SOLUBILITY AND PITZER MODEL PARAMETERS IN THALLIUM(I) CHLORIDE SYSTEMS, TLCL-MGCL2-H2O AND TLCL-CACL2-H2O

The solubility of thallium(I) chloride has been determined in aqueous solutions of magnesium chloride and calcium chloride at concentrations up to 1.5 mol kg(-1). The data were fitted to Fitter's equations with out explicit assumption of ion association. Here the beta((1)) term fo r TlCl is essentially equivalent to the beta((2)) term for 2:2 electro lytes, but with alpha = 3, instead of alpha = 2. 'Best values' of beta ((0)) and beta((1)) for TlCl are recommended together with K-s, the ac tivity solubility product. These were used to derive the mixture param eters pertaining to the systems, theta(TlN) and psi(TlNCl) (N = Ca, Mg ). The fit of the experimental data was found to be worse if higher-or der mixing terms were included in the analysis. Best values of theta(T lM) and psi(TlMCl) for M = H, NH4, Li, Na, K, Rb and Cs are also given to complete the parameter base. Activity coefficients for thallium(I) chloride in the mixtures are derived.