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?.IATIJEVIC AND
[CONTRIRUTION FROM
31. KERKER
CLARKSON COLLEGE OF
Vol. 81
TECHNOLOGY]
Heteropoly Compounds. IV.1-3 The Basicities of Some Heteropoly Tungstic and Molybdic Acids and the Charge of Their Anions4t5 BY E. MATIJEVI~ AND M. KERKER RECEIVEDJANUARY 9, 1959 The basicities of a number of heteropoly acids were determined by a spectrophotometric technique. T h e acids studied were 12-tungstosilicic, 12-tungstophosphoric, 9-tungstophosphoric, 6-mol~~bdocobaltic(III), 6-niolybdochromic(III) and 12-molybdoceric(IV). T h e method is based on the influence of the heteropoly acid upon the ionization of methyl orange, taking ionic strength effects into account. It gives conclusive results only if t h e state of agglomeration is known. This latter information was obtained by determining t h e charges on the heteropoly ions in solution using a coagulation technique. The following formulations are proposed : HkXWlzOro, H ~ P W I Z OH6P~~VI&, ~Z, H8C~Mo6011r H3CrMoa021 and H&eMolzOdr. The solubility product of silver 12-molybdocerate(IV) has been determined.
Introduction Although much has been written on the composition and strucutre of heteropoly compounds6 there is still a great deal of confusion in the literature on this subject. Various authors ascribe different formulas to the same compound. For example, for 12-tungstosilicic acid either HkSiLV120 4 0 or HBSiW12042,and for 12-tungstophosphoric acid, H3PLv12040 or H7P1$'12042 are given. This is true for almost any heteropoly acid or salt. T h e main reason for the discrepancies has to be sought in the rather complicated structure of the large heteropoly ion. Neither of the methods usually employed for such a structure deterxnination, quantitative chemical and X-ray analysis, give unambiguous results. Therefore, additional independent methods such as diffusion, basicity determinations, vapor pressure measurements, coagulation activity, light scattering, etc., have to he used in order to solve the structural problems of heteropoly compounds. The experiments have to be carried out in two directions: (a) to elucidate the state of aggregation, i.e., whether the ion is a monomer, dimer or possibly a polymer and (b) td determine the valency of the ion. In earlier papers we have eniployed light scattering1s3to determine the state of aggregation and coagulation2 to determine the charges of some heteropolytungstate ions. In the present paper we have extended the coagulation measurements to a number of heteropolymolybdate ions and in adclition have determined the basicities of the corresponding heteropoly acids using a spectrophoton:ecric method. The heteropoly ions investigated were: (a) l%tungstosilicate, (b) 12-tungstophosphzte, (c) 9-tungstophosphate, (d) G-molybdocob d t a t e ( I I I ) , (e) G-molybdochromate(III), (f) 12ii:olybdocerate(IV). In the case of 12-inolybdocerate(IV) the solubility product of its silver salt 117:~s ( 1 ) R l . Kerker, D. Lee and A. Chou, TIIISJoURixAL., 79, 3355 (1957). ( 2 ) E . RIatijeviC a n d h t . Kerker, J . Phys. Chem., 62. 1271 (1958). ( 3 ) E. MatijeviC a n d M. Kerker, Tms JOURNAL, 81, 1307 (1959). (4) Supported by t h e U. S. Atomic Energy Commission Contract h'o. AT(30-1)-1801. ( 3 ) Presented in p a r t a t t h e 134th meeting of t h e Anterican Chemical Society, Chicago, Ill., September 1958. ( t i ) Cf. Recent reviews in W. Hdckel, "Structural Chemistry of Inorganic Compounds," Elsevier, New York. S. Y . , 1 Wells, "Structiiral Inorganic Chemistry," Oxford University Press, S.Y., lY.50; J. C. Bailar, "Chemistry of t h e Coordination New York, i Compounds," Reinhold Pub. Corp., New Y o r k , N. Y.,1956; J. R. Van n'azer, "Phosphorus and its Compounds," Interscience P u l ~ i . New , York. N. Y . , 1YS8.
also determined. Our results are consistent with the following molecular formulas for the heteropoly acids: (a) H4SiW12040, (b) H7PW12042, (c) HsPzWISOP,~,(d) H3C01\106021, (e) H3CrMos021and (f) H~CeMo~20~~.
