三元体系NaCl-Na_2B_4O_7-H_2O 363.15K下介稳相平衡研究

Metastable phase equilibrium of ternary system NaCl-Na_2B_4O_7-H_2O at 363.15 K

采用等温蒸发法研究了三元体系Na Cl-Na2B4O7-H2O 363.15 K下的介稳相平衡,测定了平衡时各组分的溶解度及平衡液相的密度、p H等物化性质。该三元体系在363.15 K下的介稳相图含有1个共饱点E,2条单变量曲线AE,EB,2个结晶区。2个结晶区分别对应单盐Na Cl和单盐Na2B4O7·5H2O。共饱点E对应的平衡固相为Na Cl+Na2B4O7·5H2O,平衡液相组成为w(Na Cl)24.84%,w(Na2B4O7)7.18%,w(H2O)67.98%。研究结果表明,该三元体系为简单三元体系,无复盐和固溶体生成。

The metastable phase equilibrium of the ternary system NaCl-Na2B4O7-H2O at 363. 15 K was studied using an isothermal evaporation method. The solubilities and the physicochemical properties such as density and pH of the equilibrated solution were determined. Based on the experimental data,the phase diagram of the ternary system at 363. 15 K was plotted. The phase diagram of the system consists of one invariant point E,two univariant curves AE,EB,and two crystallization regions which correspond to the single salt NaCl,Na2B4O7·5H2O,respectively. Invariant point E corresponds to the saturated solid salt of NaCl ＋ Na2B4O7· 5H2O,with its equilibrium solution composition of w（ NaCl） 24. 84%,w（ Na2B4O7） 7. 18 %,w（ H2O） 67. 98 %. The experimental result shows that the system NaCl-Na2B4O7-H2O is of a simple type,without double-salt or solid solution formed at 363. 15 K.