Metastable Phase Equilibria of the Reciprocal Quaternary System Containing Lithium, Sodium, Chloride, and Sulfate Ions at 273.15 K†.

Experimental studies on the metastable solubilities and the physicochemical properties including density, refractive index, conductivity, and pH values in the reciprocal quaternary system containing lithium, sodium, chloride, and sulfate at 273.15 K were determined with the method of isothermal evaporation. According to the experimental results, the dry-salt phase diagram, the water phase diagram, and the physicochemical properties versus composition were plotted. In the dry-salt phase diagram, there are three invariant points, seven solubility isotherm curves, and five crystallization fields corresponding to sodium chloride, mirabilite, lithium chloride dehydrate (LiCl·2H2O), lithium sulfate monohydrate, and a double salt (Li2SO4·3Na2SO4·12H2O). There were no solid solutions formed in the reciprocal quaternary system. The crystallizing region of mirabilite is the largest, while the region of LiCl·2H2O is the smallest with the highest concentration and a strong salting-out effect to NaCl and Li2SO4·H2O. When compared with the stable phase diagram at 273.15 K, the area of the phase region of mirabilite is enlarged significantly, while the areas of the phase regions of NaCl, Li2SO4·H2O, and Li2SO4·3Na2SO4·12H2O are decreased. The calculated values of densities and refractive index in the quaternary system with empirical equations are in good agreement with the experimental values. [ABSTRACT FROM AUTHOR]