Self-diffusion of chromate ion in agar gel

Abstract

The self-diffusion coefficient of the chromate ion is determined in agar gel media over the concentration range 10 −5 to 0.25 M at 25°C. Comparison of the experimental results and the theoretical values indicates failure in the application of Onsager-Fuoss theory to the ion diffusion in swollen gel system at all the concentrations studied. The observed results are explained on the basis of water-gel, ion-water and ion-ion interactions and the obstruction effect. Diffusion rates are also determined at various gel percentages and at different temperatures, keeping the electrolyte concentration constant. The obstruction effect is found to depend on the concentration of the electrolyte and the activation energy is found to decrease with increasing gel concentration. The results are discussed in the light of transition state theory of diffusion.