Phase equilibria in the quinary system KCl-KBr-K2SO4-K2B4O7-H2O at 323 K and 348 K were studied by isothermal solution saturation method. The solubilities and densities of the solution in this system were determined experimentally. Using the experimental data, the phase diagrams of the quinary system were obtained (saturated with K2SO4). The quinary system is a solid solution. It comprises one univariant curve and two crystallization fields (saturated with K2SO4), i. e. , solid solution K (Cl, Br) and K2B4O7 ·4H2O, and does not have invariant point. K2B4O7·4H2O has larger crystallization fields, while solid solution K (Cl, Br) has smaller crystallization fields. It is also found that KBr has the salting-out effect on KC1. The density of the solution increases with the increase of KBr concentration and decreases with the increase of KC1 concentration. Compared with the stable phase diagrams at 323 K and 348 K, the crystallization fields of K2B4O7·4H2O is small at 348 K, whereas the crystallization field of solid solution K (Cl, Br) is large.%用等温溶解平衡法研究了五元体系KCl-KBr-K2SO4-K2B4O7-H2O在323 K和348 K时的相平衡关系,测定了该五元体系在相应温度条件下平衡溶液的溶解度和密度,根据相平衡实验数据绘制相应的相图(K2SO4饱和).研究结果表明:该五元体系在323 K和348 K条件下均属于固溶体型,相图中均有2个平衡固相结晶区,其平衡固相分别为固溶体K (C1,Br)和K2B4O7·4H2O,1条单变量曲线.该五元体系323 K和348 K的相图相比,348 K时K2 B4O7·4H2O结晶区变小,而固溶体K(C1,Br)结晶区变大.
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