ISSN:0365-6217    

DOI:10.1039/AR94138FP001

出版商:RSC    

年代:1941

数据来源: RSC

摘要:

ERRATUM.VOL., 1940, 37,Page Line70 6" for 66 121' & 2" '' read '( 112" & 2" ; see ref. 44, p. 1435."* From bottom

ISSN:0365-6217    

DOI:10.1039/AR9413800006

出版商:RSC    

年代:1941

数据来源: RSC

摘要:

ANNUAL REPORTSON THEPROGRESS OF CHEMISTRY.GENERAL AND PHYSICAL CHEMISTRY.1. INTRODUCTION.Owma to the lack of recently published work in physical chemistry it isbecoming increasing difficult to adhere to a planned scheme of articles overa short period of years. Any lack of balance in the present report is entirelydue to this state of affairs.Much attention is usually devoted to spectra as a means of determiningthe structure of molecules. In such surveys, however, there has been smallmention of electronic absorption spectra in the ultra-violet. Although it isdifficult to go deeply into the origin of the absorption bands in this region ofthe spectrum, yet there is much to be learned from an exact study of spectraof this type. Magneticmeasurements provide yet another tool for investigation of molecularstructure and reactions. The subject is a wide one and therefore W.R. Angusrestricts his report exclusively to results from substances exhibiting dia-magnetism. It is hoped in the future to deal with paramagnetism.If two groups of atoms are joined together by a single bond, it is knownthat these groups may or may not rotate with respect to each other. Thecriterion for non-rotation has hitherto been the isolation of the two isomers.This condition only obtains when the energy required to rotate the group ismuch greater than kT. When that energy is only somewhat greater thankT, chemical methods are inapplicable. Here, however, specific heatmeasurements, coupled with observations on infra-red spectra, revealphenomena which can only be explained if it is supposed that there is hinderedrotation.H. W. Thompson reviews the subject in his report together withsome additional infra-red work.R. A. Morton records recent advances in this field.H. W. M.2. ABSORPTION SPECTRA.The present Report deals with absorption spectra as a part of physicalchemistry, but the topic has such wide ramifications that a unified pictureof the state of the subject is not easy to achieve in a small space. Theapplications of spectrophotometry to analytical and biochemical problemshave been discussed elsewhere (see p. 26 for references).In no field has improved experimentation given a greater reward tha8 GENERBL AND PHYSICAL CHEMISTRY.in the study of absorption spectra. This is not the place to discuss the greatadvances which have been made in technique, but it is noteworthy thatfor at least 20 years the possession of adequate equipment has acted asa stimulus to the assimilation of theoretical ideas.The foundations forfundamental advances have been well laid; the need is now for better data,and, as will be seen in many of the researches reviewed below, the capacityto make use of such data is not lacking.Notation.-If lo is the intensity of light of wave-length A incident uponan absorbing medium of thickness d, and I the intensity of the emergentlight, log &/I = E (extinction) = 7cd. Beer’s law states that absorptionis proportional to the number of molecules in the light path, i e . , I =l o .l O - & d where c is molar concentration (e.g., of an absorbing solute in a“ transparent ” solvent), d is thickness in em., and E is the molecular ex-tinction coefficient. (Alternatively, I = Ioe-4nd/a, K = 0.1832~cA, A incm.) The expression stands for log I o / I for a d-em. layer of concen-tration c, and is useful as a way of describing an actual measurement, andfor specifying the intensity of absorption of mixtures or substances of un-known molecular weight, in the form E;&.. An absorption band is usuallydescribed in terms of Amax. or vmx. i.e., the wave-length in A.or millimicrons, mp, of maximum absorption, or the corresponding wave-number 1 / ~ cm.-l = ; or frequency c / h = v*, and the molecular extinctioncoefficient a t that wave-length.It is also desirable to note the half-widthof a, band, i.e., the distance in cm.-l between wave-numbers such thatE = h a x . / 2 , and the band strength SE . dv.The theoretical aspect of the intensity and width of an absorption bandis discussed by N. G. Chako and by Th. For~ter.~ Let vi stand for thefrequency of maximum absorption c (for a band sufficiently distant fromother bands) and y j a quantity measuring the damping and responsible forthe width of the band, whilst f’ measures the strength; in classical theoryfj is the number of electrons per molecule producing the band, and in quantumtheory it is a measure of the probability of the transition compared with thatof the standard classical band. The sum of all thefj’s is equal to the numberof electrons.Moat visible and ultra-violet bands are weak, i.e., the bandsmainly responsible for the refractive index lie in the vacuum ultra-violet.From the theory of dispersion (e and m, charge and mass, respectively, ofan electron)andand with E = 4xnk/A and N’ = N p (p = molecules/c.c.)1 A. E. Gillam and R. A. Morton, Proc. Roy. Soc., 1929, A, 12Q, 609.a J . Chem. Physics, 1934,2, 644.2. Elektrochem., 1939, 45, 661. * c = 3 x 1010 cm./sec., velocity of lightMORTON : ABSORPTION SPECTRA. 9and if the band is narrowFurther,ne2CrnVj$E . dv = -2. .f", which is independent of y.and if y were independent of v throughout the band, the half-width (Le.,distance between places where E = +q,& is Av = 2y.Numerically SE .dG = 2.32 x 108 cm.-l, so with a value of ca. 2000 cm.-lfor the half-width, hx. - 105. An approximate upper limit of 100,000 for E isnot inconsistent with either quantum mechanics or general experience for asingle electronic transition in a molecule. The absorption process impliesthat a molecule in its ground state Eo (lowest energy) passes to excited statesEl, E,, etc., in accordance with h v = E, - E, by an electronic transition.Vibrations may also be excited, so that a more accurate relation is h v =El - Eo + E,, where E, is the vibrational energy.Instead of attemptinga detailed exposition, it is proposed to select a number of representativerecent studies with sufficient references to enable the reader to amplify theargument where it suffers from over-condensation.Halogens.-The continuous absorption of chlorine has been studiedover the range 18-700", and analysis of the curves reveals a dual mechanismA (A=.330 my, - 1). A leads to dissoci-ation into normal atoms (2P,t), whereas B leads to one normal (2Plt) and oneexcited ("+) atom. Similarly, bromine vapour exhibits composite ab-sorption ( hAmax, 415 and 495 mp) in the near ultra-violet and visible, but lacksan ultra-violet maximum shown near 250-300 mp in solution. Liquidbromine (Amax. 405 my, hx. 350) also shows no ultra-violet maximum of thistype,g but the main band is more than twice as intense as in the vapour.I n passing through a range of solvents from water to cyclohexane, A,,,, variesfrom 393 to 422 mp and Emax from 164 (2N-sulphuric acid) to 360 (toluene).The effects of different solvents on different electronic trhnsitions are quitemarked.Iodine molecules(vapour or violet solutions) give rise to two regions of aelective absorption,the main one near 500 my resulting in dissociation to one normal and oneexcited atom, and the other (near 732 mp) in two normal atoms.738 Theseparation of these two bands (0-8 volt) reappears in the spectrum of iodineR.G. Aickin and N. S. Bayliss, Trans. Faraduy SOC., 1937, 35, 1332.R. G. Aickin, N. S. Bayliss, and A. L. G. Rees, Proc. Roy. SOC., 1939, A , 169, 234;N. S. Bayliss, ibid., 1937, A, 158, 661; A. F. Acton, N. S. Bayliss, and R. G. Aickin,J . Chem. Physics, 1936, 4, 474.Absorptive processes are of many different types.66) and B (A,,,.- 425 mp,The data on iodine are less difficult to interpret.D. Porret, Proc. Roy. SOC., 1937, A , 162, 414.W. G. Brown, Phy&ul Reu., 1931,38, 1187.7 C. B. Allsopp, &id., 1937, A, 158, 16710 GENERAL AND PHYSICAL CHEMISTRY.adsorbed on calcium fluoride with very intense absorption characteristicof a very thin adsorbed layer (AA,,,. 345 and 284 mp). The large displace-ment (1.9 volts) is an indication of the change in binding energy on adsorption.Hydrated iodide ions I- show twin maxima (11 193.5, 226.2 mp; log E 4-13),and similarly spaced bands occur in alcoholic solutions of mercuric andcadmium iodides.10 In the simple alkyl iodides 11 the A process (lmaX.256 mp) leads to an excited iodine atom (2Pt) and an unexcited alkyl group,whereas the B process (Lax.286.5 mp) liberates both in the unexcited state.The absorption of tri-iodides generally is characterised by two maximaresembling those of iodine adsorbed by calcium fluoride.The original observation by T. M. Lowry l2 that the spectra of iodoformand potassium tri-iodide are very similar raised interesting issues beyondthe scope of simple valency theories.The results in Table I make it clear that the simultaneous productionof iodine atoms in the normal and in the excited metastable state accountsTABLE I.Substance. Solvent. A,,., mp.KI, ........................... EtOH 355 'CsI, ........................... EtOH 360352358 Cs1,Br ........................ EtOHI, .............................. (on CaF,) uz.350H2O........................ TeMe,I, C6H14A d , 7 ........................... EtOHSbI, 13 ........................ EtOH17BiI, 7 ........................... EtOH(vapour) Is(VaPOW@ & P O WSnI, 7 9 14 ..................... C6H14 Ca.CI, 7 ........................... CCl, ........................... PI, 16 C6H12 CHI,16 CCl,(vapour)357356386357343356338.6365386375351345log bar..3.94.463.34.025.03-74.2 14-074.02--3.93.23.31A,,., m p . log %ax..290 3.9290 4.6290 3.44290 4.22ca. 285 5.0(very thinlayer)284 4.05294 4.34284392 4.20277 -294 4.19281304285 3.82306.5 3.20294-ca. 285 3.6for absorptive processes. The occurrence and stability of interhalogen 1'compounds in sohtion and also the phenomena of dichroism in iodinederivatives have been studied spectroscopically, as have the properties ofhydrogen iodide and bromide.l*v l9 In these compounds absorption isJ. H.de Boer, 2. physikal. Chem., 1931, B, 14, 163; 1933, B, 21, 208.lo E. Lederle, &bid., 1930, B, 10, 121.11 D. Porret and C. F. Goodeve, Proc. Roy. SOC., 1938, A , 165, 31.1' J . , 1926, 622.l4 M. I. Grant, Trans. Faraday Soc., 1935, 31, 433.l6 K. E. Gibson and T. Iredale, aid., 1936, 32, 571.l6 R. H. Potterill and 0. J. Walker, ibid., 1937, 33, 363.l7 A. E. Gillam and R. A. Morton, Zoc. c i t . ; Proc. Roy. SOC., 1931, A, 132, 152;l8 C. F. Goodeve and A. W. C. Taylor, PTOC. Roy. SOC., 1935, A , 152, ,221; 1936,le P.Fink and C. F. Goodeve, aid., 1937, A, 163, 592.19 K. Butkow, 2. Physilc, 1934, 90, 81.A. E. Gillam, Trans. Paraday SOC., 1933, 29, 1132.A, 154, 181MORTON : ABSORPTION SPECTRA. 11localised in one part of the molecule, but the position of the band (i.e.,size of h v ) may be affected by the presence of atoms or groups which disturbthe electronic levels. This is in sharp contrast with the data for mesomericsystems, which will be referred to later.Departures from Beer's law are usually a clue to some significant change,a simple example being sulphur dioxide in water.20 An absorption band withhXa 275 mp shows log Emax. 1.82 at 0 . 0 0 4 ~ ~ 2.2 at 0.04 and 0 . 4 ~ ~ and 2.4 a t0 . 1 ~ . The system consists of S02,H20 H2S0, H+ + HS03-,but HS03- and H2S03 make negligible contributions to the absorption.The absorbing entity is S02,H20, and when the equilibria are elucidated,constant E values for this substance can be calculated.In pure hexane,sulphur dioxide exists unsolvated and Beer's law is valid (Lax, 290 mpyNitrous acid (freshly prepared) exhibits a main maximum at 366 mpwith vibrational fine structure (narrow bands with a constant frequencydifference of A cm.-l 1000).21 Similar absorption appears in P-octyl nitrite 22and in methyl and ethyl nitrite,23 and the vapour of nitrous acid 24 showsA cm.-l 1000 and 250 (vibration of 0--N-0 group in an excited state).A maximum near 230 mp in octyl nitrite corresponds with an electron-affiity spectrum.26The NO,- ion (sodium nitrite in sodium hydroxide) shows Amax.353.5 mp,and crystalline sodium and potassium nitrite at - 250" 26 show absorptionin the same region with well-resolved vibrational bands (A cm.-l 600)although barium nitrite crystals show no such bands. An inflexion near287 mp is possibly indicative of a second electronic excitation. Nitro-methane shows a different weak band (Amax, 270 mpy log 1.16) sharplyillustrating the effect of an alternative structural arrangement.The NO,- ion shows a strong band (A,,, 193.6 mp, 12,000) and a weakband (Ama,. 302 mp, t 6 ~ 4 ) , ~ ' the latter due possibly to a forbidden transitionoccurring only when coupled with vibrational frequencies. In solutions theabsorption is diffuse, probably as a result of an intermolecular Stark effect.Very dehite evidence of vibrational frequencies ( A cm.-l 800) is obtainedin the spectra of crystalline nitrates at - 250" (potassium nitrate 350 and750 cm.-l). The effects of interionic forces are shown in the displacementssuffered by the NO3- band :log Ernax.2.4) -Crystals.r A\ Dilute solutions. KNO,. NaNO,. Ba(NO& Temp.302 304 291-5 277.5 mp. Room temp.307 287 272.5 - 250'4o H. Ley and E. Konig, 2. physikal. Chem., 1938, B, 41, 366.21 G. Kortum, ibid., 1939, B, 43, 418.22 W. Kuhn and H. L. Lehmann, ibid., 1932, B, 18, 32.23 G. H. Purkis and H. W . Thompson, Trans. Furaday SOC., 1936, 32, 1466.24 E. H. Melvin and 0. R. Wulf, J . Chem. Physics, 1935,3, 753.H. W. Thompson, ibid., 1939,7, 136.26 H. Schaumann, 2.Physik, 1932, 76, 106.e7 R. A. Morton and R. W. Riding, Proc. Roy. Soc., 1927, A, 113, 71712 GENERAL AND PHYSICAL CHEMISTRY.Departures from Beer's law occur in concentrated solutions owingprobably to formation of ion-pairs.28 15~-Nitric acid shows weak selectiveabsorption near 265 mp, and a similar curve occurs with 0*15~-acid in thepresence of 9-1N-perchloric acid, which is itself transparent. Nitric acidin pure hexane, however, shows end absorption (inflexion 280 mp) similarto that of ethyl nitrate. The equilibriaH,O+ + NO,- + H,O+ NO,- + HNO, + H,Oion-pairappear to cover all a.queous solutions, the concentration of homopolarmolecules being at most ca.The Mn0,- ion gives rise to groups of equidistant narrow bands 29 shownby solutions and by crystals.The solution spectra commence near 370 mpand extend to the region near 600 mp : 1 / ~ = 17520 + 747n cm.-l (n =0 . . . 8). In ethyl acetate the separation is 785 cm.-l. Various purepermanganates have been studied at low temperatures in the solid state :First principal H (half-maximum, cm.-l. A;. width).KMnO, ........................ 17632 774 200RbMnO, ........................ 17875 768 170CsMnO, ........................ 18125 757 160NMe,MnO, .................. 17622 756 110BaMnO, ........................ 1757 1 772 220Dilute mixed crystals K(Cl,Mn)O, possess rhombic symmetry and at lowtemperatures exhibit three principal spectra in which the light vibratesparallel to the a, b, and c axes :3: = 18051 + n 763 + m 273 11 a18043 + n 768 + m 310 11 b18049 + n 767 + m 286 11 cThe bands become sharper as the temperature falls; e.g., the half-widthis 130 cm.-l at 150" K., 70 cm.-l at 83" K., and 35 cm.-l at 20" K.Sodiumperchlorate possesses a different crystal structure from the potassium,rubidium, or czesium salt, and the absorption of Na(C1,Mn)04 mixed crystalsdepends markedly on crystal orientation : A cm.-l I I a. 718,l I b 796, I I c muchless intense, ill-defined absorption. Absorption by ~,(C1,Mn)o4 is leessharp than that of NMe4(Cl,Mn)04, and hydrated crystals give poorlydefined bands in many cases. The hexagonal crystals like LiC104,3H20and Ba(C10,),,3H20 exhibit very sharp bands (H 30 cm.-l) for the ordinaryray l c , whereas resolution is feeble or lacking for the extraordinary ray.The term disturbance due to water of crystallisation is thus confined to onedirection.In K(CI,Mn)O, a second electronic transition gives rise to a veryweak sequence of bands near 14570 crn.-l (A; variable, ca. 800 ; H 40-90 cm.-l depending on direction). The MnO,- band system in sodiumperchlorate shows several electronic transitions, depending to a striking28 H. v. Halban and J. Eisenbrand, 2. physikal. Chem., 1928, A, 132, 433.29 A. M. Taylor, Trans. Faraday Soc., 1929, 25, 860.ao J. Teltow, 2. physikal. Chem., 1938, B, 40, 397; 1939, B, 43, 198MORTON : ABSORPTION SPECTRA. 13extent on direction. The crystal field shows specially great anisotropy,and suitable crystals exhibit dichroism, changing colour in polarised lightbetween red and deep violet.An ultra-violet system (with E one-tenththat of the main system) near 277 mp (A cm.-l756) occurs even in solutions.This kind of electronic band spectrum with a large number of equidistantbands is characteristic of totally symmetrical vibrations (expansion andcontraction of the Mn04- tetrahedron). Osmium tetroxide, OSO,, is anexample of a similar state of affairs in a free molecule (3 ultra-violet systems :A; 811, 835, 832 cm.-1).The MnO,-- and CrO,-- ions in I<,(S,Cr,Mn)04 exhibit similarly spacedmaxima, but no resolution can be detected with the VO,--- ion. The crystalK(Cl,Mn)O, with a moderate manganese concentration shows a single verysharp line at ‘v 14446 ( H = 8 cm.-l) in the 11 b direction, but this is lackingaltogether in the 11 a direction.The line is a pure electronic transition whichcan only occur in combination with a vibration. In some instances wholeband systems are missing. The Mn04- ion possesses an incomplete shell,well shielded by valency electrons : it is the tetrahedral ions of the transitionelements which show selective absorption, unlike the transparent ClO,- ,SO,--, and PO,--- ions.The Co(Hal),-- ions are not altogether dissimilar, but the position is notquite so clear.31-37New effects appear with neodymium salt spectra at low temperature^.^^Electronic transitions in the well-shielded incomplete neodymium shell areshown, in NdCl,,GH,O crystals at the temperature of liquid hydrogen, tocouple with internal vibrational frequencies of the molecules as well as withvarious modes of vibration of the lattice.This is shown by the recurrenceof certain intense groups, the intervals between the parent pattern and therepetitions eonforming frequently with well- known vibrational frequencies : 39Substance. AV, cm.-1. A i (Raman), obs.( a ) 716, 746 7253Zn(N0&2Nd(NO3),,24H20 ............... ( b ) 1046, 1051 1056(c) 1310 1370 .............................. 995, 1011 9901342, 1120 11251640Nd2(S0,),,8H20The chloride and bromate with ordinary water of crystallisation also showAV 1640 and 1650. With heavy water A i values of 1199 and 1431 cm.-l(bromate) and 1238 and 1481 cm.-l (chloride) are recorded. From other31 W. R. Brode, PTOC. Roy. SOC., 1928, A, 118, 286; J .Amer. Chem. SOC., 1931,53, 2457.sa W. R. Brode and R. A. Morton, Proc. Roy. SOC., 1928, A , 120, 21.31 W. Feitknecht, Helv. Chim. Acta, 1937, 20, 669.3s 0. R. Howell and A. Jackson, Proc. Roy. SOC., 1933, A, 142, 587.88 R. J. Macwdter and S. Barratt, J . , 1934, 617.I* IT. Ewald, Ann. Physik, 1939, [v], 34, 209.89 K. H. Hellwege. 2. Phyaik, 1939,113, 192.A. v..Kiss and M. Gerendhs, 2. physikal. Chem., 1937, A , 180, 117.P. Job, Ann. Ckim., 1936, 6, 9714 GENERAL AND PHYSICAL CHEMISTRY.independent work the inner vibrations to be expected are 1615 cm.-l or1220 and 1460 cm.-l respective1y.m Smaller intervals are associated withlattice vibrations.Crystals of europium salts homologous with those of neodymium possesssuch sharp absorption spectra 4 ~ 4 ~ that phenomena similar to those recordedat very low temperatures can be studied at room temperature.Changes inthe environment of Eu+++ ions bring about alterations in the structure ofthe absorption spectrum. Thus EuCl, in water to which potassium nitrateis added exhibits the structures shown in Eu(NO,), as well as EuCl,.The spectra of europium salts in alcohol differ from those shown byaqueous solutions. In a, mixed solvent both spectra are shown with relativeintensities which vary according to the proportions of the components.Repetitions of prominent patterns enable lattice vibrations to be evaluated,and in some cases a given electronic level of an ion in an electrostatic field isdecomposed in strict accordance with theory into a number of sub-levels.The interpretation of absorption spectra is rooted in classical dispersiontheory, it comes to flower in the quantum-mechanics of diatomic molecules,and is reaching fruition with larger molecules.Simple saturated hydro-carbons like methane and ethane exhibit selective absorption 473 48 in thevacuum ultra-violet only (methane, lmaX. 120-130 mp). Replacement ofhydrogen by alkyl groups brings about progressive displacements towardslonger wave-lengths (n-hexane, hX. ca. 153 mp).49 If absorption occurs a twave-length8 >200 mp, the presence of a double bond is indicated.Absorption by ethylene begins near 175 mp, and following a well-definedpattern, extends to 160 mp, with additional bands near 139 and 129 mp.The separate vo values fit into a R-ydberg formula and converge to an ionis-ation potential of 10.45 v.:C,H, vg(n) = 84,750 - R/(n + 0-91)2; n = 2, 3, 4, etc.C,D4 vg(n) = 84,850 - ~ / ( n + 0 ~ 9 2 ) ~ ; ?z = 2, 3, 4, etc.The absorption bands (and ionisation potentials) refer respectively toexcitation and removal of a " x " electron (see p. 15) from the double bond.Electrons of the [a12 single G C or C-H links need much higher frequenciesfor ionisation.The vibrational structure, C,H, A crm-1 1370, C,D, A cm.-l 1290, corre-40 L. Kellner, Proc. Roy. SOC., 1937, A, 159, 414.4a S. Freed and H. F. Jacobson, ibid., p. 654." S . Freed, S. I. Weimmann, F. E. Fortress, and H. F. Jacobson, ibid., 1939, 7, 824." S. I. Wehsmann and S. Freed, ibid., 1940, 8, 227, 878." S . Freed, S.I. Weissmrtnn, andF. E. Fortress, J . Amer. Chem. SOC., 1941,63, 1079-" F. H. Spedding, C. C. Moss, and R. C. Wdler, J . Chem. Physics, 1940, 8, 908." W. Groth, 2. Ekktrochem., 1939, 45, 262.48 E. P. CarrandM. K. Walker, J . Chem. Physics, 1936,4, 751.'* E. P. Carr and H. Stucklen, i&id., p. 760; 2. IphysikaE. Chem., 1934, B, 5, 57 ;J . Amer. Chem. Xoc., 1937,59, 2138; J . Chem. Physics, 1938,6, 65.'* w . c. Price and W. T. TuttIe, Proc. Roy. SOC., 1940, A , 174, 207.61 W. C. Price and A. D. Walah, ibi&., p. 220.51S. Freed and S. I. Weissmann, J . Chenz. Physics, 1938, 6, 297MORTON : ABSORPTION SPECTRA. 15sponds with the totally symmetrical valency frequency of the double bond,which in the ground states is either C,H, A cm.-l 1623, or C,D, A cm.-l 1515.The change in frequency resulting from isotopic substitution is in accordwith expectations : 1370/1290 = 1.062 ; [16(CD2)/14(CH,)]* = 1.069.Bands near 170 mp appear in pairs, A cm.-1470 and 300 for C2H, and C,D,respectively.The mass factor (D/H)* = 1.41 is not very different from470/300 = 1.57; probably the CH, groups twist about the double bond.The spectrum of butadiene is very important because this substanceaffords the simplest example of resonance between conjugated double bonds.The first strong absorption (217 mp) is a progression of four diffuse bands,A 1440 cm.-l (isoprene, 221 mp, A 1450 cm.-l). The symmetrical C S Cvalency vibration (1634 cm.-I in the ground state) is reduced a little by theexcitation.Other electronic states are shown at higher frequencies, andtwisting vibrations (pairs, A 350 cm.-l) are recorded. Below 152 mp vibra-tionless electronic transitions lead as before to the ionisation potential(9-02 v.) : ~ 2 ) = 73115 - R/(n + 0 ~ 9 0 ) ~ ; n = 2, 3, 4, etc.= 73006 - R/(n + 0 ~ 5 0 ) ~ ; n = 3, 4, 5, etc.With alkyl substitution, simple inductive effects diminish the ionisationpotential. The absence of vibrational bands in the Rydberg transitions is adirect result of resonance; the removal of an electron shared between twobonds having a reduced effect on each.The main absorption of the C:O group also falls in the Schumann region( <200 mp) and so also does that of the carboxyl group.62-54Mesomerism in conjugated compounds is now accepted as a fact of majorsignificance.Molecular resonance in polyene and aromatic hydrocarbonshas been treated with success as a theorem in wave-mechanics 55-59 leadingto the calculation of C-C distances and of colour. The only experimentalparameter needed (a or J ) may be evaluated from heats of hydrogenation.Those dealing with wave-mechanics distinguish between localised electronpairs responsible for directed valency (interaction of Q electrons) and xelectrons.w-s2 These “ mobile electrons ” (Lennard- Jones), “ electronsof the second kind” (HU~kel),~~ are not strictly localised and in planarmolecules are antisymmetrical to the plane of the C-C links, and cannotbe paired according to their spins in a unique way to fit an ordinary structure.st W.M. Evans and W. C. Price, Nature, 1937, 139, 630.6a A. B. F. Duncan, J. Chem. Physics, 1936, 3, 131.6 s J. E. Lennard-Jones, Proc. Roy. Soc., 1937, A , 158, 280.6 6 J. E. Lennard-Jones and J. Turkevich, ibid., p. 297.b7 W. G. Penney, ibid., p. 306.s8 A. L. Sklar, J. Chem. Physics, 1937, 5, 669.6s Th. Forster, 2. physikal. Chem., 1938, 23, 41, 304; 2. Elektrochem., 1939, 45, 548.80 J. H. van Vleck and A. Sherman, Rev. Mod. Physics, 1935,7, 237.61 L. Pauling, J . Amer. Chem. Soc., 1931, 53, 1367; J . Chem. Physics, 1933, 1, 280.6* E. Hiickel, 2. Elektrochem., 1937, 43, 752, 827; J. E. Lennard-Jones, Zoc. cit.V. R. Ells, J . A m r . Chem. Soc., 1938, 60, 1864.J. C. Slater, Physical Rev., 1931, 37, 481 ; 38, 110916 GENERAL AND PHYSICAL CHEMISTRY.R,R,nSuch electrons cause links to become intermediate in distance betweenisolated double bonds and single bonds.Benzene is treated as a six-electronsystem with spin degeneracy only, and the single exchange intepal betweenadjacent carbon atoms is a. Two electrons present on adjacent atoms lowerthe energy of a structure (by forbidding resonance) by - a (a is negative)if the electrons are paired to form a bond, and raise the energy by - +a ifthey are not paired. Thus a Kekul6 form of benzene has an energy loweringof (3a -+a) 7 1.5~~. In the result for benzene, 2.6a represents the normalstate.Total Resonanceenergy. energy.Single Kekulh structure .............................. 1-5a 0Resonance between two Kekul6 structures ......2 . 4 ~ 0.9aResonance between all 5 canonical structures ... 2.605,~ 1 . 1 0 5 ~From heats of hydrogenation,M Sklar evaluates a as 1.92 v. (44 kg.-cals./mol.). The location of selective absorption can then be calculated :Fury1 Ph CH3CHO or Ph CH3CH3CHOorC0,H C0,H1, 2, 3, 4 0, 1’ 2, 3 1,3 . . . 7,11,15 1 , 2 . . . 6Molecule.Benzene .........Naphthalene ...Anthracene.. ....Pentacene ......PhenanthrenePyrene .........Naphthacene ...Excitation energies.*2 . 4 0 ~1 . 9 7 ~ (3.34~)1 . 6 0 ~ (3.0~1, 3 . 8 ~ )1.3 l a (2.62~1, 3-56u, 4.07a)1 . 0 8 ~ (2*2a, 3*lu, 4*0u, 4 . 2 ~ )1 . 9 4 ~ ( . . . )1 . 7 0 ~ ( . . . )Wave length of firstabsorption region, in mp :cab. obs.245 255295 275365 370450 460545 580300 295345 330* Approximate higher excitation states in parentheses.6MORTON : ABSORPTION SPECTRA.17l/lc/nm (vo, the first absorption band). =4x2c2nm/L, i.e., = k'n. On plotting A;4 against n, for the diphenyl polyenes,a very good straight line is obtained cutting the n axis at - 4.7, so thaton this basis each Ph equals 2.35 double bonds. The next higher vibrationallevel CAv = 2) involves increasing anharmonicity and the levels comecloser as v increases. The carotenoids show two well-marked regions ofselective absorption (e.g., p-carotene, ca. 477 mp and 270 mp; A,, &).70The ratio k,/A, is approximately constant in this class of compound at 1.7-1-85. This type of second-order band may be fairly common, but easilyobscured by absorption due t o a part of the molecule rather than theentire resonance system.69Similar relationships with polymethin dyes (pseudoisocyanine, isocyanine,and cyanine types),59 conjugated azo-dyes,71 etc., fit in with the idea of- resonating whole molecules.The p -- -/=\ - -\ /=\- polyphenyls (I) exhibit some approach \=/(-<=/=In\=/- towards double-bond character 72* 73 forthe internuclear link, but the rn-series (I.)is quite different :Solvent : CHCI,. m-Series.Hence & = 2xc,ldk/nm orp - Series. %ax. xAmax.7 Emax. A,,., cmar. NO. of be=- 'Compound. m p . x10-3. Compound. mp. x 10-9. ene nucleiDiphenyl ...... 251.5 18.3 (Diphend) ............ 251.5 18.3 9Sexiphenyl ... 317.5 56 Quinquideciphenyl ...254 309 20.6Terphenyl ... 280 25 Terphenyl ............ 251.5 44 14.7Quaterphenyl 300 39 Noviphenyl ............ 253 184 20.5Quinquiphenyl 310 62.5 Deciphenyl ............ 253 213 21.3(Stilbene ...... 295 23.4) (Tetraphenylmethane) 262 2.0 0.5The marked difference between tetraphenylmethane and the m-seriesindicates for the latter-a " semidiphenyl " chromophore ( A 253 mp, E 20,000)functioning additively. I n the p-series A,,,. is converging to a limit as nincreases, so that the plot of h2 against n would not be a straight line.6g Thiscan only mean that k (the restoring force) increases with nm, and for thehigher members the ordinary Kekul6 resonance becomes more importantthan in the lower members, which behave more like the conjugated polyenes.The conjugation effect requires a planar structure for the " mobile "electrons to play their full part.The steric effects of substituents are verymarked, thus bi~mesityl,~~ (C,H,Me,),, shows ha=. 265 mp, 560, ie.,the mesitylene spectrum doubled 280). Steric effects are also shownon p. 18 : 75-7770 R. Kuhn, Angew. Chem., 1937, 50, 703.'l W. R. Brode and J. D. Piper, J . Arner. Chem. Soc., 1935,57, 135.7e A. E. Gillam and D. H. Hey, J., 1939, 1170.78 A. E. Gillam, D. H. Hey, and A. Lambert, J., 1941, 364 (on phenylpyridines and74 L. W. Pickett, G. F. Walter, and H. France, J . Amer. Chern. Soc., 1936, 58, 2296.76 H. Ley and H. Dirking, Ber., 1934, 67, 1331.7 6 A. Smakda and A. Wassermann, 8. physikal. Chem., 1931, A, lS5, 353.7 7 H.Ley and F. Rinke, Ber., 1923, 56, 771.p yridyldiphenyls ) 18 GENERAL AND PHYSICAL CHEMISTRY.&n€u., mp. Emax. x 1oJ. AlmX.9 mp.278 9.35 222294 23-4 225 Ph*CH:CHPhPh*CMe:CHPh trans 372 18.2Ph.CMe:CMePh trans 24 1 11-7262 9.1Ph*CH:CH*CO,H { i:Zns 274 20.8324319 Ph-N:NPh 78 {ij:nsMe299<L>-N:NPh { ;;zns 32215.119.58.5SO43844 5447446F a x x lo-*.2315.61.160.292.26.8A break in conjugation by insertion of [CH,], (n = 1, 2 . . .) producesa clear-cut insulating effect and the two separated chromophores functionindependen fly.but the superposition of chromophores isoften a more complicated affair, which is not easy to disentangle. A singleisolated absorption curve drawn on a frequency scale should be symmetrical,and the band-strength SE .dv and half-width H should be significant quantities.Variants (e.g., substituents in benzene rings) giving rise to large or smallinner field effects may be strongly or weakly uariochrornic, and it is con-venient to describe displacement on the wave-length scale as ~hromolatory.~The curve for p-methoxystilbene is practically that of stilbene plus that ofanisole, p-nitrostilbene is a summation of the stilbene curve slightly displacedand that of nitrobenzene, whilst p-nitro-p’-hydroxystilbene is a summationof phenol, nitrobenzene, and stilbene (displaced) absorptions. The absorp-tion spectra of rottlerin 81 and its derivatives afford a good example of bothCH, insulation and superposition of chromophoric effects due to parts oflarge molecules functioning independently.The spectra of a@-unsaturated ketones82983 show the additive and theR*CO*$:CR, (* de- constitutive effect clearly.noting the site of the transition), is displaced by induction from (200 rnp(log zmax.ca. 4) to an extent depending on the degree of substitution :This effect is wellR The ethenoid absorption,Substitution. Am+, mp. No. of examples.Mono- a or fl .............................. 225f5 6Di- a/3 or pi3 ........................... 239&5 36Tri- a/3p ................................. 254*5 9(Pp = H, H ................................. 218)7 8 A. H. Cook, D. G. Jones, and J. B. Polya, J., 1939, 1315.7* (Mme.) Ramart-Lucas, BUZZ. SOC. chim., 1932, 51, 289 ; also Grignard’s “ Trait680 E.Hertel and H. Luhrmann, 2. physikal. Chem., 1939, B, 44, 261.81 R. A. Morton and Z. Sawires, J., 1940, 1052.82 R. B. Woodward, J. Amr. Chem.. Xoc., 1941,65, 1123.L. K. Evans and A. E. Gillam, J . , 1941, 815.de Chimie Organique,” Vol. 11, Paris, 1936MORTON : ABSORPTION SPECTRA. 19R * The above table is of great diagnostic value. The low-intensity R > G Oketone band at 275 mp in acetone is displaced to 305-325 mp in (11), E==.R * remaining low (20-80 as a rule).83 The acetone absorp-R>c-(?-(?=O tion a t 187-195 mp also appears in methyl chloride, andis not displaced to 225-250 mp.84,s5 The effects in(11.) aromatic ketones, keto-enols, hydroxy-aldehydes, andhydroxy-ketones 86987 are more complicated, but additive and constitutiveeffects are easily sorted out.The effects of substitution in benzene derivatives are complicated (ratherthan difficult) and cannot be dealt with in detail.88-92 It is perhaps preferableto deal fairly fully with an illustrative series and refer the reader to work onothers.Simple mixtures may form loose complexes breaking down ondilution, e.g., C,H5*N0, . . . . H2N*C,H,. In the 0-, m-, and p-nitroanilinesintramolecular forces displace absorption towards the visible, but a competingenvironment (containing, e.g., hydrochloric or perchloric acid) reverses thep r o c e ~ s . ~ ~ ~ gp The actual absorption is additive to the extent that a transitionlocalised in -NO, (cf. p. ll), and made more probable by induction, issuperimposed upon a benzenoid transition already familiar in aniline andother derivatives of benzene.In 10% hydrochloric acid the nitroanilinesexhibit merely the absorption of nitrobenzene. The concentration of per-chloric acid needed to achieve this result varies :HClO, concentration, N.Wo-Nitroaniline ........................ 6m- ........................ 0.1........................ 3 P-Compound. a ma,., mp. Emax. L a x . , mp. hax............... 287.2 1,950 236-9 11,500p - ............ 290.5 2,000 235.7 10,300............ 403.6 5,400 275.2 6,100............. 374 15,350 230 13,900NH, : NO,.c6E,<2 r; ............ 284.3 2,130 233.1 11,500C 6 H & C 2 {i- ......... 375 1,580 233 18,000Nitrotoluidines.KO. of isomers.0 - 404-4 1 7 5,000 284 5,000332 20,0004,5001,500(2) P- 374-379 15,000 233 7,000** L.K. Wolf and W. Herold, 2. physikal. Chem., 1929, B, 5, 124; 1931, B, 12,86 G. Scheibe and C. F. Lindstrom, ibid., 1931, B, 12, 387.6 7 R. A. Morton and A. L. Stubbs, J., 1940, 1347.8D K. L. Wolf and W. Herold, 2. physikal. Chem., 1931, B, 13, 201.so K. L. Wolf and 0. Strmser, ibid., 1933, B, 21, 389.Dl G. Scheibe, Ber., 1926, 59, 2618.sa H. Conrad-Billroth, 2. physileal. Chern., 1932, B, 19, 76; 1933, R, 20, 222, 227;OS L. Dede and A. Rosenberg, Ber., 1934, 67, 147.(4)(4)(;;;)m- 375 (352) I , 500165; 1932, B, 18, 265.R. A. Morton, A. Hassan, and T. C. Calloway, J . , 1934, 883.M. Pestemer, Angew. Chem., 1937, 60, 343.1933,B, 23, 139; 1935, B, 29, 170; 1936, B, 33, 133, 31120 GENERAL AND PHYSICAL CHEMISTRY.With two exceptions (CH, : NO, : NH, = 1 : 3 : 2 and 1 : 4 : 3) the curvesin hydrochloric acid for the nitrotoluidines agree almost exactly with thoseof the parent nitro toluene^.^^The curves for all pHH O e N 0 2 += GA \-/- so2 1 values between these ex-tremes intersect at two wave-lengths .The same " nitro " band reappears in 0- and p-nitrophenol : 93(in o .~ ~ - N ~ o H ) (in O-~N-HCIO,)lmm. 318 mp + A,,,. 400 mpandb x . 350 mp hnax. 410 mp* Denotes the site of the electronic process.Another example of equilibrium is afforded by p-nitrosophenol :-ON f i OH =+ O=/-\=N.OH95 71- \=/" Nitrosophenol " in ether.An,., mp. fmar.. &la,. - Emax..526.3 1-44,467 454.5 8.7436.7 13.2 423.7416.7294.1 25,120O=(=_)=N.O-CH, 21.4 14,800The parent substance appears to consist of 70% quinonemonoxime and30% nitrosophenol when at equilibrium in ether.The equilibrium (111) (IV) affords an even clearer example ofNO~>OCH,-- =N.NH<>/ \\J (111.) \Jdesm0tropy,~6 since in pyridine the azo-form predominates (A,.415 mp)whereas the hydrazone (A=. 480 mp) preponderates in glacial acetic acidor nitrobenzene. The two forms occur in approximately equal proportionin benzene. Confirmation of this interpretation comes from the spectraof the two methyl derivatives of fixed constitution. The o-hydroxyazo-analogues exist almost entirely as quinonehydra~ones.~7The spectra of at least some series of benzene substitution products showOP R.A. Morton and A. MoGookin, J., 1934, 901.96 L. C. Anderson and M. B. Geiger, J. Amer. Chem. SOC., 1932, 54, 3064.* 6 R. Kuhn and F. Blir, Annakn, 1935, 616, 143; see also H. Shingu, Sci. Papers*' A. Burawoy, J.pr. Chem., 1932,135.146; J.. 1937,1866;; 1939,1177.Inst. Phye. Chem. Ree. Tokyo, 1939, 36, 78MORTON : ABSORPTION SPEUTRA. 21that the electronic transition located in the benzene ring may be changed(as a result of inductive effects) in discrete steps differing by a well-knownvibration frequency (A; 1450 ~rn.-l).~' The effect of " partials " or simplechromophoric effects functioning additively is shown clearly in anthraquinone(in alcohol) : 98Am. mp ...... 405 326-5 272.0 262.8 252-5 243-5log em=. .........1-96 3.76 4.31 4.31 4-7 1 4.52( b ) (a) ( b ) ( b ) (a) (a)The ( a ) bands are due to 86H4<co (e.g., o-hydroxyacetophenone) and the( b ) bands to 0 : A . O (e.g., a-tocopherylquinone).R R\-/* R RHeterocyclic compounds of the type of pyridine and quinoline Qg exhibita marked resemblance to benzene and naphthalene. From the standpointof resonance this is not surprising, and a striking similarity between the curvesof acridine and anthracene has been recorded'l together with significantresults on acridinium and phenazinium ions.The absorption spectra of dyes in relation to resonance have been dis-cussed for triphenylmethyl derivatives (crystal-violet, etc.). 59* 69 A fewaspects of the wider problem will be reviewed.(a) Polymerisation in soZution.2 The two ionised dyes shown below donot follow Beer's law.Thionine .Met hylene-blue .Purple a 2-10 Blue p~ 2-12In both cases two resonating structures are postulated each with one or otherof the two benzene rings in the pquinonoid state :M-Band ........................ A,,, 597 m p (Thio+) 656.6 mp (MB+)(prominent in very dilute solutions)(more prominent in concentrated solutions)D-Band ....................... .Amw., 557 m p 600 m pThe deviations from Beer's law are not due to formation of undissociatedmolecules (e.g., thionine chloride) or to ion-pairs (Thio+ . . C1-). The Mbands are due to monomeric and the D bands to dimeric ions 2T+ a T,++ ;O8 R. A. Morton and W. T. Earlam, J., 1941, 159.R. A. Morton and A. J. A. de Gouveia, J., 1934, 927; D.Riidulescu andIdem, ibid.G. Ostrogovich, Ber., 1931, 64, 2233.a E. Rabinowitch and L. F. Epstein, J. Amer. Chem. SOC., 1941,83,6922 GENERAL AND PHYSICAL CHEMISTRY.K = [T+J2/[T$+] ; &&& = EMX + &g(l - x) where cdl and ED are the molecularextinction coefficients of the monomer and dimer respectively, and z is thefraction of monomer. K = 2Cx2/( 1 - x) = 10 x lo4 (thionine) or 2.8 x 104(methylene-blue); z varies from 0.359 to 1 (thionine) or from 0.232 to 0.986(methylene-blue). For thionine ion the temperature effect is given bylog,, K = 1.9886 - 1492/T and the following results are obtained : freeenergy of dimerisation AF = - RT In K (4-9 kg.-cals./mol. at 26.7");heat of dimerisation AH = RT2 (d In K/dT) (6.82 kg.-cals./mol.) ; entropy ofdimerisation A 8 = (AH - AP)/T (9-1 cals./mol.-degree).I n pure alcohol,thionine conforms with Beer's law and the band ( Amma 603 mp) is narrower ;addition of water causes the E value to fall rapidly, and this corresponds witha sharp drop in the free energy of dimerisation.Thionine fluoresces with a red light and the yield is constant for alcoholicsolutions, but decreases in aqueous solution with increasing concentration(self-quenching due to the dimer). Fluorescence does not occur if the dyemolecules are dimeric a t the moment of excitation or if they form a dimerduring the excitation period. This phenomenon is important because nearlyall water-soluble dyes show D bands 1-50 mp on the violet side of the Mbands.They often form trimers and polymers, but leuco-dyes are usuallymonomeric. The tendency to form polymers more readily in aqueous thanin alcoholic solution is at first sight strange (cf. carboxylic acids, which aredimeric in the vapour state and dissociated in water) but is explained byadditive forces of the van der Waals type. The E values are high, theexcitation probability being often >04.The absorption spectra in the visible region of cyanine and relateddyes 599 3-6 afford numerous examples of intense bands in " linear oscillators "conforming to the relation gmax. = k'n (p. 17) where n represents thenumber of -C€€=CH- groups, e.g.,A,,., nlCL. x 10-4.423 8.45~ / s ~ ~ I - n = O 1 557.5 14.8I (two identical resonance forms)G.Scheibe ti was the first to demonstrate that reversible polymerisation isresponsible for new bands in dyes. Using pinacyanol chloride, A,,,.600 mp belongs to the monomeric ion, but if the concentration is increasedor the temperature decreased a maximum a t 548 due to the dimeric ionappears. Both maxima almost disappear at higher concentrations and arereplaced by a third maximum a t 510 mp due to the polymeric ions.With pseudoisocyanine (V), Scheibe has obtained results of great(Miss) N. I. Fisher and (Miss) F. M. Hamer, Proc. Roy. SOC., 1936, A , 154, 703.4 W. Konig, Z . wiss. Phot., 1935, 34, 15.5 L. G . S. Brooker, R. H. Sprague, C. P. Smyth, and (2. L, Lewis, J. Amer. Citem.SOC., 1940, 62, 1116.6 KoEloid-Z., 1938, 82, 1MORTON : ABSORPTrON SPECTRA.23interest.'- In alcohol the dye ion is largely monomeric ( lmaX. 523 mp, E-.75,000) at 0 . 0 1 ~ ~ whereas in aqueoussolution the dimeric ion (hmax. 485 mp) is pQ=d'Of- already present a t 0.0001~, and at con-centrations >0.007~ a very narrow ( H140 cm.-l) intense band (Amm. 572 mp)appears and grows more intense withincreasing concentration. The concentrated solutions are powerfullyfluorescent, the fluorescence band coinciding in position and half-widthwith the absorption band. The appearance of the 572 mp maximum isaccompanied by a marked increase in viscosity, and the curves for viscosity-temperature) absorption-temperature ) and conductivity-concentration showsharp discontinuities. For instance, when c = 0.0144~ the 572 mp absorp-tion is strong a t 42" and has nearly gone at 44".\y'"E t(V.)The mechanismrearrangement A+ A,++ + -4, -- -+ crystalsMonomer Dimer Polymertemp.iucreasingf----fconcn. increasingis not it sufficient explanation. The minimal concentration for polymerformation is lower if the dye is adsorbed on a surface (e.g., 0.0003~ on freshlycleaved mica), and the polymer maximum a t 572 mp appears accompaniedby a further band at 579 mp. Adsorption depends on the structure of theP O4.47/0 =Position o f the K'ion in the mica surface.FIQ. 1.solid (calcium fluoride is here useless) and the crystal structure of micapresents K ions suitably disposed for the reception of planar pseudoiso-cyanhe ions as shown in Fig. 1 (adapted from Scheibe's figure).If a mixedcrystal of quinaldine ethiodide and pseudoisocyanine iodide is obtained(from alcohol) the dye ions will be parallel, and it is found that the character-' E. E. Jelley, Nature, 1937,139, 631. s G. Scheibe, Angew. Chern., 1939, 62, 03124 GENERAL AND PHYSIOAL CHEMISTRY.istic absorption in polarised light occurs only when the electric vector of thelight is parallel to the plane of the molecules (Ama. 545, 490 mp), whereasvertically to the plane only weak and modified absorption (Amx. 530 mp)occurs. The monomeric ion gives rise to two electronic transitions, cu.530 mp in the direction of the long x axis of the planar molecule, and ca.490 mp in that of the y axis. In the dirneric ion this second band is intensified,and in the polymer the 573 mp absorption arises in the x axis because a giantmolecule is formed (rather like a stack of coins) to form a cylinder or filament(Fig. 2 ; after Scheibe).FIG.2.Polymerisation in aqueous solzrtion.The directional effect has also been shown for chrysene single crystal^.^The crystal structure is known.10 The unit cell [see (VI)] contains 4 mole-cules, two oriented so that their OA directionsmake with the a and b axes angles of 102" andA of 118.4" and 29". The orientations of the othertwo molecules are obtained by reflection fromthe (010) plane. The crystal is used in the form90.5" respectively, and the OB directions angles(VI.)' K. A. Krishnan and P. I(. Seshan, PTOC. Indian Acad. Sci., 1938, 487.lo J. Iball, Pmc.Roy. Soa., 1934, A, 146, 140MORTON : ABSORPTION SPECTRA. 25of a flake parallel to the c(OO1) plane, and the molecular planes make anglesof 3 296" with the b axis. The absorptions in different directions at 397mp (first maximum) differ in intensity exactly as would be expected :ka/kb = 310/1020 = tan2 29"and the ratio of fluorescence intensities (420,438,449 mp excited by 365 mpHg) is a/b = 0.4, corresponding to 32". In addition to these neat results,it is clear that the light vibrations incident along the normal to the molecularplane are not absorbed a t all.The study of optical sensitising of silver halides in relation to the absorptionspectra and constitution of dyes has recently advanced considerably.llThe sensitising spectrum is usually closely related to the absorption spectrumof the dissolved dye, but Amas (sensitising) is > Amax.(ethyl-alcoholic solution)by at least 16 mp.l2 The absorption spectra of dyed silver halides (Le., ofadsorbed dyes) have been measured and found to coincide with the sensitisingspectra,l31 l4 so that the distribution of spectral sensitivity (in the visible)is equivalent to the adsorption spectrum.In order to give precision to the concept of adsorption energy, certainnon-ionising dyes have been studied in the vapour state. One of these, amerocyanine,ll shows at 250" Amax. 470 mp (with subsidiary bands at 505,R 0 R -0445 and 420 mp).( A cm.-l remaining -1000).The band system is displaced as a whole in solutionsThe structure recalls that of the polyenes : l5v = Vo + I 7 + mi", where if = 1590 cm.-l and 7' = 1240 cm.-1The absorption of the merocyanine in the visible arises then from an electronictransition on which are superimposed -CH=CH- vibrational quanta, etc.In aromatic hydrocarbons there is progressive relaxation of the -CH=CH-link :P h a [ CH:CH];Ph. An thracene.Naphthalene. Benzene.1600 1430 1360 900 cm.-1The greater complication of the cyanine dyes results in the superpositionof a variety of vibrational frequencies, but the predominance of -CH:CH-is often quite clear. In itself this fact affords no more than a clue, for thevalues of AA,,. and hx. are much more sensitive to structural changes thanwould be expected from aimple analogies. The location of the long-wavel1 S.E. Sheppard, R. H. Lambert, and R. D. Walker, J. Chem. Physics, 1941,9, 96.l2 E.g., (Miss) F. M. Hamer, Phot. J., 1922, 62, 8; 0. Bloch and (Miss) F. M. Hmer,ibid., 1928,68, 22; L. G. S. Brooker, G. H. Keyes, and F. L. White, J . Amer. Chem. SOC.,1935, 57, 2492.( I and m = 0, 1, 2, 3, etc.)13 S. Natanson, Nature, 1937, 140, 197 (erythrosin and phloxhe).14 J. A. Leermakera, B. H. Carroll, and C. J. Stand, J. Chem. PhysiCe, 1937, 5, 876.l5 K. W. Hausser, 2. tech. Phly&, 1934,15,1036 GENERAL AND PHYSICAL CHEMISTRY.maximum in a cyanine dye depends upon the shape of the molecule [themost extended form of the molecule (Mulliken); the greatest range in themolecule of electron transfer ( Pauling)]. The electrons make the transitby moving from atom to atom, and this " appears to be consonant with thesuperposition of a vibrational frequency possible to a given link." Thespectrum may also be decisively modified by the character of the nuclei(quinoline, thiazole, etc.) even in the visible region." Dominating everythingelse, however, is the possibility of a planar configuration for the dye mole-cule.This allows the fullest development of resonance, and of a transitionpolarised in the plane of the molecule. Even with planar structures, differentstereoisomers will differ with regard to the extent to which they undergoedge-on adsorption to silver halide. On this basis coplanar coupling ofelectronic displacements in the dye and in a congruent plane of the silverhalide lattice is a key factor in the whole problem of sensitising. I n somecyanine dyes the E values of planar isomers are twice those of non-planarisomers, and the former alone are effective sensitisers.Electrons of theBr- ions have a vector E, in the 111 plane, and this component may undergocoupling with a parallel component of the resonance energy of the adsorbeddye. This would correspond to the adsorption energy and to the displace-ment of kmSx. (adsorbed dye + vapour), and implies that the couplingproceeds prior to adsorption and hence in the ground levels. The progressof this work will be followed with interest.Attention is also drawn to the following publications :(a) Review articles.50, 193).Kortum and M. Seiler (Angew. Chem., 1939, 52,687).Potter (Ann.Rev. Biochem., 1941, 10, 509).(Institute of Chemistry, 1938).Photoelectric Spectrophotometry : G. Kortum (Angew. Chem., 1937,Colorimetric, Spectrophotometric and Spectrographic Methods : G.Spectrometric Studies in Relation to Biology : T. R. Hogness a i d V. R.Practical Aspects of Absorption Spectrophotometry : R. A. Morton(b) Books.Absorption Spectrophotometry and its Applications : Bibliography andAbstracts, 1932-1938 (866 papers) : 0. J. Walker (Adam Hilger, London,1939).Absorption Spectra of Natural Products : F. Ellinger, Tabuh Biologic=,Vol. XI1 (W. Junk, Den Haag, 1937).Losungsspektren : H. Mohler (G. Fischer, Jena).Chemical Spectroscopy : W. R. Brode (John Wiley and Sons, and Chap-man and Hall, 1939).* Cf. Morton and Stubba, Eoc.cit., ref. (87). This effect is to be distinguished fromthe superimposed ultra-violet absorption of parts of the large moleculeANGUS : DIAMAGNETISM. 27The Identification of Molecular Spectra : R. W. B. Pearse and A. G.Gaydon (Chapman and Hall, London, 1941).Absorption Spectra of Vitamins, Hormones, and Co-enzymes : R. A.Morton (Adam Hilger, London, Second edn., 1942), also Ann. Rev. Biochern.,1942, 12, article on Pat-soluble Vitamins.Proceedings of Conferences on Spectroscopy held annually a t the Massa-chusetts Institute of Technology, Vols. I-VI, Ed. G. R. Harrison (JohnWiley, New York) .Molekulspektren von Losungen and Flussigkeiten : G. Scheibe and W.Fromel (Eucken-Wolf, Hand- und Jahrbuch der chemischen Physik, Band 9,Abschnitt III-IV, 142, 1937).R. A. M.3. DIAMAGNETISM.Recent Annual Reports do not contain many references to magneto-chemistry. In the last volume the application of magnetochemistry tofree radicals was discussed,l and in 1937 H. Terrey and 0. J. Walker2reviewed its application to the rase-earth elements. No summary of workon diamagnetism has been given for a t least 10 years, and it is the aim of thisReport to summarise the present state of knowledge in this branch ofmagneto c hemist r y , to review the applications of diamagnetic - susceptibilitymeasurements to problems of molecular structure, and to indicate severalinteresting and promising new lines of application which were being studiedjust before the outbreak of war.The fundamental investigations in diamagnetism are associated with thenames of Curie, Pascal, and Langevin.On the experimental side, theextensive and systematic investigations of P. Pascal 3 on organic compoundsshowed that the diamagnetic susceptibility of a molecule, xM (xM = x .1M,where x is the mass susceptibility and M is the molecular weight), is anadditive and constitutive property. Hence, for a compound XGYbZc,X M = axx + bxp + cxz + h, where a, 6, and c are the numbers of atoms ofX, Y , and Z having, respectively, susceptibilities xx, xy, and xz, and h is aconstitutive correction constant dependent upon the nature of the chemicallinkings between the different atoms.derived mathematical expressions for the susceptibilities of atoms which showthat diamagnetism is independent of temperature.Since these investigations,a considerable amount of work has been done on both the experimentaland the theoretical side. In the main, this Report will deal with experi-mental aspects of more recent work.An excellent general review of magnetochemistry was given by (Sir)From classical theory, P. Langevin1 D. H. Hey, Ann-. Reports, 1940, 37, 263.8 Ann. Chim., 1909, 16, 531 ; 1910, 19, 5 ; Bull. Soc. chim., 1911, 9, 79, 177, 336,Ibid., 1937, 34, 126.809, 868.Ann. Chim. Phy8. 1905, 5, 7028 GENERAL AND PBYSIUAL OKEMISTRY.S. S. Bhatnagar in 1938 and general advances are discussed in severalrecent monographs.6There is still considerable confusion in the literature owing to the diverg-ence in the recorded values of x for many compounds.This may arisefrom the fact that x may be measured by a variety of methods and it isquestionable if all these are of equal accuracy. Although none of the methodsinvolves a highly-skilled technique, each possesses inherent errors and itwould help greatly in assessing recorded values if more details of experi-mental procedure were given when data are published, e.q., number ofdeterminations made, methods of calibrating apparatus, reference substances,methods of purification, criteria of purity, and temperature.(1) The XusceptibiZity of Water.-It is usual to calibrate apparatus bymeasuring the susceptibility of some compound for which the value of x iswell established, and H. R. Nettleton and S. Sugden have discussed thisproblem in detail in their investigation of the susceptibility of nickel chloride.Following P.Pascal: many investigators use water as reference substance.[Pascal records x of water as - 0.75 * but, since the value accepted today is- 0.720, all his recorded values must be corrected by multiplying themby 0.72/0*75 = 0.96.1 The employment of water as reference substancerequires that the water must be subjected to a rigorous purification process,otherwise all data will be vitiated. To obtain water of x = - 0.72 is muchmore diEcult than many investigators appear to believe.showed that xla. was - 0.72 and remained practically constant at differentfield strengths ; P. S h e 9 found - 0.72, W. J. de Haas and P. Drapier lorecorded - 0.721, and A.Piccard and A. Devaud 1°a give xZw as - 0071864,slightly less than - 0.72183, the value found by H. Auer.11 Severalinvestigators have measured x for water a t different temperatures and,generally, they found that the value increases with rising temperature.For instance, R. N. Mathur l2 found that x increased from - 0.7195 at 15”to - 0-7297 a t 75”, M. A. Azim, S. S. Bhatnagar, and R. N. Mathur l3report an increase from - 0.720 at 25” to - 0.726 a t 75”, and H. Auer,llin a very accurate determination, gives x16.30 as - 0.72145 5 0.00048 andxzon as - 0.721834 &0.00048. P. S. Varadachari,14 on the other hand,6 Proc. Twenty-fifth Indian Sci. Congress, 1938, 11, 49; summarised in Scienceatad Culture, 1938, 3, 446.6 E. C. Stoner, “ Magnetism and Matter,” Macmillan, London, 1934; L.F. Bates,“ Modern Magnetism,’’ Cambridge, 1939 ; B. Cabrera, “ Dia- et Paramagn6tisme etStructure de la MatiCxe,” Hermann, Paris, 1937; S. S. Bhatnagar and K. N. Mathur,“ Physical Principles and Applications of Magnetochemistry,” Macmillan, London,1935 ; W. Klemm, “ Magnetochemie,” Akademische Verlagsgesellschaft M.B.H.,Leipzig, 1936; J. H. van Vleck, “ Theory of Electric and Magnetic Susceptibilities,”Oxford, 1932.A.. P WillsProc. Roy. SOC., 1939, A , 173, 313.J . Physique, 1913, 3, 8.laa Arch. Sci. phya. nat., 1920, 2, 455.l2 Indian J . Physics, 1931, 6, 207.l4 Proc. Indian Acad. Sci., 1935, A, 2, 161.* All values of x in this Report have been multiplied by 10’.* Physical Rev., 1905, 20, 188.lo Ann.Physik, 1913, 42, 673.l1 Ann. Physik, 1933, 18, 693.l3 Phil. Mag., 1933, 16, 580ANGUS : DIA.MAONE!CISM. 29found a much smaller increase ( - 0.7200 a t 28"; - 0.7216 a t 55").W. Johner 15 put forward the formula xp = xzO4l + 0.00013( 8 - 20)] for thetemperature coefficient of the susceptibility of water, and later, A. P. Willsand G. F. Boeker l6 deduced a parabolic formula for the variation of x withtemperature for 14 temperatures in the range 20-66", but this is contestedby B. Cabrera and H. Fahlenbrach 17 who state that water has a positivetemperature coefficient and that x increases linearly with temperature.K. Honda and Y. Shimizu l8 have calculated theoretically the variation ofx with temperature.This variation of x with temperature appears to contravene the state-ment that diamagnetism is independent of temperature but it is probablydue to simplification of the molecular species present in water as a result ofthe breakdown of hydrogen-bonded structures a t the higher temperatures.lgSupport is lent to this view by the fact that L.Sibaiya 2o records that x forice is constant from - 120" to 0" and is - 0.708, considerably lower than thevalue for water. B. Cabrera and H. Fahlenbrach, however, have found thatthe susceptibility of ice (xoo = - 0.7019) varies linearly with temperaturebetween - 60" and OoY21 but that above 100" x of water is constant.22That the presence of isotopic analogues does not affect the value of XMhas been experimentally substantiated by P.W. Selwood and A. A. Frost,23(Miss) V. C. G. Trew and J. F. Spencer,% F. E. H ~ a r e , ~ ~ and V. Nehra andM. Qureshi26 from measurements on deuterium oxide. F. W. Gray andJ. H. Cruickshank27 measured H20-D20 mixtures containing 44, 62, and87% of D20 and concluded that H20, HOD, and D20 have identical valuesof xM, whilst, from similar measurements, H. P. Iskenderian 28 has deducedvalues of - 0.6807 and - 0.6466 for x of HOD and D20, respectively.B. Cabrera and H. Pahlenbrach have investigated the magneto-thermalbehaviour of D20 but, since they report29 that its molecular susceptibilitydiffers from that of H20, their statement 30 that, between - GO" and 150",dx/dO is faster in solid and slower in liquid D20 than in H,O must beaccepted with reserve.On the Thomas-Fermi atom model, T. Takduchi,T. Sugita, and T. Inai31 have calculated the susceptibility and dx/dOfor D,O.It would, therefore, appear that the choice of water as a standardreference substance is not a particularly happy one.(2) Effect of Temperatwe on Other Diamagnetic Substances.-Littleattention has been given to this problem, and available data are notl6 Helu. Physica Acta, 1931, 4, 238.l6 Physical Rev., 1934, 46, 907.l8 Sci. Rep. Tdhoku Imp. Univ., 1937, 25, 939.2o Current Sci., 1935, 4, 41.22 Ibid., 1934, 32, 525.24 Nature, 1936, 137, 998.26 Current Sci., 1937, 5, 533.40 Physical Rev., 1937, 51, 1092.3a Naturwiss., 1934, 22, 417.l7 2. Physik, 1933, 82, 759.W. R. Angus and W. K. Hill, Trans.Faraday SOC., 1940,36, 923.21 Anal. Pis. Quim., 1933, 31, 401.a3 J . Amer. Chm. Soc., 1933, 55, 4336.27 Nature, 1935, 135, 268.2@ Anal. Pis. Quim., 1934, 32, 538.31 Bull. Tokyo Univ. Eng., 1937, 6, 116.Ibid., p . 49730 GENERAL AND PHYSICAL CHEMISTRY.sufficiently plentiful to permit an unequivocal explanation of observedeffects. There appear to be three classes of substance : (i) a group whichshows, like water, a positive temperature coefficient, but the only data arefor n- and iso-propyl and -butyl alcohols; 13 (ii) those which have a negativetemperature coefficient and comprise, almost entirely, aromatic de-rivatives ; 12*13* 32 and (iii) those which are independent of temperature.In the h s t group are hydrogen,% the rare ga~es,~3 boron34 (from - 183" to20°), cyclohexane and carbon tetrachloride l3 (20-75"), acetic l4 (25-55")and n- and iso-butyric acids,12 butyl bromide,12 and, unexpectedly, isoamylalcohol 12 (20-80").P. S. Varadachari 14 has examined the system sodiumsulphate-water throughout the range 25-55' but finds no change at 33"the temperature of transition from decahydrate to anhydrous salt. Varioustentative explanations have been advanced. M. A. Azim, S. S. Bhatnagar,and R. N. Mathur13 have attempted to correlate their results with the,polarisability and high associating tendency of substances having a positivecoefficient. The non-polar, symmetrical characters of cyclohexane and carbontetrachloride are attributed by the same authors as reasons for the temper-ature-independence of x of these compounds ; but this is an ad hoc explanationwhich is inapplicable to butyl bromide and the fatty acids.The negativecoefficient exhibited by aromatic compounds finds no explanation, but thereis the interesting observation of S. R. Rao and S. Sriraman35 that x ofnitrobenzene, in the range 30-102", slowly diminishes to a minimum valuea t 75" and then increases, a behaviour which they attribute to changes inassociation. More work in this direction might yield some extremelyinteresting results and relationships.(3) Influence of Physical State on the Value of X.-The big increase in xMon vaporisation reported by V. I. Vaidyanathan 36 for a number of organiccompounds must be doubted because, more recently, R. Jaanus andJ. Schur 37 have reported a value for benzene vapour of - 59 &- 3 which is ofthe same order of magnitude as the accepted value of - 55.0 for liquidbenzene, the difference probably being due to the greater difficulty of measur-ing x for gases.Likewise, the influence of fusion is not clear. B. Cabreraand H. Fahlenbrach38 state that a sudden change occurs on fusion due todeformations caused by crystal forces, whereas T. Ishiwara 39 found nodiscontinuity at the melting points of silver halides. There is good reasonto believe, however, that the liquid state has a slightly higher value for xthan the solid state. This is borne out by the work of A. E. Oxley4O onorganic compounds. Also, J. Farquharson and E. Heymann41 haves2 S. S. Bhatnagar, M.B. Nevgi, and M. L. Khanna, 2. Physik, 1934, 89, 506;G . F. Boeker, Physical new., 1933, 43, 756.33 G. G. Havens, Physical Rew., 1933, 43, 992.34 L. Klemm, 2. Elektrochem., 1939, 45, 354.ae Ibid., 1927, 2, 135.3s Sci. Rep. TGhoku Imp. Univ., 3920, 9, 233.40 Phil. Trans., 1914, 214, 109; 1915, 215, 79; 1926, 220, 247.41 Trans. Faraday SOC., 1935, 31. 1004.35 Indian J . Physics, 1934, 8, 315.37 Natw-e, 1934, 134, 101.Cornpt. rend., 1933, 197, 379; 2. Physik, 1934, 89, 682ANUUS : DIAMAUNETISM. 31examined cadmium, mercurous, and lead chlorides as powders, solidifiedmelts, and in the molten state. They found that x increased in this orderand, since the value of x for an aqueous solution of cadmium chloride wasfound to decrease with increasing concentration of the salt, they suggestedthat the increase in x on melting may be due to ionisation.Y. Shimizu hasreported abrupt changes a t the melting points and transition points of anumber of metals, whilst G. E. R. Schulze 43 found a slight change a t thetransition points of ammonium bromide and nitrate, potassium and thallousnitrates, and silver iodide. Ammonium halides have also been examinedby A. Dinsdale and F. A. L ~ n g . ~ ~ a The observed effects are attributed tolattice changes. K. C. SubramaniamU attributes the increase in x ofbenzophenone on melting to breakdown of polymerides, and gives the sameexplanation for the diminution of y, on melting p-nitrotoluene. Here isanother fertile field of enquiry from which much interesting informationshould be forthcoming.(4) The Diamagnetic >CH, Increment.-The values (corrected) given byP.Pascal for the introduction of a methylene group vary from - 11436 to- 11.42. The determination of this value is fundamentally important tothe determination of values for atoms in organic molecules and for bondingand constitutive correction constants because these derived values form thebasis of the testing of the additivity of diamagnetism. Many workers haveaccepted Pascal's values, but others have pointed out discrepancies. Acritical examination of Pascal's data made by (Sir) S. S. Bhatnagar andN. G. Mitra 45 led them to suggest that the (numerically) maximum valuewas - 11.68. B. Cabrera and H. Fahlenbrach 46 give - 11.48 from measure-ments on seven alcohols ; D.B. Woodbridge 47 obtained - 11-67 from aceticacid and five alkyl acetates; F. W. Gray and J. H. Cruickshank 48 report- 11-87 from an investigation of homologous organic nitrates, nitrites,and nitro-compounds; J. Farquharson and M. V. C. Sa~tri,*~ from fivenormal aliphatic acids, deduced - 11.64; and - 11.36 was obtained by(Sir) S. S. Bhatnagar, N. G. Mitra, and G. D. Tuli 50 from an examinationof twenty compounds belonging to four different homologous series. Thiswas the unsatisfactory state of affairs in 1938 when a systematic re-investig-ation," under carefully controlled conditions, was started at the UniversityCollege of North Wales, Bangor. About 50 compounds were measuredwhen the work had to be discontinued, but analysis of the ascertained datapa Sci.Rep. T6hoku Imp. Univ., 1937, 25, 921.4a 2. physikal. Chem., 1938, B, 40, 308.49a Proc. Leeds Phil. SOC., 1937, 3, 270.44 Proc. Indian Acud. Sci., 1936, A , 3, 420.4 b J. Indian Chem. SOC., 1936, 13, 329.46 2. Physik. 1933, 85, 568.4 7 Physical Rev., 1935, 40, 672.40 Trans. Faraday SOC., 1935, 31, 1491.4D Ibid., 1937, 33, 1472. * Full details will be given in forthcoming papers by W. R. Angus, W. K. Hill, andPhil. Mag., 1934, 18, 449.E. Roberts32 GENERAL AND PaYSICAL UHEWSTRY.on aliphatic alcohols, acids, esters, aldehydes, and ketones, and aromatichydrocarbons and esters yields the value of - 11-68 0.01. This valuewas obtained by the subtraction method of P. Pascal3 and by a graphicalmethod49 in which observed values of XM are plotted against the numberof methylene groups.The straight line obtained can be represented by theequation XM = u?z - b, where b is the intercept on the XM axis and representsthe diamagnetic effect of the “ end ” group, and a is the diamagnetic incre-ment of a methylene group, of which there are n in the molecule. Bysubtracting b from the observed xu value the contribution made by n methyl-ene groups is obtained, and hence the >CH, increment. This method ispreferable to that of Pascal in that it involves each member of the seriesindependently, whereas his method yields a mean value for x CBI whichis dependent on the purity of the first and the last member of the series only-intermediate members can be neglected.E’urther work on a wide varietyof series will be continued when conditions permit, because, although thedata are self-consistent for each series, the values of x , ~ , derived for thedifferent series vary from - 11.65 to - 11.72. Other interesting resultsobtained in this investigation are (i) that when an acid is converted into itsmethyl ester the increment is - 10.66, i.e., about 1 unit less than the averagevalue of x>cIIs ; (ii) that branched methyl substitution causes the susceptibilityto increase by approximately - 12.70 irrespective of whether an iso- or asec.-compound is formed, i.e., about 1 unit greater than the average valueof x , ~ ~ * ; and (iii) a second branched methyl substitution gives the usualincrement of - 11.68.These results amply demonstrate the necessity forfundamental investigations on homologous series before applications toproblems of molecular structure can be reliably made.( 5 ) Diamagnetism of Imneride.s.-From the viewpoint of Pascal’s additiv-ity rule the susceptibilities of isomeric compounds should be identical. Manyrecorded data confirm this, but a critical examination of available dataindicates that this identity is probably fortuitous. For instance, althougha number of isomeric pairs show identical ~ a l u e s , ~ ~ ~ ~ ~ P. Pascal 51a recordsfor ethyl butyl ketones the following values : tert.-, - 82.2; iso-, - 81.9;n-, - 81.1. This sequence has been borne out by later workers, and acomprehensive discussion of the question by (Sir) S.S. Bhatnagar, R. N.Mathur, and M. B. Nevgi 52 led them to conclude that, generally, the sus-ceptibilities of isomeric compounds were : tert.- > sec.- z iso- > n- ; o > p> m ; cis > trans. They also state that the susceptibilities of the n-, iso-,and tert.-aliphatic isomerides fall into the above sequence as a result of cha’ngein the radii of the electronic orbits owing to changes in the effective electroniccharges. Various attempts to correlate these differences with other physicaldata have been made 53 but none has proved successful. This arises partlyfrom the paucity of data and partly from conflicting values, particularlyfor aromatic isomerides as is shown in the following table.Mag., 1928, 5, 636.61 (a) Pascal, Compt.r e d . , 1909, 149, 342; ( b ) Bhatnagar and C. L. Dhawan, PhiE.tia Z. Phyeik, 1931, 69, 373ANGUS : DIAMAGNETISM.Compound.Cresol ..................Nitro t oluene .........Toluidine ............Phene tidine .........Chlorophenol .........Values of - XM x 10'./-0. m.73-62 73.3273.54 72.3071-475-70 76.9471-85 72.4272.872-97 { ;::t5 74-6{ 72.4{ 74.3-- --723.72-7671-3272.170.8970.672.195.997.465.5476.7--33Ref.63b546563b645553a5553a1253b55For aliphatic isomerides the sequence given above has been found bymany workers, but widely different values for the numerical increase ingoing from the n- to the iso-isomeride have been recorded, ranging from- 0-74 to - 2.74.s6 From a recent study * of homologous series ofaliphatic alcohols, acids, and esters, carried out by Mr.W. K. HilI, the follow-ing conclusions can be drawn : (i) position isomeric esters have identicalsusceptibilities ; (ii) the susceptibility of the corresponding isomeric acid isnumerically greater by approximately 1 unit ; (iii) all n-isomeric estershave identical susceptibilities, as also have all iso-isomeric esters ; (iv) thesusceptibility of an iso-isomeride is greater than that of the n-isomeride by anapproximately constant amount ( - 1-03) ; and (v) the sequence is tert.-slightly > sec.- =: iso- > n-.(6) Atomic and Ionic Xwce~tibilities.-The derivation of values for thegram-atomic or gram-ionic susceptibilities from experimental data was firstcarried out by P.PascaL3 He obtained susceptibilities for atoms linkedtogether by homopolar bonds and, hence, his derived values contain bondingeffects. These values enabled him to demonstrate the additive nature ofdiamagnetism and are probably substantially of the correct order of magnitude.When the atom participates in forming a polar salt, the molecular susceptibilityof the salt may be considered as the sum of the susceptibilities of the ions,XM = Xcation + xanion. Values for ionic susceptibilities have been derived bytwo methods-from experimental data and, for spherically symmetricalions, from theoretical calculation. The lack of agreement in experimentaldata published by different workers renders comparison of values derivedby different methods difficult and, possibly, has led to the publication of somany methods of obtaining these values.In each method certain assump-tions are made which frequently cannot be completely justified.The divergence amongst recorded values was pointed out 57 some years63 (a) (Sir) S . S . Bhatnagar and R. N. Mathur, PhiE. Mug., 1931,11,914; (b) (Sir) S. S.64 B. Cabrera and H. Fahlenbrach, 2. Physik, 1934, 89, 682.5 5 K. Kido, Sci. Rep. Tdhoku Imp. Univ., 1936, 24, 701.66 B. Cabrera and A. Madinaveitia, Anal. Pis. Quirn., 1932, 30, 528; see also Refs.67 W. R. Angus, PTOC. Roy. SOC., 1932, A, 136, 669. * A detailed discussion will be published later by W. R. Angus and W. I(. Hill.Bhatnagar, R. N. Mathur, and R. S. Mal, ibid., 1930, 10, 101.12, 13, 510, 62, 63a, 53b.REP.-VOL.XXXVIII. 34 GENERAL AND PHYSICAL OHEMISTRY.ago in a review of the methods and is again stressed in a recent review by(Miss) V. C. G. T r e ~ , ~ ~ in which she summarises the various methods andobtains an average set of values for ionic susceptibilities derived fromexperimental results. These methods will be considered first. The widevariation in them will be self-evident, and the necessity for an early re-investigation of the whole problem will be fully apparent from an examinationof the values collected in the table below. G. Joos,~~ using the data ofJ. Koenigsberger,Go obtained values for salts having ions with an inert-gasconfiguration, e.g., potassium chloride and rubidium bromide, by assumingthat such ions contribute amounts to the molecular susceptibility which areinversely proportional to the square of the nuclear charge.K. Ikenmeyer 61applied this method to his measurements on alkali and alkaline-earth halidesbut, later, G. W. Brindley 62 modified the method by taking the suscepti-bilities as inversely proportional to the squares of the effective nuclear chargesevaluated by using the screening constants and effective quantum numbersproposed by J. C. Slater.63 G. W. Brindley and P. E. HoareG4 havemeasured the susceptibilities of crystalline alkali and alkaline-earth halidesand, taking the value of xw = - 0.7, which is the calculated value, theyderived values for the other metallic ions and for halide ions, justifying theirprocedure on the grounds that, since XLY is so small, any error in it will notgreatly influence the values for the other ions.They also showed that in-creasing co-ordination causes a slight decrease in diamagnetism, i.e., gives anumerically larger value for XN. Thus, the change from the usual 6-co-ordination of alkali halides to 8-co-ordination in cssium iodide is accom-panied by a diminution of 3.1 units.P. Weiss65 has employed two methods of obtaining values for ionicsusceptibilities. In the first, he takes Pascal's values for atoms and adds + 3 units for a univalent anion and - 3 and - 6 units for uni- and bi-valentcations, respectively. This unwarrantable procedure neglects the specificbonding effects of different ions. In the second method, he shows that dia-magnetic susceptibilities of aqueous solutions are influenced by the actionof charged ions on the water molecules in the same way as molecular re-fraction is influenced. From the relationship AR/R = 2AxIx he deducesthat the hydrogen ion has an effective paramagnetism of + 1.1 units.The value of a halogen ion will thus be more diamagnetic by 1.1 units thanthe corresponding halogen acid.By this method Weiss derived values foralkali and halide ions from the measurements of R. Hocart 6G andK. Reicheneder.67 This method has also been used by L. Abonnenq68ti* Trans. Faraday Soc., 1941, 37, 476.69 2. Physik, 1923, 19, 347; 1925, 32, 835.6o Ann. Physik, 1898, 66, 698.e2 Phil. Mag., 1931, 11, 786.64 Proc. Roy. SOC., 1935, A , 152, 342; see also F.E. Home and G. W. Brindley, ibid.,66 J . Physique, 1930, 1, 185.g7 Ann. Physik, 1929, 8, 68.61 Ibid., 1929, 1, 169.63 Physical Rev., 1930, 36, 57.1937, A , 159, 395.66 Compt. r e d . , 1929, 188, 1151.#II Compt. rend., 1934, 198, 2237ANGUS : DIAMAUNETISM. 35V. Veiel,sO and 0. E. Frivold 70 on their measurements on aqueous solutions ofmetallic halides. K. Kid0 7 1 has found, contrary to existing evidence, thatthe numerical value of XM for salts of metals in the same group of the periodic:classification with a common anion increases linearly with the number ofelectrons in the cation. When x M is plotted against the number of electronsin the cation the intercept of the x M axis will give the value correspondingwith the parent acid of the anion; and, by assuming that XH' = 0, he thusobtains a value for the anion.Miss Trew 58 has added another method,applicable only to halide ions. From Pascal's work the values of the sus-ceptibilities of halogen molecules are known. Methods are available forcalculating these molecular susceptibilities and also for calculating thesusceptibility of a halide ion. On the basis of the ratio XM(theor.)/XM~exptl.) =Most of these methods are reviewed by Miss Trew and she then averagesthe individual values and obtains the following ionic susceptibilities :F' = 9.1 1.8; Cl' = 23.4 & 1.3; Br' = 34.6 -+ 1.6; I' = 50.6 & 1.6;Li' = 1.0; Na' = 6.8; K' = 14.9; Rb' = 22.5; and Cs' = 35.0. Thejustification for including all the individual values she has used is ratherquestionable.Experimental confirmation of data is the first step towardssettling these difficulties. Then only can some rigorous treatment be applied.Empirical adjusting of values by an arbitrary choice of the susceptibilitiesof the ions from which other susceptibilities are deduced will never attainthe desired objective. After all, L. Pauling 72 by choosing values of - 5.2and - 14-5 for XNa' and XK-, respectively (in each instance numerically 4 unitsless than the values chosen by Pascal), deduced, from Pascal's data, values forions of alkali and alkaline-earth salts which were satisfactory for simple ions.for the diamagnetic susceptibilityof a spherically symmetrical atom or ion is x = - (e2/6mc2)Z?2, where p 2 isthe time average of r2, the distance of the electron from the nucleus, and thesummation is extended over all the circumnuclear electrons.In quantummechanics this formula also holds but the value of P is different. W has beencalculated, independently, by J. H. van Vleck 73 and L. Pauling ; 72 the latterhas calculated a number of ionic susceptibilities but they are, generally,higher than experimental values. D. R. Hartree's 74 space charge dis-tribution method has been utilised by E. c. Stoner 75 and G. W. Brindley 62but, again, values numerically greater than the experimental values areobtained. J. C. utilising the fact that the nodes in a wave functionare unimportant, has shown how wave functions of atoms and ions may becalculated conveniently by neglecting the nodes and taking as the radialpart of the wave function of one electron in a symmetrical atom $ =Xion(theor.)/Xion(exptl.), Trew derives values for Xion(expt1.).The classical formula of Langevin68 Ann.Physik, 1935, 24, 697.70 Avh. norsk. Vidensk.-Akad. Oslo, Mat.-mt. Kl., 1933, No. 9, 21 pp.7 1 Xci. Rep. Tdhoku Imp. Univ., 1932, 22, 149, 288, 869; and Rep. Yokohama Tech.72 Proc. Roy. SOC., 1927, A, 114, 181. 73 Proc. Nat. Acad. Sci., 1926, 12, 662.74 Proc. Camb. Phil. SOC., 1928, 24, 89, 11 1. 7 6 Proc. Leeds Phil. Soc., 1929,1,484.Coll., 1934, No. 2, 203, 223, 233Author.Experimental :Joos . .. .. . ... . .. ... . . . .. . .. . . . .Ikenmeyer . . . . . . . . . . . . . . . . . .Brindley .....................Brindley and Home .. . . . .Weiss (Pascal) ... ... ... ... ...,, (Hocart) ... ... ... ... ...,, (Reicheneder) . . . . . . . . .Abonnenc .....................Veiel .. . .. . .. . . . . . . . . . . ... . . . . . .Kido . . . . . . . . . . , . . . . . . . . . . . . . . . .Trew . . . . . . . . . . . . . . . . . . . . . . . . . . .Pauling . . . . . . . . . . . . . . . . . . . . . . .Brindley ......... ............Slater ...... ... ...... ...... ... ...AngusBrindley . . . . . . . . . . . . . . . . . . . . .Miowka ........................Hirone . . . , . . . . , . . . . . . . . . . . . . . .GombBs ......... ...............Theoretical :, . . . . + , . . . . . . . . . . . . . . . . .Li.I4.00-70.7I - -2.63.81-61-00.60.70.70.70.9 ---N&.6.510.45.26.17-68.27-59.07.66.8-4.25.24.23.75.12.91016K.14.516.913.514-616.016.516.317.413.614.9-16.713.514-413.113.58.41820Rb.-31.324.022.024.3I -25-027.222.53524.025.824.123.627.83228cs.-45.7636-835.141.0 --38-341-035-05536.839.637.236-94333-ICa.911.010.810.710.611.112.46.5---13.310.811-410.410-41117-Sr.2425-419.518.018.919.922-516.6---2819.521.520.218.718.2232r(n*-%o-~)~nf~, where n* is the effective quantum number and (2 - 8 )the effective nuclear charge.Rules are given by Slater for the evaluationof n* and 8, the screening constant, for an electron group.By integrationof the wave function t 2 = (n*)2(n* + #)(n* + l)/(Z - a)* and for eachelectron in the group x x lo6 = - 0.807F2. By means of this formulavalues for ionic susceptibilities in better agreement with experimentaldata are obtained. For many ions an improved value is obtained by amodification of Slater's method proposed by W. R. Angus.57 This consistsof treating separately s and p electrons having the same principal quantumnumber. The justifkation for this procedure has been questioned; 58 butall these methods are empirical, so criticism can be levelled at each.A. Heydweiler's refraction data at infinite wave-length 76 have been usedby G. W. Brindley 77 and B.Mrowka 78 to obtain xM by means of the relation-ghip between xN and p~larisability.~~ Values obtained on the basis of theThomas-Fermi statistics by T. Hirone 80 and P. GombAs 81 do not agreewell with experimental values. From such a diversity of methods a diversityof values is obtained which, at present, cannot be satisfactorily sorted out.The table on p. 36 illustrates these diiliculties.(7) Applications of Additivity in Simple Nolecules.-In section (6) referencehas been made only to ions which have a rare-gas configuration. If it isassumed that diamagnetism is strictly additive, the susceptibilities of otherions can be deduced from measured molecular susceptibilities by subtractingknown susceptibilities of other groups. Thus, to find x of a cation a numberof salts are examined and the anionic contributions are subtracted from themolecular susceptibilities. This procedure is of doubtful value because ofprevailing uncertainties regarding the true value of simple ions.Someworkers use one set of data, some choose another; there is, accordingly,great confusion in the derived quantities and no real basis for comparingthem. Inthe simple form outlined above the method has been employedto ascertain values for the following ions : BiIII,82#83*a BiV,84 SbIII,84 SbV,84Rb',85 Hg' and Hg",86 Sn" and SnIV,87 Ag' and Cu',88 Cd",89 T1',58* 839 9 0 ~ 9 176 Physikal. Z., 1925, 26, 526. Physical Rev., 1933, 43, 1030.7a Z . Physik, 1933, 80, 495.7 * J. G. Kirkwood, Physikal. Z., 1932,33, 5 7 ; J.P. Vinti, Physical Rev., 1932,4l, 813.ao Sci. Rep. TGhoku Imp. Univ., 1935, 24, 264.8a (Sir) S. 8. Bhatnagar and B. S. Bahl, Current Sci., 1936, 4, 153, 234.a4 V. I. Vaidyanathan, Indian J . Physics, 1930, 5, 559.-2. Physik, 1933, 87, 67.K. Kido, Sci. Rep. Tdhoku Imp. Univ., 1933, 22, 835.(Sir) S. 5. Bhatnagar, M. B. Nevgi, and M. L. Khanna, J . Indian Ohm. SOC.,80 (Sir) S. S . Bhatnagar, M. B. Nevgi, and G. L. Ohri, Proc. Indian Acud. Sci.,a 7 (Sir) S. S. Bhatnagar, M. B. Nevgi, and R. L. Shanna, J . Indian Chem. SOC.,1935, 12, 799.1939, A, 9, 86.1936, 13, 273.C. Courty, Compt. rend., 1936, 202, 1929.(Miss) W. R. A. Hollens and J. F. Spencer, J., 1934, 1062; 1935, 495. * (Miss) V. C. G. Trew, Tram. Famday SOC., 1936,82, 1658.