Phase Equilibria in the System NaCl–NaBr–NaF·Na2SO4

Differential thermal analysis (DTA), differential scanning calorimetry (DSC), and thermogravimetric (TG) physicochemical methods of analysis were used to identify phase equilibrium states in the stable secant triangle NaCl–NaBr–NaF·Na2SO4 of the four-component system NaF–NaCl–NaBr–Na2SO4. It has been established that the liquidus surface of the system consists of crystallization fields of a continuous series of NaClxBr _1 - x and NaF⋅Na2SO4 solid solutions, melting congruently. A minimum melting point of 595ºС was found at a component ratio of 22 mol % NaCl, 53 mol % NaBr, and 25 mol % NaF·Na2SO4 and a specific enthalpy of melting of 274.60 ± 8.24 J/g. It was shown that a decrease in the mass of the sample begins at 690°C.