Salt velocity correlation functions: a microscopic interpretation. Part 2.—Solution of two or more binary electrolytes with a common ion

Abstract

The new variational principle recently introduced is applied to extend the concept of the mean molecular velocity of a salt presented earlier for solutions of several electrolytes with a common ion constituent. All the isothermal vectorial transport coefficients of these systems are described in terms of the dissipative motions of the ion constituents, which are built up by two linear fully decoupled contributions. These are (1) a migrational part, associated with the movement of the ion constituent relative to its corresponding salt and (2) a diffusional part, associated to the movement of its salt relative to the solvent. Each salt velocity is dynamically orthogonal to the electric current; this guarantees that diffusion and electrical transport superpose but do not interact. The new formalism is entirely consistent with the formulations of irreversible thermodynamics and of velocity correlation integrals. By means of projection operators it is easily shown that the ionic phenomenological conductance coefficients as well as the ionic velocity correlation coefficients consist of two linear fully decoupled components which correspond to the migrational and the diffusional contributions.