K2B4O7-Na2B4O7-Li2B4O7-H2O 四元体系15℃介稳相平衡研究

采用等温蒸发平衡法研究了四元体系K2B4O7-Na2B4O7-Li2B4O7-H2O15℃时的介稳相平衡及平衡液相的物化性质(密度,粘度，电导率，折光率，pH)。根据实验数据绘制了相图，相图中有一个共饱点E，三条单变度曲线E3F，E2F，E1F；三个平衡固相分别为：K2B4O7•4H2O,Na2B4O7•10H2O和Li2B2O4•16H2O；硼酸钾具有最大溶解度，硼酸钠具有最小溶解度。同时，根据试验数据绘制了组成－物化性质关系图，从图可见溶液的密度，粘度和折光率均随着溶液浓度的增大而逐渐增大，在共饱和点F处达到最大值，而溶液的pH值和电导率却随着溶液浓度的增大呈总体下降的趋势。

Metastable Equilibria for the Quaternary System Li2B4O7+Na2B4O7+K2B4O7+H2O at 15 °C

Metastable equilibrium solubilities and such physico‐chemical properties as densities, conductivity, pH, refractive index and viscosity of the solution for the quaternary system Li₂B₄O₇+Na₂B₄O₇+K₂B₄O₇+H₂O at 15 °C were determined experimentally. According to the experimental data, the metastable equilibrium phase diagram was plotted. In the metastable phase diagram, there are one invariant point, three univariant curves, and three fields of crystallization: Li₂B₂O₄·16H₂O, Na₂B₄O₇·10H₂O, and K₂B₄O₇·4H₂O. Potassium borate (K₂B₄O₇·4H₂O) has the smallest crystallization field and sodium borate (borax) has the biggest one. Also, the relationship diagram between the properties and the ion concentration of solution was constructed. It can be seen from the relationship diagram that the metastable equilibrium solution density values, viscosity values and refractive index values are increased apparently with the rise of lithium borate concentration, reaching the maximum values at invariant point F. Electrical conductivity values and pH values, however, fall down with the rise of ion concentration on the whole.