Extension and application of the pitzer equation for vapor‐liquid equilibrium of aqueous electrolyte systems with molecular solutes

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 NH 3 ‐CO 2 aqueous solution studied by Van Krevelen et al. (1949) at 293.15°K; and the K 2 CO 3 ‐CO 2 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.