RESEARCHES ON BESI1)UAL AFFINlTY AND CO-ORDINATION. 189XX I V.-Reseawhes on Residual Aflizity and Co-ordi-nation. Pwt I. Metallic Acetylacetones an cltheii- Absorption Spectra.By GILBERT T. MORGAN and HENRY WEBSTER Moss.THE remarkable properties exhibited by many metallic acetyl-acetones, their non-ionisable character, their solubility in anhydrousorganic solvents, their stability on heating, and, in certain instances,their anomalous colours, have led to the view that in these com-pounds the metallic atoms are combined with the unsaturatedorganic complex, not only through their principal valencies, butalso by means of their residual affinity or auxiliary valency. More-over, as the univalent organic complex (formula I) consists of anopen-chain of five atoms, its intimate association with the metal isassumed to arise from the general tendency to form six-memberedrings (formula II), the metallic atom serving as the connecting linkbetween the ends of the organic group :y 3 3 ( p 3c,H<c: F-0- 0.* --+ CH<!:;>M~CH, CH3(1.1 (11.1Jii,fliLctice of Syitimetry O I L the 8tubilit,y of HetulEic Acetylucetones.The acetylacetone radicle (I) being univalent, the number ofthese groups co,rnbining with a metallic atom will depend primarily011 the principal valency of this atom, and as each acetylacetonegroup is equivalent to two associating units it follows that theacetylacetones of univalent, bivalent, tervalent, and quadrivalentmetals will be characterised respectively by a molecular arrange190 MORGAN AND MOSS: RESEARCHES ON RESIDUALment of two, four, six, and eight pointa on the sphere of influenceof the metallic atom.Of these arrangements the last two will probably correspondwith the octahedron and the cube. The second cam may corre-spond with the tetrahedron, or alternately the molecule may havethe less symmetrical plane configuration.The first case, that oftwo points on the sphere, cannot in the circumstances be a sym-metrical arrangement. I n an earlier communication (T., 1913,103, 81) the authors advocated the view that co-ordination is duenotl only to the residual affinity of the central atom, but also tothe mutual attractions of the associating units, and, this hypothesisbeing accepted, thO most stable systems will be those in which theforces interacting between the associating units are symmetricallydistributed, a condition which is satisfied by arranging these unitssymmetrically round the sphere of influence of the central atom.Acetylacetones of Univaleiat Metals (Formula II).-On the fore-going assumption, these compounds should manifest their want ofsymmetry by their instability.Lithium and thallous acetylacetoneare the most stable members of this series, an'd both are decom-posed on heating, the latter at 160° (Kurovski, Ber., 1910, 63,1078). The sodium, potassium, and czesium acetylacetones charon heating, and are unstable in solution or in a moist condition.They are decomposed by hot water into acetone and alkali acetate(Comb-, Compt.rend., 1887, 105, 871). Silver acetylacetonedecomposes spontaneously a t the ordinary temperature, with theliberation of silver.This summary of the properties of the acetylacetones of univalentmetals justifies the contention that dissymmetry leads to instability.Acetylacetones of Bivalent Metals.-The compounds of this series,which may possess either a tetrahedral (formula 111) or a plane(formula IV) configuration, are on either alternat'ive more sym-metrical than the acetylacetones of univalent metals. They alsodisplay a higher degree of stability.The acetylacetones of the metals of the second periodic serieshave all been prepared; those of the alkaline earth metals are(111.) (1V.)dwidedly more stable than the correspondiug compounds of thealkali metals (Tanatar and Kurovski, J .Russ. Phys. C'hem. .Soc.AFFINITY AND CO-ORDINATION. PART 1. 