Solid-Liquid Phase Equilibrium in the Ternary Systems (Li2B4O7 + MgB4O7 + H2O) and (Na2B4O7 + MgB4O7 + H2O) at 298.15 K

Solid-liquid phase equilibria of the two ternary systems (Li2B4O7 + MgB4O7 + H2O) and (Na2B4O7 + MgB4O7 + H2O) at T = 298.15 K and p = 0.1 MPa were studied with the isothermal dissolution equilibrium method: Solubilities, densities; pH values, and refractive indices were measured experimentally. In the ternary system (Li2B4O7 + MgB4O7 + H2O) at 298.15 K, there are one invariant point corresponding to (Li2B4O7 center dot 3H(2)O + MgB4O7 center dot 9H(2)O), two isothermal dissolution curves, and two crystallization regions. The crystallized area of MgB4O7 center dot 9H(2)O is increased obviously with the increase of temperature, while that of Li2B4O7 center dot 3H(2)O is decreased slightly. In the ternary system (Na2B4O7 + MgB4O7 + H2O) at 298.15 K, there are one invariant point (Na2B4O7 center dot 10H(2)O + MgB4O7 center dot 9H(2)O), two isothermal dissolution curves, and two crystallization regions. The crystallized area of MgB4O7 center dot 9H(2)O is increased with the increase of temperature, while that of Na2B4O7 center dot 10H(2)O is decreased obviously. Both of the systems belong to a simple eutectic type, and neither double salts nor solid solutions formed.