872 Inorganic Chemistry, Vola10, No. 4 , 1971 CONTRIBUTION FROX
DEPARTMENT OF CHEMISTRY THEJAMES FRANCK INSTITUTE, CHICAGO, CHICAGO, ILLINOIS 60637 THE
AND
THEUNIVERSITY
OF
NOTES ENTHALPIES O F +&fIXIKG
TABLE I O F BINARYLIQUIDMIXTURES OF
CADMIUM CHLORIDE W I T H C E S I U M CHLORIDE AND
LITHIUM CHLORIDEAT 690”
T h e E n t h a l p i e s of Mixing of Binary Liquid Mixtures of C a d m i u m Chloride w i t h Cesium a n d L i t h i u m Chlorides BY G . N.PAPATHEODOROU A N D 0. J. KLEPPA* Received August 24, 1970
XCdCI,
Total moles
0.052 0.105 0.174 0.251 0.326 0.400 0.474
0.1003 0.0505 0.0504 0.0502 0.0503 0.0501 0.0501
-AHhf, kcal/mol
XCDCI,
CdCIrCsC1 0.898 0.549 1.768 0.624 2.818 0.699 3.920 0.775 4.645 0.848 4.897 0.924 4.767
-AHx,
Total moles
kcal/mol
0.0500 0.0500 0.0500 0.0502 0,0502 0.0500
4.526 4.210 3.760 3.113 2.319 1.281
In recent communications we have reported the enthalpies of mixing, AHfir,for a series of charge-unsymCdCL-LiCl metrical fused-salt systems MC12-AC1, where A is an 0.100 0.1016 0,099 0.599 0.1002 0.162 alkali metal and M is Pb,’ Mg,2 Nij3Mn, Fe, or C O . ~ 0.199 0.1005 0.159 0.698 0.1002 0.134 In the present work our studies of this type of system 0,1001 0,200 0.799 0.1002 0.075 0.299 0.216 0.897 0.1005 0.027 0.398 0.1006 are extended to the binary mixtures of cadmium chlo0.1006 0.195 0.499 ride with cesium and lithium chlorides. These binaries have already been the subject of a great deal of work and especially with the MgCl2- and MnC12-containing and have been explored by a variety of different physi~ y s t e r n s . ~For ~ ~ CdC12-CsC1 there is strong depencochemical methods.j-l* Many of these earlier invesdence of AM on composition with a pronounced dip tigations have considered specifically the problem of (stabilization of the mixture) near 33y0 CdClz This “complex” formation in the melts, and various authors stabilization is not present in the CdCl2-LiC1 system. have postulated the existence in the mixtures of one or In our study of the MC12-,4Cl (M = Mn, Fe, Co, more “complexes” of the general formula CdClX2-” Ni) ~ y s t e m s , we ~ ? ~argued that the interaction pa(with n = 1, 2 , or 4). The new data reported in the rameter curve will show a pronounced minimum near present work allow a look a t this problem in the light of X ~ I C=I ~ only when appreciable tetrahedral “comthe enthalpy of mixing. plexing” MCla2- is present in the mixture. The exisThe calorimetric methods adopted were similar to tence of such MC142- configurations of tetrahedral gethose used in our earlier ~ o r k . ~ The > * temperature of ometry is consistent with spectrophotometric investigathe measurements was 690” and all the calorimetric tions of dilute and concentrated solutions of these tranvessels were made from fused silica. The cadmium sition metal chlorides in the alkali chlorides3 In parchloride and lithium chloride were Mallinckrodt Analyticular, it is noteworthy that a tetrahedral configuratical reagents and were dried by melting a t 700” in an tion for NiCIb2is found in quite concentrated mixtures atmosphere of HC1 N2 (1 : 1). The cesium chloride of NiClz with cesium chloride, in spite of the wellwas purchased from Kawecki Chemical Co. (99.9yo known preference of Ni2+ for an octahedral environpure) and was dried at 150” for several hours. All ment.12 The behavior of the interaction parameter calorimetric mixing experiments were performed under curve for the CdC12-CsCl binary suggests that a tetraan atmoshere of pure argon. The enthalpies of mixing hedral CdC142- “complex” exists and stabilizes the measured in these experiments (in kilocalories per mole mixtures. Bredig13has argued that this complex is also of mixture) are given in Table I. In the same table present in KC1-CdC12. In the CdCl2-LiC1 binary, on we give also the mole fraction of cadmium chloride the other hand, as in the case of the previously studied (XC~CI,) and the total number of moles used in each MC1z-LiC1 binaries, there is no dip in AM near 33% experiment. CdClz and presumably no significant formation of CdIn the figure we have plotted the enthalpy interaction C1d2complexes. parameter, Ahf = AH’/X2(1 - X2), ns. the mole fracIn Figure 1 we have also plotted estimated intertion of cadmium chloride. The curves for X” for these action parameter curves for the CdCls-RbC1 and Cdtwo binaries show similarities with A” for the corresponding MCl2-ACl binaries studied p r e v i ~ u s l y ~ - ~Cl2-KC1 binaries. These were calculated from the experimental values of Ab* for the CdCI2-CsC1 binary, (1) F. G. M c C a r t y a n d 0. J . K l e p p a , J . P h y s . Chem., 68, 3846 (1964). as follows. (2) 0. J . Kleppa a n d F. G. M c C a r t y , ibid., 70, 1249 (1966). (3) G . N . Papatheodorou a n d 0. J . K l e p p a , J . Iizoug. N x c l . Chem., 32,889 In reviewing our earlier data for the charge-unsym(1970). metrical binaries we noted that for a given mole fraction (4) G. N. Papatheodorou a n d 0 . J . Kleppa, ibid.,in press. ( 5 ) H . Bloom a n d J . W.Hastie, J . P h y s . Chem., 73, 2361 (1068). of transition metal chloride the ratio of the interaction ( 6 ) H . Bloom a n d J. W. Hastie, Ausi. J . C h e m . , 19, 1003 (1966) parameter of the MCl2-AC1 binary to the interaction ( 7 ) G . Bertozzi a n d G. Soldani, J . P k y s . Chcm.. 72, 353 (1968). (8) E. R . Van Artsdalen, Z . Elekliochrm., 6 0 , 172 (1956). parameter of the MC12-A’C1 binary ( i e . , the ratio (9) J . C . T h . K w a k , Thesis, University of Amsterdam, 1967. A“(A-M)/XiM:(A’-M)),is essentially constant for all the (10) UT. H. bletzger, A . Brenner, a n d H . I. Salmon, J . Electrochem. Soc., 114, 132 (196i). different MCl2 salts studied (M = Mn, Fe, Co, Ni,
+
(11) H . Bloom a n d G . B. Tricklebank, A u s l . J . C h e m . , 19, 187 (1966). (12) See, e . & . , G. P. S m i t h . C . R . Boston, and J. B r y n e s t a d , J . C h e m . P h y s . , 4 5 , 829 (1966).
