In this paper

aiming at ternary salt-water systems of Na+//Cl-

NO3--H2O

Na+//Cl-

SO42--H2O and Na+

K+//Cl--H2O

the freezing points

eutectic points and the crystallization regularities of salts were investigated; the three-dimensional phase diagrams of temperature-composition of the ternary systems were plotted according to experimental data. The results were as following:the relationships among the freezing point

eutectic point

phases and the compositions of solution for the ternary system can be expressed by triangular prism. In the three ternary systems

there were no double salts at the eutectic point temperature

and there was an eutectic point with two salts and ice

three eutectic lines with single salt and ice or two salts

a crystallization zone with ice and two single salt. The three-dimensional phase diagram of temperature-composition of solution can be used to describe the relationships among the crystalline regions

freezing points or eutectic points and the compositions of liquids for the ternary salt-water systems visually

and to determine the precipitation processes of salts or ice as cooling solution. Three empirical formulas about freezing points were established. The empirical formulas of freezing point and the excess Gibbs free energy model were used to predict the freezing point and eutectic point of the ternary systems

which turned out that the calculated values were in good agreement with the experimental values.