三元体系NaBr-Na2B4O7-H2O在373 K的相平衡研究

采用等温溶解平衡法研究了三元体系NaBr-Na2B4O7-H2O在373 K时的相平衡关系，并测定了饱和溶液的溶解度及密度。研究发现：该三元体系为简单共饱和型，无复盐及固溶体形成。根据溶解度数据绘制了相应的平衡溶解度曲线，相图中有1个共饱点，2条单变曲线，2个平衡固相分别为NaBr和Na2B4O7·5H2O；对不同温度条件下的溴化钠和硼酸钠的溶解度做了对比分析和讨论，结果表明，随着温度的增加，硼酸钠和溴化钠的溶解度均增大，但是在高温条件下，硼酸钠其溶解度数据增加明显；在该三元体系中溴化钠对硼酸钠有明显的盐析作用；并简要讨论了密度变化规律。

Experimental study on solid-liquid equilibria in ternary system NaBr-Na2B4O7-H2O at 373 K

The solid-liquid equilibria in ternary system NaBr-Na2B4O7-H2O at 373 K was studied by using isothermal solution saturation method.The solubilities of salts and densities of solution in the ternary system were determined.Research indicated the ternary system was of simple eutectic type and no double salt or solid solution was found.Based on the solubility data，the phase diagram and the relationship of density in the ternary system were plotted， respectively.The solubility diagram of the ternary system had one invariant point，two univariant curves，and two fields of crystallization（NaBr and Na2B4O7· 5H2O）.The solubilities of NaBr and Na2B4O7·5H2O under different temperatures were compared and analyzed.Results showed that solubilities of borates increased obviously with the increasing temperature. Sodium bromide had salting-out on sodium borate obviously.The change law of density was discussed simply.