1911906, 40, 580). Glucinum and zinc acetylacetones can be distilledwithout decomposition, the former under atmospheric, and the latterunder reduced pressure (Combes, Compt. rend., 1894, 119, 1222;Tanatar and Kuroveki, Zoc. cit.):The following metals functioning as diads have also yielded stableacetylacetones : copper, lead, iron, cobalt, nickel, and platinum(Combes, Compt. r e d . , 1887, 105, 868; Gach, Monatsh., 1900, 21,98; Werner, Ber., 1901, 34, 2584).The bivalent radicles, vanadyl, VOII, and uranyl, UOZI, havefurnished stable acetylacetones, which may be of this type (T., 1913,103, 86; Biltz, Zeitsch. anorg. Chem., 1904, 40, 221).From the ease with which the acetylacetones of bivalent metalsform stable additive compounds (Biltz, Zoc. cit.; Werner, Zoc. cit.)of the type RI1Ac2,2X having the co-ordination number 6, and con-sequently an octahedral symmetry, it is probable, although it doesnot necessarily follow, that these acetylacetones themselves havethe plane configuration (formula IV).Acetylacetones of TervaZent Elements.-The cam of boron is ofgreat interest; this element resembles carbon in having a verysmall atomic volume, and probably on this account it also resemblescarbon in having a maximum co-ordination number 4, as exhibitedby fluoboric acid, H(BE’,), and its salts. Boron accordingly =so-ciates only with two acetylacetone radicles, and the products havethe general formula [BAc,lX, where X is an ionisable radicle(Dilthey, AnnaleiL, 1905, 344, 326).The acetylacetones of the tervalent metals, which are the moststable examples of tmhis class, undoubtedly possess the octahedralsymmetry, although they have not yet been resolved into theirenantiornorphous components (compare T., 1913, 103, 84). Alumin-ium and indium acetylacetones can be distilled (Combes, Compt.rend., 1S89, 108, 405; Chabri6 and Rengade, ihid., 1900, 181,1300), and vaporisable acetylacetones of tervalent vanadium,chromium, manganese, iron, and cobalt have also been prepared(T., 1913, 133, 85; Urbain and Debierne, Compt.rend., 1899, 129,302). Many members of the rare earth metals (lanthanum, sama-rium, neodymium, praseodymium, and tervalent cerium) haveyielded fairly stable acetylacetones (Hantzsch and Desch, ibid.,1902, 323, 26; Biltz, Annalen, 1904, 331, 334), and the scandiumcompound can be distilled without decomposition.The behaviour on heating of this group of acetylacetones justifiesthe contention that a symmetrical arrangement of associating unitsconduces to stability.-4 cetylucetones of Quadrivalent Metals.-These compounds, whichcorrespond with an arrangement of eight associating units round192 MORGAN AND MOSS: RESEARCHES ON RESlDUALthe central atom, have in all probability a cubic symmetry, andshould be resolvable into two stereoisomeric non-enantiomorphouscomponents (V and VI):\;4c t\iFour cf these compounds are now known, namely, thorium,zirconium, ceric and uranous acetylacetones (Urbain, BdZ.SOC.chim., 1896, [iii], 15, 338, 347; Biltz, Zeitsch. anorg. Chem., 1904,40, 219; Job and Goissedet, Compt. r e d . , 1913, 157, 51).Residual Afinity of Metallic Acetplacetones : Additive Compounds.The additive cornpounds of metallic acetylacetones with water,alcohol, ammonia, or organic bases may be divided into two classes:the more stable additive compounds in which addition is accom-panied by an increase of symmetry, and an unstable class, in whichthe addition decreases the symmetry. The acetylacetones ofbivalent metals furnish the best examples of the first class, for theycombine additively with two molecular proportions of alcohol,ammonia, or organic amine, yielding in general compounds havingthe general formula, M11Ac2,2X, where X may be water, alcohol,ammonia, pyridine, or aniline (Tanatar and Kurovski, Zoc. cit.;Biltz, Zeitsch. anorg. Chem., loc. cit.). Whether the acetylacetones,M1*Ac2, have the tetrahedral or the plane configuration (formulaI11 and IV), there can be little doubt that the additive compoundshave the octahedral symmetry.The unstable additive compounds are formed by the combinationof ammonia or an organic &mine with acetylacetones of the metalsof the rare earths, including thorium; the products have the generalformula 2M*IAc3,NH3, 3MrIfAc,2NH,, and 2ThAc,,NH, (Biltz,A4?maZen, loc. cit.). It is noteworthy that the acetylacetones whichcombine in this way with ammonia also ma<nifest their residualaffinity by forming complex molecules, (MIIIAC~)~, in solution.Scandium acetylacetone, the most stable, compound of the series,lleither combines with ammonia nor exhibits association in organicsolvents, in this respect resembling aluminium acetylacetoneAFFINITY AND CO-ORDINATION.PAHT