Methods 1. Spectrophotometric Determination of Basicity.--.\ spectrophotometric method was used in order to determine the basicities of the heteropoly acids. It is a modification of a procedure originally described by Klotz' and applied bv Singleterry,* consisting essentially in measuring the optic'il density of a methyl orange solution in the presence of variori; amounts of added acid. Klotz has derived the following equation for the indicator ratio
where for a given concentration of indicator, [ A - ] and [HA] are the equilibrium concentrations of the basic and the acid forms, log ( I " / I h ,and log ( I o / I )are ~ the optical densities (if the basic and the acid forms and log ( I o / I )is~ the optical density of the indicator at a n intermediate acidity. 01 i5 the degree of ionization. The dissociation of the indicator proceeds in the tnanrier
+
HA H .4The ionizntion coi15taiit can be written
so that combining with ( I ) , and taking
(2)
YA'YA-/YHA
=
f
K = [H+]Rf
(4) The concentration of indicator must he sufficiently low coinpared to that of the added acid so that [a+] is furnished 31most entirely by the latter. For a reference solution of known hydrogen ion concentration, [H+]o K = [H+lo Rofo (5) A t comparable ionic strengths, the ratios of activity coeficients are essentially the same, i.e., f = fo, and combin:itioii of equations 4 and 5 gives [Iin pH. The ammonium 9-tungstophosphate gave results similar to the m sodium salt which shows that a t low concentration the effect of ammo- + 0 0 6 5 nium hydrolysis is not significant compared to the tremendous electrostatic effects. Upon applying equation 6 to the 0 calculation of [H"], R and Ro must be compared both a t the same acidity (NH4I3 Cr M o 60ill LOG M O L A R CONC (NH~)~COMO~O~~ and the same ionic strength. HowFig. 3.-coagulation curves of ammonium 6-molybdochromate( 111) and amever, the influence of ionic strength monium 6-molybdocobaltate( 111) for a positive silver bromide sol in statu On Ra must be from the nascendi, 1, 10 and 60 minutes after mixing the reacting components curve in Fig. 1 corresDondinP to the charge typcof the acid being Tnvestiga ted. In prac- pected basicities of 7 and 8, respectively, have not tice, a first approximation of the basicity is obtained been obtained. by utilizing values of Ro in the absence of added salt. The downturn of the basicity curves for the triUsing the approximate basicity so obtained, it is basic acids (dashed part of the curve) a t low acid then possible, by successive approximations, to concentrations illustrates the failure of the method correct this result for the ionic strength effects. when the indicator is almost completely in the Figure 2 gives the basicities of the 12-tungstosilicic, basic form. Under these circumstances, the de12 - tungstophosphoric, 9 - tungstophosphoric, 6- termination of the indicator ratio R is inaccurate. molybdocobaltic(III), 6-molybdochromic(III) and As pointed out above, in order to extend the results 12-molybdoceric(IV) acids as obtained a t different to lower heteropoly acid concentrations, it would molarities of mentioned acids. be necessary to use an indicator of higher pK. Data obtained in the presence of HC1 are de- It is very probable, in such a case, that higher noted with half blackened signs. The consistency basicities for the 12-tungstophosphoric and 12of the method is brought out by the fact that al- molybdoceric acids would be obtained, since the dethough in the presence of HC1 one is working a t a gree of ionization would increase with dilution, as indifferent part of the R curve, the same basicities are dicated by the trend of the relevant curves in Fig. 2. Charge of Heteropoly Ions.-Figure 3 represents obtained. Since the results in Fig. 2 show that identical basicities are obtained in the presence and the coagulation curves of ammonium B-molybdoabsence of HC1, this is an additional indication chromate(II1) and ammonium B-molybdocobalthat no decomposition has taken place a t higher tate(II1) for positive silver bromide sols 1, pH's. We had previously shown that in the 10 and 60 minutes after mixing the components. region up to p H 6 these compounds are stable if The shape of the coagulation curve is typical for carefully p ~ r i f i e d . ~The fact that addition of HCl either large or highly charged counterions. At does not lower the calculated basicity shows that the low concentration of coagulating ion, we have the heteropoly acids are nearly completely ionized since coagulation limit and a t a higher concentration, the mass action effect on the added [ H + ] is not the stability limit which is due to the reversal of charge. Above the stability limit, the turbidity is appreciable. According to the results presented in Fig. 2 , low because of the low scattering power of the very the 6-molybdochromic(III) and 6-molybdocobaltic- small, uncoagulated, recharged, primary particles. (111) acids are tribasic, the latter being incom- The coagulation concentration is obtained by expletely ionized a t concentrations greater than 1 x trapolating the tangent of the steepest part of the Ad. The possibility of a hexabasic dimer is coagulation curve to zero turbidity. We note that excluded on the basis of our coagulation results to there is no difference between the 10 and 60 minute be discussed below. The 12-tungstosilicic acid is limits and that the 1 minute curve gives only a tetrabasic and completely ionized over the con- slightly higher coagulation concentration. This centration range studied. The 9-tungstophos- small time dependence of the coagulation conphoric acid is hexabasic and also completely ionized centration is also characteristic for negative counterAd. The basicity of the 12- ions with charge up to four. below 3 X The coagulation concentrations are usually extungstophosphoric acid and 12-molybdoceric acids is definitely higher than six, but a t the lowest con- pressed in normalities, but we prefer to use the centrations used in these experiments they are (16) E. MatijeviC, D. Rroadhurst and n1 Kerker, J. P h y s . Client., obviously not fully ionized and therefore the ex- 63, 1552 (19.59).
