SOLVATION OF IONS IN AQUEOUS-SOLUTIONS OF HYDROPHOBIC SOLUTES

The self-diffusion of Na+, Et4N+ and I- in mixtures of water with n-propanol at 25-degrees-C and with tert-butanol at 30-degrees-C was measured as function of salt concentration and solvent composition. The limiting self-diffusion coefficients of the ions were used to compute the ionic radii. The influence of the composition of the solvent on the solvation of the ions is discussed. In aqueous solutions of both alcohols the effective ionic radii are reduced. The strongest influence is found for the same solvent composition for which the highest concentration of the alcohol clusters has been reported. Hydration of the clusters of n-propanol causes a vanishing of the second hydration shell of Na+ and the first one of Et4N+ and I-. In the case of tert-butanol even the first hydration shell of Na+ is partially reduced.