IONIZATION CONSTANTS OF WATER AT 0 TO 373°C

Abstract

Accurate values of ionization constants of water over a wide range of temperatures and pressures are needed for a quantitative description of the properties of hydrothermal ore-generating solutions. The ionization constants of water on the saturation curve between 0 and 350 C have been measured by various techniques. It was found that Kw has a maximum near 250°C and increases with the concentration of electrolytes and with pressure. The authors test some of the outlined assumptions by calculating Kw from the parameters of their model of the structure of water in the range from 0 to 370°C and to determine in more detail the mechanism by which various factors change it. It is found that the temperature dependence of Kw, with a maximum in the vicinity of 260°, is governed by two factors: an increase in the number of broken bonds between molecules as the temperature rises, and a change in the total number of filled and unfilled voids, which usually decreases after reaching a maximum between 100 to 120°C.