Experimental Study on Phase Equilibria in Na2B4O7-Na2SO4-H2O and Li2B4O7-Na2B4O7-H2O Aqueous Ternary Systems at 273 K

The solubility data for ternary systems Na2SO4-Na2B4O7-H2O and Li2B4O7-Na2B4O7-H2O at 273 K were obtained experimentally by the isothermal solution equilibrium method, and the solid phases were analyzed by X-ray diffraction. On the base of the experimental results, the stable phase equilibrium diagrams for these two systems were constructed at 273 K. The stable phase equilibrium diagrams indicate that both phase diagrams show an invariant point, two univariant solubility curves and two solid phase crystalline regions. The two solid phases corresponding to the invariant point of ternary system Na2SO4-Na2B4O7-H2O are Na2B4O7 <bold> </bold>10H(2)O and Na2SO4 <bold> </bold>10H(2)O, and the two crystallization regions of the ternary system Li2B4O7-Na2B4O7-H2O are Na2B4O7 <bold> </bold>10H(2)O and Li2B4O7 <bold> </bold>3H(2)O, respectively. Thus, the two ternary systems belong to simple co-saturated type without complex salt or solid solution.