Osmotic coefficients and activity coefficients of aqueous mixtures of sodium chloride and sodium carbonate at 25°C

Abstract

Isopiestic vapour-pressure measurements have been used to determine the osmotic coefficients of aqueous mixtures of sodium chloride and sodium carbonate at 25°C. Solutions of sodium chloride were used as the reference electrolyte. The data served to evaluate the excess free energies of mixing as well as the mixing parameters of the Scatchard and Pitzer theories. The three-parameter form of the Scatchard equation accounts well for the experimental results, and the Pitzer equation with two adjustable parameters does equally well. The activity coefficients of the individual salts in the mixtures have been calculated.