THERMODYNAMIC PROPERTIES OF AQUEOUS MIXTURES OF LICL AND LI2SO4 AT DIFFERENT TEMPERATURES

Emf measurements were made on the cell without liquid junction: Li-ISE LiCl(m(1)), Li2SO4(m(2)) Ag/AgCl. The performances of the electrode p airs constructed in our laboratory were tested and exhibited near-Nern stian behavior. The mean activity coefficients of LiCl for the system Li+-Cl--SO42--H2O have been investigated by the emf values at temperat ures of 0, 15, 35 degrees C and constant total ionic strengths of 0.05 , 0.1, 0.5, 1.0, 2.0, 3.0 and 5.0 mol . kg(-1). The activity coefficie nts decrease with increasing temperature and the ionic strength fracti on of Li2SO4 in the mixtures. The thermodynamic properties are interpr eted by use of Harned's empirical equations and Pitzer's ion interacti on approach including the contribution of higher order electrostatic t erms. The experimental results obey Harned's rule and are described by using Pitzer equations satisfactorily. The activity coefficients of L i2SO4, the osmotic coefficients and the excess free energies of mixing for the system in the experimental temperature range were reported.