1.
The stable phase equilibria of quaternary systems LiBr-NaBr-MgBr
2-H
2O and LiBr-KBr-MgBr
2-H
2O at 298.15 K were studied by both experimental measurement(isothermal solution saturation method) and theoretical prediction(Pitzer model). The solubilities of the saturated solution have been determined experimentally and two stable phase diagrams and relevant water diagrams of the two quaternary systems were obtained. Results show that quaternary system LiBr-NaBr-MgBr
2-H
2O is hydrate II type as NaBr and NaBr·2H
2O coexistence. Its phase diagram consists of only one invariant point, four univariant curves, and five crystallization fields. The quaternary system LiBr-KBr-MgBr
2-H
2O is a complex type as the double salt KBr·MgBr
2·6H
2O formed. In addition to this double salt, the three single salts LiBr·2H
2O, KBr and MgBr
2·6H
2O also crystallize. In this paper, the solubilities of phase equilibria in above quaternary systems were also calculated by the Pitzer's electrolyte solution model. All the needed parameters can be obtained from the literature or be fitted by experimental data. On the Basis of the experimental and calculated results, the phase diagram of the quaternary system was plotted for comparison. It shows that the calculation results are consistent with the experimental ones.
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