Ionic solutions under high pressures IV : effects of pressure on the mobilities and hydration of Bu4N+, Me4N+, K+ and Cl- ions

Abstract

The electrical conductivities of dilute aqueous solutions of tetra-n-butylammonium and tetramethylammonium chlorides have been measured at 15, 25 and 40℃ and at high pressures up to 5, 000atm. Then, the single-ion values of the equivalent conductances at infinite dilution were obtained from the assumption that the Walden product of tetra-n-butylammonium ion does not change with increased pressure. In order to check this assumption the cation transference numbers of KCl at infinite dilution were calculated and compared with those observed by other investigators. The calculated results are in good agreement with the observed ones. In order to cast light on the ion-water interactions, the hydration numbers, h and the Walden products, W of the ions were obtained at high pressures ; h(K^+) increases and h(Cl^-) decreases to a small extent as pressure increases, and the changes of the Walden product of the ions by pressure are in the sequence, ΔW(Cl^-)>ΔW(K^+)>ΔW(Bu_4N^+)=0>ΔW(Me_4N^+).