far been tried, the bestfit is obtained with the potential functionVfr) = B.e-r’a/(r/a) . . . . . (2)which suggests itself from the meson theory of nuclear forces,the constants having the values B = 46.8 m.v. and a = 1.2 xcm.11These values for a and B give the same value of Ba2 as that foundfor the symmetric state with opposite spin of the neutron-protoninteraction.12 This has given rise to the “ charge-independence ”hypothesis, which claims that the nuclear force between two particlesis independent of whether either of them is a neutron or a proton.13It is clear that this hypothesis is a generalisation which goes beyondthe direct experimental evidence in so far as very little is knownfrom this source about the interaction in an antisymmetric stateeither for like or for unlike particles.Similar results have been obtained by considering the bindingenergies of light nuclei containing more than two particles.Thisis usually done on the assumption that the interaction energybetween two particles is not affected by the presence of otherparticles, so that the potential energy of the nucleus is the sum ofthe interaction energies of all possible pairs of particles.Thisassumption is plausible enough; it is very exactly satisfied in the10 G. Breit, H. M. Thaxton, and L. Eisenbud, Physical Rev., 1939, 55,1018 ;L. E. Hoisington, S. S. Share, and G. Breit, ibid., 56, 884.l1 M. A. Tuve, N. P. Heydenburg, and L. R. Hafstad, ibid., 1936, 49,402;L. R. Hafstad, N. P. Heydenburg, and M. A. Tuve, ibid., 1937, 51, 1023;1938, 53, 239; R. G. Herb, D. W. Kerst, D. B. Parkinson, and G. J. Plain,ibid., 1939, 55, 998; N. P. Heydenburg, L. R. Hafstad, andM. A. TUVB, ibid.,p. 603.l2 G. Breit, L. E. Hoisington, S. 5. Share, and H. M. Thaxton, ibid.,p. 1103; cf., however, F. E.Brown and M. S. Plesset, ibid., 56, 84.13 G. Breit, E. U. Condon, and R. D. Present, ibid., 1936, 50, 825PEIERLS : THE THEORY OF NUCLEAR PORCES. 29atom, but reasons have been given why it might not hold in thenucleus . l4Once this assumption is made, the binding energy of any nucleusis known in principle, provided one knows the interaction betweentwo elementary particles for the six cases enumerated above. Theactual determination, however, requires the solution of a wave-mechanical many-body problem, which involves very lengthycalculations and cannot be reliably carried out except in the caseof the lightest nuclei.The nuclei up to mass number 4 (2H, 3H, 3He, 4He) all have wavefunctions which are very nearly symmetric in all particles, andtherefore involve only three of the six possible interaction functions.About these it is usually assumed that their dependence on distanceis the same, so that they differ merely by multiplicative factors.If, moreover, a specific assumption is made as to the shape of thepotential well, we are left with the three depth constants and thewidth (which is assumed the same for all three) as parameters.One can then, for example, determine these four parameters fromthe binding energy of the deuteron, together with the data onneutron-proton and proton-proton scattering, and can then workout the mass defects of the other light n~c1ei.l~ This leads to fairagreement, considering the simplifying assumptions on which thetheoretical values are based. It is satisfactory, in particular, thatfor the range, to which the mass defects are very sensitive, oneobtains the same order of magnitude whether one starts from themass defects or from the proton-proton scattering.A number ofdifficulties remain, but the impression is, on the whole, that the theoryis along the right lines.The position is less clear for nuclei of mass number greater than4. In these the wave function cannot be symmetric because ofPauli's principle, and the interaction functions of antisymmetricstates will come in. The calculations become progressively moredifficult as the number of particles increases. It is possible toobtain some inequalities limiting the ratio of the force constantsin the antisymmetric case to the others,16 and some more detailedwork has been d0ne.l'l4 H.Primakoff and T. Holstein, Physical Rev., 1939, 55, 1218.l6 W. Rarita and R. D. Present, ibid., 1937, 51, 788; H. Margenau andD. T. Warren, ibid., 52,790; 52, 1027; H. Margenau and W. A. Tyrrell, ibid.,1938,54, 422 ; W. Rarita and Z. I. Slawsky, ibid., p. 1053, and others.l6 G. Breit and E. Feenberg, ibid., 1936, 50, 850; H. Volz, 2. Physik,1937, 105, 537; D. R. Inglis, Physical Rev., 1937, 51, 531; N. I<emmer,Nature, 1937, 140, 192.l7 E.g., G. Breit and J. R. Stern, Physical Rev., 1938, 53, 459; E. Wigner,ibid., 1937, 51, 106; E. Wigner and E. Feenberg, ibid., p. 95; D. R. Inglis,ibid., p. 525 ; H. Margeneu, ibid., 1939, 55, 117330 RADIOACTIVITY AND SUB- ATOMIC PHENOMENA.The situation was, however, completely changed by the discovery 1that the deuteron has an electric quadripole moment.The signof this shows that the line joining the proton and the neutron ismore likely to be parallel to the direction of the resultant spin thana t right angles to it. This proves that the forces between theparticles cannot be strictly central forces. Moreover, the magnitudeof the quadripole moment suggests that the forces are not evenapproximately central, but that the directional dependence of theforce is an effect of the same order of magnitude as the wholeattractive force.18This new fact therefore throws doubt on the validity of all theprevious work. No doubt the agreement obtained in determiningthe range of the forces and other constants in different ways is notfortuitous, and some of the old calculations can certainly be justifiedwith the new, more generalised, type of force, but it will be necessaryto reconsider some of the old work from this point of view.Moreover, there may not now be any need for assuming exchangeforces, since the directional dependence will, on its own, alreadyensure saturation of the forces in heavy nuclei.In a heavy nucleus,each particle must have neighbours which adjoin it in every direction,and if the force is attractive in some directions and repulsive inothers, it is never possible to make it attractive between all particlesin the nucleus.19One particular type of directional dependence is supplied bya law of force that may be obtained from the meson theory ofnuclear forces (see below).In this, the interaction of a proton anda neutron depends on direction in the same way as that betweentwo magnetic dipoles. This law cannot be completely correct,since (just like the interaction between two dipoles) it leads to apotential which a t small distances behaves like the inverse cube,and this would make the binding energy of the deuteron infinitelylarge. One may avoid this difficulty by modifying the law ofinteraction for small distances (“ cutting-off ” 19), but in order to beconvincing this artifice would require support by further comparisonwith experimental data.An independent line of development of the theory is the mesontheory of nuclear forces. A rough outline of this was given in lastyear’s Report on the meson.20 The detailed results of the theorydepend on a number of assumptions about the spin of the mesonand the action of the meson field on the neutron or proton.If themeson has no spin, one would obtain repulsion in the normal state18 R. F. Christy and S. Kusaka, Physical Rev., 1939, 55, 665.lS H. A. Bethe, ibid., p. 1261.2o Ann. Reportu, 1938, 35, 20PEIERLS : THE THEORY OF NUCLEAR FORCES. 31of the deuteron. If the spin is one unit, the field is more closelyanalogous to the electromagnetic field, and its action on the heavyparticles may be similar either to the action of a field on a charge,or to that of a dipole, or to both. If we take the analogy of a chargeonly, it is impossible to obtain the right answer for both the (+ tf)and the (+J.f) interaction of the deuteron.If a dipole term isincluded, this produces a force similar to the force between twodipoles. I n view of what was said above about the directionaldependence of the force, this may be desirable, but it leads to aninfinite binding energy of the deuteron, unless the force is arbitrarily“ cut off ” at close approach. I f one uses the artifice of cuttingoff, it is apparently possible to obtain the right results for bothsymmetric states of the deuteron and its quadripole moment withoutusing the “ charge ” type of interaction a t all, which makes forsimplicity.19Alternatively, it has been suggested21 that one can avoid thediverging term by postulating two *kinds of mesons of different spin,and adjusting the “ charge” and “dipole” constants for bothin such a manner as to cancel the diverging terms in the nuclearforce.The theory then gives rise to a central force between neutronand proton which can be so adjusted as to yield the correct resultsfor both the (+ .ff) and the (+ J. +) interaction. The shape of thepotential well is then given by the equation ( Z ) , which has beenfound to give good agreement with the observed proton-protonscattering, but if one uses the relation between the meson mass andthe range of the force as outlined in last year’s ReportFO one wouldobtain a meson mass of 326 electron masses, which does not agreewith cosmic-ray results. This discrepancy may not be very serious,since in any case the interact’ion between like particles would betransmitted by neutral mesons,2o the mass of which is not known;indeed, if the forces are not required to be exchange forces, it iseven possible to assume that aZZ nuclear forces are transmitted byneutral mesons,19 and hence to conserve the “ charge-independencehypothesis.” If this point of view were correct, it would detractfrom the success of Yukawa’s theory in predicting the existence ofthe meson from nuclear forces, since the mesons found in cosmicrays would then have little connection with those responsible for thenuclear forces.If one adopts the artifice of avoiding the infinite terms by meansof two types of mesons,21 the forces become approximately centralforces. It is, however, likely that a more rigorous treatment, whichtakes into account relativistic effects, would again give a directional21 N. Kemmer, Proc. Roy. SOC., 1937, A , 166, 127; C . Maller and L. Rosen-feld, Nature, 1939, 144, 24132 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.dependence, and might thus account for the quadripole momentof the deuteron.22 These effects are analogous to the magneticinteraction between spin and orbit (multiplet structure) in the atom.Whereas, however, in the atom this is only a minor correction, in thenucleus it would be of greater importance; its smallness in theatom is, in the last resort, due to the smallness of the dimensionlessconstant 2xe2/hc = 1/137 (e = electronic charge, h = Planck’sconstant, c = velocity of light) which measures the interaction of theelectron with the electromagnetic field. If the correspondingconstant of the meson theory is so adjusted as to give the right orderof magnitude for the nuclear forces,23 its value becomes about 1/5.This means that the coupling of a proton or neutron with the mesonfield is very much stronger than that of an electron with the electro-magnetic field. Hence, many approximate calculations whichtreat this coupling as weak, and which are justified in the theoryof radiation, are not justified in the meson theory. The mathe-matical difficulties created by this have not yet been overcome.One of them is reflected in the fact, already mentioned, that in themeson theory the interaction force between two particles may bealtered if a third particle is present to interact with the first t ~ 0 . l ~Owing to these mathematical difficulties, a number of questionsof fact have not been answered, without which the final verdict onthe meson theory of nuclear forces cannot be given, but at presentit represents the most hopeful line of attack. R. P.0. R. FRISCEI.R. PEIERLS.22 Idem, Nature, 1939, 144, 476.23 H. Friihlich, W. Heitler, and N. Kemmor, Proc. Roy. Soc., 1938, A, 166,154

ISSN:0365-6217    

DOI:10.1039/AR9393600007

出版商:RSC    

年代:1939

数据来源: RSC

摘要:

GENERAL AND PHYSICAL CHEMISTRY.INTRODUCTION.IN this year’s Report the policy, outlined last year, of having com-plete reports on certain aspects of physical chemistry has beencontinued. For a number of years there have been articles on infra-red and Raman spectra written from the point of view of applicationt o problems in molecular structure. This year the report on thattopic treats of electronic spectra in the Schumann ultra-violet andthe information such spectra give about the electronic structure ofsimple molecules. The Report for 1937 described the revival ininterest in the structure of liquids ; the continued interest justifiesanother article reviewing the more recent work on this subject.The chemical kinetics section this year is divided into two parts.The first deals with polymerisation reactions.Within the pastfour or five years a new branch of kinetics has thereby arisen, andalthough the growth continues, the subject is now sufficiently stableto merit some discussion in a co-ordinated manner. The secondpart deals with a problem of long-standing interest, namely, theeffect of the solvent on reactions in solution. This is restricted tobiinolecular reactions in order to simplify the discussion of theresults. In the realm of surface chemistry this year the propertiesand reactions of monolayers on aqueous substrates are discussed,but the biological implications of the work are omitted. An accountis also given of work on multilayers.H. W. M.1. STRUCTURE AND MOLECULAR FORCES IN LIQUIDS.Intermolecuhr Forces and the Properties of Solutions.In the Annual Reports1 for 1937 “Intermolecular forces and theproperties of liquids” were reviewed by J.A. V. Butler. Theadvances made in recent years in our understanding of the liquidstate have had great influence on the theories of solution and ofchemical reactions in solution. These problems are being ap-proached from the standpoint of the theories of the liquid state. Theimportance of reactions in solution and of the influence of solventon the velocity and the equilibrium constants of such reactions is sogreat and widespread that the need for an understanding of thenature of solutions and of solution processes in terms of inter-molecular forces and the behaviour of molecules requires no emphasis.1 P.76.REP.-VOL. XXXVI. 34 GENERAL AND PHYSICAL CHEMISTRY.Intermolecular Forces and the ‘Heats of Solution.-One of theinteresting points about the calculation of the heats of solution ofmolecules from our knowledge of intermolecular forces is that verysimple considerations can lead to quantitatively exact results for theenergies of solution.The general model which has been adopted for these considerationsis one in which the solution process is divided into two steps : (i)the formation of a cavity in the solvent large enough to accommo-date the solute molecule, and (ii) introduction of the solute moleculeinto the cavity.2 The energy change accompanying the solution ofa molecule from the gas phase will be made up of two terms, E =E, - E,, where E, and E, represent the two respective energychanges, the former being an expenditure of energy, and the latterbeing made up of the energies of interaction between the solutemolecule and the solvent molecules.The main differences in theattempts to calculate the energies of solution processes arise fromthe different methods employed for the calculation of the two termsE, and E,. We will review here several attempts which have beenmade with different types of system.H. H. Uhlig3 determined the energy (or rather the ftee energy)of cavity formation from the surface tension of the solvent. I nforming a cavity of radius r the free energy change is 4xr2y, where yis the surface tension of the solvent. If then the solute moleculehas a radius r, Uhlig writes the free energy change as 4w2y - E,.The Ostwald solubility coefficient ct is then related to the free energychange byIf E, is small compared with the energy of forming the cavity, or ifE, is constant from one solvent to another and from one solute toanother, then the greater the radius of the solute molecule and thegreater the surface tension of the solvent the smaller will be thesolubility.Uhlig finds that J.Horiuti’s4 data for the solubility of gases inorganic solvents do obey equation (l), and that the molecular andatomic radii resulting from this expression agree fairly well withvalues obtained from other methods. In view of the simplicity ofthe model and of the fact that the entropy changes accompanyingsolution are neglected, the correspondence is remarkable.D.D. Eley5 has considered other methods of determining theenergy change of cavity formation.- k T I n a = 4 x T v - E s . . . * (1)B. Sisskind and I. Kasarnowsky, 2. anorg. Chem., 1933, 214, 385.J . Physical Chem., 1937,41, 1215.Sci. Papers Inst. Phys. Chern. Res. Tokyo, 1931, 17, 126, 222.Trans. Faraday SOC., 1939, 35, 1421EVANS : STRUCT~JRE AND MOLECULAR FORCES IN LIQUIDS. 35(a) When 1 mol. of gas dissolves in an infinite volume of solutionThe at a concentration of 1 mol./l. an expansion of V C.C. occurs.energy change accompanying this expansion is given by( W a V T = P + ~(ax/aV),and if p is negligible AE, = TaAV/P, where a and p are respectivelythe thermal expansion coefficient and the compressibility of thesolvent.In forming a cavity in a liquid one is expanding the free volumefrom vf’ to vj, and hence the change in E, accompanying this changein free volume is given approximately by E, = TaV/p if the changein free volume is identified with the actual volume change of thesolution.(b) The second method is identical with that of Uhlig exceptthat the energy (y - T2y/aT)4xr2 is used.(c) The third method is that of E.Lange and W. whohave suggested E, = Evap.(r/rr)2 for the energy of forming a cavityof radius r in a solvent of molecular radius r,. The term E, isrelated to the latent heat of vaporisation L by Evap = L - RT.The values obtained by these three methods do not agree verywell-those given by ( b ) and (c) correspond most closely.The verywide disparity which Eley finds between the values given by thethree methods in the case of water is attributed to the specialstructure of liquid water.Rather striking success has been obtained from this model ofcavity formation followed by introduction of the solute molecule inthe case of solution of organic molecules in water by J. A. V. Butlerand of gases in water by D. D. Eley.8 Butler expresses the energyrequired to bring a solute molecule from the gas phase into solutionin terms of the energy &, required to separate water molecules inorder to make a cavity of the necessary size, and w, the energy ofinteraction of the solute molecule with the water molecules a t thesurface of the cavity.Hence= x#bV, W - x$A, WConsidering only those forces acting between adjacent molecules,we haveE = *n+w,w - q L , wwhere n is the total number of water molecules at the surface of thecavity ; i.e., in making a cavity +n water-water contacts are broken.If A is an organic molecule made up of different units a, and ba, is6 8. physikal. Chem., 1937, A , 180, 238.Trans. Faraday SOC., 1937, 33, 229.* Ibid., 1939, 35, 128136 GENERAL AND PHYSICAL CHEMISTRY.the interaction energy of group a of the molecule A with an adjacentwater moleculewhere a is the number of water molecules adjacent to the group a.If the quasi-crystalline structure of water is taken as a basis, then,e.g., a methane molecule, being approximately the same size as awater molecule, will occupy a ‘‘ lattice point,” i.e., a position equi-valent to a water molecule, in the water structure.This will involvethe breaking of two water-water contacts (four are broken and twoare re-made) and the forming of four water-methane contacts.HenceTo form a cavity to accommodate an ethane molecule, it will benecessary to replace two water molecules at ‘‘ lattice points ” by themethyl groups of the ethane, thus leaving a cavity with 6 watermolecules in its surface. HenceE = &y&v - C a $ , , wECH‘ = 2$W, W - Q$CH4. W= 3&7,m - 6$CHs.WButler extends this method to include hydroxyl, ketonic and alde-hydic and amino-groups, as well as the hydrocarbon unit CH,.Having obtained a value for &, from the latent heat of vaporisationof water and the characteristic values (e.g., &, w) from experimentaldata, it is then possible to calculate with remarkable accuracy theheats of solution of a large number of organic compounds by buildingreasonable models of the cavities required.There is a difference in viewpoint between Eley and Butler on thequestion of the energy change of cavity formation.Using method(a) for calculating the energy, Eley concludes that for inert gasesin water at ordinary temperatures there is no need for a cavity tobe formed by the breaking of water-water contacts; i.e., he doesnot consider it necessary for an inert-gas molecule to take up aposition by displacing a water molecule from a lattice point, butrather that the solute molecule can be accommodated in the largefree spaces in the water lattice which can be expanded if needbe by a small expenditure of energy.At ordinary temperatures, E, being negligibly small, the heats ofsolution are given by E = nE,, where n is the number of watermolecules adjacent to the inert-gas solute molecule; and E A , theenergy of interaction between a water molecule and the inert-gasmolecule, is given bywhere the subscripts 1 and 2 refer to the inert-gas and the wateEVANS : STRUCTURE AND MOLECULAR FORCES IN LIQUIDS.37molecules respectively, a is the polarisability, p the dipole moment,r the radius, and i the ionisation potential. To obtain agreementbetween the calculated and the observed heats of solution, n isrequired to be 10 for all inert gases except helium, where 4 is foundto be the best value.Heats of Solution of Ions.--If water were an ideal insulator ofdielectric constant -q, then for an ion of charge Ze and radius r theheat change accompanying the solution of the ion from the gasphase would beThe field set up by an ion is greater than the saturation field for thedielectric and, as pointed out by P.Debye,g equation (2) will nothold under these conditions.J. D. Bernal and R. H. Fowler lo have calculated the heats ofhydration of ions by splitting up the energy into the followingterms :(a) The energy of the water molecules in the co-ordination shell ofthe ion. This is approximately given by nP, where n is the numberof water molecules co-ordinated round the ion, and P is the inter-action energy between the ion and a water molecule.( b ) The energy of the main bulk of the water outside the spherein which the field is greater than the saturation field of the dielectric.(c) The mutual energy of the water molecules which have in thefield of the ion changed their normal orientations.The heat of solution of an ion is given by[(q - 1)/2q][Z2e2/r] .. . . . (2)q - 1 Z2e22-q ' R u, = ___ - + nP - u(w)where R is the radius of the saturation sphere and u(w) is the energyof re-orientating the water molecules in the field of the ion.M. G. Evans and D. D. Eley l1 have made very similar calculationsof the heat of hydration of ions by considering the energy changesinvolved in the following steps.(a) A tetrahedral group of five water molecules is removed fromthe liquid into the gas phase. The expenditure of energy involvedin this step arises from the interactions between the tetrahedralgrouping and the neighbouring water molecules.( b ) In the gas phase the tetrahedral group is dissociated intofive separate water molecules.This expenditure of energy arisesfrom the mutual interaction of the water molecules in the tetra-hedral group.9 " Polare Molekeln," Chap. V, 1929.10 J . Chem. Physics, 1933,1,511.11 Trans. Faraday SOC., 1938, 34, 109338 GENERAL AND PHYSICAL CHEMISTRY.( c ) In the gas phase four water molecules are co-ordinated roundthe particular ion to be dissolved. This energy will be 4P, where Pis the interaction energy between the ion and a single water molecule.( d ) The new tetrahedral structure including the ion is returnedto the cavity in the liquid.The energy terms involved in thisstep will include the reorientation energy of the water molecules,because the water molecules round an ion have a different orientationfrom that round a central water molecule, and the energy of intro-ducing a charged sphere of radius ri + 2r, into a dielectric medium.(e) Finally, the fifth water molecule is returned to the liquid, astep which involves the latent heat of condensation of water. Thetotal energy change involved in these steps amounts to an expressionwhich is practically identical with that given by Bernal and Fowler.Both these methods lead to calculated heats of hydration of ionswhich agree with those determined from the heats of solution of ionpairs on the assumption that potassium and fluorine ions have thesame heats of solution.The method first given by Bernal andFowler is the basis of all the recent attempts to calculate heats ofsolution whether of ions or of non-electrolytes when special attentionis being given to the structure of the solvent and the individualbehaviour of the solvent and solute molecules.The Partition Fwnctions for Solutions.-Since the thermodynamicproperties of a, system can be calculated from the explicit partitionfunctions for that system, it is a matter of great interest and im-portance to construct such functions for liquids and solutions.The partition function for a liquid of N molecules can be written l2as f N = JNB(T).Here J is the partition function for the internalelectronic, vibrational, and rotational states of the molecule whichare independent of the position of the molecule in the liquid; B(T)is then the partition function for the translational motion of themolecule and can be writtenB(T) = 1. . . lexp (- $) dxl.. . d z ~ . dpzl. . .where W is the potential energy of the system for a particularconfiguration in phase space.The problem of obtaining a partition function for a liquid becomesthat of obtaining an explicit form for B(T).J. E. Mayer, in a series of papers,13 has attempted an evaluation ofla R. H. Fowler, “ Statistical Mechanics,” 2nd Edition, Cambridge Univ.Press, 1937; R. H.Fowler and E. A. Guggenheim, “Statistical Thermo-dynamics,” Cambridge Univ. Press, 1939.l3 J. E. Mayer, J . Chem. Phy8/sics, 1937,5,67; J. E. Mayer and P. F. Acker-mann, ibid., p. 74; J. E. Mayer and S. F. Harrison, ibid., 1938, 6, 87;J. E. Mayer, J . Phy&ul Chem., 1939,43, 71EVANS : STRUCTURE AND MOLECULAR FORCES IN LIQUIDS. 39B(T), but in most cases the problem has been approached either bydealing with those systems for which B(T) can be obtained withsome certainty or by making approximations to a general form ofB(T). Thus, for example, H. Eyring l4 expresses the translationalpartition function for a liquid as312 NB(T) = [,(’*) ] exP(-j$)Here W , which is a function of the configuration, has been replacedby its average value E, averaged over all accessible configurations,and the whole uncertainty is now contained in the volume Vf;this is termed the free volume, and is the volume which is accessibleto the centre of the molecule. Eyring and his collaborators haveconsidered several models for determining the free volume.On the assumption that the whole of the free volume of the liquidis available to each molecule (which distinguishes the liquid statefrom the solid, in which each molecule is confined to its particularcompartment of free volume), the partition function of a liquid canbe writtenA large amount of work has been carried out on the thermodynamicproperties of the liquid state, using this expression.The approximation used by Eyring, of each molecule moving ina uniform average potential field E , was first made by E. A.Guggen-heim,l5 who points out that in this approximation no account istaken of the change in interaction energy as the molecule movesabout its average position. The behaviour of the molecule willprobably be better represented on the basis of the quasi-crystallinemodel of a liquid.16 Each molecule will be moving about a ‘‘ latticepoint ” of minimum potential energy E,, and will behave as an iso-tropic three-dimensional harmonic oscillator with a characteristicfrequency v. 17 The partition function for the liquid will be given byfN = (z) kT 3N JNexp { - Eo &kT}l4 H. Eyring and J. Hirschfelder, ibid., 1937, 41, 249; J. 0. Hirschfelder,I>. Stevenson, and H. Eyring, J. Chem. Physics, 1937, 5, 896; J.F. Kincaidand H. Eyring, ibid., p. 587; ibid., 1938, 6, 620; J . Physical Chem., 1939, 43,37 ; H. Eyring and R. F. Newton, Trans. Farachy SOC., 1937,33,73.l5 Proc. Roy. Soc., 1932, A, 135, 181.The model of a liquid as an assembly of harmonic oscillators is essentiallydue to G. Mie (Ann. Physik, 1903,11,657).l7 A more general model of a liquid has been used by J. E. Lennard-Jonesand A. F. Devonshire, Proc. Roy. SOC., 1937, A, 163, G l ; 1938, A, 165, 1.It is a model of a molecule moving in the available volume in a field of forceset up by the interactions between the molecule and its neighbours40 GENERAL AND PHYSICAL CHEMISTRY.Applying the same methods to binary mixtures of non-electrolytes,we can write the partition function for a mixture of ‘N, and N2molecules of species 1 and 2 asj”1+ 3 2 = J1N1 J2NaB( T)where J , and J, are the partition functions for the internal states ofthe molecules 1 and 2 which can be separated from the configurationaldegrees of freedom, andB( T) = I.. . / exp (- $) dxl . . . dzNl .dx,’ . . . dzns’. dpZ1. . . dpz,, . dpZ1,. . . dpxN,As in the case of a liquid, Eyring replaces W by an average value E,and introduces the free volume of the mixtureHere wf is the free volume of the solution and the term Wl + N2) !NI! N , !arises from the physically different permutations of the two-specieswhich are possible.To obtain the thermodynamic properties from this partitionfunction, we can write the free energyThermodynamic Properties of Regular and Ideal 8olutwns.lgE.A. Guggenheim l 9 has discussed the thermodynamic propertiesof systems with especially simple forms for B(T). He defines aperfect solution as one satisfying the following conditions : (1) Themolecular types A and B pack in the same way. (2) The molecularvolumes are sufficiently alike so that mixtures of the two species ofmolecule can pack in the same way as each of the pure liquids. (3)The ratio of the free volumes, vj, of the pure liquids does not differfrom unity by more than 30%. (4) When the two liquids are mixedthe molecular volumes Va and VB and the free volumes vfA and v p bothremain unaltered. ( 5 ) The average potential energy of a pair ofmolecules AB is zero.18 See R. H. Fowier, op cit. ; R.H. Fowler and E. A. Guggenheim, op. cit.Is Proc. Roy. SOC., 1935, A , 150, 552; Trans. Paraday SOC., 1937, 33, 151EVANS : STRUCTURE AND MOLECULAR FORCES IN LIQUIDS. 41For such a solutionwhere a is the average potential energy of molecule A in the pureliquid A, and a similar definition obtains for xB.This expression for the partition function leads to a valuefree energy P, vix.,NB { - xB - kT In +Bug - kT + kT Inwhere $ = (2~rnkTjh~)~'~Jwhich is approximately equal to the Gibbs function G.for the+SincexA, XB, vA, and vB are independent of ATA and NB, the partial potentials,which leads to Raoult's law.The extension of these ideas to strictly regular solutions, approxi-mate methods being used, has been made by A. W. Porter,20 J. H.Hildebrand,21 and G.Scatchard22 in an attempt to evaluate thedeviation of actual solutions from perfect solutions. The physicalsignificance of the approximation, that the change of entropy onmixing is the same as for an ideal solution, is complete randommixing. By random distribution one means that the neighboursof each molecule are on the average distributed among the variousmolecular species of the mixture in the proportions of their molefractions, the average local composition in the vicinity of a moleculebeing identical with the bulk composition of the solution.In real solutions with non-vanishing heats of mixing, randomdistribution is no more than an approximation to the actual state of2o Trans. Paraday SOC., 1920, 16, 336.21 J. Amer.Chem. SOC., 1929, 51, 69.z2 Chem. Reviews, 1932, 8, 32142 GENERAL AND PHYSICAL CHEMISTRY.affairs. The problem thus resolves itself into a study of the in-fluence of deviation from random distribution on the thermodynamicfunction of the system. The average distribution of the neighboursof a molecule in solution among the various species present is deter-mined by two opposing influences-the disordering effect of thermalmotion and the ordering effect of intermolecular forces. Forexample, if in a binary mixture of A and B the intermolecularattraction between A and B is greater than between like molecules,each molecule will exert an ordering effect in its vicinity resulting ina local composition richer in molecules of the opposite species thanthe solution in bulk. An extreme case of such an ordering influenceis to be found in the case of ions dissolved in water, where thestrong ion-dipole interaction causes a (‘ freezing ” or ordering of thewater molecules in the vicinity of the ion.The extent to whichsuch local segregation of species can be established will depend uponthe thermal motion and will be greater the lower the temperature.In recent years the problem of order and disorder has become ofgreat importance in discussions of solid solutions and alloys.23This case of order in solutions differs from that in solids in that thereis no long-range order in liquid solutions and we need only dealwith local order. Recent treatments of order-disorder in liquidsolutions have been made by R.H. Fowler and G. S. Ru~hbrooke,~*using the method worked out by Bethe 23 for solid solutions, and byJ. G. Kirkw00d,2~ who shows that the local order established by amolecule among its neighbours opposes the tendency of the solutiont o separate out into two phases. This process may be considereda macroscopic mechanism for establishing order, satisfying a ten-dency for a molecule to make its environment rich in its own species.This tendency may be partly satisfied without separation into twophases through the microscopic ordering mechanism by which amolecule establishes a local composition richer in its own speciesthan in the solution in bulk.Relations between the Energy and the Entropy of Solution.The transfer of a molecule from the gas phase to a solution ischaracterised by the change of any two of the three partial molalquantities : heat content H , free energy B, and entropy X :- - -- - -A F = AH - TASA complete molecular model of the solution process would give a93 H.A. Bethe, Proc. Roy. SOC., 1935, A , 150, 552.24 Trans. Faraday Soc., 1937, 33, 1272; G. S. Rushbrooke, Proc. Roy. SOC.,P 6 J. PhycwhE Chem., 1939, 43 107. 1918, A, 166, 296EVANS : STRUCTURE AND MOLECULAR FORCES IN LIQUIDS. 43priori values for these quantities, and we have seen in the precedingparagraphs that attempts are being made in simple cases to calculatethese terms.If we consider a series of solutions in which the forces acting arequalitatively similar, it might be possible to obtain a relationbetween AF, AH, and A s which would be valid for any system inthe series.Such a relation might be valid either for ( a ) a givensolute in a series of different solvents, or for ( b ) a series of differentsolutes in the same solvent. M. G. Evans and M. Polanyi 26 sug-gested the existence of such relations by considering a continuouschange in the solvent (particular solvents being points along acontinuously changing variable). If the continuously varyingsolvent can be represented by a parameter x thena(AH)/ax = y2 - y1 and Ta(AX)/& = 8, - 8,If yl, y2, a,, and 8, are constants with respect to x , the integratedforms areAH = (y, - yl) + const.TAS = (8, - 8,) + const.---If AH:, AH;, AH; . . . AH; are the heats of solution of substanceA in a series of solvents 1,2, 3 .. . j, and AS:, As: . . . AS; arethe corresponding entropy changes, then the above equations lead to- - -- *l)" and i = 1, 2, 3, . . . j ASA AHA 2 = a 2 + const.; a =R RT (Y2 - Yl)*-Similarly, if Akf, AH:, AH: . . . are the heat changes for a seriesof solutes A, B, C . . . in the same solvent i, then(', - 81){ and P = A, B, C . . . ASP A E- = a 2 + const. ; a =R RT (Y2 - Y l hEvans and Polanyi found that such a relationship was given for thesame solute in a series of solvents, but that the relationship for thesame solvent and a series of solutes was limited in the cases theyexamined to solutes which belong to the same chemical group. Thesolutes which Evans and Polanyi considered were, in general, fairlycomplex organic substances of high molecular weight.J. A. V.Butler 27 has shown that a linear relationship between AH and A 8- -2 6 Trans. Faraday SOC., 1936, 32, 1333.2 7 Ibid., 1937, 33, 168; J. A. V. Butler and W. S. Reid, J., 1936, 117141 GENERAL AND PHYSICAL CIIEMISTRY.for the same solute in a series of solvents is given by simpler systemssuch as methyl alcohol in solvents such as benzene, hexane, carbontetrachloride, and chloroform, and moreover, that as far as dataare available there are indications of a similar relationship for othersolutes such as nitrogen, argon, and helium. R. P. Bell28 hasanalysed the data for the solubility of gases in various solvents, andfinds that for a given solvent there is a linear relation between A Sand A H for the different solutes considered. I.M. Barclay andJ. A. V. Butler 29 have extended the linear relationship between theheats and entropies of solution for a series of solutes in a given sol-vent by measuring the heats and entropies of vaporisation fromdilute solutions of several solutes in acetone and in ethyl alcohol.The theory of such relationships has not yet been worked out inany detail. We have seen that the energy of a, solution is a verycomplicated function of the molecular configuration, but indicationsof how such linear relationships do arise can be seen fairly easily.Bell 28 has shown that if the configuration of the solvent moleculesis not appreciably disturbed by the presence of the solute molecules,or at least disturbed in the same way by different solute molecules,then A H and A S both depend upon the same parameter characteris-ing the interaction between solute and solvent molecules anddepending on the solute but not the solvent.This leads to afunctional relationship between A H and A S for a series of solutesin the same solvent, but not to one for variations in the solvent.If the rotational and vibrational states of the solute moleculesare the same in solution as they are in the gas phase, and if thebehaviour of the solvent molecules is not fundamentally affectedin the neighbourhood of the solute molecules, then the most impor-tant term in the entropy change accompanying the solution processwill be A S = R In v&, where vf is the free volume available to thesolute molecules in solution, and vg the volume in the gas phase.The former is not characteristic of the solvent alone and independentof the nature of the solute molecules.Lennard-Jones and Devon-shire,l7 in discussing the entropy changes accompanying the vaporisa-tion of pure liquids, have defined the available free volume for aparticular molecule in terms of the potential-energy field set up bythe interaction between the molecule and its neighbours :vf =/e-*r)PT d7In this expression #(r) is the potential energy of the molecule as azB Ibid., 1938, 34, 1445.-28 Trans. Paraday Soc., 1937, 33, 496EVANS: STRUCTURE AND MOLECULAR FORCES IN LIQUIDS. 45function of its distance from the centre of its cavity.This sameargument can be extended to the case of a solute molecule in thepresence of its neighbouring solvent molecules, and thus there is aclear indication of a connection between the free volume and thepotential energy of the solute molecule, i.e., the heat of solution.This functional connection seems to be in the sense that the largerthe heat of solution the smaller will be the free volume available tothe solute molecule, and consequently, the smaller the entropychange accompanying the solution process.W. M. Latimer 30 has pointed out a connection between the heatsof solution of ions and the entropy of ions in solution ; this relation-ship is in the sense that the greater the exothermicity of the solutionprocess the more negative is the corresponding entropy change.If the field set up by the ion is sufficiently strong, it will cause alocal freezing out of the water molecules in the co-ordination sphereof the ions.The water molecules in the neighbourhood of the ionwill vibrate and rotate less freely than in the water itself. The lossof entropy due to the restriction of the motion of the solvent mole-cules has been estimated by Evans and Eley : l1 using the modelof the water structure given by Bernal and Fowler and a model ofthe orientation of water molecules in the co-ordination sphere ofthe ion consistent with the heats of solvation, they obtain valuesfor the entropies of ions in solutions which are in fair agreementwith the experimental values.It is outside the scope of this review to deal with the applicationof some of the ideas discussed in detail here to velocity constantsand equilibrium constants of reactions in solution, but we canindicate some of the problems which are being dealt with.R. W.GurneyY3l in discussing the variation of the dissociation constants oforganic acids with temperature, and the wide adherence to theempirical relationship of H. S. Harned and N. D. Embree,32 hassuggested that the energy of electrolytic dissociation of an acid ismade up of two terms, one of which is non-electrical and the otheran electrical term which can be expressed in terms of the Borncharging energy. It is this second term, which includes the di-electric constant of water, which leads to the parabolic form for thetemperature variation of the logarithm of the dissociation constant.The ideas put forward by Gurney have been given a more quantita-tive form by E.C. B a ~ g h a n , ~ ~ who has shown that the ionic radii30 W. M. Lather and R. M. Buffington, J . Amer. Chem. SOC., 1926,48,2297 ;31 J . Chem. Physics, 1938, 6, 499.32 J . Amer. Chem. SOC., 1934, 56, 1050; H. S. Harned and B. B. Owen,Chem Reviews, 1939, 25, 31. 33 J . Chem. Physics, 1939, '7, 951.W. M. Lather, Chem. Reviews, 1936, 18, 34846 GENERAL AND PHYSICAL CHEMISTRY.resulting from an analysis of the Harned and Embree relationshipin terms of the Born charging energy are of reasonable magnitude.They are, however, uniformly small as compared with the radii onewould expect from molecular dimensions.W. F. K. Wynne-Jones and D. H. Everett 34 have given an expressionAHR1 R In K = - _iP + gp In T + (AS: -which they claim represents the experimental results better thanHarned and Embree’s expressionIn K - In K, = p(t - f3)2Prom that expression they are able to compute the specific-heatchanges accompanying the electrolytic dissociation process, andthey point out that the specific-heat change cannot be accountedfor by the temperature variation of the dielectric constant, whichleads to magnitudes much smaller than those obtained by Wynne-Jones and Everett. They postulate, therefore, a “ freezing-out ” ofthe water molecules in the co-ordination shell of the ions. This‘‘ freezing ” process leads to the disappearance of translational degrees3 of freedom and a loss of energy of -RT per water molecule co-ordin- 2ated by an ion.This leads to changes in the specific heat accom-panying dissociation which are in agreement with their calculatedvalues. At present there seems to be some divergence between thetwo points of view : on the one hand, that the Born-charging energyis insufficient to account for the energy, entropy, and specific-heatchanges accompanying ionic processes and, on the other hand, thatthese simple electrostatic methods cannot be used when saturationeffects of the dielectric enter in. The success of J. G. Kirkwoodand F. H. We~theimer,~~ however, in calculating the ratio of the twodissociation constants of dicarboxylic acids would seem to indicatethat saturation effects in the dielectric can be neglected. Theseauthors have shown that if a correction is applied to Bjerrum’streatment to take into account the electrical effects inside the cavityin the solvent caused by a molecule, then the lengths of hydrocarbonchains predicted are in excellent agreement with those to beexpected if the chains have free rotation.The division of the energetics of ions in solution into two terms,one arising from the Born charging energy and the other from theco-ordination of solvent molecules around the ion, is quite anarbitrary one, and indicates our incomplete knowledge of the34 Proc.Roy. SOC., 1938, A, 169, 190;3 5 J. Chem. Physics, 1938, 6, 506, 513.Trans. Paraday SOC., 1939, 35, 1380PRICE : ELECTRONIC SPECTRA OF POLYATOMIC MOLECULES.47electrical behaviour of polar liquids in electrical fields of high in-tensity. A complete theory of the dielectric behaviour of polarliquids would remove this arbitrary division, and the recent work ofKirkwood36 and Onsager 37 is moving towards a more completepicture of the dielectric behaviour of polar liquids.M. G. E.2. THE ELECTRONIC SPECTRA OF POLYATOMIC MOLECULES.During the last ten years the study of infra-red and Ramanspectra has been yielding results of considerable theoretical import-ance to the chemist. Although many data on the electronic spectraof polyatomic molecules have been available for a much longer time,the difficulties in their interpretation have until recently provedinsuperable. With the solving of the major problems connectedwith the electronic spectra of diatomic molecules, more attentionhas been focused on the spectra of polyatomic molecules, and theresults indicate that much information of chemical interest may besoon forthcoming.The spectroscopic investigation of polyatomicmolecules is restricted to absorption, since electrical dischargeswith one or two exceptions disrupt the molecule into diatomicfragments. This factor has very seriously limited the field fromwhich spectroscopic information can be obtained. However theextension of the absorption measurements into the vacuum ultra-violet, which has recently been accomplished, has improved thissituation considerably. The object to be aimed at in the study ofmolecular spectra is a complete description of the electronic structuresof polyntomic molecules in both their normal and excited states,similar to that now available for atoms.It appears that even in thecase of diatomic molecules this object will only be accomplished to asmall degree, and in the case of polyatomic molecules the expectationis still less. Some of the more fundamental facts can, however,certainly be derived from the available data. Although the morecomplicated organic molecules can never be subjected to rigorousmathematical treatment, considerable progress towards under-standing their spectra and thus towards obtaining a theory of colour,can be achieved by making certain broad assumptions and byutilising the more general results of quantum theory.Severalattempts in this direction have been made in recent years.1 How-ever, in this year’s Report it has been decided to confine the materialto an ‘introduction to the spectroscopic conception of the electronic36 J . Chem. Physics, 1939, 7 , 911.37 L. Onsager, J. Amer. Chern. SOC., 1936, 58, 1486.G. N. Lewis and M. Calvin, Chem. Reviews, 1939, 25, 273; R. S. Mulliken,J . Chem. Physics, 1939, 7 , 1448 GENERAL AND PHYSICAL CHEMISTRY.structure of some of the simpler polyatomic molecules, and to adescription of the spectra associated with them.The most elementary attempt to express the electronic structureof EL molecule is that embodied in the ordinary valency bond formula.When supplemented by resonance to other structures, these formuhhelp to correlate a wide variety of chemical data.However, theygive us very little detailed information about the electrons in themolecule. Facts such as what are the types of orbits the differentelectrons are in and what are their relative energy values are theimportant ones in the interpretation of molecular spectra, and anotation indicating these characteristics is clearly to be desired.The spectroscopic notation for the electronic configuration of sodiumin its ground state is ls22s22p63s, 2X. The groups of equivalentelectrons which are most strongly bound (i.e., with the greatestionisation potentials) are written first, and are followed by thegroups having successively lower energies. The type and energyvalues of the various groups are known from spectroscopic observa-tions.Groups of equivalent electrons occur in the electronicstructure of 'molecules just as they do in atoms but they are of aslightly different type because their character (i.e., number of electronsthey can hold, etc.) is determined by the positive nuclear framework(which is no longer a point as in atoms). On the '' molecular orbital "theory of Hund, Mulliken, and Lennard-Jones, there can be ascribedto every group of equivalent electrons an independent wave functionwith symmetry properties with respect to the symmetry operationswhich the nuclear framework permits (each group has a wave func-tion which has the character of a particular representation of thesymmetry group of the molecule).Mulliken has introduced system-atic classification symbols to express the symmetry character-istics of particular electron types (small letters) and the totalelectron configuration of the molecule (large letters). These aresimply an extension of the well known m X I I notation for diatomicmolecules (which is itself, of course, an extension of the notationfor atomic spectra). He gives expressions for the electronic con-figurations of a large number of simpler polyatomic molecules interms of these symbols in a series of articles in the Journal of ChemicalPhysics from 1935 onwards. It is not intended to use this nomen-clature here more than is absolutely necessary, as the mass of sym-bols may lead to some confusion and obscure important generalresults which can be obtained without their aid.They would,however, be necessary for more detailed discussion of the spectrathan is possible within the scope of this Report.The Single Bond.-The simplest single bond is that occurringin the hydrogen molecule. Here two atomic 1s orbitals overlaPRICE : ELECTRONIC SPECTRA OF POLYATOMIC MOLECULES. 49in such a manner as to give rise to a high electron density betweenthe two nuclei, so leading to the formation of the valency bond(see Fig. la). The abbreviated notation for the molecular orbitalwhich the two electrons can now be considered as occupying is(s + S, o ~ ) ~ . The plus sign indicates that the two atomic orbitalsoverlap so as to give bonding (negative sign means antibonding),the Greek letters indicate the magnitude of the component of theorbital angular momentum resolved along the bond axis (0, x .. . =0 , l . . . .) , and the superscript means that two electrons are occupyingthis orbital.2 This a type of orbital is clearly axially symmetricaland gives a bond about which there can be free rotation if no stericfactors are involved. A single bond is always of this type, sincethe CJ orbital is the orbital of lowest energy (analogous to the 1sshell in atoms) and therefore the first two electrons must go into it.In the formation of a single bond between an s electron of one atomand a p valency electron of another, e.g., in the formation of theHB ( l b ) , HC (lc), HN ( I d ) , HO ( l e ) , and HF (If) bonds, it is necessarythat the s electron should approach along the axis of the orbitalThe symbol g means that the wave €unction does not change sign withrespect t o inversion a t the centre of gravity50 GENERAL AND PHYSICAL CHEMISTRY.of the p electron in order to give magmum overlapping of the atomicorbitals.Thus the molecular orbital formed is symmetrical aboutthe bond axis and is o in type. One important fact to whichattention should be directed is that, for an electron to enter into amolecular orbital, all restriction on its spin must be removed.This means that the atom must be excited to its valency state,,and the coupling of the spins characteristic of the normal state ofthe isolated atom broken down. In the CH, radical, for instance,it is necessary that the two valency p electrons should be in mutuallyperpendicular orbitals (the electronic configuration of bivalentcarbon is ls22s22p2). In NH, the three NH bonds have to bemutually perpendicular.Because the hydrogens are slightlypositive in NH,, their mutual electrostatic repulsion makes theHNH angle somewhat greater than 90" (actually log").* In PH,and ASH,, where the positive charge on the hydrogens is less andthe distance between them greater, the tendency for this angleto approach 90" is more marked. Recently, Sutherland, Lee, andWu have found that HPH = 99" and HASH = 97".6Although atomic oxygen ( ls2Zs22p4) has four p electrons it cannotorient all these so that their spins are independent. The best thatcan be done is to make the orbitals of two p electrons mutuallyperpendicular and then to accommodate the other two in a singleorbital perpendicular to the plane of the first two.Because of thepairing of the spins of the second two they cannot enter into chemicalcombination (Fig. le). In fluorine the necessity of putting twoelectrons into a single orbital arises twice, and thus four of its fivep electrons cannot ordinarily take part in the chemical activity ofthe atom. These electrons are the so-called '' lone pair " electrons.It will be seen later that they play a very important part in theabsorption spectra of the molecules in which they occur. Theyare of the type known as non-bonding p x electrons ( p to signifythat they belong to a p atomic orbital and 71: because the axis of thisorbital is perpendicular to the valency bond).In order to com-plete the schematic representation of Fig. 1 we should put roundthe central atom two concentric circles to represent the Is and 2sshells. They have been omitted from the diagram for the sake ofclarity.In the ordinary electronic theory of Lewis and Langmuir nodistinction is made between the lone pair of 2s electrons and theA AR. S. Mulliken, J . Chem. Physics, 1934, 2, 782.Trans. Faraday SOC., 1939, 35, 1373.The apex angle in amines and also in alcohols and ethers is probably* A similar effect would of course be expected in CH,.about 120" owing to larger repulsions arising from the alkyl groupsPRICE : ELECTRONIC SPECTRA OF POLYATOMIC MOLECULES. 51lone pair of 2p electrons.However, the former are much morestrongly bound than the latter (i.e., have considerably higherionisation potentials) and differ in other respects also. For example,Mulliken estimates that in water the 2s electrons have ionisationpotentials of about 32 v., and the electrons in OH bonds about17 v., whereas the lone pair of p x electrons only require energiesof about 13 ev. for their removal. It will be noted that the pelectrons which go into the bonds automatically acquire a higherionisation potential than the px electrons which remain non-bonding,i.e., atomic in character. This is because in ionising them additionalenergy equal to their bonding energy must be supplied. Theionisation potential of the non-bonding electrons does not differmuch from that in the free atom (13-55 v.for atomic 0,").The maximum valency which we have obtained so far is three.This was obtained in the case of nitrogen by resolving three pelectrons along three mutually perpendicular directions. Anadditional valency can be obtained by breaking the pairing of theelectrons in the s2 shell and promoting one to the p shell. Thusquadrivalent carbon with the configuration sip3 has four unpairedelectron spins and four independent orbitals can be constructed fromsuch a configuration. The s shell has a maximum valency of one,and it has just been shown that the p shell has a maximum valencyof three; hence with s and p electrons we have the well-knownmaximum covalency of four. A configuration of the type sp* (apossible configuration of N) could only be tervalent, since two ofthe p electrons would have to combine to form a lone pair.Similarly, sp5 and sp6, which are possible configurations for 0and F respectively, could only be bi- and uni-valent.Although it is fairly simple to see the main determining directionalfactors in atoms involving only p valency electrons, it is not so easyto see why the sp3 configuration of quadrivalent carbon should givein the case of saturated hydrocarbons four valencies directed towardsthe corners of a regular tetrahedron, or in the case of unsaturatedhydrocarbons three coplanar valencies at 120°, one of which is double.However, it can be shown that it is possible to construct fourequivalent independent orbits from the aggregate configuration sp3by suitable hybridisation of the s and p functions. That by mixinga certain amount of an s with a p orbital we can enhance thedirectional properties of the p function is seen from Fig.2.The p wave function has different signs on opposite sides of thecentral plane perpendicular to its axis of symmetry; the s wavefunction is, of course, spherically symmetrical. By adding the two,the positive side of the p function will be enhanced and the negative' J . Chem. Physics, 1035, 3, 50652 GENERa AND PEYSICAL CHEMISTRY.side diminished. Thus the charge distribution is directed in onedirection, and as a valency bond is formed where there can be themaximum overlapping of the wave functions, it is clear that a directedvalency bond has been produced.Up to the present we have dealt with single bonds and haveseen that their molecular orbitals are of a B type axially symmetricalabout the bond.Althoughit may seem that the foregoing discussion of electronic structures isa digression from the main subject of this Report, it must be pointedout that a background of this character is necessary for the satis-factory understanding of molecular electronic spectra.The Double and Triple Bonds.-The next bonding molecularorbital into which electrons can go after two have filled the bondingp orbital is an orbital which is known as a x orbital. It is lesssymmetrical than the a type and has a plane of symmetry passingthrough the bond instead of an axis of symmetry.Because of theWe shall now discuss the double bond.I IFIG. 2.possibility of two mutually perpendicular planes of symmetrythere are two such orbitals each of which can contain two electrons.The simple double bond is formed by the presence of two electronsin the basic a orbital and two electrons in one of these x orbitals.The triple bond has the basic o and both the x orbitals flled. Theabove statements are only good approximations since it is not alwayspossible completely to localise the electrons in a molecule withseveral bonds. The new properties of the x molecular wave func-tions give rise to the important characteristics of the double bond,such as the rigidity of the C=C bond and the optical activity ofof the C=O bond in certain ketones.The configuration sp3 of carbon can give rise to another set ofdirected valencies apart from the four axially symmetrical tetra-hedral ones.These consist of the equal coplanar type valenciesa t angles of 120" to each other, together with a fourth valencyperpendicular to the plane of the other three. In the directedvalency theory this fourth valency is represented as a pure 2pwave function. Fig. 3 indicates schematically the wave functions8 There is an antibonding a orbital (8-8, a,) but this is higher than the Rbonding orbitalsPRICE ELECTRONIC SPECTRA OF POLYATOMIC MOLECULES. 53of two carbon and four hydrogen atoms just before they cometogether to form ethylene.It can be seen that the molecular orbital corresponding to the bondformed by the overlapping of the two p electrons is not axiallysymmetrical but has a plane of symmetry which is the plane of themolecule.These p electrons have the property of confining theother bonds all to one plane. If a valency bond is formed with anytype of electron other than the adjacent p electron (as in bromina-tion or hydrogenation), then the carbon atom reverts to its morestable tetrahedral valency state. Because the amount of overlapof two adjacent p x electrons is less than that with electrons whoseorbitals are symmetrical about the bond, the strength of the xbond is slightly less than that of the basic Q bond. This, and alsothe fact that it is not mixed with strongly bound s orbitals, resultsin its ionisation potential being considerably lower than the otherelectrons in the molecule.It will be shown later that this is ofFIG. 3.considerable importance in connexion with the spectra of unsaturatedorganic molecules. The foregoing brief introduction to the spectro-scopic conception of the electronic structure of some polyatomicmolecules will facilitate the following discussion of their absorptionspectra.One of the most important advances in the subject in recentyears is the extension of observations into the short wave-lengthregion of the spectrum known as the vacuum ultra-violet. Thisregion lies below 1800 A., where air and quartz absorb. It has longbeen known that the formulae which have been found to representthe ordinary refractive dispersion and natural and magnetic rotatorydispersion of substances contained in them terms which predictabsorption bands of extraordinarily great intensity (log E - 4) lyingat very short wave-lengths below 2000 A.That it is reasonable toexpect such strong bands in this spectral region can be seen from thefollowing discussion. The ionisation potentials of most moleculeslie between 10 and 15 v., which corresponds to phto-ioni8ution b54 GENERAL AND PHYSICAL CHEMISTRY.light of wave-lengths between 1300 and 800 A. Just as in theabsorption spectra of an atom a series of strong reasonance linescan be observed converging to a photo-ionisation limit at a definitewave-length (cf. Na), so in the absorption spectrum of a moleculestrong resonance bands might be expected to appear leading up toany ionisation potential characteristic of the molecule.The firststrong resonance line of sodium is the yellow D line. That it shouldoccur at such long wave-lengths as to lie in the visible part of thespectrum is only because of the abnormally low ionisation potentialof the alkali atoms. I n most other atoms (and molecules) thefirst resonance bands do not start until about 2 0 0 0 ~ . or less, andthe other Rydberg series members corresponding to increases of theprinciple quantum number by successive units to infinity at thephoto-ionisation limit, lie a t still shorter wave-lengths in the vacuumultra-violet. As a simple illustration let us attempt to predictwhat might be expected to result from the illumination of hydrogeniodide with a continuous background of light extending into thevery short wave-length region.The four non-bonding p x electrons( i e . , the lone pairs) of the iodine atom are not greatly affected bythe combination and thus probably have about the same ionisationpotential as in the free atom [- 10 v. or 1200 a.-known from theanalysis of the spectrum of I(l)]. Thus strong resonance bandscorresponding to these electrons might be expected to start below2000 A. (6 v.) and to converge to a photo-ionisation continuumaround 1200 A. (10 v.). Because the electrons do not participatein the bond, it is to be expected that little vibration will be causedby their excitation and removal. Absorption spectra agreeingvery closely with these expectations have been ob~erved.~ Electronsgoing into the molecular orbital forming the single bond might beexpected to have an ionisation potential somewhat greater than themean of the ionisation potentials of hydrogen and iodine [ i e .,> (13 + 10)/2 = 111, i.e., probably about 12-13 v. It might beguessed that strong resonance bands of these electrons would start.about 1400 A. and culminate in a photo-ionisation continuum near1000 A. (12.3 v.). A great deal of vibration would accompany theremoval of such a bonding electron. Unfortunately, all that canbe observed of these absorption bands is some diffuse bands lyingin the region 1209-800 A. That the estimate of the ionisationpotential of the bonding electrons is correct is known from theemission spectra of the halogen acids.1° The other electrons of themolecule (Le., the inner shells of the iodine atom) ionise at stillhigher potentials and shorter wave-lengths. Experimental diffi-W.C. Price, PTOC. Roy. SOC., 1938, A , 167, 216.10 F. Norling, 2. Physik, 1935, 95, 179; 1937, 104, 638PRICE : ELECTRONIC SPECTRA OF POLYATOMIC MOLECULES. 55culties prevent their observation. It appears to be a fairly generalrule that the outer electrons of a molecule with the lowest ionisa-tion potentials (usually the non-bonding electrons in lone pairs orthe x electrons of an unsaturated molecule) give rise to the strongestand most well-defined bands in the vacuum ultra-violet. It appearsthat these electrons are also responsible for most of the near ultra-violet absorption spectra of molecules, though there are notableexceptions, such as the salts of the rare earths, where the colour isdue t o electrons in the inner f shell of the rare-earth ion.The general features of the spectra of the alkyl halides may bededuced as for the halogen acids.The photo-ionisation of the lonepairs on, e.g., the iodine atom in methyl iodide has been observedexperimentally.ll The photograph of this spectrum11 is a very goodexample of the convergence of bands to a photo-ionisation limit.For the more highly excited electronic states when the orbit of theelectron is very large compared with the dimensions of the molecule,the electron may be regarded as escaping in an approximatelycentral field. Thus these higher electronic states should fit roughlyinto a Rydberg formula.This is found to be the case, and anextrapolation of the higher members to the convergence limit bymeans of the formula gives a very accurate ‘‘ spectroscopic ” valueof the ionisation potential of the molecule. It is found that theionisation potentials of the halogen electrons in the alkyl halides are1 volt or more lower than those in the halogen acids. This is inter-preted as being evidence of a greater transfer of negative charge onto the halogen in the former molecule, and is supported by theirdipole moments [p(HI) = 0.38 D., p(CH,I) = 1.59 D.]. It will bediscussed more fully later. Two photo-ionisation limits fairlyclose together are observed for these halogen compounds, L e . ,the molecular ion is a doublet. The magnitude of the doubletseparation indicates that the ionisation limit observed is definitelythat of the p x halogen electrons and that these are of a non-bondingcharacter.The ionisation potentials of the alkyl halides diminishto a limiting value as we ascend the homologous series, the greatestdrop occurring in going from the methyl to the ethyl compound,subsequent diminutions being very much smaller. In this sense thehalogen acid may be regarded as the first member of the series.The diminutions then are : HI - CH31 = 0.88 v., CH31 - C2H51 =0.19 v., C2H51 - n-C3H,I z a few hundredths of a volt.The spectra of ammonia- and water-type molecules have beentreated by R. S. Mulliken.12 The discussion of their electronicstructure given in a previous paragraph shows that the outermost11 W.C . Price, J . Chem. Physics, 1936, 4, 539.12 J . Chem. Physics, 1935, 3, 50656 GENERAL AND PHYSICAL CHEMISTRY.electrons (Le., those with the lowest ionisation potentials) should bethe lone pair p x electrons and that the ionisation potentials ofelectrons in single bonds should be 2 or 3 volts higher than these.The experimental evidence l3 indicates that this is the case, and hereagain the lone pairs seem to dominate the absorption. Bands,which by their rotational structure indicate the excitation of a non-bonding electron, appear at very low pressures and converge to theminimum ionisation potentials of the molecules. Only in the caseof water has it been possible to obtain spectra corresponding tothe excitation of electrons in single bonds.l* It should be stressedthat the simple picture we have drawn is not quite adequate.Forinstance, Mulliken's treatment indicates the existence of twoionisation potentials fairly close together for the OH bonding elec-trons where on simple theory only one is expected. A similar state-ment is true for the bonding CH electrons in methane or the xelectrons in benzene.The most prominent bands of the alkyl-substituted compoundsof water, hydrogen sulphide, and. ammonia (ie., the alcohols andethers, thiols and sulphides, and amines) require an interpretationsimilar to that given for the parent molecule. They are displacedto longer wave-lengths with successive alkyl substitution.15 This isinterpreted as an accumulation of negative charge on the oxygen,sulphur, or nitrogen atom with increasing alkyl substitution.Although the increase in the dipoles in going from H,S throughR*SH to SR, (R being an alkyl group) supports this idea of increasein negative charge, the diminution in the similar series for theoxygen and nitrogen compounds seems to discount it.However,this diminution in dipole moment can be explained by the opposinginduced dipoles in the alkyl groups of the oxygen and the nitrogencompounds. For these light atoms the induced dipoles play amuch larger part than in the heavier atoms. Because of t'he some-what wider apex angles, they tend to diminish the main dipolerather than increase it, as they do in the thiols and sulphides.The electronic structures of aldehydes, ketones, carboxylic acids,and related molecules have been discussed by R.S. Mulliken.lGIn this class of molecule an especially large charge transfer due tothe.large dipole associated with the C=O bond (-2.7 D.) causes aconsiderable excess negative charge to accumulate on the oxygenatom. This reduces the ionisation potential of the lone pair [O]la A. B. F. Duncan, Physical Rev., 1935, 47, 822; W. C. Price, J. Chern.Physics, 1936, 4, 137.l4 G. Rathenau, 2. Physik, 1933, 87, 32.l5 H. Ley and B. Arends, 2. physikal. Chem., 1932, B, 15, 311 ; G. Herz-berg and G. Schiebe, ibid., 1930, €3, 7, 390; W. C. Price, J . Chem. Physics,1935, 3, 256. lo Ibid., p. 564PRICE : ELECTRONIC SPECTRA OF POLYATOWC MOLECULES.57electrons by more than 2 volts relative to what it might otherwisebe expected to be. In formaldehyde, for example, it might bethought, without allowance for charge transfer, that the ionisationpotential of the oxygen lone pairs should be some 13-14 volts[cf. ionisation potential of O( 1) = 13.55 v.1.l’ That of the electronsin the double bond would be expected to be greater than 1 4 ~ .by several volts, and that of the electrons in the C-HI bonds not farfrom the ionisation potential of methane (i.e., 14 v.). The spectro-scopic and the electron-impact method agree in putting the minimumionisation potential of formaldehyde a t about 11 volts, and thespectra indicate that an electron in the carbonyl part of the moleculeis being excited.18 These facts can only be reconciled with thetheoretical expectations by the assumption that the accumulationof negative charge on the oxygen atom arising from the large dipoleknown to be associated with the C=O bond causes a lowering inionisation potential of the lone-pair electrons.This is supportedby the fact that the ionisation potential of acetone was fouBd to havethe still lower value of 10.1 v.19 Additional charge transfer from thetwo methyl groups is presumed to be responsible for this furtherlowering.The spectrum of formic acid shows great similarity in the regionbelow 1600 A. to the spectrum of formaldehyde, and the bandsconverge to ionisation potentials which are fairly close together-10.83 v. and 11.3 v.respectively.20 It is clear that in the acid, as informaldehyde, this ionisation potential corresponds to the lone pairon the carbonyl oxygen. The resonance between the two CObonds is not grmt in the monomer, and it does not greatly affect thelone pair electrons.The spectrum of formaldehyde in the near ultra-violet is particu-larly important, since the rotational structure of many of thebands has been analysed by G. H. Dieke and G. B. Kistiakowski.21They deduce that the electric moment of the transition vibratesperpendicularly to the axis of symmetry and in the plane of thomolecule. This fact, together with the determined ionisation offormaldehyde, enabled Mulliken to show that the transition mostprobably corresponded to the jump of an electron from the lone pairinto an antibonding orbital of the double bond [2p,b,+l7 Actually the ionisation potential of the lone pairs when the oxygenThis is predicted byl8 T.N. Jewitt, Physical Rev., 1934, 46,616 ; W. C. Price, J . Chern. Physics,Is W. A. Noyes, A. B. F. Duncan, and W. M. Manning, ibid., 1934,2, 717.2o W. C. Price and W. M. Evans, Proc. Roy. SOC., 1937, A, 162, 110.21 Physical Rev., 1934, 45, 4.atom is in its appropriate velency state should be used.Mulliken to be 14.73 v., J . Chem. Physics, 1934, 2, 782.1935, 3, 25658 GENERAL AND PHYSICAL CHEMISTRY.(zDH, - xo, a,)]. The optical activity of certain ketones is thusinterpreted as being due to the upper state of this transition and isnot due to the excitation of electrons originally in the double bondas is usually supposed.The absence or extreme weakness of ketonicbands at 3000 A. and 2000 A. in the carboxyl compound is probablydue to the transition becoming forbidden as a result of the excitedorbital being affected by the proximity of the hydroxyl group.The absorption bands of the alkyl derivatives of formic acid areshifted to longer wave-lengths with alkyl substitution. This is sowhichever of the two hydrogen atoms is replaced by alky1,22 and itmay be taken to indicate an increase in the amount of negativecharge transferred to the carbonyl oxygen. For instance, the shiftof certain bands of methyl acetate relative to the correspondingones of formic acid is about 0.9 v., and this may be comparedwith the difference in the ionisation potentials of acetone andformaldehyde, vix., 10.83 - 10.1 = 0.7 V.The Spectra of Methane, Ethane, Ethylene, and Acetylene.-Nearly all single-bonded compounds are transparent in the visibleand near ultra-violet and absorb only in the vacuum ultra-violet.This important fact seems to support the interpretations of nearultra-violet spectra as being the excitation of an electron to an anti-bonding orbital.Only in double-bonded compounds can an upperstate involving such an orbital be stable, i.e., the antibonding powerof the excited electron is then more than compensated by the bondingpower of the remaining three or more bonding electrons. In excitedRydberg orbitals the bonding or antibonding power of an electronis very small.Methane does not absorb strongly until about1250 A. (- 10 v . ) . ~ This absorption must be regarded as thefirst strong resonance (Rydberg) absorption, since the electron-impact value for the ionisation potential of methane is about 14.5 v.The electronic configuration is obtained by pairing off the electronsof the 5p3 configuration of quadrivalent carbon. It is given inMulliken’s notation as [$all2 bt2]6, the ionisation potential of thefirst electron group being estimated as about 22 v., and that of thesecond being identified with the minimum ionisation potential at14.5 v. The diffuseness of the methane absorption is attributed tostrong predissociation. It unfortunately prevents the identificationof consecutive electronic states which might be fitted into a Rydbergformula.The spectrum of ethane is very similar to that of methaneexcept that absorption begins at slightly longer wave-lengths(- 1350 A . ) . ~ This is in agreement with the slightly lower ionisation22 G. Scheibe, F. Povenz, and C. F. Lindstrom, 2. physikal. Chem., 1933,B, 20, 283.23 A. B. F. Duncan and J. P. Howe, J . Chem. Physics, 1934, 2, 851.24 W. C. Price, Phymkal Rev., 1935, 47, 444PRICE : ELECTRONIC SPECTRA OF POLYATOMIC MOLECULES. 59potential of ethane (- 12 v.) as compared with methane. Theexcitation and ionisation really corresponds to the electrons in theC-C bond. Propane starts absorbing at slightly longer wave-lengths than ethane. It is doubtful whether any pure saturatedhydrocarbon has strong absorption above 1500 A., which is wherecyclohexane starts to absorb.25A description of the spectrum of light and heavy ethylene (C,H4and C,D4) has been given by W.C. Price and W. T. Tutte.26 Theanalysis of the spectrum, which was greatly facilitated by theuse of the deuterium-substituted compound, shows clearly thatthe strong absorption bands occurring in the region 2000-1150 A.are due to the excitation and photo-ionisation of the x electronsin the double bond. The ionisation potential to which they corre-spond is 10.43 v. The bands of ethylene are very similar to bands ofacetylene also due to the excitation of a x electron in.this case fromthe ( x ) ~ group. For acetylene, certain features of the rotationalstructure of the bands point very definitely to the x electrons as theoriginators of the spectrum.The same features are present inethylene, only they cannot be observed so easily because of a slightdiffuseness of the bands. The slightly higher ionisation potentialof acetylene (11.35 v.) relative to that of ethylene can be regardedas due partly to the greater stability of the ( x ) ~ group and partlyto a smaller charge transfer (acetylene has only half as manyhydrogen atoms from which to draw negative charge as ethylenehas, and twice as many x electrons amongst which to share it).Both ethylene and acetylene have near ultra-violet spectra of anon-Rydberg character, i.e., probably transitions of electronsfrom bonding to anti-bonding orbitals associated with an electronicconfiguration not differing from that of the ground state by a changeof principal quantum number.The discussion of these and morecomplicated spectra will be continued in a future Report.Vibrational Structure and Selection Rules.-The vibrationalpattern of bands representing an electronic transition often givesconsiderable information about where the excitation is located.Electrons excited from bonds usually give rise to vibration in thesebonds, while little vibration usually accompafries the excitationof a non-bonding electron unless it be excited to an orbital of a bond-ing or an anti-bonding character. (As will be shown in later Reports,little vibration also accompanies the Rydberg jumps of an electronwhich is shared between several bonds by the process of resonance.)As most polyatomic molecules have a large number of differentmodes of vibration, it might be thought that their spectra would bevery complex.However, it is seldom that more than two Werent2 5 G. Scheibe end H. Grieneisen, 2. phy8ika.l. Chem., 1934, B, 25, 52.2 6 Proc. Roy. SOC., in the press60 GENERAL AND PHYSICAL CHEMISTRY.types of vibration are present in one electronic band system. Amost useful criterion for identifying modes of vibration in a spec-trum is the selection rules deduced by G. Herzberg and E. Teller 27by an extension to polyatomic molecules of the Franck-Condonprinciple. This principle expresses the fact that the electronictransition occurs so quickly relative to any change occurring in thepositions or velocities of the much heavier nuclei that these can beconsidered the same the instant after the transition as they were justbefore it.Thus the nuclear symmetry is preserved. It follows thatthe electronic and therefore the total molecular symmetry of theequilibrium position is the same in both the ground and the excitedstates. From this it can be shown that in the case of an allowedelectronic transition the quantum numbers of the totally sym-metrical vibrations 28 are the only ones for which changes may occur.In forbidden. transitions (Le., corresponding to upper and lowerelectronic wave functions of different symmetry) there must occur achange of the quanta of a non-totally symmetric vibration by atleast one unit-though it may be accompanied by any change in thetotally symmetric quantum number.The reason for this is that achange in the symmetry of the vibrational part of the wave-functionis necessary in order to correct for the altered symmetry of theelectronic part. By virtue of the coupling between the electronicand the vibrational parts, the total wave function can be made toretain its symmetry during the transition. However, because thecoupling is weak, transitions of this second kind are much less intensethan those in which the symmetry of the electronic wave functiondoes not change. The 2500 A. system in benzene is an example ofthe compensating of the symmetry of the electronic wave functionby a suitable vibrationalAbsorption in a cold gas occurs mainly from the vibrationlessground state because the fraction of molecules initially vibratingis very small at normal temperatures.In absorption-band systemswhich are strong a t normal temperatures, such as those occurringin the vacuum ultra-violet, only vibrations of a totally symmetriccharacter can be expected to appear. This is true in general, and acollection of the available data on this point has been made byA. B. F. Duncan.30 More recently, M. Wehrli 31 has shown that thevibrational structure of the ultra-violet spectra of the mercuric27 2. physikal. Chem., 1933, B, 21, 410.a * Invariant with respect t o all the symmetry operations.29 A. L. Sklar, J . Chem. Physics, 1937, 5, 669; H. Sponer, G. Nordheim,30 Ibid., 1935, 3, 384.31 Naturwiss., 1937, 25, 734; Helv.Physica Acta, 1938, 11, 330; see alsoA. L. Sklar, and E. Teller, ibid., 1939,7,207.H. Sponer and E. Teller, J . Chem. Physics, 1939, 7 , 382MELVILLE : CHEMICAL KINETICS. 61halides conforms to the rules of Herzberg and Teller. A. Henriciand H. Grieneisen 32 have done the same for the 2000 A. systems ofthe alkyl iodides.It has not been possible even to touch upon the absorption spectraof conjugated hydrocarbons and many other important classes ofcompounds in this brief Report. It is hoped to deal with them infuture Reports. w. c. P.3. CHEMICAL KINETICS.During the past four or five years slow but steady progress hasbeen made in attempting to deal with the mechanism of polymeris-ation reactions by kinetic methods.The reasons for this growthof interest are due to several factors. From our present point ofview probably the most important is that chemical kinetics hadbeen developed to such a stage that it was looking for new fieldsto conquer and this field was practically untouched. Moreover,the amount of work which had been done on the structure andreactions of naturally occurring substances of high molecularweight forced upon chemists the necessity of trying to make similarmolecules synthetically and also understanding how simple mole-cules aggregate to larger entities. The industrial development,too, has played a part for, though much of it is essentially empiricalin character, it has brought to light reactions and systems which aresufficiently simple to merit their detailed academic study.In broad outline two types of process are involved in the produc-tion of big molecules.The first consists in the interaction of suitablemonomeric molecules with the simultaneous elimination of a rela-tively simple molecule such as water, ammonia, etc. Typical of thisreaction is the polymerisation of hydroxy-acids :HO*P*CO,H + HO*P*CO,H j HO*P*CO*O*P*CO,H + H20Further molecules of monomer then add on to the dimer, eachprocess being accompanied by the elimination of one molecule ofwater.The second type concerns the interaction of compounds contain-ing a double bond. Here the essential characteristic is that, insteadof the elimination of a simple molecule each time the monomerreacts, a double bond is converted into a single bond.Ethylene beingtaken as the simplest system, the reaction may be represented thus :CH2=CH, + CH,=CH, + CH,-CH,-CH-CH,or -CH2-CH2- + CH,=CH, ----+ -CH,-CH2-CH2-CH2-33 2. physikal. Chem., 1935, B, 30, 162 GENERAL AND PHYSICAL CHEMISTRY.There are, of course, some reactions in which both types of processoccur, leading to molecules of great complexity. In kinetics,however, the mechanism of the first type, which is esterification,is not yet fully understood, and therefore there is little hope a tpresent of dealing a t all satisfactorily with the kinetics of condens-ation polymerisation. The second type of polymerisation isamenable to kinetic study, for a great deal of help is afforded bythe existing knowledge relating to the reactivity of double bondsand also to the behaviour of free radicals, which may be producedwhen the double bond is opened.The most elementary kind ofpolymerisation consists in the association of two molecules eachcontaining a double bond.Association Reactions.-By a study of dimerisation reactions itshould thus become possible to obtain some information aboutthe conditions for the activation of the double bond preliminaryto further polymerisation of the monomer to long-chain compounds.The unfortunate fact is that those molecules, such as styrene,vinyl acetate, chloroprene, vinylacetylene, and met hylacetylene,which under suitable conditions do form linear polymers, do noteven dimerise, far less polymerise thermally in the vapour state.lAs a preliminary, it is of course advisable to conduct the reactionsin this phase, for which the utmost aid is available from ordinarykinetics.None the less, dimerisation has been found to occurwith the following molecules : ethylene, butadiene, isoprene,and cyclopentadiene. In addition, a number of Diels-Alder reactionsmay be induced to proceed in the gas phase.The rate (R) of a bimolecular reaction between two molecules1 and 2 is defined byR = k,[N,][N,] = PZ . exp( - E/RT)where Ic, is the velocity coefficient, N , and N , are the molecularconcentrations, PZ is a factor, and E the energy of activation ofthe reaction; Z is the number of collisions between the moleculescomputed by using " kinetic theory " diameters; P is furtherdefined as a steric factor.A reactionis considered to be normal ifP is of the order of magnitude of unity. In point of fact, however,no precise significance can be attached 60 the value of P becausethe calculation of 2 is uncertain for the particular collision involved.Consequently another quantity A is defined by the equationk = A . exp(-III/RT)1 J. B. Harkness, G. B. Kistiakowski, and W. H. Mears, J. Chem. Physics,C. N. Hinshelwood, " Kinetics," 3rd Edn., Chap. 2, Oxford; L. Kassel,1937, 5, 682." Kinetics," Chap. 3, Amer. Chem. SOC. MonographMELVILLE : CHEMICAL KINETICS. 63If P = 1, then A = Z/[N1][N2], and for molecular diameters of theorder of If there-fore a reaction has an A factor of less than this value (in order ofmagnitude), then it is presumed that although the energy of activ-ation is available during collision some further criterion must befulfilled before reaction will occur.One possible interpretationis that the criterion is purely geometrical in that the moleculeshave to be orientated in a precise configuration; but, as will beseen later, there may be other explanations.For convenience in subsequent discussion, all the reactions whichhave been thoroughly investigated are given in Table I. Indirectcm. it has the value 1014 C.C. mol.-l sec.-l.TABLE I.Reaction.EthyleneButadiene H2 + C P 4 -+ C P ,3 -VinylcycZohexene + butadieneIsopreneAaY-Pentadiene&-Dimethyl- AaY-butadienecycZoPentadieneAaY-Butadiene + acraldehydeIsoprene + acraldehydeAaY-Butadiene + crotonaldehydecycZoPentadiene + acraldehydeDecomposition.endoMethylenetetrahydrobenzaldc-DicyclopentadienehydeVelocity coefficient,C.C.mol.-l sec.-l.1.8 x 1013 ~ X P ( -43150/RT)1.95 X 10" exp( -35000/RT)6 x lo1' exp(-24600/RT)4.7 X 10" e~p(-35300/RT)1.0 X lo1' e~p(-23690/RZ')5.3 X 10l1 exp( -23900/RT)4.7 X lo1' e~p(-25900/RT)3.5 X lo1' exp( -26000IRT)1.5 X 10" exp( -25300/RT)1-3 x lo1' exp(-38000/RT)8.5 X lo7 exp(-I4900/RT)1.2 X lo9 e~p(-16700/RT)1.46 x lo9 e~p(-19700/RT)0.90 x lo9 exp(-22000/RT)1-02 X lo9 exp(-l5200/RT)Velocity coefficient, sec.-l.1.02 X 10' exp(-18700/RT)2.2 X 1012 e ~ p ( -33600/RT)1.0 X 1013 exp( -33700/RT)1.0 X exp( -34200/RT)Ref.4561, 5887577101, 71, 71, 71, 7Ref.1, 71, 78, 910estimates have also been made of a number of simple bimolecularassociation^.^ The reverse unimolecular decomposition beingassumed to be normal, then the unimolecular constant kud is givenby the equation, k d = 1013exp(-E,,i/RT) sec.-l, where Euni isC.E. H. Bawn, Trans. Faraday SOC., 1936, 32, 178.R. N. Pease, J . Amer. Chem. Soc., 1931, 53, 613.Idem, ibid., 1932, 54, 1876.W. E. Vaughan, ibid., p. 3863.G. B. Kistiakowski and J. R. Lacher, ibid., 1936, 58, 123.G. B. Kistiakowski and W. W. Ransom, J . Chem. Physics, 1939, 7 , 725.W. E. Vaughan, J . Amer. Chem. SOC., 1933, 55, 4109.lo C. A. Benford and A. Wassermann, J., 1939, 362, 367; B. S. Khambataand A. Wassermann, ibid., pp.371, 375; G. A. Benford, H. Kaufmann,B. S. Khambata, and A. Wassermann, ibid., p. 38164 GENERAL AND PHYSICAL CHEMISTRY.the energy of activation. Also k = PZ . exp(-Ebi/RT), and K ,the equilibrium constant, is given by the equationK = k,,&,i = (1013/PZ)eAH’nTwhere AH is the heat of reaction. Thus if K is known, P may becomputed. The value of P for the reaction NO2 + NO, + N,O,is 2 x for C,H, + H,O --+ C,H,*OH, P = 1.4 x lo4. SinceK may be calculated from the entropy of the molecules taking partin the reaction, the steric factor for many reactions may be cal-culated.. The obvious assumption which it is somewhat difficult tojustify in any particular case is that concerning the magnitude of theunimolecular velocity coefficient.Although the reactions are simply classified above, there aresome complications and controversy about the nature of the products.For example, in the polymerisation of ethylene, H.H. Storch l1has found that oxygen strongly accelerates the reaction, whichwould imply the intervention of some chain mechanism. Theproducts of the reaction are, however, low-molecular-weight sub-stances and it is not unlikely that the nature of the reaction dependsto a very large extent upon the manner in which it is carried out.The addition of hydrogen to ethylene is apparently a normal reaction.As will be observed from Table I, conjugated double-bond com-pounds dimerise very much more readily, as is best shown by thefact that the energy of activation for association is lower than thatfor ethylene.The butadiene reaction has been particularly wellstudied, the product being 3-vinylcycZohexene. Complicationsarise, however, since there is further reaction of this product withbutadiene to give A3‘ 3’-octahydrodiphenyl.12 Although this re-action has been less completely investigated, its energy of activationis relatively high, and the A factor, curiously enough, is quite normal.Apparently there is no appreciable polymerisati~n to products ofhigher molecular weight. Since 3-vinylcyclohexene is the product ofthe dimerisation of butadiene, the mechanism of the reaction must be2 CH2// YH g H 2\\ \/CH2 CH2+ GH (P CH CH-CH=CH, CH CH-CHXCH,i.e., 1 : 4, 1 : 2 addition. This is precisely analogous to theDiels-Alder reaction between dissimilar molecules.13 It is fortunate11 J .Amer. Chem. SOC., 1934, 56, 374.l a K. Alder and H. F. Richert, Ber., 1938, 71, 373.13 0. Diels and K. Alder, Annalen, 1928, 460, 119; 1929, 470, 370MELVILLE : CHEMICAL KINETICS. 65that the latter reaction can be induced to occur in the gas phase,because it extends the number of systems for accurate study so thata more exact picture of association reactions may be formed. Evencyclopentadiene will react with acraldehyde to give endomethylene-tetrahydrobenzaldehyde. It is noteworthy that crotonaldehyde willreact as readily as acraldehyde. * The association of cyclopentadienehas been extensively studied, not only from the point of view of thegas reaction, but with the view of establishing a correlation betweengas- and liquid-phase polymerisations.l*> l4 The product of thereaction at temperatures below 150" is undoubtedly the troughform of endodicyclopentadiene shown in Fig.1. It is importantthat the velocity coefficients for the reaction are practically thesame in the gas and in the liquid phase (solution in paraffin). 4-XC - /fF I G . 1.With the exception of perhaps ethylene the experiments on di-merisation give some indication of the energy required for inducingreactivity in the double bond and demonstrate that this is notunduly large. Whether a similar degree of activation is necessaryfor the production of molecules of high molecular weight is, how-ever, a point upon which it is difficult to decide with the data a tpresent available. As will be seen later, the over-all energy ofactivation for many liquid-phase polymerisations lies within therange 20,000--30,000 cals., which would seem to indicate that theenergies required for the two processes do not at any rate differwidely.In production of long-chain molecules the energies of thepropagation and termination reactions must of course be taken into14 B. S . Khambata and A. Wassermann, Nature, 1937, 139, 699.* Crotonaldehyde, acids and esters cannot however be polymerised to long-chain compounds.REP.-VOL. XXXVI. 66 GENERAL AND PHYSICAL CHEMISTRY.consideration, with the result that such an apparent agreementmay be vitiated.Although there is some variation in the A factors of these di-merisations there is no doubt that they are all much smaller thanthe values of a normal bimolecular reaction. The simple geometricalpicture mentioned above is probably too crude to account completelyfor these observations, and an appeal has therefore been made tothe transition-state method of calculating velocity coefficients tosee what sort of an explanation it affords of the process.16According to this theory the bimolecular coefficient is given bywhere Fc' and F, are the partition functions for the transitionand the initial state of the system and p is the reduced mass ofthe whole system.From this it may be shown that the P factordefined previously is given bywhere f v is the vibrational partition function (all assumed to beidentical) and A , B, and C are the principal moments of inertiaof the molecules.Now the value of the denominator is of the order103-106; fv = (1 - exp(- hv/kT)>-l and since hv>kT, the vi-brational partition function may be taken as unity. The valueof P will thus be small and therefore in accordance with experi-ment.3 Qualitatively this may be stated by saying that in such abimolecular process three degrees of freedom of rotational energymust be converted in the complex into vibrational degrees of free-dom, and it is the difficulty of this transformation which is re-sponsible for the tardiness of the reaction. Recently, Kistiakowskiand his co-workers1s8 have boldly utilised the theory in rather adifferent way in order to find out something about the precisestructure of the transition complex of butadiene.The other way ofexplaining the smallness of the P factor consists in supposing thathv >kT and that therefore the vibration partition function mayhave a value very much less than unity. This naturally complicatesmatters considerably for then not only is it necessary to compute theexact magnitude of the partition function for each mode of vibra-tion of the initial state of the system, but it is also necessary toknow the modes of vibration of the transition complex. More-over, there may be several possible configurations of the latter,and this still further complicates the solution of tho problem.See, e.g., H. Eyring, Trans. FaracZay Soc., 1936, 34, 3 ; dso, in particular,M. G.Evans, ibid., 1939, 35, 824MXLVIIJLE : CHEMICAL KINETICS. 67None the less if, by postulating a given configuration for the complexand carrying through the calculations to the stage of computing theA factor, agreement is obtained with experiment, then there is goodreason to suppose that the correct transition complex has been chosen.This is an important piece of information in so far as the associationof molecules containing conjugated double bonds is concerned.Here the prime essential is to try to discover whether the electronsof the double bonds are merely excited or whether a di-radical isformed. The agreement for butadiene between theory and experi-ment is good enough to support the conclusion that the transitioncomplex is indeed a free radical.Although the energy of activationof the reaction is only 23,690 cals., diradical formation thus :CH,=CH-CHXCH, CH2=CH--C1H=CH2CH;=CH=CH-CH2-CH2-CH=CH=CH2 III I Ican also be justified from energetic considerations, for then2(B - A) + A + 23, - R, - 24 < 0where B is the energy required to open the double bond to a singlebond, and A is the energy of a single bond in the middle of a hydro-carbon chain; R, and R, are the resonance energies of butadieneand the di-radical, estimated as 15,000 and 5000 cals. respectivelyfrom C. A. Coulson’a calculations.16 Thermochemical data giveB - A = 24.5 kg.-cals., and therefore A must be less than 95kg.-cals. The energy of the -C-C- bond is certainly in some doubt,but in a hydrocarbon it probably does not exceed 95 kg.-cals.andhence di-radical formation is energetically possible on thesepremises. This does not mean, of course, that opening of a doublebond is invariably the mechanism in all other molecules, but theessential demonstration is that owing to resonance it need not bean unduly energetically expensive process.The Formation of Long-chain Molecules.-The study of the ki-netics of the thermal polymerisation of vinyl derivatives in the gasphase is out of the question, but the reactions proceed smoothlyin the pure liquid or in solution. The reason for this behaviourwill become apparent in what follows. In this way styrene, methylmethacrylate, vinyl acetate, and similar molecules have beenpolymerised under a variety of conditions.I n the gas phase onlythe photochemical method of starting polymerisation can beconveniently employed. Before dealing with either of thesedevelopments we may anticipate a little along the following lines.In these reactions it has been established beyond all doubtl6 Proc. Roy. SOC., 1938, A , 164, 38368 GENERAL AND PHYSICAL CHEMISTRY.that the mechanism is of the chain type, in that when one moleculeis brought into a reactive state by light or by a catalyst a largenumber of additional molecules may react with the active polymermuch more readily than they would with a normal molecule ofmonomer. Eventually the activity is destroyed in some manner.Hence, kinetically the problems to be solved are these : How is themolecule brought into the reactive state, and what is the natureof this state? Is it possible for one molecule to possess more thanone such state ? When subsequent addition of monomer occurs,what is the efficiency of the process and how does it vary, if at all,with molecular size? Finally, by what type of reaction is theactivity destroyed ‘1 Two further problems of especial interestare whether branched reaction chains can occur with the pro-duction of either branched or three-dimensional molecules, andwhether it is practicable to cross polymerisation chains, i.e., t o formtrue interpolymers.Another problem concerns the distributionof the sizes of the various molecules produced.First, we deal with gas-phase polymerisations, and in view ofthe early state of development it will be convenient to deal with eachreaction separately before attempting any correlation.As in theliquid phase, only those monovinyl compounds having the basicgroup CH,=C < undergo polymerisation, the exception beingacetylene. Unlike the vinyl derivatives, acetylene polymerisesthermally at high temperatures, but the reaction is too complicatedto be of much use kinetical1y.l7,1*,19 If, however, acetylene isirradiated with light of wave-length ca. 2000 A., it polymerises to ityellow solid-cuprene-of the same composition as acetylene at20°.20- 21 At higher temperatures isolable amounts of benzene areformed.22y23 S. C. Lind and R. S. Livingston24 found from itsystematic investigation of the kinetics that the chain length wasabout 10 a t 20°, and the rate of polymerisation was simply pro-portional to the intensity if absorption of light was incomplete ;i.e., -d[C,H,]/dt = const.Iiin.[C2H2]e-4000’fiT, where Ii,. is theincident light intensity. Nothing is known about the constitutionof the polymer, or of its molecular weight if it is a straight-chaincompound. If the primary efficiency were unity, the molecularl7 R. N. Pease, J. Amer. Chem. SOC., 1930, 52, 1158.18 H. A. Taylor and A. van Hook, J. Physical Chem., 1935, 39, 811.P. Schliipfer and M. Brunner, Nelv. Chim. Acta, 1930, 13, 1125.20 J. R. Bates and H. S. Taylor, J. Amer. Chem. Soc., 1927, 49, 2438.21 F. Reinicke, 2. angew. Chcm., 1928, 41, 1144.22 S. Kato, BULL Inst. Phys. Chem. Res. Tokyo, 1931,10, 343; W.Kemulaand St. Mrazek, 2. physikal. Chem., 1933, B, 23, 358.23 R. S. Livingston and C. H. Schifflett, J . Physical Chem., 1934, 38, 377.24 J . Amer. Chem. SOC., 1932, 54, 103MELVILLE : CHEMICAL KINETICS. 69weight would be ten times that of acetylene. If the molecularweight was found to be appreciably higher than this figure, then theefficiency must be less than unity. Similarly, in the mercury-sensitised polymerisation the rate is given by an equation almostidentical with that for the direct reaction, vix.,- d[C,H,] /dt = const. {li,.k[C,H,]/(k[C,H2] + T ) ) ~ - ~ ~ ~ / R ~where z is the lifetime of the excited atom.25 It may be mentionedthat the apparent energy of activation decreases with increasingtemperature, finally becoming zero.In this reaction the excitedmercury atom collides with and combines with the acetylene mole-cule, further molecules of acetylene adding to the initial complex.The variation in rate with pressure in both the direct and the sensit-ised reaction is simply connected with the starting process andhas therefore nothing to do with the polymerisation itself.At this point it is desirable to indicate how some mechanismfor the reaction may be constructed from these data in order toshow how the kinetics of polymerisation may be dealt with. Themechanism involves the photoactivation of the acetylene to somereactive state which need not be specified for the moment. Mole-cules of acetylene add on, but the process comes to a stop since thequantum yield is finite.It is now generally agreed that, exclusiveof inhibitors, there are only three ways in which termination ofgrowth may occur.25 26 The first consists in the spontaneous lossof activity of the growing polymer, as for example by isomerisationand at a rate k,[P], where [PI is the total concentration of activepolymer; the second consists in the destruction of reactivity bycollision with a molecule of monomer * a t a rate k,[P][M]; thethird consists in the interaction of two active polymers in such away as to lead to mutual removal of their activity. A polymerchain reaction is in a way simpler than the usual type of chain inthat only one reactive molecule instead of two is concerned. Hencewe may write the equation defining its concentration in the stationarystate thus :d[P]/dt = I + kp[P][M] - kp[P][M] - k,[P][M] 0where I is the rate of starting and monomer termination occurs;[PI may therefore be obtained, and since the rate of polymerisationis kp[P][M] = Ikp[M]kt-l, the whole problem would appear to besolved. Naturally much complication may arise in the initiation25 H.W. Melville, Trans. Faraday SOC., 1936, 32, 258.26 J. W. Breitenbach, Monatsh., 1938, 71, 275.* The collision must of course be of a different kind compared with that inwhich the polymer grows70 GENERAL AND PHYSICAL CHEMISTRY.and termination factors but the kinetics may be worked out in ananalogous manner. There is one simplification which may not bevalid. This is that the magnitude of the propagation coefficientkp is independent of molecular size-at any rate at the beginningof the reaction.Another difficulty of this simplified treatment is that it is notpossible to calculate the distribution of molecular sizes in the productsfor the simple reason that all active polymer molecules are consideredto be kinetically identical.It is evident therefore that some con-venient method of dealing with all possible polymer molecules,alive as well as dead, must be devised. This is done in the followingway. Suppose again there is monomer termination, then for eachpolymer molecule there is a corresponding equation defining itsconcentration, that concentration being assumed to have reached astationary value. This is equivalent to assuming that the lifetimeof the active polymer is short compared with the half life of thereaction.(Exceptions to this behaviour will be discussed below.)Hence the simple equation becomesfor polymer P, [P,] = I - kp,[Pl][M] - k,,[P,][M] = 0and for P,and, in general, rki = kpT- ,[E - 1 ~ [ ~ ~ - I~,~[P,I~MI - ~,JP,I[MI = 0Therefore I = =prI[MI.P21 = k p l r p l i [ ~ i - I%,,[P,I[MI - ~,,CP,I[MI = 0As it stands this expression is not of much value for obtaining-d[M]/dt, but if the eminently reasonable assumption is made thatktJkpl = ktr/kpr = A, then it can be easily shown thatand therefore- d[M]/dt = IZ(1 + A)-?- d[M]/dt = 1(1 +if the chain length of the polymer is long. Thus it is seen that alarge number of stationary concentration equations are easily dealtwith by making this assumption.For any other type of initiationor termination process the corresponding equations may be deducedand compared with the experimental findings so that a mechanismmay be formulated. Naturally such a method precludes thepossibility of determining the magnitudes of the individual valuesof kp or of kl. For that purpose a different technique must beemployed. As will be seen later, an extension of this procedureenables molecular-weight distribution curves to be obtained.Returning to the polymerisation of acetylene, it may be shownthat the above-mentioned kinetics are only consistent with monomertermination. Apart from this not much more may be said abouMELVILLE : CHEMICAL KINETICS. 71the details of this reaction. Dideuteroacetylene polymerisesmore slowly that acetylene and with a shorter chain length.2' Thereason for the difference is probably due to the higher energy ofactivation of the propagation reaction.Methyl radicals from photodecomposing acetone also inducepolymerisation of acetylene,28 but the chain length is very short-2 to 5-at high temperatures, with the result that it is ratherdifficult to arrive at a mechanism except to say that the methylradical produces a larger free radical by reaction with acetyleneand this grows further by the addition of monomer.Providingthe iodine atoms be removed by mercury, ethyl radicals fromphotodecomposing ethyl iodide will also induce p~lymerisation.~gThe photopolymerisation of methylacetylene is rather less rapidthan that of acetylene.30Ethylene does not polymerise thermally at ordinary pressures,but at pressures of the order of 100 atm.it forms a wax-likepolymer ; 31 unfortunately no kinetic data are available to yieldany mechanism, except that it is not improbable that oxygencatalyses the reaction. In view, therefore, of the possibilityof the formation of ethylene oxide and its subsequent decom-position into free radicals, it is not unlikely that the ethylene ispolymerised by the free-radical mechanism, as happens a t ordinarypressures under suitable conditions.On being irradiated, ethylene decomposes in addition to formingsmall amounts of polymer.32 If it dissociates into acetyleneand hydrogen the polymer will simply be that of acetylene ; if it dis-sociates into 2CH2, for which there is some spectroscopic evidence,33polymerisation might occur by the primary reaction of CH, withC,H, and the subsequent addition of C,H,.Likewise, in the poly-merisation by excited mercury atoms there is probably first dis-sociation to hydrogen and a~etylene.~, Here, too, the acetylene ispolymerised, but it may be hydrogenated by atomic hydrogenproduced by mercury sensitisation, thus giving a polymer of a com-position approximating to that of ethylene itself.252 7 J. C. Jungers and H. S. Taylor, J . Chern. Physics, 1935, 3, 338.28 Idem, Trans. Paraday Soc., 1937, 33, 1353.29 G. Joris and J. C. Jungers, Bull. SOC. chirn. Belg., 1938, 47, 135.30 S. C. Lind and R. S. Livingston, J . Amer.Chem. SOC., 1933, 55, 1036.31 B.P. 471,690.32 R. B. Mooney and E. B. Ludlam, Trans. Paraday SOC., 1929, 25, 442;33 H. J. Hilgendorff', 2. Physik, 1935, 95, 781; W. C. Price, Phystkl Rev.,34 A. R. Olson and C. H. Meyers, J. Amer. Chem. SOC., 1926, 48, 389; J. R.R. D. McDonald and R. G. W. Norrish, Proc. Roy. SOC., 1936, A , 157, 480.1934, 45, 843; 1935, 47, 444.Bates and H. 8. Taylor, ibid., 1927, 49, 243872 GENERAL AND PHYSICAL CHEMISTRY.It is said that hydrogen atoms polymerise ethylene since C,hydrocarbons are one of the main products of the reaction at 20",but this is probably due to the combination of ethyl radicals formedby the addition of hydrogen atoms to the eth~lene.3~ Higherhydrocarbons, which would imply true polymerisation, are notpresent in any large quantity.At higher temperatures-up to300"-methyl radicals from thermally decomposing azomethane,36from photodecomposing acetone,,* from thermally decomposingmetal alkyl~,~' and ethyl radicals from photodecomposing ethyliodide29 polymerise ethylene to hydrocarbons up to C20. Inthese reactions the free radical adds on to the ethylene molecule,thus forming a larger free radical CH3*CH,*CH,-. Further mole-cules of ethylene then add on until the free radical reacts withanother of its kind by one of two mechanisms : (a) combination or(b) disproportionation, R*CH,CH,* -CH,*CH,R --+ R*CH:CH,CH,*CH,R. Depending on conditions, however, it happens that thefree radical may disappear a t a rate proportional, not to the squareof its concentration, but to the first power.Such a reaction mightwell be wall recombination of the radicals. An examination of thedata on the azomethane-catalysed polymerisation shows that if theassumption is made that the disappearance of the radicals is temper-ature-independent, the mean energy of activation for the propagationreaction is 8.6 kg.-cals. This is a comparatively small value, andwould indicate that marked polymerisation should occur a t temper-atures much below those, vix., 200-300°, normally employed tostudy the reaction. If, however, the interaction of free radicalsrequires activation the above figure will be correspondingly in-creased. At present there is no published evidence to settle thisquestion.The direct photopolymerisation of butadiene has not yet beeninvestigated, but since the gas is transparent compared with mercuryvapour a t 2537 A., the mercury-sensitised reaction may be con-veniently studied.38 Kinetically its behaviour is similar to that ofacetylene.The quantum yield is, however, less than unity, althougha brown non-volatile product is deposited, and hence it must besupposed that the activation of butadiene molecules is not at allefficient. Here, too, the excited mercury atom enters into chemicalcombination with the butadiene molecule, and the polymerisationis brought to a stop by collision of the active polymer with a monomer-by what type of collision is not known. The polymer would35 H. S. Taylor and D. G. Hill, J . Amer. Chem. SOC., 1929, 51, 2922.36 0.K. Rice and D. V. Sickman, ibid., 1935, 57, 1384.37 H. S. Taylor and W. H. Jones, ibid., 1930, 52, 1111.38 G. Gee, Trans. Paraday SOC., 1938, 33, 712MELVILLE : CHEMICAL KINETICS. 