MgB_4O_7-Na_2B_4O_7-Li_2B_4O_7-H_2O四元体系288K介稳相平衡的研究

Metastable phase equilibria of MgB_4O_7-Na_2B_4O_7-Li_2B_4O_7-H_2O quaternary system at 288 K

采用等温蒸发法进行了MgB4O7-Na2B4O7-Li2B4O7-H2O四元体系288 K时的介稳相平衡研究,测定了该体系介稳相平衡的溶解度和密度。研究发现该四元体系为简单共饱和型,无复盐形成。根据溶解度数据绘制了相图,相图中有一个四元共饱点E,三条单变度曲线E1-E、E2-E、E3-E。平衡固相分别为:MgB4O7.9H2O、Na2B4O7.10H2O和Li2B4O7.3H2O。由相图可知:Na2B4O7对Li2B4O7具有盐析作用,对MgB4O7有盐溶作用。

Study on metastable phase equilibria at 288K in MgB4O7 - Na2B4O7- Li2B4O7 - H2O quaternary system was done by the method of isothermal evaporation. Solubilities and densities of the metastable equilibrium solution were determined. The results showed that the system was of simple eutectic type and no double salt was formed in MgB4O7 - Na2B4O7 - Li2B4O7 - H2O quaternary system at 288K. The metastable equilibrium phase diagram was plotted by referring to the experimental data. In the phase diagram of the quaternary system, there were one invariant point E, three uninvariant curves（E1 - E, E2 - E, E3 - E） and three fields of crystallization （MgB4O7- Na2B4O7 - Li2B4O7 - H2O）. And Na2B4O7 had the salting-out effect on Li2B4O7.