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

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