Solvent activity and osmotic pressure of binary aqueous and alcoholic solutions of calcium chloride up to 368 K and high salt concentration

Abstract

The solvent activity of aqueous and alcoholic liquid solutions of calcium chloride have been determined at ambient pressure, under vapor-liquid equilibrium conditions, and critically analyzed over a wide range of temperature (from ambient to ~368 K) and salt concentrations (from very dilute to nearly saturated solutions). The results are generally in good agreement with those reported or obtainable from a variety of literature data sources. In addition, for the alcoholic salted solutions, new T-concentrations regions have been explored. A solvation-dissociation based model was first parametrized and then used to establish the behavior of the activity of the solvents and to quantify the equilibrium vapor pressure lowering and the osmotic pressure of the solutions for any temperature and salt concentration. It was found that: a) activity of the solvents decreases when salt concentration increases, while it increases with temperature; b) osmotic pressure of concentrated solutions, is a function of both solvent activity and volumetric properties of the solutions, and is much higher (up to hundred-fold MPa for the aqueous solutions) of that calculated with the van’t Hoff equation; c) the behavior of the osmotic pressure with the temperature is opposite to that predicted by the van’t Hoff equation, coherently with the exothermic nature of the dilution process and the literature values of the heat of dilution.