DIFFUSIVITY OF ZINC IONS IN AQUEOUS ALKALI-METAL CHLORIDES

The tracer-diffusion coefficients of radioactive zinc ions in aqueous potassium chloride, cesium chloride, and lithium chloride solutions of concentration between 0.005 and 2.5 mol dm(-3) are determined using a n open-ended capillary technique with stirring. The theoretical tracer -diffusion coefficients of zinc ions in aqueous salt solutions are cal culated using the Gosting-Harned equation and compared with the experi mentally determined diffusion coefficients. The measured values of tra cer-diffusion coefficients of zinc ions in the aqueous alkali-metal ch loride solutions agree with the theoretically predicted values up to a concentration of about 0.05 mol dm(-3). At higher concentrations, the tracer-diffusion coefficient of zinc ions first increases and again d ecreases with concentration, giving rise to a maximum in the plot of t he tracer-diffusion coefficient against the square root of the concent ration. A qualitative explanation of the concentration dependence of t he tracer-diffusion coefficient of zinc ions in concentrated solutions of the salts is attempted by taking into account the ion-ion and ion- water interactions.