On the molecular theory of aqueous electrolyte solutions. II. Structural and thermodynamic properties of different models at infinite dilution

This paper describes a comparative theoretical study of the infinite dilution properties of solutions of univalent ions in different water-like solvents. The theoretical results are obtained by solving the reference hypernetted-chain (RHNC) approximation as described in the first article of this series [J. Chem. Phys. 88, 7715 (1988)]. It is shown that the inclusion of the octupole moment of the water molecule in the model solvent leads to strong preferential solvation of negative ions, and that this has important effects upon certain thermodynamic properties and upon the ion–solvent and ion–ion structure. Questions concerning the definition and physical interpretation of individual ion partial molar volumes are raised and considered in detail. It is argued that in general the individual ion results obtained experimentally may not accurately reflect the true microscopic ion–solvent structure.