73appear to be complex in structure and extensively cross-linked,for it is insoluble in all the usual solvents. Accompanying thepolymerisation there is some decomposition to hydrogen and a resi-due and also the formation of dimer. Polymerisation proceedsfor a short period in the dark after the light is cut off.It will be evident from the above remarks that the polymerisationof hydrocarbons is not a reaction which occurs at all readily. If itis accelerated by employing higher temperatures, the product is notstable. Hence for more exact kinetic study it would seem that othervinyl derivatives may be suitable for experiment.There are a tleast two advantages to be gained by the substitution of the hydrogenatoms with groups such as CO,Me, CN, Cl, COMe, etc. : the poly-merisation velocity is increased and also the absorption spectrumof the molecule is extended to longer wave-lengths. Early experi-ments 39 on styrene and vinyl acetate had demonstrated that thesemolecules polymerise readily under the influence of radiation,showing typical chain characteristics, vix., high quantum yield andsensitiveness to inhibition by substances which are well recognisedas having this effect on chain oxidations. Fortunately, a numberof these vinyl derivatives have a high enough vapour pressure tomake practicable the study of their polymerisation in the vapourphase.Methyl methacrylate, for example, polymerises with ultra-violetlight of wave-length shorter than about 2600 A.sufficiently readilyto produce an easily visible cloud of solid polymer in the v a p o ~ r . ~ ~If too short wave-lengths (< 2300 A.) are used the molecule tendsto dissociate rather than polymerise, and hence it would appearthat such a molecule will only contain a limited amount of energyin order to excite the molecule in such a manner as to lead to poly-merisation. The energy limit cannot be fixed on account of the factthat the absorption at long wave-lengths is too minute to cause anypolymerisation. In the section on dimerisation it was seen that theactivation energies involved may lie as low as 20,000 cals., andtherefore it is not impossible that with methacrylate the energyrequired to start polymerisation may have a lower limit of thismagnitude.The curious thing is that the polymer so depositedis reactive long after the light is cut off, the monomer continuingto polymerise for several days afterwards. This activity maybe destroyed by atomic iodine and atomic hydrogen, i.e., sub-stances capable of reacting with double bonds or free radicals.The process is undoubtedly a condensed-phase reaction between39 H. W. Starkweather and G. B. Taylor, J . Amer. Chem. SOC., 1930, 52,40 H. W. Melville, PTOC. Roy. SOC., 1937, A , 163, 511.4708; H. S. Taylor and A. A. Vernon, ibid., 1931, 53, 252774 GENERAL AND PHYSICAL CHEMISTRY.absorbed monomer and polymer ; its overall temperature coefficientgives an apparent energy of activation of - 5.6 kg.-cals., but whenthis is corrected for desorption of monomer the real value of theactivation energy is 2.7 kg.-cals.Although molecular-weightmeasurements have not yet been made, it is probable that themolecular weight increases with time, and thus theoretically amolecule of any given size may be constructed. When anactive molecule possesses such a long lifetime, the rate of formationand destruction of these centres plays no part in the rate of poly-merisation, which is then solely determined by the velocity ofthe propagation reaction. In a way it is unfortunate that thereaction occurs in the solid phase, since its absolute efficiencycannot easily be determined.The activation energy is, however,comparable with that of other polymerisations. In treating thekinetics of reactions of this type, which at the moment are confinedto polymerisation, the stationary-state method indicated above canno longer be employed.Attempts41 have therefore been made to devise a system ofkinetics to suit this case. Suppose we deal with a finite initialconcentration of monomer [MI,, and that the active centres are pro-duced at a rate Ei[M], and further that the propagation coefficient(A$ does not vary with molecular size. There is no experimentalevidence for this assumption; in fact, Ep has been assumed to de-crease with increasing size and even to so small a value as to stopreaction altogether, but this is going too far.With methacrylate 40and chloroprene it would appear that there is no variation in kpover a very large range of molecular weights. Hence the mechanismof the reaction will beM-+ PI ktM + PI-+ p2 } k pand in general M + p, --+ P T f l JIf therefore [PI is written for C[P,] thenandOn solving for [PI, we haveThus the reaction will exhibit an induction period. Naturallyif [PI reaches a well-defined and maximum value, as, e.g., when asurface becomes completely covered with active centres, the ratewill then attain a constant value. For any other type of4 1 See, e.g., H. Dostal and H. Mark, Trans. Paraday Soc., 1936, 32, 54;G. Gee and E. K. Ridesl, ibid., p. 656MELVILLE : CHEMICAL KINETICS. 76initiation process the corresponding rate equation may be deduced.Similarly, if the number of centres gradually as, e.g.,by mutual destruction, and there is bimolecular initiation, thend[P]/dt = k1[MI2 - L2[P12- d[M]/dt = kp[P][M]whenceTherefore every type of long-lived polymer may be dealt with ina precisely analogous manner. Unfortunately, experimental dataare as yet too meagre to be of much use in formulating representativereaction schemes.The above discussion has emphasised the fact that, before con-ducting a kinetic analysis of a polymerisation reaction, the firstnecessity is determination of the lifetime of the active polymer.This is in general a fairly easy matter with photochemical reactions,at least in so far as discriminating between short and long lifetimes,but it is much more difficult for thermal or catalytic reactions inwhich the rate of the initiation reaction cannot be independentlycontrolled.In absence of this definite criterion, there is the possi-bility of determining the molecular weight of the product during thereaction. If this increases with time continuously, there is somereason to suppose that the lifetime of the active polymer is at leastcomparable with the half life of the reaction, and that thereforethe non-stationary kinetic method must be applied. In thosephotochemical polymerisations, e.g. , that of butadiene, where thereis a dark reaction with a half life of a few minutes, it may be difficultto decide which system to employ.Moreover, the reaction may becomposite in that the dark reaction is entirely separate from thelight reaction even though both are initiated by radiation.Gaseous methyl methacrylate may also polymerise on additionof hydrogen atoms. This is undoubtedly a free radical reactionin which the hydrogen atom adds on to the methacrylate moleculeto give CH,*CMe(CO,Me)*. Further molecules of monomer addon until two such radicals combine, whereupon the polymerisationstops.sec. , and therefore this free-radical polymerisation is entirely differentfrom that occurring by direct photoexcitation of the methacrylatemolecule.One of the problems arising in the polymerisation of vinyl de-rivatives as a whole is the nature of the active polymer. Opinionhas been divided between two mechanisms which may be likened to42 P.J. Flory, J . Amer. Chem. Soc., 1936, 58, 1877.The lifetime of these radicals is only of the order o76 GENERAL AND PHYSICAL CHEMISTRY.the ‘‘ hot ” molecule and radical chain of the early days of chainreactions. Here it is necessary to distinguish between the twopossible ways of activating a double bond, zfix., (a) by forming adi-radical, the mechanism of polymerisation then being*CH,*CHX* + CH,:CHX --+ *CH,*CHX*CH,*CHX*and (b) by exciting the double bond so as to facilitate addition ofa molecule of monomer, that is, reduce the energy of activation :CH2:CHX + CH2:CHX -+ CH,*CHX*CH:CHXIn the latter mechanism the distinguishing feature is that each timeaddition of monomer occurs a hydrogen atom must migrate.Somehave argued that such a process would require so much activationenergy that the polymerisation would revert to the so-called step-wise rather than the chain mechanism. In the former the activationenergies for the individual steps are of the same order of magnitudeas that of the initial step, and thus the activation of one moleculedoes not necessarily lead to the polymerisation of a large numberof monomeric molecules. The main characteristic of the chainmechanism, on the other hand, is that once the first molecule isactivated the activation energy for subsequent addition is materiallydiminished.In the polymerisation of methyl methacrylate it is very probablethat the kinetics of the di-radical mechanism would be similarto those of the reaction induced by hydrogen atoms, and thereforethe normal polymerisation should occur by the double-bondmechanism.Although this seems the most reasonable explanation,it is somewhat difficult to see why the activity persists for so long aperiod; yet in absence of evidence to the contrary this mechanismmay be provisionally accepted. Thus a molecule containing only asingle double bond may polymerise by at least two mechanisms.There is evidence in the liquid-phase polymerisation of styrenethat the two mechanisms may operate, for, under one set of conditionsa long-chain molecule is obtained whereas in another di- or tri-styrene is the product.43 The first may go via free radicals and thesecond by double bonds.Likewise in the polymerisation of methylisopropenyl ketone both long-chain molecules and dirner areformed.44Methyl acrylate polymerises rather more readily than the meth-acrylate but the greatest difference is that the lifetime of the activepolymer is short. On analogy with methacrylate it presumablypolymerises by the double-bond mechanism, and chain terminationis brought about by mutual destruction. This could easily be43 H. Staudinger, Trans. Faraday SOC., 1936, 32, 97.** T. T. Jones, private communicationMELVILLE : CHEMICAL KINETICS. 77explained by the radical mechanism but is equally probable withthe double-bond mechanism, for the two ends of the polymer mayreact thus--CH=CHX + CHX=CH,-' + ---CH2-CX=CX-CH,-One of the most surprising features of the reaction is its negativetemperature coefficient.If the active polymers are destroyed bythe addition of a small amount of oxygen or butadiene the temper-ature coefficient becomes positive. On the assumption that in-hibition is temperature-independent, the energy of activation forpropagation is computed to be about 4 kg.-cals. Thus the negativeoverall energy of activation must be due to the fact that the termin-ation reaction possesses an energy of activation greater than that forpropagation. A measure of the chain length in the photopoly-merisation may be obtained in the butadiene inhibited reactionfrom the ratio of acrylate molecules polymerised to butadienemolecules used up.The chloroprene photopolymerisation exhibits many unusualtypes of b e h a ~ i o u r .~ ~ . 46 As with methacrylate the polymerisationcontinues in the dark. Similarly, if light much shorter that 2500 A.is used for irradiation the molecule is decomposed and no poly-merisation occurs. Excited mercury atoms cause polymerisation,being simultaneously incorporated in the polymer. The photo-polymerisation occurs wholly in the polymer itself after a smallamount of this is deposited on the walls of the reaction vessel.There are two simultaneous reactions-one in which the life of theactive molecules is short and the polymerisation is terminated by theinteraction of two active ends of a molecule, and the other in whichpolymerisation continues indefinitely (over 3 weeks has been re-corded) in the dark.The energy of activation for polymer growthis again about 3 kg.-cals. Since the lifetimes of the methacrylateand chloroprene polymers are so long it is practicable to make mixedpolymers by growing methacrylate on chloroprene and vice versa.On the other hand, butadiene refuses to interpolymerise with eitherof these molecules under these conditions.Liquid-phase Polymerisation.-Much more work has been done 011liquid-phase than on gas-phase polymerisation, though it cannotbe said that the results are more illuminating kinetically. Threemolecules have received most attention, vix., vinyl acetate, methylmethacrylate, and particularly styrene. Pure styrene may bepolymerised thermally as a, liquid or in solution with or without45 W. H.Carothers, I. Williams, J. E. Kirby, and A. M. Collins, J. Amer.Chem. Soc., 1931, 53, 4203.46 J. L. Bolland and H. W. Melville, Proc. Rubber Tech. Conf., London,1938, 23978 GENERAL AND PHYSICAL CHEMISTRY.the addition of a catalyst such as benzoyl peroxide, stannic chloride,etc.In presence of air, pure liquid styrene polymerises at about 100"as a homogeneous liquid-phase reaction, the evidence being thatthe rate of reaction and molecular weight of the product are notchanged by alteration of the surface/volume ratio of the reaction~esse1.~7*~8 There is no induction period, and the rate of reactionconforms to a first-order equation.49 The average energy of activ-ation is 23.2 kg.-cals., and the molecular weight of the polymer, whichremains substantially constant during any one runso a t a constanttemperature; decreases with increasing temperature according tothe relationship M = const.e570°'RT. If the polymerisation is carriedout in an atmosphere of nitrogen, the kinetics of the reaction are notmaterially altered.51 If the temperature of the mixture of monomerand polymer is suddenly reduced the polymerisation immediatelyceases. This fact, and also the observation of the constancy ofmolecular weight, are strong indications that the lifetime of thepolymer is short compared with the half life of the reaction, andthat therefore the stationary-state method may be applied todetermine the mechanism. Here there is a difficulty, for althoughthe reaction proceeds according to a first-order equation, it is difficultto see what significance this observation can have since presumablyin the pure liquid phase the concentration of styrene remainsconstant. It is, however, probably true to say that the concen-tration of the polymer increases according to the equationc = c,(l - e-kt), where c and c, are the concentrations of deadpolymer at time t and at the end of the reaction. Hence, no con-clusion can be arrived at with regard to the collision mechanismof the initiation and termination processes.Assuming, as has beendone, that there is mutual termination of the growth of the polymer,then by employing the method indicated on p. 70 it can be shownthat R = P(I/T)l12 and M-P(IT)-'I2, where I , P, and T are theinitiation, propagation, and termination factors respectively.Since each factor is temperature-dependent, then from the datathe following relationships a t once hold : 23-2 = E, + +EI - QETand - 5-7 = Ep - $EI - $ET or EI = 28.9 kg.-cals.(XI, etc.,are the corresponding energies of activation). As will be seen, evenwith this assumption there are three unknowns and only two equa-tions; ET cannot arbitrarily be put equal to zero, as may be done47 J. W. Breitenbach and W. Jorde, 2. Elektrochem., 1937, 43, 609.48 H. Dostal and W Jorde, 2. physikal. Chem., 1937, A, 179, 23.4a G. V. Schulz and E. Husemann, ibid., 1936, B, 34, 187.50 H. Staudinger and W. Frost, Ber., 1935, 68, 2351.5 1 G. V. Schulz and E. Husemann, 2. physikal. Chem., 1937, B, 36, 184MELVILLE : CHEMICAL KINETICS.79often in ordinary chain reactions. If it were, E, would then amountto the rather high value of 17.5 kg.-cals. Consequently the con-clusion is that E, must amount to several thousand calories.It would appear, therefore, that in order further to elucidatethe mechanism it would be desirable to conduct the polymerisationin solution, so that the concentration of monomer would be betterdefined. Furthermore, the addition of a catalyst might thenenable a check to be kept on the initiation reaction. The uncatalysedpolymerisation in solution has been studied in a number of solventswhich exert a well-marked influence on the rates.although the overallenergy of activation is not changed. 52 The rates increase in the orderbenzene, toluene, hep tane , ethylbenzene, diet h ylbenzene, styrene,dichloroethane, trichloroethane, and carbon tetrachloride, but asufficiently detailed analysis is not given to explain what process orprocesses are affected by the solvent or whether the solvent acts asan inhibitor.A more detailed analysis of the benzoyl peroxide-catalysed reaction in toluene gives a better idea of the mechanismof the reaction.53 Again, the degree of polymerisation remainsconstant and is inversely proportional to the square root of thecatalyst concentration. The rate is correspondingly directlyproportional to the square root of the benzoyl peroxide concentra-tion. These facts definitely prove that the mechanism of thecessation of growth involves the interaction of two active polymers.It would appear that an endothermic catalyst-monomer complexis formed which initiates polymerisation. Whether the benzoylperoxide is eliminated on termination of growth is not known.Thisinvestigation also proves that toluene has nothing to do with thetermination reaction. Any effect it may exert is thus confined to thealteration in the equilibrium constant for complex formation or thevelocity coefficient for propagation.Stannic chloride catalyses the polymerisation of styrene moremarkedly than benzoyl peroxide, measurements of velocity beingpracticable in carbon tetrachloride at 25". 54 Provided the stannicchloride be absolutely free from hydrogen chloride, which is astrong inhibitor, there is no induction period and the rate is approxi-mately proportional to the concentration of the catalyst; also themolecular weight, though small, does not vary during the reactionand is independent of catalyst concentration.These kinetics wouldindicate that the active polymer is destroyed at a rate proportionalto its concentration-possibly by reaction with carbon tetrachloride.52 H. Suess, K. Pilch, and H. Rudorfer, ibid., 1937, A , 1'79, 361 ; H. Suessand A. Springer, ibid., 1938, A, 181, 81.53 G. V. Schulz and E. Husemann, ibid., 1938, B, 39, 246.64 G. Williams, J., 1938, 246, 104680 GENERAL AND PHYSICAL CHEMISTRY.As with benzoyl peroxide, some complex is formed between catalystand monomer which starts polymerisation. In view of the factthat there is no induction period, the time for the formation of theequilibrium amount of the complex is short compared with the timefor polymerisation.An interesting use can be made of the inhibi-tion by hydrogen chloride since by observing how the length of theinduction period varies with the concentration of this substanceand assuming that the hydrogen chloride reacts with the activepolymer, it is possible to calculate how many active polymers areproduced per unit time. The ratio of rate of polymerisation to therate of this process should then give the mean degree of polymeris-ation. There is, in fact, good agreement with the value determinedfrom the molecular weight of the polymer.What the precise nature of the active polymer is under theseconditions of polymerisation has been and still is a matter for specula-tion, but it is interesting to observe that G.V. Schulz and G. Wittig 55have succeeded in inducing a free-radical polymerisation of styreneby adding to it the free radical CPh,*CN from tetraphenylsuccino-nitrile. Moreover, the free radicals combine finally to stop thegrowth of the polymer chain.The polymerisation of vinyl acetate seems to be rather morecomplicated than that of styrene. The early observations do notpermit of a detailed analysis.39 Some have questioned the homo-geneity of the reaction.56 A more detailed analysis has shown thatwhen suitably purified reactants are used the reaction is homogeneous,and is catalysed by benzoyl peroxide, an induction period beingcharacteristic of the polymerisation.57 During the inductionperiod the catalyst interacts with the monomer to form a complexwhich on breaking down initiates a polymer chain. The kineticanalysis shows that termination is again due to mutual interactionof the active polymers. Further complication appears to arise, fora t high temperatures the polymer is insoluble, from which it isconcluded that branching and cross linking of the molecular chainsThe kinetics of the polymerisation of methyl methacrylatecatalysed by its ozonide and also by benzoyl peroxide have beenexamined.58 Here the reaction is of zero order until isothermalconditions cease to apply to the system. The rate of polymerisationis proportional to the square root of the catalyst concentration,occur.55 Naturwiss., 1939, 27, 387.56 J.W. Breitenbach arid W. Jorde, Z . lClektrochem., 1937, 43, 609.5 7 A. C. Cuthbertson, G. Gee, arid E. K. Rideal, Proc. Roy. SOC., 1939, A ,58 R. G. W. Norrish and E. E. Brookman, ibid., 171, 147.1’70, 300MELVILLE : CHEMICAL KINETICS. 81which implies mutual destruction of the active polymers whateverthese molecules may be. The molecular weight under the conditionsemployed tends to increase during polymerisation. This was a tfirst taken to mean that the life of the polymer was long, but maybe more simply explained by supposing that the lifetime of theactive polymer is short, in conformity with general experience inliquid-phase polymerisations, and that the catalyst concentrationgradually falls during the reaction owing to its decomposition.59The kinetics of the polymerisation of mixtures of styrene andmethyl methacrylate are peculiar in that there is a non-linearrelation between rate and mo1.-fraction of the components.58Interpolymerisation may occur but the precise interpretationof the data is at present rather difficult owing to lack of knowledgeabout the kinetics of the individual reactions themselves.There are two matters finally to be discussed in connection withthe kinetics of polymerisation. The first concerns branching.In ordinary gas kinetics branching of chains was first introducedto explain the appearance of sharp explosion limits, but in polymersthe idea was introduced from an examination of substances whosestructure consisted of a three-dimensional network of atoms.I npolymers, therefore, branching is detected structurally, and thequestion arises as to whether there is any way of detecting itsoccurrence during a polymerisation reaction by some characteristickinetic feature. At present there is no published evidence pointingto any deviation in normal kinetic behaviour which may be conclu-sively ascribed to branching, although products have been obtainedwhich appear to be cross-linked. This may be due to the fact thatmost polymer growth stops by mutual deactivation in pure systems.But branching can only become noticeable if the reaction goesabnormally quickly as some parameter such as concentration ortemperature is increased, and such an event only becomes possibleif the kinetic order of the branching process with respect to theactive polymer concentration is greater than the order of thereaction responsible for the destruction of the polymer.Whenactive polymer destruction is already of the second order it is thusimpossible for this condition to be fulfilled. Unless thereforebranching is brought about by the addition of some specificnew component to the system, its detection kinetically seemsunlikely.Molecular..weight distribution in synthetic polymers and its re-lationship to mechanism is still a virgin field. The ultra-centrifugalmethod of separation has been applied to polystyrene.60 G. V.59 G. Gee, Trans. Paraclay SOC., 1939, 35, 1085.6o R. Signer and R. Gross, Helv. Chim. Acta, 1934, 17, 59, 335, 72682 GENERAL AND PHYSICAL CHEMISTRY.Schulz has separated polymers by fractional precipitation andcompares such distributions with his theory, whereas H.Dostaland H. Mark 62 and P. J. Flory 63 have made calculations on suchdistributions. From the general theory of the polymerisationgiven on p. 70, it may be indicated how this kind of calculationcan be carried out. The last term in each differential equationfor the active polymer gives the concentration of '' dead " polymerorHenceand consequently the weight fraction w, is given byd[M,]/dt = ~~r[P,I[Ml = hf(l)/(l + A)?[Mrl = h2([MlO - [Ml)/(I + 1Y-lw, = P r / ( l +As a result of these calculations two kinds of average chain lengthmay be defined,64 vix., (a) a number average v, = Zr[M,]/C[M,] = I - 1,which is determined by kinetic methods, i.e., end-group determin-ations, and ( b ) a weight average v, = Cr2[&]/Zr[i&] = 2 / h , de-termined by viscosity measurements.For this particular mechan-ism it will be seen that v, is twice v,. Naturally, for each kind ofmechanism appropriate distribution functions may be derived.Whether the reverse process may be practised, vix., the confirmationof reaction mechanism by distribution measurements, is yet to beseen.This brief survey of polymerisation will have indicated thatalthough the problems encountered are innumerable and often diffi-cult of solution, the kinetic attack on the question, supplementedwhenever possible by determination of the structure of the resultantpolymer, does show some promise of successful solution.H.W. M.4. THE RGLE OF THE SOLVENT IN REACTION KINETICS.The effect of different solvents upon the velocity of chemicalreactions was one of the earliest kinetic problems to be studiedexperimentally, as, for example, in the work of Menschutkin.1Numerous attempts were made to establish empirical relationshipsbetween the reaction velocity and physical properties of the solvent61 2. physikal. Chem., 1935, B, 30, 379.62 Trans. Paraday SOC., 1936, 32, 54.63 J . Amer. Chem. SOC., 1936, 58, 1877; 1937, 59, 241.64 E. 0. Kraemer and W. D. Lansing, J . Physical Chew&., 1935, 57, 1369.1 2. physikal. Chem., 1890, 8, 41BELL: R6LE O F THE SOLVENT IN REACTION KINETICS. 83(such as the dielectric constant), but these relations had no theor-etical basis and had no wide range of applicability even in a qualit-ative sense.Later, experimental advances made it possible to studyhomogeneous gas reactions, and modern theories of reaction velocitywere applied in the f i s t instance to these on account of their greatersimplicity from a theoretical point of view. More recently, however,the focus of attention has to some extent returned to reactions insolution, partly because of the increase in our general knowledge ofthe liquid state, and partly because of the bearing of such velocitieson modern theories of organic chemistry. Most of the theoreticaladvances have been framed in terms of either the collision theory orthe trunsition-state theory.The separate application of these twomethods often leads to results which appear at first sight to bedifferent, or even contradictory, but it is gradually being realisedthat the two methods of treatment are essentially equivalent, andmust lead to the same results if correctly applied. One of theobjects of this Report is to emphasise this equivalence in the problemof solvent effects, and to indicate how each method has someadvantages in dealing with particular aspects of this problem.*It is, of course, impossible to give any complete review of theexperimental data. I n the f i s t place, this article will deal almostentirely with bimolecular reactions, since it is for this type of reactionthat the effect of the solvent is most clearly understood.We shallconsider, in particular, cases in which a direct comparison has beenmade between the reaction velocities in the gas phase and in solu-tion-clearly an important type of investigation for our presentpurpose-and also reactions which have been studied in a wide rangeof solvents. Such results provide a much more useful basis fortheoretical discussion if they refer to a range of temperatures, and thetemperature variation of the velocity has almost always beenexpressed in terms of the Arrhenius equation, Ic = Ae-E”RT, where Eis the activation energy, and A will be termed the collision factor.The effect of the solvent on E and A separately should then consti-tute a simpler problem than the effect on the velocity as such. Itshould, however, be mentioned that there are certain grounds forregarding the Arrhenius equation as only a good f i s t approximation.From a theoretical point of view the activation energy defined byE = RT2 d(1og k) /dT is the difference between the average energy ofthe reacting molecules and the average energy of all the molecules,and this difference may be expected to vary with temperature in thesame way as any heat of reaction.This fact has been realised for a* Both the apparent divergence and the essential equivalence of the twomethods are well illustrated by two discussions held recently; J., 1937, 629;Trans. Faraday SOC., 1938, 34, 1-26784 GENERAL AND PHYSICAL CHEMISTRY.long time 2 and has been more recently emphasised by V. K. LaMer,3who also pointed out that deviations from the Arrhenius equationwill be more likely if different activated states have different prob-abilities of reaction.This possibility applies particularly to reactionsinvolving the movement of light nuclei (Le., protons) where, accord-ing to quantum theory, the probability of reaction is a continuousfunction of the energy.4 On the other hand, the reported experi-mental deviations from the Arrhenius equation (apart from thosedue to a composite chemical mechanism) are neither numerous norconvincing, and even recent low-temperature measurements onproton-transfer reactions have failed to reveal such deviations. I nthis Report we shall therefore follow the usual practice of using thesimple Arrhenius equation, though it should be borne in mind thateven deviations too small for experimental detection may affect theexact interpretation of the experimental values of A and E.'There are obvious experimental difficulties in measuring thevelocity of a reaction both in the gas phase and in solution, andalthough a fairly large number of such comparisons have beenattempted, the results are often inaccurate and difficult to interpret.The following bimolecular reactions have been investigated : (a) thereaction between amines and alkyl iodides, (b) that of aceticanhydride with alcohol, (c) various esterification reactions, (d) thedimerisation of keten, ( e ) the catalysed decomposition of trioxy-methylene, (f) the hydrolysis of oxalyl chloride, (9) the decompositionof ozone, (h) the reaction between ozone and chlorine, (i) the decom-position of chlorine monoxide, (j) the decomposition of ethylenedi-iodide, (k) the dimerisation of cyclopent,adiene.Cf.F. E. C. Scheffer and W. F. Brandsma, Rec. Truw. chim., 1926, 45,522;W. F. Brandsma, ibid., 1928,47,94; 1929,48,1205.J . Chem. Physics, 1933, 1, 289.For a summary, see R. P. Bell, Trans. 3'uruday Soc., 1938, 34, 232, 259;J. 0. Hirschfelder and E. Wigner, J . Chem. Physics, 1939, 7 , 616.Cf. V. K. LaMer, J . Amer. Chem. SOC., 1935, 57, 2662, 2669, 2674; 1936,58,2413; G. F. Smith, J., 1936,1824; W. I?. K. Wynne-Jones, Trans. FuradaySOC., 1938, 34, 250. R. P. Bell and J. K. Thomas, J., 1939, 1573.R. P. Bell, Trans. Faraday SOC., 1938, 34, 232.( a ) E.A. Moelwyn-Hughes and C. N. Hinshelwood, J., 1932, 230 ; H. W.Thompson and E. E. Blandon, J., 1933, 1237; A. Gladishev and J. Sirkin,Actu Physicochim. U.R.S.S., 1938,8,323; ( b ) E. A. Moelwyn-Hughes and C . N.Hinshelwood, Zoc. cit. ; (c) C . A. Winkler and C. N. Hinshelwood, Trans. B'arudaySOC., 1935, 31, 1739; (d) F. 0. Rice and J. Greenberg, J . Amer. Chem. Soc.,1934,56,2132 ; ( e ) R. P. Bell and R. le G. Burnett, Trans. Puruduy Soc., 1939,35, 474; (f) F. Daniels, Chem. Reviews, 1935, 1'7, 8 2 ; (9) and (h) E. J. Bowen,E. A. Moelwyn-Hughes, and C . N. Hinshelwood, Proc. Roy. Soc., 1931, A , 134,211; ( i ) E. A. Moelwyn-Hughes and C. N. Hinshelwood, ibid., 1931, A , 131,127; ( j ) M. J. Polissar, J . Amer. Chem. SOC., 1930, 52, 956; H.J. Schumacher,ibid., 1930, 52, 3132 ; L. B. Arnold and G. B. Kistiakowski, J . Chem. PhysicsBELL: R ~ L E OF THE SOLVENT IN REACTION KINETICS. 85Of these reactions, (a)-(e) take place on the walls of the vessel inthe absence of solvent, whereas (f) and (9) proceed by complicatedmechanisms which are not the same in solution and in the gas.Reaction (h) is a complicated chain reaction, but in the gas phase thevalues of A and E for the rate-determining bimolecular process canbe estimated. At 50" the observed rate is almost the same in the gasand in carbon tetrachloride solution, but there is such a largedifference in the temperature coefficients that the reactionmechanism can hardly be the same in the two phases. Reaction(i) is not strictly of the second order, and the numerical values of Aand E cannot be determined; however, both the rate and thetemperature coefficient are much the same in the gas and in carbontetrachloride solution, so the A and E values are probably verysimilar in the two phases. Reaction (j) is a chain reaction, but thevelocity constant of the rate-determining bimolecular process can beestimated both in the gas and in solution. The A and E values arereported to be the same in the two phases, but the accuracy is low,i.e., about h 1 .3 in log,,,A, and &3 kg.-cals./mol. in E . Reaction(k) has been studied over a wide range of temperature in the gasphase and in eight different solvents : the velocities vary only by afactor of about 4 throughout, and the values of A and E me constantwithin the experimental error.The study of reaction velocity in a wide range of solvents offersfew experimental difficulties, but although the mass of experimentaldata is large, the number of different types of reaction coveredis regrettably small.Reaction (a), often referred to as theMenschutkin reaction, has been studied by a large number of authorsin some 20-30 different solvent^.^There is some disagreement between the individual values ofdifferent authors, but it is clear in general that the velocity can bevaried by a factor of about lo3 by change of solvent, there being ageneral tendency for higher rates in solvents of a polar type. Theeffect of the solvent appears in the values of both A and E, and thereis little correlation between the variation of the two factors.Similar1933, 1, 166; R. A. Ogg, J. Amer. Chem. SOC., 1936, 58, 607; (Ic) (Miss) B. S.Khambata and A. Wassermann, Nature, 1936, 137, 496; 1937, 138, 368;A. Wassermann, J., 1936, 1028; G. A. Benford, (Miss) B. S. Khambata, andA. Wassermann, Nature, 1937,139,669; A. Wassermann, Trans. Faraday Xoc.,1938, 34, 128; H. Kaufmann and A. Wassermann, J., 1939, 870.9 See especially H. G. Grim, H. Ruf, and H. Wolf, 2. physikal. Chem., 1931,B, 13, 299; N. J. T. Pickles and C. N. Hinshelwood, J., 1936, 1353; R. A.Fairclough and C. N. Hinshelwood, J., 1937, 538, 1573. Other papers arethose of H. W. Thompson and E. E. Blandon, J., 1933, 1237 ; J. W. Baker andW. S. Nathan, J., 1935, 519; W. C. Daviesand12.G. Cox, J., 1937,614; V. A.Goldschmidt and N. K. Voroviev, J. Phys. Chem. Russia, 1939, 13,47386 GENERAL AND PHYSICAL CHEMISTRY.results were obtained by studying a reaction of somewhat similartype, the benzoylation of m-nitroaniline, in eight different solvents.1°It has already been mentioned that the dimerisation of the non-polarmolecule cyclopentadiene has the same A and E values in the gas andin 8 diverse solvents. The addition of cydopentadiene to the fairlypolar molecule benzoquinone has also been studied in 8 solvents,11and although there are some discrepancies between the values ofdifferent authors it is clear that a change of solvent leads to a vari-ation of rather less than 100-fold in the velocity, and that thisvariation involves both the factors A and E.The above data form a slender basis for generalisation, but(together with other experimental results of a less systematiccharacter) they suggest the following tentative conclusions. Bi-molecular reactions in which both the reactants and the products areof low polarity take place a t approximately the same rate in the gasphase as in solution, and their rate varies little with the nature of thesolvent. This constancy also applies to the values of the factors Aand E under different conditions.If, on the other hand, the reactioninvolves polar molecules, then attempts to study it in the gas phasereveal only a surface reaction, and change of solvent causes largevariations of rate, these variations appearing in both the factors Aand E.Apart from these generalisations, the absolute value of the factorA in solution is of theoretical interest, and a recent survey 12 showsthat for bimolecular reactions (excluding reactions between twoions) A has values ranging from about lo3 to 1011 l./g.-mol.see.-1.All intermediate values are found, and there appears to be nofoundation for the view once held l3 that bimolecular reactions insolution could be divided into two classes, “ normal ” reactions inwhich A loll, and “ slow ” reactions with A several powers of tenlower.We must now consider the theoretical interpretation of these facts.The collision theory of bimolecular reactions is too well known toneed any description here. The reaction velocity is written in theform k, = PZe-E”RT, where Z is the collision number and P atemperature-independent factor less than unity which allows forrestrictions as to the mutual orientation and internal phase of thereacting molecules.The experimental factor A is thus written as thelo N. J. T. Pickles and C. N. Hinshelwood, J., 1936, 1353.l1 A. Wassermann, Ber., 1933, 66, 1932; Trans. Faraday SOC., 1938, 34,128; (Miss) B. S. Khambata and A. Wassermann, Nature, 1936, 137, 496;R. A. Fairclough and C. N. Hinshelwood, J., 1938, 236.12 C. N. Hinshelwood and C. A. Winkler, J., 1936, 371.13 Cf. Ann. Reports, 1934, 31, 51BELL: ROLE OF TRE SOLVENT IN REACTION KINETICS. 87product of P and 2. The value of P could in principle be calculatedif sufficiently detailed information were available as to themechanism of the reaction and the interatomic forces involved.This is not possible in practice, but we can conclude from the experi-mental data for gas reactions that P is between about 0.03 and 1.0 forreactions between simple molecules, whereas for more complexmolecules it may be as low as lo4.The transition-state theory of reaction velocity has been previouslyfully discussed in these Reports and e1~ewhere.l~ The reactionvelocity is written in the form k, = K(kT/h)K where K is.a trans-mission coefficient, and K represents a constant for the equilibriumbetween the reacting molecules and the transition state (or " criticalcomplex '7. K can be written as the product of e-E'nT and aproduct of partition functions F which (like K ) can in principle beevaluated if enough is known about the detailed course of thereaction.The necessary information is equivalent to that requiredin order to calculate P in the collision theory.In spite of their failure to give an absolute prediction of reactionvelocities in gases, both theories are useful in indicating the possibleways in which the solvent can affect the velocities. The interactionbetween the solvent and the reacting system can be of varyingdegrees of intimacy, ranging from a purely physical interference to anactual chemical combination with reactants or products. We shallfirst consider the case in which the nature of the interaction betweenthe solvent and the reactants is not appreciably modified when thereactants collide to form the " critical complex." This condition islikely to apply when both the reactants and the products are mole-cules of low polarity.According to the collision theory there arethree factors, E, P, and 2, which may be modified by the presence o fsolvent. If the activation energy E depends on short-range forcesrather than on Coulomb forces it is likely to be little affected by thepresence of solvent, and this conclusion is borne out by the experi-mental results. The steric factor P is also likely to be unaffected,since it depends on the mutual orientation of the reacting molecules.The collision number in solution has been the subject of muchdiscussion. It will depend on the translational energies and dia-meters of the solute molecules and upon the space in which they arefree to move.While the first two quantities have the same values asin the gas, the free volume will be decreased by the presence of thesolvent, with a consequent increase in collision number. It is verydifficult to make any quantitative estimate of this free space factor,l4 Ann. Reports, 1935, 33, 94 ; 1936, 34, 86 ; cf. the discussions indicated infootnote, p. 8388 GENERAL AND PHYSICAL CHEMISTRY.but a consideration of various models of the liquid state leads to theconclusion that it should certainly be less than 10, and is probablyless than 4.15This conclusion is in agreement with the inadequate experimentalevidence mentioned above, and it also receives support from measure-ments on the rate of change of pars- into ortho-hydrogen, catalysedby paramagnetic molecules.16 This change takes place a t ameasurable rate, since only a small fraction of the collisions betweenpara-hydrogen and the paramagnetic molecule are effective, but thisfraction does not depend on the temperature (i.e., does not involvean energy of activation) and would be expected theoretically to beunaffected by the presence of solvent.It is found experimentally 1 7that the conversion by nitric oxide and oxygen takes place 1.2-2times as fast in aqueous solution as in the gas phase, which providesgood evidence that the collision numbers in the two phases are aboutin the same ratio. This conclusion is further supported by a generalsurvey of the values of A in solution : - there are a large number ofcases in which A is approximately equal to 2 (calculated for a gasreaction), and very few in which A exceeds 2 by more than a factorof 10."In the formulation of the transition-state theory the effect of thesolvent appears as its effect on the equilibrium constant K , and maybe split into two factors : AE, the change in activation energy(altering the velocity by a factor e-AEIRT) ; and AX, the change in theentropy of activation, which appears in the product of partitionfunctions and alters the velocity by a factor e+ASIR.The wholesolvent effect may be conveniently expressed in terms of activitycoefficients : thus for a bimolecular reaction in solution betweenmolecules A and B we can write k2 = K(kT/h)K = (fafB/f&?2,where X is the critical complex and the index o refers to the gasl5 Cf., e.g., M.Jowett, Phil. Mag., 1929, 8, 1059; E. Rabinowitch, Trans.Faraday SOC., 1937, 33, 1224; R. H. Fowler and N. B. Slater, ibid., 1938, 34,91 ; R. P. Bell, ibid., 1939,35,324. Some of the difficulties concerned with thefree space factor depend on the different sizes of the solute and the solventmolecules, a, problem which also arises in connection with the positionalentropy of binary liquid mixtures. The latter problem has recently beentreated with some success; cf. R. H. Fowler and G. 8. Rushbrooke, Trans.Faraday SOC., 1937, 33, 1272; T. S. Chang, Proc. Camb. Phil. Soc., 1939, 35,265.l6 Cf. Ann. Reports, 1933, 30, 41.1' L. Farkas and H. Sachsse, 2.physikal. Chesn., 1933, B, 23, 1 ; L. Parkasand U. Garbatski, Trans. Faraday SOC., 1939,35,263.* The different conclusion reached by M. G. Evans and M. Polanyi (Trans.Faraday SOC., 1935, 31, 875) is due to a confusion of units : their calculated 2values refer to a pressure of 1 atm., whereas the observed A values refer to aconcentration of 1 mol. /1BELL: R ~ L E OF THE SOLVENT IN REACTION KINETICS. 89phase, in which all the activity coefficients are by definition unity.This equation is identical in form with the one proposed by Bronstedto describe salt effects in ionic reactions,l* though Bronsted himselfdid not consider that the activity factor would apply to the effect ofthe solvent itself. In dealing with the effect of electrolyte con-centration on an ionic reaction, the activity coefficient of the criticalcomplex can be predicted in terms of its charge, but in the moregeneral problem of solvent effects and uncharged reactants no suchprediction is possible.If an idealised model of the liquid state istaken, then the treatment is of course exactly analogous to that ofthe collision theory outlined above, and will give the same results.There is, however, another method of approach, namely, to treat thecritical complex as an ordinary molecule, and to apply empiricalgeneral laws about activity coefficients in solution derived fromexperimental data on vapour pressures and gas solubilibies. This hasbeen done by M. G. Evans and M. Polanyi l9 and by W. F. K. Wynne-Jones and H.Eyring,20 who conclude that for reactions betweenmolecules of low polarity the collision factor should be 100-1000times as great as in the gas phase, a result which conflicts with thepredictions of the collision theory and with the experimental data.However, it has been recently shown that the method employed bythese authors involves an over-simplification, and that when dueregard is taken of the relations known t o exist between the heats andentropies of solution,22 the transition state theory predicts thatA(so1ution) /A(gas) 2 2-3, in excellent agreement with the collisiontheory and with experiment.The above conclusions refer to the total number of collisionsbetween solute molecules, and the viscosity of the solvent has not sofar entered into consideration.On the other hand, the viscosityplays a decisive part in determining the grouping of these collisions.This may be seen by considering very viscous systems : two solutemolecules originally far apart will take a long time to diffuse towardseach other, but when they have met they will be surrounded by A“ cage” of solvent molecules and will undergo a large number ofrepeated collisions before parting company. Such a group ofrepeated collisions is conveniently termed an encounter. In asufficiently dilute system (i.e., a gas) 2~ repeated collision is a very rarel8 Cf. Ann. Reports, 1927, 24, 332 ; 1934, 31, 67.l9 Trans. Faradmy SOC., 1935, 31, 875.*o J . Chem. Physics, 1935, 3, 492.21 R. P. Bell, Trans. Faraday SOC., 1939, 35, 384.22 MI G.Evans and M.Polanyi, Trans. Farachy SOC., 1936,32,1333; J. A. V.Butler, ibid., 1937, 33, 171, 229; It. P. Bell, ibid., p. 496; I. M. Barclay andJ. A. V. Butler, ibid., 1938, 34, 144590 GENERAL AND PHYSICAL CHEMISTRY.event, and the collision number and the encounter number are almostidentical. As the system becomes more viscous the encounternumber decreases, but there is a corresponding increase in thenumber of collisions in each encounter and the total collision numberremains substantially the same. The bearing of this aspect ofcollision processes on reaction kinetics has been recently consideredby a number of authors,23 some of whom have used ingeniousmechanical models to illustrate the problem. In a process where alarge proportion of the collisions are effective? the rate will bedetermined by the encounter number rather than the collisionnumber, since only the first few collisions in each encounter will be ofimportance.This is true of the coagulation of colloids 24 and thequenching of fluorescence by solute both of which aregoverned by the. viscosity of the medium. In these cases theequiIibrium molecular distribution is much disturbed by the pro-cesses taking place, thus making it impossible to apply either thesimple collision theory or the transition-state theory, both of whichassume that the distribution is governed by the laws applying to anequilibrium state. On the other hand, if only a very small propor-tion of the collisions are effective? it is clearly a matter of indifferencewhether they occur in large or in small groups, the rate dependingonly on the total number of collisions.This applies to the majorityof chemical reactions in solution : for instance, it can be roughlyestimated that for liquids of ordinary viscosity the grouping ofcollisions will only be important if E < 2 kg.-cals./mo1.,26 while ifE = 20 kg.-cals./mol. the viscosity has to approach that of thevitreous state .27In many cases the interaction between the solvent and the reactingsystem will be a more intimate one than we have so far supposed, andthis will be especially so for reactions involving ions or molecules ofhigh polarity. The factor affecting the reaction velocity will be thechange in interaction when the reactants A and B pass into thecritical complex X.Thus in a reaction between two ions A+ and B-23 M. Leontovitch, 2. Physik, 1928, 50, 58; J. Weiss, Naturwiss., 1935, 23,229; E. Rabinowitch and W. C. Wood, Trans. Faraday SOC., 1936, 32, 1381 ;B. I. Svesnikov, Compt. rend. Acad. Sci. U.R.S.S., 1936, 3, 61 ; E. Rabino-witch, Trans. Paraday Soc., 1937, 33, 1225; R. A. Fairclough and C. N.Hinslielwood, J . , 1939, 593.24 I. Smoluchowski, Physikal. Z., 1916, 17, 594; 2. physikal. Chem., 1917,92, 129.26 S. I. Wawilow, 2. Physik, 1929,524 665; J. M. Franck and S. I. Wawilow,ibid., 1931, 69, 100; B. I. Svesnikov, Acta Physicochim. U.R.S.S., 1935, 3,257; 1936, 4, 453; 1937, 7, 755; E. J. Bowen, Trans. Faraday SOC., 1939, 35,15. 26 E. Rabinowitch, ibid., 1937, 33, 1228.27 M.G. Evans and M. Polanyi, ibicl., 1936, 32, 1353BELL : RdLE OF TRE SOLVENT I N REACTION KINETICS. 91the critical complex will have a zero net charge, and its formationfrom A+ and B- will involve a decrease in the orientation of the sol-vent molecules attached to the ions. This de-solvation will clearlycontribute to the activation energy, causing it to differ from the valuein the gas phase. Moreover, it will also affect the factor A , as maybe seen either from the transition-state theory or from the collisiontheory. According to the former theory the process of de-solvationinvolves a decrease in order and hence an increase in entropy, whichappears as an increase in the factor A.28 From a kinetic point ofview the co-operation of the solvent molecules causes the activationenergy to be distributed among a larger number of degrees offreedom (ke., the bonds holding the solvent molecules to the ions),thus increasing the fraction of collisions possessing the necessaryenergy by a factor which is roughly independent of temperature.29In the same way it can be predicted that in a reaction between ionsof like charge the effect of the solvent will be to produce a decrease inthe value of A .The same qualitative conclusions have been reachedby a purely electrostatic treatment, in which the solvent is treated asa uniform diele~tric.~~ The physical basis of this treatment isessentially the same as that outlined above, since the calculatedeffect involves the temperature coefficient of the dielectric constant,and this in turn depends on the orientation of the solventdipoles.In the case of reactions between ions it is not possible to make anexperimental comparison between the velocities in solution and in thegas phase, and there are not even data to illustrate the effect ofchange of solvent.However, the experimental values of A inaqueous solution can be compared with the theoretical collisionnumbers, and it is, in fact, found that reactions between ions of likecharge give P factors as low as lo-* (for multiply charged ions),whereas for reactions between oppositely charged ions P can becomeas great as lofs.Even in the absence of a net charge on the reactants there may bea large change of polarity during the reaction and hence a change inthe extent of solvent orientation.Considerations of this kind werefirst applied to reactions of the type NR, + RI -+ [NR,]+I-, wherethe critical complex may well be much more polar than the initialstate, and hence more solvated. The necessity for this solvent28 W. F. K. Wynne-Jones and H. Eyring, ref. (20).29 Cf. C. N. Hinshelwood, “Kinetics of Chemical Change in GaseousSystems,” p. 24 (Oxford, 1933) ; R. H. Fowler, “ Statist.ica1 Mechanics,” p. 707(Cambridge, 1936).30 E. A. Moelwyn-Hughes, Proc. Roy. h’oc., 1936, A , 155, 308; V. K. LaMor,J . Pranklin Inst., 1938, 225, 70092 GENERAL AND PHYSICAL CHEMISTRY.orientation appears as a small P factor (or a negative entropy ofa,ctivation) and should lead to low A values varying with the solvent.The chief experimental evidence on this type of reaction has beenoutlined a t the beginning of this Report, and although no directcomparison with the gas phase can be made, the A and E values varyfrom one solvent to another and the A values are lo4-lo9 timessmaller than the calculated gas values.The part played by solva-tion is further illustrated by the auto-catalytic effect exerted by thepolar reaction products when the reaction takes place in a non-polarsolvent .31The same kind of behaviour is found in reactions between aminesand acyl chlorides : on the other hand, the formally similar reactionEt,S + EtBr -+ [Et,S]+Br- has a P factor near to unity 32 (indicat-ing a critical complex of low polarity), so that it is clearly dangerousto attempt a priori conclusions as to the nature of the critical com-plex.It may be noted that the absence of any measurable homo-geneous reaction for the Menschutkin reaction in the gas phase * wasoriginally taken to indicate a low A value even in the absence ofsolvent. However, there is no experimental evidence as to thevalue of the activation energy in the gas phase, and the low velocitymay equally well result from a normal A value and a high energy ofactivation. Approximate calculations show that the solvation of apolar critical complex can materially reduce the activation energy,=and even the proximity of a surface may lower the necessary energyby several thousand calories per mol., and thus favour a wall reactionrather than a homogeneous one.=A large number of the reactions of organic chemistry are nowbelieved to take place by an ionic mechanism,35 so that when boththe reactants are uncharged molecules the formation of the transitionstate will usually involve an increase of polarity. According to theabove arguments, this will lead to a low collision factor in solution,which is found to be the case for most reactions of this type. It isnoteworthy that the reaction between lead tetra-acetate and ethyleneglycol has recently been shown to have a collision factor in acetic acidsolution which is roughly equal to the collision number calculated for31 E.A. Moelwyn-Hughes and C. N. Hinshelwood, J., 1932, 231 ; N. J. T.Pickles and C. N.Hinshelwood, J., 1936, 1353 ; G. E. Edwards, Trans. FuradaySOC., 1937, 33, 295 ; V. A. Holzschmidt and I. V. Potapov, Acta Physicochim.U.R.S.S., 1937, '7, 778.32 R. F. Corran, Trans. Faraday SOC., 1927, 23, 605.33 R. A. Ogg and M. Polanyi, Trans. Faraday SOC., 1935, 31, 605; A. G.34 R. P. Bell and R. le G. Burnett, Trans. Faraday SOC., 1939, 35,474.35 Cf. H. B. Watson, Arm. Reports, 1938, 35, 208.* LOC. cit., ref. (Sa).Evans and 35. G. Evans, ibid., p. 86BELL: RGLE OF THE SOLVENT IN REACTION KINETICS. 93the gas phase : 36 the mechanism of this reaction probably involvesradicals rather than ions.37On the other hand, for a reaction between an ion and a neutralmolecule the displacement of charge due to an ionic mechanism willhave only a small effect on the solvent orientation.This view issupported by the large number of reactions of this type in which A isapproximately equal to the gas collision number.The intervention of the solvent has so far been supposed to takeplace in an equilibrium manner ; ie., we have assumed that solvationequilibria are completely set up throughout and that the equilibriumenergy distribution is not disturbed by the reaction. (This assump-tion is involved in both the transition-state theory and the simplecollision theory.) It has been suggested that in reactions of theMenschutkin type the solvent may take part in a rate-determiningstep such as the removal of energy from the nascent un-solvatedproduct, thus stabilising it and preventing the reverse reaction.38This would lead to collision factors varying from one solvent toanother, and in general will account for many of the phenomenaassociated with this type of reaction.At first sight the hypothesisseems improbable owing to the high concentration of solvent mole-cules, but it must be remembered that the transfer of energy betweendifferent degrees of freedom is often a specific and very inefficientprocess.39 I n the case of reversible reactions it should be possible todecide between the two types of explanation. The position ofequilibrium cannot be affected by the rate of energy transfer, so thatif this process is rate-determining in the bimolecular reaction itseffect will also appear in the reverse unimolecular reaction. In thefew cases where data are available 40 the A factor of the unimolecularreaction appears to have a normal value, thus favouring the equi-librium explanation of the solvent effect in the bimolecular reaction.More experimental work on this point is to be desired.R. P. B.36 R. P. Bell, J. G. R. Sturrock, and R. L. St.D. Whitehead, J., 1940, 82.37 R. Criegee, L. Kraft, and B. Rank, Annalen, 1933, 507, 159; W. A.38 C. N. Hinshelwood, Trans. Furaduy Soc., 1936, 32, 970 ; G. E. Edwards,39 A. Eucken and H. Jaacks, 2. physikal. Chemn.., 1936, By 30, 85.40 H. Essex and 0. Gelormini, J . Amer. Chern. SOC., 1926, 48, 882; W. C .Davies and R. G. Cox, J., 1937, 614; J. K. Sirkin and M. A. Gubareva,J . Phys. Chem. Russia, 1938,11, 285.Waters, J., 1939, 1805.ibid., 1937, 33, 29594 GENERAL AJSfD PHYSICAL (IHEMISTBY.5.SURFACE CHEMISTRY.Physical Properties of Monolayers.Recently, research on monolayers has expanded to such anextent that any paper which summarises all their physical propertiesand correlates these properties directly to their three-dimensionalcounterparts in a concise and rigorously defined manner does agreat service to a student in this field. Such a paper has beenpublished by D. G. Dervichian,l and since it summarises our entireknowledge, with many new aspects, of the physical properties offilms in general, it is quoted in some detail.The method employed was to study the pressure, compressibility,viscosity, and surface potential of the same film over a wide variationin area per molecule, vix., from 100,000 A . ~ to 18.5 A . ~ . This necessit-ated measuring extremely low surface pressures of the order of0-001 dyne/cm. A simple apparatus for this purpose was con-structed by J. Guastalla,2 who magnified the movement of a greasedsilk thread on the surface of the water. This thread could besubjected to different strains by a suitably placed torsion wire.Calibration can be made geometrically and by known two-dimen-sional transition pressures, vapour-liquid. (Guastalla also usesthe damping of a surface pendulum to measure very low pressureswithout any optical magnification.) Two methods were employedfor measuring the surface viscosity :S. E. Bressler andD. L. Talmud first studied the fall of pressure with time for differentfilms, when these are caused to flow through a canal, and noticeddiscontinuities occurring at certain pressures.have adapted to the two-dimensionalsystem the ordinary measurements of viscosity by this method ofcapillary flow.The very small pressure drop through the narrowcanal was kept constant and well defined, the flow was neverturbulent, and a systematic study was made, the different factorsbeing varied. They concluded that the flow per second is pro-portional to the pressure drop and inversely proportional to thelength of the slit; but they pointed out that there is no simplelaw analogous t o Poiseuille’s law in respect to the width of the slit.They showed that there are two phenomena which are super-1. The two-dimensional capillaryjlow method.Dervichian and M.JolyJ. Physical Chern., 1939,7,931 (cf. Harkins and E. Boyd, J. Chern. Physics,Compt. rend., 1939,189, 241 ; 1938, 206, 993; 1939, 208, 973.LOG. cit., 1939.Phy&kal. 2;. Sovietunion, 1933, 4, 564.Cmpt. rend., 1937, 204, 1318.1940, 8, 129)SCHULMAN SURFACE CHEMTSTRY. 95imposed : two-dimensional viscosity of the film and entrainment ofthe substrate. A study by R. M6rigoux proves that there is afriction without slip between film and substrate, and J. H. Schulmanand T. Teorell7 have shown that, in fact, the film does carry waterwith it while flowing. The result is that the true viscosity of thefilm is gradually masked as the slit becomes wider.8R. J. Myers and W. D. Harkins 9 have used the same method and,assuming a two-dimensional Poiseuille equation with the thirdpower (a3) of the width of the slit, have published quantitative datafor the surface viscosity.Later, Harkins and J. G. Kirkwood 10proposed a new formula for the calculation of the viscosity, justifyingthe law in d3. Dervichian and Joly l1 point out that this calculationis not generally justsed : the law in d3 being a limiting law only forslits with widths smaller than 0.5 mm., at greater dimensions itgradually changes to d2 and finally becomes linear towards 5 mm.Dervichian and Joly l1 have improved upon a theory first given byTalmud and Bre~sler.~ This gives a better quantitative accord withthe experimental data even for wide slits. Harkins and Kirkwood,10however, disagree with some of this work.A detailed review of the different theories and an empiricalmethod for the calculation of the surface viscosity has been givenby J01y.l~Using a new device which enables the pressures at the entranceand exit of the slit to be maintained very constant and to producea flow under a very weak pressure gradient, Dervichian and Joly 13have been able to study with precision the variation of viscositywith the pressure for different fluid monolayers.Points of dis-continuity have been thus detected at definite molecular areas (seeDervichian 1).2. The oscillation damping method. This is a two-dimensionalapplication of the Coulomb method, the damping of oscillationsbeing measured by a viscous medium. A disc or a cylinder issuspended by a vertical torsion wire and brought into contact withthe surface.The system oscillates as a torsion pendulum. Theviscosity of the film is determined by the difference in the damping(logarithmic decrement of the successive oscillations produced bythe clean surface and the surface covered by the film). This methodCompt. rend., 1936, 202, 2049; 203, 848.Trans. Faraday SOC., 1938, 34, 1337.8 See also Joly, J . Physique, 1937, 8, 471.J . Chem. Physics, 1937, 5, 603; Nature, 1936, 140, 465.10 J . Chem. Physics, 1938, 6, 153; Nature, 1938, 141, 38.11 J . Chem. Physics, 1938, 6, 226; Nature, 1938, 141, 975.12 J . Physique, 1938, 9, 345; see also J. J . Hermans, Physica, 1939, 6, 313.l3 Compt. rend., 1938,806,326 ; 1939,208,1488 ; J.Physique, 1939,10,37596 GENERAL AND PHYSICAL CHJiXNISTRY.has been used by I. Langmuir and V. J. Scliaefer l4 and by Myersand Harkins.9The method is too insensitive to give very accurate measurementson fluid films, but on the other hand it is of great use with veryviscous or plastic monolayers; Langmuir and Schaefer l5 haveemployed it for the study of protein monolayers. L. Fourt andW. D. Harkins l6 have investigated changes of state in condensedfilms of long-chain alcohols. In the latter case and in some caseswith proteins, the measurements do not give the viscosity butrather the plasticity or rigidity of the film. In fact, although witha true liquid film the viscosity is independent of the amplitude, thisis not the case with solid or gel films.A plot of the logarithm ofthe amplitude against the number of swings gives, with fluid films,a straight line slope, the slope of which is a measure of the viscosity ;with non-fluid films, the line is curved.In order to reduce the damping due to the substrate to a minimumand increase the sensitivity of this method, Joly l7 has recently useda very narrow flat ring of mica bound to a torsion wire, but floatingon the surface. This is surrounded by a fixed and larger ring alsofloating on the water. The distance between the two concentricrings is variable according to the viscosity of the film which isspread in the free space. A special device enables the compressionof the film and measurement of the surface pressure to be under-taken by the ordinary methods.With this apparatus, the viscosityof protein films has been studied in the region where they are stillfluid, and the ageing and the existence of two types of these filmshave been noticed. l8Thermodynamical DeJinition of Transformations of DiflerentOrder.-The points of transformations of different orders have beenconsidered by P. Ehrenfest l9 as corresponding to discontinuities ofthe derivatives of different order of a thermodynamical function.has introduced in thedefinition of this function a term corresponding to the surface energy.If y is the surface tension of the surface covered by a film and yothat of the clean surface, the work done by an infinitesimal dis-placement of the barrier which changes each of the two areas bydA and - dA respectively is dwS = ( y - yo)dA.Introducing thesurface pressure x = yo - y, we have dwS = - x . dA. If XFor the surface phenomena Dervichianl4 J . Amer. Chevn. Soc., 1937, 59, 2400; Langmuir, Science, 1936, 34, 379.l6 Chem. Reviews, 1939, 24, 181.l6 J. Ph.ysica1 Chem., 1938, 42, 897..l7 J . Chim. physique, 1939, 38, 285.l8 LOC. cit.; Compt. rend., 1939, 208, 975.l9 Proc. K . Akad. Wetensch. Amsterdam, 1933, 38, 115SCHULMAN S CJRFACE CHEMISTRY. 9 7represents the t,otal entropy (surface and bulk) of the systeni, thevariation of the total energy is defined by dE = T . dS - P . du -i5 . dA. When T, P, and x are considered as independent variables,one can adopt, as thermodynamical function, the thermodynamicpotential G of Gibbs, in which one can introduce a term correspond-ing to the surface energy analogous to the term :PY : G = F +PV + xA, where F is the free energy F = E - TX, which givesG = E - - T T X + P V + x A and d G = - B .d T + V.dp+Adx,which enables successive partial derivatives to be calculated, vix.,An ordinary change of state will be called a transformation of thefirst order, since it is characterised by a discontinuity in the area ,4and consequently corresponds to a discontinuity in the first deriv-ative of G. Likewise, a transformation in which A does not undergoany sudden variation, but in which the compressibilityshows a discontinuity, will be a transformstion of the secondorder, etc.This leads to one of the most important new aspects of Der-vichian's paper,l vix., that areas corresponding to ordinary phasechanges are found as points of discontinuity of higher order in thosephases which exist at higher temperatures.Thus the area 20.5 A . ~ ,which in three dimensions exists as the B-crystal form of a fattyacid, is the sublimation point in the solid state for two-dimensionalfilms. It is found as a point of second order in the mesomorphousstate as shown by discontinuities in the compressibility-, viscosity-,and electric moment-area curves, when this specific area is reached.The table on p. 101 shows a whole series of transformation points inthe various phases, some of which have known three-dimensionalanalogies, a t given areas. This very significant analogy seems tohave been neglected by previous workers in' force-area diagrams andis extremely helpful in explaining and anticipating the various dis-continuities, on a physical basis.In the figure a combined two-dimensional phase diagram is givenfor long-chain hydrocarbon compounds for the case where thecritical temperature of crystallisation is greater than the criticaltemperature of liquefaction (except for curve VII, where the inverseholds) ; the areas given all have significant three-dimensionalanalogies irrespective of the substance, but respective to the hydro-carbon chain, t'hese appear as discontinuities in phases existing athigher temperatures. Films of the following substances give thetypical force-area curves (room temperature) : curve VI, tri-caproin ; curve VII, oleic acid ; curve V, ethyl palmitate ; curve IV,K = (l/A)(dA/dx)REP.-vOL.XxXvI. 98 GENERAL AND PHYSICAL CHEMISTRY.myristic acid ; curve 111, palmitic acid (25') ; curve 11, stearic acid ;curve I, eicosyl alcohol.Substances giving typical gaseousfilms with no condensation to the liquid state are the short-chainglycerides, which Guastalla has measured up to very large areas,Gaseous state (curve VI).showing that they obey the gas law TCA = RT. He has used thistechnique to determine the molecular weight of proteins, by measur-ing the X-A curves at pressures of 0.001 dyne/cm., where theproteins exist as a two-dimensional vapour. Guastalla found 110evidence for association as measured by S. A. Moss and E. K.Rideal,20 who obtained R/2 for the gas constant; the latter used a2o J., 1933, 1525SCHULMAN : SURFACE CHEMISTRY.99metal trough for fatty acids a t large areas. It is noteworthy thata higher-order transformation point, obtained by measuring theviscosity or surface potential of the gaseous films, appears at anarea of 3 8 ~ . ~ per hydrocarbon (for triglycerides at 115a.). Thesignificance of the area which Dervichianl relates t o the triplepoint M has no known three-dimensional counterpart ; it is probablyrelated to some structure in liquids.The triple point. This refers to the junction of the mesomorphous,liquid, and gaseous states which occurs at 38-39 A . ~ per straighthydrocarbon chain. This point reappears in the higher-trans-formation points in the viscosity, surface potential, and com-pressibility curves for the liquid or gaseous state at this area perhydrocarbon chain.A good example of this is found in theviscosity curve of triolein a t 115 A . ~ , which is given as curve VII inthe phase diagram.The liquid state. The curve MP of the phase diagram typifies theliquid state wit,h no transition to a solid state (oleic acid). Der-vichian draws a, very interesting conclusion from the similarity of theinterfacial tension at the point P to that a t the water-oil interfaceof an oil drop, vix., that the structure of the molecules at P isidentical with the structure of the surface of a liquid; i.e., the pointP represents a drop one monolayer thick. On expansion of thefilm from point P to M y the number of molecules decreases fromthat at the surface of a liquid t o that at the interior of the liquid.The proof that the point M represents the concentration of themolecules in the interior of a liquid is given by the fact that themolecular volume of the molecule to the power of 2/3 is equal t o thearea for any given substance at that point. Dervichian showsthat V2’3 equals the area occupied by the molecule at the point Mfor a whole series of substances, thus re-establishing the significanceattached to these correlations by earlier workers in this field.It isastonishing that the presence of the water has so little effect on themolecular forces involved in establishing the mean moleculardistances either on the water surface or in the interior of the liquid.It has been shown by F.Sebba and H. V. A. BriscoeY21 dealing withthe ageing of films at the air-water interface, that water does peptisethe polar groups in time and expands the film markedly. Thisis especially marked with long-chain alcohols and acids.There has been muchcontroversy as to whether tlhis transition region is electricallyhomogeneous (for the case of myristic acid) or no. Dervichian,by a self-recording device, definitely establishes that it is electricallyinhomogeneous, and suggests that this is due to islands of the solidIl’rasasition : liquid+nesomorphous states.21 J., l O W , 128100 GENERAL AN0 PHYSICAL CHEMISTRY.state floating in the liquid state. The packing of the molecules, andconsequently their number per unit area, being markedly differentin the two states, would cause large surface-potential fluctuations,even if the apparent dipole moment of the molecules in the twostates were similar.Secondly, as to whether this transition is flator gives a horizontal isotherm, Dervichian gives examples showingthat this transition, in equilibrium, over a considerable change inarea per molecule is flat, as the theory demands, and is similar tothe gas-liquid transition.Solid states. The solid state has three well-defined areas forhydrocarbon chain compounds which have significance in threedimensions. The sublimation point, where the solid is in equi-librium with its vapour pressure, is 20.5 A . ~ or a multiple of thisnumber for the glycerides. This area corresponds in threedimensions to the B-crystalline form of the fatty acids or glycerides,and appea,rs as a second-order transformation point in the meso-morphous state.There is a second transformation point in the solid state a t19.5 A.Z, which corresponds to the A-crystalline form. The filmbreaks a t 1 8 - 5 ~ .~ , which is the cross-sectional area of the unitcrystal, showing that on compression of the solid state a tilting ofthe chains takes place until they are in the vertical position.The mesomorphous state corresponding toa liquid crystal extends up to 2 3 - 5 ~ . ~ , which in three dimensionscorresponds to the C-crystalline form of the fatty acids andglycerides. There is a second-order transformation point at 22 A .~ :which has a t present no three-dimensional counterpart. There isan expansion of the mesomorphous state from 23.5 to 27 A. atconstant pressure before true two-dimensional melting takes placeand the liquid state commences at point M on the diagram. Thisexpansion is what Labrouste first observed, and is really an expandedmesomorphous state and is especially noticeable in trimyristin.This point, 27 A . ~ , appears beautifully as a higher-order trans-formation in the viscosity curve of a palmitic acid film whichexists over the expanded mesomorphous state at 25" and also as ahigher-order transformation point in the gaseous state. .Two-dimensional and three-dimensional melting points. Dervichiandefines the two-dimensional melting point as the temperature atwhich the liquid state appears a t the end of the Labrouste trans-formation. This temperature in many cases (such as with cetylalcohol) agrees with the known three-dimensional melting point ;but with the glycerides and acids the two-dimensional is much lowerthan the normal melting point.In order to explain this difference,Dervichian finds that the glycerides possess a vitreous form whichMesomorphow stateSCHULMAN : SURFACE CHEMISTRY. 101melts a t the two-dimensional m. p. Them. p. of this form agreeswith considerable correlation with the film m. p. for a whole range ofsubstances (thus the vitreous form is more stable under monolayerthan under ordinary conditions). He suggests that for the acidsthe vitreous form only exists in two dimensions, although there isdistinct evidence for a vitreous form for palmitic acid. Oneinteresting point is that the vitreous form of the glycerides spreadsspontaneously on to the water surface from the solid, whereas thecrystalline form spreads extremely slowly.Labrouste showed that the triglyceride films compressed to thesolid and removed from the surface melted a t the vitreous formtemperature, and that these solidified films after a while gave thethree-dimensional crystalline m.p.The following two tables are taken from Dervichian's paper andsummarise all the physical characteristic areas of films as deter-mined by force-area, viscosity, compressibility, and surface potentialmeasurements with their three-dimensional correlations.Characteristic three -dimensional areas, in A .~ .18-5, cross section crystalunit .....................19.5, A-crystal form ......20.5, B-crystal form ......22, unknown form .........23.5, crystal form C ......27-30, area of moleculesurface of liquid .........38, triple point ............V/72/3, vol. of molecule, in-t,erior of liquid .........Meso- ExpandedSolid morphous mesomor- Liquid Gaseousfilms. films. phous films. films. films.18.6 18.5 18.5 I -19-5 19.5 19.520.5 30.6 90.6 -- -6) <> 22 - -- 23.5 23.5 - -- -i d -Two-dimensional Three-dimensional m. p.'s.m. p. Vitreous state. Crystalline state.- Tristearin ............... 5 5 O 55"Tripalmit in ............ 45 46Trimyristin ............29 32Trilaurin ............... 2-14 14 -Cetyl alcohol ......... 50 - 49-5O--Surface Potentiak.Gatty 22 raised in the October 1939 meeting of the Faraday Societyon the Electrical Double Layer 23 a very interesting suggestion asto the meaning of " surface potentials " a t the air-water interface,quite contrary to the previously accepted view that a film oforiented molecules acted as an electrical condenser. Dean,Gatty, and Rideal 24 showed that under thermodynamical equi-librium conditions the spreading of a monolayer a t an interphase22 See also Trans. Paraday SOC., 1937, 33, 1087; 1940, 36, 173.23 Ibid., 1940, 36, 1. 24 Ibid., p. 161102 GENERAL AND PHYSICAL CHEMISTRY.plane between two phases, insoluble in both phases, and permeableto at least one ionic species, whilst producing a transitory surge ofpotential, cannot alter the interfacial potential. If diffusion istaking place between the two phases, the diffusion potential canonly be affected if the monolayer sufficiently affects the resistanceto the passage of a t least one ionic species.Gatty showed that by passing a saturation current (ca.8 x 10-l1amp.) through a stearic acid film a t an air-water interface for morethan 33 hours, no change in the surface potential of the film tookplace (to within 1 mv.); furthermore, films of various substanceshave been left for periods of a week, showing, likewise, no change insurface potential.On calculation, this shows that the capacity of the monolayermust be greater than 90 p F.cm.-2, so that if the film correspondsto a parallel plate condenser with a dielectric of 1, a separation of(2.1 A. would be necessary. A capacity of this magnitude would beimpossible for a film of stearic acid on a strong ionic solution.Alternatively, this result might show that the film has a low resistanceof the order of lG9 ohms/cm.2 at the most. On this basis, areasonable capacity being assumed for a parallel plate condenser, thesurface potential should have fallen l/eth of its value in 14 hours( E = Eoe-t’m), but since no change occurs over periods at least tentimes longer, the low resistance alternative being also excluded, allconceptions of the film’s acting as a condenser must be ruled out.Gatty further shows, by enclosing an area of the film and theair above it by a glass tube, letting the air become saturated withwater vapour, and obtaining likewise no change in the surfacepotential under these conditions, that the potential cannot be dueto diffusion of charged water ions.Gatty therefore offers the following explanation for the surfacepotential.Upon deposition of a monolayer on the surface of thewater, a diffuse layer can be immediately built up in the aqueousphase, but no such diffuse layer can be built up in the air phaseto neutralise the potential difference due t o the film, since ions inthe immediate vicinity of the film in the air would be sucked intothe aqueous solution. Gatty calculates this from consideration ofthe mirror-image forces that these ions would create in the aqueousphase-forces which on purely electrostatic grounds would suck theions into the solution.Gatty, Dean, and Dean23 show that, by replacing the air phaseby an oil in which ions can be dissolved such as amyl acetate or octylalcohol, a surface potential can be obtained by spreading films atthe interface, which decays with time to an equilibrium zero value,as would be expected from the general theorySCHULMAN : SURFACE CHEMISTRY.103Dean 23 shows that the electrical resistances of films a t an inter-face are negligible compared t)o those of the two bulk phases.Further, a stable potential can be obtained if the interface resists thcdiffusion of one ionic species (Donnan potential) as with certain dyes.A poorly oil-soluble electrolyte cannot diffuse rapidly into the oilphase and so leaves " negligible diffusion " potential in the aqueousphase, but after diffusing through the region of Donnan potentialsit is able to set up a diffusion potential in the oil phase in regionswhere its concentration is not less than that of the oil ions them-selves.Dean justifies this experimentally by controlling theseparation of two protein-covered water drops in an oil-phasemedium.These experiments appear to rule out the theories expressed by 0.Bauer and G. Ehrensviird and L. G. Sill& 25 on adsorption potentialsa t oil-water interfaces, although these workers are right in expressingthe view that the potential gradient is located very close to theinterface.Multila yers .General Properties.-The most recent development in the studyof built-up films is the investigation of compounds other than thoseof the fatty acids, which have been used exclusively by theAmerican scientists, who discovered this very interesting propertyof monolayers.26Owing to the various ways in which a film can be deposited from anaqueous solution on a solid, considerable difficulty has arisen as toa general nomenclature for different types of built-up multilayers.There are three different types of deposition, which must in noway be confused with the type of the ultimate structure of themultilayer, since the method of deposition has no bearing on thestructure of the multilayer which is entirely dependent on thechemical properties of the sub~tance.~7It is termed an X-deposition when the film comes on onlyon the downward movement of the slide through the watersurface, a Y-deposition when the film is deposited on both thedownward and the upward movement, and a 2-deposition when26 Nature, 1938, 141, 789.26 I?.M . Blodgett, J . Amer. Chem. Soc., 1935, 57, 1007; I. Langmuir, J .Pranlclin Inst., 1934, 218, 143; F. 31. Blodgett and I. Langmuir, PhysicalReu., 1937, 51, 964; Langmuir and V. J. Schaefer, J . Amer. Chem. Xoc., 1937,59, 2400; €or full references see Langmuir, Proc. Roy. Xoc., 1939, A, 170, 1.27 E. Stenhagen, Trans. Paraday SOC., 1938,34,1328; C. Holley and S. Bern-stein, Physical Rev., 1937, 52, 525; C. Holley, ibid., 1938, 53, 534; I. Fan-kuchen, ibid., p. 909; G.L. Clark and P. W. Leppla, J . Amer. Chem. Soc.,2936, 58, 310104 GENERAL AND PHYSICAL CHEMISTRY.the film is deposited only on the upward movement of the slide.The film is forced on to the slide by a surface pressure; a very con-venient way of exerting a constant surface pressure is to utilise theequilibrium spreading pressure of an oil, and this remains constantso long as an excess of the substance is on the surface, irrespective ofthe change in area of the free surface due to the deposition of thefilm.Suitable piston oils have been shown by Langmuir to be oleicacid, 31; triolein, 21; castor oil, 16; and tritolyl phosphate,10 dynes/cm.The resultant multilayer can be either a single layer or a doublelayer repeat unit according to the crystal structure of the substancein three dimensions.J. J. Bikerman 28 shows that the three typesof deposition are related to the degree of wettability of the depositedfilms : X > Y > 2. Hence, the manner of deposition is related tothe contact angle, which can be changed very readily by ions in theunderlying solutions for those substances, such as fatty acids andamines, which can react with the substrate, and by simply changingthe surface pressure for those substances, such as esters and ketones,which do not react with the substrate.The film can only be deposited when the angle which it makeswith the slide is obtuse; hence, for a strongly hydrophobic surfacethe film can only be deposited on the downward movement. If thesurface be less hydrophobic, it is possible (X-film) by varying therate of the movement of the slide to obtain an obtuse angle both onthe downward (angle > 90") and during the upward movement(contact angle < 90") ; consequently a film is deposited on bothjourneys (Y-film).If the surface of the slide is relatively hydro-philic (small contact angle) an obtuse angle can only be obtained onthe upward journey, and thus deposition only takes place on thismovement (Z- film).This can be readily demonstrated with a film of octadecyl acetate,which, being very hydrophobic, will deposit as X-films, but if thesurface pressure is made very high, thus lowering the contact angle,the film deposits in the Y - f ~ r r n . ~ ~Deposition Rates.-Langmuir, Schaefer, and Sabotka 3O found thatthe ratio of the geometrical area of the slide to the area of the filmremoved from the surface of the water was unity within experi-mental error.This is irrespective of the actual area of the slide,which is usually much greater. Bikerman31 artificially grooved ametal slide and found that the deposition ratio still remained unity.Further, he was able to deposit films on wire gauzes, proving that28 Proc. Roy. SOC., 1939, A, 170, 130.30 J . Arner. Chem. SOC., 1937, 59, 1751.29 See Stenhagen, ref. (27).31 See ref. ( 2 8 ) SCHULMAN : SURFACE CHEMISTRY, 105the area of the molecule in the film has no bearing 011 the area ofthat on the slide : this can bc shown much better wibh X-rays (seelater). The monolayer behaves like a soap bubble film on the wiregauze, and when drying, bursts and forms crystallites on soap gels.Bikerman suggests that this is what occurs on deposition of afilm on t o a metal surface, the film being spanned across theundulations.Monolayer and Multilayer Thickness.Since one can only deposit films on slides when they are in thecondensed states, and further, since these states consist of differentcrystalline forms of the substance with varying tilts of the chain tothe surface, there is no reason t o suppose that the two-dimensionalcrystal should have the same form or thickness when it is in thethree-dimensional form, as in the multilayer.One of the mostextreme cases of this difference in the layer thicknesses was shownby A. E. Alexander,32 who deposited calcium oleate films a t an area of27 A .~ as compared with 19 A . ~ for calcium stearate; this gave amultilayer of 23.5 A. thickness per layer as compared with 16 A.thickness on the surface of the water with a deposition ratio ofunity. A multilayer of this material must contain at least 50% ofopen space. This was confirmed by comparing the thickness of thelayer found by optical measurements with those found by X-raymeasurements.It is noteworthy that the different substances build up single- ordouble-layer unit multilayers with either vertically orientated orinclined chains, irrespective as to whether they have been depositedin the X - or the Y-forms. For instance, the salts of the fatty acidsand long-chain amine phosphates always build double-layer latticeswith tilted chains.Octadecyl acetate films are intermediary,building either double-layer lattices with a marked tilted orientationin the long chains or vertically orientated long-chain single lattices.33The ease with which multilayers can be made with films of thisester, and the various types of multilayer it forms, renders it anexcellent subject for detailed research on the structure of multi-layers. Other esters such as the triglycerides or ethyl and methylstearates form inclined long- chain double layers. Methyl ketonesform vertically orientated single layer lattices.34Methods of Measuring Thickness of Mu1tihyers.-Optical measwe-muzts. Blodgett 35 and Blodgett and Langmuir 36 measured the32 J., 1939, 777.34 Stenhagen, private commmiication.35 J . Plhysical Chem., 1937, 41, 975; Physical Rev., 1939, 55, 391,3G Ibid., 1937, 51, 964.33 Stenhagen, ref.(27)106 GENERAL AND PHYSICAL CHEMISTRY.thickness of the multilayers and the layer spacing by interferencecolours with polarised light which set in a t the quarter wave-lengthof light, and also by interference intensities with monochromaticlight. These methods give astonishingly accurate results, differ-ences of thickness of one monolayer being easily observed. Theycompare very favourably with the X-ray results when the mono-layer thickness and multilayer lattice thickness are identical. The'interference colours are depcndent both on the thickness of thelayers and on their refractive index.The extinction of reflection formonochromatic light is dependent also on the wave-length and angleof incidence at which the light strikes the film. By varying allthese factors most of the optical properties of multilayers can beobtained.A very useful method is to make a step scale with a known sub-stance and compare the colours under identical conditions to a stepscale of an unknown substance and ascertain the number of layersat which the colours coincide, having corrected for differences inthe refractive indexes of the two substances.This technique 37 is still inits infancy as a weapon for investigating the structure of multilayers.Since the building of multilayers is an extremely easy way to obtainthe substance in a crystalline form, and also to obtain a completeX-ray picture with quantities of the order of only 0.03 mg.of thesubstance, its importance as a means of investigating crystals ingeneral and the chemical structure of unknown substances in par-t icular c annot be overestimated.Fankuchen 27 greatly improved this technique by applying hiscondensing monochromator (for the X,) X-ray beam by reflectionfrom a pentaerythritol crystal. Films can be deposited on any base,cellulose being a very convenient one, since its x-ray picture con-sists of faint diffuse rings. Knott and Schulman 38 deposited 2000layers of octadecyl acetate on a thin cellophane sheet. The axesin the plane of the slide being x and y, x being the dipping direction,and z the axis a t right angles, then photographs were taken by per-mitting the X-ray beam to travel all the three axes in turn, rotationof the slide with increasing angles, 5", 15", 25", etc., being under-taken around either the x or the y axis during the photograph.By this means pictures were taken a t various angles along the dippingdirection and at right angles to this direction, and also a transmissionpicture. This revealed the built-up multilayer to have a beautifulthree-dimensional crystal lattice.The photographs showed layerlines with spots clustered in definite regions on the layer line,37 Holley and Bernstein; Holley; Fankuchen; Clark and Lepplrc, locc. cit.,ref. 2.7,X-Ray measurements of multilayers.38 Nature, 1940, in the pressSCHULMAN : SURFACE CHEMISTRY. 107resembling in this respect the rotation photograph of C,,W,, abovethe c-axis.39 More than 30 orders were obtained for the mainspacing, and several for the side spacings.A stationary photo-,graph, with the X-rays travelling parallel to the surface of the film,showed not only distinct layer lines with rather diffuse spots, butalso the main spacings. This shows that the reciprocal pointscorresponding to the main orders of reflection are in reality finiteplane areas.Thiswork has chiefly been done by L. M. Germer and K. H. Storks4()and by E. Havinga and J. de Wael.41 Their investigations showedthat the monolayer has a two-dimensional crystal structure, andthat the multilayers have a similar structure to the crystal of thesame substance.Transmission pictures of monolayers deposited on thin Resoglaz(200 A.thick) or nitrocellulose give beautiful pictures and are veryeasily obtained once the apparatus is constructed. It would beinteresting to study mixed monolayers or mixed two-dimensionalcrystals by this method.Interesting pictures taken by Germer and Storks42 on rubbedmultilayers showed that one could only remove or displace the filmif the rubbing direction was against the tilt of the molecules, butnot in the direction of the tilt.Electron-ray measurements of mouolayers and multilayers.Skeleton Films.Avery interesting property of multilayers, shown b y B l ~ d g e t t , ~ ~ l ~ ~ , ~ is the skeletonising of multilayers. It was shown by Langmuir andSchaefer 46 that films of stearic acid containing traces of calcium orbarium ions in the underlying solution were half converted intoneutral soaps a t a pn of 5-1 and 6.6 respectively; hence, if a multi-layer of barium stearate and stearic acid containing 50yo of free fattyacid was dipped into benzene, all the free fatty acid is readilydissolved out, leaving a stable structure called a skeleton multilayerconsisting of barium stearate.The freeing of the multilayer fromstearic acid does not involve any change in its thickness but onlyin the refractive index. Blodgett 45 now found that it was possibleto dissolve back into the skeleton multilayers hydrocarbons or39 A. Miiller, Proc. Roy. SOC., 1928, A, 110, 437.40 Physical Rev., 1936, 50, 676; 1939, 55, 648; J .Chem. Physics, 1938, 6,4 1 Rec. Trav. chim., 1937, 56, 375.42. LOC. cit., 1939.44 J . Physical Chem., 1937, 1937, 41, 973.46 Physical Rev., 1939, 55, 391.46 Ibid., 1936, 58, 284.280; PTOC. Nat. Acad. Sci., 1937, 23, 390.43 Physical Rev., 1937, 51, 966108 GENERAL AND PHYSICAL CHEMISTRY.other substances such as long-chain alcohols. It was thereforepossible to obtain a film of any desired refractive index by addingsubstances or dissolving the fatty acid out of the multilayer. Acadmium arachidate multilayer from which progressive amounts ofthe free arachidic acid had been dissolved out seemed very appro-priate for changing the refractive index. Certain substances, suchas the long-chain alcohols, could not be dissolved out again veryreadily, thus denoting complex formation in the multilayer.47Blodgett 45 has utilised this technique to change the refractiveindex of the surface of glass and the thickness of the surface layer,so that the refractive index is equal to the square root of therefractive index of the glass, and the thickness equal to a quarter ofthe wave-length of the reflected light.Under these conditions theintensity of the light reflected from the upper surface of the skeletonmultilayer is equal to the intensity of the light reflected from theinterface glass-multilayer ; hence, at the quarter wave-lengththickness no reflection from a beam of light of normal incidence canoccur, and consequently the glass surface will be invisible.Another interesting use of the technique of skeleton films 44 is toshow up the conditions necessary for X - and Y-deposition of mono-layers (for the fatty acids) into multilayers.Single-component filmscomposed of barium stearate are more hydrophobic than mixedfilms of barium stearate and free fatty acid; consequently, films ofbarium stearate will deposit in the X-manner and the mixed filmsin the Y-ma~mer.~l The X-films will not therefore skeletonise,whereas the Y-films will.It has been found possible by Blodgett 43 to change the consti-tution of a multilayer in the course of its deposition ; e.g., a mixedfilm of barium stearate and stearic acid giving a Y-deposition, will,if the built-up multilayer is left in a barium solution for a veryshort time, give an X-deposition.This shows that the com-position of the multilayer has changed in the barium solution to acomplete barium stearate multilayer although a mixed film wasdeposited.Overturning of Molecules.Molecules built up into multilayers by X-deposition and whichcrystallise as doublets must in process of deposition turn over;likewise for the inverse process, in multilayers formed by Y-deposi-tion which crystallise in single layers, the molecules must also haveturned over. Further X-deposited layers always come out hydro-phobic; consequently, the inner layer must turn over a t some47 Blodgett, private communicationSCHULMAN : SURFACE CHEMISTRY. 109point during the deposition. 'It could be suggested that thisphenomenon takes place a t the triple point slide-air-~ater.~SThe attraction of polar head-groups to one another for thosecrystallising as double layers and the protection of these polargroups by a methyl group, as in the case of octadecyl acetate, forthose crystallising in single layers, must play an important part inthe mechanism.The most important part of the deposition ofmonolayers is that water must be squeezed out from between thepolar groups, presumably by polar interaction, or by associationbetween the methyl group as in the second case.Stearic acid, which has a hydrophobic layer on the outside, willbecome hydrophilic in contact with ~ a t e r , ~ g i.e., the outside layerof molecules must have overturned.A built-up multilayer of barium stearate does not become hydro-philic on contact with water, and, more remarkable, it is alsooleophobic to hydrocarbons, in spite of the fact that hydrocarbon issupposed to be oriented in this case t o the outside.Barium stearate is not soluble in hydrocarbons or water : asimilar relation must hold for both cases.If multivalent ions of ahigher valency be dissolved into the solution surrounding a built-upfilm of the stearate, the outside layer rapidly becomes very hydro-philic. For example, a barium stearate multilayer becomeshydrophilic in the presence of aluminium or thorium ions in thesolution. The multivalent ion apparently anchors a polar groupto the surface and, being not fully saturated with fatty acid radicals,the free hydroxyl groups make the surface hydrophilic. Langmuirand S~haefer,~O who found this phenomenon, utilised it to conditionsurfaces of multilayers to absorb proteins and bile acid salts.Electrical Properties of Multilayers.Langmuir 51 suggested that the surface potentials of multilayers,first measured by E.F. Porter and J. W y ~ a n , ~ ~ were due to surfacecharging of the outer layers by the recession of the water from thefilm, and not to the actual dipoles of the stearate film, as with thesurface potentials of the film on water : R. W. Goranson and W. A.Zisman,53 reviewing all previous work on electrification of multilayers,showed that the potentials are due to the absorption of ions from theunderlying solution. They further showed that X-deposition for the48 Langmuir, Science, 1938, 87, 493, describes various ways in which thisphenomenon might take place.Devaux, Ann.Report Smithsonian Inst., 19 1 3, 26 1.6o J . Amer. Chem. SOC., 1937, 59, 1400, 1762.61 Ibid., 1938, 60, 1190.63 J . Chem. Physics, 1939, 7 , 492.52 Ibid., 1937, 59, 2746; 1938, 60, 1083110 GENERAL AND PHYSICAL CHEMISTRY.fatty acid films takes place on more alkaline solutions than theY-films ; these films are therefore composed of the salts of the fattyacids, and wiU have more positive ions adsorbed into them than theY-films, which are formed on solutions of low pa and are mixedfilms of stearic acid and stearate. Consequently, the multilayersbuilt by X-deposition will have much higher charges than those builtby Y-deposition (for the fatty acid multilayers).If the multilayer is built on an insulator, an electrostatic repulsivefield is set up which, after about 500 layers, inhibits the depositionof further layers.Films of the esters such as octadecyl acetate and ethyl stearate,whether X - or Y-deposited, can produce very highly charged multi-layers,54 presumably by mechanical adsorption of ions from theunderlying solution.One interesting experiment can be done bydepositing on a built-up layer of barium stearate with a surfacecharge of + 20 volts two layers of octadecyl acetate; this reversesthe surface charge to - 20 volts. The octadecyl acetate films mustbe picking up ions of opposite sign out of the underlying solution ascompared with the barium stearate film. Hence, the surfacepotentials of multilayers are due to induced charges in the metalsupport and electrokincsis effects.Molecular Interactions in Monohyers.-Mixed Films.-Before the work of Schulman and A.H. Hughes 56 itwas considered that no interaction took place between molecules in amixed monolayer, but they showed that, if one of the componentswas ionised, strong interaction could take place, as measured bygreat differences in the surface pressure and potential calculatedmean values and the observed values. Further, if no interactiontook place, the more stable component could eject the other com-ponent out of the monolayer, leaving a one-component film.J. Marsden and J. H. Schulman 56 and Schulman 57 enlarged uponthese interactions. It appears that the attractive and repulsiveforces between polar groups in mixed films may be interpreted uponthe hypothesis that they are due to Coulomb forces acting betweenpolar groups in systems containing (graded by their energy ofassociation)ion+-ion- > ionf-dipole > dipole-dipole > ion*-ion*.Examples in the first category are long-chain amines and acids inneutral solution ; in,the second, long-chain amines and acids in acidsolution and long-chain amines and alcohols; in the third, long-chain alcohols and ethers, or esters giving no interaction; and in5 5 Bwchem.J., 1935, 29, 1243.5 7 Ibid., 1937, 33, 1116.64 Stenhagen, loc. cit., ref. 27.66 IZ’rans. Faraday SOC., 1938, 34, 748SCHULMAN : SURFACE CHEMISTRY. 111the fourth, one-component films such as amines in acid solution,which actually show (by being vapour films) strong repulsive forcesbetween the ions.The interactions in the first category are difficult t o measure bychange in surface area, since the single-component films exist bythemselves in the solid state, but they can be measured by changesin surface potential.The most striking examples are in the second category, where avapour film of octadecylamine hydrochloride (repulsion due to likeions) is condensed to a solid when mixed with stearic acid, whichon itself is in the mesomorphous state (weak interaction due to twodipoles) at pH 2.The mixed film also has a surface potential some150 mv. above the mean. Since single-component films of acids andbases are, in nearly neutral solution, partly ionised, they also obey therule applied t o an ion-dipole system and are consequently always inthe condensed state.If a component which hinders this interactionbe added to this system, an expansion of the original film takes place,as seen with an amine-alcohol mixed film at pH 7.8. Harkins andR. T. Florence 58 essentially confirm these results, and further showthat maximum condensing effect is observed with 1 : 1 mixtures of theinteracting components. They show that with mixed films of fattyacids of varying chain length, differences with the mean values ofthe surface potentials can be obtained, suggesting therefore thatthese differences do not necessarily show interactions between polargroups.Stereochemical Effects.Schulman and Hughes 55 and Schulman 57 showed that mixedfilms of saturated long-chain compounds were very much morestable than those containing an unsaturated long-chain component.That this phenomenon was most probably due to stereochemicalconsiderations in the hydrophobic portion of the molecule, firstcame out of work done on penetration of films of cis- and trans-long-chain alcohols by sodium cetyl s ~ l p h a t e .~ ~ This substance,when injected into the underlying solution, formed stable mixedfilms only with the trans-compound at high surface pressures owingto the interlocking possible between the chains, and not with thecis-compound. Schulman and S t e ~ h a g e n , ~ ~ R. T. Florence and W. D.Harkins,60 and Marsden and Rideal showed by their examinationof mixed films of cis- and tram-unsaturated long-chain compoundswith saturated long- chain compounds that an interlock or adlineationof t,he chains was most important for their association and two-5 8 J.Chem. Physics, 1938, 6, 847.5s Nature, 1938, 141, 785; Proc. Roy. SOC., 1938, B, 126, 1356.6o J. Chem. Physics, 1938, 6, 856. 61 J., 1938, 1163112 GENERAL AND PHYSICAL CHEMISTRY.dimensional crystal packing, thus supporting the views first expressedby C. G. Lyons and Rideal.62 Marsden and Rideal further showedan important characteristic of adlineated molecules, brought aboutby their orientation in monolayers, vix., that their reactivities canbe quite different from that of the same molecules in bulk solution.This is shown here by the marked differences in the packing of thefilms of the oxidation products of the trans- and cis-unsaturated C,,fatty acid.These differences were attributed to the associationbetween hydroxyl groups, brought about by the adlineation betweenthe molecules. I n the cis-compound, a pairing of two moleculescould take place by hydroxyl bonding, resulting in weak associationbetween the paired molecules in the film and consequently theformation of vapour films. On the other hand, the trans-hydroxyl compound could cross-associate and aid the packing andassociation between the molecules in the film, thus producing strongsolid monolayers. These differences are further brought out bythe availability of the double bonds in the cis- and trans-compoundsto oxidising agents in the underlying solution induced by thedifferent packing arrangements.It is interesting that this hydroxylbonding in the dihydroxy-compounds takes place in a hydrocarbonenvironment and not in an aqueous medium.Penetration of Monoluyers.It was first shown by Schulman and Hughes 55 that, if certaincapillary-active substances were injected in minute quantities undera monolayer kept at constant area, great changes in surface pressureand surface potential of the film-forming substance occurred,although the injected substance alone a t these concentrations hardlyaffected the surface tension of an aqueous solution. Schulman andRideal e3 showed that this phenomenon was very specific andrelated to two types of interaction between the film-formingmolecule and the injected molecule. This consisted primarily ofan interaction between the polar groups of the two molecules,which anchored the soluble molecule to the film-forming molecule,thus enabling the second stage of the association to take place.This consisted in the association between the non-polar portions ofthe molecules. The energy of association is of the same magnitudeas that of the polar association, under conditions in which strongassociation between the molecules can take place.On penetration, therefore, the number of molecules in themonolayer is increased, and since the stability of the complex isgreater than that of either of the two components alone a t theinterface, an equimolecular mixed film will result , thus increasingthe surface pressure markedly and increasing or decreasing the62 Proc.Roy. SOC., 1929, A, 124, 333SCHULMAN : SURFACE CIEEMISTRY. 113surface potential to the mixed-film value of the two components.Schulman and Rideal63 gave strong proof for this hypothesis byshowing that penetration of monolayers took place (by substancesinjected into the underlying solution) with the same specificity aswith components that were known to form complexes in bulk, suchas the saponin-cholesterol complex ; for instance, saponin readilypenetrates films of cholesterol or ergosterol, but not films of chole-sterol acetate, cetyl alcohol, or calciferol, giving a direct analogy totheir association in bulk solution. Similarly, sodium cetyl sulphatepenetrates cholesterol films but not those of cholesteryl acetate orcalciferol. As shown already, this compound will penetrate cetylalcohol or elaidyl alcohol, but not oleyl alcohol, at all readily, thusshowing that the phenomenon of penetration is related equally topolar and non-polar association by van der Waals forces.Schulman and Rideal 64 utilised the technique of monolayerpenetration to grade the reactivity of polar groups to react withone another. I n this case polar groups having special biologicalsignificance were chosen. On weakly associating systems the moreunstable component can be ejected from the interface by highsurface pressures which are well defined and permit a measure ofassociation between molecules. This pressure is the equilibriumpressure attained by injecting into the underlying solution a certainquantity of the reacting component at a certain surface concentrationof the film-forming compound : according to Gibbs it is related toboth these conditions, and this has been shown experimentally bySchulman and Stenhagem65Schulman and Rideal 64 showed that by injecting equimolar con-centrations of a whole series of compounds easily soluble in waterbut containing an identical non-polar portion such as a C1, long-chain hydrocarbon, t o which various polar groups were attached,a well-defined reactivity series of these polar groups in associatingwith a common polar group, such as the hydroxyl group incholesterol, could be established. The area of the cholesterolmolecule in the film was chosen so as t o enable one molecule of theinjected substance to penetrate the monolayer. This gave thefollowing reactivity series :+-NH3+ > -SO,- > -SO3- > COO- > -NMe3 > Bile acid anionThe direct analogy of this series with the biological activity of thesesubstances has been shown by Schulman and RideaL6*Schulman and Stenhagen 65 enlarged upon the monolayer pene-tration technique by measuring the phenomenon, not only atconstant area, but a t varying areas and pressures of the film-forming63 Proc. Roy. SOC., 1937, B, 122, 29.6s Proc. Roy. SOC., 1938, B, 126, 356.64 Nature, 1939, 144, 100114 GENERAL AND PHYSIC& CHEMISTRY.component and a t different concentrations of the injected component.This established two interesting properties of mixed films. (1) Thetwo components could exist in two-dimensional crystal forms witha well-defined stable ratio of the two components. The stability ofthe various mixed two-dimensional crystalline forms depended onthe associating properties of the polar and non-polar portions ofthe two components. For instance, solidification of the mixedmonolayer and marked changes in the force-area curves of films ofthe two components took place a t definite stoicheiometrical ratiosof the two compounds. (2) The stability of the mixed film, asmeasured by the surface pressure necessary to eject the penetratingcomponent or collapse the mixed film as a unit, is markedly affectedby the concentration of the penetrating component in the underlyingsolution; e.g., a pressure of only 8 dynes/cm. is necessary to ejectsodium cetyl sulphate molecules out of an equimolecular mixed filmcontaining cholesterol as the other component, but a t a concen-tration of g./c.c. of sodium cetyl sulphate in the underlyingsolution the ejection pressure is already 35 dynes/cm. At a con-centration of 2 x g./c.c. the penetrated film collapses as a unitwithout an apparent ejection of either component at pressures ofca. 50 dyneslcm., which is much greater than the collapse pressure offilms of the components alone. This emphasises the importance ofthe diffuse layer of the penetrating material underneath the mono-layer in stabilising the complex a t the interface. The significance ofthis diffuse layer in bulk solution is demonstrated by Schulman(unpublished) in work on the stability of micelles and emulsions andon phenomenon relating to reactions taking place at cell surfaces.Schulman and Stenhagen 65 further showed the marked influenceexerted by the nature of the non-polar portion of the interactingmolecules both on the penetrating ability of the molecules and onthe stability of their resultant complexes a t the air-water surface.For instance, by increasing the chain length from C,, to CIS, theejection pressure of tbe long-chain sulphate from a mixed filmcontaining cholesterol changes from 8 dynes/cm. to 30 dynes/cm.Similarly, as has already been emphasised, stereochemical arrange-ments permitting of adlineation between molecules and interactionby van der Waals forces, such as with the cis- and trans-configurationand with long-chain hydrocarbons and ring structures, play a veryimportant part in the phenomenon of penetration.Adsorption.It has already been shown that a long-chain hydrocarbon withone polar group at the end of the chain will penetrate a monolayersimilarly constituted, raising the surface pressure and changing thesurface potential of the film-forming substance in a marked manneSCHULMAN : SURFACE CHEMISTRY. 115under the specific interacting conditions. Schulman and Rideal G3* 64and E. G. Cockbain and Schulman 66 show that, if the interactingmolecule has more than one reacting polar group and these polargroups are suitably spaced, very poor penetration of the monolayertakes place, but a very strong adsorption on the monolayer isobserved. This adsorption is measured by marked changes in thesurface potential and rigidity of the film-forming component.Schulman and Rideal 63 show that penetration of a protein film bya long-chain compound is usually followed by complete dispersionof the protein film and subsequent removal from the interface, butif a dibasic fatty acid or other multiple polar reacting compound beinjected into the underlying solution, strong adsorption or tanningof the protein film is observed. It was shown that the rate ofadsorption and resultant concentration of the adsorbed molecules isgreatly influenced by the number of reacting polar groups peradsorbing molecule. Cockbain and Schulman 66 enlarged uponthese reactions, showing that the spacing of the polar groups andthe nature of the hydrophobic portion 9f the adsorbing molecule inthe underlying layer permitting of adlineation or packing of themolecules (on this occasion) in the underlying layer was mostimportant in the rate of the adsorption and stability of the resultantbimolecular film.Cockbain and Schulman summarise the various factors which cangovern the interaction between molecules in an orientated mono-layer and compounds present in the underlying solution. Thisinteraction can vary from examples where the association is so strongthat the reacting molecules can associate into a mixed monolayerwith definite stabilities measurable at simple stoicheiometrical ratiosof the two reacting components to cases where it is so weak thatonly solution effects can be measured.The extent of the interaction can depend on the following factors :(a) The chemical nature and number of the polar groups in thetwo molecular species; ( b ) the van der Waals forces between thenon-polar residues ; ( c ) surface pressure of the monolayer ; ( d ) con-centration of the dissolvcd compound; ( e ) pE of the underlyingsolution ; (f) neutral salt concentration in the solution ; (9) stereo-chemical confgurations of the two molecular species, in both theirpolar and non-polar groups.J. H. S.R. P. BELL.M. G. EVANS.H. W. M~LVILLE.W. C. PRICE.J. H. SCHULJKAN.Tram. P’araday SOC., 1039, 35, 716