I. 193Yhe Structure of the Organic Cornpiex in the Metallic,4 ce t ylace tones.Compounds resembling the metallic acetylacetones have beenobtained with benzoylacetone, acetylmethylacetone, ethyl aceto-acetate, acetyl mesityl oxide, and numerous other 8-diketones and8-keto-esters. These substances and their metallic derivatives maybe represented by either of the formulz VII and IX, from whichit will be seen that structural isomerism is possible if the arrange-ment is regarded as static in either case, but inasmuch as a t presentthere is no experimental evidenca that isomerism of this kind existsamong these compounds, it is much more likely that these twoformuh are analogous to the two phases of KekulB’s benzeneformula.The configuration of the metallic acetylacetones andtheir analogues may oscillate between these two extreme positions,or a rearrangement may lead to an intermediate centric distributionof the chemical affinities corresponding with the Armstrong-Baeyercentric formula for benzene and its homologues. This arrangementis indicated by the formula VIII:0 0 0//CH,*C\ /H( Al‘)1 :CH,*C: H(31’)HC 6/I .. .I/\1 1 nc 0CH,*C H(iU’)--L7--1-7- HC’,\O\/C \I/ C\/CR it it(VII.) (17111.) UX.1When R=CH,, a6 in acetylacetone and its metallic derivatives,the organic complex in formula VIII becomes symmetrical on eitherside of the metallic radicle MI, and, if this symmetry exists in themolecule, the acetylacetones of bivalent metals would not be resolv-able into enantiomorphs, even although possessing the tetrahedralconfiguration indicated by formula 111.An examination of the absorption spectra of fourteen acetyl-acetones shows that, with the exception of the chromium compound,which has two bands, they all exhibit one absorption band like theparent diketone itself.The character of the absorption is notmaterially altered by substituting the benzoylacetone for the acetyl-acetone complex (T., 1913, 103, 89).Neither is any change effectedby substituting methyl for the hydrogen attached to the a-carbonatom in formula VII, VIII, or IX, as is done by the use of acetyl-methylacetone instead of acetylacetone. The absorption band, whichchazacterises this whole series of P-diketones and their metallicderivatives, is certainly not due to any oscillatory migration ofVOL. cv. 194 MORGAK AND MOSS: ICESEARCHES OK RESIDUALlabile hydrogen from its carbon attachment to an enolic combinationwith oxygen, for in the case of vanadyl bisacetylmethylacetone theband persists ev'en when both labile hydrogens have been sub-stituted, one by methyl and the other by vanadyl (T., 1913, 103,90).EXPERIMENTAL.Acetylacetones of Uniualent M e t a l s .O*C(CH 3)Lithium Acetylacetone, LiLithium carbonate does not react to any appreciable extent withacetylacetone in dilute alcohol, even after prolonged boiling.Lithium oxide, prepared by igniting lithium nitrate, was boiled ina reflux apparatus for two hours with acetylacetone in 60 per cent.alcohol.The filtered solution on concentration yielded acicularcrystals of lithium acetylacetone, but the yield was not good, asmuch of the oxide remained undissolved. A solution of lithiumhydroxide, prepared by boiling aqueous lithium carbonate withfresh lime (from calcite) in a nickel basin for two hours, was filteredthrough asbestos, and treated whilst warm with excess of acetyl-acetone, when, after concentrating, several crops of crystallinelithium acetylacetone were obtained :0.3508 gave 0.1 724 Li,SO,.Lithium acetylacetone chars on heating, without exhibiting anydefinite melting point.When pure the compound is colourless,but its alcoholic and aqueous solutions soon become yellow, owingto the decomposition of the organic complex by the alkali set freeby hydrolysis. It dissolvw readily in water, sparingly in cold, morefreely in hot alcohol, and is insoluble in benzene or chloroform.Caesium acetylacetone, a colourless, crystalline substance, wasproduced by the interaction of cesium hydroxide and acetylacetonein alcoholic solution, the filtered solution being concentrated underdiminished pressure a t the ordinary temperature until the productseparated. (Found, Cs= 59.81. C,H702Cs requires Cs= 57.33 percent.) The compound is very soluble in water or alcohol, andattempts to purify it by repeated crystallisation led to decomposi-tion.It charred on heating, and had no definite melting point.Silver -4 cetylacetone.