Vapor Pressure and Dissolution Enthalpy Measurements in Ternary {H₂O + NaCl + Na₂SO₄} System between 298 K and 363 K

A nonisothermal static device was used to make measurements of vapor pressures in the ternary {NaCl (1) + Na2SO4 (2) + H2O (3)} system between 298 K and 363 K with molality ratios m(1)/m(2) = 1/10 and m(1)/m(2) = 1/1. Experimental data were fitted using empirical relation proposed by Appelblat. Dissolution enthalpies of both anhydrous sodium chloride and sodium sulfate in water were also measured up to saturation conditions at 297.8 K, 317.5 K, and 332.4 K (with m(1)/m(2) = 1/10, m(1)/m(2) = 1/1, and m(1)/m(2) = 10/1, respectively) by using a Setaram C80D differential calorimeter. These calorimetric data were used to establish the analytical expressions of Pitzer and NRTL electrolyte's parameters as a function of temperature. The ability of both models to represent both the dissolution enthalpies and the activities of water were tested.