四元体系Li+,K+,Mg2+//B4O72——H2O 273 K相平衡

利用等温溶解平衡法研究了四元体系Li⁺， K⁺， Mg²⁺//B₄O₇^2--H₂O 273 K相平衡关系。测定了该体系平衡时各组分的溶解度和平衡液相密度。根据实验数据和固相组成分别绘制了四元体系Li⁺， K⁺， Mg²⁺//B₄O₇^2--H₂O 273 K时的稳定相图、水图以及相应的密度-组成图。结果表明：该体系组分之间没有形成复盐和固溶体，属于简单共饱和型体系；体系的稳定相图由1个共饱点，3条单变量曲线，3个固相结晶区组成，结晶区分别对应Li₂B₄O₇·3H₂O、K₂B₄O₇·4H₂O和MgB₄O₇·9H₂O；平衡液相密度在共饱点处达到最大。研究还对该四元体系在273 K、288 K和348 K不同温度时的稳定相图作了对比分析和讨论。

Phase equilibria in quaternary system Li+, K+, Mg2+//B4O72--H2O at 273 K

The stable phase equilibria of the quaternary system Li⁺, K⁺, Mg²⁺//B₄O₇^2--H₂O at 273 K were studied using isothermal solubility equilibrium method. The solubility of the salts and densities in the system were determined, respectively. According to the experimental data and the corresponding equilibrium solid phase, the isothermal solubility diagram, water content diagram about the system Li⁺, K⁺, Mg²⁺//B₄O₇^2--H₂O at 273 K and the corresponding density composition diagram were plotted, respectively. Experimental results show that there are no complex salt or solid solution, and the system belongs to a simple eutectic type. The phase diagram is constituted by an invariant point, three univariant solubility curves and three solid phase crystalline regions. The three solid phases crystalline regions correspond to Li₂B₄O₇·3H₂O, K₂B₄O₇·4H₂O and MgB₄O₇·9H₂O. In addition, the density of saturated solution reached maximum at invariant point. Finally, a comparative analysis and discussion have been made in this paper for the stable phase diagrams of the system at 273 K, 288 K, and 348 K.