Pitzer model parameters for sparingly soluble salts from solubility measurements: thallium(I) chloride in aqueous solutions of ammonium chloride, rubidium chloride and caesium chloride at 298.15 K

Abstract

Measurements are reported of the solubility of thallium(I) chloride in aqueous solutions of ammonium chloride, rubidium chloride and caesium chloride at 298.15 K at concentrations of added salt up to 4.0 mol kg–1. Pitzer model parameters for TICI, β(o) and β(1), were evaluated assuming Cϕ= 0. These parameters can account satisfactorily for the ionic interactions between Tl+ and Cl– without the need to assume ion association explicitly, thus simplifying the interpretation of the experimental data. Although the parameter α= 2, which is customarily used for a broad class of electrolytes, is found to be satisfactory for TlCl, larger values of α generally gave better fits to the experimental data. Mixture parameters, θ and ψ, relevant to the various mixed electrolytes are also reported.