SELF-DIFFUSION OF SODIUM-IONS IN HYDROUS STANNIC OXIDE FROM MIXED-SOLVENT SOLUTIONS

Self-diffusion coefficients of Na+, <(D)over bar (i)>, inside hydrous stannic oxide have been measured in aqueous and alcoholic solutions at different Na+-capacities. <(D)over bar (i)> always displays the usual decrease with capacity, which seems to be much less profound at the r elatively high capacities. There is apparently almost no effect of add ition of methanol on <(D)over bar (i)>, whereas a decrease of <(D)over bar (i)>, which disappears towards relatively high capacities, occurs on addition of propan-1-ol. These results are in marked difference wi th previous results of the effective diffusion coefficients of Na+/Hsystems. This difference seems to indicate that the effect of alcohol addition in increasing the strength of electrostatic interaction of co unter ions with the exchanger surface (a factor which, when predominat ing, decreases mobility) is higher with protons than with the Na+ ions .