ISSN:0365-6217    

DOI:10.1039/AR9393600033

出版商:RSC    

年代:1939

数据来源: RSC

摘要:

INORGANIC CHEMISTRY.INTRODUCTION AND GENERAL.As in previous years the Reporter has been able to deal in thisintroduction with only a limited number of topics. The largeand heterogeneous mass of material published during the year doesnot permit of easy summarisation and only a very rough indicationof the trend of inorganic chemistry can be given. Moreover,subjects such as isotopy, co-ordination compounds, etc., which weredealt with last year will not be discussed, although they still repre-sent some of the more fruitful fields of research.Although carbon tetrafluoride was first obtained by direct unionin an impure state by H. Moissanl in 1890, the preparationof higher homologues has presented considerable difficukies.0. Ruff and his co-workers found that in the reaction frequentexplosions took place.They thought this to be due to the formationof the white crystalline monofluoride CF,3 which explodes on heating,and suggested that with proper temperature control the fluorinationmight be induced to proceed smoothly. This condition was neverexperimentally realised, but they succeeded in isolating hexa-fluoroethane and a small amount of higher product. 'Other reactions, e.g., by the action of fluorine on hydrocarbonseither pure or in solution or on chloro-derivatives,6 which mightlead to higher molecular-weight fluorocarbons, have produced onlyhexafluoroethane and tetrafluoroethylene. I n these, explosionswere controlled by the use of a copper-gauze catalyst. Otherfluorinating agents such as antimony trifluoride have also beentried.Hexafluoroethane has been prepared by the electrolysis oftrifluoroacetic acid and is obtained together with tetrafluoroethyl-ene by the passage of carbon tetrafluoride or dichlorodifluoromethanethrough an electric arc.8 In the latter case some evidence wasfound for the formation of C6F6 and C6FI2.91 H. Moismn, Compt. rend., 1890, 110, 951 ; cf. P. Lobeau and A. Damiens,2 0. Ruff and R. Keima, 2. anorg. Chem., 1930, 192, 249.3 0. Ruff, 0. Bretschneider, and F. Ebert, ibid., 1934, 217, 1.4 H. Fredenhagen and G. Cadenbach, Ber., 1934, 67, 928.6 L. A. Bigelow and J. D. Calfee, J. Amer. Chem. Xoc., 1937, 59, 2073.6 A. L. Hesne, ibid., p. 1400.7 F. Swarts, Bull. Acad. roy. Belg., 1934, 20, 782.8 0.Ruff and 0. Bretschneider, 2. anorg. Chem., 1933, 210, 173.9 F. Swarts, Bull. Xoc. chim. Belg., 1933, 43, 114.ibid., 1930, 191, 939TERREY : INTRODUCTION AND GENERAL. 117J. H. Simon and L. P. Block lo find that the direct fluorinationcan be controlled by using mercury as a catalyst-either by theaddition of mercurous or mercuric chloride to the carbon or by theuse of amalgamated copper gauze. From the reaction product,which contains primarily the tetra- and the hexa-fluoride, they haveprepared about 150 C.C. of a liquid with a molecular weight greaterthan 138. Fractionation of this gave the following products(b. p.'s in parentheses) : C3Fs (- 38"), C4F10 (- 4*7"), C4F1,(3-0"), C,Flo (23"), C6F1, (51"), C,F1, (80"). Two higher-boilingfractions have still to be separated.It will be noticed that there aretwo isomers of decafluorobutane. The last three compounds areconsidered to be cyclic. All are colourless and practically odourless,fully saturated, and very stable chemically. The observed boilingpoints are much lower than for the corresponding hydrides, and thisis ascribed to the relatively low attractive force between the mole-cules, these fluorides approaching the inert gases in this respectmore closely than any other class of compound.Although it is not generally possible to replace chlorine completelyby fluorine through the agency of fluorides in the presence of anti-mony pentachloride, yet mixed halides, e.g., dichlorotetrafluoro-ethane, can be prepared in this way. H.J. Emeleus l1 has shownthat a similar reaction can be applied to silicon halides. On treat-ment of mono- or di-chlorosilane with antimony trifluoride andpentachloride, replacement of the chlorine takes place, SiH,Cl,yielding SiH,F,. The latter is described as an inflammable gas(b. p. - 776", m. p. - 119.1"), non-reactive towards glass andmercury.Booth l2 and his collaborators have continued their work on thefluorination of non-polar inorganic halides and have published theresults obtained from the chloride and bromide of phosphorus andphosphoryl chloride. These investigators have used the threeknown methods, vix., (a) using antimony trifluoride and penta-chloride as a catalyst, (b) heated calcium fluoride acting on the vapourof the trichloride, and ( c ) for mixed halides, the passage of phos-phorus trichloride and trifluoride through a hot tube. The lastmethod was not so useful as the others, owing t o side reactionsand the formation *of silicon tetrafluoride if glass or silica apparatuswas used.By careful control of the temperature, it was possibleto fluorinate in stages, and from both phosphorus trichloride and10 J . Amer. Chem. SOC., 1937, 59, 1407; 1939, 61, 2962.l1 Nature, 1939, 144, 328.12 H. S. Booth and A. R. Bozarth, J. Amer. Chem. SOC., 1939, 61, 2927;H. S. Booth and S. G. Frary, ibid., p. 2934; H. S. Booth and F. B. Dutton,ibid., p. 2937118 INORGA4NIC CHEMISTRY.tribromide the compounds PPCI, and PF,C1 as well as PF, wereisolated. The physical constants of these were found to be:PFCI,, m.p. - 144.0", b. p. 13.85"; PF,Cl, m. p. - 164.8", b. p.- 47.3"; PF3, m. p. - 151-5", b. p. - 101.15". All react withchlorine, giving quinquevalent chlorofluorides. These are unstable,breaking down at room temperature into the penta-fluoride and-chloride. With phosphoryl trichloride * the corresponding tri-fluoride first obtained by H. Moissan was formed, together withphosphoryl monochlorodifluoride, b. p. 3-1 ", and phosphoryl di-chloromonofluoride, b. p. 52-9".By the pyrolysis of SiloCl,,H2 the polymerised monochloride(SiCl),13 is obtained as a yellow amorphous solid stable up toabout 500", above which it breaks down into saturated siliconchlorides and free silicon. Like the other halides, it is readilyhydrolysed by water, but is stable in dry air a t room temperature;on heating, combustion readily takes place.With free halogens(chlorine or bromine) combination occurs, silicon tetrachloride andsaturated chloro- or chlorobromo-derivatives being formed. Am-monia gives rise to Si,(NH,), and Si8(NH,)lo, the other productsbeing hydrogen and ammonium chloride. Controlled hydrolysiswith moist ether produces a t low temperatures (- 25') a red com-pound (SiOH),, and at room temperature a yellow compoundSi,(OH),, hydrogen again being evolved in the latter case. Con-centrated hydrochloric acid forms the same product. From itschemical behaviour it seems to be much more reactive than itscarbon analogue, and the investigators regard it as a polymerised,unsaturated, long-chain derivative rather than as a lattice compound.Some attention has been paid in the last year to the preparationof iodides by direct union either by heating the finely divided metalin iodine vapour or by using an electrically heated wire in anatmosphere of iodine kept at a definite temperature.I n the lattercase it is possible by controlling the temperature to determine therange of stability of lower iodides if formed, and a modification canin certain cases be used for the purification of the element con-stituting the wire (by formation and decomposition of the resultingiodides). Tantalum,l* col~mbium,~~ titanium,15 and vanadium 1 4 ~ 1 613 R. Schwarz and U. Gregor, 2. anorg. Chem., 1939, 241, 395.1 4 F. Korosy, Technikai Kurir, 1938, 9, 81; J .Amer. Chem. SOC., 1939,16 J. D. Fast, Rec. Trav. chim., 1939, 58, 174; 2. anorg. Chem., 1939, 241,16 A. Morette, Compt. rend., 1938, 207, 1218.* Phosphoryl tribromide yields similar products : POF,Br, b. p. 30.50,m. p. -884.8"; POFBr,, b. p. 110*1", m. p. -117.2" (H. S. Booth and C. G.Seegmiller, J. Amer. Chem. SOC., 1939, 61, 3120).61, 838.45TERREY : INTRODUCTION AND GENERAL. 119have been investigated in this way. In the case of tantalum,€1. Moissan l7 stated that the element and iodine did not reactbelow 600", and it has been generally assumed from this that iodinewas without action on this metal. Korosy has found, however,that an incandescent tantalum wire combines readily with iodine,forming a blackish-brown solid, m.p. 365", which could be distilledunchanged a t 400" and on analysis proved to be the pentaiodide.Unlike the pentachloride, which in the fused state is an insulator 18with a specific resistance of 3 x lo6 ohms, the pentaiodide is a semi-conductor.If the amount of iodine used was below that requisite for thepentaiodide, and the vessel containing the iodine was heated to500", a reduced product was obtained but always mixed with thepentaiodide. Fractionation in a vacuum resulted in splitting, withthe formation of tantalum and its pentaiodide, and this is con-sidered to be due to a reaction of the type 5Ta1,Z 2Ta + 3TaI,,in analogy with the behaviour of the lower chloride. Extractionof the original mass with water gave a dark green solution (cf.the chloride).Analyses of the solution gave results approximatingto TaI,, but these were not sufficiently accurate to distinguishbetween this formula and compositions ascribed to the correspond-ing chloride and bromide by others, e. g., (Ts6C1,,)C1,,7H,0 ; l9H(Ta3X,),3H,0 ; 2O Ta,X70,3H,0.21 Niobium behaves somewhatsimilarly to tantalum, although the pentaiodide is less stable,dissociating at its sublimation temperature, i e . , about 400". Againthe composition of the lower chloride is doubtful. It can be eitherNb,I, (best from analytical data) or Nb,Il, in harmony with thecomplex niobium chlorides prepared by H. S. Harned.22With vanadium there is some divergence of view with regard tothe products formed. A. Morette l6 states that the two elementsunite in a vacuum a t temperatures above 150", forming the tri-iodide which decomposes above 280", and that the di-iodide isobtained by 24 hours' heating in a vacuum at 400".F. Korosy,14on the other hand, is of the opinion that an unstable pentaiodide isthe primary product and this on breaking down gives V&,.Titanium forms three iodides, Ti14, TiT,, and TiI,, by directaction. The tri-iodide decomposes in a vacuum at 350°, giving the17 Co?npt. rend., 1902, 134, 212.18 W. Biltz and A. Vogt, Z . anorg. Chem., 1921, 120, 71.19 W. H. Chapin, J . Amer. Chem. SOC., 1910, 32, 323.20 K. Lindner and H. Feit, Ber., 1923, 56, 1458; 2. anorg. Chem., 192421 0. Ruff and F. Thomas, Ber., 1923, 56, 1473; 8. anorg. Chem., 1925,2* J .Amer. Chem. Soc., 1913, 35, 1078.137, 66; 1927, 160, 57.148, 1, 1120 INORGANIC CHEMISTRY.di- and the tetra-iodide, whoreas the di-iodide decomposes at 480" :It is by taking advantage of this reaction that pure titanium can beobtained. J. D. Fast,15 starting with a titanium containing 3.5%of iron, obtained a deposit of the element which was iron-free andalmost spectroscopically pure.As mentioned in the Reports for 1937,23 bromine dioxide, onbeing cautiously warmed, decomposed through an intermediatestage giving elementary bromine and a dark brown and a whitesolid. The dark brown substance has been further investigated.24It constitutes about 20% of the total yield. Analysis shows thatit is Br,O, the simple formula being verified by molecular-weightdetermination in solution.It is readily soluble in carbon tetra-chloride with a pronounced green colour, but oxidation proceedson standing with the production of carbonyl chloride. Additionof iodine to the fresh solution results in the precipitation of iodinepentoxide. Dibromine monoxide has an odour akin to that ofhypochlorous acid and reacts smoothly with sodium hydroxide,forming sodium hypobromite; below - 40" it appears to be quitestable, though the rate of decomposition at 0" is not great. It hasa melting point of - 17.5" and at - 16" forms a black-brownliquid from which gas is continuously evolved; it is probablyformed by the reactions :2Ti1,t TiI, + TiI, 2 T i 1 2 t Ti + Ti148Br0, + 2Br20, + 2Br2 + 0, ; Br,07 + 6Br2 --+ 7Br20Attempts to isolate the white product (Br20,) have so far been un-successful.The monoxide so prepared appears to be identical withthat prepared by W. Brenschede and J. H. Schumacher 25 from theinteraction of bromine and specially active mercuric oxide.Nitride formation has been studied in the cases of the f o l l o ~ gelements : magnesium,26 aluminium,26 germanium,27 copper,28and zinc.29 Pure copper nitride may be obtained by passing ammoniaover freshly dehydrated cupric fluoride at 280"; it reacts withhydrogen at 230" and burns in oxygen at 400". The zinc compoundcan be made from zincamide, Zn(NH,),, or from ammonia and zincdust, the latter method giving a more stable form.23 P. 130.24 R. Schwltrz and H. Wiele, Naturwiss., 1938, 26, 742; J .pr, C]bem., 1939,26 2. anorg. Chern., 1936, 226, 370.26 p. Lafitto, E. Elchardus, and P. Grandada,m, Rev. Ind. min., 1936, 861.27 R. Juza, and H. Hah, Natumoiss., 1939, 27, 32.2s Iclem, Z. anwg. Chem., 1939, 241, 32.29 R, Juza, Anna Neuber, and H. Hahn, ibid., 1938, 239, 273.152, 157TERREY : INTRODUCTION AND GENERAL. 121In the Annual Reports for 1936 and 1937 mention was made of thecomplexity of the phosphorus molecule and phosphorus pentoxide.By the analysis of X-ray patterns obtained from liquid yellowphosphorus, amorphous red, and amorphous black phosphorus,atomic distribution curves have been 0btained.~0 These indicatethat the number of nearest neighbours to any atom is three, Le.,the phosphorus is present as P4.From the observations of H.Moureu and G. W e t r ~ f f , ~ ~ this molecule is stable up to 1500",because by direct union with nitrogen it forms phosphonitrile,PN; the reaction P, + 2N, + 4PN is slightly endothermic,whereas P, + N, --+ 2PN is exothermic. When an equimolecularmixture of phosphorus and nitrogen is maintained a t 400-500"in a vessel through which an electrically heated tungsten wirepasses, it is not until the wire reaches 1500" that formation of afilm of PN takes place.The vapour pressure of the metastable liquid form of phosphoricoxide is higher in quartz than in glass vessels.32 This is ascribedto a catalytic action of the glass on the change from the metastableto the stable form. The vapour pressure between 600" and 670",unsaturated with respect to the stable form, indicates that thevapour consists almost entirely of double molecules.At lowertemperatures (360") the vapour, unsaturated with respect to themetastable but supersaturated with respect to the stable form,shows increasing association.W. Biltz and his co-workers have continued with their " Syste-matic studies of affinity " and have investigated the following systems :(a) Thori~m-phosphorus.~~ The normal phosphide Th,P, wasobtained by the action of phosphorus vapour on thorium a t 650-700" in il sealed tube. It is stable up to 1100" and unaffected bywater, although acids decompose it with the evolution of phosphine.(b) Copper-ph0sphorus.3~ The phosphides Cu,P, CUP,, andCUP,.,, were formed. The isotherms of the last product showed noCUP,, indicating merely a solution of the excess phosphorus.The diphosphide is more stable than the corresponding silverderivative, but less than those of iron and nickel.(c) Ruthenium-phosphor~s.3~ Preparations of these were carriedout in a pressure flask at 650-680'.Three compounds, Ru,P,RuP, and RuP,, were isolated.30 C. D. Thomas and N. S. Gingrich, J. Chem. Physics, 1938, 6, 659.31 Compt. rend., 1938, 207, 915.32 A. Smits, J. A. A. Ketelaar, and J. L. Meyering, 2. physikal. Chem.,33 W. Biltz, E. F. Strotzer, and K. Meisel, 8. anorg. Chem., 1938, 238, 69.34 H. Haraldsen, ibid., 1939, 240, 337.35 W. Biltz, H. J. Ehrhorn, and K. Meisel, ,ibid., p. 117.1938, B, 41, 87122 INORGANIC CHEMISTRY.(d) Rheniurn-arsenic.36 A single compound, Re,As7, was ob-tained; this decomposes a t 780".The existence of only one coni-pound may be contrasted with the rhenium-phosphorus derivatives,where Rep;, Rep,, Rep, and Re,P are formed.(e) Osmiurn-phosphorus.35 At 11 9Qo, gaseous phosphorus reactswith osmium, yielding OsP,, the only stable compound formed.An attempt37 has been made to prepare the higher hydridesof nitrogen, phosphorus, and sulphur by bringing ammonia, phos-phine, and hydrogen sulphide into contact with active hydrogen,but analysis of the reaction products failed to afford any evidencefor their formation. Such hydrides could, of course, only be ex-pected if they possessed a fully covalent structure, which is not thecase if they are similar to the higher halides and if Pauling's viewsare accepted; e.g., in phosphorus pentachloride it is assumed thatthe molecule has an ionic structure, the phosphorus atom having anormal octet and a positive charge, with a negative chlorine resonat-ing among the five positions-a structure hardly feasible whenhydrogen is substituted for halogen.Although it was not actually isolated, fairly good experimentalevidence has been put forward for the formation of a perselenide inthe reduction of selenious acid with aluminium-hydrochloric acidmixtures.38 Passage of the gas into acid lead acetate or sodiumplumbite solutions led to a precipitate of PbSe,.Determinationof its reducing power by absorption in alkali, followed by additionof acid iron alum and back-titration with permanganate, showedthat its valency was one, which gives it an empirical formula ofHSe.Renewed interest has been shown in the mechanism of theformation of polythionic acids by the interaction of hydrogensulphide and sulphur dioxide.H. Stamm and M. Goehring39favour the intermediate formation of thiosulphurous acid, H2S2O2,which, contrary to earlier views, is regarded as a powerful oxidisingagent. Their evidence in support of the above lies in their workon the hydrolysis of methyl thiosulphite, ( CH,*O),S,.40 Withhydrochloric acid as the hydrolysing medium, hydrogen sulphideis liberated at the start of the reaction, but the final products arepentathionic, sulphurous, and thiosulphurous acids and sulphur.The amount of pentathionic acid formed is greater than would be36 W.Biltz, F. Weichman, and Martha Heinburg, ibid., p. 129.37 K. G. Denbigh, Trans. Paraday SOL, 1939, 35, 1432.313 J. P. Nielsen, S. Maeser, and D. S. Jennings, J . Arner. Ghem. A'oc., 1939,39 Naturwiss., 1939, 27, 317.40 H.. Stamm and H. Wentzer, Ber., 1938, 71, 2212.61, 440TERREY : INTRODUCTION AND GENERAL. 123expected from the -reaction of the hydrogen sulphide with thesulphurous acid. When the saponification takes place in thepresence of silver ions and nitric or perchloric acid, a dark redprecipitake of Ag2S,Ag2S0, is formed, and when hydriodic acid isused as the hydrolysing acid, iodine and sulphur are the finalproducts. These reactions can be expressed thus :(1) (CH3*O),S2 + 2H2O( 2 ) H2S202 + H2O + H2S + H2S03(3) H2S202 + 3 3 2 s + 3s + 2H2OH2S,O, + 2CH,.OH(4) H2S202 + 2HI -+ I, + 2s + 2H20(5) H,S,O, 3t H,S + so2Reactions (3) and (4) show the oxidising action of H,S202,, and thereversibility of the last reaction can be demonstrated by workingin anhydrous formic acid.I n an acid medium sulphurous and thiosulphurous acids interactto give tetrathionate, but with a large excess of sulphurous acidand a t pH 6.9, trithionate and thiosulphate are formed in equalamounts :(6) H2S202 + 2H2S03 = H2S406 + Z1X2‘0(7) H2S406 H2S03 = H2S306 + H2S203With thiosulphuric instead of sulphurous acid in reaction (6) higherpolythionates are formed; once formed, these are unaffected byI n the decomposition of thiosulphates in the presence of arsenicor antimony trichloride, C.J. Hansen 41 supposes that two differenttypes of reaction occur; in a strongly acid medium these saltscatalyse the reactionH2S202.5s20,” + 6H’ --+ 2S,06” + 2(5 - x)S + 3H,Oand favour the formation of polythionates, but simultaneouslythe complex ion As(S203)”’ is formed. This can decomposeto give either As2S3 and S,06” or the free ion radical S*S020’.The latter then dimerises to give S40,” or takes up sulphur to givea polythionate. I n practice no one reaction occurs exclusively,and in no case is pentathionate the initially formed polythionate.The properties of sulphur tetroxide, first isolated by R. Schwarzand H. Achenbach42 by passing sulphur dioxide and oxygenthrough an ozoniser, have been rein~estigated.~~ When passedinto potassium hydrogen sulphate solution, it forms a productsimilar to that obtained when fluorine reacts with acid sulphate*1 Ber., 1939, 72, 535.4 2 2.anorg. Chem., 1934, 219, 271; cf. Ann. Reports, 1935, 32, 1 5 1 .4 3 5’. Fichter and A. Maritz, Helv. Chim. Acta, 1939, 22, 792124 INORGANIC CHEMISTRY.and passes gradually into potassium persulphate. It was thoughtthat in the fluorine acid sulphate reaction SO,F, might be formed,but attempts to separate this by volatilisation failed.When dry air containing 10-12% of hydrazoic acid is passedinto fuming sulphuric acid about 65% is converted into imino-monopersulphuric acid, H,S04NH,a which melts a t about 210"and decomposes at a slightly higher temperature.It oxidiseshydriodic acid and is hydrolysed by water to sulphuric acid andhydroxylamine. With alcohol the compound NH,*HO*SO,*OEts formed. Dissolution in liquid ammonia results in the precipitationof ammonium sulphate, leaving a solution with oxidising and re-ducing properties. On evaporation, decomposition sets in andnitrogen is evolved, suggesting that NH:NH may be present in thesolution.Lithium peroxide in the hydrated form as Li,O,,H2O,,3H,Owas first prepared by R. de Forcrand.45 His work seemed to showthat it was not possible to dehydrate the salt without loss of oxid-ising power. A. Aguzzi and F. Genoni46 have followed thedehydration by complete analyses of the residue and find that thewater molecules are eliminated in a vacuum without loss of hydro-gen peroxide, a result in agreement with the work of G.R. Levi andF. Battaglin~.~~ X-Ray analysis of Li,O, shows that it crystallisesin the tetragonal system.48The peroxides of rubidium and caesium 49 have been shown to havethe same structure as potassium peroxide, i.e., the CaC, structure,and hence are correctly designated " dioxides " with the anionicunit 0;. Like the potassium derivative, they are paramagneticwith a molecular moment of - 1.9, i.e., they have one unpairedelectron.The rate of decomposition of potassium peroxide 50 shows nodiscontinuity, and the vapour pressure remains constant untilthe solid phase is K,O, (2K0, ---+ K,O, + 0,). This behaviourcalls into question the entity of K,O,, which is considered to beformed when solutions of potassium in liquid ammonia are treatedwith oxygen.The formation of SrO, from the monoxide and oxygen, first44 H.E. M. Specht, A. W. Browne, and K. W. Sherk, J . Amer. Chem. SOC.,46 Cornpt. rend., 1900, 130, 1465; cf. P. Pierron, Bull. SOC. chim., 1939, 6,46 Gazzetta, 1938, 68, 816.48 Ibid., 1938, 68, 810; cf. D. Feher, Angew. Chem., 1938, 51, 497.40 A. Helmo and W. Klemm, 2. anorg. Chem., 1939, 241, 97.6o S. I. Reichstein and I. A. Kazarnovski, J . Phys. Chem. Russia, 1938,1939, 61, 1083.235.47 Ibid., 1937, 67, 659.11, 743TERREY 1NTROI)UCI'ION AND GENERAL. 1%noted by P. Fischer and H. Pl0etze,~1 has been more fully investi-gated by C. Holtermann and P. Laffitte.52 They find that, startingwith a monoxide free from hydrate and carbonate, a product con-taining 996% of SrO, is formed with dry oxygen at a pressure of200-250 atm.and a temperature of 350-400". Under ordinarypressure the dissociation temperature is 357".Further work has been published on the preparation in the elemen-tary state of beryllium,53 m~lybdenum,~~ manganese,55 and the rareearths lanthanum,56 neodymium, and prase~dymium.~~ The lasttwo were made by the reduction of the corresponding chloride at200" with sodium, and lanthanum by the electrolysis of the fusedchloride. This was carried out in a graphite crucible serving asanode and a molybdenum rod as. cathode, the latter being sur-rounded by an alundum crucible. Potassium chloride and calciumfluoride were added as fluxes.The optimum yield was obtainedat 1000" with a current density of 7 amps. per sq. em.Beryllium oxide can be reduced by titanium at 1400", the metaldistilling off and condensing in a dense form. At higher temperaturesi t is contaminated with TiO. In the presence of finely dividedcopper, nickel, or iron it can be reduced by calcium or magnesium(the former being the more efficient) provided the temperaturebe sufficiently high so that the beryllium is dissolved in the addedmetal. The resulting alloys can be freed from calcium by heatingexcept in the case of copper.With molybdenum it is recommended to convert the trioxideinto the disulphide by heating in sulphur vapour or hydrogensulphide. This is mixed with calcium, and heated in a vacuumor in an inert atmosphere until reaction occurs. After cooling, theproduct is washed with alcohol and acidulated water.The fineresidue is said to contain 99.6% of molybdenum.Further investigations have been carried out on the salts ofeuropium. A large number of the tervalent derivatives of organicacids have been prepared by H. N. M~Coy,~8 as well as some of thebivalent compounds. The latter can be determined much moreaccurately by oxidation with permanganate if ferric sulphate isfirst added, a procedure which diminishes the slowness of the reaction.61 Z. anorg. Chem., 1912, 75, 30.62 Compt. rend., 1939, 208, 517.53 W. Kroll, 2. anorg. Chem., 1939, 240, 331.54 R. Sautie, Bull. SOC. chim., 1939, 6,.1236.55 P. V. Shivotinski and S.A. Zaretzki, J . Appl. Chein. Russia, 1939, 12,66 F. Weibke and J. Sieber, 2. EZektrochem., 1939, 45, 518.5 7 W. Klemm and H. Bomrner, 2. anorg. Chem., 1939, 241, 264.68 J . Amer. Chem. SOC., 1939, 61, 2465.200126 INORGANIC CHEMISTRY.In the case of the bivalent halides W. Klemm and W. Doll 59 havemeasured the susceptibilities at different temperatures and obtainedthe expected value for the molecular moment of 7.9 Bohr magnetons(except the fluoride, which gave a value of 7.4 probably due to thepresence of EuF,). By heating the chloride with excess of sulphur,selenium, or tellurium in a stream of hydrogen, the correspondingsulphide, selenide, and telluride can be made.60 These have thesodium chloride structure. For the molecular moments, valuesof 74-7.9 magnetons were obtained, in agreement with theory forionic binding.X-Ray analysis of the europous salts 61 reveal marked differencesin structure.The chloride, like samarous chloride and bariumchloride and bromide, has the lead chloride type lattice, the bromideresembles samarous and strontium bromide, and the iodide thecorresponding two iodides, but neither of the last two belongs toany of the well-known types.A. Brukl 62 recommends for the preparation and separation ofsamarium dichloride, reduction in the absence of air of a solutionof the tervalent chloride in absolute alcohol with calcium amalgam,the precipitated dichloride being collected in a centrifuge. Attemptsto prepare the selenide and telluride90 by the method mentionedabove show that it was not satisfactory, a, product containing only25% of samarium resulting.For the separation of praseodymium and neodymium, G.Beck 63suggests fusion with potassium hydroxide followed by electrolysis.Brown Pro, separates at the anode and metallic neodymiuma t the cathode. Decantation when the reaction is complete leavesa residue of Pro, which can be further purified by fusing it againwith potassium hydroxide and hydrolysing the resulting KNdO,.The removal of terbium from samarium-gadolinium fractions iseffected by fusion with potassium hydroxide and chlorate ; impureTbO, is precipitated on cooling. Purification can be effected by arepetition of the process.With regard to other methods of separation J.K. Marsh 64 hascarried out an extended series of measurements on the solubilitiesof the dimethyl phosphates of gadolinium, terbium, dysprosium,yttrium, erbium, and ytterbium and points out that for the purifica-tion of terbium, dysprosium, and holmium these phosphates are ofconsiderable practical use : James and Morgan’s view that their59 2. anorg. Cherrt., 1939, 241, 233.6o W. Klsmm and H. Senff, ibid., p. 259.61 W. Doll and W. Klemm, ibid., p. 239.6a Angew. Chem., 1939, 52, 157.Ibicl., p. 536. 64 J., 1939, 554TERREY : INTRODUCTION AND GENERAL. 127utility was seriously impaired by hydrolysis is not valid providedthat the temperature be not allowed to exceed 50".The lattice constants G5 of corresponding oxides of the rare earthshave been redetermined and when plotted give two smooth curvesintersecting a t gadolinium, and measurements of the heats of sol-tion of anhydrous chlorides 66 show that these fall into three groups :(1) La, Ce, Pr, Nd, Sm, Eu, Gd; (2) Tb, Dy ; (3) Er, Tm, Yb, Lu.The structures of the chlorides determined from X-ray analysisfall into the same three groups.For the complete purification ofgadolinium L. Rolla 67 finds that the best procedure is the fractionalcrystallisation of the benzenesulphonates of terbium and yttriumearths, followed by removal of the small quantities of samariumand europium present by reduction of the sulphates with strontiumamalgam (Holleck and Noddack's method).By dissolving gallium in nitric acid and evaporating the resultingsolution with hydrofluoric acid, W.Pugh 68 obtained the hydratedfluoride GaP,,3H2O, and by treatment of this with alkali fluorides,double salts were formed, which in the cases of lithium, sodium,and ammonium were anhydrous and of the type 3MF,GaF,,whereas potassium, rubidium, and caesium gave hydrated complexes,2KF,GaB',,H2O ; Rb(Cs)F,GaF,,BH,O. The whole of these herepresented as compounds of co-ordination number six, e.g.,Li,[GaF,], K,[GaF,,H,O], Rb[GaP,,2H20].The anhydrous fluoride cannot be obtained by direct heatingof the ammonium double salt, for ammonolysis takes place with theformation a t 220" of GaNH,F,, and at 400" of GaNHF.69 Theaction of fluorine on the oxide, telluride, or sulphide results inpartial conversion only. By decomposing (NH,),GaF, in a streamof fluorine at 250-400", GaF, was finally obtained in the form of awhite powder subliming a t 950".Most of the bivalent metals also form complexes with galliumfluoride.In general, these can be made by dissolving the oxideor carbonate in a solution of GaF3 in hydrofluoric acid.70 Thealkaline-earth compounds, like those of the alkali elements, areinsoluble in water; those of the heavy metals manganese, cobalt,nickel, copper, zinc, and cadmium, all of which are of the typeLM(H,0)6][GaF,H,0], are soluble and may be crystallised fromwater.6 5 I(. Tkmmor, %. unorg. Chem., 1939, 241, 973.ct, i€. Bomimr arid E. Hohmann, Nuturwiss., 1939, 27, 683.6 7 Atti X" Cong. inter'rh. Chine., 1938, 2, 766.GQ 0. Hannebohn and W.Khnm, 2. unorg. Chem., 1936, 229, 337.' 0 W. Pugh, J . , 1937, 1959.J . , 1937, 1046128 INORGANIC CHEMISTRY.By extraction of hydrated gallium trifluoride with liquid ammonia,the triammoniate GaF3,3NH3 is formed 71 (indium behaves similarly),This seems to be the maximum number of molecules of ammoniataken up even after cooling to - 78", though, from its dissociationisotherms, indications were obtained of the existence of a disam-moniat e.P. Neogi and S. K. Nandi 72 prepared Ga(P0,),3H20,Ga(ClO,),,H,O, Ga(10,),,2H20, and the basic iodateGa(I0,),,Ga,0,,3H20; and P. Neogi and N. K. Dutt,',by solution of Ga(OH), in alkali hydrogen oxalate solutions,prepared the double oxalates of ammonium, potassium, andsodium. These oxalates are of interest in that they are capableof being resolved into optically active isomerides.Double de-composition with E-strychnine gave Z-strychnine gallium trioxalate,Z-Ga(C,04)3[HC,,H2202N2]3,12H,0, a 1 yo solution in 50% alcoholhaving [ a ] r - 15.5". Fractional extraction with water left as aresidue Z-strychnine gallium salt, [a]F + 29", and from this bydouble decomposition salts of sodium and potassium, [ c c ] ~ + 16.5"and 15-5", respectively. The system Ga,O,-H,O closely resemblesAl2O3-H2OJ4 Between 110" and 300" the solid phase is GaO*OH,soluble in acids; from 300" to 1400" the p-oxide, insoluble in acids,is the stable form. The normal hydrate can only be prepared in abomb with a high aqueous vapour pressure, a t a temperature of167-170".Although metastable in the air, once formed it showslittle tendency to change. Dehydration curves show some indica-tions of the formation of Ga,O(OH),. The acid-soluble a-oxide isdifficult to prepare but can be obtained by precipitating a diluteboiling solution of the trichloride with sodium carbonate and dryingthe resulting solid a t 425". Even then it contains a small amountof water. At high temperatures it is converted irreversibly intothe p-form. A noted feature of this system is the very sluggishnature of the changes and extremely small tendency for crystallinegrowth to take place-a characteristic of the two earlier membersof this group.Elementary gallium becomes passive and dissolves very slowlyin ordinary mineral acids. In perchloric acid or in a mixture ofperchloric and sulphuric acids, solution takes place readily and theseconstitute the best s0lvents.7~ From perchlorate solution twohydrates can be isolated, vix., Ga(C104),,6H20 and Ga(C104),,9-5H20.71 W.Klemm and H. Kilian, 2. anorg. Chem., 1939, 241, 93.72 J . Indian Chem. SOC., 1937, 14, 492.7 3 Ibid., 1938, 15, 83.74 A. W. Laubengayer and H. R. Engle, J. Amer. Chem. SOC., 1939, 61,1210. ' 6 L. S . Foster, ibid., p. 3122TERREY : INTRODUCTION AND GENERAL. 129The latter on heating loses water, giving the former, but furtherdehydration results in the formation of basic salts. These hydratesmay be contrasted with those of aluminium, which forms salts with6, 9, 12, and 15 molecules of water, and with those of indium, whichgives an octahydrate.Owing to the scarcity of scandium we have comparatively littleexact knowledge of the chemistry of this element. The earlierwork was almost entirely due to W.Crookes 76 and R. J. Meyer.77Later, a more detailed examination of a number of scandiumcompounds was carried out by P. B. Sarkar and J. S. Stgrba-Bohm.78The sulphates, ~ e l e n a t e s , ~ ~ and carbonates 80 have been the subjectof investigation during the past year. It was realised by Crookesthat scandium could give rise to a hydrated sulphate and to basicsulphates. Bodlaender found that aqueous solutions of thesulphate gave an abnormally low value for the change in equivalentconductivity with dilution and assumed that this was due to complexformation. This was supported by the work of Meyer and H.Wirth, who obtained an unstable compound to which they assignedthe formula H,Sc( SO,),.The double sulphates with alkali sulphatesexamined by Sarkar did pot support this, for he obtained sulphatesof the type Sc2(S0,),,3R2S0, and Sc,(SO,),,R,SO,. Z. Trousil S2could not confirm Wirth’s acid salt but found that it has a com-position HSc(S0,),,2H20. Moreover, the normal sulphate separatesfrom acid solutions with 7 or 4 molecules of water instead of thepreviously reported 6, 5, or 2. The basic sulphate which is micro-crystalline in structure has the formula Sc(OH)S0,,2H20. Basicselenates corresponding to the latter, and an acid selenate corre-sponding to the acid sulphate, are formed, but the normal selenatecrystallises as the penta- or deca-hydrate.As found by Sarkarand again emphasised in this work, the sulphates and selenatesdo not correspond to those of the rare earths.Crookes reported the existence of a normal carbonate of scandiumwhich has been regarded as evidence for assuming that the elementis more basic than aluminium, and Meyer showed that doublecarbonates were formed when a scandium salt solution was treatedwith an excess of sodium or ammonium carbonates. It is now shownthat Crookes’s neutral carbonate does not exist, and that the doublecarbonates have the composition (NH,)Sc(CO,) ,,1.5-2H20 andNa,Sc(CO,), with 2, 11 or 18 H,O. Interaction of scandium formate76 Phil. Trans., 1908, A , 209, 15. 7 7 Chem. News, 1912, 106, 13.7a Ann.Chim., 1927, 87, 207. 7s Bull. SOC. chim., 1920, 27, 185.J. S . StBrba-Bohm and J. P. St6rba-Bob, Coll. Czech. Chem. Comm.,Diss., Berlin, 1915, 36, 30. 1929, 1, 1 ; 1938, 10, 8.82 Coll. Czech. Chem. C’omm., 1938, 10, 290.REP.-VOL. XXXVI. 130 INORGANIC CHEMISTRY.with potassium hydrogen carbonate and carbonate gives thecompounds KSc(C03),,H20 and K&3c(C03),,5H,0 respectively.Examination of the basic beryllium carbonates by thermalanalysis and rontgenographically 83 shows that these are mixturesof normal carbonate and hydroxide. In this respect beryllium seemsto resemble aluminium rather than magnesium. This may be con-nected with the small diameter of the beryllium ion, which is muchmore nearly like that of aluminium than that of magnesium.A slightly hydrolysed normal double carbonate of aluminium andpotassium has been prepared by 0.Grosdenes and R. Fritz.84Their method was to allow jets of solutions of aluminium iodideand potassium carbonate to impinge on each other. The productwas centrifuged and washed with alcohol and ethylene glycol.Analysis gave A1203,2-3C02,K2C03,4H,0, but the initial productis considered to be A1,C03,K2C03,5H20. It hydrolyses quiteslowly after drying, and does not lose carbon dioxide below 120-130'.HETEROGENEOUS EQUILIBRIA.An immense amount of work has been carried out in the lastfew years dealing with heterogeneous equilibria, not only in aqueoussolutions but also in the fused state. It is perhaps invidious toselect only certain systems for inclusion in these Reports, but it isstill true, as stated in the Annual Reports for 1932, that a great dealof inorganic chemistry requires revision by phase-rule methods.It is interesting to note the increasing use of X-ray photographs indeciding the existence or non-existence of any individual compound ;the time will doubtless come when such a test will be looked uponas a necessity.A series of papers on the relationship of beryllium to the vitriol-forming group and to the alkaline-earth metals have been published.These include investigations of the systems, Na2S04-BeS04-H,0,1K2S04-BeS04-H20,2 (NH,)2S04-BeS04-H,0.3 Double salts include3Na,S0,,BeS04, K2S0,,BeS04,2H20, BeS0,,(NH4),S0,,2H,0, andBeSO,,(NH,),SO,.Possibly the most interesting is the first, similarto the magnesium compound vanthoffite; the detection of this saltserves as an interesting link between beryllium and the otherelements of the second group of the Periodic Classification, the non-H.T.83 Q. Venturello, Gazzetta, 1939, 69, 73.84 Ctnnpt. rend., 1939, 209, 313.1 W. Schroder, J. Hahnrath, and E. Kehren, 2. anorg. Chem., 1938, 239,44; W. Schroder, ibid., p. 39; W. Schroder, H. Hompesch, and P. Mirbach,ibid., p. 225.8 W. Schroder, ibid., 1939, 241, 179; W. SchroderandH. Schwerdt, ibid.,1938, 240, 60.a W. Schroder and W. Kleese, ibid., p. 399TERREY : HETEROGENEOUS EQUIIJBRIA. 131isomorphism of beryllium salts with those of its congeners causingconsiderable difficulty in the early chemistry of beryllium.The use of bismuth nitrate as a wedge salt in rare-earth fkaction-ations makes a study of the system Bi,03-N,05-H,0 of importance.The early work of Rutter is fairly complete up to 20" and a numberof investigations have been carried out in regions where basic saltsare formed.J. Newton Friend and D. A. Hall have made a moreextended and thorough investigation of the domains of stabilityof the normal pentahydrate, and of the acid region, where experi-mental difficulties are unusually great. They are unable to agreewith Rutter that at the 65" quadruple point, the normal penta-hydrate is in equilibrium with the sesquihydrate, 2Bi(N03),,3H20,but infer that the second solid is an acid salt. The quintuple point,where basic, normal, and this acid salt are all in equilibrium, wasfound to be approximately 85".Although it was thought that theanhydrous normal nitrate might exist in this region, efforts toprepare it proved unavailing.and his co-workers have determined for a numberof temperatures between 0" and 100" the isotherms of the systemceric sulphate-ammonium sulphate-water. The earlier-reportedoctahydrate, Ce,(S04)3,(NH4),S0,,8H20, is always metastable withregard to the dihydrate, and the double salt, formerly reported asCe,(S0,),,5(NH4),S0,, is better represented as Ce,(S04),,4(NH,) ,SO4.In an attempt to obtain further light on the cobalt chloride colourchange, Bassett has investigated the systems : (a) CoCl,-CuCl,-H20, the solid phases being the simple salts CoCl,,GH,O andCuC1,,2H20 ; (b) CoCl,-CdCl,-H,O ; (c) NiC1,-CdC1,-H,O ;(d) NaCl-CdC12-H,0.In (b) and (c) the solid phases wereCo(Ni)CI,,GH,O, CdC1,,2-5H2O, CdC1,,H20 (metastable over mostof the range examined), 4CdC1,,Co(Ni)C1,,10H20,2CdCl,,Co (Ni)C12, 12H,O, 2CdC1, ,NiC1,,6H 20,3CdC1,,2NiC12,14H,0, and two series of solid solutions, representedby CdC12,2NiC1,,12H,0 and by (Cd,Ni)C1,,2.5H20. With cobalt,the first of these solid solutions could only be obtained in a meta-stable form by inoculation with the corresponding nickel salt.In (d) the solid phases were CdC1,,2-5H2O (metastable CdCl,,H,O),2NaC1,CdC1,,3H20, and 3NaC1,4CdC12, 14H20.Bassett has also considered the solid solutions formed in thesystems, NaCl-CdCl,-NiCl,-H,O and NaC1-CdC1,-CoC1,-H20, inorder to find why cobalt afforded the solid solution (Cd,Co)C1,,26H2O,W.SchroderTrans. Paraday SOC., 1938, 34, 777.2. anorg. Chern., 1938, 238, 209, 305.H. Bassett, J. H. Henshall, G. A. Sergeant, and R. H. Shipley, J., 1939,646; H. Bassett, J. H. Henshall, and G. A. Sergeant, ibid., p. 653132 INORGANIC CHEMISTRY.produced only when a little sodium chloride was present in thecadmium chloride used. It was found that sodium chloride couldenter isomorphously into these solid solutions until all the nickel andmost of the cobalt had been replaced. As the replacement proceedsthere is a steady decrease in the water content of the solids. Thisis held to support the view that the ion [%(H2O),1 can bereplaced by the ion [Na,(H,O),]", and that a compound such as2NaCl,CdC1,,3H20 is represented structurally by the formula[Na,(H20),]**[Cd,(H,0)2]*'**C16.It should be noted that the solidsolution (Cd,Ni)C1,,2-5H20 has a different crystalline habit from theordinary hydrate of cadmium chloride, and that CdC1,,2.5H20 isnot an end member of this series.In connection with cobalt halides, the systems L~C~-COC~,-H,O,~N~C~-COC~,-H,O,~ and NH,Br-CoBr,-H,O have been examinedover the temperature range 0-100". In the first, there are certaindivergencies from the results of Bassett and Sanderson; both theyand Benrath find three double salts, but Benrath prefers theformulae 4LiC1,CoCI2,1OH,O and 2LiC1,CoC1,,6H20 to7LiC1,2CoCI2, 18H ,Oand 3LiC1,2CoC1,,6H20, the other being LiC1,CoC1,,2H20. In thesecond system there are no double salts, and in the third only one,vix., CoBr,,2NH4Br,2H2O.Re-examination of the system Li,S04-A1,(S0,),-H,0 a t 0" shows lothat the solid phases are Li,SO,,H,O and A12(S04)3,nH20. Thevalue of n was not definitely decided but the earlier assumptionthat n = 18 is questioned.No evidence for the formation of adouble salt or solid solutions was obtained, and the temperatureof formation of the alum, reported by J. F. Spencer and (Miss) G. T.Oddie 11 to be formed when a solution of the mixed sulphates wascooled in ice and salt, must be below 0".A. E. Hill and J. H. Wills,12 from solubility measurements on thesystem Na,SO,-CaS0,-H,O over a wide temperature range, haveconfirmed the formation of the double salts Na,SO,,CaSO, and2Na,S04,CaS0,,2H,0, and shown that Na2S0,,5CaS0,,3H,0 isalso formed.With the somewhat analogous CaSe0,-(NH,),SeO,-H,O system l3 at 30°, the only solid phases obtained wereCaSeO,,ZH,O and (NH,),SeO,...7 A. Benrath, 2. anorg. Chem., 1938, 240, 87.8 A. Benrath and E. Neumann, {bid., p. 80.9 A. Benrath and B. Scheffers, ibid., p. 67.10 H. A. Horan and J. A. Skarulia, J . Amer. Chem. SOC., 1939, 61, 2689.11 Nature, 1936, 138, 169.12 J . Amer. Chem. SOC., 1938, 60, 1647.13 R. G. Welton and G. B. King, ibid., 1939, 61, 1851TERREY : HETEROGENEOUS EQUILIBRIA. 133In connection with double sulphates, mention may also be madeof the following systems : (1) NiS0,-MgS0,-H20 ;la equilibriumdata from 0" to 100" show that complete series of mixed crystalsof the heptahydrates, monoclinic hexahydrates, and monohydratesand, over a small range, tetragonal hexahydrates are formed.(2) N~SO,-COSO~-H~O;~~ over a range of 0-61" again a completeseries of four sets of mixed crystals is formed, 'uix., monoclinic andorthorhombic heptahydrates and monoclinic and quadratic hexa-hydrates.(3) ZnS0,-MgS0,-H,O (40" isotherm) ; only mixedcrystal formation was indicated. (4) CuS0,-Ni(Co)SO,-H20 17(40" isotherm) ; double salts not formed. (5) (NH,),SO,-H,SO,-H20 l8 (98.3' isotherm); here the solid phases found were3(NH4),SO4,H2SO,, NH,HSO,, and (NH,),SO,. (6) Zn( Mg)S04-H2S04-H20 (35" and 45" isotherms) ; in both cases with increasingsulphuric acid concentration, the hepta-, hexa-, and mono-hydrateswere successively obtained.(7) NiS0,-H2S04-H20 2O (isothermsover the range 0-80"); solid phases were hepta-, hexa- anddi- hydrates.In connection with (6), examination of the system MgS04-MgC12-H20 21 (25" and 35" isotherms) showed that the solid phases separ-ating were magnesium sulphate hepta-, hexa-, penta-, tetra-, andmono-hydrate. The rate of transformation of the metastablehydrates into the more stable forms was very slow, taking severaldays for completion even with vigorous stirring, and under naturalconditions the reactions are infinitely slow. This may explaintheir non-appearance in the work noted above.lgFour papers 22p 23 have been published on potassium chloride-chlorate-water or chlorate-sulphate-water systems.Double saltsare in general not formed, and it is a question of the mutual solu-bilities of the components and the determination of the optimumtemperature of evaporation of the solution for the best yield ofchlorate. When sodium is substituted for potassium in thel4 A. Benrath and E. Neumann, 2. anorg. Chem., 1939, 242, 70.1 5 R. Rohmer, Ann. Chim., 1939, 11, 611.16 N. K. Joshi and S. C. Devadatta, PTOC. Indian Acad. Sci., 1938, 7A, 138.1 7 T . S . Suratkar, S. M. Mehta, and M. Prasad, ibid., p. 393.18 N. V . Scheschken and E. D. Rochvalenske, J. Qen. Chem. Russia, 1938,l@ N. K. Joshi and S. C. Devadatta, Proc. Indian Acad. Sci., 1938,7A, 139.20 A. V. Babaeva and E. 0. Daniluschkina, Sci. Rep. Moscow State Univ.,e l V. G. Kuznetzov, Bull.Acad. Sci. U.R.S.S., 1937, 385.22 J. E. Ricci and N. S. Yareck, J. Amer. Chern. SOC., 1937, 59, 491; J.29 A. Linari, Ann. Chim. appl., 1939, 29, 189.8, 1125.1936, 49.Fleck, Bull. SOC. chim., 1937, 4, 558; M. B. Donald, J., 1937, 1325134 INORUANIO CHEMISTRY.chlorate-sulphate system, a double salt NaC103,3Na,S04 is formedat 25" and above, but it has only a short range of existence thoughcapable of existing in a metastable state over a considerable con-centration range. The mutual solubilities of sodium chloride andchlorate in aqueous solution a t the boiling point and under reducedpressure have also been recorded.23From an investigation of the system KNO,-HNO,-H,O24 ithas been shown that a compound KN03,2HN03, quite stable inthe presence of nitric acid, is formed. It dissociates at 100-120",yielding nitric acid of a purity of 994%.The difficulties en-countered in other methods of preparing pure nitric acid may makethis compound a very useful starting point.Over the temperature range 70" to - 22-4", solubility measure-ments have been obtained for the system H,O-NH4N03-(NH4),804.25 Three double salts, (NH,) ,S0,,3NH4N03,(NH4),S0,,2NH,N03, and (NH,) ,SO,,NK,NO,, have been isolatedand their domains of stability investigated.For the preparation of fluorine an exact knowledge of the alkalifluoridehydrofluoric acid systems is of importance. I. Tananaev 26has shown that the solid phases in the system KF-HF are KF,HFKF,2HF, KFy3HF, KF,4HF, and 2KF,5HF, and with the rubidiumsalt, E.B. R. Prideaux and K. R. Webb 27 have demonstrated theexistence of RbFy2HP and RbF,3HF and prepared the compoundRbF,3*5HF.At 25" the solid phases in the ternary system A1F3-HF-H20consist of AlF3,3H,0, A1F,,3HF,3H20, and AIF,,3HFJ6H,0. Theearlier-reported AlF3,HF,5M,0 could not be confirrned.*8The use of calcium arsenate as a spray makes the investigation ofthe CaO-As,O, system of importance. The 35" isotherm has beenstudied by G. W. Pearce and A. W. A v e n ~ , ~ ~ and confirmationobtained for CaHAsO,, C~,H,(ASO,)~, and Ca,(AsO,),, but no basicsalts seemed to exist at this temperature. For the 62" isotherm,0. A. Nelson and M. M. Haring 3* found CaHAsO,,Ca3(As0,),,2H20J and the basic salt 4CaO,As,O,,xH,O.Examination for the existence of lower hydrates by controlleddehydration must give in general a smaller number than areobtained from phase-rule studies The structures of the lowere4 V.I. Nikolaev, S. K. Cherkov, and A. G. Kogan, Kalii, 1935, No. 7, 23.26 V. A. Sokolov, Bull. Acud. Sci. U.R.S.S., 1938, 123.26 J. AppZ. Chem. .&SSia, 1938, 11, 214.2 7 J., 1939, 111.z 8 I. Tanmaev, J . Gen. Chem. Russia, 1938,8, 1120.29 J . A ~ w . Chem. SOC., 1937, 59, 1268.30 Ibid., p. 2216; cf. also H. Guerin, Compt. Tend., 1939, 208,1016.Ca5H,(As04),,5H,0EMEL~US : REACTIONS IN NON-AQUEOUS SOLUTIONS. 135hydrates are often of a different type, and it is not easily possible toconceive of any mechanism by means of which these can be builtup in the dehydration process. For instance, MnS04,4H,0 istransformed directly into the monohydrate by entrainment dis-tillation with liquids immiscible with water 31 or isothermaldehydration 32 with phosphoric oxide.Similarly, copper sulphatepentahydrate gives monohydrate only, and the schonitesM2S0,,MS04,6H20 give anhydrous residue only. In the rehydr-ation of magnesium sulphate, K. H. Ide34 has shown that onexposure the anhydrous salt goes fist to the hexa- and then to thehepta-hydrate, whereas the mono- goes directly to the hepta-hydrate.M. Delepine and P. Lebeau35 have shown that the known iso-morphism of the higher hydrates of the sulphates of the magnesiumseries extends to the lower hydrates. From determinations of theunit cells they have calculated the molecular volumes and haveshown that these increase in the order Ni < Co < Cu < Zn <(Fe, Mg) < Mn independently of the series of hydrates considered.The transition temperature of Na2S0,,7H,0 --+ Na2S0, hasbeen accurately determined by G.R. Washburn and W. J. Clem 36and found to be 23.465' 0.006"; this can be used as a secondarystandard in calibrating thermometers. M. P. Applebey and R. P.Cook 37 have found that in the case of LiC1,2H20 --+ LiCl,H,O ---+LiCl the most probable values are 16.1" & 0.05" and 93-55' &0.05" respectively, and A. E. Hil138 finds for the transition temper-ature CaS0,,2H20 --+ CaSO, + 2H20 a value of 42', which ' isabout 20" lower than van 't Hoff's value 63-5-66'.H. T.REACTIONS IN NON-AQUEOUS SOLUTIONS.The interest of chemists in reactions in non-aqueous solutions datesfrom the latter part of the last century, when a number of investig-ations were made on the solvent properties of liquid ammonia and on31 F.G. H. Tate and L. A. Warren, Trans. Faraday SOC., 1939,36, 1192.8a J. Perreu, Conzpt. rend., 1939, 209, 167, 311; cf., however, R. Rohmer,88 H. Holemann, 2. anorg. Chem., 1938, 239,257.24 Ibid., 1938, 235, 305.35 Ann. Chim., 1939, 11, 247.36 J. Anzer. Chem. SOC., 1938, 60, 754.37 J., 1938, 547.38 J . Arner. Chem. SOC., 1937, 59, 2242,ibid., p. 315136 INORGANIC CEEMISTRY.the reactions of some of the resultant so1utions.l The many strikingfeatures exhibited by such solutions were discovered independentlyby W. G. Cady, E. C.Franklin, and C. A. Kraus at the close of thecentury, and from the work of these three investigators there hassprung what has come to be known as the chemistry of the nitrogensystem of compounds. In this field it has been demonstrated thatthere is an astonishingly close parallel between reactions in liquidammonia and in water, and between numerous types of moleculederived from ammonia and water, respectively. Investigations onthe nitrogen system of compounds far exceed in number and com-pleteness those in any other allied field and a full account of suchwork has been published recently by 33. C. Franklin.3 These studiesare not, however, widely known, and for this reason a brief rksumk ofsome of the more important types of inorganic reaction in ammonia isgiven below.This also illustrates the analogy with reactions inwater and provides a basis for comparison with the other systemsdiscussed subsequently. Among such systems the most fullyinvestigated is that based on reactions in liquid sulphur dioxide.Among other inorganic liquids the solvent action of which has beenexamined are selenium oxychloride, carbonyl chloride, hydrogenfluoride, hydrogen sulphide, and hydrazine, and although investig-ations on reactions in these media are not in every case very recent,they are reviewed briefly below. It will be apparent that attentionhas for the most part been focused on inorganic reactions and thatlittle mention is made of the physicochemical properties of the solu-tions discussed.Liquid Ammonia.-A very large number of inorganic and organicsubstances are soluble in liquid ammonia.The alkali metalsnormally dissolve unchanged, though under special conditions theyare rapidly converted into the corresponding metal amides.Alkaline-earth metals are also soluble, but on evaporating thesolvent the residue is found to consist of an “ ammoniate ” of thetype M(NH,),. Metallic fluorides are insoluble or slightly soluble,chlorides are in some cases (e.g., NH,CI or BeCI,) very soluble ormoderately soluble, and bromides and iodides are for the most partmore soluble than chlorides. Other groups of soluble inorganicC f . Weyl, Pogg. Ann., 1863, 121, 601, 697; 1864, 123, 350; C. A. Seely,Chem. News, 1871, 23, 169; J . Franklin Inst., 1871, 91, 110; J.A. Joannis,Compt. rend., 1889, 109, 900; 1890, 110, 238; 1891, 112, 337, 392; 1891,113, 795; 1892,114,585; 1892,115, 820; 1893,116, 1370, 1518; 1894,118,713, 1149; 1894, 119, 357; G. Gore, Proc. Roy. Soc., 1872, 20, 441; 1873,21, 140; E. Divers, ibid., 1875, 21, 109; Phil. Trans., 1874, 163, 368.J . Physical Chem., 1897, 1, 707; Amer. Chem. J., 1898, 20, 820.“ The Nitrogen System of Compounds,” American Chemical SocietyMonograph Series, No. 68, 1935EMEL~US : REACTIONS IN NON-AQUEOUS SOLUTIONS. 137compounds are the nitrates, nitrites, thiocyanates, and certaincyanides, whereas the insoluble compounds include oxides, hydr-oxides, sulphates, sulphites, and the majority of sulphides, phos-phates, and arsenates.The foundation of present ideas on the chemistry of liquid-ammonia solutions is the ionisation of ammonia to give NH,' ions,which are the counterpart of OH' ions in water, and H' ions.Normally this ionisation is slight, and liquid ammonia has a verylow specific conductivity. If, however, an ammonium salt (e.g., thechloride) is dissolved in it, dissociation occurs with the production ofhydrogen ions and the resulting solution functions as an acid.Theparallel between such a solution and one of hydrogen chloride inwater is illustrated below :NH,Cl += NH; + C1'NH, + H'HCl + H20 + H,O' + C1'11H20 + H'11A solution of a metallic amide such as potassamide, which is freelysoluble in ammonia, acts as a base, since it contains free NH,' ions,and may be neutralised by an acid with formation of a salt andammonia.This may be illustrated by the interaction of ammoniasolutions of ammonium chloride and sodamide, which occursaccording to the equation NH,Cl + NaNH, = NaCl + 2NH,.The acidic nature of solutions of ammonium salts may be furtherdemonstrated by their ability to dissolve metals. For instance,ammonia solutions of ammonium nitrate will attack iron or steel, anda solution of ammonium azide will attack the metals lithium,potassium, sodium, calcium, and magnesium to form the metal azideand liberate hydr~gen.~ The analogy with the oxygen system ofcompounds has been extended to include metallic imides and nitrides,which behave towards acids of the type of ammonium chloride dis-solved in liquid ammonia in much the same way as do metallicoxides towards aqueous acids.Bismuth nitride, for example, is theanalogue of bismuth oxide, and when allowed to react with anammonia solution of ammonium iodide it dissolves, forming bismuthtri-iodide and ammonia.Numerous reactions have been studied which illustrate further theparallel with reactions in aqueous solutions. A solution of silvernitrate is soluble in liquid ammonia and will react in this solvent withpotassamide to form potassium nitrate and silver amide. Certaincurious reversals of the normal solubility relationships may also benoted. For example, calcium chloride is sparingly soluble in liquid4 A. W. Browne and A. E. Houlehan, J . Amer. Chem. Soc., 1911, 33, 1742138 INORGANIC CHEMISTRY.ammonia and is precipitated by mixing ammonia solutions ofsodium chloride and calcium nitrate.Again, the addition of anammonia solution of silver bromide to one of barium nitrate leads toprecipitation of the compound BaBr,,8NH3. Many other precipit-ation reactions, on the other hand, follow fairly closely the behaviourof aqueous solutions: to quote a case at random, a number ofmetallic sulphides have been precipitated from ammonia solution bythe addition of ammonium sulphide to a solution of the metallic salt.Among the sulphides so prepared are a few which are readily hydro-lysed by water.Solutions of metals in liquid ammonia present many interestingfeatures and have been fully studied. As already stated, the alkaliand alkaline-earth metals are soluble.The former are compar-atively stable and are converted rapidly into the correspondingamides only by the use of catalysts, among which are iron, platinum,and ferric oxide, or by exposure to light of wave-length 2150-2 5 5 0 ~ . ~ The reactions of solutions of these metals have beenreviewed recently by W. C. Fernelius and G. W. Watt.6 The metalsfunction in solution as powerful reducing agents and react with manymetallic halides, the &st stage consisting in all probability of areduction process, which is followed by the formation of a compoundof the two metals. Other inorganic reactions which have beenstudied include those with ammonium salts, non-metallic elements,and the oxides of carbon and nitrogen. The typical reactions givenin Table I are taken from the review by Fernelius and -Watt,6 whichgives many other inorganic and organic reactions and also contains acomprehensive bibliography .TABLE I.Typical Reactions of Liquid-arnnaonia Solutions of Metals.Substance.Metal. Product. Substance. Metal. Product.NH&l Ca CaC1, BiCl, Na NaBi,.,0 2SP K KP,,3?XH3HgAgCN !B" !::?ZnI, Na NaZn, NO2SnI, . Ca Ca,Snco K K(CO)zNaN,NO Na Na,N,O,NO Ba BaN,O,Ba BaNaO,Na NH,.CO,NaN a N,, NaOH, NaNH,,Mg (N3hNHaN3 2 Na,O, co2Ca CaS, CaS, N2oAmphoteric behaviour is exhibited by the amides of a number ofAmong these is zincamide, which dissolves in an ammonia metals.5 R. A. Ogg, P. A. Leighton, and F. ,W. Bergstrom, J . Arner. Chern. Soc.,1933, 55, 1754.Chem.'Reviews, 1937, 20, 195EMELfiUS : REACTIONS IN NON-AQUEOUS SOLUTIONS. 139solution of potassamide just as aluminium hydroxide dissolves inaqueous potassium hydroxide. This reaction may be represented asZn(NH2)2 -k 2 m 2 = K,[Zn(m,)41The ammonia in this compound is constitutional, just as is the waterin the aquozincate, K,[Zn(OH)4]. The two compounds differ,however, in that the ammonia compound is stable in the presence ofliquid ammonia. Lead imide, PbNH, will also dissolve in anammonia solution of potassamide, forming potassium ammono-plumbite. Potassium ammonomagnesiate is also known, and evenmore remarkable is the formation of potassium ammonosodiate,K,[Na(NH2)J, which results from the action of potassamide onsodamide in liquid ammonia solution.Basic salts also have their counterpart among these ammoniaderivatives, an excellent example of this being the substancePbNH21, which is formed from potassamide and lead iodide inammonia solution. Franklin describes a very large number of suchderivatives, and has also formulated those from mercury salts andammonia compounds on the same lines. The formula of infusiblewhite precipitate, HgNH,CI, for example, shows it to be a, compoundof this type, and certain allied substances are known as “mixedaquobasic ammonobasic mercuric salts ” (e.g., the chloride of Millon’sbase, OH*Hg*NH*HgCl).The amides of elements such as silicon, germanium, and tin behaveas acidic substances.Silicon tetrachloride undergoes a reactionwith liquid ammonia a t - 50°, and the product, Si(NH,)*, is theammonia analogue of orthosilicic acid.Certain esters of this acidhave also been obtained. The ortho-acid itself undergoes a thermaldegradation according to the scheme :00 looo 9000 Si(NH,), -+ NH-Si(NH,), + Nisi-NH, +12000 NH:(SiN), -> Si,N,The behaviour of germanium halides is rather similar, and the imide,Ge(NH),, has been prepared by several workers. W. C. Johnson andA. E. Sidwell,8 who obtained this imide in the pure state by thereaction of germanium tetraiodide with liquid ammonia, also formedits ethyl ester, Ge(NC,H,),, by acting on the iodide with ethylamine.Related compounds of tin have also been obtained; e.g., stannouschloride reacts with potassamide to form potassium ammono-s tannite .gSnC1, + SKNH, = SnNK + 2KC1+ ZNH,7 Op.cit., p. 75 et seq.8 J . Amer. Chem. SOC., 1933, 55, 1884.0 F. W. Rergstrom, J. Physical Chem., 1926, 30, 16140 INORGANIC CHEMISTRY.The present trend of experimental work in this interesting fieldappears to be in the direction of its physicochemical aspects. Heatsof dissolution and of reaction in liquid ammonia have been measured,and W. E. Larsen and H. Hunt lo have determined the activities ofammonium nitrate, chloride, bromide, and iodide a t 25". Quantit-ative measurements have also been made on the catalytic effect ofammonium salts in ammonia solution on the ammonolysis ofsantonin,ll ethyl malonate,12 and ethyl benzoate.13 In the last casethe catalytic effect of equivalent concentrations of the variousammonium salts is in the order :C6H,*COONH, > NH,Cl > NH,Br > NH,ClO,.Liquid XuZphur Dioxide.-Much of the pioneer work on solubilitiesin liquid sulphur dioxide was carried out by 9.Walden and M.Centnerszwer,l* but in the last few years the subject has been re-opened by Jander and his co-workers, and very striking analogieswith the behaviour of water and ammonia solutions have beenestablished. G. Jander and W. Ruppolt l5 have determined thesolubilities of about ninety compounds, most of which are inorganic,in liquid sulphur dioxide a t 0". Solubilities of the order of 0.2-2.0 g.per 100 C.C. were observed with sulphites of the alkali metals,ammonium and thallium, though other sulphites were insoluble.Thionyl derivatives were moderately soluble, as were certain metallichalides.Other metallic halides, thiocyanates, and acetates had lowsolubilities ( < 0.1 yo). The insoluble compounds included fluorides,chlorates, and sulphates, as well as barium and manganese sulphite.These authors point out that abnormally high solubilities in liquidsulphur dioxide (e.g., potassium iodide, 41.3 g. per 100 c.c.) areusually associated with the formation of addition compounds withthe solvent. Many of these have in fact been isolated, data for SLnumber being summarised in Table 11.The interpretation of solvate formation by liquid sulphur dioxide,and in particular the effect of ion weight and size on solvate stability,is fully discussed by Jander and H.Mesech.16 The same authors 17have carried out exhaustive measurements of the electrical con-ductivities of liquid sulphur dioxide solutions. Many of these10 J . Physical Chem., 1935, 39, 877.11 A. I. Schattenstein, Acta Physicochim. U.S.S.R., 1935, 3, 37; 1936, 5,12 C. Slobutsky rtnd L. F. Audrieth, Trans. IEZ. Acad. Sci., 1936, 29, 104;13 L. L. Fellinger and L. F. Audrieth, J . Amer. Chem. SOC., 1938, 60, 579.1 4 Ber., 1899, 32, 2862.15 2. physikal. Chem., 1937, A , 179, 43.841.Proc. Nat. Acad. Sci., 1937, 23, 611.Ibid., 1938-1939, A , 183, 121. l 7 Ibid., p. 255EMELEUS : REACTIONS IN NON-AQUEOUS SOLUTIONS. 141TABLE 11.Typical h'olvation Compounds formed in Liquid Sulphur Dioxide.No. of mols. Heat of formation Temp. for dissociationof so,.Formula. (kg.-cals./mol.). pressure of 760 mm.4 NaI,4SO , 9.63 5"Ba12,4S0 , 9.91 12.52 LiI, 2S02 9.40 -1NaI,2S02 10.01 15BaI,,2S02 11.34 49.51 LiI,SO, ~-AlCl,,SO, -K(SCN),SO, 9.9 1 12..;0.5 K(SCN) ,0.5S02 11.31 49Ca( SCN),,O*5SO , 10.74 31KI,4SO2 9.67 6;, 1ousolutions are good conductors.the common ions were found to be in the orderThe migration velocities of some ofSCN' < Br' < I' < ClO,' < C1'[N(CH,),]' < K' < NH,' < Rb'Jander and K. Wickert 18 postulated the following mode of ionisationof liquid sulphur dioxide, and from it has been developed a convincingtheory of reactions in this medium2s0, += (SO)" + (O*SO,)" =+ (SO)" + (SO,)"The parallel with the ionisation of water and liquid ammonia is atonce apparent, and on this basis it would be expected that thionylcompounds would be acidic in sulphur dioxide solution, and solut<~:;yielding the sulphite anion should behave as bases.This is borncout by the fact that thionyl compounds dissolve readily in sulphurdioxide, as do certain metallic sulphites, and solutions of these twotypes react with formation of a salt and sulphur dioxide. This pointis illustrated by the equationsCs,SO, + SOC1, = 2CsC1+ 2S0,CSOH + HC1= CsCl+ H20Comparable reactions of thionyl chloride with ammonium thio-cyanate and with silver acetate have yielded solutions containing thehitherto unknown compounds thionyl thiocyanate and thionylacetate.19Triethylamine has been shown to dissolve in liquid sulphurdioxide, forming a basic substance of the formula (I), which is(1.1 (*I-) (111.)I n Z.physikal. Chem., 1936, A, 178, 57.l 9 G. Jander and D. Ullmann, 2. anorg. Chem., 1937, 230, 405142 INORGAN0 CHEMISTRY.converted by potassium bromide into the bromide (11). Quinolinegives the related compound (III).2* Jander and his co-workershave used a similar mode of formulation for the two solid products,S02,NH3 (IV) and S0,,2NH3 (V), which are formed by the inter-w - 1 [H"N>s=o]so3 H N3 [%>s=o]o (V.1action of ammonia and sulphur dioxide. Formula (IV) is anaIogousto that of ammonium hydroxide, while (V) compares with that ofammonium oxide, (NH,),O. This basic character, which is implicitin these formulae, is borne out by the reactions of these substanceswith thionyl chloride in liquid sulphur dioxide solution, which takeplace according to the equations[(H3N)2SO]S03 + SOC1, = [(H3N),SO]C12 + 250,[(H3N)2SO]0 + SOC1, = [(H3N),SO]C12 + SO2Amphoteric behaviour has also been observed in reactions in liquidsulphur dioxide 21; e.g., aluminium sulphite may be precipitated bytetramethylammonium sulphite as shown in equation (i), but theprecipitate dissolves in excess of the precipitant (ii), while thesulphite may be reprecipitated by the addition of thionyl chloride (iii).2AlC13 + 3[Me4N],S0, = A12(SO3), + 6[Me4N]Cl .. (i)A12(S03), + 3[Me4N],S0, = 2[Me4N],{Al(SO3),) . . . (ii)2[Me4N],{Al(SO3),) + 3sOc1, = Al,(SO,), + G[Me,N]Cl+ 350, (iii)The experimental study of these reactions has been carried out bymeans of conductimetric titrations, and the same means may beemployed in investigating the oxidation of compound (I) by meansof iodine in sulphur dioxide solution.This reaction takes placeaccording to the equation12 2{[Et3N],SO)SO3 = {[Et3N]&O}SO, {[Et3NI2SO)I2 SO2A final exaHple of an oxidation reaction taking place in liquidsulphur dioxide is shown by the following equation, which has beenestablished analytically and by conductimetric titration :6KI + 3SbC1, = 2K3[SbCI,] f- SbC13 + 31,The complex formed in this reaction calls for no special comment, butits thionyl analogue, (SO),(SbC&),, which is formed by adding asolution of thionyl chloride in sulphur dioxide to antimony tri-chloride in the same solvent, is an interesting example of an acid inthe system of compounds derived from sulphur dioxide.10 G.Jrtnder, H. Knoll, and H. Tmmig, 2. anorg. Chem., 1937, 232, 229.21 G. Jander and H. Immig, ibid., 233,296EMEL~US : REACTIONS IN NON-AQUEOUS SOLUTIONS. 143Selenium Oqchloride .-Selenium oxychloride has a relatively lowspecific conductance (2-0 x mho a t 25°),22 and when electro-lysed gives chlorine at the anode. Its reactions with a large number ofsubstances have been studied by V. Lenher 23 and W. L. Ray.= Thegeneral behaviour is that of an acid chloride of oxidising character.A number of metallic chlorides (e.g., NaCl, KC1, NH,Cl, BaCI,, FeCl,)dissolve in it to form conducting solutions. The ionisation of thepure solvent has been postulated as taking place in the manner setout below,25 and is of special interest since it shows a similarity to theionisation believed to occur in liquid sulphur dioxide :2SeOC1, =+ (SeOCl*SeOCl,)* + C1'As Smith points out, the evidence for the mode of ionisation isindirect.Electrolysis of the pure liquids or of solutions of, say,potassium chloride yields chlorine at the anode. The cathodereaction is less certain, and the products in various cases haveincluded selenium monochloride and selenium dioxide. The actionof the oxychloride on metals 24 also accords with this general scheme,that on, e.g., copper being capable of representation as3Cu + 6SeOC1' == 3Cu" + Se2C1, + SeO, + 2SeOC1,~ C U " + 6C1' = 3CuC1,C. R. Wise 26 has shown that certain metallic chlorides form solvateswith selenium oxychloride.These include the alkali-metal chloridesand also the chlorides of silicon, titanium, tin, arsenic, and iron.The second group of compounds may be formulated as acids. Thusstannic chloride forms SnCl4,2SeOC1,, which may be written as(SeOC1) 2"( SnCh)", and with sulphur trioxide, which dissolves readilyin the oxychloride, the analogous compound is (SeOCl)(SO,Cl).Pyridine also forms a monosolvate, as does quinoline, and these twocompounds are given by Smith in accordance with the schemealready outlined as (C,H,N+ SeOC1)'Cl' and ( C9H,N+ Se0CI)'Cl'.In the experimental study of the above and similar compoundsuse has also been made of conductimetric titration results asevidence of compound formation.Carbonyl Chloride.-The solvent properties of liquid carbonylchloride are rather similar to those of selenium oxychloride, and maytherefore be briefly reviewed at this point.It is believed that22 A. P. Julien, J . Amer. Chem. SOC., 1925, 47, 1799.23 Ibid., 1921, 43, 29; 1922, 44, 1664.24 Ibid., 1923, 45, 2090.2 5 G . B. L. Smith, Chem. Reviews, 1938, 23, 165.2 6 J . Amer. Chem. SOC., 1923, 45, 1233144 INORGANIC CHEMISTRY.ioniaation of the pure solvent, which has a specific conductance ofonly 0.007 x takes place according to the scheme2COC1, =+ (cocl*cocl,)* + C1'COCI, + CO" + 2Cl'This solvent is able to dissolve anhydrous aluminium chloride, a non-conductor, and gives a conducting solution. The reaction has beenformulated by A.F. 0. German2' as : 2AlC13 + COCI, = COAI,CI, +CO" + Al,Cl,". Electrolysis of this solution actually yields carbonmonoxide at the cathode and chlorine a t the anode, and the solutionis capable of dissolving metals such as magnesium, calcium, potas-sium, and zinc, with liberation of carbon monoxide.28 The resultingsalts in carbonyl chloride solution are better conductors than thealuminium chloride solution itself. On electrolysis, the calcium salt,CaAl,Cls, deposits calcium initially at the cathode and yieldschlorine at the anode. This calcium compound therefore appears tobe a salt of the acid COAl2Cls. German2' points out that iodinetrichloride, arsenic trichloride, and the chlorides of antimony andsulphur, which are soluble in carbonyl chloride, might also yieldsolutions with acidic properties, but the matter has not been fullyinvestigated .Hydrogen Fluoride .-Anhydrous hydrogen fluoride is itself a poorconductor of electricity (specific conductivity 1 4 x mho), butis able to dissolve many inorganic and organic substances to yieldconducting solutions.29 According to H.FredenhagenY30 dissolu-tion in hydrogen fluoride may occur in one of four possible ways :(1) with normal dissociation into ions, as, e.g., when potassiumfluoride is dissolved; (2) with addition of HF to the solute, followedby dissociation into a complex cation and the fluoride ion ; (3) withreaction involving displacement of the acid radical of the solute byfluoride ion, and liberation of the free acid (e.g., KCN + HF =HCNt + K' + F'); (4) with reaction involving a more completechange in the solute (e.g., H,SO, + 2HF = HS0,F + H30' + F').Dissolution accompanied by simple dissociation of the solute wasuntil recently believed to be restricted to metallic fluoridesY31 butH.Fredenhagen 3O has now shown conclusively that other anions arealso stable. For instance, hydrogen chloride, bromide, and iodidehave a very low solubility in hydrogen fluoride, and free hydrogen27 J . Amer. Chem. SOC., 1925, 47, 2466.28 A. F. 0. German and K. Gagos, J . Physical Chem., 1924, 28, 965.2Q K. Fredenhagen, 8. Elektrochem., 1931, 37, 684; 8. anorg. Chem., 1933,210, 210; K. Fredenhagen and G. Cadenbach, 8. physikal. Chem., 1930, A,146, 245.30 2. anorg.Chem., 1939, 242, 23.31 Cf. K. Frodenhagen, 2. physikal. Chem., 1933, 164, 176EMEL~US : REACTIONS IN NON-AQUEOUS SOLUTIONS. 145halide is evolved when a metallic halide is dissolved; if, however,hydrogen chloride is bubbled through a solution of silver or thallousfluoride in hydrogen fluoride, silver or thallous chloride is precipit-ated. Supersaturated solutions of hydrogen chloride were alsoobtained by decomposing potassium chloride with hydrogen fluorideat -lo", and these give similar precipitates with the silver or thalloussalts. Alkali-metal iodates also dissolve unchanged at O", althoughchlorates and bromates undergo decomposition at this temperature.Alkali perchlorates were found to dissolve without decomposition,and a solution of potassium perchlorate in hydrogen fluoride wasshown to precipitate thallous perchlorate from a solution of thallousfluoride in the same solvent.Silver perchlorate could be precipit-ated in the same way, and alternative precipitating agents were :LiClO,, NaCIO,, NH,C10,, CsClO,, and Ba(ClO,),. Silver periodatewas also precipitated by potassium periodate, but permanganates,chromates, carbonates, and nitrites underwent complete decomposi-tion. Sodium sulphate, on the other hand, dissolved readily inhydrogen fluoride and was able to precipitate silver sulphate from asilver fluoride solution. It is evident, therefore, from the above ionicreactions that a limited number of ionic species can exist unchangedin this solvent.The second mode of dissolution in hydrogen fluoride, whichinvolves the formation of a complex cation, is observed mainly withorganic compounds (alcohols, aldehydes, ketones, ethers, acids, acidanhydrides, certain nitrogen compounds, and carbohydrates).Con-ducting solutions are obtained, and the nature of the ions is deducedfrom measurements of molecular conductivity and molecular elev-ation of boiling point. The nature of this ionisation is illustrated bythe following typical equations :CH3*C02H + HF = CH3*C02H,HF + [CH3*C02H*H]' + F'CH3*C02K + 2HF += K' + [CH,*CO,H*H]' + 2F'CH,*OH + HF(C2H5)20 + HFCHa*OH,HF + [CH,*OH*H]' + F'[(C2H5)2OoH]' + F'(CH,*CO),O + 2HF =+ [CH,*CO,H*H]' + F' + CH,*COFFredenhagen st>ates that with aliphatic alcohols there is no formationof alkyl fluoride and' water.He formulates these complex cations ascontaining an oxygen atom with a co-ordination number of three. Acomparable ionisation process occurs when nitric acid or an alkali-metal nitrate is dissolved in hydrogen fluoride, the ions producedbeing [HN03*H]' and F'. The case of carbohydrates is verysimilar.32 Thus the cellulose molecule breaks down when dissolved32 K:Fredenhagen and G. Cadenbach, Angew. Chem., 1933, 46, 113146 INORGANIC CHEMISTRY.and forms glucosyl fluoride, which then dissociates in the followingmanner :It should be added that certain organic compounds (e.g., thealkyl fluorides) dissolve in hydrogen fluoride but do not yield con-ducting solutions, others undergo decomposition or polymerisation,and a considerable number, among which are the hydrocarbons, arepractically insoluble.Other Solvent Systems.-Investigations of somewhat limited scopehave been carried out on reactions in various other solvents. Amongthese, hydrogen sulphide is specially noteworthy, as it should show aclose analogy with water. The specific conductivity of the pureliquid is very low (1.17 x 10-9 rnho).,, In its solvent action itresembles the typical organic solvents rather than water. Thesubstances which dissolve without reaction are mostly organic, apartfrom hydrogen chloride, hydrogen bromide, zinc chloride, and a fewsulphides.= The outstanding reaction which takes place with liquidhydrogen sulphide is the process of " thiohydrolysis," and this isobserved with chlorides of elements in the fourth, fifth, and sixthgroups of the Periodic Table. Carbon tetrachloride is miscible in allproportions with liquid hydrogen sulphide, but it does not react.Silicon tetrachloride is soluble, but again there is no reaction.Stannic chloride gives a slow reaction and stannic sulphide is formed,but other halides react more or less readily. The following list showsin parentheses the nature of the product in each case :34 TiCI,(ZTiCl,,H,S; TiCI, + S), PCI, (P,S3), PC1, (PSCl,), AsCI, (As,S,),SbCI, (SbSC1,7SbCI3), SbC& (SbSCI,), BiCI, (BiSC1,BiC13), SeC1,(SeC1,; Se,Cl,; Se + S), TeC1, (TeC1, + S; Te + S). It has alsobeen shown 35 that vanadium oxychloride when treated with liquidhydrogen sulphide forms the two compounds VSCS andVCI,(OH)(SH). There are in addition a number of organic reactionswhich occur in this s0lvent,3~ and among these the Grignard reactionis specially noteworthy. It is evident, however, that in general therange of reactions is very much more restricted than in the othersolvents discussed.Anhydrous hydrazine, as might be expected, has solvent proper-ties which are similar to those of liquid ammonia.,' The alkali33 F. A. Bickford and J. A. Wilkinson, Proc. Iowa Amd. Sci., 1933, 40, 89.34 J. A. Wilkinson, Chem. Reviews, 1931, 8, 237.36 H. F. Guest, Iowa State Coll. J . Sci., 1933, 8, 197.313 For bibliography, see ref. 34.3 7 T. W. B. Welsh and H. J. Broderson, J . Anzer. Chem. Xoc., 1915, 37,816EMEL~US : REACTIONS IN NON-AQUEOUS SOLUTIONS. 147metals are soluble, as are the alkali and alkaline-earth metal halides,cadmium halides, and a number of nitrates. Certain instances arerecorded in which a chemical reaction was observed, and it is notablethat dissolution of ammonium salts was accompanied by the evolu-tion of amonia. The same authors 37 examined a few reactions inthis solvent 38 and found that hydrazine sulphide precipitated thesulphides of zinc and cadmium from solutions of their halidea.Evidence was also obtained that zinc hydrazide, Zn(N2H3),, Waf3precipitated by sodium hydrazide from a zinc chloride solution,though the product was not analysed. The acidic nature of asolution of hydrazine hydrochloride in hydrazine is clearlydemonstrated by its reactions with sodium and with sodiumhydrazide :At this point, however, the investigation of this subject wasapparently discontinued, leaving a number of points which meritfurther investigation. H. J. E.H. J. EMEL~US.H. TERREY.38 J. Amer. Chern. Soc., 1916, 37, 825

ISSN:0365-6217    

DOI:10.1039/AR9393600116

出版商:RSC    

年代:1939

数据来源: RSC

摘要:

CRYSTALLOGRAPHY.1. INTRODUCTION.IT becomes increasingly difficult to define the scope of a modernarticle on crystallography. The old historical isolation of thesubject has, of course, long disappeared. Most of the recentinvestigations have as their immediate object the determinationof the precise spatial positions of atoms in a molecule or crystal,and if this can be carried out completely then the results form astarting point for. an accurate discussion of the structure in termsof modern theory. The same kind of information regarding positionsof atoms can frequently be obtained from gases and liquids byanalogous experimental methods, and it would obviously be amistake to relegate the discussion of such results to a separatearticle. Finally, in discussing the structure obtained by thesemethods a large variety of other data and experiments may have tobe mentioned.Considered in this wider aspect, the most outstanding contributionto the subject during the past year has undoubtedly been thepublication of “ The Nature of the Chemical Bond and the Structureof Molecules and Crystals ” by Linus Pau1ing.l The fundamentalpast played by crystallography and diffraction methods in generalin developing the ideas of modern structural chemistry is immediatelyapparent in this work. The theory of the chemical bond is developedin a lucid and straightforward manner, and questions relating tointeratomic distance and ionic sizes, and the factors which governthem, are dealt with very fully.The examples quoted to illustratethe various arguments cover an enormous range of experimentalwork. Another book dealing with crystal chemistry from anentirely different and more restricted aspect has also been publishedduring the year.2We have found it convenient to divide the present Report intothree sections, which follow roughly the classification adopted inprevious Reports.The first section deals with the more physicalaspects of crystallography. During the last few years a great dealof attention has been devoted to the difficult subject of vibrationalenergies in crystals and lattice energies generally, and, as little ofthis work has been previously reviewed in these Reports, a specialtreatment is now given from the therinodynamic point of view.1 Cornell University Press and Oxford University Press, 1939.2 K.C. Evans, “ Crystal Chemistry,” Cambridge University Press, 1939ROBERTSON : INTRODUCTION. 149The onset of molecular rotation and the structural changes whichaccompany thermal transitions in crystals are other aspects whichhave not been fully elucidated, and a review of this work is alsogiven.The remainder of the Report is devoted to a discussion of currentwork in structural chemistry and crystallography. In the past ithas been customary to describe the work in two sections under“ crystal chemistry ” and “ molecular structures.” Although thedistinction is a significant one, we feel it is not fundamental. Themolecules of closely related substances may combine to formindefinitely large polymers or remain as discrete units in the crystal,the distinction depending upon the relative sizes of atoms andstoicheiometric relations rather than upon abrupt changes in bondtype.Accordingly, we have preferred to adopt the convenientchemical classification into inorganic and organic structures. Thelatter are, of course, predominantly “ molecular ” structures.New determinations of simple inorganic structures are naturallynot so numerous as in the past, and most of the work concernsrelatively complex substances such as iron enneacarbonyl, Fe,(CO),,which has now been worked out with interesting results. Unusualco-ordination numbers have long been a matter of interest, andseveral new examples, such as in the ZrF,’ and TaF7z ions and inneodymium bromate enneahydrate, Nd(BrO,),,SH,O, have recentlybeen discovered, and the configurations of the resulting polyhedradetermined.So far no quanturn-mechanical treatment of suchcases has been made, although the 8-co-ordinated complex hasreceived some a t t e n t i ~ n . ~The application of X-ray and electron-diffraction methods to thestudy of organic compounds yields information about interatomicdistances and valency angles which is of fundamental importanceto any discussion of their structure. As the application of theresonance concept becomes more quantitative, the importance ofmore accurate data increases. The accuracy attainable even in thebest investigations, usually about &0-03 A., is insufficient for manypurposes, but if the distances can really be trusted to within theselimits a great deal of information regarding the electronic structureof the molecules can safely be deduced.Unfortunately, the accuracyof some of the earlier investigations now appears to have been over-estimated, and much revision has recently been in progress. Suchrefinement of known structures will undoubtedly become one of themore important, if less exciting, tasks for the future, particularlyas neither the electron-diffraction nor the X-ray method of analysishas yet been pushed to its limit of accuracy. For example,3 MT. G. Penney and J. S. Anderson, 7’ran.r. Faruduy SOC., 1937, 33, 1363160 CRYSTALLOGRAPHY.quantitative intensity measurements are still rare in X-ray work,and seldom, if ever, have all the measurable reflections beenutilised in deducing the details of a structure.During the year, and largely as the result of such revision, someoutstanding problems have been cleared up in connection withinteratomic distance and resonance in conjugated systems.Anomalous results obtained from acetylenic compounds have beendiscussed from different points of view, and more accurate data arenow available for a number of these compounds.New structure determinations of a detailed character have beencarried out for glycine, the cis- and the tram-form of azobenzene,and certain hydrocarbons.In simple compounds like trimethyl-amine oxide interatomic distances have been measured, and someconflicting values for the G-N distance await explanation.In-complete determinations and preliminary‘ accounts of a number ofother interesting structures are available, which must, however, bedeferred to a later Report. J. M. R.2. CRYSTAL PIIYSICS : THERMODYNAMICS AND STRUCTURE.The equilibrium locations of atoms and molecules in a crystalresult from an interplay between forces of attraction and repulsion,and various kinds of heat motion in the lattice. A discussion ofthese heat motions is thus an essential part of theories of crystalstructure. The increasing attention being paid to this subjectmakes it desirable to collect rather scattered information into aspecial section of these Reports.Peculiarities in the rate of attainment of equilibrium may restrictthe application of standard thermodynamic principles tocrystals,ll 2y 3 but when these restrictions can be neglected, theequilibrium structure is that which makes its free energy G4 aminimum.Since G = H - TS, at the absolute zero the equilibriumstructure is that with the minimum heat content Ho. When thegaseous state of the substance is chosen as reference state, fromwhich to measure changes in heat content, Ho is numerically thesame as the heat of sublimation at absolute zero, or lattice energy;the sign of Ho is, however, negative when the acquisitive conventionis followed, according to which heat absorbed by the substance isreckoned positive. At temperatures above the absolute zero, thecrystal structure may undergo continuous or discontinuous changes,so as to increase its heat content.These changes are accompaniedA. R. Ubbelohde, Proc. Roy. SOC., 1937, A, 159, 300.Idem, Tram. Paraday SOC., 1937, 33, 1198.A. Eucken, 2. Elektrochem., 1939, 45, 138, 145.,i “ Symbols for Thermodynamical Quantities,” J., 1938, 2193UBBELOHDE : CRYSTAL PHYSICS. 161by increases of the entropy 8, and the crystal must wait till aSufEciently high transition temperature T, has been reached to keepthe free-energy change AG = AH - T,AS zero. T , may refer toenantiotropic change, melting, or one of the processes discussedbelow. A systematic account of the thermodynamic properties ofcrystals would have to discuss the determination of lattice energies andof heat contents a t higher temperatures, and would have to include adescription of the various ways in which a crystal can increase itsentropy.In order to make this report fairly representative ofrecent work, only part of this programme will be dealt with.Lattice Energies.-In the absence of previous Reports, a recentarticle5 can be taken as datum line for measuring progress. Noentirely new method for the experimental determination of heatsof sublimation has been suggested, though an interesting correlationbetween the electron levels and lattice energy of metallic zincdeserves further theoretical and experimental investigation. Recentdeterminations based on vapour-pressure measurements include anumber of metals,’ polymethylene lattices 8 and alkali halide^.^When experimental difficulties prevent measurements over a,sufficient range of temperatures to give a reliable vapour-pressureequation, from which to calculate heats of sublimation, theoreticalcalculations of the entropy change on vaporisation can make even asingle measurement of some value.10 The lattice energy of alkaline-earth sulphides has been calculated from heat data and newmeasurements on the absorption spectra of the vapours.llA renewed discussion of measurements on the velocity ofvaporisation of carbon filaments l2 has been presented on the basisof spectroscopic determinations of the heat of dissociation of carbonmonoxide.By assuming that carbon atoms break three bonds andtwo bonds alternately on volatilising from graphite, the heat ofactivation determining the velocity of vaporisation (about 177 kg.-cals./mol.) has been shown to be in fair agreement with the spectro-scopic value for the sublimation process 139 l4Thermodynamic measurements show the lattice energy of theR.H. Fowler, “ Statistical Mechanics,” Cambridge, 1936.M. Sato, Sci. Rep. T6hoku Imp. Univ., 1937, 26, 341.F. Coleman and A. Egerton, Phil. Trans., 1935, 234, 177.A. R. Ubbelohde, Trans. Paraday SOC., 1938, 34, 282.W. Kangro and H. Wieking, 2. physikal. Chem., 1938, A, 183, 199.lo J. Mayer and I. Wintner, J . Chem. Physics, 1938, 6, 301.l1 L. S. Mathur, Proc. Roy. SOC., 1937, A, 162, 83.l2 A. L. Marshall and F. Norton, J . Amer. Chem. SOC., 1933, 55,431.l3 G. Herzberg, K. F. Herzfeld, and E. Teller,J. Physical Chem., 1937,41,325.l4 P. Goldfinger and W.Jeunehomme, Truns. FarMEay SOC., 1936, 32, 1591152 CRYSTALLOGRAPHY.ordinary form of diamond to be practically the same as that ofgraphite, though IIO spontaneous transition graphite -+ diamond isto be expected below about 20,000 atm.15~ 16 The lattice energy ofthe second form of diamond l7 has not yet been determined. I nview of the importance of the heat of atomisation of solid carbonin the calculation of bond energies from thermochemical data,l*further confirmation of the value 124 kg.-cals./g.-atom seemsdesirable.In theoretical calculat!ions of the lattice energy in terms of thecrystal structure, the various structures may be classified accordingto the predominant force of attraction; in decreasing order ofmagnitude, the attractions which lead to the ordering of moleculesin a crystal lattice are due to covalency, ionic and dipole effects,and to various types of molecular polarisation, of which the effectdue to the zero-point motion of the electrons (the so-called dispersioneffect) is the most widespread.lg, 2O Metals form ionic lattices inwhich special quantum-mechanical forces are operative, owing tothe small mass of the electron.21 Dipole effects in crystals contain-ing hydrogen may become unusually large owing to the formationof hydrogen bonds.22For ionic crystals, recent calculations of lattice energy in terms ofstructure have shown refinements in points of Fairlysuccessful calculations have been made for carbon di0xide,~4 andfor polymethylene lattices,25 in which dispersion forces predominate.Owing to the close approach of dipoles in crystals, these are besttreated as pairs of point charges in making the calculation.22p24Zero-point energy of crystal lattices.Although the lattice energy ismeasured at O"K., thermal vibrations and other heat motions,discussed below, affect the value of H , by their contribution ofzero-point energy. The average thermal energy of a quantisedoscillator of frequency v is 2 = hv/(ehv/kT - 1) + i h v , and thelarger tho zero-point energy contribution X i h v , the smaller theheat required for sublimation. For crystal lattices of the heavierl 5 F. D. Rossini and R. S. Jessup, J . Res. Nut. Bur. Stand., 1938,21,491.1 6 J. Basset, J . Phys. Radium, 1939, 10, 217.17 (Sir) R.Robertson, J. J. Fox, and A. E. Martin, Proc. Roy. SOC., 1936,A , 157, 579.Ann. Reports, 1931, 28, 375.19 F. London, Trans. Paraday SOC., 1937, 33, 8.20 H. Margenau, Rev. Mod. Physics, 1939, 11, 1.21 N. F. Mott and H. Jones, " Properties of Metals & Alloys," Oxford, 1936.22 E. Bauer and M. Magat, J. Phys. Radium, 1938, 9, 319; see, however,23 A. May, Physical Rev., 1938, 54, 629.24 H. Sponer and M. Bruch-Willstiitter, J . Chem. Physics, 1937, 5, 745.2 5 -4. Muller, Proc. Roy. Xoc., 1936, A , 154, 624.refs. (56) and (62)UBBELOHDE : CRYSTAL PHYSICS. 153inert gases,26 allowance for the zero-point energy only leads to acorrection term of a few units per cent. in the calculation of variousproperties of the lattice in terms of structure.For crystal latticesof less massive atoms, the zero-point energy may become comparablewith the total potential energy due to molecular attractions, as inthe case of solid H,, HD, and D,. The thermodynamic propertiesof such crystal lattices are quite abnormal.27, 28 In the case ofhelium, the forces of molecular attraction are about ten timessmaller than for hydrogen, and the zero-point energy of motionmakes any rigid crystal lattice impossible at ordinary pressures,even at 0" K. Only semi-empirical calculations of the remarkablethermodynamic properties of helium have been prop0sed.~~3 30Differences in the zero-point energy of hydrides and deuterideslead to differences in the heats of formation, which can be calculatedfrom dissociation-pressure curves, e.g., for alkali-metal hydride~.~~For NaD the heat of dissociation has been given as 15.8 kg.-cals.,for NaH 14-4 kg.-cals., for KD 14.5 kg.-cals., and for KH 14.2 kg.-cals.32 These differences are, however, subject to a large specific-heat c~rrection,~~ and until the specific heats have been determined,the results cannot be used for calculating the zero-point energy ofthe crystalline hydrides and deuterides in question.As the temperature of a crystalrises above O'K., it may acquire various forms of thermal energy,each of which is best considered separately.Thermal energy ofvibration is present in all crystals, and the vibrations of atoms andmolecules in a lattice can be studied from such phenomena as thespecific heat, the effect of temperature on the reflection of X-raysfrom crystals, thermal expansion, and infra-red and Ramanspectra.When the crystal can be treated as a set of harmonic oscillatorsof various frequencies vl, v2 .. ., in all 3N per g.-atom, the totalthermal energy of vibration isVibrational energy in crystals.where the summations extend over all the frequencies. In practiceit would be impossible to evaluate all the 3N natural frequencies2 6 J . Corner, Trans. Paraday Soc., 1939, 35, 711.27 H. D. Megew, Phil. Mag., 1939, [vii], 28, 129.28 M. E. Hobbs, J . Chem. Physics, 1939, 7, 318.29 F . London, Proc. Roy. Soc., 1936, A, 153, 576.so Idem, J . Physical Chem., 1939, 43, 49.31 E. Sollers and J. Crenshaw, J . Amer. Chem. Soc., 1937, 59, 2015, 3724.32 L.Heckspill end A. Borocco, Bull. SOC. chim., 1939, 6, 91.33 A. R. Ubbelohde, Trans. Faraday SOC., 1936, 32, 526154 CRYSTALLOGRAPHY,separately, and some assumption has to be made as to theirdistribution in a vibrational spectrum, in order to calculate E,,.A well-known method, proposed by Debye, is to replace thevibrational spectrum of actual crystal lattices by that of a continuum,for which the distribution of frequencies in the spectrum is known;the thermal energy of vibration is calculated to bewhere 0 = hvH/k, and the vibrational spectrum of the continuumis broken off at the maximum frequency vu, to correspond with thefact that crystal lattices have a maximum frequency of thermalvibration, whose wave-length is twice the lattice spacing.Thespecific heat corresponding to the thermal vibrations is simplyC, = dEv/dT.Debye's expression has the striking property of representing thevibrational energy of crystals in terms of a single parameter8 determined by the crystal structure. The assumption that thelattice vibrations of a real crystal may be replaced by those of acontinuum has been criticised 6, on the grounds that the velocityof sound waves in a crystal lattice is not constant, as assumed for acontinuum, but falls off with rising frequency. Furthermore, theactual distribution of vibrational frequencies favours certain regionsof the spectrum, instead of being smooth, so that formulae for thevibrational energy should contain more than one 8 parameter.These parameters have not yet been calculated in terms of thecrystal structure.The Debye expression for the vibrational energy gives a specificheat at constant volume which tends to the constant Dulong andPetit value 3R when 5" > 0.35 The anharmonicity of latticevibrations in crystals should, however, lead to a falling off in C,below the Dulong and Petit value, at still higher temperatures.Thisbehaviour is observed for ionic lattices such as sodium chloride andpotassium chloride and bromide, but not for metals such as copperand lead, for which C, increases above 3R.36 A still more strikingincrease in C, has been observed in the case of solid potas~ium,~7and appears to be due either to the free electrons in the metal,which may make an appreciable contribution to the specific heat at84 M.Blackman, Proc. Roy. SOC., 1935, A, 148, 365, 384; A, 149, 117;96 Landolt-Bornstein, " Physikal. Chem. Tabellen," 6th Edn., 1927,36 G. Damkohler, Ann. Phyaik, 1935, [v], 24, 1.87 L. G. Carpenter and C. J. Steward, Phil. Mag., 1939, [vii], 27, 561.1938, A, 164,62.Erg. I, 705UBBELOHDE : CRYSTAL PHYSICS. 155high temperatures, or to the break UP of the lattice as the meltingpoint is approached.Some progress has been made in calculating the specific heat ofcomplex crystals such as sulphur, carbon dioxide, and ammoniumchloride, in terms of experimentally observed Raman frequencies.38 39Molecular models have been constructed to represent latticevibrations in simple cases.4oIntensity of X-Ray ReJlections.-The chief disadvantage of specific-heat measurements in throwing light on the lattice vibrations is thevery fact that they can be expressed as a function of one or at themost a few 8 parameters.In principle, much more direct informationis obtainable from the intensity of X-ray reflections. Subject tocertain restrictions, the intensity of reflection I T from any crystalplane is related to the intensity I , at 0" K. by the equation IT ='lo e-2Jf where 211 = 2n22/a2 and 2 is the mean square displace-ment of the atoms normal to the reflecting plane whose spacingis u.In simple crystal lattices the amplitudes of the heat motions,measured by the values of (c2)4, can be correlated with a Debyevibrational spectrum, and from the values obtained for M acharacteristic temperature 0 can be calculated for the lattice, usingthe Debye-Waller formulawhere x = B/T, #(x) is the Debye function, and rn is the mass of theatoms.Recent determinations include the characteristic temper-ature of magnesium oxide41,42 and of magnesium, zinc, and45 The Debye-Waller formula does not alwaysgive satisfactory results,46y 4 7 3 48 however, and a major advantage ofthe X-ray measurements is that they give a direct measurement ofthe amplitude of atomic vibrations, independent of assumptions38 S. Sirkar and J. Gupta, Indian J . Physics, 1938, 12, 145.38 S. Bhagavantam and T. Venkatarayuda, Proc. Indian Acctd. Sci., 1938,40 V. Deitz and D. H. Andrews, J . Franklin Inst., 1935, 219, 459, 565,dl G.W. Brindley and P. Ridley, Proc. Physical SOC., 1939, 51, 69.42 H. S. Ribner and E. 0. Wollan, Physical Rev., 1938, 53, 972.43 G. W. Brindley and P. Ridley, Proc. Physical SOC., 1938, 50, 757.44 Idem, ibid., 1939, 51, 73.45 E. 0. Wollan and G. Harvey, Physical Rev., 1937, 51, 1054.4e E. A. Owen and R. Williams, Nature, 1938, 142, 915.4 7 A. H. Compton and S. Allison, " X-Rays in Theory and Experiment,"48 M. Blackman, Proc. Carnb. Phil. SOC., 1937, 33, 380.A , 8, 115.703.Macmillan, 1935, p. 435256 CRYSTALLOURAPHY .about the vibrational spectrum. cf. 49 The amplitudes of typicalatomic vibrations may be illustrated by the results for cadmium :Temp., I(. c Axis. Basal plane.86' 0.100 0.067293 0.182 0.118Amplitude of atomic vibrations, in A.The thermal vibrations of crystal lattices also affect the intensityof diffuse scattering of X-rays,5o and the reflection of cathode rays.61A formal analogy between the amplitudes of heat motions, and thedisplacement of atoms from equilibrium positions in the lattice,due to various forms of cold working, has been used in correlatingthe excess lattice energy of pyrophoric and " active " preparationsof certain crystals with observed X-ray intensity changes.52Thermal Expansion.-The normal thermal expansion of crystalsis due to the fact that the characteristic frequency v y changeswhen the volume of the crystal changes. If one writes y =- d log vM/d log V , the coefficient of thermal expansion a is given bya = y xo CVlVOwhere xo is the compressibility and Vo the volume at 0" K.Asimple derivation of this expression has been given by Mott andJones (op. cit., p. 15). A more general derivation has been givenby H. Jones,53 who points out that an expression formally similar tothe above is obtained for the thermal expansion, whenever theentropy of the solid can be expressed as a function of the temperature,and a single crystal parameter such as vM. The original should beconsulted for details, which are important in explaining anomalousthermal expansions such as those of nickel 54 and the invar alloys,55and also negative values of thermal expansion, such as are observedfor helium-I1 53 and a-silver Measurements of thermalexpansion are important in the knowledge of crystal structures, ingiving information about the anharmonicity of lattice vibrationsin various directions in the lattice.56 A number of recently devisedX-ray cameras for use at high temperatures may be mentioned in4Q C.Mauguin and J. Laval, Compt. rend., 1939, 208, 1446, 1512.50 G. E. M. Jsuncey and E. McNatt, Physical Rev., 1939, 55,498.51 D. Coster and P. Van Zanten, Physica, 1939, 6, 17.52 R. Fricke and E. Gwinner, 2. physikal. Chem., 1938, A , 183, 165, 177.53 Proc. Camb. Phil. Soc., 1938, 34, 253.54 E. A. Owen and E. Yates, Phil. Mag., 1936, [vii], 21, 809.5 5 Idem, Proc. Physical SOC., 1937, 49, 17, 178, 307 et seq.55a E. Cohen'and H. L. BredBe, Proc. K . Akad. Wetensch. Amsterdam,5 6 J. Monteath Robertson and A. R. Ubbelohde, Proc. Roy. SOC., 1939, A,1936, 39, 358.170, 222UBBELOHDE CRYSTAL PHYSICS.157this c~nnection.~’ Some of the recent experimental work relatingexpansion to structure has been summarised by H. D. mega^.^*Isotope EfSects.-In the case of crystals containing hydrogen, theeffect of lattice vibrations and other thermal motions of the moleculeson crystal structure can be investigated by a comparison with thecorresponding deuterium compounds.33 When the hydrogen isbound by metallic or ionic forces, a contraction of the lattice isnormally expected on substituting deuterium, since the zero-pointenergy is smaller for deuterium compounds, and has an effect similarto that of the thermal energy in leading to lattice expansion. Whenthe hydrogen is bound by covalency to specific atoms, the effectivemolecular radius should also be lessened.This can lead to largerheats of absorption of deuterium oxide than of water in salthydrates. 59 The smaller molecular radius in deuterium compoundsalso h a a marked effect on the transition temperature in variouslattice transformations,6l the change being usually in the samesense as that due to an increase in pressure on the crystal. Finally,when the hydrogen forms “hydrogen bonds” in the crystal, thesubstitution of deuterium leads to a lattice expan~ion.~~, 62 Thishas been interpreted as indicating the importance of special resonanceforces in hydrogen bonds.Other Sources of Thermal Energy in Crystals.-Many crystals haveother sources of thermal energy, in addition to the lattice vibrations.Uncertainties in the calculation of C, from the experimentallyobserved Cp and in using the Debye expression for the vibrationalspecific heat, make it difficult to detect other sources of energywhen their contribution to the specific heat is small.Small non-vibrational specific-heat contributions can, however, be observedat very low temperatures in certain metals, and are probably dueto the thermal energy of the free electrons.63 : and see 36, 37Many crystals are known, however, in which certain changes ofstructure are accompanied by considerable increases in heat contentand entropy. In enantiotropic transformations, or in melting, thechange in structure may take place isothermally, and the heatabsorbed at the transition temperature is called a latent heat.s 7 W.Hume-Rothery and P. Reynolds, Proc. Roy. SOC., 1938, A , 167, 25;F. Schossbarger, 2. Krist., 1938, 98, 259; A. R. Ubbelohde, J. Sci. Instr.,1939, 16, 155.5e 2. Krist., 1938, 100, 68.5B J. Bell, J., 1937, 459; but see ref. (60).6o F. Miles and A. Menzies, J . Amer. Chem. SOC., 1938, 60, 87.61 K. Clusius, 2. Elektrochem., 1938, 44, 30.62 A. R. Ubbelohde and (Miss) I. Woodward, Nature, 1939, 144, 632.s3 W. H. Keesom, Physikal. Z., 1934, 35,939; W. H. Keesom and C. Clark,Physica, 1935, 2, 513158 CRYSTALLOGRAPHY.When the transformation takes place over a range of temperatures,the heat intake is added to the normal increase in vibrational energywith rise in temperature, so that the observed specifh heat isanomalously large.In nearly all cases the specific heat " anomaly "rises sharply to a maximum, and then decreases again even moresteeply till normal values are reached. A typical example isprovided by the specific heat of crystalline methane,74 for which thecurve over a short range of temperature is given in Fig. 1.Recent work relating structural changes in crystals with latentheats and specific-heat anomalies has been too intensive to permita report covering all the various kinds of transformation in any oneyear. The order-disorder effect was the subject of a recent report,64Absohte temperature.FIG. 1.Thermal transformation in crystalline methane.and the present account will be limited to the phenomena whicharise from the onset of molecular rotation in crystals.The possibility that moleculesrotate in crystals was first suggested from a comparison of thethermodynamic properties of ortho- and para-hydrogen.sh Ortho-hydrogen rotates even in the lowest quantum state, and since it haspractically the same latent heat of fusion and evaporation as para-hydrogen, it must continue to rotate in the crystal lattice in order topreserve this equality.It was suggested by Pauling that in anumber of other crystals the molecules might oscillate aboutequilibrium orientations at low temperatures, and rotate freely athigher temperature^.^^ The following table indicates how commonMolecular rotation in crystals.Ann. Reports, 1936, 32, 185.6b K. Clusius and K. Hiller, 2. physikal.Chem., 1929, B, 4, 166.e6 L. Pauling, Physical Rev., 1930, 36, 430UBBELOHDE : CRYSTAL PHYSICS. 159this phenomenon may be even in lattices of comparatively simplemolecules.Sfhermnl Transformations in Simple Molecular Crystals.I11 _3 11. I1 --+ I. I + Liquid.P -- Molecule. T,. Range. AS. T,. Range. AS. T,,,. AS.0 2 66 ......... 23.7" s 0.9 43.7' 2.0 4.0 54.3" 2.0N, 8 7 ......... - - - 35.4 s 1.5 63.1 2.7 co 6 8 ......... - - - 61-5 s 2-5 68.1 2.9HCl 69 ......... - - - 98.4 s 2.9 158.9 3.0HBr 70 ...... 89.0 3.0 0.7 {ti: 2'5 1.5 ::;} 186.2 3.1HI 71 ......... 70.0 5-0 0.3 125 5.0 1.5 222.3 3.1H2S 72 ......... 103.6 0.8 3.5 126-2 3 0.9 187.6 3.0D2S 73 ......... 107.8 0.5 3.7 132.8 s 0.9 187.1 3.0CH, 74 ......... - - - 20.5 3.0 0.8 90.6 2.5CH3D 75 ...... 15.5 2.0 0.9 22.6 3.0 1.7 90.6 2.4CD4 76 .........21.4 1.5 0.9 26.3 4.0 2.2 89.2 2.4SiH, 7 7 ...... - I - 63.5 2.0 2.3 88.5 1.8CF, 78 ......... - - - 76.3 8 4.6 84.5 2.0CCl, 7s ...... - - - 222.5 s 4.8 250.3 2.3CBr, 80 ...... I - - 320 8 3.6 365.5 -From this table it will be observed that many molecular crystalshave one or even two thermal transformations below the meltingpoint. The range of temperatures over which the change takes placeis indicated in each case. The letter s indicates that the transform-ation is isothermal, and is accompanied by the intake of latent6 6 K. Clusius, Z.physika1. Chem., 1929, B, 3,41.6 7 W. F. Giauque and J. Claydon, J . Amer. Chem. SOC., 1933, 55, 4879;68 W. F. Giauque and R. Wiebe, J .Arner. Chem. SOC., 1928,50, 101, 2193;8g G. Hettner, E. Hettner, andR. Pohlmann, ibid., 1938,108,45.70 Cf. ref. (68) ; also G. Damkohler, Ann. Physik, 1938, [v], 31,76 ; J. Zunino,2. Physik, 1936, 100, 335.W. F. Giauque and R. Wiebe, J . Amer. Chem. SOC., 1929, 51, 1441;C. P. Smyth and C. Hitchcock, ibid., 1933, 55, 1830.72 K. Clusius and A. Franck, 2. physikal. Chem., 1936, B, 34,420; A. Kruisand K. Clusius, ibid., 1937, B, 38, 156; C. P. Hitchcock and C. P. Smyth, J .Amer. Chem. SOC., 1934, 56, 1084; E. JustiandH. Nitka, Physikal. Z., 1937,38, 514.M. Ruhernann, 2. Physik, 1932, 76, 368.F. Simon and C1. v. Simson, 2. Physik, 1924, 21, 168.73 A. Kruis and K. Clusius, 2. physikal. Chem., 1937, B, 38, 156.'* K. Clusius and A. Perliak, ibid., 1934, B, 24, 313; A.Schallamach,Proc. Roy. SOC., 1939, A, 171, 669; W. Heuse, Z . physikal. Chem., 1930, A ,147, 282.7 5 K. Clusius, Physica, 1937, 4, 1105.7 6 E. Bartolomh, G. Drikos, and A. Eucken, 2. physikal. Chem., 1938,7 7 K. Clusius, ibid., 1933, B, 23, 213.7 8 A. Eucken and E. Schroder, ibid., 1938, B, 41,307.79 R. C. Lord and E. Blanchard, J. Chem. Physics, 1936,4, 707.8o C. Finbak and 0. Hassel, 2. physikal. Chem., 1931, B, 30,301.B, 39,371160 CRYSTALLOGRAPHY.heat, where= a finite temperature range indicates a specific-heatanomaly. The entropy change corresponding with each transform-ation is of the same order of magnitude as the entropy change onmelting, which is given on the right of the table in cals./mol./degree.In the case of specific-heat anomalies the figures for the entropychanges are only approximate, and the value of T, indicates thetemperature a t which the additional specific heat reaches amaximum.Similar anomalies associated with rotational transitions havebeen reported for H2Se and D,Se, PH,, ASH,, CH,*OH, CH,*NH,,BF,, SF,, a number of paraffins, cyclohexane and its derivatives,hexamethylbenzene, NH4F, NH4Cl, ND4C1, NH,(C,H,,)Cl, NH,Br,RbNO,, AgN0,,81 NaCN,82 perchlorates and flu~borates,~, KH,PO,,KH,As04, Rochelle pentaerythrit~l,~~ camphene derivatives,s6pentade~ane,~' hexachloroethane, 88 and have been looked for inother crystals without success.89 The above list is not necessarilyexhaustive.The factors which determine whether a thermal transformationwill be associated with a latent heat, or with a specific-heat anomaly,have not yet been fully elucidated. For example, the case ofhydrogen bromide, which has three successive transformations withspecific-heat anomalies, below its melting point, may be contrastedwith hydrogen chloride, which has only one transformation takingplace sharply at 98.4" K.The justification for Pauhg's suggestionthat these entropy increases in the crystal are associated with theonset of molecular rotation in the lattice is based on the followingargument : The onset of rotation in quantised rotators is a gradualprocess when these are in the gaseous state, but in the crystal theclose packing leads to preferred orientations of the molecules, and aresultant potential barrier preventing free rotation of the moleculesat low temperatures.The thermal energy required for the f i s tfew molecules to rotate freely may be quite large, but in rotating theylessen the restraining field on their neighbours, with the result thatthe number of molecules rotating increases " autocatalytically " asND4Br7 m41, (NH4)zSO4, (ND4)2SO4, (NH4)3PO4, NaNO3, m O 3 ,*l A. Eucken, 2. Elektrochem., 1939, 45, 126.83 H. J. Verweel and J. Bijvoet, 2. Krist., 1938, 100, 201.83 C. Finbak and 0. Hassel, 2. physikal. Chem., 1936, B, 32, 130, 433.84 P. Schemer, 2. Elektrochm., 1939, 45, 171 ; W. Bantle and P. Scherrer,86 I. Nitta and K. WatanabB, Bull. Chem. SOC. Japan, 1938,13,28.8 6 W . A. Yager and S . 0. Morgan, J .Amer. Chem. SOC., 1935,67,2071.13' A. R. Ubbelohde, Trans. Faraday SOC., 1938, 34, 289.s 8 C. Finbak, Chern. Abs., 1938, 32, 1996.69 C. P. Smyth, Chem. Reviews, 1936, 19, 329.Nature, 1939, 143, 980UBBELOHDE : CRYSTAL PHYSICS. 161the temperature rises. Quantitative expression has been given tothis idea, without yet reaching very detailed agreement withe~periment.~~ An experimental test has also been carried out bydiluting the lattice of methane with argon or krypton atoms.g1As the number of inert-gas atoms in solid solution increases, themutual restraints between neighbouring molecules of methane rapidlydiminish, and for quite small percentages of krypton the specific-heat curve of solid methane no longer shows a sharp anomaly. AfterO l I 1 I75 O 20 25"Abso/ute temperature.FIG.2.Thermal transformation in mixed crystals of methane f krypton.certain adjustments, the intake of rotational heat in the methane-krypton crystals corresponds with that calculated for gaseousmethane.The specific-heat curves for crystals with increasing amounts ofkrypton (Fig. 2) should be compared with the curve for pure methane(Fig. l), which is plotted on a smaller scale. Addition of kryptonextends the range of the anomaly, decreases its maximum contribu-R. H. Fowler, Proc. Roy. SOC., 1935, A , 149, 1 ; A , 151, 1 ; T. S. Chang,Proc. Camb. Phil. SOC., 1937, 33, 524.91 A. Eucken and H. Veith, 2. physikal. Chem., 1938, B, 38, 393.REP.-VOL. XXXVI. 162 CRYSTALLOGRAPHY.tion to the specific heat, and shifts the maximum to lowertemperatures.In addition to specific-heat determinations, other physical measure-ments have been made on the crystals, in order to elucidate thenature of the structural change accompanying the entropy increaseduring a transformation.When the molecules in the crystal carrypermanent dipoles, important information is obtained fiom meamre-ments of the dielectric constant, and the dielectric loss, by usingelectric oscillations of Merent frequencies, and maintaining thecrystals at different temperatures [cf. refs.66-88 and especially 89].Permanent dipoles cannot contribute appreciably to the dielectricconstant so long as the molecules are constrained to perform harmonicoscillations about equilibrium positions, but aa soon as themolecules are free to rotate, a large increase in dielectric constant isobserved.This increase could, however, also be interpreted byassuming two or more equilibrium orientations for the dipoles inthe lattice, with different energies.The assumption that the molecules are not rotating freely, buthave increased possibilities for alternative orientation above thetransition temperature, has certain advantages in explaining theimportant phenominon of dielectric loss, i.e., the fact that energyis dissipated in the solid when acted on by an alternating electricfield.92 It may also help to explain the striking fact that the meresubstitution of deuterium for hydrogen in methane gives rise totwo thermal transitions in place of one, though here an alternativeexplanation assumes separate rotation about the different molecularaxes a t different temperatures.*l Methane only gives indicationsof the I11 +- I1 transition a t higher pressures.Other investigations on the structural changes accompanyingthermal transitions have used X-rays (e.g.,66-80, 821 839 93).Whenthe change in structure is small, a more sensitive method is to usethe polarising microscope (e.g., for the hydrogen halides).94 In thecase of ammonium chloride a change of structure below the transitiontemperature is only indicated by the fact that the crystals becomepiezoelectric .95Th&rrwdynumic CEassiJication of Rotational Transformations inCrystah-When the structural change and heat intake whichaccompany a thermal transformation in a crystal take place sharplyat one temperature, the equilibrium between the two crystal formsS2 A.H. White, J . Chem. Physics, 1939,7,58; R. W. Sillars, Proc. Roy. SOC.,1938, A , 169, 661; R. Guillien, Compt. rend., 1939, 208, 980, 1561; J. H.Bruce, Trans. Faraday SOC., 1939, 35, 706.e3 C. Finbak, Physihl. Z., 1939, 40, 26.94 A. Kruis and R. Kaischew, 8. physikal. Chem., 1938, B, 41,427.s5 S. Bahrs end J. Engl, 2. PhysS, 1937, 105,470UBBELOHDE : URYSTAL PHYSICS. 163follows the ordinary thermodynamic rules, with respect to changesof temperature and pressure. When the structural change and heatintake take place over a range of temperatures, the latent heat isreplaced by a specific-heat anomaly, and the discontinuous volumechange by abnormal coefficients of thermal expansion along thevarious crystal axes.The adaptation of formal thermodynamics tosuch transformations of the second and third order, as these gradualchanges are called, has given rise to much interesting discus~ion.~~This has not yet thrown much fresh light on crystal structure, andreference should be made to the originals for details.A thermodynamic problem of more immediate importance fortheories of crystal structure is the origin of hysteresis. Whenhysteresis is present, the state of apparent equilibrium of thecrystal is different according as the temperature is raised or loweredthrough the transition range. The existence of hysteresis has beenvariously ascribed to mechanical strain,l and to the existence ofdomains or a mosaic structure subdividing the crystalbut some of the difficulties attending a solution are indicated bythe fact that the substitution of deuterium for hydrogen lessens oreven suppresses hysteresis in transformations such as those ofresorcinol97 and ammonium chloride.9*Rotation and Melting.-The reason why a crystal melts, in spiteof the increase in heat content, is that melting is accompanied by alarge increase in entropy, due to the increase in freedom of motionin the liquid.A quantitative measure of this increase of freedomis the ratio W,l W, in the expression O9 Ah', = R log, Wl/WJ. Thisentropy increase has various contributing factors, the discussion ofwhich must be deferred to a later Report owing to the large volumeof work on the subject.It can be stated here, however, that inlattices with a rotational transformation below the melting point,the entropy increase on melting will be smaller than in comparablelattices without such a transformation. It has been suggested 100that this fact may help to explain some of the relations betweenmelting and the structure of molecular lattices. A. R. U.96 E. Justi and M. v. Laue, PhysiEaZ. Z., 1934, 35, 945; A. J. Rutgers andS. Wouthuysen, Physica, 1937, 4, 235, 515; N. F. Woerman and G. Muller,Physikal. Z., 1937, 38, 298; F. C. Frank and K. Wirtz, Naturwiss., 1938, 26,688, 697.9 7 J. Monteath Robertson and A. R. Ubbelohde, Proc. Roy. SOC., 1938, A,167, 136.9s A. Smits, G. Muller, and F.Kroger, 2. physikal. Chem., 1937, By 38,177.99 J. W. H. Oldham and A. R. Ubbelohde, Trans. F a r a d a y Soc., 1939, 35,332.1 W. 0. Baker and C. Smyth, J. Amer. Chem. Soc., 1939, 61, 1695164 CRYSTALLOGRAPHY.3. ~NOXGANIC STRUCTURES.Most of the structure determinations during the year have beenconcerned with complex compounds involving, in certain cases,unusual co-ordination, although a number of interesting investig-ations have also been made on some relatively simple compounds.Of the elements, scandium is one of the last of the metals to bennalysed; it exists in two allotropic modifications with cubicclosest -packed and hexagonal closest-packed arrangements. In theformer the twelve nearest neighbours are a t a distance of 3.205 A .,in the latter six are a t a distance of 3.30 A. and six at 3.23 A.Scandium thus fits in satisfactorily with its neighbours in thePeriodic Table. X-Ray diffraction patterns of liquid yellowphosphorus indicate that there are three permanent nearestneighbours at a distance of 2.25 A. from a given atom, this arrange-ment being in accord with the assignment of P, molecules. Thisdistance of 2.25 A. does not change with temperature, as is observedin the case of some other liquid elements where there is no suchrigid molecular aggregation. The symmetrical shape of the peakat 2.25 A. in the atomic distribution curve suggests that all thephosphorus atoms are equivalent, this equivalence giving the P,molecule in liquid yellow phosphorus the same tetrahedral sym-metry as was found for P, vapour by electron diffra~tion.~ TheP-P distance reported in the latter case was 2.21 A.The second" co-ordination sphere " corresponding to the nearest averageapproach of phosphorus atoms not in the same molecules occursa t about 3.9 A. in liquid yellow phosphorus. The atomic dis-tribution curves for amorphous red and amorphous black phosphorusalso indicate three nearest neighbours due to the covalent bondingof P atoms, the P-P distances being respectively 2.29 A. and 2.27 A.The high melting points of these substances, however, would suggestthat here there are no simple P, molecules, as in liquid yellowphosphorus, and it is possible that in these cases there is a puckerednetwork somewhat similar to that found in crystalline blackphosphorus .4there From the scattering of X-rays by liquid sulphur a t 128"1 K.Meisel, Naturwiss., 1939, 2'4, 230.C. D. Thomas and N. S . Gingrich, J . Chem. Physics, 1938, 6, 659. Forreport on the structure of liquids and amorphous solids, see J. J. Randall,Ann. Reports, 1937, 34, 169.L. R. Maxwell, S. B. Hendricks, and V. M. Moseley, J. Chem. Physics,1935, 3, 699.* R. Hultgren, N. S. Gingrich, and B. E. Warren, ibid., p. 351; Ann.Reports, 1935, 32, 157.N. S . Gingrich, Bull. Amer. Physical Soc., 1938, 13, 9HAMPSON : INORGANIC STRUCTURES. 166appear to be two nearest neighbours at a distance of 2.05 A. (cf.S-S = 2.12 A. in crystalline rhombic sulphur 6).X-Ray powder photographs of solid (HF),, at 91" cry show thatthe crystal is built up of infinite zigzag chains of FH-FH-FHmolecules, the F-H-F distance being approximately 2 .7 ~ . and theFH-FH-FH angle approximately 134". The same type of structurehas been observed in the gas phase from electron-diffraction measure-ments, the gas consisting of zig-zag polymers of comparativelylow molecular weight (trimers, tetramers, and pentamers) withlinear 3'-H-F = 2.55 A. and the F angle = 140" -J= 5". The photo-graphs rule out the suggested hexagonal polymer of compositionCyanogen iodide9 forms a lattice of separate molecules and notan ionic lattice; an exact determination of t,he positions of thecarbon and nitrogen atoms could not be made owing to the largescattering power of the iodine atom, but a linear structure with thedistances., I-C = 2.03 A.and C=N = 1.18 a. is compatible withthe observed intensities. The linear trihalide IC1,- ion is confirmedin tetramethylammonium dichloroiodide,1° the I-C1 distance(2.34 A.) being equal to the sum of the covalent radii.Of the oxides, Rb,O has the anti-fluorite structure, the distancebetween the Rb + and the four surrounding 0- - ions being 2.92 A.,whereas Cs,O has an anti-CdC1, layer structure with a Cs' to 0- -separation of 2.91 A . ~ ~ The so-called tetroxides RbO, and CsO,have been shown to contain the superoxide 0,- ion as inK0,.12A number of nitrides which have been investigated during theyear indicate once asgain the tendency in these compounds for themetal atoms to take up a closest-packed arrangement with thesmall nitrogen atoms occupying the interstices of the lattice.(HF)S.*B.E. Warren and J. J. Burwell, J . Chem. Physics, 1935, 3, 6.P. Gunther, K. Holm, and H. Strunz, 8. physikal. Chem., 1939, B, 43,S. H. Bauer, J. Y . Beech, and J. H. Simons, J . Amer. Chem. Soc., 1939.J. A. A. Ketelaar and J. W. Zmartsenberg, Rec. Trao. chim., 1939, 58,lo (Miss) R. C. I;. Mooney, 8. Krist., 1939, 100, 519; cf. ibid., 1938, 98, 324.l1 A. Helms and W. Klemm, 8. anorg. Chem., 1939, 242, 33.l a Idem, ibid., 1939, 241, 97; cf. Ann. Reports, 1936, 33, 194, 210;L. Pauling, " The Nature of the Chemical Bond," p. 252.* A careful redetermination of the F-H-F distance in crystalline KHF, hasgiven the value 2.26 f 0.01 A. (L. Helmholz and M.T. Rogers, J . Amer. Chem.SOC., 1939, 61, 2590). This is 0.29 A. shorter than the value reported forgaseous (HF), and suggests that in ths latter case the F-H-F bond is weakenedby the formation of additional hydrogen bonds.229.61, 19.448166 CRYSTAILOQRAPHY.Cu,N l3 has the three copper atoms along the edges of a cube withnitrogen atoms (1.90 A. from six copper atoms) at the cube corners.TiN l4 has the rock-salt cubic closest-packed arrangement, the Ti-Ndistance being 2.11 A., but GaN and InN l3 have the wurtzitestructure (Ga-N = 1-96 A., In-N = 2.12 A.), the axial ratios beingalmost exactly those required for hexagonal closest-packing.Ge3N4,l5 on the other hand, has a phenacite (Be,SiO,) structure,each germanium being surrounded tetrahedrally by four nitrogenatoms, three tetrahedra having one nitrogen atom in common.In the body-ceotred cubic thorium phosphide, Th3P4,16 there is asimilar sharing of tetrahedra, these being so disposed that eachthorium atom is surrounded by eight phosphorus atoms at a distanceof 2.98 A., the nearest P-P distance being 3.20 A.Some evidencehas also been obtained of a sub-phosphide ThP having the sodiumchloride structure .Of the more complex structures which have been determinedduring the past year, both by electron and X-ray diffraction, asurprisingly large number have been found to involve odd co-ordination numbers such as 5, 7, and 9, and also an increasinglylarge number of compounds have been shown to exhibit some'' randomness " in their crystal structure.17 MoC15,18 PF5,19Ip5,I9 and Fe(CO),20 have been investigated in the vapour phaseby the method of electron diffraction and all have a trigonal bi-pyramidal configuration ; the same arrangement also occurs incrystalline trimethylstibine dihalides Me,SbX2.21 This thereforewould appear to be the natural configuration for covalent com-pounds of the type AB, irrespective of the number of unsharedelectrons on the central atom (cf.the case where the valency groupdoes not exceed an octet and where the unshared electrons them-selves then appear to have definite stereochemical requirements).Chromium hexachloride,18 and chromium, molybdenum, andtungsten hexacarbonyls 22 have the expected regular octahedralstructure, but iron and cobalt carbonyl hydrides 23 are tetrahedral1s R.Juza and H. Hahn, 2. anorg. Chem., 1938,239,282.l4 A. Brager, Acta Phwicochim. U.R.S.S.. 1939, 10, 593.15 R. Juza and H. Hahn, Naturwiss., 1939, 27, 32.16 K. Meisel, 2. anorg. Chern., 1939, 240, 300.1 7 Cf. Ann. Reports, 1938, 35, 174.R. V. G. Ewens and W. M. Lister, Trans. Paraday Soc., 1938,34, 1358.19 H. Braune and P. Pinnow, 2. physikal. Chem., 1937, B, 35, 239.20 R. V. G. Ewens and W. M. Lister, Trans. Faraohy Soc., 1939, 35, 681.31 A. F. Wells, 2. Krist., 1938, 99, 367.32 L. 0. Brockway, R. V. G. Ewens, and W. M. Lister, Trans. Faraduy Xoc.,98 R. V. G. Ewens and W. M. Lister, ibid., 1939, 36, 681.1938, 34, 1350EAMPSON : MORGANIC STRUCTURES. 167and so should be formulated as Fe(CO),(COH), and Co(CO),(COH),and not as Fe(CO),H, or Co(CO),H with hydrogen atoms linkeddirectly to the metal at0m.~4 On this view the relationship betweenthe carbonyls, the nitrosyl carbonyls, and the carbonyl hydridesbecomes quite clear.In all these compounds the bonds to thecentral metal atom are shorter than the sums of the single-bondcovalent radii and this has been interpreted in terms of single-bond-double-bond resonance, though it now seems probable thatother factors besides the multiplicity of the bond are involved indetermining bond lengths.25Ill0(1.)0.>FIG. 3.The crystal structure of iron enneacarbonyl, Fe,(CO),, has beendetermined by H. M. Powell and R. V. G. Ewens26 with a veryinteresting and unexpected result.In order to give each ironatom the effective atomic number (E.A.N.) of the next inert gas,krypton, N. V. Sidgwick and R. W. Bailey2' suggested the con-stitution (I) (Fig. 3) for this compound with a co-ordination numberof five about the iron atoms as in Fe(CO),. Powell and Ewens,however, find that the iron atoms are not joined together in thisway, the molecule having a horizontal plane of symmetry. Threecarbonyl groups are co-ordinated to each iron atom in the usual24 Cf. W. Hieber and H. Schulten, 2. anwg. Chem., 1937, 232, 29.25 W. M. Lister and L. E. Sutton, Trans. Faraday Soc., 1939, 35, 495;G. C. Hampson and A. J. Stosick, J . Awr. Chem. SOC., 1938, 60, 1814.a* J., 1939, 286.27 Proc. Roy. Soc., 1934, A, 144, 521168 CRYSTALLOGRAPHY.way Fe+CzO, but the remaining three carbonyl groups arenot co-ordinated CZO groups but are bonded (through the carbon)to both of the iron atoms by ordinary single bonds, and so have astructure similar to that in ketones.The difference between thetwo sets of these groups is shown by the carbon-oxygen distances;in the C Z O groups this is 1.15 A., and in the >C=O groups itis 1.3 A. The structure is represented diagramatically in (11)(Fig. 3). If the only bonds to each iron atom are the six Fe-Cbonds, the iron atoms will have an E.A.N. of 35 with an odd elec-tron on each. It seems extremely improbable that such an arrange-ment should hold when, by the pairing of these odd electrons, theiron atoms could attain the E.A.N. of 36, the same as that ofkrypton.The observed diamagnetism of the substance shows thatthe spins of the odd electrons are opposed, and this, together withthe extremely short Fe-Fe distance of 2-46 A. (roughly twice thecovalent radius of iron), strongly suggests that the two iron atomsare linked by a covalent bond. Each iron atom therefore probablyforms seven bonds, six with carbon atoms and one with the otheriron atom. Exactly the same kind of co-ordination polyhedronhas been found for the A-modification of lanthana and other rare-earth sesquioxides 28 in which each rare-earth ion is surrounded byseven oxygen ions, and also for the ZrF7= ion in ammonium andpotassium heptafl~ozirconate.~~ 0. Hassel and H. Mark's sug-gestion 30 that (NH,),ZrF, is built up of NH,+ ions, [ZrFJ ions, andF- ions, has been shown to be incorrect, both the ammonium andthe potassium compound containing the complex ion ZrF,= in whichzirconium has the co-ordination number seven.The structure ofthe crystals is similar to that of the. face-centred cubic (NH,),A1F6,but with the AIF6= octahedra replaced by ZrF,-. The seventhfluorine atom is introduced along one of the cubic three-fold axes,the configuration of the resulting complex being that of an octa-hedron distorted by spreading one face and inserting the seventhatom at its centre, as shown in Figs. 4 and 5 . Each of the sevenZr-F distances is equal to 2.1 A., the most regular distributionof fluorine atoms about the zirconium atom giving a minimumF-F separation of 2.64 A.(only slightly less than twice the ionicradius of fluorine, 2.72 A.) and an F-Zr-F angle of 77" 50'. Theorientation of these ZrF,= complexes is not uniquely determined,however, but shows some randomness, permitting the crystals toassume higher point -group and space-group symmetry than wouldbe possible otherwise. A similar phenomenon occurs with some2 8 L. Pauling, 2. Krist., 1929, 69, 415.29 G. C. Hampson and L. Pauling, J . Amer. Chem. SOC., 1938, 60, 2702.2. Physik, 1924, 27, 89HAMPSON : INORGANIC STRUCTURES. 169ferricyanides of the type M,[Fe(CN),],, (M = Cd, Mn, Zn, Co, Cu,or Ni).31 Here again the crystals have a Laue holohedral face-centred cubic unit of structure, and as with the heptafluozirconatesthis symmetry is incompatible with the number of atoms whichhave to be arranged in the cell.The only solution is to have twoof the metallic cations distributed randomly over more than twopositions, these being the 32 positions on the octant diagonalsFIa. 4.Fra. 5.The ZrF,z complex viewed along its three-fold axis.tetrahedrally arranged about the octant centres. This rathercurious fact that a small number of atoms are distributed statistic-ally over a large number of positions has been observed before,e.g., in silver iodide.32 These salts have the anion-cation skeletontypical of perovskites and the complex cyanides of the Prussian-blue series,33 the Fe+++, M++, and (CN)- ions forming a skeleton3 1 A. K. van Bever, Rec. Trav. chirn., 1938, 57, 1259.32 L. W.Strock, 2. physikal. Chem., 1934, B, 25, 441; L. Helmholz, J .Chem. Physics, 1935, 3, 742; see also Ann. Reports, 1935, 32, 188; 1938,35, 174. 33 Ibid., 1934, 31, 213170 CRYSTALLOGRAPHY.of cubes (which are octants of the unit cell) with the (CN) groupsalong the edges of the cubes and the metal ions a t the corners. Avarying number of water molecules appear to occupy the holes inthe octant centres randomly.A different type of AB, polyhedron occurs in potassium hepta-fluoniobate, K2NbF7, and potassium heptafluotantalate, K,TaF, .34These crystals have monoclinic (pseudo-orthorhombic) symmetry,unlike the heptafluozirconates which are cubic. The NbF,= andTaF,’ groups, which are clearly shown to exist as discretecomplexes within the structure, have the configuration as shownin Fig.6. This can be visualised as being derived from an MP,group in the form of a trigonal prism by the addition of a seventhfluorine atom through the centre of one square face, followed by theappropriate distortion. The Nb-P (or Ta-F) distances lie betweenFIU. 6.1.94 A. and 2-01 A., and the thirteen shortest F-F distances withinthe anion lie between 2.41 A. and 2.98 A., with an average of 263 A.The adjacent fluorine atoms therefore approach closer within thesecomplexes than they do within the ZrF7= complex, the values in-dicating a considerable degree of interpenetration of the closedvalency shells.Fig. 6 possesses the symmetry C,, - mm, vix., a two-fold axisin which two mutually perpendicular mirror planes intersect, andso is quite different from ZrF7- which has the symmetry C3, - 3m.Considering the complexes as being built up of metal ions andfluorine ions, there seems to be little to choose between the twomodels, since for a given M-F separation the repulsions betweenthe fluorines should be about the same; similarly, if the complexesare considered as covalently bound, it is impossible to make aJ.L. Hoard, J. Amer. Chem. Soc., 1939, 61, 1252HAMPSON : INORGANIC STRUCTURES. 171choice in the absence of any quantum-mechanical treatment of7-co-ordinated covalent complexes. In view of the differencewhich has been observed, however, it would be interesting to knowwhether the configuration of the TaF,- complex was that of anoctahedron or a trigonal prism.It is surprising that no workappears to have been published on the structure of compoundscontaining the group AB,, such as TaP,= or the very stable ions[MO(CN),] --- and [Mo(CN),] ----.* Again, no theoretical pre-diction has been made regarding the disposition of eight covalentbonds from a central atom, though if the bonds are ionic the moststable co-ordination polyhedron should be a twisted cube ” orArchimedean a n t i p r i ~ m . ~ ~Other compounds which have been reported to exhibit randomnessin their structure are potassium and caesium fluorochromate 36 andneodymium bromate enneah~drate.~’ The first two are isomorphousand of the scheelite (CaWO,) type, an oxygen atom being replacedby a fluorine atom which is almost equal in size (cf.potassium osmi-amate K,OSO,N).~~ In the caesium compound the parameters ofthe oxygen and fluorine atoms could not be determined accuratelyowing to the large scattering power of the cmium atom, but inKCr0,F the [CrO,P]- group is almost a regular tetrahedron aboutthe chromium atom with a Cr-0 (or Cr-F) distance of 1-58 A. Asto the way in which a fluorine atom replaces an oxygen atom, i.e.,whether it is a completely random orientation of Cr0,F groups ora macrostructure of regions of lower individual symmetry, remainshere, as in most other cases of random structures, very uncertain.When the replacement involves such a small change in shape andsize as in [CrO,F]- the randomness is probably complete; in thecase of [ZrF,]=, on the other hand, the crystal is probably builtup of different orientations of small regions of lower symmetry,these regions being of smaller dimensions than those giving coherentX-ray scattering.36 L.Pauling, J . Amer. Chem. SOC., 1939, 61, 361.38 J. A. A. Ketelaar and (Frl.) E. Wegerif, Rec. Traw. chim., 1938, 57,37 L. Helmholz, J . Amer. Chem. Soc., 1939, 61, 1544.38 F. M. Jaeger and J. E. Zanstra, Rec. Traw. chim., 1932, 51, 1013.* Since going to press a paper has appeared in which the structure ofK4Mo(CN),,2H,O has been described (J. L. Hoard and H. H. Nordsieck,J . Amer. Chem. SOC., 1939, 61, 2853). The codguration of the MO(CN), - - - -group is shown to be that neither of a cube nor of an Archimedean antiprismbut of a duodecahedron with triangular faces and eight vertices, havingapproximately the symmetry Da.For a given Mo-CfN distance, therepulsion between adjacent CN groups in this polyhedron is very nearlythe same as that in the antiprism and coneiderably less than that in thecube.1269; 1939, 58, 948172 CRYSTALLOGRAPHY.In neodymium bromate enneahydrate Nd(BrO,),,SH,O, theneodymium ions are surrounded by nine water molecules, six atthe corners of a trigonal prism a t a distance 2.47 0.05 A. andthree out from the prism faces a t a distance 2.51 & 0.05 A. (Fig. 7).These distances are somewhat larger than the sum of the ionic radii(approximately 2.35 A.) obtained from the structure of Nd,0,,39the increase being ascribed partly to an increase in the co-ordinationnumber and partly to a difference in the character of the bond.These hydrated ions are packed on top of one another to formx --P-FIG. 8.vertical strings of Nd(H,O), groups in relatively close contact,columns of Br0,- ions fitting into the holes enclosed by six suchstrings.The arrangement is revealed in the Fourier projectionshown in Fig. 8. The water molecules of the [Nd(H,O),]+++ groupare probably linked to the oxygen atoms of the bromate ions byhydrogen bonds, the 0-H-0 separation being 2-77 0.10 A.There is some choice in the way in which the bromate ions canorient themselves, and though a pyroelectric experiment shows thec-axis to be polar, indicating that they are all oriented in onedirection, this does not agree with the observed intensities, whichcan only be explained by assuming a certain amount of random-ness.The dimensions of the Br0,- ion could not be determinedvery accurately, although the reported Br-0 distance, 1.74 & 0.07 A.,agrees with the value 1-78 A. found in sodium b r ~ r n a t e . ~ ~39 L. Pauling, 2. Krist., 1930, 75, 128.(Miss) J. E. Hamilton, ibid., 1938, 100, 104HAMPSON : INORGANIC STRUCTURES. 173An interesting new type of ABX, structure has been found inthe case of ammonium cadmium chloride NH,CdCl, 417 42 andrubidium cadmium chloride RbCdC1,.42 Cadmium is known t oexhibit octahedral co-ordination in cadmium chloride (CdCl, octa-hedra, each corner being common to three octahedra), and tetra-hedral co-ordination in the compounds K,Cd(CN),, CdS, CdSe,and CdTe, hence [CdCl,], might be expected to be built up ofCdC1, octahedra, with shared corners as in perovsbite, or of CdC1,tetrahedra with two shared corners as in the metasilicates.Actually,FIG. 9.the structures are found to be built up of CdCl, octahedra, butinstead of sharing corners they share edges to form infinite double" rutile " strings as shown in Fig. 9. Each octahedron shares twoopposite edges AB and CD to form strings of octahedra parallelto the c-axis as in rutile, and these rutile strings are then furthercondensed in pairs, each octahedron sharing two edges AE and CEwith octahedra of the adjacent string. Hence of the six chlorineatoms in each CdCI, octahedron, three of them (A, C , and E) arecommon to three octahedra, two of them (B and D) are common*l H.BrasseurctndL. Pauling, J. Amer. Chem. SOC., 1938, 60, 2886.4 2 C. H. MacGillavry, H. Nijveld, S. Dierdorp, and J. Karsten, Rec. Trav.chim., 1939, 58, 193174 CRYSTaLLOGRaPHY.to two octahedra, and P belongs to only one ootahedron. Theoctahedra themselves are very nearly regular, the average Cd-Cldistance (2.65 A.) being the same (2.66 A.) as that found in CdCl,.Each ammonium or rubidium ion is surrounded by nine chlorineatoms, the co-ordination polyhedron being of the form shown inPig. 7; the average NH,-Cl distance, 3.31 A., is very nearly thesame as that found in ammonium chloride. The structure of thesecompounds is therefore intermediate in type between that ofperovskite, in which the cation is 12-co-ordinated, and thatof ilmenite, in which the cation is 6-co-ordinated, this being inaccordance with the radius ratios.Similar columns of " rutile octahedra " occur in K,HgCl,,H,O *3and in K,SnC1,,H,0,44 but in these cases the columns are notcondensed together in pairs.In the latter compound E. G. Cox,A. J. Shorter, and W. Wardlaw45 proposed a planar configurationfor the SnCl,= ion, from the presence of a centre of symmetry, thoughit now appears probable that the SnC1, groups are derived fromSnC1, octahedra sharing two opposite edges.The planar configuration ( d q 2 hybridisation) of 4-covalentauric compounds is now well established, but an interesting andunexpected result has recently been obtained for 4-covalent aurouscorn pound^.^^ The compounds investigated were potassium 2 : 2'-dipyridyl aurous cyanide K[Au(CN) zdipy], and potassium 4 : 5(0)-phenanthroline aurous cyanide K[Au( CN) ,phenan]. That thesecompounds really involve 4-covalent gold and not 2-covalent gold,as [Kdipy][Au(CN),], is shown by the fact that an ammoniumderivative NH,[Au(CN),phenan] can readily be prepared in whichthe co-ordinating group must be associated withthe gold atom, the nitrogen of the NH, group alreadyhaving its maximum covalency.One of the unitand this must mean that the complex is either planarCN The gold atom in these corn-plexes has an E.A.N. 86, the same as that of radon,and a planar rather than a tetrahedral distribution of valenciesseems very surprising.A planar oonfiguration for the hydrated ion [Mn,4H20]++ inK2Mn(S0,),,4Hz0 has also been reported,,' with a Mn-0 separationof 2.40 A.loo, 212.cell dimensions in each case is very small (3.74a.)>A!.< cn or very nearly so.G.C. H.4s C. H. MWGillavry, J. H. D e Wilde, and J. M. Bijvoet, 2. KriSt., 1938,44 H. Brassem and A. de Rassenfosse, Nature, 1939, 143, 332.46 Ibid., 1937, 139, 71 ; Ann. Reports, 1938, 35, 162, 185.46 H. J. Dothie, F. J. Llewellyn, W. Wardlaw, and A. J. E. Welch, J.,4' H. Anspach, 2. Krbt., 1939,101, 39. 1939, 426ROBERTSON : ORGANIC STRUCTURES. 1754. ORGANIC STRUCTURES.Interatomic Distance and Resonance in Conjugated Systerns.-Thefundamental assumption in this work is that the internucleardistance between two atoms depends only upon the type of bondbetween them, and not, for example, on some invariant radiusapplying to all the bonds formed by the atom.A pure single G-Cbond should then have a constant length of about 1-54 A. irrespectiveof its surroundings, and deviations below this value will indicateresonance with multiple-bonded structures.That the situation is not really as simple as this may be inferredfrom results previously noted in these Rep0rts.l The methyl-group bond length is an important reference value in this con-nection, because it might be expected to remain a typical singlebond in all circumstances. Yet deviations from the 1-54 valuehad been noted in a number of compounds, and some of these caseshave now been revised and clarified. The present situation may besummarised : in hexamethylbenzene an accurate redeterminationof the structure by X-ray methods2 gives a methyl-group bondlength of 1-53 5 0.02 A.in agreement with electron-difFractionmeas~ements.~ In addition, the planar molecule is found to betilted out of tho (001) plane by lo, the packing of the molecules inthe crystal is rediscussed and shown to be governed by the hydrogen-hydrogen repulsions, but apart from these modifications, Lonsdale'sprevious structure 4 is fully confirmed. An attempted revisionof the durene structure 6 v 2 still leaves the methyl-group bondlength at 1.49 A., although this value may not be so accurate as inhexamethylbenzene. But electron-diffraction studies of isobutene,tetramethylethylene, and mesitylene 3 give single-bond values of1.54 & 0.02 A.On the whole, there is no evidence of any seriousdeparture from the single-bond value when the methyl group isadjacent to a double bond or a benzene ring; but when the methylgroup adjoins a triple bond definite contractions of about 0.08 A.are now established. The spectroscopic value of 1.462 & 0.005 A.for the CH3-C distance in methylacetylene has now been verifiedby electron-diffraction studies,' and in dimethylacetylene anddimethyldiacetylene similar values of 1-47 & 0.02 A. are reported,whereas in methyl cyanide the CH3-C distance is 1.49 & 0.03 A.These results have been interpreted in two different ways, byL. 0. Brockway, Ann. Reports, 1937, 34, 196.L. 0. Brockway and J.M. Robertson, J., 1939, 1324.L. Pauling and L. 0. Brockway, J . Amer. Chem. SOL, 1937, 59,(Mrs.) K. Lonsdale, Proc. Roy. SOC., 1929, A, 123, 494.J. M. Robertson, ibid., 1933, A , 142, 659.G. Herzberg, F. Patat, and H. Verleger, J. Physical Chem.,123; R. M. Badger and S. H. Bauer, J . Chem. Physics, 1937,5,599.J . Arner. Chem. SOC., 1939, 61, 927.1223.937, 41176 CRYSTALLOGRAPHY.L. Pauling, H. D. Springall, and K. J. Palmer,' and by J. B. Conn,G. B. Kistiakowski, and E. A. Smith.8 According to the formerauthors they may be due to two causes. First, the CH,-C bondmay remain a single bond, but, contrary to the usual assumption,the single-bond covalent radius of the triple-bonded carbon atommay change, owing to an increase in the s character of the hybrid8-p bond orbital, due to the formation of the triple bond.Secondly,the CH,-C bond may acquire some double-bond character owingto resonance with certain unconventional electronic structures.That the first of these causes must be significant is probable becausethe G-H bond distance is appreciably less in acetylene (1.057 A.)than in methane (1.093 A,). The hydrogen atom can only formone covalent bond, so this contraction must be due to a change inthe single-bond radius.The contraction of the methyl group bond-length in the acetyleniccompounds, however, is greater than can be explained by this causealone, and so we must infer a certain double-bond character as well.In a full discussion, Pauling, Springall, and Palmer attribute onlyabout 0.02 A.of the shortening to change in the single-bond radius,and the remainder to resonance among the structures (1)-(IV).H H I H* Y=C=&-H (11.)I(I.) H--S;r-EC-HI I H HH H + I -H C=C=C-H (IV.) II I (111.) H: C=C=&-HH HIt may be noted that the structures (11)-(IV) contain onecovalent link less than the conventional structure (I), and so wemight expect their contribution to be small. The unique featureof the postulated resonance in methylacetylene, however, is the factthat it involves the rupture of a C-H link. Apart from this it isclosely similar to the ordinary resonance in conjugated systems,e.g., in butadiene, where the contributing structures may be writtenas in (V)-(VIII).(v.) CH2=CH-CH=CH2 - 6'H2-CH=CH-6H2 - (vI.)(VII.) CH,-CH=CH-6H2 6H2-CH=CH-CH2 (VIII.)When a double bond is adjacent to a methyl group a similar butsmaller conjugation may be expected, only the C-H bonds in theC - h c plane now being involved. Any covalent radius change8 J.Amer. Chem. SOC., 1939, 61, 1868ROBERTSON : ORGANIC STRUCTURES. 177will also be small (the C-H distance in ethylene, 1.087 A . , ~ is onlyslightly less than in methane, 1-093 From these considerations,the estimated methyl-group bond-length in methylethylene and themethylbenzenes is about 1.51 A. The best observed values areabout 1.53 A. as in hexamethylbenzene, but slightly smaller valuesare not excluded by the experiments, and in fact may be expectedin the case of the less fully substituted benzenes where fewer methylgroups compete for the available conjugating power of the ring(compare the experimental result for durene 5).approach the problem in quitea different way, vix., from an extensive study of heats of hydro-genation, including those of the acetylenic compounds.11 Theirwork reveals the large magnitude of the steric hindrances exercisedby non-bonded atoms in organic molecules, and they attributethe C-H bond shortening in acetylene as compared with methanewholly to reduced steric hindrance by adjacent atoms.For theC-C bond in the methylacetylenes they consider that the shorteningmay be largely due to the same cause.Although these interpretations may differ, there is now a con-siderable amount of new data, and the six possible types of con-jugated systems involving double bonds, triple bonds, and benzenerings have been reviewed by Pauling, Springall, and Palmer withthe following results :Conn, Kistiakowski, and SmithAmount ofType of conjug- Observed C-C double bondated system.Substance. distance, A. character, yo.Butadiene la 1-46 f 0.03 18 f 10cycZoPentacliene l2 1.46 5 0.03 18 & 10Stilbene l3 1.44 & 0.02 25 & 7{ -\=p-Diphenylbenzene l4 1.46 f 0.04 18 & 12 WJ { Diphenyl 1.48 & 0.04 13 & 12<>-\Vinylacetylene -=-\Tolan l6 1.40 4 0.02 33 f 8Diacetylene 1.36 0.03 44 5 13Cyanogen 1-37 4 0-02 33 & 10(Dirnethyldiacetylene 1.38 0.03 34 f 13E. H. Eyster, J . Chem. Physics, 1938, 6, 580.lo N. Ginsburg and E.F. Barker, ibid., 1935, 3, 668.l1 T. W. J. Taylor, Ann. Reports, 1937, 34, 220.la V. Schomaker and L. Pauling, J . Amer. Chem. SOC., 1939, 61, 1769.la J. M. Robertson and (Miss) I. Woodward, Proc. Roy. Soc., 1937, A , 162,565.l4 (Miss) L. W. Pickett, ibid., 1933, A , 142, 333.l5 J. Dhar, Indian J . Physics, 1932, 7, 43.l6 J. &I. Robertson and (Miss) I. Woodward. Proc. Roy. SOC., 1938, A ,164,436178 CRYSTALLOGRAPHY.It is pointed out that roughly the same conjugating power isexpected for the first five systems, as only the pz orbitals of thetriple bond are effective in conjugation with a double bond orbenzene ring. Thus the tolan result agrees with stilbene if a single-bond covalent radius change of 0.04 A. is allowed (the observedC-H contraction in acetylene compared with methane).Pauling,Springall, and Palmer, bowever, estimate the radius change at only0.02 A. when triple bonds are formed, and this correction is appliedin calculating the double-bond character given in the last column.They suggest that the low tolan distance may rather be due tothe fact that rotational oscillation must be effective in reducingresonance to some extent in the first three systems, by bringingthe molecules into non-coplanar configurations, but not, of course,in the triple-bonded structures.The lower C-C distance and higher double-bond character of theconjugated triple-bond systems are in accordance with expectation,interaction through the pz or pDy orbitals now being possible. Itwill be interesting to compare these new electron-diffraction measure-ments for conjugated triple bonds with detailed X-ray results fordiphenyldiacetylene, about which a preliminary note has beenpub1ished.l'In conclusion, it may be noted that detailed calculations of theC-C bond length in butadiene l8 have predicted a value of 1.43 A.rather than the 1.46 A.recorded above, whereas in phenylethylene l9similar calculations give a value of 1.45 A. in agreement with thestilbene result.Other Hydrocarbon Structures.-An interesting study of certainhigh molecular-weight parafks with chains exceeding 130 and upto several thousand carbon atoms in length has been carried outby C. W. Bunn20 The great length of the chain is really a simplify-ing feature because end effects can be neglected, and the c translationof the orthorhombic cell is simply the length of the C-C\c zig-zag(2.534 A.).The C-C distance is given as 1.53 A., and the zig-zagangle as 112". Detailed electron-density maps are derived froma triple Fourier analysis, and it is concluded that the electroncloud of the CH, group is distended in the plane of the nuclei, due inpart, but not wholly, to anisotropic thermal motions. It may benoted, however, that the number of terms in the triple Fourierseries is extremely small (27) and in such cases one must beware offalse detail. A single-crystal analysis of n-triacontane, C90H62, has17 E. H. Wiebenga, Nature, 1939, 143, 980.l 8 J. E. Lennard-Jones, Proc. Roy. Xoc., 1937, A , 158, 280.'O Trans.Faraday SOC., 1939, 35, 482.W. G. Penney, ibid., p. 306ROBERTSON : ORGANIC STRUCTURES. 179also been published,21 leading to a C-C distance of 1.57 & 0.05 A.and a zig-zag angle of 106' &- 4".The study of complex condensed ring compounds has beenextended by J. Iball to 3 : 4-benzphenanthrene, CI8Hl2, and someof its derivatives, and cell dimensions, optical and magnetic dataare recorded.22A very extensive single-crystal study of anthracene by electron-diffraction methods has recently been made,23 and the results arein agreement with the structure as determined by X-rays.24 Thesignificance of this study, however, lies in the detailed interpretationof certain new features in the diffraction patterns, which are shownto be equivalent to gas diffraction patterns of oriented moleculesmoving past the electron beam.The results may be explained bysupposing the molecules to vibrate thermally as rigid units abouttheir mean positions in the lattice. The method would seem tohave considerable application to complex molecules.GZycine.-A very complete account of the crystal structure ofglycine has now been published,25 which supersedes a number ofprevious tentative structures.26* 27 The monoclinic cell containsfour asymmetric molecules, and the approach to the structure byPatterson and Harker methods of analysis is described in consider-able detail and forms an interesting contribution to the techniqueof structure analysis. The final results reveal nearly flat moleculeswith the dimensions shown in Fig.10. I n the crystal the atomsare coplanar, with the exception of the nitrogen which lies 0.27 A.above the plane of the others. The interatomic distances, which theauthors estimate to be accurate to within & 0;02 A., call for littlecomment except for the carbon-nitrogen value of 1 . 3 9 ~ . which iscertainly abnormal but agrees closely with the N-C (methylene) value(1.41 A.) in diketopiperazine reported by R. B. Corey last year.28Both these distances are well below the G-N single-bond value of1.47 A., and it is difficult to see how any form of bond-multiplicitycan account for the discrepancy. I n the crystal the moleculeprobably has the " zwitter-ion " structure, H,N+*CH,*COO-, andso the formal charge effect, recently discussed by N.Elliot,29 should21 R. Kohlhaas and K. Soremba, 2. Krist., 1938,100,47.22 Ibid., p. 234.2s A. Charlesby, G. I. Finch, and H. Wilman, Proc. Physical SOC., 1939,24 J. M. Robertson, Proc. Roy. SOC., 1933, A, 140, 79.25 G. Albrecht and R. B. Corey, J . Amer. Chem. SOC., 1939, 61, 1087.26 J. D. Bernal, 2. Krist., 1931, 78, 363.2 7 A. Kitaygorodsky, Acta Physicochim. U.R.S.S., 1936, 5, 749.28 J. Amer. Chem. SOC., 1938, 60, 1598.29 Ibid., 1937, 69, 1380.51, 479180 CRYSTALLOGRAPHY.be operative. The decrease in the C-N distance to be expectedfrom this cause would amount to only about 0.03 or 0.04 A . , ~ O butthe effect is in the right direction.The situation is made more confusing, however, by the resultsof an interesting electron-diffraction investigation on trimethyl-a'niine oxide and dimethylsulphone recently carried out by M.W.Lister and L. E. Sutton31 They find that the nitrogen atom ap-pears to have a greater radius when 4-covalent than when 3-covalent,the C-N bond length in (CH,)3&-0 being given as 1.54 & 0.03 A.,corresponding to a 4-covalent radius of 0.77 A., whereas from the;formal charge rule we might have expected a decrease in this caseas well as in glycine.@FIG. 10.I 7FIG. 11.These conflicting results call for a careful examination of theestimated limits of accuracy in the experiments, and for the studyof further cases if possible. Owing to the number of parametersinvolved, the estimated accuracy appears to the Reporter to beslightly optimistic.In the case of glycine it should be noted thatthe intensities are obtained by visual estimates, and the final co-ordinates by direct adjustment of parameters and not by E'ourierseries methods. It may be recalled that when oxalic acid dihydratewas investigated by similar methods a C-C distance of 1-58 A. wasobtained,32 whereas a later study by means of quantitative absoluteintensity measurements and Fourier series methods gave a revisedvalue for the same bond length of 1.43 A.%L. Pauling, " The Nature of the Chemical Bond," p. 159.31 Trans. Paraday SOC., 1939, 35, 495.32 W. H. Zachariasen, 2. Krist., 1934, 89, 442.33 J. M. Robertson and (Miss) I. Woodward, J., 1936, 1817ROBERTSON : ORGANIC STRTJCTURES. 181The complete determination of the glycine structure is an im-portant initial step towards an exact knowledge of the linkagespresent in protein structures, and one most interesting aspectconcerns the intermolecular connections of the glycine molecules.The crystal is composed of double layers of nearly flat moleculesheld together by hydrogen bonds and electrostatic forces operativebetween the nitrogen and oxygen atoms of adjacent molecules.Asingle layer of molecules lying nearly in the (010) plane is shown inFig. 11. Fairly strong hydrogen bonds of 2-88 and 2.76 A. holdthis layer together, and the fact that these bonds are disposed a tnearly the tetrahedral angle to themselves and to the N-C linksuggests that a third hydrogen atom may occupy the fourth tetra-hedral position, and be capable of engaging with oxygen atoms ofthe next layer.This next layer of molecules is related by a centreof symmetry to the one shown, and is found to be closely bound toit, the minimum distances being 2.93 and 3-05 A. These unusualdistances may, therefore, represent very weak hydrogen bonds, dueto the third hydrogen sharing its bond-forming capacity with thetwo nearest oxygen atoms of the adjacent layer. Between suc-cessive double layers only van der Waals forces are operative, theclosest approaches being about 3.4 A.Preliminary data have been reported for p-azotoluene 34 anddi~henylamine,~~ and a somewhat more complete study of oxamideis recorded.36 The unusual C-C distance given as 1-65 A. requiresfurther study .The Isomeric Axoben2enes.--A fully quantitative analysis of thetrans-azobenzene structure has now been completed.37 It belongsto the dibenzyl series of structures,13~ 38 and like stilbene and tolan,is complicated by the fact that two crystallographically independentmolecules contribute to the asymmetric unit.It is an interestingfact that these two molecules, which exist side by side in the crystal,do not appear to be identical. The two kinds of molecules can beclearly distinguished in the contour map reproduced in Fig. 12,where it may be noted that the resolution of the central pair ofnitrogen atoms is rather poor ; but by various methods the positionsof all the atoms can be determined with considerable accuracy.It is then found that much of the apparent difference between themolecules is due to a difference in orientation which reveals itself34 M.Prasad and M. R. Kapedia, J . Univ. Bombay, 1938, 7, 94.35 J. Dhar, Indian J . Physics, 1939, 13, 27.36 L. Misch and A. J. A. van der Wyk, Arch. Sci. ph.ys. nat., 1938, V, 20,37 J. J. de Lange, J. M. Robertson, and (Miss) I. Woodward, Proc. Roy.38 J. M. Robertson, ibid., 1935, A, 150, 348.Suppl., 96.Soc., 1939, A , 171, 398182 CRYSTALLOGRAPHY.in the projection, but when full allowance is made for this thereremains a small difference in the dimensions of the two molecules.Such differences have previously been attributed to an accumulationof experimental errors (e.g., in stilbene), but in the case of azobenzeneit seems almost certain that a real molecular difference exists...._ ....,, __.. . '. .6 j.Whereas one molecule is almost exactly flat, in the other the benzenerings appear to be rotated by ca. 15" about the C-N link, out ofthe plane containing the central atoms, and the dimensional changesare in the direction to be expected from the decrease in resonancewhich must accompany this distortion. The altered dimensionsare thus not a, permanent feature, such as would lead to a neROBERTSON : ORGANIC STRUCTURES. 183molecular species, but appear rather to be imposed by the immediatesurroundings. A full discussion of these relations has not yet beengiven.If we disregard these small-scale variations, the mean dimensionsof the trans-azobenzene molecule are as shown in Fig.13. Thesefigures are in accord with the accepted covalent radii of the atomsconcerned when allowance is made for the resonance expected forthis type of system. It may be noted, however, that, whereasFIG. 13.LFIG. 14.in stilbene the Car.-Cal. distance of 1-44 A. is just half-way betweenthe single-bond (1-54) and the double-bond (1.34) value, in azobenzenethe corresponding distance is distinctly nearer to the C-N single-bond value of 1-47 A. than to the C-N double-bond value of 1.28 A.This result is probably due to a greater tendency for the multiplebond to remain between the nitrogen atoms in azobenzene.The recently isolated cis-form of azobenzene 39 has also been sub-jected to a detailed X-ray analysis,40 but the results have not yet39 G.S. Hartley, J., 1938, 633. 40 J. M. Robertson, J., 1939, 232184 CRYSTALLOGRAPHY.been refined to the same extent as in the trans-isomer. As might beexpected, t,he crystal structure is quite different, and the cis-molecule is found to possess a two-fold axis of symmetry insteadof the centre of symmetry which exists in the trans-molecule. Thedimensions are shown in Fig. 14, and it may be noted that any chanceof a planar molecule is completely ruled out by the steric repulsionswhich would occur between the atoms of the benzene rings. Theserings are actually found to be rotated by 50" from the plane ofFig. 14, giving a clearance between the non-bonded atoms of about3.1 A. Such a result must inhibit resonance to a considerableextent, and this effect is indicated, but not proved, by the dimensionsobtained. The uncertainty in the figures is rather large a t present,but a more detailed study would be of considerable interest.Other ,Structures.-Preliminary reports are available for severalimportant structures which have not yet been published in detail.A notable advance in the difficult carbohydrate structures appearsto have been made by E. G. Cox and G. A. Jeffrey 41 in their analysisof a-chitosamine hydrobromide and hydrochloride. The iso-morphism of these compounds enables direct synthetic methods tobe employed, without any stereochemical assumptions, and theatomic positions (with one exception) can be determined to withinabout 0.08 A. The results show that chitosamine is a derivativeof glucose and not of mannose. The existence of the pyranosering in a crystalline sugar is established, and it is confirmed thatin the a-form of a d-glucose derivative the oxygen atoms on thefirst and the second carbon atom are in the cis-position.H. M. Powell and G. Huse42 have examined the 1 : 1 molecularcompound of picryl chloride and hexamethylbenzene and find thatthe two molecules lie in parallel planes with apparently no valencylinkings between them. Some degree of disorder is indicated inthe structure, which appears to be of a complex type.X-Ray analysis and dipole-moment measurements have beencombined in a study of benzi143 (reported to show a skew con-figuration) and of 1 : 2 : 4 : 5-tetrabromocycZohe~ane.~ An X-raystudy of 4 : 4'-dihydroxydiphenyl sulphide decamethylene ether 45is claimed to give a C,,.-S distance of 1-71 & 0.04 A. and an anglebetween the sulphur valencies of 112.4" & 1.5".InsuZin.-An extremely interesting account of X-ray measure-ments on wet insulin crystals has just been announced by (Miss)Nature, 1939, 143, 894. 42 Ibid., 144, 77.43 (Miss) I. E. Knaggs and (Mrs.) K. Lonsdale, ibid., 143, 1023; C. C.4c E. Halmoy and 0. Hassel, J. Amer. Chem. SOC., 1939, 61, 1601.45 R. Kohlhaas and A. Luttringhaus, Ber., 1939, 72, $97.Caldwell and R. J. W. Le FBvre, ibid., p. 803ROBERTSON : ORGANIC STRUCTURES. 185D. Crowfoot and H. Riley.46 Zinc insulin crystals in several im-mersion media are studied, and the wet unit cell is shown to be amoderately expanded version of that present in the air-driedcrystal^.^' X-Ray reflections are more numerous and there arestriking intensity changes. The results, expressed by means ofa Patterson vector diagram on the basal (0001) plane, show that themain interatomic vectors are similar in magnitude to those obtainedfrom the air-dried crystals, but are shifted through a small angle.This indicates that a reorientation of the molecules relative to thecrystal axes takes place on drying.The interpretation of the vector maps obtained from the originalair-dried crystals has been the subject of much contr~versy,~~ andwith the more extensive data now available from the wet crystalswe may perhaps expect some more fruitful discussions. J. M. €3,.G. C. HAMPSON.J. 11. ROBERTSON.A. R. UBBELOHDE.4 G Nuture, 1939, 144, 1011.4i (Miss) D. Crowfoot, Proc. Roy. SOC., 1938, A , 164, 580.4 8 (Mrs.) D. M. Wrinch and I. Langmuir, J . Arner. Chem. SOC., 1938, 60,2005, 2247; Nature, 1938, 142, 581; W. L. Bragg, J. D. Bernal, and J. M.Robertson, ibid., 1939, 143, 73; D. P. Riley and I. Fankuchen, ibid., p. 648;L. Pauling, J. Anter. Chem. SOC., 1939, 61, 1860

ISSN:0365-6217    

DOI:10.1039/AR9393600148

出版商:RSC    

年代:1939

数据来源: RSC

摘要:

ORGANIC CHEMISTRY.1. INTRODUCTION.THE year under review, like its predecessors, has witnessed rapidadvances in numerous and diverse fields of organic chemistry. Onthe more general and theoretical side the liaison with recent develop-ments in physics and mathematics has been maintained, andphysical, stereochemical and kinetic studies have all played theirpart in the elucidation of the mechanisms of the reactions of organiccompounds. Simultaneously the organic chemist has continued histask of determining the structures of many complex substances ofgreat biological significance.In last year’s Report, considerable attention was given to themechanism of aliphatic substitution, prototropy and anionotropy,and the progress of our knowledge over a period of some five yearswas reviewed; a survey of work upon molecular rearrangements,covering approximately the same period, is now included.Studiesof the Hofmann, Lossen and Curtius degradations have establishedthe intramolecular character of these changes ; their detailedmechanisms probably resemble those of the Beckmann, imino-etherand amidine transformations. The rearrangements of hydroxy-sulphones and allied compounds are similar. There are also indica-tions that changes of the pinacol-pinacolone type are intramolecular ;a mesomeric organic cation appears to be involved. Migrationsfrom side-chain nitrogen to nuclear carbon have received muchattention in the past, and the chloroamine transformation inaqueous solvents was long ago shown to be intermolecular; thishas now been confirmed by experiments using radioactive hydrogenchloride, but the position is less simple than was formerly supposed,and in anhydrous solvents a different mechanism is indicated.The intermolecular character of the diazoamino-aminoazo-con-version has been established more definitely, and the Hofmann-Martius rearrangement of alkylanilines appears to involve theseparation of the alkyl group as cation.The conversion of arylalkyl ethers into nuclear-alkylated phenols has been the subjectof a number of recent studies; there are indications that the alkylgroup becomes free as a neutral radical except in the o-migrationsof ally1 groups, which are intramolecular.In recent discussions of condensations of the aldol, Perkin,Knoevenagel and Claisen types, the close relationship existingbetween these processes has been emphasised.An aldol additioM!CRODUC!I!ION. 187product is envisaged in every case, and the function of the catalysthas been considered. Recent studies of the Perkin synthesis supportthe view that the aldehyde condenses with the anhydride, the saltacting catalytically.A comprehensive review of the effects of chemical constitutionupon the dissociation constants of organic acids has appeared.* Itis now shown that the strengths of the o-halogeno- and o-nitro-benzoic acids and -anilines do not indicate the operation of anyeffect which is not also found in the isomeric p-compounds; the'' ortho-effects " observed in many of the reactions of o-substitutedacids, acid derivatives and amines may thus often be absent inionic equilibria.The discovery of the Kharasch peroxide effect in 1933 has led toa revision of the whole subject of additions at olefinic linkages.Ithas been shown that the orientation of addition of hydrogen bromide(but not of the other halogen hydrides) is determined by the oxygenor peroxide content of the system. Further examples of theinfluence of oxygen and peroxides are rapidly emerging. Thusaddition of bromine to olefins and bromination of the side chains ofbenzene homologues are greatly affected by oxygen, and the Can-nizzaro reaction of aldehydes and the addition of bisulphite toolefins do not proceed in the absence of oxygen. Sulphuryl chloridein presence of benzoyl peroxide is a specific reagent for the chlorin-ation of benzene side chains.In the postulated mechanisms ofthese reactions, halogen atoms or organic free radicals play animportant part.Recent advances in the study of stereochemistry have beenassisted by the introduction of the valuable Stuart models withtheir accurate interatomic distances and valency angles. Opticalactivity due to restricted rotation has been observed in the benzeneseries, and the effects of numerous groups upon the rate of racemis-ation of diphenyl derivatives have been further studied. Themechanism of the asymmetric catalytic dehydration of an ally1alcohol to give an optically active allene hydrocarbon remainsobscure. Further investigation of compounds containing sym-metrically placed hydrogen and deuterium has shown that thedifference between these isotopes is insufficient to give rise todetectable optical activity.In recent work upon asymmetrictransformation or optical activation, the problem has for the firsttime been studied kinetically.The resolution of a tervalent nitrogen compound remains one ofthe outstanding problems of stereochemistry. The evidence for thenon-planar codguration of the tervalent nitrogen valencies is* J. F. J. Dippy, Chem. Review4 1939, 25, 161188 ORGANIC CHEMISTRY.reviewed in this Report, and some promising investigations onsubstituted ethyleneimines are described. The isolation of thecis-form of azobenzene by irradiation of the normal form has stimul-ated the investigation of cis-trans-isomerism in general, and it hasbeen found that the two forms of many azo-compounds can beseparated by chromatographic analysis with alumina or charcoalas adsorbent. The equilibrium between syn- and anti-diazocyanideshas also been studied, and measurements of the dipole moments haveconfirmed Hantzsch’s conclusions regarding their configurations.The elegant method employed for demonstrating the planar con-figuration of the 4-covalent plktinous atom has now been applied topalladium, and it has been shown that this metal too, in the palladouscondition, must possess planar valencies.The Report on carbohydrates deals with two aspects of thesubject only; first, the development in conceptions of opticalinversion in the sugar group makes opportune a review of work onthe anhydro-sugars and on glucosamine, and secondly the constitu-tions of starch and cellulose are discussed.It is established that thealkaline hydrolysis of a sugar p-toluenesulphonate takes placereadily and is accompanied by Walden inversion on the carbonatom to which the sulphonic acid group is attached, provided thatthere exists a free hydroxyl in the trans-position on an adjacentcarbon atom ; an anhydro-ring of the ethylene oxide type is formed.When an adjacent trans-hydroxyl group is not available, then eitherthe sugar toluenesulphonate is not hydrolysed, or hydrolysis occurswith extreme difficulty and without optical inversion. Scission ofthe anhydro-ring is effected by the further action of alkaline reagents ;the rupture is accompanied by inversion and takes place on eitherside of the oxygen atom, with the result that a mixture of twosugars is obtained from each anhydro-compound.A derivativeof dimethyl 2-amino-~-methylglucopyranoside (which is obtainableas a product of the action of ammonia on dimethyl 2 : 3-anhydro-p-methylmannoside) proves to be identical with the correspondingderivative prepared from natural glucosamine, which must thereforehave the configuration of d-glucose and not that of d-mannose.Two other types of anhydrohexoses are discussed. In the glucosanclass the reducing group is involved in the anhydro-bridge formation,and in the pentaphan ring type the anhydro-ring is six-memberedand does not involve the reducing group; the outstanding featureof the latter is the great sta.bility of the anhydro-ring, which is notruptured by the strongest acid or alkaline hydrolytic agents.Variations in the conditions of methylation of starch or the useof starches from different biological sources all yield productshaving the same proportion of end-group (tetramethyl glucose) INTRODUCTION.189corresponding to a chain length of 24-30 glucose units. Starchthus appears to be best represented by the laminated formulabelow, in which each repeating unit of 24-30 glucose residues isrepresented by a straight line terminated by an arrowhead indicatingthe reducing glucose unit.J. II4 IJ. IProlonged methylation or treatment with weak acid brings about ascission of the ( ( polymeric links ” between the repeating units and aconsequent diminution of molecular size as determined by physicalmethods. A study of the kinetics of this disaggregation processindicates that the (‘ polymeric bonds ” are of the glycosidic type.Evidence for the existence of basal repeating units in cellulose isnot so definite.The amount of end-group isolated from a methyl-ated cellulose is more or less proportional to the number of methyl-ations to which it has been submitted; if air is excluded, themolecular size diminishes as methylation proceeds, but the amountof end-group isolated from the product bears no simple relation tothe molecular weight determine’d osmotically, and indeed end-group is entirely absent when the methylation in nitrogen is notcarried beyond five or six repetitions.A simple explanation repre-sents a methylated cellulose of high molecular weight by a largeloop (a), further methylation leading to scission simultaneously attwo points as shown by the dotted line. In the absence of oxygen,the ‘( healing ” process represented by the union of the “ head ” and(( tail ” of each fragment in ( b ) produces the smaller loops ( c ) inwhich no end-group will be apparent. Oxygen appears to inhibitthis healing process, for when the methylation is conducted in airthe amount of end-group in the product indicates that most of theunits exist as terminated chains ( b ) . The retention of the loopedstructure in the fragments ( b ) is ascribed to cross-linkages as shownin ( d ) ; the nature of these cannot at present be specified.IReference is also made to investigations of the relationships ofhydrocellulose and oxycellulose with cellulose, and of the dis-ruption of the glucopyranose units in cellulose or starch when thepolysaccharides are oxidised with periodic acid190 ORGANIC OHEMISTRY.Recent researches have shown that the a-naphthaquinone nucleusis a frequent constituent of the molecular structure of naturalproducts, and 8 short account of the pigments based upon thisskeleton introduces a topic which has not previously been dealtwith in these Reports.Structural relationships have been estab-lished between juglone, plumbagin, lawsone, and phthoicol, all ofwhich are hydroxy- or methyl hydroxy- a-naphthaquinones, andechinochrome A is probably an ethylpentahydroxy-a-naphtha-quinone. Extensive studies have shown that lapachol and lomatiolare derivatives of 2-hydroxy-3-isopropenyl-1 : 4-naphthaquinone.It is probable that dunnione is a related 1 : 2-naphthaquinone, andalkannin, alkannan and shikonin are isopropenyldihydroxy- 1 : 4-naphthaquinones.The antihzemorrhagic vitamin Kl is S-phytyl-2-methyl-1 : 4-naphthaquinone ; the constitution has been establishedby degradation and by three independent syntheses of the vitamin.The marked physiological activity of 2-methyl-1 : 4-naphthaquinoneis noteworthy. Intensive attacks on the structure of gossypol,the yellow toxic principle of cotton seed, have been made; thepigment is not a quinone, but the attractive hexahydroxydinaphthylstructure composed of six isoprene units which has been suggestedis supported by degradation and synthetic evidence of considerablemagnitude and importance.Great advances have been made in the synthesis of steroidsduring the period 1937-39.The complete synthesis, by establishedmethods, of the sex hormone equilenin has been announced. z-Nor-equilenin and 2-noroestrone have been prepared by an ingeniousdouble cyclisation process. The diene synthesis has been success-fully applied to the formation of a stereoisomer (or perhaps a,structural isomer) of oestrone. In view of the difliculty of achievingthe complete synthesis of any sex hormone, special interest attachesto the development of the potent synthetic oestrogens, the C-alkylderivatives of 4 : 4’-dihydroxystilbene (“ stilbastrol ”).Con-siderable progress has been made in the synthesis of the tricyclichexatriene skeleton of the antirachitic vitamins.The review of heterocyclic compounds is again very largelydevoted to the chemistry of natural products. The section onoxygen ring compounds is a development of the topics discussed inthe Reports for 1937 and 1938; benzofuran structures have beenadvanced for euparin and egonol, extensions have been made in thecoumarin, furocoumarin, furochromone, and furoflavone groups,and an investigation on fustin has established the natural occurrenceof the flavanonol structure. Among heterocyclic nitrogen ringderivatives, adermin, the rat-dermatitis-preventing factor of thevitamin B complex, proves to be a comparatively simple thougWATSON : REACTION MECHANISMS.191highly substituted pyridine derivative. Interesting advances havebeen made in the chemistry of the bicycb-aza-alkanes. Newmethods have been devised for the preparation of bicyclic basesof types I (n = 1 or 2), I1 (n = 2 or 3), I11 (1% = 3 or 4) and IV.An earlier unconventional stereochemical explanation of the exist-ence of two forms of norlupinan (I11 ; n = 4) must now be discarded,as norlupinan B has been proved to be identical with the syntheticbase (IV). Attempts to utilise these bicyclic bases in the synthesisof quinine derivatives have been made, and developments in thisdirection will be awaited with interest.The alkaloidal field has not produced any spectacular advancesduring the year, and this section of the Report is devoted mainlyto the speculative structures with the aid of which the chemistryof calycanthine, matrine, artabotrine and the ergot bases is inter-preted. An extremely ready rupture of the terminal pyrrolidinering of the eserethole molecule has been discovered.R.D. HAWORTH.P. MAITLAND.S. PEAT.J. C. SMITH.H. D. SPRINGALL.H. B. WATSON.2 . REACTION MECHANISMS.(Continued from Ann. Reports, 1938, 35, 208.)(a) Rearrangements.Attention continues to be given to those changes in which agroup migrates from one position in a compound to another, eitherwith or without the elimination of water, halogen acid or someother simple molecule.Work in this field up to 1933 has beensummarised in earlier Reports,l and a comprehensive account of1 Ann. Reports, 1923,20,116; 1924,21,96; 1925, 22, 113; 1927, 24, 154;1928,25, 133; 1929, 26,122; 1930, 27,114; 1933,30,176192 ORGANIC CHEMISTRY.the mechanisms which have from time to time been suggested torepresent certain rearrangements has recently appeared.2 In anumber of instances there is definite evidence for the intermolecularcharacter of the change, the migrating group becoming detachedfrom the molecule at some intermediate stage, while certain otherrearrangements (e.g., the benzidine change) have been. shown tobe truly intramolecular. The evidence is often far from con-clusive, however ; moreover, even if the transformation is knownto be intermolecular, the nature of the intermediate may not beclear, while the exact mechanism of an intramolecular rearrange-ment is not always easy to determine.It is therefore not sur-prising that the literature should contain a large number of postu-lated schemes in which compounds such as olefms or alkyl halides,cyclic compounds, ions, radicals or molecules with free valenciesappear as intermediates, in addition to mechanisms of an intra-molecular type involving partial valencies or their electronicequivalent,The Hofmann, Lossen, and Curtius Rearrangements.-Accordingt o the general scheme put forward by F. C. Whitmore,* thesechanges (in all of which an isocyanate precedes the ultimate product)are to be represented as follows :The removal of A as a negative ion (or nitrogen molecule in theCurtius degradation) leaves the adjacent nitrogen atom with anincomplete electronic group (sextet), and R is then transferred,with the R-C electron pair, from carbon to nitrogen.This schemedoes not differ in principle from C. K. Ingold’s representation ofthe pinacol and Wagner transformations.Kinetic studies of the rearrangements of the salts of a numberof nuclear- subst itut ed benz obromoamides , X C,H,*CO*NHBr,and dibenzhydroxamic acids, X*C,H4*CO*NH*O*CO*C,H5 and~ , H , * ~ O * ~ ~ O ~ C O * ~ , H , X ‘ , in aqueous ammonia have been con-ducted by C. R. Hauser and his collaborators,6 who conclude thatthe rate-determining step is the release of Br, O*CO*C,H, orE.S. Wallis in Gilman’s “ Organic Chemistry,” New York, 1938, Vol. 1,p. 720.See Ann. Reports, 1933, 30, 178.Ibid., 1928, 25, 133.4 3. Amer. Chem. SOC., 1932, 54, 3274; Ann. Reports, 1933, 30, 176.6 C. R. Hauser and W. B. Renfrow, J . Amer. Chem. SOC., 1937, 59, 121,2308; R. D. Bright and C. R. Hauser, ibid., 1939, 61, 618w m s o N : REACTION MECHANISMS. 193O*CO*~,H,X’ as anion. The rearrangements are facilitated byelectron-repulsive characters in X and electron-attractive charactersin X’. Further, the logarithms of the velocity coefficients for thetransformations of C,H5’CO*NH’OoCO*C6H4X‘ give a straight linewhen plotted against the values of log K for the acids X’*C,H,*CO,Heven when X’ is in the o-position, but the linear relationship is notfound for the series X*C,H,*CO*NH*O*CO*C,H, ; i.e., the quanti-tative correlation of log k with log K holds only when the variablegroup is in the anionic portion of the compound (as it is, of course,in the acid).The further step, R*CO*N-+ CO:NR, consists in the trans-ference of R from carbon to nitrogen, and the absence of racemis-ation during the Curtius, Hofmann, and Lossen degradations ofoptically active derivatives of benzylmethylacetic acid, and theidentity of the rotations of the amines or ure2s obtained from theazide, the bromoamide and the hydroxamate, observed by E.S.Wallis and his co-~orkers,~ point, very strongly to the conclusionthat the process is truly intramolecular. This view is confirmedby the production of only one isocyanate when benzylmethylacet-azide is degraded in presence of triphenylmethyl radicals,S by thequantitative yield of tert.-butylmethylamine (neopentylamine) fromtert.-butylacetamide (whereas reactions in which dissociation maybe supposed t o occur lead to tert.-amyl derivatives by isomerisationof the cation CMe,*CH,+), and by the complete preservation ofoptical activity (due in this case t o restricted rotation) during theHofmann degradation of d-3 : 5-dinitro-6-a-naphthylbenzamide7where dissociation a t any stage of the reaction would have per-mitted free rotation and resulted in a racemic product.lO More-over, C. L. Arcus and J. Kenyon11 have recently observed analmost quantitative retention of asymmetry when optically activehydratropamide , CHPhMe- CO *NH,, undergoes the Hofmanndegradation ; this offers a striking contrast to the very considerableor almost complete racemisation which occurs when optically activegroups migrate in certain other systems, e.g., from oxygen to sulphurin the change CHPhMe*O*SOC,H, --+ CHPhMe-SO,*C,H,.l2 It7 L. W. Jones and E. S . Wallis, J . Anzer. Chem. Soc., 1926, 48, 169;5:. S . Wallis and S. C. Nagel, ibid., 1931, 53, 2787; E. S. Wallis and R. D.Dripps, ibid., 1933, 55, 1701.8 E. S. Wallis, ibid., 1929, 51, 2982.9 P. C. Whitmore and A. H. Homeyer, ibicl., 1932, 54, 3435.lo E. S . Wallis and W. W. Moyer, ibid., 1933, 55, 2598; Ann. Reports,1 1 J . , 1939, 916.l!):3:3, 30, 178. Compare F. Bell, Cherrh. ant1 Id., 1932, 52, 584.<J. Ihrlyorl ant1 H. l’hillip, J., 1930, 1 ( i i c i ; CJ.I;. Arms, &I. P. Balfe,mid J. Kenyon, J . , 1938, 483.REP.-VOL. XXXVI. 194 ORGANIC CHEMISTRY.must be concluded, on the basis of the above evidence, that intransformations of the Hofmann, Lossen, and Curtius types themigrating group never achieves freedom as radical or as ion. Al-though it appears that a carbanion ( L e e , a negatively charged alkylgroup which has separated from a molecule in such a way thatthe carbon has its complete octet) may retain its asymmetry to alarge degree,13 the observations referred to above are not easilyexplicable in any other manner.F. C. Whitmore considers that the rearrangement is intramole-cular,14 but it is nevertheless difficult to visualise the transferenceof the group R with its electron pair without postulating its freedomfor an instant of time.This difficulty is overcome in the followingslightly modified scheme,15 where the arrows indicate movementsof electrons :The removal of A is followed (or accompanied) by the migrationof the R-C electron pair to the C-N bond and the attachment ofR by the unshared electrons of the nitrogen (Le., R is severed fromcarbon and linked to nitrogen at one and the same time). In thecase of a dibenzhydroxamate the mechanism becomes‘A! R’ d 7R Nk-O-C/ R N R-N\ / i \O \A!/ //- - - f G - - - + f l0 0 G 0Electron-attractive substituents in R‘ will promote the removal ofOCOR’ as anion, and the observed relationship with the dis-sociation constants of substituted benzoic acids is to be anticipated ;on the other hand, electron-repulsive groups in R will facilitate themigration of electrons from the R-C bond, and the analogy withtheir effects upon the ionisation of a benzoic acid disappears.Theinfluence of the nature of R upon the R-C bond also explains theeffect of phenyl in the series CPh,*CO*NH*OH > CHPh,*CO*NH*OH> CH,Ph*CO*NH*OH, and NPh,*CO*NH*OH > NHPh*CO*NH*OH.16The Beckmann rearrangement may also be represented by al3 E. S. Wallis and F. H. Adams, J . Anter. Chem. SOL, 1933, 55, 3838.1 4 Sce J . Amer. Claeiir. SOC., 1934, 56, 1427; J., 1934, 1269.15 H. B. Watson, “ Modern Theories of Organic Chemistry,” Oxford16 L. W. Jones and C. I>. Hurd, J . Amer. Cfien,.b‘oc., 1921, 43, 2422; C. D.University Press, 1937, Chap. X.Hurd, {bid., 1923, 45, 1472WATSON : REACTION MECHANISMS. 195mechanism of a similar type (the group A does not here leavethe molecule), and the transformations of imino-ethers and amid-ines l7 and the rearrangements of quaternary ammonium saltsobserved by Stevens and co-workers l7 appear to be comparable.The following mechanism for the last-named change is the same inits essentials as that suggested by the workers themselves, and isin harmony with the observed effects of variations in the natureof R and R’ :tR-CH2-NMe, R-CH-he, c ( -+ R*CHR’*NMe2L WI +R’All these rearrangements have one feature in common; thegroup migrates to an atom possessing unshared electrons, and it iseasy to visualise its attachment by these electrons simultaneouslywith the release of the pair by which it was linked originally.It isless easy to visualise an intramolecular process which occurs underconditions other than these.The Benxilic, Pinacol, Wagner, and Allied Transformations.-Akinetic study of the transformation of benzil into benzilic acid in32% alcohol (where interference by production of benzoate andbenzaldehyde is but slight) has shown that it is of the first orderwith respect to both diketone and hydroxyl ion.l8 This confirmsthe view, already put forward by R. Robinson and others, that anintermediate negative ion Ph*CO*C(OH)Ph*6 is formed.19 Thesame conclusion is drawn from the observation that benzil exchangeswith heavy oxygen water far more rapidly in alkaline than inneutral solution.2° Further, if the o-positions of both nuclei areoccupied by methyl groups (so that addition to carbonyl is “ steric-ally ” hindered), the rearrangement does not occur.21P.D. Bartlett and I. Pockel’s observations of the pinacolicrearrangements of cis- and trans-1 : 2-dimethylcyclohexane-1 : 2-diols indicate that the elimination of hydroxyl and the attach-ment of the migrating group occur on opposite sides of the ringcarbon atom.22 Confirmation is found in the further observation 23l7 See Ann. Reports, 1930, 27, 121.l 8 F. H. Westheimer, J . Amer. Chewe. SOC., 1936, 58, 2809.Ann. Reports, 1923, 20, 118. The author here summarises a number ofobservations which are. in harmony with this conclusion, particularly theisolation of an addition compound of benzil with potassium hydroxide, whichwnrrangcs to give potassium benzilate (G.Scheuing, Ber., 1923, 56, 252).2o I. Roberts and H. C. Urey, J . Amer. Chem. SOC., 1938, 60, 880.2 1 13. P. Kohler a i d R. Baltzly, ibid., 1932, 54, 4019.22 Ibid., 1937, 59, 820.23 P. D. Bartlett and A. Bavley, 2’6id., 1938, 60, 2416196 ORGANIC CHEMISTRY.that when the geometrical isomerides of 1 : 2-diniethylcyclopentane-1 : 2-diol are refiuxed with 30% sulphuric acid, the cis-form gives2 : 2-dimethylcycbpentanone in 137% yield whereas the trans-isomeride produces only brown tars ; the migration occurs Onlywhen the methyl group can displace the hydroxyl by attacking theopposite side of the carbon atom holding it.A similar " rearwardattack " is indicated by the fact tha,t the semipinacolinic deamin-ation of (I) to (11) involves a Walden inversion : 2pPh PhMe II I)C-c-Ph M e \ L - P h (11.)H' II (1.)0 H2N OHTetramethylethylene bromohydrin loses hydrogen bromide at 100"or on treatment with silver oxide or nitrate or with sodium thio-sulphate, to yield pinacolone. The corresponding iodohydrin isstable only in solution ; the solid decomposes spontaneously togive pinacolone and otherCertain new facts have emerged regarding the Wagner-Meerweinrearrangement, which is closely related to the pinacol transform-ation. P. D. Bartlett and I. Pockel find26 that the change ofcamphene hydrochloride t o isobornyl chloride does not proceedspontaneously, but is induced by hydrogen chloride or o-cresol ;the chloride ion is not a catalyst.T. P. Nevell, E. de Salas, andC. L. Wilson have made the further observation 27 that in presenceof hydrochloric acid containing radioactive chlorine the rate ofchlorine exchange in chloroform medium a t 0" is about fifteentimes greater than that of rearrangement, and they conclude thatthe rapid establishment of an ionic equilibrium (as in Meerwein'sscheme) is followed by a slow bimolecular reaction of the organiccation with a molecule of hydrogen chloride.The benzilic, pinacol, and Wagner-Meerwein transformationsdiffer from those dealt with in the preceding section (Hofmann,Lossen, etc.) in that they involve a migration not t o an atomwhich has unshared electrons but to one which is actually deficientin electrons.Nevertheless, the opposite behaviour of cis- andtrans-1 : 2-dimethylcyclopentane-1 : 2-diols (see above) and theabsence of by-products which might be expected if an alkyl groupwere a t any time free as an ion point to an intramolecular migration.Perhaps the organic cation or anion which is presumably firstO4 H. I. Bernstein and F. C. Whitmore, J . Awer. G'hem. Soc., 1939. 61, 1394.25 (2. W. Ayers, ibid., 1938, 60, 2957.O G Ibid.. p. 1585.2 7 J., 1939, 1188WATSON : REACTION MECHANISMS. 197formed in each case is actually a mesonieric structure ; * for pinacoland camphene hydrochloride this ma07 be represented as follows :This view appears to be in harmony with the relative “ migratoryaptitudes ” of different groups in the pinacol change (e.y., aryl >alphyl ; anisyl > phenyl) .z8A number of rearrangements of alkyl groups have been studiedduring recent years by P.C. Whitmore and his collaborators.P. C. Whitmore, E. L. Wittle, and A. H. Popkinzs find that,whereas the reaction of neopentyl iodide with concentrated alcoholicpotassium hydroxide leads to no rearranged products, the far morefacile attack by silver nitrate or mercuric nitrate gives almostcomplete rearrangement to tert.-amyl alcohol. The authors suggestthat in the first example the addition of hydroxyl or ethoxyl ionand the removal of iodide ion proceed simultaneously; the carbonatom is at no time deficient in electrons, and rearrangement doesnot occur.The preparation of neopentyl iodide and bromide byconversion of neopentylmagnesium chloride into the correspondingmercury compound, followed by treatment with the appropriatehalogen, is probably made possible by the same factor; the neo-pentyl group retains its full quota of electrons throughout.30 Thesilver or mercuric ion, on the other hand, first removes iodide ionand the positively charged neopentyl system rearranges to tert.-amyl. Mechanisms of both of these types appear to be involvedin the reaction with potassium acetate, which leads t o both normaland rearrangement products, their proportAons depending upon themedium .z9Rearrangements of Hydroxy-sulphones and Related Compounds,-The investigations of S.Smiles and his collaborators, t o which refer-28 Ann. Reports, 1928, 25, 134; 1930, 2’7, 118.29 J . Arner. Chem. SOC., 1939, 61, 1586.30 F. C. Whitmore, E. L. Wittle, and B. R. Harriman, ibid., p. 1585.* Suggestion by Professor C. K. Ingold (private communication) (comparealso ref. 27). It may be regarded as the electronic equivalent of the earlier‘‘ partial valencies ” view (R. Robinson, Mem. Munchester Lit. Phil. SOC., 1920,64, No. 4).c1 c1 c1Phosphorus pentachloride may prosent an analogous case, ‘uiz.,\hcI . cf ’Y-1L-----198 ORGAMC CHEMISTRY.ence was made in the Report for 1933,31 have been continuedand extended to include the rearrangements of further hydroxy- ,amino-, and acetamido-siilphones, -sulphoxides, and -sulphides.These changes appear to be intramolecular.Thus, in the analogousconversion of a thiol oxide into a hydroxysulphide (X = 0,YH = SHY in I11 and IV), no evidence of fission of the moleculecould be found,32 and, further, the o-hydroxysulphone (I) rearrangeseasily whereas the p-hydroxy-derivative (11) does not rearrange.33It is probable that the transformation occurs in the ion, since it ispromoted by alkali and becomes more facile when the strength orconcentration of the alkali is increased ; for example, when differentbases are used,34 the velocity increases in the order NaOH <NaOMe < NaOEt < NaOPrb, this being the order of effects of thesame bases on three-carbon taut0merism.3~The rearrangements may thus be represented by the generalscheme (111) + (IV), where X = SO,, SO, or S and YH = NHAc,NH,, or OH.The ionisation of the proton from Y may, of course,occur simultaneously with the processes indicated by the curvedarrows. n(111.)c/BCZy/ArThis mechanism is similar in principle t o that suggested above(p. 194) for the Hofmann and allied rearrangements, and is in har-mony with the observed effects of varying X or Y or of introducingsubstituent groups. The constitutional factors which determinethe ease of the rearrangement are (a) the positive character of thecarbon atom of Ar which is linked directly t o X, (b) the positivecharacter of X, ( c ) the tendency of YH t o yield its proton to theacceptor present in the medium, and (a) the capacity of Y t o actas electron donor.The effect of (a) is illustrated by examples in which Ar containsvarious electron-attractive groups. Thus, qualitative experiments31 Ann.Reports, 1933, 30, 188.32 L. A. Warren and S. Smiles, J . , 1931, 914.33 A. A. Levi and S. Smiles, J . , 1932, 1488.34 B. A. Kent and S. Smiles, J., 1934, 422.G . A. R. Ron and R. P. Linstead, J., 1929, 1269WATSON : REACTLON MECHANISMS. 199indicated a decreasing facility of rearrangement in the series%NO,*C,H, > 4-N02*C,H, > 4-MeS0,*C,H,.33. 36 Quantitative de-terminations (by a colorimetric method) of the times necessaryfor the completion of rearrangement of the sulphone (V) to thesulphinic acid (VI) under fixed conditions gave the order 2 : 4-di-NO, > 2-N02 : 4-C1 > 2-N02 > %NO2 for substituents in the Bn~cleus.3~ This is the order of decreasing electron-attractivecharacter as indicated by the dissociation constants of the corre-sponding benzoic acids, and therefore the order of decreasing posi-tive nature of the carbon marked with an asterisk.Other vari-ations of the B nucleus have also been studied.37A similar acceleration by electron-attractive substituent,s in themigrating group has been found in the rearrangements of imino-ethers, amidines,l7 and quaternary ammonium salts,17 and it wouldappear that in all these transformations the important factor isthe facility with which the group can accept electrons from thedonating atom to which it migrates. On the other hand, in theBeckmann, Hofmann, and Lossen degradation^,^^ electron-repulsivesubstituenhs in the migrating group have a favourable effect; thenitrogen which here acts as donor is actually deficient in electrons(owing to the departure or tendency towards departure of ananionic group), and the important factor is the supply of electronsto the C-N bond (a process which has no analogue in the othersystems referred to).Substituents in the A nucleus (B = 2-N02*C,H4) facilitate therearrangement in accordance with their electron-repulsive char-acters, which will, of course, increase the electron-donating capacityof the phenolic oxygen (factor d above).This is in harmony withthe effects of substituents in the non-migrating groups of imino-ethers, amidines and quaternary ammonium salts.It is indicated 34by the sequences 5 : 6-C4H4 > 3 : 5-diMe > $Me, and 5-6 >5-OMe > 4-0. The approximate equality of the effects of 5-Meand 5-OMe is probably due to the intervention of factor ( c ) whenthe group is powerfully electron-releasing. A 6-Me group is extra-s~ L. A. Warren and 5. Smiles, J., 1932, 1040.37 F. Galbraith and S. Smiles, J., 1935, 1234.38 See above, p. 192200 ORGANIC CHEMISTRY.ordinarily effective in facilitating the change ; 39 this appearspeculiar, but may perhaps be due to hydrogen bonding with thesulphone oxygen, the positive character of the sulphur atom thusbeing increased (factor b ) ; the effect is probably analogous to therelatively high strength of o-toluic acid.*The co-operation of factors ( b ) , (c), and (d) is well illustrated bythe effects observed when X and Y (in 111) are varied.34.409 41When Ar = 2-N0,*C,H4 and YH = NHAc, the rearrangementoccurs (under the experimental conditions employed) in the sul-phone, the sulphoxide and the sulphide (X = SO,, SO or S),but when YH = OH (aryl; i.e., C-C in I11 is a portion of thearomatic nucleus) only the sulphone rearranges, and if YH = OH(alphyl) or NH, (aryl) the sulphide does not change.The sulphuratom becomes progressively less positive in the series SO, > SO > S,and hence, owing to factor ( b ) , the rearrangement is most facile inthe sulphone and least in the sulphide. For different YH groups,the ease of rearrangement decreases in the series NHAc > NH, > OH,and OH (alphyl) > OH (aryl).The superiority of alcoholic tophenolic hydroxyl is probably due to the smaller electron-donatingpower of the oxygen in the latter owing to mesomerism. Theorder of basic (electron-donating) characters of the amino- andacetamido-groups is NH, > NHAc, and the above reversal of thisorder must be attributed to the intervention of factor (c). Thecombination of factors ( c ) and (d) is shown further in a moreextended series of substituted amino-gr~ups.~~ In the series "€€Me,NH,, NHAc, NH*SO,Ph, the donor capacity of the nitrogen decreasesand the tendency to release the proton increases. These opposingeffects lead, in the sulphone (VII), to a maximum facility ofrearrangement a t the middle members, where the optimum balanceof the two appears t o be achieved.Moreover, in the correspond-ing sulphides (VIII); where YH is NMe,, NHMe, NH,, NHAc,SO 42 H *NO,(o) /\/S*C,H4*NO,(o)(VIII.) /\/I t (VII.) I IV \ Y H V \ Y HNH*COC,H,*NO,(o), NH*C,H,(NO,),, NH*SO,Ph (in decreasingorder of basicity) only the acetamido- and 2-nitrobenzoyl derivativesrearranged in hot ~/3-sodium hydroxide.The rearrangements of o-aminodiphenyl ethers, studied by K. C.39 C. S . MeClement and S . Smiles, J., 1937, 1016.4O A. Levi, L. A. Warren, and S. Smiles, J., 1933, 1490.41 W. J. Evans and S. Smiles, .7., 1935, 181.* Seep. 216WATSON : REACTION MECHANISMS. 20 1Roberts and his collab0rators,~2 (IX -+ X : R = H or acyl), areof the same type as those considered above. They occur in solvents(X.)./\/OR O*C6H3(NO‘3),(IX.) fi/ _3 I\ANHR ‘/\NH*c6H3(No2) ,such as alcohol and pyridine, and particularly in mixtures of thesewith water, but are retarded by the presence of ions.They arecontrolled by the same constitutional factors as are the rearrange-ments of sulphones and other compounds studied by Smiles, andwhen different substituents, ranging from strongly electron-attrac-five to strongly electron-repelling groups, are introduced into thenucleus, the opposite effects upon factors ( c ) and (d) (above) leadto the observation of a decreased rate of transformation by groupsof both types. The peculiarity of the rearrangement lies in thefact that, when R is an acyl group, this group is found linked tooxygen in the product; the authors suggest that, like hydrogen.the acyl group migrates as a positively charged radical.An extension of the work of Smiles and his collaborators hasembraced systems of the type (XI) ---+ (XII)Ar (XII.)/\/XH - v\,.y/ (XI.)where Ar = C,H,*NO,, Z = CO or SO,, X =SO,, S or 0, andYH = NH, , NHPh, or NHMe.43 Analogous cases are (XIII) ->(XIV) and (XV) --+ (XVI).(XTV.) ~H,*SO,*C,H,*NO, CH,*SO,HCO*NHPh CO*NPh*C,H,*NO,CH,*O*C6H40N0, - CH,*OH ,(xv*) CO-NHAc CO*NAc*C,H,=NO,(XTII.)(XVT.)The reverse transformation ( X I 1 4 XI) occurs on treatment ofcertnin aryl salicylates and phenol-o-sulphonates (Z = CO, SO, ;/\/O9C6H4*~02(XVII.) (\(OH - 1 1 (XVIII.)\/\Co *o *C6H,*NO, \/\CO*OH42 I<. C. Roberts and C. G. M. de Worms, J ., 1934, 727; 1935, 1309;43 W. J. Evans anti S . Smiles, J . , 19.36, 329; R. T. Tozer and S. Smiles,K. C. Roberts, C. G. M. de Worms, and (Miss) H. B. Clark, J., 1935, 196.J., 1938, 2052202 ORGANIC CHEMISTRY.X = 0; YH = OH) with N-sodium hydroxide at lOOO.44 Ex-amples are (XVII) --+ (XVIII) and (XIX) ---+ (XX).0 C H4*N0,SO,*OH(XX.) (XIX.)Migrations from Side-chain to Nucleus.-The well-known work ofK. J. P. Orton and his collaborators upon the transformation ofN-chloroacetanilide into o- and p-chloroacetanilides in aqueousmedia has led to the acceptance of this “rearrangement ” as atypical intermolecular change, involving the intermediate form-ation of acetanilide and chlorine. A recent investigation of thetransformation in 20% alcohol under the influence of radioactivehydrogen chloride 45 has provided further confirmation; all theN-ch1oroacetanili.de which rearranges comes into radioactiveequilibrium with chloride ions and therefore passes through thechlorine stage.Although, however, the production and disappear-ance of chlorine are well established, the position appears to beless simple than was formerly supposed. The existence of a sidereaction producing chloride ions was observed by J. J. Blanksma.46This side reaction was catalysed by acids other than hydrochloric,and Orton and W. H. Gray4’ concluded that hypochlorous acid,formed by hydrolysis of the chloroamine, was reduced by theaniline resulting from further hydrolysis of the anilide. In therecent experiments with radioactive hydrochloric acid 45 a con-siderable correction for the chloride ions thus formed was foundt o be necessary, and A.R. Olson and J. C. Hornel have made afurther study of the side reaction.48 They conclude from theresults of kinetic experiments that three mols. of N-chloroacetanilidegive a compound X and two chloride ions, the reaction beingcatalysed by hydrogen ion. The compound X, which liberatesiodine instantaneously from hydrogen iodide, decomposes slowly,giving another chloride ion and a compound Y, which does notoxidise hydrogen iodide. The proportion of the N-chloroacet-44 Idem, J . , 1938, p. 1897.45 A. R. Olson, C. W. Porter, F. A. Long, and R. S. Halford, J . Amer.Chem. SOC., 1936, 58, 2467; A. R. OIson, R.S . Halford, and J. C. Hornel,ibid., 1937, 59, 1613.Compare F. D. Chattaway and K. J. P.Orton, Proc. Chem. SOC., 1902, 18, 200; K. J. P. Orton and W. J. Jones,Rep. Brit. Assoc., 1910, 85.46 Rec. Trav. chim., 1903, 22, 290.47 Rep. Brit. ASSOC., 1913, 136.4 8 J . Org. Chem., 1938, 3, 7 6 WATSON : REACTION MECHANISMS. 203anilide which gives C-chloroacetanilides in 20% alcohol a t 40” fallsfrom 70% to about 25% when the concentration of hydrochloricacid is decreased from 0 . 0 4 ~ to 0.005~. They conclude that‘‘ the second reaction apparently is prominent enough t o warranta very full investigation of it before any general conclusions basedupon the quantitative study of this rearrangement can be accepted.”The simultaneous occurrence of more than one reaction may per-haps be not unconnected with the apparent dependence of theenergy of activation upon the temperature, as observed by J.0.Percival and V. K. LaMer.4gThe transformations of N - halogenoacylanilides in anhydroussolvents have been examined by R. P. Bell and his co-~orkers.~OI n the case of N-chloroacetanilide, of N-bromoacetanilide and alsoof N-iodoformanilide, general acid catalysis is observed. More-over, no free halogen could be detected in the bromoacetanilidesystem and a small amount of iodine which appeared in the solutionof N-iodoformanilide was quite insufficient to account for the rateof production of p-iodoformanilide. It is concluded that the trans-formations are intramolecular in these solvents. The behaviourof N-bromobenzanilide also resembles that of N-bromoacetanilide.51There has long been evidence (e.g., the wandering of the ArN,group to a foreign nucleus) that the diazoamino-aminoazo-conversionis an intermolecular process. H. V. Kidd 52 has now reported theisolation of benzeneazo-p-naphthol and aniline in 90% of thetheoretical quantities from an acidic solution of diazoamino-and he finds further that, under the correct conditionsof acidity, benzenediazonium chloride and aniline condense to givep-aminoazobenzene without the intermediate production of diazo-amin~benzene.~~ Similarly, E. Rosanhauer and H. Unger 55 findthat the coupling of benzenediazonium chloride with aniline inneutral, feebly basic, or weakly acidic solutions proceeds by twoindependent routes, one leading to diazoaminobenzene and theother to p-aminoazobenzene ; increasing acidity favours the latter,which becomes the exclusive product a t a certain acid concen-tration. All these results lead inevitably t o the conclusion thatthe conversion of diazoaminobenzene into p-aminoazobenzene pro-4 9 J .Amer. Chem. Xoc., 1936, 58, 2413.50 Proc. Roy. SOC., 1934, A , 143, 377; 1935, A , 151, 211; J., 1936, 1154,51 R. P. Bell and 0. M. Lidwell, J . , 1939, 1096.52 J . Org. Chem., 1937, 2, 198.53 Compare J. C. Earl, Chem. and Ind., 1936, 55, 192.54 Compare K. H. Meyer, Ber., 1921, 54, 2265.5 5 Ibid., 1928, 61, 39?.1520; 1939, 1774.204 ORGANIC CHEMISTRY.ceeds through a fission of the molecule giving benzenediazoniumchloride and aniline, followed by p-~oupling,5~ and Kidd has putforward the following scheme :PhN,*NHPh + HCl PhN,Cl + PH < 7, fastpH > 7, very fastpH < 7, very slowPhNH, <-- -+ PhN,*C,H,*NH, 4- HClHe suggests that benzenediazoaminoazobenzene, which has beenpostulated as an intermediate product,57 may be formed by a sidereaction between the aminoazobenzene and benzenediazoniumchloride.Certain of Goldschmidt's earlier results are also dis-cussed in their relation to the newly-proposed mechanism.W. J. Hickinbottom has suggested 58 that the production ofnuclear-alkylated anilines by the Hofmann-Martius method or byheating N-alkylanilines with metallic salts may involve the separ-ation of the alkyl group as a positive ion ; the production of neutralradicals is unlikely, since the known products of decomposition ofthese radicals have not been detected.On this view, olefins andalkyl halides, which are frequently produced, and which havebeen suggested as intermediates in the rearrangements, are theresult of side reactions. Thus, an olefin would arise from thestabilisation of the positive alkyl group by loss of a proton assuggested by Whitrn~re.~ I n the case of certain branched groupssuch as isobutyl, tert.-butyl and isoamyl, however, the formationof olefin appears to become of greater importance, and it is sug-gested that the rearrangement may here proceed largely throughthe action of the olefin upon the nucleus,59 since aminoalkyl-benzenes are shown to be formed in this way.60 The Hofmann-Martius rearrangement now becomesprr > I .I(% \low+ R.c,T-&H~+ l t ' Y I C,H,-NH,R -+ C,H,*NH,C,H,*NH;+ + olefinThe necessity for postulating two routes is shown by the factthat, whereas toluidines are formed in considerable quantities by56 Compare C. K. Ingold, E. W. Smit.h, and C. C. N. Vass, J., 1927, 1245.5 7 J. C. Earl, Ber., 1930, 63, 1666.5 8 J., 1934, 1700.59 W. J. Hickinbottom and S. E. A. Ryder, .7., 19.31, 1281 ; IT. J. Hickin-bottom, J., 1932, 2396 ; 1937, 404.60 Idem, J., 1935, 1279WATSON : REACTION MZCHANISMS. 205heating methylaniline hydrobromide or hydriodide a t 300" in openvessels,5* very little if any p-amino-tert.-butylbenzene is obtainedby heating tert.-butylaniline hydrochloride a t 212" or by heatingthe base with cobalt chloride or bromide under such conditionsthai; volatile products can escape; high yields of butylene areformed, h0wever.5~The positive-alliyl-group mechanism provides a simple explan-ation of the presence of nuclear-alkylated alkylanilines in theproducts of some rearrangements (migration to a foreign nucleus)and of the formation of 2 : 4-dibenzylaniline when benzylaniline isheated with cobalt chloride.61 Branched alkyl groups frequentlyundergo isomerisation, and this change probably occurs in theion.Sometimes isomerisation of the alkyl group occurs when thehydrobromide is heated, but not when the amine is heated with ametallic salt. Hickinbottom suggests that in the latter case thesalt may stabilise the ion or accelerate its reaction with thenucleus.In the rearrangements of allyl (and subst,ituted allyl) aryl ethersto give nuclear-slkylated phenols, shown by L.Claiseii 62 to occuron heating a t about 200°, the allyl group takes up the o-positionpreferentially ; thus, no detectable quantity of p-allylphenol isformed when phenyl allyl ether is heated.63 The group becomeslinked to the nucleus by the terminal (7) carbon atom,64 and thechange is kinetically uniinolecular (this has recently been demon-strated for p-tolyl allyl ether in diphenyl ether solution).65 Vinylallyl ether, containing the essential part of the allyl aryl etherskeleton, undergoes a similar rearrangement to yield allylacet-aldehyde.G6 Definite proof of the intramolecular character of themigration of a substituted allyl group from oxygen t o the o-carbonatom has been provided by C.D. Hurd and L. Schmerling.67When a mixture oE phenyl cinnaniyl ether and p-naphthyl allyl etherwas heated, each compound rearranged independently ; the pro-duct contained no o-allylphenol, for example. Similar results wereobtained when a mixture of P-naphthyl allyl ether and 2-hexenylphenyl ether was heated. There can be little doubt, therefore,61 Iclena, J., 1937, I 1 19.63 Ber., 1912, 45, 3157.63 W. M. Lauer and R. M. Leekley, J . Amer. Chefre. SOC., 1939, 61,30-13.6 i L. Claisen and E. Tietze, Ber., 1925, 58, 275; C. D. Hurd and F. L.Cohen, J. Amcr. Chem. SOC., 1931, 53, 1917.G 5 J. F. Kincaici and D.S. Tarbell, ibid., 1939, 61, 3085.6 6 C. D. Hurd and M. A. Pollack, ibid., 193X, 60, IOO.?; J . Or!/. Chem.,67 J . Anier. Clietts. Soc., 1937, 59, 1 O i .1938, 3, 550206 ORGANIC CHEMISTRY.that the thermal rearrangements of aryl allyl ethers to o-ally1phenols are to be represented by a scheme such as the following :Such a mechanism would be possible only in a system which permitsthe electromeric changes indicated by the curved arrows, and it isin systems of this type that ortho-migration has been observed mostfrequently on the application of heat alone. In the rearrangementof phenyl y-ethylallyl ether (I), o- ay-dimethylallylphenol (111) isproduced in addition to o-y-ethylallylphenol (I1 ; the anticipatedproduct, with the y-carbon atom of the allyl group linked to thenucleus), and a similar " abnormal '' product has been found inother rearrangements. 68(1.) (11.) (111.)If the o-positions are already occupied, the migrating allyl grouptakes up the p - p o ~ i t i o n , ~ ~ and there is evidence that the carbonatom which now becomes linked t o the nucleus may be that whichwas originally attached t o oxygenY70 e.g., (IV) to (V).The mechanism of this p-migration is clearly different from thatof the ortho-rearrangement. If the p-position and both o-positionsare occupied (as in 2 : 4 : 6-trialkylphenyl allyl ethers), olefin iseliminated on heating, and, indeed, products which could arise6 8 W.M. Lauer et al., J. Amer. Chem. Soc., 1936,58, 1388; 1939,61,3039,3043, 3047; C.D. Hurd and M. A. Pollack, J . Org. Chem., 1938, 3, 550.69 L. Claisen and C. Eisleb, Annalen, 1913, 401, 21.70 0. M u m and F. Mailer, Ber., 1937, 70, 2214. Compare 0. Muminet al., ibid., 1939, 72, 100WATSON : REACTION MECHANISMS. 207only by an initial scission of the molecule have been found in somecases where the normal reawangement occurs; 71 e.g., during therearrangement of (VI) to (VII) some (VIII) is formed.It is quite reasonable, therefore, to suppose that, when thep-alkylated phenol is formed by rearrangement of the ether, thechange is intermolecular, the mobile group being removed com-pletely from the molecule and replaced at the p-position. Theortho-rearrangement of allyl aryl ethers must be regarded, however,as essentially intramolecular, with the possibility of an inter-molecular process as a subsidiary change.In all the rearrangements of ethers to which reference has thusfar been made, the migrating group is allyl or substituted allyl,and the electromeric changes depicted in the suggested scheme(above) can occur.Several cases are on record, however, in whicha tertiary alkyl or a benzyl group migrates from oxygen to thenucleus under the action of heat. The new linkage is now formedby the carbon atom which was originally bound to oxygen, and itmay take up either the o- or the p-position; e.g., phenyl tert.-butylether gives p-tert.-b~tylphenol,~~* 73 benzyl phenyl, benzyl o-tolyl,and benzyl guaiacyl ethers on heating at about 250" yield thecorresponding p-benzyl and dibenzyl derivatives in addition tophenol, o-cresol and guaiacol respectively, and benzyl a- and p-naphthyl ethers give respectively 4-benzyl-a-naphthol and l-benzyl-p-naphthol together with the naphthols fhem~elves.7~ The migra-tion of the benzyl group to a foreign nucleus has been observed incertain cases ; e.g., a mixture of benzyl phenyl ether and p-naphtholyields l-ben~yl-~-naphthol,~~ and when a quinoline solution ofbenzyl phenyl ether is heated at 250°, the products are o- andp-hydroxydiphenylmethanes, benzylquinolines, phenoxyquinolines,phenol and toluene ; by controlling the experimental conditions,the yields of benzylquinolines and phenoxyquinolines may beincreased considerably at the expense of the normal products(hydroxydiphenylmethanes) .7571 C. D. Hurd and W. A. Yarnall, J. A ~ n e r . C h e m Soc., 1937, 59, 1686.74 R. A. Smit,h, ibid., 1933, 55, 3718.7 3 S. Natelson, ibid., 1934, 56, 1583.$4 0. Behagel and H. Freiensehnor, Ber., 1934, 61, 1368.7 5 W. J. Hickinbottom, Nature, 1938, 142, 830; 1939, 143, 520208 ORGANIC CHEMISTRY.There are also numerous instances in which phenyl alkyl ethersrearrange to alkylated phenols, not under the influence of heatalone, but in presence of a catalyst. The groups which migrateunder these conditions include isopropyl, isobutyl and see.-butyl,but not n-alkyl groups; isomerisation of the group may occurduring the rearrangement. The migrations of tert.-butyl and benzylhave also been studied in presence of a catalystl.The catalystswhich promote these changes are hydrogen chloride,76, 77 sulphuricacid in glacial acetic zinc chloride,77 zinc chloride andhydrogen chloride,79 zinc chloride and acetic acid,80 boron fluoride 81and aluminium chloride.s2 These may all be classed as electron-acceptors, and it is quite probable that the ether is activated byoxonium compound formation; 77p 78 an addition compound ofboron fluoride with a phenolic ether is actually known. As inthe migrations of benzyl and tert.-alkyl groups under the action ofheat alone, the atom severed from oxygen becomes attached tothe nucleus, and the group may enter either the ortho- or the para-position. Moreover, in a number of these cstalysed rearrange-ments the migration of the group to a foreign nucleus has beenrealised.Thus, when a mixture of 2 : 4 : 6-triisopropylphenylisopropyl ether with phenol was treated with boron fluoride, allthe possible o- and p-alkylated phenols and ethers were isolated,and on passing boron fluoride into phenyl isopropyl ether con-siderable quantities of the mono-, di-, and tri-alkylated phenolsand ethers, in addition to phenol, were found in the product ; 81 thetolyl isopropyl ethers gave similar results. W. F. Short andM. L. Stewart 79 have observed that benzyl phenyl ether in presenceof zinc chloride and hydrochloric acid gives up more than half itsbenzyl to an anisole nucleus; and R. A. Smiths3 has shown thatphenyl and p-tolyl isopropyl ethers on treatment with aluminiumchloride in presence of diphenyl ether give alkylated diphenylethers, while p-tolyl isopropyl and phenyl isobutyl ethers in presenceof benzene and aluminium chloride give isopropyl- and tert.-butyl-benzenes respectively as main product (the alkyl group isomerisesin the last case).7 6 N. I. Kursanov, J . Rms. Phys. Chem. Soc., 1914, 46, 815.7 7 J. van Alphen, Rec. Trav. chim., 1927, 46, 799.J. B. Niederl and S. Natelson, J . Amer. Chena. Xoc., 1931, 53, 1928;J. B. Niederl and E. A. Storch, ibid., 1933, 55, 284.79 W. F. Short, J., 1928, 528; W. F. Short and M. L. Stewart, J., 1929,553.8o J . Ainer. Chewi. SOC., 1934, 56, 1715.81 F. J. Sowa, H. D. HiIlton, and J. ,4. Nieuu71aiic1, ibid., 1932, 54, 201'3;82 R. A. Smith, ibid., 1933, 55, 849, 3718. '1933, 55, 3402.83 Ibid., 1934, 56, 7 WATSON : REACTION MECHANISMS.20'3M. M. Sprung and E. S. Wallisso find that some optical activityis retained in the products of rearrangement of certain aryl sec.-butyl ethers, although extensive racemisation occurs ; this con-trasts with the almost complete retention of optical activity in theCurtius, Hofmann, and Lossen degradations,7? l1 and can hardlybe regarded as evidence of an intramolecular mechanism. Thebalance of evidence, indeed, leaves no doubt as to the intermolecularcharacter of the changes considered above. It is less easy todraw conclusions regarding the form in which the group migrates.The presence of considerable quantities of olefin as by-product inmany cases might perhaps be considered to lend probability to theformation of an alkyl cation which could stabilise itself by loss ofa proton ; the absence of dibenzyl in the products of rearrangementof benzyl phenyl ether has been used as an argument againstneutral radical formation, 79 but union of phenyl radicals in solutionwas not observed by D.H. Hey and W. A. Waters.s4 W. J. Hick-inbottom finds, ix~oreover,~~ that on heating benzyl phenyl ether inquinoline solution the benzyl and phenoxy-groups attack the sameposition of the quinoline nucleus ; this renders it unlikely that theyreact as oppositely-charged ions, but is consistent with the viewthat the ether dissociates into neutral radicals.The catalysed rearrangements of phenolic ethers appear to becomparable with the formation of liydroxy-aromatic ketones fromphenolic esters in presence of aluminium chloride, zinc chloride orferric chloride (Fries reaction).Migration of the acyl group to aforeign nucleus has been demonstrated here also by S. Skraup andK. Poller s5 and by K. W. Rosenmund and W. Schnurr; 86 E. H.Cox finds, too, that, if the reaction is carried out in diphenyl etheras solvent, the acyl group migrates to the ether, while the presenceof alcohol leads t o the product'ion of ethyl ester.87The evidence appears to lead t o the following general conclusions :(1) The rearrangements of aryl ally1 ethers under the influence ofheat to give o-allylphenols are iiitramolecular ; the necessaryelectromeric changes are here possible. (2) p-Rearrangements ofthe same ethers are intermolecular. (3) Benzyl and tert.-alkyl arylethers rearrange under the action of heat by an intermolecularprocess, the group taking up either the o- or the p-position. Thereis evidence that the group migrates as a neutral radical.(4) Therearrangements of sec.- and tert.-alkyl and of benzyl aryl ethers inpresence of catalysts (the group migrating to the o- or the p-position)R4 Chem. Reviews, 1937, 21, 19.1.8 B B e y . , 1994, 57, 2033.R i J . ArrLer. Chenz. SOC., 1930,52, 352. This paper contains a useful summaryof suggested mechanisms.X G Annalen, 1928, 460, 56210 ORGANIC CHEMISTRY.are intermolecular. It appears that the group must be sufficientlyelectron-repulsive, since n-alkyl groups do not migrate ; this mayalso be a factor in (3).The catalyst serves to weaken the bondlinking the mobile group to oxygen; the withdrawal of electronsfrom this group by the linking of an acceptor to the molecule is afeature of many intermolecular rearrangements.56The transformations of alkyl salicylates to alkylated salicylicacids by boron fluoride B8 are also intermolecular, since salicylicacid and dialkylated acids are found in the products, and migrationto a foreign nucleus has been observed. The alkyl group frequentlyisomerises (e.g., n-propyl to isopropyl, n-butyl to sec.-butyl, isobutylto tert.-butyl).A summary of our knowledge of the migrations of alkyl groupsor halogens from one position in the nucleus to another in presenceof aluminium chloride or concentrated sulphuric acid (Jacobsenreaction) has a~peared.8~(b) Condensations of Carbonyl Compounds.A recent investigation by D.S. Breslow and C. R. Hauser 1 hasled them to the conclusion that the Perkin synthesis of cinnamicacids involves the condensation of the aldehyde with the anhydride,the salt acting catalytically. This is in harmony with Perkin'soriginal view, which has been supported by Michael and others,but contrary to the interpretation of the reaction first put forwardby Fittig and assumed in most recent writings on the subject.Breslow and Hauser obtained the same relative quantities ofcinnamic and a-ethylcinnamic acids when benzaldehyde was treatedwith a mixture of either acetic anhydride and sodium butyrateor butyric anhydride and sodium acetate which had in each casebeen heated for several hours in order to establish equilibrium.At100" the equilibrium mixture contains far more butyric anhydridethan acetic anhydride, and the yield of ethylcinnamic acid is fourtimes greater than that of cinnamic acid; at 180" there is a largerproportion of acetic anhydride in the mixture, and a correspondingrelatively higher yield of cinnamic acid results. The effect oftemperature upon the proportions of the two acids obtained frombenzaldehyde, acetic anhydride, and sodium butyrate was, of course,observed in the original work of Fittig, who, however, interpretedit wrongly. Breslow and Hauser have shown further that theW. J. Croxall, F. J. Sowa, and J. A. Nieuwland, J . Org. Chem., 1937, 2,253.See also L.I.Smith and M. A. Kiess, J . Amer. Chem. SOC., 1939, 61, 989.89 C. L. Moyle and L. I. Smith, J . Org. Chem., 1937, 2, 112.* J . Amer. Chem. SOC., 1939, 61, 786WATSON REACTION MECHANISMS. 21 1condensation of benzaldehyde with sodium malonate (which cannotgive an anhydride by reaction with acetic anhydride), reported byStuart in 1883, does not occur. These observations provide sub-stantial evidence that it is the anhydride and not the salt whichundergoes condensation with the aldehyde. Certain results ofother workers lead to the same conclusion. P. Kalnin has shownthat benzaldehyde condenses readily with acetic anhydride inpresence of inorganic and organic bases (e.g., potassium carbonate,triethylamine), whereas it does not condense with sodium acetatein presence of the same substances; the significance of this observ-ation may have been overlooked on account of the very improb-able mechanism which Kalnin put forward, and which has beendi~proved.~ Moreover, benxaldehytie does not condense withsodium acetate in presence of inorganic dehydrating agents.4 Afurther related observation is that of R.Kuhn and S. I~hikawa,~who find that a-vinylcinnamic acid is formed from benzaldehydeand crotonic anhydride in presence of tertiary bases but not inpresence of potassium crotonate.In recent discussions of the mechanisms of the Perkin, Knoeve-nagel and aldol condensations,6, the close relationship of theprocesses with one another and with the Claisen acetoacetic estercondensation has been recognised.Reactions of the Perkin andKnoevenagel types may be represented by appropriate modificationsof the general schemeR*CHO + CH,R’It” + RCIXCR’R” + H,O(aldehyde (methylenecomponent) component)where at least one of the groups R’, R” is of such a character thatthe methylene group is activated (Le., the protons are incipientlyionised). As early as 1904, A. C. 0. Hann and A. Lapworth 8suggested that, in reactions of the Knoevenagel type, the methylenecomponent becomes an anion, which then forms an aldol additionproduct with the aldehyde. This was an alternative to Knoeve-nagel’s original view that the aldehyde and the base react initially;it accounts for the catalytic influence of tertiary bases, and forthe favourable effect of an increase in the strength of the base.Helv.Chim. Acta, 1938, 11, 977.E. Miiller, Annalen, 1931, 491, 251 ; C. D. Hurd and C. L. Thomas, J .Amer. Chenz. Xoc., 1933, 55, 278.* (Signa) M. Balmnin and D. Peccerillo, CTazxctta, 1935, 65, 1145.6 F. Arndt and R. Eistert, Ber., 1936, 69, 2381.Ber., 1931, 64, 2347.C. R. Hauser slid D. S. Breslow, J . At,cer. Chew. Xoc., 1939, 61, 793.t J . , 1905, 85, 46212 ORGANIC CHEMISTRY.The aldol addition product a’ppears as an intermediate in practicallyall subsequent 10 and in some cases has been i~olated.~A similar view has been held with regard to the Perkin reaction.It was based originally upon Fittig’s reported preparation of an“ aldol ” by the interaction of benzaldehyde, isobutyric anhydride,and sodium isobutyrate (where subsequent elimination of water isnot possible), but E.Muller and his co-workers failed to repeatFittig’s result.lf C. R. Hauser and D. S. Breslow have nowprepared this compound, using sodium triphenylmethyl as con-densing agent; they have also obtained “ aldols ” from benz-aldehyde and ethyl isobutyrate [CHPh( OH)-CMe,*CO,Et] andfrom benzaldehyde and ethyl acetate [CHPh( OH)*CH,*CO,Et],using the same agent. The “aldol ” view of the Perkin andKnoevenagel reactions may thus be regarded as established ex-perimentally.The mechanisms recently put forward by Arndt and Eistertand by Hauser and Bre~low,~ which incorporate the essentials ofthat suggested by Hann and Lapworth, may be written as follows(B = basic catalyst) :R + CH,R’R” 2 BJ? + 8HR’R’’/H H(1.) RW’ + EHR’R” (11.1 2 RC-CHR’R” (111.1\O \O” *H@ /H - H,O --+ ROC-CHR’R” (1v.1 -+ R*CH:CR’R‘’ (17.1 <- ‘OHArndt and Eistert, however, omit the addition of hydrion to formthe true aldol (IV); they also suggest that, as an alternative t oforming the unsaturated compound R*CH:CR’R‘’, the ion (111)may react with another molecule of the methylene component asfollows :CHR’R”R-C-CHR’R” /H + CH,R’R” -+ RCH/ + OH’\O” \CHR/RIIIt may be pointed out, however, that, if the unsaturated compoundis first formed, the addition of a second molecule of the methylenecomponent is an ordinary Michael reaction.See, e.g., E. P.Kohler and B. B. Corson, J . Amer. Chem. Soc., 1923, 45,1975.lo See, e.g., A.C. Cope, ibid., 1937, 59, 2327.l1 Annalen, 1935, 515, 97WATSON : REACTION MECHANISMS. 213For condensations occurring under the catalytic influence ofacids, Arndt and Eistert write a mechanism of the following type :R.C/H -???!+ k*C<:J C1 A+ R;C*CHR’R” + HC1 CEI R’R” /H\O ‘OHIn the Claisen acetoacetic ester synthesis,ROC/,,OEt + CHR’R”*COX _I, R*COCR’R’‘*COX + HOEt(second\‘O(estercomponent) component)the ester which replaces the aldehyde of the Perkin and IZnoevenagelcondensations will take part in the addition process less readily,owing to the resonance of the carbethoxyl group, but it possessesan anionic group which is split off more easily than is the carbonyloxygen itself.6 It follows that the aldol phase is less likely to beisolated here than in the Perkin and Ihoevenagel syntheses.Arndtand Eistert suggest that the necessary driving factor for the con-densation is the tendency for the formation of a conjugated systemwith the additional stability gained from mesomerism. Thepresence of two cc-hydrogen atoms in the second component is notnecessary here. Thus, although ethyl isobutyrate does not con-dense with a second molecule of itself under the influence of sodiumethoxide, condensations where the “ second component ” has onlyone cc-hydrogen have been effected by this agent in certain caseswhere both reacting groups are in the same molecule.12 Moreover,it has recently been shown l3 that sodium triphenylmethyl, theaction of which is more powerful than that of sodium ethoxide(since it is a stronger base) but does not appear to differ from it inprinciple, brings about the condensation Jf ethyl isobutyrate withitself (to give CHMe,*CO*CMe,*CO,Et) or with ethyl benzoate(giving Ph*CO*CMe,*CO,Et). Ethyl isobutyrate can also be con-densed by means of mesitylmagnesium bromide, which also inducesreaction in certain cases (e.g., CMe,*CH,CO,Et) where two a-hydro-gen atoms are present but where sodium ethoxide is neverthelessineffective. l4Some of the earlier mechanisms for the acetoacetic ester synthesis(Claisen, Dieckmann) postulate reaction of the second component3934, 58, 1173.Compare C.R. Hauser, ibid., 1938, 60, 1967.13 R. I?. B. Cox, E. H. Kroeker, and S. M. McElvain, J .Anaer. Chem. SOC.,13 C. R. Hauser and W. B. Renfrow, ibid., 1937, 59, 1923; 1938. 60, 483.14 M. A. Spiclman and M. T. Schmidt, ibid., 1937, 59, 2009214 ORGANIC CHEMISTRY.with an addition complex of ester and ethoxide, to form thesodium derivative of the p-diketone or ketonic ester. A schemein which the ion of Ohe second component adds to the ester wasput forward by A. La~w0rth.l~ H. Scheibler has more recentlysuggested a mechanism l6 involving the formation of certain inter-mediates which, as Arndt and Eistert point out, have no experi-mental foundation.6 C. R. Hauser and W. B. Renfrow 13 havenow adopted Lapworth’s “ ionic ” conception in a scheme whichresembles their representation of the Perkin and Knoevenagelcondensations (see above) :OEt /OEtRO’ + ~R~RWOX-> +- R*C-CR’R”*COX --+N O \oe R*CO*CR’R”*COX + OE?The product obtained when R” = H, vix., the sodium derivative ofthe diketone or ketonic ester, is regarded as being formed by afurther reaction of the ketonic form with the base.In anothermechanism, due to Arndt and Eistert,6 the enol ion is formed byelimination of alcohol from the addition complex ; this, however,makes necessary the presence of two or-hydrogen atoms in thesecond component (R” = H), which is not the case. If the reactingentity is the anion CR!R”*COX, the postulate of enolisation of thesecond component is redundant, since the ion is a mesomeric-structure C-C-O:There is no proof that the only function of the base (or even itsmain function) is the conversion of the “ second component ” intoanion. Undoubtedly such ionisation can and does occur; e.g.,J.Kenyon and D. P. Young have recently observed the almostcomplete (though slow) racemisation of certain optically activeesters of formula CHR’R’’*CO2Et in contact with sodium ethoxide,l’which would indicate an equilibrium between ester, base, andmesomeric anion. Nevertheless, the most important pa,rt playedby the base in the Knoevenagel, Perkin, and Claisen condensationsmay be the activation of the carbonyl group of the aldehyde orester by the formation of an addition product which reacts rapidly(perhaps instantaneously) with the “ second component ” (or itsion). Such a mechanism might account for the unimolecularkinetics of the aldol condensation of acetaldehyde observed byR.P. Bell,ls who interprets this feature by supposing’that thel5 J., 1901, 79, 1269. Compare J. U. Nef, Annden, 1897, 298, 218;A. Michael, Ber., 1900, 33, 3731.l6 See Ann. Reports, 1934, 31, 200.l 7 J., 1940, 216. J., 1937, 1637WATSON : REACTION MECHANISMS. 215dehydration of a hydrated aldehyde molecule a t measurable speed(catalysed by the base) is followed by a rapid condensation (alsobase-catalysed) with a second hydrated molecule. The rapidreaction might, however, be that between the complex and thesecond aldehyde molecule. If the base adds in this way to thealdehyde or ester, the Knoevenagel and Claisen condensationswould be represented in the following way :Knoevenagel.CH,R’R” +/H _____, /HN O \0- 1 0 -HROC/ + B 3 ROC-B -+- ROC-CHR’R’’ + BH+fr R-C-CHR’R’’ /H + B ---f R*CH:CR’R” + H,O + 13\OHClaisen.ROC/ + OEt- 3 R d O E tOEt OEt CHR’R”*COX /OEtR*C-CR’R”*COX + HOEtN O ‘0- \0-4 R*CO*CR‘R”COX + OEt- + HOEt/OEt CR’COX(or, if R” = H, RC-CHRWOX + ROC// + HOEt)\O- \O-(c) The ortho-Eflect.(Continued from Ann.Reports, 1938, 35, 243.)H. 0. Jenkins l9 has calculated values of the field intensity, atthe nuclear carbon atom to which the carboxyl group is linked,due to the C-Hal dipole in the halogenobenzoic acids. The relevantexpression is P = ~ ( 1 + 3 cos2 0)*/r3, where p is the dipole momentof the appropriate halogenobenzene, and r is the distance from thecentre of the dipole, the axis of which is inclined at an angle 8 to r.He finds that, for each series of halogenated acids, the plot of fieldintensities against logarithms of dissociation constants is linear ;the same applies when the values for the nitrobenzoic acids aretreated similarly.Actually the p-nitro- and p-fluoro-acids showsmall divergences from the linear relationship, owing presumablyto mesomeric effects which may not be quantitatively identical inC,H,X and C0,H*C6H4X.20 The conclusion is drawn that theortho-substituted acids show no abnormality, the relatively highvalues of their dissociation constants being due merely to theshort distances from which the inductive effects operate. Suchl9 J., 1039, 640. ao Compare Ann. Reports, 1938, 35, 341216 ORGANIC CHEMISTRY.an interpretation is probably applicable also to o-methoxybenzoicacid, but not to salicylic and o-toluic acids.All three are strongerthan benzoic acid, whereas their p-isomerides are weaker. In thefirst case, however, the inductive effect of OMe (- I ) operatinga t close range might overcome the mesomeric effect which isresponsible for the low value of the dissociation constant of p-anisicacid, but the much higher strength of salicylic acid and the increaseof strength conferred by o-Me (a + I group) make necessary thechelation hypothesis, to which reference was made in last year’sReport.When, instead of the field intensity, the electrostatic potential# = 1.1 cos e p , at the same carbon atom, is plotted against log K ,a linear relationship is found for the o-, m-, and p-substituted acidsof the above series, but the lines do not pass through the pointfor the unsubstituted acid.Again no ortho-effects are found, andthe slopes of the lines agree quite well with the values calculatedfrom the expression NEIRT. A similar treatment of the halogeno-phenols and -anilines 21 gives a linear relationship between the pointsfor the unsubstituted, o- and p-compounds of each series, and againthe slopes approximate to NE/RT, but the m-halogeno-compoundsnow diverge. This divergence is ascribed to the non-operation ofthe mesomeric effects from the m-position, and the geometry ofthe figure indicates a proportionality between the inductive andmesomeric effects (which would, of course, be expected if they hada common origin).In the case of the nitroanilines, the plot of $against log K is linear for unsubstituted, o- and m-compounds, butthe p-derivative diverges as in the acids.The significant result of this work is that the o-halogeno- ando-nitro-benzoic acids, -anilines and -phenols appear to show noeffects which are not found also in the p-isomerides, except thato-nitrophenol has an abnormally low dissociation constant , due nodoubt t o chelation of the phenolic hydrogen with the elcctron-donating oxygen of N02.22A kinetic investigation of the addition of methyl iodide to anumber of o-substituted dimethylanilines in methyl-alcoholicsolution has been reported recently.23 The energies of activationhave throughout higher values than those found for the corre-sponding p-substituted compounds ; the differences between theE values for the u- and p-isomerides (Eo - E,) cover a wide rangeand sometimes exceed 6000 calories.For o-fluorodimethylanilinethe magnitude of the PZ term of the kinetic equation does not21 J., 1939, 1137.22 Compare N. V. Sidgwick and R. K. Callow, J . , 1924, 125, 527.2n D. P. Evans, 13. B. Watson, and R. Williams, J . , 1939, 1348WATSON : REACTION MECHANISMS. 21 7differ perceptibly from that relating t o the same reaction of unsub-stituted dimethylaniline and its m- and psubstituted derivatives(this term is not changed by rn- or p-substitution).24 As in thealkaline hydrolysis of ethyl o‘-flu~robenzoate,~~ therefore, fluorineexhibits no unusual effect when present in the o-position to thereacting group.The remaining six groups examined, however,cause an increase in the value of PZ by a factor which varies from3 to 400. In this reaction, therefore, as in the esterification ofcarboxylic acids and the acid hydrolysis of esters,26 an “ortho-effect ” is indicated by a simultaneous increase in E and in PZ.The magnitude of the effect increases in the order F < OPh <OMe (NO,) < C1 < Me < Ph, a sequence which is quite uncon-nected with the weights, volumes, or chemical characters of thegroups. The effect is ascribed to an interaction, in the transitioncomplex, between the group and the unshared electrons of thenitrogen ; this is actually an electronic expression of J. von Braun’ssuggestion that the free affinity of the nitrogen is to some extentsaturated by the group attached t o the o-carbon atom.27 Thesame conception was discussed in last year’s Report 25 in connectionwith esterification and ester hydrolysis, where the electron-donatingatom is carbonyl oxygen.I n the present case tervalent nitrogenis the donor atom, and it is possible to envisage a series of groupswhich, when suitably placed, would give a steadily increasing‘’ degree of interaction.” The extreme members of this serieswould be fluorine, where interaction is impossible, and carboxyl,which transfers a proton completely to nitrogen, forming an electro-valent bond. Intermediate between these would stand groupscapable of forming a hydrogen bond with the nitrogen, and it issuggested that o-Me and o-Ph come into this category.The pro-cess would render the unshared electrons of the nitrogen less avail-able for reaction with the alkyl halide, thus raising E ; it wouldalso confer a charge upon the reactive portion of the complex, thelife of which would be increased with a resulting rise in the valueof PZ.25 This is in harmony with observation. The remaininggroups studied (Cl, NO,, OMe, OPh) have much smaller effects,and it is postulated that there is here some form of interactionwithout the formation of an actual “ bond.’’ It was suggestedin last year’s Report that some interaction of this nature might24 I(. J. Laidler, J . , 1938, 1786; D. P. Evans, H. B. VC7atson, and R.Williams, J ., 1939, 1346.z 5 See ibid., p. 246.26 C. N. Hinshelwood and A. R. Legard, J., 1935, 587; E. W. Timm a.nd2 7 Rer., 1916, 49, 1101; 3918, 51, 282.Compare Ann. Reports, 1938, 35, 237.C. N. Hinshelwood, J., 1938, 862218 ORGANIC CHEMISTRY.explain the rather low strengths of some o-substituted anilines. Inview of the recent findings of H. 0. Jenkins,21 however, the con-ception of an " ortho-effect '' in o-chloro- and o-nitro-anilines mustbe abandoned; the postulated interaction is manifested only inreactions and not in equilibria. A chelation hypothesis still appearsto be necessary to interpret the basic strength of o-toluidine, how-ever (compare o-toluic acid, above).The order o-Me > o-C1 > o-OMe for the energies of activationin the addition of methyl iodide to dimethylanilines is in harmonywith the relative yields of quaternary iodide obtained by vonBraun2' from the same compounds under fixed conditions.Healso found that the p-positions were rendered less active, the sameorder of effects being maintained. It is now suggested23 that theinteraction of the unshared electrons of nitrogen with the o-sub-stituent reduces the electromeric effect of the dimethylamino-group.A reduction of mesomerism by o-methyl groups has been demon-strated by C. E. Ingham and G. C. Hampson28 by determinationsof the dipole moments of a number of derivatives of durene andmesitylene. The moments of aminodurene and mesidine areidentical within experimental error, but slightly lower (by 0.13 D)than that of aniline; a larger difference (0.55 D) is found betweenthe moments of dimethylmesidine and dimethylaniline.A relatedfact is the nitration of the acetyl derivative of m-2-xylidine atCompare R. H. Birtles and G. C. Hampson, J . , 1937, 10. 28 J., 1939, 981SMITH : THE PEROXIDE EFFECT. 219positions 4 and 6 ; the mesomeric effect (and by implication theelectromeric effect also) of the acetamido-group is so reduced thatthe directive influence of the methyl groups takes control. Nitro-aminodurene also has a lower moment (by 1-12 D) than p-nitro-aniline, and almost the same lowering is observed in 2-nitro-m-5-xylidine, which has methyl groups o- t o the nitro- but not t o thoamino-group. The greatest depression observed is in nitrodi-methylaminodurene, which has a moment lower by 2.76 unitsthan that of p-nitrodimethylaniline. The results are summarisedabove, where the figures in the centre of the formulz denote thedipole moments .The authors ascribe this lowering of the dipole moment to asteric effect of the o-methyl groups which prevents the system fromtaking up a planar configuration and thus reduces the mesomerism.The formation of hydrogen bonds between the methyl groups andthe adjacent electron-doncrs (oxygen of NO,, nitrogen of NH,or NR,) appears to furnish an alternative explanation, however.It is also in harmony with the absence of the effect in durenol(compare absence of abnormal properties in o-cresol, for example) .22The greater effect in the dimethylamino- than in the amino-com-pounds is not interpreted so easily on this basis; it is strange thatthe reverse is found in the basic strengths of o-toluidine and di-methyl-o-toluidine.29 A complete interpretation of the observedphenomena would perhaps include both factors.H. B. W.3. THE PEROXIDE EFFECT.According to a patent applied for by W. Bauer in 1922 acetyleneadds hydrogen bromide at the ordinary temperature in presence ofgaseous oxidising agents (air, oxygen, nitrogen peroxide) to give90% yields of ethylene dibromide ; the second molecule of hydrogenbromide is oriented contrary to the Markownikoff rule.2CH,:CHBr + HBr + CH,Br*CH,Br(Bauer’s claim for a similar effect with other halogen acids has notbeen substantiated.) This publication seems to have been overlookedand additions of hydrogen bromide to olefins continued to giveconfusing and inexplicable results until 1933.Y. Urushibara and29 Compare Ann. Reports, 1938, 35, 248.U.S. Patent, 1,540,748 (1925); British Chem. Abstr., 1925, B, 692.W. B. Markownikoff, Annalen, 1870, 153, 256. (i) “If an unsym-metrical hydrocarbon combines with halogen acid the halogen adds to thecarbon atom with fewer hydrogen atoms, i.e., t o the carbon which is moreunder the influence of the other carbon atoms; (ii) by addition of halogenacid to vinyl chloride or chlorinated propylene, etc., the halogen will alwaysadd to the carbon which is already combined with halogen.220 ORGANIC CHEMISTRY.R. Robinson reported that the orientation of addition to Ale-undecenoic acid depended on whether the reaction vessel was opento the air or not (they provisionallyattributed the effect to moisture)."M.S. Kharasch and F. R. may^,^ carrying out reactions betweenhydrogen bromide and ally1 bromide in sealed tubes, noticed thatwhen air was left in the tubes yields of 85-90% of 1 : 3-dibromo-propane were obtained; if the tubes were cooled and evacuatedbefore sealing, reaction was much slower and the product wasmainly 1 : 2-dibromopropane. The American authors extended thework to vinyl bromide and to propylene,6 finding in each casethat the presence of oxygen and/or peroxides €avowed an orient-ation of addition opposite to that predicted by the Markownikoffrules. The results obtained by Kharasch and Mayo have beenconfirmed in several laboratories and the hypothesis that the" abnormal " or " peroxide catalysed " reaction is due to the presenceof bromine atoms (formed from hydrogen bromide and the " oxidant")is now widely accepted.The subject has already been dealt within two reviews; 7 9 7a in this Report the emphasis will be on thepublications of 1938 and 1939.oxide in benzene to yield the saturated diketone (LXXXII), ofwhich the ll-keto-group could be reduced catalytically to CH,.Demethylation of the product gave x-norequilenin (LXXXIII).(LXXXII.) (LXXXIII.)Recently 37 x-noroestrone has been prepared from (LXXXI,R = OMe) (see p. 293). H. A. Weidlich and G. H. Daniels 59 haveused the ring closure of y-diketones in the preparation of the interest-ing 3-naphthyl-2-methylcyclopentttnone (LXXXVI) (the methodis a development of early work by W.Borsche60). They con-densed ethyl sodio- P-ketovalerate with w-bromo-p-acetylnaphth-alene, obtaining (LXXXIV). This, on decarboxylation and ringclosure, gave the naphthylmethylcyclopentenone (LXXXV) , whichwas hydrogenated to (LXXXVI).(LXXXIV.) (LXXXV. ) (LXXXVI. )C. K. Chuang and his collaborators58 J., 1938, 1994.60 W. Borsche and A. FeIs, Ber., 1906, 39, 1813; W. Borsche and W.Mentz, ibid., 1908, 41, 194.C. K. Chuang,Y. L. Tien, and Y. T. Huang, Ber., 1937, 70, 858; C. K.Chuang, Y . T. Huang, and C. M. Ma, ibid., 1939, 72, 713 ; C. K. Chuang,C. M. Ma, Y . L. Tien, and Y. T. Huang, ibid., p. 949.have described severalSD Ber., 1939, 72, 1590SPRINGALL : SYNTHESIS OF STEROIDS.299syntheses by the Robinson-Schlittler-Walker method.62 Themethyl 5-keto-8-m-methoxyphenyloctoate of (Sir) R. Robinsonand E. Schlittler (LXXXVII) was cyclised with sulphuric acid togive methyl y-(6-methoxy-3 : 4-dihydro-l-naphthy1)butyrate(LXXXVIII) . Hydrolysis, dehydrogenation with sulphur, andesterscation yielded the corresponding naphthalene ester (LXXXIX) .Repetition of the Robinson-Schlittler condensation with ethylsodio-a-acetylglutarate led to 5-kefo-8-(6’-methoxy-l’-naphthyl)-octoic acid (XC). The corresponding keto-ester was cyclised withsodium ethoxide t o the 1 : 3-diketocyclohexane derivative (XCI),which in turn was cyclised in the presence of either phosphoricoxide in benzene or cold sulphuric acid to the methoxyketohexa-hydrochrysene (XCII).(LXXXVII.) (LXXXVIII.) (LXXXIX.)The cyclopentenophenanthrene (XCIII) corresponding to (XCII)was prepared from the acid of (LXXXIX) by the same process,ethyl sodioacetylsuccinate being used. An attempt to introducethe angle methyl group on C,, (of the cholane system) failed. Thea-methyl-y-( 6-methoxy-l-naphthy1)butyryl chloride appeared tocondense with the ethyl sodioacetylsuccinate, but hydrolysis gaveonly the original acids and not the desired (XCIV). (Severale2 (Sir) R. Robinson and E. Schlittler, J., 1935, 1288; (Sir) R. Robinsonand J. Walker, J., 1936, 192; Ann. -Reports, 1936, 33, 334300 ORGANIC CHEMISTRY.similar failures of the Robinson keto-acid ~ynthesis,~~ in caseswhere a methyl group should appear a to the keto-group, have beenr e ~ o r d e d .~ ~ ~ ) This development of the Robinson-Schlittler-Walkermethod had been independently investigated by (Sir) R. Robinsonand J. M. C. T h ~ m p s o n , ~ ~ ~ who also prepared the ketomethoxy-hexahydrochrysene (XCII). G. Haberland 64b built up the 4-keto-5-methyllieptoic acid system from a-methyl-y-( 6-methoxy- 1 -naphthy1)butyryl chloride by the successive action of diazomethane,hydrobromic acid and ethyl sodiomalonate. The resulting ester(XCV) was cyclised with sulphuric acid to give methyl 7-methoxy-.%methyl3 : 4-dihydrophenanthrene-l-propionate (XCVI).The possibility of preparing keto-esters of the type (XCVII) bythe Friedel-Crafts reaction with ethyl y-m-methoxyphenylbutyrate and y-carbo-p10red.~~ By double ring closure suchMe01 ,)!,) compounds should give valuable oestrone\\ (xcvll') intermediates.Difficulties arose, how-ever, due to substitution o to the methoxy-group and to prematurering closures.The ring closure of diketones and keto-acids has been used inthe preparation of hydrophenanthrenes related to morphine 66and to the diterpene~.~'co /\/co2Me C0,E.t methoxybutyryl chloride has been ex-/\/ /(vi) Formation of Cyclic Ketones from Monocarboxylic Acids andtheir Derivatives.The early work on the preparation of cyclic ketones by the lossof water from acids (in the presence of sulphuric acid) and of hydro-gen chloride from acid chlorides (in the presence of aluminium63 (Lady) G.M. Robinson, J., 1930, 745.64 (a) D. A. Peake and (Sir) R. Robinson, J., 1937, 1581; (b) G. Heberland,Ber., 1939, 72, 1215; (c) (Sir) R. Robinson and J. M. C. Thompson, J., 1939,1739.65 (Sir) R. Robinson and J. Walker, J., 1937, 60; K. H. Lin, J. Resuggan,(Sir) R. Robinson, and J. Walker, ibid., p. 68; (Sir) R. Robinson and J.Walker, J., 1938, 183; K. H. Lin and (Sir) R. Robinson, ibid., p. 2005;(Sir) R. Robinson and J. M. C. Thompson, ibid., p. 2009.G 6 L. F. Fieser and H. L. Holmes, J. Arner. Chem. SOC., 1938, 60, 2548.6 7 H. Plimmer, W. F. Short,, and P. Hill, J., 1938, 694SPRINGALL : SYNTHESIS OF STEROIDS. 301chloride or stannic chloride) has been reviewed previously.68 Thering closures may be performed on aromatic rings (following F.S.Kipping or on unsaturated alicyclic rings (following G. Darzens 70).Both methods have been employed in recent steroid work.(a) Ring Closures involving Aromatic Rings.-G. Haberland andE. Blade 71 condensed 6-methoxy-l-~-bromoethyltetralin withethyl sodiomethylmalonate and decarboxylated and dehydro-genated the product, obtaining the acid (XCVIII). Cyclisation ofthis acid with sulphuric acid, followed by demethylation, yieldedthe valuable l-ket,o-7-methoxy-2-methyl-l : 2 : 3 : 4-tetrahydro-phenanthrene (XCIX). This was subjected to the Reformatskyreaction with ethyl p-bromopropionate, giving the lactone (C) ,which was converted into the chloride of the dehydrated acid (CI)and cyclised with stannic chloride, yielding either (CII) or (CIII) 72(dehydrogenation occurring during the cyclisation).0The methyl 7-methoxy-2-methyl-3 : 4-dihydrophenanthrene-l-pro-pionate (XCVI) (p. 300) was also converted into the acid chloride(CI) and gave (CII) or (CIII) on treatment with stannic chloride.64bWhen the cyclisation was performed a t - Z O O , dehydrogenationwas avoided and the 3 : 4-dihydrophenanthrene compound corre-sponding to (CII) or (CIII) was obtained.KetocycZopentenophenanthrenes with the five-membered ringfused in various positions have been prepared from p-1-, p-2-,Ann.Reports, 1936, 33, 336.C m p t . rend., 1910, 150, 707.69 J., 1894, 65, 480.'il Ber., 1937, 70, 169.'i2 G. Haberland and E. Heinrich, Ber., 1939, 72, 1222302 ORGANfC CHEMfSTRY.p-3- and p- 10-phenanthrylpropionyl chlorides.73 The first twooyclisations bear on the steroid problem. The 1 -substitutedphenanthrene gave only 4% of the 1 : 2-cyclisation product (CIV),and 25% of the 1 : 10-product (CV). The 2-substituted phen-anthrene gave exclusively the 1 : 2-product (CVI).The 9 : 10-dihydro-derivative of P-2-phenanthrylpropionic acid,however, gave both 1 : 2- and 2 : 3-cyclisation products.74 Thering closure of the 1 : 2 : 3 : 4-tetrahydro-derivative of p-l-phen-anthrylpropionyl chloride has been studied by J. Hoch : 75 thecompound ring closes to the 10-position of the phenanthrenenucleus. From y-l-phenanthrylbutyric acid, the ketotetrahydro-chrysene was obtained. A synthesis along these lines of a nor-equilenin methyl ether has been described in a German patent.767-Methoxy- 1 : 2 : 3 : 4-tetrahydrophenanthrene-1 -propionic acid(CVII) was cyclised, and the product described as a norequileninmethyl ether (CVIII).It would appear more probable, however,that ring closure would occur to the lo-, rather than the 2-position,giving (CIX), especially as in this case the C, atom is part of asaturated alicyclic system (such saturated systems are known not tocondense readily, if at all, with carboxylic acid derivatives77).0(CVII.)The method was also employed in the preparation of (CXI),'878 W. E. Brtchmann and M. C. Kloetzel, J. dmer. Chern. SOC., 1937, 59,74 A. Burger and E. Mosettig, ibid., p. 1303.713 Bull. Soc. dim., 1938, [v], 5, 264; Compt. rend., 1938, 207, 921.76 Chem.Abstracts, 1938, 32, 4176.7 7 A. E. Bradfield, E. R. Jones, and J. L. Sirnonsen, J., 1934, 1810; J. W.Barrett, A. H. Cook, and R. P. Linstead, J., 1936, 1067; J. W. Cook mid C. A.Lawrence, ibid., p. 1637.2207.7 8 (Sir) R. Robinson and J. M. C. Thompson, J., 1938, 2009SPRINGALL : SYNTHESIS OF STEROIDS. 303a model for (CXII) desired as an oestrone intermediate. TheMichael addition of ethyl cyanoacetate to ethyl Ab-dihydromuconate,C02Et/ CO,Etand condensation of the product with p-phenylethyl bromide, gave(CX), which, as the free acid, cyclised with sulphuric acid to (CXI).In the course of syntheses in the diterpene series the formation ofa, seven-membered ring by this cyclisation method has been ob-served.7g The acid (CXIII) gave (CXIV) as well as the expectedproduct (CXV).,rl CH2TH2 70 p 2\/\//\/\ A/\/\() fl /v\ co2I-p. I II I I II I I II I\A/ \/\/OMe OMe(CXIII.) (CXIV.) (CXV.)The preparation of keto- and hydroxy-chrysenes starting frombenzalacetophenone, two such ring closures being used, has beendescribed.sO The introduction of two new reagents for these cyclicketone syntheses, namely, acetic anhydride, acetic acid and zincchloride,s1 and liquid hydrogen fluoride,82 has been announced.(b) Ring Closures involving Unsaturated Alicyclic Ring8.-Developing earlier M T O ~ ~ , ~ ~ J. W. Cook and C. A. Lawrcnce 84 haveOMe79 G. A. R. Kon and F. C. J. Ruzicka, J . , 1936, 187; P. Hill, W. F. Short,and H. Stromberg, J., 1937, 1619; J. Lockett and W. F.Short, J., 1939,787; G. A. R. Kon and H. R. Soper, ibid., p. 790; see also L. F. Fieser andM. A. Peters, J . Amer. Chem. Soc., 1932, 54, 4347; L. F. Fieser and M. Fieser,ibid., 1933, 55, 3342.8o M. S. Newman, J . Amer. Chem. SOC., 1938, 60, 2947.L. F. Fieser and E. B. Hershberg, ibid., 1937, 59, 1028.82 L. F. Fieser and E. B. Hershberg, ibid., 1939, 61, 1272; W. S. Calcott,83 J. W. Cook and C. A. Lawrence, J., 1935, 1637.J- M. Tinker, and V. Weinmap, ibid., p. 949.84 J., 1937, 817304 ORGANIC CHEMISTRY.prepared the methyloctalone (CXVII) [and, by reduction, themethyldecalone (CXVIII)] from 1 -methyl-A1-cycZohexene-2-y-butyrylchloride (CXVI). Similar preparation of (CXVIII) had beenreported previously 85 and was again described subsequently.Inthe hope of obtaining the methoxymethyldecalone (CXX), 4-methoxy-l-methyl-A1-cycZohexene-2-y-butyric acid (CXIX) was prepared.86Cyclisation was accompanied by loss of methyl alcohol, however,and only the ketohexahydronaphfhalene (CXXI) was isolated.CO,H 0 0 I \ II ...c/v Me0 p,J) PI", \/\/(CXXI. )\/\/(CXIX.) (CXX.)(Sir) R. Robinson and J. WalkerJ8' extending their original workon this cyclisationJs8 prepared y-6-methoxy-3 : 4-dihydronaphth-alene-l-butyryl chloride (CXXII) from methyl 5-keto-8-m-methoxy-phenyloctoate. It was hoped that the action of aluminium chlorideon this might cause simultaneous ring closure and reduction togive the already known, but inaccessible 62 (CXXIV). The reduc-tion did not occur, however, and the known unsaturated ketone(CXXIII) 62 was produced.The cyclisation of monocarboxylic acids has been used in thediterpene g9 and morphine fields.85 C.K. Chuang, Y. L. Tien, and C. M. Ma, Ber., 1936, 69, 1494.a7 J . , 1937, 60. J., 1936, 192.8Q D. E. Adelson and M. T. Bogert, J . Amer. Chem. SOC., 1937, 59, 399;P. Hill, W. F. Short, and H. Stromberg, J., 1937, 937; H. Plimmer, F. W.Short, and P. Hill, J., 1938, 694; G. A. R. Kon, E. S. Narracott, and C.Reid, ibid., p. 778.90 G. Haberland and G. Kleinert, Ber., 1938, 71, 470; G. Haberland andH. J. Siegert, ibid., p. 2619; G. Haberland, G. Kleinert, and H. J. Siegert,ibid., p. 2623.J. W. Cook and C. A. Lawrence, J., 1938, 58SPRINGALL : SYNTHESIS OF STEROIDS. 305(vii) Formation of Cyclic Ketones from Dicarboxylic Acids.Much work has been done on hydrophenanthrene derivativeshaving carboxylic acid residues on C, and C, suitable for pyrolyticor Dieckmann cyclisation to ketoc yclopentenohydrophenanthrenes.The preparation of the ketomethoxyoctahydrophenanthrene(CXXIV) from the hexahydro-ketone (CXXIII) 62 via the saturatedalcohol (CXXV) has been improved.The oxidation (CXXV) +(CXXIV) was originally performed with chromic oxide. (Sir)R. Robinson and J. Walker found cupric oxide to be betterJgl andthe Oppenauer method best of all.92,\/CO*C02EtP V H I 1 (CXXVI.)/ \ / \ A 0(CXXV. )/ \ / \ / \ O ~\/\/ Me01 11 ,) \/\ Me01 11 IIn the latter paper, improved conditions are given for the con-version of (CXXIV) through the glyoxylic acid derivative (CXXVI)into the 2-carbethoxy-2-methyl derivative (CXXVII) first preparedin 1936.93 The synthesis of oestrone from (CXXVII) has beeninvestigated.In the course of model experiments on 2-carbo-methoxy-2-methylcyclohexanone (CXXVIII) 94 [from which 1-carbomethoxy- 1 -methylcycEohexane-2-acetic acid (CXXIX) had(CXXVII.)I /\//co2Et/\/\/I\()Me01 II I \/v (CXXVIII.) (CXXIX. )already been obtained '1 (CXXX) was finally prepared by theaction of y-methoxypropylmagnesium chloride, and, thence, theacid (CXXXI). Pyrolysis of the barium salt of this acid gave8-methylhydrindan-l-one (CXXXII).(CXXX.) (CXXXI. ) (CXXXII.)G. A. R. Kon, R. P. Linstead, and C. Simons 95 had independentlyThe applic- prepared (CXXXII) by t'he same series of reactions.B1 J ., 1937, 60.93 (Sir) R. Robinson and 6. Walker, J . , 1936, 747.m4 Idem, J., 1937, 1160.B2 J., 1938, 183.95 Ibid., p. 814306 ORGANIC CHEMISTRY.atian of such reactions to oestrone (CXXXIII) was studied by F.Litvan and (Sir) R. Robinson,96 who oxidised the methyl ether ofnatural oestrone via the isonitroso-compound (CXXXIV) to themethyl ether of the oestric acid (CXXXV) first obtained by G. F.Marrian and G. A. D. Haslew~od.~~ The methyl half-ester wassubjected to Amdt-Eistert 98 chain-lengthening to give the half-ester of (CXXXVI). The lead salt of (CXXXVI) on pyrolysis anddemethylation gave again oestrone.0 0(CXXXIII.) /\ /\ I1 / \ , A 7/\A+ (CXXXIV.)I l lA/\/--Me01 11 I \/v(Sir) R. Robinson and H. N. R y d ~ n , ~ ? having obtained thecompound (CXXXVII) by the new Robinson synthesis (p.293) andfound direct hydrogenation unprofitable, opened the five-memberedring by a, modification of the Litvan-Robinson procedure via theisoformyl derivative (CXXXVIII) and the nitrile (CXXXIX),obtaining the acid (CXL). Hydrogenation of the methyl ester of(CXL) with the Adams catalyst gave some of the compound (CXLI).Pyrolysis of the lead salt of the corresponding acid and demethyl-ation yielded x-noroestrone (CXLII), which probably has the cis-cis- configuration.0~XXXVII.) (CXXXVIII. ) (CXXXIX. )O6 J., 1938, 1997. J. SOC. Chem. Ind., 1932, 51, 277.F. Arndt snd B. Eistert, Ber., 1935, 68, 200SPRINGALL : SYNTHESIS OF S!i!EROIDS, 307W. E. Bachmann, W.Cole, and A. L. Wilds have announced ina, letter gQ the synthesis of equilenin by the use of methods similarto those outlined above. The l-keto-7-methoxy-1 : 2 : 3 : 4-tetra-hydrophenanthrene of A. Butenandt and G. Schramml was pre-pared from l-aminonaphthalene-6-sulphonic acid and was condensedwith methyl oxalate. The glyoxylic acid derivative (CXLIII,R = OMe) lost carbon monoxide on heating, giving the 2-carbo-methoxy-compound (CXLIV). [R. D. Haworth 2 had preparedthe corresponding ethyl glyoxylate (CXLIII, R = H) but had beenunable to degrade it.] This was methylated in the 2-position andsubjected successively to the Reformatsky reaction with methylbromoacetate, dehydration, and reduction, yielding a mixture ofthe cis- and truns-esters (CXLV).The free acids were separatedand both were subjected to the Arndt-Eistert chain-lengthening,giving the propionic acids in cis- and truns-forms. The methylester of the trans-acid (CXLVI) was submitted to the Dieckmannreaction and the resulting P-keto-ester (CXLVII) was hydrolysed,decarboxylat ed and deme thylate d, yielding dl- equilenin. Resolu-tion through the Z-menthoxyacetic ester gave the form identicalwith the natural hormone. In view of the reduction of equileninto oestrone reported by R. E. Marker the' above synthesis mayconstitute also an oestrone synthesis./\//COzMe/w"02M;*2Me /\ /Pi9 \//\/\/ \CH,*CO,Me /\ / Y O z M e \\ No Me01 I1 I\/\/(CXLV.)Me01 It I \/\/(CXLIV.)011 C0,MeA/ \CH2,CHZ Me01 11 I \/\/(CXLVI.) (CXLVII.)IOa J. Amer. Ckm. Soc., 1939,61,974. 1 Ber., 1935, 68, 2083.3 J. Amer. Chem. Soc., 1938,60,1897. J., 1932, 1126308 ORGANIC CHEMISTRY.The pyrolysis of barium salts of carboxylic acids has been usedby R. P. Linstesd and his collaborators for the formation of hydrind-anones in the degradation of hydronaphthalene derivatives. 6pA. Cohen and F. L. Warren used a Dieckmann cycli~ation.~~They treated 1 : 2-dicarbomethoxy-1 : 2 : 3 : 4-tetrahydrophen-anthrene (CXLIX) with ethyl acetate, but the product on hydrolysisand decarboxylation gave not the expected diketone but its de-hydrogenation product (CL).Synthetic Oestrogens.The great difficulties involved in the complete synthesis of thesteroid sex hormones have led to the search for synthetic oe~trogens.~The discovery of the slight but definite oestrogenic activity ofl-keto-1 : 2 : 3 : 4-tetrahydr0phenanthrene,~ 4 : 4‘-dihydroxy-diphenyl and 4-hydro~y-n-propylbenzene,~ 4 : 4’-dihydroxydi-phenylethane and 4 : 4’-dihydroxystilbene 7 indicated that moleculesof weight, shape, and hydroxyl situation similar to those of oestronemight indeed prove valuable oestrogens despite the absence of thecharacteristic steroid tetracyclic system ; E.C. Dodds, L. Golberg,W. Lawson, and (Sir) R. Robinson 13 have therefore prepared C-alkylated derivatives of 4 : 4’-dihydroxystilbene (“ stilboestrol ” )and have found in trans-diethylstilboestrol (CLI) the most potentFor a review of the early work, see G. F. Marrian, Ergebn. Vitamin- u.ti J.W. Cook, E. C. Dodds, C. L. Hewstt, and W. Lawson, Proc. Roy. SOC.,Horrnonforsch., 1938, 1, 443.1934, By 114, 272.E. C. Dodds and W. Lawson, ibid., 1938, €3,125, 222.E. C. Dodds and W. Lawson, Nature, 1937, 139, 627, 1068; E. C. Dodds,M. E. H. Fitzgerald and W. Lawson, ibid., 1937, 140, 772.Ibid., 1938, 141, 247 ; 1938, 142, 34, 211 ; Proc. Roy. SOC., 1939, B, 127,140SPRINGALL : SYNTHESIS OF STEROIDS. 300oestrogen known. These C-alkylstilboestrols were prepared by thefollowing general procedure. Deoxyanisoin (CLII) was treatedwith an alkyl halide, RI, and sodium ethoxide to give (CLIII),which with the Grignard reagent, R’MgI, gave the carbinol (CLIV).This was dehydrated, by phosphorus tribromide in chloroform orby potassium hydrogen sulphate, and the product (CLV) de-methylated by alcoholic pot’assium hydroxide, yielding the dialkyl-stilboestrol.Me0 C,H,*CO*CK,*C,H,*OMe + MeO*C,H,*CO -CHR*C6B4*OMe -->MeO*C,H,*CR’( OH)*CHR*C,H,*OMe --+(CLII.) (CLIII.)(CLIV.)MeO*C6H4.CR’:CR*C6H4*OMe: --+ HO*C,H,.C~R‘:CR*C,H,.OH(CLV.)A nt i rachi t i c V it am i ns .The establishment of the tricyclic hexatriene structures ofvitamin D, (calciferol) (CLVI) and tachysterol (CLVII) or?9*17/\/\/\I \/--\/\/(CLVIII.)C%l 1 1\/\/ I II HO(CLVI.) (CLVII.)HO!(CLVIII) has led to attempts at their synthesis.The preparation,from 1 -formyl-2-~-cyclohexylethylcycZohexane, of (CLIX) con -taining the correct ring system, was early anno~nced.~Two independent approaches depending on the condensation ofcyclohexylideneacetaldehyde (CLX) with cyclohexanones haveappeared.(CLIX.) (CLX.) (CLXI.),J. B.Aldersley and N. Burkhardt prepared (CLXI, R = OAc) ;K. Dimroth l1 prepared (CLXI, R = H) and investigated replace-S. Natelson and s. P. Gott’fried, J . Amer. Chem. SOC., 1936, 58, 1432.l o J., 1038, 545. l1 Ber., 1938, 71, 1333, 1346310 ORGAMO CHEMISTRY.ment of the oxygen atom by CH,, via the Grignard reaction andthe compound (CLXII, R = CH3), and via the Reformatskyreaction and the compound (CLXII, R = CH,*CO,Et) (following0. Wallach 12).Such compounds on dehydration should yield either (CLXIII)(calciferol type) or (CLXIV) (alternative tachysterol type). Theabsorption spectra of the products indicate that they are of thelatter type.Extending this work, K. Dimroth and H. Jonsson l3have prepared (CLXI, R = OMe) and (CLXV).N. Burkhardt and N. C. Hindley 14 have obtained from l-ethinyl-cyclohexanol the dicyclohexenylethylene (CLXVI) containing thetriene system of the other alternative tachysterol type.As a model for calciferol, 3-( 2’-methylenecyclohexylidene-1‘-)-propene (CLXVIII) has been prepared from the methiodide ofthe Mannich base (CLXVII).15CH,(CLXVII.) 0’cH2*NMe311 VN0 C>(,iH2 (CLXVIII.)H. D. S.8. .HETEROCYCLIC COMPOUNDS.Oxygen Ring Cmpounds.Raney nickel is an effective catalyst for the reduction of furansto the corresponding tetrahydro-derivatives,l and an examinationof the action of acetic anhydride-zinc chloride on tetrahydrofuransindicates that the ring is ruptured more readily than the hydropyranring.The products are either diacetates (I) or unsaturated mono-la Annalen, 1909, 365, 255. 14 J., 1938, 987.1E N. A. Milss and W. L. Alderson, J . Arner. Chem. SOC., 1939, 61, 2534.R. Paul, Bull. SOC. chim., 1937,4, 846; 1939,6, 1162; Compt. rend., 1938,206,1028; R. Paul and G. Hilly, ibid., 1939,208,359; N. I. Shinkin and V. I.Bunina, J . Gem. Chem. Russia, 1938, 8, 669.l8 Ber., 1938, 71, 2658HAWORTH : HETEROCYCLIC COMPOUNDS. 31 1acetates (11) and the presence of a-side chains containing carb-ethoxy-groups facilitates the formation of (I) ., The greater stabilityof the six-membered ring is also indicated by the conversion of (111)into (IV) by the action of alumina at 400°.3/"\HZAcO*[CH,],,,,*OAc H 2 7 7 H 2 H& GHAcO*[CH,],,~*CH:CH~ 0(1.) E&C CH-QH-OH H2C CMe\/ 0Me(11.) (111.) (IV.)The formation of hydroxytetrahydrofurans of types (V) and (VI)during the reduction of @-unsaturated aldehydes with magnesiumand acetic acid is of interestY4 and 2-hydroxyfuran has been preparedby the action of sodium hydroxide and a trace of potassium chlorateupon 5-sulphofuroic acid at 3-Hydroxyfuran has beenprepared by debromination of 2-bromo-3-hydroxyfuran obtainedCH*C02HR*CH:CH*CH CH*OH R*CKCH*CH CHR 02c*HQ 11 11 R-QH-VH, HO*VH-QH, H LH 2 c v vCH, 0(v=)\d \4(V.1by the action of bromine and water on furoic acid, and the nitros-ation and nitration of the hydroxyfurans have been investigated.6The difficulty of preparation of simple 2- and 3-aminofurans isillustrated by the work crf B.H. Stevenson and J. R. Johnson andH. M. Singleton and W. R. Edwards.8 The former prepared3-amino-2-methyl- and 3-amino-2 : 5-dimethyl-furan ; the amino-group was introduced by conversion of a 3-carbethoxy-group intothe azide, which with formic acid gave the 3-formamido-derivative,hydrolysed by steam to the unstable amine. This yielded a diazo-solution which coupled with @-naphthol but showed no other diazo-reactions. The second authors obtained furyl-2-carbimide by heat -ing the azide of furoic acid, but although the carbimide was convertedinto the 2-alkylamido-derivative by treatment with Grignardreagents, attempts to obtain 2-aminofuran were unsuccessful.The diene synthesis proceeds normally with furan and its homo-logues: and the products have the endo-configuration because theyR.Paul, Compt. rend., 1939, 208, 587.Idem, Bull. Xoc. chim., 1938, 5, 919.Z. C. Glace1 and J. Wiemann, Compt. rend., 1939, 208, 1233, 1323.H. H. Hodgson and R. R. Davies, J., 1939, 806.Ibid., p. 1013.J . Amer. Chem. Soc., 1937, 59, 2525.K. Alder emd K. H. Backendorf, Annalen, 1938,535, 101.Ibid., 1938, 60, 540312 ORGANIC CHEMISTRY.are converted into bromolactonic acids inaqueous + Br,accordance with theR CO,H3-Hydroxyfuran also condenses normally with maleic anhydride,but the extranuclear double bond of furylethylene enters into thereaction ; the product, containing two double bonds, is regarded as(VII) because no formaldehyde was detected on ozonisation.1°Natural Products containing Oxygen Rings.-Euparin, isolatedfrom gravel root, is a phenolic ketone containing two double bonds.llOxidation of the O-methyl ether with permanganate yielded an acidof known structure (I; R = C0,H) and, as ozonisation gave the0H O / W \ - :CH, (11.1 I lie (1.1 M~O/\OHCH,*CO//R CH,*CO(,--corresponding aldehyde (I ; R = CHO) and formaldehyde, structure(11) was advanced for euparin.This has been confirmed by thesynthesis of tetrahydroeupa,rin (111) as follows :0redn. of 0HOf'\/\FH*CHMe,oxime J7-CH.bH20 0HO()A?H*CHMe, & HO\/\$*CHMe,J/--CH0HOm\FH*CHMe, (111.)CH3*CO"-CH210 R. Paul, Compt. rend., 1939, 208, 1028.l1 B. Kamthong and A.Robertson, J., 1939, 933HAWORTH : HETEROCYCLIC COMPOUNDS. 313The benzofuran structure (I) has been suggested for egonolobtained from ethereal extracts of the fruits of Styrux Juponica.12Egonol contains one hydroxyl and one methoxyl group and it yieldspiperonylic acid on oxidation with permanganate. Ozonisation ofacetylegonol gave the acetyl derivative of styraxin aldehyde (11),which was hydrolysed to piperonylic acid and styraxinolic aldehyde(111; R = CHO). Styraxinolic acid (111; R = C0,H) on methyl-ation and subsequent oxidation gave (IV), and on distillation itHO*[CH,],*/\R/)OH (111.)yielded dihydroconiferyl alcohol (I11 ; R = EL). The structures ofthe products (111) are well established and consequently the positionof the substituents in egonol is proved.Structure (I) for egonolhas been confirmed synthetically. Dihydroconiferyl alcohol (I11 ;= H) was converted by the Reimer-Tiemann rea,ction into thealdehyde (I11 ; R = CHO), which yielded (V) on condensation withethyl a-chloro-3 : 4-methylenedioxyphenylacetate ; hydrolysis anddecarboxylation of the ester (V) gave egonol (I). When acetyl-egonol was oxidised with hydrogen peroxide, it was converted intothe highly coloured noregonolidene acetate ; this lacks methoxylgroups but exhibits properties consistent with those of thequinone (VI) .A decision has now been made between the alternative structures(I) and (11) discussed in these Reports for 1938 (p. 311) for equol.As equol dimethyl ether did not give acetic acid by the Kuhn-Rothl2 S.Kawai and T. Miyahi, Ber., 1938, 71, 1457; S. Kawai and M. Snga,ibid., p. 2071 ; S. Kawai and F. Yoshimura, ibid., p. 2415; S. Kawai and N.Sugiyama, ibid., p. 2421 ; Proc. Imp. Acad. Tokyo, 1938, 14, 352 ; 1939, 15,46; Ber., 1939, 72, 367; S. Kawai, K. Sugimoto, and N. Sugiyama, Ber.,1932,72,963 ; S. Kawai, T. Xakamura, and N. Sugiyama, ibid., p. 1146314 ORGANIC CHEMISTRY.test, structure (I) becomes unlikely. Reduction of diadzin gave animpure dl-form of (11), but the absorption spectra of the purifieddiacetate and dimethyl ether were identical with those of diacetyland dimethyl equol re~pective1y.l~ More satisfactory evidence infavour of (11) has been obtained by oxidising equol dimethyl etherwith chromic acid.14 The resultant lavorotatory ketone (111) wasracemised by acids or alkalis, and the dl-form has been synthesisedfrom p - met hox yp hen ylace t onit rile and re sor cinol monome t h y 1 ether.The intermediate ketone (IV) was converted into the isoflavone (V)by condensation with ethyl formate, and catalytic reduction of (V)co(IV.) (V.)yielded the dl-ketone (111), reduced by Clemmensen’s method todl-equol dimethyl ether.Progress continues to be made in the natural coumarin field (seeAnn. Reports, 1937, 34, 343). Aurapten, a fish poison obtainedfrom orange-peel oil, has been assigned structure 15 (I; R =CH-CH-CMeJ. Oxidation gave acetone and 7-methoxy-coumarin-8-acetic acid, identical with the acid obtained fromosthol.16 The oxide ring is indicated by hydration with dilute oxalicacid and oxidation of the hydrate with lead tetra-acetate to 7-meth-oxycoumarin-8-aldehyde. Osthol (I ; R = CH,*CH:CMe,) has beenoxidised with perphthalic acid to dl-aurapten, which was isomerised13 F.Wesely and F. Prillinger, Ber., 1939, 72, 629.1* Miss E. L. Anderson and G. F. Merrian, J. Bhl. Chem., 1939,127, 649.15 H. Bohme and G. Pietsch, Arch. Pha~m., 1938, 276, 482 ; Bw., 1939, 72.773; H. Bohme and E. Schneider, ibid., p. 780.16 E. Spiith and 0. Pesta, Ber., 1933,66, 764./oHAWORTH : HETEROCYCLIC COMPOUNDS. 315by sulphuric acid into the ketone (I ; R = CH,*CO-CHNe,) ; thisketone was also obtained in a similar ma.nner from natural aurapten.OR OMeToddalolactone l7 is regarded as (11) because hydrolysis ethylationyielded an o-ethoxycinnamic acid giving 2 : 4-dimethoxy-6-ethoxy-benzene-1 : 3-dicarboxylic acid on oxidation ; the constitution of thedibasic acid was established synthetically.Advances in the furocoumarin group include a synthesis ofisoimperatorin (I11 ; R = CH,*CH:CMe,) from bergaptol (I11 ;R = H) and y-methyl-Ab-butenyl bromide.18 Byak-angelicin [IV ;R = CH,-CH(OH)-CMe,*OH] and byak-angelic01 (IV; R = .CH2CHGMe,) have been isolated from the roots of Angelica gl~ba.1~The former, containing two hydroxyl groups, gave furan-2 : 3-di-carboxylic acid, ct-hydroxyisobutyric acid, and bergapten quinoneon oxidation with peroxide, permanganate, and chromic acid respect-ively, and on treatment with sulphuric-acetic acid it yielded 8-hydr-oxy-5-methoxypsoralen (IV; R = H), which was synthesised fromaminobergapten.Byak-angelic01 was also converted into (IV ;R = H) by the action of sulphuric-acetic acid and into byak-angelicin by hydration.The furochromone structure (I) has been established for kellin,isolated from Ammi visnagu in 1897.20 The presence of the furanring is proved by degradation to furan-2 : 3-dicarboxylic acid, andAOMe CO OMe OMe(1.) (11.1 (111.)B. B. Dey and P. P. Pillay, Arch. Pharm., 1935, 273, 223; E. SpBth,E. Spath and E. Dobrovolny, Ber., 1939, 72, 52.T. Noguchi and M. Kawanami, Ber., 1938,71,344,1428; 1939,72, 483.B. B. Dey, and E. Tyraz, Ber., 1938,71, 1825; 1939,72,53.2o P. Font1 and S. I. Salem, Biochem. Z., 1930, 226, 166; E.Spiith and W.Gruber, Ber., 1938, 72, 10631% ORGANIC CHEMISTRY.alkaline hydrolysis yielded acetic acid and kellinone (11). Ethyl-ation and subsequent ozonisation gave (111; R1 = CHO, R2 = H),which was ethylated, oxidised, and decarboxylated to (I11 ; R1= H,R2 = Et), the structure of which was established synthetically.Kellinone (11) may be reconverted into kellin (I) by the action ofsodium acetate and acetic anhydride.Karangin, obta,ined from Pongamia glabra, is regarded as the furo-flavone 21 (I ; R = H). Alkaline hydrolysis gave benzoic acid, aphenolic ketone, probably (I1 ; R = CH,*OMe), and a phenolic acid(11; R = OH). The structure of the acid (11; R = OH) wasconfirmed by oxidation to furan-2 : 3-dicarboxylic acid, decarboxyl-ation to 4-hydroxybenzofuran, and ozonisation to (111).The ketoneR W \ , 0- <? f h O H(11.1',,,,,J\/C*OMe .-' \ P O RH*CO 0 (1.1 f70HO/\/'\C /-\ CHO L,, )\,tLoMe'-/'(111.) HO/\OH \/ b02H 0 Fl w.1(I1 ; R = CH,*OMe) was reconverted into karangin by condensationwith benzoic anhydride and sodium benzoate, but the completion ofthe synthesis by the preparation of (11; R = CH,-OMe) has notbeen effected. An acid (I; R = CO,H), prepared from ethylbromoacetate and the flavone aldehyde (IV), resisted decarboxyl-ation to karangin (I ; R = H).22The chromene structure (I) 23 has been established for seselin,obtained from Slcimmia japonica 2* and Seseli indi~in.~~ Seselinwas converted into umbelliferone (11) by the action of sulphuric-acetic acid, and it gave acetone and resorcinol-2 : 4-dialdehyde onozonisation and cc-hydroxyisobutyric acid on permanganate oxid-ation.Hydrolytic methylation yielded an o-methoxycinnamic acid,which was oxidised to the acid (111), and the structure of (111) wasproved by synthesis. Seselin (I) has been synthesised in small21 B. L. Manjkath, A. Seetharamiah, and S. Siddappa, Ber., 1939, 72, 93.22 S. Rangaswami and T. R. Seshadri, Proc. Indian Acad. Sci., 1939, 9, 259.23 E. Spath, P. K. Bose, J. Matzke, and N. C. Guha, Ber., 1939, 72, 821;24 Y. Asahina and M. Inubuse, Ber., 1930, 63, 2052; E. SpBth and 0.z 5 P. K. Bose and N. C. Guha, Science and Culture, 1936, 2, 326.E. Spath and R. Hillel, ibid., p. 963.Neufeld, ibid., 1938, 71, 353HAWORTH : HETEROCYCLIC COMPOUNDS. 317yield from umbelliferone (11) and p-methyl- Ar-butin- p-01, and theformation of the angular structure of seselin is noteworthy in viewof the previous synthesis of dihydroxanthyletin (IV) from umbellifer-one and isoprene.26Structure (I) has now been established for the substance firstisolated by T.A. Buckley27 from derris. The Izvorotatory pre-cursor, known as Z-elliptone, has been isolated from Derris eZZiptica,and racemised by sodium acetate to Buckley's compound (dl-ellipt-one).28 The identity of rings A, B, and C with those of rotenone isproved by the conversion of Z-elliptone into derric acid, and thestructure of rings D and E was established by hydrolysis of Z-elliptoneinto (11), which was synthesised from 4-hydroxycoumarone byKolbe's method.Dehydrotetrahydrosumatrol has been syn-thesised ; 29 the nitrile (111) was converted by Hoesch's method intoMe0(IV), which on condensation with acetic anhydride and sodiumacetate yielded a diacetate, hydrolysed to dehydrotetrahydro-sumatrol (V.)26 E. Spath and W. Mocnik, Bey., 1937, 70, 2276.27 J. SOC. Chem. In&., 1936, 55, 2 8 5 ~ .28 D. R. Koolhaas and T. M. Meyer, Rec. T ~ a v . chim., 1939, 58, 207, 875;28 T. S . Kenny, A. Robertson, and S . W. George, J., 1939, 1601.S . H. Harper, J . , 1939, 1099, 1424318 ORGANIC CHEMISTRY.Formulm (I) and (11) suggested previously for rottlerone areuntenable, as tetrahydrorottlerone differs from the synthetic tetra-hydro-derivatives of (I) and (II).3O Rottlerone is now regarded as9H:CHPh7H:CH"Ph $lH:CHPhP e 2 C / y j O H 0 (P q;;"I..e2 FO// -CH,OH (111.) OH(111) because hydrolysis of octahydrorottlerone (previously calledtetrahydrorottlerone) yielded a substance identical with the synthetictetrahydro-derivative of (11) ; in addition the tetrahydro-derivativeof (11) and formaldehyde reacted to yield octahydrorottlerone.These modifications do not invalidate previous views on the structureof rottlerin, but of the two structures (111) and (IV) discussed in theAnnual Reports for 1938 (p.314) the latter formula is now preferred.A modification in the structural formulz of isorottlerin has beensuggested .31The difficulties arising from demethylation of flavone derivativeshave been mentioned in earlier Reports.32 It has now been shownthat 2 : 4-dihydroxy-3 : 6-dimethylacetophenone and benzoic an-hydride react to give the flavone (I), which with aluminium chloridemay be completely or partially demethylated to 5 : 7 : 8-trihydroxy-flavone or to wogonin (a dihydroxymethoxyflavone).Structuralchange does not occur, because methylation of (I) and of wogonin\\gives the same trimethoxyflavone. WithOMe 0 0OH CO(1.) (11.1hydriodic acid, however,0(111.)30 T. Backhaus and A. Robertson, J., 1939,1257; A. McGookin, A. Robert-son, and E. Tittensor, ibid., p. 1579.31 Formula (VI) given in an earlier report (Ann. Reports, 1938, 35, 314) iserroneous ; the 2-keto-4-phenylchromone should be replaaed by a 4-keto-2-phen y lchromone structure .32 Ann.Reports, 1931, 28, 148HAWORTH : HETEROCYCLIO COMPOUNDS. 31 9structural change accompanies the demethyhtion, and baicalein(11) is obtained.33 Primetin, isolated from the leaves of Primulumodesta, has previously been assumed to be 5 : 6-dihydroxyflavone(III).34 This substance (111) was synthesised in an impure formby S. Sugasawa,36 who regarded the product as 5 : 8-dihydroxy-flavone. An unambiguous synthesis of 5 : 6-dihydroxyflavone hasnow been effected ; 36 the compound differs markedly from primetinand it is considered that the latter is probably 5 : 8-dihydroxy-flavone. Nobiletin, isolated from Citrus nobilis, is 5 : 6 : 7 : 8 : 3' : 4'-hexamethoxyflavone ; it contains six methoxyl groups, yields veratricacid and acetoveratrone on hydrolysis, and a hexahydroxyflavone,which is only pentamethylated with dia~omethane,~' on demethyl-ation.An investigation on fustin,38 a colourless crystalline substanceisolated from various Rhw species, disproves the earlier ideas of theglycosidic nature of the compound and reveals for the first time thenatural occurrence of the flavanonol type (I).Methylation of fustinyielded a trimethyl ether (I ; R = Me), which on alkaline hydrolysisgave trimethylfisetin (11), presumably by oxidation, and a phenolicacid known as trirnethylhazeinic acid (111). In accordance withstructure (111) the acid may be converted into a y-lactone, anMeO/\OH Me0a@-unsaturated acid, or a ketone (IV). The constitution of the last(IV) was deduced from an examination of the Beckmann change onthe oxime, which yielded an amide identical with that synthesisedfrom homoveratric acid and 4-aminoresorcinol dimethyl ether.Theformation of (111) from (I; R = Me) is accounted for by a benzilicacid transformation of the intermediate diketone (V). The con-33 R. C. Shah, C. R. Mehta, and T . s. Wheeler, J., 1938,1555.34 S. Rattori and W. Nagai, J . Chem. SQC. Japan, 1930,51, 162.35 J., 1933,1621 ; J . Pharm. Soc. Japan, 1936,56, 105.37 K. F. Tseng, J., 1938,1003; R. Robinson and K. F. Tseng, ibid., p. 1004.38 T. Oyamah, Annalen, 1939,538, 44.W. Baker, J., 1939, 956320 ORGANIC CHEMISTRY.stitution of fustin (I ; R = H) was confirmed by the synthesis of thetrimethyl ether (I ; R = Me) ; the dibromo-derivative (VI ; R = MeoooAc -CO*QH*QH- OoMe OMeR R(VI.)OMeMe,@ vH2-C>OMePo co (V.)Br), obtained from the corresponding chalkone, was converted intothe diacetate (VI ; R = OAc), which with hydrochloric acid yieldeda compound identical with trimethylfustin (I; R = Me).Nitrogen Ring Compounds.Pyridines, Quinoline and isoQuino1ine.-The reactivity of themethyl group of a- and y-picolines has been utilised in the prepar-ation of homologues of pyridine.Thus a-picoline, heated with analkyl halide in presence of finely powdered sodamide, gives alkyl-picolines in good yield and dialkylpicolines are frequently obtainedas higher-boiling fractions. The reaction is of wide application ;simple, complex and unsaturated alkyl groups and other groupssuch as p-ethoxyethyl and P-dimethylaminoethyl may be introducedinto the molecule of reactive Similar reactivity is displayedwhen a-picoline and benzophenone are heated in presence ofsodamide; the carbinol (I) is obtained, but when() esters, aldehydes or nitriles are employed, smallyields only of condensation products are obtained.4ON (1.1 When 2 : 4-dimethylpyridine is condensed withbenzaldehyde, a mixture of 2-styryl-4-methylpyridine and 2 : 4-distyrylpyridine is produced ; oxidation of the former to 4-methyl-pyridine-2-carboxylic acid and subsequent decarboxylation providesa convenient method for the preparation of y-~icoline.~lF.W. Bergstrom 42 had previously shown that the hydrogenatoms of the methyl groups of a- and y-picoline were replaceable bysodium and used the metallic compounds in the preparation of alkylderivatives.This author has since shown that 2-aminoquinolineis obtained in good yield from quinoline and (a) barium amide inliquid ammonia at room temperature 43 or (b) potassamide in presenceof oxidising agents such as potassium nitrate.44 Potassamide hasYH.CH2*CPh239 A. E. Tschitschibabin, Bull. SOC. chim., 1936, 3, 1607; 1937, 5, 429, 436;40 A. E. Tschitschibabjn, Rec. Trav. chim., 1938, 6, 582.4 1 G. R. Clerno and W. M. Gourlay, J., 1938, 478.42 J . Amer. Chern. Soc., 1931, 53, 1846, 3027, 4065.43 Ibid., 1934, 56, 1748.G. A. Knight and B. D. Shaw, J . , 1938, 682.44 J . Org. Chem., 1938, 2, 411HAWORTH : HETEROCYCLIC COMPOUNDS. 321also been used for the conversion of iso- and 2-phenyl-quinoline into2 - aminoiso quinoline and 4 -amino - 2 - p heny lquinoline respectively .45It has been shown 46 that a-picolinic, quinaldinic and isoquin-aldinic acids are decarboxylated by heating with aldehydes orketones, and carbinols containing heterocyclic radicals are producedin accordance with the equation :R’*C02H + R”R”‘C0 -+ R’R”R”’C*OH + CO,The reaction is specific for a-imino-acids and it is suggested that itdepends upon the intermediate formation of an anion radical con-taining the modified cyanide ion group [-5--C-]-.The additionof this ion to the carbonyl group would be analogous to cyanohydrinformation.bicycloAxa-aZEanes.-Considerable developments have occurredin the synthesis of these compounds since the subject was reviewedin 1937.*’ It has been shown that bicycZo[l : 2 : 21-aza-l-heptane(I; n = l), prepared from piperidine-4-carboxylic acid, is not anoil as previously reported but a crystalline solid identical with thatobtained from tetrahydropyran-4-carboxylic acid (I1 ; R = C02H).48Tetrahydropyran-4-carboxylic acid has been employed in severalnew directions for the preparation of bicyclo-compounds.By theaction of organo-metallic compounds on the acid chloride, alkyl oraryl tetrahydropyranyl ketones are obtained which yield the corre-sponding carbinols on reduction with sodium in presence of aqueoussodium carbonate and ether. The carbinols are converted intotribromides (111) by treatment with hydrogen bromide and thesubsequent action of ammonia leads to the formation of alkylbicycZo[l : 2 : 21-aza-l-heptanes (IV).49 Ethyl tetrahydropyran-4-carboxylate (11; R = C0,Et) is converted by means of hydrogenbromide into the dibromide (V ; R = C02Et), which with potassium45 J .Org. Chem., 1938, 3, 233, 424; Annalen, 1934, 515, 34.4 6 P. DysonandD. L. Hammick, J., 1937, 1724; M. R. F. Ashworth, R. P.4 7 Ann. Reports, 1937, 34, 380.4 8 G. R. Clemo and V. Prelog, J., 1938, 400.49 V. Prelog, E. Cerkovnikov, and (Miss) S . Heimbach, CoZZ. Czech. C’hem.REP.-VOL. XXXVI. LDaffern, and D. L. Hammick, J., 1939: 809.Coinm., 1938, 10, 399322 ORGANIO CHEMISTBY.sulphide yields the thiopyran (VI; R = C0,Et). This ester maythen be reduced to the corresponding primary alcohol (VI; R =CH2*OH) , which is transformed by concentrated hydrochloric acidCHR CHRH 2 d ' p 2BrH,C CH2Br H&, ,CH,/ \H2Q p 2(V-) s (VI.)into bicycZo[l : 2 : 21-thianium-l-heptane salts (VII; n = l).m Ina similar manner ethyl tetrahydropyran-4-acetate (I1 ; R =CH,*CO,Et) has been converted into (VII ; n = 2).514-Amino-, 4-aminome t hyl- , and 4- p-aminoet hyl- tetrahydropyran(I1 ; R = NH,, CH,*NH,, and CH2*CH2*NH, respectively) havebeen obtained by the action of sodium azide and sulphuric acid onthe appropriate carboxylic acids. A bicyclic base could not beobtained from (11; R = NH,), but in the other cases treatment ofthe amine with hydrogen bromide gave the dibromides (V; R =CH,*NH,) and (V; R = CH,*CH,*NH,), which with sodium hydr-oxide gave the bicyclic bases (I ; n = 1) and (I ; n = 2) respectivelyin good yield.52The meta-bridging of a piperidine derivative has been realised.533-p-Hydroxyethylpiperidine (VIII ; n = 2), synthesised from nico-tinic acid,= was converted into the corresponding bromide andthence into bicycZo[l : 2 : 31-aza-l-octane (IX; n = 2).bicycb-[l : 3 : 31-Aza-l-nonane (IX ; n = 3) has also been prepared ; ethylnicotinylacetoacetate was catalytically reduced to the P-piperidyl-3-propionic acid, which on Bouveault-Blanc reduction gave thealcohol (VIII ; n = 3), and the corresponding bromide was readilyconverted into the bicyclic base (IX; n = 3).5560 V. Prelog and E. Cerkovnikov, Annulen, 1939, 537, 214.5 1 V. Prelog and D. Kohlbach, Ber., 1939,72, 672.52 V.PreIog, E. Cerkovnikov, and G. Ustrichev, Annulen, 1938, 535, 37.53 V. Prelog, (Miss) S. Heimbach, end E. Cerkovnikov, J., 1939, 677.64 R. Marchant and C. S. Marvel, J . Amer. Chem. SOC., 1928, 50, 1197.56 V. Prslog, (Miss) S. Heimbach, and R. Seiwerth, Ber., 1939, '72, 1319HAWORTH : HETEROCYCLIC COMPOUNDS. 323Another method for the synthesis of bicyclic bases is indicatedby the following scheme :In this way bicycZo[O : 3 : 31-aza-l-octane (X; x = y = 3) 56 andbicycZo[O : 4 : 41-aza-l-decane (X ; x = y = 4) 57 have been prepared.The latter base was identical with norlupinan A, which was obtainedby G. R. Clemo and G. R. Ramage 58 during experiments on thelupin alkaloids and later by G. R. Clemo, T. P. Metcalfe, and R.Raper 59 by Wolff-Kishner reduction of l-ketonorlupinan (XI ;R = H).Clemmensen reduction of (XI ; R = H), however, yieldedan isomeric base, norlupinan B, which was considered to be astereoisomer of the A base, and the isomerism was regarded asresulting from the non-planar arrangement of the nitrogen valencybonds. This explanation is no longer necessary, because norlupinanB has now been shown to be identical with bicycb[O : 3 : 5l-aza-l-decane (X; x = 5 ; y = 3), which has been synthesised by themethod outlined above.60 It is suggested, therefore, that structuraland not stereochemical differences probably account for the isomericCHR CO CH2 CH, CO/ \ / \ / \ / \ / \H27 7H ( 7 3 2 H2C CH-?O H27 p 9H2\ / \ / \ / \ / \ / \ /H,C N CH, H,C N CH, H,C CH CH,CH, NH CH, CH,(XI.) (XII.) (XIII.)CH2 CH2CH, CH,/ \ / \H2V p CH2\ / \ / \(XIV.) \ / \ /CH2 CH2CH2H,C CH CH "' \7H2(XV-1 I ( CH\/ / \ '*CH2 y pH,C CH, r 70 H,C CH,5 6 V.Prelog and (Miss) S. Heimbach, Ber., 1939, 72, 1101.6 7 V. Prelog and K. Bozicevic, ibid., p. 1103.5 8 J., 1931, 437.60 V. Prelog and R. Seiwerth, Ber., 1939, 72, 1638.59 J., 1936, 1430324 ORGANIC CHEMISTRY.bases encountered during reduction of (XI ; K, = Me), (XII), (XII1) ,(XIV) and (XV).slInteresting results have been obtained during attempts to extendthese experiments to the preparation of quinine derivatives.62 Ethyltetrahydropyran-4-p-propionate (I1 ; R = CH2*CH2*C02Et) con-denses with ethyl cinchonate and quinate to yield the ketones(XVI; R = H) and (XVI; R = OMe) respectively. Successivetreatment with hydrobromic acid and bromine converts (XVI) intothe tribromide (XVII), but attempts to transform this into therubatoxanone-9 (XVIII) haveco-(XVI.)P \ C H 2FH212 I I ,,CH2- CH(XVIII.)been unsuccessful.The piperidine@r Br Br(XVII.)(XIX.)(XIX; X = NH) and thiopyran (XIX; X = S) derivatives havebeen prepared from (XVI) by Wolff-Kishner reduction of thecarbonyl group, followed by rupture of the pyran ring with hydro-bromic acid and subsequent ring closure to (XIX) by ammonia orpot a ssium sulp hide.Another interesting approach to the quinine structure dependsupon the condensation of 3-ketoquinuclidine (XX) with quinoline-4-CHoc’ j \CH,I ECH212ITH=C 1 ,CH,/’‘\,,/\ \N/i l l\/‘W (XXI.)aldehyde to give the unsaturated ketone (XXI), which was reducedto 5-ketoruban (XXII).63 The latter ketone was converted byG.R. Clemo and G. R. Ramage, J . , 1932, 2970; G. R. Clemo, J. G. Cook,andR. Raper, J., 1938, 1184, 1318.V. Prelog, R. Seiwerth, V. Hahn, and E. Cerkovnikov, Ber., 1939,72,1325.63 G. R. Clemo and E. Hoggarth, J., 1939, 1241HAWORTH : HETEROCYCLIC COMPOUNDS. 325aluminium isopropoxide and ethylmagnesium iodide into ruban-5-01(XXIII; R = H) and 5-ethylruban-5-01 (XXIII; R = Et) respect-ively, but the constitution of the product obtained by the action ofethylmagnesium iodide on the unsaturated ketone (XXI) has notbeen established. /?*\ OC I CH,-CHI ,CH,I PH212I\N* '(XXII.)Adermin.-This name has been suggested for vitamin B,, therat-dermatitis-preventing factor of the vitamin B complex.Adermin has been obtained from rice bran as a crystalline hydro-chloride of an optically inactive, weak tertiary base, C,Hi,O,N,containing one C-methyl, one phenolic, and two primary alcoholicgroups.64 The absorption spectrum of adermin resembles that of3-hydroxypyridine and differs considerably from those of 2- and4-hydro~ypyridine,6~ and tests with the Folin-Denis reagent confirmthe 3-hydroxypyridine structure.The methyl ether of adermin isunattacked by lead tetra-acetate, but oxidation with alkalinepermanganate gives a methoxypyridine tricarboxylic acid whichloses carbon dioxide and yields a methoxypyridinedicarboxylic acidon heating.The carbon dioxide is probably eliminated from thea-position, because the dicarboxylic acid, unlike the tribasic acid,does not give the ferrous sulphate test. Structure (I), assigned tothe dibasic acid on the basis of the degradation work, has been con-firmed synthetically,66 and the tribasic acid must therefore beeither (11; R = CO,H) or (111; R = C0,H). Oxidation ofadermin methyl ether with barium permanganate 67 gives a methoxy-methylpyridinedicarboxylic acid, which gives a negative ferroustest and yields a 3-hydroxy-a-picoline on decarboxylation ; adecision between (I1 ; R = Me) and (I11 ; R = Me) has been madein favour of the former by synthesis from 4-methoxy-3-methyliso-64 P. Gyorgy, J . Am.er. Chern. SOC., 1938,60, 983; R.Kuhn and G. Wendt,Ber., 1938, 71, 780, 1118,1534; J. C. Keresztesy and J. R. Stevens, Proc. Exp.Biol. Med., 1938, 38, 64; J . Amer. Chem. SOL, 1938, 60, 1267.65 R. Kuhn and G. Wendt, Ber., 1939, 72, 305; E. T. Stiller, J. C.Koresztesy, and J. R. Stevens, J. Amer. Chem. SOC., 1939, 61, 1237.6 6 R. Kuhn, H. Andersag, K. Westphal, and G. Wendt, Ber., 1939,72, 309.67 R. Kuhn, G. Wendt, and K. Westphal, ibid., p. 310; E. T. Stiller, J. C.Keresztesy, and J. R. Stevens, loc. cit326 ORGANIC CHEMISTRY.quinoline by oxidation.ss Additional evidence is provided by theoxidation of adermin methyl ether with neutral permanganate ; 69HO,C/\,OMe H02C/)gMe H0,CPOMeC0,H C0,H C0,H\N/ R\J(111.)\N/(1.) (11.)O-FH, CH,*OHHO*CH,/)g: (V.)OqJ:? (N/(IV.)a lactone, C9H,0,N, is obtained for which structure (IV) has beenestablished synthetically. It follows that adermin must havestructure (V), which has been confirmed by the two independentsyntheses (A) and (B) outlined below :CH,eOEt CH,*OEt CH,*CO*CH,*CO*CH,*OEt (4 'O + N C A HE0; NC/\NO,NC*CH,*CO*NH, --+ HO HO. &,!MeA lkaloids.Indole Group-Final confirmation of the structure of eserine( I ; R = NH*CO,Et) was obtained by the synthesis of 1- and68 R. Kuhn, K. Westphal, G. Wendt, and 0. Westphal, Naturwiss., 1939,27, 469.69 E. T. Stiller, J. C. Keresztesy, and J. R. Stevens, J. Amer. Chem. SOC.,1939, 61, 1237; A. Ichiba and K. Micbi, Sci. Papers Inst. Phys. Chem. Res.Tokyo, 1938, 35, 73.70 E. A. Harris, E.T. Stiller, and K. Folkers, J . Amer. Chem. SOC., 1939,61, 1242, 1245HAWORTH : HETEROCYCLIC COMPOUNDS. 327&I-eserethole (I; R = Et) by P. L. Julian and J. Pikl in 1935.71An isomeric synthetic base was regarded a8 a cis-trans-isomer ofdl-eserethole by F. E. King, M. Liguori, and R. Robinson, but otherworkers preferred structure (11) . This improbable structure (11)has now been replaced by structure (I11 ; R = NMe2).V2 The base,which contains a dimethylamino-group but no active hydrogen atom,yielded on thermal decomposition 5-ethoxy-3-methylindole, andstructure (I11 ; R = m e , ) has been established synthetically.Me CH,(1.)NMe m e 2Magnesium 5-ethoxy-3-methylindole was condensed with ethylenedibromide, and the product (I11 ; R = Br) yielded (I11 ; R = NMe,)with dimethylamine.The formation of this indole derivative (111 ;R = NMe,) takes place during methylation of (IV; R1 = R2 = H),(IV; R1 = H ; R2 = Me), and, under certain conditions, from(IV ; R1 = Me ; R2 = H) and the fission of the terminal pyrrolidinering is noteworthy.Calycanthine, isolated from Calycanthus species , mas given theformula C,,H2,N,,H20 by E. Spath and W. Stroh in 1925.73 Thealkaloid contains an NMe group, the presence of a secondary amino-group was indicated by the formation of a nitrosoamine, andZerewitinoff determinations gave results varying with the temper-ature of the experiment. Oxidation of the amorphous benzoylderivative with permanganate yielded benzoyl-N-methyltryptamine(I) 74 and selenium dehydrogenation gave norharman (11) and abase, C,6H182.75 G.Barger, J. Madinaveitia, and P. Streuli i 6 haverecently suggested C22H26N4 as the molecular formula for caly-canthine. They obtained N-methyltryptamine by heating caly-canthine with soda lime, and a base, possibly a methyl-4-carboline,by distilling the alkaloid with lime. The two products are regardedas arising from different parts of the molecule of the alkaloid. WhenAnn. Reports, 1935, 32, 343.T. Yobayashi, Annalen, 1938,536, 143; 1939, 539, 213.73 Ber., 1925, 58, 2131.74 R. H. F. Manske, Canadian J. Res., 1931, 4, 275.7 5 L. Marion and R. H. F. Mmske, {bid., 1938,16,432.76 J., 1939, 610328 ORGANIC CHEMISTRY.calycanthine is distilled with numerous reagents or oxidised withchromic acid, it yields the extremely stable, weak base, C,,HIoN2,CH,NH CHMenamed calycanine, for which structure (111) is tentatively advanced.The base contains both secondary and tertiary nitrogen atoms andthe structure is supported by the formation of quinoline by theaction of hydriodic acid on the alkaloid or of soda lime on benzoyl-calycanthine.Structure (IV) suggested for the alkaloid must beregarded as highly speculative, but a reversible colour reaction withp-dimethylaminobenzaldehyde, which appears t o be characteristicof tetrahydroharman derivatives) leads to the assumption of areduced pyridine nucleus.A new base, calycanthidine, which accompanies calycanthinehas the formula C,,H,,N2. It contains an NMe group, a secondaryamino-group, and possibly a C-methyl group and it may be Z-N-methyltetrahydroharman (V).The dl-form of (V) has been syn-thesised, but attempts to resolve this base or t o racemise caly-canthidine were unsuccessful and, as some differences in reactivitywere observed between the synthetic and the natural product, thestructure of the alkaloid remains uncertain.Lupinan Goup-Structure (I), assigned to cytisine by H. R. Ingin 1931, was modified to (11) by E. Spiith and F. Galinovsky in 1932.i \ / Y H - P (\( VH2 VHCH2QH-(F2 / \N CH-CH, CH, CH,CH,*[CH,],*yH FHMe N yH2 SJH\/ \CMe-CH, \do \CH2 \ /NAcco(1.1 (11.) (111.)'' G. Bargor, (Miss) A. Jacob, and J. Madinaveitia, Rec. Trav. chim., 1938,57, 548HAWORTH : HETEROCYCLIC COMPOUNDS.329By a combination of reduction and exhaustive methylation methodsthe alkaloid was converted into (111), the constitution of which wasindicated by dehydrogenation and oxidation to S-methylpyridine-5-carboxylic acid,78 thus establishing the piperidine structure (11).Further evidence supporting (11) was obtained by degrading cytisineto (IV),79 the structure of which has recently received the followingsvnthetical confirmation : 8oCHMe CH,/ / \ Me/\(A\ / \ / \/ b< H 2 7 MeCH b N YH2 CH2 --+ p,, hIeI N I (IV.1CH, COdl-Lupinine (I), the synthesis of which was reported in 1937,81has been resolvedB2 and the Z-base is identical with the naturalalkaloid. The alkaloids aphyllidine and aphylline, isolated fromAnabasis aphylla, are members of the lupinan group ; aphylline is astereoisomer of oxysparteine (11) , and aphyllidine, which is con-verted into aphylline by catalytic reduction and into d-sparteineby electrolytic reduction, is regarded as A5: 6-dehydro-oxysparteine.83Octalupine, isolated from Lupinus sericeus, yields sparteine andd-lupanine on reductionIand it is regarded as 2 : 16-diketo~parteine.~~CH, CH?H,*OH /'I \CH, CH H274 6VH 177H287H2H,C3 'N CH15N9 (TI.)\"/ v A 1 0w/CH2/\A=/ CH, CO >H14 7H2 (1.) Hz? p 7H2H,C N CH,H,C13 CH,"CH, CH,The alkaloid matrine, isolated from Sophora species, is isomericIt is a tertiary with and shows certain resemblances to lupanine.E. Spath and F. Galinovsky, Ber., 1933,66, 1338.Idem, ibid., 1936, 69, 761.81 Ann.Reports, 1937, 34, 359.B3 G. R. Clemo, W. McG. Morgan, and R. Raper, J . , 1938, 1574.83 A. Orhkhov and G. Menachikov, Ber., 1932,65, 234; A. Orekhov, J . Gen.84 J. F. Couch, J . Amer. Chern. SOC., 1939, 61, 1523.80 Idem, ibid., 1938, 71, 721.Chem. Russia, 1937,7, 2048330 ORGANIC UHF&tISTRY.base and contains a Iactam group which is readily hydrolysed to givematrinic acid. When matrinic acid is distilled with zinc dust, amixture of matridine, C16H26N2, and p-lupinan (I; R = Me) isobtained, and distillation with soda lime yields a- and p-matridines,C , , H , ~ , , together with a fraction giving 2-butylpiperidine andnorlupinan (I; R = H) 85 on reduction.CH, CHRH,C N CH2\A/ CH, CH,NHAc-CH, COGH, 03 (111.)N0 5 H 2 H 2 6 Z 2 CH CHStructure (11), which is suggested for a-matridine, is consistentwith its reduction to a dihydro-derivative, the formation of theketone (111) with acetic anhydride, and with the dehydrogenationto (IV; R =Me), which gives a benzylidene derivative.86 Thedehydro-derivative (IV ; R = Me) gives a lithium derivative whichwith ethyl bromide yields (IV; R = CH,*CH,Me), identical with abase, C14H20N2, obtained by dehydrogenating matrine with palladiuma t 300".On the basis of (11), structure (V) 87 has been suggestedfor matrine and the piperidine nature of ring A is more probablethan a methylpyrrolidine structure because of the isolation ofglutaric and succinic (and not methylsuccinic) acids as productsof oxidation of methyl matrinate. The structure of the alkaloid is,however, still unsettled and alternative formulae more closely relatedthan (V) to other lupinan alkaloids cannot be excluded. Oxy-matrine, isolated from Xophra JEaveScens,88 is probably matrineN-oxide and it may be prepared by the action of hydrogen peroxideon matrine.89isoQuinoZine &oup.-Structure (I; R = H) has been established85 H.Kondo, E. Ochiai, K. Tsuda, and S. Yoshida, Ber., 1935, 68, 570.8 6 H. Kondo, E. Ochiai, andK. Tsuda, ibid., 1936, 68, 1899.8 7 K. Tsuda, ibid., 1936, 69, 429; J. Pharm. SOC. Japan, 1937, 57, 68.** H. Kondo, E. Ochiai, and K. Tsude, Arch. Pharm., 1937, 275, 493.** E. Ochiai and Y . Ito, Ber., 1938,71, 938HAWORTH : HETEROCYCLIC COMPOUNDS. 33 1for Z-tudarinine;90 the diethyl derivative (I; R = Et) has beensynthesised and the Hoffmann degradation products are identicalwith those obtained from the naturally occurring base.Arta-botrine, isolated from the bark of Artabotrys swveolens Bl., is anaporphine base containing an alcoholic hydroxyl group for whichE Z g Y R E g f O N M e MeOpH:CH, M e 0 8structure (11; R = Me) has been sugge~ted.~~ Hofmann degrad-ation yielded first an optically active methine and finally aphenanthrol, probably (111), which gave a, stable dimethoxy-lactonic acid on oxidation with permanganate. The properties ofthe lactonic acid are not consistent with a structure such as (IV),and structure (V) is regarded as probable. On this assumption itis concluded that ring A of the alkaloid contains two methoxylgroups and the 5 : 6-arrangement is based on analogy. Artabotrine(11; R =Me) is the O-methyl ether of an accompanying base,suaveline (I1 ; R = H), which gives the Pellagri reaction, indicatingRO DycH*oH Me0(111.)RO( 2/(1.) ( 11.1coMeO( Meo2 CO,H(V. 1 (VI.)that the p-position of the phenolic group is unsubstituted. Thisexcludes positions 2 and 3 for the hydroxyl and the methoxyl groupin ring D of suaveline and artabotrine respectively and position 4is selected because the remaining position 1 is unoccupied in allknown alkaloids of the group. A third alkaloid, artabotrinine,contains a methoxyl, a methylenedioxy-, and a secondary amino-group, and it probably represents the O-methyl ether of anolobineErgot AZkuZ~ids.~~-The difficult constitutional problem of these(VI) .92K. Goto and H. Shishodo, Annalen, 1939, 539, 262.O1 G. Barger and L. J. Sargent, J., 1939, 991.s2 Ann. Reports, 1938, 35, 326. 93 Ibid., 1935, 32, 345; 1936,33,374332 ORGANIC CHEMISTRY,alkaloids is still unsolved. Since the last review a fifth pair ofalkaloids, zlix., ergocristine and ergocristinine, has been isolated,g4the identity of erg~metrine?~ erg~basine,~~ and ergotocine 97 hasbeen confirmed,98 and ergosine and ergosinine have been shown toyield lysergic acid, ammonia, d-proline, l-leucine, and pyruvic acid onhydrolysis .99An important advance concerning the mode of attachment oflysergic acid to the amino-acids of the molecule has been made.The ergotoxine-ergotinine and ergotamine-ergotaminine pairs havebeen reduced to their corresponding dihydro-derivatives, which onhydrolysis yield isobutyrylformic and pyruvic acids respectively.As these keto-acids are reduced to the corresponding hydroxy-acidsunder similar conditions, it follows that the keto-acids do not occuras such in the alkaloids and it is suggested that they occur ascc- hydroxyvaline and cc- hydroxyalanine residues respectively asshown in (I), where L = lysergyl and R = Me for ergotamine andCHMe, for erg0toxine.l The outstanding problem in connectionY (11.1 (111.)with the ergot bases is the structure of the lysergic acids which areobtained by hydrolysis of the alkaloids. S. Smith and G. M.Timmis 2 established the following relationships of the isomericlysergic acids :boil H,Oalkalidl-lysergic acid (Ba(oH)a d-lysergic acid -f d-isolysergic acidA. Stoll and A. Hoffmann treated ergot bases with hydrazineand obtained dl-isolyserghydrazide, which gave dl-isolysergic acid94 A. Stoll and E. Burckhardt, 2. ph,ysioZ. Chem., 1937, 250, 1 ; 1938, 251,287.96 H. W. Dudley, Phurm. J . , 1935,134, 709.913 A. Stoll and E. Burckhardt, Compt. rend., 1935, 200, 1680.97 M. S. Kharasch and R. R. Legault, J . Amer. Chem. SOC., 1935, 5'9, 956.98 A. Stoll and E. Burckhardt, Schweiz. med. Woch., 1936, 66, 353.99 S. Smith and G. M. Timmis, J., 1937, 396.1 W. A. Jacobs and L. C. Craig, J . Biol. Chem., 1938,122,419.2 J., 1936, 1440.9 2. physiol. Chem., 1937, 250, 7 ; 1938, 251, 155HAWORTH : HETEROCYCLIC COMPOUNDS. 333by hydrolysis of the corresponding azide with sodium bicarbonate,but hydrolysis of the hydrazide with strong alkali gave d2-lysergicacid. d2-isolysergic acid was resolvea with nor-Z-ephedrine andhydrolysis of the salts with strong alkali was accompanied byisomeric change, and the formation of d- and Z-lysergic acids. Bycombination of dl-isolysergazide with d-p-aminoisopropyl alcoholand separation with alumina, d-isolysergo-d-p-hydroxyisopropyl-amide, identical with d-ergometrinine, was obtained ; it was con-verted by phosphoric acid into d-ergometrine. The 2-forms of thealkaloidal pair were obtained simildy. As a result of these experi-ments it is concluded that the &(physiologically weak) and 2-(physio-logically active) ergot bases are related to the isolysergic andlysergic acid series respectively. Structure (11), introduced in 1936for lysergic acid, accounts for many properties of the acid, and theconversion into isolysergic acid is interpreted by a migration of the5 : 10 double bond. A base, ergoline (111), giving several colourreactions of lysergic acid, has been synthesised as follows : 4%Amino- 1 -naph-thoic acidSkraupreaction +-INa + butylalcohol(WRecently a modification has been introduced and lysergic acid isregarded as the p-amino-acid (V).5 Since the basicity of lysergicacid is smaller than that of isolysergic and dihydrolysergic acids, thedouble bond is placed in the 5 : 10- and 9 : 10-positions in lysergicand the iso-acid respectively. Two-stage reduction of the meth-iodide of base (IV) yielded 6-methylergoline (I11 ; with NMeinstead of NH in position 6),6 and the difference in basic dissociationconstant between this base and lysergic acid corresponds to thesubstitution of a carboxyl group in the P-position with respect tothe NMe group. Structure (V) for lysergic acid is consistent withthe formation of 3 : 4-dimethylindole by fusion of dihydrolysergic4 W. A. Jacobs and R. G. Gould, J . Biol. Chem., 1937,120,141.6 W. A. Jacobs, L. C. Craig, G. Shedlovsky, and R. G. Gould, ibid., 1938,6 W. A. Jacobs and R. G. Gould, ibid., 1938,126, 67.W. A. Jacobs and L. C. Craig, ibid., 1939, 128, 715.125, 289334 ORGANIC CHEMISTRY.acid with alkali, and a new compound, C,,H1,ON,, obtained bydistillation of dihydrolysergic acid at 25 mm., is represented bystructure (VI).8ergoline, the dl-form of which has been synthesised.9Catalytic reduction of (VI) gave 6 : 8-dimethyl-R. D. H.W. A. Jacobs and L. C . Craig, J . Amer. Chem. SOC., 1938,60,1701.* W. A. Jacobs and R. G. Gould, J . Biol. Chem., 1939,130,399

ISSN:0365-6217    

DOI:10.1039/AR9393600186

出版商:RSC    

年代:1939

数据来源: RSC

摘要:

BIOCHEMISTRY.ANIMAL BIOCHEMISTRY.Vitamins and Nutrition.THE current output of literature on nutrition has reached the almost" astronomical " figure of about 6 x lo3 new papers per annum,and not less than one-third to one-half of these deal with the vita-mins.* The explanation of this flood is that the ground to becovered is so large : new and accurate methods, chemical, physical,or biological, are gradually being evolved for estimating each ofthe numerous recognised essential-food-factors ; determinations arebeing completed on a great range of natural food products in allregions of the globe ; the effects of storage, preservation, canningand ageing have to be examined; a new technique is quickly beingelaborated for assessing the nutritional status of human subjectsin respect of various specific vitamins ; and fresh knowledge is beingwon about methods of isolating, concentrating or synthesising thevitamins; about their chemical behaviour; about their mode ofaction in metabolism; and about the varied effects of deficiencyin man or experimental animals, and about their use in the clinicor in veterinary practice.Obviously it is not possible in so brief areview as this to deal with more than a minute fraction of thisgreat mass of new knowledge, and we shall concentrate our attentionhere on a few items of general rather than of technical interest.The trend at present is for attention to shift from the better knownto the less known vitamins. For the four classical deficiencydiseases (beri-beri, scurvy, rickets and xerosis) and their corre-sponding vitamins (Bl, C, D and A) knowledge is now relativelycomplete-the vitamin structures are known in their severaldifferent forms and virtually all have been synthesised.The pastyear has seen the identification and synthesis of the newer vitaminsB, and I<, and the beginning of the applications of the latter inmedicine. The structure of vitamin E has been confirmed. Wideclinical use has already been made of nicotinic acid (pellagra-pre-venting vitamin) and knowledge is fast growing about the metabolicr6les of a t least two components of the B,-complex, vix., riboflavinand nicotinic acid. The position with regard to a third corn-* This is the number of communications abstracted yearly in NutritionAbstracts and Reviews (private communication from Miss A.M. Copping)BIOCHEMISTRY. 336ponent has been happily simplified by the discovery that the“ chick-dermatitis factor,” the “ filtrate factor,’’ and pantothenicacid are three names for probably one and the same substance. Inthis connection the warning must be added that certain additionalcomplexities seem now to be threatening, for the most recentexperiments on rats suggest that several distinct dietary essentialsmay be associated together in the so-called “ filtrate fraction.”Vitamin A .Estimation of Vitamin A.-The task of assaying a vitamin israrely simple, and for vitamin A the technical difficulties are provingmore than usually troublesome. An interim statement by thesecretary of an expert committee which is still engaged in anexamination of this problem describes some of the complicationswhich have to be faced, such, for example, as the conversion ofspectrophotometric observations into biological units.The problemis rendered more complex by the fact that biological activity is aproperty shared by carotene and various other carotenoids, as wellas by vitamin A proper and by its esters (and some other relatedsubstances) and that the relative potencies of these substances maynot remain strictly constant under all conditions, but will varyaccording to the level at which they are dosed or with the nature ofthe medium in which they are administered, these being factorswhich can alter the extent of their absorption or utilisation.2K. Hickman pleads the need for a new international standard.Isomerisation of Carotene.-Since p-carotene is not only a pre-cursor of vitamin A, but is the chosen international standard forvitamin A activity, special importance must be attached to the recentdiscovery 4* 5 that its well-known isomerisation to 3-a-carotene is aspontaneous reaction, and does not depend, as was formerly thought,on the action of any adsorbent.An equilibrium exists betweenthese two isomers, depending on the temperature; and to preventundue change of p-carotene in solutions used as standard they shouldbe stored at a low ternperat~re.~ Such relations hold for lycopeneand kryptoxanthin * as well as for 6- and p-~arotenes.~Yet another carotenoid pigment proved to have vitamin-A1 E.M. H u e , Nature, 1938, 143, 22.2 See, e.g., H. Goss and H. R. Guilbert, J . Nutrition, 1939, 18, 169; E. J.Lease, J. G. Lease, H. Steenbock, and C. A. Baumann, ibid., 1939, 1’7, 91;V. E. Munsey, J. Assoc. Off. Agric. Chem., 1938, 21, 626.3 J . BioE. Chem., 1939, 128, Proc. xliii.4 L. Zechmeister and P. Tuzson, Nature, 1938, 141, 249; Biocheirt. J.,5 G. P. Carter and A. E. Gillam, ibid., 1939, 33, 1325.1938, 32, 1305HARRIS : ANIMAL. 337activity, and to be converted into vitamin A within the animalorganism, is p-apo-2-carotenaL6(' Vitamin A , )' and Other Related Substances.-The reviewer inthe last two volumes of these Reports dealt very clearly with therecognition of a new form of vitamin A, named vitamin A,, which ispresent in fresh-water fishes and differs from vitamin A in its chromo-genic properties. During the past year further studies have beenrecorded of the distribution of vitamins A and A, in the tissues offishes and seabirds : it has been shown that carotene acts as theprecursor of A, for fresh-water fish in the same way that it is theprecursor of the " classical " vitamin A (A,) for mammals. In thecourse of a fascinating paper G.Wald makes the interesting pointthat this " transfer from vitamin A, to A, metabolism appears to beassociated phylogenetically with the migration of marine teleostsinto fresh water."It is now well known that in many sites, as, for example, in themucosa of the intestine of the halibut, where it is present in re-markably high concentrations, vitamin A occurs in a combinedform, namely, as an ester.8 A biologically inactive, " spurious," or" cyclised )' form of the vitamin is also found in fish-liver oils,g oris produced from them during distillation.Synthesis of the Methyl Ester of Vitamin A.-A short preliminarycommunication from P.B. Iiipping and F. Wild lo makes the iin-portant announcement of the synthesis of the methyl ester of vitaminA. Whereas all previous attempts a t synthesis had been based ontlhe stepwise lengthening of the side chain of p-ionone, these authorshad the inspiration of building up the chain first and then attachedit to the ionone residue en bloc. The report adds : " The analyses,physical properties, etc., of this substance and the intermediatecompounds, leave little doubt that the final product has the structureshown.Full details of this work will be published after the vacation,together with biological tests which we are unable to carry out atpresent."15'flects of Dejiciency of Vitamin A.-E. Mellanby l1 has publisheda detailed description of his experiments on the production of deaf-H. v. Euler, G. Giinther, M. Malmberg, and P. ICarrer, Helv. Chim. Acta,1'338, 21, 1619.R. A. M-orton and R. H. Creed, Biochem. J., 1939, 33, 318; J. A. Lovernand R. A. Morton, ibid., p. 330; J. A. Lovern, R. A. Morton, and J. Ireland,ibid., p. 325; G. Wald, J. Gen. Physiol., 1939, 22, 391; E. Lederer, M. L.Verrier, R. Glaser, and C. Huttrer, Bull. SOC. Ch4.m.biol., 1939, 21, 629.J. A. Lovern, T. H. Mead, and R. A. Morton, Biochem. J., 1939, 33, 338.N. D. Embree, J. Biol. Chem., 1939, 128, 187.lo Chetw. and Ind., 1939, 58, 802.l1 J . Physwl., 1938, 94, 380338 BIOCHEillISTRY.new in young dogs by means of diets deficient in vitamin A. Themost remarkable feature was the bony overgrowth and deformityseen at the base of the skull, and this is held to be probably re-sponsible for the degenerative changes noted in the cochlear andvestibular divisions of the eighth nerve and other cranial nerves suchas the optic and trigeminal. In further observations l2 it has beenshown that similar bony overgrowth may occur also in the vertebralcolumn, and elsewhere, and be responsible inter alia for an increasedpressure of cerebrospinal fluid.L.A. Moore,13 in continuation of earlier work published in 1935,has shown very clearly that in calves a deficiency of vitamin Acauses a remarkable sequence of changes, including bony malforma-tion, increased intracranial pressure, papillary edema, and apermanent blindness due directly to the constriction of the opticnerve. This papillary cedema and permanent blindness are not tobe confused with nyctalopia, which is to be regarded as a separateeffect of deficiency of vitamin A.The Dark-adaptation Test for Hypovitaminosis A .-L. J. Harrisand his co-workers l4 examined a group of boys in a, home for waifsand strays where the diet was abundantly supplied with vitamin A.Virtually all were found to be normal, in contrast with the largeproportion found subnormal among elementary school children inpoor working-class districts.Children found subnormal returned tonormal after dosing with vitamin A for some time, but not otherwise.The general conclusion reached by these authors was that thedark-adaptation test is sound in principle but that numerous pre-cautions need to be taken and it is essential that the details of thetechnique be very carefully controlled. Several workers on theother hand have experienced difficulties with dark-adaptation tests,15but a consensus of opinion now seems to be developing that thesecriticisms relate to minor points of procedure and do not invalidatethe potential usefulness of the method as a whole. In AmericaS. Hecht and J.Mandelbaum l6 showed that human volunteersdeprived of vitamin A began to show diminished visual function fromalmost the very first day of the experiment, and then returned slowlyla E. Mellanby, J . Physiol, 1939, 96, 3 6 ~ .lS J . Nutrition, 1939, 17, 443.14 B. Ahmad and L. J. Harris, Chem. and Ind., 1938, 57, 1190; L. J. Harrisand M. A. Abbasy, ibicE., p. 86; Lancet, 1939, ii, 1299, 1355.16 A. M. Thornson, 13. D. Griffith, J. R. Mutch, and D. M. Lubbock, Brit. J .Ophthalmol., 1939, 23, 461, 697; C. E. Snelling, J . Pediat., 1938, 13, 506;C. E. Palmer, Amer. J . Pub. Health, 1938, 28, 309; B. L. Isaacs, F. T. Jung,and A. C. Ivy, J . Amer. Med. As~oc., 1938, 111, 777, quoted by Bull. Hyg.,1939, 14, 147.16 J . Amer. Me&. Assoc., 1939, 112, 1910HARRIS : ANIMAL.339to normal when vitamin A was once again given. They conclude“ as a result of these observations we feel certain that measurementof dark adaptation when carried out under properly standardisedconditions can be used as an aid in the determination of the vitaminA condition of the body. Normal dark adaptation means a normalvitamin-A content of the body, and an abnormal dark adaptationmeans a disturbance of the vitamin-A content.” Similar observa-tions of the production of experimental dysadaptation in humanvolunteers deprived of vitamin A have been recorded by severalother American workers,17 and a rapidly growing number of in-vestigators l8 are now expressing their conviction as to the valueof the method, although often admitting that further refinementsin procedure are still to be desired.That dysadaptation is indeedclosely correlated with a subnormal level of vitamin A in the blood-stream has been stressed by T. Lindqvist,lg A. Juhksz-Schaffer 2oand others. Moreover, in experimental animals deficiency of vitaminA likewise leads to dy~adaptation.1~Vitamin B, (Aneurin, Thiamin).R8Ze in 2MetaboZism.-Notwithstanding some earlier uncertain-ties,21 it is now generally agreed 22 that vitamin B, functions inanimal tissues in the form of its pyrophosphate ester, co-carboxy-lase, as first indicated by K. Lohmann and P. S c h u ~ t e r . ~ ~ Thus itis now clearly recognised that the precise r81e of the vitamin in theintermediate metabolism of carbohydrates lies in the disposal ofpyruvic acid.The complexities of the system in question arel7 L. E. Booher, E. C. Callison, E. M. Hewston, and R. Loughlin, J . Nutrition,1939, 17, suppl. 10; G. Wald, H. Jeghers, and J. Arminio, Amer. J . Physiol.,1938, 123, 732; H. Jeghers, J . Amer. Med. ASSOC., 1937, 109, 756; cf. alsoL. B. Pett, Nature, 1938, 143, 23.l* A. McKenzie, E. African Med. J., 1938, 15, 143; Trans. Roy. SOC. Trop.Med. Hyg., 1939,32,717 ; E. J. Bigwood, “ Guiding Principles for Studies on theNutrition of Populations,’’ 1939, p. 197 ; 0. H. Schettler, R. F. Bisbee, andB. H. Goodenougli, J . Ind. Hyg., 1939, 21, 53; H. Frandsen, Acta Ophthal.,1937,4, suppl. 1 ; M. B. Corlette, J. B. Youmans, H. Frank, and M. G. Corlette,Amer. J . Med.Sci., 1938, 195, 54; R. T. M. Haines, Ophthal. SOC. Trans.,1938, 58, 103; E. Groth-Petersen, Acta Med. Scand., 1938, 95, 110; T.Gantzel, Hospitalstidende, 1938, 81, 85; H. R. Getz, G. B. Hildebrand, andM . Finn, J . Amer. Med. ASSOC., 1939, 112, 1308; W. v. Drigalski, H. KUDZ,and K. Schlupmann, Klin. Woch., 1939, 18, 875; E. Abramson andH. Oigaard, Skand. Arch. Ph,ysiol., 1939, 82, 49.Is Acta Med. Scand., 1938, 98, suppl. 97.2o Klin. Woch., 1938, 17, 407.21 R. A. Peters, Biochena. J., 1937, 31, 2240.22 I. Banga, S . Ochoa, and R. A. Peters, ibid., 1939, 33, 1109.23 Biochem. Z., 1937, 294, 188340 BIOCHEMISTRY.gradually becoming apparent and perhaps one of the most interest-ing developments during the past year has been the involvement ofadenylic acid in the scheme.Already in 1936 T. W. Birch and L. W.Mapsona had incriminated this substance as of significance inavitaminosis B,, and F. L i ~ m a n n , ~ ~ working on bacterial metabolism,has recently made the observation, no doubt a fundamental one,that the vitamin by acting on pyruvic acid is also able to bring about,as a secondary or coupled reaction, the phosphoryhtion of adenylicacid. In Lipmann’s words, “the dehydrogenation of pyruvic to aceticacid (through the agency of thiamin pyrophosphate) supplies theenergy necessary for the phosphorylation of adenylic acid.”I. Banga, S. Ochoa, and R. A. Peters,26 working on pigeon brain,concluded that the pyruvate oxidation system includes all of thefollowing components : co-carboxylase (vitamin B, pyrophosphateester), fumarate, inorganic phosphate, adenylic acid and cozymase.Magnesium is likewise needed to activate the reaction, both inyeast 23 and in brain.27 (Incidentally it is of interest that keto-butyric acid, and to a less extent a-ketovaleric acid, are capable ofacting as substitutes in the place of the pyruvic acid for thesesystems.28) Thus the details in this fascinating department of bio-chemical dynamics are gradually becoming filled in.Bradycardia and Vitamin B,.-A characteristic effect of deficiencyof vitamin B, in rats is the occurrence of a bradycardia of sinusorigin 29 and S.Weiss and his co-workers 30 have confirmed theoriginal finding of Drury and Harris that the symptom is curable byvitamin B, alone, even during temporary withdrawal of food, andhence is due essentially to the deficiency itself and not to theassociated inaniti~n.~, G.D. Lu,32 and also L. Kalaja andR. N a r ~ a n e n , ~ ~ have further substantiated the view of T. W. Birchand L. J. Harris 29 that the bradycardia goes parallel with the in-crease in lactic or pyruvic acids in the blood and tissues. IndeedKalaja and Narvanen record that they have been able to producethe symptoms of the bradycardia artificially in the absence of anyactual vitamin deficiency, by injections of either (a) pyruvic acidor ( b ) (in confirmation of Birch and Mapson) of adenylic acid or24 Nature, 1936, 138, 27; confirmatory work has recently been publishedby L. Kalaja and R. Narvanen, Skand.Arch. Physiol., 1938, 79, 303.25 Nature, 1939, 143, 281.27 S . Ochoa, ibid., p. 834.28 C. Long and R. A. Peters, Biochenz. J., 1939,33, 759.29 A. N. Drury and L. J. Harris, Ghem. and Ind., 1930,49,851; T. W. Birch30 S . Weiss, F. W. Haynes, and P. M. Zoll, Amer. Heart J . , 1 38, 15, 206.31 Cf. G. W. Parade, 2. Vitaminforschung, 1938, 7 , 35.Ibid., 144, 74.and L. J. Harris, Biochem. J., 1934, 28, 602HARRIS : ,4NIMAL. 341adenosine. Lu’s attempts 32 in this same direction, using pyruvicacid, however, gave negative results, and further work is thereforeto be desired.Whereas in rats avitaminosis B, causes a diminished rate of beatof the heart, in humans on the contrary a quickening of the rhythmresults. The reason for this surprising difference is not yet known,but it has recently been shown 33 that the pigeon resembles the ratin developing a bradycardia when submitted to uncomplicateddeficiency of vitamin B,.The effect is not to be confused with the“ bradycardia and heart block ” seen in pigeons on a diet of polishedrice, and attributable to the absence not of vitamin B, but of anunidentified factor, the “ heart-block factor.” 34, 35The Assay of Vitamin B,.-A. Z. Baker and M. D. Wright36s37have published two papers setting out the results of over five years’experience of the rat-bradycardia test ; 38 they express satisfactionwith its accuracy and specificity’ and give a very useful descriptionof various technical precautions which should be taken. Similarreports come from G.Lunde and co-w~rkers,~~ who used the methodfor a comprehensive survey of many dozens of Norwegian foodstuffs,from H. F. Pedersen,@ and from others.The pigeon test has been studied statistically by K. H. Cowardand B. G. E. Morgan,4l who conclude that it is by far the leastaccurate of all the standard methods of assay for this vitamin.H. Prebluda and E. V. McCollum 42 have now published a full accountof their promising colour test, and conclude that there are variousobstacles which still have to be overcome before it can be of generalapplicability; various modifications of it are suggested by D.Melnick and H. Field,& who use the reaction for estimating and fordifferentiating between free and bound (pyrophosphats) vitamin BThe Schopfer test, depending on the growth of a mould, has been32 Biochem.J., 1939, 33, 774.33 L. J. Harris, Chem. and Ind., 1939, 58, 472.34 C. W. Carter and A. N. Drury, J . Physiol., 1929, 68, Proc. 1 .35 C. W. Carter, Biochem. J., 1930, 24, 1811.36 Ibid., 1938, 32, 2156.37 Ibid., 1939, 33, 1370.38 T. W. Birch and L. J. Harris, ibid., 1934, 28, 602; L. J. Harris, Compt.rend ., Ve Congr2s International Technique et Chimique des Industries Agricoles,39 G. Lunde, H. Kringstad, and A. Olsen, Norske Vidensk. Skr., I . Ma.t.-Naturv. Klasse, 1938, No. 7 ; G. Lunde, Nord. med. Tidsskr., 1938, 15,444.p. 100.40 Dansk Tidsskr. Farm., 1938, 12, 137.41 Biochem. J., 1939, 33, 658.42 J. Biol. Chem., 1939, 127, 495.43 IbicE., pp. 505, 515, 531342 BIOCHEMISTRY.tested by H.M. Sinclair for estimating vitamin B, in blood : heconcludes that this method is not specific but may be useful forpurposes of comparison.Vurious Forms of Vitamin B,.-In the course of tests on milkdiscrepancies have been noted between the results as obtained bythe fluorimetric and biological methods of assay, and the explanationis offered that some hitherto unrecognised complex of vitamin B,with protein may be present.45 Further it appears that in the bloodserum there exists some form of the vitamin similarly combined withprotein.46The very interesting suggestion has been advanced by C. R.Harington and R. C. G. Moggridge4’ that a precursor of vitaminB, in the animal body may be the related a-amino-acid, a-amino-~-(4-methylthiazole-5)-propionic acid.As these authors say, it isnot difficult to picture how this amino-acid could itself arise frommethionine, acetaldehyde, and ammonia.Assessment of Level of Nutrition.-In the method originally pro-posed for the detection of “ partial deficiency ” of vitamin B, inman 48 the excretion of the vitamin in the urine was measured bymeans of a biological test. This had tho disadvantage that itnecessitated access to a well-equipped biochemical laboratory.The attempt to simplify the procedure by substituting a chemicalfor the biological method of determination was attended withvarious due to interference from non-specific substances,and various other sources of error. A simple chemical procedurenow described has been found reliable when repeatedly checkedagainst direct biological standardisation on the identical samplesof ~rine.~O The normal excretion ranges from about 50 to 80 I.U.daily, and low values are common in pregnancy or when absorptionor utilisation is impaired (“ conditioned deficiency ”).Experiments with rats suggest the possibility that the specificdefects in carbohydratle tolerance associated with hypovitaminosisB, may be utilised as the basis for an alternative method of assessingthe level of n~trition.~1L4 Biochrn.J., 1938, 32, 2185.45 J. Houston, S. K. Kon, and S. Y. Thompson, Chem. and Ind., 1939,58, 651.R. S. Goodhart and H. M. Sinclair, Biochem. J . , 1939, 33, 1099.47 J., 1939, 443.48 L. J. Harris and P. C. Leong, Lancet, 1936, i, 886; L.J. Harris, P. C.*9 M. Pyke, Lancet, 1939, i, 415.50 Y. L. Wang and L. J. Harris, Biochern. J., 1939, 33, 1356.51 G. G. Banerji and L. J. Harris, ibid., p. 1346 ; see further B. S. Platt andLeong, and C. C. Ungley, ibid., 1938, i, 639.G. D. Lu, ibid., pp. 1525, 1538HARRIS : ANIMAL. 343Vitamin B, Complex.The " vitamin B, complex " includes at least four separate vita-m i n ~ , ~ ~ wix., riboflavin, nicotinic acid, vitamin B,, and the so-called " chick-dermatitis " factor. During the past year a con-siderable number of important papers have been published dealingwith this complex, and nearly all are of significance to the expert;here we can hope t o do no more than draw attention to one or twoof the more outstanding points.Ribo$avin.-Riboflavin deficiency in man, as produced experi-mentally 53 or seen ~linically,~~ is marked by inflammation and scali-ness of the lips and cracks at the angle of the mouth (angularstomatitis ; " cheilosis "), or in dogs by sudden collapse 55 or " yellowliver " 56-it responds promptly to treatment with the vitamin.An observation which promises to prove of physiological importanceis that the prosthetic group of d-amino-acid oxidase has beenidentified as a flavin derivative, vix., an alloxazine-adenine-di-nucleotide; 57 it is now thought that the " yellow enzyme '' ofWarburg and Christian, the classical carrier of riboflavin, may notactually occur as such in Nature but result from the decompositionof this nucleotide.At least five distinct enzymes containing ribo-flavin have now been described.58 Fuller details are given on p.354.Nicotinic Acid (Pellagra-preventing Factor) .-It can be anticipatedthat progress should be stimulated by the publication of methodsfor estimating nicotinic acid in foods 59 or for assessing the level ofnutrition by tests on urine.60 Most pyridine derivatives other thannicotinic acid or amide have been found to be biologically inactive,but quinolinic acid is an exception and has been shown to be curativeof ,human pellagra.c1Vitamin B, (Adermin, Pyridozin 62 or '' Eluate Factor ").-52 Cf. Ann. Reports, 1937, 34, 403; 1938, 35, 336.53 TV. H. Sebrell and R. E. Butler, Pub. Hlth. Reps., Wash., 1938,53,2282.64 J. W. Oden, L. H. Oden, and W.H. Sebrell, ibid., 1939, 54, 790; T. D.5 5 H. R. Street and G. R. Cowgill, Amer. J . PhysioZ., 1939,125,323.56 W. H. Sebrell and R. H. Onstott, Pub. Hlth. Reps., Wash., 1938, 53,6 7 0. Warburg and W. Christian, Biochem. Z., 1938, 298, 150.Spies, Southern Med. J., 1939, 32, 618.83.0. Warburg and W. Christian, ibid., p. 368; see further H. S . Corm,59 E.g., M. Swaminathan, Nature, 1938, 141, 830; Indian J . Med. Res.,6o L. J. Harris and W. D. Raymond, Chern. and Ind., 1939, 58, 652;61 R. W. Vilter and T. D. Spies, Lancet, 1939, ii, 423.62 P. Gyorgy and R. E. Eckardt, Nature, 1939,144, 512.J. G. Dewan, A. H. Gordon, and D. E. Green, Bwchem. J., 1939,33,1694.1939, 26, 427.Biochem., J., 1939, 33, No. 12344 BIOCHEMISTRY.Following the isolation of crystalline vitamin its structure hasbeen eliicidatedyM it has been ~ynthesised,~~ and the syntheticmaterial has been proved to be 66Like nicotinic acid, it is a pyridine derivative,HO/\CH,-OH but it contains a methyl, a hydroxyl and twoH,Cll 1 hydroxymethyl groups.Its relation to humannutrition still remains obscure, but a very in-teresting and probably important finding isthat a prolonged deficiency in rats gives rise to fits,G7 similar tothose previous noted in pigs.G*Chick Dermatitis Factor (Pantothenic Acid, (‘ Filtrate Factor ”) .-Rapid progress has been made since the demonstration a little overa year ago 69 that the ‘( chick dermatitis ” factor is not, as previouslysupposed, identical with the pellagra-preventing vitamin.Thatthis chick dermatitis factor closely resembles the so-called panto-thenic acid of R. J. Williams 70 (a factor which, it will be recalled,stimulates the growth of yeast, and a great variety of other micro-organisms) was first pointed out by T. H. Jukes ; 71 and the identity ofthe two is now generally accepted. Pantothenic acid, thus needed bychicks, and probably also by 72a as well as by micro-organisms,seems to consist 70, 73 of p-alanine united, possibly through a sub-E. T. Stiller, J. C. Keresztesy, and J. R. Stevens, J . Amer. Chem. SOC.,1939, 61, 1237; S. A. Harris, E. T. Stiller, and K. Folkers, ibid., p. 1242;R. Kuhn and G. Wendt, Ber., 1939, 72, 305; R. Kuhn, H. Andersag, K.Westphal, and G. Wendt, ibid., p. 309 ; R. Kuhn, G. Wendt, and K.Westphal,ibid., p. 310; cf. also A. Itiba snd K. Miti, Sci. Papers Inst. Phys. Chem.Res. Tokyo, 1938, 35, 73.65 S. A. Harris and K. Folkers, J . Amer. Chem. SOC., 1939, 61, 1245; R.Kuhn, K. Westphal, G. Wendt, and 0. Westphal, Naturwiss., 1939, 27,469.CH,*OH\N/63 Cf. Ann. Reports, 1938, 35, 337.6 6 E. F. Moller, 0. Zima, F. Jung, and T. Moll., ibid., p. 228.67 H. Chick, A. N. Worden, and 81. M . El-Sadr, Chem. and I n d . , 1939, 58,68 H. Chick, T. F. Macrae, A. J. P. Martin, and C. J. Martin, Biochem. J.,1019.1938, 32, 2207.W. J. Dann and Y . Subbarow, J . Nutrition, 1938, 16, 183.70 R. J. Williams, H. H. Weinstock, E. Rohrmann, J. R. Truesdail, H. K.71 Ibid., p . 975; see likewise D. W. Woolley, H. A. Waisman, and C. A.72 Y .Subbarow and G. H. Hitchings, ibid., p. 1615.72a T. F. Macrae, A. R. Todd, B. Lythgoe, C. E. Work, H. G. Hind, andM . M . El-Sadr. Biochem. J., 1939, 33, 1681.7s H. H. Weinstock, H. I<. Mitchell, E. F. Pratt, and R. J. Williams, J.Arner. Chem. SOC., 1939, 61, 1421; D. W. Woolley, H. A. Waisman, andC. A. Elvehjem, ibid., p. 977; J . Riol. Chem., 1939, 129, 673; D. MT. Woolley,ibid., 1939, 130, 417.Mitchell, and C. E. Meyer, J . Amer. Chem. Soc., 1939, 61, 454.Elvehjem, ibid., p. 977HARRIS : ANIMAL. 346stituted amide group, with a hydroxy-acid (perhaps a hydroxyvalericacid). p-Alanine given by itself is said to be almost as active for ratsbut not for chi~ks.~4 As already mentioned, the “ filtrate factor ”needed by rats is probably not a single sub~tnnce.~~aVitamin C .The past year has been marked not so much by any outstandingnew developments as by an immense activity in the application ofalready existing knowledge.Thus, many dozens of papers haveappeared on the assessment of the level of nutrition by means of thesaturation test,75 as carried out in many different regions of the globeand under all kinds of condition^.^^ (War-time considerations revealthemselves in the controversy between W. Stepp and H. Schroeder 7 7on the one hand, and H. Rietschel and J. Mensching 78 on the other.The latter contend against the former : “ The economic inconvenienceto Germany of having to supply a requirement of 50 mg. per headdaily is stressed, and the desirability is indicated of persuading thepeople that it is not necessary.”) There is general confirmation ofthe finding of a depletion of reserves during especially intuberculosis ; 8o and further indications are forthcoming of thecorrelation existing between the vitamin-C level and the complementtitre.81There have been almost as many publications dealing withthe question of analytical methods; and most workers are nowprepared to accept the view that the amount of vitamin C infruits and vegetables is accurately measured by titration withthe indophenol dye, provided the extraction and the titration areperformed sufficiently rapidly and in strongly acid solution.82The suggestion of “ inert ” or “ bound ” ascorbic acid is not usually74 M.Hoffer and T. Reichstein, Nature, 1939, 144, 72.7 5 Cf.Ann. Reports, 1937, 34, 408.7 6 E.g., see especially surveys on medical students by R. J. Harrison, A. E.Mourant, and A. Wormall, St. Bartholomew’s Hosp. J., 1939,46,224; accountof seasonal variations in Palestine by K. Guggenheim, J . Hyg., 1939, 39, 35 ;a masterly review of literature by Sybil L. Smith, J . Amer. Med. ASSOC., 1938,111, 1753.7 7 Klin. Woch., 1939, 18, 414.7 8 Ibid., p. 273.79 K. Dam, K. Boyd, and W. D. Paul, Proc. Xoc. Exp. Riol. Med., 1939,40, 129; Falke, Klin. Woch., 1939, 18, 818.ao W. W. Jetter and T. S. Bumbalo, Amer. J . Med. Sci., 1938, 195, 362;M. N. Rudra, Current Sci., 1939, 8, 210.81 E.g., €4. E. Ecker, L. Pillemer, J. J. Griffitts, and W. P. Schwartz,J . Amer. Med. As-soc., 1939, 112, 1449.a2 Cf. Ann.Reports, 1937, 34, 404346 BIOUHEMISTRY.ac~epted,8~9 84, 85 and the proposed precipitation process with mercuryacetate is generally considered of doubtful value.86Vitamin D.The complexity of each new advance accomplished by the bio-chemist often merely adds to the perplexities of the clinician, andfor a time there has been uncertainty whether for the humanchild vitamin D, is more potent than vitamin D,-as it is for thechick-or equaEEy potent-as for the rat. There can now no longerbe any doubt that it is the latter alternative which is the correctone, for the thoroughgoing comparisons instituted by N. Morris andM. M. Stevenson 87 should satisfy the most exacting critic. Anotherpaper of clinical interest is the study by J.C. Drummond, C. H.Gray, and N. E. G. Richardson88 on the antirachitic potency ofhuman milk; and organic chemists will be thankful to T. Kennedyand F. S. Spring a9 for a detailed discussion of the structural re-1 ationships of various isomers of vitamin D,, including calciferol,ergosterol, lumisterol, pyrocalciferol and isopyrocalciferol.Purther interesting work has been published on the anticalcifyingaction of cereals, and its relation to the peculiar form in whichtheir phosphorus is bound as inositol phosphoric acid (phytin).H. Steenbock and his colleagues in America, working with chicks,give further support for the contention that the explanation is thatthe phosphorus of the phytin is not available for curing rickets,and similarly J.H. Jones,g1 working with rats, is unable to findthat cereals contain any specific anticalcifying factor. As againstthis, however, D. C. Harrison and E. Mellanby 92 from experimentson dogs have concluded that " the rachitogenic action of cereals isnormally due not, as has often been suggested, to the unavailabilityof their P, but to the action of the cereal phytic acid in inhibitingthe absorption of Ca from the alimentary canal."E. Mathiesen, Tids. Hemetikind., 1938, 24, 410; 1939, 25, 18.84 M. v. Eekelen, 2. Vitaminforschung, 1938,7, 254.as W. D. Leech, J . Proc. Austral. Chem. Inst., 1938, 5, 163; A. Fujita, and86 E.g., K. A. Evelyn, H. T. Malloy, and C . Roseq, J . Biol. Chem., 1938,87 Lancet, 1939, ii, 876.88 Brit. Med. J . , 1939, 2, 757.89 J., 1939, 250.T.Ebihara, Biochem. Z., 1938-9, 300, 143.126, 645.J. T. Lowe, H. Steenbock, and C. H. Krieger, Poultry A%., 1939, 18,40.9 1 J . Nutrition, 1939, 18, 507.@a Biochem. J . , 1939, 33, 1660HaRRIS: ANIMAL. 347Vitamin E.Full confirmation has been forthcoming of the structure pro-visionally indicated for ct- and @-tocopherols in last year’s Report ; 93that is, as chroman derivatives-or, to look at the same formulationin another way, as duroquinone derivatives united to a phytol chain.Various homologues have been synthesi~ed,~~ and it is clear thatsome degree of biological activity may be exhibited by many related96 Attention has been concentrated recently on anumber of effects of deficiency distinct from the better knownfailure in the birth mechanism, e.g., on the degeneration in the kidneysand the discoloration of the uterus,97,g8 the muscular d y s t r ~ p h y , ~ ~ , ~ ~and the “ alimentary exudative diathesis ” : 1 all of these can beprevented by synthetic a-tocopherol.Further progress should begreatly stimulated by the introduction of chemical and physicalmethods of estimation, e.g., the potentiometric method with auricchloride,2 the colour reaction with ferric chloride-dipyridylY3 ornitric acid: and the measurement of ultra-violet absorption.Vitamin K.of theimportant developments concerning vitamin K, the “ KoagulationVitamin.” It only remains to add that, thanks to the work ofE. A. Doisy, of H. J. Almquist, and of L. F. Fieser and theirrespective collaborators, vitamin K has now been characterisedA very full account was given in last year’s Report93 Ann.Reports, 1938, 35, 339.s4 L. I. Smith and H. E. Ungnade, J . Org. Chem., 1939, 4, 298; A. Jacob,M. Steiger, A. R. Todd, and T. S. Work, J . , 1939, 542; P. Karrer and H.Fritzsohe, Helv. Chim. Acta, 1939,.22, 260 ; P. Karrer and B. H. Ringier, ibid.,p. 610; P. Karrer and 0. Hoffmann, ibid., p. 654; P. Karrer, H. Fritzsche,and R. Escher, ibid., p. 661.Q5 P. Karrer and K. A. Jensen, ibid., 1938, 21, 1622.Q6 “ Vitamin E,” A Symposium held under the auspices of the Food Group(Nutrition Panel) of the Society of Chemical Industry, 1939.s7 T. Moore, Chem. and Ind., 1939, 58, 651.Q8 A. J. P. Martin and T. Moore, J . Hyg., 1939, 39, No.6.ag C. G. Mackenzie and E. V. McCollum, Science, 1939, 89, 370; N. Shimo-tori, G. A. Emerson, and H. M. Evans, ibid., 1939, 90, 80; V. Demole andH. Pfaltz, Schweiz. med. Woch., 1939, 69, 123.1 W. Dam and J. Glavind, Nature, 1939, 143, 810.P. Karrer and W. Jaeger, Helv. Chirn. Acta, 1939, 22, 314.A. Emmerie and C. Engel, Rec. Trav. chim., 1939, 58, 283.M. Furter and R. E. Meyer, Helv. Chim. Acta, 1939, 22, 240.6 A. J. P. Martin, T. Moore, andM. Schmidt, Nature, 1934, 134,.a Ann. Reporte, 1938, 35, 340.214348 BIOCHEMISTRY.conclusively as a 1 : 4-naphthaquinone derivative, that biologicalactivity has been correlated with the presence of substituents inthe 2-, or 2- and 3-p0sitions,~ and that the vitamins " K, " and" K2" as actually found in Nature have almost certainly the structure(I) and (11) respecti~ely,~ that is, K, is 2-methyl-3-phytyl-1 : 4-naphthaquinone and K, is 2 : 3-difarnesyl-1 : 4-naphthaquinone.These and many other related compounds have been synthesised,and their biological activities compared.A particularly fascinatingpoint, about which no doubt more will be heard, is the structuralrelationship between vitamin K, and vitamin E ; and in the mean-time indications are accumulating of a probable clinical significance00 CH, I CH, I 7H3~\~\.CH,=CH:C*CH,*CH,*C~ :C*CH,*CK,*CH:C*CH,('I.) I 11 II*CH,*CH: CH,*CH,*CH:C*CH,*CH2*CH:C*CH31 1CH3 CH3\/\/ F0 CH3for vitamin K, e.g., in haemorrhagic states in infancy,1° in obstructivejaundice in adults,ll or with simple dietary lack.127 R.W. McKee, S. B. Binkley, D. W. MacCorquodale, S. A. Thayer, andE. A. Doisy, J. Amer. Chem. SOC., 1939, 61, 1295; H. J. Almquist and A. A.Klose, ibid., p. 1611; S. B. Binkely, D. W. MacCorquodale, L. C. Cheney,S. A. Thayer, R. W. McKee, and E. A. Doisy, ibid., p. 1612.* H. J. Almquist and A. A. Klose, ibid., pp. 1611, 1923; S. Ansbacherand E. Fernholz, ibid., p. 1924; L. F. Fieser, D. M. Bowen, W. P. Campbell, M.Fieser, E. M. Fry, R. N. Jones, B. Riegel, C. E. Schweitzer, and P. G. Smith,ibid., p. 1925; L. F. Fieser, D. M. Bowen, W. P. Campbell, E. M. Fry, andM. D. Gates, {bid., p. 1926 ; D. W. MacCorquodale, S. B. Binkley, S. A. Thayer,and E. A. Doisy, ibid., p. 1928; S. A. Thayer, L. C. Cheney, S. B.Binkley,D. W. MacCorquodale, and E. A. Doisy, ibid., 1932 ; S. B. Binkley, D. W. Mac-Corquodale, S. A. Thayer, and E. A. Doisy, J. Biol. Chem., 1939, 130, 219;H. J. Almquist and A. A. Klose, ibid., p. 787.9 L. F. Fieser, W. P. Campbell, and E. M. Fry, J . Amer. Chem. SOC., 1939,61, 2206; D. W. MacCorquodale, R. W. McKee, S. B. Binkley, L. C. Cheney,W. F. Holcomb, S. A. Thayer, and E. A. Doisy, J. Biol. Chem., 1939, 130,433; H. J. Almquist and A. A. Klose, ibid., p. 791.lo W. M. Waddell, D. Guerry, W. E. Bray, and 0. R. Kelley, Proc. SOC.Exp. Biol. Med., 1939, 40, 432; H. Dam, E. Tage-Hansen, and P. Plum,Lancet, 1939, ii, 1157.l1 A. M. Snell, H. R. Butt, and A. E. Osterberg, Amer. J. Digest. Dis.,1938, 5, 590; R. L. Clark, C. F. Dixon, H.R. Butt, and A. M. Snell, Proc.S t a , Meetings Mayo Clinic, 1939,14,407 ; J. E. Rhoads, Surgery, 1939,5,794;J. M. Macfie, -4. L. Bacharach, and M. R. A. Chance, Brit. Med. J., 1939,ii, 1220. l2 R. Kark and E. L. Lozner, Lancet, 1939, ii, 1162HAKRIS : ANIMAL. 349Various Factors in Diet.Protein.-There seems no doubt that the amino-acid valine mustnow be added to the list of dietary indispensables. Rats deprivedof it develop symptoms of incoordination of a characteristic type.13Therefore the amino-acids now recognised as essential for growthin the young, and equally by the adult animal, include histidine,isoleucine, leucine, lysine, methionine, phenylalanine, threonine,tlryptophan and valine.l*Mineral Elements.-It was long held that the amounts of thebivalent and tervalent metals (such as Ca, Mg, and Fe) circulatingwithin the body were controlled in some way by the rate of theirre-excretion into the gastro-intestinal tract.Recent experiments,l5however, have led to a revolutionary change of view, for it is nowbelieved that little or no re-excretion actually occurs. With ironfor example (which is not excreted in the urine in significantquantities) the needs of the body seem to determine the amountwhich is absorbed in the first instance. When large doses of ironare given, this normal control, it is true, may be overruled andrelatively large amounts are then absorbed and stored in the body.In spite of this it has been found that in order to arrest the steadyfall in the hemoglobin level which commonly accompaniespregnancy the continuous administration of iron in massive dosesis needed.As E. M. Widdowson16 comments, “It might veryreasonably be held that, if the hemoglobin fell to its original levelwhen the iron was discontinued, no pathological state had beendisclosed. Against this view must be set the weight of clinicalopinion, which has pronounced definitely in favour of raising thehemoglobins of babies and pregnant women. ”Copper has been recognised for some years now as a dietaryessential, since minute amounts of it must be present in the food ifnutritional anemia is to be prevented. It is only recently thatT. Mann and D. Keilin l7 have made the fundamental observation13 W. C. Rose and S. H. Eppstein, J. Biol.Chem., 1939, 127, (377.l4 See papers by R. C. Corley, P. A. Wolf, and E. K. Nielsen, ibid., 1938,123, Proc. xxvi, concerning the needs of adult rats; by W. C. Rose and E. E.Rice, Science, 1939, 90, 186, concerning the similarity between dogs and rat ;and a general review of the whole problem by W. C. Rose, PhysioZ. Rev., 1938,l5 R. A. McCance and E. M. Widdowson, Lancet, 1937, ii, 680 ; P. F. Hahn,W. F. Bale, E. 0. Lawrence, and G. H. Whipple, J . Amer. Med. ASSOC., 1938,111, 2285; J. Exper. Med., 1939, 69, 739; It. A. McCance and E. MWiddowson, Biochem. J . , 1939, 33, 523; J. Pliysiol., 1938, 94, 148.18, 109.Lancet, 1939, ii, 640.Nature. 1938,142, 148; Proc. Roy. SOC., 1938, €3, 126, 303350 BIOCHEMIS!l?RY.that the copper found in blood occurs in the form of a copper-protein derivative, to which they have given the name haemo-cuprein.This discovery raises important problems concerning thephysiological activity of the new compound, but it has not beenpossible to show that haemocuprein is more effective than ordinaryinorganic copper in curing “ copper anzemia ” when injected intra-peritoneally.lBDietetics.-The reports issued by the Technical Commission ofthe League of Nations bear the unmistakable stamp of authority,and indeed all workers in nutrition will be glad of the expert guidancefurnished in a new publication,19 which deals inter alia with theminimal human requirements for various vitamins and otheressentials, and gives a review of the current position in nutritionalresearch.Other works of unusual interest include the delightful and in-formative historical survey of the Englishman’s food by J.C.Drummond and Anne Wilbraham,20 a new edition of that old classic“ The Newer Knowledge of Nutrition,” 21 and last but not least arevealing study about the prevalence of malnutrition in India.22L. J. H.The Configuration of the Glutamic Acid in Turnours.Few exceptions are known to the generalisation that the amino-acids which occur in proteins belong to the Z-series and it is generallyheld that the small amounts of d-isomer that have been found arethe result of racemisation during hydrolysis. F. Kogl and H.Erxleben 1 have claimed that there are abnormally large amountsof the d-isomers in tumour tissue ; this is especially true of glutamicacid.The evidence in the first paper was not sufficiently definite for aready acceptance of this unexpected statement and A.C. Chibnallet aL2 and S. Graff3 were unable to confirm it and reported theisolation of the pure Z-isomer. Kogl and Erxleben * then publishedla L. J. Harris and T. Mann, unpublished work.l@ Bull. Health Org., 1938, 7 , 460.2o “ The Englishman’s Food. A History of Five Centuries of English21 E. V. McCollum, E. Orent-Keiles, and H. G. Day, “ The Newer Know-z8 N. Gangulee, ‘‘ Health and Nutrition in India.”Diet.” 1939.ledge of Nutrition.” Fifth edition, 1939.1939.2. physiol. Chem., 1939, 258, 57.A. C. Chibriall, M. W. Rees, G. R. Tristram, E. F. Williams andE. Boyland, Nature, 1939, 144, 71.a J .BWE. Chem., 1939, 130, 13. Nature, 1939, 144, 111PIRIE: ANIMAL. 351data showing that the Foreman technique which these authors hadused fractionated a mixture of the Z- and dl-isomers. Using Kogl’stechnique, L. E. Arnow and J. C. Opsahlhave also isolated dl-glutamic acid from tumours. Chibnall et aListill deny the reality of the phenomenon and in a detailed study ofnormal and tumour proteins they find no differences in the extentof racemisation. This observation is a direct contradiction of thestatements of others 1,s that normal tissue, by Kogl’s technique,gives only the Z-isomer, but it is pointed out that the degree of con-centration of the d-isomer into certain amino-acid fractions might beexpected to vary with the particular amino-acid mixture from whichand J.and I?. R. Whiteit is being isolated. N. w. P.Amino-acid Analysis and Protein Structure.Bergmann and Niemann’s interesting generalisation a bout proteinstructure was lucidly explained in this Report for 1937.l Ouropinions on its validity must depend on the reliability and complete-ness of the amino-acid analyses on which it is based, for in theseries of numbers expressible as 2 n x 3 m (where n and rn are integers)the only long gaps are 19-23 and 3 7 4 7 . The other intervals aresmall compared with the probable error in most amino-acid estima-tions on protein hydrolysates; it is therefore the absence of figuressuch as 21 and 42 in the list of values of N , (the number of occurrencesof an individual amino-acid in a protein molecule) that tests thehypothesis.Through overlooking the small errors involved infitting a purely random distribution of values of N , on to the21~ x 3m series of numbers, T. W. J. Taylor and W. T. Astbury2were satisfied with the agreement between dubious analytical datafor flavoprotein and the p-keratin of wool and the Bergmann seriesof numbers.Amino-acid analysis usually involves the isolation of the acidor a derivative in the largest possible yield and the correction ofthis yield for the known or assumed solubility in the mother-liquor of the substance isolated. G. R. Tristram3 has publisheda useful critique of this principle when applied to the basic amino-acids and J. G. Sharp has demonstrated its fallibility in some othercases.A different principle is now used by M. Bergmann and W. H.Stein,5 for they aim at the incomplete precipitation of a slightlyScience, 1939, 90, 257.Biochem. J., 1940, 34, in the press.T. W. J. Taylor, Ann. Reports, 1937, 34, 302.Nature, 1937, 140, 968.Ibid., p. 679.ti J . Biol. Chem., 1939, 130, 435.Biochem. J . , 1939, 33, 1271.J . Bwl. Chem., 1939, 128, 217352 BIOCHEMISTRY.soluble salt of the amino-acid in the presence of two or more concen-trations of the precipitant. If the solubility product of the saltremains constant under the carefully controlled conditions used,the concentration of the amino-acid solution can be calculated.Rhodanilic, dioxpyridic, dioxanilic {Le., H[Cr(C,H,*NH,),(SCN),],H[ a( c204) 2py2], H [ Cr (c ,04),( c ,H5*NH2) ,I) and naphthalene -f3-sulphonic acids have been used, but few results have as yet beenpublished.6,It has been obvious to all workers in the field that the productionof " labelled " amino-acids, e.g., containing deuterium, heavynitrogen or, better still, heavy carbon, should give us a valuabletechnique of estimation.If a quantity of a rigorously purifiedamino-acid is isolated from the hydrolysate of a protein to whicha known proportion of labelled amino-acid has been added, the ratioof " labelled " to normal amino-acid in the sample should equal theratio of added amino-acid to that originally present in the protein.No useful figures have yet been published in which this principle isused, but a note has appeared on the isolation of " labelled ''leucine from hzemoglobin and casein hydrolysates.The proline content of collagen seems to demand the anomalousfrequency of seven ; Bergmann and Stein have suggested guardedlythat two frequencies may be concerned in this case.has described a colour reaction for citrullin that is given by severalproteins, and M.Wada lo isolated citrullin from casein and showedthat under the conditions of acid hydrolysis it would yield proline.Glutamic acid is another example of an amino-acid which mayappear in a hydrolysatc from more than one source, for it is nowgenerally accepted that part of it is derived from glutamine.R. L. M. Synge 11 has isolated from the hydrolysate of gliadin thathad been treated with hypobromite, an amount of ay-diaminobutyricacid corresponding to 16% of the glutamic acid and he suggeststhat the amino-group is formed by the Hofmann degradation of theamide group of glutamine.In general the sum of two numbersexpressible as 2 n x 3m is not itself expressible in this way; it istherefore curious that the glutamic acid content of several proteinshas satisfied the numerical generalisation if it arises from twoindependent amino-acid frequencies.Our views on protein structure have been clarified somewhat bya symposium to which 20 workers contributed l2 and by PaulingW. R. Fearon6 H. R. Ing and M. Bergmrtnn, J. BioZ. Chena., 1939, 129, 603.8 H. H. Ussing, Nature, 1939, 144. 977.Q Biochem. J., 1939, 33, 902.l1 Biochem. J., 1939, 33, 671.M.Bergmann and W. H. Stein, ibid., p. 609.l o Biochem. Z., 1933, 257, 1.l2 Froc. Roy. Xoc., 1939, B, 127, 1PIRIE : ANIMAL. 353and C. Niemann’s 13 masterly criticism of the more extravaganthypotheses on the subject; their conclusion is : “. . . the poly-peptide chain structure of proteins, with hydrogen bonds and otherinteratomic forces (weaker than those corresponding to covalentbond formation) acting between polypeptide chains, parts of chains,and side-chains, is compatible not only with the chemical and physicalproperties of proteins but also with the detailed information aboutmolecular structure in general. . . .”Among the more interesting recent protein studies may bementioned, firstly, the demonstration that pepsin l4 from one animalmay contain several enzymically active constituents, and, secondly,the crystallisation of myogen.15 The latter is apparently homo-geneous on the centrifuge 16 and has a molecular weight ca.150,000.The isolation from the sap of plants infected with potato virus“ Y ” l7 and tobacco ringspot 18 of infective nucleoproteins withrelatively constant properties raises to 12 the number of plant virusinfections which have given rise to these characteristic products.The relationship between these preparations and the virus as itoccurs in the sap is still obscure l9 and it would be premature to lookon most of these products as unmodified virus.The chemical and physical properties of purified enzymes havebeen summarised in a review and a book by J.H. Northrop 2o andthose of purified viruses in two reviews and a book.21, 22, 23N. W. P.Riboadenine-Ribityljlavin * Diphosphate-Protein Comglexes asOxidation Catalysts.A number of very potent enzyme preparations isolated fromvarious sources (Table) have recently been shown to owe theirl3 J . Amer. Chem. SOC., 1939, 61, 1860.l4 V. Desreux and R. M. Herriott, Nature, 1939, 144, 287.l5 T. Baranowski, 2. physiol. Chem., 1939,260,43.l6 N. Gralen, Biochem. J., 1939, 33, 1342.l7 F. C. Bawden and N. W. Pirie, Brit. J . Exp. Path., 1939, 20, 322.W. M. Stanley, J . Biol. Chem., 1939, 129, 405.Nature, 1938, 142, 841.2o Tabulm Biologicm, 1939, 18, 76 and “Crystalline Enzymes,” Univ.31 F. C. Bawden and N. W. Pirie, Tabulm Biologicm, 1938, 16, 355.22 W.M. Stanley, Physiol. Rev., 1939, 19, 524.23 F. C. Bawden, “ Plant Viruses and Virus Diseases,” Chronica Botanica,Leiden. 1939.* Since these substances are derived from ribitol, and not ribose, ribityl-flrtvin seems to express the composition more correctly than t,he ambiguousname riboflavin.Columbia Press, 1939.BEP.-VOL. XXXVI. 354 BIOCHEMISTRY.activity to the presence of a protein linked to a prosthetic groupcomposed of adenylic acid and ribitylfiavin phosphate united ina manner in some ways analogous to the union in a dinucleotide.Workers in this field generally refer to them as “flavoproteins.”They should not be confused, with the “ yellow enzyme ” of0. Warburg and W. Christian (a ribitylflavin phosphate-proteincomplex of relatively weak activity), which is now believed to be adegradation product of true flavoproteins (see this vol., p.343).To date, five distinct flavoprotein enzymes have been prepared :Source. Catalyses oxidation o f : Reference.Yeast Dihydrocoenzymes I and P. H a a ~ . ~Liver and kidney d-Amino-acids F. B. Straub 3; 0. WarburgHeart (but of wide Dihydrocoenzymes I and F. B. Straub 6 ; H. S. Cor-distribution) I1 ran, D. E. Green, andMilk (also in liver) Hypoxanthine, aldehydes, E. Ball 7 ; H. S. Corran anddihydrocoenzyme I D. E. Green H. S. Cor-ran, J. G. Dewan, H. Gor-don, and D. E. Green.9Liver Aldehydes V. Subrahmanyan, H. Gor-don, and D. E. Green.loI1and W. Christian.4F. B. Straub.sThe prosthetic group of these enzymes has been demonstratedto undergo a cycle of reduction and oxidation in turn by the substrateand by molecular oxygen or some other suitable hydrogen acceptor.The catalytic activity of some of these $reparations is remarkable;the most active, heart flavoprotein, will catalyse the oxidation ofca.8000 molecules of dihydrocoenzyme I per molecule of enzymeper minute, assuming that all the flavin is catalytically active.D. J. B.Galactose in the Animal Kingdom.This subject seems to have been neglected in these Reports forsome time back, yet it is one of those most demanding investigation,for it is by no means clear what metabolic function is fulfilled by thissugar in the animal organism. Besides occurring in various situa-tions in the body, galactose can serve as a metabolisable carbo-hydrate to the mammal, despite the almost entire absence of akidney threshold, but no direct evidence of its utilisation by anyBiochem.Z., 1932, 257, 438.Nature, 1938, 141, 603.Ibid., 1938, 298, 378.Biochem. Z., 1938, 295, 261.Ibid., p. 793.Biochem. J., 1938, 32, 2231.ti Biochem. J., 1939, 33, 787.7 J . Biol. Chem., 1938, 128, 57.* Ibid., 1939, 33,1694. lo Nature, 1939, 144, 1016BELL: ANIMAL. 355particular mammalian tissue has yet been obtained. For example,lgalactose injected intravenously into normal dogs is removed fromthe blood in two hours, 10-30y0 being found in the urine. I n thehepatectomised dog, however, 50-60y0 of the galactose iseliminated by this pathway, but the remainder is not converted intoglucose, since the hypoglycemia of these animals is not altered.Some unknown extrahepatic tissue must therefore be utilising thesugar. The storage of glycogen in the livers of fasted rabbitssubsequent to the ingestion of large doses of galactose has beeninvestigated by D.J. who found that the polysaccharide con-tained no galactose and differed from the normal glycogen of theseanimals by having a chemical molecule composed of 18 glucoseunits compared with the usual 12. H. W. Kosterlitz has examinedthe livers of these rabbits for possible intermediaries in the conver-sion of galactose into glucose and has isolated 9-10 mg.1100 g.of tissue of a non-reducing galactose 1-phosphate, the structureof which he has confirmed by synthesis. S.P. Colowick also hasannounced the synthesis of such a compound and states that hisproduct, which has the same properties as that of Kosterlit~,~ isnot affected by any known enzymes of dialysed muscle extracts,liver or dried yeast. Kosterlitz,6 however, has recently shownthat his material is fermented by dried galactose-adapted 8. cere-visice Frohberg a t the same rate as glucose, whereas free galactoseis fermented only slowly.The origin of lactose has been the subject of investigation byG. A. Grant.' Detecting the sugar by a fermentation methodusing 8. fragilis, he showed that slices of lactating guinea-pigmammary gland could form lactose from glucose, but not fromfructose, maltose or galactose or from mixtures of these sugars.No p-galactosidase could be detected in the tissue, nor did anyof the then known intermediates in the glycolytic system increaselactose formation under the conditions used.Galactose metabolism in the snail, Helix pomatia, has for someyears attracted attention.The animal synthesises in a specialisedtissue, the '' albumin gland," a galactosan, termed galactogen inanalogy with glycogen, which has been investigated by the methyl-ation method by E. Baldwin and D. J. They found that the1 J . L. Bollman, F. C. Mann, and M. H. Power, Amer. J . Physiol., 1935,Ibid., 1937, 31, 2217; J . Physiol., 1938, 93, 3 4 ~ .J . Biol. Chem., 1938, 124, 657.Biochem. J., 1939, 33, 1087.Biochern. J., 1935, 29, 1905; 1936, 30, 2037.J., 1938, 1461.111, 483.Biochem. J., 1936, 30, 1612.Nature, 1939, 144, 635356 BIOCHEMISTRY.polysaccharide structure seems to be based on one or other of thefollowing repeating units :- - -O-CH,OHF. May has shown that galactogen accumulates in the albumingland prior to egg-laying and is formed in quantities larger than canbe accounted for by the galactose ingested. The new-laid eggsare rich in a galactosan (presumably galactogen). If the snailsare starved, the accumulated galactogen disappears and is utilisedby the organism, no eggs being then laid. It therefore seemslikely, in Helix, that glucose (or glycogen) and galactose (or galac-togen) are inter~hangeable.~ In this connection, E. Baldwin lohas shown that addition of either galactose or galactogen to slicesof the hepatopancreas caused a marked increase in the oxygen-uptake of the preparation, whereas glucose caused no such effect,which, incidentally, could not be obtained during the " winterperiod."The presence of a galactosan in snail eggs is paralleled by theobservation that frog-spawn l1 is '.'.iewise rich in galactose. This,coupled with the seeming necessity of supplying lactose to the youngmammal, presents an unsolved problem in developmental bio-chemistry. D. J. B.2. Biol., 1932, 92, 321, 325; 1934, 95, 277, 401, 606, 614.lo Biochem. J., 1938, 32, 1225.11 W. A. van Ekenstein and J. J. Blanksma, Cheni.. Weekblad, 1907, 4,407; N. W. Pirie, Brit. J. Exp. Path., 1936, 17, 269BELL : ANIMAL. 357l’he Aerobic Meta,boEism of Muscle.lThis is largely a mystery. Resting muscle is an aerobic tissue;it consumes oxygen and gives off carbon dioxide, and this gaseousexchange is markedly increased when the muscle is exercised. Alarge number of dehydrogenases are known to be associated with thetissue and moreover the muscle cell is provided with a specialvariety of haemoglobin possessing an affinity for oxygen greaterthan that of blood haemoglobin, so that the cell can always obtainsupplies of oxygen as long as the demand does not exceed thecirculatory supply.The chief dehydrogenases referred to are ableto carry out the following oxidations :Lactate + PyruvateMalate + OxalacetateTriose phosphateTriose -4 Glyceric acida-Glycerophosphate + Triose phosphateSuccinate --+ Fumaratep-Hydroxybutyrate + Acetoacetate--+ Glyceric acid phosphateIt will be noted that no one of these enzymes breaks a carbon-carbon link, that is, no carbon dioxide is evolved as a result of theiraction.It is not clear what is the source of muscle carbon dioxide;H. A. Krebs has made several suggestions (see the Report for 1937).K. Harrison3 has little more than negative results to describe asa result of examining exercising frog muscle with respect t o anumber of acidic metabolites. It still remains to be provedwhether, in fully aerobic exercising muscle, any lactic acid is formeda t all ; e.g., recent experiments by Scandanavian workers indicatethat a t the immediate commencement of exercise there is a rise inblood lactate, but this rapidly falls to normal and does not rise againunless the exercise is prolonged and severe.This tends to the viewthat lactate leaves the muscle only if the immediate circulatoryoxygen supply is inadequate, in which contingency the glycolyticsystem can still provide a source of muscular energy.5 It may bethat lactate is always produced, but in a fully aerobic muscle isoxidised to an unknown product, not pyruvate.6 According to1 E. Lundsgaard, Harvey Lecture, 1937-8, 33, 66.2 R. Hill, Proc. Roy. SOC., 1936, By 120, 427; “Perspectives in Bio-chemistry,” p. 130 (Cambridge, 1937). 3 Riochent. J., 1939, 33, 1465.* 0. Bang, 0. Boje, and M. Nielsen, Skand. Arch. Physiol., 1936, 74,suppl. 10, 1 ; E. V. Flock, D. J. Ingle, and J. J. Bollman, J .BioZ. Chem.,1939, 129, 99.5 Cf. J. Sacks, Amer. J. Physiol., 1939, 125, 761.6 Cf. P. Foa and P. Fornaroli, Boll. SOC. ital. BioZ. sperim., 1938, 13, 664358 BIOCHEMISTaY.S. B. Barker, E. Shorr, and M. Malam iodoacetate does not inhibitmammalian muscle from oxidising carbohydrate. In this connectionalso, I. S. Cherry and L. A. CrandallB have been unable todemonstrate any significant glucose =+ lactate cycle involvingthe liver in normal animals. D. J. B.The Chemical Mechanism of Anaerobic Muscle Glycolysis."Since the appearance of the last report on this subject the mechan-ism of anaerobic glycolysis has undergone considerable clarification.Up till about two years ago our knowledge of the key position ofadenyl pyrophosphate, coupled with the isolation of intermediarysubstances, made possible the following schematic representation ofthe process :.---------_------____ 1 $ 1Glycogen + APP + Fructofuranose 1 : 6-&phosphate + AA1II IIIII1 In I : 2 Pyruvate + 2 Triose phosphate(Glyceraldehyde 3-phosphate +Dihydroxyacetone phosphate) ; I I : j L ri ii i 8 : i 2 Lactate + 2 Glyceric acid 3-phosphate.; I : :2 Glyceric acid 2-phosphat)e : i I: i: ! 2 enol-Pyruvic acid phosphate + AA +-------: ; ' L; +J II I kim ; i IIII1 I tI .I !i ii ! 2 Pyruvate + APP: iY J 4.I 1 1# I : i I I I1 1I--__--__--------_-----------------------------------,APP = adenyl pyrophosphate.A A = adenylic acid.Recent developments in our knowledge of the various numberedreactions will be discussed in turn.Remarkable advances have recently been made inthe elucidation of the primary stages of glycolysis.C. F. Cori,S. P. Colowick, and G. T. Cori4 found that, when dialysed muscleextract was incubated with glycogen, POL", and adenylic acid, anon-reducing glucose monophosphate was formed which was stableReaction I .J. Biol. Chem., 1939, 129, 33. Amer. J. Physiol., 1939, 125, 41.* See reviews by 0. Meyerhof,l J. K. Parnas,a and D. M. Needham.31 Ergebn. Physiol., 1937, 39, 10; New England J. Med., 1939, 220, 49.2 Enzymologia, 1938, 5, 166.4 J. Bwl. Chem., 1937, 121, 465.Ibid., p. 158BEliL: AlUMAL. 359to alkaline hydrolysis and could be isolated as the barium salt.The substance was considered to be glucose l-phosphate and wasfound to be identical with the product obtained by a syntheticmethod.Muscle extract (accelerated by Mg") converted the newester successively into glucose 6-phosphate, then the " Embdenester," and finally into lactic acid. These authors have namedthe enzyme which carries out the first of these transformations,'' phosphoglucomutase " and have described its preparation andproper tie^.^ The same authors then found that short incubation( 10-30 mins.) of dialysed muscle extract with glycogen, POa"',and magnesium chloride resulted in the conversion of 93-97%of the glycogen into hexose monophosphate and that in the absenceof POr'" no glycogen was broken down. This was in accordancewith the earlier observations of J.K. Parnas and T. Baranowskiand of P. Ostern et al. that autolysed muscle extract and PO4"'converted glycogen into hexose monophosphate while mono- anddi-saccharides were unaffected. The most recent and remarkabledevelopment in this aspect of glycolysis is that this " phosphoro-lysis " of glycogen is apparently a reversible phenomenon. C. F.Cori, G. Schmidt, and G. T. Cori9 have shown that their enzymesystem, acting on glucose l-phosphate, produces a polysaccharidesubstance which, however, gives with iodine a blue, or sometimespurple-brown colour, instead of the customary reddish-brown.Reaction I may now be written thus :Glycogen + Glucopyranose 1 -phosphate -+ Glucopyranose6-phosphate =+ Fructofuranose 6-phosphate + Fructofuranose1 : 6-diphosphate.In this connection it is interesting to note that C.S. Hanes9a hasemployed an enzyme present in pea meal to effect, from glucose1 -phosphate, a synthesis of a polysaccharide showing the generalproperties of starch.Reaction I I . The chief interest centred around recent workon the fission of hexose diphosphate into 2 molecuIes of triosephosphate by zymohexase is concerned with the synthetic capacityof the enzyme. K. Lohmann lo has found that dioxyacetone phos-phate in the presence of dialysed muscle or yeast extracts will undergoan aldol condensation with numerous aldehydes. In this wayacetaldehyde gives rise to a 5-deoxyketopentose phosphate, andJ . Biol. Chem., 1938, 124, 543.2. physiol. Chem., 1936, 243, 9.Compt.rend. SOC. Biol., 1936, 124, 252.Proc. Roy. SOC., B, in the press.8 Ibid., 1939, 127, 772.Science, 1939, 89, 464.lo Angew. Chem., 1936, 49, 327360 BIOCHEMISTRY.d-glyceraldehyde yields fructose 1 -phosphate. The action of thisenzyme leads to asymmetric syntheses ; for example, if Z-glyceralde-hyde is used in place of the d-isomer, Z-sorbose l-phosphate is formed.This discovery seems to point the way towards explaining the bio-logical synthesis and interconversion of sugars. H. Fischer andE. Baer,ll following up the original acrose synthesis of Emil Fischer,have effected purely chemical asymmetric condensation of d-glycer-aldehyde with dioxyacetone. In this way, an equimolar mixtureof d-fructose and d-sorbose was obtained with no evidence of theformation of either d-psicose or d-tagatose.0.Meyerhof l2 has studied the isolation of glyceraldehyde3-phosphate formed by the action of zymohexase on fructofuranose1 : 6-diphosphate in the presence of fixatives, and has shown thatthe following equilibria exist :Glyceraldehyde 3-phosphateDioxyacetone phosphateHexose diphosphateReaction 111. D. M. Needham and G. D. Lu l3 state that twostages can be distinguished in the oxido-reduction between glycer-aldehyde phosphate and pyruvate : (a) the oxidation of triosephosphate by co-enzyme I and the dehydrogenase is accompaniedby esterification of PO4”’, (b) the oxidation of reduced co-enzymeby pyruvate involves no such esterification. Free triose will reactwith pyruvate without esterification.Examining the same stagein yeast fermentation, E. Negelein and H. Bromel l4 have reportedthat glyceraldehyde phosphate plus PO4”’ forms a diphosphatewhich is oxidised by co-enzyme I and a specific protein of yeast, toform a very labile diphosphate of glyceric acid, probably having thephosphoryl groups in positions 1 and 3. 0. Warburg and W.Christian l5 have isolated in crystalline form such a protein fromyeast which oxidises glyceraldehyde 1 : 3-diphosphate but not the 3-monophosphate. This reaction may therefore probably be written :Glyceraldehyde 3-phosphate --+ The 1 : 3-diphosphate --+Glyceric acid 1 : 3-diphosphate -+ The 3-phosphateIt seems likely that further work on muscle enzymes will showl1 Helv. Chim. Acta, 1936, 19, 519.12 Bull.SOC. Chim. biol., 1938, 20, 1033, 1345; 1939, 21, 965.l3 Biochem. J., 1935, 32, 8040.l4 Biochem. Z., 1939, 301, 135.l5 Ibid., p. 221BELL : ANIMAL. 361that Needham and Lu's observations can be interpreted in thisway.Radioactive Phosphorus as an Indicutor in G1ycolysis.-See reviewsby 0. Meyerhof et a1.,l6 by G. Hevesy et a1.,17 and by 0.Me yerhof -18D. J. B.The Reversible Enzymic Breakdown of Glycogen in Liver and Yeast.The exact manner in which liver glycogen is hydrolysed toglucose has long been a matter for speculation. Suggested combina-tions of amylase and maltase did not account for the extremelypowerful glycogenolytic action of the liver, particularly since H. A.Davenport had shown that the blood-free liver contained verylittle amylase.From the observations of J. K. Parnas and hisschool on muscle glycogenolysis the idea of an entirely new typeof polysaccharide breakdown, " phosphorolysis," came into being.G. T. and C. F. Cori suggested that this mechanism is concernedin liver glycogenolysis, and these authors with S. P. Colowick3were able to show that liver, as also heart, brain and yeast, containedan enzymic system which, like that of muscle, converts glycogeninto glucose l-phosphate. This was confirmed for yeast by W.Kie~sling,~ who found that the reaction was reversible in that apolysaccharide superficially resembling glycogen could be formedfrom glucose 1 -phosphate. An equilibrium between those two sub-stances in the liver enzymic system has also been demonstrated byG.T. Cori, C. F. Cori, and G. S ~ h m i d t , ~ who have been able toseparate the phosphorylase (glycogen to hexose monophosphate)from the phosphatase (forming free glucose). Moreover they havefound that glucose l-phosphate in the presence of adenylic acid canbe enzymically converted by a liver system into a polysaccharidehaving the properties of glycogen. Independent work byP. Ostern and E. Holmes and by P. Ostern, D. Herbert, andE. Holmes has confirmed and extended these findings.It has thus been shown that glycogen breakdown to glucose inl6 Biochem. Z., 1938, 298, 396.l7 Actcs Biol. Exp., 1938, 12, 34.l8 Bull. SOC. Chim. biol., 1939, 21, 1094.J. Biol. Chem., 1926, 66, 625.Proc. SOC. Exp. Biol. Med., 1938, 39, 337.J .Biol. Chem., 1938, 123, 375.1 Biochem. Z., 1938, 298, 421; 1939, 308, 5 0 ; Xatuwiss., 1939, 27, 129.5 J . Biol. Chem., 1939, 129, 629.Nature, 1939, 144, 34.Biochem. J., 1939, 33, 1858362 BIOOHXMISTRY.liver follows an initial path identical with the primary stages ofmuscle glycolysis and yeast fermentation :Glycogen += Glucose 1 -phosphateGlucose 6-phosphate j-f GlucoseI III -------_______--__------------- I $Alcohol and CO,I Yeast. II ._________-----_-..D. J. B.D. J. BELL.L. J. HAREIS.N. W. PIRIE.PLANT BIOCHEMISTRY.Introductory.A large proportion of this year’s Report has been devoted to thegrowth substances of plants, a subject on which increasing attentionis being focused. Indeed, the present spate of papers dealing withvarious aspects of growth substances recalls the earlier days ofvitamin research, and it is possible that in the near future the out-put on the former subject may equal that on the latter.There are,of course, many points of contact between them: the chemist,the biochemist and the physiologist are equally interested andconcerned in these developments, and the trend of investigationon the plant factors has already shown that these have much incommon with those of the animal.There follows a brief account of starch and amylases and of .recentwork on pectin. The latter affords yet another example of a poly-saccharide chain molecule and thus comes into line with othermembers of the class. An attempt has been made, within veryconfined limits of space, to indicate the trend of research on theconstitution of lignin.This difficult subject is yielding results,but none would yet claim finality.A concluding section deals with new metabolic products ofAspergillus and Penicillium species.Growth Xubstunces.Higher Plants.-In the space available it is not possible to referin detail to more than a few of the many pa,pers tihat have beeNORaIS: PLA.NT. 363published on this subject since it was last discussed in these Reports.1More lengthy summaries of recent advances have been publishedelsewhere, notably by F. W. WentY2 K. V. ThimannY3 and W. J.R~bbins.~Auxins and Root Formation-A large number of investigationsdeal with the stimulation of root-formation by indolylacetic acid.R.Gautheret finds that plantules and plantule fragments ofPhaseolus vulgaris show considerable branching of roots underauxin stimulation; high concentrations of the auxin favour theproduction of nodes on the root, but inhibit development of thegemmule and radicle. According to M. M. Gocholaschvili andN. A. Maximov,6 the rooting of subtropical wood cuttings wasincreased by heteroauxin treatment and the effects were morenoticeable in leafy than in leafless cuttings, and also when physio-logical activity was normally high, as in the spring.In a later paper N. A. Maximov, M. M. Gocholaschvili, and V. L.Tschoidze confirm the value of heteroauxin in inducing rootgrowth in subtropical plants which do not normally root easilyfrom cuttings.Similar results were obtained by R. C. Trureckaja 8with cuttings from orange, lemon and feroja. As might be anti-cipated, increase in root formation occurs to a more marked extentunder the influence of heteroauxin in subjects where rooting morereadily occurs normally. J. B. Biale and F. F. Halma9 find thatthe effective concentration of heteroauxin varies with the speciesand also with the type of cutting in the same species. In mostinstances, however, it is observed that there is a maximum con-centration above which retardation instead of stimulation takesplace, and high concentrations are very frequently lethal. Inpractice the injurious effect of overdosage may be minimised bytreating seeds, for example, with dusts impregnated with theauxin; N.H. Grace l o finds that such a method is preferable inthis respect to the use of aqueous solutions. Indolyl-acetic,-propionicy and -butyric and naphthylacetic acids behave similarly.Phaseolus, Pisum, Zea mais, Brassica, Aucuba and dahlias havelikewise been investigated by J. Lefkvrell in respect of rootformation by indolylacetic acid, and in every case enhancedproduction was observed with solutions in water containingAnn. Reports, 1935, 32, 425.Biol. Rev., 1939, 14, 314.Compt. rend. SOC. Biol., 1937, 126, 312.Compt. rend. Acad. Sci. U.S.S.R., 1937, I?, 51.Ibid., 1938, 21, 187.@ Proc. Amer. SOC. Hort. Sci. (1937), 1938, 35, 443.Ann. Rev. Biochern., 1939, 8, 521.Science, 1939, 89, 303.Ibid., 1937, 17, 143.lo Canadian J .Res., 1937, 15, C , 538.1' Cornpt. rend., 1937, 205, 1437364 BIOCHEMISTRY.O - O l ~ o of heteroauxin. In the case of Zea mais thick rootsare formed surrounded by tufts of lateral roots and on treat-ment with O.lyo dichloroethylene an elongation of the roots wasobserved. Similar effects on root production were observed withthe other subjects; in the case of dahlias the tubers were formedearlier in the treated specimens than in the untreated.In a series of experiments on the effect of growth substanceson gladiolus corms, P. W. Zimmerman and A. E. Hitchcock 12 notethat naphthylacetic, indolylbutyric and indolylacetic acids stimulateroot development unequally, response depending on the substanceand its concentration. Contractile roots, which develop normallyonly prior to flowering time, were generally produced very soonafter application of the auxin substance and under certain con-ditions roots could be induced at the upper end of the corm, andindeed, all over the corm instead of at the base as is normally thecase.The growth substances were not rapidly dissipated, as in-dicated by the fact that substances giving the indole test could befound in roots and shoots 24 days after the application of indolyl-butyric acid.J. Lefbvre l3 also has noticed a difference in the action of naphthyl-acetic acid on root formation as compared with that of indolyl-acetic acid. Whereas in the latter case, as indicated above, thehypocotyl thickens and produces secondary rootlets, with naphthyl-acetic acid the thickening and secondary rootlet production occurat the epicotyl axis.These observations were made with Pisumsativum, and with Phaseolus vulgaris the action was still moremarked.Closely related homologues of indolylacetic acid have alreadybeen shown to be active and confirmation is further provided byH. L. Pearse,14 who has carried out experiments on leafless willowcuttings and finds that indolylbutyric acid is an active agent instimulating root formation. Treatment a t the basal end resultedin stimulation of root formation at that end, whilst treatment atthe apex of the cutting induced a maximum response at the nodenearest the apex, but rooting was induced throughout the lengthof the cutting.Preliminary treatment of the cuttings in a warm water bath hasbeen found to enhance the production of roots whether the cuttingsare allowed to develop normally, or supplied with heteroauxin at alater stage.In all cases the optimum temperature of the pre-liminary bath was found to be 25", the largest root production in12 Contr. Royce Thompson Inst., 1935, 10, 5.l3 Compt. rend. SOC. Biol., 1938, 128, 765.l4 Ann. Bot., 1938, 2, 227NORRIS : PLANT. 365untreated cuttings being observed after such treatment, and a stilllarger production occurring after heteroauxin treatment (H. U.Amlong). l5Auxins and Growth-promotion.-The naturally occurring hetero-auxin, indolylacetic acid, is not the most active agent in promotingcell extension in intact plants as indicated by experiments of F.Pfahler.16 The substances were applied in aqueous solution tothe epidermis, and the greatest activation was evinced in the caseof naphthylacetic acid, whilst indolylbutyric acid gave the sameresults as indolylacetic acid.Other possible substances, includingascorbic acid, were without stimulating action.An important survey of some 46 synthetic substances in relationto their growth-promoting (cell-elongating) activity has been madeby J. B. Koepfli, K. V. Thimann, and F. W. Went.17 The specScaction of these substances was determined by the simple biologicaltests which have been devised to give qualitative and, understandardised conditions, quantitative results. In general, if a givensubstance is to be active, certain structural requirements of themolecule must be met, although the physiological activity dependsnot so much upon the nucleus of the molecule, but rather on someparticular configuration.The minimum requirements of such amolecule are : a ring system as nucleus, such ring system to containa double bond; a side chain bearing a carboxyl group (or groupeasily converted into carboxyl), such carboxyl group to be separatedfrom the ring by a t least one carbon atom; and finally a particularspace relationship must hold as between the ring and the carboxylgroup. The activity thus depends on a combination of structuralcharacteristics, and though a t first sight some active compounds willappear to be wholly unrelated, further examination will show thatthey do possess certain combined characteristics in common.Numerous attempts are being made to elucidate the mechanismof auxin action, amongst which may be mentioned that of K.V.Thimann and B. M. Sweeney,l* who record observations on the effectof indolylacetic acid and other substances on protoplasmic stream-ing in cells of Avena coleoptiles. A transient acceleration is ob-servable with the auxin in low concentration, but above a concen-tration of 0-5 mg. per litre a retardation takes place. Coumaryl-acetic acid and aZZocinnamic acid behaved similarly but with lessintense effect. The authors conclude that the effects on streamingare preliminary to the auxin effect on the growth and thatl 5 Ber. deut. bot. Ges., 1938, 56, 239.l C Jahrb. wiss. Bot., 1938, 86, 675.l 7 J .Biol. Chem., 1938, 122, 763.l8 Nature, 1937, 140, 807; J . Gen. Physiol., 1937, 21, 123366 BIOCHEMISTRY,respiratory action is involved, since the effect of increasing con-centrations of auxin was controlled by the oxygen supply available.If sufficient oxygen were present, auxin reaction proceeded withincreased effect at higher concentrations, but where insufficientoxygen was available retardation of auxin action was apparent.In a further contribution on the action of heteroauxin on proto-plasmic streaming in epidermal cells of Avena, B. M. Sweeney andK. V. Thimann l9 explain the shortness of the action as being dueto exhaustion of carbohydrate supply. The action may be pro-longed by addition of fructose, and it is shown that auxin actioninvolves an increase in the oxygen consumption of the coleoptiles.Thus it has been observed that high concentrations of auxin causenormally a decrease in protoplasmic streaming, but in the presenceof oxygenated water, ensuring an adequate supply of oxygen, anincrease in streaming rate takes place.Substances which them-selves cause an increase in oxygen consumption, such as 2 : 4-dinitrophenol, may reverse the enhanced effect normally inducedby the auxin ; conversely, substances which reduce respirationwill tend to restore the auxin effect, even in oxygen-deficient cases.Histidine, in 6 x lo-' molar concentration, is adequate to restorenormality in such cases.The authors consider that the action of the auxin is upon thecell substances rather than the cell wall.In other phases of auxinaction, where, for example, swelling is observed, it becomes ofinterest to determine the nature of the substances undergoingsuch swelling. A variety of substances behave in this way underthe action of indolylacetic acid, and as a result of study of thephenomenon and comparison with a number of plant materials,U. Ruge 20 comes to the conclusion that such substances are inter-mediate between pectin and a compound cellulose-typical cell wallmaterial.Accessory Growth Fuctors.-In addition to the two auxins andheteroauxin a number of other substances have been found toexert concomitant effects on growth, root formation, etc. Amongstthese, aneurin is of special importance and recent investigationshave shown that the animal hormones may play a part.Aninteresting review of aneurin (thiamin) in relation to plant growthis supplied by W. J. rob bin^.^F. W. Went, J. Bonner, and G. C. Warner,21 as a result of ex-periments with pea stems, consider that aneurin is a limiting factorin root stimulation by heteroauxin. The latter initiates rootJ. Gen. Physiol., 1938, 21, 439.2o Biochem. Z., 1937, 295, 29.21 Science, 1938, 8'9, 170NORRIS : PLANT. 367formation and unless sufficient aneurin is present or added after theinitiatory period the effect of ahxins is limited. A concentrationof aneurin of only 1 per 1,000,000 was sufficient to produce a vigorousresponse some 7 days after auxin treatment.It was also found by J. Bonner and D.Bonner 22 that excisedpea embryos in sterile media showed in some cases increased growthwhen ascorbic acid was added supplementary to accessory growthsubstances. The response to ascorbic acid appeared to be a varietalcharacteristic ; some varieties of pea were able to synthesise ascorbicacid from sucrose and hence did not show the extra response due toadded ascorbic acid.Aneurin has also been found by W. Rytz 23 to be a growth factorfor Pisum. The amount of the vitamin increases steadily duringgermination until the sixth day and then gradually falls to theoriginal value. It is also an essential constituent of the medium,containing sucrose and Pfeff er's solution, in which excised tomatoshoots are growing. Vitamin-B, also increases the growth in thiscase, but aneurin is the more important, according to W.J. Robbinsand M. B. Schmidt.24Aneurin in low concentrations has been found to increase germin-ations of pollen from Caricu quercifolia and Carim papaya, accordingto W. B. Dandliker, W. C. Cooper, and H. P. T r a ~ b . ~ ~ The vitaminis also effective in supporting the growth of isolated pea shootsand if nicotinic acid is also added, F. T. Addicott and J. Bonner 26find a steady increase in growth rate. The effect was also enhancedby amino-acid mixtures.B. W. Doak 27 has confirmed the value of aneurin as an accessoryagent in the stimulation of root formation, and suggests that thereis an optimum period which should elapse between treatment withhormone and subsequent treatment with the vitamin.Amino-acids also have been indicated as of importance in assisting insatisfactory root formation, notably by I?. W. Went, J. Bonner,and G. C. Warner 2 1 and P. R. White.28 The amino-acids particu-larly mentioned included some of the monoamino-acids, glutamicacid, histidine, lysine and proline. B. W. Doak2' has employeda mixture of these acids in two concentrations, and cuttings ofrhododendron were soaked in these solutions and in water afterpreliminary treatment with naphthylacetic acid. The resultsshowed good and complete rooting on all cuttings which had22 Proc. Nut. Acad. Sci., 1938, 24, 70.23 Comnpt. rend. SOC. Biol., 1938, 129, 814.24 Proc. Nut. Acad. Sci., 1939, 25, 1.26 Ibid., p. 577.ae Plant Phy.siol., 1937, 12, 703.26 Science, 1938, 88, 662.27 Nature, 1939, 144, 370368 BIOCHEMISTRY.received amino-acid treatment, but cuttings soaked only in waterdid not root.Further work is in progress to determine which ofthe amino-acids in the mixture may be regarded as most essential.Amongst several amino-acids, proline is of particular importance,according to D. M. Bonner and A. J. Haagen-Smit,29 as an accessorygrowth factor for leaf discs in 1% sucrose solution. Other nitro-genous substances-yeast nucleic acid, purines, especially adenine,and nicotinamide-have all been found to stimulate leaf growth inthe case of Raphanus, radish, Nicotiana and Cosmos.Further additions to the growing family of plant hormones andgrowth accessories are probable, since F.W. Went 3O has obtainedfurther evidence that auxin alone is not sufficient to cause growthstimulation, but that accessory substances, which he terms “ calines,”are also required, these being redistributed by auxin in the plantto various centres. Thus, “ caulocaline ” of roots is requisite forelongation of stems and lateral buds; “ rhizocaline ” of the cotyl-edons is necessary, with auxin, for root formation, and the growthof leaves is in part determined by “ phylloca,line.”Wound Hormones.-It has long been known that, when plantcells suffer injury, the adjacent uninjured cells divide in order tomake good the loss with production of wound tissue, etc. Thesubstances which promote this abnormal cell activity have beencalled wound hormones and one of them is the object of investig-ation by J.English, jun., and J. B~nner.~l They have attemptedthe isolation of the substance, which they call traumatin, and haveemployed a modification of the “ bean ” test to follow the activityof the products during the separation. Intact parenchymatouscells of the bean pod respond to the traumatin solution and anintumescence arises under the point of application, whose heightis a measure of activity. I n a later paper 32 the authors find thatthe value of the test is enhanced by the fact that it is specific forthe wound hormone, and is not, therefore, given by a number ofplant constituents, including auxin and other growth substances.A further measure of activity is obtained by determining theminimum concentration of traumatin giving a typical response.After a somewhat complex series of extractions, adsorptions andprecipitations of the original dried bean powder a methyl esterof what is regarded as the almost pure hormone w-as obtained, havingan empirical formula C,,H,,04N. The hormone was amorphous,acidic in aqueous solution, and was highly active in a dilution of29 Proc.Nat. Acad. Sci., 1939, 25, 184.30 Plant Physwl., 1938, 13, 55.31 J. Biol. Chent., 1937, 121, 791.32 Plant Physiol., 1938, 13, 331NORRIS PLANT. 3691 : 100,000. The nitrogen present does not react with nitrous acid,hence the presence of a primary amino-group seems improbable.The isolation of another wound hormone in crystalline form isannounced by J.English, J. Bonner, and A. J. Haage~~-Smit.~~The substance is a dibasic acid of formula C,,H,,04 and was isolatedfrom fresh bean pods. The substance shows activity in the purestate, but this activity is greatly increased by the presence of in-active co-factors. In addition to the hormone isolated there areprobably other active substances in the original extract.consider that the increasein photosynthesis which is observable after injury to a leaf is duea t least in part to the accumulation of phytohormones a t the siteof injury. This suggestion is based on the observation that aconcentration of indolylacetic acid of 1 mg. per litre introducedinto the green leaf tissue causes a rise in photosynthetic activityof 100-200~0, which falls, however, after several hours to a sub-normal level.Exigencies of space preclude further detailed account of muchinteresting work in this field, but reference must be made to pro-perties of the auxins which show marked contrast with those alreadyindicated.The auxins, then, not only exhibit growth-promotingproperties, but also act as growth inhibitors. They have beenshown in normal physiological circumstances to inhibit the growthof shoots and of lateral buds, and they also inhibit the elongationof roots. An excellent review, giving many recent references ofthis aspect of auxin action, is provided by K. V. Thimann.3Bios.-As a result of recent investigations the position withregard to bios appears t o be considerably clarified, and if the presentrate of progress is maintained there can be little doubt that themain problems will be speedily solved.Much confusion in thepast, perhaps inevitable, has been due to the lack of a single systemof nomenclature, and to the fact that different races of yeast varyconsiderably in their requirements for specific nutritional factors.C. Rainbow 35 ascribes many of the apparent differences in theresults obtained by various workers as due to variation in (i) yeasttype ; (ii) composition of the synthetic medium ; (iii) methods of sub-culture of the seeding yeast ; (iv) general experimental technique.At the present time, five components of bios may be dis-tinguished :(i) meso-Inositol is a well-established component and has beenshown to be required by most yeasts.N.G. Cholodni and A. G. Gorbovski33 Pvoc. Nut. Acad. Sci., 1939, 25, 333.34 Compt. rend. Acud. Sci. U.S.S.R., 1939, 22, 4.52.35 J . In&. Brew., 1939, 45, 553370 BIOCHEMISTRY.(ii) Pantothenic acid-p-alanine was found by R. J. Williams andE. Rohrmann36 to stimulate the growth of yeast in pure chemicalmedia; in fact, these authors claimed that this was the first demon-stration of the growth of yeast from small seedings in sugar-saltsmedium. They distinguished also between such a medium andone containing asparagine in addition; p-alanine was effective onlyin absence of asparagine, whereas the latter appeared to be necessaryin experiments with pantothenic acid. The composition of panto-thenic acid is becoming more obvious as a result of continuedinvestigations by R.J. Williams and collaborators. R. J. Williams,H. H. Weinstock, E. Rohrmann, J. H. Truesdail, H. K. Mitchell,and C. E. Meyer 37 were able to assign the formula (C8H,,05N),Cato the calcium salt of the acid and to indicate the presence of onecarboxyl, two hydroxyls and a substituted amide group. A littlelater 'H. H. Weinstock, H. K. Mitchell, E. F. Pratt, and R. J.Williams 38 showed that p-alanine was a cleavage product of panto-thenic acid, and it now appears that the latter is a complex of p-alanine and an unknown hydroxy-acid.The close fundamental relationship between superficially un-related biochemical and physiological phenomena is now a common-place, and the case of pantothenic acid provides a further example.Evidence has been adduced by R.J. Williams, W. A. Mosher, andE. Rohrmann39 that the acid plays some part in carbohydratemetabolism; it is present in large concentrations in liver andmuscle, very active sites in that respect. Quite recently T. H.Jukes40 has shown the close identity between pantothenic acidand the chick antidermatitis factor. Almost simultaneously, andindependently, D. W. Woolley, H. A. Waisman, and C. A.Elvehjem41 confirm that the properties of the acid and the factorare very similar, and consider that the latter is a hydroxy-acid inamide linkage with (3-alanine. Nor does this exhaust the widesignificance of pantothenic acid. Y. Subbarow and G. H. Hitch-ings 42 find that it stimulates the growth of rats.They co&m thefindings of J. H. Mueller and A. W. Klotz43 that it is a growth€actor for the diphtheria bacillus, and Y. Subbarow and L. Rane 44have shown that it is a growth factor for Streptococcus hemolyticus.This component is of major importance to mostA comprehensive, though necessarily condensed, reviewof work on plant growth substances is provided by F. K0gl,45 whose(iii) Biotin.. yeasts.36 J . Amer. Chem. SOC., 1936, 58, 695.38 Ibid., p. 1421.40 J . Arner. Chem. SOC., 1939, 61, 975.42 Ibid., p. 1615.4 4 Ibid.,!1939, 61, 1616.37 Ibid., 1939, 61, 454.Brn Biochem. J., 1936, 30, 2036.4 1 Ibid., p. 977.43 Ibid., 1938, 60, 3086.45 Ghern. and Ind., 1938, 57, 49NORRIS : PLANT. 37 1brilliant contributions to the chemistry of these substances are wellknown. The substance biotin, which appears to be closely similarto the bios IIB of W.L. Miller, E. V. Eastcott, and J. E. Macho-nachie 46 and the IIB of L. R. Bishop and C. RainbowY4' has beenobtained in crystalline form by Kogl and, like aneurin, containssulphur. The tentative empirical formula is CllH1803N2S. Biotinis universally present but in minute concentrations; it is probablyone of the most physiologically potent substances known, havingmarked effect even in a dilution of 1 : 4 x loll.L. R. Bishop and C. Rainbow47 provide a summary of biosinvestigations and suggest the classification of bios compounds usedin this article. They have proposed methods for the rapid isolationof bios concentrates for use in synthetic media and for the con-centration and purification of their preparations bios IIA (panto-thenic acid) and IIB (biotin).They suggest the formula C7Hl,03N2for the latter and find only traces of sulphur of doubtful significance.As yet, the constitution of biotin remains obscure : it may containsulphur, basic units and a carboxyl group (Kiigl**); and onecarboxyl or potential carboxyl group and nitrogen in a pyrimidinering (Bishop and Rainbow 47).(iv) Aneurin is one of the more highly potent bios factors, butit is not essential to the growth of a number of yeasts. It is neededby the " old process " yeast of R. J. Williams and D. H. S a ~ n d e r s , ~ ~and by X. valbyensis according to L. N. FarrelL50 At the time itwas a supposedly new factor-bios V (W.L. Miller 51)-and wasprepared by M. E. Elder,52 but was later shown t o be identical withaneurin by W. L. Miller.53The acceleration induced by aneurin in the fermentation byPleischmann yeast of buffered glucose solutions, as indicated byincreased carbon dioxide production, was utilised by A. S. Schultz,L. Atkin, and C. N. Prey 54 for the determination of the vitamin,and further experiments on the method led to the examination ofthe effects of the vitamin and its components and intermediates.Only the vitamin and 6-amino-2 -methyl-5-ethoxymethylpyrimidine(together with certain natural sources such as soy-bean meal andbeet molasses) gave increased fermentation, the thiazole derivativesbeing inactive.4 6 J . Amer.Chem. SOC., 1933, 55, 1502.4 7 J . Inst. Brew., 1939, 45, 593.40 Naturwiss., 1937, 25, 465.5O Trans. Roy. SOC. Canada, 1935, [iii], 29, 111, 167.s1 Ibid., 1936, [iii], 30, 111, 99.53 Ibid., 1937, [iii], 31, 111, 159.b4 J . Amer. Chem. SOC., 1937, 59, 948.4g Biochem. J., 1934, 28, 1887.52 Ibid., p. 89372 BIOCHEMISTRY.(v) Vitamin B6 is now to be regarded as an established biosfactor for certain yeasts. It has been found effective by E. F.Moller 55 and also by A. S. Schultz, L. Atkin, and C. N. F r e ~ . ~ ,The latter show that fermentation is accelerated in the presence ofvitamin B, and conclude that, if all other accessory factors arepresent, the increase will be in proportion to the amount of thevitamin present. It may be pointed out here that there may beanother factor which influences fermentation apart from actualyeast growth.The importance of vitamin B, is also demonstratedby R. J. Williams and R. E. Eakin.57 They found nearly a two-fold increase in the number of yeast cells produced in controlledexperiments in which yeast was grown in a culture medium con-taining aspartic acid, aneurin, @-alanine and autolysed yeast extractas well as the usual nutrients, vitamin B, being added in minutebut increasing amounts.The position in the bios field is thus considerably clearer nowthan even a few months ago, and the importance of vitamins ofthe B group needs no stressing. Highly potent substances such asbiotin and aneurin probably play the part of catalysts and it issignificant in this relation that aneurin, with phosphoric acid,constitutes the prosthetic group of the enzyme carboxylase.Nosuch r61e is as yet suggested for biotin and further development inthis field will probably depend on the elucidation of its structure.Other Lower Organisms.-W. H. Schopfer 58 has examined theaction of components of aneurin on yeasts of Rhodotoruh speciesand finds that aneurin or its pyrimidine moiety accelerates thegrowth of R. rubra and R. jlava. The thiazole portion of aneurinis in general only very slightly active in itself, although both halvesare capable of replacing the combined form in the case of the yeastscited and also of some M u ~ o r i n a e . ~ ~The activity of thiazole and pyrimidine derivatives related tothose occurring in aneurin with respect to the growth of MucorRamnnianus, Moll, have also been examined by W.Miiller andW. H. Schopfer.60 Stimulation occurs with some thiazole deriv-atives but not with the pyrimidines and it is suggested that theorganism synthesises the pyrimidine, but that the thiazole moietymust be supplied, either as such or as the complete vitamin.W. J. Robbins 61 suggests a classification of lower organisms5 5 2. physiol. Chern., 1938, 254, 285.56 J . Amer. Chem. SOC., 1939, 61, 1931.5 7 Ibid., p. 1932.59 Compt. rend. SOC. Biol., 1937, 126, 842.6o Compt. rend., 1937, 205, 687.61 Proc. Nat. Acad. Sci., 1938, 24, 53.60 Cornpt. rend., 1937, 205, 445NORRIS : PLANT. 373according to their requirement for growth of aneurin, pyrimidine,thiazole, or mixtures of the last two.Growth substances which are effective for lower organisms havebeen demonstrated 62 in the seeds of Zea mais and of TriticurnvuZgure; they occur predominantly in the embryo and scutellumand their amount increases during germination.Similar sub-stances have been observed in certain buds and leaves, and a seasonalvariation in the amount of growth substance occurs. Increasedmultiplication of yeast and of A . niger was observed and the factorsare thought, on physico-chemical grounds, to be similar to bios.Growth substance in saps has also been examined and is apparentlydifferent from bios; it was active only in the case of A . niger andnot of yeast, It is thermostable, since it is possible to obtain amore active substance from the sap by autoclaving a fructose-malic acid solution.F. Kogl and N.Fries 63 have applied methods used for yeaststo the case of moulds. Aneurin is required by Polyporus adustuswhen grown in a synthetic medium. Interesting results wereobtained with Nemtospora gossypii which had been shown byH. W. Buston et u Z . ~ ~ ~ ' 65 to require bios ; a striking increase in growthwas observed when biotin was added as well as inositol, and additionalaneurin stimulated even greater growth.Similarly, growth substances have been shown to be of importanceto bacteria. B. C. J. G. Knight 66 has examined the effect of aneurinand substances related to it, and of nicotinic acid, on the aerobicgrowth of X~phyZococcus aureus.Aneurin itself is an active growthpromoter, but derivatives in general are not. The pyrimidines areactive only if certain structural considerations hold, as, for example :methyl group in position 2 ; amino-group a t 4; and a substitutedmethyl group, such as CH,-OH, at position 5. Thiazole derivativeshave in some cases a reduced activity, and it is suggested that theorganism can synthesise aneurin or closely related substances fromthe pyrimidine and thiazole moieties. Nicotinamide was foundto support growth better than nicotinic acid.The results by Knight are confirmed by F. Kogl and W. J. vanWagtend0&,~7 who establish the greatly enhanced effect inducedby biotin. The effect of any pair of the substances, biotin, aneurinand nicotinic acid, was great but, when all three were added together,Ga J.Dagys, Protoplasma, 1935, 24, 14.6 3 8. physiol. Chem., 1937, 249, 93.64 Biochem. J., 1931, 25, 1656, 1671.6 5 Ibid., 1933, 27, 1859.6 6 Ibid., 1938, 32, 1241.6 7 Rec. Trav. chim., 1938, 57, 747374 BIOCHEMISTRY.the result was greatest of all.observed with 5 pg. each of aneurin and nicotinic acid, and 5 xg. of biotin per C.C. of the medium.A growth increase of SOOyo wasSome Plant Products.Starch and Amylases.-A number of studies on wheat starchhave been described by 0. E. Stamberg and C. H. Bailey. Thefirst of these 6* deals with the separation and characterisation ofthe constituent amylose and amylopectin. Doughs made from anumber of flours were treated with sodium chloride to inhibitdiastatic action, the gluten removed by washing, and the starchrecovered in the centrifuge. The starches were separated intolarge and small granules by fractional sedimentation and the groundsamples were then further fractionated by electrophoresis. Inthis way the amylopectin was usually precipitated as a slimy massin three days.After repeated re-dkpersion and separation, theamylopectin was found in all cases to represent from 15-17y0 ofthe starch. The amylopectin contained most of the phosphorusof the original starch, only traces being found in the amylosefraction. Similar results were found for both large and smallgranule types of the starch. The authors conclude that the differ-ences in amylopectin and phosphorus content commonly observedby different workers are due to differences in the methods ofseparation.The action of amylases on raw wheat starches is next c~nsidered.~~Two a-amylases and two p-amylases were prepared; in the formercase an aqueous extract was precipitated directly with 60% alcoholto give one ct-amylase, and the other was obtained by heating at70" for 15 minutes to inactivate the p-amylase and subsequentprecipitation with alcohol.The a-amylase was obtained directlyby precipitation with 80% alcohol, and a second sample by treat-ment with hydrochloric acid at pa 3-3 a t 0" to inactivate thea-amylase, followed by precipitation with alcohol. The hydrolysisof the raw wheat starches proceeded only to the extent of about1% with the p-amylase preparations, and to between 4 and 10%with the a-amylases.The hydrolysis depended upon the amountof enzyme used and on the particular type of wheat from whichthe starch was obtained. If the starches were finely powdered,hydrolysis was easily effected by all the amylase preparations.The authors were unable to establish any correlation betweenenzyme action and the size and phosphorus content of the starchgranules. They consider, therefore, that the differences observed88 Cereal Chem., 1939, 16, 309. 69 Ibid., p. 319NORRIS: PLANT. 375between the varieties of starch are due to different morphologicalfeatures of the granules.In a separate contribution 70 the preparation of the amylasesis described and their action on soluble starch investigated.Itwas found that the second type of a-amylase above hydrolysedthe starch to about 40%, the products consisting of non-fermentablereducing dextrins and fermentable reducing sugars. a-Amylase ofthe first type, and a commercial sample of malt diastase, hydrolysedthe starch to some 85%, and both types of P-amylase affected about60% hydrolysis. The percentage hydrolysis is based on the reduc-ing power in terms of maltose, and in the last three cases fermentablereducing sugars were formed in amounts conforming to the estimatedreducing powers.In the latest paper to date 71 the authors investigate the actionof the amylase preparations on the amylose and amylopectin ofwheat starches previously described. Amylopectin is much moreresistant to hydrolysis by a- and P-amylaee, or mixtures of the two,than is amylose.p-Amylase is the least effective agent in thehydrolysis of amylopectin and the greatest hydrolysis is obtainedwith a mixture of the two types of enzyme. As is well known, asolution of amylose becomes turbid on standing for a day or twoand such retrograde solutions showed an increased resistance toamylase action; the change in the case of amylopectin solutions onstanding was negligible.K. Myrback and B. Ortenblad 72 continue their investigations onthe action of amylases in relation to the structure of the starchmolecule as indicated in the previous Report.73 The subjects ofexperiment include native starch and degradation products obtainedby well-known methods such as heating with glycerol, treatmentwith cold hydrochloric acid, and by enzyme action.The actionof @-amylase usually produces maltose to about 60% and dextrinsof about the same molecular size as the original substrate. Thereason that various starches saccharify to very varying degreesis thought to lie in differences or anomalies of their structure.Such an " anomaly " in the maltose chains might consist of a sidechain, and it is thought that the enzyme detaches a molecule ofmaltose from the end of the chain and this proceeds until a sidechain is reached, when the process stops.The hydrolysis of starch by the cr-amylase of malt results firstlyin the production of dextrins of molecular weight correspondingto about 45 glucose residues; little maltose is produced, theviscosity is considerably lowered, and the products show definite70 J.Biol. Chem., 1938, 126, 479.7% Svensk Kern. Tidskr., 1938, 50, 284.7 1 Cereal Chem., 1939, 16, 330.'3 Ann. Reports, 1938, 35, 360376 BIOCHEMISTRY.reduction, indicating the disruption of glucose residues. Thea-amylase thus breaks definite linkages which are not necessarilythe normal p-glucosidic type but may be a-glucosidic 1 : 6 or 1 : 3,or possibly abnormal 1 : 4-linkages.Natural mixtures of a- and P-amylases and some which are heldto be uniform a-amylases hydrolyse starch with the production oflarge but varying amounts of maltose and the so-called limit'dextrins which are of low molecular weight equivalent to 4-6glucose units. Hydrolysis of native starch by amylases appearsto follow such a course that linkages of other than normal maltoseunions must be present.Substances which are able to attack suchabnormal linkages must therefore be present in natural amylasesin addition to the normal amylases so far recognised. Such sub-stances would influence the degree of saccharification. Observ-ations on degradation products of starch confirm such suggestions,although it is thought that the number of abnormal linkages issmall.M. L. Caldwell and co-workers have in recent years published aseries of papers on amylases, one of which deals with the effect ofheavy water on the stability and activity of pancreatic amylase.This was found by M. L. Caldwell, S. E. Doebbeling, and S. H.Manian 74 to deteriorate more rapidly in 99% heavy water than inordinary water, and the ill effect was still more marked with equalvolumes of the two.The activity of the enzyme, as measuredby the iodine reaction and by maltose production, was unaffectedby heavy water as compared with ordinary water, but again themixture of the two involved lower values.In another paper, M. L. Caldwell and S. E. Doebbeling 75 in-vestigated the characters of the two malt amylases and found thatdifferences in stability and other conditions which involved markeddifferences in tke impure preparations disappeared with purifiedspecimens. Both the amylases appeared to be free from carbo-hydrate, but gave protein reactions; their behaviour was such asto suggest that no specific activator or kinase was necessary for theiraction.At a later date a quantitative study of the influence of factorssuch as hydrogen-ion and electrolyte concentration on the activityof amylase from AspergiZZus Oryzce was undertaken by the sameauthors.76 A number of commercial samples as well as thoseprepared in the laboratory were examined under similar and care-fully controlled conditions for dextrinogenic and saccharogenicv4 J .Amer. Chem. SOC., 1936, 58, 84..75 J . Biol. Chem., 1935, 110, 739.7 8 J . Amer. Chem. Soc., 1937, 59, 1835NORRIS : PLANT. 377activity. Sodium chloride was used in varying concentrations asthe electrolyte, and variations in pH were secured by the use ofsodium acetate-acetic acid buffers. Optimal dextrinogenic actionis obtained a t pn 5.0 in the presence of O-O5~-sodium chloride, andsaccharogenic activity is greatest a t pH 5.0 in presence of 0.02M-sodium chloride, or a t pH 5-3-55 in absence of the salt.Noconclusions were drawn as to the significance of the slightly differentoptimum conditions for the two types of action with respect to thepresence of one or two enzymes in the preparatioiis. The optimumconditions found were valid for preparations of all types and gradesof purity and such a finding has significance with regard to theimportance of determining activity of the enzymes a t differentstages during their preparation and purification.I n a still more recent paper the effect of heavy water is againdiscussed, this time in relation to the amylases of barley and malt.M.L. Caldwell, S. E. Doebbeling, and F. C. von Wicklen 7 7 findthat with the p-amylase of barley and the a- and p-amylases ofmalt the production of maltose from 1% soluble starch at pE 4.5and 40" rises rapidly in the first 30 minutes, after which the pro-duction is not so rapid, a constant rate being observed after 100minutes. Similar results were obtained whether ordinary or heavywater was used, nor was the dextrinogenic activity of malt a-amylase affected under the two conditions. Stability experimentswere also carried out by diluting the preparation with ordinaryand with heavy water in the cold, and subsequently raising thetemperature to 65" for definite periods. Malt p-amylase showedmuch less loss of activity in heavy water than in ordinary water,in contrast with the observation already made and indicated abovein the case of pancreatic amylase.No explanation of the differencesobserved with different enzymes and types of water is as yet forth-coming.Soybean amylase has as yet been little studied, and as far as theReporter is aware methods for complete extraction and purificationhave not been evolved. Interest therefore attaches to a communic-ation by J. M. Newton and N. M. Naylor 78 dealing with this subject.They find that an aqueous suspension of the powdered bean or aconcentrate precipitated by 65% alcohol shows saccharogenicpower ; but dextrinogenic power in these and the fractions obtainedin the preparation of the concentrate is so small as to be negligible.They conclude, therefore, that the amylase is principally of theP-type, and consider that with further improvement in the methodsof preparation and purification, soybean should be a useful sourceof the amylase.i7 J .Amer. chem. SOC.~ 1939, 61, 125. c 8 Cereal Chem!., 1939, 16, 71378 BIOCJHEMISTRY.Pectin.-An important series of papers on the pectic substancesof plants has been published by E. L. Hirst and J. K. N. Jones,who confirm and augment suggestions of authors mentioned in theprevious Report, The polysaccharides of the seeds of Arachishypoguea (pea-nut) have been isolated 79 and shown to includestarch, cellulose and a complex of pectic acid and araban. Thethallium derivative of the complex is methylated with methyliodide and in this manner the methylated araban can be separatedand hydrolysed.The results obtained lead to the conclusion thatthe araban consists of branched chains built up solely of arabo-furanose residues. It has been held, on somewhat slender evidence,that the natural occurrence of pentose sugars and polysaccharidesmight be explained on the assumption that oxidation of hexoseresidues takes place, followed by direct decarboxylation. Sucha theory requires careful review at the present time, and it isnecessary to determine the precise nature of the ring structures ofpentoses in naturally occurring substances such as pectin. Thetype of change indicated by recent work involves the conversionof hexopyranose into pentofuranose residues, and such a changecannot be effected by the simple means indicated above.In a second communication 8O the araban of the pea-nut isobtained by extraction of the complex with aqueous alcohol andsubsequent purification is effected through the acetate.Thearaban is hydrolysed quantitatively t o Z-arabinose and the presenceof arabofuranose residues is indicated. The isolation of a purearaban of determined properties is of interest in view of the factthat, although arabans occur frequently in nature, they are normallyassociated with large amounts of pectic material, galactans, etc.,and separation is correspondingly difficult. Pea-nut was employedas source in the present instance because the amount of such inter-fering material is relatively small.The araban appears to beclosely identical with that isolated by P. Ehrlich81 from beetpectin.The araban of apple pectin 82 is identical in structure with thatof pea-nut, consisting of arabofuranose residues. It is present inthe pectin in admixture with a galactan and the methyl ester ofpectic acid. The pectic acid appears to be composed mainly ifnot entirely of anhydrogalacturonic acid residues.G. H. Beaven and J. K. N. Jones 83 have examined the productsof methylation and subsequent hydrolysis of strawberry pecticacid and further support is lent to the theories of pectin structure79 J., 1938, 496.s2 J., 1939, 454.8o J., 1939, 452.83 Chern. and Ind., 1939, 58, 363.Biochem. Z . , 1926, 168, 263; 1928, 203, 243NORRIS: PLANT.379recently developed, namely, that pectic acid consists of chains ofgalacturonic acid linked together through the 1 : 4-positions. Itis again pointed out that, as the araban associated with pectin hasa furanose structure, it cannot be derived from pectic acid by simpledecarboxylation of the galacturonic acid residues.Additional confirmation of the structure of pectic acid is providedby F. Smith,S3 who has investigated a pectic acid derived fromcitrus pectin and corresponding closely to the pectolic acid of P.Ehrlich and R. G ~ t t m a n n . ~ ~ This product also consists of a d -galacturonic acid units joined in 1 : 4-linkageY and is identical inthis respect with the strawberry pectic acid above.An outstanding property of a pectin is that it shall form a sugar-acid jelly under certain well-defined conditions, and it seems probablethat many of the pectins described in the literature would not becapable of producing such a jelly.The relation between chemicalcomposition and jelly strength or viscosity is very slight, accordingto E. W. Bennison and F. W. N0rris.8~ A high content of uronicacid generally connotes satisfactory jelly strength, but methoxylcontent is no criterion and was shown in a number of cases to haveno relation to jelly strength. The method of preparation is oneof the most important factors with respect to the jelly strength ofthe final product; the use of high temperatures and pressures, asin the autoclave, invariably inhibits jelly formation. It was foundthat there is a close parallel between viscosity of pectin solutionsand jelly strength, and the latter is considered therefore to dependlargely on molecular size as indicated by viscosity.Similar conclusions are reached by A.G. Olsen, R. H. Stuewer,E. R. Pehlberg, and N. M. Beach,S6 who state that jelly strengthand viscosity of solutions of pectin are functions of molecular chainlength. They point out, however, that the viscosity, especiallyof pectins of low combining weight, is subject to abnormalitiesdue to the effects of salts and pH.The nature of the pectic acid chain of a-d-galacturonic acidunits with 1 : 4-linkage may now be said to be definitely established,and it is noteworthy that the same type of chain is indicated, atleast in part, in the case of another polysaccharide, alginic acid.This is a constituent of some seaweeds and is notable in that itappears to be built up entirely of d-mannuronic acid residues.Recent investigation by E.L. Hirst, J. K. N. Jones, and W. 0.Jones 87 has shown that, although alginic acid is so resistant tohydrolysis that quantitative preparation of mannuronic acid fromit has not so far been achieved, the acid may be obtained by thes4 Biochem. Z . , 1933, 259, 100.8 6 Ind. Eng. Chem., 1939,31, 1015.8 5 Biochem. J . , 1939, 33, 1443.87 Nature, 1939, 143, 857380 BIOCHEMISTRY.action of methyl-alcoholic hydrogen chloride. The same reagentalso yielded an alginic acid of lower molecular weight which wasmore amenable to treatment than the undegraded acid.A fullymethylated derivative was obtained and a study of its oxidationproducts led to the conclusion that linkage in the chain of mannu-ronic acid residues must be at 1 : 4 or 1 : 5. In view of the ex-tremely stable nature and the large negative rotation of alginicacid, it is inferred that the pyranose (1 : 4) structure is more probable,and a t least part of the molecule is considered to consist of P-d-mannuronic acid chains linked through the (1 : 4) positions.In the analysis of pectin, hemicelluloses and polyuronides ingeneral, the difficulty of differentiation between carbon dioxideliberated from small amounts of uronic acids, when treated withboiling 12y0 hydrochloric acid, and that derived from hexoses andpolysaccharides which do not contain uronic acid groups wasreferred to in the previous R8eport.g8 In a more recent communic-ation, A.G. Norman 89 proposes a method of distinction betweenthe two, based on the observed fact that the rates of production ofcarbon dioxide by the standard analytical method are different inthe two cases. Substances such as pectin which contain uronicacid groups showed a rapid evolution of carbon dioxide, with a sharppeak a t 20-30 minutes from tjhe time that boiling commenced,50% of the total carbon dioxide being evolved after one hour.Glucose showed no such peak, the evolution being small and main-tained at a low level for many hours. Starch behaved similarly,but cellulose ga've results which appeared to combine some of thecharacters of both types of substance-the pure uronic type and thehexose type.It is thought that observation of the rate of evolutionof carbon dioxide might lead to definite indication of uronic groupsin polysaccharides containing such groups in small amount.Lignin.-It is now some years since lignin was discussed in theseReports and in the meantime considerable development has takenplace in our knowledge of the chemistry of the substance. Muchof the credit for present achievement is due to the schools of Hibbertand of Freudenberg, although it has to be admitted that muchremains to be done before knowledge is complete.Lignin has presented peculiar difficulties to the investigatorowing to its resistant nature, which finds expression in the difficultiesof isolation and of subsequent chemical treatment.Every modernresource of the organic chemist has been utilised in the attack onthe problem, and physical methods such as X-ray examinationhave also been called on. A large number of workers have regardedR * Ann. Reports, 1938, 35, 362. Nature, 1939, 143, 284NORRIS : PLANT. 351lignin as a homogeneous substance, but this view has largelygiven place to a realisation that lignin must be regarded as a mixtureof more or less closely related substances. It may also be men-tioned that R. S. Hilpert and co-workersso have even suggestedthat lignin has no real existence, but is an artefact produced bythe drastic reagents which are commonly used in its preparation.This view, however, has been shown to be untenable.Methods of preparation of lignin fall under several heads, accord-ing as the lignin is to be obtained as such or in the form of differenttypes of derivative.In one type of method, acid treatment isemployed whereby the lignin remains after all other substanceshave been removed. Alternatively, alkali may be used to removelignin, leaving many of the accompanying substances untouched.A common type of derivative is the sulphonic acid resulting fromtreatment of the woody material with sulphites. A somewhatdifferent principle is involved in those methods which depend onthe solubility, under certain conditions, of lignin in alcohols, includingmethyl, ethyl and higher alcohols, ethylene glycol and phenol.A. Friedrich and J.Diwald 91 prepared a primary lignin by treat-ment with acid alcohol, but their claim that the lignin so preparedrepresented natural lignin cannot be defended. They also preparedmethanol lignins which have since been the object of much researchby H. Hibbert et dS2 The lignin extracted by acid methanol isonly some %yo of the total, but H. W. Mackinney and H. Hibbert 93were able to show that there is only a small apparent differencebetween the two fractions. H. Hibbert et uLS4 have also preparedglycol lignin by treating the resin-free dry wood with dry ethyleneglycol and @5y0 dry hydrogen chloride. The glycol appears toenter into combination with the lignin as indicated by the observ-ation that, when glycol monomethyl ether is used, the product,which is a complex mixture, contains more methoxyl than does theglycol l i g n i ~ ~ .~ ~ The complex phenol-lignin is well known and hasbeen recently investigated by W. F u c ~ s , ~ ~ who has improved themethods of preparation, and has also carried out extensive fraction-ations, although none of seven fractions obtained appeared to beuniform. Amongst other extractives may be mentioned ethylacetoacetate (L. Lemmels6), used a t room temperature on woodmoistened with hydrochloric acid, and formic acid (G. F. Wrightand H. EbbedQ7).go Rer., 1935, 68, 380; 1937, 70, 113. 9 1 ilrlonatsh., 1925, 46, 31.92 Canadian J . Res., 1935, 13, B, 28; 1936, 14, B, 12, 115.93 Ibid., 1936, 14, B, 55.9 5 J . Amer. Chem. SOC., 1936, 58, 673.96 Anal.Fis. Quim., 1935, 33, 389.97 J . Amer. Chem. SOC., 1937, 59, 135.y4 Ibid., 1935, 13, B, 36382 BIOCHEMISTRY.Constitution of Lignin.-Methoxyl groups. The presence ofmethoxyl groups in lignin is universally recognised, and theirrecognition in different types of lignin and lignin derivative has ledto further understanding of the structure of the molecule. Thereis evidence that the amount of methoxyl present in lignin varieswith the age of the plant, as shown, for instance, by M. Phillipsand M. J. G o s ~ . ~ ~ There is a,lso considerable variation in themethoxyl content of prepared lignins, the literature containingfigures varying between 14 and 21%. The methoxyl groups arenot easily removed and hence an ether type of linkage is inferred.Moreover, the lignin is not completely methylated, since the totalmethoxyl content may be increased to 30% or more by methylationwith diazomethane, which accomplishes a.further limited methyl-ation, and by methyl sulphate in alkali, which, by suitable gradationof the alkali concentration, may be shown to effect a step-wisemethylation until all available hydroxyl groups are substituted(E. E. Harris, et ~ 1 . ~ 9 ; H. Hibbert et ~ 1 . 1 ) .The latter workers, as a result of such studies, principally onlignin and lignin derivatives from spruce, have suggested a unitfor native lignin represented as C42H3206(O*CH3)5( OH),, and formethanol fignin C,,H3,06( O*cH,),( OH),. The methoxyl groups innative lignin are not uniform, some being attached to an aromaticnucleus. Of the five hydroxyl groups, three are aliphatic, one isenolic or phenolic, and the last differs from the previous four andis highly reactive.In later communications H.Hibbert and H. W. Ma~kinney,~~and G. H. Tomlinson and H. Hibbert have expanded the aboveformula for native lignin in a manner which expresses the relationbetween the different types of hydroxyl and methoxyl groups.The basal unit is thus represented asHibbert considers that the greater part of the unit may consistof heterocyclic rings probably related to hydropyrone.Evidence for presence of phenolic groups. Whilst methoxylgroups are universally accepted and easy to estimate, the presenceof phenolic groups in the original lignin has been the subject ofm-~lch discussion and experimental work.Many of the degradationJ. Agric. Res., 1935, 51, 301.9g J. Arner. Chem. Xoc., 1934, 56, 889; 1936, 58, 894.1 Canadian J . Res., 1935, 13, R, 61.J. Amer. Chem. Xoc., 1936, 58, 340, 315, 348NORRIS : PLANT. 383products of lignin have been of the aromatic type and the followingexamples are typical. K. Freudenberg, A. Janson, E. Knopf,and A. Haag3 obtained a number of complex phenolic degradationproducts from a potash melt, subsequent methylation and oxidationgiving rise to such products as veratric acid, veratroylformic acidand isohemipinic acid. Protocatechuic acid was invariably, andcatechol frequently, found. G. F. Wright and H. Hibbert foundthat vanillin was produced by the action of hot aqueous alkali onsulphite lignins from hard woods; the corresponding treatment ofsoft wood lignins yielded vanillin and methoxyconiferaldehyde.These products were conclusively shown to be produced from theisolated lignin.The authors drew the cautious conclusion that,although lignin may be of a truly aromatic nature, the phenolicderivatives described may be artefacts.The ease of nitration and the nature of the products obtainedhave been held to indicate the presence of phenolic groups (H.Hibbert and L. Marion 5).Methods involving vacuum distillation have been employed byM. Phillips 6$ and M. Phillips and M. J. Goss.* Alkali lignin fromcorn cobs was thus treated in a hydrogen atmosphere at temperaturesup to 400" ; catechol, guaiacol and substituted hfdroxybenzeneswere obtained, and a fraction of the distillate on oxidation withpermanganate gave anisic acid.Similar results were obtained bydry distillation in carbon dioxide at 25 mm. The products includedacetic acid, phenol, p - cresol, hydroxybenzene derivatives, and onoxidation as previously, anisic acid. A further fraction containedn-nonacosane.Theories of structure. P. Klason has recently modified hisoriginal suggestion that lignin was a condensation product of coni-feryl alcohol and now proposes a repeated group of the type (I),which, although not definitely established, explains some of thedegradation reactions of lignin. Later, Klason l o isolated tetra-coniferyl aldehyde from pine lignin and envisaged lignin as a chainmolecule of molecular weight between 3000 and 4000 in whichconiferyl aldehyde complexes are condensed together in much thesame way as sugars in polysaccharide chains.K.Freudenberg favours the existence of chain molecules in thecase of lignin and points out that such an arrangement has beenrecognised in recent times as one of the most commonly occurring3 Ber., 1936, 69, 1415.5 Canadian J. Res., 1930, 3, 130.7 Science, 1931, 73, 568.@ Svensk Kern. T'idskr., 1930, 42, 259; 1931, 43, 226.Ber., 1934, 67, 302.4 J . A,ner. Chem. SOC., 1937, 59, 2447.li J . Amer. Chem. SOC., 1931, 53, 768.J . Amer. Chem. SOC., 1932, 54, 1518384 BIOCHEMISTRY.forms in natural products of high molecular weight. He differsfrom Klason and others as to the nature of the primary unit, whichin his view is based on phenylpropane, a view, incidentally, whichis gaining considerable favour. Thus, K.Freudenberg and W.Diirr,ll and K. Freudenberg, F. Sohns, W. Diirr, and C. Niemann 1,suggest that primary lignin is derived by union of two basal acids(11) and (111). The primary form polymerises to secondary lignin,the form isolated from the plant.CH,*O€I 7H2*OHHQOH H*C*OHCH*OH(11.) (111.)The suggestion of a chain molecule for lignin has been held bysome to indicate the acceptance of lignin as a homogeneous sub-stance. This is not conclusive, since by analogy with other chainmolecules, such chains may be branched, or alternatively othersubstances may be closely bound, although not a definite chemicalpart of the main chain.The presence of such substances in varyingamount would account for the lack of uniformity in lignin prepar-ations. Moreover, as K. Freudenberg, F. Sohns, and A. Janson l3have proposed, chains may be built up from several similar butdistinct basal units. Thus, the analytical and other data are inaccordance with the presence of three groups in the proportionsrespectively of 69, 9 and 22y0 :AIn a brief review it is impossible to deal adequately with severalhundreds of published papers, but it is hoped that some impressionof the magnitude of the problem has been conveyed. For morelengthy reviews the reader is referred to those of A. G. Normanand K. Freudenberg.16l L Ber., 1930, 63, 2713. l2 Cellulosechern., 1931, 12, 263.l3 Annalen, 1935, 518, 62.l4 " Biochemistry of Cellulose, the Polyuronides, Lignin, etc.," Oxford, 1937.l6 Ann.Rev. Biochem., 1939, 8, 88NORRIS : PLANT. 386Metabolic Products of Moulds.Penicil1ium.-A new species of Pemkillium vinij'erum obtainedfrom bottled grape juice has been described by K. Sakaguchi andT. Inoue.16 Good growth was obtained at 32-34' and p , 4.4-6.9 on the usual media. A number of enzymes, including amylase,emulsin, proteinases, catalase and zymase, were present, and themould fermented starch, glycogen, dextrin and the usual ferment-able sugars, including galactose. I n media containing glucosethere was production of ethylene oxide-orp-dicarboxylic acid.In an examination of over 50 species of Penicillium, A. J. Moyer,0. E. May, and H. T. Herrick l7 found that P. chrysogenum producedthe highest yield of gluconic acid when grown in media with lowsalt concentrations and about 20% of sugar. The presence of smallamounts of iron had an enhanced effect on the yields obtained.Amongst the metabolic products of Penicillium funiculosum,Thom, is a red pigment, funiculosin, which has been isolated byH. Igaraci la from a decoction of koji. Derivatives were preparedand the degradation reactions led to the conclusion that the pigmentwas a di- or tri-hydroxymethylanthraquinone. Malonic acid wasalso produced after 15-25 days in a koji decoction, but if syntheticmedia containing glucose and ammonium sulphate were employedsuccinic acid also was obtained, and oxalic acid alone appearedafter 45 days.A new metabolite of Penicillium griseo-fulvum is described byA. E. Oxford, H. Raistrick, and P. Simonart,19 who isolated griseo-fulvin from the mycelium of the mould when this was grown in amodified Czapek-Dox solution. The new substance is notable inthat it contains a chlorine atom and, whilst a final structure forthe product is not yet quite certain, an examination of derivativesand degradation products leads the authors to suggest the formula(IV) as extremely probable :OGHa CHHO,C OCH,Aspergillus.-Chlorine-containing products had also been obtainedby H. Raistrick and G. Smith 20 in 1936 from cultures of Aspergillusl6 J . Agric. Chem. SOC. Japan, 1938, 14, 1517.l7 Zentr. Bakt. Par., 1936, 11, 95, 311.l8 J . Agric. Chem. SOC. Japan, 1939, 15, 225, 229.lS Biochem. J., 1939, 33, 240.2O Biochem. J., 1936, 30, 1315.REP.-VOL. XXXVI. 386 BIOCHEMISTRY.terrezcs, Thom. These were called geodin and erdin and were shownto yield dihydro-derivatives on catalytic reduction. Dihydrogeodinis the methyl ester of dihydroerdin. By methods of analysis andsynthesis and particularly a study of the products of reductive andhydrolytic fission, C. T. Calam, P. W. Clutterbuck, A. E. Oxford,and H. Raistrick21 have shown that the more probable of twopossible formulze for dihydroerdin is (V).Itaconic acid has only once been reported as a metabolic productof Aspergillus and on this occasion it was suggested by K. Kinoshita 22that the product was derived from the sugar of the medium viagluconic, citric and aconitic acids. In studying a newly isolatedstrain of A . terreus, C. T . Calam, A. E. Oxford, and H. Raistrick 23found that none of the usual metabolites were obtained but insteadconsiderable quantities of itaconic acid were present. It is doubtfulwhether the acid is produced according to the scheme suggestedabove, since no evidence of the presence of citric acid could beobtained at any time during the experiments. Of other strainsstudied, none gave any itaconic acid, but succinic, fumaric andoxalic acids were produced in different cases.In a continuation of the study of the pigments of the driedmycelium of Aspergillus ghucus, N . Ashley, H . Raistrick, and T.Richards 24 have re-examined the case of one of the three pigments,soluble in light petroleum, previously described. This is the redpigment rubroglaucin, which has now been shown to consist of amixture of two substances, physcion and a new pigment. Theformer is 4 : 5-dihydroxy-7-rnethoxy-2-methylanthraquinoney andthe latter is the monomethyl ether of a tetrahydroxymethylanthra-quinone and has been named erythroglaucin. In some speciestwo reduction products of physcion were present, these anthranolshaving been reported by A. G. Perkin and J. J. Hummel 25 as longago as 1894 in the root-bark of a climbing shrub.Growth and pigment formation by A . niger with special relationto the amount of magnesium in the medium have been studied inilr series of publications by J. Lavollay and F. Laborey.26 Theyshowed that the maximum development of the mycelium occurredin Raulin’s solution containing 1-05 mg. of magnesium per 100 ml.A lower concentration of magnesium was more favourable topigmentation, which was almost completely suppressed by smallamounts of ascorbic acid. The presence of the latter accelerated21 Biochem. J., 1939, 33, 579.23 Biochem. J . , 1939, 33, 1488.2 5 J . , 1894, 85, 923.26 Compt. rend., 1937, 204, 1686; 1937, 205, 179; 1938, 206, 1055; 1939,22 Acta Phytochim., 1931, 5, 271.24 Ibid., p. 1291.208, 1056NORRIS : PLANT. 387germination and sporulation and increased the yield of myceliumto varying extents in relation to the magnesium content of themedium.In later papers, the production of pigment was found tlo dependon the composition of the medium and it was observed that underanaerobic conditions more pigment w-as formed although there wasgreat retardation of growth. The pigmentation was yellow-green,and it was shown that the pigment consisted a t least in part oflactoflavin. The medium employed was partly deficient in mag-nesium and contained 0.3 mg. yo. The lactoflavin producedafter a period of growth of the organism a t 34" was adsorbed onmontmorillonite and subsequently eluted with a water-methylalcohol-pyridine mixture. I n addition to lactoflavin a browniron-containing pigment was present.F. W. NORRIS