5
E. MATIJEVI?AND AT. KERKER
5564
T'ol.
s1
It is obvious that in the critical coagulation region, the concentrawithout KBr tioiis of molybdocerate(1V) and \ 0 I95 silver ions are below the limit nec\ essary to form silver 12-molyl~ \ 9,' 60 M I N docerate(1V). G ,' In Fig. 4, we have plotted the -I \,e' K Br E ''\ precipitation curve (denoted with 2 x IO-^ N 0 4 0 130squares) obtained using only S X */,/* t t I' T AgN03and a gradient of h k a concentrations of 12-molybdo2 ceric(1V) acid (without adding m n KBr). This precipitation curve 3 does not interfere with the coagut-0 0 6 5 2 lation curve. However, in the M stabilityregion of AgBr H8CeILlo12042), the turbidity in the presence of KBr is much lower 0 than when i t is absent. This is because, in the presence of KBr, LOG.M O L A R CONC H ~ c ~ M o , Z ~ ~ Z . a great part of the Ag+ is used up Fig. 4.-Coagulation curves of 12-molybdocerie(I V ) acid for a positive silver in forming very small prilllary parbromide sol., 1, 10 and 60 minutes after mixing the reacting components. T h e pre- ticles of A ~ and B also ~ for adsorpcipitation curve for t h e system A g l i 0 8 (8 X N ) + HsCehfolz04t (varied) is tion as stabilizing ions. ~ 1 ~ denoted with squares. amount of Ag+ is therefore not molarity scale in this work since the charge of the available for formation of silver molybdocerate. ions was not known with certainty. When the Furthermore, the concentration of molybdocerate values obtained in Fig. 3 are compared with co- ions is also reduced because of their adsorption on the agulation concentrations of other trivalent anions, primary particles. It is this adsorption, with the such as citrate, they show a somewhat lower accompanying reversal of charge, which accounts coagulation concentration. This is explained by for the stability region in the first place. the large size of the heteropoly ion. It is known TABLE I that increase in size causes a decrease in coagulation SOLUBILITY PRODUCT, K,,, OF AgsCehIouOa? concentration, this effect being more pronounced Molar concn. Xlolar concn. Ksp with ions of lower ~a1encies.l~The coagulation of A g + of C e R l i x a O d I A f + j g X [Cchloi!OcQ values obtained are still higher than those for four 3.0 x 10-5 7 . 7 x 10-36 1 . 5 x 10-4 valent counterions of similar size, such as 121 . 6 x 10-4 2 . 0 x 10-5 Y.6 X tungstosilicate.2 For all these reasons, we con1 . 0 x 10-5 7 . 0 x 10-30 1 . 7 x 10-4 clude that G-molybdochromate(II1) and 6-molyb4 . 0 x 10-6 10.2 x 10-30 2 . 0 x 10-4 docobaltate(II1) ions are trivalent in solution. Mean 8 . 4 X lW3G Figure 4 represents the coagulation curves of Finally, Fig. 5 shows the comparison of the silver bromide sols using 12-inolybdoceric(IV) acid as the coagulating agent. In this case, the co- coagulation limits of all six heteropoly ions invesagulation values decrease markedly with time, a tigated. The sequence of these curves, which debehavior which is typical of highly charged counter- pends on the ionic charge of the coagulation anions, ions. The critical coagulation time is GO minutes. justifies the formulas used in the diagram. Only in The coagulation Concentration is very low (1.5 X the case of 12-molybdoceric(IV) acid is the order AI), comparable to that for 12-tungstophos- somewhat distorted. Two reasons might account phate but definitely lower than 9-tungstophos- for this. Either the acid is not fully ionized, even phate.2 This would indicate a charge of about in as low concentration as used in the critical coseven, in agreement with the basicity measurements. agulation region, or for very highly charged ions, The silver salt of the 12-molybdocerate(IV) is factors other than charge become important aiid the known to be sparingly soluble,'- but no data on coagulation process ceases to follow the simple form solubility are reported. Since we were coagulating of the Schulze-Hardy rule. positive silver bromide sol using excess of AgXO3 Structural Considerations and Conclusions it was necessary t o establish whether the soluThe Heteropoly Tungstic Acids.