*l M.B. Nevgi, J , Univ. Bombay, 1938,7, 1938 GENERAL AND PHYSICAL CHEMISTRY.K. Kid0 83 has combined the subtraction method with a graphicalextrapolation method and thereby deduced values for TiIV, CeIV, LaIII,0”, S”, ClO,’, SO4”, PO4”’, PO,’, and NO,’ ions and, recently, Miss Trew 58has used a graphical method to assist in deducing values for NO,‘, CN’,CNO’, CNS’, C03”, SOi’, NH,’, halogenate, and perhalogenate ions. K.Kid0 93 has derived values for oxy-acid ions and finds that the susceptibilityof an ion with a similar co-molecular structure decreases with increase of thenuclear charge on the central atom in the same group and increases withincrease of the nuclear charge on the central atom in the same series.In their work on alkali halides, G.W. Brindley and F. E. Hoare64 foundthat, with the exception of lithium and czsium chlorides, bromides, and iodides,the other crystalline salts were strictly additive within the limits of experi-mental error. They suggest reasons. I n a lithium halide there is a smallcation and a relatively large anion. The anions approach closely and thegreater electrostatic repulsions produce larger interatomic distances thanwould normally be expected. The caesium halides, on the other hand, have adifferent crystal structure from other alkali halides (sodium chloride structure)and this is responsible for their deviation from strict additivity. The sameauthorsss have also pointed out that ammonium iodide, which has thesodium chloride structure, gives the normal value of x, whereas ammoniumchloride and bromide give low values.Solid lithium hydride gives a valueabout half that calculated, and this is attributed1 to a factor which, in-operative in isolated ions, introduces in crystals a paramagnetism practicallyindependent of temperature.I n deducing values for the formate, acetate, iodate, nitrite, nitrate, andselenite ions, S. R. Rao and S. Sriramang4 found that the values obtaineddepended on whether they used crystalline salts or aqueous solutions. Thesusceptibilities in solution were greater than those for the crystalline salt.Similar observations have been reported in respect of metallic halides byK. C. Subramaniam 95 but, on the other hand-again using metallic halides-M. Flordal and 0.E. Frivold 96 found no substantial difference. The morerecent work of F. E. Hoare and G. W. Brindley 97 conclusively supports theIndian workers and leads to the following conclusions : (i) the susceptibilitiesof ions in solution are closely additive, (ii) the susceptibility of a large uni-valent ion in solution is approximately equal to its value in the crystallinestate, (iii) the susceptibilities of small and bivalent ions in solution are lessthan in the crystalline state owing to hydration effects, (iv) the differencebetween the values in solution and in the crystalline state (xcryst.), zlix.,x ~ ~ ~ ~ . - xcrsst., varies progressively with Cn/R2, where n/Ra is the field at theboundary of the ion and C is the degree of hydration.92 S . P. Ranganadham and M.Qureshi, Indian J . Physics, 1940,14, 129.B3 Xci. Rep, Tdhoku Imp. Uniz)., 1932,21, 069.s4 Current Sci., 1937, 8, 64; Phil. Mag., 1937, 24, 1025; J . Annamalai Univ., 1938,95 Proc. Indian Acad. Sci., 1936, A , 4, 404.96 Ann. Physik, 1935, 23, 425.97 Trans. Faraday SOC., 1937, 33, 268; Proc. Physical Soc., 1937, 49, 619.7, 187ANQUS : DIAMAGNETISM. 39Very few data exist for salts in non-aqueous solvents, The suscepti-bilities of mercuric halides in pyridine are less than in the crystalline state,86and 0. E. Frivold and H. Sogn 98 found that susceptibilities of salts in non-aqueous solvents were less than in aqueous solution.Measuredvalues are for combined atoms, and F. W. Gray and his collaborators postulatethat experimental values should be less than the calculated values (Pauling 72)and that the difference is due to depression of diamagnetism resulting frombond formation. Estimates of the magnitude of bond depressions weremade for a large number of compounds 2 before a new and intricate techniquewas published by F.W. Gray and J. H. Cruickshank3 which may be sum-marised as follows. Selecting Pauling’s 7, method of calculating ionicsusceptibilities, they modify it so as to calculate the susceptibility of anatom which is not exhibiting its extreme values of positive or negativevalency corresponding with inert-gas structures. For example, withcarbon they calculate values for C+4, C+3, V2, C+1, Co, C-l, C2, C3,and (3-4. To each atom in a molecule residual charges are assigned on thebasis of dipole moments of links, Ae, the residual charge being equal t o thebond moment /internuclear separation.These residual charges representthe fraction of time spent in a particular valency state by a particular atom.Thus, since the residual charges on carbon and hydrogen in a C-H bond are,respectively - 0-04 and + 0.04, the CH, group is H+O.04#*Hf0*O4.The theoretical diamagnetic susceptibility of this group is computed asfollows : the carbon atom is 0.08 of the time C-1 and 0.92 of the time Go,and analogously for each hydrogen ; therefore, XM(theor.) = 0 . 0 8 ~ ~ - 1 + 0 . 9 2 ~ ~ 0 + 2(0.04xH+1 + 0.96m) = - 14.90. The experimental value (Pascal)is - 11.86 and the difference, - 3.04, is the depression arising from oneC-C single bond and two C-H bonds.Depressions for a large number ofbonds of different types have been computed, and the values are used tointerpret the diamagnetic measurements and to discuss the molecularconfiguration and resonating species of benzene, naphthalene, the carboxylgroup, water, and hydrogen peroxide ; urea and its derivatives ; * organicsulphur compounds; and derivatives of SO4”, S203”, SOs“, and S,O,”radicals.6 The agreement between experimental values and calculated valuesis astonishingly close. The method involves a knowledge of screeningconstants, bond moments, and internuclear distances, quantities which arenot known for very many bonds and, even when known, are not known withcomplete certainty. I n the discussions of molecular structure more attentionmight have been paid to researches on molecular structure by other andCalculated values of x A are for isolated, free atoms or ions.Ann.Physik, 1935, 23, 413.( a ) F. W. Gray and J. Fsrquharson, PhiE. Mag., 1930, 10, 191; ( b ) F. W. Gray’* Nature, 1935, 100, 473.1 S. FreedandH. G. Thode, J. Chm. Physics, 1935,3,212.and J. Dakers, ibid., 1931, 11, 81, 297; (c) J. Farquharson, ibid., 1932, 14, 1003.a Trans. Faraday SOC., 1935, 51, 1491. 4 A. Clow, ibid., 1937, 33, 381.A. Clow and J. M. C. Thompson, ibid., p. 894.A. Clow, H. M. Kirton and J. M. C. Thompson, ibid., 1940, 36, 101840 GENERAL AND PHySIOaL OHEMISTRY.more firmly established methods. The existence of bond depressionsis indisputable; they are implied in Pascal’s corrections although he makes,unlike Gray and his collaborators, no adjustments for single bonds.MissTrew 58 has recently published values, deduced by a different method, forthe C1-0, Br-0, and 1-0 bonds. Likewise, the variability of the valencyof certain atoms has been recognised for a long time and other attempts toevaluate the appropriate susceptibilities have been made.M. Prasad and S. S. Dharmatti have recently published data on com-pounds of selenium,s teUuriurn,g and sulphur lo which they interpret interms of bi-, quahi-, and sexa-valent Group VI atoms and for each statededuce susceptibilities, using a modification of Angus’s method.57 Thecompounds yield experimental values in reasonable agreement with thecalculated values.K. Kid0 has also derived values for “ intermediate ”valencies of atoms from his ionic values and applies them to aliphatic com-pounds 1la and to mono- and di-substituted derivatives of benzene.llbSummation of Pascal’s values has yielded results in agreement withmeasured data in many instances and has been widely adopted. G. B.Bonino and R. Manzoni-Ansidei 12 use it with success for thiophen, furan,pyrrole, and their derivatives, and it yields values in excellent accord withexperimental data on uu’-phenylpolyenes l3 and the diamagnetic hexa-ar~lethanes.1~ Its applications to inorganic compounds have been equallysuccessful. It has aided in investigations which have shown the non-existence of single-electron links in dimethyltellurium halides l5 and in basicberyllium acetate and higher analogues ; 16 in demonstrating the non-existence of cadmous compounds; 89 and in the study of rhenium com-pounds l7-t0 cite only a few random examples.This variety of treatment betokens the present unhealthy state of thesubject. Much of the Mculty will remain until accurate and independentlyconfirmed experimental values are available through which generalisedtreatments can be accomplished.Then, and only then, will it be possible fordiamagnetism to occupy that important place among the methods of de-termining molecular structure which many feel it should.(8) Polymerisation.-In 1936 two papers appeared dealing with thechanges occurring during and after polymerisation. (Sir) S. S. Bhatnagar,M.B. Nevgi, and R. N. Mathur 18 reported a decrease in diamagnetism of aSee, e.g., M. B. Nevgi, J . Univ. Bombay, 1938, 7, 82.Proc. Indian Acad. Sci., 1940, A , 12, 185.@ Ibid., p. 212.l1 ( a ) Sci. Rep. Tdhoku Imp. Univ., 1936, Honda Anniversary Vol., p. 329; (b) ibid.,l2 Ric. sci., 1936, 7, Reprint.l3 E. Miiller and I. Dammerau, Ber., 1937, 70, 2561.l* E. Miiller and W. k c k , ibid., 1938, 71, 1778.l6 W. R. Angus and J. Farquherson, Proc. Roy. SOC., 1932, A, 136, 579. ’’ N. Perakis and L. Capatos, J . Phya. Radium, 1935, 6, 462; W. Klemm andlo Ibid., 1941, A , 13, 369.1936, 24, 701.(Sir) S . S. Bhatnagar and T. K. Lahiri, 2. Physik, 1933, 84, 671.G . Frischmuth, 2. anorg. Chem., 1937, 230, 220.l8 2. P&&, 1936, 100, 141ANGUS : DIAMAGNETISM.41number of compounds, including anthracene and furfuraldehyde, onpolymerisatim. The other paper, by J. Farquharson,lg discusses the poly-merisa tion of py -dime t h y lbu t adiene , cy clopen t adiene , c y anogen chloride , andnitrosobenzene and the molecular susceptibility of a n-polymeride of X isgiven by xM = nXx + (n - 1)A, where A is the correction factor for the newchemical bonds, these being assumed to be all of one type. The dis-appearance of a double bond in the polymerisation of &-dimethylbutadienecauses, as predicted from Pascal’s correction factors, a progressive increasein x with time. This enables Farquharson to combine his magnetic datawith existing chemical evidence and to calculate the mean molecular weightunder different conditions.A later paper 2o reports that in the uncatalysedpolymerisation of dimethylbutadiene x decreases for the first 3 hours andthen increases. This is attributed to the preliminary stage of poly-merisation being the formation of paramagnetic free radicals of the bufadienewith one electron missing, and their concentration has been calculated.Although double bonds also disappear in the polymerisation of cyclopenta-diene, the anticipated increase in diamagnetism is not found; insteadthere is a fall which, it is tentatively suggested, may be due to the bridgedring of the polymeride. The ring closure which accompanies the polymeris-ation of cyanogen chloride to cyanuric chloride may be responsible, as wellas the change from CiN to C:N bonds, for the marked diminution in dia-magnetism which is encountered.More recently 21 it has been found thatring formation in hydrogen-bonded structures-formed by either inter- orintra-molecular hydrogen bonds-of benzoic or monohydroxybenzoic acidsin solvents of different proton-attracting powers leads to a value of xnumerically less than the anticipated additive value and diminishing as theconcentration of solute increases. On the other hand, when an “open”addition compound is formed by intermolecular hydrogen bonding betweensolute and solvent %,,lute increases with solute concentration.J. Farquharson 22 has used magnetic measurements and a modificationof his earlier formula for x of the polymeride to evaluate the diamagneticsusceptibility of the recurring -CH20- group in polyoxymethylene diacetatesand to calculate the number of these groups in a- and P-polyoxymethylenes.This treatment yields an explanation of the earlier results of W.Good 23 ona-, p-, y-, and 8-polyoxymethylenes.Dianthracene is produced by photopolymerisation, in a vacuum, ofanthracene in the solid state or in benzene solution, and the net result is thatthe anthracene molecule loses two double bonds and gains a bridged four ring.This is accompanied by a fall in diamagnetism according to (Sir) S. S.Bhatnagar, P. L. Kapur, and (Miss) G. Kaur,= who have also studied thepolymerisation of styrene in oxygen and in a vacuum.2518 Tram. Paraday SOC., 1936, 32, 219.20 J. Farquharson and (Miss) P. Ady, Nature, 1939, 143, 1067.21 See ref.(19), p. 29.24 Proc. Indian A d . Sci., 1939, A, 10,468.23 Trans. Paraday SOC., 1937, 88, 824.J . Indian Chmn. SOC., 1940, 17,177.J . Roy. Tech. CoU. G b g o w , 1931, 2, 40142 GENERAL AND PHYSICAL CHEMISTRY.Diamagnetic measurements in the temperature range - 40” to + 10”have been invoked by J. Farquharson, C. F. Goodeve, and F. D. Richard-son26 to determine the concentrations of CIO, in mixtures of C10, andCl,O, and, hence, the corresponding equilibrium constants. CIO, is an odd-electron molecule and is, therefore, paramagnetic ; its susceptibility wascalculated from the van Vleck formula. Since all the mixtures were dia-magnetic it follows that Cl,O, is diamagnetic and must, therefore, be in the1Z state.Although it was impossible by magnetic measurements to differentiatebetween the odd-electron (KO,) and the even-electron (K,O,) formu1atio1-1,~~the following formuls have been adduced as preferable to KBH,, KBH,*OH,and NaSO,, respectively : &B2H6,28 &B,H,( OH),,,8 and Na,S,04.29(9) Addition Compounds and CompEexes.-Although the addition com-pounds formed between m-dinitrobenzene or picric acid and amines orhydrocarbons were found, in the solid state, to be more diamagnetic thanwas t o be expected from additivity relationships,3* the same compoundsexhibit less diamagnetism in benzene solution than in the solid state.31KHgI, (solid 86 and in solution 32), NH,Hg13,2H,0,86 K,HgI, and Na,HgI, 32have x values approximately equal to those obtained by additivity, whereasAg,HgI, 33 gives a value about 30% less than the additivity value.Many complexes of transition elements containing CO or CN groupsexhibit diamagnetism, e.g., carbonyls.Recent work has shown that thefollowing are diamagnetic : K4Mo( CN),,= KT13[Re0,(CN)4],35[Re(NH3)s]C1,.36 [Fe(NO,),]”’ and [Co(NO,),]’” are diamagnetic, but[CO(NO,)~]’”’ and [Cu(NO,) 6]’”’ are paramagneti~.~, DiamagneticAg,[Co(H,O)(CN),] changes colour from yellow to blue and becomes feeblyparamagnetic on dehydrati~n.~~ The diamagnetism of nickel complexes ofdiazoaminobenzene and 4 : 4‘-dimethyldiazoaminobenzene indicates that theycontain square co-ordinated nickel atoms and that the triazene group func-tions as a chelate(10) Binary Mixtures.-From 1918, when A.W. and A. W. Smith 39showed that the mixtures COMe2-H,O, AcOH-C,H,, and COMe,-EtOHa6 Trans. Faraday SOC., 1936, 32, 790.a7 W. Klemm and H. Sodomann, 2. anorg. Chem., 1935, 225, 273; E. W. Neumann28 L. Klemm and W. Klemm, 2. anorg. Chem., 1935, 225, 258.29 L. Klemm, ibid., 1937, 231, 136.so (Sir) S. S. Bhatnagar, M. J. Verma, and P. L. Kapur, Indian J . Physics, 1935, 0,3 1 (Sir) S. S. Bhatnagar, M. B. Nevgi, and G. Tuli, ibid., p. 311.33 F. GalIais, Compt. rend., 1937, 205, 1052.as Idem, ibid., 1932, 195, 1390.34 W. A. Rawlinson, J . Proc. Austral. Chem. Inst., 1941, 8, 42.* 6 W. Klemm and G. Frischmuth, 2. anorg. Chem., 1937, 230, 220.36 L. Cambi and A. Ferrari, Cazzetta, 1935, 65, 1162.37 P. Ray and N. K. Dutt, Current Sci., 1937, 5, 476.s* F.P. Dwyer and D. P. Mellor, J . Amer. Chem. SOC., 1941, 63, 81.( J . Chem. Physics, 1934, 2, 31) reported that the superoxide was paramagnetic.131.J . Amer. Chem. SOC., 1918, 40, 1218ANGUS : DIAMAGNETISM. 43obeyed the additivity relationship, until about 1931 little attention was paidto the variation of x with the concentration of the components of a binarymixture. Since then a number of papers have appeared40 which indicatethat the additivity relationship holds approximately ; there are slightdeviations from linearity attributed to co-ordination and de-associationeffects by some workers,40ci m and to the mutual influence of electricallypolar molecules by Rangant~dham,~Oe although Rao and Narayanaswamy,hfrom an investigation of the susceptibilities of mixtures of formic and aceticacids with methyl and ethyl alcohol, acetone, and ethyl ether, maintain thatthe slight deviations are independent of the electric moments of the com-ponents of the mixtures.On the basis of additivity, aqueous solutions of formic acid show small butdefinite diminution in diamagnetism with maximum deviation at 70% ofacid, which may be due to the formation of the monohydrate or to the di-merisation of the acid.41 Acetic acid solutions, on the other hand, obey the ad-ditivity rule.14‘~.2 8 ) s 39* 40n With aqueous solutions of inorganic acids irregu-larities in the X-concentration curves occur which are interpreted as due toformation of hydrates. For hydrogen chloride, J.Farquharson 42 found anumber of maxima corresponding with all the hydrates from 3 to 10H20,but A. F. Scott and C. M. Blair43 could find no maximum or minimum.Farquharson 42 reports irregularities corresponding with H,S0,,H20 andH,S04,3H20, to which P. S. Varadachari l 4 ( P . 28) has added H2S0,,18H20,H2S04,6H20, and 2H2S04,H20; but B. N. Rao 44 could find none of theseand reports only H2S04,2H20. The departures from linearity in the curvesfor nitric acid correspond with the four hydrates HI)U’O3,50H,O, HN03,6H20,HN03,4H20, and 2HN03,5H,0.45 Recently M. R. Nayar and N. K. Mundle 46have examined solutions of iodic acid (0.01-1.0~) and found breaks in theX-N curves at 0.04 and 0 . 0 8 ~ .(1 1) Gases.-Molecules with an even number of circumnuclear electronsare diamagnetic if they are in a 1 2 state. Oxygen, although it containsan even number of electrons, is in a 3C state and is, consequently, para-magnetic.Nitrogen mono- and di-oxide and chlorine di- and tri-oxideare paramagnetic by virtue of their unbalanced structure resulting from at40 (a) H. Buchner, Nature, 1931, 128, 301; ( b ) J. Farquharson, ibid., 1932, 129,25; (c) J. E. Garssen, Compt. rend., 1933, 196, 541; ( d ) K. Kido, Sci. Rep. T6hokuImp. Univ., 1932, 21, 385; ( e ) S . P. Ranganadham, Indian J . Physics, 1931, 6, 421;(f) S. R. Rao, ibid., 1933, 8, 483; ( 9 ) S. R. Rao and G. Sivaramakrishnan, ibid., 1931,6, 609; ( h ) S. R. Rao and P. 8. Varadachari, Proc. Indian Acad. Sci., 1934, A, 1, 7 7 ;( 6 ) C. Salceanu and D.Gheorghiu, Compt. rend., 1935, 200, 120; ( j ) S. Seely, PhysicalRev., 1936, 49, 812; (k) J. F. Spencer and (Miss) V. C. G. Trew, Nature, 1936, 138, 974;( I ) (Miss) V. C. G. Trew and J. F. Spencer, Trans. Furuday Xoc., 1936, 32, 701 ; (m) (Miss)V. C. G. Trew and (Miss) G. M. C. Watkins, ibid., 1933,29,1310; (n) S. R. Rao and A. S.Narayanaswamy, Proc. Indian Acad. Xci., 1939, A , 9, 35; see also Ref. 56.See also Ref. 40n. *l S. R. Rao and S . Sriraman, J . Anmmalai Univ., 1938, 7, 187.42 Phil. Mag., 1931, 12, 283.44 Proc. Indian Acad. Sci., 1936, A , 3, 188.O6 8. P. Ranganadham and M. Qureshi, 2. physikal. Chm., 1936, B, 33, 290.46 Current Sci., 1941, 10, 76,43 J . Physical Chem., 1933, 37, 47544 GENERAL AND PHYSIOAL UHEMISTRY.least one electron not being paired.However, if such molecules undergodimerisation the dimeride will contain an even number of circumnuclearelectrons and will be diamagnetic, e.g., C1,0,26 and N20,,47*64 or feeblyparamagnetic.Experimental difliculties are most probably the cause of the limitedamount of data in this field and particularly in respect of organic vapours.The experimental procedure of J. Schur 46 was the most promising, and byit, the constancy of x for both the liquid and the gaseous state of carbondisulphide, and bromine 49 has been established. Much more workin this direction is required to adjudge the existing conflicting evidence withregard to the probable alteration in x on vaporisation.The values of x obtained experimentally and theoretically for the raregases, hydrogen, and an isosteric pair are collected in the table below.- x x 106.Author.He. Ne. A. Kr. Xe. Ha. N,. CO.Ealperimental :Willa and Hector ...... 1-95 3.96Hector ..................... 1.88 6.66 18.1 11.83Abonnenc ............... 19-2 29.2 44.1Gerlach .................. 19.7Havens .................. 1.91 7-65 19.2 4.01 11-94Mann ..................... 6.75 19.5 28.0 42.4Jaanus and Schur ...... 11.8Pauling .................. 1.54 6.7 21.6 42 66Slater ..................... 1.68 6.7 18.9 31.7 48.0Angus ..................... 1.68 6.1 16-95 29.3 44.8Brindley .................. 1.97 6.1 16.7 29.3 45.6Vinti ........................ 1.97 6-97van Vleck and Frank 4.2Wick ..................... 3-96Witmer .................. 3-87Honda and Hirone ......3.85Theoretical :WFg ..................... 1-53 4.7 1* References denoted thus relate to the second one so numbered.Ref.60*61*52*63*54*55*66*7263677757*58*69*60+61*62*By means of the methods discussed in section (6) for the calculation ofthe susceptibility of an ion with a rare-gas configuration, values of x for raregases can be obtained. The agreement with experimental data is notparticularly good for any method; but the measured values are in tolerableagreement with each other. Comparison with the experimental data for therare gases must surely be the criterion by which a method of calculationcan be judged, and the failure of Pauling's method in this respect suggeststhat it is unsuitable for use in calculating ionic suaceptibilities.Neverthe-less, as has already been pointed out, Gray et found that values calculated47 G. G. Havens, Physical Rev., 1932, 41, 337.48 Physikal. Z . Sovietunion, 1937, 11, 194.$9 J. Schur and R. Jamus, ibid., 1935, 7, 601.6o Physical Rev., 1924, 23, 209.s3 Compt. rend., 1939, 208, 986.64 Phy8ical Rev., 1932, 41, 337.68 Physikal. 2. rSov&union, 1935, 7, 19.51 Ibid., 1924, 24, 418.53 Z . Phyaik, 1933, 85, 545.65 2. Phy8ik. 1936, 98, 648.6 7 Phyaical Rev., 1933, 4l, 813by a method basically related to Pauling's agreed very closely with theirmeasured values. To reconcile these opposing facts most satisfactorilywould involve remeasurement of the rare gases; confirmation of the exist-ing values would indicate a fundamental error in the interpretation of thedata on the plyatomic molecules and necessitate a readjustment of ideasregarding bond diamagnetism.Quantum-mechanical treatment is possible only with the simplestaystems and for helium and hydrogen yields values 68-62 which are, on thewhole, acceptably close to the experimental data.It is noteworthy that the isosteric molecules, carbon monoxide andnitrogen, have identical susceptibilities.This is in line with other physicalproperties of the pair. T. Son6 found values very close to each other forcarbon dioxide 63 and nitrous oxide,64 another isosteric pair. Unfortunately,his method appears to be a t fault because his value for carbon dioxide is- 18-61, which is considerably less than - 20.9 found by other investigators.66No reliable comparative datum for nitrous oxide exists.( 12) MisceZlaneous.-An interesting application to molecular structurehas been made recently by R.W. Asmussen.66 On X-ray evidence incompounds of the type Rb2SbC1, all antimony atoms are equivalent. Thesimplest explanation would be to assign a valency of four to antimony,which would then possess an odd-electron structure and, consequently,would confer paramagnetism on the molecule. From measurements on eightcompounds, all of which are diamagnetic, it is concluded that these com-pounds do not contain SbIV but, probably, alternate SbIII and SbV. Theseconclusions support the earlier suggestion of N. Elliott 67 that (NH,),SbBr6contained no single molecules but only dimerides.Magnetic measurements by P.W. Selwood have recently shown that i t isunlikely that hexaphenyldigermane 68 is dissociated in the solid state orto more than 20% in benzene a t 25", whilst for hexaphenyldiplumbane 69the upper limit of dissociation to triphenyl-lead in benzene is 104% and in thesolid state O*lyo a t temperatures from 30" to 80". Trimethyltin and tri-cyclohexyl-lead do not exist in the monomeric form in dilute benzene s0lution.7~These results cast doubt on the existence of long-life organometallic freeradicals. The fact that the vapour of calomel is diamagnetic between250" and 375" excludes the formula HgC1.7168 Proc. Nat. Acad. Sci., 1929, 15, 539.8o 2. Physik, 1933, 85, 25; Nuovo Cim., 1933, 10, 118.59 Ibid., 1927, 13, 798.82 2.Physik, 1933, 84, 208. Physical Rev., 1935, 48, 380.Sci. Rep. TGhoku Imp. Univ., 1919, 8, 116.E. Lehrer, Ann. Physik, 1926, 81, 229; S. R. Rao ctnd G. Sivaramakrishntm,O4 Ibid., 1922, 11, 139.Proc. Physical SOC,. 1934, 46, 318; and Ref. 54 (p. 33).86 2. Ekktrochem., 1939, 45, 698.67 J . Chem. Physics, 1934, 2, 419.J . Amr. Chem. SOC., 1939, 61, 3168.R. Preckel and P. W. Selwood, ibid., 1940, 62, 2765.70 H. Morris and P. W. Selwood, ihid., 1941, 63, 2609.71 P. W. Selwood and R. Preckel, ibid., 1940,62, 306646 GENERAL AND PHYSICAL CHEMISTRY.G. N. Tyson and S. C. Adams 72 prove that the salicylaldimine complexof nickel is planar and diamagnetic whereas, although planar, the cupriccomplex is paramagnetic.The paramagnetic salicylaldehyde complexesof nickel(I1) and cobalt(I1) are tetrahedral but the corresponding cupriccomplex is planar. Most probably cupric disalicylaldehyde is also planar.73C. M. Beeson and C. D. C ~ r y e l l , ~ ~ from measurements on gaseouv nitrosylchloride at 25", concluded that it was diamagnetic and in a 1x state; itresembles sulphur dioxide in physical properties. This, and the fact thatthe x values for additive compounds of nitrosyl chloride with inorganicchlorides indicate that it is diamagnetic, led R. W. Asmussen 75 to postulateresonance between the forms Cl-(NO)+, Cl-NXO, and CEN-+O, J. A. A.Ketelaar 76 showed, on electron-diff raction evidence, that there is resonancebetween the two structures, Cl-KO and Cl-(NO)+.An examination of solid sodium and potassium salts of acetic, propionic,and butyric acids has shown that the experimental values agree with thosecalculated.On the other hand, the corresponding salts of palmitic, stearic,oleic, and myristic acids give values less than the calculated values; this isattributed by M. B. Nevgi 77 to the formation of micelles of large particlesof colloidal dimensions.I n view of the limitations necessarily imposed on the size of a Reportof this kind it has been decided to omit certain topics in spite of their intrinsicinterest and importance ; notable omissions are anisotropy and the dia-magnetism of metals, with the influences exerted by pretreatment of thesamples, particle size, and crystal structure.W. R. A.4. MOLECULAR SPECTRA AND THERMODYNAMICS.I n recent years thermodynamics has received considerable help fromaccurate spectroscopic measurements, since the evaluation of the energylevels occupied by molecules enables specific heats to be computed. Mostof the data come from infra-red and Raman spectra, and therefore in thefollowing survey little reference is made to ultra-violet spectra, which werereviewed two years ago.1Internal Rotation in NoZecuZes.-The application of physicochemicalmethods to the study of internal rotation in molecules has been mentionedin previous Reports.2 During recent years information about this hasaccumulated rapidly. Some advance has come from the measurement ofdipole moments and the effect of temperature upon them,3 and from X-rayand electron-diff raction measurements, but the main progress has been madeby the use of optical methods, and the correlation of optical data with otherphysicochemical results.72 J , Amer.Chern. Soc., 1940, 62, 1228.78 G. N. Tyson and R. E. Vivian, ibid., 1941, 63, 1403.74 J . Chem. Physics, 1938, 8, 666. 7 b 2. arorg. Chem., 1939, 243, 127.7o J . Uniu. Bombay, 1938, 7, 74. Atti X Cong. intern. China., 1938, 11, 301.Ann. Reports, 1939, 36, 47. Ibid., 1938, 35,42.3 G. I. M. Bloom and L. E. Sutton, J., 1941, 727THOMPSON : MOLECULAR SPECTRA AND THERMODYNAMICS. 47In a molecule such as ethane, rotation of one end of the molecule withrespect to the other will lead to two sets of three identical positions.Onlyone form of ethane is known. Hence, either the potential barrier resistingthe torsion must be very small, so that effectively free rotation occurs, or itmust be high, leading to an effectively fixed relative orientation of the twoend groups. I n all such cases the state of affairs can only be understoodcompletely by a knowledge of the potential energy as a function of theazimuthal angle of internal rotation, which gives the height of the barriers ( Uo).If kT is much greater than Uo we have free rotation, and if k!Z' is less thanU , we have a torsional oscillation, and the problem is therefore essentiallya determination of the heights of the restricting barrier potentials. Acomparison of these barriers in different compounds should throw light onthe causes of such restriction potentials.Herein lies the real reason for therecent advances, since estimates of the barriers in a series of related moleculesare now available, and although in some respects the values determinedmust still be accepted with reserve, it is probable that refinement of therelevant theory will soon lead to important progress. One factor which isdirectly relevant to the understanding of the origin and size of potentialsrestricting the rotation about bonds is the mutual influence of neighbouringnon-bonded atoms upon each other. For instance, if in ethane the hydrogenatoms of different methyl groups had a mutual attraction, the stable structuremight be expected to be that in which the three pairs of hydrogen atoms areopposite each other, i.e., one end of the molecule " eclipsing " the other,with a symmetry of the class D3h.On the other hand, repulsive forcesbetween the pairs of hydrogen atoms will lead to a " staggered " structure(symmetry OM), obtained from the eclipsed form by rotation of one methylgroup through 60" with respect to the other methyl group. There hasconsequently been much discussion about the relative stability of theeclipsed and the staggered configuration, and this relative stability affectsthe structure of certain molecules in other ways discussed below.Apart from less studied phenomena such as the Kerr effect, there arethree principal optical approaches to this question, viz., (1) the use of Ramanspectral data, (2) the analysis of the rotational fine structure of infra-redvibrational absorption bands, and (3) the comparison of thermodynamicalproperties of molecules calculated statistically, using the energy levels deter-mined spectroscopically, with the values of these properties determined byother experimental methods.Of these three independent lines of work, thethird has been the most productive, and will be considered first.The thermodynamical-statistical procedure may be summarised asfollow^.^ It is first necessary to determine, by a correlation of data from theinfra-red and Raman spectra, the vibration frequencies of the moleculeconcerned, as regards both magnitude and assignment to vibrational types.Values for the moments of inertia must then be obtained, either from the' See S.Glasstone, Ann. Reports, 1936, 32, 66; L. Kassel, Chem. Reviews, 1936, 18,277; R. H. Fowler and E. A. Guggenheim " Statistical Thermodynamics," Cambridge,19-1048 GENERAL AND PHYSIUAL (XtEMISTRY.rotational structure of vibrational absorption bands, or by other methodssuch as electron diffraction. These either lead directly to the values of therotational energy levels, or in more complex cases of asymmetrical rotatorsto less specific but nevertheless adequate data about these levels, since thetotal rotational partition function for molecules at reasonable temperaturesis given by an explicit function of the moments of inertia. Similar knowledgeof the electronic energy levels above the electronic ground state may also berequired, although as a rule the comparatively high value of all such levelsabove the lowest makes this information unnecessary.The molecularpartition function, Q = Zpi e-Ej/kT, in which pi is the degeneracy of an energylevel Ei, may then be calculated. Actually, the total partition functionQ = &.&hd.&vib.Qrot., and since it appears in the expressions for all thethermodynamic functions as log &, the several contributions from the differenttypes of energy are additive. As a rule Qel. = 1, and at reasonably hightemperatures for polyatomic molecules = ( 2xM)3‘~~5’2TS’2/h3pIV312, inwhich M is the molecular weight, P the pressure, N the Avogadro number,and k and h the Boltzmann and the Planck constant respectively. AlsoQ,t.= 8x2(2xJCT)312d1m&3~ in which I*, IB, and I. are the principalmoments of inertia, and o the “ symmetry number,” i.e., the number of indis-tinguishable configurations which may be arrived a t by rotations of the moleculein space ; and Qdb. = II( 1 - e-Wkr)-l, a product which is taken over all thevibrational frequencies v. By statistical methods the total partitionfunction can now be related directly to the various thermodynamic functions.The expressions for the molar entropy, free energy, and specific heat atconstant pressure are as follows :X = R In & + RT. d In &/dTCP = RT2d2 In Q/dP + 2RT. d In Q/dTG = - R T I n QReduced expressions for S , G, and Cp as functions only of the several mole-cular magnitudes aftpvr numerical substitution of the fundamental constantshave been given by E.B. Wilson.5 It is customary in practice to calculatethe “ virtual ” entropy, which ignores any contribution of nuclear spin effectsto the partition function, since for all molecules other than hydrogen theyare negligible a t reasonable temperatures.The same thermodynamic quantities can, on the other hand, be measured,the specsc heat directly, the entropy by integration of a Cp-h T plot, thethird law of thermodynamics being assumed and due allowance made forchanges in state and any “ order-disorder ” phenomena in the solid state,and the free energy from the experimental determination of equilibriumconstants. The measured values, which must be referred to some standardstate such as one atmosphere pressure, will in general require wmection fornon-ideality of the gas laws applying to the real vapours, for which purposesome knowledge of the equation of state or virial coefficients is required.Chm.Revku(8, 1940,27, 17THOMPSON : MOLECUIJR SPEUTRA AND THERMODYNAMICS. 49Suitable approximations for the latter can be derived if the critical data areknown.It has long been known that satisfactory agreement exists between thecalculated and the measured thermodynamic properties for many simplemolecules having a rigid framework. This indicates the validity of assumingthe third law of thermodynamics as well as the general correctness of thestatistical method, which has therefore been used extensively for calculatingunknown magnitudes.Discrepancies were noticed, however, with othermolecules, such as those in which a torsional motion, or double minimumpotential energy function (e.g., invertable pyramid) may occur. Thesediscrepancies were, moreover, greater than those to be expected because ofthe anharmonic character of vibrations, and must be explained in some otherway. If a twisting vibration of an essentially rigid framework passes intoa free internal rotation, an alteration will be necessary in both the vibrationaland the rotational partition functions. The torsional vibration frequency isthen omitted from the product in calculating QVlb., and a further Q for theinternal rotation is introduced given by 2~(27cIkT)lE/nh ; I is the reducedmoment of inertia of the two mutually rotating end groups, and n the internalsymmetry number defined below.If the torsional motion is neither free norvibrational, but intermediate in character, the form of the partition function&,,t. cannot be given explicitly, but will depend on several factors such as theform of the function relating potential energy and azimuthal angle of rotation,and upon the absolute height of the restricting potential barriers. K. S. Pitzer,first gave a fundamental treatment of this problem,6 assuming a potentialbarrier function of the type U = U0/2( 1 - cos n0). He has given tables for S, G,and Cp from which for given values of U,,, I , and n the contributions towardsthe several properties can be read off. This makes it possible to reverse theprocedure and, from the disparity between observed and calculated values, toestimate the value of U, which will give agreement.This method has beenused by most workers. B. L. Crawford 7 has attempted to extend andimprove Pitzer’s theory, by considering the general system of several topsattached to a rigid framework, and has suggested that in some cases calcula-tions by Pitzer’s method may lead to serious errors in the values determinedfor U,. This argument has been questioned by K. S. Pitzer and W. D.Gwinn,* who draw attention to several defects in Crawford’s treatment.Neither theory appears yet to be entirely satisfactory, if for no other reasonthan that there is uncertainty in the form of the function relating potentialenergy and azimuthal angle of rotation, but the main principles of the methodcan be regarded as established.Of the various properties which may beused in the comparison, the specific heat seems to be the most sensitive, butif this is used rather than entropy, there must be complete certainty aboutthe values of the molecular vibration frequencies.In considering experimental results, we take the classical case of ethane’ Ibid., 1940,8,273; see also €3. L. Crawford and E. B. Wilson, ibid., 1941,9, 323.J . Chem. Physics, 1937, 5, 469.Ibid., p. 48550 GENERAL AND PHYRTCAL CHEMISTRY.first. Earlier specific-heat measurements by Eucken and the analysis ofthe vibrational spectrum by E. Bartholomb and J. Karweil suggested freeinternal rotation in this molecule, but it is now certain that a considerablerestricting potential exists.J. D. Kemp and K. S. Pitzer 10 compared themeasured and the calculated entropies and inferred a barrier of 3150 cals.per mol. The analysis of the vibrational spectra of ethane and hexadeutero-ethane led F. Stitt l1 to a more precise assignment of the vibration frequencies,and a comparison of the measured and the calculatcd specific heats by G. B.Kistiakowsky, J. R. Lacher, and F. Stitt l2 then gave a value of 2750 cals.Confirmation of a value close to 3000 cals. is obtained from the statisticalcalculation of the ethylene-hydrogen-thane equilibrium by E. A. Guggen-heim.13 Neither the spectroscopic data nor a consideration of the symmetrynumber throws much light on whether the molecule is eclipsed or staggered,although for other reasons it now seems that the stable configuration is prob-ably the staggered form.Both the entropy and the specific heat of dimethyl-acetylene show that in this molecule, by contrast, the restricting barrier isclose to zero l4 and certainly less than 500 cals. per mole. It might then beinferred that mere separation of the two methyl groups is a controlling factorin fixing the height of the barrier. Against this hypothesis, however, is theestimate by Stitt l5 of 4000-6000 cals. for the barrier in diborane by acomparison of the measured and the calculated specific heats. The separ-ation of the methyl groups in diborane is greater than in ethane. With neo-pentane, C(CH3)4, J. G. Aston, R. M. Kennedy, and G.H. Messerly l6 estimatea barrier of about 4200 cals. restricting each methyl group, whereas intetramethylsilicon17 it is about 1300 cals. These facts suggest that moresubtle factors than mere separation of the rotating groups are operative, andthere is a suggestion that a repulsive force may exist between the interactingcentres which varies with a high power of the distance. Specific-heat data,together with the vibrational assignment of R. G. Owens and E. F. Barker,18led J. G. Aston and P. M. Doty 10 to a value of 1500 cals. for the barrier inmethylamine, and J. G. Aston, M. L. Eidinoff, and W. S. Forster 20 similarlyfind a potential of 3460 cals. per methyl group in dimethylamine. Torsionof each methyl group in dimethyl sulphide 21 appears to be impeded by a* Z.physika1.Chem., 1938, B, 39, 1.l 1 J . Chem. Physics, 1939, 7, 297.lJ Trans. Faraday SOC., 1941, 37, 97.1' D. W. Osborne, C. S. Garner, and D. M. Yost, J . Amer. Chem. SOC., 1941,63,3492 ;l6 I b d . , 1940, 8, 981.1' J . Amer. Chem. Soc., 1936,58,2354; 1937,59,1743 ; see also K. S. Pitzer, J . Chem.l7 J . Amer. Chem. SOC., 1940, 62, 2567; 1941, 65, 2343.la J . Chem. Physics, 1940, 8, 229.l' Ibid., p. 637.*O J . Amer. Chem. SOC., 1939, 61, 1539.t1 D. W. Osborne, R. N. Doescher, and D. M. Yost, J . Chem. Physica, 1940, 8, 506;10 J . Amer. Chem. SOC., 1937, 59, 276.Ibid., p. 289; see also G. B. Kistiakowsky and W. W. Rice, ibid., pp. 281, 289.J . Chem. Physics, 1940,8, 131; B. L. Crawford and W. W. Rice, ibid., 1939, 7, 437.Physiw, 1937,5,469, and J.G. Aston, Chem. Reviews, 1940, 27, 59.H. W. Thompson, Trans. Faraduy SOC., 1941, 37, 3852 GENERAL AND PHYSICAL UHEMISTBY.cases. The usefulness of such a treatment, though as yet necessarily approxi-mate, is already apparent, and it is to be expected that refinements will shortlyfollow.Reference should also be made to earlier measurements of the entropy ofdinitrogen tetroxide by W. F. Giauque and J. D. Kemp; 38 the vibrationalfrequency assignment of this molecule is still somewhat uncertain, but thedata appear definitely to suggest a fairly high potential preventing the twoNO, end groups from rotating with respect to each other. In an attempt toestimate the barrier in ethyl chloride, J. W. Linnett 39 has compared themeasured equilibrium constants of the reaction ethylene-hydrogen chloride-ethyl chloride with those calculated on the assumption of different barrierheights.Unfortunately here, as in many other cases, the experimental dataon the equilibrium constants do not seem sufficiently accurate for the purposerequired.The rotational structure of the infra-red absorption bands of a few lightermolecules provides semi-quantitative data about internal rotation. For thepurpose of considering this rotational structure, molecules are usually classi-fied according to their symmetry, since, in part, this determines the arrange-ment of the rotation lines. In reality, however, most molecules are asym-metrical rotators, having all three moments of inertia unequal, and therotational structure in these cases is very complex.At the same time, somemolecules approximate sufficiently closely to a symmetrical top (IA = IB .t.Io) for the rotational structure of their vibration bands to deviate onlyslightly from that to be expected for the symmetrical rotator. The absorp-tion bands may be of two types, according as the change in electric momentis parallel or perpendicular to the symmetry axis, and these respectiverotational structures have been described in a recent Report.4* For ourpresent purpose the main point is that the structure of a perpendicular typeband may be fundamentally affected by the occurrence of internal rotation.A theoretical treatment of the energy levels of a torsional oscillator was firstgiven by A.H. Nielsen.41 Qualitatively the results may be expressed bysaying that if there is free internal rotation the spacing between the Qbranches of the perpendicular type bands is much increased above its valuefor the rigid molecule. The exact theoretical background of the phenomenonis not yet fully worked out, but the effect can conveniently be sought in theinfra-red bands of such molecules as ethane, methyl alcohol, and methylamine.J. B. Howard 42 first showed that the rotational structure of certain infra-redbands of ethane is consistent with a barrier of about 2000 cala. resistingrotation about the C-C bond. This value compares reasonably with thevalue given in the preceding paragraphs. The rotational structure of aharmonic band of the 0-H bond vibration in methyl alcohol, photographedby R.M. Badger and S. H. Bauer,43 is consistent with a fairly high restrictingpotential about this bond. The analysis of the absorption bands of this38 J . Ohem. Physics, 1938, 6, 40.do Ann. Reports, 1935, 82, 53.4a J . Chem. P h y h , 1937,5, 461.I* Trana. Famday SOC., 1940, 86, 627.4 1 Phy8ic.d Rev., 1932, 40, 446.48 Ibid., 1936, 4, 469THOMPSON : MOLECULBR SPECW AND "HERMODYNAMICS. 53molecule at longer wave-lengths led A. Borden and E. F. Barker 44 to a valueof about 1500 cals., which seems on other grounds to be too low. Their datahave also been discussed by J. S. Koehler and D. M. Denni~on.~~ Therotational analysis of a photographic infra-red band of methylamine byH.W. Thornpson4s shows that this molecule is essentially rigid. A. P.Cleaves, H. Sponer, and L. G. Bonner 47 agree with this conclusion, whichaccords with the thermodynamic-statistical considerations given above.Many papers continue t o appear dealing with the application of Ramanspectral data to this problem. If rotational isomers exist, arising from aninternal potential barrier resisting torsion, the number of Raman intervalsfor a given substance will be greater than might be expected for a singlecomponent, and by the application of selection rules and the measurementof polarisation properties it might, in theory, be possible to assign thedifferent frequency intervals to characteristic vibrations of different sym-metry types, such as eclipsed and staggered configurations.K. W. F. Kohl-rausch48 and his collaborators have examined a wide range of compoundsin which torsion is possible, and claim defmite conclusions in many cases.The majority prefer to think, however, that this method can rarely be un-ambiguous. W. F. Edgell and G. Glockler 49 have reviewed the whole posi-tion with particular reference to the alkyl halides and dihalogenoethanes.They point out that, although there seems to be clear evidence that the higheralkyl halides exist in two forms, the evidence as to their form--&-, trans-,or other-is far less conclusive. With the dihalogenoethanes the facts arethought to be in best agreement with the hypothesis that the two forms arethe tram-form and the pair of identical C, staggered structures, the latterbeing obtained from the former by an internal rotation through 120"Edgell and Glockler conclude that there is no evidence for a cis-(eclipsed) formof a molecule of the ethane type.G. Glockler and C. Sage 50 also believethat the staggered forms are predominant .in a series of multihalogenatedethanes. Ta You Wu 61 arrives at a different result, and A. Langseth,H. J. Bernstein, and B. Bak 52 claim that &man measurements on 2-bromo-1 -deuteroethane show that the rotational isomers have the eclipsed (opposed)configurations, from which an eclipsed structure of ethane is inferred. Lang-Seth and Bak 53 have extended their hypothesis of the stability of opposedstructures to a consideration of the form of cyclohexane. The Raman dataof this molecule and of deutero-substituted cyclohexanes are said to be con-sistent with a planar cyclohexane ring, with the hydrogen atoms in opposedpositions with respect to neighbouring hydrogen atoms.Langseth andBernsteina applied the hypothesis of opposed structures further in con-44 J . Chm. Physics, 1938, 6, 553.46 J . Chem. Physice, 1938,6, 7 7 5 ; 1939, 7, 448.47 Ibid., 1940, 8, 784.155; 1939, B, 45, 329, 341 ; 1940, B, 48, 1.61 Ibid., 1939, 7, 965.4 5 Physical Rev., 1940, 57, 1006.See 8 series of papers in 2. physikal. Chem., especially 1940, B, 46,165 ; B, 47, 65," J. Chem. PhYhC8, 1941, 9, 376. Ibid., p. 375.Ibid., 1940, 8, 430.Ibid., p. 403. I4 Ibid., p. 41054 GENERAL AND PHYSICAL CHEMISTRY.nexion with the Raman spectrum of tetrachloroethane and the effect oftemperature upon it. That eclipsed structures, as proposed by Langsethand his colleagues, are unsatisfactory, has been pointed out by severalauthors.Many workers appear to overlook the fact that with liquids theselection rules for the Raman effect may cease to operate rigidly, because ofdistortions leading to alteration of the molecular symmetry. In particular,V. Schomaker and D. P. Stevenson 55 and K. S. Pitzer 56 have shown thatevidence of different kinds strongly favours the staggered forms, and someform of repulsive interaction between neighbouring non-bonded atoms.Measurements on the heats of bromination of certain unsaturated cyclichydrocarbons seem also to support this idea.57General Thermodynamics.-In addition to the examples referred to in theprevious section, the thermodynamic properties of many other molecules havebeen computed from spectroscopically determined molecular magnitudes.In some cases the calculated values have been compared with direct measure-ments, and in nearly all cases a close agreement has been found.Thus,measured and calculated entropies have been compared for methyl chloride,5*hydrogen cyanide,5Q cyanogen,SO and arsenic trifluoride ; 61 and specificheats for ethylene,62 cyanogen, 63 and several lower hydrocarbons. 64 Certainequilibrium data have been used to compare calculated and measured freeenergies. This last method has been applied to check the frequency assign-ment in nitrosyl chloride,65 to derive a more probable value for the heat offormation of carbonyl chloride,66 and to show the desirability of a re-examina-tion of the thermal dissociation of sulphuryl chloride.67 D.Grafe, K. Clusius,and A. Kruis 68 obtain satisfactory agreement between the measured and thecalculated equilibrium D, + H,S =+ D,S + H,. A series of papers dealswith the thermodynamic properties of hydrocarbons which are of particularimportance in modern fuels.Other calculated values are available for phosphorus,"-) phosphine, the55 J . Chem. Physics, 1940, 8, 637.56 J . Amer. Chem. SOC., 1941, 63, 3313; see also J. G. Aston, S. G. Schumann,6 7 M. W. Lister, ibid., p. 143; G. R. Kistiakowsky, ibid., 1939, 61, 1868.58 G. H. Messerly and J.G. Aston, &id., 1940, 62, 887.5' R. A. Ruehrwein and W. F. Giauque, ibid., 1939,61,2626.60 Idem, ibid., p. 2940.61 H. Powell, R. E. Rundle, and D. M. Yost, ibid., 1941, 63, 2825.61 E. J. Burcik, E. H. Eyster, and D. M. Yost, J. Chem. Physics, 1941, 9, 118.6s E. J. Burcik and D. 31. Yost, ibid., 1939, 7, 1114; F. Stitt, ibid., p. 1115.6' J. G. Aston and G. H. Messerly, J . Amer. Chem. Soc., 1940,62,1917 ; J. G. Aston,R. M. Kennedy, and S. G. Schumann, ibid., p. 2059; J. D. Kemp and C. J. Egan, ibid.,1938, 60, 1521.H. L. Fink, and P. M. Doty, ibid., p. 2029.6 5 C. M. Beeson and D. M. Yost, J . Chem. Physics, 1939, 7 , 44.66 H. W. Thompson, Trans. Puruday SOC., 1941, 37, 251.67 Idem, ibid., p. 340.( 8 Z.physikaZ. Chem., 1939, B, 43, 1.6' See J .Amer. Chem. SOC., 1940,62, 1224, 1917, 2988; 1941, 63, 1133, 2039, 2413;70 D. P. Stevenson and D. M. Yost, J . Chem. Physics, 1941, 9, 403.J . Chem. Physics, 1940, 8, 711 ; Chem. Reviews, 1940, 27, 39THOMPSON : MOLECULAR SPECTRA AND THERMODYNAMICS. 55phosphorus halides, several halogenomethanes, 71 formaldehyde and deutero-formaldehyde, 72 diatomic hydrides and halides, 73 hydrazoic acid,7* thecyanogen halides, 75 methyl cyanide 76 and isocyanide, hydrogen fluoride,The specitic-heat measurements of G. B. Kistiakowsky and his collabor-ators in recent years have made it possible to correct previously measuredheats of hydrogenation of unsaturated hydrocarbons to absolute zero and tothe non-vibrating states of molecules.79 As a result it is found that the heatchange in a hydrogenation reaction definitely depends on the nature of thegroups adjacent to the bonds being reduced, and it must be concluded thatthese contiguous groups appreciably influence the bonding strength of theunsaturated link.In a very interesting attempt t o obtain a general formulafor the entropy of long-chain compounds, M. L. Huggins 80 has used anapproximate model to derive simple expressions for the contribution of thevarious degrees of freedom to this property, which agrees well with values sofar measured for short-chain paraffis. The problem of the energy levels,partition function, and thermodynamic properties of molecules like ammoniawith a double minimum potential energy function, has been considered byK.S. Pitzer,81 and by R. F. Haupt and E. Teller.82 Reference should alsobe made to a general symposium on thermodynamic^,^^ where other referencesare compiled.Concurrently with these developments in our knowledge of thermo-dynamic functions, further studies have been made of the best equations ofstate for vapours, and virial coefficients have been determined in some cases.The considerable progress made in developing a theory of liquids must beleft over for a future report.Infru-red and Raman Spectra.-Since about 1930 valuable and highlyaccurate data about molecular structure have been obtained from the studyof the absorption bands of the vapours of some simpler polyatomic moleculesin the photographic region of the infra-red, viz., between 0.7 and 1 .2 ~ (7000and 12,000 A.). The success of this method lies in the ease with which highresolving power can be obtained by means of an ordinary diffraction grating.It was clear from the start, however, that this region would have limitedapplicability, since in order to bring the absorption into this spectral range,several vibrational quanta must be absorbed simultaneously, and the path71 W. F. Edge11 and G. Glockler, J. Chem. Physics, 1941, 9, 484; D. W. Osborne,C. S. Garner, R. N. Doescher, and D. M. Yost, J. Amer. Chem. SOC., 1941, 63, 3496.72 H. W. Thompson, Trans. Paraday Soc., 1941, 37, 251.75 D. P. Stevenson, J. Chem. PhyBic8, 1941, 9, 898.74 E. H. Eyster and R. H. GilIette, ibid., 1940, 8, 369.7 6 D. P. Stevenson, i b d ., p. 171.76 R. H. Ewe11 and J. F. Bourland, ibid., p. 365.7 7 G. M. Murphy and J. E. Vance, ibid., 1939, 7, 806.78 H. W. Thompson, Trans. Paraday Soc., 1940, 37, 249.79 G. B. Kistiakowsky, J. B. Lacher, and R. W. Ransom, J . Chem. Physics, 1940, 8,*O Ibid., p. 181.84 Ibid., p. 925.and carbon s~boxide.~*970.81 Ibid., 1939, 7, 251.83 Chem. Reviews, 1940, 27, 1-8556 QENERAL BND PHYSIOAL CHEMISTRY.length of vapour required increases very rapidly for each successive harmonic.Thus even with compounds containing a C-H bond of relatively high vibra-tion frequency, three or four will be required, and for heavier molecules manymore. In the case of heavier molecules, too, the larger moments of inertiawill preclude the resolution of fine structure. Hence, the usefulness of thisspectral region appears now to have been exhausted, so far at least as resolu-tion of the rotational structure of bands is concerned.It is therefore oppor-tune to review some of the most recent investigations in this field.Perhaps the most striking of these is the measurement by L. Zumwaltand P. A. Gigubre of the absorption of the second overtone of the 0-H bondvibration in hydrogen peroxide vapour at 0.97p. The rotational structurefound for this band is of particular importance, since it appears to settlefinally the question as to whether the molecule has a planar or a non-planarstructure. In principle, the OH groups of hydrogen peroxide may be eitherin the cis- or the trans-position with respect to each other, or in some inter-mediate non-planar position.If the molecule is non-planar, the hinderingpotential towards internal rotation will have two minima of equal depth andtwo barriers of unequal height, and there will be two enantiomorphic forms.According to the height of the potential barrier, there will be free rotation,restricted rotation, or a, torsional oscillation. If the molecule had a cis-structure, the change in electric moment accompanying the 0-H link vibra-tion would be either entirely parallel or entirely perpendicular to the sym-metry axis. The band observed appears, in fact, to be double and to have apeculiar hybrid structure, with features characteristic of both the paralleland the perpendicular band types, thus implying that the structure is notcis-.The large dipole moment measured by E. P. Linton and 0. Maass 85shows, on the other hand, that it is not trans-. A non-planar structure istherefore the only alternative. At the same time the finer detail8 of therotational structure of the infra-red band show that the molecule is not quitea symmetrical rotator, as it would be if the azimuthal angle between thedirections of the two O-H bonds were go", since then two of the moments ofinertia would be equal. An azimuthal angle of about 106" is suggested, sothat the 0-H bonds are set obliquely to each other. These conclusions areespecially interesting in view of the earlier considerations of G. B. B. M.Sutherland and W. G. Penney.86E. H. Eyster87 has measured the third and fourth harmonics of thePIT-H stretching vibration in hydrazoic acid vapour, and the rotationalstructure of the bands shows that the molecule is not completely linear, ashas been suggested by some investigators.The bond lengths calculatedare N-H, 1-012 A. ; N,-N,, 1.241 A. ; N,-N,, 1.128 A. ; and the angle HNNis 110" 52'. Eands of methylamine vapour have been photographed byH. W. Thompson,88 one only showing resolved rotational structure charac-Aa4 J . Chem. Physics, 1941, 9, 458.g6 J . Chern. Phyeics, 1934, 8,492.88 Ibid., 1939, 7, 448.as Canadian J . Re&, 1932, 6, 81.Bid., 1940, 8, 136, 369TIfOMPSON : MOLEUULAR SPECTRA AND TECERMODYNBMICS. 57teristic of the perpendicular type vibration of a slightly asymmetrical rotator,and the rotational analysis gives results which agree with the molecularstructural constants to be expected on other grounds, vix., C-N, 1.47 A.;N-H, 1.02 A,; and CNH angle of 108" with a tetrahedral methyl group.This result has been confirmed by A?P. Cleaves, H. Sponer, and L. G. B ~ n n e r , ~ ~who also measured bands of dimethylamine.After much discussion the structure of ethylene appears now to have beenfixed by the measurement of two bands90 in the region of lp, one beingessentially parallel type, and the other perpendicular. Values for all themoments of inertia have been deduced, and the (3-H bond length beingassumed to be 1.085 A., it is found that the carbon-carbon bond length is1.331 A. and the angle HCH 118". These values have been confirmed by acompletely independent measurement of some in€ra-red bands by L.G. Smith.91The fourth harmonic of the 0-H vibration in formic acid vapour,measured by H. W. Thompson,92 has a hybrid structure in which the perpen-dicular component is very marked, similar to that of the third harmonicpreviously photographed by R. M. Badger and 8. H. B a ~ e r . ~ ~ Althoughexact figures for the molecular dimensions cannot be obtained, the structureof these bands gives a qualitative picture of the form of the molecule. Similarqualitative information is obtained from the structure of a band of formald-oxime vapour measured by L. Zumwalt and R. M. Badger.94 H. W. Thomp-son 95 has surveyed the absorption between 0.7 and 1 . 2 ~ of a residuum ofmolecules thought likely to have bands with resolvable rotational structure.W.H. J. Childs and H. A. Jahn 96 have measured the spectrum of deutero-methane in the photographic infra-red. A band a t 1-lp has a simple struc-ture, which leads to a C-€€ bond length of 1.093 A. These authors have alsodiscussed some complexities in certain bands of methane, one of which is oftheoretical significance for all molecules having a three-fold or higher axis ofsymmetry. Interesting features of the absorption by pyrrole vapour atabout 1p have been noted by Zumwalt andRecent infra-red work a t longer wave-lengths covers a wide field, and itis not possible to refer to all the subjects studied by measurement of themolecular absorption spectra in this region. The importance of the methodas a means of analysis is now being fully r e a l i ~ e d .~ ~ As a means of simplifyingvibrational analysis and the assignment of frequencies to particular normalmodes, the spectra of molecules and their deuterium analogues have beenemployed. In this way F. Stitt 99 has established the normal vibrationalAAJ . Ohem. Physics, 1940, 8, 784.J . Chem. Physk.8, 1941, 8, 798.go H. W. Thompson, Tran8. Paraday Soc., 1939, 35, 697.OS Ibid., 1936, 4, 469.90 Proc. Roy. SOL, 1939, A, 169, 428, 451 ; A , 1'71, 460.O P J . Chem. Phy~6~8, 1939, 7, 629.B2 Ibid., 1939, 7, 463.Ob Ibid., p. 441. O4 Ibid., 1939, 7, 235.See, e.g., N. Wright, Ind. Eng. Chem. (Anal.), 1941, 13, 1 ; W. K. Avery, J . Opt.SOC. Amer., 1941, 31, 633.@' J .C h n . Physia, 1939,7, 29768 GENERAL AND PHYSIUAL CHEMISTRY.frequencies of ethane and hexadeuteroethane, and of acetylene and thedeuteroacety1enes.l G. K. T. Conn and G . B. B. M. Sutherland2 havesimilarly studied tetradeuteroethylene and have cleared up some doubtfulpoints connected with the vibrations of ethylene.have analysed the rotational structure of some vibration bands of arsine,trideuteroarsine, and trideuterophosphine, and from the resulting dataSutherland, Lee, and Wu have estimated the dimensions of the molecularpyramid in each chse. In phosphine the barrier restricting the passage ofthe phosphorus atom through the plane of the hydrogen atoms is about2000 cm.-l (about 6 kg.-cals.), a value close to that previously suggested forammonia by D.M. Dennison and G. E. Uhlenbe~k.~ Calculations suggest,however, that in the case of phosphine the substitution of large massivegroups in place of the hydrogen atoms may give a molecule for which thefrequency of inversion is small enough to permit the separation of opticallyactive isomers at sufficiently low temperatures. A study of the spectra ofhydrogen selenide, deuterium selenide, and deuterium hydrogen selenide byD. M. Cameron, W. C. Sears, and H. H. Nielsen 6 has suggested a triangularstructure for these molecules with an apex angle somewhat greater than aright angle. In this work the correctness of the vibrational assignment waschecked by use of the product rules of 0. Redlich.' Structure of methylchloride infra-red bands has been used to re-determine the C-C1 bond1 eng t h .8High resolving power has also been used in measuring the infra-red bandsof other molecules. C.K. Wu and E. F. Barker9 partially resolved therotational structure of several absorption bands of propane, and R. G. Owensand E. F. Barker 10 obtained similar data for methylamine. The spectrumof the latter has been measured with lower resolution by C. R. Bailey,S. C. Carson, and E. F. Daly,ll and by A. P. Cleaves and E. K. Plyler,12but a satisfactory vibrational analysis was achieved only with the help ofthe rotational fine structure found by Owens and Barker.13 D. H. Gage andE. F. Barker l4 measured the vibrational spectrum of boron trifluoride andpartially resolved certain bands. An estimated moment of inertia gives1.29 A.for the B-P distance, but a considerable vibrational-rotational inter-action complicates the structure of some of the bands of this substance. Thegeneral problem of interaction between vibrational and rotational energy ofpolyatomic molecules has been examined by H. H. Nielsen, by S. Silver,W. H. Shaffer, and by Shaffer,15 and relevant effects in two parallel bands ofE. Lee and C. K. Wul J . C h . Physics, 1940, 8, 56.8 Trans. Faraday Soc., 1939, 35, 1366.6 Physical Rev., 1932, 41, 313.8 G. B. B. M. Sutherland, ibid., 1939,7, 1066.lL Proc. Roy. Soc., 1940, A , 173, 339.l9 LOC. cd., ref. (10).l6 H. H. Nielsen, Physical Rev., 1941,60, 794; S . Silver and W. H. Shaffer, J . Chem.Proc. Roy. SOC., 1939, A , 172, 172.Ibid., p.1373.J . Chem. Physics, 1939, 7, 994.2.physikal. Chem., 1935, B, 28, 371; J . Chem. Phy&, 1937.5, 529.Ibid., 1941, 9, 487. lo Ibid., 1940, 8, 229.la J . Chem. Physics, 1939,7, 563.I4 J . Chem. Physics, 1939, 7, 455.Physics, 1941, 9, 599; W. H. Shaffer, ibid., p. 607THOMPSON : MOLECULAR SPECTRA AND THERMODYNAMICS. 59ammonia have been described by H. Y. Sheng, E. F. Barker, and D. M. Denni-son.16 A. H. Nielsen measured rotational structure in some bands ofdeuteroacetylene,l' and H. H. Nielsen has re-examined certain absorptionbands of water vapour.l* L. G. Smith l9 used the rotational structure of aparallel type band of ethylene to deduce the moments of inertia, as referredto above. A Coriolis perturbation similar to that discussed by W.H. J. Childsand H. A. Jahn for methane bands has been observed and measured byG. M. Murphy 2o in the spectra of silane and germane.Some molecules which have been studied in order to determine the funda-mental vibration frequencies include cyanogen,21 nitromethane,22 pr~pylene,~~methylacetylene,= and dimethyla~etylene.~~ Absorption bands of hydrazoicacid vapour have been measured by M. M. DaviesJ26 and by EysterY2' whoalso examined methyl azide and methyl isocyanate. The spectrum ofhydrazine has been recorded by W. Fresenius and J. Karweil.28 The vibra-tion frequencies of ethylene sulphide have been determined by H. W.Thompson and D. J. D ~ p r t 5 , ~ ~ of dimethyl sulphide by R. Fonteyne 3O andby H. W. Thompson,3l and of methylthiol by H.W. Thompson and N. P.Skerrett.32 Other molecules investigated in this connexion include dimethylether,33 dimethylzinc J34 eth~leneimine,~~ a~etaldehyde,~~ and several hydro-carbons such as n-pentane.37J. J. Fox and A. E. Martin 38 have examined the variation in the char-acteristic vibration bands of the C-H bond in the region of 3p in a series ofparafKns and olefins. The characteristic frequencies of this bond differslightly according to the precise group of which it forms a part, but theyseem to remain reasonably constant for a given type of C-H bond in a largeseries of molecules. Similarly, in cc- and p-methylnaphthalenes, quinolineand isoquinoline, and similar molecules, small differences are traced in theregion of absorption of C-H bond vibrations which appear to provide a basisfor the analysis of these compounds.39 Infra-red studies on the proteins andrelated substances continue$O and the effect of state of aggregation uponl6 Physical Rev., 1941, 60, 786.l8 Ibid., 1940, 50, 665.2o Ibid., 1940, 8, 71.22 A.J. Wells and E . B. Wilson, ibid., 1941, 9, 314.23 E. B. Wilson and A. J. Wells, ibid., p. 319.24 B. L. Crawford, ibid., 1939, 7, 140; 1940, 8, 526.25 Idem, ibid., 1939, 7, 553.27 J . Chem. Physics, 1940, 8, 369.29 Trans. Farccday Soc., 1940, 36, 805.31 Trans. Paraday Soc., 1941, 37, 38.33 B. L. Crawford and L. Joyce, J . Chem. Physics, 1939,7,307.34 H. W. Thompson, J. W. Linnett, and F. J. Wagstaffe, Trans. Faraday Soc., 1940,35 H. W. Thompson and W.G. Leeds, ibid., in the press,36 H. W. Thompson and G. P. Harris, ibid., in the press.37 G. C. Stinchcomb, J . Chern. Physics, 1939,7, 853.38 Proc. Roy. SOC., 1939, A, 175, 208.40 J. W. Bath and J. Ellis, J . Physical Chem., 1941, 45, 204; A. M. Buswell, K. F.l7 Ibid., 1940, 57, 346.l9 J . Chem. Physics, 1941, 9, 798.21 Ibid., 1939, 7 , 859.26 Trans. Faraday SOC., 1939, 35, 1184.28 2. physikal. Chem., 1940, B, 44, 1.30 J . Chem. Physics, 1940,8, 60.32 Ibid., 1940, 36, 812.36, 797.39 J., 1939, 318.Brebs, end W. H. Rodebush, J . Chem. Physics, 1940, 8, 112660 GENERAL AND PHYSIOAL UHEMISTBY.infra-red absorption bands has been e~amined.~l Fox and Martin42 havemeasured the spectra of both liquid water and ice and discussed their resultsin relation to the structure of liquid water.On the theoretical side referencemust be made to a further article by D. M. Dennison on the infra-red spectraof polyatomic molecules.*3Of the many measurements of Raman spectra recently made, only a fewcan be mentioned here. Apparatus is described by J. S. Kirby-Smith andL. G. Bonner 44 for obtaining the Raman displacements with gases, usingreasonable exposure times, and these authors have first studied methylaminevapour. The fine structure of Raman lines of carbon tetrachloride has beenmeasured by A. C . Men~ies,4~ and found to be consistent with an explanationin terms of chlorine isotopy, and also with the abundance ratio to be expected.The carbon isotope shifts have been calculated for a series of acetyleniccompounds by F.F. Cleveland and M. T. Murray,46 and compared withexperimental data.A particularly interesting series of Raman measurements has been carriedout by G. Glockler 47 and his collaborators for the halogenated methanes.The alteration in the observed displacements as the substituents are changedone by one is valuable in assigning the magnitudes to different vibrationalmodes, and these data should prove valuable for the calculation of forceconstants and force fields for this type of molecule. Another series ofmolecules whose Raman spectra have proved interesting is a group of metallicand non-metallic a l k y l ~ . ~ ~ The displacements observed with octane, decane,and higher hydrocarbons are complex and not easily interpreted.49Potential Energy Functions, Force Constank, and General Xtructurd.Relationships.-The importance of force constants as a measure of the natureand strengths of linkages has been referred to in previous Reports, in whichthe principles underlying these calculations and the approximations necessaryhave been explained.60 Serious discrepancies were noticed, however, in someof the earlier computations by different workers for the same molecules.Itis clear that the exact significance of the magnitudes described as forceconstants depends upon the particular potential energy function used todescribe the molecular vibrations. Several types of function have from timeto time been adopted, the most common being that which assumes forcesconsistent with the idea of conventional valency bonds, and known asvalency force field.Internal molecular interactions, however, which are41 See, e.g., W. West, J . Chem. Phy8iics, 1939, 7 , 795; G. B. B. M. Sutherland et al.,Proc. Roy. SOC., 1941, A , 176, 484, 493.Ibid., 1940, A , 174, 234.p3 Rev. Mod. Physics, 1940, 12, 175; 1931, 3, 280." J. Chem. PhySii28, 1939, 7, 880.46 Proc. Roy. SOC., 1939, A , 172, 89.47 G. Glockler and G. R. Leader, ibid., 1940, 8, 125, 699; G. Glockler and C. Sage,ibd., p. 291 ; J. Kahovec and J. Wagner, 2. physikal. Chem., 1940, B, 47,48; B, 48,188. '* E. J. Rosenbaum, D. J. Rubin, and C. R. Sandberg, J . Chem. Physics, 1940,8,366.40 E . J. Rosenbaum, ibid., 1941, 0, 295.llQ Ann. Reports, 1936, 88, 69.46 J .Chem. Physics, 1941, 9, 390THOMPSON : MOLEUUIXR SPEUTRA AND !CHERXODYNAMIOS. 61to a large extent specific, make this simple type of force field seldom rigidlyapplicable, although in some cases an apparently satisfactory solution isobtained, perhaps by a fortuitous cancellation of a series of inaccuracies. Itis customary to find that a simple potential function of this type fails toaccount satisfactorily for the entire array of frequencies of a molecule.More complex functions must therefore be assumed, and tested by theirindividual performance. In some cases the number of “ constants ” whichhave to be introduced in order to obtain a complete prediction of all vibrationfrequencies for a, given molecule may exceed the actual number of these fre-quencies.In such cases the reverse procedure of estimating the “con-stants ” from the measured frequencies is usually not possible, unless addi-tional vibration frequencies of an isotopic molecule which has the samepotential function are available. It has been suggested, in fact, that thecorrectness of a given potential function may be measured by its ability toreproduce, not only the vibration frequencies of the molecule to which itapplies, but also those of an isotopic molecule of the same composition.This use of the isotope effect is particularly applicable to structures inwhich hydrogen may be replaced by deuterium, and several cases of thiskind have now been examined. Por example, F. Stitt obtained a self-consistent potential energy function for ethane and he~adeuteroethane,~~which accounts very well for all the fundamentals of these molecules.Stittalso studied acetylene and the deuteroacetylenes in the same way. Measure-ment of some of the infra-red bands of tetradeuteroethylene enabled G. K. T.Conn and G. B. B. M. Sutherland 52 to compare the rglative merits of differentpotential functions which have been proposed for ethylene.It cannot be denied that the above method is a powerful one, but thenumber of molecules to which it can be applied in practice is small, sinceisotopic frequency changes are in general too small to be easily determinable.Another approach which has seemed attractive is to add to the conventionalpotential functions of simple valency force field such interaction terms asseem likely to be significant in the particular case, and to consider whetherin a series of related molecules force constants can be carried over from onemolecule to the next and predict its vibration frequencies correctly. Thismethod was used some years ago by H.W. Thompson and J. W. Linnett 63and has since been adopted with success by several authors. In this wayLinnett6* calculated the force constants of bonds in ethane, the methyl halides,methyl cyanide and isocyanide, and concluded that in methyl cyanide thecarbon-carbon bond has some double-bond character, as suggested on othergrounds by L. Pauling, H. D. Springall, and K. J. Palmer.65 Interesting vari-ations in the bending constantswere also noted by Linnett. Z. I.Slawsky andD. M. Dennison’s treatment 66 of the same molecules does not appear to be sosatisfactory. B. L. Crawford and S. R. Brinckley 57 have also given a61 J . Chem. Physics, 1939, 7, 297; 1940, 8, 56.64 J . Chem. Physics, 1940, 8, 91.66 J. Chern. Physics, 1939, 7, 622.Proa. Roy. SOC., 1939, A , 172, 172. 63 J . , 1937, 1376.5 5 J . Amer. Chem. Soc., 1939, 61, 927.6 7 Ibid., 1941, 9, 6962 QENERAL AND PHYSICAL CHEMISTRY.normal co-ordinate treatment of hydrogen cyanide, methyl cyanide, and themethyl halides which is closely similar to that of Linnett. They are able tocalculate satisfactorily 52 vibration frequencies of this series of moleculesfrom potential functions involving only 20 constants, and the main stretchingconstants of the bonds can be carried over from one molecule for use with thenext.In a later paper, Linnett 58 has shown, however, that Crawford andBrinckley have used a carbon-carbon bond force constant which is probablyin error, and has discussed a simple potential function not only for use withthe methyl halides but also for methyl- and dimethyl-acetylene, which werepreviously treated by C r a ~ f o r d . ~ ~ Ta You Wu 60 has also considered thepotential function of acetylene, and it is perhaps relevant here to refer to animportant paper by E. C. Baughan, M. G. Evans, and M. Polanyi on thenature of carbon-carbon linkages.Other normal co-ordinate treatments have been carried out by S. Silverfor structures of the type M(CH,),, by E. J. Rosenbaum, D. J. Rubin, andC.R. Sandberg 63 for trimethyl-phosphine and -arsine (and by J. Wagner 64for the methylene halides); and S. E. Whitcomb, H. H. Nielsen, andL. H. Thomas 65 have analysed the vibrations of a normal hydrocarbon chainwith particular reference to undecane. L. Kellner 66 has carried through anextensive calculation on the force constants of links in urea and the guani-donium ion, but in a case of this kind it is doubtful whether the simple treat-ment used can be of much value, particularly in view of the uncertainexperimental data.The technique of the calculations involved in determining force constantshas been further examined by E. B. Wilson, and simpler methods of dealingwith the complex secular equations usually encountered have been suggestedby B.J. 0. Hirschfelder 68 has provided a compact formula bywhich the moments of inertia of irregular structures may be rapidly calculated.0. Redlich 69 studied the effect of vibrational anharmonicity on the potentialfunction of polyatomic molecules.All the above remarks imply the importance for chemical theory ofknowing the potential functions of polyatomic molecules. Meanwhile acompletely satisfactory general expression for the variation of potentialenergy of a diatomic molecule with internuclear separation is not yet known.The limitations of using the Morse equation for nuclear separations far re-moved from the stable position have been realised for some time, and effortsto obtain a better relationship have been made by H. M. Hulbert and J. 0.Trans. Paraday Soc., 1941, 37, 469.69 J. Chern. Physics, 1939, 7, 140, 553; 1940,8, 526.6o Ibid., 1939, 7, 178; 1940, 8, 489.e2 J. Chem. Physics, 1941, 8, 919.G4 2. physikul. Chem., 1939, €3, 45, 69.G 5 J. Chern. Physics, 1940, 8, 143.6 6 Proc. Roy. Xoc., 1941, A, 177, 447, 456.67 E. B. Wilson, J. Chem. Physics, 1941, 9, 76; 1939, 7, 1047; B. Hicks, ibid., 1940,68 Ibid., p. 431. 69 Ibid., 1941, 9, 298.Xruns. Paraday SOC., 1941, 37, 377.63 Ibid., 1940, 8, 366.8, 569THOMPSON : MOLECULAR SPECTRA AND THERMODYNAMICS. 63Hirschfelder ' 0 and by J. W. Linnett.71 The last-named has examined theusefulness of a " reciprocal-exponential " function U = a r m - be-"', whichincorporates features of both the standard Morse equation and the generaldouble reciprocal formula U = a?+ - br-9a. G. B. B. M. Sutherland 72 hasrecently used the double reciprocal function in attempting a derivation of therelation between force constant and equilibrium nuclear separation. Linnetthas drawn attention to the shortcomings in Sutherland's treatment, andprovides evidence on a wide variety of diatomic molecules to show that thereciprocal-exponential function is an improvement on other existing relation-ships. Incidentally, there is some indication that the relationship betweenforce constant and nuclear separation Eer,6 = const. ? originally proposed byC. H. D. Clark, is more satisfactory than the Badger equation (re - dij)3 =C,/lc,, which has been found so useful in much recent work. In a furtherseries of papers, Clark 73 has developed his formuke further and comparedthe relative merits of the various relationships.J. J. Fox and A. E. Martin 74 have also directed attention to some inter-esting relationships between force constant? bond length, and energy of somecarbon-carbon bonds. A typical instance of the use of these semi-empiricalrelationships is found in the use by D. P. Stevenson '5 of Badger's rule todetermine the P-H bond length in phosphine (1.40 A.) which, taken with thesingle moment of inertia obtained from the spectrum, leads to a value of theapex bond angles close to 93". Stevenson also considered the structure ofother hydrides. The connexion between bond length and bond strengthhas also been discussed by R. F. Barrow,76 D. Wrinch and D. Harker,77M. Burt0n,~8 and C. A. C o ~ l s o n . ~ ~Miscellaneous Xpectrosmpy.-Recent developments in ultra-violet spectro-scopy include diverse topics, but these must be reserved for a future Report.Attention may be directed, however, to a review by H. Sponer and E. Teller 80on the ultra-violet spectra of polyatomic molecules, and some progress hasbeen made in analysing the rotational structure of some of the bands.N. Metropolis 81 has considered the relevant theory for this rotationalstructure, which has been analysed for bands of sulphur dioxide and carbon di-sulphide.82 Spectroscopy in the far ultra-violet is described by J. C. Boyce,83and the rBle of optical measurements in the borderland of physical chemistryand biology has been outlined by J. R. Loofbourow.%The Hydrogen Bond.-Progress in this subject has been reviewed fullyin a recent discus~ion.~~ In this, W. T. Astbury has outlined the evidence70 J . Chem. Physics, 1941, 9,61. 71 Trans. Faraday SOC., 1940, 36, 1123.7a J. Chem. Physics, 1940, 8, 161.75 Trans. Paraday SOC., 1940, 36, 370; 1941, 37, 293, 299.74 J., 1939, 884.76 Trans. B'araday SOC., 1940,36, 624, 1053.78 Ibid., p. 743.82 Ibid., pp. 295, 496.a4 Ibid., 1940, 12, 272.T 5 J . Chern. Physics, 1940, 8, 285.7 7 J . Chern. Physics, 1940,8, 602.79 Ibid., 1939, 7, 1069.Physical Rev., 1941, 60, 283.83 Rev. Mod. Physics, 1941, IS, 1.Rev. Mod. Physics, 1941, 13, 75.Trans. Paraday SOC., 1940, 30, 871-92864 UENERAL AND PHYS1gA.L UHEMISTRP.for the existence of hydrogen bridges in proteins, and C. E. H. Bawn, E. L.Hirst, and E. T. Young have concluded that some properties of starch areconsistent with the union of macromolecules with each other through thistype of link to form particles. G. B. B. M. Sutherland has summarised theapplication of infra-red spectroscopy to the problem, and J. J. Fox and A. E.Martin from a similar standpoint have given data, on the specific cases ofassociation of alcohols, and carboxylic acids, and internally chelated mole-cules. In the same symposium, J. M. Robertson has discussed the X-rayevidence for hydrogen bonds, and W. R. Angus and W. K. Hill have describedpreliminary work on diamagnetic susceptibilities (see this vol., p. 29) whichappear to be capable of revealing the occurrence of this phenomenon.Models for proteins involving hydrogen bonds have also been consideredby M. L. Huggins,86 and a series of papers deal with the associating propertiesof different solvents.87 The infra-red association bands of several hydroxy-compounds in solution and in the solid state have been examined by M. M.Davies,8* and polymerisation of hydrogen fluoride has been measured byA. Wahrhaftig 89 and by A. M. Buswell, R. L. Maycock, and W. H. Rodebush.90R. Mecke and his co-workers 91 have developed a new technique for studyingthe association bands of alcohols in the photographic infra-red and havemade calculations on the equilibrium relationships of the association. Aconsideration of boiling points and other physical properties, such as solu-bility in donor solvents, of a variety of pyrazole and indazole derivativescontaining the imino-group has led to the suggestion that there is a bond ofthe type N-H-N in these molecules.92H. W. T.W. R. haws.H. W. MELVILLE.R. A. MORTON.H. W. THONPSON.8@ J . Chem. Physics, 1940, 8, 598.See, e.g., W. Gordy et at,, J. Chem. Physica, 1939, 7 , 93, 99, 163, 167; 1940,8, 170,516; 1941, 9, 204, 216; J. Amer. Chem. SOC., 1940, 62, 497, 1247; E. S. Barr andG. J. Craven, J. Chern. Physics, 1939, 7, 8.Ibid., 1940, 8, 677; Trans. Faraday Soc., 1940, 36, 333, 1114.89 J . Chem. Physics, 1940, 8, 349. So Ibid., 1939, 7, 857.O1 2. physikal. Chern., 1939, B, 44, 299; 1940, B, 46, 229; B, 40, 309; see also0. Wulf and E. J. Jones, J . Chem. Physics, 1940, 8, 745, 753; and L. Zumwalt andR. M. Badger, J . Amer. Chem. SOC., 1940, 62, 305.ga H. T. Hayes and L. Hunter, J., 1941, 3

