LAUSR

Abstract Through using the isothermal dissolution equilibrium method, phase equilibria in the quaternary system KBr–CaBr 2 –MgBr 2 –H 2 O were studied at (298 and 323) K. Based on the experimental data, the phase diagrams were obtained. It can be seen that two phase diagrams all contain complex salts. In quaternary system KBr–CaBr 2 –MgBr 2 –H 2 O at 298 K, there are two invariant points, five univariant curves, and four crystallization fields, corresponding to KBr, CaBr 2 ·6H 2 O, MgBr 2 ·6H 2 O and KBr·MgBr 2 ·6H 2 O. At 323 K, a new double salt 2MgBr 2 ·CaBr 2 ·12H 2 O could be found in this quaternary system. As a result, it has three invariant points, seven univariant curves, and five crystallization regions fields, corresponding to KBr, CaBr 2 ·4H 2 O, MgBr 2 ·6H 2 O, KBr·MgBr 2 ·6H 2 O and 2MgBr 2 ·CaBr 2 ·12H 2 O. Moreover, the phase diagrams for the quaternary system do not consist new precipitated solids at 298 K and 323 K in comparision with the phase diagrams for ternary subsystems. Using Pitzer theoretical and mathematical calculation tool, the solubilities of the quaternary system were calculated under the condition of (298 and 323) K. And make a comparison with the experimental data. It shows that the calculation results are in good agreement with experimental values.