--Our earlier bility of silver 12-molybdocerate(IV) was suf- coagulation work,2 reinforced b y the studies preficiently high to avoid the formation of two insoluble salts simultaneously, viz., AgBr and silver sented in this paper, shows that the basicity of 12and that of 912-molybdocerate(IV). Vre determined the solu- tungstophosphoric acid is sevenQualitative results tungstophosphoric acid is six. bility of the latter and found the values given in based $H,'S as well as earlier analytical work'g upon Table I , where the solubility product is calculated also support this view. Similarly, the basicity of for four different pairs of [Agf] and [CeXf0~?012~-]. I
'
/
-
(17) B T e t a k , E. Matijevii- and K. F. Schulr. THISJ O O R N A L , 69, 7GQ (1955); E. MatijeviC, K. F. Schulz and B T e j a k , Cuoaf. Chem. A d a 28, 81 (19.56).
(18) RI. C. Baker, P. A. Lyons and S. J. Singer, J . Phrs. ( h r m . , 69, 1074 (1955). (19) A. Rosenheim arid J. Jaenicke, E . anoug. (,hein., 100, 304 (1917).
i
~
Nov. 5, 1959
BASICITIES OF HETEROPOLY TUNGSTIC AND MOLYBDIC ACIDS
5565
I 12-tungstosilicic acid was found t o I KBr 2 x N , AgNO, 8. N be four. The state of aggregation of each of these compounds (;.e., (NH4) monomer, dimer, etc.) was estab0'95 lished by light scattering. 1 $ 3 , 2 0 Much of the current literature assumes a tribasicity for 12-tung- 7 ' stophosphoric acid. This was first $ o 130--- proposed by Pauling2' based upon structural considerations and further elucidated by Keggin,22based 5 on X-ray studies. D The basicity of such a compound - is dependent upon two structural b0065factors, vzz.,the coordination of the central phosphorus and the extent of the condensation between the parent acids-phosphoric and tungstic acids. 01 I I I -6 -7 -8 Although it is almost impossible to LOG. MOLAR CONC. OF THE HETEROPOLY ION. fix the oxygens directly by X-ray Fig. 5.-A comparison of the coagulation limits of ammonium 6-molybdowork, the presently available evidence indicates tetrahedral coordi- chromate(III), a"onium 6-molybdocobaltate(lI1), 12-tungstosilicic acid, nation for the central phosphorus. 9-tungstophosphoric acid, 12-molybdoceric(IV) acid and 12-tungstophosphoric However, this alone does not de- acid as obtained for a positive silver bromide sol in stutzi msccndi. termine the basicity which is also dependent upon cluding 6-molybdochromic (111) and 6-molybdocothe number of condensations among the parent baltic(II1) acids. They present a detailed arguacids, with the formation of oxygen bridges. ment, based on chemical evidence, to show that the Thus, although 9-tungstophosphoric acid probably formula of such acids may be represented by has tetrahedral coordination of the central phos- (H&MoeOzl) n, where X represents the octahedrally phorous atoms similar to tetrabasic pyrophosphoric coordinated, tervalent, central atom. Our basicity acid, its basicity is six rather than four. In the results agree with this formulation, i.e., three same way, the basicity of 12-tungstophosphoric ionizable hydrogens per central atom, but as pointed acid (seven) need not be the same as the parent out earlier, basicity determination alone cannot phosphoric acid (three). It is not yet possible, define the state of aggregation, n. then, to decide this question from purely structural We attempted to determine the molecular weight considerations and physicocheniical experiments of of these acids by light scattering, but were not the type described above must be carried out. successful for two reasons. First, the solubility For the 12-tungstophosphoric acid, the apparent was too low to obtain solutions of high enough discrepancy between the