LaCl_3-HCl-H_2O体系部分相图的测定

Determination of Fractional Phase Diagram of LaCl_3-HCl-H_2O System

在 2 5 ,3 5和 45℃下 ,测定了LaCl3在纯水及低于 3 0 %的盐酸中的溶解度 ,盐酸的浓度范围为 0～ 9.5 83mol·L- 1 。HCl的含量用NaOH滴定 ,用甲基橙作指示剂 ,Cl- 的总浓度用AgNO3滴定 ,以K2 CrO4 为指示剂 ,滴定时溶液的pH值为 4～ 6,LaCl3的含量通过总的Cl- 含量和H+ 量的差值计算而得。采用湿固相法构建了上述温度下的LaCl3 HCl H2 O体系的部分相图。相图表明 ,在上述各温度下从LaCl3饱和溶液中析出的固相组成均为LaCl3·7H2 O。

The solubilities of LaCl 3 in HCl aqueous solution at 25, 35 and 45 ℃ were measured, the concentration of HCl ranged from 0 to 9.583 mol·L -1 . The content of HCl was determined by the content H +. The solution was titrated first by NaOH solution to pH value 4～6, then was titrated secondly by 0 100 mol·L -1 AgNO 3 solution with K 2CrO 4 as an indicator to determine the total content of Cl -. The fractional phase diagram of LaCl 3 HCl H 2O system was determined employing solid liquid phase method. This diagram indicates that components of the solid phases deposited from saturated solutions at 25, 35 and 45 ℃ all are LaCl 3·7H 2O.