-Interaction between silver nitrate andacetylacetone in aqueous or aqueous-alcoholic solution generally ledt o the production of a silver mirror. The compound was obtained asit white, granular mass by shaking freshly prepared moist silveroxide in the cold with excess of acetylacetone. The productrapidly blackened on exposure ; i t was sparingly soluble in water,Li = 6-27.C,H,O,Li requires Li = 6.55 per centAFFINITY AND CO-ORDINATION. PAKl‘ I. 195but the solution was unstable, generally depositing the silver as amirror.Thallous acetylacetone (compare E.Kurovski, Uer., 1910, 43,1078).-Interaction between thallous hydroxide and acetylacetone inaqueous solution gave rise to a basic product crystallising fromalcohol, which even after recrystallisation contained approximatelyone molecular proportion of thallous hydroxide combined with thenormal acetylacetone. The normal compound wm prepared byisolating thallous hydroxide, obtained by the double decompositionof thallous sulphate, and crystallised barium hydroxide ; the yellow,acicular crystals were dissolved in alcohol containing acetylacetone,and the solution concentrated a t the ordinary temperature underdiminished pressure. Thallous acetylacetone separated in well-defined, colourless, flattened needles and flakes, very soluble inwarm alcohol; it melted sharply, and decomposed a t 1 5 3 O ..Acetylacetones of B i v a l e n t H e t a l s (compare Tanatar andKurovski, J .Buss. Phys. Chem ~SOC., 1908, 40, 580).Ca.lcaurn acetylacetone, Ca[\o.C(C,3)~CH] ./O :C( CHJ \ , prepared by theinteraction of aqueous carcium hydroxide and alcoholic acetyl-acetone, crystdlised in needles, and was freed from water of crystal-lisation by drying in a vacuum desiccator over sulphuric acida t 60°:0.4134 gave 0.2442 CaSO,.The calcium compound had no definite melting point, but charredCa = 17.37.CloH1404Ca requires Ca = 16.80 per cent.on heating. -Barium acetylacetone, Ba >CHI , prepared by dis-solving crystallised barium hydroxide in warm water and boilingwith alcoholic acetylacetone fir a few minutes; the filtrate yieldedthe compound in nacreous flakes and plates, the yield being practi-cally quantitative.The dihydrated acetylacetone (Found, Ba =36.47. Calc., Ba=36.92 per cent.) was dehydrated in a vacuumover sulphuric acid a t 60°:0.7350 gave 0.5053 BaSO,.The compound charred on heating.xiiu ucetyltrcetone, Zn < 0 : C ( C H 3 b ~ ti , iorrrierly describedas a yellow compound (Tanatar and Kurovski, loc. cit.), wasobtained in well-defined, colourlw needles by boiling zinc hydroxidewith aqueous acetylacetone, and allowing the filtrate to cool :0 2Ba = 40.46.C,,H,,O,Ba requires Ba = 40.89 per cent;.[ O*C(CH,)’ 1196 MORGAN AND MOSS: RESEARCHES ON RESIDUAL0.1385 gave 0.0435 ZnO.Zinc acetylacetone melted to an opaque, white liquid a t 138O.Cadmium acefylacetone, which is much less soluble than its zincanalogue, was prepared by digesting cadmium hydroxide withexcess of aqueous acetylacetone, and also by double decompositionfrom cadmium acetate and sodium acetylacetone :Zn= 25-20.CloH1,O4Zn requires Zn = 24-81 per cent.0.5084 gave 0.3402 CdSO,.Cl,HI,O,Cd requires Cd = 36.21 per cent.llejrcuric acetylacetone was obtained by mixing equivalmtamounts of mercuric chloride and sodium acetylacetone in aqueoussolution; it separated at once as a sparingly soluble, granular, whiteprecipitate.When mercurous nitrate was employed in this reaction, partialreduction occurred, the precipitate containing mercury and mercuricacetylacetone.Copper acetylacetone was prepared by the inter-action Of cupric chloride, acetylacetone, and aqueous sodiumacetate, the powdery, pale blue precipitate crystallising from chloro-for= in deep violet-blue needles. This compound dissolved inquinoline, and the solution on cooling deposited green crystals ofan additive compound.Cd = 36.08.A c e t y lace tomes o f T erval e n t M e t a h .Scandium A cetylacetome, Sc[ <0:C(CH3)>CH O*C(CH 3)R. J. Meyer and Winter, Zeifsch.. anorg. Chem., 1910, 67, 398).For the scandia employed in the following experiments, theauthors are indebted to Sir William Crookes, and