tribasicity found in the concentration to get appreciable scattering. solid state by X-ray analysis and the heptabasicity Secondly, the compounds are highly absorbing so which we find in dilute solution can be reconciled that whatever light was scattered was strongly by considering that in solution, the trivalent ion attenuated before leaving the solution. takes up two oxygen ions (hydrolysis of two oxygen However, our coagulation studies definitely indibridges). Since our spectrophotometric results cate an ionic charge of minus three, so that we have a t lJ-J.5 -11 (see Fig. 2 ) and our coagulation results proposed the monomeric formulations, H3C03h6021 at M (see Fig. 5) both indicate heptabasicity, and H 3 C r ~ T 0 6 0 ~RosenheimZ5 ~. and Pau1ingz1had we have formulated the acid as heptabasic. We assumed these were monomers. Baker, Foster, are planning to extend our spectrophotometric Scholnick and McCutcheon had argued on strucexperiments to lower concentrations, using an tural grounds for a dimeric formulation but indicator of higher p K , in order to see whether the Tsigdines, Pope and Bakerz6 have recently respectrophotometric curve (Fig. 2), which appears ported cryoscopic measurements in sodium sulfate to be approaching a limit of seven, actually does decahydrate which indicate the monomeric strucso. There is the possibility of a continued uptake tures. of oxygen ions, leading to even higher basicities. Our results for the 12-molybdoceric(IV) acid, However, in view of the coagulation results, we H8Cehfo12042, are consistent with octahedral cobelieve this is unlikely. ordination of the central atom, and this agrees The Heteropoly Molybdic Acids.-Baker, et with the early formulation by BarbierilZ and al.,23924have recently discussed the structural the later confirmation by Baker." problem of the 6-heteropoly molybdic acids, inAcknowledgment.--We are indebted to Professor (20) M. J. Kronman and S. N. Timasheff, J . Phys. Chem., 63, G29 L. C. W. Baker of Boston University for a supply (195'3). of ammonium 6-molybdocobaltate(III) and ani(21) L. Pailling, THISJ O U R N A L , 51, 2888 (1929).
5
(22) J. F. Keggin, Proc. Roy. SOL. (London), 8 1 4 4 , 75 (1934). (23) L. C. W. Baker, G. Foster, W. T a n , F. Scholnick a n d T . P. McCutcheon, TEISJ O U R N A L , 77. 2130 (1055). ( 2 4 ) C. W.Wnlfe, AI. L. Block and L. C. W.Baker, ibid., 7 1 , 2200 (1955).
(25) A. Rosenheim in Abegg's "Handbuch der anorganisclieii Chemie," Vol. I V , P a r t 1, Leipzig 1921. (26) G . A. Tsigdines, M. T. Pope and L. C. W. Baker, Abstracts of Papers, 135th Meeting, American Chemical Society, Boston, M a s s . , April 5 t o 10, 1959.
LVAYNEW. DUNKING AND DONS. MARTIN, JR.
5566
monium 6-molybdochromate(III) as well as his refined directions for preparation of ammonium 12molybdocerate(1V). \Ye are also indebted to Mr. William A. Light for assistance in obtaining some of
[COSTRIBUTION Xo. 717
FROM THE
Vol.
s1
the preliminary basicity data and Mr. Donald Broadhurst for obtaining some of the coagulation data. POTSDAM,
SEW
YORK
INSTITUTE FOR ATOMICRESEARCH ASD DEPARTMEST OF CHEMISTRY, IOWA STATE COLLEGE]
Mixed Tetra-(ch1orobromo)-platinates(I1). Equilibrium Constants for Formation in Aqueous Solution' BY i $ r i a ~ n -W. ~ DUNNING AND DONS. ~UXRTIP';, JR. RECEIVED APRIL I, 1959 A radiochemical procedure, combined with a least squares treatment, has been used to obtain the four equilibrium constants for the stepwise replacement by bromide of t h e ligands in [PtClr]'. The equilibrium constants for t h e single ligand replacement reactions a t 25' are 14.5, 8.3, 2.0 and 1.65. T h e AHo for each step is estimated t o be -1.8 0.3 kcal. The results fail t o show that the higher stability of the bromide ligand bond results primarily from x-bonding. Upper limits for the acid hydrolysis equilibrium constants in the system were also obtained.
