Thermodynamic Properties of Concentrated Solutions of Strong Electrolytes I. Activity Coefficients of Water From Freezing‐Point Depressions for Alkali Chlorides

Abstract

A systematic study of thermodynamic properties of concentrated solutions of strong electrolytes is undertaken. Accurate freezing‐point depressions for all the alkali chlorides up to very high concentrations (> 3m) are measured and the corresponding rational activity coefficients of the water determined. “Best” values are recalculated for the parameters of the Debye‐Hückel theory (short‐range interactions being accounted for according to the “effective dielectric constant” model and the effects of “higher terms” being included).Curve‐fitting procedures are carried out for various concentration intervals so as to test the theory with increasing concentration. The ion size parameter a is found to be almost independent of the concentration interval for all of the salts considered, but for lithium chloride. Standard deviations change from ± 1.10−3 °C to ± 1.10−2 °C in passing from the smallest to the largest concentration interval, whereas they are nearly the same for all of the alkali chlorides at any one concentration interval.