Phase Equilibria and Physicochemical Properties of the Ternary System (LiBO2 + NaBO2 + H2O) and Quaternary system (NaBO2 + NaCl + Na2SO4 + H2O) at 323.15 K

Solid-liquid phase equilibria of ternary system (LiBO2 + NaBO2 + H2O) and quaternary system (NaBO2 + NaCl + Na2SO4 + H2O) at 323.15 K and 0.1 MPa were determined by isothermal solution equilibrium method. The experimental results show that there are one invariant point, two univariant solubility curves and two crystallization regions in the ternary system (LiBO2 + NaBO2 + H2O). The phase region of LiBO2·2H2O is the largest, indicating that its solubility is the smallest, and no double salt and solid solution was formed in this system. In the quaternary system (NaBO2 + NaCl + Na2SO4 + H2O), there are two invariant points, five univariant solubility curves, and four crystallization regions. Among them, the crystallization region of Na2SO4 is the largest, and the double salt (NaCl·NaBO2·2H2O) is formed in the system. The physicochemical properties including refractive index, density and pH value of saturated solutions in the ternary system and quaternary system all changes regularly with the increasing of NaBO2/NaCl concentration.