Measurements and calculations of solid-liquid equilibria in the quaternary system NaBr-KBr-CaBr2-H2O at 298Â K

The solubilities and densities of the quaternary system NaBr-KBr-CaBr2-H2O were investigated by the method of isothermal solution saturation at 298 K. On the basis of the experimental data, the phase diagram, water content diagram and the density-composition diagram were plotted, respectively. In the phase diagram of quaternary system NaBr-KBr-CaBr2-H2O at 298 K, no complex salt or solid solution was found. There are two invariant points, five univariant curves, and four crystallization fields corresponding to NaBr, NaBr·2H2O, KBr and CaBr2·6H2O. Pitzer's equations based model has been applied to calculate bromide minerals solubilities in the quaternary system NaBr-KBr-CaBr2-H2O at 298 K. All binary and mixing ion interaction parameters and solubility products of bromide solids are taken from previously published T-variation model for the system under study, adapted to 298 K. The predicted and experimental solubilities are in a very good agreement up to a very high total concentration of the quaternary system.