tender their bestthanks. The oxide (1.0164 grams) was covered with pure concen-trated nitric acid, and digested f o r about four hours on the steam-bath.The product was syrupy scandium nitrate with about 6 percent. of undissolved oxide. After dilution with water and filtration,the solution was digested in a reflux apparatus with a moderateexcess of acetylacetone and ammonia in the presence of benzene.The organic solvent removed quantitatively the scandium acetyl-acetone from the aqueous solntion, and after concentration depositedcolourless plates of scandium acetylacetone. The substance waspurified by dissolving in benzene, in which it was readily soluble,and precipitating with light petroleum, when it separated in colour-less needles. From chloroform, scandium acetylacetone crystallisedin colourless, square plates, and it also separated from alcohol insimilar, colourless, acicular prisms.The mother liquors f rom thesAFFINITY AND CO-ORDINATION. PART I. 197crystallisations become yellow, and on warming evolved an odourresembling that of p-benzoquinons :0.1985 gave 0.0402 Sc,O,. Sc = 13.14.0.2520 ,, 0.0525 Sc,O,. Sc=13.15.( a ) 0-1186 gave 0.2264 CO, and 0.0755 H,O. C=52.14 ; H = 7.08.( b ) 0.1228 ,, 0.2340 CO, ,, 0.0728 HZO. C=51.95; H=6*58.C,,H210,Sc requires Sc= 12.90 ; C = 52-78 ; H = 6-15 per cent.The preparations used in the foregoing analyses were purifiedby crystallisation (a) from benzene and light petroleum, ( b ) fromalcohol. When dried a t the ordinary temperature these prepara-tions melted somewhat indefinitely from 177O to 1 8 7 O . The indefi-niteness of the melting points of acetylacetones .of other metals ofthe rare earths was previously commented on by Biltz ( A ~ z n a l : ! ~ ~ ,Zoc.cit., p. 349). Comparative experiments on the distillation ofthe acetylacetones of scandium and thorium showed that scandiumacetylacetone was the more stable a t temperatures near its meltingpoint.Volatility of Scandium A cety1acetone.-Recrystallised specimensof this compound dried a t SOo were heated in small tubes placedin a metal bath, the pressure being reduced to 8-10 mm. A t 157Othe substance began to sublime appreciably, and condensed on thecooler parts of the tubes in small, well-defined, brilliant, colourleescrystals of cubical form. The sublimation proceeded smoothly untilthe melting point ( 1 8 7 O ) mas reached, when the distillation wasrapidly completed.The purified specimens, as prepared foranalysis, sublimed completely below the melting point, and leftno non-volatile rmidue. There was no charring, and the sublimedcontents of the tubes had no d o u r of acetylacetone or other organicmaterial.Sublimed scandium acetylacetone melted sharply a t 187-1873O.Under atmospheric pressure very little scandium acetylacetonedistilled below 190° ; colourless crystals sublimed from 210° to 250O.At 260° the sublimate showed a yellow tinge, but even a t 360°very little decomposition was noticed.Thorium acetylacetone, purified by crystallisation and throughits ammonia additive compound (Biltz, Zoc. cit.), melted at 168-169O(Urbain gives 171-172O, Bztll.SOC. chim., 1896, [iii], 15, 338).When heated under 8-10 mm. pressure it began to sublime a t160° in colourless crysfals, closely resembling those of the scandiumcompound. Very little volatilisakion occurred below the meltingpoint; the compound boiled a t about 260-270°, and the condensedsolid showed a faint yellow tinge.Under the atmospheric pressure very little thorium acetylacetonesublimed below 210O. At 250° the distillate was yellow, and onl198 MORGAN AND MOSS: RESEARCHES ON RESlDITAT,partly solid. At 260° further decomposition occurred, and a brown,charred residue remained.These comparakive experiments showed that scandium acetyl-acetone could be distilled under atmospheric pressure withoutdecomposition, whereas in similar circumstances the thoriumcompound underwent considerable decomposition.Molecular-weight determinations by the ebullioscopic methodshowed that scandium acetylacetone did not undergo associationin boiling chloroform or benzene:0.074 in 20.00 CHC1, gave At=0.039. M.W.=347.0.1016 ,, 12.40 ,, At=0*060.M.W.