Size, shape and charge effects in the partial molal volume, compressibility and electrostriction behaviour of sulphur and chlorine oxyanions in water

Abstract

Ionic size, shape and charge effects in the interaction of a series of Cl and S oxyanions with water have been investigated by means of apparent molal volume and adiabatic compressibility measurements. Electrostriction volumes have been calculated from the partial molal volumes of the ions at infinite dilution using intrinsic ionic volumes evaluated by four methods which are critically compared. The evaluation of reliable intrinsic volumes of oxyanions with corrections for the dead-space in packing is shown to be a major problem in derivation of electrostriction volumes and in interpretation of the volumetric behaviour of oxyanions in solution.

A relation between electrostriction volumes and compressibilities of ions is demonstrated and compared with the results of earlier a priori calculations. Both the compressibilities and partial molal volumes of the series of oxyanions and simple halide ions are almost linearly related to the respective standard entropies of solution of these ions.