The Cation-Cation Interactions in Aqueous Mixed Electrolyte Solutions of Quaternary Phosphonium Chlorides

Abstract

Abstract Density measurements were carried out at six temperatures between 1 and 55 °C for three series of aqueous mixed electrolyte solutions, each of which contained (n-Bu)4PCl and Ph4PCl with the mole ratios, 3:1, 1:1, and 1:3, respectively. The mixed solutions are assumed to be the model solutions of the phosphonium chlorides, (n-Bu)4−n PhnPCl(n=1,2, and 3), with respect to the pair-wise interactions between the cations, for which a model has been proposed in a previous paper. The volume B-coefficients(Bv) determined for the model salts are in good agreement with those for the corresponding pure salts and those reproduced by the equation derived from the model. The results indicate that the phenyl groups affect weakly the butyl cospheres in both the intermolecular processes and intramolecular processes and that among the ion-ion interactions the cation-cation interactions are the main factor for determining the Bv′s. These can be decomposed into three parts, arising from the butyl-butyl, phenyl-phenyl, and butyl-phenyl interactions.