=312.Sc(C5H,02), requires M.W. = 341.The acetylacetones of tervalent chromium, iron and cobalt wereprepared by the general method (Urbain and Debierne, Compt.mnd., 1899, 129, 302), and for the purpose of comparison the corre-sponding compound of bivalent cobalt was also obtained (Gach,Monatsli., 1900, 21, 98).Ulf,*a-violet A bsorption Spectra of Metallic A cetylacetone.The compounds were dissolved in absolute alcohol to N / S O O O -solutions, and examined in thicknesses of 1.6, 2.5, 4.0, 6.3, 10*0,20.0, 31.6, 50.1, and 100.0 mm.with a one-prism Hilger spectro-meter and an iron arc. In Fig. la the absorption curve of lithiumacetylacetone (unbroken line) is compared with that of acetylacetoneitself (dot and dash line). The two curves are closely coincident,but the band of the lithium compound is less persistent than thatof the parent B-diketone. This comparison is of interest becausenext to hydrogen, lithium is the element of least atomic weightavailable for the purpose of these comparative experiments.On Fig. 2a the absorption curve for thallous acetylacetone isshown by the broken line (dash and two dots). The metal in thiscompound has the high atomic weight of 204, and functions as aunivalent element.The absorption band is as persistent as thatof the lithium compound, but is decidedly narrower.The third curve on Fig. l a (dotted line) representing the absorp-tion band of copper acetylacetone is remarkably like the absorptionof vanadyl bisacetylacetone (T., 1913, 103, SS), the band beingequally persistent, but shifted towards ths more refrangible end ofthe spectrum.The five curves of Fig. 16 are those of certain bivalent metalsof the second vertical series of the periodic classification. Thecalcium acetylacetone curve (unbroken line) has an absorption bandwith its head a t l / h 3500; the barium acetylacetone curve (dasAFFINITY AND CO-ORDINATION. PART I. 199and two dots) has a wider, shallower absorption band, with its headat l / h 3650.The zinc acetylacetone curve (dotted line) and theF I G . la.Oscill&n~ ~?Y?q26ellCiCS.Lithium ncct?jImelone --Copper _ . - - - - - - - -Acely lncetonl: _ _ _ - _ - - $ 92400 6 8 3000 2 4 6 8 4000 2 420181614cadmium acetyIacetone curve (dot and dash) are closely coincident,but the former has the deeper band. The mercuric acetylacetonecurve (dash and three dots) shows a shallower band than those du200 RESEARCHES ON RESIDUAL AFFINITY AND CO-ORDTNATION.to zinc and cadmium, with a decided shift towards the more refrang-ible end, the bands being situated as follows: Zn 1/h 3550,Cd 1/ A 3500, and HgII 1 / h 3700.FIG. 213.Oscillnt ion fmqueitcics.Scandium nectglncetone --Thnllous ,,Ytlriicm ,, _ _ _ - _ _ _ _ _ _- - _ - - - -2400 6 8 3000 2 4 6 8 4000 2 4Fig. 2b show3 the absorption curves of the acetylacetones ofchromium (unbroken line), iron (dotted line), tervalent cobalt (dashand three dots), and bivalent cobalt (dash and two dots). The curvCHEMICAL EXAMINATION O F SARSAPARILLA ROOT. 201for the chromium compound is exceptional in showing two bands,the more refrangible being undoubt,edly the acetylacetone band,whereas that towards the red end is probably due to the metallicradicle.The curve for ferric acetylacetone shows a shallow band withhead a t l / h 3750. The curve for cobaltic acetylacetone, like thepreceding curve, exhibits a somewhat shallow band, the band forcobaltous acetylacetone being much deeper.The change from cobaltous to cobaltic acetylacetone involves ashifting of the band towards the more refrangible end, similar tothe change observed in passing from vanadyl bisacetylacetone tovanadium teracetylacetone (T., 1913, 103, 89), the heads of thebands being situated as follows:VOII 1 / h 3300 ; CoII 1 / h 3500.V1IX l / h 3600; CoIII l/h3600.Fig. 2a shows the absorption curves for scandium acetylacetone(unbroken line) and yttrium acetylacetone (dotted line) ; the twocurves are almost superposable, each exhibiting a strong band at1 / A 3450. The absorption spectrum of thorium acetylacetone, whichwas previously examined by Baly and Desch (T., 1904, 86, 1029;1905, 87, 766), exhibited a strong band a t 1 / ~ 3600.The authors desire to express their thanks to the Research GrantCommittee of the Royal Society for a grant which has partlydefrayed the expenses of this investigation.ROYAL COLLEGE OF ~ C I E N C ' R FOP, IRELAS'I~,DUBLIN