K_2B_4O_7-K_2SO_4-KCl-H_2O四元体系298K相平衡研究

Study on metastable phase equilibrium of quaternary system K_2B_4O_7-K_2SO_4-KCl-H_2O at 298 K

采用等温溶解平衡法研究了四元体系K2B4O7-K2SO4-KC l-H2O在298 K的相平衡及平衡液相,测定了平衡液相的溶解度及密度。研究结果表明:该四元体系为简单共饱和型,无复盐及固溶体形成。根据实验数据绘制了相应的相图。相图中有1个共饱点E,3条单变曲线E1E,E2E和E3E;3个结晶区平衡固相分别为:K2B4O7.4H2O,K2SO4和KC l,并简要讨论了密度变化规律。实验结果表明,KC l对K2B4O7.4H2O和K2SO4有盐析作用。

The metastable equilibrium and equilibrium liquid-phase in quaternary system K2B4O7-K2SO4-KCl-H2O at 298 K were studied by isothermal equilibrium method, and the solubility and density of the equilibrium solution were measured. The result shows that the quaternary system is a type of simple common-saturation and without complex salt and solid solution. Based on the solubility data, the phase diagram of the system was plotted, consisting of three univariant curves of E1E, E2E and EaE, one invariant point E and three crystallization fields of K2B4O7 · 4H2O, K2SO4 and KCl. The densities transformation rules were discussed simply. The experimental results show that KCl has the salting-out effect on K2B4O7 · 4H2O and K2SO4.