Thermodynamic Study of the NaCl + Na2SO4 + H2O System by Emf Measurements at Four Temperatures.

Activity coefficients for sodium chloride in the NaCl + Na₂SO₄ + H₂O ternary system were determined from emf measurements of the cell at 15, 25, 35, and 45°C and at total ionic strengths from 0.1 to 6 mol-kg⁻¹. These activity coefficient were analyzed by using the Harned rule and the treatments of Scatchard–Rush–Johnson and Pitzer. The analysis of activity coefficients at “trace” concentration was also achieved and qualitatively interpreted by considering the ionic interactions that can take place in the mixed system. Finally, the excess Gibbs energy of the mixtures was calculated and qualitatively analyzed against the composition of the system. [ABSTRACT FROM AUTHOR]