ISSN:0365-6217    

DOI:10.1039/AR9393600335

出版商:RSC    

年代:1939

数据来源: RSC

摘要:

ANALYTICAL CHEMISTRY.1. INTRODUCTION.IN continuation of our policy of last year we have preferred thechoice of a few themes t o an attempt a t a Report covering all phasesof Analytical Chemistry. By this preference, most of the subjectsdealt with have been given fairer and more detailed treatment thanwould have been possible had our range been extended over a widerfield.The microscope is a familiar instrument in the analytical labor-atory. A review of its diverse uses for identification and estimationand of recent advances and extensions of its applicability is given.A note on a related method of identification dependent uponcrystalline form is included under the heading of crystallochemicalanalysis.The marked scientific attention which industrial hygiene hasdemanded during the past ten or fifteen years has prompted anaccount of the analysis of dusts and smokes.It is primarily fromthe industrial aspect that the progress in gas analysis is also reported,and the account which follows may be regarded as being supple-mentary to the article on gas analysis which appeared in the AnnualReports, 1933.To the analyst the occurrence of pronounced adsorption is usuallyan unwelcome phenomenon in analytical procedure, resulting as itdoes in the loss of a fraction of the material to be estimated inpreliminary processes of separation, or in contamination of theultimate precipitate, and this is one aspect of sulphide precipitationwhich is discussed below. Adsorption has, however, been put tocertain analytical uses.These are usually specific, as for examplein the collection of minute amounts of bismuth from solution bycoprecipitation with ferric hydroxide, but a widely applicableanalytical technique, namely, chromatographic analysis, has beenfounded on adsorption phenomena.2. MICROSCOPY.It has been mentioned that any property of a substance, physicalor chemical, which is characteristic of that substance may be utilisedto identify that substance and determine its proportions inmixtures,l and it has been said that the chance of two differentAnn. Reports, 1938, 35, 380GRIFFITHS, GULL, AND WHALLEY. 389substances having the same 10 or 12 characters directly observablemicroscopically is about 1 in lo6, so it is not surprising that incertain fields of analytical chemistry, the microscope can play avery important part.The fact that without undue difficulty it is possible to observemicroscopically the shape or crystal habit of particles of the orderof 10 p in diameter means that in principle it is possible to identifya particle weighing about g., i.e., 1 pg., in so far as the shape,colour, refractive index, action on polarised light, fluorescence andother features, and in addition changes brought about in these byexternal agency, are observable microscopically and are indicativeof a particular substance.Perhaps the simplest case is that of adding a drop of reagent to adrop of the solution of the unknown on a microscope slide or in acapillary tube and observing microscopically the properties of anysolid, amorphous or crystalline, which may separate out.Thisparticular method has been developed during many decades, andwhen compared with ordinary qualitative analysis has advantagesof speed, since it is evident that a drop of fluid can be decanted,filtered, or evaporated much more rapidly than 10 ml. There arealso advantages of economy and certainty, the latter being due tothe fact that some physical attributes of the solid separating are notgenerally noted in ordinary “ macro ” qualitative analysis, but areeasily observed under the microscope and have considerablediagnostic value. An authoritative description of microscopicalqualitative inorganic analysis was published in 1931 and progresshas continued steadily in the inorganic and the organic fields in thedirection of discovering more sensitive and more highly selectivereactions and in the analysis of mixtures, but owing to the volumeof work, only a small portion can be referred to directly in thisReport.In order to identify a substance by micro-crystal methods, itis frequently necessary to remove certain other material ; e.g.,0.5% aqueous anthranilic acid gives characteristic crystallineprecipitates serving for the detection of not less than 0.013 pg.ofcopper, 0.06 pg. of mercurous, 0.015 pg. of palladous, 0.05 pg. ofzinc, and 0.24 pg. of silver ions in the presence of each other andother metals, but cobaltous, ferric, and ceric ions must be a b ~ e n t . ~In view of the interference of one element with the tests for another,methods of separation into groups have been devised.In the caseE. M. Chamot and C. W. Mason, “ Handbook of Chemical Microscopy,Vol. 11, Chemical Methods and Inorganic Qualitative Analysis,” Chapmanand Hall.0. G. Scheintzis, J. Gen. Uhern. Russia, 1938, 8, 596390 ANALYTICAL CHEMISTRY.of non-ferrous alloys, separation may be effected by dissolution innitric acid followed by the use of a series of reagents not all normallyregarded as (( group reagents " in ordinary qualitative analy~is.~Progress has also been made in the direction of finding veryselective and sensitive reagents for ions, as in the case of lead, with0-02 pg. of which, at a concentration of 1 part in 40,000 of pure dilutenitric acid, a crystal of thiourea gives characteristic crystals.Onlythallium and some platinum metals give similar crystals, but excessof silver or copper may alter the cryst'al form, and together withbismuth should be removed by a preliminary electrolysis, lead beingdeposited on a platinum anode.5 Zinc in concentration as low as1 in 100,000 can be detected by the characteristic crystals of zinchydrogen p-naphthaquinoline thiocyanate in the presence of calcium,magnesium, beryllium, aluminium, tervalent chromium and cerium,ter- and quinque-valent arsenic, manganese, and nickel, as well asalkali metals.6 Silver, mercury, and lead may be detected in thepresence of each other without separation, by dividing the test dropinto three portions, one each of which serves for the identificationof silver as chromate, mercury as cobalt mercury thiocyanate, andlead as its triple nitrite with copper and potassium.'As illustrative of the close connection between organic and in-organic microscopical analysis, it may be mentioned that previousmethods of detecting yohimbine, a potent alkaloidal stimulant, havebeen neither highly selective nor very sensitive, but if a solution of notless than 2 pg.of the hydrochloride at a concentration of not less than1 in 5000 is heated with a particle of potassium cyanide, character-istic crystals are obtained, as is also the case when borax, sodiumselenite, sodium tellurite, and potassium oxalate are used'as reagents.Conversely, yohimbine can be used to detect borate, selenite, tellur-ite, and oxalate ions.8Microcrystalline tests are of particular value in the recognition ofalkaloids, drugs, and other organic substances, and only a limitedamount of work done in this field can be referred to.A saturatedsolution of lead iodide in potassium acetate is a sensitive reagentgiving characteristic crystals with 15 alkaloids and synthetic drugs,and a number of drugs give amorphous precipitate^.^ A newsystematic classification of some 100 reagents in use for identifyingalkaloids is suggested; and a table is given showing them in the4 W. F. Whitmore and F. Schneider, Ind. Eng. Chem. (Anal.), 1930, 2, 173.C . Mahr, Mikrochem., 1939, 26, 67.E. B. Sandell, D. M. Wishnick, and E. L. Wishnick, Milcrochim. Acta,B. Berisso, Mikrochem., 1939, 26, 221.A.Martini, ibid., p. 227.G. H. Wagenaar, Pharm. Weekblad, 1939, 76, 276.1938, 3, 204GRIFFITHS, m L , AND WHALLEY. 39 1order of their precipitating power.1° Work on the recognition ofthe ingredients of commonly occurring mixtures of drugs is proceed-ing. For example, Reinecke's reagent, [Cr(NH,),,(SCN),]NH,, givescharacteristic crystals with 1 pa'rt of brucine in 500 parts ofstrychnine, and morphine may be detected in the presence of otheropium alkaloids.ll Brucine and strychnine give widely differentcrystals with rhodium chloride, and both can be recognised therebyin certain mixtures.12 Recently, the use of mixtures of hydroxy-benzoic acids and their esters came into prominence, as preservativesof foodstuffs, and it was necessary to distinguish between smallquantities of salicylic and p-hydroxybenzoic acids.It was foundthat the latter, alone or in presence of the former, gives characteristiccrystals with copper ~u1phate.l~In addition to the general nature of the crystal habit, otherproperties assist discrimination. The angles between crystal faceshave long been used as a means of identifying substances, and arecent development of this method is referred to later (p. 398).The use of measurements of the angular constants of microcrystallineprofiles and silhouettes in the conclusive identification of substancesis discussed.14 Such measurements may be made microscopicallyby means of a rotating stage or a goniometer eyepiece. In thisconnection, the effect on crystal angles of depositing thin filmsof crystallisable substances on glass has been investigated.As anexample, it is found that sodium thiogulphate so deposited can beidentified from the crystal data.15A knowledge of the refractive index is a valuable adjunct to therecognition of a pure substance, and in the case of a solid particle itmay be determined by microscopic observations when the particleis immersed in liquids of known refractive index, but in which theparticle is insoluble. This requires series of suitable liquids whichdiffer in refractive index by small and regular intervals over theappropriate range. In view of difficulties in collecting such a setof pure liquid compounds, mixtures having definite refractive indicesdetermined refractometrically have been used.In order to ensureconstancy of composition during use, the components should havevery similar vapour pressures. In the case of inorganic substances,a-bromonaphthalene, butyl phthalate, and heptoic acid mixturescover the range 1.658-1.423, and mesitylene-ethyl propionatelo C. C. Fulton, Amer. J. P h m . , 1939, 3, 184.l1 P. Duquenois and Mlle. Faller, Bull. SOC. chim., 1939, 6, 998.l2 A. Martini, Mikrochem., 1937-1938, 23, 164.l3 F. W. Edwards, H. R. Nanji, andM. K. Hassan, Analyst, 1937,62, 178.l4 A. C. Shead, I n d . Eng. Chem. ( A w l . ) , 1938,10, 662.l5 G. Cesko and J. MBlon, Bull. Acad. roy. Belg., 1938, [v], 24, 558392 ANALYnCAL CHEMISTRY.mixtures cover the range 1.498-1.384.16 The refractive indexof small quantities of organic liquids is determined by observationson a scratch at the bottom of a hole 5 mm.deep and 1 mm. indiameter in which the fluid in question is placed.17 Characteristiccrystal habits and optical data are described for the salts of picrol-onic acid with 27 amino-acids, and in nearly all cases the refractiveindex of the crystals can serve for identification.lsThe polarising microscope is of assistance in identifying crystallinematerial, particularly as many organic compounds exhibit bire-fringence, and the magnitudes of the properties are of diagnosticvalue. A new technique depends on allowing the substance tofreeze under a cover glass supported a t one side so as to form wedge-shaped crystals, the polarisation colours of which are examinedbetween crossed Nicol prisms with a grating microspectrograph.The patterns obtained assist comparison and identification ofsubstances. The utility of a grating microspectrograph in recognis-ing small quantities of material by means of their absorption spectra(cf.Ann. Reports, 1938, 35, 394) is self-evident, and an instrumentin which these and polarisation phenomena can be photographed isdescribed.lg In another case, optic axial angles of binary mixturesof acet- and propion-p-bromoanilide were determined at five wave-lengths, and two of the three types of crystal dispersion exhibitedare found to be functions of composition, thereby providing a basisfor identifying small amounts of acetic and propionic acids anddetermining approximately the composition of Thepolarising microscope can be used in detecting and identifyingotherwise unworkably small quantities of material, in identifyingproducts of reaction, often in a crude state, and in detecting andidentifying unsuspected products of reaction,21 and it is consideredthat any crystalline substance is adequately defined by the followingdata taken together : solubility, elementary composition, m.p., andthe magnitudes of the refractive indices, all of which are derivableby micro-met hods .22Fluorescence microscopy has found considerable application inthe examination of biological material, and i s used analytically as asorting test, as, e.g., in a mixture of novocaine and cocaine, theparticles of the first ingredient fluoresce whilst those of the secondare not luminescent in ultra-violet light, thereby showing that the16 A.H. Kunz and J. Spulnik, I n d . Eng. Chem. (Anal.), 1936, 8, 485.l7 P. L. Kirk and C. S. Gibson, ibid., 1939, 11, 403.R. Dunn, K. Inouye, andP. L. Kirk, Mikrochem., 1939, 2'7, 154.l9 E. E. Jelley, J . Roy. Microscop. SOC., 1936, [iii], 56, 101.2o W. M. D. Bryant, J . Amer. Chem. SOC., 1938, 60, 1934.21 H. C. Benedict, I n d . Eng. Chem. (Anal.), 1930, 2, 91.22 P. L. Kirk and C. S. Gibson, Zoc. cit., ref. (17)GRIFFITRS, GULL, AND WHALLEY. 393powder is not homogeneo~s.~~ The method, incorporating a micro-spectroscope, has been used quantitatively, as in the detection anddetermination of approximately g.of samarium and dysprosiumin a borax bead.24Within recent years, the accuracy of the determination of themelting point of substances by means of a microscope heating blockhas been increased, and it is advantageous, particularly in the caseof dark-coloured crystals, especially porphyrins, to illuminate thecrystals with polarised light and observe the material through ananalysing eyepiece. Birefringent solids shine brightly when thesurrounding field is at maximum extinction. The colour fades atthe m. p., but reappears with s~lidification.~~ The identification oforganic substances by the m. p. and refractive index of the melt,determined microscopically, has been described.26 The separation,isolation and identification of traces of substances and discriminationbetween chemically similar organic compounds is frequently facilit-ated by forming derivatives having well-defined melting points.Thefield in which the microscopic method is available is merely indicatedby reference to some of the papers describing the characterisation ofsubstances by means of the m. p. of derivatives. Certain aromaticpolynitro-compounds are identified thus by means of their additioncompounds with na~hthalene,~' and a number of naphthyl ethersafford suitable picrates.28 Dinitro-derivatives of certain sulphonesare highly chara~teristic.~9 Isomeric hexanols are differentiated bythe m. p. of their dinitrobenzoates and the additive compoundsof these esters with a-naphthylamine.30 Many organic acidsform suitable salts with benzylisothiourea,3l monobasic saturatedaliphatic acids are characterised by the m.p. of their derivativeswith pp'-diaminodiphenylmethane 32 and by ' the m. p. andoptical crystallographic properties of their p-bromoanilides.33Examples of the use of 3 : 5-dinitrobenzoyl chloride for identifyingamino-acids and peptides are given.34 P. P. T. Sah and his co-workers describe the use of semicarbazides for the identification of23 M. Servione, Ann. Chim. analyt., 1937, [iii], 19, 313.24 M. Haitinger, Mikrochem., 1934-1935, 16, 321.25 C. Rimington and P. Symons, Mikrochim. Acta, 1938, 3, 4.2 6 L. Kofler, Angew. Chem., 1938, 51, 703.27 0. C. Dermer and R. B. Smith, J . Amer. Chem. SOC., 1939, 61, 748.28 V. H. Dermer and 0. C. Dermer, J .Org. Chem., 1938, 3, 289.29 C. A. Buehler and J. E. Masters, ibid., 1939, 4, 262.30 P. Sulter, Helv. Chim. Acta, 1938, 21, 1266.31 S. Veibel and K. Ottung, Bull. SOC. chim., 1939, 6, 1434.32 A. W. Ralston and M. R. McCorckle, J . Amer. Chem. SOC., 1939, 61, 1604.33 W. M. D. Bryant and J. Mitchell, jun., ibid., 1938,80, 2748.34 B. C. Saunders, J., 1938, 1397394 ANALYTICAL CHEMISTRY.aldehydes and ketones, and azides in the case of amines, alcohols,and phen0ls.3~ Ethers may be identified by heating a small sampleto 500" and converting the products into a tolylsemicarbazide or abenzhydrazide by which the aldehyde or ketone is identified and theether deduced.36 Small quantities of alkyl halides easily affordS-alkylisothiourea picrates with convenient m.p.37Many organic compounds can be identified by means of thecharacteristic forms of their microsublimates, and, incidentally,separated from admixed non-volatile substances. Fresh cases ofthe utility of this method are still forthcoming, as for example in theidentification of a large number of organic pigments by means oftheir microsublimates .38The microscope serves for the identification of the ingredientsof mixtures frequently without any form of mechanical separation,for, in a thin layer, particles of different ingredients may be observedisolated from other constituents which may be tested in situ optically,chemically, and by their m. p. A relatively recent feature of suchanalysis has been the use of micro-manipulators operated by micro-meters whereby tests may be carried out on specks, invisible to thenaked eye, a t magnifications as great as 200-fold.For instance,the action of hydrochloric and nitric acids on a speck supported ona hook can be investigated by holding under the particle an electric-ally heated micro-crucible containing acid, whereby the liquid isdistilled on to the particle. After evaporation of the acid, chloridesand nitrates have been found with protruding crystal faces suffi-ciently well developed to permit recognition of the crystals bydeterminations of crystal angles and polarisation effects.39The value of observations of shape, markings and linear dimensionsof particles in microscopical analysis cannot be over-estimated ,particularly when it is by such means as these that naturallyoccurring substances of different origin, but chemically almostidentical, are recognised in mixtures, as, e.g., the various starches,and pollen as found in honey.Measurements with micrometereyepieces are time-consuming, since each particle has to bebrought under the scale, and two alternative methods have beendeveloped.Photomicrography affords a permanent record of the particles inthe microscope field, and these images can be counted and measuredat leisure. As an example of the utility of this method, reference35 Rec. Trav. chim., 1939, 58, 8, 12, 453, 459, 582.36 Ibid., p. 758.37 (Miss) W. J. Levy and N. Campbell, J., 1939, 1442.3* A. Kutzelnigg and E. Eraake, Mikrochirn. Acta, 1938, 3, 33.39 R.N. TitusandH. L. Gray, Ind. Eng. Chem. (Anal.), 1930, 2, 368GRIFFITHS, GULL, AND WHALLEY. 395may be made to the photomicrography of lithopone in ultra-violetlight. Cumar gum is used as mountant, and zinc sulphide particles,being opaque to ultra-violet light, give black images on the positive,whilst the barium sulphate particles, transparent to ultra-violetlight, appear white against a grey background due t o the gum whichis intermediate in tran~parency.~~The projection of real images on to a white opaque screen or atransparent screen is also finding increasing favour. The dimensionsof the images in the field can be determined by means of transparentscales or graduations on the screen, etc., and slight adjustments offocus for the detailed examination of particles in different parts ofthe field and of different thickness can be made with e a ~ e .~ 1 Mostmicroscopes can be used as microscope projectors provided asufficiently powerful light source of small dimensions, e.g., a smallPoint-o-lite lamp, is available.42For quantitative work, it is very desirable that the particles ofthe different substances in the mixture be easily distinguishable,and it may be necessary to have recourse t o preliminary treatment.For example, the quartz content of ground felspars used in ceramicsis important and is not accurately or conveniently determined bypurely chemical means. A preliminary treatment with hydrogenfluoride etches the felspars, leaving the quartz clear, and subsequenttreatment with sodium cobaltinitrite stains the potassium felspargrains yellow, thereby permitting microscopical differentiationbetween quartz, orthoclase, and plagioclase felspar fragments.43The merits and limitations of staining methods and observations ofthe effect of reagents are well.illustrated in a recent report onmicroscopic methods used in identifying commercial fibres.44Quantitative Microscopical Methods.There are certain problems in analysis which involve the determin-ation in mixtures of entities which are very similar or even identicalchemically but can be distinguished microscopically. I n such cases,microscopical methods are the only ones available. In addition,there are problems which are capable of solution by ordinarychemical means, but are more rapidly solved microscopically, andspeed of operation is frequently decisive when a routine process is40 G.S. Haslam and C. H. Hall, J. Opt. SOC. Amer., 1934, 24, 14.41 C. E. Brown and W. P. Yant, U.S. Bur. Mines Re@. Invest., 3289, Oct.,42 J. G. A. Griffiths, Analyst, 1937, 62, 519.43 A. Gabriel and E. P. Cox, Amer. Min., 1929, 14, 290.44 T. M. Platt, U.S. Department of Commerce National Bureau of Standards,1935.Circular C. 423396 ANALYTICAL CHEMISTRY.being selected. Microscopical methods are, however, subject tocertain limitations, and recent progress has been concerned withthe examination and extension of the range of validity of thesemethods.Inasmuch as microscopical observation is limited to objects in theplane on which the instrument is focused, only material in thatplane can be observed with any accuracy.Observation is thereforelimited to surfaces with but small irregularities in a direction parallelto the optical axis of the instrument or to particles of which thedepth is small or such as not to interfere with observations of the“ silhouettes.” A random plane through a compacted mass ofparticles does not cut all grains at their maximum diameters, andthe effect of this in determining grain size has been considered in thecase of alloys.45If a plane or a line is passed through an aggregate of hetero-geneous material orientated a t random, the total intercepts of eachconstituent with that plane or line are proportional to the volumes,and the weights of the respective constituents can be deduced ifthe densities are known.The microscopic method is suited, there-fore, to the analysis of compact mixtures which are easily surfaced,such as certain alloys, rocks, and fragmented materials which areunited into a mass by means of a suitable cement. The accuracy ofsuch methods has been investigated with particular reference t o theanalysis of rocks.46 The frequencies of the different ingredientsfound by noting the substances present at regularly spaced pointsalong the line are proportional to the volumes, and an integratingdevice for making rapidly the 1000 or so observations necessary forthe analysis of an alloy or an ore, etc., has been de~eloped.~’The principles on which these methods are based do not applyaccurately to loose grains of material which have not been sectioned,but satisfactory results have been obtained, without sectioning, inthe case of ground quartz-felspar mixtures.48 A comprehensiveexposition of these and other aspects of microscopical analysis isgiven by E.M. Chamot and C. W. Mason.49The complexity of the problem involved in the analysis of apowder consisting of several ingredients, A, B, etc., is evidentfrom the equation by which the proportion by weight of ingredient45 J. J. B. Rutherford, R. H. Aborn, and E. C. Bain, Metals and AZZoys,1937, 8, 345.4 8 H. L. Alling and W. G. Valentine, Arner. J. Sci., 1927, 14, 50.47 A. A. Glagolev, Eng. Min. J., 1934, 135, 399.49 “Handbook of Chemical Miscoscopy, Vol.I, Principles and Use ofPhysical Methods for the Study of ChemicalC. L. Thompson, Bull. Amer. Ceram. SOC., 1934, 17, 257.Microscopes and Accessories.Problems,” 1938, Chapman and Hall, LondonGRIBFITHS, GULL, AND WHALLEY. 397A can be deduced from the relative numbers nA, nB, etc., of theparticles :Simplification may, however, be possible, since the specificgravities, p,, etc., may be neglected if they are nearly identical, andthe diameters, d,, etc., may be neglected if they all lie within afairly narrow range, and in these circumstances, only the numbersof particles need be counted. The nature of the material may notpermit such simplifications, or it may be impracticable to count allthe particles. Sampling is not a serious source of error whenadequate precautions are taken to prevent ~egregation,~~ and whenthe significant ingredient of a powder is of fairly uniform grain size,two different methods may be adopted for the analysis.One procedure consists in suspending uniformly in a viscousmedium a known small weight of the powder, spreading a smallaliquot of the suspension uniformly over a prescribed area, andcounting the particles in question in a number of microscope fields.Statistical analysis shows that in some cases, the distribution of theparticular particles over the prescribed area is not random, owingto surface tension or other effects, and serious error may be causedthereby.51 This error, and others due to the difficulty of measuringsmall aliquots accurately and ensuring the uniform spreading of thesuspension, etc., are obviated in the second method.This consistsin mixing with the powder a definite proportion of a referencesubstance of uniform particle size approximately equal to that ofthe particular particles to be determined, but easily distinguishedtherefrom visually, preparing a uniform suspension of the mixture,and determining the numbers of reference particles and particularparticles in several microscope fields. If the number of referenceparticles per unit weight is known, the number of particular particlesper unit weight of the original powder can be calculated from theobserved ratio of reference particles to particular particles.For the analysis of mixtures containing particles ranging fromabout 10 p to 100 p in diameter, lycopodium powder (spores of theclub-moss) is frequently used as reference substance;52 in the caseof finer powders, the standard particles must be smaller, and of manysubstances tested for use in the determination of bacteria in soil aspecially prepared suspension of indigotin proved most suitable.51The reference substance method has been extended recently to50 J. D. Wildman, J. Assoc. Off. Agric. Chem., 1931, 14, 563.61 H. G. Thornton and P. H. H. Gray, Proc. Roy. Soc., 1934, B, 115, 522.52 T. E. Wallis, Analyst, 1916, 41, 357398 ANALYTICAL CHEMISTRY.complex mixtures in which the particles of two of the ingredients tobe determined are identical chemically and as regards shape, andonly differ in that the ranges within which the diameters of thegrains fall do not wholly c0incide.~33.CRYSTALLO-CHEMICAL ANALYSIS.The possibility of using the crystal form of a material as the basisof an analytical method has long been recognised. Since ampledata are available, by the measurement of the angles between thefaces of a crystal-which angles are characteristic of a substance-identification is in theory possible. In practice, however, the modeof recording and classifying crystallographic data has made identifi-cation by means of crystal form a difficult and tedious process.For example, in Groth’s “ Chemische Crystallographie ” the 7,000substances listed are classified according to chemicaZ composition.In contrast, the classification of the late Dr. T.V. Barker makescrystallo-chemical analysis feasible, and M. W. Porter and R. C.Spiller have described the progress made in the continuation of thissystem.Barker’s classification was based, not on chemical composition oron theories of crystal structure (as Federov’s system was), but ongeometrical form. Within each crystal system, for every crystal amain classification angle was chosen according to a simple set ofrules.3 Though subsequent work has required minor modificationsand additions to be made to the system, its simplicity has not beenlost. Its practical value has been demonstrated by a particular teston substances belonging to the orthorhombic and monoclinic systems.From 1,230 substances, 16 were chosen by an independent selectorand submitted for identification.These included : 01-2 : 4-dinitro-phenylethylaniline, ammonium sulphate, l-phenyl- 3-methyl-4-benzylidenepyrazalone, potassium dihydrogen orthophosphate. Allthe 16 were identified save one, of which the crystal faces were sopoor that not even fair reflexions could be obtained, and consequentlymeasurement on the reflecting goniometer was impracticable. Thetime taken per sample was Since crystals as small as1 cu. mm. can be measured ‘accurately, the classification whencomplete will make crystallo-chemical analysis a reality.hours.63 J. G. A. Griffiths, AnaZyst, 1937, 62, 510.See, e.g., Ann. Reports, 1923, 20, 289.Nature, 1939,144,298.“ Systematic Crystallography,” Thomas Murby, London, 1930, p.2GRIFFITHS, GULL, AND WHALLEY. 3994. DUSTS AND SMOKES.The investigation of the properties of dusts and smokes 1 duringthe past decade has been stimulated by a number of social problemssuch as atmospheric pollution, and the dangers to health of certainindustrial and mine dusts. Not many years ago the law of com-pensation in cases of silicosis was based upon the analysis of the rockbelieved to be the source of the dangerous dust, but since that timeit has been recognised that the percentages of the different mineralsin the dust of the rock are not necessarily the same as those in therock itself, and the problem of dust analysis has gained added socialimportance and increased scientific attention.Changes of timeand temperature alter certain of its characteristics : e.g., by aggrega-tion and partial and preferential precipitation, the number ofparticles per unit volume, the particle size distribution, and theaverage chemical composition of the cloud may change.The takingof a sample, therefore, presents greater difficulties than those offeredby a stable system, heterogeneous though it may be. Frequently itis necessary to maintain a constant temperature throughout theprocess of sampling to prevent any change in concentration of thedisperse phase. The fineness of the disperse phase frequently makescomplete collection of the dispersed medium difficult even whenmethods relying upon aggregation are used, and the danger that theminor fraction of the material which escapes the collecting instru-ment may differ both physically and chemically from the majorfraction which is trapped, cannot be ignored.The true sample, i.e.,100% separation of the disperse from the continuous phase, and itscollection without any change in its chemical and physical character-istics, is virtually unobtainable. The seriousness of this defect isminimised by the fact that a satisfactory analysis can often be madeby a series of separate determinations, none of which requires a truesample as defined above but for each of which a sample is obtained insuch a way that the particular property which the determinationmeasures is unchanged. Further, since comparative data betweentwo or more dusts are often adequate, complete sampling is rarely anecessity.Sampling.-A sample of the disperse phase may be collected bydeposition, filtration, precipitation, or impact methods. Theexposure of a plate or vessel of known surface area to the aerosol fora known time is the basis of the deposition method.It is commonlyemployed for the determination of the amount of material thatsettles from the air in, say, one year per square metre. Though theSee, e.g., '' Disperse Systems in Gases; Dust, Smoke, and Fog," Trans.Faraday SOC., 1936, 32, 1041.A dust or smoke is usually an unstable system400 ANALYTICAL CHEMISTRY.deposit so obtained may be ample for chemical and microscopicexamination, results obtained can only be approximate, andevidently only apply to that fraction of the suspended matter whichhas settled.has used this principle in determining iron,lead, and tar in dust samples.When a stream of particles impinges on a surface, depositiondepends upon the velocity and temperature of the particles, thetemperature and the physical and chemical character of the surface.The stream may impinge upon a surface or pass between areascoated with glycerol or vaselin, and the plates so obtained may beexamined microscopically, or the adhesive film dissolved off and thesuspension so obtained examined directly, or filtered. The koni-meter is an instrument based on this principle, and J. B. Littlefield,C. E. Brown,’and H. H. Schrenk have described a typical one. Thedensity of koaimeter dust spots has been measured photoelectricallyby W. H. Walton? who found that with dusts from two types ofshale, anthracite, and coal, the method allowed the determination ofthree times the maximum number of particles which could beconveniently counted.For dusts of similar particle size, the ratio ofthe light absorbed to the number of particles was found to beconstant and almost independent of the nature of the material.Owens’s method4 has been the subject of much development.The incoming dust cloud is saturated with water vapour, and as itpasses out of a jet to impinge on a microscope slide, almost adiabaticexpansion occurs and water vapour condenses on the particles sothat on striking they stick the more easily. By using a high velocityof air in certain cases 90% efficiency is claimed. S. W. Gurney, C.R.Williams, and R. R. Meigs 5 describe a typical instrument based onthese principles, in which the essentials are an air pump, moisteningchamber, slit 6 x 0.4 mm., circular glass slide, and microscope. Thefactors influencing dust determinations by the impinger method, e.g.,the importance of using dust-free water and of removing air byboiling, are discussed by M. H. Kronenberg, A. N. Setterlind, andC. H. McClure.6The risk of changing the character of finely ground felspar andquartz and dried spores of Penicillium oxalicum by the act of collec-tion has been examined.’ It was found that on dry surfaces thefineness to which particles shatter appeared to be limited to approxi-A. HellerGesundh.-Ing., 1934, 57,322.U.S. Bur. Mines, 1938, Inf.Circ. 6993.J . I n d . Hyg., 1936, 18, 689.Proc. R o y . SOC., 1922, A , 101, 18.IbicE., 1937, 19, 198.J. B. Ficklen and L. L. Goolden, Science, 1937, 85, 587.ti J . I n d . Hyg., 1938, 20, 24GRIFFTTHS, GULL, AND WHALLEY. 401mately lp, and on a wetted surface to 0 . 5 ~ . It was deduced thatwith felspar and quartz any estimate of particle size distribution inair from the resultant particles was erroneous, and with each of thethree dusts the determined number of particles in air samples wasuntrustworthy. E. L. Anderson 8 has reached a similar conclusion.The impinger method has also been used by P. Drinker and W. G .Hazard to measure, record, and control dilute dust concentrations,the dusty air being drawn through a slit-shaped jet to impinge on amoving sensitised film.An alternative apparatus based on the impinger principle butemploying a liquid collecting medium is described by H.H. Schrenkand his co-workers.1° The dust impinges on a smooth surface undera bubbling column of liquid, and is picked up from this surface bythe liquid, or removed from the air as it passes through the liquid.In the earlier stages of the work water was used as the collectingmedium, but owing to the solubility of even siliceous dusts if keptfor 24 hours before testing, ethyl alcohol or ethyl alcohol-watermixture (1 : 3) was preferred. The latter has the additionaladvantages of lower freezing point, bactericidal action, wetting andretaining dusts difficultly wetted by water, and preventing " clump-ing " of asbestos dust.Ropy1 and isopropyl alcohol were alsofound to be suitable. A washing technique suitable for zinc chlorideclouds in hydrochloric acid vapour, and for phosphoric oxide andsulphur trioxide has been devised by A. Czernotzky.llFiltration of the disperse phase is a special form of impinging anddeposition, since the fibres of the filter act primarily not as a sievebut as a number of surfaces to which the particles adhere. Collec-tion is assisted by the relatively high velocity of the aerosol throughthe channels of the filter and by the eddy currents set up therein.As a method of collection it is suited to coarse particles, preferably ofhigh concentration. The character of the aerosol, of course, deter-mines the choice of filter. Further reference to this method is madelater.A fourth method of sampling depends upon precipitation, whichmay be effected electrostatically or thermally. Electrostaticprecipitation is suited to coarse and to fine suspensions, and a recentapparatus employing this principle is described by E.C. Barnes andG. W. Penney.12 A ground, cylindrical, aluminium tube serves asthe collecting electrode, a central electrode being the ionising an(J . In&. Hyg., 1939, 21, 39.U.S.P. 2,076,554; 2,076,553, 13.4.37.lo C. E. Brown and H. H. Schrenk, U.S. Bur. Min., 1938, Inf. Circ. 7026l1 Chem. Pabr., 1937, 10, 218.lZ J. I n d . Hyg., 1938, 20, 259.F. L. Feicht and H. H. Schrenk, U.S. Bur. Min., 1937, Rept. Invost. 3360402 ANALYTICAL CHEMISTRY.precipitating electrode.The rate at which the air is drawn throughis measured by a manometer, and precautions are taken to avoid anychange in weight of the apparatus during use. For greater accuracya glass tube bearing a conducting glaze is used, with a platinum-rhodium wire as the central electrode. Under certain conditions100% efficiency of all particulate matter is claimed. S. Blacktin l3has described a collecting instrument , the essential component ofwhich is a rotating ebonite or celluloid disc which is electrified byfriction, and over which the aerosol is. pulled.The basis of thermal precipitation is that when an aerosol passesbetween two coaxial tubes maintained at different temperatures,precipitation on the colder tube occurs.H. H Watson l4 describesthe use of such a precipitator, claimed to be 100% efficient, whichmay be regarded as a standard method. Coagulation and precipita-tion by sonic and supersonic waves are known to occur in certaincases.l?Andy&.- The identification and analysis of the sample collectedis necessarily specific in character and dependent upon the particularproblem in hand. Optical methods may be used. Schrenk and hiscollaborators l6 describe a microprojection method for countingimpinged dust particles which differs from the normal microscopicmethod in that the images of the dust particles are magnified to 1000diameters and projected on a ruled translucent screen. This pro-cedure permits more concentrated samples to be counted withoutthe need for secondary dilution. Identification based upon themeasurement of the optical properties, e.g., the refractive index,birefringence, and extinction angle, is described by C.R. Wi1liams.l'Petrographic work with particles as small as 5p is, however, ingeneral difficult, whilst identification of particles less than 2p isalmost impossible, and as many industrial dusts fall within thiscategory, the value of this technique-so useful in other fields-isminimised. As a result of their observations on the optical examina-tion of quartz dusts, W. D. Foster and H. H. Schrenk l8 deducedthat most particles were so small that ordinary petrographic methodswere of little use.A general scheme for the chemical examination of aerosols,l3 J .Ind. Hyg., 1936, 18, 613.Bull. Inst. Min. Met., Nov. 1036 ; H. L. Green and H. H. Watson, MedicalResearch Council, Spec. Report Series, No. 199, H.M.S.O., 1935.l5 0. Brandt and E. Hiedemann, Z'runs. Furuduy SOC., 1936, 32, 1101;E. N. da C. Andrade, ibid., p. 1111 ; R. C. Parker, ibid., p. 1115.l6 C. E. Brown, L. A. H. Baum, W. P. Tant, and H. H. Schrenk, U.S. Bur.Min., 1938, Rept. 3373.17 J . Ind. Hyg., 1937, 19, 44.l8 U.S. Bur. Min., 1938, Rept. Invest. 3368GRIFF'ITHS, GULL, AND WHALLEY. 403dependent as it must be upon the amount of sample available, itsnature, and the degree of accuracy required, cannot be laid down.Once a satisfactory sample has been obtained, any difficultiespresented by its analysis will be similar to those encountered ingeneral macro- or, more usually, micro-analysis. Colorimetric andnephelometric methods are frequently suitable.A. Heller l9 detectedthe presence of iron particles in dust by collecting a sample on a slidecoated with gelatin containing 30 yo of potassium ferricyanide andadding hydrochloric acid; the appearance of blue specks ofTurnbull's blue was a positive test. Similarly, for the detection oflead, potassium iodide was used, and after exposure to the air,contact with acetic acid vapour gave a yellow precipitate of leadiodide. The exposure of pure gelatin followed by treatment withchloroform vapour revealed the presence of tar particles by thedevelopment of a brown halo round each particle. D. N.Finkelstein 2o determined copper in aerosols by filtration of theair through a 20-cm.cotton-wool layer, ashing the filter, dissolvingthe residue in hydrochloric acid, precipitating iron by excess ofammonia, and estimating the copper nephelometrically with salicyl-aldoxime. Inorganic cations and anions were found not to interfere.The same worker 21 absorbed fumes of selenium dioxide in a mixtureof hydrochloric acid, potassium bromide, and bromine, and reducedthe solution with sodium sulphite t o yield selenium hydrosol, whichwas then determined nephelornetrically or colorimetrically. Iron,copper, and arsenic were found not to interfere, but tellurium shouldbe absent.Fog nuclei have been condensed on the surfaces of flasks containingcooling mixtures of ether, ice and salt, liquid air, or solid carbondioxide.22 The precipitated water waa analysed in 0.2-ml.portionsfor chloride, sulphate, sulphite, nitrate, nitrite, carbonate,ammonia, and hydrogen peroxide, and its p , determined by knowncolorimetric and turbidimetric methods.Since most methods used to isolate mineral dust in the lung fail todifferentiate between the dust and the mineral content of the lungtissue, or to avoid the risk of chemical and mineralogical changesoccurring, N. Sundius and A. Bygd6n 23 recommend dissolving thelung tissue in hydrogen peroxide which has only a negligible actionon ordinary dust minerals save a moderate oxidation of ferrous toferric iron. Since the action of the peroxide is to give dilute organicGesundh.-Ing., 1934, 57, 322.2o J.Appl. Chem. Russia, 1937,10, 2123.21 Ibid., 1938,11, 1033.22 E. Quitman and H. Cauer, 2. anal. Chem., 1939, 116, 81.2s J . I n d . Hyg., 1938, 20, 351404 ANALYTICAL CHEmSTRT.acids (pH 5-6) in the resulting liquid, the method cannot be usedwhen carbonates are present.The valuable work of H. V. A. Briscoe and his collaborators on theanalysis of siliceous dusts has been summarised by J. W. Matthews.24Two types of collectors for the dusts-of which the physiologicallydangerous concentration was of the order of 1 mg. /cam.-wereemployed. In the first type the air was filtered through a pad ofsolid (e.g., benzoic acid, naphthalene, anthracene) removable bysublimation, or a filter pad of porous solid removable by solution innon-aqueous media from which the dust particles were separated bycentrifuging : the latter type being the most suitable for low con-centrations of dust.“ A.R.” Salicylic acid, sieved through a 40-mesh sieve, and of mean crystal length lop, was packed on stainlesssteel gauzes 7 cm. in diameter to a thickness of 4 mm. At thebeginning of a run, penetration was appreciable, but the leakagerapidly fell to a negligible amount as the collected dust itself beganto act as a filter: for this reason the filter was unsuited to thecollection of more than a few grams of dust. The salicylic acid wasremoved by absolute alcohol.The second type, the “ labyrinth ”, was used for prolonged runsand collected 1 4 0 0 g. of sample in 1-8 weeks. It consisted of atube holding a number of copper baffle-plates on which the dust wasdeposited as the air stream was drawn through the tube.Itsefficiency was found to vary considerably with the rate of air flowand the type of dust, though this factor is unimportant as long asa representative sample is obtained. The labyrinth has theadvantages of giving a large sample which requires no furthertreatment, such as alcohol extraction, and of automaticallyfractionating the dust, i.e., the sample is graded in particle size alongthe baffled tube. A microtechnique with an accuracy of 5 0.2-0.5% was used for the chemical examination of the sample obtained,water, silica, iron, aluminium, calcium, magnesium, sodium, andpotassium being determined. In the determination of silica,platinum crucibles weighing about 2 g.and of 2-3 ml. capacity wereused; for alkali metals, platinum microbeakers of 5 ml. capacity;for other elements, glass beakers of about 5 m1. capacity. Forfiltration, porcelain filter-sticks and the Emich filtering techniquewere employed.X-Ray diffraction methods of analysis have been used, forexample, by W. 3’. Bale and W. W. Fray,25 and by H. C. Sweaney,R. Klaas, and G. L. Clark 26 for the detection of quartz in lungtissue, and the size of crystallites in metal and metal oxide smokes has24 Analyst, 1938, 63, 467.26 Radiology, 1938, 31, 299.25 J . I n d . Hyg., 1935, 17, 30GRIFFITHS, GULL, AND WHALLEY. 405been determined with X-ray and electron-diffraction diagrams andwith electron microscope ph0tographs.~75.GAS ANALYSIS.Since the last comprehensive reports on this subject were made,ldevelopments have proceeded according to analytical requirements,in three main directions.(a) Problems involving the analysis of small quantities ofmaterial have led to the perfection of micro-methods for the precisehandling of very small quantities of gas. An excellent illustrationof such a problem and its analytical solution is provided by thedetermination of minute quantities of free alkaline-earth metals inthe oxide coatings of thermionic valve filaments to which reference ismade later.( b ) The development of methods for the detection and determin-ation of small concentrations of gaseous impurities (e.g., in the atmo-sphere) has been stimulated partly by the exigencies of modern war-fare but mainly by the increasing industrial use of solvents andvolatile materials known hitherto only in the laboratory.Manysuch vapours have unexpected and dangerous effects on humanbeings at concentrations as low as 1 in lo4. Analytical methods forthis type of work often involve automatic apparatus enablingcontinuous records to be made; many are simple and specific incharacter, enabling tests to be made, as required, by unskilled hands.( c ) Several new reagents are noted, together with improvements inthe technique of using old ones. Certain physical methods havebeen developed for some constituents, and factors limiting generalaccuracy have been examined.Methods of micro-gas analysis which have undergone recentdevelopment are of two types : those in which the necessary volumemeasurements are made by drawing the sample into a calibratedcapillary tube and measuring its length in that tube, and those whichemploy the principle of the .McLeod gauge.T. Carlton Sutton2describes apparatus and technique of the former type and gives anexcellent bibliography of the subject. The sample (0-1-0.3 c.c.) isconfined by mercury and is measured dry (P,O,) in a horizontalcapillary tube. This is closed at one end by a piece of rubber tubingand screw clips, which are manipulated so as to move the sample upand down the capillary as required. The other end is bent down-wards at right angles and sealed to a short length of wider tubingwhich dips into a mercury trough and serves as a reaction vessel,Reagents are introduced through the mercury seal on loops of27 F.Krause and D. Beischer, 2. Elektrochem., 1939, 45, 117.1 Ann. Reports, 1933, 1934, J . Sci. Instr., 1938, 15, 133406 ANALYTICAL CHEMISTRY.platinum wire or on beads of porous earthenware fused to platinumwire. An ingenious steel guide prevents the reagent holders fromtouching or fouling the sides of the reaction vessel so that theapparatus keeps perfectly clean. Since minimum quantities ofreagents are used, errors due to the solubility of non-reacting com-ponents of the gas sample are reduced to vanishing point. I n thismanner, every reaction employed in macro-analysis can be utilisedwith a similar degree of accuracy. The design of measuring tubesfor vertical apparatus of this type is discussed by D.Grahame? anda similar apparatus is described by D. Gilm~ur.~ It is essential thatapparatus of this type should be easy to clean, since a little dirt onthe walls of the capillary completely upsets any attempt at accuratemeasurement.The McLeod type of micro-apparatus has been neglected for someyears, but C. H. Prescott and J. Morrison describe an apparatus ofthis kind for the rapid analysis (1 hour) of 5-25 cu. mm. with errorsnot greater than 2%. Samples of 1 cu. mm. can be analysed with anaccuracy of 5y0, and under special conditions it is claimed that thesmallest quantity of a component that can be detected is0-025 cu. mm., equivalent to the carbon monoxide in 1 sq. cm.of aunimolecular film. The observed errors appear to be due largely toadsorption and desorption of gas on the apparatus, particularly onthe powdered reagents employed. Gas samples are handled at lowpressure with Toepler pumps over mercury, and the scheme describedprovides for the determination of water, hydrogen, carbon monoxideand dioxide, oxygen, or methane, the residue being taken as nitrogen.Water and carbon dioxide are removed by conventional reagents, butthe use of a heated platinum or platinum-rhodium wire is limited tothe combustion of oxygen in excess of carbon monoxide or hydrogen,since it is attacked by excess of oxygen at temperatures above 700".The apparatus and technique were used for the oxidation withcarbon dioxide of the free metal in the oxide coatings of thermionicvalve filaments referred to previously.Further observations on theuse of platinum for combustions are made by G. Thanheiser and H.Ploum They findthat combustion of hydrogen in excess of oxygen and nitrogen leadsto slight production of oxides of nitrogen with a consequent highresult for hydrogen, but even with this disadvantage, the method isbetter than explosion or combustion over copper oxide.The detection and determination of small quantities of gaseousimpurities in the air likely to have undesirable effects on humanInd. Eng. Chem. (Anal.), 1939, 11, 351.Austral. J . Exp. Biol., 1938, 16, 208.Ind. Eng. Chem. (Anal.), 1939, 11, 230.6 ATcTL. Eisenhiittenw., 1937-1938, 11, 81.in a paper on analysis of the gases from steelGRIFFITHS, G U U , AND W€€ALLEY.407beings have received much attention recently. S. H. Wilkes andD. Matheson direct attention to some of the more commonexamples, such as oxides of nitrogen (produced in closed orpoorly ventilated places by the use of oxy-acetylene torches uponmasses of cold steel), hydrogen sulphide, chlorine, carbon monoxide,etc.I n some cases, automatic apparatus for the continuous or periodicdetermination of expected impurities in the surrounding atmospherehas been devised. Such apparatus is often connected to some formof warning device which operates when the concentration of gaseousimpurity reaches a predetermined limit. Hydrogen sulphide, said tohave ill effects when present in concentrations exceeding 1 in 30,000,8is continuously recorded by J.Bell and W. K. Hall,9 who use areversible indicator consisting of sodium nitroprusside in sodiumcarbonate + bicarbonate solution. This turns red in the presenceof hydrogen sulphide but is bleached by pure air. Another record-ing lo apparatus employs lead acetate paper combined with aphotoelectric cell. This gas has also been determined by absorptionin a solution of zinc acetate and acetic acid, the zinc sulphide beingdetermined by titration with iodine and thiosulphate.llL. B. Berger and H. H. SchrenkI2 discuss methods for thedetection and determination of carbon monoxide in air, including thepyrotannic acid method (0.01-0.2 yo), the activated iodine pcnt-oxide method (0.1-1 - O ~ o ) , methods utilising palladous chloride(2-10 parts in lo4), together with gas volumetric and thermalconductivity methods, and methods involving measurement of theheat liberated by combustion of the carbon monoxide.An accountof the U.S. Bureau of Mines’ continuous carbon monoxide recorderfor use in vehicular tunnels is also given ; this records concentrationsexceeding 1 part in a million of air. I n a colorimetric method 13 thegas is passed through a suspension of platinum on silica gel in adilute solution of ferric sulphate containing potassium ferrocyanide.A blue coloration, approximately proportional to the concentrationof carbon monoxide, is obtained. Apparatus suitable for applicationof the “ wet ” iodine pentoxide (solution in sulphuric acid containing10% of sulphur trioxide) method to concentrations exceeding 0.1 YoChem.and Ind., 1939, 58, 316.“ Methods for the Detection of Toxic Gases in Industry,” Leaflet No. 1,H.M. Stationery Office, 1937.9 Chem. and Ind., 1936, 55, 89.lo S. Roberts and G. Minors, ibid., 1934, 53, 526.l1 M. Strada and A. Macri, Ann. Chim. appl., 1939, 29, 64.l2 U.S. Bur. Mines, Tech. Paper No. 582, 1938.l3 S. M. Tschumanov and M. B. Axelrod, J . Appl. Chem. Russia, 1938, 11,1236408 ANALYTICAL CHEMISTRY.and for the haemoglobin method (0~003-0~1~0) has also beendescribed .14Carbon dioxide has been measured by changes in the light trans-mission of a solution of methyl-red l5 or by changes in the con-ductivity of a solution of barium hydroxide l 6 when gas containingsmall amounts of the dioxide is passed through it.Methods for the detection of mercury vapour in air have beenreviewed by L.R. Briggs,l' including those involving the blackeningof selenium sulphide paper and the absorption of ultra-violet light bytraces of the vapour.F. A. Paneth and J. L. Edgar l8 deal with errors in previousmethods for the determination of ozone in the atmosphere. In theirown method the ozone from not less than 500 1. is condensed on silicagel at liquid-air temperature. It is then redistilled below - 120°,when all the nitrogen dioxide in the original sample is held back (andcan be finally determined by the m-4-xylenol method); the ozonemay then be determined with potassium iodide and starch, or it maybe collected in a glass tube with quartz windows and determined bymeans of its ultra-violet absorption spectrum.The determination of iodine and bromine together in air hasreceived attention.lg Since sea air was examined, it is probable thatthese substances were present as salts or sprays.The importance of ethylene in the ripening and storage of fruit hasled to methods for its determination. R.C. Nelson 2o purifies thegas extracted from the fruit and oxidises the ethylene with standardpotassium permanganate, whereas B. E. Christensen and his co-workers 21 prefer bromination with standard bromate solution, andin this way 0.0014-06 C.C. of ethylene can be determined in a totalvolume of 3 5 4 0 C.C.Present knowledge of the toxicity of volatile solvents used inindustry is reviewed by T.McClurkin,22 and the detection andapproximate determination, together with what are regarded as safeand dangerous concentrations of most of them, are given in a paperby R. B. Vallender.23 A form of hand pump for general use insampling is described. Each stroke of the pump serves as a unitmeasure of volume, and the air being sampled is drawn through14 H. A. J. Pieters and K. Penners, Het Gas, 1938, 58, 252.15 R. J. Winzler and J. P. Baumberger, Ind. Eng. Chem. (Anal.), 1939, 11,16 A. Lassieur, Compt. rend., 1938,206,606 ; T . Krasso, Tech. Kurir, 1938,9,63.l7 J . Ind. Hyg., 1938, 20, 161.l9 E. S. Burkser and V. V. Burkser, J . Appl. Chem. Russia, 1937,10, 2153.2o Plant Physiol., 1937, 12, 1004.21 Ind.Eng. Chem. (Anal.), 1939, 11, 114.22 Chem. and Ind., 1939, 58,339.371.l8 Nature, 1938, 142, 112.23 Ibid., p. 330GRIFFITHS, GULL, AND WHALLEY. 409standard test papers or solutions. Approximate determinations arethen made by comparing stains on the papers or colorations of thesolutions with sets of standards. In this way hydrogen sulphide(1 in 150,000) is determined with lead acetate paper, hydrogencyanide (1 in 100,000) by the production of a blue stain on paperimpregnated with benzidine and copper acetates or by the change incolour of paper containing silver nitrate and Congo-red (productionof nitric acid), arsine (1 in 250,000) with mercuric chloride paper,sulphur dioxide (1 in 250,000) with paper impregnated with starch,potassium iodide and iodate, and glycerol, carbonyl chloride (1 inlo6) by the production of a yellow stain on paper containing di-phenylamine-p-dimethylaminobenzaldehyde.Oxides of nitrogen(1 in 100,000) are determined by the Griess-Ilosvay test understandard conditions, chlorine (1 in lo6) by the production of a yellowcolour in an acid solution of o-tolidine, carbon disulphide by theorange-brown colour produced in a solution of diethylamine andcopper acetate, aniline (1 in 100,000) by absorption in acid solutionfollowed by the addition of a few drops of bleaching powder solutionand then an ammoniacal solution of phenol-this produces a bluecolour suitable for colorimetric comparison. Benzene is determinedby absorption in concentrated sulphuric acid containing a littleformalin, and the reddish-brown colour produced is compared with astandard solution of sodium nitroprusside.The determination ofcarbon monoxide in this scheme is not so satisfactory, but someresults were obtained with palladium chloride paper. Chlorinatedhydrocarbons in general use are detected by a ‘‘ halide lamp.” Thetraces of vapour are drawn into the flame of a small, alcohol-fedblast lamp which impinges on a small copper screw where they aredecomposed with the formation of small quantities of copper halides.These impart green colorations to the flame, and it is understood 24that the range of coloration from a faint greenish tinge to brightgreen covers concentrations of the chlorinated hydrocarbons ingeneral use ranging from 1 in 25,000 to 1 in 10,000.It is apparentthat, although these tests are of great use in indicating dangerousconcentrations of the various vapours, they are not necessarilyspecific ; for instance, the test for benzene vapour is given even morereadily by toluene and also to a certain extent by coal-tar naphthaand other hydrocarbon vapours.Industrial developments have led to a search for new reagents.One for the absorption of hydrogen from a mixture containingsaturated hydrocarbons and nitrogen 25 consists of an aqueoussuspension of dinitroresorcinol and kieselguhr covered with nickel24 Private communication.25 H. N. Bannerjea, L. H. Bhatt, and R. B. Forster, Analyst, 1939,64,77410 ANALYTICAL CHEMISTRY.catalyst freshly prepared by reduction of nickel carbonate ; thecatalyst is not poisoned by traces of carbon monoxide.The absorption of gaseous olefins and hydrocarbons by sulphuricacid has been examined fully,26 and apparatus and techniquedevised to make the determination accurate for low and high con-centrations. For the production of hydrogen from commercialhydrocarbon mixtures containing hydrogen sulphide, nitrogen, andthe oxides of carbon by heating with steam over a catalyst, it isnecessary to know the general formula C,H, of the material involved ;a scheme for doing this, involving a combination of fractional com-bustion and absorption reagents, has been devised.27 For theanalysis of gases consisting mainly of hydrogen but containinghydrocarbons and some carbon monoxide, A.G. Fleiger 28 removesthe hydrogen by diffusion through a palladium tube at 300".Higher hydrocarbons are previously frozen out at - 180", and afterremoval of the hydrogen the residual gas is examined for methaneand carbon monoxide by combustion over heated copper oxide. Afurther scheme for the analysis of light hydrocarbon mixtures hasbeen prepared by E. C. Ward ; 29 150 C.C. of the sample are liquefied,and fractionally distilled at a pressure of 1 mm. Hg. Fractionationis controlled with liquid air, and an accuracy of 0-02-0-1~, isclaimed. The use of heated calcium as an absorbent has beenexamined; 30 absorption of nitrogen begins at 370" and is quantita-tive a t 385". Hydrogen is absorbed best at 360" but carbon dioxideis only absorbed weakly a t 730-930".Methane is stronglyabsorbed at 530-650", and at 700" a 1 : 1 mixture of nitrogen andmethane gets richer in nitrogen. The absorption of oxygen andcarbon dioxide by calcium nitride is also described.The use of alkaline pyrogallol solutions for the absorption ofoxygen has been condemned by several workers, but A. V. Mazov 31finds that it is quite satisfactory until it has absorbed 20 C.C. ofoxygen per g.-mol., after which it should be replaced. The use ofthis reagent is made more rapid by spraying the absorbent throughthe gas, and the same technique can be applied with advantage toother reagents hitherto regarded as too slow in their action.32 Thepreparation and use of neutral or acid solutions of chromous chloridehas been examined and recommended 33 as an absorbent for oxygen,26 M.P . Matuszak, Ind. Eng. Chem. (Anal.), 1938, 10, 354.27 G. Pastonesi, Chim. e E'Ind., 1939, 21, 4.28 lnd. Eng. Chem. (AnaZ.), 1938, 10, 544.30 P. de Cori, Congr. int. Quim. pura appl., 1934, 9, vi, 225.31 Zavod. Lab., 1938, 7 , 359.32 C. M. Blair and J. H. Purse, Ind. Eng. Chem. (Anal.), 1939, 11, 166.33 W. J. Gooderham, J . SOC. Chem. Ind., 1938, 57, 388; J. R. Branham,29 Ibid., p . 169.J . Res. Nat. Bur. Stand., 1938, 21, 45GRIFFITRS, GULL, AND WHALLEY. 41 1and a further reagent for this gas is indicated by J. Boeseken’sobservation 34 that a solution of thiocarbamide dioxide in aqueousammonia is an excellent absorbent for it.Carbon dioxide at very low concentrations is absorbed by anaqueous solution of dipiperidyl~.~~ The absorbent can be used attemperatures up to 80°, and when spent it may be prepared for useafresh by distilling it at 140°, all the carbon dioxide then beingdriven off.The absorption of carbon monoxide by ammoniacal solutions ofcopper carbonate 36 and of copper chromate has been examined indetail by K.Leschewski 37 and his co-workers, and G. Venturoli 38has devised a method based on the oxidation to carbon dioxide byN/lO-potassium permanganate solution.Further work on the absorption of oxides of nitrogen by alkalinesolutions is reported.39 It was already well known that the degreeof absorption varied with the rate of gas flow, and the generalkinetics of reactions involved have been further investigated.Ithas also been shown that traces of sulphur dioxide can be measuredin the presence of oxides of nitrogen by absorption in neutralhydrogen peroxide solution, and the sulphuric acid formed deter-mined by a precipitation method with ben~idine.~~Of the developments in physical methods of gas analysis, two maybe mentioned. The difficulties encountered in the quantitativespectroscopic analysis of mixtures of gases and the methods adoptedto overcome them are discussed by R. A. Wolfe and 0. S.Duffendack,4l including the “ cleaning-up ” effect of the discharge ingases which varies with the type of discharge and the electrodevoltage. The electrodeless or glow discharge appears to be best foranalytical work, although the intensities of the lines of some elementsvary with the amounts of other gases present. This difficulty isparticularly marked where an inert gas is present.Interferences ofthis type are overcome by using helium in excess as a carrier of thedischarge and a small addition of argon as an internal control. Themethod has been used to determine hydrogen, oxygen, nitrogen, andcarbon monoxide and dioxide.The general aspects of thermal separation processes in gases have34 Proc. K. Akad. Wetensch. Amsterdam, 1938, 41, 70.35 R. B. Evans and D. W. Parkes, J . SOC. Chem. Ind., 1938, 57, 302.36 2. anorg. Chem., 1938, 235, 369.37 Ibid., 1939, 240, 322.38 Boll. Chim. farm., 1939, 78, 1.39 V. I. Atroschtschenko, Ukrain. Chem. J., 1937, 12, 442 ; J .Appl. Chem.4Q G. V. Rakovski, Zavod. Lab., 1938, 7 , 174.41 Proc. 6th Cod. Spectros., 1938, 66.Russsia, 1939,12, 167412 ANALYTICAL CHEMISTRY.been discussed by A. Eucken42 and W. van der Grinten,43 and themethod has been applied by K. Clusius and G. Dickel 4 with a viewto separating gaseous isotopes. The apparatus consists of a verticalhot surface opposite to a cold one. Thermal diffusion and convec-tion result in the heavier component of the mixture becomingrelatively more concentrated at the bottom of the apparatus. A1 : 3 mixture of bromine and helium was completely separated bythis process, and good results were also obtained with a 2 : 3 mixtureof carbon dioxide and hydrogen and with air. Normal neon andalso hydrogen chloride were partly separated into their respectiveisotopes.The thermal conductivity method has been further examined inrelation to the analysis of binary mixtures, and errors of less than0.1% are claimed in the cases of N, + H, and CO + H,.45 Thetechnique consists in using a conductivity wire as one arm of aWheatstone bridge and measuring the voltage necessary to keep thetemperature of the wire constant.The major developments in technique and apparatus have alreadybeen dealt with, but improvements in the familiar constant-volumeapparatus and in the technique of coal-gas analysis effected by W.J.Gooderham 46 should be noted ; further, attention is directed to thedisplacement of nitrogen and other inert gases from, and theirdissolution in, certain reagents during analy~es.~’ Errors arisingfrom this source have been shown to depend on the solubility of theinert gas in the reagent, the rate of absorption of other componentsof the gas phase, and the form of the apparatus.A 1” layer of oildoes not appreciably affect the passage of oxygen or nitrogenthrough the open surface of the liquid phase.6. CHROMATOGRAPHIC ANALYSIS.whenworking on the separation of plant pigments, and it has undergoneconsiderable development recently as an analytical tool.A solution of tlie material in some suitable solvent is allowed tofilter slowly through a very evenly packed column of a suitableadsorbing material such as alumina, whereupon the various solutesare preferentially adsorbed at different levels in the column.Afterpassage of the solution, the so-called chromatogram is developed byThis interesting method was introduced by Tswett in 190642 Osterr. Chem.-Ztg., 1938, 41, 137.43 Naturwiss., 1939, 27, 317.45 F. Ishikawa and K. Hijikata, Bull. Inst. Phys. Chem. Res. Tokyo, 1939,P6 LOC. cit. (ref. 33).47 J. R. Branham and M. Sucher, J. Res. Nat. Bur. Stand., 1938,21, 63.1 Ber. deut. bot. Ges., 1906, 24, 316.44 Ibid., 1938, 26, 546.18, 401GRIFFITHS, GULL, AND WHALLEY. 413washing the column many times with clean solvent. Successiveelutriations and readsorptions occur resulting in the separation of theadsorbed materials into sharply defined zones down the column.The various adsorbates may then be separated mechanically or theymay be elutriated separately with different solvents.The choice ofsolvents and general operation of the method have been discussed byH. G. Cassidy.2 Water, chloroform, ether, benzene, petroleum, andcarbon disulphide are suitable solvents for the original mixture, andthe same solvent with various small additions usually serves for thesubsequent elutriation of the various zones. Thus, chromatogramsfrom benzene or petroleum solution can usually be elutriated quitereadily with the same solvent containing a little alcohol, whereasthose adsorbed from aqueous solution can often be broken up byaqueous solutions of salts adjusted to a definite pH. The adsorbingmaterial most used is alumina, and its preparation for this purposehas been studied by H.N. Holmes, E. Delfs, and H. G. Ca~sidy.~Other adsorbents are : sugar for chlorophyll,* calcium hydroxide forcarotenoids and vitamin-A ,53 calcium carbonate for ~anthophylls,~~and magnesium oxide for carotenes and other plant pigment^.^Application of a potential to the adsorbing column is said toproduce a more rapid and effective separation, and this combinationof chromatographic and cataphoretic methods extends the utilityand application of both.1°More recently a micro-method for the separation of green-leafpigments from carbon disulphide solution has been devised in whichthe adsorbing material consists of a piece of white blotting paper orfilter-paper clamped between two glass plates, the upper one havinga hole in the centre. The test solution, followed by more solvent, ispoured through this hole and the component pigments pass outwardsin the paper in concentric rings, which may be examined by chemicalor physical methods.l1R. T. Arnold l2 has examined the relation of dipoles to chromato-graphic adsorption, and suggests that among isomeric moleculescontaining the same number and kind of functional groups, thosewith the larger dipole moment are more strongly adsorbed on polara J . Chem. Educ., 1939, 10, 88. J . Biol. Chem., 1933, 99, 417.I. M. Heilbron and co-workers, Biochem. J., 1934, 28, 1702.P. Karrer and F. M. Strong, Helv. Chim. Acta, 1936, 19, 25.H. Willstaedt and T. K. With, 2. physiol. Chem., 1938, 253, 40.7 L. Zechmeister and L. von Cholnoky, Annalen, 1934, 509, 269.A. Winterstein and G.Stein, 2. physiol. Chem., 1933, 220, 247.H. H. Strain, Science, 1934, 325; J . Biol. Chem., 1934, 105, 523.lo H. H. Strain, J . Amer. Chem. SOC., 1939, 01, 1292.l1 W. G. Brown, Nature, 1939, 143, 377.12 J . Amer. Chem. SOC., 1939, 61, 1611414 ANALYTICAL CHEMISTRY.media such as alumina. Where no permanent dipole exists, thosecomponents with highest polarisability should be the most stronglyadsorbed. Basicity and acidity of the substances are unimportant.This view is supported to a certain extent by the observations of W.Freundlich and W. Heller l3 on the adsorption of cis- and trans-azobenzene on various adsorbents from Werent solvents.Hitherto, the method has found most application in the analysis ofplant and animal products. As a qualitative method it can be verysensitive, as in the analysis of blood serum for pro-vitamin A andother carotenoids.14, l5 After hydrolysis of the serum with potassiumhydroxide the petroleum extract is passed through a column ofalumina and 0.5 pg.of a- or p-carotene or of cryptoxanthene may bedetected in the resultant chromatogram as definite rings, and thesemay be removed in sequence with definite mixtures of light petroleumand benzene.15 Carotenoids in milk have been determined in asimilar way, alumina or, less effectively, calcium hydroxide beingused as adsorbent , followed by elutriation with benzene-petroleumor benzene-me t h yl alcohol.With a view to separating aliphatic amines and the products ofprotein hydrolysis by these methods, the adsorption isotherms of themore important of such products and of ammonia, ammonium salts,mono- and di-amines have been studied.16 A preparation of aluminawas found to give the best results.It appears that ammonia isadsorbed better at low than at higli p,, and that adsorption ofammonium salts is but little affected by the valency of the anion.The adsorption of the hydrochlorides of primary, secondary, andtertiary amines increases with molecular weight, and is not influencedby branching of the carbon chain. The adsorbability of homologousamino-monocarboxylic acids decreases with increasing molecularweight, and among the dicarboxylic acids lysine dihydrochloride,tyrosine and 3 : 5-di-iodotyrosine are not adsorbed at all and can,therefore, be separated from all other products.Adsorption ofheterocyclic amino-acids decreases in the following order : histidine> tryptophan > oxyproline > proline. Considerable purificationof callicrein 1 7 from human urine is achieved by dialysis againstrunning water, followed by adsorption on alumina and subsequentelution with aqueous N-sodium hydrogen carbonate.Chitinase can be separated from emulsin and may then itself bel3 J . Arner. Chem. SOC., 1939, 61, 2228.l4 A. G. van Veen and J. C . Lanzing, Proc. K . Akad. Wetensch. Amsterdam,15 J. C. Lanzing, Med. Dienst. Volks. Ned.-Indiie, 1938, 27, 213.l6 A. Lottermoser and K. Edelmann, Kolloid-Z., 1938, 83, 262.1 7 E. Werle and A. Marcus, Biochem. Z . , 1938, 296, 275.1937, 40, 779GRIBFITHS, GULL, AND WHALLEY.415separated into two components by further chromatographic treat-ment.18 Separation of the opium alkaloids morphine, codeine,narcotine, and papaverine has been accomplished on a specialdecolorising earth from benzene s01ution.l~In inorganic analysis the method has been applied to the detectionof traces of impurities.20 Cations are adsorbed on alumina fromneutral aqueous solution in the following order : Sb***, Bi***, Cr'**,Fe"', UO,", Pb", Hg", Cue', Ag**, Zn**, CO.', Cd'., Ni", Mn". Thisorder is unaffected by any combination of cations or anions. Insome parts of the series the separation is very narrow, but thedistinction between the bands due to two ions can be made moreobvious by the addition of an element lying between them. Thehydrogen ion is adsorbed like a metal.The above order is quitedifferent when adsorption takes place from an aqueous ammoniacalor alkaline tartrate solution. Anions may be separated anddetected21 by adsorption on a column of alumina which has beentreated previously with dilute nitric acid. The order is OH', PO4"',F', CrO," and Fe(CN),"", SO4", Cr,O," and Fe(CN)6'", Cl', NO,',MnO,', ClO,', S".The ions Na', K , Cl', and Br' are adsorbed by pure kaolin and maybe separated in this way from Mg", Ca**, and whilst certainhydrogen-ion saturated base-exchange substances such as thesulphonic acid permutits 23 may be used to separate Na' from Cl',SO,", NO,', and HPO," ; Cu" from NO,' ; Cr"' from SO," ; Fe"'from C1' ; V"" from SO,'' ; Fe"' from alum solutions, and Fee** andMg" from SO," + PO,"' + H,S04.The passage of a mixture offerric sulphate, cupric chloride and hydrochloric acid through asodium permutit completely removes Fe"' and Cu" and leaves thefiltrate neutral. Treatment of the permutit with N-nitric acid thenyields a solution free from chloride ion. The possible advantages tobe gained by application of these separations to ordinary analyticalprocesses are apparent, for example, in the determination of sulphatein the presence of ions that interfere with the precipitation bybarium chloride or in the removal of hydrogen ions and heavymetals before a Mohr titration of chloride. Other workers 245 25I R L. Zeichmeister and G. Toth, Naturwiss., 1939, 27, 367.l9 G.R. Levi and 3'. Castelli, Gazzetta, 1938, 68, 459.2o G. M. Schwab and K. Jockers, Naturwiss., 1937, 25, 44.21 G. M. Schwab and B. Dattler, Angew. Chem., 1937, 50, 691.22 V. I. Nikolaev and E. I. Rudenko, Compt. rend. Acad. Sci. U.R.S.S., 1938,23 I. 0. Samuelson, 2. anal. Chem., 1939, 116, 328.24 S. S. Bhatnagar, A. N. Kapur, and M. S. Bhatnagar, J. Indian Chem. SOC.,2 5 G. Broughton and Y. N. Lee, J . Physical Chem., 1939, 43, 737.21, 237.1939, 16, 249416 ANALYTICAL CHEMISTRY.have examined the adsorptive properties of synthetic resins of theaniline- and m-phenylenediamine-formaldehyde types towardsorganic and inorganic anions.A considerable volume of work on adsorption phenomena bearingindirectly on this subject has been carried out but is outside the scopeof this report.A review of work on chromatographic analysis priorto 1936 has been given by A. H. Cook.267. SULPHIDE PRECIPITATION.Though systems of analysis without the use of hydrogen sulphidehave been devised,l it is not likely that a reagent which precipitatescompletely or in large part 22 elements from acid solution alone willreadily be replaced. In all, 33 elements form insoluble sulphides,and the means of separating qualitatively and quantitatively some ofthe millions of possible combinations continue to receive attention.Recent work increasingly reveals that it is one thing to defineprecisely the conditions for obtaining a sulphide precipitate, quanti-tatively and in manageable form, from a solution of MA, where M isthe metal ion and A the anion, and quite another when the cationsN, 0, P, Q, .. . and the anions, By C, D, E, . . . arealso present,together with, possibly, residues of organic reagents, colloidalmaterial, and, not unusually, small quantities of elements which onlyin theory have been completely removed by preceding analyticalprocesses.In devising an analytical separation based upon the precipitationof sulphides three factors have, broadly, to be considered. The firstis the condition of the solution from which precipitation is made :its temperature, concentration, pE, the presence of other anions andcations, etc. ; the second is the mechanism of precipitation, underwhich heading the possibilities of co-precipitation and post-precipita-tion have to be included; and thirdly, the physical state of theprecipitate ultimately obtained.The well-known separation in acid solution (of approximately0 .3 ~ ) of copper, germanium, arsenic, selenium, molybdenum,ruthenium, rhodium, palladium, silver, cadmium, tin, antimony,tellurium, rhenium, osmium, iridium, platinum, gold, mercury, lead,bismuth, and polonium from vanadium, iron, cobalt, nickel, zinc,indium, thallium, gallium, tungsten, manganese, and uranium isillustrative of the first factor, as are the separations of arsenic fromantimony, and copper or bismuth from cadmium by acidity adjust-26 Chem. and I n d . , 1936, 55, 724.1 J. Cornog, J. Chem. Educ., 1938,15,420; J. T. Dobbins, E. C. Markham,and H.L. Edwards, ibicl., 1939, 16, 94; C. J. Brockman, ibid., p. 133GRIFFITHS, GULL, AND WHALLEY. 41 7ment. G. E. F. Lundell and J. I. Hoffman give a useful survey ofthe conditions of sulphide precipitation. A recent example is theseparation of cadmium from zinc by the precipitation of cadmiumsulphide quantitatively in an easily filtrable form from a solutioncontaining 15 ml. of concentrated sulphuric acid per 100 ml. in theabsence of chloride^.^ H. Kato has examined in some detail theseparation of zinc from nickel and from cobalt. He states that sincezinc may be precipitated completely with hydrogen sulphide if thefinal pH exceeds 1, irreFpective of the initial p , of the solution, and asnickel sulphide is completely precipitated if the initial pH exceeds 3,the separation of zinc from nickel is obtained in a solution of pH 2.4,buffered to neutralise the strong acid liberated.Similarly, for theseparation of zinc from cobalt a separation p , of 2.3 exists. Thedevice of complex formation to prevent precipitation by hydrogensulphide is well known, and a recent application is reported by N.L ~ v g r e n . ~ Antimony may be detected in the presence of excess ofquadrivalent tin by precipitation with hydrogen sulphide in thepresence of phosphoric acid and concentrated hydrochloric acid, thetin remaining in solution as a complex with the phosphoric acid.The systematic investigation of precipitation processes by Kolthoffand his co-workers has included work upon sulphide precipitation.It has been shown that ferrous sulphide is post-precipitated withcopper sulphide from acid solutions, slowly at ordinary temperaturesand rapidly at 70-95".The amount of iron sulphide so precipitatedincreases with the concentrations of iron and of copper sulphide, andwith the p,. The promoting effect of the copper sulphide was foundto decrease on ageing at 90". I. M. Kolthoff and F. S. Griffith alsoobserved that the post-precipitation of zinc sulphide with bismuthsulphide can be avoided if the hydrochloric acid concentration is notless than 0 . 3 ~ after precipitation, and the solution is filtered within afew minutes. The rate of post-precipitation with bismuth sulphide,as with copper sulphide, rises with the time of contact and itsefficiency increases with short periods of ageing, falling after longerperiods.The addition of sodium chloride to the solution inhibitedthe post-precipitation of zinc sulphide. The zinc sulphide can beextracted from mixtures with the sulphides of bismuth and copperby 2~-hydrochloric acid, but when it is post-precipitated with1938, p. 49 et seq.2 " Outlines of Methods of Chemical Analysis," Chapman and Hall Ltd.,3 C. Zollner, Z. anal. Chem., 1938, 114, 8.Sci. Rep. TGhoku Imp. Univ., 1938, 26, 714, 733.Svenslc Kem. Tidskr., 1939, 51, 2 .6 I. M. Kolthoff and F. S. Griffith, J . Amer. Chem. SOC., 1938, 60,7 J . Physical Chern., 1938, 42, 531.REP.-VOL. XXXVI. 02036418 ANALYTICAL CHEMISTRY.mercuric sulphide, mixed crystals are formed from which the zinc isnot removed by this acid treatment. The same workers have in-vestigated the post-precipitation processes of nickel sulphide with thesulphides of copper, bivalent mercury, and zinc, and their variationswith acidity and temperature. B. Sagortschev examined certainprecipitation processes in which bismuth and lead ions take part bymeans of the corresponding radioactive isotopes thorium-B andthorium-0, and found that bismuth sulphide is completely precipi-tated even in 1.5~-hydrochloric acid. In Kato's separation of zincfrom nickel referred to above, precautions must be taken to preventthe induced precipitation of nickel sulphide, which catalyses its ownprecipitation. loThe physical state of a sulphide precipitate is frequently ofimportance : a coarsely crystalline precipitate, for example, facili-tates filtration, whilst a colloidal sulphide may be desirable forcolorimetric estimation. E. A. Ostroumovll has found that byadding 30 ml. of neutral 20% aqueous pyridine to 75 ml. of hotcobalt or nickel salt solution from which the sulphide is to beprecipitated, a coarsely crystalline precipitate is obtained. He hasalso observed l2 that the presence of 2 g. of hexamethylenetetraminein 100 ml. of slightly acid solution of a manganous salt ensures thatthe manganous sulphide subsequently precipitated is crystalline.The colorimetric determination of bismuth 13 as sulphide is aided byusing gum arabic or polyvinyl alcohol as a stabiliser. Cadmium hasbeen determined colorimetrically 14 in a solution by making italkaline with ammonia, adding potassium cyanide, ammoniumsulphate, and 1% gelatin solution, and adding the mixture to asaturated solution of hydrogen sulphide. The effect of varying theamount of gelatin used in the colorimetric determination of arsenic(0-1-1 mg.) as sulphide has been examined.15The determination of an element by weighing its sulphide is notusual, save in the case of arsenic, though this method may beemployed for molybdenum, mercury, and bismuth sulphides driedbelow 110" ; for antimonous sulphide dried at 280-300" in an inertatmosphere; and for the sulphides of copper, zinc, mercury, andbismuth by ignition under a layer of sulphur in an atmosphere ofJ . Physical Chem., 1938, 42, 541.2. anal. Chem., 1939, 116, 21.lo I. M. Kolthoff and F . S. G r a t h , loc. cit., ref. (8).l1 Zavod. Lab., 1938, 7 , 20.l2 Ibid., p. 1233.l3 T. Yamamoto, Bull. Inst. Phys. Chem. Res. Tokyo, 1937, 16, 1312.l4 R. Juze and R. Langheim, 2. anal. Chem., 1937,110, 262.l5 F. Gaudy and M . P. Antola. Anal. Assoc. Quim. Argentina, 1937, 25,76GRIFFITHS, GULL, AND -ALLEY. 419hydrogen. A recent addition t,o this series is lead, as determined by0. Brunck.16 The sample is dissolved in 10 ml. of nitric acid (d 1-18>,heated to expel nitric acid, diluted to 150-200 ml., and saturatedwith hydrogen sulphide. After Q hour the crystalline precipitate iscollected on a weighed sintered-glass crucible, washed wit4 coldwater, and dried at 110-120". If the zinc concentration is lessthan 0.2 g./100 ml. no precipitation of zinc occurs, nor are other ionsadsorbed on the precipitate.J. G. A. GRIFFITHS.H. C. GULL.H. K. WHALLEY.l6 2. anal. Chem., 1938,113, 385

ISSN:0365-6217    

DOI:10.1039/AR9393600388

出版商:RSC    

年代:1939

数据来源: RSC

摘要:

