Excess Volume of Mixing of 1:1 Electrolyte Solutions at 298.15 K in the Aquo-1,4-Dioxane Mixed-Solvent System

Excess volumes of mixing for six possible binary combinations of solutions of NaCl, KCl, NaBr and KBr have been determined at constant ionic strengths of 1.000 and 2.000 mol-kg^{− 1} at 298.15 K using a dilatometer in the water + 1,4-dioxane mixed-solvent system. Pitzer’s ion-interaction model has been utilized to obtain binary and triplet interaction parameters, i.e., θ^V and ψ^V. The data were also analyzed by the Friedman Model and it is suggested that interactions between solvated ions are dictated not only by coulombic interactions but also by appreciable asymmetric effects. The data are dependent on the nature of the common ion and do not support Young’s cross-square rule. The deviation from the cross-square rule is considered to arise from preferential solvation of the ions and ion clusters in the mixed-solvent system as reflected by the appreciable contribution of triplet interactions.