Acta Phys.-Chim. Sin.

The phase diagrams of Na2CrO4-(NH4)(2)CrO4-H2O system at 20 degrees C and 50 degrees C have been determined by solubility method. The experimental results have also been verified by mathematical method. The phase diagrams show that there is a double salt of NaNH4CrO4 . 2H(2)O formed in the system, which will decrease the purity of (NH4)(2)CrO4. Consequently, a method is found to separate the mixture of ammonium chromate and double salt by analysing the phase diagrams.The phase diagrams of Na2CrO4-(NH4)(2)CrO4-H2O system at 20 degrees C and 50 degrees C have been determined by solubility method. The experimental results have also been verified by mathematical method. The phase diagrams show that there is a double salt of NaNH4CrO4 . 2H(2)O formed in the system, which will decrease the purity of (NH4)(2)CrO4. Consequently, a method is found to separate the mixture of ammonium chromate and double salt by analysing the phase diagrams