INDEX OF AUTHORS’ NAMES.ABBASY, M. A., 338.Abelson, P., 11, 12.Aborn, R. H., 396.Abraham, E. P., 220, 223.Abramson, E., 339.Achenbach, H., 123.Ackermann, 38.Adams, F. H., 194.Adams, R., 236, 237, 238, 239, 243,247, 256, 257, 284.Addicoat, F. T., 367.Adelson, D. E., 304.Adler, F., 17.Aguzzi, A., 124.Ahmad, B., 338.Akin, R. B., 290.Albrecht, G., 179.Albrecht, O., 250.Alder, K., 64, 292, 311.Aldersley, J. B., 309.Alderson, W. L., 310.Alexander, A. E., 105.Allen, C., 243.Alling, H. L., 396.Allison, S., 155.Almquist, H. J., 283, 348.Alphen, J. van, 208.Alsop, W. G., 236.Alvazez, L. W., 9, 18, 24.Amaldi, E., 27.Amaldi, F., 8.Amlong, H. U., 365.Andersag, H., 325, 344.Anderson, C. ‘C., 259.Anderson, E. L., 314, 401.Anderson, H.L., 15.Anderson, J. S., 149.Anderson, R. J., 278.Andrade, E. N. da C., 402.AndrBe, M., 264.Andrews, D. H., 155.Andrich, K., 231.Angermann, L., 241.Ansbacher, S., 348.Anspach, H., 174.Antola, M. P., 418.Applebey, M. P., 135.Aradine, P. W., 20.Arcus, C. L., 193, 251.Arends, B., 56.Arminio, J., 339.Arndt, F., 211, 306.Arnold, L. B., 84.Arnold, R. T., 413.Arnow, L. E., 351.Arntzen, C. E., 231.Asahina, Y., 316.Ashley, N., 386.Ashton, R., 222, 229.Ashworth, F., 235.Ashworth, M. R. F., 321.Astbury, W. T., 351.Aten, A. H. W., jun., 13.Atkin, L., 371, 372.Atkinson, R. G., 251.Atroschtschenko, V. I., 411.Audrieth, L. F., 140, 241.Austacher, S., 283.Auwers, K. von, 253.Avens, A. W., 134.Averill, F.J., 271, 272.Axelrod, M. B., 407.Ayers, G. W., 196.Babaeva, A. V., 133.Bacharach, A. L., 348.Bacher, R. F., 25.Bachmann, W. E., 294, 302, 307,Backendoe, K. H., 311.Backhaus, T., 318.Badger, R. M., 175, 241.Baer, E., 239, 360.Bahrs, S., 162.Bailey, C. H., 374, 375.Bailey, R. W., 167.Bain, (Miss) A. M., 243.Bain, E. C., 396.Baker, A. Z., 341.Baker, J. W., 85.Baker, W., 319.Baker, W. O., 163.Bakker, C. J., 13.Bakunin, (Signa.) M., 211.Baldinger, L. H., 221.Baldwin, E., 355, 356.Bale, W. F., 349, 404.Balfe, M. P., 193.Ball, E., 354.Banerji, G. G., 342.42 422 INDEX OF AUTHORS' NAMES.Bang, O., 357.Banga, I., 339, 340.Bannerjea, H. N., 409.Bantle, W., 160.Baranowski, T., 353, 359.Barclay, I.M., 44, 89.Bardhan, J. C., 288.Barger, G., 327, 328, 331.Barker, E. F., 177, 241.Barker, R. L., 290.Barker, S. B., 358.Barnes, E. C., 401.Barnes, S. W., 20.Barrett, J. W., 302.Barrow, F., 251.Barschall, H. H., 18.Bartlett, P. D., 195, 196.'Bartolome, E., 159.Basset, J., 152.Bassett, H., 131.Bates, J. R., 68, 71.Battaglino, F., 124.Bauer, E., 152.Bauer, S. H., 165, 175.Bauer, W., 219.Bauer, W. H., 232.Baughan, E. C., 45.Baum, L. A. H., 402.Baumann, C. A., 336.Baumberger, J. P., 408.Bavley, A., 195.Bawden, F. C., 353.Bawn, C. E. H., 63.Beach, J. Y., 165.Beach, N. M., 379.Beaven, G. H., 378.Beck, G,, 10, 14, 126.Behagel, O., 207.Beischer, D., 405.Beisswenger, O., 247.Bell, D. J., 355.Bell, F., 193.Bell, J., 157, 407.Bell, R.P., 44, 84, 88, 89, 92, 93, 203,Benedict, H. C., 393.Benford, G. A., 63, 85.Bennison, E. W., 379.Benrath, A., 132, 133.Berchet, G. J., 231.Berger, L. B., 407.Bergmann, E., 290, 293.Bergmann, F., 293.Bergmann, M., 351, 352.Bergstrom, F. W., 138, 139, 140,Berisso, B., 390.Bernd, J. D., 37, 179, 185.Bernstein, H. I., 196.Bernstein, S., 103.Bertram, J., 287.Bethe, H. A., 22, 25, 30, 42.Bever, A. K. van, 169.214.320.Bhagavantam, S., 155.Bhatnagar, M. S., 415.Bhatnagar, S. S., 415.Bhatt, L. H., 409.Biale, J. B., 363.Bickford, F. A., 146.Bigelow, L. A., 116.Bigwood, E. J., 339.Bijvoet, J. M., 160, 174.Bikerman, J. J., 104.Biltz, W., 119, 121, 122.Bindseil, A. W., 291.Binkley, S.B., 348.Birch, T. W., 340, 341.Birtles, R. H., 218.Bisbee, R. F., 339.Bishop, L. R., 371.Blackman, M., 154, 155.Blacktin, S., 402.Blair, C. M., 410.Blanchard, E., 159.Blandon, E. E., 84, 85.Blanke, E., 301.Blanksma, J. J., 202, 233, 356.Block, L. P., 117.Blodgett, F. M., 103, 105, 107, 108.Bloodeld, G. F., 236.Bocciarelli, D., 27.Bockemiiller, W., 226.Bodlaender, 129.Boeseken, J., 411.Bogert, M. T., 288, 290, 304.Bohme, H., 314.Bohr, N., 11, 18.Boje, O., 357.Bolland, J. L., 77.Bollman, J. J., 357.Bollman, J. L., 355.Bommer, H., 125, 127.Bonner, D., 367.Bonner, D. M., 368.Bonner, J., 366, 367, 368, 369.Booher, L. E., 339.Booth, E. T., 10, 18.Booth, H. S., 117, 118.Borocco, A., 153.Borsche, W., 298.Bose, P.K., 316.Bousset, R., 252.Bowen, D. M., 348.Bowen, E. J., 84, 90.Boyd, E., 94.Boyd, K., 345.Boyland, E., 350.Bozarth, A. R., 117.Bozicevic, K., 323.BradGeld, A. E., 302.Bradsher, C. K., 294.Brager, A., 166.Bragg, W. L., 185.Brand, K., 281.Brandsma, W. F., 84.Brandt, O., 402INDEX OF AUTHORS’ NAMES. 423Branham, J. R., 410, 412.Braaseur, H., 173, 174.Braun, J. von, 217.Braun, R., 295.Braune, H., 166.Bray, W. E., 348.Breckenridge, J. G., 247.Bredhe, H. L., 156.Breit, G., 28, 29.Breitenbach, J. W., 69, 78, 80.Brenschede, W., 120.Breslow, D. S., 210, 211.Bressler, 95.Bretscher, E., 11, 12.Bretschneider, O., 116.Brickwedde, F. G., 27.Briggs, L. R., 408.Bright, R. D., 192.Brindley, G.W., 155.Briscoe, H. V. A., 99.Brockman, C. J., 416.Brockmann, H., 281, 282.Brockway, L. O., 166, 175.Broderson, H. J., 146, 147.Bromel, H., 360.Bronsted, J. N., 89.Brookman, E. F., 80.Brostram, K. J., 18.Broughton, G., 415.Brouwer, L. G., 221.Brown, C. E., 395, 400, 401, 402.Brown, F. E., 28.Brown, H., 25.Brown, H. C., 232, 233.Brown, W. G., 413.Browne, A. W., 124, 137.Bruce, J. H., 162.Bruch-Willstiitter, M., 152.Brukl, A., 126.Brunck, O., 419.Brunner, M., 68.Bryant, W. M. D., 392, 393.Buchanan, C., 237.Buckley, T. A., 317.Buehler, C. A., 393.Buffington, R. M., 45.Bumbalo, T. S., 345.Bunina, V. I., 310.BUM, C. W., 178.Burckhardt, E., 332.Burger, A., 302.Burkhardt, G. N., 235, 236, 309,Burkser, E.S., 408.Burkser, V. V., 408.Burnett, R. le G., 84, 92.Burrows, G. J., 246.Burwell, J. J., 165.Buston, H. W., 373.Butenandt, A., 307.Butler, J. A. V., 35, 43, 44, 89.Butler, R. E., 343.Butt, H. IL., 348.310.Butz, L. W., 294.BygdBn, A., 403.Cadenbach, G., 116, 144, 145.Cady, W. G., 136.Cairns, T. L., 243, 257.Calam, C. T., 386.Calcott, W. S., 303.Caldwell, C. C., 184.Caldwell, M. L., 376, 377.Calfee, J. D., 116.Callison, E. C., 339.Callow, R. K., 216.Calvin, M., 47.Campbell, N., 394.Campbell, W. P., 348.Carothers, W. H., 77, 231.Carpenter, L. G., 154.Carrington, H. C., 276.Carter, C. W., 341.Carter, G. P., 336.Carter, S. R., 272.Cassidy, H. G., 413.Castelli, F., 415.Cauer, H., 403.Centnerszwer, M., 140.Cerkovnikov, E., 321, 322, 324.CesAro, G., 391.Chalmers, T.A., 21.Chamot, E. M., 389, 396.Chance, M. R. A., 348.Chang, T. S., 88, 161.Chapin, W. H., 119.Charlesby, A., 179.Chatt, J., 246, 247.Chattaway, F. D., 202.Cheney, L. C., 348.Cherkov, S. K., 134.Cherry, I. S., 358.Chibnall, A. C., 350.Chick, H., 344.Cholnoky, L. von, 413.Cholodni, N. G., 369.Chou, L. H., 243.Christensen, B. E., 408.Christian, W., 343, 354, 360.Christy, R. F., 30.Chuang, C. K., 288, 298, 304.Claisen, L., 205, 206.Clark, C., 157.Clark, E. P., 284.Clark, G. L., 103, 404.Clark, (Miss) H. B., 201.Clark, R. E. D., 250.Clark, R. L., 348.Claydon, J., 159.Clem, W. J., 135.Clemo, G. R., 233, 237, 239, 240,Clusius, K., 157, 158, 159, 412.Clutterbuck, P.W., 386.Cockbain, 1 15.320, 321, 323, 324, 329424 INDEX OF AUTHORS’ NAMES.Cohen, A., 293.Cohen, E., 156.Cohen, F. L., 205.Cole, W., 307.Coleman, F., 151.Collins, A. M., 77.Collins, G. B., 20.Colowick, S. P., 355, 358, 361.Compton, A. H., 155.Condon, E. U., 28.Conn, J. B., 176, 229.Cook, A. H., 253, 302, 416.Cook, J. G., 324.Cook, J. W., 289, 290, 293, 302, 303,Cook, L. G., 12.Cook, R. P., 135.Cooke, R. G., 281.Cooper, W. C., 367.Cope, A. C., 212.Copping, (Miss) A. M., 335.Coppock, J. B. M., 238.Corey, R. B., 179, 240.Cori, C. F., 358, 359, 361.Cori, G. T., 358, 359, 361.Corlette, M. B., 339.Corlette, M. G., 339.Corley, R. C., 349.Corner, J., 153.Cornog, J., 416.Cornog, R., 24.Corran, H.S., 343, 354.Corran, R. F., 92.Corruccini, R. J., 253.Corson, B. B., 212.Corson, D. R., 9.Coster, D., 156.Couch, J. F., 329.Coulson, C. A., 67.Coumoulos, G., 252.Coward, K. H., 341.Cowgill, G. R., 343.Cox, E. G., 174,184.Cox, E. H., 209.Cox, E. P., 395.Cox, R. F. B., 213.Cox, R. G., 85, 93.Craig, L. C., 332, 333, 334.Crandall, L. A., 358.Creed, R. H., 337.Creighton, M. M., 278.Crenshaw, J., 153.Creutz, E. C., 25.Criegee, R., 93.Crookes, (Sir) W., 129.Crowder, J. A,, 278.Crowfoot, (Miss) D., 185.Crowley, G. P., 296.Croxall, W. J., 210.Curie, (Mme.) I., 8, 13.Cuthbertson, A. C., 80.Cutler, W. O., 260, 270.Czernotzky, A., 401.304, 308.Daffern, R. P., 321.D’Agostino, O., 8.Dagys, J., 373.Dam, H., 283, 348.Dam, W., 347.Damiens, A., 116.Damkohler, G., 154, 159.Dandliker, W.B., 367.Dane, E., 291, 292.Daniels, F., 84, 232.Daniels, G. H., 298.Daniluschkina, E. O., 133.Dann, W. J., 344.Darkis, F. R., 224.Darzens, G., 301.Dattler, B., 415.D a m , K., 345.Davenport, H. A., 361.Davidson, D., 290.Davies, R. R., 311.Davies, W. C., 85, 93.Day, H. G., 350.Dazeley, G. H., 2.56.Dean, 101.Deanesly, R. M., 232.Debye, P., 37.De Cori, P., 410.Dee, P. I., 27.De Forcrand, R., 124.Deitz, V., 155.De Lange, J. J., 181.DelBpine, M., 135.Delfs, E., 413.Delsasso, L. A., 25.Demole, V., 347.Denbigh, K. G., 122.Dennison, D. M., 241.De Rassenfosse, A., 174.Dermer, 0. C., 393.Demer, V. H., 393.Dervichian, D.G., 94, 95.De Sttlas, E., 196.De Smedt, I., 241.Desreux, V., 353.Devadatta, S. C., 133.De Vault, D. C., 21.Devaux, 109.Devonshire, A. F., 39.De Wad, J., 107.Dewan, J. G., 343, 354.De Wilde, J. H., 174.De Worms, C. G. M., 201.Dey, B. B., 315.Dhar, J., 177, 181.Dickel, G., 412.Dickinson, R. G., 240.Dieke, G. H., 57.Diels, O., 64.Dierdorp, S., 173.Dimroth, K., 309, 310.Dippy, J. F. J., 187.Divers, E., 136.Diwald, J., 381INDEX OF AUTHORS’ NAMES. 425Dixon, C. F., 348.Doak, B. W., 367.Dobbins, J. T., 416.Dobrovolny, E., 315.Dodds, E. C., 308.Dodson, R. W., 9, 12.Doebbeling, S. E., 376, 377.Doll, W., 126.Doisy, E. A., 283, 348.Donald, M. B., 133.Dostal, H., 74, 78, 82.Dothie, H.J., 174.Drigalski, W. von, 339.Drikos, G., 159.Drinker, P., 401.Dripps, R. D., 193.Droste, G. von, 10, 15.Drummond, J. C., 350.Drury, A. N., 340, 341.Dudley, H. W., 332.Diirr, W., 384.Du Feu, E. C., 295.Duffendack, 0. S., 411.Duncan, A. B. F., 56, 57, 58, 60.Dunlop, H. G., 266.Dunn, J. T., 278, 294.Dunn, R., 392.Dunning, J. R., 10, 18, 27.Duquenois, P., 391.Dutt, N. K., 128.Dutt, S., 278.Dutton, F. B., 117.Dyson, P., 321.Eakin, R. E., 372.Earl, J. C., 203, 204.Eastcott, E. V., 371.Ebert, F., 116.Eckardt, R. E., 343.Ecker, E. E., 345.Edelmann, K., 414.Eder, K., 291, 292.Edgar, J. L., 408.Edwards, F. W., 391.Edwards, G. E., 93.Edwards, H. L., 416.Edwards, W. R., 311.Egerton, A., 151.Ehrenfest, P., 96.Ehrensvard, G., 103.Ehrhorn, H.J., 121.Ehrlich, F., 378, 379.Eichelberger, L., 233.Eisenbud, L., 28.Eisenlohr, F., 252.Eisleb, C., 206.Eistert, B., 211, 306.Ekenstein, W. A. van, 356.Elchardus, E., 120.Elder, M. E., 371.Eley, D. D., 34, 35, 37.Elliot, N., 179.Wiott, G. H., 288.Sllis, L. S. E., 222.Zlvehjem, C. A., 344, 370.Zmbree, N. D., 45, 337.Zmel6us, H. J., 117.Zmerson, G. A., 347.3mmerie, A., 347.Engel, C., 347.Engelmann, H., 222.Engl, J., 162.Engle, H. R., 128.English, J., jun., 368, 369.Eppstein, S. H., 349.Erlbach, H., 259.Erlenmeyer, H., 238.Errington, K. D., 287, 288.Erxleben, H., 350.Escher, R., 347.Essex, H., 93.Eucken, A., 93, 150, 159, 160, 161,Euler, E., 264.Euler, H. von, 337.Evans, A.G., 92.Evans, D. P., 216, 217.Evans, H. M., 347.Evans, M. G., 37, 43, 66, 88, 89, 90,Evans, R. B., 411.Evans, R. C., 148.Evans, W. J., 200, 201.Evans, W. M., 57.Everett, D. H., 45.Everett, M. R., 252.Ewens, R. V. G., 166, 167.Eyring, H., 39, 66, 89, 91.Eysler, E. H., 177.Zl-Sadr, M. M., 344.412.92.Fairclough, R. A,, 85, 86, 90.Falke, 345.Faller, (Mlle.), 391.Fankuchen, I,, 103, 185.Parkas, L., 88.Farmer, E. H., 236.Farrell, L. N., 371.Fast, J. D., 118, 120.Faulkner, D., 240.Fearon, W. R., 352.Feather, N., 11, 18.Feenberg, E., 29.Feher, D., 124.Fehlberg, E. R., 379.Feicht, F. L., 401.Feit, H., 119.Fellinger, L. L., 140.Fels, A., 298.Fermi, E., 8, 15.Fernelius, W. C., 138.Fernholz, E., 283, 348.Fichter, F., 123.Ficklen, J.B., 400426 INDEX OF AUTHORS’ NAMES.Field, H., 341.Fieser, L. F., 278, 279, 283, 294, 300,Fieser, M., 303, 348.Finbak, C., 159, 160, 162.Finch, G. I., 179.Fineman, M. Z., 232.Finger, G. C., 257.Finkelstein, D. N., 403.Finn, M., 339.Finn, O., 241.Fischer, E., 259.Fischer, F., 125.Fischer, F. G., 283.Fischer, H., 360.Fischer, H. 0. L., 239.Fitzgerald, M. E. H., 308.Fleck, J., 133.Fleiger, A. G., 410.Flock, E. V., 357.Florence, R. T., 111.Flory, P. J., 75, 82.Flugge, S., 14.Foa, P., 357.Folkers, K., 326, 344.Fontl, P., 315.Forbes, I. A., 269.Fornaroli, P., 357.Forster, R. B., 409.Foster, L. S., 128.Foster, W. D., 402.Fourt, L., 96.Fowler, R. D., 9, 12.Fowler, R.H., 37, 40, 42, 88, 91,151, 161.Fox, J. G., 25.Fox, J. J., 152.Foy, (Mrs.) M., 233.Franck, A., 159.Franck, J. M., 90.Frandsen, H., 339.Frank, F. C., 163.Frank, H., 339.Franke, E., 394.Franklin, E. C., 136.Frary, S. G., 117.Fray, W. W., 404.Fredenhagen, H., 11 6.Fredenhagen, K., 144, 145.Frehden, O., 253.Freiensehner, H., 207.Freudenberg, K., 259, 260, 383, 384.Freundlich, H., 245, 253, 414.Frey, C. N., 371, 372.Fricke, R., 156.Friedman, B. S., 236.Friedrich, A., 381.Friend, J. N., 131.Fries, N., 373.Frisch, 0. R., 9, 11.Fritz, R., 130.Fritzsche, H., 347.Frohlich, H., 32.303, 348.Frost, W., 78.Fry, E. M., 348.Fuchs, W., 381.Fujise, S., 252.Fulton, C. C., 391.Furter, M., 347.Gabriel, A., 395.Gagos, K., 144.Galbraith, F., 199.Galinovsky, F., 329.Gangulee, N., 350.Gent, D.H. T., 19.Gantzel, T., 339.Garbatski, U., 88.Gates, M. D., 348.Gatty, 101.Gaubert, P., 222.Gaudy, F., 418.Gautheret, R., 363.Gee, G., 72, 74, 80, 81.Gelormini, O., 93.Genoni, F., 124.George, S. W., 317.German, A. F. O., 144.Germer, L. H., 107.Getz, H. R., 339.Giauque, W. F., 159.Gibbs, D. F., 18.Gibson, C. S., 392.Gilbert, C. W., 27.Gilbert, E. C., 253.Gillam, A. E., 336.Gilmour, D., 406.Gingrich, N. S., 121, 164.Ginsburg, N., 177.Glacel, Z. C., 311.Gladishev, A., 84.Glagolev, A. A., 396.G h e r , R., 337.Glasoe, G. N., 13.Glass, D. B., 237.Glavind, J., 347.Gocholaschvili, M. M., 363.Godman, G. L., 276.Goehring, M., 122.Gotze, J., 252.Golberg, L., 308.Goldberg, M.W., 294.Goldfinger, P., 151.Goldhaber, M., 19, 20, 27.Goldschmidt, V. A., 85.Goloborodko, T., 27.Goodenough, B. H., 339.Gooderham, W. J., 410, 412.Goodhart, R. S., 342.Goolden, L. L., 400.Goranson, R. W., 109.Gorbovski, A. G., 369.Gordon, A. H., 343.Gordon, H., 354.Gore, G., 136INDEX OF AUTHORS’ NAMES. 427GOSS, H., 336.Goss, M. J., 382, 383.Goto, K., 331.Gottfried, S. P., 290, 309.Gould, R. G., 333, 334.Gourlay, W. M., 320.Grace, N. H., 363.Graff, S., 350.Graham, S. B., 233.Grahame, D., 406.Gralen, N., 353.Grandadam, P., 120.Grant, G. A., 355.Gray, H. L., 394.Gray, P. H. H., 397.Gray, W. H., 202.Green, D. E., 343, 354.Green, G.K., 9, 18.Green, H. L., 402.Greenberg, J., 84.Gregor, U., 118.Grewe, R., 291.Grieneisen, H., 59, 61.Griffith, C . F., 260.Griffith, F. S., 417, 418.Griffith, H. D., 338.Griffiths, J. G. A., 395, 398.Griffitts, J. J., 345.Grimm, H. G., 85.Grimshaw, D. C., 224.Grinten, W. van der, 413.Grosdenes, O., 130.Gross, R., 81.Grosse, A. V., 18, 230.Groth-Petersen, E., 339.Gruber, W., 315.Guastalla, J., 94.Gubareva, M. A., 93.G a t h e r , G., 337.G a t h e r , P., 165.Guerin, H., 134.Guerry, D., 348.Guest, H. F., 146.Guggenheim, E. A., 38, 39, 40.Guggenheim, K., 345.Guha, N. C., 316.Guilbert, H. R., 336.Guillien, R., 162.Gupta, J., 155.Gurney, R. W., 45.Gurney, S. W., 400.Guttmann, R., 379.Guy, J. B., 224.Gwinner, E., 156.Gyorgy, P., 325, 343.Haag, A., 383.Haagen-Smit, A.J., 368, 369.Haas, P., 354.Haberland, G., 300, 301, 304.Hackspill, L., 153.Hafstad, L. R., 9, 12, 18, 27, 28.Hahmoy, E . , 184.Hahn, H., 120, 166.Hahn, O., 8, 11, 12, 13, 14.Hahn, P. F., 349.Hahn, V., 324.Hahnrath, J., 130.Haines, R. T. M., 339.Haitinger, M., 393.Halban, H. von, jun., 15, 17.Hale, J. B., 257.Halford, R. S., 20, 202.Hall, C. H., 395.Hall, D. A., 131.Hall, W. K., 407.Halma, F. F., 363.Hamilton, (Miss) J. E., 172.Hammick, D. L., 232, 321.Hampson, G. C., 167, 168, 218.Hands, S., 269.Hnnes, C. S., 359.Hann, A. C . O., 211.Hannebohn, O., 127.Hannon, J., 231.Hannum, C., 220.Hansen, C . J., 123.Hanstein, H. B., 16.Haraldsen, H., 121.Haring, M.M., 134.Harington, C. R., 342.Harkins, W. D., 94, 95, 96, 111.Harkness, J. B., 62.Harned, H. S., 45, 119.Harper, S. H., 317.Harriman, B. R., 197.Harris, E. A., 326.Harris, E. E., 382.Harris, L. J., 338, 340, 341, 342, 343,Harris, P. L., 223, 224, 229.Harris, S. A., 344.Harris, W. T., 18.Harrison, K., 357.Harrison, R. J., 345.Harrison, S. F., 38.Hartley, G. S., 183, 253, 254.Harvey, G., 155.Haskins, W. T., 251.Haslam, G. S., 395.Haslewood, G. A. D., 306.Hassel, O., 159, 160, 168, 184.Hattori, S., 319.Hauser, C. R., 192, 210, 211, 213.Havas, P., 10, 14.Havinga, E., 107.Haworth, R. D., 290, 297, 307.Haworth, W. N., 260, 263, 267, 269,Haynes, F. W., 340.Hazard, W. G., 401.Heane, A.L., 116.Hecht, S., 338.Heilbron, I. M., 413.Heimbach, (Miss) S., 321, 322, 323.350.270, 271, 273, 274, 27642 8 INDEX OF AUTHORS’ NAMES.Hein, F., 252.Heinburg, M., 122.Heinrich, E., 301.Heisenberg, W., 25.Heitler, W., 32.Helferich, B., 264.Heller, A., 400, 403.Heller, W., 253, 414.Helmholz, L., 165, 169, 171.Helms, A., 124, 165.Henderson, G. M., 252.Henderson, M. C., 10.Hendricks, S. B., 164.Hennion, G. F., 221.Henrici, A., 61.Henshall, J. H., 131.Herb, R. G., 28.Herbert, D., 361.Hermans, J. J., 95.Herrick, H. T., 385.Herriott, R. M., 353.Hershberg, E. B., 303.Herzberg, G., 56, 60, 151, 175.Herzfeld, K. F., 151.Hess, K., 276.Hettner, E., 159.Hettner, G., 159.Heuse, W., 159.Hevesy, G., 361.Hewett, C.L., 290, 308.Hewston, E. M., 339.Hey, D. H., 209, 225, 234.Heydenburg, N. P., 28.Heyn, F. A,, 13.Hibbert, H., 381, 382, 383.Hickinbottom, W. J., 204, 207, 209.Hieber, W., 167.Hiedemann, E., 402.Higginbottom, A,, 290.Hijikata, K., 412.Hildebrand, G. B., 339.Hildebrand, J. H., 41.Hilgendorff, H. J., 71.Hill, A. E., 132, 135.Hill, D. G., 72.Hill, P., 290, 300, 303, 304.Hill, R., 357.Hill, R. D., 19.Hillel, R., 316.Hiller, K., 158.Hilly, G., 310.Hilpert, R. S., 381.Hind, H. G., 344.Hindley, N. C., 310.Hinshelwood, C. N., 62, 84, 85, 86,90, 91, 92, 93, 217.Hinton, H. D., 208.Hirschfelder, J. O., 39, 84.Hirst, E. L., 260, 271, 273, 276, 378,Hitchcock, A. E., 364.Hitchcock, C., 159.Hitchings, G.H., 344, 370.379.Hoard, J. L.,. 170, 171.Hobbs, M. E., 153.Hoch, J., 302.Hodgson, H. H., 311.Holemann, H., 135.Hoss, O., 291.Hoffer, M., 345.Hoffman, J. I., 417.Hoffmann, A., 332.Hoffmann, O., 347.Hoge, H. J., 27.Hoggarth, E., 324.Hohmann, E., 127.Hoisington, L. E., 28.Holcomb, W. F., 348.Holley, C., 103.Holm, K., 165.Holmes, E., 361.Holmes, H. L., 294, 300.Holmes, H. N., 413.Holmes, P. E., 361.Holstein, T., 29.Holtermann, C., 125,Holzschmidt, V. A., 92.Homeyer, A. H., 193.Hompesch, H., 130.Hook, A. van, 68.Hooker, S. C., 279, 280.Hopf, P. P., 252.Horan, H. A., 132.Horiuti, J;, 34.Hornel, J. C., 202.Houlehan, A. E., 137.Houston, J., 342.Howard, J. B., 242.Howe, J. P., 58.Huang, Y. T., 288, 298.Huber, W., 297.Hudson, C.S., 251, 252, 259, 277.Huckel, W., 287.Hughes, 110, 112.Hultgren, R., 164.Hume, E. M., 336.Hume-Rothery, W., 157.Hummel, J. J., 386.Hunt, H., 140.Hurd, C. D., 194, 205, 206, 207,Huse, G., 184.Husemann, E., 78, 79.Huttrer, C., 337.Hynd, A., 270.211.[ball, J., 179.Ichibe, A., 326.Idanoff, A., 9.Ide, K. H., 135.Igaraci, H., 385.Cgler, P., 297.Cmanishi, S., 241.Cmmig, H., 142.Cng, H. R., 352INDEX OF AUTHORS’ NAMES.Joris, G., 71.Joshi, N. K., 133.Jowett, M., 88.Juhasz-Schiiffer, A., 339.Jukes, T. H., 344, 370.Julian, P. L., 327.Julien, A. P., 143.Jung, F., 344.Jung, F. T., 338.Jungers, J. C., 71.Just, F., 264.Justi, E., 159, 163.Juza, R., 120, 166, 418.429Ingham, C.E., 218.Ingle, D. J., 357.Inglis, D. R., 25, 29.Ingold, C. K., 192, 197, 204.Inoue, T., 385.Inouye, K., 392.Inubuse, M., 316.Ipatiev, V. N., 227, 236.Ireland, J., 337.Irvine, (Sir) J. C., 267, 270.Irvine, 5. W., 11.Isaacs, B. L., 338.Isherwood, F. A., 273.Ishikawa, F., 412.Ishikawa, S., 211.Itiba, A., 344.Ito, Y., 330.Ivers, O., 260.Ivy, A. C., 338.Jaacks, H., 93.Jackson, E. L., 277.Jackson, J., 269.Jacob, A., 347.Jacob, (Miss) A,, 328.Jacobs, W. A., 332, 333, 334.Jaeger, F. M., 171.Jaeger, W., 347.Jamison, (Miss) M. M., 248.Jander, G., 140, 141, 142.Janson, A., 383, 384.Jauncey, G. E. M., 156.Jeffrey, G. A., 184.Jeghers, H., 339.Jelley, E. E., 392.Jenkins, H. O., 215.Jennings, D. S., 122.Jensen, K.A., 347.Jentschke, W., 10.Jessup, R. S., 152.Jetter, W. W., 345.Jeunehomme, W., 15 1.Jewitt, T. N., 57.Joannis, J. A., 136.Jockers, K., 415.Jorgenson, P. F., 253.Johnson, J. R., 311.Johnson, W. C., 139.Joliot, F., 9, 10, 15.Joly, M., 94, 95, 96.Jones, D. G., 253.Jones, E. R., 302.Jones, H., 152, 156.Jones, J. K. N., 378, 379.Jones, L. W., 193, 194.Jones, R. N., 348.Jones, T. T., 76.Jones, W. H., 72.Jones, W. J., 202.Jones, W. O., 379.Jonsson, H., 310.Jorde, W., 78, 80.Kaischew, R., 162.Kalaja, L., 340.Kalnin, P., 211.Kamai, G., 246.Kamthong, B., 312.Kangro, W., 151.Kanner, M. H., 18.Kapadia, M. R., 181.Kapur, A. N., 415.Karagunis, G., 252.Kark, R., 348.Karrer, P., 283, 284, 337, 347, 413.Karsten, J., 173.Kasarnowsky, I., 34.Kassan, M.K., 391.Kassel, L., 62.Kato, H., 417.Kato, S., 68.Kaufmann, H., 63, 85.Kawai, S., 313.Kawanami, M., 315.Kazarnovski, I. A., 124.Keesom, W. H., 157.Keffler, L., 228.Kehren, E., 130.Kehrer, E. A., 297.Keilin, D., 349.Keima, R., 116.Kelham, R. M., 247, 255, 257.Kelley, 0. R., 348.Kellogg, J. H. B., 24.Kemmer, N., 29, 31, 32.Kemula, W., 68.Kennedy, J. W., 21.Kenner, J., 231.Kenny, T. S., 317.Kent, B. A., 198.Kenyon, J., 193, 214, 238, 251.Keresztesy, J. E., 325, 326, 344.Kerst, D. W., 28.Ketelaar, J. A. A., 121, 165, 171.Khambata, (Miss) B. S., 63, 65, 85,86.Kharasch, M. S., 220, 221, 222, 223,224, 225, 230, 231, 232, 233, 234,235, 236, 332.Kidd, H.V., 203.Kiess, M. A., 210430 INDEX OF AUTHORS’ NAMES.Kiessling, W., 361.Kilian, H., 128.Kilpatrick, E. C., 288.Kincaid, J. F., 39, 205.King, G. B., 132.King, H., 247.Kinoshita, K., 386.Kipping, F. B., 337.Kipping, F. S., 301.Kirby, J. E., 77.Kirk, P. L., 392.Kirkwood, J. G., 42, 46, 47, 95.Kistiakowski, G. B., 57, 62, 63, 84,176, 221, 229.Kitaygorodsky, A., 179.Klaas, R., 404.Klason, P., 383.Kleese, W., 130.Kleiger, (Miss) S. C., 220.Kleinert, G., 304.Klemm, W., 124, 125, 126, 127, 128,Kloetzel, M. C., 294, 302.Klose, A, A., 283, 348.Klotz, A. W., 370.Knaggs, (Miss) I. E., 184.Knight, B. C. J. G., 373.Knight, G. A., 320.Knoll, H., 142.Knopf, E., 383.Knott, 106.Koch, J., 18.Koebner, A., 298.Kogl, F,, 350, 370, 371, 373.Koepfli, J.B., 365.Korosy, F., 118, 119.Kofler, L., 393.Kogan, A. G., 134.Kohlbach, D., 322.Kohler, E. P., 212.Kohlhaas, R., 179, 184.Kolthoff, I. M., 417, 418.Kon, G. A. R., 197, 289, 303, 304,Kon, S. K., 342.Kondo, H., 330.Koolhaas, D. R., 317.Kosterlitz, H. W., 355.Kowarski, L., 15.Kraemer, E. O., 82.Kraft, L., 93.Krasso, T., 408.Kraus, C. A., 136.Krause, F., 405.Kringstad, H., 341.Kritschevski, I., 230.Kroger, F., 163.Kroeker, E. B., 213.Kroll, W., 125.Kronenberg, M. H., 400.Kruis, 9., 159, 162.Kuhn, R., 211, 225, 248, 250, 281,325, 326, 344.165.305.Kunz, A. H,, 392.Kunz, H., 339.Kuroda, C., 282.Kursanov, N. I., 208.Kusaka, S., 30.Kutzelnigg, A., 394.Kuznetzov, V.G., 133.Laborey, F., 386.Lacher, J. R., 63,Laffitte, P., 120, 125.Laidler, K. J., 217.Lake, W. H. G., 263, 265.Lal, J. R., 278.La Mer, V. K., 84, 91, 203.Lange, E., 35.Langheim, R., 418.Langmuir, I., 96, 103, 104, 105, 107,109, 185.Langrish, (Miss) D., 232.Langsdorf, A., jun., 13.Lansing, W. D., 82.Lanzing, J. C., 414.Lapworth, A., 211, 214.Lark-Horovitz, K., 20.Larsen, W. E., 140.Lassieur, A., 408.Latimer, W. M., 45.Laubengayer, A. W., 128.Laue, M. von, 163.Lauer, W. M., 205, 206, 224.Lauritsen, T., 18.Laval, J., 156.Lavollay, J., 386.Lawrence, C. A., 293, 302, 303, 304.Lawrence, E. O.,, 349.Lawson, W., 308.Lazard, A., 20.Lease, E. J., 336.Lease, J. G., 336.Lebeau, P., 116, 135.Le Blanc, M., 231.Lederer, E., 337.Lee, E., 50, 242.Lee, Y.N., 415.Leekley, R. M., 205.Leenderste, J. J., 221.LefAvre, J., 363, 364.Le FBvre, R. J. W., 184, 252, 253,Legard, A. R., 217.Legault, R. R., 332.Leighton, P. A., 138. ,Leipunski, A., 27.Lemmel, L., 381.Lenher, V., 143.Lennard-Jones, J. E., 39, 178.Leong, P. C., 342.Leontovitch, M., 90.Leppla, P. W., 103.Leschewski, K., 411.Lesslie, (Miss) M. S., 257.254INDEX OF AUTHORS’ NAMES. 43 1Leuchs, H., 247.Levi, A. A., 198, 200.Levi, G. R., 124, 415.Levitz, M., 290.Levy, (Miss) W. J., 394.Lewis, G. N., 47.Ley, H., 56.Libby, W. F., 19, 21.Lidstone, A. G., 254.Lidwell, 0. M., 203.Lieber, C., 13.Lin, K. H., 222, 300.Linari, A., 133.Lind, S. C., 68, 71.Lindner, K., 119.Lindqvist, T., 339.Lindstrom, C.F., 58.Linn, G. B., 220.Linstead, R. P., 198, 222, 287, 288,302, 305, 308.Lipmann, F., 340.Lister, M. W., 166, 167, 180.Littlefield, J. B., 400.Litvan, F., 306.Livingood, J. J., 21.Livingston, R. S., 68, 71.Llewellyn, F. J., 174.Lockett, J., 290, 303.Lohmann, A., 281.Lohmann, K., 339, 359.London, F., 152, 153.Long, C., 340.Long, F. A., 202.Lonsdale, (Mrs.) K., 175, 184.Lord, R. C., 159.Lottermoser, A., 414.Loughlin, R., 339.Lovern, J. A., 337.Lovgren, N., 417.Lowenberg, K., 283.Lozner, E. L., 348.Lu, G. D., 340, 341, 342, 360.Lubbock, D. M., 338.Lucas, H. J., 224, 228.Ludlam, E. B., 71.Lunde, G., 341.Lundell, G. E. F., 417.Lundsgaard, E., 357.Luttringhaus, A., 184.Lythgoe, B., 344.Lyons, 112.MMMMMMMMMM:a, C.M., 298, 304.:acbeth, A. K., 281.:cCance, R. A., 349.:cClement, C. S., 200.:cClure, C. H., 400.:cClurkin, T., 408.:cCollum, E. V., 341, 347, 350.:cCorckle, M. R., 393.:acCorquodale, D. W., 348.:cCoy, H. N., 125.McCreath, D., 258.McDonald, R. D., 71.McElvain, S. M., 213.Macfie, J. M., 348.MacGillavry, C. H., 173, 174.McGookin, A., 318.McGrew, F. C., 238.Machonachie, J. E., 371.McKee, R. W., 348.McKenzie, A., 250, 339.Mackenzie, C. G., 347.Mackinney, H. W., 381.McLean, J. H., 228.McMillan, E., 9, 10.McNab, J. G., 224.McNab, M. C., 220, 224.McNatt, E., 156.McNicoll, D., 270.McQuillen, A., 237.McQuillin, F. J., 290, 295.Macrae, T.F., 344.Macri, A., 407.Madinaveitia, J., 327, 328.Maeser, S., 122.Magat, M., 152.Magnan, C., 19.Mahr, C., 390.Maitland, P., 238, 239, 243, 252.Majorana, E., 25.Malam, M., 358.Malerczyk, W., 264.Malmberg, M., 337.Mandelbaum, J., 338.Manian, S. H., 376.Manjunath, B. L., 316.Manley, J. H., 27.Mann, F. C., 355.Maw, F. G., 246, 247.Mann, T., 349, 350.Mannich, C., 295.Manning, M. F., 242.Manning, W. M., 57.Mansfield, J. V., 225.Manske, R. H. F., 327.Mapson, L. W., 340.Marchant, R., 322.Marcus, A., 414.Margenau, H., 29, 152.Margolis, E. T., 230, 231.Marion, L., 327, 383.Maritz, A., 123.Mark, H., 74, 82, 168, 241.Marker, R. E., 307.Markham, E. C., 416.Markownikoff, W. B., 219.Marrian, G.F., 306, 308, 314.Marsden, J., 110, 111, 112.Marsh, J. K., 126.Marshall, A. L., 151.Martin, A. E., 152.Martin, A. J. P., 344, 347.Martin, C. J., 344.Martin, W., 35432 INDEX OF AUTHORS’ NAMES.Martini, A., 390, 391.Marvel, C. S., 236, 237, 239, 288, 322.Maaon, C. W., 389, 396.Masters, J. E., 393.Matheson, D., 407.Mathur, L. S., 151.Matlack, (Miss) E. S., 224.Matthews, J. W., 404.Matuszak, M. P., 410.Matzke, J., 316.Mauguin, C., 156.Maximov, N. A., 363.Maxwell, L. R., 164.Maxwell, R. W., 256.May, A., 152.May, E. M., 234.May, F., 356.May, 0. E., 385.Mayer, J., 151.Mayer, J. E., 38.Mayo, F. R., 220, 221, 222, 223, 224,225, 230, 231, 232, 234, 235, 236.Mazov, A. V., 410.Mead, T. H., 337.Mears, W. H., 62.Megaw, H.D., 153, 157.Meggy, A. B., 293.Mehta, C. R., 319.Mehta, S. M., 133.Meier, G., 252.Meigs, R. R., 400.Meisel, K., 121, 164, 166.Meisenheimer, J., 241, 243, 247.Meitner, L., 8, 9, 11, 13.Mellanby, E., 337, 338.Melnick, D., 341.Mblon, J., 391.Melville, H. W., 69, 73, 77.Menschikov, G., 329.Mensching, J., 345.Mentz, W., 298.Menzies, A., 157.Mbrigoux, R., 95.Mertens, W., 265.Mesech, H., 140.Metcalfe, T. P., 240, 323.Meyer, C. E., 344, 370.Meyer, K. H., 203.Meyer, R. E., 347.Meyer, R. J., 129.Meyer, T. M., 317.Meyerhof, O., 358, 360, 361.Meyering, J. L., 121.Meyers, C. H., 71.Meyers, R. C., 9, 12, 18.Michael, A., 221, 225, 228, 236.Michi, K., 326.Michiels, J. L., 15.Mie, G., 39.Migeotte, M.V., 241.Milas, N. A., 310.Miles, F., 157.Miller, W. L., 371.Millidge, A. F., 287, 288.Mills, W. H., 238, 239, 243, 246, 247,Minors, G., 407.Mirbach, P., 130.Misch, L., 181.Mitchell, H. K., 344, 370.Mitchell, J., jun., 393.Miti, K., 344.Mittag, R., 264.Miyahi, T., 313.Mocnik, W., 317.M~ller, C., 31.Moller, E. F., 344, 372.Moller, F., 206.Moelwyn-Hughes, E. A., 34, 91, 92.Moggridge, R. C. G., 270, 342.Moissan, H., 116, 119.Mohr, R., 274.Mole, (Miss) J. D. C., 243.Moll, T., 344.Molt, E. L., 233.Montonna, R. E., 274.Mooney, R. B., 71.Mooney, (Miss) R. C. L., 165.Moore, L. A., 338.Moore, T., 347.Morette, A., 118, 119.Morgan, B. G. E., 341.Morgan, S. O., 160.Morgan, W. M., 329..Moricz, M., 260.Morrison, J.R., 406.Morton, R. A., 337.Moseley, V. M., 164.Mosettig, E., 302.Mosher, W. A., 370.MOSS, S. A., 98.Mott, N. F., 152.Mourant, A. E., 345.Moureu, H., 121.Moussa, A., 12.Mowat, E. L. R., 223.Moyer, A. J., 385.Moyer, W. W., 193.Moyse, H. W., 224.Mozingo, R., 288.Mrazek, S., 68.Huller, Alex, 107, 152.Muller, Alexander, 260, 261, 266.Huller, E., 211, 212.Mueller, J. H., 370.Huller, K., 282.Huller, P., 294.Miiller, W., 372.Uuller, G., 163.Mulliken, R. S., 47, 50, 51, 55, 56.M u m m , O., 206.Munsey, V. E., 336.Mutch, J. R., 338.Myers, R. J., 95, 96.Myers, W. H., 271.250, 252, 254, 255, 256, 257.Moyle, c. L., 210INDEX OF AUTHORS’ NAMES. 433MyrbBck, I<., 375.Myssowsky, L., 9.Narvlinen, R., 340.Nagai, W., 319.Nagel, C., 193.Nakamura, T., 313.Nametkin, S., 287.Nandi, S.K., 128.Nanji, H. R., 391.Narracott, E. S., 289, 304.Natelson, S., 207, 208, 290, 309.Nathan, W. S., 85.Naylor, N. M., 377.Needham, D. M., 358, 360.Negelein, E., 360.Nelson, 0. A., 134.Nelson, R. C., 408.Neogi, P., 128.Nespital, W., 241.Nesty, G. A., 288.Neuber, A., 120.Neuberger, A., 270.Neufeld, O., 316.Neumann, E., 132, 133.Neumann, F., 276.Nevell, T. P., 196.Newman, M. S., 278, 303.Newton, J. M., 377.Newton, R. F., 39.Niederl, J. B., 208,Nielsen, E. K., 349.Nielsen, J. P., 122.Nielsen, M., 357.Niemann, C., 353, 384.Nieuwland, J. A., 208, 210, 224.Nijveld, H., 173.Nikolaev, V. I., 134, 415.Nitka, H., 159.Nitta, I., 160.Noguchi, T., 315.Nordheim, G., 60.Nordsieck, H.H., 171.Norling, F., 54.Norman, A. G., 380, 384.Norris, F. W., 379.Norrish, R. G. W., 71, 80.Northrop, J. H., 353.Norton, F., 151.Norton, J. A., 221.Noyes, W. A., 57.Ochiai, E., 330.Ochoa, S., 339, 340.O’Connor, S. F., 221.Oddie, (Miss) G. T., 132.Oden, J. W., 343.Oden, L. H., 343,Ogg, R. A., 85, 92, 138.Ohle, H., 259, 261, 264, 265.Oigaard, H., 339.Oldham. J . W. H., 163, 267.Olsen, A., 341.Olsen, A. G., 379.Olson, A. R., 71, 202.Onsager, L., 47,Onstott, R. H., 343.Opsahl, J. C., 351.Orcutt, R. M., 290.OrAkhov, A., 329.Orent-Keiles, E., 350.Ortenblad, B., 375.Orton, K. J. P., 202.Osterberg, A. E., 348.Ostern, P., 359, 361.Ostroumov, E. A., 418.Ottung, K., 393.Owen, B.B., 45.Owen, E. A., 155, 156.Owen, L. N., 267, 271.Oxford, A. E., 385, 386.Oyamada, T., 319.Palmer, C. E., 338.Palmer, K. J., 176.Paneth, F. A., 408.Pannizon, L., 260.Papa, D., 290.Parade, G. W., 340.Parker, R. C., 402.Parkes, D. W., 411.Parkinson, D. B., 28.Parnas, J. K., 358, 359.Parry, G., 15.Partridge, S. M., 238.Pastonesi, G., 410.Patat, F., 175.Paul, R., 310, 311, 312.Paul, W. D., 345.Pauling, L., 148, 158, 165, 168, 171,172, 173, 175, 176, 177, 180, 185,353.Peak, D. A., 296, 300.Pearce, G. W., 134.Pearse, H. L., 364.Pearson, D. E., 288.Pease, R. N., 63, 68.Peat, S., 260, 263, 265, 269, 270, 271,Peccerillo, D., 211.Pedersen, H. F., 341.Penners, K., 408.Penney, G.W., 401.Penney, W. G., 149, 178, 241.Percival, E. G. V., 269.Percival, J. O., 203.Perey, M., 23.Perkin, A. G., 386.Perkin, W. H., jun., 245.Perlick, A., 159.Perlman, D., 290.Perreu, J., 135.Pcrrin, F., 15, 16, 17.274, 276434 INDEX OF A~JTHORS’ NAMES.Pesta, O., 314.Peters, M. A., 303.Peters, R. A., 339, 340.Pett, L. B., 339.Pfahler, F., 365.Pfaltz, H., 347.P f e d e r , L., 226.Phillips, H., 193.Phillips, M., 382, 383.Pickett, (Miss) L. W., 177.Pickles, N. J. T., 85, 86, 92.Pierron, P., 124.Pieters, H. A. J., 408.Pietsch, G., 314.Pikl, J., 327.Pilch, K., 79.Pillay, P. P., 315.Pillemer, L., 345.Pines, H., 227, 236.Pinkney, P. S., 288.Pinnow, P., 166.Pirie, N. W., 353, 356.Plain, G. J., 28.Platt, B., 342.Platt, T.M., 395.Plesset, M. S., 28.Plimmer, H., 290, 300, 304.Ploetze, H., 125.Ploum, H., 406.Plum, P., 348.Pockel, I., 195, 196.Pohland, E., 241.Pohlmann, R., 159.Polanyi, M., 43, 88, 89, 90, 92.Polissar, M. J., 84.Pollack, M. A., 205, 206.Poller, K., 209.Pontecorvo, B., 20.Popkin, A. H., 197.Porter, A. W., 41.Porter, C. W., 202.Porter, E. F., 109.Porter, M. W., 398.Posner, T., 236.Potapov, I. V., 92.Potts, W. M., 221, 222.Povenz, F., 58.Powell, H. M., 167, 184.Power, M. H., 355.Prankl, F., 10.Prasad, M., 133, 181.Prater, A. N., 224.Pratt, E. F., 344, 370.Prebluda, H., 341.Prelog, V., 240, 322, 323, 324.Prescott, C. H., 406.Present, R . D., 28, 29.Price, C. C., 231.Price, D., 290.Price, J.R., 280.Price, W. C., 54, 55, 56, 57, 58, 59,Prideaux, E. B. R., 134.71.Prillinger, F., 314.Primakoff, H., 29.Pugh, W., 127.Purse, J. H., 410.Pyke, M., 342.Quibell, T. H. H., 254.Quitman, E., 403.1Rabi, I. I., 24.Rabinowitch, E., 88, 90.Rainbow, C., 369, 371.Raistrick, H., 385, 386.Rakovski, G. V., 411.Ralston, A. W., 393.Ramage, G. R., 323, 324.Ramsay, N. F., 24.Randall, H. M., 241.Randall, J. J., 164.Rane, L., 370.Rangaswami, S., 316.Rank, B., 93.Ransom, W. w., 63.Raper, R., 237, 239, 246, 323, 324,Rapson, W. S., 295.Rarita, W., 29.Rasetti, F., 8, 27.Rathenau, G., 56.Rautenstrauch, C., 291.Ray, W. L., 143.Raymond, A. L., 240.Raymond, W. D., 343.Read, (Mrs.) A. T., 234, 236.Record, B. R., 272.Reddemann, H., 15.Reed, C.F., 233.Rees, M. W., 350.Regler, H., 252.Reichstein, S. I., 124.Reichstein, T., 345.Reid, C., 304.Reid, W. S., 43.Reinicke, F., 68.Renfrow, W. B., 192, 213.Resuggan, J., 300.Reynolds, P,, 157.Rhoads, J. E., 348.Ribner, H. S., 155.Ricci, J. E., 133.Rice, E. E., 349.Rice, F. O., 84.Rice, 0. K., 72.Richards, T., 386.Richert, H. F., 64.Richtmyer, N. K., 252, 259.Rideal, E. K., 74, 80, 98, 101, 111,Ridley, P., 155.Riegel, B., 348.Rietschel, H., 345.329.112, 113INDEX OF AUTHORS’ NAMES. 435Riley, D. P., 185.Riley, H., 185.Rimington, C., 393.Ringier, B. H., 347.Risser, J. R., 20.Robbins, W. J., 363, 367, 372.Roberts, I., 195.Roberts, K. C., 201.Roberts, R.B., 9, 12, 18.Roberts, S., 407.Robertson, A., 312, 317, 318.Robertson, G. J., 260, 266, 267,271.Robertson, J. M., 156, 163, 175, 177,179, 180, 181, 183, 185.Robertson, (Sir) R., 152.Robinson, (Mrs.) A. M., 290.Robinson, (Lady), 300.Robinson, (Sir) R., 197, 220, 222,280, 290, 291, 293, 295, 296, 297,298, 299, 300, 302, 304, 305, 306,308, 319.Robson, A. C., 237, 239.Rochvalenske, E. D., 133.Rogers, M. T., 165.Rohmer, R., 133, 135.Rohrmann, E., 344, 370.Rolla, L., 127.Rosanhauer, E., 203.Rose, W. C., 349.Rosenfeld, L., 31.Rosenmund, K. MT., 209.Rossini, F. D., 152.Roussinow, L. I., 20.Rudenko, E. I., 415.Rudorfer, H., 79.Rudra, M. N., 345.Ruf, H., 85.Ruff, O., 116, 119.Ruge, U., 366.Ruhemann, M., 159.Rule, H.G., 252.Ruppolt, W., 140.Rushbrooke, G. S., 42, 88.Rutgers, A. J., 163.Rutherford, J. J. B., 396.Ruzicka, F. C. J., 303.Ryder, S. E. A., 204.Rydon, H. N., 222, 293, 306.Rytz, W., 367.Sachsse, H., 88.Sacks, J., 357.Sagortschev, B., 418.Sah, P. P. T., 394.Sakaguchi, K., 385.Salem, S. I., 315.Salomon, G., 245.Sampson, W. L., 283.Samuelson, I. O., 415.Sandell, E. B., 390.Sargent, L. J., 331.Sarkar, J., 129.Sasaki, H., 252.Sato, M., 151.Saunders, B. C., 243, 393.Saunders, D. H., 371.Sautie, R., 125.Savitch, P., 8, 13.Scatchard, G., 41.Schaefer, V. J., 96, 103, 104, 107, 109.Schallamach, A., 159.Schattenstein, A. I., 140.Scheffer, F. E. C., 84.Scheffers, B., 132.Scheibe, G., 56, 58, 50.Scheibler, H., 214.Scheintzis, 0.G., 389.Schenck, R. T. R., 235.Schemer, P., 160.Scheschken, N. V., 133.Schettler, 0. H., 339.Scheuing, G., 195.Schifflett, C. H., 68.Schindler, H., 243.Schjgnberg, E., 220.Schliipfer, P., 68.Schlittler, E., 299.Schlupmann, K., 339.Schmerling, L., 205.Schmidt, G., 359, 361.Schmidt, J., 291, 292.Schmidt, M., 347.Schmidt, M. B., 367.Schmidt, M. T., 213.Schneider, E., 314.Schneider, F., 390.Schnurr, W., 209.Schon, O., 291.Schomaker, V., 177.Schopfer, W. H., 372.Schossberger, F., 157.Schramm, G., 307.Schrenk, H. H., 400, 401, 402, 407.Schroder, E., 159.Schroeder, H., 345.Schroder, W., 130, 131.Schulman, J. H., 95, 106, 110, 111,112, 113, 115.Schulten, H., 167.Schultz, A.S., 371, 372.Schultz, C. A., 264.Schultze, G. R., 232.Schulz, G. V., 78, 79, 80, 82.Schumacher, H. J., 84, 120.Schuster, P., 339.Schwab, G. M., 415.Schwartz, W. P., 345.Schwarz, R., 118, 120, 123.Schweitzer, C. E., 348.Schwerdt, H., 130.Seaborg, G. T., 12, 20, 21.Searle, N. E., 257.Sebba, F., 99.Sebrell, W. H., 343436 INDEX OF AUTHORS’ NAMES.Seegmiller, C. G., 118.Segrh, E., 8, 11, 12, 20.Seely, C. A., 136.Sestharamiah, A., 316.Seiwerth, R., 240, 322, 323, 324Sementzov, A., 252.S e a , H., 126.Sengupta, S. C., 288.Sergeant, G. A., 131.Servione, M., 393.Seshadri, T. R., 316.Setterlind, A. N., 400.Shadinger, G. H., 225.Shah, It. C., 319.Share, S. S., 28.Sharp, J. G., 351.Shaw, B. D., 320.Shead, A. C., 391.Shedlovsky, G., 333.Sheldrick, G., 297.Sheppard, F., 252.Sherk, K.W., 124.Sherrill, (Miss) M. L., 224, 225.Shimatori, N., 347.Shinkin, N. I., 310.Shipley, R. H., 131.Shishodo, H., 331.Shivotinski, P. V., 125.Shorr, E., 358.Short, W. F., 208, 290, 300, 303,Shorter, A. J., 174.Shriner, R. L., 236, 239.Sickman, D. V., 72.Siddappa, S., 316.Sidgwick, N. V., 167, 216.Sidwell, A. E., 139.Sieber, J., 125.Sisgert, H. J., 304.Signer, R., 81.Sillars, R. W., 1G2.Sillen, L. G., 103.Simamura, O., 225,227,228,232.Simon, F., 159.Simon, J. H., 117.Simonart, P., 385.Simons, C., 305.Simons, J. H., 165.Simonsen, J. L., 302.Simpson, C. T., 289.Simson, C. von, 159.Sinclair, H. M., 342.Singleton, H. M., 311.Sirkar, S., 155.Sirkin, J.K., 84, 93.Sisskind, B., 34.Skarulia, J. A., 132.Sklar, A. L., 60.Skraup, S., 209.Slack, F. G., 10, 18.Slater, N. B., 88.Slawsky, Z. I., 29.Slobutsky, C., 140.Smiles, S., 198, 199, 200, 201.l Smith, E. A., 176, 229.Smith, E. W., 204.Smith, F., 258, 267, 269, 379.Smith, G., 385.Smith, G. B. L., 143.Smith, G. F., 84.Smith, J. C., 220, 222, 223, 224, 225,Smith, L. I., 210, 347.Smith, P. G., 348.Smith, R. A., 207, 208.Smith, R. B., 393.Smith, R. N., 20.Smith, S., 332.Smith, S. L., 345.Smits, A., 121, 163.Smoluchowski, I., 90.Smyth, C. P., 159, 160, 163.Snell, A. M., 348.Snelling, C. E., 338.Snyder, H. R., 257.Sobotka, H., 104.Sohns, F., 384.Sokolov, V. A., 134.Sollers, E., 153.Somerville, J.C., 269.Soper, H. R., 303.Soremba, K., 179.Sowa, F. J., 208, 210.229.Spiith, E., 314,. 315, 316, 317, 327,304* I 329.Specht, H. E. M., 124.Spencer, J. F., 132.Spielman, M. A., 213.Spies, T. D., 343.Spiller, R. C., 398.Sponer, H., 60, 152.Springall, H. D., 176.Springer, A., 79.Sprung, M. M., 209.Spulnik, J., 392.Stacey, M., 276.Stamatoff, G. S., 290.Stamberg, 0. E., 374, 375.Stamm, H., 122.Stanley, W. M., 353.Starkweather, H. W., 73.Staudinger, H., 76, 78, 274.Stauffer, C. H., 221.Steenbock, H., 336.Steiger, M., 347.Steigman, J., 13.Stein, G., 292, 413.Stein, W. H., 351, 352.Stenhagen, E., 103, 105, 111, 113.Stephenson, O., 254.Stepp, W., 345.St6rba-Bohm, J. P., 129.Stgrba-Bohm, J.S., 129.Sterling, E. C., 290.Stern, J. R., 29.Sternfeld, E., 225.Stevens, 195INDEX OF AUTHORS' NAMES. 437Stevens, J. R., 325, 326, 344.Stevenson, B. H., 311.Stevenson, D., 39.Steward, C. J., 154.'Stewart, M. L., 208.Stewart, T. D., 243.Stiller, E. T., 325, 326, 344.Stodola, F. H., 224.Stoll, A., 332.Storch, E. A., 208.Storch, H. H., 64.Storks, K. H., 107.Stosick, A. K., 167.Strada, M., 407.Strain, H. H., 413.Strassmann, F., 8, 11, 12, 13, 14.Straub, F. B., 354.Street, H. R., 343.Streuli, P., 327.Strock, L. W., 169.Stroh, W., 327.Stromberg, H., 290, 303, 304.Strong, F. M., 413.Strotzer, E. F., 121.Strunz, H., 165.Stuart, H. A., 236.Stubblefield, E. M., 20.Stuewer, R. H., 379.Sturrock, J. G. R., 93.Subbarow, Y., 344, 370.Subrahmanyan, V., 354.Sucher, M., 412.Suess, H., 79.Suga, M., 313.Sugasawa, S., 319.Sugimoto, K., 313.Sugiyama, N., 313.Sulter, P., 393.Sundius, N., 403.Suratkar, T.S., 133.Sutherland, G. B. B. M., 50, 241, 242.Sutton, L. E., 167, 180.Sutton, T. C., 405.Svesnikov, B. I., 90.Swaminathan, M., 343.Swan, G. A., 237.Swarts, F., 116.Sweaney, H. C., 404.Sweeney, B. M., 365, 366.Symons, P., 393.Synge, R. L. M., 352.Szilard, L., 15, 19, 21.Tage-Hansen, E., 348.Takebayashi, M., 228, 229, 232, 233.Talmud, 95.Tananaev, I., 134.Tant, W. P., 402.Tarbell, D. S., 205, 237.Tate, F. G. H., 135.Taylor, G. B., 73.Taylor, H. A., 68.Taylor, H. S., 68, 71, 72, 73.Taylor, T. W. J., 177, 351.Teller, E., 27, 60, 151.Teorell, T., 95.Terry, E.M., 233.Tessmar, K., 264.Tetlow, W. E., 271.Thanheiser, G., 406.Thaxton, H. M., 28.Thayer, S. A., 348.Theilacker, W., 247.Thibaud, J., 12.Thiel, H., 261.Thimann, K. V., 363, 365, 366.Thomas, C. D., 121, 164.Thomas, C. L., 211.Thomas, F., 119.Thomas, J. K., 84.Thomas, W., 247.Thompson, C. L., 396.Thompson, H. W., 84, 85.Thompson, J. M. C., 300, 302.Thompson, S. Y., 342.Thomson, A. M., 338.Thomson, G. P., 15, 18.Thornton, H. G,, 397.Thornton, R. L., 9.Thorpe, (Sir) J. F., 245.Tien, Y. L., 288, 298, 304.Tietze, E., 205.Timm, E. W., 217.Timmis, G. M., 332.Tinker, J. M., 303.Tishler, M., 283.Tittensor, E,, 318.Titus, R. N., 394.Tobler, E., 284.Todd, A.R., 291, 344, 347.Toepffer, H., 259.Tomlinson, G. H., 382.Toth, G., 415.Tozer, B. T., 201.Trabacchi, G. C., 27.Traub, H. P., 367.Tristram, G. R., 350, 351.Trousil, Z., 129.Truesdail, J. H., 344, 370.Trureckaja, R. C., 363.Tschitschibabin, A. E., 320.Tschoidze, V. L., 363.Tschugaeff, L., 289.Tschumanov, S. M., 407.Tseng, K. F., 319.Tsuda, K., 330.Tswett, 412.Turner, E. E., 237, 243, 246, 248,Turner, L. A., 18.Tutte, W. T., 59.Tuve, M. A., 27, 28.Tuzson, P., 336Tyraz, E., 315.Tyrrell, W. A., 29.257438 INDEX OF AUTHORS’ NBMES.Ubbelohde, A. R., 150, 151, 153,156, 157, 160, 163.Uhlenbeck, G. E., 241.Uhlig, H. H., 34.Ulich, H., 241.Ullmann, D., 141.Unger, H., 203.Ungley, C. C., 342.Ungnade, H. E., 347.Urey, H.C., 195.Urushibara, Y., 219, 225, 227, 228,229, 232, 233.Ussing, H. H., 352.Ustrichev, G., 322.Valentin, F., 261.Valentine, W. G., 396.Vallender, R. B., 408.Vargha, L. von, 259.Vass, C. C. N., 204.Vaughan, W. E., 63.Veen, A. G. van, 414.Veibel, S., 393.Veith, H., 161.Venkatarayada, T., 155.Venturello, G., 130.Venturoli, G., 411.Verleger, H., 175.Verner, G., 260.Vernon, A. A., 73.Verrier, M. L., 337.Verweel, H. J., 160.Vieweg, E., 241.Vilter, R. W., 343.Vine, H., 254.Vogel, A. I., 237.Vogt, A., 119.Vogt, R. R., 221, 222.Voigt, R., 230.Volz, H., 29.Voroviev, N. K., 85.VoulliBme, R., 264.Wackher, R. C., 227.Wade, M., 282, 352.Waddell, W. M., 348.Wagenaar, G. H., 390.Wagtendonk, W.J. van, 373.Waisman, H. A., 344, 370.Wald, G., 337, 339.Walden, P., 140.Waldman, B., 20.Walker, J., 299, 300, 304, 305.Wallach, O., 310.Wallensfels, K., 281.Walling, C., 223, 224.Wallis, E. S., 192, 193, 194, 209.Wallis, T. E., 397.Walpole, A. L., 287.Walton, W. H., 400.Wang, A. B. L., 287.Wang, Y. L., 342.Warburg, O., 343, 354, 360.Ward, E. C., 410.Wardlaw, W., 174.Warner, G. C., 366, 367.Warren, B. E., 164, 165.Warren, D. T., 29.Warren, F. L., 293.Warren, L. A., 135, 198, 199, 200.Washbuni, G. R., 135.Wassermann, A., 63, 65, 85, 86.WatanabB, K., 160.Waters, W. A., 93, 209, 225, 254.Watson, H. B., 92, 194, 216, 217,Watson, H. E., 240.Watson, H. H., 402.Watt, G. W., 138.Wawilow, S. I., 90.Weaver, C., 231.Webb, K.R., 134.Wegerif, (Frl.) E., 171.Wehrli, M., 60.Weibke, F., 125.Weichman, F., 122.Weidlich, H. A., 298.Weiner, N., 221.Weinmayr, V., 303.Weinstock, H. H., 344, 370.Weiss, J., 90.Weiss, S., 340.Weizmann, (Miss) A., 290.Weizsacker, C. F. von, 23.Welch, A. J. E., 174.Wells, A. F., 166.Welsh, T. W. B., 146, 147.Welton, R. G., 132.Wendt, G., 325, 326, 344.Went, F. W., 363, 365, 366, 367, 368.Wentzer, H., 122.Werle, E., 414.Werner, A., 247.Wesely, F., 314.Westheimer, F. H., 46, 195.Westphal, K., 325, 326, 344.Westphal, O., 326, 344.Wetroff, G., 121.Weyl, C., 136.Wheeler, J. A., 18.Wheeler, T. S., 319.Whipple, G. H., 349.White, A. H., 162.White, F. R., 351.White, J., 351.White, M. G., 25.White, P. C., 231.White, P. R., 367.Whitehead, R. L. St. D., 93.Whitmore, F. C., 192, 193, 194, 196,Whitmore, W. F., 390.Wibaut, J. P., 221, 237.Wickert, 141.230.197, 289INDEX OF AUTHORS’ NAMES. 439Wicklen, F. C. von, 377.Widdowson, E. M., 349.Wiebe, R., 159.Wiebenga, E. H., 178.Wieking, H., 151.Wiele, H., 120.Wiemann, J., 311.Wiggins, L. F., 260, 261.Wigner, E., 29, 84.Wilbraham, A., 350.Wild, F., 337.Wildman, J. D., 397.Wilds, A. L., 307.Wiles, A. E., 290.Wilkes, S. H., 407.Wilkinson, J. A., 146.Williams, C. R., 400, 402.Williams, E. F., 350.Williams, G., 79.Williams, I., 77.Williams, J. H., 287.Williams, R., 155, 216, 217.Williams, R. J., 344, 370, 371, 372.Wills, J. H., 132.Willstaedt, H., 413.Wilman, H., 179.Wilson, C. L., 196.Wilson, E. B., 242.Wilson, W. J., 276.Winkler, C. A., 84, 86.Winstein, s., 228.Wintner, I., 151.Winzler, R. J., 408.Winzor, F. L., 281.Wirtz, K., 163.Wise, 143.Wishnick, D. M., 390.Wishnick, E. L., 390.With, T. K., 413.nTittig, G., 80.Wittle, E. L., 197.Woerman, N. F., 163.Woldendorf, J. J., 247.Wolf, H., 85.Wolf, P. A., 349.Wolfe, R. A., 411.Wollan, E. O., 155.Wood, A. D., 250.Wood, W. C., 90.Woodward, (Miss) I., 157, 177, 180,Woolley, D. W., 344, 370.181.Worden, A. N., 344.Work, C. E., 344.Work, P., 347.Wormall, A., 345.Wouthuysen, S., 163.Wright, G. F., 381, 383.Wright, M. D., 341.Wright, N., 241.Wrinch, (Mrs) D. M., 185,Wu, C. K., 50, 242.Wutke, J., 247.Wuyts, H., 252.Wyckoff, R. W. G., 240.Wyk, A. J. A. van der, 181.Wyman, J., 109.Wynne-Jones, W. F. K., 46, 84,89,91.Yager, W. A., 160.Yamamoto, T., 418.Yant, W. P., 395.Yareck, N. S., 133.Yarnall, W. Y., 207.Yates, E., 156.Yobayashi, T., 327.Yoshida, S., 330.Yoshimura, F., 313.Youmans, J. B., 339.Young, C. A., 224.Young, D. P., 214.Young, G. T., 271.Yuan, H. C., 247.Yusephovich, A. A., 20.Zaaijer, W. H., 233.Zach, K., 259.Zacharias, J. R., 24.Zachariasen, W. H., 180.Zahn, C. J., 240.Zanstra, J. E., 171.Zanten, P. G. van, 156.Zaretzki, S. A., 125.Zechmeister, L., 253, 336, 413, 415.Zime, O., 344.Zimmerman, P. W., 364.Zinn, W. H., 15.Zisman, W. A., 109.Zoll, P. M., 340.Zollner, C., 417.Zunino, J., 159.Zwartsenberg, J, W., 165

ISSN:0365-6217    

DOI:10.1039/AR9393600421

出版商:RSC    

年代:1939

数据来源: RSC

摘要:

INDEX OF SUBJECTS.ACETANILIDE, N-chloro-, transform-Acetic acid, detection of, 392.ation of, 202.lead salt, reaction of, with ethyleneoctadecyl ester, films, X-ray struc-undecenyl ester, hydrogen bromidevinyl ester, polymerisation of, 80.Acetic acid, thiol-, addition of, 235.Acetic anhydride, reaction of, withethyl alcohol, 84.reagent from, for cyclic ketonesyntheses, 303.Acetoacetic acid, ethyl ester, Claisensynthesis of, 213.Acetoacetic acid, a-bromo-, ethylester, rearrangement of, 225.3 : 4-Acetone j3-1 : 6-anhydrogalac-tom, 258.Acetone 5 : 6-anhydroglucofuranose,259.Acetone 5 : 6-anhydroglucose, 264.Acetone 6-diphenylaminoglucose, 264.Acetone d-glucofuranose, 265.Acetone 1-idofuranose, 265.Acetylene, hydrogen bromide addi-glycol, 92.ture of, 106.addition to, 222.tion to, 219.polymerisation of, 68.spectrum of, ultra-violet, 59.bond-length in, 176.phonic acid, 256.of, 56.of, 46.45, 187.Acetylenic compounds, methyl groupN-Acetyl-N-methyl-p-toluidine-3- sul-Acids, carboxylic, electronic structuredicarboxylic, dissociation constantsorganic, dissociation conetants of,&Acids, resolution of, 25 1.Acraldehyde, reaction of, with cyclo-pentadiene, 65.Actinium-K, 23.Actino-uranium, 11.Acrylic acid, hydrogen bromide addi-tion to, 223.methyl ester, polymerisation of, 76.Ac ylanilides, N - halogeno-, transform-Adenyl pyrophosphate in muscle, 358.stions of, 203.4Adenylic acid, phosphorylation of,Adermin, 190, 325.Adsorbents for chromatographic ana-lysis, 413.for gases, 409.Adsorption in analysis, 413.on films, 114.resolution by, 252.Btiocholane, 295.Agar-agar, 3 : 6-anhydro-1-galactosederivative from, 269.Air.See Atmosphere.6-N-Alaninoglucose, 264." Albumin gland " in snails, 355.Alcohols, aromatic, cyclo-dehydr-unsaturated, cyclo-dehydration of,340.ation of, 288.287.dl-Alcohols, resolution of, 251.Aldehydes, detection of, 394.electronic structure of, 56.Aldol condensation, 2 1 1.Aldols, 212.Alginic acid, structure of, 379.Alkali fluorides, equilibria of, withhydrofluoric acid and water, 134.hydrides;heats of formation of, andof deuterides, 153.Alkaline-earth metals, determinationof, in thermionic valve filamentcoatings, 405.sulphides, lattice energies of, 151.identification of, 390.Alkaloids, 326.Alkanna tinctoria, 281.Alkannin, structure of, 281.Alkyl groups, migration of, in nucleus,rearrangement of, 197.210.halides, spectra of, 55.iodides, reaction of, with amines, 84.Alkylhydrophenanthrenes, prepara-Alkylphenanthrenes, preparation of,Allene compounds, resolution of, 239.Alloys, analysis of, 396.non-ferrous, analysis of, 390.order-disorder in, 42.Ally1 aryl ethers, rearrangements of,to nuclear-alkylated phenols, 205.Dtion of, 290.290INDEX OF SUBJECTS.44 1Ally1 bromide, hydrogen bromideAllylbenzene, hydrogen bromide ad-d-Altrosan, 259.Altrose, 2-amino-, derivatives of, 271.Aluminium chloride, solubility of, incarbonyl chloride, 144.fluoride, equilibrium of, with hydro-fluoric acid and water, 134.oxide, as adsorbent in chromato-graphic analysis, 413.potassium carbonate, 130.sulphate, equilibrium of, withlithium sulphate and water, 132.Amidines, rearrangements of, 199.Amines, aliphatic, separation of, byadsorption, 414.reaction of, with alkyl iodides, 84.tertiary, resolution of, 243.Amino-acids, adsorption of, 414.analysis of, in proteins, 351.detection of, 393.Amino-sugars, 2 69.Ammi uisnccga, 3 15.Ammonia, compounds of, with sul-dipole moment and molecularliquid, reactions in, 136.spectrum of, absorption, 241.addition to, 220, 227, 229.dition to, 222.phur dioxide, 142.shape of, 240.electronic, 55.Ammonium bromide, equilibrium of,with cobalt bromide and water,132.cadmium chloride, crystal struc-ture of, 173.chloride, specific heat of, 155.heptafluoaluminate, crystal struc-ture of, 168.heptafluozirconate, crystal struc-ture of, 168.nitrate and sulphate, equilibriumof, with water, 134.salts, activities of, in ammoniaquaternary, rearrangements of,selenate, equilibrium of, with cal-cium selenate and water, 132.sulphate, equilibrium of, with sul-phuric acid and water, 133.Amylase, soya bean, 377.Amylases, action of, on starch, 374.activity of, effect of heavy waterAmylopectin, separation of, fromAmylose, separation of, from starch,Anabasis aphylla, 329,AnEmia, nutritional, prevention andcure of, 349, 350.solution, 140.199.on, 376, 377.starch, 374.374.Analysis, chromatographic, 412.crystallo-chemical, 398.gas, 405.inorgamc, detection of impuritiesmicroscopical, 388.of dusts and smokes, 402.spectroscopic, quantitative, ofsulphide precipitation in, 416.Aneurin as plant growth substance,as yeast growth substance, 371.determination of, 371.See also Vitamin-B,.in, 415.quantitative, 395.gases, 41 1.366.Angelica glabra, 3 15.Anhydro-acetone glucofuranoses, 261.3 : 6-Anhydrogalactose, 262.3 : 6-Anhydroaldeh,ydo-galactose di-methyl acetal, 269.3 : 6-Anhydroglucose, 259.Anhydrogossypol, 284,2 : 3-Anhydromannose, action ofammonia on, 270.3 : 6-Anhydromannose, 262.Anhydromethylallosides, 26 1.3 : 4-Anhydro-/?-methylgalactopyran-3 : 4-Anhydromethylgalactoside, 261.3 : 6-Anhydro - up-methylglucofuran-oside, 267.3 : 6-Anhydro-/3-methylglucopyran-oside, 267.a-3 : 6-Anhydromethylglucopyran-oside, conversion of, into thefuranoside, 268.2 : 3-Anhydromethylmannoside, 261.Anhydro-sugars, 258.Aniline, determination of, 409.Anilines, nuclear-alkylated, form-ation of, 204.Anions, adsorption and detection of,415.Anthracene, crystal structure of,179.Antimony as fission product ofuranium, 12.detection of, in presence of tin,417.Antimony' pentachloride, reaction of,with potassium iodide in liquidsulphur dioxide, 142.oside, 260.Aphyllidine, 329.Aphylline, 329.p-Apo-2 -car0 t enal, 3 3 7.Apogossypol, 285.Apples, araban of pectin from, 378.Araban, pea-nut, 378.Arachis hypogaea, seeds, constituentsArbacia pustulosa, 281.Arsenic, determination of, 418.of, 378442 INDEX OF SUBJECTS.Arsenic compounds, stereochemistryof, 246.trihydride, determination of, 409.Artabotrine, 33 1.Artabotrinine, 33 1.Artabotrys suaveolens, 331.j3-Arylethylcyclohexanols, cyclisationj3-Arylethylcyclopentanols, cyclisationAspergillus glaucus, pigments of, 386.Aspergillus niger, growth and pigmentAspergillus oryzce, amylase from,Aspergillus terreus, metabolic pro-Asymmetric induction, 250.syntheses, 252.transformation, 247.Atmosphere, detection and deter-mination of gases in, 406.Atoms, nuclei, fission of, 8.Aurapten, structure of, 314.Auxins, growth inhibition by, 369.root formation induced by, 363,Avena coleoptiles, effect of auxins onprotoplasm of, 365.bicyclo-Aza-alkanes, 191.bicyclo[O : 4 : 4]-Aza-l-decaneY 323.bicyclo[l : 2 : 2]-Aze-l-heptme, 321.bicyclo[l : 3 : 31-Aza-l-nonane, 322.bicyclo[O : 3 : 3]-Aza-l-octane, 323.bicycZo[l : 2 : 3]-Aza-l-octane, 322.cis- Azobenzene, 253.Azobenzenes, isomeric, crystal struc-p-Azotoluene, crystal structure of,of, 288.of, 288.formation by, 386.activity of, 376.ducts of, 386.ture of, 181.181.Bacilli, diphtheria, growth of, withpantothenic acid, 370.tubercle, pigment of, 278.Bacteria, determination of, in soils,397.growth substances for, 373.Baicalein, 319.Bean pods, wound hormones from,Beckmann rearrangement, 194.Benzaldehyde, condensation of, withBenzene, determination of, 409.Benzil, benzilic transformation of,368, 369.anhydrides, 21 1.105.crystal structure of, 184.Benzobromoamides, salts, rearrange-ment of, 192.Benzoic acid, ethyl ester, ammono-lysis of, in liquid ammonia, 140.Benzoic acids, halogeno-, field in-tensity at nuclear carbon in, 215.Benzoyl chloride, 3 : 5-dinitro-, asreagent for amino-acid and pep-tide detection, 393.3 : 4-Benzphenanthrene, crystal struc-ture of, 179.Benzylmethylacetic acid, opticallyrtctive derivatives, degradationof, 193.Benzyl phenyl ether, rearrangementof, 209.Beri-beri, 335.Beryllium, preparation of, 125.Beryllium carbonates, 130.double sulphates, 130.Biochemistry, animal, 335.plant, 362.Bios, constituents of, 369.Biotin, 370.Bisethylenediaminopalladous ions,substituted, 254.Bismuth, determination of, 418.Bismuth nitrate, formation of,Bisulphites, addition of, 234.Blindness due to vitamin-A defi-Blood, determination in, of vitamin-Blood-serum, determination in, ofBond lengths in conjugated systems,Bonds, double and triple, 52.double, polymerisation of com-single, 48.Bradycardia caused by vitamin-B,Bromination catalysed by oxygen,Bromine, determination of, in air,radioactive, separation of nuclear131.ciency, 338.B,, 342.carotenoids, 4 14.177.pounds containing, 61.deficiency, 340.231.408.isomerides of, 20.Bromine oxides, 120.Brucine, detection of, 391.Butadiene, dimerisation of, 62.hydrogen bromide and chlorideaddition to, 230.polymerisation of, 64, 72.n-Bukylacetylene, hydrogen bromideaddition to, 224.isoButylene, thiolacetic acid additionto, 235.d2-Butylene, 2-bromo-, hydrogen bro-mide addition to, 224.isoButylenediaminomesostilbenedi-aminopalladous salts, resolutionof, 255.isoButyric acid, ethyl ester, condens-ations of, 213.Byak-angelicin, 315.Byak-angelicol, 315INDEX OF SUBJECTS. 443Cadmium, determination of, 418.lattice temperature of, 155.separation of, from zinc, 417.Cadmium chloride, equilibria of, withcobalt, nickel, and sodiumchlorides and water, 31.Czsium fluorochromate, crystal struc-ture of, 171.peroxide, 124..oxides, crystal structure of, 165.Calciferol, structure of, 309.Calcium, heated, absorbent proper-ties of, 410.Calcium arsenates, equilibria of for-mation of, 134.selenate, equilibrium of, with am-monium selenate and water, 132.sulphate, equilibrium of, withsodium sulphate and water, 132.sulphate dihydrate, dehydration of,135.Calines, 368.Callicrein, purification of, from urine,414.Calycanine, 328.Calycanthidine, 328.Calycanthine, structure of, 327.Camphene hydrochloride, conversionof, to isobornyl chloride, 196.d- Camphor -v-sulphonic acid, a-bromo-, 252.Cannizzaro reaction, 233.Carbohydrates, 258.Carbon, electronic structure of, 51,52.filaments, velocity of vaporisationof, 151.Carbon tetraiodide, hydrolysis of, 236.monoxide, absorbents for, 41 1.detection and determination of,heat of dissociation of, 151.piperidyls, 41 1.determination of, 408.specific heat of, 155.in air, 407.dioxide, absorption of, by di-disulphide, determination of, 409.Carbonyl chloride, determination of,compounds, condensation of, 210.Carica papaya and quercifolia, pollengermination in, stimulated byaneurin, 367.Carotene, isomerisation of, 336.Carotenoids, determination of, 414.Catalysts,.polymerisation, 79.promotmg group migration, 208.Cations, adsorption and detection of,Caulocaline, 368.Cellulose, constitution of, 189.409.reactions in, 143.415.disaggregation and structure of,273.Cellulose, methylation of, 271.oxidation of, 278.solubility of, in hydrofluoric acid,Cereals, anticalcifying action of, 346.Ceric sulphate, equilibrium of, withammonium sulphate and water,13 1,.Cetyl sodium sulphate, penetration offilms by, 111, 113.Chitinase, separation of, 414.a-Chitosamine hydrobromide andhydrochloride, crystal structureof, 184.Chlorination by sulphuryl chloride,233.Chlorine, reaction of, with ozone, 84.Chlorine monoxide, decompositionChloroprene, polymerisation of, 77.Chromatographic analysis, 412.Chromium hezacarbonyl and hexa-chloride, crystal structure of,166.Chromous chloride as absorbent foroxygen, 410.Chrysenes, hydroxy-, synthesis of,303.Cinnamic acid, bromination of, 232.alZoCinnamic acid, methyl ester,Cinnamic acids, synthesis of, Perkin,Citrulline, colour reaction for, 352.Citrus nobilis, 3 19.Claisen condensation, 213.Coal gas, analysis of, 412.Cobalt bromide, equilibrium of, withammonium bromide and water,132.carbonyl hydride, crystal structureof, 166.chloride, equilibria of, withcadmium and copper chlor-ides and water, 131.with lithium and sodiumchlorides and water, 132.sulphate, equilibria of, with copperand nickel sulphates and water,133.Cocaine, analysis of mixtures of, withnovocaine, 392.Co-carboxylase, rela$ion of, to vita-min-B,, 339.Collagen, proline content of, 352.Copper, action of selenium oxy-chloride on, 143.detection of, in aerosols, 403.dietary value of, 349.preparation of, 120.145.of, 84.isomerisation of, 232.210.Copper nitride, crystal structure of,166.phosphides, 121444 INDEX OF SUBJECTS.Crotonic acid, hydrogen bromideaddition to, 224.Crystals, isotope effects in, 157.lattice energy of, 151.melting and rotation of, 163.molecular rotation in, 158.molecular, thermal transformationsphysics of, 150.X-ray reflexion from, 155.rot at ion transformations in,thermodynamics of, 162.thermal energy in, 157.thermal expansion of, 156.vibrational energy in, 153.in, 159.Crystallo-chemical analysis, 398.Crystallography, 148.Cuprene, 68.Curtius rearrangement , 192.Cyanogen iodide, crystal structureof, 165.Cyclisation with a double bond andwith double bonds in differentwith two double bonds, 287.classiflcation in, 398.' an aromatic nucleus, 288.molecules, 2 9 1.Cytisine, structure of, 328.Deafness due to vitamin-A deficiency,Deapogossypol hexamethyl ether,Deapogossypolone, 285.Debye-Waller formula, 155.Dehydro-a-noroestrone methyl ether,Dehydrotetrahydrosumrttrol, syn-Dermatitis, chick, anti-factor for,Derris elliptica, 31 7.Deuterium oxide (heavy water), effectof, on amylases, 376, 377.Deutero-compounds, optical activityof, 237.Deuterons, electric quadripolemoment of, 30.Diacetone galactose, 258.1 : 2-Diacetylethylene, use of, indiene syntheses, 294.d-Diacetylmatteucinol, 253.Diazoaminobenzene, conversion of,into p-aminoazobenzene, 203.Diazoamino-compounds, conversionof, into aminoazo-compounds,203.Diazocyanides, isomeric, 254.Dibenzhydroxamic acids, salts,Dideuteroacetylene, polymerisation337.285.292.thesis of, 317.344.rearrangement of, 192.of, 71.Diels-Alder reaction, 64.Diene synthesis, 291.Diet, factors in, 349.Dietetics, 350.trans-Diethylstilboestrol, 308.Dihydroconiferyl alcohol, 313.4 : 7-Diketo-7-p-naphthylheptoic acid,preparation and cyclisation of,297.Diketones, cyclo-dehydration of, 294.Dimerisation, 62.Dimethyl 3 : 4-anhydro-&methyl-altroside, 266.Dimethyl 2 : 3-anhydro-8-methyl-mannopyranoside, hydrolysis of,270.Dimethyl 2 : 3-t.mhydro-/3-methyl-mannoside, 266.Dimethylanilines, o-substituted,addition of methyl iodide to,216.2 : 3-Dimethylbutadiene, reactions of,with 1 : 2-naphthaquinones, 294.1 : 9-Dimethyldecalol, 288.6.: 8-Dimethylergoline, 334.czs- and trans- 1 : 2-DimethylcycZo-hexane- 1 : 2-diols, pinacolicrearrangement of, 195.cis- and trans-1 : 2-Dimethylcyclo-pentane-1 : 2-diols, action ofsulphuric acid on, 196.o- (/3/3-Dimethyl-u-i8opropylvinyl) -phenyltrimethylammonium iod-ide, 256.D imeth y lsulphone, crystal structureof, 180.endoDicycZopentadiene, 65.Diphenic acid, 4 : 4'-dinitro-, esters,rotation of, 250.Diphenyls, tri-o-substituted, racemis-ation of, 257.Diphenyl ethers, o-amino-, re-arrangements of, 200.sulphide decamethylene ether,4 : 4'-dihydroxy-, crystal struc-tureof, 184.Diphenylamine, crystal structure of,181.uy-Diphenyl- ay-di- 1 -naphthylallylalcohol, catalytic dehydration of,239.Dipoles, relation of, to chromato-graphic adsorption, 413.Diseases, deficiency, 335.Dissociation constants and temper-ature, 45.5 : 6-Ditosyl acetone glucofur~ose,hydrolysis of, 262.Drugs, identification of, 390.Dunnione, structure of, 280.zlloDunnione, 281.Durene derivatives, dipole momentsof, 218INDEX OFDust collectors, 404.Dusts, analysis of, 399.Dysprosium, detection and determin-ation of, 393.siliceous, analysis of, 404.Earths, rare, compounds of, structureEchinochrome A, structure of, 281.Egonol, structure of, 313.Eicosyl alcohol, films, force-areaElements, heavy, in stars, 23.Z-Elliptone, structure of, 317.Energy and entropy of solutions, 42.of cavity formation in solutions,Entropy and energy of solutions,Enzymes, flavoprotein, 354.p-ure, properties of, 353.riboflavin in, 343.Equation, Arrhenius, 83.Equilenin, synthesis of, 307.Equilibria, heterogeneous, 130.Equol, structure of, 313.Erdin, 386.Ergocristine, 332.Ergocristinine, 332.Ergoline, 333.Ergosine, hydrolysis of, 332.Ergosinine, hydrolysis of, 332.Ergot alkaloids, 33 1.Erythroglaucin, 386.Eserine, structure of, 326.Ethane, spectrum of, ultra-violet,Ethane, dichlorotetmfluoro-, 117.Ethers, detection of, 394.of, 127.separation of, 126.curves for, 98.“ transuranic,” 11.34.42.58.hezafluoro-, 116.rearrangements of, group migrationin, 207.Ethyl .alcohol, reaction of, withEthylene, determination of, in gasesacetic anhydride, 84.from ripening f r u i t , 408.dimerisation of, 62.polymerisation of, 64, 71.spectrum of, ultra-violet, 58.Ethylene, tetrafluoro-, 116.E thylene-aj?-bis( phenyl-n-butyl-arsine), resolution of, 246.Ethylene glycol, reaction of, withlead tetra-acetate, 92.Ethyleneimines, substituted, prepar-ation of, 244.Ethylene diiodide, decompositionof, 84.Euparin, structure of, 312.Europium salts, 125.UB JECTS.445Felspar, determination in, of quartz,Ferricyanides, crystal structure of,Films, adsorption on, 115.395.169.built-up, 103.mixed, properties of, 114.physical properties of, 94.skeleton, 107.stereochemistry in, 11 1.tables of, 101.Filtrate factor, 344.Flavone, 5 : 6-dihydroxy-, synthesisFlavones, demethylation of, 318.Flavoprotein enzymes, 354.Fluorescence microscopy, 392.Fluorination, 11 7.Fluorine, electronic structure of, 50.Foods, hydroxybenzoic acids as pre-servatives for, 391.Formaldehyde, electron structure andspectrum of, 57.Formic acid, electronic structure andspectrum of, 57.Frog-spawn, galactose in, 356.Funiculosin, 385.Furans, reduction of, 310.Furans, amino- and hydroxy-, 311.Furfurylideneacetophenone, hydro-Fury1-2-carbimidey 3 11.Fustin, structure of, 319.of, 319.lysis of, 297.Galactogen, 355.Galactose in animals, 354.Gallium fluoride, and its complexes,127.nitride, crystal structure of, 166.salts, 128.by thermal conductivity, 412.microchemical, 405.spectroscopic, 41 1.Gas analysis, 405.Gases, detection and determinationGeodin, 386.Germanium imide, 139.nitride, crystal structure of, 166.Gladiolus corms, root formation on,364.Glass, with altered refractive index,108.D-Gluco-D-guloheptolactone, 2-[D-gluco-D-gulohepto]hexahydroxy -hexylbenziminazole from, 25 1.Glucosamine, configuration of, 269.Glucose ethers, 264.Glucose, %amino-, derivatives of, 271.d-Glucose, derivatives, conversion of,into d-idose derivatives, 265.of, in atmosphere, 407.6-halogenohydrins, 2 67446 INDEX OF SUBJECTS.Glucosyl fluoride, 146.Glutamic acid, in protein hydrolys-tumour, configuration of, 350.Glycine, crystal structure of, 179.Glycogen, enzymic hydrolysis of, inliver and yeast, 361.hosphorolysis of, 359.torage of, in liver after galactoseingestion, 355.ates, 352.dlycol-lignin, 381.Gossic acid, 285.Gossypol, structure of, 284.Gossypolone tetramethyl ether, 285.Grignard reaction in hydrogen sul-Griseofulvin, 385.Growth substances, plant, 362.phide, 146.Haemocuprein, cure of anzemia with,Haemoglobin, muscle, 357.Halogens, migration of, in nucleus,Heat of solution, from intermolecular350.210.forces, 34.ionic, 37.Helium, isotope, 3He, 24.Helium-11, thermal expansion of, 156.HeEiz pomatia, galactose metabolismHemicelluloses, analysis of, 380.Heteroauxin, root formation inducedHeterocyclic compounds, 310.Hexamethylbenzene, crystal struc-cycZoHexane, chlorination of, 233.cycEoHexane, 1 : 2 : 4 : 5-tetrabromo-,crystal structure of, 184.Hexanols, detection of, 393.Hexatriene, use of, in diene syntheses,294.Hexose &phosphate, fission of, byzymohexase, 359.cycZoHexylideneacetaldehyde, con-densation of, with cyclohexa-nones, 309.Hofmann rearrangement, 192, 251.Hof mam-mar tius rearrangement, 204.Hormones, plant, wound, 368.Hydratropamide, Hofmann degrada-( + )-Hydratropamide, Hofmann re-Hydrazine, solvent properties of, 146.Hydrindanones from hydronaphtha-Hydrocarbons, chlorinated, detectionin, 355.by, 363.ture of, 175.sulphonation of, 234.tion of, 193.arrangement of, 25 1.lene derivatives, 308.of, 409.mixed, analysis of, 410.Hydrocarbon compounds, long-chain,phase diagram for, 97.Hydrogen, absorbent for, 409.ortho- and para-, thermodynamicsof, 158.para-ortho transition of, 88.single bond in, 48.HydrGgen bromide, addition of, 2 19,220, 221, 225.thermal transformation of, 160.chloride, thermal transformation of,cyanide, determination of, 409.fluoride, crystal structure of, 165.. liquid, as reagent for cyclicketone syntheses, 303.iodide, photo-ionisation and spec-trum of, 54.perselenide, 122.sulphide, determination of, 409.liquid, solvent action of, 146.Hydroxy-acids, polymerisation of,61.160.reactions in, 144.in air, 407.Hydroxy- sulphones, rearrangementsof. 197.Hypochlorous acid, addition of, 236.Hypovitaminosis-A, dark-adaptationtest for, 338.Imino-ethers, rearrangements of, 199.Iminopersulphuric acid, 124.isoImperatorin, synthesis of, 315.Indigotin suspensions for determin-ation of bacteria in soils, 397.Indium nitride, crystal structure of,166.Indium nucleus, isomerism of, 19.Indole alkaloids, 326.Indolylacetic acid, root formationinduced by, 363.Indolylbutyric acid, rooting of cut-tings due to, 364.mesoInosito1 in bios, 369.Insulin, crystal structure of, 184.Intermolecular forces in solutions,Invar alloys, thermal expansion of,Iodides, preparation of, 11 8.Iodine, as fission product of uranium,Iodine pentafluoride, crystal structureIons, heats of hydration and solutionIron, detection of, in dusts, 403.33.156.12.determination of, in air, 408.of, 166.of, 37.reagents for, 390.determination of, in dusts, 400.dietary value of, 349INDEX OF SUBJECTS.447Iron carbonyl hydride, crystal struc-enneacarbonyl, crystal structurepentacarbonyl, crystal structureture of, 166.of, 167.of, 166.nuclear, 19.Isomerisation, cis-trans-, 232.Isomerism, cis-trans-, 253.Isoprene, dimerisation of, 62.Isotopes, gaseous, separation of, 412.Itaconic acid from Aspergillus, 386.Juglone, 278.Karangin, structure of, 316.Kellin, structure of, 315.Kellinone, 316.Keten, dimerisation of, 84.Ketochrysenes, synthesis of, 303.1 -Keto-7-methoxy-2-methyl-1 : 2 : 3 : 4-tetrahydrophen-anthrene, 30 1.2 -Keto - 10-methyl-A1~s-oc talin, 295.Ketones, cyclic, formation of, fromfrom dicarboxylic acid, 305.3-Ketoquinuclidine, condensation of,5-Ketoruban, 324.Kinetics, chemical, 61.Knoevenagel condensation, 2 11.monocarboxylic acids, 300.detection of, 394.electronic structure of, 56.with quinoline-4-aldehyde, 324.Lactose, origin of, in animals, 355.LLevoglucosan, 258.Lanthanum, preparation of, 128.Lapachol, structure of, 278.Lawsone, 278.Lawsonia alba, 278.Lead, detection of, 390, 403.in presence of mercury andsilver, 390.in dusts, 400.Lead imide, amphoteric action of,139.iodide, potassium acetate solutionsof, as reagent for alkaloids anddrugs, 390.Leucine, labelled, isolation of, fromprotein hydrolysates, 352.Lignin, 380.determination of, 419.distillation of, 383.preparation of, 381.structure of, 383.of known refractive index forLiquids, molecular forces in, 33.microscopy, 39 1.Liquids, organic, refractive index of,Liquid state, 99.Lithium chloride, equilibrium of,with cobalt chloride and water,132.chloride dihydrate, dehydration of,135.peroxide, 124.sulphate, equilibrium of, withaluminium sulphate and water,132.Lithopone, photomicrography of,ultra-violet, 395.Lithospermin erythrorhizon, 282.Liver, glycogen hydrolysis in, 36 1.Lomatiol, structure of, 280.isolomatiol, 280.Lossen rearrangement, 192.Lungs, detection in, of quartz, 404.mineral dust in, 403.8-Lupinan, 330.Lupinan alkaloids, 328.dl-Lupinine, resolution of, 329.Lupinus sericeus, 329.Lycopodium powder as referencesubstance in powder analysis,397.dl-isolysergic acid, 332.Lysergic acids, 332.392.Magnesium, lattice temperature of,Magnesium oxide, lattice temperaturesulphate, equilibria of, with mag-nesium chloride, nickel sul-phate, zinc sulphate, and water,133.Maleic acid, methyl ester, isomeris-Malonic acid, ethyl ester, ammono-Manganese, preparation of, 125.Manganese sulphate, hydrates, 135.a- and p-Matridines, 330.Matrine, 329.Matrinic acid, 330.Melting point, determination of, withMelting points, two- and three-Mercury, detection of, in presence ofvapour, detection of, in air, 408.Mesitylene derivatives, dipolemoments of, 218.Mesitylmagnesium bromide, condens-ations with, 213.Mesomorphous state, 100.Mesons, 30.155.of, 155.hydrates, 135.ation of, 232.lysis of, in liquid ammonia, 140.microscopic heating block, 393.dimensional, 100.lead and silver, 390448 INDEX OF SUBJECTS.8-Methklhydrindan-l-one," 305.'1 1-Methyloctahydrophenanthrene,Metals, action of selenium 0x3solubility of, in ammonium saltrsolutions of, in liquid ammoniaMethacrylic acid, methyl ester, polyMethane, crystals, specific heat ofmixed crystals of, with kryptonspectrum of, ultra-violet, 58.y-6-Methoxy-3 : 4-dihydronaphth-alene-1-butyryl chloride, 304.2'-Methoxydiphenyl-6-carboxylicacid, 2-nitro-, 257.6-Methoxy-l-ethinyltetralin, 1-hydr.oxy-, 291.4-Methoxy- 1 -methyl-d l-cycZohexene-2-y-butyric acid, 304.4-Methyl acetone fructose, 264.3-Methyl acetone sorbose, 264.Methylacetylene, hydrogen bromideaddition to, 224.polymerisation of, 7 1.9-Methyldecalin, 287.16-Methyldodecahydrochrysenes, 297.3-( 2'-Methylenecyclohexylidene- 1'-)propene, 310.Methylene radical, electronic struc-ture of, 60.endoMethy lenetetrahydrobenzalde-hyde, 65.6-Methylergoline, 333.Methylglucosaminide, structure of,270.Methyl group, bond length in, 175.o-Methyl groups, reduction of meso-4-MethylcycZohexanol, asymmstrica-Methvlhexoside chlorohvdrins.267.chloride on, 143.137.138.merisation of, 73, 80.158.161.merism by, 218.dehydration of, 252. Gapht haquinone pigments , 2 7 8.Qaphthyl ethers, detection of, bymeans of picrates, 393.Naphthylacetic acid, root formationMicrospectrograph, grating, 392.Migration from side-chain to nucleus,Milk, determination in, of carotenoids,human, antirachitic potency of,Molecules, polyatomic, electronic202.414.346.spectra of, 47.electronic structure of, 48.long-chain, formation of, 67.overturning of, 108.Molybdenum, preparation of, 125.Molybdenum hezacarbonyl, crystalstructure of, 166.pentachloride, crystal structure of,166.Monolayers, electron-ray structureof, 107.molecular interactions in, 110.penetration of, 112.physical properties of, 94.thickness of, 105.Morphine, detection of, 391.Moulds, growth substances for, 373.Mucor ramannianus, growth stimul-Multilayers, 103.metabolic products of, 385.ation of, 372.electrical properties of, 109.electron-ray structure of, 107.X-ray structure of, 106.skeleton, 107.thickness of, 105.Uuscle, aerobic metabolism of, 357.anaerobic glycolysis in, 358.Kyogen, crystallisation of, 353.Myristic acid, films, force-area curvesfor, 98.3-lv~ubllylu~ballll, L O I .2-Methylcyclopentene-3 : 4-dione,5-Methyl- 1 : 2-cyclopentenonaphth-291.u,-u-a-A\ a~~ibiiyiuuii~cILtiiiiuu, a : i)-w~,-nitro-, Hofmann degradation of,193.Nematospora gossypii, growth sub-stances for- 373.cursor, 342.122.Methyl thiosulphite, hydrolysis of,1 -Met hy 1 - 2 - vinylcy clohexene, 2 93.2-Methyl- 1 -vinylcycZohexene, 293.Micro-manipulators, 394.Microscope, polarising, 392.Microscope heating block, 393.Microscopy, 388.fluorescence, 392.crystal structure of, 171.Neutrons, emission of, in nuclearfission, 14.Nickel, thermal expansion of, 156.Nickel chloride, equilibrium of, withcadmium chloride and water,131.sulphate, equilibria of, with cobalt,copper, and magnesium sul-phates and water, 133IKDEX OF SUBJECTS.449Nicotinic acid, 343.Niobium iodides, 119.Nitrides, crystal structure of, 165.preparation of, 120.PolyNitro-compounds, detection of,Nitrogen, electronic structure of, 51.Nitrogen compounds, containing393.three-membered ring, 243.ring, 320.tervalent, resolution of, 187.stereochemistry of, 239.oxides, absorption of, 411.determination of, 409.Sobiletin, structurt.of, 31 9.2-Norequilenin, 298.Norequilenin methyl ether, synthesisof, 303.Norlupinan, I9 1 .Norlupinan -4 and B, 323.z-Noroestrone, 798, 306.Novocaine, analysis of mixtures of,Nuclear forces, theory of, -34.Nutrition and vitamins, 335.level of, 342.Nyctalopia, 33s.with cocaine, 392.d3 : 3’-Octahydrodipheny1 from butsz-Octahydropyridocoline, isomerism of,Octahydrorottlerone, 31 8.Octalupine, 329.Oestric acid methyl ether, 306.Oestrogens, synthetic, 190, 308.Oestrone, synthesis of, 305.Olefinic linkings, addition at, 187.Olefins, absorpt<ion of, by sulphuricOleic acid, films, force-area curves of,Opium alkaloids, separation of, 415.Optical activation, 249.actirity, transient, detection of, 248.Orange-peel oil, fish poison from, 314.Ores, analysis of, 396.Organic chemistry, 186.compounds, crystal structure of,detection of, by m.p.and refrac-solubility of, in hydrofluoric acid,diene, 64.240.* : lo- Octalin, 287.acid, 410.bisulphite addition to, 234.97.175.tive index, 393.145.Ortho-effect, 215.Osmium phosphide, 122.Osthol, 314.Oxalic acid, dihydrate, crystal struc-ture of, 180.1-strychnine gallium salt, 128.REP.-VOL.XXXVI.Oxalyl chloride, hydrolysis of, 84.Oxamide, crystal structure of, 181.Oxidants for hydrogen bromideOxidation in liquid sulphur dioxide,Oxygen, absorption of, 410.as catalyst in hydrogen bromideelect,ronic structure of, 50.Oxygen ring compounds, 310.Oxymatrine, 330.Ozone, decomposition of, 84.addition, 22 1.142.addition, 228.determination of, in air, 408.reaction of, with chlorine, 84.Palladous atoms, 4-covalent, valencyPalmitic acid, and its ethyl ester,Pantothenic acid, 344.Pantothenic acid-/3-alanine asParafKns, high molecular-weight ,Pea-nuts. See Arachis hypogaea.Pectic acid, structure of, 379.Pectin, 378.Pectins, jelly formation by, 359.Pellagra, cure for, 343.Penicillium chrysogenum, inetabolicPenicillium funiculosum, metabolicPenicillium griseo- f ulvum, metabolicPenicillium viniferum, metabolic pro-a-Pentadeu terophenylbenzylamine,cycloPentadiene, bromination of, 232.configuration of, 254.films, force-area curves for, 97.growth substance, 370.structure of, 178.analysis of, 380.products of, 385.products of, 385.products of, 385.ducts of, 385.resolution of, 237.dimerisation of, 62, 84.polymerisation of, 65.reaction of, with acraldehyde, 65.d 2-Pentene, hydrogen bromide addi-da-Pentinen-y-01, resolution of, 238.neoPentyl iodide, rearrangement of,197.neoPentylmagnesium chloride, neo-pentyl bromide and iodide from,197.Pepsin, enzymically active constitu-ents of, 353.Peptides, detection of, 393.Periodic acid, action of, on celluloseand starch, 277.Perkin condensation, 2 1 1.Peroxide effect, 219.Peroxides as catalysts in Cannizzarotion to, 223.reaction, 233.450 INDEX OF SUBJECTS.Phaseolus vulgaris, root formation in:363, 364.Phenanthrene, bromination of, 231.Phenol-lignin, 381.Phenolic ethers, catalysed rearrange.ments of, 209.dl -p - Phenylenebi siminoc amphor , re 1solution of, 252.Phenyl y-ethylallyl ether, rearrange-ment of, 206.Phosphides, 12 1.P hosp hoglucomut ase, 3 5 9.Phosphonitrile, 121.Phosphorolysis, 361.Phosphorus, crystal structure of, 164.molecular structure of, 121.radioactive, as indicator in glyco-pentafluoride, crystal structure of,166.pentoxide, molecular structure of,121.Photomicrography in microscopicanalysis, 394.6 -Phthalimidoglucose, 264.Phthoicol, 278.Phyllocaline, 368.Fhysics, crystal, 150.Physcion, 386.Picrolonic acid, salts, with amino-acids, crystal habit and opticaldata for, 392.Pigments, green-leaf, separation of,from solution, 413.naphthaquinone, 2 7 8.organic, detection of, by micro-sublimation, 394.Pinacol transformation, 195.Piperidine derivatives, meta- bridgingof, 322.6-Piperidylglucose, 264.Piston oils, for use in pressuremeasurement of films, 104.Pisum, aneurin as growth factor for,367.Pisum sativum, root formation in,364.Plants, growth inhibitors of, 369.lysis, 361.Fhosphorus chlorofluorides, 118.growth substances of, 362.promoting cell extension, 365.pectic substances of, 378.root formation induced in, byauxins, 363.sub-tropical, root formation in-duced in, 363.wound hormones of, 368.Plant viruses, 353.Plumbagin, 278.Polar groups, reactivity of, gradedfrom monolayer penetration,113.Polymers, active, lifetime of, 75.Polymerisation, gas-phase, 68.Polyporus adustus, growth of, withPolystyrene, ultracentrifugal separ-Polythionic acids, formation of, 122.Polyuronides, analysis of, 380.Pongamia glabi-a, 3 16.Potassium, vibrational energy of, 154.Potassium ammono-magnesiate,-plumbite, and -sodiate, 139.pmmonostannite, 139.2 : 2’-dipyridyl and 4 : 5(o)-phen-anthroline aurous cyanides, crys-tal structure of, 174.fluorochromate, crystal structureof, 171.heptafluoniobate, crystal structureof, 170.heptafluotantalate, crystal struc-ture of, 170.iodide, reaction of, with antimonypentachloride in liquid sulphurdioxide, 142.nitrate, equilibrium of, with nitricacid and water, 134.peroxide.decomposition of, 124.salts, equilibria in systems of, withkinetics of, 61.liquid-phase, 77.aneurin, 373.ation of, 81.water, 133.Potential, surface, 101.Powders, analysis of, 397.Praseodymium, preparation of, 125.Precipitation apparatus, electro-static, 401.thermal, 402.Primetin, structure of, 319.Primula modesta, 319.Proline as plant growth substance,cycZoPropane, bromination of, 231.Propionic acid, detection of, 392.Propylene, hydrogen bromide addi-Propylene, 1- and 2-bromo-, hydrogenProteins, films, viscosity of, 96.of dusts, 401.368.tion to, 220.bromide addition to, 223.in diet, 349.structure of, and amino-acidProtoactinium, nuclear fission of, 18.Pump, hand, for sampling, 408.Pyridine, homologues, preparationof, 320.Pyridoxin. See Vitamin-B,.Pyruvic acid, disposal of, in relationto vitamin-B,, 339.analysis, 35 1.Quartz, detection of, in lungs, 404.determination of, in felspar, 395INDEX OF SUBJECTS.451Quinine derivatives, preparation of,Quinoline, %amino-, preparation of,isoQuinoline alkaloids, 330.Quinolinic acid as cure for pellagra,324.320.343.Radioactivity, 7.natural, 23.X-Rays, cameras for, 156.dsraction of, use of, in analysisreflection of, by crystals, 155.of dusts, 404.Reactions, bimolecular, r61e of sol-vents in, 83.theories of, 86.chain, nuclear fission in, 16.in non-aqueous solutions, 133.mechanism of, 191.Reagents, microchemical, for ions,Rearrangements, 191.Refractive index as criterion ofpurity, 391.390.of organic acids, 392.Reinecke’s reagent for alkaloids, 391.Resins, synthetic, as adsorbents, 416.Rhenium arsenide, 122.Rhizocaline, 368.Rhodotorula, growth stimulation of,372.Riboflavin, 343.Rickets, 335.Ring closures with aromatic rings,301.with unsaturated alicyclic rings,303.Rocks, analysis of, 396.Rotation, molecular, in crystals, 168.restricted, 255.isoRottlerin, structure of, 318.Rottlerone, structure of, 318.Ruban-5-01, 325.Rubntoxanone-9, 324.Rubidium cadmium chloride, crystalstructure of, 173.peroxide, 124.oxides, crystal structure of, 163.Rubroglaucin, 386.Ruthenium phosphides, 12 1.Salicylic acid, distinction of, fromp-hydroxybenzoic acid, 391.Samarium, detection and detennin-ation of, 393.Samarium salts, 126.Sampling of dusts, 390.Santonin, ammonolysis or, in liquidammonia, 140.Saponin, penetration of films by, 113.Scandium, crystal structure of, 164.Scandium compounds, 129.Seaweeds, alginic acid from, 379.Selenium, determination of, insmokes, 403.Selenium oxychloride, reactions in,143.Semiertrbazides, use of, for detectionof aldehydes, ketones, and azides,394.scurvy, 335.Seseli indicin, 316.Seselin, structure of, 316.Shikonin, structure of, 282.Silane, difluoro-, 117.Silicon compounds, 118.Silver, detection of, in presence ofa-Silver iodide, thermal expansion of,Skiinmia japonica, 3 16.Smokes, analysis of, 399.Snails.See Helix pornatkz.Sodium, electronic structure of, 48.Sodium chloride, equilibria of, withcadmium chloride and water,131.with cobalt chloride and water,132.sulphate, equilibrium of, with cal-cium sulphate and water, 132.heptahydrate, dehydration of,135.triphenylmethyl, condensationswith, 213.Soils, determination in, of bacteria,397.Solid state, 100.Solubility in hydrofluoric acid, 145.in liquid sulphur dioxide, 140.Solutions, energy and entropy of, 42.ideal and regular, thermodynamicsintermolecular forces in, 33.non-aqueous, reactions in, 135.partition functions for, 38.solid, order-disorder in, 42.tetramide, 139.lead and mercury, 390.156.of, 40.Solvents, effect of, on reaction velo-city, 82.industrial, toxicity of, and theirdetection and determination,408.non-aqueous, reactions, in, 136.Sophora jlavescens, 330.Soya beans, amylase of, 377.Spectra, electronic, of polyatomicmolecules, 47.ultra-violet, vacuum, 53.vibrational, and structure, 59.Staphylococcus aureus, growth sub-Stars, nuclear reactions in, 22.stances for, 373452 INDEX OF SUBJECTS.Starch, constitution of, 188.disaggregationand structure of, 272.methylation of, 271.oxidation of, 277.wheat, 374.for, 98.Stearic acid, films, force-area curvessurface potential of, 102.Stearic acid, barium salt, skeletonmultilayers of, 107.Steel, analysis of gases from, 406.Stereochemistry, 236.Steroids, synthesis of, 190, 286.Stilbene dibromide, 227.isostilbene, conversion of, into stil-bene, 225, 232.Stilboestrol, C-alkyl derivatives, 308.Strawberries, pectic acid from, 378.Streptococcus dunnii, 280.Streptococcus hmmolyticus, growth of,with pantothenic acid, 370.Strontium peroxide, 124.Strychnine, detection of, 391.Xtyrax japonica, 3 13.Styraxin aldehyde, 313.Styraxinolic acid, 3 13.Styrene, bisulphite addition to, 234.hydrogen bromide addition to, 222.polymerisation of, 77.thiolacetic acid addition to, 235.thiophenol addition to, 236.Suaveline, 33 1.Sugar anhydrides, 258.p-toluenesulphonates, hydrolysisSugars, asymmetric oxidation of, 252.isomeric, from fission of anhydro-Sulphates, determination of, 415.Sulphides, precipitation of, 416.Sulphonation by sulphuryl chloride,Sulphones, detection of, 393.Sulphur, crystal structure of, 164.Sulphur dioxide, absorption of, 41 1.of, 259.rings, 263.234.specific heat of, 155.compounds of, with ammonia,determination of, 409.liquid, conductivity of, 140.reactions in, 140.Sulphuryl chloride, chlorination by,Surface potentials, 101.Surface pressure, measurement of,Surfaces, chemistry of, 94.142.tetroxide, properties of, 123.233.sulphonation by, 234.94.Tachysterol, structure of, 309.Tantalum iodides, 119.Tar, determination of, in dusts, 400.Tellurium, as fission product ofTe tradeuterethylene, spectrum of,Tetrahydroeuparin, synthesis of,Tetrahydrofurans, hydroxy-, 31 1.Tetrahydropyran-4-carboxylic acid,preparation of bicyclo-compoundsfrom, 321.a-Tetralone, condensation of, withacetylcyclohexene, 295.Te trame t hy lammonium dichloro -iodide, crystal structure of,165.Te trame t h ylet h ylene bromoh ydrin ,pinacolone from, 196.Thermal expansion of crystals, 156.Thermodynamics and structure ofcrystals, 150.of solutions, 40.Thiamin.See Vitamin-B,.Thiohydrolysis, 146.Thionyl acetate and thiocyanate,Thiosulphates, decomposition of, 123.Thiosulphurous acid, 122.Thorium, fission products of, 14.uranium, 12.isotopes, isomeric, 21.59.312.141.neutron emission by, 18.phosphide, 12 1.phosphides, crystal structure of,Titanium iodides, 119.nitride, crystal structure of, 166.a- and fi-Tocopherols, structure of,Toddalolactone, structure of, 315.Toluene, bromination of, 231.chlorination of, 233.o-Toluidine-5: 5-disulphonic acid,resolution of, 252.3-Tosyl diacetone glucose, removalof tosyl from, 260.Tosyl groups, removal of, 260.3-Tosyl methyl glucopyranoside,hydrolysis of, 261.2-Tosyl fi-mathylglucoside, hydro-lysis of, 260, 265.Transformations of different order,thermodynamics of, 96.Traumatin, 368.Triacetyl acetone fructose, 264.Triacetyl glucose 1 : 2-anhydride, 258.Triacetyl 4-mesyl /3-methylgalacto-pyranoside, :action of sodiummethoxide on, 260.Triacetyl 4-mesyl ,!3-methylgluco-pyranoside, action of sodiummethoxide on, 260.n-Triacontane, crystal structure of,178.166.347INDEX OF SUBJECTS.45 3Tricaproin, films, force-area curvesTriethylamine, solution of, in liquidsulphur dioxide, 141.Trimethylamine oxide, crystalstructure of, 180.Trimethyle thylene, hydrogenbromide addition to, 221, 224.Trimethylhazeinic acid, 319.2 : 4 : 6-Trimethyl p-methyl-d-ido-pyranoside from 2 : 3-anhydro-methylmanno side, 2 65.Trioxymethylene, catalytic de-composition of, 84.Triple point, 99.2 : 4 : 6-Triisopropylphenyl iso-propyl ether, treatment of, withphenol and boron fluoride,208.Triticum vulgare, seeds, growth sub-stances in, 373.Z-Tudarinine, 331.Tumours, glutamic acid in, configur-ation of, 350.Tungsten hezacarbonyl, crystalstructure of, 166.of, 97.dg-Undecenoic acid, hydrogenbromide addition to, 223.d 1°-Undecenoic acid, hydrogenbromide addition to, 220,229.bg-Undecenol, hydrogen bromideaddition to, 223.dg-Undecynoic acid, hydration of,225.dl*-Undecynoic acid, hydrogenbromide addition to, 224.Uranium, disintegration of, 8.fission products of, 14.isotopes, 11.separation of, 16.neutron emission by, 18.Urine, human, callicrein from, 414.Valine, dietary value of, 349.Valves, thermionic, determination ofalkaline-earth metals in coatingsof filaments of, 405.Vanadium iodides, 11 9.oxychloride, action of liquidhydrogen sulphide on, 146.Vanthoffite, 130.Velocity of reaction, solvent r61e in,Vibrational energy, Debye expressionVinyl bromide, hydrogen bromidecompounds, polymerisation of, 67.Vinylacetylene, hydrogen bromideand chloride addition to, 231.82.for, 154.addition to, 220.a-Vinylcinnamic acid from benz-aldehyde and crotonic anhydride,211.1 -VinylcycZohexene, 293.3-Vinylcyclohexene from butadiene,Viscosity, surface, measurement of,Vitamins, and nutrition, 335.Vitamin-A, deficiency of, effects of,64.94.antirachitic, 309.337.determination of, 336.methyl ester, synthesis of, 337.Vitamin-A,, 337.Vitamin-B,, 339.assay of, 341.deficiency of, bradycardia in, 340.detection of partial deficiency of,342.Vitamin-B, complex, 343.Vitamin-B,, 325, 343.as yeast growth substance, 372.See also Aderrnin.Vitamin-C, 345.Vitamin-D, 346.Vitamin-D,, isomers of, 346.Vitamin-E, 347.Vitamin-K, 347.Vitamin-K,, constitution of, 282.synthesis of oil resembling, 283.structure of, 309.Wagner-Meerwein rearrangement,Water, spectrum of, electronic, 55.Wettability and deposition of films,Wheat starch, 374.196.104.Xerosis, 335.m-Xylem, chlorination of, 233.m-2-Xylidine, acetyl derivative, nitr-ation of, 218.Yeast, glycogen hydrolysis in, 361.growth substances of, 369.Yohimbine, detection of, 390.Zea mais, root formation in, 364.Zinc, detection of, 390.seeds, growth substances in, 373.lattice temperature of, 155.separation of, from cadmium,Zinc amide, amphoteric action of, 238.nitride, 120.sulphate, equilibria of, withmagnesium sulphate, sulphuricacid, and water, 133.<ymohexase, action of, on hexosediphosphate, 359.cobalt, or nickel, 417

ISSN:0365-6217    

DOI:10.1039/AR9393600440

出版商:RSC    

年代:1939

数据来源: RSC