Mutual Diffusion Coefficients of Various ZnCl2  ( 0.5M )  ‐ KCl ‐  H 2 O  Mixtures at 298.15 K by Rayleigh Interferometry

Abstract

Mutual diffusion coefficients were measured at 298.15 K for aqueous mixtures of with at concentrations of 0.5, 1.25, 2.0, and 4.0 mol‐dm−3, using Rayleigh interferometry. These systems correspond to a fully charged zinc‐chlorine storage battery at various supporting electrolyte concentrations. The main term diffusion coefficient is nearly independent of concentration, whereas the main term varies by one‐third. The cross term is small and positive. The cross term varies from moderately large and positive to quite large and negative as the concentration increases. The experimental values cannot be reliably approximated by Nernst‐Hartley type equations, even with speciation assumptions. Mutual diffusion data, together with transference number and conductivity data (when available), can be used to calculate ion transport in systems with combined electrical and diffusive transport.