Studies on the Stable Phase Equilibria of Quinary System Li+, K+, Mg2+//Cl-, B4O72--H2O at 273 K

The isothermal equilibrium method was used to study the stable phase equilibria of the quinary system Li+, K+, Mg2+//Cl-, B4O72--H2O at 273 K. The solubility data of each component in this system were measured through experiments, and the isothermal phase diagram of this system was also drawn. For the identification of the equilibrium solid phases of the invariant points, X-ray diffraction characterization was used. The projection surface of the stable phase diagram of the quinary system Li+, K+, Mg2+//Cl-, B4O72--H2O at 273 K was drawn under the saturation condition of MgB4O7. The simplified dry-salt diagram has carnallite (KCl center dot MgCl2 center dot 6H(2)O) and lithium carnallite (LiCl center dot MgCl2 center dot 7H(2)O), and it contains eleven univariate solubility curves, five invariant points and seven crystallization regions corresponding to K2B4O7 center dot 4H(2)O, Li2B4O7 center dot 3H(2)O, KCl, MgCl2 center dot 6H(2)O, and LiCl center dot 2H(2)O and double salts carnallite (KCl center dot MgCl2 center dot 6H(2)O) and lithium carnallite (LiCl center dot MgCl2 center dot 7H(2)O). In the quinary system, by comparing the area of each crystalline phase zone, lithium chloride is a highly soluble salt, therefore, in the solubility diagram, in comparison with magnesium tetraborate, it corresponds to the smallest crystallization area.