The Effect of the Pressure on the Electrical Conductivity of Zinc Sulfate in Water

The electrical conductivity of ZnSO4 in water was measured at high pressures up to 3000 kg/cm2 and at 25 °C. The dissociation constant of the ion pair (Km) increased with an increase in the pressure. The volume change (ΔV°) accompanying the dissociation was −8.0±0.5 ml/mol at 25 °C. The distance of the closest approach (a) of the ion pair, calculated using the observed Km value and the theoretical equation of Bjerrum, increased with an increase in the pressure. In view of these ΔV° and a values, the ion pair of ZnSO4 was assumed to be of the solvent-separated type. It was also concluded that the number of water molecules separating the ions constituting an ion pair increases with an increase in the pressure.