Water activities, activity coefficients and solubility in the binary and ternary aqueous solutions [formula omitted] with [formula omitted

Abstract

In this investigation, the ternary aqueous solutions of lithium chloride with alkaline earth metal { yLiCl+(1− y)Y Cl 2}(aq) with Y Mg 2+; Ca 2+; and Ba 2+ have been studied using the hygrometric method at 298.15 K. The water activities are measured at total molalities from 0.20 mol kg −1 to saturation for different ionic-strength fractions y of LiCl with y = 0.20 , 0.50 and 0.80. The obtained data allow the deduction of osmotic coefficients. From these measurements, the mixing ionic parameters θ LiY and ψ LiY Cl are determined and used to predict the solute activity coefficients in the mixtures. Also, we have completed measurements of water activities from 6 mol kg −1 to saturation of the pure electrolyte solutions of CaCl 2(aq) using the hygrometric method. Few studies have extended their measurements to saturation (11.00 mol kg −1 for CaCl 2⋅2H 2O). These results are compared with those obtained by other techniques. The values of the pure electrolyte and mixing ionic-interaction parameters, which give the best fit of the activity data in binary, ternary solutions and solubility data are tabulated. Thermodynamic characteristics, solubility products K s p ∘ and the standard molar Gibbs energy of formation Δ G f m 0 of the crystallizing solids are given. The predicted solubility isotherms are compared with the literature data. The behaviour of aqueous electrolyte solutions of alkaline-earth with lithium of chlorides { yLiCl+(1− y)Y Cl 2}(aq) with Y Mg 2+; Ca 2+ or Ba 2+, is correlated and the results show that the ionic interactions in these solutions are essentially related to the nature of solute combined with the solute LiCl.