Calculation of phase equilibria in the NaF-Na2SO4-NaCl-H2O system at 25°C

Using Fitter's equations, a diagram of solubility at 25 degrees C for the NaF-Na2SO4-NaCl-H2O system, including NaF, NaCl, Na2SO4. 10H(2)O, Na2SO4, and NaF . Na2SO4 crystallization fields, was calculated from the data on binary and ternary subsystems. The calculated water activity in the saturated solutions was used to classify nonvariant equilibria from the standpoint of the isomorphism of fusibility diagrams for triple systems and solubility diagrams for ternary systems in the coordinates water activity-Jaenicke's indices of salts.