Velocity correlation coefficients as an expression of particle–particle interactions in (electrolyte) solutions

Equations are obtained for the six velocity cross-correlation coefficients for ion–ion, ion–solvent and solvent–solvent correlations in a binary system consisting of an electrolyte dissolved in an ionising solvent. These coefficients, which represent the ensemble average time integrals of the velocity correlation functions, are calculated for ten aqueous electrolyte systems at 25°C. The calculations use data for the equivalent conductance, cation transference number, mutual and tracer-diffusion coefficients and activity coefficient derivatives. Expressions are given in terms of the velocity correlation coefficients for the equivalent conductance and cation transference number and the complex expression for the mutual diffusion coefficient is shown to reduce at infinite dilution to the Nernst–Hartley limiting law.