Water activities, activity coefficients and solubility in the binary and ternary aqueous solutions LiCl + YCl2 + H2O with Y Mg2+; Ca2+; or Ba2+

In this investigation, the ternary aqueous solutions of lithium chloride with alkaline earth metal {yLiCl + (1 - y)YCl2}(aq) with Y Mg2+; Ca2+; and Ba2+ 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 theta(LiY) and psi(LiYCl) 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 CaCl2(aq) using the hygrometric method. Few studies have extended their measurements to saturation (11.00 mol kg(-1) for CaCl2 center dot 2H(2)O). 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-sp degrees and the standard molar Gibbs energy of formation Delta 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)YCl2)(aq) with Y Mg2+; Ca2+ or Ba2+, 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. (C) 2009 Published by Elsevier Ltd