Solid–Liquid Phase Equilibria of Ba2+//Cl–, S2–, OH––H2O Quaternary and Subsystems at 298.15 K

The solid–liquid phase equilibria of the Ba2+//Cl–, S2–, and OH––H2O quaternary system and its three subternary systems at 298.15 K are studied via the isothermal solubility phase equilibrium method. The solubility data, liquid properties of density and pH, and phase diagrams of the ternary and quaternary systems are obtained. Solid species of Ba(OH)2·8H2O, BaCl2·2H2O, Ba(OH)Cl·2H2O, and BaS exist in the quaternary system and corresponding ternary systems at 298.15 K. The four solid species build up two invariant points, one disproportionate and one proportionate, and four phase regions. The largest phase area is covered by Ba(OH)·8H2O, and the lowest water point is the proportionate invariant point saturated by BaCl2·2H2O, Ba(OH)Cl·2H2O, and BaS.