Effect of pressure on the dissociation of electrolytic solution : III. Electrical conductivity of hexammine cobalt (III) sulphate at high pressures

Abstract

The degree of dissociation, α and dissociation constant, K of [Co(NH_3)_6](SO_4)^+ have been determined from the equivalent conductivity, Λ, of the dilute solution (1.0×10^4～8.0×10^-4N) of [Co(NH_3)_6]_2(SO_4)_3 at 25～40℃ under high pressures up to 600kg/cm^2. Λ, α and K increase with increasing pressure. The entropy change for dissociation, ΔS is negative and becomes less negative with increasing pressure and temperature. The volume change, ΔV is negative and becomes more negative with increasing pressure at 25 and 30℃ and less negative at 40℃. These phenomena have been explained with the properties of solvated water under high pressure. The increase of Λ with pressure is mainly ascribed to the increase of the ionic mobility at 25 and 30℃, and the increase of the degree of dissociation at 40℃ ; the ionic mobility decreases with pressure at this temperature.