THERMODYNAMIC SIMULATION OF 4-COMPONENT CARNALLITE TYPE SYSTEMS

The standard method of Fitter for predicting the solubility isotherms of systems in which solid phases with a constant composition crystalli ze is applied to cases when mixed crystals are formed. The four-compon ent carnallite type systems RbCl-CsCl-MgCl2-H2O, RbCl-KCl-MgCl2-H2O, a nd RbCl-RbBr-MgCl2-MgBr2-H2O and the corresponding subsystems are ther modynamically simulated at 25 degrees C. It is established that the so lubility diagrams consist of crystallization regions of the simple sal ts MX, M'X', MgX(2).6H(2)O, and MgX'(2).6H(2)O and of the correspondin g carnallite type double salts with the composition 1:1:6. A method of calculation of the integral Gibbs energy of mixing G(mix)(s) of cryst als formed in water-salt systems has been proposed. The results on the systems RbCl-KCl-H2O, RbCl-RbBr-H2O, and MgCl2-MgBr2-H2O are compared with experimental data from the literature and with values calculated using various models.