ISSN:0365-6217    

DOI:10.1039/AR9413800007

出版商:RSC    

年代:1941

数据来源: RSC

摘要:

INORGANIC CHEMISTRY.1, INTRODUCTION AND GENERAL.THE general arrangement of this Report is the same as in past years. Twotopics have been selected for special treatment. The first deals with recentdevelopments in the chemistry of the carbonyls and nitrosyls. Though thissubject was discussed in the Annual Reports for 1934 much new researchhas been published since, many of the developments being based on applic-ation of high-pressure technique to the production of carbonyls. The secondtopic, isotope exchange in inorganic chemistry, is one which is of growingimportance in several fields. Radioactive isotopes of all the elements exist,many of them being of suitable half-period for exchange work, while usefulmethods of separating non-radioactive isotopes have also been worked out.The potential value of this method of studying problems in inorganicchemistry is, therefore, very great.The first section of the Report deals with a comparatively small number ofrecent investigations in scattered fields.No detailed discussion is given ofpapers on complex salts, but attention may be directed to the BakerianLecture on Stereochemical Types and Valency Groups 1 and to the LiversidgeLecture on Complex Formation.2 These two lectures present a systematicbasis for the formulation of a wide range of compounds and are a contributionwhich is of major importance in the development of the theory of valency.A further publication of wide interest is the Report of the Committee for theReform of Inorganic Chemical Nomenclature.3 The recommendations madecover specifically many points which at present are confusing, though in themajority of cases they call for no departure from common practice.A compound of xenon with phenol having the composition Xe,2PhOH hasbeen prepared by B.A. Nikitin.4 This has a dissociation pressure of 760mm. at 4O, its stability being approximately 0.3 of that of the compoundH,S,SPhOH. This work follows earlier investigations by the same authorin which indications of compound formation by radon were obtained.5Brief reference was made in the Annual Reports for 1940 to an entirelynew group of boron hydride derivatives, the metallo-borohydrides. Detailsof fhe preparation and properties of three substances of this type werepublished at the end of 1940.6 The table on p.66 shows their formulze,melting points, and boiling points, together with data for diboranc.N. V. Sidgwick and H. M. Powell, Proc. Roy. Soc., L940, A, 176, 153.N. V. Sidgwick, J., 1941, 433.W. P. Jorissen, H. Basseft, A. Damiens, F. Fichter, and K. Remy, J., 3940,Compt. rend. Acad. Sci. U.R.S.S., 1940, 29, 571.H. I. Schlesinger, R. T . Sanderson, and A. B. Burg, J . Amer. Chem. SOC., 1940,62, 3421; A. B. Burg and H. I. Schlesinger, ibid., p. 3425; H. I. Schlesinger andH. C. Brown, ibid., p. 3429.*1404; J . Amer. Chern. SOC., 1941, 63, 889.Ibid., 1939, 24, 565.REP .-VOL. XXXVIII . 66 INORGANIC CHEMISTRY,Formula. BzH'a. A1B,Hl2. BeBS,. LBH ,M. p. ..................... -165.5" - 64.5" 123' 275"B. p...................... - 92.5" 44.5" 91.3" decomp. 275"1'. p. at 0", mm. ......... very high 119 0.5 < 10-6The first of these compounds, aluminium borohydride, was prepared byheating diborane with trimethylaluminium at 60" for several hours. In thepreparation of the beryllium compound an unstable intermediate productof the approximate formula CH,*Be*BH, was first produced by the inter-action of dimethylberyllium and diborane. Subsequent reaction of thiswith further diborane gave beryllium borohydride, BeB,H,, together with anon-volatile by-product of the empirical formula BeBH,. The lithiumborohydride was prepared directly by the reaction of ethyl-lithium and di-borane. The only other major products in these reactions were the boronalkyls.The technique employed throughout was similar to that used inearlier investigations of the boron hydrides by Schlesinger and his co-workersand was based largely on methods developed by A. Stock.There are interesting differences in the physical properties of the threeborohydrides. For instance, the relatively high melting point and lowvolatility of the lithium compound, together with its insolubility in benzene,suggest a t once that the bonding is polar in character. The volatility ofaluminium borohydride and its ready solubility in benzene show that it isprobably non-polar and may be classed with diborane itself. The berylliumcompound is intermediate in type, but the indications are that it is moreakin to lithium borohydride.This difference in properties is borne out by the chemical behaviour, forlithium borohydrids, unlike diborane, is stable in dry air a t ordinary tem-peratures whereas the aluminium compound is spontaneously inflammable,as is diborane.The beryllium compound also reacts very readily with air.The reactions of these various molecules with trimethylamine again exhibita striking gradation. Diborane and trimethylamine react at temperaturesdown to - looo, yielding BH,,N(CH,),. Aluminium borohydride reacts a t-80" to 25*, and although the changes are complex and have not been fullyelucidated, the crystalline compound AlB,H,,,N(CH,), has been isolatedfrom the products of reaction of equimolecular quantities at - 80'. Whenheated to 100' this breaks up and borine trimethylamine, BH3,N(CH,),, hasbeen identified as one of the products.At -80" compounds containing ahigher molecular proportion of trimethylamine are formed. Berylliumborohydrids forms the addition compound BeB,H,,N( CH,), with trimethyl-aminc and this reacts further with the amine according to the equationBeB,H,,N(CH,), + N(CH3), + BeBH5,N(CH3), + N(CH,),,BH,Lithium borohydride, on the other hand, does not react with trimethylamine,a fact which emphasises the difference between this compound and thealuminium and beryllium borohydrides.The ionic character of lithium borohydride is further supported by therapid reaction of a benzene solution of aluminium borohydride with ethylEMELBITS : INTRODTTCTTON AND C~EENERAT,. 67lithium to produce lithium borohydride as a white precipitate.This appearsto be an ionic double decomposition. The suggestion is made that all threeof the borohydrides contain the [BH,]- ion, but that i t undergoes a certainamount of distortion. This is a minimum in the lithium compound, and isgreatest under the influence of the smaller and more highly charged alumin-ium ion, with the result that the aluminium compound approximates to thecovalent type. The configuration of AIB,H,, has been determined byelectron diffraction,' and it is found that the aluminium atom and the threeBH, groups are coplanar with angles of 120" between the A1-B bonds.The compounds A1(BH4),, Be(BH,),, and LiBH, have each a two-electrondeficit per BH, group and the B-H distances are greater than those expectedfor electron-pair bonds.They are equal, in fact, to the distances in di-borane, tetraborane, and pentaborane, and there is little doubt that theconstitution of the borohydrides can be considered in terms of the theory ofresonance in the same manner as that of other boron hydrides.A number of reactions of the borohydrides have been studied bySchlesinger, Burg, and their co-workers. All are readily hydrolysed. Theyalso react with hydrogen chloride at - SO", producing hydrogen, diborane,and the metal chloride. The aluminium compound was shown to undergoa complex reaction with ammonia, and it also reacted with dimethyl etherto form the compound AlB3H1,,0(CH,)2, which decomposed a t 50". Lithiumborohydride reacted with methyl alcohol according to the equationLiBH, + 4CH,*OH --+ LiB(OCH,), + 4H2 --+ LiOCH, + B(OCH,),A derivative of the type Li(BR,) was obtained by the interaction ofethyl-lithium with trimethylboron, either in presence or in absence of asolvent.A white crystalline product with the formula ' LiB( CH,),C,H,resulted. It is evident that there are many aspects of these investigationsin which important progress may be expected as the experiments areextended.The association of the alkyls of aluminium, gallium, and indium in thevapour phase has been studied by vapour-density determinations.8 Tri-methylaluminium proved to be anomalous in that the vapour consistsof the dimer a t 70". It dissociates with increase of temperature up to1 SOo, at which point decomposition sets in.Triethylaluminium is 12 yoassociated to the dimer at 150". Trimethylga'llium and trimethylindium werefound to yield monomeric vapours, and the trimethyl and triethyl derivativesof boron are also known to be monomeri~.~ The monomeric charact'er oftrimethylindium is also shown by electron-diffraction measurements.10The oxychlorides of silicon have been reinvestigated by W. C. Schumband D. F. Holloway.11 These compounds, which hitherto were ill defined,J. Y. Beach and S. H. Bauer, J. Amer. Chem. SOC., 1940, 62, 3440.A. W. Laubengayer and W. F. Gilliam, ibid., 1941, 63, 477.9 A. Stock and F. Zeidler, Ber., 1921, 54, 531.lo L. Pauling and A. W. Laubengayer, J. Arner. Chem. h'oc., 1941, 63, 480.l1 Ibid., p. 275368 INORGANIC CHEMISTRY.were prepared by the action of a mixture of chlorine and oxygen on crystal-line silicon at a dull red heat.The reaction product on fractionation yieldedcompounds of the formulae (SiOCI,)4, Si20C1,, Si,02C1,, Si,O,C1lo, Si,O,Cl,,,Si60,CI,, and Si,0,Cll6. The first was a crystalline solid, the others beingliquids of low volatility, all of which were of the type SLO, - ,C1,, + 2, andwere analogous to the oxybromides of silicon.12Reaction of these oxychlorides with absolute alcohol has so far yieldedthe following esters : Siz0(OC2H5),, Si302(OC2H5),, Si403(OC2H5)lo andSi,05( OC2H5) 14. These are non-inflammable high-boiling liquids whichresist hydrolysis by water at 100'. In an extension of these investigationshexacyclohexyloxydisiloxane, ( C,HllO),Si-O-Si( C6H110),, has been preparedfrom cyclohexanol and the oxychloride Si,0C16.13Attempts to prepare silicon compounds of the type SiR,*SiR, andSiR,*O*SiR, from the corresponding silicon halides by the Wurtz synthesisnormally lead to fission of the Si-Si or Si-0-Si bonds.It has been found,however, that by first preparing the sodium compound from an aryl halideand then allowing it to react with the silicon halide, compounds of the requiredtype may be obtained.14 For example, phenylsodium, prepared from chloro-benzene and sodium, reacts with Si20Br6 to yield (C,H5),Si20, and Si2C16gives hexaphenyldisilane .Polymers derived from methylsilicon oxides have assumed considerableimportance during the past year owing to the possibility of their technicalapplication.The simplest starting materials for preparing such polymersare the methylsilicon chlorides, which have been described by W. F. Gilliam,H. A. Liebhafsky, and A. F. Winslow.15 Dimethylsilicon dichloride andmethylsilicon trichloride are formed by the interaction of methylmagnesiumchloride and silicon tetrachloride in the appropriate proportions. Theproducts were fractionally distilled and the boiling points of the two halidesin an approximately pure state were found to be 69.0-70*2° and 66.2-67.09, respectively. These values are anomalous in that they lie outside therange fixed by the boiling points of tetramethylsilicon and silicon tetra-chloride. IPolymeric methylsilicon oxides may be produced by hydrolysis of eitherthe separated or the mixed alkylsilicon halides.16 In either case the halogencompound, dissolved in ether, was poured on ice.The resulting methyl-silicols dissolved in the ether and remained on evaporation of the solvent asa syrup which could be hardened. With an average of 1-0-1-3 methylgroups per silicon atom, the condensation proceeded a t room temperaturethrough a sticky, syrupy stage to a hard, transparent resin, which becamebrittle when warmed. With a ratio of 1.3-1.5, the product a t room tem-perature was an oily liquid, the viscosity of which increased with risingtemperature dntil at 150-200" gelation occurred in a few hours. The gel12 W. C. Schumb and C . H. Klein, J . Amer. Chem. SOC., 1937, 59, 261.1s W. C. Schumb and D.F. Holloway, ibid., 1941, 63, 2853.l4 W. C. Schumb and C . M. Saffer, jm., ibid., p. 93.16 Ibid., p. 801. l6 E. G. Rochow and W. F. Gilliam, &id., p. 795EMEL~TJS : INTRODUCTION AND GENERAL. 69then set gradually to a transparent, horny resin. With CH, : Si ratios of16-1-9 a gel formed in a few hours at 200°, and this product became brittleonly when heated for several weeks at 200". With a CH, : Si ratio of 1.3-1.5 the initial condensation products were soluble in hydrocarbons or alcohols,although the fully hardened resin was insoluble and infusible. The hardenedresin had a high thermal stability; e.g., when a sample was heated in air fora year a t 200' no perceptible change occurred. At 300' in air surface oxid-ation took place. Samples heated for 16 hours in a vacuum at 550' or for 1hour in hydrogen at 450' suffered only a discolouration.A further investigation on this important group of compounds has beenpublished by J.F. Hyde and R. C. DeL0ng.l' These authors studied thehydrolysis of phenylethyl- , phenylmethyl- , diphenyl- , diethyl-, and dimethyl-dichlorosilanes. The products were liquid except those from the diphenylcompound, the diol from which was a crystalline solid. This when treatedin hot alcoholic solution with dilute ammonia or dilute sodium hydroxidewas converted into a cyclic trimer, which was characterised. When theliquid hydrolysis products of tho compounds containing phenyl groups weretreated at high temperatures with aqueous hydrochloric acid there was agradual increase in viscosity, accompanied by evolution of benzene.Theultimate product was an insoluble resin. The dialkyl derivatives werefound, in general, to be more gel-like than those containing a phenyl group,but they had less physical strength after curing than the latter. All filmsformed from solutions of the various resins lost their tackiness and solubilitywith appropriate baking. The final products resembled films formed bydrying oils, though they were superior in thermal stability.There is at present an insufficient basis for discussion of the constitutionof these polymers, but E. G. Rochow and W. F. Gilliam16 suggest thatthe cross-linked siloxane structure shown below probably represents anessential part.-R2Si-O-R~i-O-R2Si-O- .. .-R,Si-O-RSi-O-Ryi-O- . . .Two new iodo-derivatives of monosilane, vix., SiH31 and SiH,I,, havebeen prepared by the interaction of dry hydrogen iodide and monosilane inthe presence of aluminium tri-iodide, which acts as a catalyst.ls The boilingpoints are 45.4' and 149.5', respectively. Neither of the compounds isspontaneously inflammable in air, although both burn readily. In moist air,simultaneous oxidation and hydrolysis take place. Silyl iodide, SiH,I,reacts with mercury in sunlight, yielding mercurous iodide, silane, anddbilane. The liquid iodide and mercury in absence of sunlight farm anunstable, white, crystalline solid which decomposes into mercurous iodideand silane. There is a similarreaction with zinc. With magnesium in diisoamyl ether there is strong5)This may be mercurysilyl iodide, SiH,*HgI.J.Amer. Chem. SOC., 1941, 63, 1194.H. J. Emelbus, A. G. Maddock, andC. Reid, J., 1941, 36370 INORGANIC CHEMISTRY.evidence that a Grignard compound is produced, and treatment of this withwater gives monosilane. Liquid silyl iodide reacts explosively with silvercyanide, forming silver iodide and a brown polymeric solid. By passing thevapour of silyl iodide over silver cyanide a t room temperature the compoundSiH,CN, in. p. 34", is produced. Silyl iodide reacts with sodium, formingdisilane.The reducing action of sodium, potassium, or calcium on liquid ammoniasolutions of nickel salts has been shown to yield free nickel.19 The metal ispyrophoric and catalyses further reaction between alkali or alkaline-earthmetal and ammonia.Nitroxyl perchlorate, NCIO,, has been prepared by the controlled inter-action of chlorine dioxide and an air stream containing ozone and nitrogenoxides.20 It is a white crystalline solid with a vapour pressure less than 0.05mm. a t room temperature.It decomposes at 120' and reacts violently withmost organic liquids. Reaction with water yields a mixture of nitric andperchloric acids, and the compound is regarded as a mixed anhydride ofthese two acids.The direct oxidation of phosphorus tribromide to the oxybromide bymeans of oxygen is not readily controlled and is liable to occur explosively, inwhich case phosphoric oxide and free bromine are among the products. Ithas been shown, however, that under the catalytic influence of nitrogendioxide and with carefully controlled reaction conditions a smooth reactionmay be obtained.21 The direct preparation of phosphorus-halogen com-pounds from phosphoric oxide and metal halides has also been reported.22When mixtures of phosphoric oxide and calcium fluoride are heated to 550°,phosphorus oxyfluoride is the chief volatile product.In iron vessels acertain amount of reduction to the trifluoride also takes place. Whenmixtures of calcium fluoride and sodium chloride were used, the productswere PF,, POF,, POFzCI, POFCI,, and POCI,. I n these reactions the hithertounknown difluorophosphoric acid, HP02F,, which was probably formed bypartial hydrolysis of phosphorus oxyfluoride, was also isolated.In a group of publications dealing with polyiodides of the alkali metals,T.R. Briggs and his co-workers report extensive phase-rule studies.2, Inthe system sodium iodide-iodinewater they obtained the three polyiodidesNa41,4,13-15H20, Na,I,1,17-19H20, and Na,18,10-11H20. There wasno indication of a solid tri-iodide. Similar studies with rubidium iodideshowed the existence of anhydrous RbI,, and in the system czsium iodide-iodine-water the existence of the two binary compounds, CsI, and CsI,.was established. Two compounds of the formule K13,C6H, and KI,,2C6H,Small amounts of nickel amide may also be formed.l D W. M. Burgess and J. W. Eastes, J . Amer. Chem. SOC., 1941,63, 2674.2O W. E. Gordon and J. W. T. Spinks, Canadian J. Res., 1940, 18, B, 358.21 C.R. Johnson and L. G. Nunn, jun., J . Amer. Cheni. Xoc., 1941, 63, 141.p p G. Tarbutton, E. P. Egan, jun., and 8 . G. Frary, ;bid., p. 1782.23 T. R. Briggs, W. F. Geigle, and J. L. Eaton, J . Physical Chem., 1941, 45,, 59.5;1'. E. Briggs, C. C. Conrad, C. C. Gregg, and W. H. Reed, ibid., p. 614; T. R. Briggs antiS. S. Hubard, ibid., p. 806WELCH : METALLTC CARBONYLS AND NTTROSYLS, $1have been prepared by the addition of potassium iodide to a saturatedsolution of iodine in ben~ene.~4In a study of the action of chlorine on hydroxides of lithium and potassiumin presence of iodine, R. K. Bahl and S. Singh 25 have shown that the productfrom a boiling solution of iodine in lithium hydroxide is Li,I,011,2H,U,whereas potassium hydroxide under similar conditions gives KIO,.Whenchlorine is passed into hot solutions of barium or strontium hydroxide, or ahot suspension of calcium hydroxide, containing dissolved iodine, the iodatesBa(I03),,H20, Sr(103)2,H,0 and Ca(103)2,H20 are precipitated, no periodatebeing formed. €3. J. E.2. METALLIC CARBONYLS AND NITROSYLS.Since the chemistry of the carbonyls and nitrosyls was last discpssedin these Reports1 a number of notable developments in this field havebeen reported. Some of these have already been reviewed,29 but a generalsurvey including details of the most recent advances is opportune.The known metallic carbonyls, carbonyl hydrides, and carbonyl halidesare listed in the table on p. 72. Of these compounds the most accessibleare nickel tetracarbonyl and iron pentacarbonyl, both liquids under normaltemperature and pressure conditions, which are obtained on the com-mercial scale by the direct action of carbon monoxide on the finely-dividedmetals.2, Nickel tetracarbonyl is unique in that it is prepared in excellentyield by this direct method without the use of high pressures ; " dry " methodsfor the preparation of the other carbonyls, including iron pentacarbonyl (fromwhich the other iron carbonyls 4 and the tetracarbonyl hydride are prepared),require the use of high-pressure technique, and it is to the systematicapplication of this technique that many of the recent advances are due.The high-pressure apparatus and methods used by W.Hieber andhis collaborators in their more recent studies on the carbonyls havebeen described.5 The rotating autoclave and auxiliary apparatus aredesigned to withstand pressures up to 350 atm.The chief constructionaldifficulty lies in the choice of material for those parts of the apparatuswhich come into contact with carbon monoxide under pressure; alloyscontaining iron, nickel, etc., cannot be used since these metals combinereadily with carbon monoxide to form their carbonyls. Copper-silveralloys have been found to be most suitable for the autoclave lining; purecqper can be used a t temperatures up to 200°, but above this temperature24 J. A. Fialkov and A. B. Polischtschuk, Ber. Inst. Chem. Ahad. Wiss. Ukrain.,25 J . Indian Chem. SOG., 1940,17, 167, 397.W. Wardlaw, Ann. Reports, 1934, 31, 99.W.Hieber, 8. Ekktrochem., 1937, 43, 390.A. 9. Blanchard, Chem. Reviews, 1937, 21, 3 .1940, 7, 95.4 E. Speyer and H. Wolf, Ber., 1927, 60, 1424 [J?e,(CO),];6 W. Hieber, H. Schulten, and R. Marin, ibid., 1939, 240, 261.W. Hieber, 2. anorg.Chem., 1932, 204, 165 ([Fe(CO),]3)72 IXORQAMC CHEMISTRY.co 27Ni 28the various components become welded together and the apparatus cannotbe dismantled. The high-pressure technique used in the preparation ofthe ruthenium carbonyls has also been described.6Metaltic Carbonyls, Carbonyl Hydrides, and Carbonyl Halides.Carbonyl CarbonylElement. At. no. Carbonyls. hydrides. halides.Group I ' {Z 2979~t$o j3X4iPt(CO)X,'cu(c0jx"Au( C0)XjNotea :(a) In the table X represents chlorine, bromine, or iodine; metallic carbonyl(b) Compounds to which references are not appended are referred to in the text of0 Details not yet available; cf.W. Hieber, Z. anorg. C?mn,, 1941, 248.c W. Manchot and J. Konig, Ber., 1924, 57, 2130.d W. Manchot md E. Enk, ibd., 1930, 63, 1635.8 W. Mrtnchot and J. Konig, &id., 1925, 58, 2173.f Idem, ibid., 1926, 59, 883.0 Reported by W. Hieber; work not yet published.h W. Manchot and J. Konig, Ber., 1925, 58, 229.4 P. Schutmnberger, Bull. SOC. chim., 1868, [ii], 10, 188; Ann. Chim. Phys., 1868,j W. Manchot and H. Gall, Ber., 1925, 58, 2175.The direct preparation of cobalt tetracarbonyl from cobalt and carbonmonoxide is inconvenient, since carefully reduced cobalt must be employed.The methods of Schubert and of Coleman and Blanchard 7 use readilyaccessible materials, but give relatively small yields.These disadvantagesW. Manchot and W. J. Manchot, 2. Anorg. Chem., 1936, 226, 385; cf. alsoW. Hieber and H. Fischer, D.R.-P. 695,689 (1940), for ruthenium carbonyls.fluorides have not yet been reported.this Report.Idem, ibid., 1931, 201, 329.[iv], 15, 100; 1870, [iv],2l, 350. *7 Cf. p. 76, refs. (18) and (19)WELCH : METALLIC CARBONYLS AND NITROSYIS. 73are overcome in Hieber's method,5 in which cobalt sulphide is heated a t200" with carbon monoxide under 200 atm. pressure; the reaction proceedsquantitatively according to the equation 2CoS + 8CO + 4Cu + [CO(CO)~], 3-2Cu,S. The copper required in this reaction is obtained from the auto-clave lining, or from copper powder added to the cobalt sulphide.Thecarbonyl is extracted from the solid products with an organic solvent.If water is present in the reacting materials, considerable yields of thevolatile cobalt tstracarbonyl hydride, HCo(CO),, are obtained ; thishydride can also be prepared by high-pressure synthesis from (a) cobaltsulphide, carbon monoxide, and hydrogen ; ( b ) cobalt tetracarbonyl andhydrogen; ( c ) cobalt, carbon monoxide, and hydrogen; or ( d ) cobalthydride (CoH,) and carbon monoxide.The action of carbon monoxide at high pressures on cobaltous halides inpresence of certain other metals also affords cobalt tetracarbonyl, or, inpresence of water or hydrogen, the tetracarbonyl hydride.6 The conditionsand mechanism of formation of the tetracarbonyl by this process havebeen studied in some detail.8 Cobaltous iodide is completely converted intothe carbonyl by heating a t 150' for 15 hours with carbon monoxide under200 atm.pressure; the bromide and chloride give small yields of the car-bony1 at 200-300", but the fluoride does not react. The halogen is eventu-ally eliminated from the reaction by combination with copper in the auto-clave wall : 2C01, + 4Cu + 8CO + [Co(CO),], + 4CuI. This mode ofreaction persists even if direct contact between the cobaltous halide andthe autoclave is prevented by a glass sleeve, showing that some volatileintermediate is involved. In the case of cobaltous iodide this intermediateis probably Co(CO)I,, which can be obtained as brownish-black crystals bythe action of carbon monoxide at 100400 atm.on the anhydrous iodide,a t room temperature ; Co(CO)I, has a high dissociation pressure of carbonmonoxide and decomposes in a few seconds at normal temperatures andpressures. The yields of cobalt tetracarbonyl obtained from cobaltousbromide or chloride and carbon monoxide are considerably increased bymixing a metal powder with the halide in order to facilitate elimination ofthe halogen. The effectiveness of the metals tried decreases in the ordercopper, silver, platinum, gold; the heats of formation of the appropriatehalides also decrease in this order, showing that a controlling factor in theformation of the carboxayl is the reaction between the solid cobaltous halideand the admixed metal, e.g., CoBr, + 2Ag-> Co + 2AgBr. If argon issubstituted for carbon monoxide, reactions of this type give equilibriummixtures containing relatively little cobalt ; this indicates that carbonmonoxide plays an essential part in the reaction between the metal andthe halide, and does not merely combine with free cobalt formed in anindependent reaction.The use of a more electropositive metal, such aszinc or cadmium, leads to the formation of a crystalline, appreciably volatile" mixed carbonyl " of the metal and cobalf, probably to be regarded as aderivative of cobalt carbonyl hydride, e.g., Zn[Co(CO)&. It is stated 8* W. Hieber and H. Schulten, 2. a m g . Ckern., 1939,243, 14654 INORGANIC CHEMISTRY.that reactions corresponding with those described above also occur withnickel and iron halides.Cobalt tricarbonyl, [Co(CO),],, is readily obtained by heating the tetra-carbonyl a t about 52O.9Although a dicarbonyl chloride of iridium, Ir( CO),Cl,, has been knownfor some time,l0 simple carbonyls of iridium have not been described untilrecently.The tricarbonyl, [Ir(C0)3]n, has been prepared by the action ofcarbon monoxide at 200 atm. pressure on a trihalide of iridium.11 Thehalogen is again eliminated by combination with copper from the autoclavelining :IrCl, + ~ C U + 6CO --+ Ir(CO), + 3CuC1,COPolymerThe chloride, bromide, and iodide react in this way at 140°, 110-120°,and 90-lOO', respectively ; conversion of the trichloride into the carbonylis complete after 24--48 hours at 140'.The product can be sublimed incarbon monoxide a t 200-210". In this reaction, actual addition of a halo-gen-absorbing metal, such as copper or silver, is avoided, since immediatereduction of the iridium halide to metallic iridium would occur on heatingto the requisite temperature, and the iridium would not react with carbonmonoxide under the conditions given. If complex iridium halides, such asK21rBr6, are used instead of the trihalides, addition of copper or silver is,however, necessary if the halogen is to be displaced completely; K,IrBr6and carbon monoxide, without added metal, give a new carbonyl halide,Ir(C0)3Br. Although the tricarbonyl is the main product of the reactionof iridium trihalides and carbon monoxide, the complex halides (withcopper or silver) give mixtures of the yellow tricarbonyl and a greenish-yellow crystalline tetracarbonyl, [Ir( CO),], ; the mixtures can be separatedby extraction with carbon tetrachloride or ethyl ether, in which the tetra-carbonyl is slightly soluble, or by fractional sublimation, the tetracarbonylsubliming at about 160' in carbon monoxide a t normal pressure.Iridiumtetracarbonyl is very readily converted into the tricarbonyl, which is suffi-ciently stable to resist attack by concentrated acids, dilute alkalis, or freehalogens at room temperature. The molecular weights of the iridiumcarbonyls could not be determined owing to their low solubility; theproperties of the tetracarbonyl are consistent with the dimeric formula,[Ir(C0),I2 (indicated by analogy with the cobalt compounds), whereas thetricarbonyl is clearly more complex ([Ir(CO),],?) since it is less volatile andless soluble.The formation of cobalt tetracarbonyl hydride from cobalt compounds,carbon monoxide, and substances containing hydrogen has been notedabove. Apparently an iridium carbonyl hydride, probably HIr( CO),, isformed under similar conditions, for the action of carbon monoxide oniridium trihalides in presence of water or hydrogen affords a volatile andvery unstable substance containing iridium ; this gives a colourless solid* W.IZieber, F. Muhlbauer, and E. A. Ehmann, Ber., 1932, 65, 1090.lo W. Manchot and H. Gall, &id., 1925, 58, 232WELOH : METALLIC CARBONYLS AND NITROSYLS.75compound with mercuric chloride solution.11 It appears, therefore, that aclose analogy exists between the carbonyl derivatives of cobalt and iridium.The hexacarbonyls of chromium, molybdenum, and tungsten were firstprepared in quantities sufficient for analysis by the action of carbon mon-oxide and a Grignard reagent on the anhydrous halides of the metals.12The yields obtained by this method are small. Molybdenum and tungstenhexacarbonyls are better prepared by treating the reduced metal withcarbon monoxide (at 200 atm. and about 225') in presence of another metal(e.g., copper or iron) ; 13 these carbonyls have also been obtained by treatingthe chlorides or bromides of the metals, or corresponding complex salts(e.g., K3MoC16, K3W,C1,), with carbon monoxide under pressure, in presenceof a metal to remove the halogen.14 Chromium hexacarbonyl apparentlycannot be prepared by either of these methods, and only the original methodof Job12 is available in this case.The hexacarbonyls of the Group V Imetals, which are colourless crystalline solids, are considerably more stablethan the simpler carbonyls of the Group VIII elements, probably becausethe attainment of the effective atomic number of a rare gas by the centralmetal atom coincides with the formation of the inherently stable six-co-ordinate complex.Brief reference has already been made to the tetracarbonyl hydrides ofiron, cobalt, and iridium; it appears likely that a similar compound ofruthenium [presumably H,Ru( CO),, maintaining the analogy betweenruthenium and iron] also exists, since ruthenium pentacarbonyl reacts withalkalis to give fairly stable solutions with strong reducing properties,6 justas iron pentacarbonyl reacts to give strongly reducing solutions of the irontetracarbonyl hydride.Iron and cobalt tetracarbonyl hydrides have been isolated and studiedin some detail; they are very volatile liquids, stable only a t temperatureswell below 0'.The free iron compound was first obtained by Hieber andhis collaborators15 by the action of an aqueous solution of a base (pre-ferably barium hydroxide) on iron pentacarbonyl, followed by acidificationof the solution. A similar reaction with cobalt tetracarbonyl affords freecobalt tetracarbonyl hydride.1691'Several reactions have now been studied in which cobalt tetracarbonylhydride derivatives are obtained by the action of carbon monoxide onsolutions (or suspensions) of cobalt salts.These reactions take place a tl1 W. Hieber and €3. Lagally, 2. anorg. Chem., 1940, 245, 321.l2 A. Job and A. Cassal, Cornpt. rend., 1926,183, 58, 392; Bull. SOC. chim,., 1927, [iv],41, 1041; A. Job and J. Rouvillois, Compt. rend., 1928, 187, 564; W. Hieber andE. Romberg, 2. anorg. Chem., 1935, 221, 321.Is I. G. Farbenindustrie A.-G., F.P. 708,379, 708,260 (1930) ; B.P. 367,481 (1930);D.R.-P. 547,025 (1931).l4 W. Hieber et aE., details not yet published.l6 W. Hieber and F. Leutert, Naturwiss., 1931, 19, 360; Ber., 1931, 84, 2832; 2.18 W. Hieber, Angew.Chem., 1936, 49, 463.l7 W. Hieber and H. Schulten, 2. anorg. Chem., 1937, 232, 17, 29.anorg. Chem,., 1932, 204, 145; W. Hieber and H. Vetter, ibid., 1933, 212, 14576 INORGANIC CHEMISTRY.normal pressures, and provide means of preparing cobalt tetracarbonylhydride and the tetracarbonyl (which is readily obtained by decompositionof the hydride on warming) with readily available apparatus and materials.Unfortunately, the reactions are slow and accumulation of moderate quan-tities of the products is tedious. An alkaline solution of cobalt chloridewill not absorb carbon monoxide, but on addition of cysteine to this solutionthe gas is absorbed, and cobalt tetracarbonyl hydride is liberated on acidi-fication of the resulting liquid.18, l9 This reaction probably occurs by theintermediate formation of complexes of cobalt and cysteine containingcarbon monoxide; such complexes have not yet been isolated, althoughiron compounds of a corresponding type are known.18 A mechanism hasbeen worked out for the above reaction,18 involving “ disproportionation ”of a bivalent cobalt complex to a cobalt tetracarbonyl hydride derivative(presumably the alkali salt) and a tervalent cobalt complex; the latter isreduced by carbon monoxide in a subsequent stage of the reaction. Cer-tain other substances, notably tartrates, can replace cysteine in this re-acti0n.1~ Nickel tetracarbonyl is readily prepared by the action of carbonmonoxide on an alkaline suspension of nickel cyanide or sulphide,20-22 andcarbon monoxide is also absorbed by alkaline suspensions of cobalt cyanideor sulphide; cobalt tetracarbonyl or the hydride has not, however, beenisolated from the reaction products, although cobalt nitrosyl carbonyl,Co(CO),NO (see below), has been obtained by passing nitric oxide into thesolution.22 An interesting addition compound of cobalt tetracarbonyl,[Co(CO),],,EtOH, has been prepared by the action of carbon monoxide onan alcoholic solution of cobaltous chloride and potassium ethyl anth hate.^^In all these processes it appears likely that intermediates containing carbonmonoxide are formed, and a further study of the reactions involved maylead to an interesting new branch of carbonyl chemistry.It is noteworthythat linkings between metal and sulphur atoms are, for some reason notyet understood, particularly susceptible to reaction with carbon monoxide.The tetracarbonyl hydrides of iron and cobalt form an interesting seriesof crystalline derivatives with complex cations containing ammonia oro-phenanthroline (phenan) .24 Typical members of the series arewhich are prepared by addition of a solution containing the appropriatecomplex cation to an ammoniacal solution of the carbonyl hydride.Theammonia compounds are stable in the absence of air, but react readilywith ammonia, pyridine, etc., and slowly with methyl alcohol; the o-phen-anthroline compounds are stable in air and notably less reactive. With18 M. P. Schubert, J . Amer. Chem. SOC., 1933, 55, 4663.1’ G. W. Coleman and A. A. Blanchard, ibid., 1936, 58, 2160; cf.also A. A. Blan-2o W. Manchot and H. Gall, Ber., 1929, 62, 678.s1 M. M. Windsor and A. A. Blanchard, J . Amer. Chem. SOC., 1933, 55, 1877.2* A. A. Blanchard, J. R. Rafter, and W. B. Adams, ibid., 1924, 58, 16.2s W. Hieber, Angew. Chem., 1936, 49, 463.24 W. Hieber and E. Fack, 2. anorg. Chern., 1938,238, 83.“i(NH,),I[Co(CO),I,, [Mn(NH,),l[HFe(C0)412, and Cco(Phenan),l[Co(CO),l,,chard and P. Gilmont, ibid., 1940, 62, 1192WELCH : METALLIC CARBONYLS AND NITROSYLS. 77zinc, cadmium, and copper salts the ammoniacal solution of iron tetra-carbonyl hydride reacts to give compounds of a different type, &.,Zn(NH,),,Fe(CO),, Cd(NH3),,Fe(C0),,25 and Cu,(NH,),,Fe(CO),, in whichboth hydrogen atoms are displaced from the carbonyl hydride.The hex-ammine and o-phenanthroline compounds are regarded by Hieber as truesalts of iron tetracarbonyl hydride, since they are shown by electrical con-ductivity measurements to dissociate in methanol and acetone solutions.The zinc, copper, and cadmium compounds are non-electrolytes, however,and these are considered to be polynuclear complexes which are possiblysimilar in constitution to substituted carbonyls, such as Fe2( CO),( C5H,N),.Conductivity measurements also show that the free iron and cobalt tetra-carbonyl hydrides are dissociated in pyridine solution.The table given on p. 72 shows the large number of carbonyl halidesnow known to exist. The properties and reactions of the iron compoundshave been studied in considerable detail.2s At low temperatures ironpentacarbonyl adds free halogens to give unstable compounds of the typeFe(CO),X,; these decompose at temperatures varying from - 35' to Oo,more stable tetracarbonyl derivatives, Fe( C0),X2, being formed. Thetetracarbonyl iodide is also formed on treating iron tetracarbonyl hydridewith iodine, or by the action of carbon monoxide under high pressure onanhydrous ferrous iodide ; 27 the kinetics of the latter reaction show certainunusual features." Mixed " iron tetracarbonyl halides, Fe(CO),IBr andFe(CO),ICl, have now been prepared 2s by the action of iodine monobromideor monochloride on iron pentacarbonyl ; these compounds decomposereadily into mixtures of the two simple carbonyl halides. As expected,the " mixed " halides possess, in general, properties intermediate betweenthose of the two corresponding simple carbonyl halides.The possible reactions of iron pentacarbonyl with halides of metals intheir higher states of oxidation have recently been examined.28 The fir$possible type of reaction, in which part of the carbon monoxide is displacedfrom the carbonyl and oxidised to carbon dioxide, occurs with mercuricchloride in aqueous solution : z9Fe(CO), + 2HgC1, + H20 --+ Fe(CO),,Hg2C12 + CO, + 2HC1The compound Fe(CO),,Hg,Cl, should probably be regarded a8 a doublesalt of the mercury derivative of iron tetracarbonyl hydride, HgFe( CO),,HgCl, ;the simple mercury derivative, HgFe(CO),, is obtained by using mercuricsulphate instead of the chl0ride.2~ The reactions of iron pentacarbonylwith stannic chloride and antimony pentachloride are of a second type inwhich carbon monoxide is displaced but not oxidised :Fe(CQ), + SbCl,+ Fe(CO),SbCl, + COFe(CO), + SnC14 4 Fe(CO),SnCl, + CO26 Cf.also F. Feigl and P. Knunholz, 2. anorg. Chem., 1933, 215, 242.26 W. Hieber et al., ibid., 1930, 190, 192, 215; 1931, 201, 329.27 W. Hieber and H. Lagally, ibad., 1940, 245, 305.28 W. Hieber and A. Wirsching, ibid., p. 36.2s H. Hock and H. Stuhlmann, Bey., 1928, 61, 2097; 1929, 62, 431, 269078 INORGANIC CHEMISTRY.The new compounds obtained are shown by their reactions to contain ironin the bivalent condition, with tervalent antimony or bivalent tin. Theyare more stable than the iron tetracarbonyl halides to which they appear tobe related; the antimony compound is dissociated in benzene or nitro-benzene solution :Fe(C0)4SbC15 =+ Fe(CO),Cl, +but the tin compound shows a normal molecularas a binuclear complex : c1 C1(CO),Fe/ ‘Sn’‘Clf ‘c1SbC1,weight and is regardedWith other halides (e.g., ferric and cupric chlorides) both the above typesof reaction appear to occur together, both carbon monoxide and carbondioxide being evolved ; additive compounds analogous to those justdescribed have not, however, been isolated.Iron pentacarbonyl shows a strong tendency to displace halogens fromlion-metallic halides, as the following reactions show : 28Fe(CO), + 2CC14 --+ C,CI, + FeCI, + 5COFe(CO)5 + SO,CI, + SO, + FeC1, + 5COIn each case an iron carbonyl halide is probably formed as an intermediateproduct.The corresponding reaction with thionyl chloride is more com-plex, and affords evidence for the existence of an iron dicarbonyl chloride,Fe(CO),CI, ; this compound, a reactive, brown, crystalline solid, is isolatedby using iron tetracarbonyl iodide instead of iron pentacarbonyl :Fe(CO),I, + 2SOC1, + Fe(CO),Cl, + I, + 2CO + SO, + SC1,The tetracarbonyl bromide reacts in a similar manner. It is noteworthyt,hat a ruthenium dicarbonyl chloride, Ru(CO),CI,, analogous to the newiron derivative, has been known for some time.31Although a number of iron carbonyl derivatives containing co-ordinatedsubstituents (amines, etc.) contain from one to four molecules of carbonmonoxide per atom of iron,S2 the dicarbonyl chloride discussed above is thefirst known example of a simple iron carbonyl halide with a CO : Fe ratioof less than 4.Further investigation33 has shown that a similar com-pound, Fe(CO),I,, is formed as a product of the thermal decomposition ofiron tetracarbonyl iodide in an inert atmosphere ; other products, obtainedunder different conditions, are Fe(CO),I and the hitherto unknown iodideof univalent iron, FeI. Fe(CO),I, is a reddish-brown solid; its alcoholicsolution gives dark red Fe(CO),I,,phenan with o-phenanthroline, and greenFe(CO),I,(C,H,N) with pyridine. Fe(CO),I and FeI are extremely un-stable; the latter is it bright red solid which reduces silver nitrate in acid3u A. Mittasch, 2. angew. Chem., 1928, Q1, 827.3 1 11‘.Manchot and J. Konig, Ber., 1924, 57, 2130.33 IfT. Hieber and G. Bader, 2. aaorg. Chem., 1930, 190, 193.33 W. Hieber and H. Lagally, ibid., 1940, 245, 295WELCH : METALLIC CARBONYLS AND NTTROSYLS. 79solution to metallic silver and reacts with water to form ferrous hydroxideand hydrogen. The molecular weights of these new compounds have notbeen determined, and the formuke given are empirical.Brief reference has been made above to a tricarbonyl halide of iridiumof the type Ir(CO),X; the other halides of this type have now been pre-pared and e~amined.~4 When dry carbon monoxide a t atmospheric pres-sure is passed over the monohydrate of the iridium trihalide, IrX,,H20, atabout 150°, a mixture of Ir(CO),X, Ir(CO),X,, and [Ir(CO),], sublimes on tothe cooler parts of the apparatus.The dark brown, crystalline tricarbonylhalides sublime on heating the mixture a t 115', and the dicarbonyl com-pounds, which are colourless or yellow, sublime at 150'. Although thedicarbonyl halides are unstable and decompose on exposure to air, thetricarbonyl compounds are stable. It is interesting that halides of thetype Ir(CO),X are not obtained from anhydrous iridium halides and carbonmonoxide under the conditions described, although small yields of Ir(CO),X,have been prepared from these reactants; 35 the necessity for the presenceof water of hydration provides an interesting parallel to the use of methylalcohol vapour as a catalyst in certain reactions in which carbonyl com-pounds are f0rmed.M It is noteworthy that in the reaction just describediridium tricarbonyl is prepared, although in small yield, without the use ofhigh-pressure technique.Hieber considers that formation of the iridiumcarbonyls, at both normal and high pressures, occurs by successive dis-placement of the halogen atoms in the halide by carbon monoxide.Until recently, attempts to prepare carbonyls of the metals of Group VII(manganese, masurium, and rhenium) were unsuccessful, although theexistence of well-defined carbonyl derivatives of Group VI and Group VIIImetals led to a careful search for related compounds of the interveningGroup VII elements, particularly manganese. The recent preparation ofrhenium pentacarbonyl halides 3' is therefore of special interest. Thesecompounds, which have the formula Re(CO),X, are prepared by heating achloride of rhenium (ReC1, or ReCl,), or potassium rhenibromide or rheni-iodide (K,ReX,) mixed with copper powder, in carbon monoxide a t 200 atm.and 200-230'.Under these conditions the rhenium compounds are con-verted completely into the pentacarbonyl halide after about 30 hours; thepentacarbonyl derivatives are extracted from the products with benzeneor light petroleum. The new compounds are stable, odourless, colourlessor yellow crystalline solids which sublime unchanged in carbon monoxidebut are decomposed on heating in air at about 400'. They are soluble inorganic solvents but insoluble in water. The rhenium pentacarbonylhalides are similar in character and stability to the hexacarbonyls of theGroup VI metals.3J W.Hieber, H. Lagally, and A. Mayr, 2. anorg. Chem., 1941, 246, 138.36 W. Manchot and H. Gall, Ber., 1925, 58, 232.36 E.g., in formation of Pd(CO)Cl,, W. Manchot and J. Konig, ibid., 1926, 59,37 W. Hieber and H. Schulten, 2. anorg. Chem., 1939, 243, 164-88.380 INORGANIC CHEMISTRY.The unusual facility with which carbon monoxide reacts with certainmetallic compounds containing sulphur directly bound to the metal atomhas been noted above. This has led to a study of the chemistry of sub-stituted carbonyls containing various groups attached to the metal atomby one or more atoms of sulphur; such compounds might occur as inter-mediates in the reactions in question. The tetracarbonyls of iron andcobalt react readily with ethyl- and phenyl-thiol to form stable, well-crystal-l i d , red derivatives,s7a> 3s [B’e(C0)3SEt],,39 [Co( CO),SEtJ,, Fe( CO),SPh,and Co( CO),SPh, with elimination of carbon monoxide and hydrogen.These are typical non-polar compounds.Diphenyl disulphide gives thesame phenyl compound with iron tetracarbonyl, without elimination ofhydrogen. Mercaptobenzthiazole in solution in light petroleum reacta withiron tetracarbonyl to give a red crystalline compound, Fe,(CO),,<>CH,,which is also formed in very small quantities from parathioformaldehyde,( CH,S),. a-Thionaphthol readily gives a dimeric compound analogous toFe(CO),SPh, but P-thionaphthol reacts with difficulty to form a derivativewhich is at least trimeric.Attempts to prepare chelate derivatives fromiron tetracarbonyl and thiosemicarbazide, thiocatechol, thioacetamide, orthiosalicylic acid were unsuccessful ; a chelateiron carbonyl halide derivative (I) containing co-CH,- r ordinated sulphur is, however, kn0~n.40 Alkyl I ‘Fe(CO),X, sulphides in light petroleum solution react withCH2-YZ iron tetracarbonyl to form compounds of the typeE t (I.) Fe(CO),SR,; some Fe(CO),SR is also formed, itsamount increasing as the temperature is raised ;iron pentacarbonyl gives similar products. Dimethyl disulphide and thetetracarbonyl afford [Fe(CO),SMe],, which is not conveniently preparedfrom the more volatile methyl sulphide. Amine-substituted carbonyls suchas Fe,(CO),(C5H5N), with phenylthiol give Fe(CO),SPh, but no amine-substituted derivatives of a similar type are formed; the compoundsFe(CO)SPh,phenan and Co( CO),SEt,phenan are formed, however, on treat-ing Fe(CO),SPh and [Co(CO),SEt], with o-phenanthroline.The hexacarbonyls ofthe Group VI metals do not react, but the substituted compoundMo( CO),( C5H5N), gives a dark brown crystalline derivative,Mo(CO),(C5H5N)SPh,showing that the partly substituted carbonyls may be more reactive thantheir parent compound^.^^Little reference has been made above to the very numerous substitutedcarbonyls and carbonyl halides in which part of the carbon monoxide isreplaced by amine, alcohol, or other groups; these are discussed in theNickel tetracarbonyl does not react with thiols.37a W.Hieber and P.Spacu, 2. amrg. Chem., 1937, 233, 353.38 W. Hieber and C. Scharfenberg, Ber., 1940, 78, 1012.39 H. Reihlen, A. Gruhl, and G. von Hessling, AnnaEen, 1929, 472, 268.40 W. Hieber, 2. a w g . Chem., 1931, 201, 329WELCH : METALLIC CARBONYLS AND NITROSYLS. 81reviews cited 2* and in the references given below.41 A few of thesecompounds, e.g., the o-phenanthroline derivative (11) ofnickel tetracarbonyl, can be formulated without difficultyas compounds in which the metal atom has the sameco4 /r N\/’.\ I electron configuration as in the parent carbonyl. MostCoflNikN,,/ of the substituted carbonyls, however, are more complex,and their structures deserve further study.The “ carbonyls ” of the alkali metals have not beenincluded, since there is no evidence that they are truecarbonyls containing co-ordinated carbon monoxide molecules.Closely related to the carbonyls are the volatile nitrosyl curbonyls ofcobalt and iron, Co(CO),NO 42 and Fe(CO)2(N0),,43 which are the onlycompounds of their class so far discovered; both may be prepared by thereaction of nitric oxide with either of the corresponding polynuclear car-bonyls under appropriate conditions.The cobalt compound is convenientlyprepared by a method involving the cobalt cysteine complexes discussedabove; carbon monoxide is passed into the alkaline cobalt salt solutioncontaining cysteine, which is then acidified; on passing in nitric oxide thenitrosyl carbonyl is evolved as a red vap0ur.1~ Cobalt nitrosyl carbonylcan also be obtained, in a similar manner, from an alkaline suspension ofcobalt cyanide or sulphide in which carbon monoxide has been absorbed.22A nitrosyl carbonyl of nickel has not yet been isolated, although a com-pound Ni(NO),CO might be expected to exist; the action of nitric oxideon nickel tetracarbonyl affords compounds of a univalent radical Ni(NO),e.g., Ni(N0)OH.aReference has been made in the literature and in patents 46 to a volatilecobalt nitrosyl, Co(NO),, but the properties of this interesting compoundhave not been described.Non-volatile “ nitrosyla ” of iron, Fe(N0),,46and ruthenium, Ru(NO), or R U ( N O ) ~ , ~ ~ have also been described, but theformer is probably a hyponitrite, Fe(NO),N,O,, and the latter requiresfurther investigation to clarify its constitution.An interesting new group of cobalt nitrosyl halides, Co(NO),X, hasAI I(11.)41 Work by W.Hieber and his collaborators: (iron compounds) Ber., 1928, 61,558, 2421 ; Sitzungsber. Heidelberg. Akad. Wiss,, math.-nat. KE., 1929, Part 3, 3-9; Ber.,1930, 63, 973; 2. anorg. Chern., 1930, 190, 193; Ber., 1930, 63, 1405; 1931, 64, 2340;2. anorg. Chem., 1931, 201, 329; Ber., 1932, 65, 1082; (nickel and cobalt compounds)ibid., p. 1090; (chromium and molybdenum compounds) 2. anorg. Chem., 1936, 221,337; (tungsten compounds) ibid., p. 349.42 R. L. Mond and A. E. Wallis, J., 1922, 121, 32.43 W. Hieber and J. S. Anderson, 2. anorg. Chem., 1932, 208, 238. For Bornereactions of the iron and cobalt nitrosyl carbonyls, see idem, ibid., 1933, 211,132.44 J.8. Anderson, ibid., 1936, 229, 357; cf. also J. C. W. Frazer and W. E. Trout,J. Amer. Chem. SOC., 1936, 58, 2201.46 W. Hieber, Angew. Chem., 1936, 49, 463; I. G. Farbenindustrie A.-G., D.R.-P.613,400, 613,401 (1932).46 W. Manchot and E. Enk, Anncalen, 1929, 470, 276.47 W. Manchot and W. J. Manchot, 2. anorg. ChRm., 1936,226,41082 INORGANIC CHEMISTRY.recently been described.48 These compounds are prepared by the actionof nitric oxide on the anhydrous cobalt halide a t about 60'. The iodide ismost readily prepared and forms dark brown or black, shining crystals. Inthe case of the bromide or chloride the reaction proceeds to completion onlyin presence of a metal, such as zinc or cobalt, which absorbs the halogen.An alcoholic solution of cobaltous iodide also reacts with nitric oxide,affording the dinitrosyl iodide.The cobalt dinitrosyl halides are extremelystable substances which can be sublimed without decomposition in air,carbon monoxide, or hydrogen a t normal pressures; a t high pressurescarbon monoxide reacts to give cobalt tetracarbonyl and cobalt nitrosylcarbonyl. The compounds are regarded as true nitrosyl derivatives ; theyreact readily with alkali thiosulphate solutions, giving deep green solutionsof [Co(NO)2(Sz03)2]"',49 and also with alkali sulphide solutions ; in the lattercase compounds of the type Co(NO),SM (where M is a univalent metal),analogous to Roussin's red salts, are possibly formed. Organic amines givevarious additive and substitution products of the nitrosyl halides ; pyridinegives CO(NO)I,(C~H~N)~, whereas o-phenanthroline does not displace nitricoxide, but forms Co(NO),I,phenan. The cobalt nitrosyl halides are clearlyrelated to the carbonyl mercaptides described above, and also to the knowncompounds Fe(NO),X,5O Fe(NO),SM (Roussin's red salts), Fe(NO),SR,Co (NO),SR, Ni (NO) SR, et c.Little attention has been paid above to the molecular constitution ofthe carbonyls and nitrosyls, since the general principles governing theirstructures have been adequately dealt with in these Reports 1 and in arecent review ; 52 this review also considers a number of nitrosyl cyanideswhich have not been included in this Report.Special importance attaches,however, to the examination by electron-diffraction and X-ray methods ofthe structures of iron penta~arbonyl,~~ the Group VI metal he~acarbonyls,~4nickel tetracarbonyl, cobalt nitrosyl carbonyl, iron nitrosyl ~ a r b o n y l , ~ ~ ironenneacarbonyl [Fez( CO),] ,56 and the cobalt and iron tetracarbonyl hydride~.~'The structures of the carbonyl hydrides are of particular interest, since thehydrogen atoms are not attached directly to the metal atoms but to thecarbonyl group, M-C-O-H (the lines here do not indicate the character of4 8 W.Hieber and R. Marin, 2. anorg. Chem., 1939, 240, 241.49 W. Manchot et al., Ber., 1926, 59, 2445; 2929, 62, 681.60 W. Manchot and H. Fischer, Diss., Tech. Hochschule, Munchen, 1937. For5 1 H. Reihlen etal., Annulen, 1927, 457, 7 1 ; 1928, 465, 72; 1929, 472, 268; 1930,52 A.A. Blanchard, Chem. Reviews, 1940, 26, 409.63 R. V. G. Ewens and M. W. Lister, Trans. Faraday Xoc., 1939, 35, 681 ; ,4?m64 L. 0. Brockway, R. V. G. Ewens, and M. W. Lister, Trans. Faraday SOC., 1938,6 6 L. 0. Brockway and P. C. Cross, J . Chem. Physics, 1935, 3, 828 ; L. 0. BrockwayLe H. M. Powell and R. V. G. Ewens, J., 1939, 286.6 1 R. V. G. Ewens and M. W. Lister, Trans. Faraday SOC., 1939, 35, 681,other iron nitrosyl compounds, cf. ref. (51).482, 161; W. Manchot and F. Davidson, Ber., 1929, 62, 681.Reports, 1939, 36, 166.34, 1350.and J. S. Anderson, Trans. Faraday SOC., 1937, 33, 1233REES : ISOTOPE EXCHANGE IN INORGANIC CHEMISTRY. 83the bonds). The hydrides may therefore be formulated as Co(CO),COH andFe(CO),(COH),; the valency relation of the COH groups to the metalatoms appears to be analogous to that of the nitrosyl groups in the nitrosylcarbonyls.A. J. E. W.3. ISOTOPE EXCHANGE IN INORGANIC CHEMISTRY.In recent years considerable use has been made of partly enriched non-radioactive isotope mixtures and also of radioactive isotopes in the elucid-ation of many of the problems of inorganic chemistry. Much of the workhas been concerned primarily with problems of a more or less physicalnature, but in many cases the bearing on inorganic chemistry has beenconsiderable, and t,his is here reviewed.Isotopic Concentration by Methods of Chemical E’xchnge.Of the various methods available for the concentration of isotopes intheir mixtures, those dependent on gaseous diffusion, fractional distillation,and fractional electrolysis have been extensively employed and are alreadywidely known.The more recent application of thermal diffusion in gasesand liquids to the separation of isotopic mixtures was reviewed in lastyear’s Report.1 However, apart from sections devoted to it in generalreviews on methods of isotopic separation,, no account of the chemicalexchange methods of separation has yet appeared.That chemical exchange reactions could be employed in the practicalseparation of isotopes was first suggested by H. C. Urey and L. J. Grieff.3The existence of equilibria in exchange reactions and the experimentalverification that the constants of these equilibria can be evaluated bystatistical methods, permit the evaluation from spectroscopic data of equi-librium constants and enrichment factors for possible exchange reactions.In the case of exchanges involving only one isotopic pair the enrichmentfactor is defined as (X,/N2)/(nl/n2), where N , and N , are the numbers oflight and of heavy atoms in the one compound, and n, and 72, the corre-sponding numbers for the other.Provided that the assumption that theatoms distribute themselves statistically among the various molecules ismade, and that the fundamental molecular constants for the two isotopicspecies are available, then the calculation of this enrichment factor can bemade with reasonable accuracy. On the basis of their calculations, it wassuggested by Urey and Grieff that isotopes of lighter elements might beseparated by chemical exchange methods and that the equilibria might beestablished in liquid-gas two-phase systems by a counter-current operation.Theoretical calculations of the overall enrichment factors to be expectedin scrubbing columns of a theoretical design were made.These calculationsP. 153.‘2 N. S . Bayliss and R. W. Pickering, J . Proc. Austral. Cheni. Irist., 1950, 7 , 51;H. C. Urey, Rep. Prog. Physics, 1939, 8, 48.J . Amer. Chem. SOC., 1935, 57, 32184 INORGANIC CHEMISTRY.indicated that the process was favourable for enrichment of certain of therare isotopes.The practical application of this method involves the use of three dis-tillation units in cascade 4* 5 as had been suggested earlier by H.c. Urey,J. R. Huffman, H. G. Thode, and M. Fox.6 If each stage of the cascadeincreases the concentration by a factor p, then the first unit should have aflow p times that of the second, and the second a flow p times that of thethird, the isotopic ratio being increased theoretically by a factor p3, whilstthe total transport should be the same in each unit. The original distillationapparatus5 consisted of three units with an effective column length of115 feet, in sections some 15 feet long. Only the second and the third unitof this apparatus being used for the exchange reaction between gaseousammonia and ammonium nitrate solution, wix.,15NH, (g.) + l411y'H4+ (sol.) + 14NH, (g.) + WH4+ (sol.)( K = 1.023)a 46-fold increase in the isotopic ratio 15N/14N was obtained in the solutionin 2 weeks' operation, the sample containing l4.8Y0 of W .4 With all threeunits in operation, 8.8 g . of 70.6% 15N were obtained in 4 days.5The sulphur isotope 34s has been obtained in 6-Sy0 concentration in theliquid in 7 days, only one unit of the apparatus being used, for the exchangebetween gaseous sulphur dioxide and sodium bisulphate solution.*Exchange has also been observed in the system H,S (g.)-NaHS (sol.), the84S being concentrated in the gas phase.' D. W. Stewart and K. Cohen *have found satisfactory exchange to take place between gaseous sulphurdioxide and an aqueous solution of sodium bisulphite according to theequationThe maximum concentration of 34s was 27% after 21 days at a rate of 0.8 g.of per day.Successful concentration of the heavy carbon isotope 13C has also beenaccomplished by exchange between gaseous hydrogen cyanide and sodiumcyanide solution by a similar m e t h ~ d .~ ~ 10 The possible reactions involvedareH12CN + 13CN' =+ H1WN + 12CN' ( K = 1.026)and HC14N + C15N' HC15N + CI4N' ( K = 1.003)The equilibrium constants quoted have been derived from the knownvibrational fiequenciee of HCN and CN'. 15N is concentrated to a small3450, (g.) + ~ 3 2 ~ 0 ; (sol.) + 3 2 ~ 0 , (g.) + H~~SO; (sol.)4 H. G. Thode, J. E. Gorham, and H. C. Urey, J . Chern. Phyaks, 1938, 6, 296.6 H. G. mode and H. C. Urey, ibid., 1939, 7, 34.* Ibid., 1937, 6, 856.7 H. C. Urey, A. Mills, I. Roberts, H. G. Thode, and J. R. Huffman, ibid., 1939,7, 138.Ibid., 1940, 8, 905.I.Roberts, H. G. Thode, and H. C. Umy, ibid., 1939, 7, 137.10 C. A. Hutchison, D. W. Stewart, and H. C. Urey, ibid., 1940, 8, 532REES : ISOTOPE EXOHANGE M INORGANIC CHEMISTRY. 85extent in the liquid phase, whereas 13C is concentrated to a greater extentin the gas. The average production of 13C was 0.150 g. (in sodium cyanidecontaining 23% of 13C) per day.Base exchange reactions of zeolites with the chlorides of potassium,lithium, and ammonium are the basis of a method of isotopic concentrationof 41K, 7Li, and 15N.11 The concentration of these isotopes is made possibleby the difference in binding of the two isotopic ions with water and withzeolite in each case. Changes of 25% in the abundance ratio 'Li/gLi, andof 10% in 39K/41K and 14NW/14N15N were observed.Exchange Reactions involving Non-radioactive iTsobpes.-Exchange re-actions occurring with non-radioactive isotopes have been investigatedexhaustively in the cases of deuterium and to a less extent of the heavyoxygen isotope lSO and the heavy nitrogen isotope 15N.A very com-prehensive account of the exchange reactions involving deuterium has beengiven by H. C. Urey and G. K. Teal,l2 and they will not be further discussedhere.Interchange of 180 from heavy-oxygen water withsulphate ions was reported by S. C. Datta, J. N. E. Day, and C. K. Ingold 1sto be very slow in neutral solution at I O O O , whereas in alkaline solutionrapid interchange was found a t the same temperature. These workerspostulated a mechanism for the exchange, assuming the active agent to bethe hydroxide ion ISOH'.However, subsequent investigations by E. R. S.Winter, (Miss) M. Carlton, and H. V. A. Briscoe14 have shown that heavy-oxygen water, having an excess density due to l80 of 150-200 yd, doesnot interchange with sulphate in neutral, acid, or alkaline solution at 100'.It was suggested that the interchange observed by Ingold et al. was actuallyan interchange with silicate ions produced by alkali attack upon the glasscontainer. T. Titani and K. Goto 15 reported partial exchange of potassiumbisulphate with H,lsO and this has been confirmed by G. A. Mills,16 whosuggests that the mechanism responsible for the exchange is one of reversibleanhydride formation, H2S04 H,O + SO,, a reaction favoured by acidicconditions.A further investigation l7 confirms that no exchange occursbetween H21s0 and sulphate in neutral or alkaline solution, but that hydrogenchloride catalyses the exchange. The latter result is in good agreement withTitani and Goto, but not with Briscoe et at?., who used sulphuric acid.Furthermore, J. L. Hyde 18 has recently published results which indicatethat the H21s0 exchange with sulphate ions is catalysed by H but not byOH'. No exchange was observed in neutral solution. It appears that themost satisfactory mechanism is one of reversible anhydride formation inacid solutions, as was suggested by Mills.Oxygen exchange.l1 T. I. Taylor and H. C. Urey, J. Chem. Physics, 1938, 6, 429.l2 Rev.Mod. Physics, 1935, 7, 34.l6 J . Amer. Chem. SOC., 1940, 62, 2833.l7 N. F. Hall and 0. R. Alexander, ibid., p. 3455.l8 Ibid., 1941, 63, 873.l3 J., 1937, 1968.l5 Bull. Chem. SOC. Japan, 1939, 14, 77. J., 1940, 13186 INORCt ANTC CHEMISTRY.A similar situation obtains in the case of phosphate, where a basecatalysis has been reported by E. Blumenthal and J. B. M. Herbert l9 andT. Titani, N. Morita, and K. Goto,,O but could not be repeated when stepswere taken to eliminate the possibility of alkali attack on the glasscontainers .I4Chlorate and nitrate have been found by Briscoe et aZ.14 to interchangecompletely in acid solution, but not in neutral or alkaline solution, althoughother workers17 find that addition of acid has little influence on the non-exchange in nitrate.Rapid and complete exchange in neutral solution has been observedin the-case of SiO,”, BO,’, BO,”’, B 0 ”, Cr207”, CrO,”, MOO:’, Woe”,Cost’, MnO,‘, IO;, SeO;’, SO,”, S 2 4 ” , 7 A ~ 0 ~ ” , and AsOi, but not withNO,’, ClO:, ClO,‘, and SeO,”.141161 l7 It is- possible that the exchangemay take place in one of three ways : (i) Direct interchange of oxygen atoms.(ii) Addition, and subsequent removal, of water or hydroxyl ion to theanion with possible exchange.(iii) Formation of undissociated acid byhydrolysis, followed by reversible anhydride formation, as has alreadybeen formulated in the case of sulphate exchange. The experimental dataappear to be adequately explained by the last of these possibilities, for inall cases the rate of 1*0 exchange is related to the acid strength of thecorresponding acid.16Isotope exchange between gaseous oxygen and water vapour on catalyticoxide surfaces has been reported by N.Morita.,l For aluminium oxidesurfaces, it was found that the rate of exchange is almost independent ofthe composition of the gas mixture, indicating that the determining factoris the activated adsorption of water on the oxide surface. The activationenergy of this exchange is calculated to be 18-20 kg.-cals.The exchange of 15N between nitrogen di- andmon-oxide in the gas phase has given a very interesting confirmation ofthe structure of the dinitrogen trioxide molecule, which is known to occurin these mixtures.22Nitrogen exchange.The exchange reaction, wix.,1 4 ~ 0 + 1 5 ~ 0 , 1 5 ~ 0 + 1 4 ~ 0 ,was found to be rapid and only the lower limit of the exchange rate couldbe established.Assuming the intermediate formation of N,O,, the exist-ence of which has been demonstrated by measurements of the equilibriumconstant and by absorption-spectra data, the mere fact of exchange requiresan oxygen bridge in the N203 molecule, such as O=N-0-N=O. Thisstructure is to be expected on account of the symmetry of the resonancestate.Several recent investigations have been directed a t the possibility ofexchange between gaseous and combined nitrogen, in an endeavour toelucidate the mechanism of nitrogen fixation by plants. Exchange wasreported to occur between gaseous nitrogen containing radioactive 13N andeo Bull.Chem. SOC. Japan, 1938, 13, 329.22 E, Leifer, J . Chem. Physics, 1940, 8, 301.lB Trans. Faraday SOC., 1937, 33, 849.21 Ibid., 1940, 15, 47, 298REES : ISOTOPE EXCHANGE IN INORGANIC CHEMISTRY. 87solutions of sodium nitrite, sodium nitrate, hydroxylamine hydrochloride,and sodium hexanitrocobaltiate(II1) by Y. Nishina, T. Iimori, H. Kuto,and H. N a k a ~ a m a , ~ ~ but other workers, using heavy nitrogen gas (15N) 2 4 ~ ~ 5and radioactive nitrogen gas (13N),26 failed to observe any exchange withcombined nitrogen in solution. It appears, therefore, that the fixation ofnitrogen in plants does not occur by direct exchange of gaseous and com-bined nitrogen.The adsorption and nitrogen isotope exchange on iron, tungsten, andosmium catalytic surfaces have been investigated recently by H.S. Taylorand his co-w~rkers.~~~ 28 The exchange may be represented thus :28Nz + 30N2 =p Z28N30N and appears to be of the second order. Smallquantities of hydrogen were found to inhibit the exchange on osmium,and large amounts to suppress it, whereas on iron surfaces the presence ofhydrogen accelerated the exchange. This exchange process apparentlyrequires migration of atoms to positions favourable to exchange; in thecase of osmium, the adsorbed hydrogen (where the adsorption is some 15times greater than that of nitrogen) impedes this migration. The factthat the activation energy of exchange is 50 kg.-cals. for iron and 22 kg.-cals.for osmium surfaces indicates a greater lability of nitrogen on the osmiumsurface and a weaker Os-N than Fe-N bond.This is in agreement withthe stability of the known iron nitrides and the non-existence of analogousosmium compounds.Exchange Reactions involving Radioactive Isotopes.-Exchange reactionsbetween radioactive isotopes and inorganic compounds have been recentlydiscussed in an excellent and comprehensive review on artificial radio-activity by G. T. S e a b ~ r g . ~ ~ This section will be entirely supplementaryto Seaborg’s article, indicating only those radioactive exchanges of inorganicinterest which have been investigated in the last two years.L. C. Liberatore and E. 0. Wiig 30 have made a study of the exchangeof radioactive bromine (produced by the bombardment of selenium withprotons) with hydrogen bromide in the gas phase.Calculations indicatethat the postulate of an intermediate cluster of molecules would lead toan exchange rate some 10l2 times too small, whereas a chain mechanismleads to a rate of the same order as that determined experimentally. Freebromine atoms are produced by the reactions (where Br* indicates a radio-active bromine atom)H + BrBr* ---+ HBr $- Br*H + HBr* + H, + Br*a3 J . Chern. Physics, 1941, 9, 571.24 R. H. Burris and C . E. Miller, Science, 1941, 93, 114.25 G. 0. Joris, J . Chem. Physics, 1941, 9, 775.2* T. H. Norris, S. Ruben, and M. D. Kamen, ibid., p. 726.2 8 W. R. F. Guyer, G. G. Joris, and H. S. Taylor, ibid., 1941, 9, 287.28 Chem. Reviews, 1940, 27, 199.30 J . Chem. Physics, 1940, 8, 165.G.G. Joris and H. S . Taylor, ibid., 1939, 7 , 89388 INORGANIC CHEMISTRY.after which equilibrium is attained by the partition of the Br* betweenmolecular bromine and hydrogen bromide :Br* + Br, .+ BrBr* + BrBr* + HBr + HBr* -t BrW. F. Libby,31 however, on the basis of exchange carried out a t reducedradioactive concentrations, suggests that the alternative bimolecularmechanism of intermediate formation of HBr, is correct. Liberatore andWiig in a further publication32 report no exchange of radioactive brominewith gaseous ethyl bromide at room temperature, but on heating to 200-300" rapid exchange was found to set in. The fact that the C1-Br bond isweaker than the H-Br bond would require exchange of bromine with ethylbromide also to occur at room temperature if Libby's mechanism werecorrect. The atomic exchange mechanism requires activation energies of25 and <5 kg.-cab.for ethyl bromide and hydrogen bromide, respectively,the latter exchange therefore being the only one which can proceed at roomtemperature.Phosphoric acid containing radioactive 32P (half-life 14.3 days), in solu-tion with disodium hydrogen phosphate, has been used as an end-pointindicator in the volumetric estimation of cations which form insolublephosphates, e.g., Mg", Ag', Ba**, Pb.', Tho***, and U0,".33It has been shown that no exchange of radioactive 32P occurs betweenortho-, pyro-, and meta-phosphoric acids in acid or alkaline s0lutions.3~Furthermore, by using S2P as an indicator, the completeness of separationof meta- from other phosphoric acids by precipitation with barium ionshas been demonstrated, whereas in the precipitation of pyrophosphatewith Cd" a small amount of co-precipitation of ortho-phosphate occurs.Elementary radioactive sulphur (35S) has been shown 36 to exchangewith sulphur monochloride according to the reactionthe rate of exchange being directly proportional to the concentration of S,molecules.The most satisfactory mechanism involves a slow stages, + 86 + s,, followed by a rapid stage s, + s2c1, + 2S2c1,.Applications to the Chemistry of Complex Compounds.-Several recentinvestigations have demonstrated the usefulness of isotopic exchangereactions in solving problems associated with the chemistry of co-ordin-ation complexes.Up to the present, only radioactive exchange has beenemployed in this field, but with obvious success. A. A. Grunberg andP. M. Filinov36 have used radioactive bromine to demonstrate the freeexchange between the complex anions, tetrabromoplatinate(II), [PtBr,]",and hexabromoplatinate(IV), [PtBr6]", (containing radiobromine) andThis is in accordance with the experimental results.ClSSCl + 35ss, =+ c1s35sc1 + s,31 J . Chem. Physics, 1940, 8, 348.33 A. Langer, J . Physical Chem., 1941, 45, 639.34 D. E. Hull, J . Amer. Chem. SOC., 1941, 83, 1269.36 R. A. Cooley and D. M. Yost, d i d . , 1940, 82, 2474.30 Compt. rend. Acad. Sci. U.R.S.S., 1939, 23, 912.32 Ibid., p. 349REES : ISOTOPE EXOHANGE IN INORUANIC CHEMISTRY.89bromine ions in solution. This work has been extended by A. A. Griin-berg?' Codinnation of the existence of an equilibrium between Br' andthe above platinum complexes was obtained, as the exchange can take placeonly if the complex dissociates with subsequent recombination. The func-tional equivalence of the bromine atoms in the complex anions was demon-strated by the equilibriumK,[PtBr,*] L+ II,[PtBr4*] + Br,*Interchange between tho complexes themselves has also been establishedin the twa following observed exchanges :(i) KdPtBr41 + cis-[Pt(NH,),Br,*](ii) K2[PtBr4] + K,[PtBr,*] + K,[PtBr,*] + K,[PtBr,*Br,]K2[PtBr,*Br2] + [Pt(NH3),Br,]but, on using the radioactive isotopes of platinum and iridium, no exchangewas found to occur between stable complexes such as K,[PtCI,] and[Pt(NH,),Cl,] ; (NH4)2[IrC1,] and [Ir py2 cl,] ; (K€14)3[IrC1,] andH[Ir py2 Cl,,].Cobalt(II1) in certain complex compounds has been found not to ex-change with radioactive Co" ions in solution38 according to the expectedreaction Co" Co"'.The only stable forms of cobalt(II1) occur in cobaltcomplexes, and in aqueous solutions of these a small concentration of Co"'in equilibrium with the complexes is to be expected. However, exchangecould only be observed if (i) the exchange Go" + Co"' were operative,and (ii) the exchange were more rapid than the reduction of Co"' by water.As exchange due to electron transfer is very probable, then the failure toobserve it may be due to decomposition by reduction before measurableexchange can occur.F. A. Long39 has studied the exchange of oxalate ions with the tri-oxalato-compounds of the tervalent metals cobalt, iron, aluminium, andchromium (containing the radioactive 11C isotope). Exchange was foundto occur with potassium trioxalato-ferrate(II1) and -aluminate(III) ,K,[M(C,O,),], but not with the analogous chromium and cobalt compounds.Theoretical considerations indicate that the bonds in various co-ordinationcomplexes can approach either covalent or ionic types fairly closely. Wherestrong s-p-d hybridisation occurs covalent bonding is expected, as is indi-cated in the case of the cobalt and chromium complexes by the values oftheir magnetic su~ceptibilities.~O With aluminium compounds, however,s-p-d hybridisation is improbable, and in the case of the iron complexes,analogous complexes have been shown to possess bonds of the ionic type.Furthermore, the most recent work 40 indicates that Fe(II1) and Al(II1)complexes are not capable of resolution into optical isomers, and this shouldbe possible if the oxalate-central atom bonds were of the ionic rather thanthe covalent type. The resolution of Co(II1) and Cr(II1) complexes is awell-established fact, indicating covalent bond types. This is in complete37 Bull. Acad. Sci. U.R.S.S., SQr. Phys., 1940, 4, 342.38 J. F. Flagg, J. Amer. Chem. SOC., 1941, 63, 557.3* Ibid., 1939, 61, 570; 1941, 63, 1353.40 C. H. Johnson, Trans. Paraday SOC., 1932, 28, 84690 INORGANIC CTIEMTSTRY.agreement with the exchange measurements, where exchange is expectedonly in those complexes involving ionic bond types, such as those of Fe(II1)and AI(III), but not those of Cr(II1) and Co(II1).Exchange has been found to occur between mercuric iodide and am-monium iodide (containing radioactive iodine) when the complex (NH,),HgI,is formed and subsequently decomposed. Similar results have been obtainedin the reactions of ammonium iodide with bismuth iodide and lead iodidethrough the intermediate formation of the complex anions [BiI,]‘ anti[PbI,]”, suggesting that no essential difference exists between normal andco-ordinate covalencies in these complexes .41Although the isotope effect in band spectra of molecules has been wellknown for many years, only one case is on record where the visual colouror light absorption of a compound has been affected to a large extent byisotopic substitution. S. H. Maron and V. K. LaMer 42 have reported achange in the colour of the CH,*CH:NO,’ ion on substitution of the a-hydrogenatom by a deuterium atom. The addition of barium deuteroxide, Ba(OD),,to nitroethane in heavy water yields the colourless ion CH,*CH:NO,’, which,on addition of D,SO,, yields the compound CH,*CHD*NO,. Addition ofBa(OD), to this produces a light yellow colour due to the formation of theion CH,*CD:NO,’, according to the reaction2CH,*CHD*NO, + Ba” + 20D’ ---+ BCH,*CD:NO,’ + Ba” + 2HODAbsorption-spectra measurements of solutions containing this ion show anabsorption starting in the region hh 5000-5200 A. and continuing into theultra-violet. It is possible that similar differences in colour may be foundlater in inorganic isotopic pairs. A. L. G. R.H. J. EMEL~US.A. L. G. REES.A. J. E. WELCH.*I S. Chatterjee and P. Ray, J . Indian Chem. SOC., 1940, 17, 524.4 p J . Chem. Physics, 1938, 6, 299

ISSN:0365-6217    

DOI:10.1039/AR9413800065

出版商:RSC    

年代:1941

数据来源: RSC

摘要:

CRYSTALLOGRAPHY.1. INTRODUCTION.THIS Report is divided into four main sections, dealing with the morcphysical aspects of crystallography (Z), metal structures (3), inorganicstructures (4), and organic structures (5). Space does not permit a veryfull treatment of all these subjects, and in some cases it has been necessaryto confine the account to certain special topics only. Attention should bedrawn, however, to a number of general articles which have recently appeareddealing with various aspects of X-ray technique, including the determin-ation of equilibrium diagrams,l the accurate determination of lattice spac-ings,2 the construction of powder cameras,3 photometry,* and relatedsubjects.In last year’s Report we referred briefly to the subject of “diffuse”reflections from crystals, which are additional to the normal Laue pattern,and can be obtained with monochromatic X-rays.A very large amountof new literature on this subject has been published during the year, andthis is reviewed in Section 2 . At first sight, and taken as a whole, theeffect of these new contributions may be to confuse rather than to clarify.Nevertheless, the experimental study of the subject is now much morecomplete, and it is clear that the extra, non-Laue reflections may havemore than one origin. Some of these reflections are “ structure sensitive ” :they depend on the history and treatment of the particular crystal speci-men, vary but little with temperature, and are no doubt associated withsome kind of internal strain. On the other hand, we have the true “ tem-perature sensitive ” diffuse spots, which are greatly enhanced at hightemperatures and disappear at low temperatures. The balance of theevidence appears to indicate that the latter are due to elastic thermalvibrations in the crystal, which give rise to new regularities in the densitydistribution, and hence to new crystal reflections at high temperatures.In the field of metal and alloy structures (Section 3) relatively few newtypes have been discovered in recent years.There have been many im-provements in technique, however, and details of some of the earlier struc-tures can now be more accurately defined. A notable example of suchwork is the precise location of the carbon atoms in cementite, Fe,C.Anotherimportant field which is now being actively pursued lies in the study ofintermediate structures during transformations in the solid state, such asthe nature of the precipitation of copper in an alloy of copper and aluminium.Another interesting study of structural imperfections of another sort hasbeen carried out in the case of cobalt, and an explanation of the existencel A. J. Bradley, (Sir) W. L. Bragg, C. Sykes, J . Iron Steel Inst., 1940, 141, 63.H. Lipson and A. J. C. Wilson, J . Sci. Iwtr., 1941, 18, 144.A. J. Bradley, H. Lipson, and N. J. Petch, ibid., p. 216.J. M. Robertson, R. H. V. M. Dawton, and A. H. Jay, ibid., pp. 126, 12892 CRYSTALLOGRAPHY.of aharp and " fuzzy " diffraction lines in the X-ray photographs has beengiven.A large amount of new data has been obtained from the general in-organic structures (Section 4) and this includes many new values for inter-atomic distances, by both X-ray and electron-diffraction methods.A fewgeneral papers have been published, and a rather drastic revision of co-valent single bond radii for F, 0, and N has been proposed. One feelsthat the new values should be treated with some reserve until the numerousstructures which involve their use have been further studied by the mostaccurate methods. Some further interesting results have been obtainedduring the year among structures containing complex ions, and these includedata bearing on the constitution of the ferrocyanides. From the niobatesfurther information has been obtained on the nature of the 7-co-ordinatedcomplex, with the analysis of two almost equally stable types.Very few complete investigations have been made for organic structuresduring the year, and this field is reviewed briefly in Section 5.The natureof the intramolecular fold in a-keratin and a-myosin has been discussed atlength, and the result promises to be fundamental in protein structure, notonly for the fibrous proteins, but for the corpuscular or globular proteinsas well. It remains to be seen whether more detailed analysis of existingdata, when that becomes possible, will bear out and refine the new ideas.J. M. R.2 . TEMPERATURE EFFECTS IN THE REFLECTION OF X-RAYS FROMCRYSTALS.The Report for 1940 1 described preliminary experimental and theoreticalwork on the " diffuse " reflections found on well-exposed Laue photographsof many crystalline substances.The year 1941 has greatly increased theliterature on this subject, notably by means of a Discussion in the Pro-ceedings of the Royal SocietyY2-l1 by a series of papers in the Proceedings ofthe Indian Academy of Sciences,12-15 and in the Phygical Review,16-24 andby articles and letters inAnn. Reports, 1940, 37, 167.* G. D. Preston, Proc. Roy. SOC., 1941, A, 179, 1 (cf. 1939, A , 172, 116).3 (Mrs.) I(. Lonsdale and H. Smith, ibid., 1941, A, 179, 8 [28 Plates].4 (Sir) W. H. Bragg, ibid., pp. 51, 94.6 C. G. Darwin, ibid., p. 65. G. I. Finch, ibid., p. 67.8 M. Born and (Miss) K. Sarginson, ibid., p . 69.9 (Sir) C. V. Raman, ibid., pp.289, 302.10 (Mrs.) I(. Lonsdale, ibid., p . 315.l2 (Sir) C. V. Raman and P. Nilakantan, Proc. Indian Acad. Sci., 1940, 11, A, 379,13 ( S i r ) C. V. Raman and N. S. Nagendra Nath, ibid., 12, A , 83, 427.14 (Sir) C. V . Raman, ibid., 1941, 13, A, 1.15 S. Bhagavmtam and J. Bhimasenachar, ibid., 1940,12, A, 337; 1941,13, A, 266.l6 G. E. M. Jauncey md 0. J. Baltzer, Physical Rev., 1940,68, 1116; 1941, 59, 699.17 G. E. M. Jauncey, ibid., p. 456.18 G. E. M. Jauncey, 0. J. Bdtzer, and D. C. Miller, ibid., p. 908.6 (Sir) W. L. Bragg, ibid., p. 61.l1 H. A. Jahn, ibid., p. 320.389, 398; 12, A, 141LONSDALE : TEMPERATURE EFFECTS. 93The earliest example of diffuse reflection (by white radiation) is to befound on Laue photographs taken by Friedrich in 1913; this was correctlyinterpreted as a temperature effect by H.F a x h in 1923.35 A more com-plete mathematical treatment of the effect of thermal vibrations in crystalsgenerally upon the interference of X-rays was given, in terms of the earlierquantum mechanics, by I. Waller in 1925.36have verified Waller's formulae by means of a more rigorous quanfum-mechanical deduction. The first deliberate experimental test of this theory,which indicates that the diffuse reflection depends upon the crystal orient-ation and thus conflicts with the better-known Debye theory, was madoby J. L a ~ a l , ~ ~ who, using ionisation spectrometer methods and mono-chromatised Cu and Mo radiation, showed that the general predictions ofthe Waller theory were essentially correct for the crystals examined (potas-sium and sodium chlorides, aluminium, calcite, diamond, and a powderedspecimen of silver, the first over a temperature range of 289" to 665" K.).Preston 2* 29 independently made similar observations by photographicmethods; but his suggestion that the results could be interpreted by theassumption of small groups of atoms scattering independently of neigh-bouring groups, although receiving considerable early support,43 6~ 16, 179 25* 28was also adversely criticised.59 193 323 33(Sir) C. V. Raman and his collaborators, who put forward an entirelydifferent theory, vix., that the X-rays excite the characteristic lattice vibra-tions and are reflected with a very small change of frequency by the newstratifications of density thus set up,12, 139 149 26n 279 *O have published someexcellent diffuse spot photographs of sodium nitrate, calcium carbonate,and sodium chloride; and have shown that in the first case a big tem-perature effect exists which varies for the different crystal planes.Asomewhat different derivation of the thermal theory has been given byZachariasen 19 and it has been shown that the various reported results forpotassium and sodium chlorides 12, 16, 2o are in quantitative agreement withOther mathematicians 379 389W. H. Zachariasen, Physical Rev., 1941, 59, 207, 766, 860, 909.Zo S. Siege], ibid., p. 371 ; R. Q. Gregg and N. S. Gingrich, ibid., p. 619.21 P. Kirkpatrick, ibid., p. 452.23 (Sir) C. V. Raman and P.Nilakantan, ibid., p. 63.24 (Mrs.) K. Lonsdale and H. Smith, ibid., p. 617.2 5 (Sir) W. H. Bragg, Nature, 1940, 146, 509; 1941, 148, 112.26 (Sir) C. V. Raman and P. Nilakantan, ibid., 1940, 146, 523, 686 ; 1941, 147, 1 1 8.* 7 (Sir) C. V. Raman, P. Nilakantan, and P. Rama Pisharoty, aid., p. 805.28 G. E. M. Jauncey, ibid., p. 146.30 (Mrs.) K. Lonsdale, ibid., 1940, 146, 806; 1941, 147, 481.s1 H. A. Jahn and (Mrs.) K. Lonsdale, ibid., p. 88.32 M. Born, ibid., p. 674. 33 H. A. Jahn, ibid., p. 511.34 (Mrs.) K. Lonsdale and H. Smith, ibid., 1941, 148, 112, 257, 628.35 2. Physik, 1923, 17, 266. 36 Diss., Uppsala, 1926.37 M. v. Lam, Ann. Physik, 1926, 81, 877; 2. Krist., 1927, 65, 493.38 H. Ott, Ann. Physik, 1935, 23, 169.39 Conipt. rend., 1938, 207, 169; 1939, 208, 1612; Bull.SOC. franc. Min., 1939, 62,40 (Sir) C. V. Raman and P. Nilakantan, Current 8&, 1940, 9, 165.0. J. Baltzer, ibid., 1941, 60, 460.29 G. D. Preston, ibid., pp. 358, 467.137 ; C. Mauguin and J. Laval, Compt. rend., 1939, 208, 144694 CRYSTALT,OCtRAPT€Y.his formula, which, like those of Faxen and Waller, take account of theelastic constants of the crystal, since these influence the frequencies andamplitudes of the elastic (thermal) vibrations. Raman 93 14 and Nila-kantan23 claim, however, that their results for diamond provide the mostrigorous proof that it is the optical (characteristic) frequencies and not theacoustical (elastic) frequencies which are chiefly instrumental in giving theextra non-Laue reflections. Lonsdale and Smith, who have contributed awide experimental survey of the geometrical and physical conditions govern-ing the appearance of diffuse reflections for crystals of organic and inorganicc~mpounds,~ have shown that diamond is very far from being either anideal or a typical crystal.l0.24* 32 The relatively sharp anomalous reflec-tions from diamond, to which Raman and Nilakantan first called attention,are in fact due to some structure-sensitive cause. They are given in varyingintensity by normal diamonds, but are completely absent from photo-graphs of the (more perfect?) diamonds classed as type 11.41 They areonly slightly, if at all, temperature-sensitive. All diamonds show thediffuse " temperature " spots predicted by the thermal theory; these aregreatly enhanced at sufficiently high temperatures and disappear a t lowtemperatures, thus conforming to the usual behaviour of such diffnsereflections.The most reasonable conclusion appears to be that the structure-sensitivereflections found for normal diamonds are associated with some kind ofinternal strain.Lonsdale and Smith have pointed out 3* 24 that cleaved orfractured crystals frequently give non-Laue reflections which are quitedifferent in quality from the true diffuse reflections; and Kirkpatrick 21has reported an increase in anomalous reflecting power of cleaved calcitesurfaces, when ground, which is undoubtedly due to the presence of verysmall disordered crystal particles.It is clear, therefore, that care must be taken to distinguish betweenanomalous, structure-sensitive reflections due to crystal strains, whetherintrinsic or externally applied, and those diffuse reflections which aretemperature-sensitive and due to crystal vibrations.Jahn 33 has pointedout that if the extension of reflecting power about the normal (Bragg)reflecting positions is due to the finiteness of the reflecting crystal particles,the distribution will be essentially similar for different planes,42 whereas thedistribution of diffuse reflecting power due to the existence of elastic vibra-tions will be different for different planes; and he has illustrated the vari-ations to be expected in the latter case by application of the Waller formulato sodium single crystals,11,33 which are soft and elastically very aniso-tropic.An experimental investigation of sodium and lithium singlecrystals 34 has shown that the observable diffuse reflections, which aredetailed, intense, and persistent, are in entire agreement with the pre-4 1 (Sir) R. Robertson, J. J. Fox, and A. E. Martin, PhiZ. Tram., 1934, A, 232,42 M. v. Lam, Ann. Physik, 1936, 26, 55; M. v. Laue and K. H. Riewe, 2. Kri.st.,463; Proc. Roy. Sac., 1936, A , 157, 579.1936, 85, 408; P. P. Ewald, Proc. Physical Sac., 1940, 52, 167LIPSON : METAL STRUCTURES. 95dictions of the elastic vibration (thermal) theory, as interpreted by Jahn.The fact that these monatomic cubic crystals, for which no optical vibrationsare ~ I ~ O W I Q ~ do show diffuse reflections at all, is a strong indication that theobserved effects are due to the elastic thermal atomic vibrations.The factthat “ layer ” and “ chain ” type structures each give typical and easily-recognisable diffuse photographs has already proved to be of assistance incrystal-structure determination.a* If, as has been suggested, these diffusepatterns can in time be used to determine the elastic properties of singlecrystals at various temperatures, then it is clear that a new and usefulfield of research is being opened up. K. L.3. METAL STRUCTURES.It is perhaps natural that the rate of discovery of new alloy structuresshould now tend to diminish. In the first place, it is probable that allthe simple types of structure are known, so that any left are those whosedeterminations require much more time and patience.In the second place,interest in complicated structures is less, since they cannot be expected toproduce any important modification of the general rules for the occurrenceof the commoner structures such as the “ electron compounds ” (W. Hume-Rothery),l the ‘( interstitial compounds ” (G. Hiigg),2 and the (‘ AB,compounds ” (G. E. R. Schulze).3 Of the structures determined in aboutthe last two years only three-C~Mg,,~ A u ~ A ~ , ~ and CaZn, 6-seem t o benew ; others, such as V,Si 7 and Li,,Pb,,* are similar to established structures.There is evident, however, a tendency to go over the ground of earlierwork in order to clear up problems left unsolved. Cementite, Fe3C, is anexample of this.The detection of the carbon atoms by X-rays had previouslybeen considered almost impossible, but with accurate photometry and theuse of three-dimensional Fourier series, H. Lipson and N. J. Petch haveshown that they can be located unequivocally. Petch 10 has also beenable to detect the carbon atoms in austenite, the face-centred cubic solidsolution of carbon in iron.Improvements in technique have also shown that there are still problemsassociated with structures previously considered well established. H. Lipsonand A. R. Stokesll have found that thallium has a body-centred cubicS. Bhagavantam, Proc. Indian Acad. Sci., 1941, 13, A , 543.O4 (Mrs.) K. Lonsdale, PTOC. Roy. Soc., 1941, A , 177, 272; (Mrs.) K. Lonsdale,J. M. Robertson, and (Miss) I.Woodward, ibid., 1941, A, 178, 43.“ The Metallic State,” 1931, p. 328, Oxford.a 2. physikal. Chem., 1931, B, 12, 33.G. Ekwall and A. Westgren, Arkiv Kemi, Min. Geol., 1940, 14, B, 7.0. E. Ullner, ibid., 1940, 14, A , 3.W. Haucke, 2. anorg. Chem., 1940, 244, 17. ’ H. J. Wallbaum, 2. MetaElk., 1939, 31, 362.M. Albert0 and E. Arreghini, 2. Krist., 1939, 101, 470.J . Iron Steel Inst., 1940, 142, 95.a 2. Ekktrochem., 1939, 45, 849.lo I&id. (in press).l1 Nature, 1941, 148, 43796 CRYSTALLOGRAPHY.structure at 262", although it is commonly accepted as face-centred cubica t this temperature.12 A. Taylor and D. Laidler l3 have pointed out thatgraphite, when it is in a well-crystallised state, gives extra diffraction lineswhich have as yet received no convincing explanation.There is thusevidence that a survey of older work by the present more accurate methodswould be well worth while.Other improvements, such as the use of crystal-reflected radiation 1*and of cameras of large resolution,15 have opened up a new and importantfield of investigation-the study of the intermediate structures that formduring transformations in the solid state. Perhaps the most importantinvestigations have been those of G. D. PrestonI6 and A. Guinier 1' onthe change with time of an alloy of 4% copper in aluminium. At 500"this alloy is a solid solution; at lower temperatures the copper is graduallyprecipitated. This precipitation is accompanied by changes in hardness,and the effect-known as " age-hardening "---has been widely discussed.l*From X-ray photographs, Preston and Guinier, independently but in strik-ing agreement, have produced evidence of the exact nature of the pre-cipitation, and this must form an important point in the ultimate explanationof the phenomenon.Photographs of a single crystal of the alloyquenched from 500" show faint streaks as well as the ordinary reflections.That these streaks are associated with structural changes in the alloy isshown by the fact that their intensity increases with time.The conclusionwas reached that they are due to the formation of plates of copper atoms,and analysis showed that these plates must be parallel to the (100) planesof the aluminium lattice. The fact that the streaks are directed awayfrom the origin confirms the suggestion that they are due to the precipitationof atoms smaller than aluminium, and from their lengths it was decidedthat the plates are only about two atoms thick.Preston19 has continued the work by maintaining the crystal at 200"in the X-ray camera.As expected, the process continues a t a faster ratethan at room temperature; it also goes further, as the streaks, after becom-ing more intense, break up into spots. These, it was found, can be accountedfor by the formation OE a definite structure with a definite orientation withrespect to the aluminium lattice. The atomic arrangement of this, however,is not the same as that of the 8 phase20 which has been established byD. Stockdale21 as the equilibrium structure. Instead, the atoms adoptthe arrangement typified by calcium fluoride,22 and this is such that, withthe orientation found, it fits neatly on the (100) planes of the aluminiumlattice.The 8 structure cannot do this, and so it appears that the presenceThe evidence is as follows.l2 S. Sekito, Z. . K T i B t . , 1930, 74, 189.14 I. Fankuchen, ibid., 1937, 139, 193.l6 Froc. Roy. SOC., 1938, A , 167, 526.l8 " Age Hardening of Metals," 1940, Amer. SOC. for Metals, Cleveland.la Nature, 1940, 146, 130.l6 H. Lipson, ibid., 1940, 146, 798.l i Compt. rend., 1938, 206, 1641.Phil. Mag., 1938, 26, 855.J. B. Friauf, J . Arner. Chem. SOC., 1927, 49, 310721 J. Inst. Metals, 1933, 52, 111. " Strukturbericht," I, 1931, 148LIPSON ; MET& STBUCTURES.97of ready-made structural elements in the parent lattice can favour theformation of a structure that is not the one of lowest free energy.C. S. Barrett and A. H. Geisler 23 have made similar investigations ofan alloy of 20% silver in aluminium. This alloy is also a single phase at500" and its X-ray photographs also show streaks when it is quenched toroom temperature. The orientations of these streaks show that the planesof precipitation are the (111) set, and this fits in well with the structurethat is ultimately precipitated. This structure is that of AgsAl which hasbeen shown by A. Westgren and A. J. Bradley% to be close-packed hex-agonal with a random distribution of silver and aluminium atoms. It cantherefore fit on to the cubic aluminium structure since both are formed ofsimilar close-packed planes of atoms ; the relative orientations agree withthis suggestion.Barrett and Geisler think that there may be other ex-planations of the streaks, but G. D. Preston26 has published more datawhich tend to, confirm that given here.C. Samans26 has discussed the changes in the aluminium-copper alloyand has shown how the " calcium fluoride " structure can be derived fromthe plates of copper atoms formed initially.The alloy Cu,FeNi, has been shown by A. J. Bradley 27 to dissociate ina way which has some similarity to these other cases. In equilibrium a troom temperature this alloy contains almost equal amounts of two face-centred cubic structures; 28 this state is formed by the splitting-up of asingle face-centred cubic structure at about 800".At temperatures belowthis, diffusion is not very rapid and the process of change is slow, so thatby quenching the alloy after different times of annealing a t about 700" itcan be preserved in different stages of decomposition. X-Ray powderphotographs of the alloy quenched from 800" show, of course, only one setof spectra, while those of the alloy annealed a t 650" for one week showtwo sets due to the two phases. The intermediate structure, however,shows some lines (e.g., 222) that are double, as for the two-phase state,but others (e.g., 311) that have more comp0nents.2~ The explanation pro-posed by Bradley is that in this intermediate state two tetragonal structuresexist with a common (001) face.These two structures are nearly cubicbut one has an axial ratio greater than unity, the other, less. In this waythe two structures preserve their respective atomic volumes and yet retainmuch of their relation to the parent cubic lattice.A similar state of affairs has been found by electron diffraction for thedeposition of aluminium on platinum.30 The aluminium is constrained toadopt the slightly smaller spacing of platinum, but it preserves its atomic23 J . Appl. Physics, 1940, 11, 733.26 J . Sci. Iwtr., 1941, 18, 154.26 Amer. Inst. Min. Met. Eng., 1940, 137, 85.27 Proc. Physical Soc., 1940, 52, 80.28 W. Koster and W. Dannohl, 2. Metallk., 1935, 27, 220; A. J. Bradley, W. F. Cox,28 A. J. Bradley, W. L. Bragg, and C. Sykerr, J.Iron Steel Inst., 1940, 141, 113.so Proc. Roy. SOC., 1933, A, 141, 398.24 Phil. Mag., 1928, 6, 280.and H. J. Goldschmidt, J . Inst. Metals, 1941, 6'9, 189.REP.-VOL. XXXVIII. 98 CRYSTALLOGRAPHY ,volume by becoming tetragonal with an axial ratio greater than unity.This tetragonal aluminium can, however, exist only as unstable thin films.This is oneof the few elements whose structural history has never been satisfactorilye~tablished,~~ and specimens that have been heat-treated in the solid stateusually contain two phases, face-centred cubic and close-packed hexagonal.The hexagonal phase gives a remarkable mixture of sharp and “ fuzzy ’’diffraction lines, and the following explanation of this has been given by0. S. Edwards, H. Lipson, and A.J. C. Wilson.32Close-packed structures can be considered as composed of layers ofclose-packed atoms, each layer fitting neatly on the one below. Con-sideration of the figure shows that there are two possible positions in whichthe second layer can fit on the firstone, A ; these two positions are shownas small circles and crosses respect-ively. Suppose the second layer goesinto the B positions; then the thirdlayer can take either the first position, 0;o;o;o A , or the position C. A close-packedstructure can be built up of anyrandom arrangement of types ofplanes A , B, and C, the only limit-ation being that no two successiveplanes shall be the same. In practice,however, only two arrangements areof importance : ABCABCA . . .whichis cubic, and ABABABA . . . . which is hexagonal.Hexagonal cobalt approximates t o this second sequence, as is shownby the positions of lines on powder photographs. how-ever, that mistakes occur occasionally, the sequence changing fromABABABA , . . to, say, ACACACA . . . Some of the reflections, suchas the orders of 0001, will not be affected by the resultant faults; theseremain sharp; but all others will be blurred t o an extent depending onthe average size of the regions of perfect sequence and on the orientationof the reflecting planes.Oscillation photographs of cobalt33 bring out the peculiarity of thestructure very markedly. The sharp reflections are represented by ordinaryspots; the others are drawn out into streaks which nearly merge into oneanother forming long lines on the photographs with periodic maxima andminima.It is interesting that Barrett and Geisler 23 have suggested this samedefect as a possible cause of the streaks 011 their silver-aluminiumphotographs.Imperfections of another sort have been found in cobalt.0 ~ , o , O ,0 0;o;o;O+*@+O+O+FIU.1 .It is31 A. E. van Arkel, “ Reine Metslle,” 1939, p. 327, Berlin.32 Nature, 1941, 148, 166.s3 0. S. Edwards and H. Lipson, Proc. Roy. Xoc., 1942, A , (in press)POWETITi : INORGANIC! STRUCTTJRRS. 99The general use of X-rays in the study of the properties of metals andalloys has been well summarised by several recent publications. On thedetermination of equilibrium diagrams there are papers by A. J.Bradley,W. L. Bragg, and C. Sykes,u and by W. H~me-Rothery,~~ both summarisingseveral years’ work by their respective schools. The report of a conferenceon “ Internal Strains in Metals,” 36 organised by the Physical Society,contains many papers on X-ray investigations, particularly by W. A. Woodand by G. W. Brindley on distorted lattices; it also contains, in greaterdetail, much of the material in the present report. Finally, the Instituteof Physics has collected together a number of papers on the application ofX-rays to industrial problems,37 and on particular branches of X-raytechnique.38 These papers taken together form a useful review of thepresent state of development in the use of X-rays for the examination ofmetals. H. L.4. INORGANIC STRUCTURES.In a general discussion of the presentation of crystal chemistry, A.F.Wells 1 suggests that the most satisfactory classification of crystal structuresfor this purpose is one which is primarily geometrical, and based as far aspossible on observed interatomic distances. In a classification of thekind described, the first division, following Weissenberg, is into four groups,in which the complexes that may be distinguished in the structure arefinite, or infinite in one, two, or three dimensions. The recognition of thecomplex rests largely on interatomic distances, supported by the propertiesof the crystal. Sub-divisions are then made according as there are in thecrystal, structural units all of one kind or of more than one kind; furthersub-divisions arise according as the complexes are joined by van der Waals,hydrogen, or ionic bonds.The recognition of a particular type of geo-metrical complex does not imply any special bond type-inert gases, metalsand alloys, and ionic and homopolar crystals are all classed under crystalscontaining 3-dimensional complexes-but the scheme is designed to allowa discussion of the nature of the bonds in a given structure without theissue having been prejudged.Critical reviews of the classification of structures according to bond typeand of the sub-division of ionic structures according to electrostatic bondstrength are included, and the treatment of these topics in recent textbooksof crystal chemistry is discussed. In the detailed classification given, thechlorite minerals are by accident omitted as the example of a class contain-ing infinite two-dimensional ions of opposite charge.In another paper 2finite complexes in crystals are classified according to the number ands4 J . Iron Steel Inst., 1940, 141, 63.35 Research Reports of the British Non-Ferrous Metals Research Association,38 Proc. Physical Xoc., 1940, 52, 1.38 Ibid., p. 126.1941, No. 562.37 J . Sci. Inetr., 1941, 18, 69.Phil. Mag., 1941, [vii], 32, 106.2 A. F. Wells, ibid., 1940, [vii], SO, 103100 URYSTALLOORLPF€Y.arrangement of the atoms of one kind only, this being in general the moreelectropositive atom.K. Fajans3 discusses the effect of polarisation of ions on the departureof interionic distances from additivity in the oxides, fluorides, and hydridesof the alkali metals and the oxides and fluorides of calcium, strontium,and barium.The difference between the metal-oxygen and the samemetal-fluorine ion separations increases in the alkali-metal salts fromlithium to potassium, ie., in the order of increasing radius and decreasingfield strength of the alkali ion; the same is true for the difference betweenmetal-hydrogen and metal-fluorine distances, and a similar result is foundin the comparison of the oxides and fluorides of the doubly charge cationsCa**, Sr", and Ba". Since 0- and H- are more polarisable than F-, it isconcluded that the decrease in size of anion in the field of the cation con-tributes distinctly to the deviations from additivity.Further, since thedifference between the hydride and fluoride separations has a maximumfor the rubidium compounds, there is a second effect which is interpretedas a stronger " loosening " action of F- compared to H- on the more easilypolarisable of the cations.V. Schomaker and D. P. Stevenson propose a revision upwards of thecovalent single-bond radii of fluorine, oxygen, and nitrogen. They suggestN = 0.74 (0*70), 0 = 0.74 (0*66), F = 0.72 (0.64) ; the figures in parenthesesare those of L. Pauling and M. L. hug gin^.^ With the new values, whichare based on electron-diff raction results for hydrazine,6 hydrogen peroxide,sand fl~orine,~, many bond lengths which formerly obeyed the additivityrule are now less than the sum of the covalent radii r, + T,.The bondlength r, is obtained from the expressionTAB = rA + rB - P ( x A - xB);p = 0.09, xA and X, are the values of the Pauling electronegativities of thebonded atoms. It is inferred that the deviation from addivity representedby - p(x, - x,) is associated with the extra ionic character of the bondA-B as compared to the ionic character of the normal covalent bond betweenlike atoms.W. Hume-Rothery and G. V. Raynorg discuss the apparent sizes ofatoms in metallic crystals with special reference to aluminium and indium,and the electronic state of magnesium.Recent Structures.-From X-ray diffraction by Liquid and plastic sulphurat temperatures from 124" to 340" N. S. Gingrich10 has obtained atomicdistribution curves. The nearest neighbour for an atom in plastic sulphuris at 2.08, and at approximately 2-07 A.for liquid sulphur a t all temper-atures. In plastic sulphur each atom has two near neighbours, and theJ J . Chem. Physics, 1941, 9, 281. J. Amer. Chem. SOC., 1941, 63, 37.2. K T ~ s ~ . , 1934, 87, 205.P. A. Giguere and V. Schomaker, quoted in (4).M. T. Rogers, V. Schomaker, and D. P. Stevenson, ibid., 1941, 63, 2610.Proc. Roy. SOC., 1940, A , 177, 27.7 L. 0. Brockway, J . Amer. Chem. SOC., 1938, 60, 1348.lo J. Chem. Physics, 1940, 8, 29P0WEI;L : INORQANIC STRUOTUBHS. 101estimated number of neighbours for liquid sulphur is 1.7. This showsthat liquid sulphur is not a close-packed liquid, such as mercury. Also,if all the liquid consisted of closed rings, 2 near neighbours should be foundand the observed 1.7 means that an average of 30% of the atoms have oneneighbour only. The physical properties preclude the presence of S,molecules, but if the S, rings, that exist in the solid, break into chains onmelting, this gives approximately the right proportion of atoms with onlyone near neighbour.The disrupted rings may join to form irregular chainswith larger numbers of atoms.A. H. White and L. H. Germer 11 have made electron-diffraction experi-ments on extremely small crystallites of carbon deposited on silica bypyrolysis of methane, and conclude that this carbon-black consists ofpseudo-crystals, in each of which carbon atoms are hexagonally arranged,as in graphite, but successive atomic layers are displaced so that no regu-larities exist other than the uniform separation of the planes, and theregular arrangement of atoms in each of these.The spacing betweenplanes is found to be 3.6, A., 9% larger than the spacing, 3-35 A., in graphitecry st als.The unit cell and space-group of jamesonite, 4PbS,E’eS,3Sb2S,, havebeen determined, from single- crystal photographs.12 Powder photographsagree with those previously published, and it is shown that a previousattempt l3 to obtain the dimensions of the large monoclinic cell failedowing to the inherent limitations of the powder method. By electron-diffraction methods I. H. Usmani l4 finds that copper sulphide film formedelectrolytically and film formed by direct action of hydrogen sulphide oncopper crystals give structures which do not agree with the structure ofeither cuprous or cupric sulphide as given by X-ray studies.A re-examination of lead monoxide by W.J. Moore and L. Pauling l5has proved that the structure of the red tetragonal form is that previouslyreported by R. G. Dickinson and J. B. E’riauf,l6 and not that of G. R. Leviand E. G. Natta.17 In the structure now confirmed each oxygen has fourlead atoms arranged tetrahedrally around it and each metal atom is bondedto four oxygens which form a square to one side of it. It is suggestedthat the orbital arrangement of PbII (and of SnII) is that of a square pyramidwith four bonds directed from the metal within the pyramid towards thefour corners of the base, and a fifth orbital occupied by a stereochemicallyactive unshared pair, directed towards the apex.This stereochemical typeis in contrast with the trigonal bipyramid arrangement found for manyother compounds where the valency group is a decet, and it would be ofgreat interest to know whether it persists in finite complexes, or whether,like the trigonal prismatic arrangement for six bonds, it is confined to giantmolecules as in this structure. Stannous oxide has a similar structure tol1 J. Chm. Physics,, 1941, 9, 492.J. E. Hiller, 2. Krist., 1938, 100, 128-l6 J . Amer. Chem. SOC., 1941, 63, 1392.le Ibid., 1924, 46, 2461.l2 L. G. Berry, Min. Mag., 1940,25,597.l4 Phil. Mag., 1941, [vii], 82, 89.l7 N w o ah., 1926, 8, (3)102 CRYSTAT&OGRAPHY.lead momxide, but palladous and platinous oxides, though tetragonal,have a structure quite different in its essentials, which are that it is a com-promise arrangement whereby each metal atom has four neighbours at thecorners of a rectangle, O-M-0 = 82" and 98", and each oxygen has fournearly tetrahedral neighbouring metal atoms, M-O-M = 98" and 116";Tellurite, Te02,18 has a structure resembling that of brookite (TiO,),each tellurium being surrounded octahedrally by six oxygens.The relativedisposition of octahedra is the same as in brookite but is greatly deformed.In lithium hydroxide monohydrate19 each lithium is at the centre of atetrahedron of oxygens and two such tetrahedra share an edge in a reflec-tion plane while the upper and lower corners are shared with tetrahedrain the unit cells above and below, resulting in unending chains of pairedtetrahedra along one axis of the crystal.These chains are linked sidewaysby hydroxyl bonding. Between cornera of adjacent tetrahedra the 0-0distance is 2.68, and there are therefore hydroxyl bonds here, two reachingfrom each oxygen to other oxygens. The oxygens of the shared tetra-hedron edges in the reflection plane are shown to be in hydroxyl groups,and the oxygens of the upper and lower tetrahedron corners are in watergroups. The tetrahedra are linked sideways by hydroxyl bonding betweenthe hydroxyls and water.Li-O,, 1.95, Li-OnB,o 1.97, OOH-OH,O 2.68, OO,-OoH 3.74, OH,O-OHInO 3.48 A .The compound20 CoSe, has metallic properties and the iron pyritestype of structure.The inter-atomic distances now found are Co-Se 2.43 -j= 0.01, Se-Se 2.49 & 0.04.The latter value is a slight correction of an earlier reported value and isstill 0.21 A. greater than the Se-Se distance in crystalline selenium.The a-modification of iodic acid is orthorhombic. A structure deter-mination by M. T. Rogers and L. Helmholz 21 shows the existence of dis-crete 10, groups with 1-0 = 1.80 and 1-81 A,, and the 0-1-0 angles 96",98", and 101". Three oxygen atoms in positions approximately opposed tothe three bonded atoms are a t distances 2-45, 2.7, and 2-95 A. These com-plete a distorted octahedron of oxygen around the iodine, with three strongand three weaker bonds. In addition the HIO, molecules are held togetherby hydrogen bonds, the hydrogen atom of the hydroxyl group preferringin this structure to form two weak bonds (the bifurcated type) 22 to twoother oxygens, rather than one strong bond to one only of the availableoxygen atoms.Electron diffraction of nitric acid agrees with a planar model of thein~lecule.~~ There is an NO, group with N-0 = 1-22 for both distancesPd-0 = 2.01 0.01, Pt-0 = 2.02 & 0.02.Observed interatomic distances are :The cube edge has a = 54345 &- 0.005.T.Ito and H. Sawada, 2. Krist., 1939, 102, 13.19 R. Pepinsky, ibid., p. 119.fo B. Lewis and N. Elliott, J. Amer. Cheni. SOC., 1940, 62, 3180.*l Ibid., 1941, 68, 278.24 See Ann. Reports, 1940, 87, 193; 1939, 36, 181.2s L. R. Maxwell and V. M. Mosley, J. Chem. Physics, 1940, 8, 738POWELL : INORQ-ANTC STRUCTURES.103and angle 0-N-0 = 130", which is also found for nitrogen dioxide. Thethird oxygen is a t 1.41 & 0.02 A. from the nitrogen atom and equidistantfrom the other oxygen atoms. Methyl borate= has a planar BO, groupwith B-0 = 1.38 0.02, 0-C = 1-43 & 0.03 A., and angle B-O-C =113" & 3". Trimethyltriboranetrioxan 24 has the structure (I), which iscompletely planar, except for the hydrogen atoms.BB-O = 1-39 & 0.02 A.B-C = 1.57 & 0.03 A. / \(1.1 Q $)B B /O\ AA B B = 112" & P oCH, 0 CH,A1B,H12,25 by electron diffraction, has aluminium bonded to BH4 groupsa t angles of 120", making the molecule planar except for the hydrogen.The boron atoms are located near the centres of trigonal bipyramids formedby the four hydrogen atoms of each BH, and the central aluminium :A1-B = 2.14 -J-- 0.02, B-H = 1-24 & 0.04.Hexamethyldilead 26 gives byelectron diffraction Pb-Pb = 2.88 & 0-03 and Pb-C = 2.25 & 0.06 andhas a tetrahedral arrangement of the lead bonds. Electron-diff ractionmethods give values for interatomic distances in a large number of halidesof elements of Groups 11, IV, and VI. The cadmium halides27 are prob-ably linear, and Cd-C1 = 2.235 & 0.03, Cd-Br = 2.39 rfi 0.03, Cd-I =2-56 & 0.03. The halides of bivalent tin and lead are not linear : Sn-C1 =2.42 & 0.02, Sn-Br = 2.55 & 0902, Sn-I = 2.73 & 0.02, Pb-C1 = 2-465 &0.02, Pb-Br = 2.60 & 0.03, Pb-I = 2.79 &- 0.02. In the tetrahalides 28the distance from the central atom to halogen is for C-Br = 1-94 & 0.02,G I = 2.15 -J= 0-02, Si-Br = 2.14 & 0.02, Si-I = 2-43 0.02, Ge-Br =2.29 0.02, &-I = 2-50 & 0.03, Sn-Br = 2.44 & 0.02, Sn-I = 2.64 &0.04, Ti-C1 = 2.18 ,t0-04, Ti-Br = 2.31 & 0.02, Zr-C1 = 2.335 & 0.05,There is some uncertainty regarding the value given for Se-C1 in thetetrachloride, which is not quoted here.The discussion given on thedepartures from additivity in these and other interatomic distances mayrequire some modification in view of the proposed change in the standardcovalent radii referred to above. For thionyl bromide, D. P. Stevensonand R. A. Cooley 29 find S-Br = 2.27 & 0.02, Br-0 = 3-05 & 0.03, andBr-S-Br = 96" 2".Among structures containing complex ions is that of tetraphenylarsoniumiodide,m where the arsenic bonds are strictly tetrahedral : As-C = 1-95 A.Th-C1 = 2.61 -+ 0.03.24 S.H. Bauer and J. Y. Beach, J. Amer. Chern. SOC., 1941, 63, 1394.26 Idem, ibid., 1940, 62, 3440.26 H. A. Skinner and L. E. Sutton, Trans. Faruday SOC., 1940, 36, 1209.2 7 M. 1%'. Lister and L. E. Sutton, ibid., 1941, 37, 406.28 Idem,, ibid., p. 393.30 R. C. L. Mooney, ibid., p. 2965.29 J . Arner. Chem. SOC., 1940, 62, 2477104 CRYSTALLOGRAPHY.Details of the phosphorus pentachloride structure?l which is roughly ofthe cEsium chloride type with PC14+ and Pc16- ions, are the dist>ancesP-Cl (PCI,) = 1.98, P-Cl (PCl,) = 2-06 A. Barium fluosilicate and fluo-germanate32 have a l-molecule rhombohedra1 cell in a structure with aformal resemblance to caesium chloride, containing Ba++ and a nearlyregular octahedral complex anion.Bunsen’s salt 33 has the constitution(NH,),Fe(CN),Cl,, with a regular octahedral ferrocyanide ion and distinctC1- ions. The structure of hexamethylisonitriloferrous ~ h I o r i d e , ~ ~Fe( CNCH3),C12,3H20, gives a clue to the constitution of the ferr~cyanides.~~The hexagonal structure gives an accurate view of the octahedral complexcation with the atoms linked in the order FeCNC : Fe-C = 1.85, C-N =1-18 A. The iron-carbon distance is approximately that calculated for a50% single-double bond character of the link, as in L. Pauling’s suggestedformula 35 for the ferrocyanide ion ; the pure single- and double-bond lengthswould be 2.0 and 1-79 A., respectively.A bend of 7” a t the nitrogen atombrings the methyl groups out of line with an otherwise linear sequenceFeCNC, and provides additional evidence for the partial double-bondcharacter, since, although the form Fe-CEN-C is naturally linear, theform FG(=N\C would bend a t the nitrogen atom.Further work by J. L. Hoard and W. J. Martins6 on complex niobateshas led t o interesting results. They find that several salts which areobtained from but slightly different aqueous solutions contain complexniobate ions of different stereochemical types. K,HNbOF, is an aggregateof K+, HF2-, and octahedral [NbOF,]= ions ; &NbOF,,H,O also containsthe octahedral complex. I n GNbF, the [NbF,]= ion has the arrange-ment of seven bonds derived from the trigonal prismatic type for six bondsby the addition of an extra fluorine over one of the prism faces.s7 I nK,NbOF,, however, the group [NbOF,] has the alternative codgurationfor a 7-co-ordinated complex, derived from the octahedron by addition ofthe seventh atom over the centre of an octahedron face, a configurationwhich is found in K,ZrF,.3* It appears therefore that these two 7-co-ordinated types are about equally stable, and it would not be surprisingif both the [NbF,] = and [NbOF,] (or [ZrF,] =) groups should be found incompounds where they have the opposite configurations to those so farfound for them.Apart from the case of lead and tin monoxides referred to above, thestereochemical type for a group of ten valency electrons is usually derivedfrom the trigonal bipyramid, and a particularly interesting case is thatS1 D.Clark, H. M. Powell, and A. F. Wells, in publication.32 J. L. Hoard and W. B. Vincent, J . Amer. Chem. XOC., 1940, 62, 3126.33 H. M. Powell and G. W. R. Bartindale; see H. Irving and G. W. Cherry, J . ,34 H. M. Powell and U. W. R. Bartindale, in publication.s6 “ Nature of the Chemical Bond,” 1939, p. 235.30 J . Amr. Chem. Soc., 1941, 63, 11.mi^ G. C. Hampaon and L. Pauling, J . Am?. C h . SOC., 1938, 60, 2702.1941, 25.37 See Ann. Reports, 1939, 36, 170POWELL : INORGANIU STRUOTURES. 105where there are four attached groups. The arrangement found for [IO&?,]-and suggested for TeC1, 39 has now been observed by J.D. MoCullough andG. Hamburger 40 for diphenylselenium bromide. The molecule approx-imates very closely to a trigonal bipyramid with the two bromine ahmaopposed to each other a t the apices, and the phenyl groups in two of thethree equatorial positions : Br-Se-Br = 180" & 3", C-Se-C = 110" rt: lo",Se-Br = 2.52 & 0.01, Se-C = 1-91 -J= 0.03 A.Accurate quantitative methods of structure determination have beenapplied by S. H. Chao, A. Hargreaves, and W. H. Taylor41 to a typicalorthoclase, and confirm the essential accuracy of the felspar structurespreviously determined by qualitative methods. Co-ordinates for all atomsin the cell are determined to an accuracy probably better than 0.1 A. Thecell contents, 4KAlSi,O,, are treated as containing two groups of atoms" SSi, " and " 8SiII," which really oomprise l2Si and 4A.l atoms.In $hetetrahedral group of oxygen around SiI the Si-0 distances are within thelimits 1-66-1-70, and for SiII the limits are 1.57-1.60 A. It is assumedtherefore that while the SiI1 contain silicon only, the 8Si, with the slightlylarger average size of tetrahedron contain 4Si and 4A1 atoms, with a,randomdistribution among the atomic sites. The potassium ion is surrounded bynine oxygens in a group of rather irregular shape.S. H. Chao and W. H. Taylor42 by a detailed examination find thatthere are different types of lamellar structure of the soda-potash felsparsaccording as the proportion of soda felspar is less or greater than ca.30%.The low-soda type comprises monoclinic potash felspar with triclinic sodafelspar lamellze in mutual orientation characteristic of pericline twins, andthe high-soda structure comprises monoclinic potash felspar with triclinicsoda felspar lamella orientated in accordance with the albite twin law.The same authors 43 find for the plagioclase felspars of known compositionsranging from nearly pure soda felspar to nearly pure lime felspar, thatX-ray observations are consistent with the existence of two separate iso-morphous series. One, with the albite structure, extends from pure sodafelspar to at least 22% lime felspar, the other with the anorthite structureextends from pure lime felspar to 20-30~0 soda felspar. In addition,there is a group of intermediate plagioclases recognisable by a characteristicarrangement of subsidiary layer lines in c-axis photographs.Experimentalwork, but as yet no complete structure, has been reported for tricalciumaluminate 3Ca0,A120,.44 The cell is ecubic, a = 15.235 A. Libethenite,Cu,( OH)P0,,45 has deformed PO, tetrahedra, a deformed octahedral arrange-ment of four oxygens and two hydroxyls around some copper atoms, and a,pseudotrigonal-bipyramal grouping of four oxygens and one hydroxyl3Q Ann. Reports, 1940, 37, 181.41 Min. Mag., 1940, 25, 49842 Proc. Roy. Xoc., 1940, A, 174, 57.43 Ibid., 1940, A, 176, 76.44 L. J. Brady and W. P. Davey, J . Chem. Physics, 1941, 9, 663.46 H. Heritsch, 2. Krist., 1939, 102, 1.40 J . Arner. Chern. SOC., 1941, 63, 803106 CRYSTALLOGRAPHY.around other copper atoms, similar to the corresponding five-co-ordinatedgroups in andalusite, adamine, and 01ivenite.~~From a study of absorption and fluorescent spectra of yttrofluorite,N.Chatterjee 47 concludes that solid solutions of yttrium fluoride in calciumfluoride are of the substitution type, since the interstitial type would pro-duce greater disturbances than are observed in the spectra. The sub-stitution lattice persists up to 50% of YF,, but above this other crystaltypes develop. A. L. Greenberg andG. H. Walden 48 studied the system KMnO4-KC10,-H,O by equilibriumand X-ray methods. I n the continuous series of solid solutions of thesalts, Vegard’s additivity law is followed for the a and the c unit cell dimen-sions but not for 6 .The system NH,Cl-MnCI,-H,O shows three solid-solutionseries. I n one of these, interstitial inclusion of manganese in the ammoniumchloride lattice is accompanied by random substitution of water for NH,+to maintain electrical neutrality. The compound 2NH,C1,MnC12,2H,0 issimilar in structure to the corresponding cupric compound. It has beenfound 49 that the alkali sulphates a-K2S0,, cr-Na,SO,, and glaserite,(K,Na),SO,, constitute an isomorphous series of simple hexagonal structurewith the alkali alkaline-earth phosphates MIMIIPO,, and with the calciumphosphate-silicates, Ca,( SiO,,PO,), and the series may be expected toinclude other XO, groups.This trifluoride itself is not cubic.H. M. P.5. ORGANIC STRUCTURES.Very few new structures have been fully determined by accurate methodssince the last Report.A detailed analysis of the cis-form of azobenzenehas now been completed and the results of the Fourier analysis confirmin general the conclusions reported in the earlier analysis.2 The maininterest of this structure lies in the dimensional effects due to suppressionof resonance. The molecule is unable to attain a planar configuration,and hence structures of the type (I) cannot make any large contributionto the normal state. This is reflected in ameasured C-N distance of 1.46 A. (&O-03) ascompared with a corresponding distance of1.41 A. in the molecule of the t~ans-form.~There is also apparently a small distortionin the normal valency angles (N-C-C) in adirection which permits the two benzene rings to become as nearly coplanaras possible, while the approach of the non-bonded carbon atoms is main-tained at 3.3-3-4 A.//N-N\(1.1//-I \--! .L//46 See Ann.Reports, 1937, 34, 166.J. Chem. Physic8, 1940, 8, 645.49 M. A. Bredig, J . Amer. Chem. SOC., 1941, 63, 2533.G. C. Harnpson and J. M. Robertson, J., 1941, 409.Ann. Reports, 1939, 36, 183.J. J. de Lnnge, J. M. Robertson, and (Miss) I. Woodward, PTOC. Roy. Soc., 1939,4 7 2. Krist., 1940, 102, 246.A, 171, 398ROBERTSON : ORGANIC! STRUCTURES. 107A very detailed study by electron-diffraction methods has been carried out011 1 : 3 : 5-tribromobenzene, 4 : 5-dibromo-o-xylene, 5 : 6-dibromohydrindene,and 6 : 7-dibromotetralin with a view to observe the effect of strain onthe benzene ring (Mills-Nixon effect).In structures as complicated asthese it is not possible in any sense to measure all the interatomic distancesby electron diffraction, but the method consists rather in testing certainspecified models. It is concluded that the Mills-Nixon effect is concernedprimarily with changes in the contributions of the excited states of themolecule (which should lead to small but not easily measurable dimen-sional changes) and not with the “freezing” of the double bonds of thering into a particular Kekul6 structure.An interesting quantitative study of a fibre diagram has been recordedfor polyvinyl alcohol, [-CH,*CH( OH)-],.5 About 30 reflections have beentaken into account, and although the agreement between the measuredand the calculated intensities is poor, yet the essential outlines of the struc-ture appear to be clear.There are two chain segments (CH,*CH*OH) inthe unit cell (periodicity along the fibre axis, 2.52 A.). The long chainsof the molecule are so oriented that pairs of chains are linked throughhydroxyl bonds.Preliminary X-ray studies have been recorded for a number of com-pounds. Amongst these may be mentioned an extensive study of thianthren,selenanthren, phenazine, diphenylene dioxide, and related compounds byR). G. Wood and co-workers.sa 79 8 The structural work on these com-pounds should be of interest in view of existing work on their dipolemoments,g* 10 and the unsuccessful attempts which have been made toaccomplish their optical resolution,ll which have been attributed to in-sufficient rigidity in the molecule.The present work brings to light certaininteresting relationships in the crystal structures of these compounds,which do not appear to be too complicated for detailed analysis. Somepossible structurm are described, but as X-ray intensity measurementsare not even mentioned, it would be quite unprofitable for us to discussthese at present.The structure of melamine, C,N,H,, has been discussed by (Miss) I. E.Knaggs and (Mrs.) K. Lonsdale,12 the results being based on X-ray andmagnetic measurements. The amide structure is based on the cyanuricring, and is of a layer type similar to that of other compounds in this class.Amino-groups appear to be connected to the ring nitrogens of adjoiningA. Kossiakoff and H.D. Springall, J . Amer. Chem. SOC., 1941, 63, 2223.(Miss) R. C. L. Mooney, ibid., p. 2828.13. C. Wood and J. E. Crackstone, Phil. Mag., 1941, 31, 62.R. G. Wood, C. H. McCale, and G. Williams, ibid., p. 71.R. G. Wood and G. Williams, ibid., p. 115.G. M. Bennett and S. Glasstone, J., 1934, 128.lo (Miss) I. G. M. Campbell, (Mrs.) C. G. LeFBvre, R. J. W. LeFBvre, and E. E.l 1 G. M. Bennett, (Miss) M. Lesslie, and F. $2. Turner, J., 1937, 444.l2 Proc. Roy. SOC., 1940, A , 177, 140.Turner, J., 1938, 404108 CRYSTALLOURAPHY.molecules by means of weak hydrogen bridges. The results of more detailedX-ray measurements will be of interest.Sorbic acid13 has been analysed to a first approximation by means ofabsolute intensity measurements, and the orientation of the molecules isconfirmed by magnetic measurements, and by the shape and size of thediffuse spots occurring on well-exposed Laue photographs (see Section 2 ofthis Report).The magnetic anisotropy due to resonance in the conjugatedcarbon chain is shown to be about half as large as that in the benzene ring.The molecules, which are linked in pairs by hydrogen bonds, appear to liein rather favourable positions for accurate interatomic-distance measure-ments, but detailed work in this direction has not yet been completed.Symmetry determinations on a number of substituted stilbene anddibenzyl compounds l4 have been carried out, with results of importancein structural chemistry.A preliminary account of the X-ray analysis ofcalycanine, CI6Hl0N2, and of a series of substituted diphenyls,15 and a fullaccount of the structure of dl-alanine l6 by accurate methods have beenpublished, but details are not yet available.Sterok.-It is only possible to refer very briefly to a, comprehensiveaccount of the crystallography and chemistry of some eighty sterol deriv-atives which has now been published by J. D. Bernal, (Miss) D. Crowfoot,and I. Fankuchen.17 Following Bernal’s original X-ray studies,l8 whichgave a clue to the structural formula of cholesterol, the present work hasbeen carried on parallel with much of the chemical work of the last eightyears. The derivatives described belong mainly to the cholesterol and theergosterol series, but include calciferol and other photo-derivatives ofergosterol, and some higher plant and animal sterols.Crystallographicand optical data for all these compounds are classified in a number of con-venient tables, and a detailed study is made of the effect of substituentson the crystal structures. More detailed analyses, involving intensityobservations and Patterson projections on the (010) planes, have been madefor cholesterol chloride, bromide, and cholesteryl chloride hydrochloride,with results which confirm the earlier deductions regarding the shape andsize of the sterol mo1ecules, and give some indication of the arrangementof the carbon and halogen atoms in the ring system. No exact structuralanalysis determining the position of every atom in the molecule has yetbeen attempted.The present paper, however, is an essential preliminaryto such an undertaking, because it indicates those compounds which arecrystallographically simple enough to make such an attempt feasible. Fromthis point of view alone the survey is of extreme value, because many of the13 (Mrs.) K. Lonsdale, J. M. Robertson, and (Miss) I. Woodward, Proc. Roy. SOC.,l4 C. H. Carlisle and (Miss) D. Crowfoot, J., 1941, 6.l5 A. Hargreaves and W. H. Taylor, J. Sci. Instr., 1941,18, 138.l6 H. A. Levy and R. B. Corey, J . Amer. Chem. Soc., 1941, 63, 2095.l7 Phil. Tram., 1940, A, 239, 135.l8 Nature, 1932, 129, 277.1941, A, 178, 43ROBERTSON : ORaANIC STRUOTIJRES. 109outstanding structural problems of the sterols can only be solved by suchexact analyses.Protein Structures : Keratin and Myosin.-Perhaps the most hopefulapproach to any detailed picture of protein structure by X-ray methodslies in the study of the fibrous proteins keratin and myosin.Recently,Astbury and his co-workers 19* 2** 21 have given a new impetus and orientationto this field by their revised discussion of the nature of the intramolecularfold in a-keratin and a-myosin. The earlier theory of the transformationwhich takes place when these fibres are stretched, involving the openingof hexagonal rings (incidentally, this led to D. Wrinch's cyclol hypothesis)has been abandoned in favour of a reversible intramolecular fold of thegeneral type (11).This kind of fold permits the close packing of the side chains (R) in asimple, regular pattern, alternately on one side and the other of the planeU = Side chain up.D = Side chain down.of the fold.The model may, in fact, be reached bydeduction from the principle of close packing, whichis necessarily involved on account of the very Uniformdensities of proteins in general. The various ex-perimental and structural conditions, such as thelong-range elastic properties, and the fold repeatdistance of 5.1 A., then become consequences of theclose packing of the side chains. By means of sucha model it is possible to account for the great rangeof chemical constitutions in the keratin-myosingroup, merely by interchanging side-chain residues ;moreover, the fundamental structural similarities,as revealed by X-rays, are explained by the invariabIep ol ypep t i de skeleton.More detailed analysis of the structure is now ofgreat importance, and the data appear to be availablein certain new and very perfect photographs byMacArthur22 on porcupine quill.In these photo-graphs the striking feature that a large fibre axisperiodicity and its dominant orders are foundexpressible in 2m 3" terms of the probable amino-acidlength promises to be of great significance in elucidat-ing the actual sequence of amino-acid residues.Plant-virus Preparations.-J. D. Bernal and I.Fankuchen 23 have now published a very full preliminaryaccount of their X-ray crystallographic work ontobacco-mosaic virus, enation-mosaic virus, aucuba-mosaic virus, cucumberW. T. Astbury and (Miss) F. 0. Bell, Nature, 1941, 147, 696.2o W. T. Astbury, Chem. and Ind., 1941, 40, 41, 491.21 W. T. Astbury, J., 1942 (in publication) (Lecture to the Chemical Society, Nov.s2 Wool Rev., 1940, 9; unpublished work.20th, 1941).28 J . Oes. Phg&l., 1941,26, 111110 CRYSTALLOGRAPHY.virus, potato virus, and tomato bushy-stunt virus. The tobacco-mosaic viruspreparations were studied in most detail, and the recorded data refer chieflyto them. These preparations have a remarkable capacity for formingdoubly refracting aggregates. In dilute solution they exhibit flow orient-ation and other peculiarities indicating the presence of long, thin particles.In concentrated solution the orientation is spontaneous, and in fact anysmall region behaves like a uniaxial positive crystal. X-Ray investigationshows that even in solution the particles are equidistant, the distancebetween them depending on the concentration. At concentrations of 30?/,and over, gel-like properties are found, and the preparations become stifferas the water content decreases, but there are no abrupt transitions. Theforces maintaining the particles equidistant and parallel in the gel areattributed to the ionic atmospheres surrounding them, and there is no doubtthat the results obtained in this field will have wide extensions to othercolloid systems.The arrangement isSO perfect that each specimen is in fact a two-dimensional single crystal.It is concluded from the evidence that the virus preparations consist ofparticles of about 150 A. in diameter and with a minimum length of 1500 A.24These extraordinary particles are in a sense intermediate between themolecule and the crystal. With regard to inner structure there is evidenceof the existence of sub-units of approximately 11 A . ~ fitted together in ahexagonal or pseudo-hexagonal lattice of dimensions a = 87 A . , c r= 68 A.The particle itself seems to be virtually unchanged by drying, and so mustcontain but little water. In the case of bushy-stunt tomato virus there isevidence of spherical rather than long particles, and so it seems likely thatthe elongated particle form has no essential biological significance.In the dry gel the interparticle distance is 152 A.J. M. R.H. LIPSON.(Mrs.) K. LONSDALE.H. M. POWELL.J. M. ROBERTSON.za G. A. Kausche, E. Yfankuck, arid H. Rusktt, Nuturwiss., 1939, 27, 292

ISSN:0365-6217    

DOI:10.1039/AR9413800091

出版商:RSC    

年代:1941

数据来源: RSC

摘要:

ORGANIC CHEMISTRY.I. INTRODUCTION.A DISCUSSION on the “ Mechanisms and Chemical Kinetics of Organic.Reactions in Liquid Systems” was held by the Faraday Society in Sep-tember, 1941, and the complete text of the various contributions is nowavailable.1 A wide field was covered, including aliphatic substitution,elimination reactions, esterifkation and hydrolysis, additions to olefiniccompounds, nuclear and side-chain substitution in aromatic compounds,condensations of carbonyl compounds, prototropic and anionotropic changes,the Cannizzaro and the Friedel-Crafts reaction, ring closure, and reactionsinvolving radicals. Many of these have been dealt with in the AnnualReports of 1 9 3 8 4 0 , and in Part 2 of the present section some recentinvestigations of condensations, alkylation reactions, rearrangements, andthe influences of groups in ortho-positions are summarised.The values ofdissociation constants in a single solvent and a t an arbitrarily fixed tem-perature have long been accepted as providing a correct series of relativestrengths of acids and bases, and hence of the polar effects of substituents;the justification for this conventional view is examined in this Report.Systematic organometallic chemistry has been extended by the dis-covery, in triethylscandium and triethylyttrium, of the first purely organicderivatives of the transitional elements ( L e . , those “ framed ” in Bohr’sPeriodic Table) showing the group valency. Gallium and indium com-pounds have been studied in more detail, the simple organic types R,Tland Me,Pt have been prepared, and organic derivatives of titanium, vanad-ium, tantalum, molybdenum, tungsten, manganese and rhenium are reported.The formulation of the curious phenylchromium compounds has been recon-sidered, and that of the dimeric trimethylaluminium presents a problem invalency theory.Numerous compounds of the heavy metals have beenprepared from R*B( OH),, R*SO,H, R*HgCI or especially R-N,CI, by treat-ment with the metallic halide; in this way it is possible to prepare organo-metallic compounds containing hydroxyl or other reactive substituents.Alkyl, and sometimes aryl, residues attached to mercury or elements of the tingroup undergo remarkably facile disproportionation in presence of catalysts ;e.g., Me,Hg + Et2HgZ2MeEtHg.All this work is dealt with in Part 3of this section.It is now possible to present a general picture of the chief structuralpatterns upon which the natural polysaccharides are built, and to pick outcertain definite types (see Part 4). The polysaccharides may be describedas “ simple ” or “ complex ” according to whether they are composed oft3he same or varied monosaccharide building units; thus, starch conld be1 Trans. Faraday Soc., 1941, 37, 601112 ORGANIU CHEMISTRY.described as “simple” in that it is composed solely of glucose, whereasarabic acid is “ complex,” being constituted of galactose, glucuronic acid,arabinose, and rhamnose. A second method of classification depends uponthe observation that in many well-known polysaccharides the glycosidiclinkages between monosaccharide units are mainly or entirely of one type.For example, only p-1 : 4-glycosidic links occur in cellulose, a-1 : 4-links inpectic acid, and 8-1 : 4-linkages in alginic acid.On the other hand, thearabans which are found in constant association with pectins are composedof arabofuranose residues combined by 1 : 5- as well as by 1 : 3-glycosidiclinks; yeast mannan is constituted solely of mannopyranose units, butthree types of linkage, 1 : 2, 1 : 3, and 1 : 6, are present; in srabic acid,1 : 3-, 1 : 6-, and 1 : 4-links are found. Damson gum, which is probablybuilt on the game structural pattern as arabic acid, is known to contain1 : 2-glycosidic linkages; this type of union is commonly associated withmannose residues, just as 1 : 3-links are often found associated with galactose(e.g., in agar) and 1 : 4-links with glucose.A third basis for the classi-fication of polysaccharides is illustrated as follows. Cellulose, starch, pecticacid, alginio acid, laminarin, and dextrans have unbranched chains ofmonosaccharide residues, but in many other polysaccharides the repeatingunits are more or Iess highly ramified structures, a feature which is shownparticularly by the plant gums (e.g., gum arabic, damson or cherry gum),and found also in the simple arabans, galactans, yeast mannan, in the poly-saccharide associated with /%amylase, and in the mucilages. Snail galactogen(containing d- and I-galactose) differs from agar in possessing a branched-chain repeating unit.The plant gums and the mucilages are thereforecomplex ” in two senses; they contain more than one type of mono-saccharide unit and these are united by more than one kind of glycosidiclinkage. In addition, these natural products are acid polysaccharides, theacid character being contributed by the uronic acid residues, glucuronicacid in the former and galacturonic acid in the latter. I n all the substancesmentioned above, the repeating units contain one residue with a free reduc-ing group and it is by virtue of this that aggregation takes place. A carbo-hydrate isolated from egg-albumin is of great interest in that, although itis constituted on a similar plan to the others, it appears not to be a truepolysaccharide; the smallest unit in its structure is composed of elevenmonosaccharide residues and does not display a free reducing group.Thiscompound is perhaps more correctly described as a non-reducing hendeca-saccharide; about 60% of it is composed of N-acetylglucosamine, theremaining residues being of mannose and galactose.The most recent development in the chemistry of starch has been therecognition of the probability that it contains a t least two componentswhich are structurally different. One of these, amylopectin (or erythro-amylose), forms 80-95~0 of the whole starch, and is composed of aggregationsof repeating units which are themselves constituted of chains of 24-30glucose residues linked by a-1 : 4-glycosidic bonds. It has now been demon-strated that the polymeric links between the repeating units are a-1 : 6-(INTBODUCTION.113glycosidic. The second component of starch (amylose or amyloamylose)appears to be composed of much longer chains (100-300 glucose members),which may not form aggregates; it is perhaps identical with Hanes’ssynthetic starch, the chain-length of which has been shown to be a t least80 to 90 glucose residues. Amylose and synthetic starch are each degradedcompletely to maltose by p-amylase, whereas with amylopectin thedegradation ceases a t 60% conversion.Part 5 of this section reviews recent studies of the synthesis of aliphaticand aromatic compounds containing a multiplicity of conjugated ethyleniclinkages (polyenes), which have led to the discovery of new syntheticroutes and also to the improvement and extension of the classical syntheticmethods.Investigations have also been directed towards the synthesisof the more complicated naturally occurring polyenes such as the caro-tenoids and vitamin A, and although no outstanding successes have as yetresulted, the preparation of material possessing some vitamin A activityhas been reported and a number of promising intermediates have beenobtained. Aldehyde condensations of fundamental importance in thesynthetic polyene field, particularly those of citral with aldehydes, havebeen investigated in some detail from the preparative aspect. Higherpolyene carboxylic acids have been made available, and from them directsyntheses of palmitic and stearic acids have been achieved.Two newroutes to the polyene dicarboxylic acids have also been developed, a biologicalpreparation presenting novel features.A considerable number of papers on polyterpenes have appeared duringthe period under review ; these are distributed fairly evenly between sesqui-terpenes and allied substances, diterpenes and triterpenes. In view oflimitations of space, Part 6 of this section deals only with abietic acid andthe p-amyrin and lupeol groups of triterpenes. The vexed question of thelocation of the ethylenic linkages in abietic acid has been finally settledby the elegant degradation experiments of Ruzicka and co-workers ; theacid has the structure (I). Considerable progress has been made in thep-amyrin group of triterpenes, although it cannot be claimed that the basicstructure of the group has been elucidated.It now comprises at least tenmembers, each of which has been transformed into p-amyrin or an estab-lished derivative. Betulin has been converted into lupeol, and the longsuspected difference between these triterpenes and the members of thep-amyrin group has been established by the proof that the former containan isopropenyl side chain. The presence of this unsaturated centremeans, according to Ruzicka and Rosenkranz, that the lupeol groupcannot be hydropicene derivatives, a conclusion which invokes the isoprenerule.Following the discussion of natural naphthaquinone pigments in theAnnual Reports for 1939, a review is now given (Part 7) of the presentstate of knowledge of the large group of natural colouring matters whichare derivatives of benzoquinone, naphthaquinone, phenanthraquinone, andanthraquinone.In the benzoquinone group, particular interest attache114 OR0 ANTC CHEMISTRY.to the simple quinones produced by certain fungi and to perezone, whichis closely related to the sesquiterpenes. Similarly, tanshinone I is note-worthy among the derivatives of phenanthrene, since the available evidencesuggests a relationship with the diterpenoids. Degradative evidence hasbeen adduced in favour of the view that the antihsmorrhagic vitamin K,is 3-difarnesyl-2-methyl- 1 : 4-naphthaquinone, and work on the naphtha-quinone pigments of sea urchin eggs has recently been extended. Echino-chrome A, the sols pigment isolated from fully mature ovaries of Arbacia,i q accompanied in ovaries collected a t different seasons by echinochromesB and C; echinochrome A appears to exist in the eggs as a complex ofhigh molecular weight, which is more potent than the free pigment inconferring motility on spermatozoa.Considerable attention has beendevoted in recent years to the production of anthraquinone derivatives bymoulds, and an account is given of pigments of this type isolated fromHelminthosporium, Penicillium, and Aspergillus species. Investigationson mould pigments from Penicilliopsis and on hypericin, the photodynamicpigment of St. John’s wort, have revealed striking resemblances betweenthem, and the interesting suggestion has been made that hypericin andoxypenicilliopsin may be helianthrone derivatives.The reactivity of heterocyclic nuclei towards cationoid and anionoidreagents, and of methyl side-chains towards aldehydes, has been dis-cussed in general terms, and much experimental work reported.Numerousnuclear transformations of furans, pyrroles and the azoles are recorded,most of which depend upon ring fission and re-synthesis to another hetero-cyclic type. An interesting new case of stereoisomerism depends upon thehindered rotation of the substituted benzene nucleus of a quinol poly-methylene ether (11) relatively to the (moderately) large ring. The simpleoxygen-ring compound dioxadiene has been prepared. Interest in corn -pounds related to vitamin E has led to a thorough study of methods forthe synthesis of chromans and coumarans.Some twenty quinoline homo-logues have been isolated from straight-run gasoline ; their structures havebeen established and show some curious regularities. Evidence is sub-mitted that a nucleus C,N,, consi&ing of three fused cyanuric rings, ispresent in melem, cyameluric acid and other long-known products of thepyrolysis of thiocyanates. The pterins, pigments occurring in the wingsof butterflies and in other insects, are now found to be relatively simplecompounds closely related to the purines ; leuco- and xantho-pterins havebeen synthesised from 2 : 4 : 5-triamino-6-hydroxypyrimidine with oxalicand dichloroacetic acids respectively. These advances in the chemistrWATSON : PHYSICO-ORGANIC TOPICS. 115of heterocyclic compounds are summarised in the final part (8) of thissection of the report.J.F. J. DIPPY.E. R. H. JONES.8. PEAT.F. S. SPRING.T. S. STEVENS.,4. R. TODD.H. B. WATSON.2. PHYSICO-ORGANIC TOPICS.(a) Mechanisms of Condensations and Alkylation Reactions.The mechanisms of condensations of the aldol, Knoevenagel, Perkin andClaisen types were discussed in the AnnuaZ Reports for 1939,l where referencewas made to the recent work of C. R. Hauser and his collaborators.2 W. G .Brown and K. Eberly have now investigated the base-catalysed exchangeof hydrogen for deuterium between a number of esters and deuteroalcohol,EtOD, and they find that the facility of exchange may be correlated with thereactivity of the ester in the Claisen condensation.For a series of estersR*CH,*CO,Et where R is varied, the order is Ph > H > Me > Et > Pra> C,,H,, > C,&, > cyclo-C6Hll > Prs; a second alkyl group as inCHMe,*CO,Et leads to a further decrease in reactivity. The correlationis not a quantitative one, however, and the authors suggest that the influenceof structure upon reactivity in the Claisen condensation is threefold, beingmanifested in the extent of the initial anion formation? the rate at whichthe anion reacts with the second ester molecule? and the extent to whichthe equilibrium is shifted by salt formation on the part of the p-keto-ester.A similar correlation between deuterium exchange and alkylation in malonicesters R*CH(CO,Et), is suggested.The investigations of C.R.'Hauser and co-workers have been extendedto include a study of reactions of the Michael type, i.e., the addition of acompound having incipiently-ionised hydrogen at an olefinic linkage whichis rendered susceptible to the attack of a nucleophilic reagent by an adjacentgroup :>c--$-x + >CH-X~ --+ >Y-hH-X(Component A) (Component B) - >c-X'In the most familiar examples, where X and X' are carbonyl or ester group-ings, this becomes :C. R. Hauser and B. Abraniovitch 4 represent this condensation (the revers-Soe also J . Amer. Chem. SOC., 1940, 82, 62, 593,Ibid., p. 1763.A ? m Reports, 1939, 36, 210.Ibid., p. 113116 ORGANIC CHEMISTRY.ibility of which was demonstrated twenty years ago 5, by a scheme whichis completely analogous to that usually accepted for the aldol, Knoevenageland Perkin reactions (B- = OEt’, CPh,’, or other basic catalyst) :>CH-V=O + B- >C-Y=O + HBThe factors which influence the Michael condensation, and the effectsof structure upon reactivity, have been summarised by R.Connor andW. R. McClellan.6 The groups which may function as X or X’ are CO,R,COR, CHO, CN, CO-NH,, NO,, S0,R (references to typical examples arequoted), and component A may be acetylenic rather than olefinic. Theoccurrence of other reactions (see below) is avoided by using as catalyst asecondary amine such as piperidine, but the change is slow, and long reflux-ing is necessary even in favourable cases; one-third t o one-sixth of anequivalent of sodium ethoxide may bring about condensation where aminesare ineffective (Hauser and Abramovitch used the still more powerful agentsodium triphenylmethyl), and long standing at room temperature now yieldsthe best results.As solvent, methyl and ethyl alcohols, benzene, ether anddioxan have been used satisfactorily. Substituents in either componentusually decrease rea~tivity,~ but there are exceptions and, as suggestedoriginally by C. K. Ingold, E. A. Perren, and J. F. Thorpe,8 both spatialand polar influences may be involved.Actually the products obtained under the conditions which lead to theMichael condensation are of three types : ( a ) in presence of a small quantityof sodium ethoxide or piperidine the product is normal; ( b ) one equivalentof ethoxide leads, in some instances, to a “ rearrangement product,” e.g.,CH,CH:CH*CO,Et CH,CH *CH (CH,) *CO,Et + + I* CH,*CH( CO,Et), CH( CO,Et),(c) there are sometimes “ rearrangement-retrogression products,” whichcould arise from the cleavage of a rearrangement product, e.g.,Ph*CH:CH*COPh + CH,*CH( CO,Et),PhCH CH(C0,Et)COPh+ I CH,*CH*CO,Et J.Ph*CH:C( CH,)*CO,Et + Ph*CO*CH,*CO,EtThe formation of “rearrangement products,’’ according to the views ofJ. F. Thorpe 10 and of A. Michael and J. Ross,11 depends upon the cleavageti C. K. Ingold and W. J. Powell, J., 1921,119, 1976.9 See R. Connor and D. B. Andrews, J . Amer. Chem. SOC., 1934, 56, 2713.lo J., 1900, 77, 923.J . Org. Chem., 1939, 3, 570. 7 See also ref.9. J., 1922, 121, 1771.11 J . Amer. Chem. SOC., 1930, 52, 4608WATSON : PHYSICO-ORGANIC TOPICS. 117of the substituted malonic ester into portions such as CH3 and CH(CO,Et),,but N. E. Holden and A. Lapworth la postulate a normal addition, followedby migration of carbethoxyl (or similar group), a view which has beensupported more recently by J. A. Gardner and H. N. Ryd0n.1~Although the most familiar condensations of the aldol, Knoevenagel,Perkin, Claisen and Michael types occur under the catalytic influence ofbases (electron-donators) , examples of catalysis by acids (electron-acceptors)are known. D. S. Breslow and C. R. Hauser l4 have now carried out anumber of condensations in presence of the electron-accepting agents boronfluoride and aluminium chloride.These include the condensation of aceticanhydride with acetophenone (Claisen type) and the condensation of benz-aldehyde with malonic ester and with acetic anhydride (only a small yieldof cinnamic acid was isolated, however). The reaction of benzaldehyde withethyl malonate was followed by a Michael addition, giving ethyl benzylidene-dimalonate. I n presence of boron fluoride, ethyl acetoacetate is alkylatedboth by benzyl chloride l4 and by isopropyl acetate l5 [givingand CH,*CO-CH( CHMe,)*CO,Et respectively].I n a general discussion of reactions of the types referred to above, C. R.Hauser and D. S. Breslow l6 point out that component B is always a com-pound having incipiently-ionised hydrogen, and component A may be analkyl halide (alkylation of ethyl acetoacetate, etc.), an aldehyde or ketone(aldol, Knoevenagel, Perkin), an ester, anhydride or acid chloride (Claisen),or a suitably activated olefinic compound (Michael).In accordance withthe usually accepted view,l they suppose that bases activate component Bby converting it into anion, whereas acidic (electron-accepting) catalystsactivate component A by forming a co-ordination complex. For a givencomponent A, the eage of condensation should follow the activity of thelabile hydrogen of component B, and they quote examples to 8how thatsuch is the case. Further, compounds which are not sufficiently reactiveto function as component A in presence of a base might do so under theinfluence of an acid catalyst, and it is found that both diisopropyl etherand isopropyl alcohol condense with acetoacetic ester in presence of boronfluoride.Hauser and Breslow envisage the possibility of an attack of thecatalyst upon both reacting substances ; for example, an acidic catalystmight, in addition to activating component A, also co-ordinate with carbonyloxygen in component By and a basic catalyst might form an addition com-plex with component A. The last possibility was considered in the AnnualReporb for 1939.l I f the base co-ordinated with component A to give acomplex possessing sufficient energy to react with component B, the energyof activation would be needed for the formation of this complex, and wouldbe influenced by constitutional changes in A, but almost indifferent tochanges in B.This is actually the case in the reaction of benzaldehydeCompare EL Meerwein, Ber., 1933, 66, 411.CH,*CO*CH( CH,Ph)CO,Etl2 J., 1931, 2368. 13 J., 1938, 48.14 J . Amer. Chem. Soc., 1940, 62, 2385.16 J . Amer. Chern. Soc., 1940, 62, 2611. l6 Ibid., p. 2389I18 ORGANTC CHEMISTRY.with acetophenone in 90% alcohol with sodium ethoxide as catalyst.17There are, however, objections to this mechanism of basic catalysis,lB andfurther experimental studies are necessary.The rate of the reaction of benzaldehyde with acetophenone is propor-tional to the concentrations of both; l7 on the other hand, the aldol con-densation of acetaldehyde is of the first order with respect to the aldehyde,and the corresponding reactions of acetone and isobutyraldehyde are of thesecond and an intermediate order respectively .l9The influence of aluminium chloride and boron fluoride upon thesecondensations, referred to on p. 117, finds an analogy in the catalytic effectof boron fluoride in the esterification of acetic, propionic and a number ofaromatic acids by various alcohols, observed by J. A. Nieuwland and co-workers,20 who suggest that the mechanism is doubtless similar to that ofthe hydrion-catalysed reaction ; addition compounds of boron fluoride withacids, alcohols, and esters are known to exist.21 Esters are also formedwhen alcohols react with amides in presence of boron fluoride,22 and by thereaction of acids with olefins under the influence of the same catalyst ; 23boron fluoride also catalyses the acidolysis of esters.=A consideration of some aspects of the Friedel-Crafts reaction forms anatural sequel to the above, although boron fluoride is apparently noteffective in nuclear alkylation by alkyl halides,25 nor has it been employedin acylations by the Friedel-Crafts method.In the AnnuaE Reports for1937,26 reference was made to the use of substances other than alkyl halides(alcohols, ethers, esters, olefins) for alkylation in presence of aluminiumchloride, and similar processes have been oarried out with boron fluorideas the catalyst. anisole 29 and all threehydroxybenzoic acids have been converted into nuclear isopropyl deriv-atives by propylene in presence of boron fluoride (in $he case of phenol andthe hydroxybenzoic acids, etherification or esterification may be followed1 7 (Miss) E.Coombs and D. P. Evans, J., 1940, 1295.18 See discussion on the Mechanism and Chemical Kinetics of Organic Reactions19 R. P. Bell, ibid., p. 716.20 H. D. Hinton and J. A. Nieuwland, J . Arner. Chem. SOC., 1932, 54, 2017; F. J.21 H. Bowlus and J. A. Nieuwland, ibid., 1931, 63, 3835.21 F. J. Sowa and J. A. Nieuwland, ibid., 1933, 55, 5052.23 T. B. Dorris, F. J. Sowa, and J. A. Nieuwland, ibid., 1934, 56, 2689; T. B. Dorris24 F. J. Sowa, ibid., p. 654.25 A. Wohl and E. Wertyporoch, Ber., 1931, 64, 1357.*6 P. 260. Compare N. 0. Calloway, Chena. Reviews, 1935, 17, 327; (Miss) D. V.27 S. J. Slanina, F. J. Sowa, and J. A . Nieuwland, J . Amer. Chern. SOC., 1935, 57,ee F.J. Sowa, H. D. Hinton, and J. A. Wieuwland, ibid., 1932, 54, 3694.38 W. J. Croxall, F. J . Sowa, and J. A. Nieuwland, ibid., 1934, 56, 2054; 1935,For instance, benzene,27in Liquid Systems, Trans. Faraday SOC., 1941, 37, 718.Sowa and J. A. Nieuwland, ibid., 1936, 58, 271.and F. J. Sowa, ibid., 1938, 60, 358.Nightingale, ibid., 1939, 25, 329.1547,Eidem, ibid., 1933,56, 3402.67, 1549WATSON : PHYSICO-ORGANIC TOPICS. 119by rearrangement), and under the influence of the same catalyst, benzene 31and naphthalene 32 have been alkylated by alcohols ; esters 33 and etherscan also alkylate. The Claisen rearrrangement of phenolic ethers, whichis catalysed by boron fluoride, aluminium chloride and other agents, isprobably an intermolecular process involving nuclear alkylati0n,~5 and theFries rearrangement similarly involves acylation.Other reactions whichare catalysed by boron fluoride include the addition of alcohols to acetyleneto give aceta1s,21 and the preparation of phenolphthalein and flu~rescein.~~The view that alcohols, esters and ethers are first converted into olefin,which is the active agent in alkylati~ns,~l* 33* has been shown to be un-tenable 32 on the following grounds : ( a ) although cyclohexanol alkylatesnaphthalene in presence of boron fluoride, the alcohol can be recovered un-changed after treatment with the catalyst under conditions more drasticthan those required for alkylation, and ( b ) olefin formation is not possiblefrom benzyl alcohol, which nevertheless alkylates.,’ Price and Ciskowskitherefore suggest that a carbonium ion is the active intermediate, e.g.,RT + R’O-BF,/\Y R’+ + RO-BF,g > O + BF, 7 $>O-+BF,where R = alkyl and R’ = alkyl or acyl.A similar mechanism is suggestedfor alkylation by olefiiis and for the catalysed polymerisation of olefins, thefirst step being>C=C< + BF, ;+ >C-O-BF,C. C. Price and M. Meister 38 consider that the catalysis of geometrical invcr-sion depends upon the co-ordination of the catalyst (e.g., BF,) a t one of theunsaturated carbon atoms, the freedom of rotation consequent upon thetransformation of the olefinic linkage to a single bond making the inversionpossible, e.g.,4$HPh H--M--PhPh-C-H + BF3 CHPh BFa -I- Ph-9-HPh-C-H-BF,It may be noted, however, that the occurrence of the hydrion-catalysedchange of maleic into fumaric acid in this way is unlikely, since the presenceof deuterium chloride does not lead to a product containing deuteriumY3931 J.F. McKenna and F. J. Sowa, J . Amer. Chem Soc., 1937, 59,470; N. F. Toussaintand G. F. Hennion, ibid., 1940, 62, 1145.a* C. C. Price and J. M. Ciskowski, ibid., 1938, 60, 2499.33 J. F. McKenna and F. J. Sowa, &id., 1937, 59, 1204.34 M. J. O’Connor and F. J. Sowa, ibid., 1938, 60, 123; A. J. Iiolka and H. H . Vogt,s5 See Ann. Reports, 1939, 36, 208.36 J. F. McKenna and F. J. Sowa, e J . Amer. Cheti?. Soc., 1038, 60, 124.3 7 Compare E. Bowden, ibid., p. 645.3g C. Horrex, Tram. Faraday SOC., 1937, 33, 570.ibid., 1939, 61, 1463.38 Ibid., 1939, 61, 1595120 ORGANIC CHEMISTRY.and K.Nozaki and R. Ogg 40 have put forward a mechanism in which theacid catalyst here co-ordinates at oxygen of carboxyl, and anions, whichalso appear to play a part, may become attached a t one of the olefiniccarbon atoms; inversion under the influence of amines is representedsimilarly .41The catalytic effects of boron fluoride and aluminium chloride must,of course, be dependent upon the ability of these molecules to accept anelectron pair, and the resulting production of alkyl ions is in harmony withthe strongly acidic qualities of BF3-alcohol complexes.21 The existence ofan ionised complex at an intermediate stage in the familiar Friedel-Craftsreactions involving akyl halides has frequently been postulated, and isrendered more probable by the work of E.Wertyporoch and of F. Fair-brother.42 Fairbrother has shown recently that, for a number of pairs ofinorganic and organic bromides, the ease of exchange of radioactive bromineis closely parallel to the reactivity in the Friedel-Crafts synthesis, and theformation of highly polar complexes is indicated by dielectric-constantmeasurement^.^^ The " activation " of the alkyl halide, alcohol, ether,ester or olefin by the catalyst must consist fundamentally in its conversioninto a complex which is a strongly electrophilic reagent, for ( a ) the orientationof nuclear alkylation is, with certain exceptions, the same as in nuclearhalogenation, nitration and sulphonation, and ( b ) alkylation of a nucleusalready containing a powerfully activating group such as hydroxyl mayoccur in presence of a less powerful catalyst, and a reagent such as benzylchloride which is already strongly electrophilic owing to the facility ofionisation, Ph*CH,-CI, can alkylate in absence of a catalyst. The co-ordination compounds of boron fluoride with alcohols, ethers and esters maybe represented as follows :0*>O-BF3 Rwhich means probably that ionised structures in which R+ is dissociatedfrom the remainder of the molecule participate in the mesomeric state,This accounts for the observation that a normal alkyl group of more thantwo carbon atoms usually isomerises (e.g., CH3*CH,GH, will exist as++CH,-CH*CH,).I n the case of an olefin, the alkylating agent is no doubt'.,TJ,,'I.I.that formulated by Price and Ciskowski, and it is easy to understand why,for example, propylene introduces an isopropyl group via the complexCH36H-CH2-BF,. The co-ordination complex of aluminium chloride40 J . Amer. Chern. SOC., 1941, 83, 2583.See Ann. Reports, 1937, 34, 252. V. N. Ipatieff, H. Pines, and L. Schmerling( J . Org. Chem., 1940, 5, 253) include similar complexes in their alkylation mechanisms;they also discuss the isomerisation of groups.4f Ibid., p. 2681.43 J . , 1941, 293; Trans. Faraday Soc., 1941, 37, 763WATSON : PHYSICO-OWANIC TOPICS. 121with an alkyl halide will be R-X+AlCl,, which will give rise to ionisedstructures such as [k-X-MC1, C1-1, [k xAiC13], [A XAlC1, C1-1, and+ +[R AICI, X-] ; the participation of [R AlC1, X-] accounts for the equivalenceof the four halogen atoms observed by Fairbrother.42 Since boron fluorideapparently does not catalyse alkylation by alkyl halides, the structures inwhich the alkyl group is ionised may not be of much importance in the+n complex R-X+BF3, i.e., the process R-X-GF, does not occur sufficientlyto render the complex strongly electrophilic.The entry of a second alkylgroup into the m-position has been ascribed to the reversibility of theFriedel-Crafts reaction, the 1 : 2 : 4-trialkylated compound being formedand the l-alkyl group then expelled.The view that the alkylating agent is a carbonium ion (or a mesomericform in which ionised structures participate to an important extent) appearsa t first sight to be a t variance with Hickinbottom's view that, in the Claisenrearrangement, the group migrates as a neutral radical.44 This view is based,however, upon observations of the rearrangement brought about by heatalone, and the mechanism of the catalysed change is not necessarily the same.(b) Rearrangements.(Continued from Ann.Reports, 1939, 36, 191.)Continuing previous work in which optically active hydratropamide,CHPhMe*CO*NH,, was shown to be converted into a-phenylethylaminewith a 95.8% retention of optical activity,45 J. Kenyon and D. P. Young 46find that the Curtius degradation of hydratropic azide gives an &mine of99.3% optics1 purity. The intramolecular character of the Curtius changeis thus confirmed.The authors suggest that the loss of optical activityobserved in the Hofmann rearrangement of the amide, which, thoughsmall, is reaI, may be attributed to some racemisation of the intermediateisocyanate, a view which is based upon an earlier observation by E. S.Wallis and R. D. Dripps,*' who found that an optically active isocyanateis racemised on alkaline hydrolysis (as in the Hofmann change) but not onacid hydrolysis (as in the Curtius reaction). The intramolecular nature ofthe Beckmann transformation is demonstrated by the retention of opticalactivity in the conversion of methyl y-heptyl ketoxime into aceto-y-heptyl-amide. Kenyon and Young point out that an optically active radicalwhich is transferred in a Hofmann, Curtius or Beckmann change retainsnot only its asymmetry but also its configuration, Le., no Walden inversionoccurs.This was formerly assumed,** and P.D. Bartlett and L. H. Knox 49showed that the Hofmann rearrangement could occur in a case whereinversion was not possible. Direct evidence of the absence of optical44 See Ann. Reporta, 1939, 36, 209.46 J., 1941, 263.Ber., 1933, 66, 684.4 5 Ibid., p. 193.d 7 J . Amer. Chem. Xoc., 1933, 55, 1701.E. S. Wallis and S. C. Nagel, ibid., 1931, 53, 2787 ; J. von Braun and E. Friehmelt,4s J . Amsr. Chem. SOC., 1939, 61, 3184I22 ORGANIC! CHEMISTRY.inversion in the Hofmann rearrangement is provided by some earlier resultsof W. A. Noyes and co-workers,a who converted the half' smide of camphoricacid into the corresponding amino-acid without inversion, and the proofof the identity in configuration between benzylmethylacetic acid anda- benzylethylamine hydrochloride of the same sign of rotation togetherwith the conversion of the former into the latter via the amide or the azide *52gives another demonstration.The stereochemical method has also been used in J.I?. Lane and E. S.Wallis's study of the Wolff rearrangement of diazo-ketones, which occurswhen these compounds are treated with ammoniacal silver nitrate and certainother reagents. The mechanismis as follows :R*CO*CHN,R CHsuggested some time ago by B. Eistert 54--+ R*CO*CH + N,R---CHR*CH:CO + AH --+ RCH,*CO*A(where AH = NH,, H,O, ReNH, or R-OH)A case of this rearrangement without accompanying racemisation had beenreported at an earlier date,55 and in order to obtain further evidence of itsintramolecular character Lane and Wallis rearranged the diazo-ketoneCMeBuPh*CO*CHN2 in boiling aniline and also in aqueous dioxan containingsilver oxide and sodium thiosulphate; in neither case did the opticallyactive diazo-ketone give a racemic product.The compound (I) was sub-mitted to the same treatment, this substance being chosen because F. Bellhad previously shown that when optically active specimens of the acid(11) are degraded by either the Hofmann or the Curtius reaction the resultingamine is active ; 56 again no racemisation was observed. It is concluded thathere, as in the Hofmann and the Curtius change, the group is never released,and it would appear that the Wolff rearrangement is quite similar to thesedegradations, being represented most probably as in (III)?'(>,,.,,NO, c /ca,C0 II(TII.)50 See S.Archer, J . Amer. Chem. SOC., 1940, 82, 1872.51 J. Kenyon, H. Phillips, and (Miss) V. P. Pittman, J., 1935, 1072.58 E. S. Wallis et at. See Ann. Reports, 1939, 36, 193.63 J . Org. Chem., 1941, 8, 443. 64 Ber., 1935, 68, 208.5 5 N. A. Preobrashenski, A. M. Poljakova, and V. A. Preobrashenski, ibid., p. 860.5 6 J., 1934, 836. 67 Compare Ann. Reports, 1939, 36, 194WATSON : PHYSICO-ORGANIC TOPICS. 123Optically active benzylmethyldiazoacetone, CH,Ph*CHMe*CO*CHN,, how-ever, rearranges to give a partially or completely mcemised product 58 andit is suggested that this may be due to the presence of an enolisable hydrogen.The catalytic effect of phenols on the Wagner-Meerwein rearrangementhas been discussed by P.D. Bartlett and J. D. Gill.59 They find that theefficiencies of four phenols as catalysts of the change of camphene hydro-chloride into isobornyl chloride stand in the order of their hydrogen-bondingpowers, and conclude that the phenol solvates the chloride ion ; the variationof the reaction rate with the concentration of the phenol indicates that theattack takes place in two ways, involving one and two molecules of the phenol.It is interesting that F. C. Whitmore, A. H. Popkin, H. I. Bernstein,and J. P. Wilkins 6O were unable to isolate any tert.-amyl derivatives fromthe products of the action of metallic sodium upon neopentyl chloride;the Wurtz reaction proceeds via free radica1sy61 and it appears that underconditions giving radicals the neopentyl group does not undergo the changeto tert.-amyl which occurs in processes where it appears as a positive ion.A few studies of certain migrations from the side chain to the nucleusof aromatic compounds have been recorded since the Annual Report for1939.P. J. Dmmm, W. F. O'Connor, and J. Reilly e2 have examined theproducts of the Hofmann-Martius rearrangement of dibenzylaniline hydro-chloride, and fmd p-aminodiphenylmethane, 1 -amino-2 : 4-dibenzylbenzeneand also an aminotribenzylbenzene, probably the 2 : 4 : 6-compound; thisappears to be the first example of the introduction of more than two groupsby this reaction.The electronic mechanism of the benzidine transformationhas been discussed by Sir R. Robinson in his Presidential Address to theChemical Society,63 and E. D. Hughes and C. K. Ingold 6* have publishedsonie comments on this reaction. A summary of our knowledge of the Friesreaction, with a discussion of proposed mechanisms, has appeared.65 A. W.Ralston, M. R. McCorkle, and S. T. Bauer 66 find that variations in thequantity of aluminium chloride and in the solvent influence the o/p ratioin the Fries rearrangement and in the Friedel-Crafts reaction similarly,indicating an analogy between the two processes.D. S. Tarbell and J. F. Kincaid 67 have shown that the Claisen rearrange-ment of 2 : 6-dimethylphenyl allyl ether to 2 : 6-dimethyl-4-allylphenol iskinetically unimolecular.There is further evidence that in the p-rearrange-nient the a-carbon, and not the y-carbon as in the o-rearrangement of arylallyl ethers, becomes linked to the nucleus,6* and stereochemical consider-ations indicate that the former change must be intermolecular. Neverthe-5 8 J. P. Lane, J. Willenz, A. Weissberger, and E. S . Wallis, J . Org. Chenb., 1940,5, 276.5g ? J . drner. Chem. SOC., 1941, 63, 1273.G 1 See Ann. Reports, 1940, 37, 286,F,s J . , 1941, 220.6 5 A. H. Blatt, Chem. Heviewu, 1940, 27, 413.6 8 . I . Org. Chem., 1940, 5, 645.6 B 0. Mumm and J. Diederichsen, Ber., 1939, 73, 1523; E. Spath and I?. Kuffrier,6O Ibid., p. 124.62 J . Amr. Chent. SOC., 1940, 62, 1241.lbid., p.608.6 7 J . Amw. C'hem. SOC., 1940, 62, 7'38.ibid., p. 1580124 ORUANIC OHEMISTRY.less, W. I. Gilbert and E. S. Wallis 69 detected no migration of a group toa, foreign nucleus when phenyl isopropyl ether and p-tolyl sec.-butyl etherwere rearranged in the same solution in presence of sulphuric acid, and theyconclude that the mobile group is at all times within the sphere of influenceof the molecule. There are instances, however, where this group has beenfound linked to another molecule.70 A comprehensive account of the factsrelating to the Claisen rearrangement has been published by D. S. Tarbell.71Compounds such as vinyl allyl ether, which contain the essential partof the aryl allyl ether skeleton, undergo a change exactly similar to theClaisen rearrangement, and an analogous change in certain three-carbonsystems has now been discovered by A.C. Cope and c o - ~ o r k e r s . ~ ~ Onheating to temperatures between 135" and 200" the following occurs (X andY = CN or C0,Et) : >c=b*; _3 >C-b=qy Xb 5 C3HSIThe rearrangement becomes less easy in the order malonitriles > cyano-acetic esters > malonic esters, and is kinetically unimolecular. In the re-arrangement of the related crotyl compounds, it has been shown that themigrating group becomes linked through the y-carbon atom; e.g.,CHR:CMe><; 9 HR-CMe , y XCHMe:CH*CH, CHMe-CH:CH, Yand if two esters containing severally allyl and crotyl groups are rearrangedtogether, no interchange of migrating groups occurs.There can thereforebe little doubt that the change is intramolecular.(c) The ortho-Effect ; Xteric Inhibition of Mesomerisrn.(Continued from Annual Reporb, 1939, 36, 215.)A reduction of the mesomeric effects of the nitro- and dimethylamino-groups by two methyl groups standing in o-positions with respect to them,as in dimethylmesidine, nitrodurene and nitrodimethylaminoduene, waspostulated by Hampson and co-workers 73 in their discussion of the dipolemoments of these compounds, which are considerably lower than those ofthe corresponding compounds in which the methyl groups are absent; itwas considered that the o-methyl groups would make it dif5cult for the NO,or NMe, to come into the plane of the nucleus, thus producing conditionsunfavourable to mesomerism.The study of cases of this kind has now beenextended, particularly by workers at the University of Chicago. R. G.Kadesch and S. W. Weller 74 find that the dipole moments of acetylmesitylene( 2 * 7 1 ~ . ) and acetyldurene (2-68) are almost identical with those of aliphatic' 0 J . Org. Chem., 1940, 5, 184.71 Chew&. Revkw8, 1940, 27, 496.74 J . Aw. Chm. SOC., 1940, 62, 441; 1941, 63, 1843, 1862. '' J., 1937, 10; 1939, 981.7O See Ann. Reports, 1939, 30, 207.14 J . Amer. Chem. SOC., 1041, 88, 1310WATSON : PHYSIOO-ORQBNI13 TOPIOS. 126ketones, and suppose that the o-methyl groups inhibit the meaomeric effectof the carbonyl group which operates in acetophenone (p = 2.88); ob-servations of the absorption spectra of acetylmesitylene and 2 : 4 : 6-tri-isopropylacetophenone point to the same concl~sion.~~ On the other hand,o-methyl groups produce no diminution of the moment of benzaldehyde(2.92; p for mesitylaldehyde = 2-96>, and models show that, whereas thesegroups interfere very considerably with methyl of the CO-CH, in acetophen-one, any such interference with the hydrogen of the aldehyde is almostnegligible.The moment of 2 : 4 : 6-trimethylbenzoyl chloride (2-95), again,is appreciably less than that of the unsubstituted acid chloride (3-32).Hampson's conception of a steric inhibition of mesomerism has stimulatedinterest in the chemical aspects of the " ortho-effect," and was adopted byG. Baddeley 76 as the basis of the interpretation of a number of the peculi-arities associated with compounds in which two groups stand in o-positionswith respect to each other.An inhibition of mesomerism is also postulatedby G. W. Wheland and A. A. Danish 77 in order to explain the reduction ofthe acidic character of 4 : 4' ; 4"-trinitrotriphenylmethane by methyl groupsin the six positions ortho to the nitro-groups. R. T. Arnold, G. Peirce, andR. A. Barnes 7t3 find, too, that 4-nitrodimethyl-a-naphthylamine is a muchstronger base than 4-nitro-a-naphthylamine, and they suppose that theinterference of the second ring with the bulky dimethylamino-group hererenders it difiicult or impossible for this group to become coplanar with thenucleus, thus reducing the mesomerism with a consequent increase in basicstrength ; confirmation is found in the lower melting points of the N-dialkylcompounds as compared with the primary amine (R-NH,, 191". R-NMe,, 65".R*NEt,, liquid), which indicate a less polar character.On the other hand,R. D. Kleene, F. H. Westheimer, and G. W. Wheland 79 have observed thatthe relative strengths of substituted cis- and trans-cinnamic acids cannotbe accounted for on the basis of the steric inhibition of mesomerism; forinstance, the dissociation constant (in 40% acetone) of trans-3 : 4 : 6-tri-methylcinnamic acid is greater by a factor of 2.5 than that of the cis-isomeride,although the former is probably planar whereas the latter is certainly not.From measurements of the reactions of piperidine with some nitro- andcyano-bromobenzenes, W.C . Spitzer and G. W. Wheland 80 conclude thatmesomerism can be inhibited in suitably substituted aromatic nitro-com-pounds but not in the corresponding cyano-derivatives, although in theformer case the effect is smaller than would be expected from the dipole-moment measurements of R. H. Birtles and G. C. Hamps0n.7~ F. H.Westheimer and R. P. Metcalf's study of the alkaline hydrolysis of a numberof substituted ethyl benzoates having NO,, NH, or NMe, in the p-position 81has shown that the effects of these groups (of which NO, accelerates and theothers retard the reaction) are rendered smaller by methyl groups at the75 M. T. O'Shaughnessy and W. H. Rodebush, J . Amer. Chm. SOC., 1940, 62, 2906.7 6 Nature, 1939, 144, 444.7 8 Ibid., p. 1627.80 Ibid., 1940, 62, 2996.77 J.Amer. Chern. SOC., 1940, 62, 1125.79 Ibid., 1941, 63, 791.Ibid., 1941, 63, 1339126 ORCI ANICl CHEMTSTRY.3 : 5-positions; this is particularly striking in the case of ethyl 4-dimethyl-a mino-3 : 5-dimethylbenzoate, as illnstrated by the velocity coefficientsbelow :ethyl 4-dimethylarninobenzoate .................. 0.00152 1 = Ratio 30 4ethyl benzoate 0.052ethyl 3 : 5-dimethylbenzoate ..................... 0.373 Ratio""{ethyl 4-dimethylamino-3 : 5-dimethylbenzoate 0406 1 = 1-8A reduction in the reactivity of the p-position owing to the presence ofa group placed ortho to NMe, was observed by von Braun in 1916,82 and inan investigation of the deuteration of derivatives of dimethylaniline, W. G.Brown, A. H.Widiger, and N. J. Letang 83 find a similar effect in o-bromo-and o-chloro-dimethylaniline, but very little in the o-fluoro-compound.When the nitrogen is linked to the ortho-carbon atom to form a five-, six-or seven-membered ring system, as in N-methylindoline (I), N-methyl-tetrahydroquinoline (11), and IY-methylhomotetrahydroquinoline (111),however, the reactivity is dependent upon the size of the second ring; in(I) and (11), where it is coplanar with the benzene ring (or almost so), thereactivity is high, exceeding that in dimethylaniline itself, but the puckeredseven-membered ring in (111) leads to a relatively slow reaction........................................ a t 30°{(\AVH3 i'lF2-g\/\ PH, N I \,A w P H 2 KCH, CH,(111.)CH3(1.) (11.)The authors consider that " these results provide rather convincing evidencethat the key to the situation really lies in the ability of the dialkylamino-group to come into the plane of the benzene ring " ; ie., the mesomeric (and,in a reaction, the electromeric) effect of the group is inhibited when it isnot able to do so.I n a, recent paper,s* Brown and Letang have demonstrateda reduction of reactivity (in the deuteration reaction) in dimethyl-a-naphthyl-amine by chlorine or a nitro-group in the 8-position, and also a mutualhindrance of dimethylamino-groups in the peri-positions. Extension ofthis work to carbazole derivatives (V), however, has given results which areless easy to interpret, for these compounds are less reactive than the cor-responding diphenylamine derivatives (IV) in spite of their favourable planarstructure, Dihydroacridine derivatives (VI) also show a depression of82 See Ann, Reports, 1939, 36, 218.84 Ibid., 1941, 63, 358.83 J .Artier. Chan. L!OC., 1839, 61, 2597DIPPY : PHYSICO-ORGANIC TOPICS. 127reactivity as coinpared with (IV), but this may be due to a folded structuresimilar to that of dihydroanthracene and NN'-dimethyldihydrophenazine. 85These new results appear to confirm the suggestion made in the AnnualReports for 1939 that the various manifestations of the " ortho-effect ''cannot be interpreted on the basis of a single conception; steric inhibitionof mesomerism, interaction between groups in o-positions, and perhaps alsogeometrical steric hindrance as envisaged by Victor Meyer wiIl probablyall find their place in a final and comprehensive interpretation of the observedphenoniena when such an interpretation is achieved.H.B. W.(d) The Strengths of Organic Acids and Bases.The classical dissociation constants of Wilhelm Ostwald provided theearliest numerical data which reflected the changes in reactivity attendantupon systematic variations in chemical structure, and the rise of the theoryof interionic attraction has led more recently to the computation of thermo-dynamic dissociation constants ( K ) which furnish a better measure of thestrengths of organic acids than do the older values. The later data aresuperior not only because the corrections made necessary by modern theoryare taken into account in their derivation, but also by reason of improve-ments in experimental technique. Wide use has been made of the dis-sociation constants for aqueous solution in discussion of the polar influencesof substituent groups, and several investigators have been able to relatethem quantitatively with reactivities and other characteristics of organicmolecules.1, 2 A collection of the more reliable dissociation constants ofmonobasic organic acids and the strengths of organic bases (for one tem-perature) has been published re~ently,~ and to this may now be addedfurther values for formic, n-butyric and cyanoacetic acids.4Most of the available data relate to aqueous solution a t 25", and quiterecently doubts have been expressed as to the correctness of basing com-parisons of acid strengths upon the values of dissociation constants for anarbitrarily fixed temperature and a single selected solvent.The factors governing acid dissociation will be affected by elevation oftemperature, both the solvent and the electrolyte being directly concerned.The dielectric constant of a liquid diminishes with increasing temperature,and so with the decreasing electric field there will be a smaller tendencyfor ions to separate. Again, there is less solvation and also loss of com-plexity in both solute and solvent.There exist comparatively few data relating to the variation of dis-sociation constants of organic acids with temperature, and those of a reliable85 (Miss) I.G. M. Campbell, (Mrs.) C.G . Le Fevre, R. J. W. Le FBvre, and l4. E.See Ann. Reports, 1937, 34, 52; 1938, 35, 239; 1939, 38, 216.H. 0. Jenkins, J., 1940, 1447.J. F. J. Dippy, Chem. Reviews, 1939, 25, 151.B. Sexton and L. S. Darken, J . Amer. Chem. SOC., 1940, 82, 846.Turner, J., 1938, 404128 ORGANIC OEEMISTRY.character are still further limited.* The last-mentioned refer in the mainto some common monocarboxylic acids (including ampholytes), mostlyin aqueous solution over a temperature range of usually 0-60" (determinedlargely by the e.m.f. method perfected by Harned), although some measure-ments on partially aqueous solutions have been performed.It is plain from the available values that the dissociation constants ofuncharged acids pass through maxima with rise of temperature, and variousattempts to relate K with temperature have been made with acids of thischarge type.fitted their earlierresults to the four-constant equation,In the first place Harned and co-workerslogK=-a/T+blogT+cT+d . . . - (1)where 27 is the temperature in degrees absolute. This they replaced Iaterby a further empirical equation: for temperatures in the vicinity of themaximum, which has the general form,log K -logK, = - p ( t - 0)2 . . . . (2)where K , is the maximum dissociation constant, 8 the corresponding tem-perature ('a), K the dissociation constant a t some other temperature t("c), and p a constant.1° An excellent account of the applicability of thisequation to the experimental data has been published by H.S. Harned andB. B. Owen,5 and a qualitative interpretation provided by R. W. Gurney.llSince then a relationship arising from theoretical treatment, and applicable,like equation (2), in the neighbourhood of K,,,, has been put forward byJ. L. Magee, T. Ri, and H. Eyring,12 vix.,In K - In K, = p(t - O)a + q(t - e)3 + . . . (3)in which the constants p and q are dependent largely on the propertiesof the solvent, in the case of water. This is similar to equation (2) apartfrom the cubic and higher terms; the inclusion of the cubic term leads to aslightly different curve in the plot of log K against t, which the authorsconsider to fit the experimental points better.* These have been listed by :H. S. Harned and B. B. Owen, Chent. Reviews, 1939, 25, 31.D.H. Everett and W. F . K. Wynne-Jones, Trams. Faraday SOC., 1939, 35, 1380.7 J. F. 5. Dippy and H. 0. Jenkins, ibid., 1941, 37, 366.Additional measurements have lately been provided by : W. F. K. Wynne- Jones andG. Salomon, ibid., 1938, 34, 1321; H. S. Harned, J . Physical Chem., 1939, 43, 275;H. Suter and K. Lutz, Helv. Chirn. A&, 1940,23, 1191 ; J. E. Ablard, D. S. McKinney,and J. C. Warner, J . Amer. Chern. SOC., 1940, 62, 2181; F. C. Hickey, ibid., p. 2916;D. H. Everett and W. F. K. Wynne-Jones, Proc. Roy. SOC., 1941, A, 177, 499; J. H.Elliott and M. Kilpatrick, J. Physical Chem., 1941, 45, 466; H. S . Herned and R. S .Done, J . Amer. Chem. SOC., 1941, 63, 2579.H. S. Harned and R. W. Ehlers, J . Amer. Chem. SOC., 1933, 55, 2379.9 H.S. Harned and N. D. Embree, a i d . , 1934, 56, 1060.lo See Ann. Reports, 1937, 34, 101-105.11 J . Chem. Pity&, 1938, 6, 499.la Ibid., 1941, 9, 419DIPPY : PHYSICO-ORGANIC TOPIUS. 129K. S. Pitzer l3 has claimed superiority for the equation. . . . (4)A AC, In T I n K = g j + B +(where A and B are constants) in that it has wider applicability, althoughit is agreed that, within limits, this is essentially the same as the Harnedand Embree relationship. In this equation Pitzer assumes for the fattyacids a value of - 40 cals./degree for AC,, the heat capacity change, invariantwith respect to temperature within the experimental range.D. H. Everett and W. I?. K. Wynne-Jones 6 propose the equationwhich they believe to be an improvement on others; this is similar toPitzer's equation except that significance is given to constants A and B.The quantities AHo, A.Xoo and AC, (the heat and entropy of ionisation a tabsolute zero and the change of heat capacity at constant pressure, re-spectively) are considered to be unaffected by temperature. It has beenpointed out,' however, that the temperature invariance of ACp in chemicalreactions has certainly not been proved, and such an assumption is, at best,an approximation applying over a very limited temperature range.In a review of the position, H.S. Harned and R. A. Robinson 1* havecompared equation (2) with three other equations, all considered likely toaccount for change of K with temperature [one being essentially that pro-posed by Everett and Wynne-Jones, i.e., equation ( 5 ) ] .They concludethat, whereas the Harned-Embree expression is only a first approximation,the other three equations are all capable of representing the data withinthe limits of experimental accuracy, and state that on the present evidencethey are of equal merit. It is emphasised by Harned and Robinson thatexperiments over the present limited temperature ranges fail to decidewhether or not AC, is independent of temperature, because, although thethree equations mentioned seem to be of equal applicability, two of thempredict a heat capacity term proportional to the tFmperature, whilst accord-ing to the other equation (that of the form proposed by Everett and Wynne-Jones) it is independent of temperature.For practical purposes Harnedand Robinson decide in favour of the equation which lends itself best tocalculation, and thus the dissociation constant is expressed aswhere A , B and C are empirical constants derived from the experimentaldata.15 H. S. Harned and R. S. Donels have lately shown that thisequation represents well their observed values of K for formic acid in fourwater-dioxan mixtures at temperatures ranging from 0" to 50".*logK=--A/T+B-CT . . . . . (6)lS J . Amw. Chem. SOC., 1937, 59, 2365. l4 Tram. Faraday SOL, 1940,36, 078.l5 Compare with the equation of E. C. Baughan (J. Chem. Physics, 1930, 7, 951).l6 J . Amer. Chern. SOC., 1041, 03, 2579.* H. S. Harned and T. R. Dedell (J. Arner. Chem. SOC., 1941, 83, 3308) heve sinoeshown that the ionisation constants of aoetic and propionic acids in dioxan-watmmixtures can also be expressed by the Harned-Robinson equation.REP.--vOL.XXXVIII. 130 ORGANIC CHEMISTRY.At the present time, therefore, there exist a number of different equations,embodying by no means identical premises, but all capable of accountingreasonably well for the experimental facts ; their reliability for extrapolationpurposes is uncertain, however. This forms the basis of a criticism 7 of Everettand Wynne-Jones's use of the values of AHo as representing the relative" intrinsic strengths " of series of acids. Thus, it is contended that theorder of strengths n-butyric > propionic > acetic > formic, arrived a t bythese authors, is opposed t o the abundant evidence from other fields ofinquiry [which shows that alkyl attached to carbon is electron-repulsive(+ I , + M ) ] , and that it is probably the outcome of unjustifiable extra-polation.It is evident, nevertheless, that in the case of n-butyric acid thecurve obtained by plotting log K against t is displaced with respect to thecurves for the other aliphatic acids so far studied,* and that, aa a consequencethe strengths of the simpler fatty acids might not present the same sequenceat all temperatures.? This anomaly is identified with a suggested restrictingpotential arising from an attraction between the C-CH, and C=O dipoles(hydrogen- bonding), particularly in the ani0n.l' Independent evidencefavouring this suggestion has been supplied by J.P. McReynolds and J. R.Witmeyer 18 in a study of the stabilities to racemisation of certain saltscontaining aliphatic acid radicals. Also, Magee, Ri, and Eyring,l2 dis-cussing the enhanced K for n-butyric acid a t 25", indicate that for a regulargradation of dissociation constants in the fatty series the heat of ionisationof n-butyric acid would be about - 250 cals., and not - 691 cals., andthey give the postulated hydrogen-bonding as the probable reason for thislarge value. It appears probable, therefore, that the dissociation constantsof the simple fatty acids at any fixed temperature will present an orderwhich is consistent with the known influences of alkyl groups, provided thatallowance is made for an additional spatial interaction in n-butyric acidand higher acids. The use of AHo as a measure of true acid strength seemsto apply no more successfully in the benzoic acid series, where it leads toa number of conclusions which conflict with the well-defined polar effectsof substituents such as iodine and nitroxyl.Another basis of comparing acid strengths, regarded as less arbitrarythan the use of dissociation constants a t some fixed temperature, has beenproposed by Harned and Embree.g They recommend that the values of1 7 J.F. J. Dippy, J., 1938, 1222; H. 0. Jenkins and J. F. J. Dippy, J. Amer. ChenX.18 J . Amer. Chern. SOC., 1940, 62, 3148.* B. W. Gurney (ref. 11) has already indicated that there is no correlation betweenthe degree of dissociation of an acid and the value of 8.He regards the value of thelatter as dependent on the relative magnitudes of the electrostatic and non-electro-static pads of the dissociation energy. t Only in the cases of ampholytes have different sequences of acid strength beenobtained in practice by varying the temperature (compare J. F. J. Dippy and H. 0.Jenkins, ref. 7, and D. H. Everett and W. F. K. Wynne-Jones, Trans. Faruduy Soc.,1941, 38, 374), although it is not certain to what extent this is accounted for byconstitutional changes.SOC., 1940, 62, 483; see Ann. Reports, 1938, 35, 2bl.See also Everett and Wynne-Jones (ref. 6)DIPPY : PHYSTCO-ORGANIC TOPICS. 131dissociation constants at their maxima ( L e . , where AH is zero) should beselected. It seems, however, on examination of the available data (ex-cluding ampholytes), that no different sequence of strengths is exhibitedwhere this method of comparison is ad0pted.1~ Everett and Wynne-Jonesconsider that this method is inadequate.L.P. Hammett 20 has called attention to the fact that different conclu-sions regarding the influences of substituent groups would be derived fromconsideration of heats of ionisation (AH = RT2d In K/dT) on the one hand.and free energies of ionisation (AF = -RT In K ) on the other, since theeffect of a substituent on the two quantities is far from comparable. It isclear, however, that values for the free energy change can be ascertainedwith much the greater certainty, and actually AF does represent the maximumwork which the system is capable of performing.In this connexion it isnoteworthy that Harned and Done,lG in an estimate of the accuracy of thedeterminations of the thermodynamic functions evaluated from dissociationconstant-temperature data, emphasise that the value of the heat of ionisationis subject to large errors because of the difficultyof determining a quantityby differentiation.It is significant, however, that J. G. Kirkwood, F. H. Westheimer, andcollaborators 21 have successfully elaborated N. Bjerrum’s original pro-position g2 that the effect on K due to the introduction of a polar substituentinto an organic acid is primarily electrostatic in origin. On this basis, theratio of the strengths of two acids has been calculated from the electrostaticwork done in transferring a proton from one acid to the anion of the other ;the formulation takes into account the position of the substituent and theshape of the molecule.Monobasic and dibasic aliphatic and monobasicaromatic acids and certain phenols have been examined, and, on the whole,a close correspondence between predicted and observed strengths has beennoted. A similar fundamental assumption is implicit in H. 0. Jenkins’scorrelations.In short, the foregoing criticisms have to contend with the fact thatdissociation constants for a fixed temperature display pronounced regularitieswhich are in harmony with a mass of observations proceeding from otherinvestigations, and that such agreement would scarcely have existed unlessthe method of comparing acid and base strengths was, in the main, a goodapproximation to the truth.There remains the question as to whether identical conclusions would bereached regarding the relative polar effects of substituent groups if data fororganic acids in solvents other than water were taken into account, It wasindicated by W.F. K. Wynne-Jones that examination of the data for acollection of acids in alcohols and water showed differing orders of strengths,1s See J. F. J. Dippy, J., 1938, 1222. 2o J . Chem. Physics, 1936, 4, 613.21 Ibid,, 1938, 6, 50’7, 513; J . A m r . Chena. SOC., 1939, 61, 555, 1977; cornparsA. Eucken, Angew. Chem., 1932, 45, 203; G . Schwarzenbach and H. Egli, Helv. Chini.Acta, 1934, 7, 1183.a2 Z . physikal. Chena., 1923, 108, 219. 29 Chem, and I n d ., 1933, 52, 273132 ORaAKIU UHEMISTRY.but G. N. Burkhardt pointed out that the irregularities were due to theinclusion of certain acids already recognised as exhibiting abnormally highatrengths. Nevertheless, by means of these data Wynne-Jones 25 tested satis-factorily his linear relationship, log K, oc 1 /D (where K, is the ratio of the dis-sociation constant of a given acid to the dissociation constant of a referenceacid, often the parent acid, and D is the dielectric constant of the solvent),deduoed on the basis of electrostatic theory and involving simplifyingassumptions such &B neglect of non-electrostatic factors.26 He suggested,for purposes of comparison, the use of '' intrinsic strengths " derived byextrapolation to i&nite dielectric constant ; it is noteworthy, however,that these intrinsic strengths show the same sequence as the dissociationconstants of the acids in water.3A bibliography of measurements on acid strengths in non-aqueoussolvents up to the year 1931 was provided by N.F. Hall; 27 a list of thereferences to later data for acids and bases in non-aqueous and partiallyaqueous solutions is included in the footnotes below.2848 Almost always thetemperature of experiment was 25".I n a number of these investigations the Wynne- Jones relationship hasbeen tested and found to be applicable 379 39,42*45~46, 473 49 (in the case ofpartially aqueous solutions the dielectric constant of the mixed solvent isvaried by adjusting the proportions of the components). M.Kilpatrick24 Chem. and Ind., 1933,62, 330.26 Proc. Roy. SOC., 1933, A , 140, 440; see also L. J. Minnick and M. Kilpatrick,20 Compare Ann. Reports, 1934, 31, 7 8 .28 J. 0. Halford, J . Amer. Chem. SOC., 1931, 53, 2944.80 V. K. LaMer and H. S. Domes, J . Amer. Chem. SOC., 1933, 55, 1840; Clieijz.31 G. E. K. Branch, D. L. Yabroff, and collaborators, J . Amer. Chem. Xoc., 1933,32 J. W. Murray and N. E. Gordon, ibid., 1935, 57, 110.s3 L. A. Wooten and L. P. Hammett, ibid., p. 2289.3J, G. M. Bennett, G. L. Brooks, and S. Glasstone, J., 1935, 1821.36 S. KiIpi and H. Warsila, 2. physikal. Chem., 1936, A , 177, 427.30 F. H. Verhoek, J . Amer. Chem. SOC., 1936, 58, 2577.37 R. B. Mason and M. Kilpatrick, ibid., 1937, 59, 572.3 8 D.C. Griffiths, J., 1938, 818.39 C. C. Lynch and V. K. LaMer, J . Amer. Chem. SOC., 1938, 60, 1252.40 W. C. Davies, J., 1938, 1866.41 H. H. Hodgson and R. Smith, J., 1939, 263.42 L. J. Minnick and M. Kilpatrick, J . Physical Chem., 1939, 43, 259.43 N. A. Izmailov, M. B. Schustova, and N. Vorodez, J . Qen. Chent. Russia, 1939,44 J. N. Beliaev, Kolloid Schurn., 1940, 6, 531.4 5 13. Adell, 2. physikal. Chem., 1940, 186, 27.4 6 M. Kilpatrick and W. H. Mears, J . Amer. Chem. SOC., 1940, 62, 3047, 3051.4 1 J. H. Elliott and M. Kilpatrick, J . Physical Chem., 1941, 45, 454, 466, 472, 485.48 R. D. Kleene, F. H. Westheher, and G. W. Wheland, J . Amer. Chem. Suc.,4' H. S . Harned, J . Physical Chem., 1939, 43, 275.J . Physical Chem., 1939, 43, 259.21 Chem.Reviews, 1931, 8, 191.M. Kilpatrick and M. L. Kilpatrick, Chem. Reviews, 1933, 13, 131.Reviews, 1933, 13, 47.55, 2935; 1934, 56, 937, 1850, 1865.9, 698.1941,63, 791DIPPY PHYSICO-ORQBNIC TOPICS. 133and co-workers 42p47 and C. C. Lynch and V. K. LaMer 39 have demonstrated,nevertheless, that that the relationship does not hold when the mediumpossesses a dielectric constant of less than 20-25. J. H. Elliott and M.Kilpafrick 47 believe that this may be due to the larger part played by dipoleinteractions between acid and solvent, and E. C. Baughan 50 considers thatsuch a breakdown might be expected. The first-mentioned authors alsoencountered lack of linearity with substituted benzoic acids in dioxan-water mixtures of D varying from 55 to 15, and they suggest that thispossibly arises from a preferential orientation of dioxan molecules aroundthe solute, which would cause a lower dielectric constant in the immediatevicinity of the acid molecules; L.A. Woofen and L. P. Hammett 33 alsoobtained little better than qualitative agreement. It is noteworthy thatorharily the slopes of the straight lines obtained in the plot of log K ,against 1/D have a positive slope, e.g., almost all m- and p-substitutedbenzoic acids, and are often roughly parallel; with o-substituted benzoicacids the lines are inclined in the opposite direction, although salicylic acidproves exceptional in this respect. Elliott and Kilpatrick attribute thisfeature to chelation between the substituent and the hydrogen of carboxylin the case o-chloro- and o-nitro-benzoic acids, a view which conflicts withH.0. Jenkins’s suggestion 51 that the strengths of these acids (in water)can be adequately accounted for simply by ascribing to the groups theirordinary polar characteristics.There can be no doubt that, despite the success which the Wynne-Jonesrelation has achieved, the chemical r61e of the solvent is by no means aninsignificant factor governing the extent of acid dissociation. The infer-vention of this factor has been mentioned in earlier Reports and elsewhere.52It is interesting to note that, although Minnick and Kilpatrick have statedthat the relative strengths of carboxylic acids are the same in two solventsof identical dielectric constant, vix., methyl and ethyl alcohols, on the onehand, and dioxan-water mixtures on the other, Elliott and Kilpatrick47now contradict this claim after further measurements with similar solventsbut using a different method of procedure.Actually, it has been stressedmore than once 37, 53 that in order to test the Wynne-Jones expressionsatisfactorily, data referring to solvents of similar chemical type should beselected, and, moreover, the data should all be derived from a consistentexperimental method.42* 47 It is possible that in these circumstances thechemical factor introduced by the solvent will be cancelled out. In supportof this stipulation a few instances may be quoted in which a change in thechemical character of the solvent brings about a distinct increase in thestrength of the dissolved acid, which cannot be attributed to the alterationGo J .Chem. Physics, 1939, 7 , 951.62 L. P. Hammett, J . Amer. Chem. SOC., 1928, 50, 2666; “ Physical OrganicChemistry,” New York, 1940, p. 256; Ann. Reports, 1930,27,326-356; J. 0. Half’ord,J . Amer. Chem. SOC., 1931, 53, 2939; C. A. Kraus, J . Franklin Inst., 1938, 225,702-7 0 7 ; J. F. J. Dippy, Chem. Reviews, 1939, 25, 166; J., 1941, 650; W. F. Luder, Chem.Reviews, 1940, 27, 555-568.ti1 J., 1939, 640.6s J. F. J. Dippy, J., 1941, 660134 ORGANIC CHEMISTRY.in the dielectric constant. Thus the acidity of hydrochloric acid in dioxanis increased by small additions of certain phenols and alcohols; * this isthought to be due to hydrogen-bond formation between hydroxyl and chlorine.Again, the strengths of seven common monocarboxylic acids have beenfound to be slightly greater in 20% aqueous sucrose than in water, althought,he dielectric constant of the former solvent is appreciably smaller thanthat of the latter.53 It is also noteworthy that acids of the ammonium-iontype (BH+), the dissociation of which should be scarcely affected by a changeof dielectric constant, show an increased acidity in ethyl alcohol as comparedwith water.55 *The various solvents employed so far include methyl, ethyl, and n-butyl alcohols, glycol, benzene, chlorobenzene, formamide and acetonitrile,and also aqueous methyl and ethyl alcohols, glycerol, dioxan, acetone andsucrose (the solvent in certain cases also contained some inert electrolyte,cq., lithium chloride).Among the acids and bases examined have beenaliphatic acids, substituted benzoic, cinnainic and phenylboric acids, halo-geno-phenols and -anilines, and substituted dimethylanilines. For the mostpart, potentiometric and colorimetric methods of measurement have beenused.In discussing the relative strengths of acids in a pair of solvents, J. 0.Halford 56, 28 has pointed out that, although variations in relative strengthwith change of solvent are only minor among acids of one charge type, itmight be unwise to draw conclusions, especially of a quantitative nature,where differences in absolute strength are less than 1pK unit, i.e., a, factorof 10 in K.57 Nevertheless, examination of the present evidence showsthat the order of strengths is quite well preserved from solvent to solventamong uncharged acids differing in K by much less than this factor.Anumber of investigators have actually stated that their measurements onseries of acids (and bases) in a given solvent reveal a close correspondencewith the order of strengths in water. In some cases quantitative agree-ment has been noted ; e.g., N. F. Hall 58 has shown that the relative strengthsof a large number of organic bases in acetic acid and in water are nearlyproportional. P. H. Verhoek 36 obtained straight lines on plotting p~ forsolutions of a variety of carboxylic acids and phenols in formamide againstvalues for aqueous solutions, and Wooten and Hammett 33 arrived a t asimilar result with m- and p-substituted benzoic acids in m-butyl alcohol andwater. Again, V.K. LaMer and H. C. Downes30 record that unchargedorganic acids in benzene retain the same differences in strength among them-selves that exist in water (salicylic acid is exceptional), thus going further54 P. D. Bartlett and H. J. Dauben, J. Amer. Chem. SOC., 1940, 62, 1339.6 6 See L. P. Hammett, " Physical Organic Chemistry," New York, 1940, p. 260.6 6 J. Amer. Chem. SOC., 1931, 53, 2939. 67 Compare Ann. Reports, 1934, 31, 78.s0 J . Amer. Chem. SOC., 1930, 52, 5115.* F. J. Moore and S. B. Johns ( J . ArneT. Chem. SOC., 1941, 83, 3336) have recentlyrecorded that the ionisation constants of picric acid in acetone, methyl ethyl ketone,acetophenone, propionitrile, and benzonitrile depend less on the dielectric constant ofthe medium than on the electron-sharing ability of the radicals in the solvent moleculeDIPPY : PHYSICO-ORGAMC! TOPTCS.135than J. N. Bronsted,59 who showed good qualitative correspondence forbenzene solutions; a similar conclusion warns reached by I). G. G r i f f i t h ~ , ~ ~who used chlorobenzene as solvent. It is interesting that agreement isfound with the measurements in aprotic solvents, i.e., inert diluents havingneither proton-accepting nor proton-donating character, in which it is tobe expected that acids will exhibit their true relative strengths. This givesstrong support for the practice of employing dissociation constants foraqueous solutions of acids in discussions concerning the polar influences ofsubstituents.Indeed, the conclusion has been drawn 3, 53 that existingdata show that, in general, organic acids (uncharged) exhibit the samerelative strengths in proceeding from solvent to solvent, provided thatcertain well-defined acids are excluded, particularly those in which thereexists some specific interaction of groups. The qualification might be addedthat it is safer to restrict correlations to acids of similar c1assJ6O i.e., where thereacting groups are alike. For instance, i t is better to consider mono-carboxylic acids as apart from phenols ; thus Verhoek 36 found that thedata for these two classes of acid gave separate straight lines in the plotof for formamide and aqueous solutions. Notable anomalies are salicylicand o-toluic acids, where the hydroxyl and methyl snbstituents are believedto form a hydrogen-bond with the carboxyl group (on this basis n-butyricand higher aliphatic acids should also be anomalous).Wooten and Ham-mett 33 have made the important observation that, in transferring fromwater to n-butyl alcohol, any substituent whidh causes a rise in absolutestrength causes an increase in relative strength (hence the positive slope inthe plot of log K, against l/D), the converse being true for a substituentwhich depresses absolute strength. They exclude from this generalisationnot only o-substituted benzoic acids but a-substituted aliphatic acids as well(proximity effect). o-Substituted benzoic acids were among those acidswhich Burkhardt described as anomalous, and furthermore, they provideexamples of negative slopes in the log Kr-l/D plot.In such cases theabnormality caused by the operation of the additional factor might notbe reproduced systematically in all sovents,3 because, as Hammett 61indicates, the chemical nature of the solvent can influence the extent ofthe abnormality. It is noteworthy, therefore, that whereas Elliott andKilpatrick 47 have asserted that the relative strengths of o-, m- and p -nitro-, -halogeno-, -methyl-, -hydroxy- and -methoxy-benzoic acids inmethyl, ethyl, and n-butyl alcohols and ethylene glycol do not present thesame sequence as in water, a detailed examination of their results 63 revealsthat, when the above anomalous acids are excluded, a very close correspond-ence with the data for aqueous solutions exists.I n conclusion, it may be said that, until an ideal method of comparing thestrengths of weak acids is forthcoming, i t would appear that the selection59 Ber., 1928, 61, 2049.*O See G. M.Bennett, G. L. Brooks, and S. Glasstone (ref. 34), and J. F. J. Dippy81 L. P. Hammett, “ Physical Organic Chemistry,” New York, 1940, p. 207.(ref. 3)136 0RUA.NIC OHEMISTRY.of thermodynamic dissociation constants referring to the solvent waterand a temperature of 25” is reasonable. The pronounced regularities dis-closed by inspection of the existing data certainly seem to give it justifimtion,and changes in the sequences of acid strengths occasioned by variations oftemperature and solvent appear likely to be only of a minor character andto admit of a simple explanation consistent with the present views regardingthe polar effects of substituents.J. F. J. D.3. ORGANOMETALLIC COMPOUNDS.Since the appearance of the last reports1 on this subject, continuedattention has been given to compounds of metals from all parts of theperiodic table, largely in order to systematise on a broader basis their existence,composition, and reactions, and partly in view of their importance in medicineand the arts. Compounds of the less typically metallic elements have beenexcluded from the following account except for purposes of comparison.General.2* 3The preparation of organic compounds of further elements or of newtypes is significant in view of attempts to define the kinds of derivativespossible to elements in the various regions of the periodic table.Triethyl-scandium and triethylyttrium * appear to be the first exceptions to A. vonGrosse’s generalisation that the transition elements do not give compoundsof the type R,M, where n is the group valency of M towards hydrogen.Among newer types may also be cited the reactive tri-alkyl or -arylderivatives of gallium,6* 7. indium,*# and thalliurn,lO~ l1 together with the“ mixed ’’ gallium compounds Me,GaCl and MeGaC1,; compounds ofunivalent thallium may also exist.ll V. M. Pletz reports highly unstablebutyltitanium ethoxides,12 and there are indications of the formation ofAnn. Reporta, 1928, 25, 92; 1932, 29, 96, 98; see also 1937, 34, 243.2 E.Krause and A. von Grosse, “ Chemie der metall-organischen Verbindungen ”(1937).K. Gilman, “ Organic Chemistry,” Chap. 4 (1938).2. anorg. Chm., 1926, 152, 145.4 V. M. Pletz, Compt. rend. Acad. Sci. U.R.S.S., 1938, 20, 27.6 G. Renwanz, Ber., 1932, 65, 1308; C. A. Kraus and F. E. Toonder, Proc. Nut.Acad. Sci., 1933,19, 292, 298; J . Amer. Chem. Soc., 1933, 65, 3547; L. M. Dennis andW. Patnode, %id., 1932, 54, 182.7 H. Gilman and R. G. Jones, ibid., 1940, 62, 980. * A. W. Laubengayer and W. F. Gilliam, ibid., 1941, 63, 477.s L. M. Dennis, R. W. Work, E. G. Rochow, and E. M. Chamot, ibid., 1934, 56,1047; W. C. Sohumb and H. I. Crane, ibid., 1938,60, 306; H. Gilman and R. G. Jones,ibid., 1940, 82, 2353.10 S. F. Birch, J., 1934, 1132; E.G. Rochow and L. M. Dennis, J . Amer. Chem.~ o c . , 1935, 57, 486.11 H. Gilman and R. G. Jones, ibid., 1939, 61, 1613; 1940, 62, 2357.1’ J . Ben. Chem. Russia, 1938, 8, 1298; cf. L. G. Makarova and A. N. Nesmejanov,aid., 1939, 9, 771STEVENS : ORGANOMETALLIC COMPOUNDS. 137organo-vanadium l3 and -tantalum c0mpounds.1~ Phenyl derivatives ofmolybdenum,15 tungsten,ls and manganese 1' have been recorded, but fulldescription is still lacking ; tri( ?)methylrhenium is described in a brief note.18H. Gilman and M. Lichtenwalter l9 have prepared the first " simple "organoplatinum compounds, Me,Pt and Me6Pt,.Et,Sc,Et20 ......Et,Y ,Et20 .........Me,Ga ............Et,T1 ...............PhMnI ............Me,Re ............Me,Pt ...............Me,h ...............M.p.-- 19"89- 63solidcryst.-TABLE I.B. p. Action of: air. water. cold HCI.170-172" ++ +222-225 + +55.7 ++ ICH, ZCH,50/24 mm. + 2CH,54.8/1.5 mm. - 1C2H, 1C2H,ca. 60 -- ICH,- + - ++ I+ + spontaneously inflammable.Physiwcherniuzl Properties.-The vapour density of trimethylaluminiumat 70" corresponds to the formula Al,Me,, and the values at higher temper-atures indicate a heat of dissociation of some 20 cals., comparable with thatof the dimeric aluminium halides. The usual formulation (I) for the latteris not applicable to the alkyls, and the possibility of AI-A1 bonding is con-sidered20 to be supported by determinations of the dipole moments oftrimethylaluminium and the methylaluminium halides.x\Al,x, Triethylaluminium also is associated in the vapourAn elaborate study 21 has been made of the molecular Xvolumes, heats of combustion, and refractivities ofnumerous alkyl derivatives of mercury, tin, lead, and the group V metals.A.von Grosse 2* discusses the physical constants of organic compoundsof the elements in relation to the periodic table.Electrolysis of a series of alkylmagnesium halides in ethyl or butylether 22 gave one equivalent of magnesium per Faraday at the cathode,and one molecule of magnesium halide at the anode. With methylmagnesiumhalides ethane is the predominant gaseous product at high current densities ;l3 C. C. Vernon, J . Amer. Chem. SOC., 1931, 53, 3831; A. V. Kirsanov and T. V.l4 B. N. Afanasyev, Chem. and Jnd., 1940, 59, 631.l6 F.Hein, Angew. Chem., 1938, 51, 503.l6 F. Rein and E. Nebe, Naturwiss., 1940, 28, 93.l7 H. Gilman and J. C. Bailie, J . Org. Chem., 1937, 2, 84.la J. G. F. Druce, J., 1934, 1129; cf. H. Gilmrtn, R. G. Jones, F. W. Moore, and/ kx/' \x state, but triethylgallium and trimethylindium are(1.1Sazonova, J . Gen. Chem. Russia, 1935, 5, 956.M. J. Kolbezen, J . Amer. Chem. SOC., 1941, 63, 2525.Ibid., 1938, 60, 3085.2o R. H. Wiswall and C. P. Smyth, J . Chem. Physics, 1941, 9, 352; of. L. 0.Brockwey and N. R. Davidson, J . Amer. Chem. Soc., 1941, 63, 3287.21 W. J. Jones et al., J . , 1931, 2109; 1932, 2284; 1935, 39; Bull. SOC. chim., 1931,49, 187 ; J . P h y k l Chem., 1933, 37, 583.22 W. V. Evans et al., J .Amer. C k . Soc., 1934, 56, 654; 1936, S7, 489; 1936, 58,720, 2284; 1939,61,898; 1940,62, 534; 1941,63, 2514138 ORGANIC CHEMISTRY.its nearly complete supersession by methane (derived from reaction with thesolvent) a t low c. d.’s suggests that the methyls are not liberated in pairs.The higher alkylmagnesium compounds give the corresponding alkane andalkylene with quantities of dialkyl increasing from traces with the ethyland isopropyl through tert.-butyl and n-propyl to nearly exclusive productionof octanes from the other butyl derivatives and of dodecane from the n-hexyl.The main reactions are formulated :Arylmagnesium halides give much polyaryl, some diaryl, and much styrenefrom interaction with the solvent.Conductivity measurements and general considerations led K.A.Jensen 23 to attribute covalent structures to mixed organometallic com-pounds, their conductivity in water and in many cases their solubilitydepending on the formation of aquo-complexes-R,SnX + H,O +[R,Sn*OH,]X. C. P. S m ~ t h , ~ , from studies of the dipole moments, con-cludes that many metal-halogen bonds are largely ionic, although the carbon-metal linkages are covalent.The compounds formulated as Ph,CrX, Ph,CrX, and Ph,CrX havemagnetic moments approximating to 1.73 Bohr magnetons and are believedto contain quinquevalent chromium. It is suggested 25 that these substances,some of which yield much diphenyl on decomposition, may really containdiphenylyl groups and be [C,H,Ph*CrPh,]X, [C,H,Ph*CrPh,H]X, and[C,H,Ph*CrPhH,] X.Mercury-oZeJin Complexes.-Mercuric salts in water or alcohol combinewith ethylene, yielding products which are usually formulated asRO*CH2*CH,*HgX (Ia) and O[CH2*CH2*HgX], ; owing to the ready regener-ation of ethylene they have also been regarded as Werner complexes:26[RO*Hg*C,H,]X (Ib) and [C2H4*Hg*O*Hg*C2H4]X2. After it had been dis-covered 27 that diaryltin dichlorides react with inorganic mercury corn-pounds to give diarylmercury but with alkylmercury halides furnish mixedalkylarylmercury, the reaction was applied 26 to the compound (I ; R = H,X = Br).This gave only hydroxyethyl-p-tolylmercury (which affordedethylene quantitatively with hydrochloric acid !). On the other hand,28 2. anorg. Chem., 1937, 230, 277.24 J .Org. Chern., 1941, 6, 421; G. L. Lewis, P. F. Oesper, and C. P, Smyth,J . Arner. Chem. SOC., 1940, 62, 3243.26 W. Klemm and (Frl.) A. Neuber, Z. anorg. Chem., 1936, 227, 261; F. Hein,ibid., p. 272.26 Summary: A. N. Nesmejanov and R. C . Freidlina, Compt. rend. Acad. Sci.U.R.S.S., 1940, 26, 60; Ber., 1936, 69, 1631; R. N. Keller, Chem. Reviews, 1941,28, 229.27 A. N. Nesmejanov and K. -4. Kotscheschkov, Ber., 1934, 67, 317; idem andR. C. Freidlina, Ber., 1936, 68, 665STEVENS : ORQANOblETALLIC COMPOUNDS. 139the substances HgCl,,C2H2 and HgCl2,2C2H, yielded diarylmercury, andtriphenylphosphine displaced acetylene from them, giving HgCl,,PPh3.26I n an attempted rational synthesis of (Ia, R = Et),28 the saItEtOCH,*CH2*S0,*HgCl was boiled with water, but ethylene was producedquantitatively. Since ethylene is formed from EtOCH,*CH,Br and Mg,29and from CPh,*CH,*CH,I and Na,m and the volatile and no doubt correctlyformulated '' Lewisite, ' ' CHCI:CH*AsCl,, affords acetylene on treatmentwith alkali, it seems dangerous to base co-ordination formulae on the mereready regeneration of unsaturated hydrocarbon.R. C. Freidlina and A. N.Nesmejanov 26 emphasise the continuity in behaviour from admittedprincipal valency compounds through substances of controversial structureto recognised Werner complexes, and offer spectroscopic evidence thatresonance between the two types occurs in mercuric chloride-acetylenecompounds.General Chemical Behaviour.-With compounds containing activehydrogen, organometallic substances undergo fission, RM + HX --+ RH +MX, which proceeds with very different degrees of facility, the more easily,broadly speaking, the baser the metal (compare Tables I and 11).Freehydrogen at room temperature decomposes reactive organometallic com-pounds analogou~ly,~~ PhNa + H, + PhH + NaH, the speed increasingin the order PhCaI, PhLi, PhNa, PhK, PhRb, PhCs. The reaction may beinfluenced by other, more specific, properties of the reagent as well as by itsacidity. Thus tetraethyl-lead and triethyl- bismuth are unaffected by organicacids under mild conditions, but yield ethane quantitatively with thiols,and have been recommended for the " Zerevitinov " determination of SHin presence of OH or NH.33Different organic radicals, moreover, are not detached equally readily.The partial scission of unsymmetrical mercury compounds enables radicalsto be arranged in a series l* 34 of decreasing lability which is regarded as aseries of diminishing electronegativity : a-thienyl > o- and p-anisyl >a-naphthyl > o-, m-, andp-tolyl > phenyl and halogenophenyl > n- andmany other alkyls > benzyl > tert.-butyl and neopentyl.Compounds ofother metals furnish series very similar but less elaborately investigated-germanium : 35 p-tolyl > m-tolyl > phenyl > benzyl; tin : 36 a-thienyl >H. J. Lucas and S. Winstein have expressed similar views.312 8 J. D. Loudon and N. Shulman, J., 1939, 1066.*@ R. C. Tallman, J . Amer. Chem SOC., 1934, 58, 126.3O C.B. Wooster and R. A. Morse, ibid., p. 1735.31 Ibid., 1938,80, 836; 1939, 81, 3102 (with F. R. Hepner).32 H. Gilman, A. L. Jacoby, and (Miss) H. Ludeman, J . Amer. Chent. SOC., 1938,33 H. Gilman and J. F. Nelson, ibid., 1937,59, 935.34 M. S. Kharasch, H. Pines, and (Miss) J. H. Levine, J . Org. Chem., 1938, 3, 347;M. S. Kharasch and S. Swartz, ibid., p. 405; M. S. Kharasch, R. R. Legault, andW. R. Sprouls, ibid., p. 409; F. C. Whitmore and H. Bernstein, J . Amer. Chem. SOC.,1935, 80, 2626.60, 2336 ; see also W. H. Zartrnan and H. Adkins, ibid., 1932,54, 3398.36 J. K. Simons, ibid., 1935, 57, 1299.a * T. S. Bobaschinskaja and K. A. Kotscheschkov, J . Qen. C'henb. Russia, 1938,8, 1860140 ORGANIC CHEMISTRY.p-anisyl > a-naphthyl > phenyl > cyclohexyl ; Z e d : 37 a-fury1 > a-thienyl,p-ltnisyl > phenyl > ethyl, benzyl; or-naphthyl > phenyl.A. N. Nesme-janov and K. A. Kotscheschkov3s describe a transformation in whichelimination of a radical as hydrocarbon is in competition with an alternativemode of reaction :(A) Hg + R2SnC12+-R2Hg + SnC1, (+EtOH)+Hg +2RH + (EtO),SnCI, (B)Dominance of the mode (A) is associated with " electronegativity " of R,and decreases in the order : p-C6H,*NH2, pC,H,*OH, o-anisyl, p-naphthyl,o- and p-tolyl, p-halogenophenyl, phenyl, p-C6H4*C02Et, benzyl, ethyl.Much elaborate work has been done on the relation between the reactivityof an organometallic compound and the nature of the metal, especially itsposition in the periodic table. Mutually compatible results are obtainedonly with important restrictions as to the reactions employed in assessingreactivities.Thus ease of thermal decomposition and of atmosphericoxidation show little connection with one another or with sensitiveness towater and acids, but the last property runs roughly parallel with thesynthetically important power of addition to multiple linkages. Table I1shows the behaviour of derivatives of a number of metals towards differentreagents ; more precise comparisons, often with benzonitrile as substrate,have led H. Gilman to the following inequalities in " reactivity " : RCs >RRb > RK > RNa > RLi > RMgBr (R = CPhiC.) ; 39 RLi > RMgXor R a g ; 4O PhLi > PhCaI > PhMgI ; 41 RMgX > R3AI > R,B > R&n ; 42R2Zn > R2Cd > R2Hg ; 43 R3A1 >> R3Tl ; Ph,In > Ph3Ga 9 Ph3T1.7*TABLE 11.2 + G + a, 0 0ON ; B o o 6 g z v 0, G s d i w r n ON 9++ ++ RNa ++ ++ ++ ++ ++ ++ RCu46 ++ ++RBEX ++ ++ ++ R,Zn + + + + + + + + +RCaX44 ? ++ - ? ++ ++ RzCd43047 + + ++ ++ - + - ++- ++ RMgX -46 ++ ++ ++ ++ ++ RZHg ++ ++ R4Pb- ++ + R4SnRa-R3Ga 6* 7 + + - ++++ RSbR,In 0 + + - ++++R3T1 11 + ++ ++ ++m d m xRLi ++ ++ ++ ++ ++ ++ RAg4;* + +++ - + + +--- --- - - ++4a++ +- ?$?149 + + + + + + + + + R3BiRapid action at or near room temp.is indicated by ++, no action under ordinary8 7 H. Gilman and E. B. Tome, Rec. Trav. chim., 1932, 61, 1054; J . Amer. Chem.38 Ber., 1930, 63, 2496; Sci. Rep. M08eW State Univ., 1934, No.3, 283.3s H. Gilman and R. V. Young, J . Org. Chern., 1936, 1, 315.40 H. Gilman and R. H. Kirby, J . Amer. Chem. Soc., 1933, 55, 1265; H. Gilman4 1 H. Gilman, R. H. Kirby, M. Lichtenwalter, and R. V. Young, ibid., p. 79.48 H. Gilman and K. E. Marple, ibid., p. 133.43 H. Gilrnan and J. F. Nelson, ibid., p. 518.conditions by - ; mere addition of NH, is disregarded.Soc., 1933, 55, 4689 (with H. L. Jones) ; 1939, 61, 739.See also ref. 3.and M. Lichtenwalter Rec. Trav. chim., 1936, 55, 561STEVENS : ORCIANOMETALLIC COMPOUNDS. 141H. ailman associates the alternative courses of some reactions withthe reactivity of the organometdlic participant. Derivativea of the alkalimetals and calcium undergo predominantly normal addition t o the carbonylgroup of benzylideneacetone and the like, whereas many others affordfinally the saturated ketone CHPhR*CH,*COMe-" I : 4-addition ".Qp 49The former reagents similarly convert benzophenoneanil normally intotriphenylmethylaniline,(9 and phenylmagnesium bromide attacks thenucleus, giving o-phenylbenzhydrylaniline, C,H,Ph*CHPh*NHPh. Withazobenzene,17 aryl compounds of potassium and calcium afford triphenyl-hydrazine, whereas those of other metals, including sodium and lithium,yield hydrazobenzene and/or aniline by reduction.H.Gilman and J. F. Nelson3*43 relate the reactivity of organometalliccompounds to the position of the metal in the periodic table by a series ofrules which somewhat outrun the experimental data. Broadly speaking,in each group, Li-Cs, Be-Ca, B-Al, G-Pb, and N-Bi, the reactivityof the organic derivatives rises with the atomic weight of the metal, and fallswith increasing group number from I to IV. In each B group, Cu-Ag,Zn-Hg, and Ga-T1, the reactivity is less than in the corresponding Agroup and appears to fall with increasing atomic weight of the metal. Inmany cases the mixed organic compounds of a metal are a little less reactivethan the simple ones, but substances of the types RBX, and R,TlX areextraordinarily inert in comparison with R3B or R,TI.Attempts to correlate by various methods the reactivity of Grignardreagents with the nature of the hydrocarbon radical have given contra-dictory results. 60A redistribution of organic radicals between metallic atoms, as in thecase Me,Hg + Et,Hg 2MeEtHg, has been occasionally encountered,and now forms the subject of an elaborate study by G. Calingaert and co-w0rkers.~1 In the example cited, the equilibrium mixture attained fromeither direction contains 50 molecules yo of the mixed dialkylmercury and25% of each of the simple ones, corresponding to a random distribution ofradicals between the metallic atoms. If excess of one dialkylmercury istaken, the new equilibrium corresponds to a new random distribution,and the same holds for the more complicated case of a pair of alkyl-leadswhich gives a mixture of R,Pb, R,R'Pb, R,R',Pb, RR',Pb, and R',Pb.STEVENS : HETEROCYCLIC COMPOUNDS. 227L. Pauling and J. H. Sturdivant63 suggested that cyameluric andhydromelonic a,cids, melam, melem, and melon, compounds derived directlyor indirectly from pyrolysis of thiocyanogen derivatives,were related to a nucleus C6N7 in the same way as the/ \ cyanuric compounds to the C,N, ring. For this nucleusthey proposed the structure (XI) with the large calculated ' resonance energy of 150 Caltls. C. E. Redemann andH. J. Lucasa show that hydromelonic acid, regarded asC6N7(NH*CN),, like tricyanomelamine, C,N,( NH-CN),,is too strong an acid for its dissociation constant to bemeasured, and cyameluric acid, C6N,( OH),, like cyanuric,is much weaker. Hydromelonic acid gives on hydrolysiscyameluric acid which has been converted into thechloride C6N,C1, and into (mainly N - ) alkyl derivatives and which yieldsone molecule only of cyanuric acid on further hydrolysis. Melam is nowbelieved to be an imide (NH2),C3N3*NH*C,N3(NH,),, and melem to becyameluramide. Melon is probably a mixture of intermediate stages of" deammonation " between melem and a graphite-like (C3N&.Pterins.-These pigments of butterflies, wasps, and other insects, arenot easily purified and characterised and are also difficult to combust. Acareful revision of the analyses removes the necessity of assigning to themformulae containing nineteen carbon atoms with three pyrimidine or purinenuclei.65 Leucopterin is now formulated C6H503N5 (the trimethyl derivativegives the expected molecular weight in phenol)70 and has been synthesisedby fusing 2 : 4 : 5-triamino-6-hydroxyyrimidine with oxalic acid.66 Theformulse (XII) and (XIII) are suggested for the s~bstance.~5~6*~ 69 Con-densation under milder conditions with dichloroacetic in place of oxalic acidgives xanthopterin C6H302N5,6g which yields on oxidation leucopterin (not,as previously reported, an iminoleucopterin) ,65 " Anhydroleucopterin '' isshown to be a deoxyleucopterin, distinct from 6-deoxyleucopterin preparedfrom the 6-chloro-compound.67 Guanopterin is identical with isoguanine.66(XII.) HN=V fi-NH>c.Co2H HN=V G-NH-70 (XTlJ.)

ISSN:0365-6217    

DOI:10.1039/AR9413800111

出版商:RSC    

年代:1941

数据来源: RSC

摘要:

BIOCHEMISTRY.SOME of the most interesting developments in biochemistry during thepast year have had to do with the following topics : vitamins, intermediatemetabolism of proteins, biochemistry of muscle, intracellular gels, bio-chemical systems in plants, carboxylation and decarboxylation in bacterialsystems, metabolism of moulds. The specialists invited to cover the corre-sponding reviews in these pages are Dr. L. J. Harris, Dr. A. Neuberger,Dr. Dorothy Needham, Dr. J. F. Danielli, nr. F. W. Norris, Dr. H. Krebsand Dr. Marjory Stephenson, and Professor H. Raistrick.1. VITAMINS.In consequence perhaps of the special needs of war-time most attentionseems to have been given of late to two problems of immediate practicalimportance, namely, the devising of methods, first for the more accuratedetermination of vitamins in foodstuffs (see also the Report on AnalyticalChemistry), and secondly for assessing the nutritional status of humans.The old idea that vitamins were only “ qualitative ” factors, and that theamount present in the food did not matter provided they were there in themerest trace, has gone by the board.A definite minimal quantity of eachvitamin is now recognised as needed to prevent deficiency disease, and alarger quantity to prevent ‘ ‘ subclinical deficiencies. ” Dietetic essentialsnot recognised until a few years ago are now well established and havealready found important clinical uses ; such are nicotinamide, riboflavinand vitamin K : knowledge is accumulating too about the significance ofthe still “newer ” vitamins, for example, adermin (vitamin BJ, biotin(vitamin H), choline, p-aminobenzoic acid, inositol.Particularly interestingis the recent work relating to choline, the absence of which producesremarkable changes in the animal organism.Water-soluble Vitamins : Vitamin B,.Methoas of Assay.-Probably the most comprehensive study of techniquefor estimating a vitamin in foodstuffs which has so far appeared is that ofL. J. Harris and Y. L. W8ng.l They describe a series of modifications inthe thiochrome method, based on the procedure previously used for urine.2Their results were checked by biological assays, three different methodsbeing used, on more than 50 foodstuffs of all types. With the improve-ments recommended, the chemical and biological values generally differedby less than 15%.The reliability of this modified chemical method hasalso been confirmed by E. C. Slater and other workers. Another procedure1 Biochem. J., 1941, 35, 1050; Chem. and I n d . , 1942, 61, 27.2 Y . L. Wang and L. J . Harris, Biochem. J., 1939, 33, 1356; 1941, 35, 1068.3 Aust. J . Exp. Biol. Med., 1941, 19, 29F€ARRIs: VITAMINS. 229which is being made increasingly specific, and is likewise relatively simpleto perform, depends on a measurement of the carbon dioxide evolved duringthe fermentation of yeast, which is stimulated by the addition of vitamin B,.To distinguish between specific fermentation due to the vitamin and thenon-specific “ blank,” tests are done before and after addition of ferricyanide,or better of sulphite, to the unknown.These substances destroy the vitaminand the products formed have no activity in the ferrnentati~n.~have confirmed theobservation 6 that an elevation in pyruvic acid may be used to reoord thepresence of a deficiency of vitamin B, in the experimental animal. Fordetecting partial deficiencies in the human subject, as in animals, tests oftolerance to carbohydrate loading 7 were recommended and these haveproved of practical use clinically.8R61e of Vitctmin B, in Carbohydrate 4letabolism.-Observations of E. S. G.Barron and co-workers 9 just published may help to remove confusionabout the chemical reactions brought about in mammalian tissues byvitamin B,. It has long been accepted that in yeast, vitamin B,, in theform of its pyrophosphate ester, is the co-enzyme for the decarboxylationof pyruvic acid, an essential intermediate in the metabolism of carbo-hydrates. In animal tissues the reactions have been found much lesssimple to study.The point is made in the papers just mentioned that inorder to examine the effect of vitamin B, on animal tissues in vitro, it isnecessary to incubate the vitamin first with the tissue, in order presumablyto convert it into the active pyrophosphate derivative. With this proviso,it can then be shown that vitamin B, catalyses a variety of reactions, suchas oxidation, dismutation and condensation, all of which, however, seemto involve decarboxylation a t some stage. In the latter respect, there-fore, animal tissues now seem to come fundamentally into line with yeast.Much other important work10 on the biochemical function of vitamin B,as a co-enzyme has appeared, and it will be more convenient to reviewthe whole problem when a longer perspective is possible after the lapse ofanother year.Assessment of Level of Nutrition.-Several workersA.S. Schultz, L. Atkin, and C. N. Frey, J . Biol. Chem., 1940, 136, 713; A. S.Schultz, L. Atkin, C. N. Frey, and R. R. Williams, J . Amer. Chem. SOC., 1941, 63, 633;H. Laser, Biochem. J . , 1941, 35, 488.M. E. Shills, H. G. Day, and E. V. McCollum, J . Biol. Chem., 1941, 139, 145;H. A. Harper and H. J. Deuel, ibid., 1941, 137, 233.G. G. Banerji and L. J. Harris, Biochem. J., 1939, 33, 1346.See Ann.Reports, 1940, 31, 387.E. 0’s. Elsom, F. D. H. Lukems, and E. H. Montgomery, J. Clin. Inveat., 1940,19, 153. ’ E. S. G. Barron and C. M. Lyman, J . Biol. Chem., 1941,141, 951 ; E. S. G. Barron,C. M. Lyman, M. A. Lipton, and J. M. Goldinger, ibid., p. 957; E. S. G. Barron, J. M.Goldinger, M. A. Lipton, and C. M. Lyman, ibid., p. 976.lo E.g., F. J. Stare, M. A. Lipton, and J. ill. Goldinger, ibid., p. 981; H. A. Sober,M. A. Lipton, and C. A. EIvehjem, ibid., 1940, 134, 605; M. A. Lipton and C. A.Elvehjem, aid., 1940, 136, 637; S. Ochoa, ibid., 1941, 188, 761; J. H. Quastel andD. M. Webley, Bhltem. J., 1941, $6, 192230 BIOCHEMISTRY.Vitamin B, Complex.RiboJlavin.-The polarograph is proving of increasing use in thedetermination of vitarnins,ll and offers a convenient method, for example,with riboflavin.12 With attention to detail, the chemical method (measure-ment of fluorescence) also gives results in agreement with biological assays.13Cheilosis (angular stomatitis) has in the past year or two come to beconsidered as the characteristic sign of riboflavin deficiency in man, but tojudge from the clinical observations of T.E. Machella l4 it may be a relativelynon-specgc lesion, the primary cause being sometimes a deficiency ofvitamin B,, sometimes nicotinic acid or sometimes even ascorbic acid.Nicotinamide.-Pellagra has been very prevalent in Spain since thecivil war,15 and, possibly as a result of the present war or perhaps only asa result of better searching for it, an increased incidence is recorded inNorthern Ireland.16 To assess the level of nutrition in the anti-pellagravitamin,17 the modified procedure recommended by E.KQdicek and Y. L.Wang l8 involves dosing with nicotinamide while the patient is kept on a dietfree from trigonelline, and measurement of the urinary response in excretionof trigonelline plus nicotinic a ~ i d . 1 ~ An observation which may throwlight on the mode of action of the vitamin is that it inhibits the breakdownof co-zymase by the nucleotidases present in animal tissues.20Microbiological Methods.-Relatively specific methods now exist fordifferentiating and determining the various components of the vitamin-B,complex by means of their stimulating action on various micro-organismsunder appropriately standardised conditions.Recent literature describingmch methods for pantothenic acid 21 and for nicotinic acid 22 may be citedas excellent examples from an important and quickly growing literature.Vitamin C.Methods of Assay.-Further evidence 23 is available of the applicabilityof the polarograph for estimating vitamin C.24 A source of error whichhad too often been overlooked in the chemical determination of vitamin Cl1 E. Kodicek and K. Wenig, Nature, 1938, 142, 35.l 3 J. J. Lingane and 0. L. Davis, J. Biol. Chem., 1941, 137, 567.l3 F. 0. Van Duyne, ibid., 1941, 139, 207.l4 Amer. J. Med. Sci., 1942, 1, 114.l5 Quoted by Lancet, 1941, ii, 458.l6 J. Deeny, Brit. Med. J., 1942, i, 157.l 7 Cf. L. J. Harris and W. D. Raymond, Biochein.J., 1939, 33, 2037.l 8 Nature, 1941, 148, 23.See further W. A. Perlzweig, H. P. Sarett, and J. W. Huff, J . Bid. C'kem., 1941,2o P. J. G. Mann and J. H. Quastel, Nature, 1941, 147, 326; Biochem. J . , 1941,21 M. J. Pelczar and J. It. Porter, J. Biol. Chem., 1941, 139, 111.28 H. Isbell, J. G. Wooley, R. E. Butler, and W. H. Sehrell, ibid., p. 499; E. E.23 T. Osterud, Tek. Ulcebhd, 1939, 86, 216.24 Cf. E. Kodicek and K. Wenig, Nature, 1938, 142, 35.140, proc. C; H. P. Sarett, J . Nutrition, 1942, 23, 23.35, 502.Snell and L. D. Wright, ibid., p. 675TTARRIS : VITAMTNS. 23 1is that any sulphur dioxide present as a preservative in fruit pulps, juices,etc., will seriously interfere unless special precautions 25 are taken.War-time Considerations.-With the diminished supply of importedfruits, our bodies’ reserves of vitamin C are likely to be far lower than theywere before the war, and it is therefore useful to have the authoritativememorandum dealing with the preparation and cooking of green vegetables,which gives rules for treatments calculated to cause the least loss.26 Incooking sour fruits a limited amount of alkali (sodium bicarbonate) cansafely be added to save sugar.27 Valuable compilations by M.Olliver 28and W. B. Adam29 deal comprehensively with the effects of cooking andcanning respectively on the nutritive value of vegetables.“ Partial De$ciency ” of Vitamin C.-Various views are taken about thereality of sub-clinical deficiency. On the one hand S. S. Zilva 3O has argued :“ As far as the civilian population of this country, leading a normal life, isconcerned, the natural supply of vitamin C during the greater part of theyear is so superabundant that, even allowing the widest margin for destruc-tion in the cooking and the preparation of the food, the intake is more thanadequate to supply the vitamin C requirements.” On the other hand,tests in Germany proved that the addition of extra vitamin C (50 mg.perday) to the diet of over a million children increased their resistance toinfection and improved their yearly gains in weight and height-althoughthere had been little or no actual clinical ~urvey.~l Similar tests have beendone in a large training school in Britain on 1500 adolescents : in the controlgroup receiving no added vitamin C there occurred 17 cases of pneumoniaand 16 of rheumatic fever, whereas there was no case of either in the groupgiven added vitamin C ; tonsillitis occurred in both groups but the averageduration of illness in the control group was much longer, the difference beingof undoubted statistical significance.31a Addition of vitamin C to the diethas also been found to diminish the incidence of gingivo-stomatitis, or aidin its cure,31b and to promote healing after dental extraction.31c Again thehealing of wounds after surgical operation is usually found to be better insubjects receiving ample vitamin C32 than in those whose intake is lower.There is in fact ample evidence that in man, as in animals, sub-clinicaldeficiency of vitamins produces a variety of somewhat ill-defined but nonethe less real faults in nutrition 33-f0r vitamin C these may include sub-25 L.W. Mapson, Ghem. and Ind., 1941, 60, 802.36 Accessory Food Factors Committee, Medical Research Council, Brit. .&led. J.,97 L. W. Mapson and J. Barker, Ghem and Ind., 1941, 60, 661.2 8 Ibid., p. 586.30 Biochem. J . , 1941, 35, 1240.31 Bull. War Med., 1941, 2, 6.310 A. J. Glazebrook and S. Thomson, J. Hyg., 1942, 42, 1.311 F. S. Roff and A. J. Glazebrook, J . Roy. Nav. Med. Sew., 1939, 25, 340; Brit.1941, ii, 26.2s Ibid., p. 627.Dent. J., 1940, 68, 135; H. G. Campbell and R. P. Cook, Brit. Med. J., 1941, i, 360.H. G. Campbell and R. P. Cook, Brit. Dent. J., 1942, 72, 6.C. C. Lund and J.H. Crandon, Ann. Surgery, 1941, 114, 776.33 See L. J. Harris, Proc. Nutrition SOC., 1941, No. 1 ; also Food, 1942, 11, 23232 BIOOHEMISTRY.optimal growth, diminished resistance to infection, impaired formation ofscar tissues, and irregularities in teeth and gums.Therapeutic Uses of ‘Vitamin C.-Apart from its value in securing theadequate healing of there is evidence also that an abundantsupply of vitamin C prolongs the life of experimental animals submittedto severe bleeding This it may do bysecuring a more adequate supply of oxygen to the tissues.Mode of Action of Vitamin C.-In the last-mentioned connection it maybe noted that S. S. Zilva and his colleagues36 have codrmed the findingof D. C. Harrison 37 that addition of ascorbic acid in vitro to the liver tissuesof scorbutic animals augments their uptake of oxygen.The exact meaningof this finding is not yet clear, but G. A. Snow and S. S. Zilva discuss itspossible connection with carbohydrate metabolism. Various types ofenzyme systems are however also activated by vitamin C, e.g., liver esterase,succinic dehydrogenase, and to a less extent cytochrome oxidase, andphosphatases from the kidney and intestine; 38 the degree of specificity ofsuch activations still remains in doubt. In cauliflower juice dehydroascorbicacid is reduced by SH-glutathione, and the enzyme which catalyses thereaction has now been separated : it is suggested that it may have a r61eas an ‘‘ end syetem ” in plants.39or to low oxygenFat-Soluble Vitamins : Vitamin A.Factors influencing Utilisation of Vitamin A .-It is becoming apparentthat the efficiency with which vitamin A or carotene prevents deficiencydisease in animals (and presumably in humans) varies with other factors inthe diet : e.g., the utilisation of carotene by the rat depends on the chemicalnature of the oil administered with it ; 40 prolonged deficiency of vitamin Ecauses a secondary deficiency of vitamin A ; 41 and the quantity of foodconsumed of course also influences the growth rate with any given intake ofvitamin A.42Assessment of Level of Nutrition.---S. Yudkin43 has made a careful re-investigation of dark adaptation as a means of detecting sub-clinical deficiencyof vitamin A.Of 24 subjects tested for “night blindness,” all exceptthree improved with vitamin A.The method, which is in any case relativelyspecific, can thus be made completely so by taking as the criterion animprovement or otherwise after dosing with vitamin A.44 S. Yudkin4334 C. P. Stewart, J. R. Learmonth, and G. A. Pollock, Lancet, 1941, i, 818.35 B. G. B. Lucas, quoted by J. M. Peterson, Nature, 1941, 148, 84.36 A. E. Kellie and S. S. Zilva, Riochem. J., 1941, 35, 783; G. A. Snow and S. S.37 Ibid., 1933, 27, 1501.Zilva, ibid., p. 878.C. J. Harrer and C. G. King, J . Biol. Chem., 1941, 138, 1 1 1.E. M. Crook, Biochem. J., 1941, 86, 226.40 W. C. Sherman, J . Nutrition, 1941, 22, 153.4 1 A. W. Davies and T. Moore, Ndure, 1941, 147, 794.42 K. D. Muelder and E. Kelly, J . Nutrition, 1941, 21, 13.43 Lamed, 1941, i i 787.44 See, e.g., Ann. Rqwt.8, 1939, 36, 338EKARRIS : VITAMINS. 233emphasises that it may be necessary to give massive doses, and that withsmaller doses especially the cure may be only transient. For any givensubject there is a critical low level for the vitamin A in the blood, and belowit dark adaptation is adversely affected ; unfortunately, however, thereappeared to be no such standard level applicable for all subjects. Benz-edrine or alcohol produced transient improvement, but the supposed adju-vant action of vitamin C45 could not be confirmed. An alternative pro-cedure, biomicroscopy with the ~ l i t - l a m p , ~ ~ has been used by H. D. Kruseand his fellow investigators in the course of their impressive surveys onthe evaluation of nutritional status; 47 but Kruse is rightly a t pains topoint out that the ocular lesion (keratosis) is not the sole, first or mostimportant abnormality : '' xerophthalmia is not synonymous with avita-minosis A."Efseects of De$ciency.-E.Mellanby 48 has published the detailed accountof his observations on the skeletal changes produced in young dogs bydeficiency of vitamin A. The bony overgrowths in the skull and vertebralcolumn may produce deformities in the brain and spinal cord. Mellanbyconcludes that vitamin A controls the degree of activity of the osteoblastsand osteoclasts.Vitamin A in Blood and Urine.-Reference to vitamin A in the bloodand its connection with dark adaptation in humans has been made above.Similarly it has been shown that in dogs the level of vitamin A in the bloodis proportional to the intake in the diet, and during depletion the level dropgradually : a low level in the blood cannot however be taken to indicatethat the reserves have become depleted.49 In humans vitamin A is notfound in the urine except in certain diseases, notably pneumonia and chronicnephritis. It is probably significant that in these two diseases, amongothers, there is a great disappearance of the reserves of vitamin A from theliver.A strange phenomenon, still lacking explanation, is that in dogs,by contrast with humans, vitamin A is a normal constituent of the urine.60Vitamin D.InJEuence on Metabolism.-Extended observations by S. H. Liu51 inChina on patients with osteomalacia have proved once again that vitamin Dis the primary factor controlling cure of the disease, and have confirmedalso that its mode of action is to decrease the fzecal loss of calcium.52Factors inJEuencing Rachitogenesis.-It has been emphasised 53 that fat isone of many factors-others include the acid-base reaction, the Ca-P ratio,presence of heavy metals, sugars, etc.-which have an effect on the pro-45 Cf.C . P. Stewart, Edinburgh Med. J., 1941, 48, 217.46 Milbank Memorial Fund Quarterly, 1941, 19, 207.47 Ibid., 1939--1941.49 P. C . Leong, Biochem. J., 1941, 35, 806.61 Chinese Med. J., 1940, 57, 101.62 Cf. L. J. Harris, Lancet, 1932, i, 1031.69 *4. Knudson and R. J. Fbody, J . Nutrition, 1940, a0, 317.'* J . PhpiOl., 1941, 99, 467.N.R. Lawrie, T. Moore, and K. R. Rajagopal, ibid., p. 825234 BIOCHEMISTRY.duction or healing of rickets. Phytic acid is another such, and important,factor, and to it the rickets-producing action of cereals is attributable.The cause of the deleterious action of the phytic acid seems to be partlythat it precipitates the calcium in the intestine and partly that it rendersthe calcium non-ionised and thus impedes its absorption.54 But, fortun-ately, when wheat flour is baked with yeast, an enzyme, phytase, presentin the flour largely destroys the phytic acid.55Other Pat-soluble Vitamins.Of importance to all researchchemists and analysts working on vitamins is the adoption of racemica-tocopherol acetate as the international standard for vitamin E.56 Thetwo chemical methods for estimating the vitamin, potentiometrically withauric chloride, or colorimetrically with the ferric reagent, have been sys-tematically reinvestigated by Karrer and his colleagues and found to giveresults in satisfactoryIt is pleasing for once to be able to recorda diminution instead of an increase in the apparent number of the vitamins.A variety of symptoms in various species, sometimes attributed in the pastto lack of still unidentified factors, have been found to respond to syntheticvitamin E.There is accordingly no longer any need to call in hypotheticalnew vitamins to account for the following disorders : " nutritional ence-phalomalacia " of chicks, " nutritional myopathy " of ducklings and " giz-zard disease " of turkeys, " muscular dystrophy " of guinea pigs, rabbitsand young rats,58 generalised edema in " alimentary exudativediathesis " in chicks.6oAlthough admittedly lack of vitamin E causes muscularatrophy in experimental animals, it seems dangerous to jump to the con-clusion, as has sometimes been done, that vitamin E is therefore useful ina wide range of neuromuscular disorders in man.Controversy on this issuestill continues.61 For habitual abortion in women, however, a statisticaltreatment of the results of treatment is distinctly encouraging.62An observation which for the firsttime promises to throw light on the mode of action of vitamin F (nutri-54 E. F. Yang, Nature, 1940, 145, 745; D. C. Harrison and E. Mellanby, ibid.,p.745.5 6 E. M. Widdowson, ibid., 1941, 148, 219.6 6 E. M. Hume, ibid., pp. 472, 473.67 p. Karrer, W. Jaeger, and H. Keller, Helv. Chint. Acta, 1940, 23, 464; see alsoA. Emmerie, Rev. Trav. china., 1940, 59, 246; F. Grandel and H. Newman, 2. Untem.Lebenam., 1940, 79, 57-6 8 A. M. Pappenheimer, J . Mt Sinai Hosp., N.Y., 1940, 7, 65; H. M. Evans andG. A. Emerson, Proc. Xoc. Ezp. Bid., Med., 1940, 44, 636; C. G . Mackenzie, J. B.Mackenzie, and E. V. McCollum, J . Nutrition, 1941, 21, 225.6s H. R. Bird and T. G. Culton, Proc. SOC. Exp. Biol. Med., 1940, 44, 543.60 H. Dam and J. Glavind, Naturwiss., 1940, 28, 207.61 see, e.g., Lancet, 1941, ii, 619; Brit. Med. J., 1941, ii, 618.62 A. L. Bacharach, Brit. Med. J . , 1940, i, 890; 1941, ii, 709.Vitamin E.-#tandards and methods.Symptoms of avitaminosis E .CZinicaZ uses.Vitamin F.-Physiological actionHARRIS : VTTAMNS.235tionally essential fatty acids) is that in its deficiency there is an impairedabsorption of ordinaryReports continue to appear stressing thevalue of vitamin K in preventing hzemorrhage after operation for obstruc-tive jaundice, or in new-born infants ; the comprehensive monograph onthis vitamin by H. R. Butt and C. T. Snell 64 will be welcomed.Vitamin K.-Clinical uses.The Newer Vitamins.Enumeration.-The ‘‘ vitamin-B, complex ” includes, by definition, ribo-flavin and nicotinamide (pellagra-preventing factor), both of which havealready been referred to above, and also adermin (pyridoxin, vitamin B,)and pantothenic acid (filtrate factor, bios IIA), which have been discussedin a recent issue of these Reports.65 Other vitamins more recently charac-terised, which could logically be classified as of the “B, group,” includevitamin H (biotin, bios IIB, co-enzyme R), choline, inositol (bios I), andp-aminobenzoic acid (possibly identical with the ‘‘ anti-grey-hair factor ’,),Vitamin H (Biotin, Bios IIB).-Vitamin H is the factor needed by ratsor chicks for protection against the nutritional injury which arises whentheir diet contains much raw egg-white.It is identical with biotin (orbios IIB, a factor needed by yeast and other micro-organisms) and alsowith the so-called ‘‘ co-enzyme R ” which stimulates the growth of micro-organisms in the nodules of the roots of certain leguminous plants.66 Theaction of the raw egg-white in inducing the deficiency in rats has beentraced to a component in the crude protein which unites with the vitamin Hand thus renders it unavailable to the organism.67 This component hasbeen named ‘‘ avidin,” and methods have been worked out for fractionatingit, and estimating i t .G 8 Vitamin H itself has also been isolated and itsempirical formula established (C,,H,,0,N2S) ; 69 its behaviour to variousreagents has been ~tudied,~O and it has been shown to be a carboxylic acidcontaining an “’-substituted cyclic urea group and a-cozH thioether linkage (annexed formula).71 As to the physio-C,H,, -zz>CO logical nature of the ‘‘ egg-white injury ” and the actionof vitamin H in preventing it, it may perhaps be ofsignificance that G.Gavin and E. W. McHenry 72 havefound that biotin given to rats induces fatty livers, whereas the simul-taneous administration of egg-white (or of inositol) prevents this effect.Cho1ine.-Perhaps the most spectacular work on vitamins during thepast two or three years is that relating to choline. This substance is underI,,,63 R. H. Barnes, E. S. Miller, and G. 0. Burr, J. BioZ. CJLem., 1941, 140, 773.64 ‘. Vitamin K,” 1941.6 5 Ann. Reports, 1940, 37, 389, 390.6 7 R. E. Eakin, E. E. Snell, and R. J. Williams, J . BioZ. Chem., 1940, 136, 801.6 8 Idem, ibid., 1941, 140, 535.19 V. du Vigneaud, K. Hofmann, D. B. Melville, and P. Gyorgy, ibid., p. 643.70 C. B. Brown and V. du Vigneaud, ibid., 1941, 141, 85.7 1 K.Hofmann, D. B. Melville, and V. du Vigneand, ibid., p. 207.TZ Ibid., p. 620.66 Ibid., p. 392236 BIOOHEMISTBY.certain conditions a dietary essential for rats,73 absence of it caushg anexcessive deposition of fat in the liver and hzemorrhages in the kidney; 74it is needed also by poultry for the prevention of p e r ~ s i s . ~ ~ It seems thatcholine is concerned in the organism in carrying out transmethylation.For this purpose it can be replaced either by methionine or by betaine :the more of the latter substances there are in the diet the less choline isneeded. On the other hand the need for choline increases when there isincreasing cystine (or fat) in the diet. Viewed from another angle, cholineor betaine, as biological methylating agents, enable the animal to utilisehomocystine in place of methionine.76 There may be similar inter-relationsbetween oholine on the one hand and vitamin B,, nicotinic acid, or other" B " vitamins on the other.72* 77 As yet there is no evidence whethercholine (or its biological equivalents) is needed by man.Amti-grey-hair fuctor ( ? p-aminobenzoic acid). Loss of pigmentation inthe f w of rats kept on deficient diets had been noted by numerous inves-t i g a t o r ~ . ~ ~ Work by A. F. Morgan et aZ.,79 G. Lunde and H. Kringstad,mand J. J. Olsen et uLma made it clear that a hitherto unidentified vitaminwas concerned in preventing this disorder. It has been shown that silverfoxes, dogs and guinea pigs also are susceptible to the deficiency.81S.Ansbacher 82 claims to have identified p-aminobenzoic acid, previouslyrecognised as a growth-promoting factor for plants, as the anti-grey-hairvitamin. Clinical applications for it have already been put f0rward,~3 butthere is still a conflict of evidence whether p-aminobenzoic acid, or maybe73 C. H. Best, M. E. Huntsman, E. W. McHenry, and J. H. Ridout, J . Physiol.,1935, 84, 38.74 W. H. Griffith and N. J. Wade, J . Biol. Chem., 1939, 131, 567; B. Sure,J . Nutrition, 1940, 19, 71; R. W. Engel and W. D. Salmon, ibid., 1941, 22, 109.7 6 0. D. Abbott and C. U. DeMasters, ibid., 1940, 19, 47; T. H. Jukes, J . Biol.Chem., 1940, 134, 789; J . Nutrition, 1940, 20, 445; A. G. Hogan, L. R. Richardson,H. Patrick, and H. L. Kempster, ibid., 1941, 21, 327; J .Biol. Chem., 1941, 138, 459.76 J. P. Chandler and V. du Vigneaud, ibid., 1940, 135, 223; H. J. Channon, M. C.Madfold, and A. P. Platt, Bi0~he7la. J., 1940, 34, 866; A. D. Welch, J . Biol. Chem.,1941, 137, 173; H. P. Jacobi, C. A. Baumann, and W. J. Meek, ibid., 1941, 138, 571;W. H. Griffith, J . Nutrition, 1941, 21, 291 ; W. H. Griffith and D. J. Mulford, J . Amer.Chern. Xoc., 1941, 63, 929.77 p. Gyorgy and R. E. Eckardt, Biochem. J., 1940, 34, 1143; P. Gyorgy and H.Goldblatt, J . Exp. Med., 1940, 72, 1; W. H. GriEith and D. J. Mulford, J . Nutrition,1941, 21, 633; J. C. Forbes, ibid., 1941, 22, 359.78 For early literature, see A. Bakke, V. Aschehoug, and C . Zbinden, Compt. rend.A&. Sci. U.R.S.S., 1930,191, 1157; F.J. Gorter, Nature, 1934,134, 382; 2. Vitumin-forsch., 1935, 4, 277; G. A. HartweI1, Biochem. J., 1923, 17, 547; P. Gyorgy, aid.,1935, 29,741.'70 A. $. Morgan, B. B. Cook, andH. G. Davison, J . Nutrition, 1938, 15, 27.80 2. physiol. Chm., 1939, 25'7, 201; J . Nutrition, 1940, 19, 321.800 J. J. Oleson, C. A. Elvehjem, and E. €3. Hart, Proc. XOC. Exp. BioZ. Med.,1939, 42, 283.81 G. Lunde and H. Kringstad, Naturwiss., 1939, 27, 755; A. F. Morgan andH. D. &nuns, J . Nutrition, 1940, 20, 627.82 Science, 1941, 93, 164.83 B. F. Sieve, ibid., 1941, 94, 257NEUBERGER : THE METABOLISM OF NITROGENOUS COMPOUNDS. 237alternative €actora--e.g., biotin, pantothenic aeid-do or do not in factcure rats of their grey hairs.84Anti-alopecia Factor for .Mice ( ? Inositol, Bios I ) .-Inositol, cyclohexane-hexol, has been known since 1928 s5 to be a growth stimulant for yeast,classified as “ bios I.” I n 1940 D.W. Woolley,86 by feeding mice on arestricted diet, produced in them a disease characterised by hairlessness ofthe trunk and cessation of growth. Later he stated that the protectivesubstance was inosit01.~~ Certain related substances, e.g. , inositol hexa-acetate, cephalin, and phytic acid (inositol hexaphosphate), were foundactive.88 We seem therefore to have the entertaining anomaly that, whereassmall amounts of phytic acid act as a. vitamin for mice, or as a growthstimulant for yeast, yet larger amounts act as a “ toxamin ” or ‘‘ anti-vitamin.” g9Folk Acid, Grass Juice Factor.-Folic acid, a substance necessary forthe nutrition of yeast, occurs abundantly (as its name implies) in theleaves of plants.It has recently been isolated,g0 and its possible relationto the grass juice factor>l needed by guinea pigs, still remains to be decided.Classijkation of ‘‘ Bios ” Factors.-Since the various components of“ bios ” (the growth-promoting stimulant for yeast whose effects were firstdescribed in 1901 92) have lately been identified with certain vitaminsneeded by mammals, the following table of synonyms may help to removeconfusion :Bios I1Biosdimethylbutyryl- p -alanine)IIB = Biotin (vitamin H, co-enzyme R)L. J. H.2. THE METABOLISM OF NITROGENOUS COMPOUNDS.Recent advances in our knowledge of the intermediary metabolism ofnitrogenous compounds have been due mainly to the application of threedifferent methods : (1) the study of nutritional requirements of animals(mainly non-ruminants) and the replacement of naturally occurrhg sub-stances by related compounds, (2) the investigation of biochemical reactionscatalysed by tissue slices, cell extracts and purified enzymes, (3) the use of“ labelled ” compounds, i.e., substances containing heavy or radioactive84 K.Unna, G. V. Richards, and W. L. Sampson, J . Nutrition, 1941, 22, 553;L. M. Henderson, J. M. McIntre, H. A. Waisman, and C. A. Elvehjem, ibid., 1942, 23,47; R. R. Williams, Science, 1940, 92, 561; P. Gyorgy and C . E. Poling, Proc. SOC.Exp. Biol. Med., 1940, 45, 773.1E. V. Eastcott, J . Physical Chew,., 1928, 32, 1094.86 J.Bid. Chem., 1940, 136, 113.D. W. Woolley, Science, 1940, 92, 384; J . Biol. Chrn., 1941, 139, 29.Idern, ibid., 1941, 140, 461.H. K. Mitchell, E. E. Snell, and R. J. Williams, J . Amer. Chern. XOC., 1941, 63,See Ann. Reports, 1940, 37, 393. 9a E. Wildiers, La Oelhle, 1901,18,313.Cf. above, p. 234.2284238 BIOCHEMISTRY,isotopes.space a.vailable, but a few general problems may be discussed.It is impossible to review the whole field adequately within theEssential Amino-acids.It has been known for a considerable time that animals, with thepossible exception of ruminants, require certain amino-acids in their diets.These " essential " amino-acids may be necessary for two purposes : theyhave to serve as the building material of the body proteins (" structural "requirements) and will therefore be particularly important for the growinganimal, or may be needed for some specific chemical function (" functional ''requirements).In some cases such a specific function is known, e.g., arginineis necessary for the formation of creatine and methionine is needed as supplierof methyl groups. I n other cases, however, a specific biochemical functioncan be inferred, although its precise nature may be still obscure. Valinedeficiency, e.g., leads to severe nervous symptoms in the rat,l from whichit appears likely that this amino-acid is important for some specific biologicalreaction. The distinction between essential and non-essential amino-acidsis, however, not very sharp, The absolutely non-essential amino-acids aremainly those which are related to keto-acids occurring in the metabolismof carbohydrates, such as glutamic and aspartic acids and alanine; othernon-essential amino-acids are serine, proline and hydroxyproline.A secondgroup of amino-acids consists of compounds which may be called " semi-essential " ; thus arginine, although it is synthesised by the rat,2 is not formedfast enough to permit optimal growth ; for the chick arginine is indispensable,since it cannot form it at all or only very slowly.4 Glycine also is not essentialfor the rat and is apparently necessary for optimal growth in the chick.5Choline is another nitrogenous compound which is synthesised by animalsin amounts insufficient for metabolic requirements a t least under certaindietary conditions.' Another type of " semi-essential " amino-acid is onlydispensable if a related essential amino-acid is provided in the diet in amountssufficient to cover the requirements of both substances.Thus cystine, whichcan be made from methionine, is without growth effect if large amounts ofmethionine are fed ; 8 cystine stimulates growth, however, if methionine issupplied in suboptimal amounts.9 A similar position may possibly existfor tyrosine and its relationship to phenylalanine.The third group comprises the truly " essential " amino-acids, leucine,isoleucine, valine, threonine, histidine, lysine, phenylalanine, tryptophanW. C. Rose and S. H. Eppstein, J . Biol. Ghem., 1939, 127, 677.C.W. Scull and W. C. Rose, ibid., 1930, 89, 109.W. C. Roae, PhysioZ. Rev., 1938, 18, 109.A. Arnold, 0. L. Kline, C. A. Elvehjem, and E. B. Hart, J . Biol. C'hem., 1936, 116,H. T. Almquist and E. Mecchi, ibid., 1940, 135, 365.H. P. Jacobi, C . A. Ba~unann, and W. J. Meek, ibid., 1941, 138, 577.See the review by W. J. Griffith, J . hrutrition, 1941, 22, 239.M. Womack and If'. C. Rose, ibid., 1941, 141, 375.699.* M. Womack, K. S. Kemmerer, and W. C. Rose, J . Biol. Chem., 1937, 121, 403NEURERGER : THE METAROLTSI~T OF NTTROGENOUS COMPOUNDS. 239and methionine, which are indispensable for growth3 and cannot be madefrom substances normally present in animal diets. It has been claimed thatall these nine amino-acids are also necessary for maintenance of nitrogenequilibrium in the adult; 10 E.W. Burroughs, H. S. Burroughs, and H. H.Mitchel1,lf however, find that all the essential amino-acids are not equallyimportant for maintenance ; thus threonine and isoleucine occupy somewhata key position, whilst lysine and histidine are considered non-essentialfor the adult rat. These authors also consider phenylalanine not essentialfor the adult if tyrosine is provided. The duration of these experimentsseems, however, too short for such very definite conclusions to be drawn.Investigations using Isotopes.This particular field has been reviewed recently by R. Schoenheimer andD. Rittenberg l2 and only those results are discussed here which are of a verygeneral character. If isotopic nitrogen is fed to rats in the form of ammoniumsalts,13 I ( - )-leucine,l* d( +)-leucine,l5 glycine 16 or dZ-tyrosine,17 a consider-able part of the marked nitrogen is recovered from the tissue proteins.The isotopic nitrogen was found to be present in all amino-acids with theexception of lysine.The authors concluded that a rapid and extensiveinterchange of nitrogen takes place between dietary amino-acids and tissueproteins, involving the opening of peptide linkages, deamination, reaminationor possibly transamination of amino-acid residues. It would follow thatthe old distinction between endogenous and exogenous nitrogen metabolismwhich is due to 0. Folin 18 must be abandoned. This old conception, whichhas recently been restated and defended,lg can certainly not be maintainedin its original form, since i t has been shown that a considerable fraction of thenitrogen of creatinine which was supposed to be a measure of the endogenousmetabolism is provided by normal constituents of the food.There is,however, evidence that some proteins, such as the serum proteins, aremetabolically more active than others, and there may even be some proteinswhich are completely inert.This interchange between dietary nitrogen and the amino-acid residuesbound in the tissue proteins is interpreted as involving the oxidative de-amination of amino-acids to keto-acids and resynthesis. That such a forin-ation of amino-acids from the corresponding keto-acids actually takes placeis shown by the fact that most keto- and a-hydroxy-acids replace theircorresponding essential amino-acids.20 Lysine, however, cannot be replacedlo P.A. Wolf and R. C. Corley, Amer. J . PhysioE., 1939, 127, 589.l 3 G . L. Foster, R. Schoenheimer, and D. Rittenberg, J . Riol. Chem., 1939, 127, 319.lJ R. Schoenheimer, S. Ratner, and D. Rittenberg, ibid., 1939, 130, 703. ’’ s. Ratner, R. Schoenheimer, and D. Rittenberg, ibid., 1940, 134, 653.l6 D. Rittenberg, R. Schoenheimer, and A. S. Keston, ibid., 1939, 128, 319.I ’ R. Schoenheimer, S. Ratner, and D. Rittenberg, ibid., 1939, 127, 333.J . Nutrition, 1940, 19, 363, 385. l2 Physiol. Rev., 1940, 20, 218.Amer. J . physiol., 1905, 13, 117.Em w. Burroughs, H. S. Burroughs, and H. H. Mitchell, J . Nutrition, 1940, 19, 271.2o biT. C. Rose, Phpiol.Rev., 1938, 18, 109240 BIOOEEMISTRY.by or-hydroxy-s-aminohexoic acid; 21 this fact is in accordance withthe results obtained with the use of isotopes,22 which shows that for lysinedeamination ia irreversible. The availability of the hydroxy- or keto-acidanalogue of threonine has not been examined.d-Amino-acids can be deaminated in vitro by the d-amino-acid oxidase;it is therefore to be expected that all essential Z-amino-acids which can bereplaced by their corresponding keto-acids should also be replaceable bytheir d-isomerides. This is actually the case for histidine, tryptophan,phenylalanine and methionine ; Z-leucine, Z-isoleucine and Z-valine cannot,however, be replaced by the d-compounds,2* although in vitro experimentsindicate a fairly high rate of deaminati~n.~~ The reason for this discrepancyis quite obscure.The observation that phenylalanine can cover the dietary requirementsof both phenylalanine and tyrosine for the growing animal must mean thatphenylalanine can be converted into tyrosine and that the reaction isirreversible.This interpretation was confirmed by A. R. Moss and R.Schoenheimer,24 who fed dZ-deuterophenylalanine to rats and recoveredisotopic tyrosine from the tissue proteins. The conversion of hydroxy-acidsinto the corresponding amino-acids which follows from the feeding experi-ments mentioned has also been demonstrated directly by feeding deutero-dZ-P-phenyl-lactic acid and the recovery of labelled t y r ~ s i n e . ~ ~The special function which a particular amino-acid may have to servehas been very clearly demonstrated in the case of methionine. This amino-acid is necessary to build up the tissue proteins and it can replace-asmentioned above-cystine.H. Tarver and C. L. A. Schmidt 26 have investi-gated the fate of methionine containing radioactive sulphur and were able toshow the presence of isotopic sulphur in the cystine isolated from the tissues.But the most interesting function of methionine is probably its ability tosupply methyl groups for two important biosyntheses, the formation ofcholine and creatine.Choline Metabolism.It has been known for some time that dietary choline can prevent theaccumulation of fats in the livers of animals fed on certain diets.27 It wasnoticed later that methionine has a similar " lipotropic " effect,28 whereascystine produces an increase in the deposition of liver fat.29 I n the meantime,evidence of the inter-relationship between choline and methionine wasobtained by du Vigneaud and his co-workers. They demonstrated thathomocystine and homocysteine are incapable of supporting growth of animals*l 0.A. McGinty, H. B. Lewis, and C. S. Marvel, J . Biol. Chem., 1924, 62, 75.22 N. Weissman and R. Schoenheimer, ibid., 1941, 140, 779.23 H. A. Krebs, Biochem. J., 1935, 29, 1620.a6 A. R. Mom, ibid., 1940, 137, 739.27 C. H. Best and T. M. Hershey, J . Physiol., 1932, 75, 56.28 H. F. Tucker and H. C. Eckstein, J . Biol. Chem., 1937, 121, 479.*@ H. J. Channon, M. C. Manifold, and A. P. Platt, Biochem.J . , 1938, 32, 969;24 J . Biol. Chem., 1940, 135, 416.26 Ibid., 1939, 130, 67.A. W. Beeston and H. J. Channon, ibicl., 1936, SO, 280NEEDHAM : THE MECHANISM OF MUSCLE CONTRACTION. 241on a diet devoid of cystine and methionine; administration of chohe,however, enables the animal to utilise homocystine instead of methi~nine.~~The conclusions drawn from these experiments that methyl groups can betransferred reversibly between methionine and choline and that the presenceof donors of labile methyl groups is essential in diets, have been confirmedby later work using labelled methyl groups. If methionine containing adeuteromethyl group is fed to rats, choline containing a high concentrationof deuterium in its methyl groups can be isolated from the tissues.31Choline deficiency may also lead to a severe haemorrhagic renal de-which can be prevented by choline, methionine and betaine 33and is aggravated by cystine and chole~terol.~~Creatine Metabolism.H.Borsook and J. W. Dubnoff 35 showed that guanidoacetic acid wasslowly converted by tissue slices into creatine and that methionine aloneof many substances tested increased greatly the rate of this reaction. Theactual transfer of the methyl group from methionine to creatine in vivowas later clearly demonstrated by du Vigneaud et aZ.31 with the aid of labelledmethyl groups. Guanidoacetic acid is formed in the body mainly fromarginine and g l y ~ i n e , ~ ~ but other nitrogenous substances act only as potentialprecursors of creatine in so far as their nitrogen is utilised for the synthesisof glycine and arginine.It could also be shown that arginine provides theamidine part of the molecule, and glycine supplies the sarcosine moiety.The shift of methyl groups which is demonstrated by all these investigationsis, however, not completely reversible. Methyl groups are interchangeablebetween choline and methionine and both choline and methionine can functionas methyl donors to creatine. The latter reaction appears, however, to beirreversible.37 A. N.3. THE MECHANISM OF MUSCLE CONTRACTION.Knowledge of the nature of the protein myosin, of which the contractilemuscle fibril is composed, has been greatly extended during the last fewyears. have studied the amino-acid contentof myosin.Bailey estimated the cystine, methionine, tyrosine and tryp-tophan, and Sharp the basic amino-acids, dicarboxylic acids and mono-amino-acids, with the result that 85% of the protein is now identified.30 V. du Vigneaud, J. P. Chandler, A. W. Moyer, and D. M. Keppel, J. Biol. Chem.,1939, 131, 57.31 V. du Vigneaud, M. Cohn, J. P. Chandler, J. R. Schenck, and S. Simmonds, ibid.,1941, 140, 625.32 W. H. Griffith and N. J. Wade, ibid., 1939, 131, 567.33 W. H. Griffith, J . Nutrition, 1941, 21, 291.34 W. H. GrifFith and 0. J. Mulford, ibid., p. 633.a6 J . Biol. Chern., 1940, 132, 559.s6 K. Bloch and R. Schoenheimer, aid., 1941, 138, 167.37 V. du Vigneaud, J. P. Chandler, and A. W. Moyer, ibid., 1941, 139, 917.K. Bailey 1 and J.G . SharpBiochem. J . 1937, 31, 1406. a Ibid., 1939, 33, 679242 BTOCHRMTSTRY.Myosin contains very little cystine sulphur, most of the sulphur being inthe form of methionine; some of the cystine is present in the reduced -8Hform even in native myosin and the effect of various treatments upon the--SH content has been much studied.3* 4*have made an important X-ray and elastic study of strips of myosin film,made by drying the sol, and prepared in such a way that the myosin chainmolecules are oriented. When oriented but unstretched, they give an a-photograph, almost indistinguishable from that of a-keratin ; when stretched,they give a p-photograph. The X-ray and elastic properties of myosinresemble those of keratin that has suffered breakdown among the crosslinkages, including S--S bridges, of the polypeptide grid, i.e., the super-contracting form of keratin.Quantitative study by means of X-rays ofthe structural changes accompanying super-contraction of myosin filmsshows that the effect must be due to further regular folding of the poly-peptide chains, and cannot be due merely to disorientation of long thinunits. The hypothesis is put forward that muscle contraction arises fromsuper-contraction of its myosin component,. Astbury ' 1 * has suggesteda new view of the nature of the intramolecular fold in a-keratin and a-myosin; in the transformation from the flat polypeptide grid to the newa-configuration, all the experimental and structural conditions are satisfied,in particular, space is available for the side-chains standing out alternatelyon one side and the other of the plane of the fold.In view of the structural importance of myosin, it is of very great interestto learn that enzyme properties are also associated with this protein,especially as this enzyme activity consists precisely in bringing about thatreaction (the hydrolysis of adenosine triphosphate, henceforward referredto as ATP) which has for some time past been recognised as the chemicalchange providing the energy for the muscle contraction.V. A. Engelhardtand M. N. Ljubimova and Ljubimova and Engelhardt lo first showedthat adenosine triphosphatase activity is associated with the myosin fractionof the muscle proteins ; whch the myosin is purified by several precipitations,the power (shown by muscle brei and less purified myosin) to split off thesecond phosphate group is lost..The action of the myosin thus consists insplitting off one phosphate group from ATP with formation of adenosinediphosphate (ADP). These fundamental observations have been confirmedand extended by workers in several lahoratories.ll* 12* 13* 14, lQQ Bailey l4W. T. Astbury and S. DickinsonA. T. Todrick and F. Walker, ibid., 1937, 31, 392.A. E. Mirsky, J . Gen. Physiol., 1936, 19, 559.Proc. Roy. SOC., 1940, B, 128, 307.4 J. P. Greenstein and J. Edsall, J . Biol. Chem., 1940, 133, 397.7 Nature, 1941, 147, 696.* Nature, 1939, 144, 668. 8 Chem. and Ind., 1941, 60, 491.lo Biochimia, 1939, 4, 716.l 1 M. N. Ljubimova and D.Pevsner, &id., 1941, 6, 178.I f A. Szent-Gyorgyi, and I. Banga, Science, 1941, 93, 158.Is J. Needham, S. C. Shen, D. M, Needham, and A. 8. C. Lawrence, Nature, 1041,1' K. Bailey, in the press.147, 766.14a D. M. Needham, in the pressNEEDHAM THE MECHANISM OF MUSCLE CONTRACTION. 243has studied the kinetics and specificity of the reaction, and its activation bymetallic ions, of which Ca" is the most efficient. Needham, Shen, Needham,and Lawrence 13 found a large reversible fall in flow birefringence whenATP was added to myosin sol. This large effect, specific for ATP amongstmany substances tried, may indicate a combination between the myosinand the ATP, such as might be expected between enzyme and substrate.When the stimulus to contraction reaches the muscle fibril, the im-mediate change providing energy seems to be the breakdown of ATP withformation of ADP and inorganic phosphate.(It is at present uncertainwhether this breakdown is simultaneous with the shortening of the fibrils,or whether it is the first of the " recovery processes " bringing about lengthen-ing and '' recharging " of the contracted fibrils.) It is well known that theATP thus broken down is built up again by three distinct processes : (a)by reaction with creatine phosphate ; ( b ) by reaction with phosphopyruvate ;( c ) by esterification of phosphate coupled with the oxido-reduction betweentriose phosphate and pyruvate. The nature of the last process has recentlybeen elucidated by 0. Warburg and W. Chri~tian.1~ It had beenshown 16, 17, 18. 19 that the part of this oxido-reduction essential for theesterification is the reaction between triose phosphate and co-enzyme I :Triose phosphate + Co + ADP + H,PO, --+Phosphoglyceric acid + CoH, + ATP .. (1)D. M. Needham and R. K. Pillai,m using extracts of muscle acetone powder,had shown that arsenate affects the course of the reactions in that theoxido-reduction continues in its presence while the disappearance of inorganicphosphate and the formation of ATP is prevented. Meyerhof et aZ.,19using more purified enzyme preparations from yeast, had shown that thereaction between triose phosphate and co-enzyme alone proceeds onlyslowly and soon stops. The reaction goes further if ADP and inorganicphosphate are present, and practically to completion if glucose is alsopresent.Meyerhof et ul.19* 21 had recognised that the whole process (equation1) is reversible; further, they had found that in presence of arsenate, evenin absence of ADP, the reaction between triose phosphate and co-enzymegoes to completionTriose phosphate + Co --+ Phosphoglyceric acid + CoH, . . (2)E. Adler and G. Gunther,22 using partly purified preparations from brainand yeast, had also drawn attention to the fact that this reaction (2) comesto a standstill before the reactants are exhausted, as if at an equilibriumBiochem. Z., 1939, 305, 40.l6 D. M. Needham and R. K. Pillai, Biochem. J., 1937, 81, 1837.0. Meyerhof, W. Schulz, and P. Schuster, Biochm. Z., 1937, 298, 309.D.M. Needham and G. D. Lu, Biochem. J . , 1938, 32, 2040.0. Meyerhof, P. Ohlmeyer, and W. Mohle, Biochem. Z., 1938, Zg7, 90.2n Nature, 1937, 140, 165.2 1 0. Meyerhof, P. Ohlmeyer, and W. Mohlo, Biochem. %., 1938, 297, 193. '' Z . physiol. Chem., 1938, 258, 153244 BIOUHEMTSTRY .point. This equilibrium, however, cannot be altered by adding phospho-glyceric acid, and they had concluded that an unknown intermediate mustbe involved. They also had found an effect of arsenate, which caused thereaction to go rapidly to completion. Warburg and Christian were ableto link together and explain all these facts. They obtained from yeast apure crystalline preparation of the enzyme responsible for the oxidationof glyceraldehyde phosphate by co-enzyme. Like Adler and Gunther,they observed an apparent equilibrium point not affected by addition ofphosphoglyceric acid, and in presence of arsenate the reaction went tocompletion.They observed also that, in absence of arsenate, phosphateis necessary for the reaction, and phosphate concentration affects theequilibrium point. These observations led to the isolation by E. Negeleinand H. Bromel 23 of the intermediate 1 : 3-diphosphoglyceric acid. Further,by addition of another specific enzyme preparation to the crystalline triosephosphate dehydrogenase, a system was obtained which could transferphosphate from the diphosphoglyceric acid formed to ADP. The seriesof reactions involved in the coupled phosphorylation of ADP may thereforebe formulated thus :Glyceraldehyde phosphate + H,PO, 2 Glyceraldehyde diphosphateGlyceraldehyde diphosphate + Co 2 Diphosphoglyceric acid+CoH,Diphosphoglyceric acid + ADP 2 Phosphoglyceric acid + ATPThe effect of arsenate is explained by Warburg and Christian in the followingway.Arsenate can replace phosphate in the reaction and an arsenylatedglyceraldehyde phosphate is formed and oxidised ; the arsenylated phospho-glyceric acid is, however, unlike the diphosphoglyceric acid, unstable underthe experimental conditions, and breaks down irreversibly. 1 : 3-Di-phosphoglyceric acid thus takes its place with creatine phosphate andphosphopyruvic acid in the chemistry of muscle contraction as one of thesources of energy and of phosphate for the reconstitution of ATP. Thewhole subject of the importance of the guanidine phosphate, enolphosphate and carboxyl phosphate groupings for transfer of energy has beenconsidered by H.Kalckar.= D. M. N.4. PHYSICOCHEMICAL PHENOMENA.Intracellular Gels and Studies on Gel-forming Systems of the Cytoplasm.In the last two or three decades many interesting studies were made ongelatin sols and gels. These studies have been profitable from a physico-chemical point of view but, except in the most abstract manner, have notcontributed to our knowledge of the part played by gels in biological systems.For this there are two causes : gelatin is not, so far as we know, one of thesubstances responsible for intracellular gelation ; nor has the informationavailable on the cytological level made it at all plain, until quite recently, what23 Biochem.Z., 1939, 303, 231.24 Chem. Rewiewa, 1941, 28, 71; Biol. Rev., 1941 17, 28DANIELLI : PHYSICOCIHEMICBL PHENOMXNA. 245importance must be attached to intracellular gels, or from what point of viewthe intracellular gels may most profitably be studied. In the last five or tenyears there has been a substantial incregse in our knowledge of the functionof gels in cells, and also a growing volume of work on the properties of myosin,the chief gel-forming substance in muscle cells.Micro-dissection 1 has made a most useful contribution by demonstratingthat the cortical cytopltwmic layer of many cells is gelled and that in theresting cell the bulk of the remaining part of the cytoplasm is comparativelyfluid. The asters, spindle and chromosomes of dividing cells are gelled elasticbodies, and in some instances are known to be birefringent.2 One of the mostvaluable results is that of E.N. Harvey and D. A. Mar~land,~ who observedcells through the microscope during the process of centrifugation. They foundthat, even in the “ fluid ” part of the cytoplasm, intracellular particles maymove in an intermittent fashion under centrifugal force ; this is an indicationthat even the fluid part of the cytoplasm may be weakly gelled or undergointermittent sol gel transformations. These various observations havemade it certain that gels exist in living cells, and that many of the observablebodies in the interior of cells are elastic gels : from birefringence studies ithas been concluded that many of these bodies consist of adlineated needle-shaped protein particles.2 Some of these gels are known to be thixotropic.1The importance of these observations on the physicochemical conditionof the interior of the cell has been emphasised by a series of studies on theeffect of moderately high pressure on cells.Earlier work in this field has beenreviewed by McK. CatteL4 The important feature of more recent work is thedemonstration that in a wide variety of cell types the application of pressurereduces the cytoplasmic viscosity and eventually liquefies the cortical gellayer. The liquefaction usually occurs at a pressure of the order of 400 atms. ;it is followed immediately by profound changes in behaviour.Cells ofirregular shape round up into ~pheres,~ long tentacles break up under surfacetension forces into a string of spherical droplets,6 protoplasmic streamingceases,’ and dividing cells which have reached the “ dumbell ” stage revertto the spherical state.* The liquefaction of the gel is reversible. For eachincrement of 68 atms. pressure a number of cell characteristics were found tobe diminished to 0.76 of their former value. This is true of the cytoplasmicviscosity of ova of two species of Arbacia, the viscosity of two species ofA m d a and of the leaf cells of Elodea ; the rate of impingement of the cleav-age furrow on the division axis in two species of Arbacia; and the velocityof protoplasmic streaming in Elodea. The view has been advanced that theliquefaction of the gels is due to hydration of protein molecules; but, asR. Chambers, 1924, in “ General Cytology,” Ed.Cowdray, Chicago ; J . Cell. Comp.L. E. R. Picken, Biol. Rev., 1940,15, 133.J . Cell. Comp. Physwl., 1932, 2, 75.Physiol., 1938, 12, 149.4 Biol. Rev., 1936, 11, 486.6 D. A. Marsland and D. E. S . Brown, J . Cell. Comp. Physiol., 1936,8, 167, 171.8 J. A. Kitching and D. C. Pease, aid., 1939,14,133.7 D. A. Marsland, &id., 1938,12,57. D. A. Marslsnd, ibid., 1939,13, 15,23246 RTOCHEMISTRY.Cattell remarks, at present the possibility has not been eliminated that " thechanges in viscosity are secondary to changes resulting from stimulation orchemical reactions." It is known that even globular proteins such as oval-bumin, serum albumin and insulin form thixotropic gels and show anisotropyof flow when denatured, or when their SS bonds are reduced to SH.g What-ever the explanation of these changes may be, it is now clear that sol * gelchanges play an essential r61e in cell behaviour, and that physicochemicalstudies on the molecules concerned in these changes are of great interest.These studies have so far been restricted, with few exceptions, to observ-ations on myosin, the protein forming the spontaneously birefringent gel ofmuscle fibres.* Several observers lo have found that when a muscle passesinto rigor a large part of the myosin is no longer soluble in potassium chloridesolution.A. E. Mirsky 11, 12, l3 has investigated the nature of this changeand its relation to muscular activity.When the thixotropic gel formed bynative (soluble) frog myosin is heated to 38-39", its solubility is lost. TheQ1, for this reaction is about 1,000. There is little change in the SH groups.A small diminution in transparency of the gel occurs. If the temperatureis raised further ( 4 1 4 5 " ) , the gel-structure is destroyed, opaque clumpsforming, and SH groups appearing. The reaction resulting in appearanceof SH groups has a much lower Qlo than the reaction producing insolubility.With previously studied proteins these two steps (loss of solubility andappearance of SH groups) appear to be more closely linked than with myosin.Physiological processes corresponding to these changes are thermal (revers-ible) shortening of frog muscle,14, l5 which has a sudden onset a t 38".Thisthermal contracture, which Mirsky considers to be due to the first step inmyosin denaturation (loss of solubility), is of the same order of magnitude asthe contraction in an electrically produced tetanus. A further shorteningoccurs when the muscle is heated from 39" to 45" ; this process is irreversibleand is regarded by Mirsky as due to the change in insoluble myosin which isaccompanied by appearance of SH groups.I n vitro the initial denaturation change (loss of solubility) may also beproduced by simple physical means, such as dehydration by cold and bysubstances such as caffeine, nicotine, chloroform and glycocholate. Vera-trine does not initiate or accelerate denaturation.This may be regarded asstrong evidence for the view that the initial stage of denaturation is involvedin muscular contraction, for the first group of substances throw a muscle intoD W. G. Myers, Cold Spring Harbor Sympot&rn, 1938, 6, 120; H. Neurath, ibid.,10 P. Sax], Beitr. Chem. Physiol., 1907, 9, 1 ; A. E. Mirsky, J . Qen. Physiol., 1935,11 J . Gen. Physiol., 1937, 20, 455.12 Ibid., p. 461.13 Cold Spring Harbor Symposiun~, 1938, 6, 153.14 E, Gottschlich, Pflugers Arch., 1893, 54, 109; 55, 339.16 P. Jensen, ibid., 1914, 160, 333.* The physical chemistry of the gels of the nucleus has had some slight attention,p. 1 1 8 ; C. Stern, ibid., p. 119 ; A. White, ibid., p. 265.19, 571 ; E. B. Smith, Proc. Roy. SOC., 1937, B, 124, 136.but not sufficient for discussion hereDANIELLI : PHYSICOCHEMICAL PHENOMENA.247a reversible contracture 16 (sustained single contraction), whereas veratrineproduces a similar result, but by acting on the nervous system to give atetanus 17 (many consecutive twitches).A similar change in solubility after activity has been demonstrated in themyosin of crab limb muscle,l* and in a myosin-like protein found in sea-urchin eggs.19A second approach to the subject has been made by Needham et aZ.,20who have endeavoured to link the phosphorylation cycles, whereby it is nowbelieved that the energy obtained from carbohydrate oxidation is transferredto the contractile apparatus of the muscle, with the long-established fall inbirefringence of a muscle occurring during contraction.It had previouslybeen shown by A. Muralt and J. T. Edsal121 that myosin solution shows doublerefraction of flow. More recently W. A. Engelhardt and M. N. Ljubimova 22have found that myosin is so closely associated with the enzyme adenylpyro-phosphatase that it is possible that myosin is itself the enzyme. As thebreakdown of adenylpyrophosphate is believed to be the nearest in time tocontraction of the known chemical processes occurring in active muscle,studies were made of the effect of adenylpyrophosphate on the flow birefring-ence of myosin. These experiments were carried out with a sol containingabout 3% of myosin in O.75~-potassium chloride and other solutions of equiv-alent ionic strength at pa: 7. Adenylpyrophosphate causes a large andprolonged fall in birefringence, which occurs in less than one minute at about18" and takes considerably longer a t 0".This change is reversible. Thebirefringence returns to its original value in about two hours at 37", andmore slowly at lower temperatures.This observation may well prove to be a key to the connection betweenmuscle intermediary metabolism and the transformation of energy intomechanical work, especially if it proves possible to combine studies of viscosityand birefringence with X-ray studies. W. T. Astbury and S. Dickinson 23have now shown that a process occurs in muscle protein during contractionwhich is closely analogous to supercontraction of keratin in which the cross-linkages of adjacent polypeptide chains of keratin have been broken byreduction of SS bonds : observation of the occurrence of such processes inrelation to the action of adenylpyrophosphate would clinch the argumentthat this in vitro action of adenylpyrophosphate is closely analogous to theprocesses occurring in living muscle. In addition, X-ray studies are probablyessential for making a detailed analysis of the action of adenylpyrophosphate,16 K.J. A. Secher, Arch. exp. Path. Pharm., 1914, 77, 83; H. N. Langley, J PI~ysiol.,1907, a, 347; G. Schwenker, Pjluqers Arch., 1914, 157, 443.1 7 G. Lamm, 2. Biol., 1911, 56, 223; 1912, 68, 37.18 J. F. Danielli, J . Physiol., 1938, 92, 3P. A . E. Mirsky, Science, 1936,84,333.20 J. Needham, S . C. Shen, D. M. Needham, and A.S. C. Lawrence, Nature, 1941,147,'1 J . B i d . Che))i., 1930, 89, 315, 351.22 Nature, 1939, 14, 668;23 Proc. Roy. Soc., 1940, B, la, 307.766.Biochiwia, 1939, 4, 716: A. Szent-cyorgi an<i 1. Bang,Science, 1941, 93, 158248 BIOCHEMISTRY.for this probably cannot be achieved from studies of viscosity and doublerefraction only.Other studies of the action of ions on myosin flow birefringence have beenmade by Edsall and his colleague^.^^ The properties of threads of gelledmyosin have also received attention.2sAll of the studies so far reported have, implicitly or explicitly, left theproblem of intermicellar forces untouched. Since myosin in the muscle fibreis gelled, these forces must be of significant magnitude, and it may be thattheir study will enable a connection to be established between the responseof a muscle fibre to a stimulus, and the observed changes in myosin bire-fringence and X-ray scattering during contraction : this connection is a tpresent quite obscure. Important theoretical studies of intermicellar forceshave been made by Langmuir and Levene.26 J.F. D.5. SOME PLANT PRODUCTS AXD ENZYMES.With the advent of the United Stateg as a full belligerent, the diminutionin the number of publications observable in recent months will doubtlessbecome more marked. There appears to be no major development in plantbiochemistry during the past year, but steady advances in knowledge havebeen maintained. The plant growth substances are amongst the mostinteresting and important of plant products. I n this field, following thepreparation of crystalline biotin, the constitution of this somewhat elusivemember of the bios group is likely to be determined in the near future.Knowledge of the chemistry of the hydrolytic enzymes has lagged behindthat of those enzymes concerned in oxidation and allied processes, Theisolation in the crystalline state of increasing numbers of the former and thestudy of the properties of the pure enzymes are leading steadily to morecomplete understanding.These topics, together with some notes on plantproteins, are discussed in the following pages.Growth Substances.-A concise review of growth substances in theirpractical and commercial aspects is contributed by M. A. H. Tincker.1The methods of detection and estimation of growth substances are under-going continuous modification and elaboration; but a tendency is alsot o be noted towards simplification.Thus, the Avena method of auxindetermination requires elaborate apparatus and technique not readilyavailable to many workers. An upright-growth method which can beapplied to cut pea shoots is described by E. G. Brain,2 who has found i t ofvalue in comparative experiments under ordinary greenhouse conditions,24 J. P. Greenstein and J. T. Edsall, J . Biol. Chem., 1940,133, 397; J. T. EdsaIl andJ. W. Mehl, ibid., p. 409.26 H. H. Weber and K. Meyer, Biochem. Z . , 1933, 266, 137 ; H. H. Weber, PJEiigersArch., 1935, 235, 205; W. A. Engelhardt, 3%. N. Ljubimova, and R. A. Meitina, C m p t .rend.U.R.S.S., 1941, 30, 644.26 I. Langmuir, J. Chem. Physics, 1938,6, 873; S. Levene, Proe. Roy. SOC., 1939, A ,17'0, 145.Nature, 1941, 147, 439. ' Ibid., 1941, 148, 666NORSCIS : SOME PLANT PRODUCTS AND ENZYMES. 249and although not as exact as the more refined methods there are indicationsthat its accuracy may be increased as the result of further experiments.G . E. Turfitt3 has described a rapid method of testing substances forphytohormone activity, using yeast growth as the criterion, such growthbeing assessed by multiplication rates based on cell counts. p-Indolyl-,a- and p-naphthyl-, and phenyl-acetic acids in concentrations of i$ to 1 partper million cause varying degrees of stimulation; further increases in con-centration may cause a diminution or even inhibition of growth.As nostimulation is observable with washed yeast, it is thought that the action ofsubstances such as those mentioned is combined with that of the biossubstances, which would be removed by washing.Experiments by E. J. Kraus and J. W. Mitchell,47 5 on bean plants, whichshowed characteristic responses, indicate that a-naphthylacetamide may beadded to the extending list of plant growth substances. Treatment oncut stems was carried out with the compound in lanolin, or in aqueousemulsion with lanolin ; seedlings were also sprayed.The wound hormone, traumatic acid, which promotes wound peridermformation in potato, has been shown to be Al-decene-1 : 10-dicarboxylicacid and it is of interest to enquire whether acids of the same general typeare equally effective.J. English has prepared by synthesis a number ofanalogues of the acid of the general type C02H*[CH2]n*CH:CH*C02H andCQ,H*[CH2],~CH2*CH,*C0,H. A5-Undecene- I : 1 P-dicarboxylic acid andA1 : 7-octadiene-l : 8-dicarboxylic acid were also prepared and examined.All the acids thus synthesised were found to be active plant wound hormones.Bios.-As indicated in last year’s Annual Reports,7 it has been sug-gested that biotin is identical with vitamin H, a substance which protectsrats from “ egg-white injury.” Full confirmation of the identity appearsto be forthcoming as the result of experiments which demonstrated that theactivity of the vitamin in stimulating yeast growth is identical with that ofbios, and conversely that biotin may be used to remedy deficiency of thevitamin in rats.These confirmatory results were obtained by V. du Vigneaud,D. B. Melville, P. Gyorgy, and C. S. Rose.s It is also probable that coenzymeR, a growth factor for many strains of legume nodule bacteria, is identicalwith biotin and vitamin H (see also this vol., p. 235).The isolation of biotin as the free acid rather than the ester marksa considerable step forward, since not only is it desirable in some biologicalinvestigations t o employ the free acid, but a line of chemical attack onconstitution has been opened up. The isolation of the free acid in crystallineform is described by V. du Vigneaud, K. Hofmann, D. B. Melville, andJ. R. Ra~hele.~ The empirical formula ascribed to it is ClOHl6O3N2S,and titration curves indicate that the compound is a monocarboxylic acid.There is no specific absorption in the ultra-violet.Biochem.J., 1941, 35, 237.J. W. Mitchell and W. S. Stewart, ibid., p. 410.J . Arner. Chem. SOC., 1941, 63, 941.Science, 1940, 92, 62.Bot. Baz., 1939, 101, 204.Ann. Reports, 1940, 37, 393. * J . Biol. Chern., 1941, 1Q0, 763250 BTOCHRMTSTBY.Using the crystalline preparation above, G. B. Brown and V. diiVigneaud lo have studied the stability of biotin towards a variety of reagentsand treatments, employing yeast growth as a criterion of activity. It ha?sbeen found that alkali or acid treatment results in inactivation, and that,whilst biotin is inactivated by many reagents which react with a-amino-acids, it is not affected by ninhydrin, a fact held to indicate strongly thatbiotin is not an a-amino-acid.Acylating, alkylating and carbonyl reagentsdo not inactivate biotin. Aeration under various conditions with air oroxygen has no effect, but activity is rapidly lost under the action of strongeroxidising agents such as hydrogen peroxide or bromine water ; it is concludedthat biotin contains an easily oxidisable group or groups. These experimentson activation have led to a direct chemical attack on the crystalline biotinwith a view to disclosing the nature of the functional groups present in themolecule. The conclusion arrived at in the previous communication, thatno a-amino-groups are present in the molecule, is confirmed by K.Hofmann,D. B. Melville, and V. du Vigneaud; 11 no nitrogen is produced whenbiotin is treated with nitrous acid by the van Slyke method, and the ninhydrinreaction is negative. Treatment of biotin with baryta at 140" for 20 hoursled to the isolation as sulphate of a " diaminocarboxylic acid," C9Hls02N2S,which gave a dibenzoyl derivative, contained two free amino-groups and musthave been derived from the parent biotin with the loss of one carbon and oneoxygen atom. The most likely explanation of such a change suggests that acleavage of a cyclic urea derivative is involved as below :+02H + C8H13S -NH2 ( [ zzo2H) 'SH13'[ ~~~~The nature of the sulphur atom was indicated as follows : Biotin containsno alkali-labile sulphur and does not liberate hydrogen sulphide when treatedwith zinc dust and hydrochloric acid. Further, no positive nitroprussidetest could be obtained in presence or absence of sodium cyanide.Thestability of the sulphur therefore indicates a probable thioether structure andexperimental evidence supports this. Thus, biotin (I) on treatment withhydrogen peroxide and glacial acetic acid gives a crystalline sulphone (11)in 90% yield. There is no loss of carbon or hydrogen involved in the change,but two oxygen atoms are added. The production of a strong yellow colourwhen biotin and the diamino-carboxylic acid are treated with tetranitro-methane, and the failure to produce a colour when the oxidation product issimilarly treated, are also consonant with the suggestion that a thioetherstructure is involved, At this stage, then, the authors conclude that biotinis a carboxylic acid containing an NN'-substituted cyclic urea grouping,and sulphur in thioether linkage.-C02H--NH -NH>C 0 (11.) 1 -so,lo J .Biol. Chem., 1941, 141, 85. l1 Ibid-, p. 207NORRIS : SOME PLANT PRODUCTS AND ENYZMES. 251M. J. Pelczar, jun., and J. R. Porter 12 have shown that pantothenic acidis one of the growth factors for Proteus morganii, and in a later paper l3observe that this organism is specially suitable for the biological assay ofpantothenic acid in natural materials. The response of the organism topantothenic acid is extremely sensitive and specific, since 0.0002 pg. of thecalcium salt is sufficient to initiate visible growth.In a number of teststhe amounts indicated by the result of the assay corresponded closely withthe amounts known to be present. The extreme sensitivity of the organismrenders it specially suitable for dealing with small amounts of the materialto be examined.Methods of estimation of inositol involving isolation of the product fromthe material under investigation have not proved satisfactory, and more-over are unsuitable when dealing with small quantities. D. W. Woolley l4has developed a method of estimation based on the growth response of yeastto the presence of inositol in a medium' which in its absence supportedpractically no growth. Graded amounts of inositol were found to inducegraded responses, such growth being measured by a turbidimetric method.Quantitative results were obtained with a number of natural products.I>.W. Woolley l5 has also studied the biological specificity of meso-inositolin respect of mice and of yeast, and shown that in the latter case suchspecscity is virtually absolute. Thus for yeast, the following substancesare inactive : d-inositol, Z-inositol, pinitol, quebrachitol and quercitol ;inositol hexa-acetate, phytin and soy bean cephalin; quinic acid andinosose. Mono- and tetra-phosphates of inositol were only 5 and 20,;respectively as potent for yeast as inositol, and mytilitol (probably methylinositol) had about one-tenth of the activity of inositol.Additions to the list of growth factors for lower organisms are still forth-coming. Thus, following the observation of E. E.Snell and W. H. Peterson l6that there existed a new growth factor, probably a purine, for Lactobacilluscasei, E. L. R. Stakstad 1' reports the isolation of a dinucleotide or mixtureof nucleotides from solubilised liver. This was obtained by adsorption onnorit, followed by elution with a dilute solution of ammonia in 70% methanol.The product was purified until no increase in activity could be observed.It had the properties of a nucleotide, since it contained nitrogen, phosphorusand a pentose (not deoxyribose). Hydrolysis showed that the factorcontained a purine and a pyrimidine nucleotide, the purine base beingguanine, the pyrimidine base still awaiting identification. The " dinucleo-tide " may be partially replaced by guanine and thymine, and the formercould be effectively replaced by adenine, hypoxanthine and xanthine. Uracilor cytosine could not replace thymine.This work is in line with that ofE. E. Snell and H. K. Mitchell,l8 who have found that both purine andpyrimidine bases are essential factors in the growth of Lnctobacillus nra binosus,Lactobacillus pentosus and Leuw nostoc rnesenteroides.l2 Proc. Xoc. Exp. Biol. Med., 1940, 43, 151.l4 Ibid., 1941, 140, 453. l6 Ibid., p. 461.l3 J. Bid. C'hein., 1941, 139, 1 1 1 .16 J. Bact., 1940, 56, 273.J. BioE. Chem., 1941, 139, 478. l* Proc. Nat. Acad. Sci., 1941, 27, 1252 BIOOHEMISTRY.In concluding this section, reference may be made to an excellent review ofgrowth-promoting nutrilites for yeasts by R.J. Williams.19Following the preparation of crystalline papainby A. K. Balls and H. LineweaverY2O a further communication by A. K.Balls and E. F. Jensen 21 describes the preparation of a new crystallineenzyme, which the authors propose to term chymopapain, by analogywith the chymotrypsin of M. Kunitz and J. H. N ~ r t h r o p . ~ ~ The newenzyme is extremely stable a t 10" and pH 2.0, and this fact was utilised inits preparation. At pn 2.0 an extenaive precipitation of protein from asuspension of coagulated papaya latex is effected by hydrochloric acid, andthe protein remaining in solution is proteolytically active, but an inertfraction is still present. This is precipitated by half saturation with sodiumchloride at pH 4.0, and the active crystallisable material may be precipitatedby addition of hydrochloric acid to the solution fully saturated with sodiumchloride. The crystals obtained were much more soluble than the originalpapain under the same conditions, showed a strong positive nitroprussidereaction, and the amount present in latex was much greater than that ofpapain.In further studies of the action of papain on proteins, H.Lineweaverand S. R. Hoover 23 find additional support for the suggestion that enzymeaction is greater on denatured proteins than on the native protein. Thus,in the case of papain, it was found that the initial rate of digestion of haemo-globin in the presence of a t least six molar concentrations of urea is verymuch greater than in water solution only.The increase in digestibility issimilar to, but not exactly parallel to, the decrease in solubility of haemo-globin when denatured by urea. The increase in rate of hydrolysis ofproteins when denatured appears to be comparable to the increase in re-activity of -SH, S - S - and tyrosine phenol groups. The method wherebydenaturation is effected seems to have little effect on the rate of digestion.The increase in rate of digestion of a denatured protein is different for eachenzyme, and that for a number of diff erent proteins treated by a single enzymeis also different.The widely adopted oxidation-reduction theory of papain activationis not in harmony with experimental facts observed by J. S. Fruton andM. Bergmann,24 and, in a later paper, by these authors and G.W. Irving,jun.,Z5 who do not accept this explanation. In the first instance, papainwas activated by hydrocyanic acid, inactivated by precipitation withhopropy1 alcohol, and the whole process repeated, at the end of whichalmost complete recovery of the original activity of the enzyme was observed.These facts are difficult of interpretation in terms of the disulphide-sulphydryltheory; moreover, the action of hydrocyanic acid on disulphide linkageswill produce only one sulphydryl group : R-S-SR' + HCN + R*SH +Enzymes.-Papain.lS Biol. Rev., 1941, 18, 49.z1 J . Bid. Chern., 1941, 137, 459.48 J. Biol. Chern., 1941, 137, 325.f6 IN., 1941, 130, 669.20 Ann. Reports, 1940, 37, 429.aa J . Gen. Physiol., 1935, 18, 433.z4 Ibid., 1940,133, 153NORRIS : SOME PLANT PRODUCTS AND EXZYMES.263R’oSCN. The authors suggest that a better explanation is afforded bysupposing that hydrocyanic acid combines with papain to form a dissociablepapain-hydrogen cyanide compound corresponding to the hydrogen cyanideactivated enzyme. On precipitation with isopropyl alcohol, the compounddissociates and the precipitate consists of the hydrogen cyanide-free enzyme,inactive towards synthetic substrates. In the later paper it is pointedout that natural activators are usually present in preparations of proteinaaes,and minute quantities of these activators profoundly affect the response t oadded activators. In the case of papain it was found that, if the naturalactivators were removed by careful dialysis, subsequent addition of hydro-cyanic acid involved no activation of the enzyme.The activation normallyobserved with hydrocyanic acid thus depends on the presence of naturalactivators, which may occur only in minute traces. Benzoyl-Z-arginineamidebeing used as artificial substrate in the study of reaction kinetics, it has beenfound that the component of papain (and of beef spleen cathepsin) whichhydrolyses the substrate may exist in two inactive forms. The a-form isnot activated by hydrocyanic acid, but may be converted into the p-form,which is, and the activation consists in the formation of dissociable com-pounds of the activator and the p-form. It is noteworthy also that theactivation does not involve the mutual transformation of disuIphide andsulphydryl groups, nor is there any evidence of reduction or oxidationprocesses.Urease.-The presence of sulphydryl groups in urease has been established,and the activation of the enzyme by certain reducing agents, and its inactiv-ation by oxidising agents, suggest that the activity of the enzyme may be afunction of oxidation-reduction potential.The activity of crystallineurease was determined by I. W. Sizer and A. A. Tyte11,26 who employedsubstrates which were adjusted a t varying Eh by a number of oxidisingand reducing agents used separately or in mixture, and also by the use ofsodium sulphide and potassium permanganate at various concentrations.Curves similar to the familiar activity-p, curves were obtained in all cases,and an optimum Eh of + 150 mv.was indicated. The activity of crudeurease, in contrast to that of crystalline urease, was unaffected by variationsin Eh of the substrate. In a note to the paper it is pointed out that the Ehof the jack bean after soaking in water is + 190 mv., a value in such closeagreement with the optimum Eh of the enzyme as to suggest some phy&o-logical significance. The authors stress the somewhat empirical nature oftheir observations; but this is probably the first example of the productionof activity-& curves, and examination of other enzymes in this aspect mayyield important results.An improved method for the preparation of crystalline urease is de-scribed by A. L. D o ~ n c e , ~ ~ whose modification of the original method ofJ. B.Sumner 28 involves a very considerable shortening of the time requiredfor crystallisation, thus avoiding denaturation of the enzyme.26 J . Biol. Chern., 1941, 138, 631.28 Ibid., 1926, 70, 97.t 7 Jbid., 1941, 140, 307254 BTQCREMISTRY.RibonucZease.4rystalline ribonuclease isolated from fresh ox pancreasdigests yeast nucleic acid, the products being of low molecular weight.M. Kunitz describes the isolation and properties of the crystalline enzyme,which appears to be a protein of the albumin type of molecular weightabout 15,000. The enzyme is stable over a wide range of pPa and particularlyover the range pE 2 . 0 4 . 5 . Denaturation of the protein comprising theenzyme involves a corresponding loss in its activity.Similar values for themolecular weight have been found by A. Rothen,3O who gives 12,700 fromrate of sedimentation and diffusion data, and 13,000 from equilibriummeasurements. The purified crystalline enzyme had an isoelectric pointat pa 7.8 by electrophoresis. All these values are in good agreement withthose computed by I. Pank~chen,~l who has made crystallographic andX-ray studies of the enzyme and calculates 15,700 and 13,700 for the hydratedand the anhydrous protein respectively.F. W. Allen and J. J. Eiler 32 also have prepared the crystalline ribonucleaseand have employed it in studies of its action on ribonucleic acid. It is possiblethat the enzyme is in the nature of a depolymerase, but available evidencepoints to the probability of a low degree, if any, of polymersation in thecase of ribonucleic acid, although deoxyribonucleic acid probably exists in ahighly polymerised state.K. Makino 33 and J. M. Gulland 34 hold that ribo-nucleic acid shows four primary phosphoric acid dissociable groups and nosecondary phosphoric acid dissociations, and titration experiments by theabove authors confirm this. The liberation of a, fifth acidic group by thecrystalline enzyme is thought to denote the opening of a cyclic structure suchas that envisaged by H. Takaha~hi.~~The preparation of the proteins of green leaveshas involved a number of technical difficulties, and, since the preparationof spinach proteins by T. B. Osborne and A. J. Wakeman36 in 1920, theinvestigations in this field have been carried out largely by A.C. Chibnalland his school. This work is so well known that a reference to his im-portant book3' must suffice here. Amongst recent publications on thesubject, those of J. W. H. Lugg may be mentioned. In an early paper38he deals with the estimation of tyrosine and tryptophan in the hydrolysatesof leaf proteins and suggests means of overcoming previous difficultiesinvolving unsatisfactory results. This was followed 39 by a, series of experi-ments whose main object was to determine the most satisfactory hydrolysisprocedures with a, view to subsequent estimation of tyrosine and tryptophanin the hydrolysates. Hydrolysis in sealed tubes at 100" with alkali or alkalistannite solutions was found to be satisfactory. Two further papers appearedin 1938 4O devoted to the partial analysis of protein preparations from grasses,Proteins.-Leaf proteins.29 J.Qen. Physiol., 1940, 24, 15.31 Ibid., p. 315.33 2. phgsioll. Chem., 1935, 236, 201.s 5 J . Biochem. Japan, 1932, 16, 463.3' " Protein Metabolism in the Plant," Pale Univ. Press, 1939.38 Biochern. J., 1937, 31, 1422.40 Ibid., pp. 2114, 2123.Ibid., p. 203.32 J . Biol. Chem., 1941, 137,34 J . , 1938, 1722.36 J . Biol. Chem., 1920, 42,3e Ibid., 1938, 32, 775.757NORRIS: SOME PLANT PRODUCTS AND ENZYMES. 255including cocksfoot and lucerne. The proteins were prepared by methodslargely elaborated by A. C. Chibnal14143 and co-workers, and in the firstinstance the sulphur distribution was determined, it being shown that thecontents of cystine and methionine were sufficiently high to conform tonormal standards of the nutritional requirements of animals.Secondly, inaddition to the sulphur distribution, the amide, tyrosine and tryptophancontents of leaf proteins of various Chaminern, Leguminosce and Chenopodiaceawere determined. Here again it was shown that in respect of the aboveamino-acids, the leaf proteins compared favourably with other proteins ofthe animal diet. Later,44 various methods of extraction of leaf proteinswere employed, and the samples examined for representativeness. Additionof lipoid solvents to mildly alkaline leaf juices allows most of the granuleprotein to pass into solution, whereas difficulty in avoiding loss of this fractionhad previously been experienced.It was also shown that the presence ofalcohol in the protein solutions near their isoelectric point rendered floccul-ation by acid, and coagulation by heat, more complete. In the latest paperto date, J. W. H. L ~ g g * ~ finds that the amide, tryptophanand tyrosine contentsof proteins of the photosynthesising tissues of some cryptogams are of thesame order of magnitude as those of the leaf proteins of angiosperms of thespermatophyte division ; the tryptophan content of preparations fromPteridium aquilinum is lower than any previously encountered.The basic amino-acids of leaf proteins have been determined by G. R.Tri~tram,~'j who made a critical examination of methods available, andstudied the influence of the presence of carbohydrates on the results obtained.More satisfactory estimation of the three bases in leaf proteins containing12-16% of nitrogen was secured, but where the material was poor in protein,containing less than 8% of protein nitrogen, lysine only could be estimatedreliably.As in the case of the amino-acids determined by J. W. H. Lugg( v J . ) , there appears to be very little variation in content from species tospecies, nor is there much seasonal variation within a single species.A. M. Smith and T. Wang4' also have prepared proteins from grassesand have determined the sulphur distribution in proteins from four species.The amounts of cystine and methionine were substantially the same in allspecies; but it was observed that in proteins from samples that had reachedor passed the flowering stage the amounts present were significantly higher thanin those from young grass, or grass kept short by grazing.General.-Knowledge of the proteins of the latex of Hevea brasiliensis issomewhat scanty, although there are strong indications of their importancein the complicated bio- and physico-chemical mechanism of rubber latexcoagulation.Thus, it has been shown by C. Bondy and H. Freundlich48and by A. R. Kemp and W. G. Straitiff 49 that the stability of latex is41 Biochem. J . , 1921, 15, 60; 1922, 16, 334.*% J . Biol. Chem., 1923, 55, 333; 1924, 61, 303.43 Biochern. J . , 1926, 20, 108; 1933, 27, 1879.44 Ibid., 1939, 33, 110.46 Ibid., 1939, 33, 1271.48 Compt. rend. Lab. Carlsberg, 1938, 22, 89.4 6 Ibid., 1940, 34, 1549.4 7 Ibid., 1941, 35, 404.49 J . Physical Chem., 1940, 44, 78256 BIOOHEML9TRY.dependent upon the proteins present, and the coagulation point of the latexcorresponds to their isoelectric point.G. R. Tristram 50 has isolated a proteinfrom dried latex films and this product has a composition similar in manyrespects to that of the leaf proteins. The similarity is particularly markedin the case of the diamino- and dicarboxylic acids, and suggests a possiblerelationship, which is under investigation, between the proteins of the latexand of the leaves. In a further communication, G. R. Tristram 51 givesanalytical data for a protein prepared from crepe rubber. Close similaritiesbetween this and the latex protein suggest that there is only one proteinin the latter, or that the product obtained from the latex is a mixture of severalproteins.The main bulk of protein is undoubtedly precipitated from thelatex and may be regarded as a representative fraction of the total protein.A loss of tryptophan in the crepe rubber protein is attributed to changesundergone in manufacture. G. S. Whitby and H. Greenberg 52 provide asummary of the arnino-acid composition of latex and latex proteins aspublished to date by previous workers. They have investigated the amino-acids present in the latex of Hevea brasiliensis and have isolated tyrosine,Z-leucine, d-isolewine, d-valine, d-arginine, E-aspartic acid and i-proline.Phenyhhnine is also present but was not isolated.The occurrence of the amino-acid citrulline, discovered by M.Wada 53in the juice of the water melon (Citrullus vulgaris), has suggested to P. S.Krishnan and T. K. Krishnaswamy64 the possibility that the seeds ofthe fruit may be a source of the amino-acid. The proteins and other nitro-genous substances of the seeds were investigated and a crystalline globulinwas prepared. This represented the bulk of the protein, but a glutelin wasalso obtained in pure condition. Both proteins were analysed and bothcitrulline and canavaaine, free or combined, were absent. Canavanine wasoriginally isolated from jack bean by M. Kitagawa and T. Tomita 55 in 1929,and from soya bean meal by M. Kitagawa and S. Monobe 56 in 1933. It hasbeen shown 67, 58 to have the formulaNH,*C( XH)*NH*O*CH,-CH,*CH( NH,)-CO,H.A modified method of preparation is proposed by M.Damodoran and K. G. A.Namyanim 59 whereby increased yields of the amino-acid may be obtainedfrom the seeds of Canuvalia obtzlsifolia.Reference has already been made to recent modifications in the methods ofhydrolysis of proteins, and of the isolation and estimation of the products.In the space remaining, brief reference only may be made to further de-velopments in protein analysis. For example, B. W. Town 6o publishes, incontinuation of his studies 61,62 on the separation of arnino-acids by means60 Biochena. J., 1940, 34, 301. s1 Ibid., 1941, 35, 413.82 Iba., p. 640. 63 Proc. Imp. Acad., Tokyo, 1930, 6, 15.54 Biochem. J., 1939, 33, 1285.S t Proc. Imp. Acad., Tokyo, 1929,5,380.5 6 J . Biochem. Japan, 1933, 18, 333.5' M. Kitagawa et al., J . Agric. Chem. Soc., Japan, 1933, 9, 845.58 J. M. Gnlland and C. J. 0. R. Morris, J., 1935, 763.59 Biochem. J., 1939, 53, 1742.a1 Ibid., 1928, 22, 1083.so Ibid., 1941, 35, 417.6a Ibid., 1936, 30, 1837STEPHENSON AND KREBS : THE UTEISATION OF CARBON DIOXIDE. 257of their copper salts, an investigation of the dicarboxylic acids of gliadin.He reports the isolation of r-glutamic acid, thought to be a true hydrolysisproduct and not an artefact. Some of the methods of hydrolysis and ofestimation of the hydrolysis products adopted by J. W. H. Lugg (21.8.)have been utilised and found satisfactory by D. M. Doty,sS who proposesmore rapid methods for the estimation of some of the amino-acids, includingtyrosine, tryptophan, arginine, histidine and cystine, in the grain of corn(maize).Amongst methods which have been applied almost solely toanimal proteins, but which may be equally capable of application to plantproteins may be mentioned a micro-method for the determination of basicamino-acids based on a preliminary separation of these substances from theother hydrolysis products by electrical transport. A. A. Albane~e,~* theauthor of the method, follows this procedure by separation of arginine asflavianate with subsequent precipitation of the histidine as the mercuricchloride complex, and estimation of lysine from the residual nitrogen.Finally, M. Bergmann and his associates are developing a new principlewhereby the components of a protein hydrolysate are determined by partialprecipitation as salts, the amount remaining in solution being estimatedfrom a known solubility product. Thus, M.Bergmann and W. H. SteinG5estimate glycine by precipitation with potassium trioxalatochromate, andproline similarly with ammonium rhodanilate. The method has beenadapted to a semimicro-scale by M. Bergmann and H. R. Ing,ss the reactionproducts being filtered a t the centrifuge. Glycine has been estimated in thiscase by means of sodium dioxpyridate, and proline as previously indicated.F. W. N.6. 'YHE UT~LISATION OF CARBON DIOXIDE BY HETEROTROPHIC BACTERIABND ANIMAL TISSUES.Carbon dioxide was €or long regarded as a physiologically inert gas exceptin the case of photosynthetic and chemosynthetic organisms.The firstsuggestion to the contrary was the discovery that carbon dioxide facilitatedthe cultivation of the organism of contagious abortion, BruceZZa abortus.'In 1935 it was found that a number of common bacteria failed to developin media from which carbon dioxide was rigorously removed.2 It is nowknown that this gas reacts chemically in various organisms. So far tworeactions can be defined :(1) CO, + 8H = CH, + 2H20( 2 ) C02 + CH,*CO*CO2H = COzH*CH~*CO*COzHIt is highly probable that other reactions occur.63 I n d . E ? L ~ . Chem. (Anal.), 1941, 13, 1696 6 Ibid., 1939, 128, 217.T. Smith, J . Exp- Med., 1924, 40, 219.a G. P. Gladstone, P. Fildes, and G. M. Richardson, B d .J . Zap. Pa&, 1936, 16,For a review of the literature up t o 1938, see Hes, Ann. Perme&., 1938,4,647.J . Biol. Chem., 1940, 134, 467.d B Ibid., 1939, 129, 603.335.REP .-VOL . XXXVIII 258 BIOCHEMISTRY,Early work on reaction (1) is well sunimarised by H. A. Barker.3 Thekey observation was that of SOhx~gen,~ who showed that enrichment culturesfrom soil fermented a mixture of hydrogen and carbon dioxide to methane;this is to be regarded as a reduction of carbon dioxide by molecular hydrogenanalogous to the reduction of sulphate and nitrate catalysed by hydrogenaseon the one hand and by sulphatase and nitratase respectively on the other.This analogy was pointed out by van Niel (quoted by Barker 3), who postulatedthat the production of methane known to occur anmobicallyfrom a richvarietyof substrates was really an oxidation of the substrate with carbon dioxide act-ing as the hydrogen acceptor.Recently Barker and his co-workers have dem-onstrated that in a number of cases this is indeed so ; the difficulty of isolatingmethane bacteria has been largely overcome and each species isolated has beenshown to effect the oxidation of certain groups of compounds by hydrogentransfer to carbon dioxide. It now seems probable that the reductionof carbon dioxide is the sole means by which methane is formed in ferment-ations. Thus Methanobacterium Omelianski, isolated by Barker,4 oxidisesthe following alcohols in the presence of carbon dioxide to their correspond-ing acids : ethanol, n-propanol, n-butanol, sec.-butanol and n-pentanol ;methanol and tert.-butanol are not attacked ; isopropanol and isobutanolare oxidised to acetone and methyl ethyl ketone respectively.The ferment-ation of ethanol in growth experiments on synthetic media with ethanol assole source of carbon occurs closely in accordance with the equation2C2H,*OH + CO, = 2CH3*C0,H + CH,, the slight deficit found in thesubstances on the right side of the equation being due to the fact that about6% of the carbon of the ethanol and 1.5% of the carbon dioxide are used toform cell material.5Where mixed enrichment cultures from mud are used for the oxidationof the alcohols by carbon dioxide a second reaction sets in whereby theacids formed are further oxidised. Two organisms carrying out this secondoxidation have been isolated, Methanococcus Muxei and MethanobacteriumSohngenii ; both ferment acetic and butyric acids but none of the alcohols.The fermentation of acetic acid proceeds according to the equationCH3*C0,H + 2H20 + CO, = 2C0, + CH, + 2H,O.Butyric acid appearsto give rise first to acetic acid, which is then further oxidised as above. Theseexperiments, carried out on 2Mb. Omelianski and Methanosarcine methanica,showed furthermore that cell material as well as methane is produced byreduction of carbon dioxide.6The reduction of carbon dioxide to acetic acid has been described byK. T. Wieringa.' This observer repeated Sohngen's synthesis of metha.nefrom hydrogen and carbon dioxide with crude cultures from mud.Onpasteurising the culture and plating out, he obtained a spore-forming organismby means of which carbon dioxide was reduced by hydrogen, giving noArch. MilcrobioZ., 1936, 1, 7, 404.Idem, J . Biol. Chem., 1941, 137, 153.H. A. Barker, S. Ruben, and M. D. Kamen, Proc. Nut. Acad. Sci., 19 .O, 26, 426.Antonie van Leeuwenhoek, 1936, 8, 263.H. A. Barker, ibid., 1936, ii, 7, 420STEPHENSON AND KREBS THE UTILTSATTON OF CARBON DIOXIDE. 259methane but a quantitative yield of acetic acid. There is no reason, how-ever, to postulate acetic acid as an invariable intermediate in the Sohngenreaction, since there is a case on record in which the reaction has beeneffected by a culture derived from a single cell which was incapable ofproducing methane from any compound with more than one carbon atom.8A special ‘case of carbon dioxide reduction is that due to CZ.acidi u r i ~ i . ~This organism decomposes uric acid, xanthine, hypoxanthine and guanineanaxobically, giving only ammonia, carbon dioxide, and acetic acid :purine, urea, allantoin, uracil and caffeine are unattacked ; adenine,adenosine, guanosine and yeast nucleic acid are attacked slowly. Uricacid and hypoxanthine are decomposed closely in accordance with equations(3) and (4) respectively :The fact that in (4) more than 1 mole of acetic acid was produced froin1 mole of hypoxanthine led to the hypothesis that the decomposition was dueto an oxidoreduction with carbon dioxide, which is itself reduced to aceticacid as in the reaction reported by Wieringa.This was supported by experi-ments in which suspensions of the organism fermented uric acid in the presenceof radioactive 11C02.10 The results showed that the acetic acid produced wasradioactive and that the llC was present in the methyl as well as in the carbonylgroup; also that l1C had passed into cell material. So far the evidencesupports the reduction of carbon dioxide to acetic acid. On the other hand,in experiments in which uric acid was fermented in a rapid stream of hydrogenfree from carbon dioxide the rate of breakdown was the same as in the control ;this evidence is against carbon dioxide acting as the hydrogen acceptorunless its concentration within the cell is sufficient to maintain the optimumrate in spite of its rapid removal from the solution,A second line of investigation relating to carbon dioxide utilisationoriginated from work on the fermentation of propionic acid bacteria.In1936 H. G. Wood and C. H. Werkman,ll studying the fermentation of glycerol~ J Y these organisms, made the unexpected observation that the end-productsof the fermentation-mainly propionic and succinic acids-contained morecarbon than the fermented glycerol. A closer investigation showed that theadditional carbon was derived from calcium carbonate which had been addedto the medium, as is customary, to neutralise acids formed during the ferment-ation. In 1938 Wood and Werkman l2 showed that the quantities of succinicacid formed and carbon dioxide (or carbonate ion) used were approximatelyequimolecular. The experimental data conform with the assumption thatthere are two main reactions when glycerol is fermented, namely,( 5 ) CH,(OH)*CH(OH)*CH,*OH --+ CH3*CH,*C0,H + H,O* M.Stephenson and L. H. Stickland, Biochem. J . , 1933, 27, 1617.(6) CH,( OH)*CH( OH).CH2*OH + C02 -+ CO2H*CH2*CH2*CO,H -+ H2OH. A. Barker and J. V. Beck, J . Bid. Chem., 1941, 41, 3.lo H. A. Barker, S. Ruben, and J. V. Beck, Proc. Nut. Acad. Sci., 1940, 26, 477.l1 Biochein. J., 1936, 30, 4s. l2 Ibid., 1938, 32, 1262260 BIOCH.EMISTRY.Later work lS:l4 has shown that the intermediate stages of reaction (6) areprobably as follows :This scheme is supported by the facts that the carbon dioxide used and thesuccinic acid formed are equimolecular ; l2 that the utilised carbon dioxide ispresent in the carboxyl group of succinic acid l3 (as shown by experimentswith W ) ; that fumaric and malic acids are formed along with succinicacid ; 14 that the reactions postulated readily 0ccur.1~Many micro-organisms form succinic acid when fermenting carbohydrates,glycerol, or pyruvic acid.It is likely that in most cases succinic acid isformed according to reactions (2) and (7). That this is true for Bad. colihas been shown with the help of carbon isotopes.13*14Reaction (2) probably plays a r81e in the synthesis of citric acid, fumaricacid and related substances in mou1ds.l6* 1'That carbon dioxide can be utilised in animal tissues by combiningwith pyruvic acid [reaction (2)] was first suggested by H.A. Krebs andL. V. Eggleston,l* who showed that in pigeon liver pyruvic acid yieldsthe same products as oxaloacetic acid,lg vix., citric acid, a-ketoglutaric acid,mccinic acid, fumaric acid and malic acid. The obvious, and in fact onlysatisfactory, explanation was the assumption that pyruvic acid is firstconverted into oxaloacetic acid, by way of reaction (2); this hypothesiswas supported by the fact that the concentration of carbon dioxide determinedthe rate of conversion of pyruvic acid into the above-named products.Final proof for the occurrence of reaction (2) in pigeon liver was suppliedby E. A. Evans, jun., and L. Slotin,20 who added bicarbonate containing11C and found a-ketoglutaric acid to contain the isotope. This was con-firmed by Wood et aZ.,13 who used the isotope 13C. These authors determinedthe position of the fixed carbon dioxide and found that all the fixed carbon wasin the carboxyl group next to the ketone group. This indicates that citric acidis not an intermediate in the formation of a-ketoglutaric acid, for if the latter acidwas derived from a symmetrical molecule the fixed carbon should be equallydistributed in the two carboxyl groups.. The authors suggest the followingla H.G. Wood, C. H. Werkman, A. Hemingway, and A. D. Nier, J . Biol. Chem.,1940,135, 781 ; 1941,139, 365, 377 ; S. F. Carson and S. Ruben, Proc. Nat. Acad. Sci.,1940, 28, 422; S. F. Carson, J. W. Foster, S. Ruben, and H. A. Barker, ibid., 1941, 27,229.l4 H. A. Kmbs and L. V.Eggleston, Biochem. J., 1941, 35, 676.l6 H. A. Krebs, Nature, 1941, 147, 560.l6 Y. Nishina, S. Endo, and H. Nakayama, Sci. Papers Inst. Phys. Cheni. Res.l7 H. G. Wood and C . H. Werkman, Biochem. J., 1940, 34, 7.Tokyo, 1941, 38, 341.Ibid., p. 1383.See Ann. Reporte, 1937, 34, 418.J . Biol. Chern., 1940, 136, 301; 1941, 141, 439RAISTRICK: METABOLIC PRODUCTS OF THE L O m R 261scheme for the formation of a-ketoglutaric acid : pyruvic acid + oxltloaceticacid + cis-aconitic acid _I, isocitric acid a-ketoglutaric acid + COz.Solomon et a1.21 injected NaHWO, and lactate into fasting rats and foundthe liver glycogen t o contain 11C. This can be explained on the assumptionthat the primary reaction is again reaction (2).Prior to this work S. Ruben and M.D. Kamen 22 had already shown withthe help of isotopes that liver incorporates carbon dioxide or bicarbonateinto organic compounds. These authors, however, did not define the com-pounds containing the isotope; it may have been urea, which has long beensupposed to be formed from carbon dioxide and ammonia; 23 E. A. Evansand L. Slotin, using W 0 2 , have recently supplied final proof for thecorrectness of this ass~rnption.~~+HZ0M. S.H. A. K.7. METABOLIC PRODUCTS OF THE LOWER FuNar.In the short space available it is not possible to review adequatelyprogress in this field since it was last dealt with in these Annual Reports.Interested readers are therefore referred to Annual Review of Biochemistry,1940, 9, 571, for a detailed account to the end of 1939.Attention will beconfined here to work published subsequently.(a) Derivatives of To1uquinone.-Fumigatin was fmt described a8 ametabolic product of Aspergillus fumigatus Fresenius by W. K. Anslowand H. Raistrick.l The molecular constitution, 3-hydroxy-4-methoxy-2 : 6-toluquinoneY ascribed t'o it by these authors has been confirmed bysynthesis .2(b) Derivatives of 2-Methylanthmquinone.--C~~tenarin, present in themycelium of different species of Helminthosporium, particularly Helmintho-sporium catenarium Dre~hsler,~ has now been shown to be 1 : 4 : 5 : 7-tetra-hydro~y-2-methylanthraquinone.~ This conclusion was confirmed bysynthesis. Erythroglaucin, from species in the Aspergillus ghucus series,6has been shown by Anslow and Raistrick 7 to be 1 : 4 : 5-trihydroxy-7-inethoxy-2-methylanthraquinone and was prepared by them in uitro bymethylating cateiiarin with methyl iodide and sodium methoxide in methanolsolution.Cynodontin, 1 : 4 : 5 : 8-tetrahydroxy-2-methylanthraquinone,21 A. K. Solomon, B. Vennesland, F. W. Klemperer, J. 34. Buchanan, and A. B.22 Proc. Nut. Acad. Sci., 1940, 27, 418.23 H. A. Iirebs and K. Kenseleit, 2. physiol. Chem., 1932. 210, 33.24 J . Biol. Chem., 1940. 138, 806.Hastings, J . Biol. Chem., 1941, 140, 171.1 Biochem. J., 1938, 32, 687.W. Raker and H. Raistrick, J., 1941, 670.J. H. V. Charles, H. Ibistrick, (Sir) R. Robinson, and A. R. Todd, Biochem. J . ,W. K. Anslow and H. Raistrick, ibid., 1940, 34, 1124.Idem, ibid., 1941, 35, 1006.J.N. Ashley, H. Raistrick, andT. Richards, ibid., 1939, 33, 1291.Ibid., 1940, 34, 1124.1933, 27, 499; H. Raistrick, (Sir) R. Robinson, and A. R. Todd, ibid., 1934, 28, 569262 BIOCHEMISTRY,from Helminthosporium cynodontis Marignoni,s has also been synthesisedby Anslow and Raistri~k.~H. G. Hind 10 isolated from cultures of Penicillium cnrmino-viohceumBiourge two polyhydroxyanthraquinones, carviolacin, C,H,,O,, andcarviolin, C16H1206, and later 11 showed that carviolin is a monomethylether of o-hydroxyemodin, 4 : 5 : 7-trihydroxy-2-hydroxymethylanthra-quinone, which was itself isolated from cultures of Penicillium cyclopiurnWestling by W. K. Apslow, J. Breen, and H. Raistrick l2 and from Peni-cillium citreo-roseum Dierckx by T. P0~ternak.l~ Posternak l4 showed thatroseopurpurin, which he isolated from Penicillium roseo-purpureurn Dierckx,is the 4-methyl ether of w-hydroxyemodin, i.e., 5 : 7-dihydroxy-4-methoxy-2-hydroxymethylanthraquinone. The present reviewer (unpublished ob-servation) has compared Hind’s carviolin and Posternak’s roseopurpurin,received from their respective discoverers, and has shown that they are oneand the same substance.Penicilliopsin, C,H,,08, the orange crystalline colouring matter ofPenicilliopsis clavariae formis Solrns-Lauba~h,~~ when oxidised in air andsubsequently irradiated , gives chocolate-brown needles of irradiated oxy-penicilliopsin, C30H200s.This substance is closely related to, but notidentical with, hypericin, the photodynamically active colouring matterof St. John’s wort, Hypericum perforaturn. Penicilliopsin, whose constitu-tion is a t present unknown, is a derivative of 2-methylanthraquinone, sinceit gives tetranitroemodin on oxidation with nitric acid.(c) Chlorine-containing MetuboEic Products.-The conversion by mouldsof inorganic chlorides in the culture medium, e.g., potassium chloride, intoorganic chlorine-containing metabolic products is becoming increasinglyrecognised. A survey of the subject was made by P. W. Clutterbuck,S. L. Mukhopadhyay, A. E. Oxford, and H. Raistrick,16 and these workersisolated from the metabolism solution of Caldariomyces ficmago Woronichincrystalline caldariomycin, C5H802C12, the most probable structure for whichis 2 : 2-dichlorocyclopentane-1 : 3-diol. T. P. Curtin and J. Reilly l7isolated from the mycelium of Yenicillium sclerotiorurn van Beyma a yellowcrystalline colouring matter, sclerotiorine, to which the improbable empiricalformula C,oH,,05C1 was assigned. Its molecular structure has not yetbeen determined.(d) Anti-bacterial Substances from Moulds.-The fact that many mouldmetabolic products have marked bacteriostatic or even bactericidal pro-perties is becoming increasingly cvident. A. Fleming showed that cultureH. Raistrick, R. Robinson, and ,4. 11. Todd, Biochem. J . , 1933, 27, 1170.Ibid., 1940, 34, 1546. 10 Ibid., p. 67.l1 Ibid., p. 577. l2 Ibid., p. 159.13 Compt. rend. Xoc. Phys. Hist. mat. GenBve, 1939, 56, 28; T. Posternak and J. P.l4 Helv. Chinz. Acta, 1940, 23, 1046.lG Ibid., p. 664.18 Brit. J . Exp. Path., 1929, 10, 226.Jacob, Helv. Chim. Acta, 1940, 23, 237A. E. Oxford and H. Raistrick, Biochenh. J . , 1940, 34, 790.1 7 Ibid., p. 1419RAISTRIUK : METABOLIC PRODUCTS OF THE LOWER FUNGT. 263filtrates from a strain of Penicillium notaturn Westling contain a substance,penicillin, which is highly bacteriostatic against Gram-positive micro-organisms. Optimum cultural conditions for the formation of penicillinand the fact that it is extractable with ether were established by P. W.Clutterbuck, R. Lovell, and H. Raistrick.19 H. W. Florey et aL20 have recordedstriking successes in the use of penicillin concentrates in clinical trialsand describe the preparation of an intensely active, but a t present impure,barium salt of penicillin. Penicillin is relatively non-toxic to animals.14;. C!. White 21 reports that culture filtrates from strains in the AspergiZEusLfZavusseries contain a bactericidal agent and G . A. Glister z2 has shown that an un-named species of Aspergillus produces a powerful anti-bacterial agent whichis particularly active against Gram-negative organisms. Neither of thesesubstances has a t present been isolated in a pure condition. S. A. Waksmanand H. B. Woodruff 23 have isolated from soil a new species, dctinomycesuntibioticus,24 which produces two crystalline substances, actinomycin Aand actinomycin B. Actinomycin A is intensely bacteriostatic againstGram-positive bacteria, but only moderately so against Gram-negativebacteria. Actinomycin B has littlebacteriostatic action but is strongly bactericidal. Citrinin, CI3Hl4O5, asemi-quinonoid crystalline metabolic product of PeniciZEium citrinurnand penicillic acid, the P-methyl ether of y-hydroxy-y-isopropylidene-tetronic acid, a crystalline metabolic product of PeniciEEium cyclopiumWe~tling,~’ have been shown to be powerful anti-bacterial agents.28 Theiractivity against a wide range of micro-organisms has been determined byA. E. Oxford.29 None of the above-mentioned substances, except possiblyactinomycin A, is as active as penicillin against Gram-positive organisms,t,hough Glister’s substance, penicillic acid, and citrinin arc much more activethan penicillin against Gram-negative organisms.It is extremely toxic to animals.25H. K.J. F. DANIELLI.I,. J. HARRIS.H. A. KREBS.D. M. NEEDHAM.A. NEUBERGER.F. W. NORRIS.H. RAISTRICK.M. STEPHENSON.l9 Biochezn. J., 1932, 26, 1907. *’ ~ ‘ c ~ F I c ~ , 1940, 92, 127.23 Proc. Xoc. Exp. Biol. Med., 1940, 45, 009.2 6 S. A. Waksman, H. Robinson, H. 5. Metzger, and H. B. Woodruff, Proc. SOC. Exp.2 6 A. C. Hetherington and H. Raistrick, Phil. Trans., 1931, B, 220, 209; F. P.27 J. K. Birkinshaw, A. E. Oxford, and H. Raistrick, Biochem. J . , 1936, 30, 394.28 H. Raistrick and a. Smith, Chem. and Ind., 1941, 60, 838: &A. E. Oxford, H.Raistrick, and G. Smith, ibid., 1942, 61, 22.29 Ibid., 1942, 61, 48.2o Lancet, 1940, 239, 226 ; 1941,241, 177.22 Nature, 1941, 148, 470.24 Idem, J . Bact., 1911, 42, 231.Riol. Med., 1941, 47, 261.Coyne, H. Raistrick, and (Sir) R. Robinson, ibid., p. 297

