The equilibrium data on the ternary system of NH4Cl—CaCl2—H2O at 50°C were investigated using the wet-residue method. The experimental results show that there are three pure phase crystal areas of NH4Cl, 2NH4Cl·CaCl2·3H2O and CaCl·2H2O, two mixture phase crystal areas of NH4Cl and 2NH4Cl·CaCl·3H2O, and 2NH4Cl·CaCl2·3H2O and CaCl·2H2O in the system. A new hydration double salt (2NH4Cl·CaCl·3H2O) was found in the ternary equilibrium system for the first time.
