Thermodynamics metastable phase equilibria of aqueous quaternary system LiCl + KCl + RbCl + H2O at 323.15 K

The solubilities and physicochemical properties (densities and refractive indices) in the aqueous quaternary system LiCl + KCl + RbCl + H2O were investigated at 323.15 K using an isothermal evaporation method. The stereo phase diagram, the projected diagram, the water content diagram and the physicochemical properties versus composition diagrams were plotted based on the measured data. There are two invariant points, five univariant curves and four crystallization fields corresponding to single salts potassium chloride (KCl), rubidium chloride (RbCl), lithium chloride monohydrate (LiCl·H2O) and a solid solution of potassium and rubidium chloride [(K, Rb)Cl] in the projected diagram. No double salt was formed. Comparisons between the metastable phase diagrams at 298.15 K and 323.15 K show that the crystallization zones of solid solution [(K, Rb)Cl] decreased at 323.15 K, while the crystallization zones of single salts KCl, RbCl, and LiCl·H2O enlarged at 323.15 K. The calculated refractive indices using empirical equations have a maximum relative error less than 0.008.