Excess Volumes of Mixing of Cl– and Br– with Na+ and K+ at 308.15 K in Aqueous Dioxane Mixed Solvent

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 308.15 K using a dilatometer in a water +1,4-dioxane mixed solvent system. Pitzer’s ion interaction model has been utilized to obtain binary and triplet interaction parameters, i.e. θV and ψV. The data were also analysed in the light of the Friedman model. Data are dependent on the nature of the common ion and do not support the cross square rule (CSR). The  deviation from the CSR increased with increasing ionic strength and is considered to arise from the appreciable contribution of triplet interactions and preferential solvation of the ions and ion-clusters in the mixed solvent system.KEYWORDS: Excess volumes of mixing, Friedman model, Pitzer model, cross square rule

Excess Enthalpies of Mixing of Binary Mixtures of NaCl, KCl, NaBr and KBr in Mixed Ternary Solvent Systems at 298.15 K

Excess enthalpies of mixing for six possible binary combinations of solutions of NaCl, KCl, NaBr and KBr in mixed ternary solvents composed of formamide, 1,4-dioxane and water have been determined using a flow microcalorimeter at constant ionic strengths of 0.500 and 1.000 mol kg–1 at 298.15 K. Unlike the case of water, the data do not supportYoung’s cross square rule. Pitzer’s virial coefficient theory has been utilized to obtain binary and ternary interaction parameters, i.e. θH and ψH. The data were also analysed in terms of the Friedman model and it was found that interactions between solvated ions are dictated not only by coulombic interactions but also by appreciable asymmetric effects.Keywords: Enthalpy of mixing, ternary solvents, Pitzer theory, Friedman model, cross square rule