Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

The thermodynamics phase equilibria of the aqueous ternary systems LiCl + MgCl2 + H2O and LiCl + KCl + H2O at 348 K were investigated using an isothermal evaporation method. The solubilities and physicochemical properties such as density and refractive index of the equilibrated solution were determined. The compositions of solid phases were confirmed using the Scherinemakers wet residue method. In accordance with the experimental data, the phase diagrams and physicochemical vs composition diagrams were constructed. The ternary system LiCl + MgCl2 + H2O is of a complex type with double salt LiCl*MgCl2*7H2O (lithium carnallite) formed at 348 K, and its phase diagram consists of two invariant points, three univariant curves, and three crystallization fields corresponding to lithium chloride monohydrate (LiCl*H2O), magnesium chloride hexahydrate (MgCl2*6H2O), and lithium carnallite (LiCl*MgCl2*7H2O). The ternary system LiCl + KCl + H2O is of a simple eutectic type at 348 K, and its phase diagram is composed of one invariant point, two univariant curves and two crystallization fields corresponding to potassium chloride (KCl) and lithium chloride monohydrate (LiCl*H2O). Lithium chloride has a salting out effect on magnesium chloride or potassium chloride. Comparisons between the metastable and stable phase diagrams at 348 K of these two ternary systems have been drawn. In the system LiCl + MgCl2 + H2O, the crystallization region of MgCl2*6H2O under the metastable equilibrium is smaller, while the crystallization region of the LiCl*MgCl2*7H2O is larger. In the system LiCl + KCl + H2O, the crystallization regions of LiCl*H2O and KCl under metastable equilibrium are both smaller. Comparisons between the metastable phase diagrams of system LiCl + KCl + H2O at (298, 323, and 348) K show that the crystallization region of LiCl*H2O increased with the rise of temperature, whereas the crystallization region of salt KCl is decreased.