Phase Equilibria in the Ternary Systems K2SO4–K2B4O7–H2O and Na2SO4–Na2B4O7–H2O at 348 K

Abstract

Phase equilibria in the ternary systems K2SO4–K2B4O7–H2O and Na2SO4–Na2B4O7–H2O at 348 K were studied by the isothermal solution saturation method. The solubilities and densities of the solution in these ternary systems were determined experimentally. Using the experimental data, the phase diagrams of the two ternary systems were obtained. The ternary systems K2SO4–K2B4O7–H2O and Na2SO4–Na2B4O7–H2O at 348 K are a type of simple common saturation and without complex salt and solid solution. In the phase diagrams and both the two ternary systems at 348 K, all have one invariant point, two univariant curves, and two regions of crystallization. The two crystallization regions of the ternary system K2SO4–K2B4O7–H2O at 348 K correspond to potassium borate tetrahydrate (K2B4O7·4H2O) and potassium sulfate (K2SO4). The two single-salt crystallization regions are sodium borate pentahydrate (Na2B4O7·5H2O) and sodium sulfate (Na2SO4) in the ternary system Na2SO4–Na2B4O7–H2O at 348 K.