THERMODYNAMICS OF CALCIUM-CHLORIDE IN CONCENTRATED AQUEOUS-SOLUTIONS AND IN CRYSTALS

A variety of experimental measurements for CaCl2(aq) in the range from 5 mol.kg-1 to saturation at temperatures from 323 to 523 K, including the vapor pressures of the saturated solutions, are combined to yield a comprehensive thermodynamic treatment. The new equation was generated first for the osmotic coefficient phi. It was fitted to the value of phi and its molality derivative at 5 mol.kg-1 to a new comprehensive treatment for dilute solutions of Holmes et al. (J. Chem. Thermodyn. 1994,26,271), and to the available data for higher molality. The combination of the equation of Holmes et al. to 5 m and the new equation to saturation molality then yields a complete treatment for aqueous CaCl2. The chemical potentials in the saturated solution were then used, with other information, to give a general treatment of the thermodynamics of solid CaCl2 and its hydrates with 1/3, 1, and 2 H2O. This treatment for the range above 323 K supplements a recent treatment of Pitzer and Shi (J. Solution Chem. 1993, 22, 99) for lower temperatures which considered both aqueous CaCl2, and its solid hydrates with 4 and 6 H2O.