Transport in aqueous solutions of group IIB metal salts (298.15 K). Part 4.—Interpretation and prediction of isotopic diffusion coefficients for cadmium in dilute solutions of cadmium iodide

Abstract

A method for predicting isotopic diffusion coefficients for component ions in a self-complexed electrolyte has been developed. In an irreversible thermodynamic analysis the diffusion coefficient has been shown to be a function of the mobility coefficients of the free ion and its complexes together with the interionic coupling coefficients between labelled and unlabelled species. It is shown that these coefficients may be evaluated by an extension of the methods developed earlier to predict isothermal transport in such systems. Cadmium ion diffusion coefficients in aqueous cadmium iodide, D_aa, have been predicted (0.003–0.10 mol dm^–3). These describe the maximum anticipated experimentally. Observed and calculated D_aa agree to within 3 % at 0.1 mol dm^–3.