+
Introduction
a-bonding. Electron pairs of the platinum ion, normally considered as non-bonding, are utilized evaluate the set of four equilibrium constants for in the a-bonds which therefore give multiple bond the successive substitution reactions indicated by character for the complexes. Chatt and Wilkinsg have found that AHo for the isomerization of ciseq. 1 to trans-dichlorobis-(triethy1phosphine)-platinum[PtC14-nBrn]- B r - % (11) is nearly +2.5 kcal./mole. They suggested [PtC13--nBrn+1]-4- C1-, K , (1) that the stability of the cis-isomer was possibly where n = 0 , I , 2 , 3. Platinum(I1) belongs to the due to the a-bonding, since the two n-bonds to rather limited group of ions for which the order phosphorus could utilize both the d,, and d,, of stability for halide ligand bonds is reversed from orbitals of platinum, whereas in the trans-isomer the normal, z.e., Br- is bonded more strongly than only one of these orbitals is suitable for forming C1-.2 L a t h e r 3 has estimated that for the over- a-bonds to the phosphorus atoms. Therefore, a n-bonding ligand is expected to detract from the all reaction n-bond trans to itself. [PtC14]4Br- --+ [PtBrr]' + 4C1(2) It appeared worthwhile to attempt an evaluation L I F O is -6.7 kcal. In addition, Leden and Chatt4 of the successive bromide substitution equilibrium found an equilibrium constant of 3.4 (AFO = -0.72 constants for [PtC14]-. If the stability of the kcal.) for the replacement by bromide of labile chlo- platinum-bromide bond does result froiri its ride trans to ethylene in trichloro-(ethylene)-plati- n-bond character, i t is expected that [PtCl,Br]= nate(I1). and cis- [PtC12Br2]', which have no bromides trans The higher stability of the bromide bond, com- to other bromides, will be especially stable. If the pared tochloride, may result from additional a- equilibrium constants could be deterniinetl with bonding for the bromide. Bromide has a stronger sufficient accuracy, it was expected that high values trans-directing effect than chloride, and Chatt, for KOand possibly K 1 would lend support to the et al.,5 and OrgeP have attributed the trans- n-bonding hypothesis. directing property of a ligand to its a-bonding Platinum(I1) forms the well-known square conicharacter. plexes which are inert. Consequently, halide In addition, bromide ligands in platinum(11) complexes with coordination number greater than complexes are more labile than chloride toward 4 have not been considered. Ample time must he exchange with the free ion.' Banerjea, Basolo provided to attain equilibrium in the systems. and Pearsons have presented evidence that the At moderate halide concentration, the acid hysubstitutions for ligands in platinum(I1) coni- drolysis (or aquation) can yield the trihalide complexes are rapid for entering groups which are plexes according to reaction 3 generally considered to provide a high degree of [PtCla- nBrn]- + H,O f, (1) Work was performed in the Ames Laboratory of t h e TI.S. Atomic [PtCl3-,,Br,(H2O)]C1-, K,,, ( 3 ) Energy Commission. wheren = 0, 1, 2, 3. (2) R. G. F. Carleson and H. Irving, J . Chem. Soc., 4390 (1954). (3) W. R l . L a t i m e r , "Oxidation Potentials," 2nd E d . , Prentice-Hall, Grantham, Elleman and ?\Iartin!O reported Inc., New York, h-.Y., 1952, p. 54, 59, 205. 0.018 mole/l. a t 25' for Ka0, the equilibrium con(4) I. Leden a n d J. C h a t t , J . Chem. Soc., 2936 (1955). stant for the nquation of [PtC14]=. An evaluation ( 5 ) J. C h a t t , L. A. Duncanson a n d I,, AI. Venazi, Chemist73 3 I n d u s Lvy, 749 (1935). of the acid hydrolysis equilibria of the mixed ( 0 ) L. E. Orgel, J . Inorg. Nuclear C h e v i , , 2 , 137 (1956) complexes is interdependent upon the dctermi-
X radiochemical procedure has been used to
+
+
+
(7) A. A . Grinberg and L. E . Nikolskaga, Z h u v . Puzklad. Khiwz,, 22, 5.42 (1949). (8) D. Banerjea, I'. Basolo a n d R. G . Pearson, TIXIS J O U R Z A L , 79, 4 0 j 5 (1957).
(9) J. C h a t t and R. G. Wilkins, -7. C h e i i i . Soc., 4300 (19Z2). (10) L . F. G r a n t h a m , T. S. Elleman and D. S. I I a r t i n , J r , J O L J R N A L . 77, 296.5 (1955).
7'111s
