EFFECTS OF PRESSURE AND TEMPERATURE ON THE VISCOSITY B COEFFICIENT FOR POTASSIUM CHLORIDE IN WATER

Abstract

Viscosity of aqueous potassium chloride (KCl) solution was measured at temperatures of 283.2 and 323.2K and pressures up to 375MPa by means of a rolling-ball viscometer. The Jones-Dole B coefficient of KCl at both temperatures increased with increasing pressure and then decreased after passing over a maximum as well as previously observed one at 298.2K. The maximum became more pronounced at lower temperatures. In comparison with the dielectric friction theory, the observation of the maximum is ascribed to a balance between two contributions; pressure breaks any water structure (B increases) and reduces the dielectric friction between ion and solvent (B decreases). The temperature coefficient ∂B/∂T was observed to be positive at all pressures and decreases with increasing pressure. The fact suggests that the structure-breaking effect of KCl for water reduces with increasing pressure, and the reduction of the effect may be ascribed that the water structure which should be broken by addition of the electrolyte is already broken by pressure.