EQUILIBRIA IN PROPYLENE CARBONATE
3965 Aclcnowledgment. The authors gratefully acknowledge the support of this work by the Office of Saline Water, U. S. Department of the Interior. The authors also wish to thank Miss Nalini Bhatt for help with the calorimetric measurements, Mr. Alan Levine for checking the BaClz with LiCl measurement a t I = 3, and Dr. Peter Reilly and Professor R. A. Robinson for helpful discussions.
Anderson extended to constant E mixings correct for all triplet interactions except like-charged triplets while neglecting ion-atmosphere effects. This will probably be the most accurate method of predicting the properties of charge-asymmetric mixtures a t high concentration since the concentration dependence of triplet interactions is probably much higher than the concentration dependence of ion-atmosphere effects.
Equilibria in Propylene Carbonate.
I.
Viscosity and Conductance
Studiesla of Some Lithium and Quaternary Ammonium Salts by L. M. Mukherjeelband David P. Boden Chemistry Department, Polytechnic Institute of Brooklyn, Brooklyn, New York 11001 (Received February 17, 1969)
Results of conductance and viscosity measurements of solutions of LiCl, LiBr, LiC104, EtdNCI, Et4NC104 n-Bu4NBr,and n-Bu4NC104in propylene carbonate are reported. All conductance data have been treated by the method of Fuoss and Accascina. Lithium chloride and lithium bromide are found to be associated, having association constants of 557 and 19, respectively, whereas no association could be detected for the other systems. The significance of the values of viscosity F coefficient and a0 parameter in different cases is discussed. tration dependence indicating the existence of very Introduction large ionic interactions. Butlere studied potentioPropylene carbonate (PC) is a stable substance of metrically the equilibria of the chloro complexes of convenient liquid range (mp -49.2’; bp 241.7’) and silver(1) in PC, and Boden’ and Reddy and McClure8 moderately high dielectric conntant (64.42 a t 2.5’). It have investigated the behavior of glass electrodes in sois a good solvent2-6 for a variety of inorganic and lutions of alkali metal and alkaline earth metal salts in quaternary ammonium salts. I n recent years, it has this solvent. been considered a specially suitable solvent for “high I n this work, solutions of a selected group of 1: 1 elecenergy” electrochemical reaction^.^ trolytes in PC have been carefully investigated through Reports on fundamental s t ~ d i e s ~of- the ~ behavior of conductance and viscosity measurements. The syssolutions of electrolytes in PC, however, are few and indicate lack of correlation in some instances. FUOSS,~ (1) (a) Presented a t the 157th National Meeting of the American et al., studied the conductance of tetra-n-butylamChemical Society, Minneapolis, Minn., April 1969. The material monium tetraphenylboride in this solvent and conforms a part of a thesis to be submitted by D. P. Boden to the Graduate School of the Polytechnic Institute of Brooklyn, Brooklyn, N. Y., cluded that ion association was negligible. Wu and in partial fulfillment of the requirements for the degree of Doctor of Friedman5 investigated the conductances and heats of Philosophy; (b) Chemistry Department, Illinois State University, solution of several alkali metal iodides, perchlorates, Normal, Ill. 61761, to which all correspondence should be sent, (2) W. H. Harris, Ph.D. Thesis, University of California, Berkeley, trifluoroacetates, and tetraphenylborates. Their preCalif., 1958, UCRL Report 8381. liminary studies indicate that the perchlorates in (3) R. J. Jasinski, “High Energy Batteries,” Plenum Press, New general are “strong” electrolytes whereas the correYork, N. Y., 1967. sponding trifluoroacetates give evidence of considerable (4) R. M. Fuoss, 5. B. Berkowitz, E. Hirsch, and S. Petrucci, Proc. Nat. Acad. Sci. U.S., 44,27 (1958). ion association, and suggest that the predominant asso(5) Y-C Wu and H. L.Friedman, J . Phgs. Chem., 70,501 (1966). ciated form of lithium trifluoroacetate is an ion-pair (6) J. N. Butler, Anal. Chem., 39, 1799 (1967). dimer. I n the case of lithium perchlorate solutions, the (7) D. P. Boden, paper presented a t the Electrochemical Society conductance datas indicate negligible ion association Meeting, Dallas, Texas, May 1967. whereas those on heat of solution show a strong concen(8) J. E. McClure and T. B. Reddy, Anat. Chem., 40,2064 (1968). Volume 78, Number 11 November 1969
L. M. MUKHERJEE AND DAVIDP. BODEN
3966 tems studied include lithium chloride, lithium bromide, lithium perchlorate, tetraethylammonium chloride, tetraethylammonium perchlorate, tetra-n-butylammonium bromide, and tetra-n-butylammonium perchlorate. The behavior of these different salts in P C is explained on the basis of the limiting equivalent conductance, the viscosity effects, the a" parameter and, where appropriate, the association constant.
Theory In cases where ion association cannot be neglected, the conductance equation for a 1: 1 electrolyte takes the formg A(1
+ Fc)
= A0
- S C ' / ~f~ E~ ' c~log ~ (CY) + J c -~ KACyf'A(1 + Fc)
(1)
where c is the molar concentration, y is the degree of dissociation of the solute, and K A is the association constant defined as 1-7
KA = W2.f2
f being the mean ionic activity coefficient. For PC at 25" S, E , and J can be expressed as
S
=
0.3O833Ao
+ 24.27178
E
= 0.95694Ao
- 11.03182
+ 7.4838 + 8 . 0 7 5 4 ~-~ 9.58178 [In ao + 0.003651 +
J = 0.8311ho[h0 In a0 - 0.105951
The coefficient F can be obtained from the viscosity data by the use of the Jones and Dole equation which is usually expressed in the form 7/70 = 1
+ Ac"~+ FC
(3)
Thus, by plotting (7/qo - l)/c'/? us. cl/' a straight line should be obtained whose slope would give F and intercept, A . If, on the other hand, ion association is negligible the conductance equation for a 1 : 1 electrolyte simplifies to A = Ao - SC'"
+ EC log c + JC - FAOC
(4)
Since the J term is always larger than the term in E and since in general the F term is small, the experimental A vs. c'" plot will lie above the limiting tangent given by the Onsager equation. The latter behavior can be used as a criterion to judge whether ion association exists since if association is appreciable, the y term in the conductance equation (cf. eq 1) will depress the curve below the limiting tangent. Electrolytes in general can then be divided into two classes: (1) where the measured conductance curve lies below the limiting tangent and therefore eq 1 is to be used to evaluate the data, and (2) where the measured conductance curve lies above the limiting tangent and eq 4 is applicable. The method of treating conductance T h e Journal of Physical Chemistry
data using eq 1 or 4 has been thoroughly discussed in the monograph by Fuoss and Accascina'O and a detailed description has been omitted in this paper.
Experimental Section Chemicals. Solvent. Technical grade PC (Jefferson) was distilled twice under vacuum (1 mm) from anhydrous CaO, a middle fraction being taken each time. The specific conductance of the twice-distilled solvent and 2.0 X lo-* ohm-' ranged between -1.0 X cm-l. Analysis by vapor phase chromatography indicated the absence of any appreciable impurities. The COZ content is estimated t o be