ISSN:0365-6217    

DOI:10.1039/AR9413800228

出版商:RSC    

年代:1941

数据来源: RSC

摘要:

ANALYTICAL CHEMISTRY.1. INTRODUCTION.ALTHOUGH the scope and utility of the newer physical methods of analysisreported in the past three years cover the whole field of Chemistry, never-theless reference to much of the progress in inorganic and organic analysishas of necessity been hitherto omitted, an omission which in this Report is inpart remedied.It is usually comparatively simple to detect and determine a substancewhen it is not accompanied by chemically related entities, but the analyst isfrequently confronted with the problem of determining one or more consti-tuents of a mixture of substances having similar characteristics. The alkalimetals form a well-known group presenting such difficulties, and a section ofthis Report records recent progress and the application of the LundegBrdhand the Ramage technique which depend on the volatility and light-emittingproperties of these elements in flames. Organic analysis has many problemspresented by mixtures, and amongst them is the analysis of essential oils whichhas not so far been considered in these Reports.In view of the extensiveand widening range of application of these oils in perfumery, medicine,etc., in recent years, the subject seems of sufficient importance to beconsidered here.The use, in commerce, of the simpler oxygen-containing organic compoundshas expanded considerably within recent years. This is doubtless due to themore ready availability of such materials on account of their increasedproduction by methods, often novel, that have now been introduced intolarge-scale manufacture, while the substitution of compounds, e.g., isopropylalcohol in place of ethy1 alcohol, that is thus rendered possible frequentlyrelieves the material of legal restriction.Since the last report on alcohols(Ann. Reports, 1933, 30,275) many new methods of analysis, as well as modi-fications of existing methods, have been proposed for detecting and estimatingthese compounds, with increased accuracy, in materials that often varyenormously in type and complexity. In this Report, some salient features ofthese advances are recorded.The significance of trace substances in meta#bolism is receiving increasingrecognition, and in spite of the general decline in the volume of work publishedduring the past year, vitamins have not suffered from lack of interest.Theimportance of carbohydrates in industry and in metabolism needs no emphasis,and the papers which have appeared since the Report of 1938 justify furthersections on the analysis of carbohydrates and of vitamins.2. VITAMINS.Much of the published work relates to improved processes for extracting thevitamins for analysis from natural products and to modifications of methodBOORMAN, GRIFFZTHS, MAULENNAN, AND WBBLLEY. 265oftoOf,determination already reported, l but limitations of space permit referenceonly a proportion of the papers which illustrate, rather than include allthe progress which has been made.'Vitamin-A .-Discrepancies between biological, ohemical, and spectro-photometric determinations of vitamin-A continue to be investigated.2Physicochemical determination of vitamin-A in fish-liver oils leads to a lowervalue than biological assay owing to the presence of esterified vitamin-Awhich is more stable than the free alcoh01.~ The esterified vitamin appearsto be more potent than the n~n-esterified,~ and some results lead to the viewthat the esters vary in activity among themselves.6 Investigations with thecrystalline vitamin and its esters may be expected to throw light on theorigin of the discrepancies.The necessity for precaution against loss of vitamin as a result of oxidationduring extraction for determination is well known, but significant loss byphotodecomposition may also occur unless ultra-violet light is excluded, forexample, by using amber-glass apparatus.' When the unsaponifiable matterfrom cod-liver oil is dissolved in isopropyl alcohol or dehydrated ethylalcohol, the spectrophotometric results are about 12% higher than when cyclo-hexane is used,B which emphasises the importance of the solvent.Vitamin-B Fac~~.-Optimum conditions have been investigated forthe extraction of vitamin-B, (thiamin,'aneurin), the hydrolysis of the phos-phorylated aneurin with enzyme preparations, adsorption of the total vitaminon zeolites whereby interfering substances are removed, elution, and theoxidation with sodium hydroxide and potassium ferricyanide to thiochrome,which is determined by fluorescence mea~urement.~ In the initial extractionwith dilute sulphuric acid, riboflavin (a member of the vitamin-B, complex)accompanies the -B, and, after the enzymic hydrolysis, may be separatedby passing the solution f i s t through " Decalso " (a synthetic zeolite) whichadsorbs the -B, and then through " Supersorb " fuller's earth which adsorbsthe riboflavin.The vitamins are eluted, and determined by measurementof fluorescence.10A microbiological method 11 for riboJEavin, in which the growth responseof bacteria is measured in terms either of culture turbidity after 24 hours'incubation or of acidity produced as a result of 72 hours' incubation, showsgood selectivity and repEoducibility, and other vitamins, even in largeAnn. Reports, 1938, 35, 399; 1940, 37, 463, 465, 467.E.g., J. B. Wilkie, I n d .Eng. Chem. (Anal.), 1941, 13, 209; N. H. Coy, H. L.W. Grab and T. Moll, Klin. Woch., 1939, 18, 563.T. Moll and A. Reid, 2. physiol. Chem., 1939, $460, 9.G. Lunde and H. Kringstad, Tids. Kjemi, 1940, 20, 14.J. G. Baxter and C. D. Robeson, Science, 1940, 92, 203.N. D. Embree, Ind. Erag. Chem. (Anal.), 1941, 13, 144.D. C. M. Adamson and N. Evers, Analyst, 1941, 66, 106.Sassaman, and A. Black, &id., p. 74.9 D. J. Hennessy and L. R. Cerecedo, J . Amer. Chem. SOC., 1939, 61, 179; R. T.Connor and G. J. Straub, I d . Eng. Chem. ( A w l . ) , 1941,13, 380.lo Idem, &id., p. 385.l1 E. E. Snell and F. M. Strong, aid., 1939,11, 346266 ANALYTICAL CHEMISTRY.excess, do not interfere.12 Microbiological l1 and fluorescence l3 methodsare preferred to a colorimetric meth0ci.1~Vitamin-B, (adermin, pyridoxin) is extracted from dilute solution bymeans of butyl alcohol or on zeolite, and is determined by means of theblue colour produced by 2 : 6-dichlorobenzoquinonechloroimide and asolution containing not less than 0.05 mg.% of -B6.Methods of eliminat-ing many interfering substances are described.15 The colour reaction withdiazotised sulphanilic acid is not specific for -B6, but interfering substancescan be removed, and results are in approximate accord with bio-assays.16Chemical methods for nicotinic acid and -B, have been reviewed.1'The application of the polarograph l8 to the detection and determinationof trace substances is being investigated extensively, and it is found thatvitamin-B,, nicotinic acid (pellagra-preventive factor), pantothenic acid(chick-pellagra factor), Vitamin-B,, and, most easily, riboflavin are reducedat the dropping-mercury electrode and give characteristic polarographicwaves by which it is suggested that these substances, especially riboflavin,may be determined in natural product^.^^Yita,min-D.-The sensitivity of the pink colour reaction (a bsorptionMax.a t 5000 A.) with antimony trichloride is increased by the presence of2% of acetyl chloride, thereby permitting 2 pg. of vitamins-D2 and/or -I& tobe determined.*O Fair agreement G t h bio-assays has been obtained whenthe antimony trichloride reaction is applied either to fish-liver oils contain-ing more than 10,000 I.U. per g. and corrections are applied for the presenceof sterols and vitamin-A, or to the non-saponifiable fraction which has beentreated with maleic anhydride to destroy vitamin- A, carotenoids, and7 -dehydrocholesterol.21Of several colour reactions investigated,22 the most selective is said tobe that of Tortelli and JaffB in which a blue colour (absorption bands at5450-5500 and 5900-6000 A.) is produced by the action of a solution ofbromine in chloroform, and since vitamin-& carotene, and oxidation productsand isomerides of vitamin-D do not interfere, the reaction permits thedetermination of vitamin-D in, e.g.: 0.01-0-05 ml.of cod-liver oil.Discrepancies between different determinations of the extinction co-efficient of calciferol (vitamin-D,) have been traced to decomposition by the19 A.D. Emmett, 0. D. Bird, R. A. Brown, C. Peacock, and J. M. Vandenbelt, Ind.13 A. Z. Hodson and L. C. Norris, J . Biol. Cheni., 1939, 131, 621.1 4 A. R. Kemmerer, J. Assoc. O$. Agvk. C'henb., 1940, 23, 346 ; 1941, 24, 413.1 5 J. V. Scudi, J. Biol. Chem., 1941, 139, 707.16 &I. Swaminathan, Nutzwe, 1940, 145, 780.17 H. A. Wrtisman and C. A. Elvehjem, Ind. Eny. C'hem. ( A w l . ) , 1941, 13,18 Cf. Ann. Reports, 1938, 35, 389.1s J. J. Lingane and 0. L. Davis, J . Biol. Chem., 1941, 137, 567.20 C. H. Nield, W. C. Russell, and A. Zimmerli, ibid., 1940, 136, 73.2 1 N. A. Milas, R. Heggie, and J. A. Reynolds, I d . Eng. Chem. (Anal.), 1941,22 V. L. Solianikova, Biochitnia, 1939, 4, 483.Eng. Chem. (Anal.), 1941, 13, 219.221.13, 227BOORMAN, QRIFFITHS, MACLBNNAN, AND WHALLEY .267light used in the determination, and a continuous-flow technique is recom-mended to eliminate the effect .23Biturnin-K .-Vitamin-K2 (2- methyl-3-phytyl- 1 : 4-naphthaquinone) isdetermined polarographically in solution of potassium chloride in aqueousisopropyl and -K, and related quinones are determined in 95%n-butyl alcohol by reduction and subsequent titration with 2 : 6-dichloro-phenolindophenol. Vegetable and cod-liver oils and vitamins-A and -Ecaiise no interference.25In a colorimetric method less than 0.1 mg. of 2-methyl-1 : 4-naphtha-quinone or related compound in a drop of alcohol is treated with 2 : 4-dinh-o-phenylhydrazine and then successively with ammonia, amyl alcohol, andwater, whereby a stable green colour, proportional to the quantity of thequinone, is extracted in the amyl alcohol.263.ANALYSIS OF ALKALI METALS.A. (-‘hemica1 Methods.The removal of all other metals, and all non-metals save chloride andoccasionally sulphate ions, is the usuaJ preliminary to the determinationof the alkali metals. Recent editions of standard analytical works describein detail accepted procedures of assembling the alkali metals. When onlyone member of the group is present i t may be weighed as sulphate, butwhen, as is more usual, two or more members are together then it iscustomary to obtain a solution of their chlorides. Occasionally this maybe easily achieved by dissolution in hydrochloric acid, but commonly thissimple treatment fails, and one of the standard procedures of opening upthe sample has to be employed.One such method, originally used by J. J.Berzelius, is the treatment of the sample with a mixture of hydrofluoricand sulphuric acids, followed by removal of all other metals and conversionof the sulphates into chlorides with barium chloride, the excess bariumbeing removed by treatment with ammonium hydroxide and carbonate.Alternatively, the method of J. Lawrence Smith may be used, in which thesample is decomposed by heating with a mixture of ammonium chloride andcalcium carbonate ; the water extract contains the alkali chlorides, sulphates,and considerable amounts of calcium. This classical method has theadvantage of leaving in the insoluble residue the bulk of any boronpresent in the sample, and all but a trace of magnesium.Most of theextracted calcium is removed by ammonium hydroxide and carbonate, andtraces by ammonium oxalate.Modifications of the Lawrence Smith method have recently been report,ed.W. van Tongeren first prepares a, liquid by treating 0.5 g. of calcium23 S. K. Crews and E. L. Smith, Analyst, 1939, 64, 668.24 E. B. Hershberg, J. K. Wolfe, and L. I?. Fieser, J . AmeT. Chem. SLOG., 19404s N. R. Trenner and F. A. Baoher, J . Biol. Chem., 1941, 137, 745.28 A. Novelli, Science, 1941, 93, 358.’62, 3616.Zentr. >!in., 1936, A . , 243; Chem. Zentr., 1936, ii, 3929268 ANALYTICAL CHEMISTRY.carbonate with an amount of concentrated hydrochloric acid just insufficientto cause complete dissolution. Under this liquid the sample is powdered,and additional calcium carbonate is added, together with a little ethylalcohol.After drying and fusion, the cooled melt disintegrates in hot water.The use of barium chloride as a flux in place of the arnonium chloride hasalso been recommended : the preliminary slow heating to remove ammoniais thereby eliminated, and sulphates are automatically removed. Recentcomparison of the Berzelius with the Lawrence Smith method and its modi-fications has been made.3 The possibility of boric, lead, or bismuth oxidesbeing used as the decomposing agent has long been known; E. Schulekand L. Szlatinay have recommended the use of boric acid in the analysisof organic compounds and mixtures containing alkali metal, halogon, sulphur,and arsenic.The addition of glucose ensured the reduction of arsenates andsulphates. J. Haslam and J. Beeley have determined sodium and potassiumin refractory materials by means of a modification of the Lawrence Smithmethod, the potassium being finally determined as perchlorate, and thesodium by zinc uranyl acetate.The alkali metals having been separated from the other groups, theiridentification and determination present problems which continue to receiveattention. Confirmatory drop tests for lithium, sodium, potassium, andczesium have been described.g 0. G. Scheintzis finds that characteristicmicrocrystals form when a drop of borofluoric acid is added to a drop ofsolution containing amounts of potassium, rubidium, or cesium of the orderof 1 pg.; some thirty elements and radicals were found not to interfere,Nickelous ions, in the presence of disodium hydrogen phosphate, have beenobserved 8 to give characteristic crystals of NiCsPO, and NiRbPO, withcesium and rubidium respectively.The test may be used for the detectionof as little as 0.01% of czsium, or 0.1% of rubidium. Naphthol-yellow-S(the potassium salt of 2 : 4-dinitro-a-naphthol-7-sulphonic acid) gives a yellowprecipitate with rubidium or potassium, but not with other alkali metals;this observation is made the basis of a microscopic detection method for aslittle as 6.8 pg. of rubidium.There have been no recent developments in the chloropkrtinate method,whereby potassium, rubidium, and cesium are precipitated by chloroplatinicacid from solutions of the alkali chlorides from which ammonium salts areabsent.The cost of the reagent, and the fact that the composition of theprecipitate may differ slightly from M,PtCI, (M = K, Rb, or Cs), havecombined in causing the perchkrate method to be pref:rred. Using thelatter method, T. Kato extracts the perchlorates of the alkali metals withmethyl acetate. The residue consists of the potassium, rubidium, and2 R. E. Stevens, Ind. Ens. Chem. (Anal.), 1940, 12, 413.a E. Biittner, Keram. Runds., 1939, 47, 101.2. anal. Chem., 1938,112, 336.J. I. Adams, A. A. Benedetti-Pichler, and J. T. Bryant, Mikrochem., 1939, 26, 29.J . Appl. Chem. Russia, 1940, 13, 1101.J . Electrochem. Assoe.Japan, 1938, 3, 276.Analyst, 1941, 66, 185.M. V. Gapchenko, ibid., p. 1264BOORMAN, GRIFFITHS, MACLENNAN, AND WFKALLEY. 269caesium salts which are separated by differences in the solubilities of theiracid tartrates and phosphotungstates. Lithium and sodium are separated bythe difference in solubility of their chlorides in aqueous ammonia. Moreusually, of course, the alkali chlorides are converted into perchlorates, andthc sodium and lithium extracted with ethyl alcohol or with a mixture ofn-butyl alcohol and ethyl acetate.10 From the latter solution the sodiummay be precipitated as chloride by adding butyl alcohol saturated withhydrochloric acid gas, and the lithium in the filtrate converted into sulphate.The use of zinc uranyl acetate 11 as a quantitative precipitant for sodiumhas been extensively developed.The precipitation of the complex(UO,),ZnPu'a( CH3*C0,),,6H,0 is satisfactorily obtained from the solution ofthe alkali chlorides; NH,+, Mg++, Ca++, Bit++, K+ (if > 50 mg./ml.), do notinterfere, but Li+, Sr++, certain organic acids, phosphates, and sulphates inthe presence of potassium, should be absent. R. Lindner and P. L. Kirk l2report the use of this reagent for the determination of 0 . 1 3 4 . 1 3 x g.of sodium. The precipitate is redissolved in 5% sulphuric acid solution,reduced with metallic cadmium, and the uranium titrated with ceric sulphate.The method is applicable to biological materials. The sodium content ofbiological fluids (e.g., serum, urine) has also been determined volumetrically(by titration of the triple salt with 0-1N-sodium hydroxide), and gravi-metrically by means of modifications of the zinc uranyl acetate method.The use of this reagent in the gravimetric determination of sodium in naturalwaters has been described.14 The conditions for the precipitation of sodiumby magnesium uranyl acetate have also been investigated by E.C. Elliott,15with particular reference to the possibility of interference by certain elements.The moisture content of NaMg( or Zn) (UO,),( CH,*C02)e has been found to be64430/d according to the humidity of the air.16 Certain uranyl acetatereagents for sodium also precipitate lithium from concentrated solutions, butcopper uranyl acetate 1' appears to be nearly specific €or sodium, to which itis moderately sensitive.Methods for lithium include its determination as stearate ; 18 phosphate ; l9arsenafe ; 2o and the triple acetate,21 LiZn(UO,),( CH3*C0,),,6H,O, afterextraction of the lithium by amyl alcohol and acetone.Many methods arebased on the differential solubility of lithium chloride. and a number ofsolvents have served this purpose : ethyl alcoho1,22 a mixture of butyl alcohollo Numerous workers, including H. H. Willard and G. F. Smith, J . Amer. Chem.SOC., 1922, 44, 2816; G. F. Smith and J. R. Ross, ibid., 1925, 47, 774, 1020.l1 H. H. Barber and I. M. Kolthoff, ibid., 1928, 50, 1629.l a Mikrochem., 1938, 23, 269.l4 0. Oparha, Hydrochem. Mat., 1939, 11, 96.lS Ind. Eng. Chem. (Anal.), 1940, 12, 410.l6 N.Schoorl, Chem. Weeekblad, 1939, 36, 122.M. Dreguss, Biochem. Z., 1939, 303, 69.E. R. Caley and W. 0. Baker, Ind. Eng. Chem. (Anal.), 1939,11, 604.E. R. Caley, J . Amer. Chem. Soc., 1930, 52, 2754.l' B. Brauner, Coll. Czech. Chem. Comm., 1930, 2, 442.2o T. Gaspar, Anal. Fis. Quim., 1932, 30, 406.a1 C. C. Miller and F. Traves, J., 1936, 1395.z2 S. Palkin, J . Amer. Chein. SOC., 1916, 38, 2326270 ANALYTICAL CHEMISTRY.and ethyl acetate,l* amyl alcohol and pyridine,z3 A sensitive testfor lithium, the sensitivity of which is so increased by the presence of sodiumthat 0.05 pg. may be detected, has been de~cribed.2~ The reagent, whichgives a yellow precipitate with lithium, is a solution of 2 g. of potassiuniperiodate in 10 ml. of B~-potassium hydroxide diluted to 50 ml.and towhich 3 ml. of 10% aqueous hydrated ferric chloride have been added, thewhole being made up to 100 ml. Additional data of the sensitivity of this test,and a discussion of the difficulties encountered in the extraction of lithiumchloride from mixed alkali chlorides, with particular reference to the deter-mination of lithium in mineral waters and silicate rocks, have been given by0. Hack1.26 A microtechnique, employing the carbonate test for lithium!enables a few tenths of a mg. to be detected,27 and high selectivity of thetest is claimed.Differences in the solubilities of certain of their salts form the basis ofmethods for the determination of rubidium and ccesizcm when they occurtogether, though either may be determined satisfactorily, as the perchlorateor chloroplatinate in the absence of the other, or in the presence of sodiumand lithium.The separation of rubidium and caesium by precipitation ofthe complex chloride 4CsC1,4SbC1,,FeC13 28 is not wholly satisfactory, sincethe precipitation of caesium is incomplete under conditions that avoid co-precipitation of rubidium. Reliable methods for the clean separation ofrubidium, or rubidium and caesium, from potassium have not yet beenstandardised. The precipitation of rubidium and cmium as their chlorc-stannates is fairly satisfactory when little potassium is present, but theprecipitation of the triple nitrites, M,NaBi(NO,),, where M = Cs or Rb, isusually ~referred.2~ The application of stannic bromide to the determinationof cmium in the presence of rubidium and potassium has been described : 30from a solution of the bromides Cs,SnBr6 is thrown ont by an alcoholicsolution of stannic bromide.Standard chemical methods for the determination of potassium itrenumerous and include precipitation ( a ) as the chloroplatinate followed byreduction and weighing of the platinum (the method has wide applicabilitysince many of the commonly occurring anions and cations do not interfere) ;( b ) as the perchlorate in butyl- or ethyl-alcoholic solution; (c) by sodiumcobaltinitrite.During recent years the use of the cobaltinitrite complexhas been investigated 31 and considerably extended. For the determination28 J. Bardet, A. Tchakirian, and R.Lagrange, Compt. rend., 1937,204, 443.24 M. H. Brown and J. H. Reedy, I n d . Ens. Chem. (Arutl.), 1930, 2, 304.26 0. Procke and R. Uzel, Mikrochim. Acta, 1938, 3, 106.27 E. R. Caley and A. L. Baker, jun., Ind. Eng. Chem. (AnaE.), 1939,11, 101.2. anal. Chem., 1939, 118, 1.F. Godeffroy, Ber., 1874, 7, 374; W. Strecker and F. 0. Diaz, 2. anal. Chem.,2s W. C.Ball,J., 1909,95,2126; W.C.BallandH.H.Abram,J., 1913,103,2110,213031 L. V. Wilcox, I d . Bng. Chem. (AnaE.), 1937, 9, 136; A. Kamw, 2. anal. Chent.192516, 87, 321 ; L. Moser and E. Ritschel, ibid., 1927, 70, 184.R. V. Feldman, J. Appl. Chem. Russia, 1938, 11, 1017.1939,115, 385BOORMAN, GRIFFTTHSI MACLENNAN, AND WHALLEY. 271of minute amounts of potassium, I. A. Kaye 32 recommends dissolving theprecipitate in excess of ceric sulphate, addition of excess potassium iodidesolution and titration of the liberated iodine with thiosulphate.For 0.036-0.120 mg. of potassium the average error was + 0.5%. Zinc cobaltinitritehas been prepared as a precipitant33 and is useful when sodium has tobe determined after the removal of the potassium. The use of silvercobaltinitrite 34 has been recommended as the precipitant for the determin-ation of small amounts of potassium in blood serum ; 35 the silver is deter-mined titrimetrically, the NO,’ manometrically, and under well-definedconditions the composition of the precipitate is constant. B. Klein andM. Jacobi 36 prefer to titrate the NO,’ in the potassium silver cobaltinitritewith ceric sulphate in the presence of ferroin (o-phenanthroline-ferrouscomplex), the error being 2% on 0.1-0.2 mg.of potassium. J. E. Harris 37states that by a modified silver cobaltinitrite method a precipitate is obtainedin which the NO,’/K ratio is constant.As in the determination of rubidium and caesium, triple nitrites maybe used for the rapid determination of potassium. Results obtained gravi-metrically by the precipitation of K,CUP~(NO,)~ 38 differed by only 0.2-0.4% from those given by the perchlorate method.H. H. Willard and A. J. Boyle s9 have reported an interesting methodfor the separation and determination of potassium by precipitation asperiodate from nitrate solution. The potassium may, in this way, beseparated from calcium, zinc, magnesium, aluminium, sodium (70 times theamount of potassium), lithium, nickel, and cobalt.The method is rapid,and accurate for not less than 4 mg. of potassium.The use of organic reagents as precipitants for potassium continues togrow. 1. M. Kolthoff and G. H. Bendix 4O have examined the gravimetricand volumetric methods for the determination of macro- and micro-quantitiesof potassium as the salt of hexanitrodiphenylamine (dipicrylamine), i.e.,NH[C6H,( NO,),],. The potassium is precipitated from neutral or alkalinesolution by the magnesium or sodium salt of the precipitant, ammoniumsalts being absent. If the sodium present is more than 80 times that of thepotassium, a preliminary separation by the cobaItinitrite method is recom-mended. The use of the magnesium salt of dipicrylamine for the micro-determination of potassium, and a separation of potassium from 100 timesits concentration of sodium has also been described by R.Dworzak andH. B a l l ~ z o . ~ ~ V. H. Dermer and 0. C. Dermer 42 have determined thesolubilities of the potassium and sodium salts of 2-chloro-3-nitrotoluene-32 Ind. Eng. Chem. (Anal.), 1940, 12, 310.33 J. Adams, M. Hall, and W. F. Bailey, Ind. Emg. Chem. (Anal.), 1935, 7 , 310.34 See, e.g., R. J. Robinson and G . L. Putnam, ibid., 1936, 8, 221; A. S. Ismail and36 T. E. Weichselbaum, M. Somogy, and H. A. Rusk, J . Biol. Chem., 1940,132, 343.36 Ind. Eng. Chem. (Anal.), 1940, 12, 687.3 8 V. M. Tichomarov and S . N. Cholmogorov, Zavod. Lab., 1938, 7 , 33.sB Ind. Eng.Chem. (Anal.), 1941,13, 137.*l Mikrochem., 1939, 26, 322.H. F. Harwood, Analyst, 1937, 62, 443.J . BioZ. Chem,, 1940, 136, 619.*O Ibid., 1939, 11, 94.4 2 ,7. Amer. Chem. Soc., 1938, 60, 1272 ANALYTICAL CHEMISTRY.5-sulphonic acid and related compounds. Only the 2-bromo-compound wasfound to be as suitable as the chloro-compound. The use of dinitronaphthol-sulphonic acid has also been examined.43Recent volumetric methods include the determination of potassium byprecipitation of K,P04, 12Mo0, by the addition of phosphomolybdic acid,filtration, dissolution of the precipitate in standard potassium hydroxidesolution, and titration of the excess.44 The determination has also beenmade by evaporation of the neutral solution with exoess of calciumferrocyanide, extraction with aqueous-alcoholic calcium chloride solution,dissolution of the precipitate in dilute sulphurio acid solution, and titrationwith 0-1N-potassium ~ermanganate.4~B.Physical Methods.1. Colorimetric.-Since details of numerous methods are to be foundin Snells “ Colorimetric Methods of Analysis,” 46 in this account the morerecent developments will be given emphasis. Methods for the determinationof potassium include the use of the chloroplatinate, the cobaltinitrite, andthe picrate. The chloroplatinate may be dissolved in water, and on theaddition of potassium iodide a red colour is produced by only 0.1 p.p.m. Thesame colour is given by ammonium chloroplatinate, and therefore ammoniaand its salts must be Alternatively, the chloroplatinate maybe reduced with stannous chloride ; the yellow colour produced ia proportionalto the platinum and hence to the potassium present.48 Methods involvingthe use of cobaltinitrite rely upon the formation of certain dyes by means ofthe nitrite in the precipitate.49 Precipitation as the picrate is made fromalcoholic solution, and the precipitate subsequently dissolved, in the absenceof sulphates.60 Calcium, magnesium, aluminium, iron, phosphates, and silicado not interfere.In the investigation of I.M. Kolthoff and G. H. Bendix,@ potassium isdetermined colorimetrically after precipitation by dipicrylamine by dissolutionin acetone, dilution with water containing 1 ml. of 0-1N-sodium hydroxidesolution/lOO ml., and the yellow to orange-red colour determined by a photo-electric colorimeter or Nessler tubes, since Beer’s law does not hold.Theaccuracy and reproducibility of the dipicrylamine colorimetric method hasbeen examined, and thermodynamic data of the amine and its potassiumsalt evaluated.51 A modification of the method is reported by E. A r n d ~ r , ~ ~and its use in the microdetermination of potassium described. 534a E. P. Volotschneva, J. Appl. Chem. Russia, 1938, 11, 369.4 5 I. V. Tananaev and E. Dshaparidze, ibid., p. 1079.46 F. D. Snell and C. T. Snell, Chapman & Hall, Ltd., 1936.4 7 B. J. V. Cuvelier, Natuurw. Tijds., 1932, 14, 107.2 s A. Nemec, Biochem. Z., 1927, 189, 50.49 See, e.g., C. P. Sideris, Ind. Eng. Chem. (Anal.), 1937, 9, 145.bo E.R. Caley, J . Amer. Chem. SOC., 1931, 53, 639; I. N. Antipov-Karataev andA. R . Myasnikova, Proc. Leningrad Dept. I n s t . Fert., 1933, 17, 81.61 J. Kielland, Ber., 1938, 71, 220.65 C, R. Harington, Bwchem. J., 1941, 35, 545.M. I. Ilmenev, Zavod. Lub., 1937, 6, 1018..62 Ind. Eng. Chem. (AWE.), 1940, 12, 731BOORRIALN, ClRIFFITHS, MACLENNAN, -4ND WHALLEY . 273Sodium may be determined as the complex with zinc or magnesium uranylacetate, by means of the greenish colour of the aqueous solution of thep r e c i ~ i t a t e , ~ ~ or by conversion of the uranyl radical into the brownish-reduranyl potassium ferrocyanide.46~ 54 M. C. Darnel1 and B. S. Walker 55prefer to dissolve the zinc sodium uranyl acetate in water and by using a4400 A. filter to determine the colour developed by the addition of sodiumacetate trihydrate and sulphosalicylic acid.A recent development, withparticular reference to the analysis of urine and blood serum, is that ofW. C. W0eIfe1,~~ in which sodium is determined colorimetrically as uranylmanganese sodium acetate. The precipitate is finally treated with potassiumperiodate in phosphoric acid solution, and the permanganate colour developedis compared with standards. The method has been examined by E. Leva,57who reports that the presence of potassium causes high results if the ratioK : Na exceeds 1.6 ; 0-0084-01 mg. of sodium may be determined with anaccuracy of & 8%. Sodium may also be determined colorimetrically by(a) precipitation as the pyroantimonate, followed by determination of theantimony as the orange colloidal sulphide; and (b) precipitation as thesodium cesium bismuth nitrite, and subsequent formation of a bright redcolour with sulphanilic acid and na~hthylamine.~~E.S.Burkser and R. V. Feldman 5t3 have estimated cesium colorimetrically byfirst precipitating it with sodium silicomolybdate, centrifuging, and finallyadding stannous chloride solution to the washed precipitate suspended indilute hydrochloric acid. The blue colour which develops is not interferedwith by aluminium, potassium, sodium, lithium, iron, magnesium, orsulphate; but lead must be absent.2. Spectrographic.-In 1834 W. H. Fox Talbot observed that byspectroscopic means lithium may be distinguished from strontium ; hethereupon began spectrochemical analysis and in particular its application tothe alkali metals.G. Kirchhoff and R. Bunsen's work on the metals ofthis group in 1860, and their discovery of cesium and rubidium, demonstratedearly in the history of this field the scope and reliability of spectroscopicmethods.The means of excitation of the spectra, namely, by the arc, spark,or flame, form a convenient mode of classification of spectrographic methods.Arc and spark methods are of general applicability to the detection anddetermination of about 70 of the 92 elements, and the alkali metals arenumbered with these. The flame is of limited applicability, but because oftheir low excitation potentials the alkali metals are easily determined bythis method.D.T. Ewing, M. P. Wilson, and R. P. Hibbard 69 employed an arc betweengraphite electrodes for the determination of potassium, lithium, rubidium,Colorimetric methods for the remaining alkali metals are few.64 B. T. Mulwani, J . Unit,. Bombay, 1940, ii, 8, 128.6 5 Ind. Eng. Chem.. (Anal.), 1940, 12, 242.h i Zbid., 1940, 132, 487.5 6 J . BioE. Chem., 1938, 125, 219.G 8 Zauod. Lab., 1938, 7, 166.Tnd. Eng. Chem. ( A w l . ) , 1937, 9, 410274 ANALYTICAL CHEMTSTRY.caesium, and other elements in hydrochloric acid solutions of samples of ash ;and K. Pfeilsticker 6o determined alkali metals in the waters of variousGerman rivers by means of an interrupted arc with copper electrodes. Thereciprocal effect of alkali metals on the sensitivity of their detection in thearc has been investigated.61 An arc technique has recently been employedin the determination of sodium in blood serum.62 With solutions on graphite,the standard deviation for a single determination is -j= 30/,.An accuracy of 2% in the determination of sodium, arid of 3 O 4 forpotassium present in urine was claimed by 0.S. D~ffendack,~~ who used aspark technique similar to that of Twymaii and Hitchen. A. Iwamura haspreferred to pass the spark between tablets made of the solution to beexamined, syrup, and carbon; csesium and lithium were determined in thisway. The spark technique has also been employed for the determinationof sodium in aluminium-silicon all0ys.6~ A. K. Rusanov made quan-titative analyses of solutions for lithium, sodium, and certain other metalsby visual examination of the spark spectra and also by photographicphotometry with the logarithmic sector on the acetylene flame.The Ramage and the Lundeghrdh technique are both of particular value inthe determination of alkali metals in solution by means of jlame excitation.In the Ramage method a known volume of the solution is absorbed on astandard strip of filter-paper, which is then dried, rolled, and burned in anoxy-coal or oxy-acetylene flame ; with the Lundeghrdh technique the solutionis sprayed in the air supply of an air-acetylene flame.Comparison of theaccuracy of the two methods has recently been made by R. L. Mitchell,67who finds that approximately equal accuracy is obtained from quadruplicatedeterminations by the Ramage and duplicates by the Lundegkrdh.ThoughT. Torok 68 has preferred the use of chemical reactions which produce agas to mechanical spraying, the latter is evidently preferred by many workers.Modifications of the LundegArdh method have been described. 6g, 70 Notabledevelopments and applications of the Ramage technique have been madeby W. A. R0ach,~1 by F. C. Steward and J. A. Ha,rrison,72 who determinedrubidium in potatoes, and by N. L. Kent 73 (lithium in plant tissue).Several recent uses of the Lundeghrdh method have been reported whichinclude the determination of the alkali metals in soils; 74 in oranges, beans,#as- u. Wasserfach, 1936, 79, 638.61 M. Wada, J . SOC. Chem. Ind., Japan, 1938, 41, 377.68 L.T. Steadman, J . Biol. Chem., 1941, 138, 603.63 U.S.P. 1,979,964, March 14, 1932; B.P. 418,298.64 Bull. Chem. Soc. Japan, 1938, 1312, 260, 265.G 5 J. A. C. McClelland and H. K. Whalley, Spectrochim. Acla, 1939, 1, 21.6 6 Bull. Acad. Sci. U.R.S.S., 1940, 4, 195.6 7 *J. Xoc. Chem. Ind., 1941, 60, 94.7o M. A. Griggs, R. Johnston, and B. E. Elledge, Ind. Eng. Chem. (Anal.), 1941,13, 99.71 Nature, 1939, 144, 1047.72 Ann. Bot., 1939, 3 (N.S.), 427.6 8 Z. anal. Chem., 1939, 116, 29.H. LundegArdh and T. Philipson, Agric. Coll. Sweden Ann., 1938, 5, 249.'3 J . Soc. Chem. Ifid., 1940, 59, 148.R . L. Mitchell and M. Robertson, ibid., 1936, 55, 2691.BOORMAN, GRIFFITHS, RIACLENNAN, AND WHALLEY. 275a i d blood; ' 0 in tobacco ashes; 75 in flue dusts, alloys, precipitates, andmiscellaneous chemicals.76 The direct determination of some elements,including the alkali metals, from their flame spectra by the use of suitablychosen filters and a photoelectric cell has been de~cribed.~'The possibility that one element may influence the intensity of theradiation due to another has to be recognised by spectrochemical analysts.The effect of sodium, potassium, and lithium introduced into an acetonevapour-air flame on the intensity of the rubidium emissions has beenexamined.78 Sodium bromide, sodium iodide, and lithium chloride weakenedthe rubidium line, whilst potassium chloride, sodium fluoride, and sodiumsulphate produced a negligible effect, The degree of weakening of therubidium line was correlated with the heat of formation of the added salt.Calculations of this effect have also been recorded and discussed by S.L.Mandelstam. 794. ALcozEobs.The most important substance considered is still ethyl alcohol, theaccurate determination of which is rendered the more necessary by the legalrequirements, both criminal and fiscal, of many countries. Little changehas been made recently in the accepted methods for its estimation, and themain advance has been made in investigations on substances which interfere.with its determination, whereby they are either removed from the alcoholbefore its final determination, or are themselves determined and suitablecorrection is then applied to the apparent alcoholic concentration. In thelatter type of analysis, however, agreement between results obtained by morethan one method is desirable.The Thorpe and Holmes process 1 is still the most important for ethylalcohol. In this, a partition is made of the sample between brine and lightpetroleum, the interfering substances being largely dissolved in the latter,while the alcohol is quantitatively retained in the brine, distillation of whichyields an aqueous solution of alcohol.Partly on this account, practically all the methods described are foraqueous solutions, as the number of compounds which affect the accuracy ofthe determinations is limited by this process to very few.Certain methods,however, are used which do not rely on this, E. G. Kellett 2 has modifiedAgulhon's test by using a 5% solution of concentrated nitric acid in glacialacetic acid for the detection of small amounts of alcohols by their oxidationwith 0.1 ml.of 1504, aqueous sodium chroinate ; by comparison of the bluecolour produced with appropriate standards it can now be used as a qiianti-F. G. H. Tate and H. K. Whalley, Analyst, 1940, 65, 587." J. A. C. McClelland and H. K. Whalley, J. SOC. Chem. Ind., 1941, 80, 288.1.. '' L. Mazza, Atti X Cong. intern. Chim., 1938, 111, 438; M. LundegBrdh and'* T. Borovick-Romanova, Compt. rend. Acad. Sci. [J.R.S.S., 1938, 21, 328.K. Boratynski, Svensk Kern. Tidskr., 1938, 50, 135.Ibid., 1839, 22, 403.(Sir) T. E. Thorpe and J. Holmes, J., 1903, 83, 314.Analyst, 1937, 62, 728276 ANALYTICAL CHEMISTRY.tative limit test in the presence of many ethers, esters, and ketones withoutpreliminary treatment, a8 secondary reactions are suppressed.A pyrolytictechnique has been perfected by 0. Grane, B. Lofstrom, and R. Wir~dbladh,~in which passage of ethyl, n- and iso-propyl, and the butyl alcohols overahminiurn oxide at 300" leads to the quantitative formation of ethylene,propylene, and butylene, respectively, which may be determined by conver-sion into the corresponding bromides; the method is also applicable tomixtures of alcohols. An unusual physical method for alcohol in aqueoussolution is by the determination of the viscosity, an accuracy of @057/,being claimed by A. Niinia4 W. Meyer considers that the iodine valueand melting point of potassium xanthates formed from alcohols can be usedonly to " judge " the constitution of mixed alcohols.T.Piccoli 6 has suggested a new qualitative test for methyl ulcohol afterits concentration in aqueous solution by repeated distillation in the presenceof potassium hydroxide. Oxidation by acid permanganate and filtration isfollowed by the addition of morphine hydrochloride in concentrated sulphuricacid, a red-violet colour being produced. T. von Fellenberg 7 has found thatDenigbs's test is still the most satisfactory, whereby the alcohol is oxidisedto formaldehyde by acid and permanganate, and the solution is thendecolourised by adding oxalic acid. Addition of Schiff's reagent yields ablue-mauve colour with the fcrmaldehyde, and the development of colourby any acetaldehyde present is prevented by the presence of a minimumconcentration of acid.He recommends optimum conditions for quantitativepractice. It has been improved by W. Preiss,8 who advocates photoelectriccomparison of the colours, and by C. M. Jephcott,9 who discovered thatunexpectedly the presence of a certain amount of ethyl alcohol, as well asclose control of conditions, are necessary to achieve maximum sensitivity, thelimit of detection in solution being 5 p.p.m. I n the titrimetric method ofW. Ender 10 sodium nitrite and acid are added to the solution and themethyl nitrite evolved is collected in aqueous potassium iodide, the iodineliberated after addition of acid being titrated.In the quantitative oxidation of solutions of methyl and/or ethyl alcoholby standard potassium dichromate and sulphuric acid, the use of a pressurebottle has been advocated by A.Rapin 11 in order to eliminate the trouble-some loss of aldehydes that occurs during the usual reflux procedure. E. J.Harris l2 claims that a more dilute (10%) sulphuric acid enables the oxid-ation of both alcohols to be carried out to the corresponding acids; aftertitmtion of the residual dichromate, the formic acid may be oxidised com-pletely by a more concentrated acid dichromate solution. The use of anya Ingenwrs Vetensk. Akad. Handl., 1938. No. 147.S m e n Kern., 1938,11, A, 45.Atti Congr. naz. Chirn. p r a appl., 1933, 4, 773.Proc. 5th Intern. Congr. Tech. Chem. Agric. Ind. Holland, 1837, 1, 184.8 2. Unters. Lebemm., 1939. 77, 272.Analyst, 1935, 60, 558.l1 Heb.Chim. Acta, 1939, 22, 72.la Analyst, 1937, 62, 729.Pharm. Zentr., 1937, 78, 669.la Angew. Chem., 1934, 47, 227BOORMAN, GRIFFITHS, MACLENNrLN, AND WHALLEY. 277heat is deprecated by I,. Semichon and M. Flanzy,13 who state thatoxidation is complete at 15" if a much more concentrated acid is used,primary alcohols and glycols being converted into the corresponding acids,and secondary alcohols into ketones, without further reaction. Undesirablesecondary reactions may also be suppressed by the u8e of hot dichromaband dilute nitric acid.14Lees attention has been given t o gravimetric methods, though someprogress has been made. The dimedon Precipitation of formaldehyde hmbeen improved by J. H. Yoe and M. C.Reid,15 who show that accuratecontrol of the pH of the solution by buffers, and of the excess of the reagent,are essential for maximum precipitation, while drying the precipitate at55-66' is recommended, since at 100" there is some loss by sublimation.J. B. Wilson, in his discussion,16 objects to oxidation methods and, findingM. Flanzy's method l7 too tedious, suggests that the alkyl iodida preparedfrom mixed methyl and ethyl alcohols, after partial separation by distillation,should be allowed to react with trimethylamine. The tetramethylammoniumiodide so formed is insoluble in absolute alcohol and is thus separated fromthe trimethylethylammonium iodide and weighed.There has still been but little interest in n-propyl alcohol, as it is notfrequently in use.One method l8 proposed for its determination is oxidationby distillation with chromic and sulphuric acids, and comparison of thecolours developed in the distillate on reaction with vanillin and concentratedhydrochloric acid with similarly prepared standards.The Boehm-Bodendorff m-nitrobemaldehyde test for isopropyl andhigher alcohols has been rendered specific for the former by J. A. Miller ; 19exposure of the red-brown ring to ultra-violet light yields an ochre-yellowcolour with isopropyl alcohol. A Prussian-blue colour is produced by theaction of concentrated sulphuric acid on the aqueous alcohol containing alittle vanillin; 2O although amyl alcohol affords a similar colour, it is seldompresent in a Thorpe and Holmes distillate.The mercury sulphate test which,according to C. Stainer and A. Lauwart21 and others, yields a yellowprecipitate with isopropyl alcohol, has been found by S. H. Fleming22 togive negative results with the pure substance. Several other tests depend onits oxidation to acetone; indeed, the preferable methods of estimating itare based on this. For instance, M. Metra, L. Lesage, and F. Deecatoire,23after oxidising i t with bromine water and alkaline hydrogen peroxide, applya modification of Imbert's reaction with sodium nitroprusside to the distillatein order to determine the acetone so formed.One colour test for acetone in aqueous solution which is more sensitivel 3 Compt. rend., 1932, 195, 254.l4 M. H. Cordebard, J . Pharm. China., 1939, 30, 263.l 5 Ind.Eng. Chem. (Anal.), 1941, 13, 238.l 6 J . Assoc. Off. Agric. Chem., 1935, 18, 277.It) Apoth.-Ztg., 1938, 53, 1328, 1339."O C. L. M. Brown, Phctrm. J . , 1934, 133, 560.22 Me7adeZ Bd., 1936, 7, 99.Ann. PaZsif., 1935, 28, 260. l* 0. Noetzel, Z. Unters. Lebensm., 1932, 64, 288.*l J . Pharm. Belg., 1928, 10, 167.23 Compt. rend., 1938, 808, 102827% ANAT~YTICATr CHEMISTRY.than either the nitroprusside or the o-nitrobemaldehyde method, isA. Ravin’s 24 application of the Frommer-Emilowicz reaction as used byI. N. K ~ r e n r n a n . ~ ~ The red colour given with an alcoholic solution ofsalicylaldehyde in presence of concentrated (40%) aqueous sodium hydroxidemakes possible the detection and estimation of 0.005 mg. of acetone. Twoof the better known titrimetric methods for determining it have been criticallyexamined by C.0. Houghton,26 who finds that with pure acetone Messinger’siodoform method yields high results ( 102.5%) while Marasco’s oxime reactionleads to low figures (97.1y0).The use of the paraformaldehyde method of R. W. Hoff and J. M.Macoun 27 for the removal of acetone from aqueous-alcoholic solutions hasbeen found to lead to the formation of traces of methyl alcohol, a fact whichimmediately prohibits its use for many purposes. The disadvantage is avoidedby precipitation of the acetone as the complex by Denigbs’s acid mercurysulphate. C. It.Hoskins28 finds that this loss is greatly diminished by the addition of asmall amount of sodium formate to the solution during the formation of themercury sulphate complex a t about SO”, using a known excess of reagent,and precipitation of the remaining mercury in solution by potassium oxalatebefore distillation.Some work has recently been published on the investigation of morecomplex mixtures of these oxygenated solvents.Two may be mentionedas having introduced novel principles. E. J. Boorman 29 determines ethylalcohol in the presence of methyl and isopropyl alcohols and acetone by thesimultaneous quantitative oxidation of methyl alcohol to carbon dioxide andwater, of isopropyl alcohol to acetone, and of ethyl alcohol to acetic acid(which is determined)? by potassium dichromate and sulphuric acid in thepresence of mercury sulphate, the total acetone being retained as a stablemercury chromate complex.G. L. Stahly, 0. L. Osburn, and C. H.Werkman have analysed mixtures of acetone and ethyl, isopropyl, andbutyl alcohols by distillation? after oxidation with potassium dichromate andphosphoric acid, and determination of the acetone in the distillate by amodified Messinger’s method and of the acetic and butyric acids by theirpartition between ether and water under standardised conditions.Also of interest is the method of S. T. Schicktanz, A. D. Etienne, andW. I. Steele 31 for the analysis of fuse1 oil, in which the azeotropes formed bythe individual alcohols and. carbon tetrachloride are separated by fractionaldistillation.This, however, entails a loss of alcohol by oxidation.5 . CARBOHYDRATES.Since the last Report,] although new methods have been suggested toseparate mixtures of sugars, analysis has progressed rather by the modificationand improvement of existing methods.2p J .Biol. Chem., 1936, 115, 511. 25 J . -4ppl. Chem. Russia, 1933, 6, 1002.Ind. Eng. Chem. (Anal.), 1937, 9, 167. 2 7 Analyst, 1933, 58, 749.28 Ibid., 1937, 62, 530.31 Ind. Eng. Chern. (Anal.), 1939,11, 421.28 Ibid., 1939, 64, 791, 30 Ibid., 1934, 59, 319.1 Ann. Reports, 1938, 35, 404BOORMAN, GRIFFITHS, MACLENNAN, AND WHALLEY. 279Pentoses.-An example of a modification in the determination of pentosesis tlhe refluxing of a pentose with acid in the usual way, but in the presenceof a suitable high-boiling immiscible solvent, e.g., xylene.2 The furfuraldehydeformed is rapidly extracted by the solvent, and colorimetric determinationof its concentration enables the total amount of furfuraldehyde, and henceof the pentose, to be calculated. The advantages of this procedure areincreased accuracy and eliininatlion of the time-consuming steam-distillationof the classical method.Mixtures of methylpentoses and many other sugars have been analysedby treating them with periodic acid, the acetaldehyde from methylpentosesand the formic acid from other sugars being determined.3Hexoses and Disaccharides.-1.Iodine oxidation. The oxidation ofaldoses to aldonic acids by hypoiodite, a familiar method for the estimation ofthese ~ u g a r s , ~ has been used as a basis for the characterisation of carbo-h y d r a t e ~ .~ By treatment a t -40’ with potassium hypoiodite in methylalcohol, aldoses are converted into aldonic acids, which are precipitated inthe cold as the potassium salts in the case of glucose, galactose, and arabinose,or as the crude barium salts after addition of barium iodide in methyl alcoholin the case of other aldoses. These salts are condensed with o-phenyl-enediarnine to give benziminazoles, which crystallise readily, have sharpmelting points, yield good crystalline derivatives, and are claimed to possessinany advantages over osazones for characterising sugars.A method has been described for the micro-determination of lactoseill the presence of monosaccharides.6 Lactose is oxidised by alkaline iodinesolution to lactobionic acid, which is then hydrolysed with aqueoushydrochloric acid.The resulting galactose is determined by the Hagedorn-Jensen procedure.Yotentioinetric methods have been applied to thcdetermination of glucose. H. T. S. Britton and L. Phillips 7 have shownthat, a’lthough not so rapid as the orthodox volumetric method of J. H. Laneand L. Eyiion,8 potentiometric titrations of Fehling’s solution with glucosesolution are possible. Since low and negative “ redox ” potentials prevailnear the end-point of the titration, there is a tendency for the cuprousoxide to be oxidised, and consequently the USC of external indicators, e.g.,potassium ferricyanide, in Fehling’s titrations must result in inaccuracies.It is confirmed that methylene-blue used internally, as in the Lane andE,ynon method, is a suitable indicator.The oxidation of glucose in alkaline solution bypotassium ferricyanide, the basis of the method of estimation associated wit.h2.Fehling’s sohtion.3. Ferricyanide solution.R. E. Reeves and J. Munro, Ind. Eng. Chern. (Anal.), 1940,12, 551.B. H. Nicolet and L. A. Shim, J. Anier. Chem. SOC., 1941, 63, 1456.a G. M. Kline and S. F. Acree, Ind. Eng. Chem. (Awl.), 1930, 2, 413.S. Moore and K. P. Link, J. Bid. Chem., 1940, 133, 293.tl S. M. Strepkov and N. K. Succhorukova, Biochimia, 1940, 5, 140.Analyst, 1940, 65, 18.a J . SOC. Chem. Id., 1923,42, 32~280 ANALYTICAL CHEMISTRY.the names of H. C. Hagedorn and B. N. J e n ~ e n , ~ has been shown to be moresuitable for potentiometric titration than the Fehling's method.H. T. S.Britton and L. Phillips lo have investigated the changes in oxidation-reductionpotential as glucose is progressively added to a solution of potassiumferricyanide and sodium carbonate. The potentials before the oxidation ofglucose is complete are higher than in the case of Fehling's solution, andafter passing the end-point are more negative. The excellent inflexionsobtained in the titration curve give greater accuracy to the titration than inthe Fehling method. Methylene-blue is shown to be a serviceable indicatorin this case also.A ferricyanide method, which uses as reagent potassium ferricyanide,sodium carbonate, and disodium hydrogen phosphate solution, has been usedby H. C. Becker and D. T. Inglis 11 to determine fructose in the presence ofglucose and sucrose, reduction taking place a t 50".Glucose has a smallbut definite reducing action on this reagent, and a correction factor has to beintroduced, but sucrose has very little reducing action and does not interfereeven in large quantities. With fructose concentration <20% of the sugarmixture, an accuracy of 0.5% is claimed for the method, but the errorincreases rapidly with decreasing concentrations of fructose. The methodis not applicable in the presence of maltose or lactose, since both have areducing action approximately equivalent to that of glucose.Potassium ferricyanide and ceric sulphate have been used to determinethe reducing properties of Z-sorbose and fructose.12A rapid method of determining reducing sugars, depending on thephotocolorimetric measurement of the decolorisation of a standard solutionof potassium ferricyanide under prescribed conditions, and using quantitiesof sugar up to 1.2 mg., has also been de~cribed.1~Mixtures containing glucose, fructose, maltose, andlactose have been analysed by F.W. Zerban and L. Sattler.14 Lactose isestimated separately either by oxidation to mucic acid, or better by removalof the other sugars by fermentation with yeast, and subsequent estimation ofthe residual lactose by copper reduction. Modified Nijns' and Barfoed'sreagents are used to estimate glucose and fructose, and the total reducingsugars are determined by Fehling 's reduction. Since, however, the reagentsused to determine monosaccharides and fructose are slightly reduced bymaltose and lactose, corrections are necessary to ensure satisfactory results.The values obtained in the various estimations are introduced into a set offour progressive algebraic equations, and a series of approximate calculationsare made until two successive computations are in close agreement.Theresults obtained on synthetic mixtures agree well with the quantities taken,except in the case of maltose, which is determined by difference.The reducing power of various sugars with alkaline copper citrate4. Other methods.Biochem. Z., 1923,135, 145. lo Analyst, 1940, 65, 149.l1 Id. Eng. Chem. (Anal.), 1939, 11, 145; 1941, 13, 13.la F. K. Broome and W. M. Sandstrom, ibid., p. 234.la S.A. Morell, ibid., p. 249. l4 Ibid., 1938, 10, 669BOORMAN, URIFFITHS, MACLENNAN, AND W€€ALLEY. 281reagent has been investigated.15 The highest reducing power was possessedby sugars with OH at CO) trans to OH at C,4, and Cf5). Sugars with OH at Ca)or C,,, in the cis-position had a lower reducing power. The configurationof OH a t C,2, did not affect the reducing power greatly. Disaccharideshaving the glycosidic linkage at CO) had a molecular reducing power lessthan that of the corresponding monosaccharide, but if the linkage was a tC,4) or C,6), the reducing power was slightly greater than that of themonosaccharide.Other methods described include the estimation of glucose and fructosein blood and urine,l6 the blue colour formed by treatment with diphenyl-amine and hydrochloric acid being used to estimate the latter, the analysisof malt extract by selective fermentation,l' and the microscopic identificationof certain sugars by precipitation from saturated aqueous solution by acetone,ethyl alcohol, acetonitrile, and dioxan.l*LYepnration of Sugars.-When esterified with azobenzene-p-benzoylchloride, sugars yield coloured esters, which are readily separated bychromatographic adsorption on pure precipitated silica.This has beensuggested as a method of separating glucose and fructose,lg penta-azobenzene-p-benzoyl glucose and the corresponding fructose ester being separated byfiltration-through a column of precipitated s i l i c e o f the ester mixturedissolved in a mixed solvent. Two dark orange zones are formed, separatedby a broad colourless zone containing one narrow orange ring. On elution,the top zone yields almost pure fructose ester, the bottom zone almost pureglucose ester.C. D. Hurd and S. M. Cantor 20 have elaborated a procedureby means of which sugars of different classes may be separated from oneanother, and the relative proportions of each in the original mixture esti-mated. The sugars are converted by stages into the methyl esters, whichare then separated by fractional distillation at pressures below 0.02 mm. ofmercury. The physical constants of the ester fractions serve to identify theoriginal sugars, and the relative weights of the isolated esters are claimed toagree with the sugars in the original mixture within a few units "/o.Themethod has yielded satisfactory results with a variety of sugars, e.g., xylose,rhamnose, glucose, maltose, lactose, gentiobiose, and sucrose, but is notapplicable to fructose.Starch.-The precipitation of " starch-iodide " has been used to estimatestarch in plant rnate~ial,~l and W. Whale has applied the starch-iodidemethod volumetrically.22 Other methods of estimating starch, includingmethods of hydrolysis with hydrochloric acid, and with diastase and acid,l5 H. S. Isbell, W. W. Pipan, and H. L. Frush, J. Res. Nut. Bur. Stand., 1940, 24,241.l6 R. W. Martin, 2. physiol. Chem., 1939, 259, 62.l7 R. Gardner, Analyst, 1939, 64, 103.l 8 J. A. Quesne and W. M. Dehn, Ind. Enq. Chenz. (Anal.), 1939, 11, 555; 1940, 12,lo W.S. Reich, Biochem. J., 1939, 33, 1000.** J . Amer. Chem. Xoc., 1938, 60, 2677.21 J. d. Chinoy, AnaZyst, 1938, 63, 876.656.22 Ibbid., 1939, 64, 688282 ANALYTICAL CHEMISTRY.have been reviewed,23 and a method of determining starch has been de-scribed, based upon the use of the enzyme ptyalin in human saliva t oconvert solubilised starch into maltose, the latter being estimated by heat-ing with alkaline potassium ferricyanide solution, and titration with cericsnlphate .24Raw starch decomposes in hot aqueous alkali to give simple acidicsubstances, principally formic, acetic, and lactic acids, as well as pymvioaldehyde. Decomposition proceeds more rapidly with acid-modified starches,indicative of increased aldehydic content, and provides an empirical indexof hydrolysis.T. J. Schoch and C . C . Jensen25 have used this property of" alkali lability '' to investigate a number of theoretical and practical starchproblems. The procedure resembles that employed for the saponificationnumber of a fat : digestion of the starch in a measured volume of standardsodium hydroxide, followed by titration of the unconsumed alkali. Therate of decomposition of the starch-termed the '' alkali number "-isexpressed as the number of C.C. of 0-1N-sodium hydroxide consumed by1 g. of starch during digestion in alkali for 1 hour a t 100".When starches are heated with water, the cloudy suspensions formedgradually become translucent as pasting occurs. W. L. Morgan 26 has fol-lowed this change a t various temperatures by photoelectric means and hasobtained characteristic curves for each type of starch.By simple mathem-atical relations, the curves may be applied. to the analysis of mixtures of8 tare hes.6. ESSENTIAL OILS.Essential oils are aromatic, volatile substances, soluble in alcohol andmost organic solvents, and slightly soluble in water. They are obtained bysteam-distillation of vegetable products, and in general are liquids, thoughsome are semi-solid a t room temperature. I n composition, they are oftencomplex and may contain terpenes, alcohols, phenols, esters, aldehydes, andketones. For instance, lavender oil contains linalool, geraniol, nerol, linalylacetate, pinene, limonene, traces of cineole and thymol, and a small quantityof sesquiterpenes ; and camphor oil contains camphor, terpineol, saff role,eugenol, cineole, pinene, phellandrene, dipentene, and cadinene. Some oils,however, consist mainly of one ingredient, e.g., bitter almond oil, blackmustard oil, and wintergreen oil, which are essentially benzaldehyde, ally1isothiocyanate, and methyl salicylate, respectively.The character of anessential oil may be modified by seasonal variation, and by the method ofdistillation used in preparing it. This variability of composition complicatesanalysis, and make difficult the detection of the adulteration of expensivewith cheaper oils. I n examining essential oils, the expert relies considerablyon odour; but to the chemist who is concerned only infrequently with43 M. P.Etheridge, J . Assoc. Off. Agric. Chem., 1941, 24, 113.W. Z. Hassid, R. M. McCready, and R. S. Rosenfels, Ind. Eng. Chem. (Anal.),1940, 12, 142.25 Ibid., p. 531. 26 Ibid., p. 313BOORMAN, GRIFFITHS, MACLENNAN, AND WHALLEY. 283essential-oil analysis, odour can be of value only when there is availablean authentic sample of the oil €or comparison.Separation of Essential Oils.-In general, distillation a i d extractionmethods are used to separate essential oils in perfumes, drugs, etc. Thedistillation may be with boiling water or low-pressure steam, or may takeadvantage of the fact that, in a vacuum, the volatile fractions of mostperfumes are entrained in the vapour of ethylene g1ycol.lAlternatively, an extraction method may be employed.2 Steam-distillation and alcoholic extraction methods of determining coumarin insweet clover have been compared, the coumarin being determined colori-metrically by the colour produced by addition of diazotised p-nitroaniline tothe extract.3AnaEysis.-In identifying and estimating essential oils, both physical andchemical methods are employed.The general characters of the oils extendover a wide range, the specific gravity being in most cases less than 1.000,although several oils are known which are heavier than water. The refrac-tive index varies from 1.432 (rue oil) to 1.605 (cassia oil). Many oils areoptically active to polarised light, and the optical rotation is a property ofimportance in assessing purity. The physical properties mentioned, togetherwith boiling range, melting point, colour, solubility in alcohol, and propor-tion of non-volatile matter present, serve to identify the oil.On thechemical side, the general methods employed are acetylation or phthal-ation for the alcoholic constituents, oximation for aldehydic and ketonicgroups, and saponification for esters. Adulteration is detected mainly bythe interpretation of the results obtained from the various tests.Physical Methods.-Analytical procedure has been considered for severalyears by a sub-committee which has made recommendations to the “ Stand-ing Committee on Uniformity of Analytical Methods of the Society of PublicAnalysts ” on the methods found most trustworthy in essential-oil examin-ation. The sub-committee has prescribed precise methods and apparatus fordetermining physical properties and solubilities,4 and has considered thedetermination of cineole in cajuput and eucalyptus oils by measurement ofthe freezing point of a mixture of the dried oil and o-~resol.~ A subsequentreport extends this method to other cineole-containing oils, in whichalcohols, esters, aldehydes, and ketones are present in such quantity as toraise the freezing point of the o-cresol compound and so indicate a highercineole content than is actually present.6 I n such cases, the committeerecommends use of the term “Apparent cineole content by o-cresol,” itfigure which may be of value in detecting adulteration.T.T. Cocking and G. Middleton, Pharm. J . , 1932, 129, 253; L. W. Raymond,Perfume and Essential Oil Record, 1936, 27, 393; S.Sabetay, Ann. Chim. anal., 1939, 21,173.H. J. Van GifYen, €‘?iarm. It’eekbhd, 1936, 73, 641.I. J. Duncan and R. B. Dustinan, Ind. Eng. Chew&. (AT~uE.), 1937, 9, 471.AtLalyst, 1927, 52, 53; 1929, 54, 335; 1930, 55, 386.Ibid., 1927, 52, 276. 6 Ibid., 1931, 56, 738284 rn&YTICAIJ CHEMISTRY.A large number of essential oils and allied substances fluoresce wheiiexposed to ultra-violet radiation. The fluorescence observed, although notsufficient to characterise oils as natural or synthetic, was of assistance inthe classification of oils as regards their principal constituent, and in thedetection of adulterants. D. Van 0 s and K. Dykstra 8 have examinedessential oils by measurement of the ultra-violet absorption, Lambert-Beerabsorption curves being obtained for the range 3000--4000 A. They haveused the extinction coefficients of the main absorption bands to determinethe amount of anethole in oil of anise, to detect adulterants of oil of anise(which lower the anethole content), and to estimate this oil in other oils.Carvone in caraway oil, eugenol in clove oil, citral in lemon oil, etc., werealso determined.Some oils, however, e.g., cajuput, citronella, eucalyptus,etc., since they give no characteristic absorption, cannot be estimated inthis way. The method is of value in detecting those adulterants whichmodify the shapes of the absorption curves. Details have been given ofabsorption maxima for colour reactions of various essential oils with theEhrlich-Mullerreagent, which consists of two solutions : 5% p-dimethylamino-benzaldehyde in acetic acid, and 10% phosphoric acid in acetic acid.9The use of Raman frequencies in the identification of essential oils, andin the distinction of their isomerides, has been suggested.10The sub-committee, already referred to, has con-sidered in detail the chemical methods of determining the various groups inessential oils.Thus, the determination of the acetylisable, i.e., alcoholic,constituents (by acetylation of the oil with acetic anhydride, followed byseparation and saponification of the acetylated compound) has beendescribed.11 In general, acetylation methods are known to give variableresults, and to indicate as alcohols, certain non-alcoholic constituents, e.g.,aldehydes, amines, phenols, esters, etc., which are acetylated along withthe alcohols.L. H. Baldinger,12 varying the times of both acetylation andsaponification, found that although the former may vary within wide Limits,yet the latter should be restricted to 45-60 mins. He suggested thatresinification or polymerisation of certain constituents is induced by pro-longed heating with potassium hydroxide, and that some of the base isused up, leading to erroneous results. The observation of C. E. Redemannand H. J. Lucas 13 that more rapid hydrolysis of esters results if diethyleneglycol is substituted for ethyl alcohol as a solvent for potassium hydroxide,has been verified by R. T. Hall, J. H. Holcomb, and D. B.Griffin,f4 who haveapplied the method to the analysis of the isomers of menthol.Modifications of the acetylation method have been proposed, using anC. P. Wimmer and M . H . Kennedy, Perfume and Essential Oil Record, 1930,21, 163.I J . Phamn. Chirn., 1937, [viii], 25, 437, 485.A. Miiller, J . pr. Chm., 1938, 151, 233; 1939,153, 77.ChemicaZ methods.10 L. M. Labaune, Rev. Marques Parfurn. Savon., 1936, 14, 145.l1 Analyst, 1928, 53, 214.le J . Amer. Ph.am. ASSOC., 1939, 28, 165.13 I d . Eng. Chem. ( A d . ) , 1937, 9, 521.ld Ibid., 1940, 12, 187BOORMAN, QRIFFITHS, MACLENNAN, AND WHALLEY. 285acetylating mixture of pyridine and acetic anhydride.15 The authors ofthe first paper state that, under the prescribed conditions, primary alcohols,primary amines, and phenols are quantitatively acetylated in less than anhour, secondary alcohols almost quantitatively in an hour, whilst tertiaryalcohols and aldehydes react only with difficulty.T. W. Brignall16 replacesthe pyridine in the acetylating mixture by a less objectionable solvent-n-butyl ether-the boiling point of which (142") is near that of aceticanhydride (140"). The method described avoids saponification of theseparated acetylated compound, a major source of error (the amount ofacetic anhydride used in the reaction being measured), and is claimed tobe applicable to the analysis of free primary and secondary alcohols in anyessential oil.Phthalation in warm pyridine solution has been used as a method ofdetermining primary and secondary alcohols, which are identified as theiracid phthalates.17The estimation of aldehydic and ketonic groups by the lrydroxylaminehydrochloride method has been recommended by the sub-committee inseveral reports.18 The method has also been applied to aldehydic andketonic perfumed ingredients by S.Sabetay,lg the reaction being carriedout in the cold, except with compounds such as pulegone and camphor,which form oximes only with difficulty, and require heating for an hour ina water-bath at boiling point. V. E. Tischtschenko and M. A. Grechnevmhave also used hydroxylarnine hydrochloride to estimate camphor.The sub-committee 21 has prescribed precise conditions for the saponific-ation of esters, and has discussed the determination of phenolic constituentsof essential oils by absorption in 5% aqueous potatmiurn hydroxide.22 P.A.Rowaan and J. A. Insinger23 have recommended a procedure for thedetermination of the eugenol content of essential oils, after comparingsodium hydroxide and potassium hydroxide solutions of varying concen-trations as extraction liquids a t temperatures of 20-100". The structure ofascaridole, the pharmacologically active constituent of the anthelminticchenopodium oil, has been investigated,= and its determination discussedby the sub-committee.25The "diene " value is a measure of the extent to which combinationtakes place between compounds containing systems of double bonds, e.g.,terpenes, and maleic anhydride. It is an empirical constant of the samel5 R.DeIaby and S. Sabetay, BUZZ. Soc. chirn., 1935, [v], 2, 1716; M. Freed andl8 Ibid., 1941, 13, 166.l7 Y. R. Naves and S. Sabetay, Ann. Chim. anal., 1937, 19, 286; S. Sabetay, ibid.,l8 Alzalyst, 1930,55, 109; 1932, 57, 378, 773; 1934, 59, 105.Bull. SOC. chim., 1938, [v], 5, 1419.2o J . Appl. Chem. Russia, 1936, 9, 1700.Analyst, 1937, 62, 541.23 Chem. Weekblad, 1939, 36, 642.H. J. Paget, J., 1938, 829.A.M. Wynne, Id. Eng. Chem. (Anal.), 1936, 8, 278.1939, 21, 289.e2 Ibid., 1928, 53, 216.2 B Analgst, 1936, 61, 179286 ANALVTTCAT, CHEMTSTRI-.type as saponification value, etc., and has been used to investigate thephellandrenes 26 and to detect and estimate ~-terpinene.~7An interesting method for the determination of the essential oils ofwhite and brown mustards by resolution of the glycosides-which containthe oils-with the enzyme myrosin has been described.28 The sulphateproduced by the hydrolysis is determined by precipitation with benzidineand titration of the separated benzidine sulphate.A new optically active reagent for carbonyl compounds, E-menthylN-aminocarbamate, has been described 29 which gives crystalline derivativesof sharp melting points and definite specific rotations with numerouscarbonyl compounds, and has been used successfully in the resolution ofdl- camphor.Oils, such as bergamot andlavender, may contain artificial esters, but sophistication must obviously belimited to esters of high ester value and slight odour, and which are easilyobtainable commercially. I n general, adulteration is detected by the inter-pretation of the results obtained from the various tests. The figure men-tioned earlier, " apparent cineole content by o-cresol," will often indicatethat adulteration has taken place, as, for example, where lavender oil hasbeen sophisticated by addition of linalyl acetate or spike-lavender oil, orwhere rosemary oil has been adulterated with light camphor-oil fractions.D. C . Garratt has applied the furfuraldehyde-aniline acetate colour testto detect adulteration. Por example, Japanese oil (from Mentha arvemis)contains more furfuraldehyde than the better varieties of peppermint oil(from Mentha piperita). This test has proved of value also in detectinglight camphor oil in rosemary oil, and clove oil in bay or pimento berry,the adulterants having in both cases a higher furfuraldehyde content.Ethyl phthalate is an adulterant of essential oils (as well as being a fixativein perfumes). Y. R. Naves and S. Sabetay31 estimate this material inperfumes and balsams by hydrolysis with anhydrous alcoholic potassiumhydroxide to potassium phthalate (insoluble in anhydrous alcohol), whichmay be weighed direct; if, as for example, in balsams, esters such asbenzoate or cinnamate are present which also give insoluble potassium salts,the precipitated potassium salts are dissolved in dilute acetic acid, and thephthalate precipitated from the filtrate as the lead saIt.Adulteration of essential oils is common.E. J. BOORMAN.J. G. A. GRIFFITHS.G. W. G. MACLENNAN.H. K. WHALLEY.28 N. F. Goodway and T. F. West, J . SOC. Chena. Ind., 1938, 57, 3 7 ~ ; A. J. Birch,2 7 R. M. Gascoigne, &id., 1940, 74, 353.28 R. C. Terry and J. W. Corran, Analyst, 1939, 64, 165.J . Proc. Roy. SOC. N.S.W., 1938, 71, 54.R. B. Woodward, T. P. Kohman, and G. C. Harris, J . Amer. Chem. Soc., 1941, 63,120.30 Awalyst, 1935, 60, 369, 595. 31 Bull. SOC. chim., 1938, [v], 5, 102

ISSN:0365-6217    

DOI:10.1039/AR9413800264

出版商:RSC    

年代:1941

数据来源: RSC

摘要:

RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.OWING to war conditions it has become increasingly difficult to get a clearpicture of the progress of science. Many periodicals have become inac-cessible and an ever-growing proportion of the research work is being carriedout under the seal of military secrecy. To the Reporter, this seems asuitable time for a general survey of our present knowledge of nuclearprocesses and of the concepts used in explaining and predicting them.This survey is preceded by a historical introduction which briefly recapitulatesthe steps in which this knowledge was acquired.During the last decade our knowledge of the atomic nuclei has enormouslyincreased, with regard both to the number of observed facts and to thedegree of understanding of their significance.(1932) of theneutron, a particle with practically the same mass as the proton but withoutclect'ric charge.The discovery of such a particle did away with the necessityto assume the existence of electrons inside the nucleus (an assumptionwhich caused great theoretical difficulties) in order to explain the fact thatthe atomic weight A is in general greater than the atomic number 2. Instead,it is now generally believed that the atomic nucleus is composed of 2 protonsand A - 2 neutrons, and this assumption, together with plausible assump-tions about the forces acting between these elementary particles, accountsfor most of the known properties of nuclei, such as their size, spin, statisticsand binding energy.Neutrons were first observed in the disintegration of beryllium bycc-particles, and this process is still one of the most convenient ways of pro-ducing them, although much larger intensities can be obtained by meansof a cyclotron.I n passing through matter, neutrons are not influencedby the shell electrons, and they are not repelled by the electric charge ofthe nuclei. Each neutron is therefore bound to hit a nucleus eventually,even though it may have to pass through several centimetres of solid matterbefore this happens. The effectivity of neutrons in causing certain nuclearreactions increases considerably if their energy is reduced, and the studyof " slow neutrons )' (obtained by passing neutrons through water or paraffinwax) has revealed some exceedingly interesting phenomena,2 the inter-pretation of which led to Bohr's theory of the heavy atomic nuclei (1936).The next important step, only a few months later, was the successfulattempt by J.D. Cockcroft and E. T. S. Walton3 (1932) to disintegratenuclei by means of ions which had been accelerated through large electricfields. This " artificial " disintegration is not essentially different fromThe first fundamental step was J. Chadwick's discoveryNatwe, 1932, 129, 312; PTOC. Roy. SOC., 1932, A , 136, 692.See, e.g., E. Amaldi and E. Fermi, PhyekaE Rev., 1936, 50, 899.Proc. Roy. SOC., 1932, A , 137, 229288 RADIOACTIVITY BND SUB-ATOMIC PHENOMENA.the disintegration by natural a-particles, discovered by Rutherford in 1919.It gives, however, a much larger number of disintegrations per unit time andthereby makes their study much less laborious. It also permits the use c;fprojectiles other than a-particles (helium nuclei), thus greatly extendingthis field of research.Thus the discovery of heavy hydrogen (deuterium)was quickly followed by the use of its ion (the deuteron) as a projectileparticularly effective in nuclear disintegration. E. 0. Lawrence’s ingeniousinvention of a device in which ions are given very high energies by beingaccelerated many times in a moderate electric field has made its name“ cyclotron ” a household word in iiuclear laboratories. Lawrence’s latestinstallation produces deuterons of 16 MeV (millions electron volts) andhelium nuclei (“ artificial a-particles ”) of 32 MeV.Particles of suchenergies can overcome the electrical repulsion of even the heaviest nuclei.For the disintegration of light elements, the straightforward accelerationof ions by high electric potentials (up to about 3 MV) has still someadvantages, such as simpler operation and more uniform particle energy.The next great step was the discovery of artificial (or induced) radio-activity.4 Again, it must be said that there is no fundamental differencebetween artificial and natural radioactivity. The great number, however,of radioactive isotopes which can be produced by disintegration of stableelements makes it possible to study many aspects of radioactivity much morecompletely than was possible before. Neutrons, for the reasons given above,have been found particularly effective in producing radioactive substances.Furthermore, new modes of radioactive disintegration were discovered,such as the emission of positrons (positive electrons), the capture ofK-electrons and the transition between isomeric nuclear states.The discovery of nuclear fission is perhaps not of such fundamentalimportance, but it showed, for the first time, a possible way of utilisingnuclear energies on an engineering scale.A detailed discussion of thefission phenomena and of the possibility of nuclear chain reactions wasgiven in this Report for 1939. Further progress in this field is bound tobe slow, and little further evidence has been published since.Radioactivity.This term may be taken to indicate the spontaneous transformationof one nuclear species into another.The transformation, being a uni-molecular reaction, follows the well-known equation N = Noe-Al. Instead ofthe decay constant h, the half-value period (half-life) T = 0.69311 isgenerally used to indicate the rate of decay.The term “ spontaneous ” involves a certain ambiguity, since, strictlyspeaking, the decay of an artificially radioactive substance is not spontaneousbut it consequence of a preceding nuclear disintegration. In practice, thosetransformations which follow the impact of a projectile within a very shorttime are reckoned as part of the disintegration process while those with LL4 IF’. Joliot and IrAne Curie, Ndure, 1934, 183, 201FRISCH . 289macroscopic half-life are regarded as spontaneous (radioactive) transform-ations of the nucleus formed in the disintegration process.a-Radioactivity.-The emission of helium nuclei (a-rays, a-particles) isvery common among the natural radioactive elements, but only onea-active isotope has been produced artificially (by bombarding bismuth withfast He ions from a cyclotron) (see the Report for 1940).The theory ofa-activity 4a was developed in 1929 and has not changed since. It is simplyan application of quantum mechanics to the problem of the motion of ahelium nucleus under the forces which the residual nucleus exerts upon it.In leaving the nucleus the a-particle, after overcoming the nuclear attrac-tion, is subjected to repulsion in the electrostatic (Coulomb) field of thenucleus.The joint effect of these two forces is that the particle mustcross a “ potential barrier,” and the quantum-mechanical treatmentshowed that a particle bass a finife probability of doing so even if its energyis too small for it to surmount the barrier. The probability for this “ tunneleffect ” increases rapidly with increasing particle energy, in quantitativeagreement with the experimental facts which are summarised in the Geiger-Nuttall relation log A = A + B log E, which connects the decay constantA of the substance with the energy E of the cc-particles emitted.a-Radioactivity is observed among the heaviest elements only, samariumbeing the lightest element that shows it. This can be explained from thetrend of the mass defect curve, according to which a-activity becomesenergetically possible only above Z = about 50 and the energy of &in-tegration (and therefore the rate of decay) gets sufEciently high only a tconsiderably higher 2.p-Radioactivity.-The theory of this phenomenon is far less well estab-lished than that of cc-decay.The kinetic energy of the p-particles emittedby any particular substance shows a continuous distribution of valuesbetween zero and an upper limit which is equal to the energy available.This means that always some energy “ disappears,” and to account for thisthe assumption has been made that in addition to the @-particle, a hypo-thetical Encharged particle-called neutrino-is emitted and escapesunnoticed, thanks to its lack of electric or other interaction with matter.This assumption forms the basis of E.Fermi’s theory of @-decay5 and ofseveral variants of this theory, such as the one due to E. J. Konopinskiand G. U. Uhlenbeck.6 For a discussion of these theories and of theirconnection with the recently discovered meson (a particle, occurring in thecosmic radiation, with a mass intermediate between those of electron andproton) we must refer to the Report for 1039.Direct attempts to find effects of the neutrinos from strong radioactivesources have so far been unsu~cessful.~ This does not argue against their*a E. U. Condon and R. W. Gurney, Physical Rev., 1929, 33, 127; G. Garnow,6 2. Physik, 1934, 88, 161.Z . Physik, 1929, 53, 610.6 Physical Rev., 1935, 48, 7.M. E. Nahmias, PTGC.C a d . Phil. Xoc., 1936, 31, 99; H. R. Crane, Physical Rev.,1939, 55, 501.REP.-VOL. XXXVIII. 290 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.existence, since their interaction with matter, as predicted by Fermi’stheory, is many million times below the range of the most sensitive methodsnow available. Positive results have been reported * of an attempt todetect the recoil which a p-active nucleus suffers on account of the emissionof the neutrino. These experiments are, however, exceedingly difficult andtheir interpretation is perhaps not absolutely convincing.It has been suggested9 that neutrinos may be responsible for the so-called new stars (novze). The authors show that, according to Fermi’stheory, production of neutrinos on a vast scale must set in at a certain veryhigh temperature, which may be reached at the centre of some stars.Theneutrinos escape, taking large amounts of energy with them, and this coolingeffect at the centre of the star causes, in the authors’ view, a collapse of thestar and an enormous flare-up in its outer layers.The half-life of p-active substances increases with decreasing transform-ation energy (upper limit of the pray spectrum), though less steeply than inthe case of a-decay. This dependence (Sargent’s rule) lo follows also fromFermi’s theory. There are, however, many substances whose half-life ismuch longer than Sargent’s rule would indicate ; in these cases it is believedthat the spins of the radioactive nucleus and the daughter nucleus differby one or more units, causing the transformation to be “ forbidden,’’ inanalogy to the forbidden transitions between atomic energy levels.The shape of the @-ray spectrum has been studied for a great numberof @-emitters.The interpretation of the results is complicated by the factthat most of the spectra are complex, Le., that the nucleus in question hastwo or more alternative ways of decay, which leave the resulting nucleusin different states of excitation. The excitation energy is nearly alwayswithin a very short time emitted as y-radiation. The so-called coincidencemethod has often been successfully employed in disentangling the sequenceof events. It is, for instance, possible to study the spectrum of thosep-particles only which coincide with (i.e,, are followed within a very shorttime by) a y-quantum, detected by a separate counter. By skilfullycombining such experiments, it has been possible in some caws to analysea complex p-ray spectrum into its simple components.The results, however,do not yet permit a decision between the various p-theories.The latter arealso called positrons, and by contrast the word electron is often used todenote negative electrons only, though sometimes the word negatron isemployed for this.If the term @-decay is to include any process by which a nucleus is trans-formed into an isobaric nucleus (one with the same mass number but differentcharge), then the capture of a K-electron l1 into the nucleus must be mentionedhere. From the point of view of Dirac’s hole theory this process is notThe @-particles may be negative or positive electrons.8 H.R. Crane and J. Halpern, Physical Rev., 1938, 53, 798; 1939, 5e, 732.9 G. Gamow and M. Schoenberg, {bid., 1941, 59, 539.10 €3. W. Sargent, PTOC. Roy. SOC., 1933, A, 139, 659.11 L. W. Alvarez, Physical Rev., 1938, 54, 406FRTSCH . 291fundamentally different from the eniission of a positron. The latter pro-cess can be regarded as the capture of one of the (infinitely many) electronsin states of negative energy; the hole left through its removal is the positronobserved, according to Dirac. The K-capture is a rather curious kind of" radioactivity " : no radiation (save the elusive neutrino) is emitted by thenucleus. The shell electrons, however, have to rearrange themselves afterthe loss of one of their order and X-rays are therefore emitted which betraywhat has happened.The existence of only a limited number of isotopes for each element isintimately bound up with the question of (3-stability .Regarding nucleiwith odd mass number, it has been long known that each mass numberoccurs only once among the stable elements, with a few exceptions. Thisis because, of all the possible isobars of a given odd mass number, only oneis stable against B-decay. I n those few cases where two adjacent isobarsare found in Nature (such as le70s and ls7Re) one of the two is probablyalways unstable, although the decay may be too slow to be detected.I n the case of nuclei with even mass number, pairs and even triplets ofisobars frequently occur, but they occupy only even atomic numbers.Forinstance, the mass number 124 occurs among the isotopes of tin, telluriumand xenon (2 = 50, 52, and 54), but the intervening isobars 124Sb and lz4Iare not found in Nature and have indeed been proved to be (3-active.This marked difference between odd and even mass numbers can beexplained by the assumption (which is supported by other facts) that boththe protons and the neutrons tend to associate themselves in pairs in thenucleus. For any odd mass number, this tendency can never be completelysatisfied, since either a proton or a neutron is always left over. For evenmass number, however, there is a difference between odd and even atomicnumbers. The latter are strongly bound and stable because all the protonsand neutrons are associated in pairs, while in the former one proton and oneneutron is left, making the structure less stable.Isomeric Transitions.These are transitions from an excited state of exceptionally long half-life to the ground state of the same nucleus.The reason for these longhalf-lives is a difference of several units between the spins of the two states(which causes the transition to be highly " forbidden '7 and the absence ofany levels in between which might permit a stepwise transition. A fairlyextensive discussion of this phenomenon was given in last year's Report.Nuclear Collisions.After discussing the spontaneous transformations of nuclei, we now turnto those processes which are provoked by the impact of a nuclear particleupon a nucleus.The particular reaction in which the nucleus A is hit bythe particle a, emits the particles by c, d . . . . and is thereby transformedinto the nucleus By is briefly denoted by A(a, b, c, d . . . .)B. If A and a aregiven, B, b, c, d . . . . must fulfil the condition that the sums of their mas292 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.and charge numbers must be equal to the corresponding sums for A and a.But this is not all : the energy liberated in the process must be positive,or if it is negative (if energy is absorbed) it must not be greater than thetotal kinetic energy of A and a, referred to their centre of gravity (if A is,as usually, much heavier than a, this is practically the kinetic energy of A).In most cases it is found that all the possible reactions within the abovelimitations do actually occur, at least with light elements.With heavierelements the emission of charged particles is less probable and nearly allcollisions result in the emission either of one or more neutrons or of y-rays(or of both). In many cases the energy of the bombarding particle has astrong effect on the yield and on the character of the reaction.A complete theory of these phenomena, capable of predicting them indetail, is at present entirely out of the question. Such a theory wouldindeed require the complete mathematical treatment of the motion of a largenumber of particles, all strongly interacting, a task inkitely more difficultthan the corresponding one concerned with the motion of the atomic elec-trons in the Coulomb field of the nucleus, where the mutual interactions ofthe electrons can be regarded as a mere perturbation.Furthermore, theway in which the force between nuclear particles varies with their distanceis still not well known, and doubts have even been raised as to theapplicability of quantum mechanics to problems in which distances as smallas the nuclear radius are involved.It was N. Bohr l2 who showed that a comparatively simple phenomeno-logical theory of nuclear collisions can be developed just because of the stronginteraction of the particles in the nucleus. Because of it, the energy of theimpinging particle becomes rapidly distributed over all the other particlesof the nucleus, and the resulting system, the " compound nucleus," remainstogether until by a chance fluctuation enough energy is concentrated in oneparticle to enable it to break away from the nucleus.If this is the originalparticle or one of its kind, we say it has been scattered; if it emerges withless than its original energy, we speak of inelastic scattering. If it is adifferent particle, we speak of a nuclear disintegration. After the emissionof one particle the nucleus may still retain enough energy to emit a secondone, and even after this a third one. The compound nucleus may also loseenergy by y-radiation or internal conversion (ejection of an inner shellelectron); after this, there may or may not be enough energy left for theemission of a particle, or of further y-radiation.Finally, for the heaviestnuclei, another process, called nuclear fission, is possible ; the nucleusdivides itself into two smaller nuclei of roughly equal size.The important point about it is that these things happen one at a time,and can be regarded separately. The impact of the projectile forms thecompound nucleus, zt system which is characterised by the number of protonsand neutrons in it and by its energy and would have the same propertiesif it had been formed in a different way. The compound nucleus behavesexactly like a radioactive nucleus with several alternative modes of decay,l2 Nature, 1936, 137, 344, 361FRISCW. 293each with its probability per unit time (decay constant). Its half-life is ofthe order of 10-20 t o 10-15 sec., very short on a human scale but long com-pared with the time of about sec.which a particle with several MeVenergy requires to travel its own diameter and which may be regarded as arough “ nuclear time unit.’’ If the compound nucleus emits a particleor a y-quantum, a new system is thereby created, which again has alternativemodes of decay, and so on until a stable nucleus is formed.I n its neglect of details (such as the fate of an individual particle in thecompound nucleus) this theory is essentially thermodynamical, and thethermodynamical analogy can indeed be pushed to a considerable extent.13The impact of the projectile can be compared to the impact of a fast moleculeupon the surface of a very sinall liquid droplet.The formation of thecompound nucleus corresponds to the condensation of the molecule, wherebythe temperature of the droplet is raised, on account both of the heat ofcondensation and of the kinetic energy of the molccule. The droplet canthen lose energy either by the evaporation of one or more molecules or byradiation (analogous to the y-radiation of the nucleus). In order to picturefission as well one would have to endow the droplet with an electrical chargesufficient to lower its effective surface tension almost to zero.I n pursuing this analogy, one must remember that the number of particlesin an atomic nucleus is quite small, vastly smaller than the number of mole-cules in any ordinary thermodynaniical system.Furthermore, the “ nucleartemperatures,” although of the order of 1010 degrees for average excitation,are very low in the sense that only a few of the many degrees of freedomof the nucleus are excited. For these reasons, a nucleus cannot take anyarbitrary energy value but has discrete energy levels, like an atom.There is, however, an important difference between a nucleus and anatom. In an atom the levels come closer and closer together with increasingenergy until we reach the ionisation limit, where the spectrum becomescontinuous : the atom now accepts any amount of energy and immediatelysplits up into an ion and a free electron which carries away the excess energy.A nucleus, however, does not immediately emit a particle even if there isenough energy for this, but has to wait until enough energy happens tobecome concentrated upon one particle. With nuclei the transition t o thecontinuous spectrum is, therefore, gradual : * as the energy is increased, theescape of a particle becomes easier, the energy states get broader, and atsufficiently high excitation they merge into a practically continuous spectrum.Our experimental knowledge of nuclear energy levels is still very in-complete, but as far as it goes it is in good accord with Bohr’s nuclear theory.A good deal of evidence has been accumulated about the lowest levels ofthe lighter elements, by the accurate study of the energy balance in dis-integrations.For instance, bombardment of fluorine with a-particles of5 MeV energy produces several groups of protons, with energies of 5.2,4.0, 2-2 and 1.3 MeV.If we assume that the emission of a proton with 5.2Is See, e.g., R. Peierls, “ Reports of Progress in Physics,” 1941.* In molecules, a similar gradual transition is known ae prediesocbtion294 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.MeV leaves the resulting nucleus in the ground state (the resulting reactionenergy Q = + 1.4 MeV tallies with that calculated from the packingfractions of the nuclei involved), then the emission of the other protonsmust leave the nucleus with an excitation energy of 1 4 , 3.4 or 4.5 MeV.(In calculating the figures, the recoil energy of the nucleus has been allowedfor.) Of course there may be other energy levels in between which are notproduced by this particular disintegration, but this appears unlikely for variousreasons.I n some cases where the same nucleus can be obtained from twodifferent disintegration processes [e.g., l*B (a, H) 13C and 12C (D, H) 13C]the same energy levels have been found to be excited.As long as only the natural a-particles were available these investigationswere restricted to the lightest elements (roughly up to calcium), but the useof artificially accelerated ions should permit their extension to higher atomicnumbers. The difficulty arises, however, that with increasing atomicnumber the emission of neutrons rather than charged particles (which arehampered by the ( ( Gamow barrier ”) becomes prevalent, and energyineasurements on neutrons are laborious and inaccurate.For high atomic numbers some information comes from the y-rays ofthe natural radioactive elements.Their energies have been accuratelymeasured (largely by studying the fast electrons produced by their internalconversion) and level schemes have been deduced. They show that thelowest levels of the heavy elements lie, on the whole, considerably closertogether than those of the light elements. This agrees well with the liquid-drop model if one assumes that the lowest excitations correspond to deform-ation oscillations of the nucleus as a whole ; a large drop has slower oscillations,with correspondingly lower quantum energies. Some investigations on they-rays of artificial radioactive elements support this general trend but showgreat irregularity in the locations of the lowest levels, indicating that theanalogy with a droplet must not be taken too literally.Performed and interpreted in a different way, disintegration experimentscan also give information on much higher energy states, this time not of theresulting but of the compound nucleus.For instance, bombardment of19F with protons results, as the &st step, in the formation of a 20Ne nucleuswith an excitatioii energy equal to the sum of the kinetic energy of the protonand its binding energy of 12-9 MeV. Only if this happens to fit one of thelevels of 20Ne can the compound nucleus be formed, and one would expectthe reaction to take place only for certain discrete values of the protonenergy.In fact, however, the reaction occurs for all energies over a considerablerange, although the yield shows pronounced maxima and minima.Thisbroadening-to the extent of partial overlapping-of the levels is due tothe instability of the corresponding nuclear states. According to quantummechanics, the half-width r of any energy level is connected with its decayconstant (The wave function of the unstabltlstate has the character of a damped train of waves, and it is well known thatresonance becomes less sharp if the damping is increased.)bv the relation r = hh/xFRISCH. 295As the excitation energy is increased, the escape of particles from thenucleus becomes easier and therefore the levels increase in broadness. A tthe same time the complexity of motion increases, and therefore the averagedistance between levels gets smaller and smaller. Both trends are clearlyshown in the above-mentioned experiments l4 where the intensity of y-radiation obtained from fluorine under proton bombardment was measuredas a function of the proton energy.At low energies (up to about 1 MeV)the graph shows individual peaks of small but measurable width (a fewKeV), and at the highest voltage used (2.2 MV) the levels have nearlymerged into a continuous mass. Incidentally these peaks have been foundvery useful in calibrating the energies of artificially accelerated protons, muchin the way that spectral lines are used to calibrate optical spectrographs.The increase of level density with excitation energy is shown impres-sively by the fact that the average distance between the lowest levels ofneon is a few MeV, whereas at an excitation of about 15 MeV it is only afew ten thousand electron volts, or a hundred times less.The intermediateregion cannot be observed, since with decreasing proton energy the repulsiveelectric field of the nucleus (the " Gamow barrier ") becomes a greater andgreater obstacle.No such repulsion exists in the case of neutrons, and the nuclear reactionsproduced by slow neutrons offer some of the most striking illustrations ofthe characteristics of nuclear levels, or as it is often called, of nuclearresonance.Neutrons are slowed down by passage through light elements, in par-ticular hydrogen (or hydrogen compounds). The term is generally taken toinclude both those neutrons which have lost all their energy and are inthermal equlibrium with the slowing-down medium (called thermal neutronsor C-neutrons) and those of energies up to a few hundred electron volts.It was found by Fermi et al.that some elements show enormous absorptionfor slow neutrons. Among them, the behaviour of lithium and boron(more exactly of 6Li and l o g ) is particularly interesting. The absorptionof the neutron leads in both cases to the emission of a fast a-particle; it iseasy to detect these a-particles by means of an ionisation chamber and aproportional amplifier, and such a chamber, lined with lithium or boronor filled with boron trifluoride, is a very convenient and sensitive detectorof slow neutrons.Furthermore, from our other experience of the width and spacing ofnuclear levels, we can be certain that there is no marked influence of nuclearresonance in elements as light as lithium and boron, if the energy of theneutrons is varied, say, between 0 and 1000 eV.From such a light nucleusit is very easy for the a-particle to escape, and the levels should have a widthof much more than 1000 eV. In such a case quantum mechanics predictthat the absorption should be inversely proportional to the velocity of theneutrons. This absorption law-often briefly called the 1 /v-law-is equiv-alent to the statement that the probability for a boron nucleus to absorbE. G. Bernet, R. G. Herb, and D. B. Parkinson, Phyeicai Rev., 1938, 54, 398296 RADIOACTIVITY AND SUB-ATOMIC PHENOMENA.a slow neutron depends only on the density of neutrons in its neighbuurhood ;for if the velocity of a given stream of neutrons is doubled, their density isobviously halved.It is not possible to visualise the l/w-law by thinkingof collisions between small spheres; the de Broglie wave-length of a slowneutron is much larger than the diameter of a nucleus and the process istherefore rather analogous to the absorption of a light quantum by an atom.For the same reason, the fact that the absorption cross-section for slowneutrons is often many hundred or even thousand times larger than the truesize of the nucleus does not indicate any contradiction to the generallyaccepted view that the forces between nuclear particles are practically zeroat distances larger than 10-12 cm.I n most of the heavier elements, however, the capture of a slow neutronis followed by the emission not of an cc-particle but of y-radiation. Thewidth of the level is therefore only of the order of one eV or less, Thisfigure has been derived from plausible assumptions as to the mechanism ofradiation and agrees with the width of those neutron resonances which havebeen studied.Such a study is easiest in those cases where the nucleus formed by thecapture of the neutron is radioactive.Let us, for instance, consider the caseof gold. If gold foils are exposed to a beam of slow neutrons, under boronabsorbers of varying thickness, their activity is found to decrease at firstrapidly and then more slowly with increasing boron thickness.Analysisof the absorption curves shows that there are roughly two groups of neutrons,with absorption coefficients in boron of about 30 and 3 cm.2/g. The firstgroup has been identified with the thermal neutrons, for instance, from thefact that their absorption in boron depends on the temperature of theslowing-down medium. Since the energy of thermal neutrons (at roomtemperature) is about 0.025 eV, the neutrons in the other group must beten times as fast, or their energy 2.5 eV. They are very strongly absorbedin gold and yet the activity they produce is not very strong. We concludethat there are not many of these particular neutrons, and since we can calcu-late the energy distribution of the slow neutrons in any given slowing-downmedium (e,g., water) from a statistical consideration of their collision in themedium, we can estimate that only neutrons within an energy region ofabout 0.1 eV show this selective absorption in gold.Similar experiments have been carried out with a number of otherelements.In all cases the boron absorption curve shows the presence ofthermal neutrons, and nearly always a group of resonance neutrons, of energycharacterktic of each element. I n some cases there are indications of thepresence of more than one group of resonance neutrons. Of course, eachelement must really have a large number of resonance levels, but only thosewith the lowest energy are readily detected by these experiments. Cadmiumis of particular interest, since it has a resonance level a t about 0.1 eV.Itis therefore a strong absorber for thermal neutrons and, at the same time,practically transparent for neutrons of 1 eV or more. Cadmium sheetsare therefore widelynsed either t o cut out thermal neutrons when they arFRISCH. 297not wanted or to study their properties by taking alternate measurementswith and without a screen of cadmium.It may seem that the experimental evidence for these resonance pheno-mena is somewhat indirect and unconvincing. Actually there are a greatmany more experiments in their support, most of them carried out withvery simple equipment but devised and interpreted with great ingenuity,and the totality of their evidence is very convincing indeed. Furthermore,very direct evidence has been obtained recently by C.P. Baker and R. F.Bacher.15 These authors virtually produced slow neutron beams of homo-geneous velocity by using a modulated neutron source, giving short periodicalbursts of neutrons, and by counting only those which arrived with a, givendelay at the counter, which was placed at some distance from the source. Byvarying the time of delay, they were able to plot the absorption of boron,cadmium and indium as a function of the neutron energy, and their resultsagree well with the conclusions from the earlier, indirect evidence.Nuclear Photo-eJffect .This phenomenon is not essentially different from other disintegrations,if we regard the y-quantum as just another kind of nuclear projectile. Itsabsorption by the nucleus forms a “ compound nucleus,” in this case simplythe original nucleus with an excitation energy equal to the energy of they-quantum. Onlyemission of neutrons has so far been observed, and comparatively little isknown about this “ nuclear photo-effect,” on account of the low yieldobtainable, except for deuterium and beryllium, where the threshold isabnormally low (2-2 and 1.6 MeV respectively, instead of 6 to 10 MeV as inmost elements). Deuterium and beryllium, irradiated with y-rays fromradium or thorium-C, are therefore occasionally used as a neutron source.If the energy is sufficient, a particle may be emitted.Very Light Nwlei.For nuclei containing only a few particles the statistical considerationsof Bob’s nuclear theory are no longer applicable. On the other hand, themathematical difficulties in the way of a complete treatment are less formid-able, and the experimental study of the collisions between the simplestnuclei is our main source of information about the forces acting betweennuclear particles. So far, this information agrees fairly well with the pre-dictions of the meson theory of nuclear forces (see this Report for 1939),but this theory moves at the very edge of quantum mechanics, and realprogress will probably depend on some revolutionary change in the funda-ments of quantum theory. 0. R. FRISCH.l 6 Physical Rev., 1941, 59, 332

ISSN:0365-6217    

DOI:10.1039/AR9413800287

出版商:RSC    

年代:1941

数据来源: RSC

摘要:

INDEX OF AUTHORS’ NAMES.ABBOTT, 0. I.)., 236.Ablard, J. E., 128.Abonnenc, L., 34.Abram, H. H., 270.Abramovitch, B., 115.Acree, S. F., 279.Acton, A. F., 9.Adam, W. B., 231.Adams, J., 271.Adams, J. I., 268.Adams, R., 206, 217.Adams, S. C., 46.Adams, W. B., 76.Adamon, D. C. M., 265.Adkins, H., 139.Adler, E., 243.Ady, (Miss) P., 41.Afanasyev, B. N., 137.Aickin, R. G., 9.Ajello, T., 218, 219.Albanese, A. A., 257.Alberto, M., 95.Aldersley, J. B., 174.Alexander, 0. R., 85.Alexandrov, A. P., 142, 144.Allen, F. W., 254.Allsopp, C. B., 9.Almquist, H. T., 238.Alvarez, L. W., 290.Amaldi, E., 287.Amdur, E., 272.Ammann, C., 172.Anderson, E., 163, 164.Anderson, J. S., 81, 82.Anderson, L. C., 20.Andrews, D. B., 116.Angus, W.R., 29, 31, 33, 37,Anker, R. M., 226.Ankersmit, P. J., 187.Ansbacher, S., 236.Anslow, W. K., 205,212,261,Antipov-Karataev, I. N., 272.Apperson, L. D., 145.Archer, S., 122.Arens, J. F., 224.Arkel, A. E. van, 98.Arnold, A., 238.Arnold, R. T., 125, 178.Arreghini, E., 95.Asahina, Y., 213.Asano, M., 207.Aschehoug, V., 236.Asendorf, E., 224.Ashley, J. N., 213, 261.Asmussen, R. W., 45, 46.Aspinall, S. R., 226.40, 64.262.Astbury, W. T., 63, 109,242,Aston, J. G., 50, 51, 54.Atkin, L., 229.Auer, H., 28.Avery, W. H., 57.Azim, M. A., 28, 30.247.Bacharach, A. L., 234.Bacher, F. A., 267.Bacher, R. F., 297.Bacon, R. G. R., 187.Baddeley, G., 125.Bader, G., 78.Badger, R. M., 52, 57, 64.Badstubner, W., 172.BBr, F., 20.Bahl, B.S., 37.Bahl, R. K., 71.Bailey, C. R., 58.Bailey, J. R., 225.Bailey, K., 164, 241, 242.Bailey, W. F., 271.Bailie, J. C., 137, 142.Baine, O,, 147.Bak, B., 53.Baker, A. L., jun., 270.Baker, C. P., 297.Baker, W., 205, 261.Baker, W. O., 269.Bakke, A., 236.Baldinger, L. H., 284.Baldwin, E., 155, 156.Ball, W. C., 270.Ballczo, H., 271.Balls, A. K., 252.Baltzer, 0. J., 92, 93.Banerji, G. G., 229.Banga, I., 242, 247.Barber, H. H., 269.Bardet, J., 270.Barker, C. C., 168.Barker, E. F., 50, 53, 58,Barker, H. A., 258, 269, 260.Barker, J., 231.Barnes, R. A., 125.Barnes, R. H., 235.Barnett, M. M., 143.Barr, E. S., 64.Barraclough, E., 175.Barratt, S., 13.Barrett, C. S., 97, 98.Barron, E.S. G., 229.Barrow, R. F., 63.Barry, V. C., 153.BartholomC, E., 50.59.208Bartindale, G. W. R., 104.Bartlett, P. D., 121, 123, 134.Bassett, H., 65.Bates, L. F., 28.Bath, J. W., 59.Batt, L., 184.Batty, J. W., 176, 176.Bauer, S. H., 52, 57, 67, 103.Bauer, S. T., 123.Baughan, E. C., 62, 129, 133.Baumann, C. A., 236, 238.Baur, L., 152.Bswn, C. E. H., 64, 167.Baxter, J. G., 265.Bayliss, M., 148.Bayliss, N. S., 9, 83.Beach, J. Y., 67, 103.Beavan, G. H., 151, 157.Bechmann, C. O., 170.Beck, J. V., 259.Becker, H., 206.Becker, H. C., 280.Beeley, J., 268.Beeson, C. M., 46, 54.Beeston, A. W., 240.Beliaev, J. N., 132.Bell, D. J., 155, 156.Bell, F., 122.Bell, (Miss) F. O., 109.Bell, R. P., 118.Bendix, G.H., 271, 272.Benedetti-Pichler, A. A., 268.Bennett, G. M., 107, 132, 135,Bergel, F., 222.Bergmann, M., 252,257.Bergsteinsson, I., 200.Bernal, J. D., 108, 109.Bernet, E. G., 295.Bernfeld, P., 168, 170.Bernhauer, K., 172, 185.Bernstein, H. I., 53, 123, 139.Berry, L. G., 101.Bersin, T., 177.Best, C. H., 236, 240.Beynon, J. H., 193, 195.BBzard, A. von, 220.Bhagavantam, S., 92.Bhatnagar, (Sir) S. S., 28, 30,31, 32, 33, 37, 40, 41, 42.Bhide, B. W., 207.Bhimasenachar, J., 92.Bickley, E. A., 147.Biedebach, F., 203.Bilham, P., 193, 198, 201.Billman, J. H., 149.Binkley, 8. B., 207.Birch, S. I?., 13G.220INDEX OF AIJTHORS’ NAMES. 299Bird, H. It., 231.Bird, 0. D., 266.Birkinshaw, J. H., 263.Birtles, R,. 11,.125.Bitto, B. von, 172.Bjerrum, N., 13 1.Black, A., 265.Blair, C. M., 43.Blanchard, A. A., 71, 72, 70,Blatt, A. H., 123.Bloch, K., 241.Bloch, O., 25.Blochin, N., 181.Bloom, G. I. M., 46.Blout, E. R., 220.Blumenthal, E., 86.Bobaschinskaja, T. S., 139.Boeker, G. F., 29, 30.Boer, A. G., 207.Bogert, M. T., 171.Bohr, N., 292.Bondy, C., 255.Bonino, G. B., 40.Bonner, L. G., 53, 57, GO.Boorman, E. J., 278.Boppel, H., 168.Boratynski, K., 275.Borden, A., 53.Born, M., 92, 93.Rorovick-Romanova, T., 275.Borsche, W., 179. 218.Borsook, H., 241.Bose, P. K., 207, 223.Bourland, J. F., 55.Bowden, E., 119.Bowlus, H., 118.Boyce, J. C., 63.Boyle, A. J., 271.Boyle, J. S. W., 149.Bradley, A. J., 91, 97, 99.Brady, L.J., 105.Bragg, (Sir) W. H., 92, 93.Bragg, (Sir) W. L., 91, 92,Brain, E. G., 248.Branch, G. E. K., 132.Bras, G. J., 144.Braumer, B., 269.Braun, J. von, 121, 126, 175,Bredig, M. A., 106.Breen, J., 212, 262.Brenner, M., 193, 203, 204.Breslow, D. S., 117.Breuer, B., 149.Briggs, T. R., 70.Brignall, T. W., 285.Brinckley, S. R., 61, 62.Brindley, G. W., 34, 35, 37,Briscoe, H. V. A., 86, 86.Britton, H. T. S., 279, 280.Brockmann, H., 215.Brockway, L. O., 82,100,137.Brode, W. R., 13, 17, 26.82.97, 99.182, 226.38, 99.Brijinel, H., 244.Bronsted, J. N., 135.Brooker, L. G. S., 22, 25.Brooks, G. L., 132, 135.Broome, F. K., 280.Brown, C. L. M., 27‘7.Brown, D. E. S., 245.Brown, G. B., 235, 250.Brown, H. C., 65.Brown, M.H., 270.Brown, R. A., 266.Brown, W. G., 9, 115, 126.Bruker, A. B., 144.Bryant, J. T., 268.Buchanan, J. M., 261.Buchman, E. R., 226.Buchner, H., 43.Biittner, E., 268.Burawoy, A., 20, 175, 176,Burcik, E. J., 54.Burg, A. B., 65.Burgess, W. M., 70.Burkhardt, G. M., 132, 174.Burkser, E. S., 273.Burr, G. O., 235.Burris, R. H., 87.Burroughs, E. W., 239.Burroughs, H. S., 239.Burton, M., 63.Buswell, A. M., 59, 64.Butkow, K., 10.Butler, C. L., 163.Butler, R. E., 230.Butt, H. R., 235.182, 187.Cabrera, B., 28, 29, 30, 31,Caley, E. R., 269, 270, 272.Calingaert, G., 141.Calloway, N. O., 118.Calloway, T. C., 19.Calvin, M., 16.Cambi, L., 42.Zameron, D. M., 58.Zampbell, H. G., 231.Zampbell, (Miss) I.G. M.,C’ampbell, K. N., 149.Zampbell, W. G., 156, 188.Zantor, S. M., 281.Zapatos, L., 40.Zarlisle, C. H., 108.Zarlton, (Miss) N., 8.5.2am, E. P., 14.Clarroll, B. H., 25.:arson, S. C., 58.2arson, 8. F., 260.=assal, A., 75.?attell, McK., 245, 246.?erecedo, L. R., 265.>hadwick, J., 287.>hake, N. G., 8.Zhallenger, F., 144, 145, 146.>ballinor, S. W., 162.33.107, 127.Chambers, R., 245.Chamot, E. M., 136.Chandler, J. P., 236, 241.Channon, H. J., 236, 240.Chao, S. H., 105.Charles, J. H. V., 211, 261.Chatt, J., 143, 216.Chatterjee, N., 106.Chatterjee, S., 90.Cherry, G. W., 104.Chibnall, A. C., 254, 255.Childs, W. H. J., 57.Chinoy, J. J., 281.Chitrik, S. N., 185.Cholmogorov, S. N., 271.Chow, T.S., 150.Christ, R. E., 174.Christian, W., 243.Christman, C. C., 163, 220.Chute, W. J., 148.Ciakowski, J. M., 119.Clark, C. H. D., 63.Clark, D., 104.Cleaves, A. P., 53, 57, 58.Cleveland, F. F., 60.Clow, A., 39.Clusius, K., 54.Clutterbnck, P. W., 262, 263.Cocking, T. T., 283.Cockroft, J. D., 287.Cohen, K., 84.Cohen, S. L., 192, 196, 197,198, 199.Cohn, M., 241.Coleman, G. H., 149.Coleman, G. W., 72, 76.Coles, J. C., 170.Condon, E. U., 289.Conn, G. K. T., 58, 61.Connor, R., 116, 220.Connor, R. T., 265.Conrad, C. C., 70.Conrad-Billroth, H., 19.Cook, A. H., 18, 226.Cook, B. B., 236.Zook, J. W., 149.Zook, R. P., 231.Zooke, H. G., 178.Zooley, R. A., 88, 103.Coombs, (Miss) E., 118.Zope, A. C., 124, 143, 179.Zordebard, M.H., 277.Zorey, R. B., 108.Zorley, R. C., 239.Zorran, J. W., 286.Zorse, J., 148.Cloryell, C. D., 46.>oulson, C. A., 63.?ouper, M., 218.:outurier, P. L., 148.Zowie, D. W., 148.Zox, W. F., 97.Yoy, N. H., 265.Yoyne, F. P., 263.?rackston, J. E., 107, 217.:ourty, c., 37300 INDEX OF AUTHORS’ NAMES.Crandon, J. H., 231.Crane, H. I., 136.Crane, H. R., 289,290.Craven, G. J., 64.Crawford, B. L., 49, 50, 51Cretcher, L. H., 163, 164.Crews, S. K., 267.Crook, E. M., 232.Cross, P. C., 82.Crowfoot, (Miss) D., 108.Croxall, W. J., 118.Cruickshank, J. H., 29, 31!Culton, T. G., 234.Curie, I., 288.Curtin, T. P., 262.Cusmano, S., 219.Cuvelier, B. J. V., 272.59, 61, 62.39.Daehn, E., 178,183.Daker, W.D., 153.Dakers, J., 39.Ddy, E. I?., 68.Dam, H., 234.Damiens, A., 65.Dammerau, I., 40.Damodoran, M., 256.Danielli, J. F., 247.Danish, A. A,, 125.Dannohl, w., 97.Darken, L. S., 127.Darnell, M. C., 273.Darwin, C. G., 92.Datta, S. C., 85.Dauben, H. J., 134.Davey, W. P., 105.Davidson, F., 82.Davidson, N. R., 137.Davies, A. W., 232.Davies, M. M., 59, 64.Davies, W. C., 132.Davies, W. H., 182.Davis, 0. L., 230, 266.Davison, H. G., 236.Dawton, R. H. V. M., 91.Day, A. R., 226.Day, H. G., 229.Day, J. N. E., 85.De Benneville, P. L., 148,De Boer, J. H., 10.Decker, P., 227.Dede, L., 19.Dedell, T. R., 129.Deeny, J., 230.De Gouveia, A. J. A., 21.De Haas, W. J., 28.D e b , W. M., 281.Deijs, W. B., 211.Delaby, R., 285.De Lange, J.J., 106.Dehng, R. C., 69.De Masters, C. U., 236.Dennis, L. M., 136.220.Dennison, D. M., 51, 53, 58Dermer, 0. C., 271.Dermer, V. H., 271.Descatoire, F., 277.Deuel, H. J., 229.Devaud, A., 28.Dharmatti, S. S., 40.Dhawan, C. L., 32.Diaz, 3’. O., 270.Dickinson, R. G., 101.Dickinson, S., 242, 247.Diederichsen, J., 123.Dieterle, H., 203.Dimroth, K., 186.Dimroth, O., 214.Dinsdale, A., 31.Dippy, J. F. J., 127,128,130,131, 133, 135.Dirking, H., 17.Doak, G. O., 144.Dobrovolny, E., 223.Doebner, O., 178.Doescher, R. N., 50, 55.Doisy, E. A., 207.Done, R. S., 128, 129, 131.Dornow, A., 224.Dorris, T. B., 118.Doty, D. M., 257.Doty, P. M., 50, 54.Dounce, A. L., 253.Downes, H.C., 134.Downes, H. S., 132.Drapier, P., 28.Dreguss, M., 269.Dripps, R. D., 121.Drobnick, R., 172.Droge, H., 146.Druce, J. G. F., 137.Drumm, P. J., 123, 180.Dshaparidze, E., 272.Dubnoff, J. W., 241.Duerden, A., 202, 203.Duff, R. B., 154.Duffendack, 0. S., 274.Du Mont, H. L., 173.Dunaevskaja, C. S., 226.Duncan, A. B. F., 15.Duncan, I. J., 283.Dunker, M. F. W., 144.Dunlop, (Miss) H. G., 217.3upr6, D. J., 59.Dustman, R. B., 283.h t t , N. K., 42.htt, P., 207.htt, S., 207.l u Vigneaud, V., 235, 236,241, 249, 250.lworzak, R., 271.lwyer, F. P., 42.lykstra, K., 284.59, 60, 61.{akin, R. E., 235.Sarlam, W. T., 21.Zastcott, E. V., 237.Eastes, J. W., 70.Eaton, 5. L., 70.Eberly, K., 115.Eckardt, R. E., 236.Eckstein, H.C., 240.Eder, R., 210.Edgell, W. F., 53, 55.Edsall, J., 242, 247, 248.Edwards, 0. S., 98.Egan, C. J., 54.Egan, E. P., jun., 70.Eggleston, L. V., 260.Egli, H., 131.Ehlers, R. W., 128.Ehmann, E. A., 74.Eidinoff, M. L., 50.Eiler, J. J., 254.Eisenbrand, J., 12.Eistert, B., 122.Ekwall, G., 95.Elderfield, R. C., 220, 224.Elledge, B. E., 274.Ellinger, F., 26.Elliott, D. I?., 201.Elliott, E. C., 269.Elliott, J. H., 128, 132, 133,Elliott, N., 45, 102.Ellis, J., 59.Ells, V. R., 15.Elsom, E. O’S., 229.Elvehjem, C. A., 229, 236,237, 238, 266.Embree, N. D., 128, 130,265.Emelkus, H. J., 69.Emerson, G. A., 234.Emerson, 0. H., 221.Emmert, B., 224.Emmett, A. D., 266.Ender, W., 276.Endo, S., 260.Engel, R. W., 236.Engelhardt, W.A., 242, 247,Engleberg, G., 183.English, J., 249.Enk, E., 72, 81.Entemann, C. E., 148.Epifanski, P. T., 144.Eppinger, H. O., 220.Eppstein, S. H., 238.Epstein, L. F., 21.Erlenmeyer, E., 179.Ertel, L., 174.Edeben, H., 206,208,209.Escher, R., 221.Etheridge, M. P., 282.Etienne, A. D., 278.Euken, A., 131.Evans, D. P., 118,142.Evans, E. A., jun., 260, 261.Evans, H. M., 221, 234.Evans, L. K., 18.Evans, M. G., 62.Evans, W. M., 15.Evans, W. V., 137.135.248INDEX or AUTHORS’ N A ~ S . 301Everest, A. E., 210.Everett, D. H., 128, 129, 130,131.Evm, N., 265.Ewald, H., 13.Ewald; P. P., 94.Ewell, R. H., 55.Ewens, R. V. G., 82.Ewing, D. T., 273.Eynon, L., 279.Eyring, H., 128, 130.Eyster, E. H., 64, 55, 56, 59.Fack, E., 76.Fahlenbrach, H., 29, 30, 31,33.Fairbrother, F., 120.Fajans, K., 100.Fankuchen, I., 96, 108, 109,Faraday Society, 109.Farquharson, J., 30, 31, 39,40, 41, 42, 43.Faxdn, H., 93.Feigl, F., 77.Feitknecht, W., 13.Feldman, R.V., 270,273.Fellenberg, T. von, 276.Fermi, E., 287.Ferrari, A., 42.Fialkov, J. A., 70.Fichter, F., 65.Fields, E. K., 147.Fieser, L. F., 188, 221, 267.Fildes, P., 257.Files, J. It., 144.Filinov, P. M., 88.Finch, G. I., 92.Fink, H. L., 54.Fink, P., 10.Finkelstein, J., 224.Fireman, M., 163.Fischer, E., 178, 183.Fischer, F. G., 172, 173, 174,Fischer, H., 72, 82, 219.Fischer, H. 0. L., 225.Fisher, (Miss) N. I., 22.Fittig, R., 184.E’lagg, J.F., 89.Flaig, W., 173.Flanzy, M., 277.Fleck, E. E., 198.Flegontov, A. I., 144.Fleischhauer, H., 173.Fleming, A., 262.Fleming, S. H., 277.Floody, R. J., 233.Flordal, M., 38.Florey, H. W., 263.Foldi, Z., 149.Forster, Th., 8, 15.Folin, O., 239.Fonteyne, R., 59.Forbes, I. A,, 154.254.177, 179.Forbes, J. C., 236.Ford, L. H., 164.Forster, W. S., 50.Fortress, F. E., 14.Foster, G. L., 239.Foster, J. W., 260.Fowler, R. H., 47.Fox, J. J., 59, 60, 63, 64, 94.Fox, M., 84.France, H., 17.Frank, B., 187.Frary, S. G,, 70.Frazer, J. C. W., 81.Freed, N., 285.Freed, S., 14, 39.Freeman, G., 169.Freidlina, R. C., 138, 139.Fresenius, W., 59, 205.Freudenberg, K., 168.Freundlich, H., 256.Prey, C. N., 229.Friauf, J.B., 96, 101.Fried, J., 220.Friedmann, E., 179.Friehmelt, E., 121.Frischmuth, G., 40,42.Fritzsche, H., 221.Frivold, 0. E., 35, 38, 39.Fromel, W., 27.Frost, A. A., 29.Frush, H. L., 281.Fmton, J. S., 252.Fuhrmann, G., 146.Fukushima, T., 209.Fuller, C. H. F., 170.Furter, M., 197, 198.FUSCO, R., 225.Fuson, R. C., 148, 174, 178.E’uzikawa, F., 213.Gage, D. H., 58.Gall, H., 72, 74, 76, 79.Gallias, F., 42.Gamow, G., 289,290.Gapchenko, M. V., 268.Gardner, J. A., 117.Gardner, J. H., 147.Gardner, R., 281.Garner, C. S., 50,55.Garratt, D. C., 286.Garssen, J. E., 43.Gascoigne, R. M., 286.Gaspar, T., 269.Gavin, G., 235.Gaydon, A. G., 27.Geiger, M. B., 20.Geigle, W. F., 70.Geisler, A. H., 97, 98.GerendSs, M., 13.Germer, L.H., 101.Gheorghiu, D., 43.Giacolone, A., 181.Giacomello, G., 193, 194.Giauque, W. F., 52, 54.Gibson, D. T., 148.Gibson, G. M., 146.Gibson, K. E., 10.Giguhre, P. A., 66, 100.Gilbert, W. I., 124.Gill, J. D., 123.Gill, R. E., 163.Gillam, A. E., 8, 10, 17, 18.Gdette, L. A., 164.Gillette, R. H., 55.Gilliam, W. F., 67, 68, 69,Gillis, R., 224.Gilman, H., 136, 137, 139,140, 141, 142, 143, 144,145, 147, 149, 171.Gilmont, P., 76.Gingrich, N. S., 93, 100.Glacet, C., 141.Gladstone, G. P., 267.Glasstone, S., 47, 107, 132,Glavind, J., 234.Glazebrook, A. J., 231.Glister, G. A., 263.Glockler, G., 53, 56,60.Gluschnev, N. T., 144.Godeffroy, F., 270.Goebel, W. F., 165.Godde, O., 173.Goldberg, &I.W., 187.Goldblatt, H., 236.Goldenberg, N., 170.Goldinger, J. M., 229.Goldschmidt, H. J., 97.Gollub, F., 147.Gombhs, P., 37.Good, W., 41.Goodeve, C. F., 10,42.Goodson, J. A,, 193.Goodway, N. F., 286.Gordon, N. E., 132.Gordon, W. E., 70.Gordy, W., 64.Gorham, J. E., 84.Gorter, I?. J., 236.Goto, K., 85, 86.Gottschlich, E., 246.Gould, R. G., 183.Grab, W., 265.Grafe, D., 54.Gralheer, H., 217.Grammaticakis, P., 149.Grandel, F., 234.Grane, O., 276.Granger, R., 148.Granick, S., 216.Grant, M. I., 10.Gratscheva, G. P., 142.Gray, F. W., 29,31, 39,44.Grechnev, M. A., 286.Greenberg, A. L., 106.Greenberg, H., 266.Greenstein, J. P., 242,248.Gregg, C. C., 70.G ~ g g , R. Q., 93.Gneff, L. J., 83.136.135302 INDEX OF AUTHORS' NAMES.GrifIin, I). B., 284.Griffith, W.H., 236, 241.Griffith, W. J., 238.Griffiths, D. C., 132.Griffiths, D. G., 135.Griggs, M. A., 274.Chignard, V., 150.Grosheintz, J. M., 226.Grosse, A. von, 136, 137, 142.Groth, W., 14.Griinberg, A. A., 88, 89.Gruhl, A., 80.Grundmann, C., 172, 173,174, 177, 179, 180, 186.Gunther, G., 243.Gunther, P., 222.Guggemos, H., 219.Guggenheim, E. A., 47,50.Guinier, A., 96.Gulland, J. M., 254, 256.Gurney, R. W., 128,130,289.Gustus, E. L., 194.Guyer, W. R. F., 87.Gwinn, W. D., 49.Gyorgy, P., 236, 237, 249.Hackl, O., 270.Hligg, G., 95.Hafez, M. M., 220.Hagedorn, H. C., 280.Halban, H. v., 12.Halford, J. O., 132, 133, 134.Hall, M., 271.Hall, N.F., 85, 132, 134.Hall, R. T., 284.Halpern, J., 290.Hamburg, H., 213.Hamburger, G., 105.Hamer, (Miss) F. M., 22, 25.Hammett, L. P., 131, 132,Hampson, G. C., 104, 1G6,Hands, S., 154.Hanes, C. S., 155, 168.Hansley, V. L., 147.Hargreaves, A., 105, 108.Harington, C. R., 272.Harker, D., 63.Harned, H. S., 128, 129, 130,131, 132.Harper, H. A., 220.Harper, S. H., 176.Harrer, C. J., 232.Harriman, B. R., 147.Harris, E. J., 276.Harris, G. C., 286.Harris, G. H., 193, 200.Harris, G. P., 51, 69.Harris, J. E., 271.Harris, L. J., 228, 229, 230,Harrison, L). C., 232, 234.Harrison, E. G. R., 27.Harrison, J. A., 274.133, 134, 135.124, 125.231, 233.Hart, E. B., 236, 238.Hartmann, H., 179.Hartmann, M., 208.Hartree, D.R., 35.Hartwell, G. A., 236.Harvey, E. N., 245.Harwood, H. F., 271.Hasan, K. H., 207.Haschad, M. N., 215.Haslam, J., 268.Hass, H. B., 149.Hassan, A., 19.Hassid, W. Z., 153, 169, 282.Hastings, A. B., 261.Haucke, W., 95.Haupt, R. F., 55.Hauser, C. R., 115, 117.Hausser, K. W., 16, 25, 186.Havens, G. G., 30, 44.Hawkins, E. G. E., 167.Haworth, E., 177.Haworth, R. D., 193.Haworth, W. N., 155, 157,162, 167, 168, 169.Hayasi, K., 164.Hayes, H. T., 64.Heath, R. L., 157, 169.Heen, E., 153.Heggie, R., 266.Heilbron, I. M., 174, 175,176,177,182,187,193,202,203,204.Hein, F., 137, 138.Hellwege, K. H., 13.Helmholz, L., 102.Hemingway, A., 260.Henderson, L. M., 237.Hennessy, D. J., 265.Hennion, G. F., 119.Henseleit, K., 261.Hepner, F.R., 139.Herb, R. G., 295.Herbert, J. B. M., 86.Heritsch, H., 105.Herold, W., 19.Hershberg, E. B., 267.Hershey, T. M., 240.Hertel, E., 18.Hess, K., 169, 170.Hessling, G. von, 80.Hetherington, A. C., 263.Hewett, C. L., 149.Hey, D. H., 17, 27.Heydweiler, A., 37.Heymann, E., 30.Hibbard, R. P., 273.Hickey, F. C., 128.Hicks, B., 62.Hieber, W., 71, 72, 73, 74,75, 76, 77, 78, 79, 80, 81,82.Higani, I<., 217.Hill, A. J., 226.Hill, W. I<., 29, 31, 33, 64.Hiller, J. E., 101.Hind, H. G., 213, 262.Hinton, H. D., 118.Hiramoto, M., 207.Hirone, T., 37.Hirschfelder, J. O., 62, 63.Hirst, E. L., 64, 1.50, 152,156,157, 161, 162, 163,167,168.Hnizda, V. I!., 143.Hoard, J. L., 104.Hoare, F.E., 29, 34, 38.Hocart, R., 34.Hock, H., 77.Hodgson, H. H., 132.Hodson, A. Z., 286.Hoehn, H. H., 220,222.Hoff, R. W., 278.Hoffer, M., 172, 178.Hoffman, W. A., 221.Hoffmann, O., 221.Hofmann, K., 194, 236, 240,Hogan, A. G., 236.Hogness, T. R., 26.Holcomb, J. H., 284.Holden, N. E., 117.Hollens, (Miss) W. It. A., 37.Holloway, D. F., 67, 68.Holmes, J., 275.Honda, K., 29.Hoover, S. R., 252.Hopkins, R. H., 169.Horrex, C., 119.Hoskins, C. R., 278.Houghton, C. O., 278.Howard, J. B., 52.Howell, 0. R., 13.Hubard, S. S., 70.Huebner, C. F., 223.Huckel, E., 15.Huff, J. W., 230.Huffman, J. R., 84.Huggins, M. L., 65, 64, 100.Hughes, E. D., 123.Hughes, G. K., 224.Hulbert, H. M., 62.Hull, D. E., 88.Hultzsch, K., 173, 174.Hume, E.M., 234.Hume-Rothery, W., 95, 99,Hunter, L., 64.Huntsman, M. E., 236.Hurd, C. D., 221, 281.Hutchinson, C. A., 84.Huyser, H. W., 187, 201.Hyde, J. F., 69.Hyde, J. L., 85.250.100.I. Q. Farbeniiidustrie A.-U.,75, 81.mail, J., 24.Igarasi, H., 213.Iimori, T., 87.Ikenmeyer, K., 34.Ilmenev, M. I., 272INDEX OF AUTHORS’ NAMES. 303Inai, T., 29.Ing, H. R., 257.Inglis, D. T., 280.tngold, C. K., 85, 116, 123.Insinger, J. A., 285.Ipatieff, V. N., 120.Iredale, T., 10.Trrgang, K., 172.Irving, G. W., jun., 252.Irving, H., 104.Irwin, F., 147.Irwin, (Miss) W. B., 222.Isbell, H., 230.Isbell, H. S., 144, 281.Isherwood, F. A., 157, 168.Ishiwara, T., 30.Iskenderian, H. P., 29.Ismail, A.S., 271.Ito, T., 102.Ivanov, A,, 181.Iwamura, A., 274.Izmdov, N. A., 132.Jaanus, R., 30, 44.Jackson, A., 13.Jackson, J., 155, 159.Jacob, (Miss) A., 221, 222.Jacob, J. P., 262.Jacobi, H. P., 236, 238.Jacobi, M., 271.Jacobs, W. A., 194, 198.Jacobson, H. F., 14.Jacoby, A. L., 139.Jaeger, W., 234.Jiinecke, L., 209.Jahn, H. A., 57, 92, 93, 94.,Jauncey, G. E. M., 92, 93.Jay, A. H., 91.,Jeger, O., 190.Jelley, E. E., 23.Jenkins, G. L., 144.Jenkins, H. O., 127, 128, 130,Jensen, B. N., 280.Jensen, C. C., 282.Jensen, E. F., 252.,lensen, K. A., 138, 221.Jensen, P., 246.Jephcott, C. M., 276.Job, A., 75.Job, P., 13.John, W., 222.Johner, W., 29.Johns, S. B., 134.Johnson, A. W., 177.Johnson, C. H., 89.Johnson, C.R., 70.Johnson, J. R., 148.Johnston, R., 274.Joiner, R. R., 215, 224.Joliot, F., 288.Jones, D. G., 18.,Jones, E. J., 64.Jones, E. R. H., 202, 203,131, 133.205.Jones, E. T., 21 1.Jones, H. L., 140.Jones, J. K. N., 150, 151,152,156,157,161, 162,163,167.Jones, R. G., 136, 137, 142.Jones, W. E., 174, 175, 176,Jones, W. G. M., 15.1.Jones, W. J., 137..Jones, W. O., 152.Joos, G., 34.Joris, G. G., 87.Jorissen, W. P., 65.Joseph, L., 147.Joslyn, M. A., 153.Joyce, L., 59.Jukes, T. H., 236.Juriev, J. K., 218.Justoni, R., 219, 225.177, 182.Kadesch, R. G., 124.Kiimmerer, H., 214.Kafuku, K., 211.Kahovec, J., 60.ICalckar, H., 244.Kamen, M. D., 87, 258, 261.Kapur, P. L., 41, 42.Karrer, P., 178,182,221,234.Karrer, W., 205.Karweil, J., 50, 59.Kassel, L., 47.Kato, T., 268.Kaul, R., 207.Kaur, (Miss) G., 41.Kausche, G.A., 110.Kawe, A., 270.Kaye, I. A., 271.KekulB, A., 172, 178.Keller, H., 234.Keller, R. N., 138.Kellett, E. G., 275.Kellie, A. E., 232.Kellner, L., 14, 62.Kelly, E., 232.Kemmerer, A. R., 266.Kemmerer, K. S., 238.Kemp, A. R., 255.Kemp, J. D., 50, 52, 54.Kempster, H. L., 236.Kennedy, M. H., 284.Kennedy, R. M., 50, 51,54.Kennedy, T., 202,203, 204.Kent, N. L, 274.Kenyon, J., 121, 122.Keppel, D. M., 241.Ketelaar, J. A. A., 46.Kethur, R., 183.Keyes, G. H., 25.Khanna, M. L., 30, 37.Kharasch, M. S., 139, 141,142, 144, 147, 177.Kibler, C. J., 218.Kido, K., 33, 35, 37, 38, 40,43.Kielland, J., 272.Kilpatrick, M., 128, 132, 133,Kilpatrick, M.L., 132.Kilpi, S., 132.Kincaid, J. F., 123.King, C. G., 232.King, J. A., 220.Kinney, C. R., 141.Kipping, F. B., 181.Kirby, R. H., 140, 141.Kirby-Smith, J. S., 60.Kirk, P. L., 269.Kirkpatrick, P., 93, 94.Kirkwood, J. G., 37, 131.Kirsanov, A. V., 137.Kirton, H. M., 39.Kiss, A. v., 13.Kistiakowsky, G. B., 16, 50,51, 54, 55.Kitagawa, M., 256.Kitasato, Z., 195, 197.Kitching, J. A., 245.Kleene, R. D., 125, 133.Klein, A., 185.Klein, B., 271.Klein, C. H., 68.Klemm, L., 30, 42.Klemm, W., 28, 40, 42, 138.Klemperer, F. W., 261.Klimova, V. A., 144.Kline, G. M., 279.Kline, 0. L., 238.Knaggs, (Miss) I. E., 107.Knoevenagel, E., 172.Knox, L. H., 121.Knudson, A., 233.Kodicek, E., 230.Kogl, F., 206, 207, 208, 208,ICohler, F., 180.Koehler, J.S., 51, 53.Kohler, L., 180.Konig, E., 11.Koenig, H., 221.Konig, J., 72, 78, 79.Konig, W., 22, 184, 186.Koenigsberger, J., 34.Koster, W., 97.Kohlrausch, K. W. F., 53.ICohman, T. P., 286.Kolbezen, M. J., 137.Kolka, A. J., 119.Koller, G., 213.Kolthoff, I. M., 269,271,275.Kon, G. A. R., 192, 193, 198,Konopinski, E. J., 289.Korenman, I. N., 278.Kornblum, N., 217.Kortum, G., 11, 26.Kossiekoff, A., 107.Kotscheschkov, K. A., 138,139,140,142, 143,144,145,149.135.211.200, 201.Kraft, K., 188304 INDEX OF AUTHORS’ NAMES.Krajnc, B., 169.Krau~, C. A., 133, 136,143.Kraus, E. J., 249.Krause, E., 136.Krauze, M. V., 181.Krebs, H.A., 240,260,261.Krebs, K. F., 59.Kreuchen, K. H., 16.Kringstad, H., 236, 265.Krishnan, K. A., 24.Krishnan, P. S., 256.Krishnaswamy, T. K., 256.Kruck, W., 40.Kruis, A., 54.Krumholz, P., 77.Kruse, H. D., 233.Kuffner, F., 123.Kuhn, E., 16.Kuhn, R., 16, 17, 20, 171,172,173,174,177,178,179,180,182,183,184,185,186,208.Kuhn, W., 11.Kuna, M., 157.Kunitz, M., 252,254.Kunze, K., 178, 183.Kuroda, C., 208.Kurtz, P., 175.Kuto, H., 87.Labaune, L. M., 284.Lacher, J. R., 50, 51, 55.Lagally, H., 75, 77, 78, 79.Lagrange, R., 270.Lahiri, T. K., 40.Laidler, D., 96.Lambert, A., 17.Lambert, R. H., 25.LaMer, V. K., 90, 132, 133,L a m , G., 247.Lampitt, L. H., 170.Lane, J. F., 122, 123.Lane, J. IF., 279.Lang, A., 206.Lange, K., 218.Langenbeck, W., 173.Langer, A., 88.Langevin, P., 27, 35.Langley, H.N., 247.Langmuir, I., 248.Langseth, A., 53.Lapworth, A., 117, 179.Lamen, R. G., 141.Laubengayer, A. W., 67, 136.Laue, M. v., 93, 94.Lauwart, A, 277.Laval, J., 93.Lawrence, A. S. C., 242, 243,Lawrence, C. A., 149.Lawrie, N. R., 233.Leader, G. R., 60.Learmonth, J. R., 232.Lederle, E., 10.134.247.Leditschke, H., 218.Lee, E., 58.Leeds, W. G., 59.Leermakers, J. A., 26.Le FBvre, (Mrs.) C. G., 107,Le FBvre, R. J. W., 107, 127.Legault, R. R., 139.Lehmann, H. L., 11.Lehrer, E., 45.Leifer, E., 86.Lemard-Jones, J. E., 15.Leong, P. C., 233.Lesage, L., 277.Leabre, M., 143.Lesslie, (Miss) M., 107.Letang, N.J., 126.Leuenberger, H., 192, 199.Leutert, F., 75.Leva, E., 273.Levene, P. A., 157, 163.Levene, S., 248.Levi, G. R., 101.Levine, (Miss) J. H., 139.Levy, H. A., 108.Levy, P., 188, 190.Lewinsohn, M., 143.Lewia, B., 102.Lewis, G. L., 22, 138.Lewis, G. N., 16.Lewis, H. B., 240.Ley, H., 11, 17.Libby, W. F., 88.Liberatore, L. C., 87.Lichtenmalter, M., 137, 140,Liebhafsky, H. A., 68.Lindner, R., 269.Lindstrom, C. F., 19.Lineweaver, H., 252.Lingane, J. J., 230, 266.Link, K. P., 152, 223, 279.Linnett, J. W., 52, 59, 61,Linton, E. P., 66.Linville, R. G., 220.Lions, F., 217, 224.Lipson, H., 91, 95, 96, 98.Lipton, M. A., 229.Lister, M. W., 54, 82.Liu, S. H., 233.Ljubimova, M. N., 242, 247,Lofstrom, B., 276.Lowenberg, K., 174, 177.Long, F.A., 31, 89.Lonsdale, (Mrs.) K., 92, 93,94, 95, 107, 108.Loofbowow, J. R., 63.Loudon, J. D., 139, 144.Lovell, R., 263.Lowe, A., 175, 182.Lowry, T. M., 10.Lu, G. D., 243.Lucas, B. G. B., 232.Luae, H. J., 139, 227, 284.127.141.62, 63.248.Tuckett, S., 151.Ludeman, (Miss) H., 139.Luder, W. F., 133.Ludy, P., 214.Luhrmann, H., 18.Liittringhaus, A., 150, 217.Lugg, J. W. H., 254, 255,Lukems, F. D. H., 229.h n d , C. C., 231.Lunde, G., 236,265.Lundeghdh, H., 274, 275.Lutz, K., 128.Lutz, R. E., 218.Lyman, C. If., 229.Lynch, C. C., 132, 133.257.Maass, O., 56.McAlevy, A., 180.MacArthur, 109.McCale, C. H., 107, 217.McClellan, W. R., 116.McClelland, J. A. C., 274,McClure, F.T., 147.McCollum, E. V., 229, 234.McCorkle, M. R., 123.McCorquodale, D. W., 207.McCready, R. M., 153, 169,McCullough, J. D., 105.McElvain, S. M., 150.McGinty, 0. A., 240.McGookin, A., 20.McGregor, A., 149.Machella, T. E., 230.McHenry, E. W., 235,236.McIntyre, J. M., 237.McKee, R. W., 207.McKenna, J. F., 119, 149.RlcKenzie, A., 149.Mackenzie, C. G., 234.Mackenzie, J. B., 234.XlcKinney, D. S., 128.Mackinney, G., 215.McMeeking, W., 202,203.Macoun, J. M., 278.McReynolds, J. P., 130.Macwalter, R. J., 13.Maddock, A. G., 69.Madinaveitia, A., 33.Magee, J. L., 128, 130.Mai, H., 179.Maier, K., 215.Makarova, L. G., 136, 141,144, 145.Makino, K., 254.Mal, R. S., 33.Manchot, W., 72, 74, 76, 78,79, 81, 82.Manchot, W.J., 72, 81.Mandelstarn, S. L., 275.Manifold, M. C., 236, 240.Mann, F. G., 143,216.Mann, P. J. G., 230.275.282INDEX OF AUTHOBS’ NAMES. 305Manteuffel, R., 179.Manzoni-Ansidei, R., 40.Mapson, L. W,, 231.Marin, R., 71,82.Marker, R., 142,Maron, S. H., 90.Marple, K. E., 140.Marschall, A,, 172.Marsland, D. A., 246.Martin, A. E., 59,60,63, 64,Martin, R. W., 281.Martin, W. J., 104.Marvel, C. S., 240.Marxer, A., 193, 199,200.Mason, R. B., 132.Mathur, R. N., 28, 30, 32,Mauguin, C., 93.Msvity, J. M., 142.Mavrodineanu, R., 148.Maxim, N., 148.Maxwell, L. R., 102.Maycock, R. L., 64.Mayr, A,, 79.Mazza, L., 275.Meakins, R. J., 202,203,205.Mears, W. H., 132.Mecchi, E., 238.Mecke, R., 64.Meek, W.J., 236,238.Meerwein, H., 117.Mehl, J. W., 248.Meister, M., 119.Meitina, R. A., 248.Mellanby, E., 233, 234.Mellor, D. P., 42.Melnikov, N. N., 141, 142,Melville, D. B., 235, 249,Melvin, E. H., 11.Menzies, A. C., 60.Messerly, G. H., 50, 54.Metcalf, R. P., 125.Metra, M., 277.Metropolis, N., 63.Metzger, H. J., 263.Meyer, G. M., 157.Meyer, J., 188.Meyer, K., 248.Meyer, K. H., 168, 170.Meyer, W., 276.Meyerhof, O., 243.Michael, A., 116.Michaelis, L., 216.Michel, J., 180.Middleton, G., 283.Milas, N. A., 180, 181, 266.Miller, C. C., 269.Miller, C. E., 87.Miller, D. C., 92.Miller, E. S., 235.Miller, J. A., 277.Miller, S. A., 146.Mills, A., 84.94.33, 40.144.250.MMMMMMMMMMMMMMMMMMMnI:MMMMMMMiMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMiva s , G.A., 85.:innick, L. J., 132, 133.Iirsky, A. E., 242, 246, 247.itchell, H. H., 239.itchell, H. K., 237, 251.itchell, J. W., 249.:itchell, R. L., 274.itchell, W., 149.3tm, N. G., 31.Yttasch, A., 78.:iyagawa, I., 214.iyake, S., 164.:ohle, W., 243.Iohler, H., 26.1011, T., 265.:and, R. L., 81.:onobe, S., 256.Iontgomery, E. H., 229.Iookerjee, A., 223.Iooney, (Miss) R. C. L., 103,:oore, F. J., 134.Ioore, F. W., 137, 142, 147.:oore, S., 279.:oore, T., 232, 233.loore, W. J., 101.:orell, S., 152.:orell, S. A., 280.:orf, R., 178, 182.:organ, A. F., 236.:organ, W.L., 282.:orita, N., 86.:orris, C. J. 0. R., 182, 256.:orris, H., 45.:orrison, A. L., 177.:orse, R. A., 139.:orton, A. A., 143.:orton, R. A., 8, 10, 11, 13,18, 19, 20, 21, 26, 27, 186.:oser, L., 270.Iosley, V. M., 102.:ass, A. R., 240.:ow, C. C., 14.:ousseron, M., 148. :eyer, A. W., 241.Irowka, B., 37.:iihlbauer, F., 74.Iuelder, K. D., 232.Iiiller, A., 284.:uller, E., 40, 147.Iuller, G., 195.Iukhopadhyay, S. L., 262.idford, D. J., 236, 241.Iullan, J., 163.:ulwctni, B. T., 273.~umm, O., 123.:undle, N. K., 43.:unro, J., 279.luralt, A., 247.:urphy, G. M., 55, 59.:urray, J. W., 132.:urray, M. T., 60.:usante, C., 225.lyasnikova, A. R., 372.:yere, D. R., 168.[yem, W. G., 246.107.Myrblick, K., 168.Nadj, M.M., 142, 143, 145.Nagasawa, F., 215.Nagel, S. C., 121.Nagendra Nath, N. S., 92.Nahmias, M. E., 289.Nakao, M., 209.Nakayama, H., 87,260.Narayanan, K. G. A., 266.Narayanaswamy, A. S., 43.Nargund, K. S., 207.Natanson, S., 25.Natta, E. G., 101.Naves, Y. R., 286, 286.Nayar, M. R., 43.Nebe, E., 137.Needham, D. M., 242, 243,Needham, J., 242, 243, 247.Negelein, E., 244.Nehra, V., 29.Nelson, J. F., 139, 140, 141,Nemec, A., 272.Nesmejanov, A. N., 136, 138,139, 140, 141, 144.Nettleton, H. R., 28.Neubauer, E., 172.Neuber, (Frl.) A., 138.Neubeg, C., 154.Neumann E. W., 42.Neurath, k., 246.Neuwirth, M., 172.Nevgi, M. B., 30, 32, 37,Newman, H., 234.Nicolet, B. H., 279.Nield, C. H., 266.Nielsen, A.H., 52, 59.Nielsen, H. H., 58, 62.Nier, A. D., 260.Nieuwland, J. A., 118.Nightingale, (Miss) D. V., I 1 8.Niini, A., 276.Nikitin, B. A., 65.Nilakantan, P., 92, 93, 94.Nishina, Y., 87, 260.Noetzel, O., 277.Noller, C. R., 143, 193, 200.Norris, F. W., 164.N o d , L. C., 266.Norris, T. H., 87.Northrop, J. H., 252.Norton, F. H., 149.Novelli, A., 267.Noyes, W. A., 122.Nozaki, K., 120.Nudenberg, W., 177.Nunn, L. G., jun., 70.247.149.40,42, 46.Ochiai, E., 216.Ochoa, S., 229.O’Connor, M. J., 119306 INDEX OF AUTHORS’ NAMES.O’Connor, W. F., 123.Oddo, B., 218.Oesper, P. F., 138.gsterud, T., 230.Ogg, R., 120.Ohlmeyer, P., 243.Ohri, G. L., 37.Ohshima, H., 208.Oldham, J. W. H., 147.Oleson, J. J., 236.Oliver, E., 167.Olliver, M., 231.Oparina, O., 269.Opie, J.W., 221.Orchard, W. M., 148.Osborne, D. W., 50,55.Osborne, T. B., 254.Osburn, 0. L., 278.O’Shaughnessy, M. T., 125.Ostrogovich, G., 21.Ott, H., 93.Overhoff, J., 147.Owen, B. B., 128.Owens, R. G., 50,58.Oxford, A. E., 214, 262, 263tOxley, A. E., 30.Pace, N., 215.Pacevitz, H. A., 143.Paget, H. J., 285.Paist, W. D., 220.Palkin, S., 269.Palmer, K. J., 61.Panizzi, L., 225.Pappenheimer, A. M., 234.Parker, (Miss) B., 144.Parkineon, D. B., 295.Parks, 51.Pascal, P., 27, 28, 31, 32,Patnode, W., 136.Patrick, H., 236.Pauling, L., 15, 35, 39, 61,Peacock, C., 266.Pearse, R. W. B., 27.Pease, D. C., 245.Peat, S., 153, 154, 157, 164,Peierls, R., 293.Peirce, G., 125.Pelczar, M.J., 230, 251.Pelkis, P. S., 226.Penney, W. G., 15, 56.Pepinsky, R., 102.Perakis, N., 40.Percival, E. G. V., 153, 154,Perkin, A. G., 210.Perlzweig, W. A., 230.Perren, E. A., 116.Pestemer, M., 19.Petch, N. J., 91, 95.Peterson, J. &I., 232.Peterson, W. H., 251.33.67, 100, 101, 104, 227.169.163.Petrov, A. D., 148.Pevsner, D., 242.Pfankuch, E., 110.Pfeiffer, M., 801.Pfeilsticker, K., 274.Philipson, T., 274.Phillips, H., 122.Phillips, L., 279, 280.Picard, C. W., 195, 196, 197Piccard, A., 28.Piccoli, T., 276.Picken, L. E. R., 246.Pickering, R. W., 83.Pickett, L. W., 17.Pielemeier, W. H., 51.Pigman, W. W., 281.Pillai, R. K., 243.Pines, H., 120, 139.Piper, J. D., 17.Pirie, N.W., 154.Pirot, E., 224.Pittman, (Miss) V. P., 122.Pitzer, K. S., 49, 50, 51, 54,Platt, A. P., 236, 240.Platzer, G., 186.Platzer, N., 223.Pletz, V. M., 136.Plyler, E. K., 58.Pockels, U., 146.Pohl, F., 215.Polanyi, M., 62.Poling, C. E., 237.Polischtschuk, A. B., 70.Poljakova, A. M., 122.Pollock, G. A., 232.Polya, J. B., 18, 177.Popkin, A. H., 123.Porret, D., 9, 10.Porter, J. R., 230, 251.Posternak, T., 206, 213,262.Postowsky, J., 206, 21 1.Potter, V. R., 26.Potterill, R. H., 10.Powell, H., 54, 65.Powell, H. M., 82, 104.Powell, W. J., 116.Prager, B., 179.Prasad, M., 40.Preckel, R., 45.Preiss, W., 276.Preobrashenski, N. A., 122.Preobrashenski, V. A., 122.Preston, G. D., 92, 93, 96,97.Price, C.C., 119.Price, W. C., 14, 15.Prichard, W. W., 221, 222.Procke, O., 270.Proost, W., 147.Purkis, G. H., 11.Purrmann, R., 227.Putnam, G. L., 271.198.55, 129.Juastel, J. H., 229, 230.Quense, J. A., 281.Quilico, A., 226.Qureshi, M., 29, 38, 43.Rabinowitch, E., 21.Rachele, J. R., 249.Riidulescu, D., 21.Rafter, J. R., 76.Raistrick, H., 205, 211, 212,213, 214, 261, 262, 263.Rajagopal, K. R., 233.Ralston, A. W., 123.Rama Pisharoty, P., 93.Raman, (Sir) C. V., 92, 93,Ramart-Lucas, (Mme.), 18.Ranganadham, S. P., 38, 43.Ransom, W. W., 51, 55.Rao, B. N., 43.Rao, S. R., 30, 38, 43, 45.Rapin, A,, 276.Ratner, S. ,239.Ravin, A., 278.Rawlinson, W. A., 42.Ray, A. C., 207.Ray, P., 42, 90.Raymond, L. W., 283.Raymond, W.D., 230.Raynor, G. V., 100.Redemann, C. E., 227, 28-3.Redlich, O., 58, 62.Reed, W. H., 70.Reedy, J. H., 270.Ekes, A. L. G., 9.Reeves, R. E., 165, 279.Reich, W. S., 281.Reicheneder, K., 34.Reichstein, T., 172.Reid, A., 265.Reid, C., 69.Reid, M. C., 277.Reihlen, H., 80, 82.Redly, J., 123, 262.Reims, A. O., 226.Remy, H., 65.Renfrew, A. G., 164.Rentschler, H., 221.Renwam, G., 136.Reveley, W. G., 218.Reynolds, J. A., 266.Reynolds, W. B., 147.Ri, T., 128, 130.Rice, W. W., 50, 51.Richards, G. V., 237.Richards, 0. V., 145.Richards, T., 213, 261.%tichardson, F. D., 42.lichardson, G. M., 257.aichardson, L. R., 236.Gchter, D., 211.liding, R. W., 11.lidout, J. H., 236.Xiewe, K. H., 94.3ingier, B. H., 221.<inke, F., 17,94Ritchie, E., 217, 224.Ritschel, E., 270.Rittenberg, D., 239.Ititz, J., 150.Roach, W.A., 274.Roberts, E., 31.Roberts, I., 84.Robertson, A., 211.Robertson, 3. M., 64, 91, 95,Robertson, M., 274.Robertson, (Sir) R., 94, 123.Robeson, C. D., 265.Robinson, H., 263.Robinson, (Sir) R., 211, 212,213, 261, 262, 263.Robinson, R. A., 129.Robinson, R. J., 271.Rochow, E. G., 68,69, 136.Rodebush, W. H., 59,64,125.Roeder, C. H., 226.Roff, F. S., 231.Roger, R., 149.Rogers, M. T., 100, 102.Rokitskaja, M. S., 141, 144.Roland, J. R., 150.Romberg, E., 75.Rose, C. S., 249.Rose, W. C., 238, 239.Rosenbaum, E. J., 60, 62.Rosenberg, A., 19.Rosenfels, R. S., 282.Rosenkranz, G., 202,203,204.Rosenthaler, L., 210.Roslova, N.A., 148.Ross, J., 116.Ross, J. R., 269.Ross, W. E., 148.Rothen, A., 254.Rouvillois, J., 75.Rovno, I., 181.Rowaan, P. A., 285.Ruben, S., 87, 258, 259, 260,Rubin, D. J., 60, 62.Rubin, M., 220.Rudolph, W., 175, 226.Riiegger, A,, 182.Ruehrwein, R. A., S4.Ruhoff, 3. R., 16.Rundle, R. E., 54.Ruoff, P. M., 222.Rusanov, A. K., 274.Rusk, H. A., 271.Ruska, H., 110.Russ, H., 213.Russell, W. C., 266.Ruzicka, L., 187, 188, 189,190,192,193,194,195,197,198,199,200,201,202,203,204.106, 108.261.Rydon, H. N., 117.S&=if, (Frl.) G. von, 160.Sabetay, S., 283, 285, 286.INDEX OF AUTHORS’ NAMISaffer, C. M., 68.Sage, C., 53, 60.Sagenkahn, M., 51.St. John, (Miss) E. L., 141.St.John, (Miss) N. B., 141.Salceanu, C., 43.Salkind, J., 181.Salmon, W. D., 236.Salomon, A., 203.Salomon, G., 128.Salomon, H., 178, 221.Samans, C., 97.Ssmec, M., 169.Sampson, W. L., 237.Santlberg, C. R., 60, 62.Sandermann, W., 188.Sanderson, R. T., 65.Sandin, R. B., 147.Sandstrom, W. RI., 280.Sarett, H. P., 230.Sargent, B. W., 290.Sargent, H., 226.Sarginson, (Miss) K., 92.Sassaman, H. L., 266.Sastri, M. V. C., 31.Sattler, L., 280.Sawada, H., 102.Samires, Z., 18.Saxl, P., 246.Sazonova, T. V., 137.Schiifer, A., 219.Scharfenberg, C., 80.Schartau, O., 208.Schaumann, H., 14.Scheibe, G., 19, 22, 23, 27.Scheintzis, 0. G., 268.Schellenberg, H., 192, 195,Schenck, J. R., 241.Scherlin, S. &I., 144.Scheverdina, N.I., 149.Schicktanz, S. T., 278.Schildneck, P. R., 206.Schlesinger, H. I., 65.Schliichterer, E., 153.Schmeil, M., 222.Schmelkes, F. C., 224.Schmerling, L., 120.Schmid, H., 223.Schmidt, C. L. A., 240.Schmidt, J., 173, 181, 184,Schoch, T. J., 282.Schoenberg, M., 290.Schoenheimer, R., 239, ‘240,Schopf, C., 227.Schopp, K., 182.Schomaker, V., 54, 100.Schoorl, N., 269.Schubert, M. P., 72, 76, 216.Schutzenberger, P., 7‘3.Schulek, E., 268.Schulten, H., 71, 73, 75, 79.Schultz, A. S., ‘2‘29.Schultz, K., 188.203.185.341.307Schulz, W., 243.Schulze, G. E. R., 31, 93.Schumann, S. G., 54.Schumb, W. C., 67, 68, 136.Schur, J., 30,44.Schuster, P., 243.Schustova, M. B., 132.Schwarzenbach, G., 131.Schweitzer, C.H., 154.Schwenker, G., 247.Scott, A. F., 43.Scott, N. D., 147.Scudi, J. V., 266.Scull, C. W., 238.Seaborg, G. T., 87.Sears, W. C., 58.Sebe, K., 211.Sebrell, W. H., 230.Secher, K. J. A., 247.Seeley, M. G., 164.Seely, S., 43.Seide, 0. A., 144.Seidel, C. F., 187, 201.Seiler, M., 26.Seitz, G., 16.Sekito, S., 96.Selwood, P. W., 29, 45.Semichon, L., 277.Seshan, P. K., 24.She, P., 28.Sexton, B., 127.Shaffer, W. H., 58.Sharma, R. L., 37.Sharp, A. G., 222.Sharp, J. G., 241.Sharples, K. S., 195, 197.Shen, S. C., 242, 243, 247.Sheng, H. Y., 59.Sheppard, S. E., 25.Sherman, A., 16.Sherman, W. C., 232.ShihIs, M. E., 229.Shimizu, Y., 29, 31.Sh$gu, H., 20.Shmn, L. A., 279.Shreve, R. N., 144.Shriner, R.L., 222.Shulman, N., 139.Sibaiya, L., 29.Sideris, C. P., 272.Sidgwick, N. V., 65.Siegel, S., 93.Siegfried, B., 210.Sieve, B. F., 236.Silver, S., 58, 62.Simmonds, S., 241.Simms, H. D., 236.Simons, J. K., 139.Simpson, J. C. E., 195, 198.Singh, S., 71.Sivaramakrishnan, C., 48,45.Sizer, I. W., 253.Skeeters, M. J., 144.Skerrett, N. P., 59.Skinner, H. A., 103.Sklar, A. L., 15, 16308 INDEX OF AUTHORS' NAMES.Skudrzyk, I., 185.Slanina, S. J., 118.Slater, E. C., 228.Slater, J. C., 15, 34, 35.Slawsky, Z. I., 61.Slobodin, J. M., 181.Slotin, L., 260, 261.Sluys-Veer, F. C. van der,195, 197, 198.Smakula, A., 16, 17.Smedley, I., 172.Smith, A. M., 255.Smith, Alpheus W., 42.Smith, Alva W., 42.Smith, C.M., 149.Smith, E. B., 246.Smith, E. L., 267.Smith, F., 151, 155, 159.Smith, G., 263.Smith, G. F., 269.Smith, H., 92, 93, 94.Smith, H. A., 16.Smith, J. M., 218.Smith, L. G., 57, 59.Smith, L. I., 148, 149, 220,221, 222.Smith, R., 132.Smith, T., 257.Smyth, C. P., 22, 137, 138.Snell, C. T., 235, 272.Snell, E. E., 230, 235, 237,Snell, F. D., 272.Snow, G. A., 232.Sober, H. A., 229.Sodomann, H., 42.Sohngen, 258.Sogn, H., 39.Solianikova, V. L., 266.Solms-Laubach, 214, 262.Solomon, A. K., 261.Somerville, J. C., 153, 154.Somogy, M., 271.Son6, T., 45.Soper, H. R., 192, 201.Soutar, T. H., 154.Sowa, F. J., 118, 119.Spacu, P., 80.Spiith, E., 123, 223.Spatz, S. M., 146.Spedding, F. H., 14.Spencer, J. F., 29, 37, 43.Speyer, E., 71.Spinks, A., 175.Spinks, J.W. T., 70.Spitzer, W. C., 125.Spoerri, P. E., 215.Sponer, H., 53, 67, 63.Sprague, R. H., 22.Spring, F. S., 193, 195, 196,197, 198, 202,203, 204.Springall, H. D., 61, 107.Sprouls, W. R., 139.Sriraman, S., 30,38, 43.Stacey, M., 153, 166.Stahly, G. L., 278.251, 265.Stahmann, M. A., 223.Stainer, C., 277.Stand, C. J., 26.Stare, F. J., 229.Starkey, E. B., 144.Steadman, L. T., 274.Stedman, E., 207.Steele, W. I., 278.Steiger, (Miss) M., 221.Stein, G., 193, 201.Stein, W. H., 257.Steinmetz, H., 205.Stephen, H., 183.Stephenson, M., 269.Stern, C., 246.Sternbach, L., 188, 189,Sternfeld, E., 177.Steurer, E., 170.Stevens, J. R., 220.Stevens, R. E., 268.Stevenson, D.P., 54, 55, 63,Steward, F. C., 274.Stewart, C. P., 232,233.Stewart, D. W., 84.Stewart, W. S., 249.Stickland, L. H., 259.Stinchcomb, G. C., 69.Stitt, F., 50, 54, 57, 61.Stock, A., 67.Stokes, A. R., 95.Stokstad, E. L. R., 251.Stoner, E. E., 28, 35.Straitiff, W. G., 256.Straley, J. M., 141.Strasser, O., 19.Straub, G. J., 265.Strecker, W., 270.Strepkov, S. M., 279.Strong, F. M., 265.Stuart, A. H., 218.Stubbs, A. L., 19.Stucklen, H., 14.Stuhlmann, H., 77.Sturdivant, J. H., 227.Subramaniam, K. C., 31,Succhorukova, N. K., 279.Sugden, S., 28.Sugita, T., 29.Summerbell, R. K., 220.Sumner, J. B., 253.Sure, B., 236.Sutcliffe, F. K., 221.Suter, H., 128.Sutherland, G. B. B. M., 56,58, 60, 61, 63, 64.Sutton, L.E., 46, 103.Svigoon, A. C., 142, 144.3waminathan, M., 266.Swaney, W. M., 144.3wartz, S., 139.Sykea, C., 91, 97, 99.Szent-Gyorgyi, A., 242, 247.Szlatinay, L., 268.190.100, 103.38.Ta You Wu, 53,62.Taeuffenbach, G. v., 209.Takahashi, H., 264.Takkuchi, T., 29.Talaleva, T. V., 145.Tallman, R. C., 139.Tananaev, I. V., 272.Tarbell, D. S., 123, 124.Tarbutton, G., 70.Tartter, A., 227.Tarver, H., 240.Tate, F. G. H., 275.Taylor, A., 96.Taylor, A. M., 12.Taylor, A. W. C., 10.Taylor, F. L., 149.Taylor, H. S., 87.Taylor, T. I., 85.Ta lor, W. H., 105, 108.Tciakirian, A., 143,270.Teal, G. K., 85.Telfair, D., 51.Teller, E., 55, 63.Teltow, J., 12.Terrey, H., 27.Terry, R. C., 286.Teterin, V., 181.Thayer, S.A., 207.Thode, H. G., 39, 84.Thomas, L. H., 62.Thompson, A. F., 181, 183.Thompson, H. W., 11, 50,61, 53, 54, 55, 56, 57, 59,61.rhompson, J. M. C., 39.rhomson, S., 231.l'horpe, J. F., 116.rhorpe, (Sir) T. E., 275.L'ichomarov, V. M., 271.Fincker, M. A. H., 248.ripson, R. S., 163.rischtschenko, V. E., 285.Mshler, M., 221.ritani, T., 85, 86.L'odd, A. R., 211, 212, 213,Codd, D., 193, 200.rodrick, A. T., 242.fopel, T., 147.romita, T., 256.rongeren, W. van, 267.Coonder, F. E., 136.rorok, T., 274.roussaint, N. F., 119.Cown, B. W., 256.Come, E. B., 140.b c y , (Miss) A. H., 224.hves, F., 269.Creibs, A., 205.Crenner, N. R., 267.Crew, (&a) V. C. G., 29, 34,35, 37, 38, 40, 43.Crischmann, H., 173.Cristram, G.R., 266, 256.Crivelli, G., 172.h u t , W. E., 81.221, 222, 261, 262INDEX OF AUTHORS’ NAMES. 309Tschirch, A., 214.Tseou, H. F., 160.Tucker, H. F., 240.Tucker, S. H., 217.Tuli, G. D., 31,42.Tuot, M., 148.Tudtt, G. E., 249.Turkevich, J., 15.Turner, E. E., 107, 127.Tuttle, W. T., 14.Tyson, G. N., 46.Tytell, A. A., 253.Ubbelohde, A. R., 147.Uhle, F. C., 220.Uhlenbeck, G. E., 58, 289.Ullner, 0. E., 95.Umhoefer, R. R., 220.Ungnade, H. E., 220,222.Unna, K., 237.Urey, H. C., 83, 84, 85.Usmani, I. H., 101.Uzel, R., 270.Vaidyanathan, V. I., 30,37.Van Campen, J. H., 148.Vance, J. E., 55.Vandenbelt, J. M., 266.Van Duyne, F. O., 230.Van Ess, P. R., 149.Van Giffen, H. J., 283.Van Os, D., 284.Varadachari, P.S., 28, 30,Vaughan, W. E., 16.Veiel, V., 35.Vennesland, B., 261.Verhoek, F. H., 132,134,135.Verma, M. J., 42.Vernon, C. C., 137.Vetter, H., 75.Vickerstaff, T., 196.Vincent, W. B., 104.Vinti, J. P., 37.Vivian, R. E., 46.Vleck, J. H. van, 15, 28, 35.Vocke, F., 188.Vogt, R. It., 119.Volotschneva, E. P., 272.Vorliinder, D., 178, 183.Vorodez, N., 132.43.Wacek, A. von, 220.Wads, M., 256, 274.Wade, N. J., 236, 241.Wagner, J., 60, 62.Wagstaffe, F. J., 59.Wahrhaftig, A., 64.Waisman, H. A., 237, 266.Wakeman, A. J., 254.Waksman, S. A., 263.Walden, G. H., 106.Waldachmidt-Leitz, E., 169.Walker, B. S., 273.Walker, F., 242.Walker, J. F., 147.Walker, M. K., 14.Walker, O., 178.Walker, 0. J., 10, 26, 27.Walker, R.D., 25.Wallbaum, H. J., 95.Wallenfels, K., 178, 183, 184,186, 208.Waller, I., 93.Waller, R. C., 14.Wallis, A. E., 81.Wallis, E. S., 121, 122, 123,Walsh, A. D., 14.Walter, G. F., 17.Walton, E. T. S., 287.Wang, S., 209.Wang, T., 255.Wang, Y. L., 228,230.Wang, Y. T., 150.Warburg, O., 243.Wardlaw, W., 71.Warner, J. C., 128.Warsila, H., 132.Wassermann, A., 17.Watkins, (Miss) G. M. C., 43.Wawzonek, S., 220, 221, 222.Weber, H. H., 248.Webley, D. M., 229.Weichselbaum, T. E., 271.Weinhouse, S., 141.Weiss, P., 34.Weissberger, A., 123.Weissman, N., 240.Weissman, S. I., 14.Welch, A. D., 236.Weller, S. W., 124.Wells, A. F., 99, 104.Wells, A. J., 51, 59.Wendler, N. L., 221.Wenig, K., 230.Werkman, C.H., 259, 260,Wertheim, M., 170.Wertyporoch, E., 118, 120.Wessely, F. v., 209.West, T. F., 286.West, W., 60.Westgren, A., 95, 97.Westheimer, F. H., 125, 131,Whale, W., 281.Whalley, H. K., 274, 275.Wheland, G. W., 125, 132.Whitby, G. S., 256.Whitcomb, S. E., 62.White, A., 246.White, A. H., 101.White, E. C., 263.White, F. L., 25.White, W. R., 143, 200.Whitmore, F. C., 123, 139,Whitney, A. G., 222.124.278.132.147, 148.Wibaut, J. P., 147, 224.Widdowson, E. M., 234.Widiger, A. H., 126.Wiedemann, O., 172, 179.Wieland, H., 227.Wieringa, K. T., 258.Wiig, E. O., 87.Wilcox, L. V., 270.Wild, F., 181.Wildiens, E., 237.Wilkie, J. B., 265.Wilkins, J. P., 123.Willard, H. H., 269, 271.Willenz, J., 123.Williams, G., 107, 217.Williams, R. J., 235,237,252.Williams, R. R., 229, 237.Wills, A. P., 28,29.Wilson, A. J. C., 91, 98.Wilson, E. B., 48, 51, 59, 62.Wilson, J. B., 277.Wilson, M. F., 273.Wimmer, C. P., 284.Windbladh, R., 276.Windsor, M. M., 76.Winslow, A. F., 68.Winstein, S., 139.Winter, E. R. S., 85.Winterstein, A., 183, 184,185, 186, 193, 201.Wirsching, A,, 77.Wirz, W., 192, 193.Wiswall, R. H., 137.Witmeyer, J. R., 130.Wittig, G., 146, 179, 183, 185.Wittle, E. L., 147.Woelfel, W. C., 273.Wohl, A., 118.Woldan, E., 172.Wolf, D. E., 148.Wolf, H., 71.Wolf, K. L., 19.Wolf, P. A., 239.Wolfe, J. K., 267.Wolfrom, M. L., 168.Womack, M., 238.Wood, H. G., 259,260.Wood, R. G., 107, 217.Wood, W. A., 99.Woodbridge, D. B., 31.Woodruff, H. B., 263.Woodward, (Miss) I., 95, 106,Woodward, R. B., 18, 286.Wooley, J. G., 230.WoolIey, D. W., 237,251.Woolley, J. M., 166.Wooster, C. B., 139.Wooten, L. A., 132, 133, 134,Work, R. W., 136.Work, T. S., 221, 222.Wright, G. F., 144, 148.Wright, H. R., 182.Wright, L. D., 230.Wright, N., 57.108.135310 INDEX OF ATTTHOM’ NAMES.Wrinch, D., 63.Wu, C. K., 58.Wulf, 0. R., 11, 64.Wynne, A. M., 285.Wynne-Jones, W. F. K., 118,129, 130, 131, 132.Yablunky, H. L., 142, 143,144, 145, 147.Yabroff, D. L., 132.Yamaguti, K., 207.Yang, E. F., 234.Pap, K. S., 221.Yoe, J. H., 277.Yost,, D. &I*, 60,51,54,66,88.Young, D. P., 121.Young, E. T., 64.Young, G. T., 167, 168.Young, R. V., 140.Young, W. C., 149.Yudkin, S., 232.Zachariasen, W. H., 93.Zartman, W. H., 139.Zbinden, C., 236.Zeidler, F., 67.Zerban, I!. W., 280.Ziesel, S., 172.Zilva, S. S., 231, 232.Zimmerli, A., 266.Zimmermann, J., 192.Zonis, S., 181.Zumwalt, I,., 56, 57, 64

ISSN:0365-6217    

DOI:10.1039/AR9413800298

出版商:RSC    

年代:1941

数据来源: RSC