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Abstract

The semi-empirical Pitzer equation for modeling equilibrium in aqueous electrolyte systems has been extended in a thermodynamically consistent manner to allow for molecular as well as ionic solutes. Under limiting conditions, the extended model reduces to the well-known Setschenow equation for the salting out effect of molecular solutes. To test the validity of the model, correlations of vapor-liquid equilibrium data were carried out for three systems: the hydrochloric acid aqueous solution at 298.15°K and concentrations up to 18 molal; the NH3-CO2 aqueous solution studied by Van Krevelen et al. (1949) at 293.15°K; and the K2CO3-CO2 aqueous solution of the Hot Carbonate Process with temperatures from 343.15°K to 413.15°K and concentrations up to 40 weight percent equivalent potassium carbonate. The success of the correlations suggests the validity of the model for aqueous electrolyte systems of industrial interest.