On the partitioning of the viscosity B coefficient and the correlation of ionic B coefficients with partial molar volumes of ions for aqueous and non-aqueous solutions

Abstract

A new method of partitioning the viscosity B coefficients has been proposed on the basis of the assumption that ionic B values should be a monotonie function of crystal radii cubed, independent of the sign of the charge, for aqueous and various non-aqueous systems. Ionic B values thus obtained in different solvents by a single method of division provide a basis for uniform comparison among themselves as well as with the existing values. The usual assumption of equal contributions of K+ and Cl− ions has been discarded. The internal consistency of the derived set of Bi values is demonstrated by correlation with the ionic radii, hydrated ionic radii, partial molal volumes, temperature coefficient of equivalent conductance, and partial molal ionic entropy. The salient feature of the set of Bi values is noted by its linear relationship not only with the partial molal volumes but the same is also observed with the ionic radii of ions of different valence and charge types. Eyring's equation for viscosity using Frank–Wen's model of ion–solvent interaction has been utilised for the calculation of void viscosity and electrostriction viscosity. The latter is compared with the corresponding component of partial molal volumes using the Drude–Nernst equation based on the continuum model for solvent. Keywords: ion–solvent model, ionic B values, B coefficients, division of B coefficient, void viscosity, micro viscosity.