(13) M . A. Bredig in “ M o l t e n Salts,” G. M a m a n t o v , E d , Marcel Dekker, New York, N . Y . ,1969.
Inorganic Chemistry, Vol. 10, No. 4,1971 873
NOTES
KCl system a t 780") calculated by Bredig13 from the partial enthalpy data of Metzger, Brenner, and Salmon.l0 We see that there is quite good agreement between the two interaction parameter curves a t mole fraction of CdCla below about 0.5. However, the agreement is less satisfactory a t higher contents of CdC12, where the difference between the two curves is as large as about 2.5 kcal/mol a t X C d C l l 0.85. Due to the "intermediate)) character of the NaClMC124binaries the X'(Cs-M)/hM(Na-M) ratios (and the XM(Cs-M)/XM(Li-M) ratios) vary as much as 50% for the different MCl2-ACl systems. Thus a reliable estimate of AM for the CdCl2-NaCl mixtures is not possible.
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Acknowledgments.-This work has been supported by the National Science Foundation. It also has benefited from the general support of Materials Science a t the University of Chicago by ARPA.
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CONTRIBUTION FROM THE DEPARTMENT OF CHEhfISTRY, UNIVERSITY OF IOWA,IOWACITY, IOWA 52240
CdCl,
'CdC12-
Figure 1.-Experimental enthalpy interaction parameters A M = AHM/X1(1 X Z )vs. X C d C l r at 690' for the mixtures of CdClz with LiCl and CsCl. Dotted curves give calculated values of A M for CdCln-RbC1 and for CdClZ-KCl. Solid curve for the latter system was calculated by Bredig" from the partial enthalpy data at 780' of Metzger, Brenner, and Salmon.Io
-
Mg; A, A' = K, Rb, Cs). For example, for the binaries of MnC12, FeC12, CoClp, NiC12, and MgC12, with CsCl and RbC1, the ratios XM(Cs-M)/XM(Rb-M) a t X M C= I ~ are 1.17, 1.15, 1.18, 1.17, and 1.19, respectively. In Table I1 we list some average values of the TABLEI1 xMcl2---
c -
A'(Cs-M)/ AM (Rb-M) A'(Cs-M)/ A M (IC-M)
7
0 1.16 zk 0.04
1.17f 0.02
1 1.17f 0.02 1.25f 0.06
1.37zt 0.07
1.44f 0.03
1.42f 0 06 1.58 zt 0.00
'/8
1/2
ratios XM (Cs-M)/AM (Rb-M) and XM(Cs-M)/XM(K-M), evaluated a t different compositions of the mixture. If we assume that these ratios hold also for the CdChAC1 binaries, we can use them to calculate the interaction parameters XM(Cd-Rb) and X'(Cd-K), from the curve for the CdC12-CsC1 system. The calculated curves for X(Cd-Rb) and X(Cd-K) are given as dotted lines in Figure l . I 4 In this figure we give also the "experimental" interaction parameter curve for the CdC12(14) The dotted curves drawn in Figure 1 are the result of a somewhat more laborious calculation of the AM(Ca-M)/XM(A-M) ratios, including compositions other than those listed in Table 11.
Mechanistic Implications of the Role of Phenol in the Uranium (1V)-Chlorine(II1)Phenol Reaction BY EUGENEB. GRIMLEY, ROBERT BUCHACEK, AND GILBERT GORDON*' Received August 31, 1970
Evidence has been reported for the presence of a reactive chlorine intermediate in the reaction of uranium(IV) with chlorine(II1) in acidic aqueous solution.2 When phenol is added to this system as an initial reactant, the resultant kinetics, stoichiometry, and product identification indicate that an intermediate chlorine species has been scavenged by phenol. The purpose of this note is to discuss the results of the present study which was aimed at the determination of the scavenged intermediate chlorine species in the above reaction. The stoichiometry of the uranium(1V)-chlorine(II1) reaction was reported to be variable in the absence of phenol. The criterion for monitoring reactant stoichiometry was the ([Cl(III) ]/ [U(IV) ])consumed ratio. In the absence of phenol, this ratio was found to vary from 1.5 to 2.5, depending upon reaction conditions. The reaction was accompanied by the production of chlorate ion as one of the products. The formation of chlorate ion under the strongly reducing conditions imposed by uranium(1V) and a greater than expected consumption of chlorine(II1) are two unusual features of the reaction (1) T o whom correspondenceshould be addressed. (2) G. Gordonand F. Feldman, Inorg. Chew , 8 , 1728 (1964).
