Thermodynamic properties of electrolyte solutions: emf study of the system NaCl–Na2SO4–H2O at 25, 35 and 45 °C

Abstract

Electromotive force measurements have been carried out on the system NaCl–Na₂SO₄–H₂O at l= 0.5, 1.0, 2.0, and 3.0 mol kg^–1 and 25, 35 and 45 °C using a cell consisting of a sodium ion-selective electrode and an Ag/AgCl electrode. The binary and ternary interaction parameters of the Pitzer formalism and their temperature derivatives have been evaluated. The osmotic coefficients, excess free energies and heats of mixing of the system have been predicted at all the temperatures and ionic strengths studied. The activity coefficients of the second salt, Na₂SO₄, have been calculated.