四元体系硼酸锂-硼酸钾-硼酸镁-水在308.15 K时固液相平衡研究

采用等温溶解平衡法研究四元体系硼酸锂-硼酸钾-硼酸镁-水在308.15 K时固液相平衡,测定了体系溶解度和平衡液相的密度、折光率和pH。研究发现：该体系308.15 K时的稳定相图中包含一个共饱点（L+Li₂B₄O₇·3H₂O+K₂B₄O₇·4H₂O+Mg₂B₆O₁₁·15H₂O）,其液相组成：w（Li₂B₄O₇）=3.112%、w（K₂B₄O₇）=16.64%、w（Mg₂B₆O₁₁）=0.101 8%;3个固相结晶区：Li₂B₄O₇·3H₂O、K₂B₄O₇·4H₂O、Mg₂B₆O₁₁·15H₂O,体系无复盐或固溶体生成。溶液中硼酸锂、硼酸钾对多水硼镁石有很强的盐析效应,液相的密度、折光率和pH随溶液中硼酸盐浓度的增加呈规律性变化。

Solid-liquid phase equilibria in quaternary system lithium borate-potassium borate-magnesium borate-water at 308.15 K

The phase equilibrium of the quaternary system lithium borate-potassium borate-magnesium borate-water was studied at 308.15 K with isothermal solution saturation method.Solubilities,densities,refractive indices and pH of the system were determined.Stability phase diagram of this system contains one invariant point L+Li₂B₄O₇·3H₂O+K₂B₄O₇·4H₂O+Mg₂B₆O₁₁·15H₂O） which liquid compositions were as follows：w（Li₂B₄O₇）=3.11%,w（K₂B₄O₇）=16.64% and w（Mg₂B₆O₁₁）=0.10%; and three crystallization regions corresponding to Li₂B₄O₇·3H₂O,K₂B₄O₇·4H₂O and Mg₂B₆O₁₁·15H₂O,respectively. Neither double salts nor solid solutions formed in this system,and the K₂B₄O₇ and Li₂B₄O₇ in solution both had a strong salting-out effect on inderite.The solution density,refractive index and pH of the quaternary system changes regularly with the increasing of borate concentration.