酸性铬蓝K分光光度法测定水的硬度

THE DETERMINATION OF THE HARDNESS OF WATER BY ACBK SPECTROPHOTOMETRY

系统研究了酸性铬蓝Ｋ（ＡＣＢＫ） 与钙镁同时作用的显色体系，采用Ｃａ２＋ 、Ｍｇ２＋ 摩尔浓度相同的混合标准溶液试验了影响该显色体系的灵敏度和稳定性的各项因素，确定了最佳操作条件。试验表明，在ｐＨ＝１０－２ 的氨—氯化铵缓冲介质中，Ｃａ２＋ 、Ｍｇ２＋ 离子均可与ＡＣＢＫ 显色剂形成１∶１ 的配合物，在４６８ ｎｍ 波长处，两种配合物存在一等摩尔吸收点，对应于该点的等摩尔吸光系数ε＝７－４×１０３ Ｌ／（ｍｏｌ·ｃｍ） ，在此波长及最佳操作条件下，Ｃａ２＋ 和Ｍｇ２＋ 的总含量在０ ～３ ×１０ －５ ｍｏｌ／Ｌ浓度范围内符合比耳定律。在试验了１３ 种常见共存离子干扰的基础上将本法用于６ 种水样的硬度测定，回收率在９６－５％ ～９９－９ ％ 之间，结果与ＥＤＴＡ 滴定法颇为一致。

This paper is about the chromogenic reaction of calcium and magnesium with ACBK at the same time. All factors affecting the sensitivity and stability of the system are tested by using the mixture in which Ca 2+ and Mg 2+ are of equal molar concentration. In addition, the best conditions are decided. The results show that Ca 2+ and Mg 2+ with ACBK form 1∶1 complex in NH 3H 2O-NH 4Cl buffer medium of pH10.2, which give an equal absorption peak at 468 nm with the molar absorption coefficient of 7.4×10 3 L/(mol·cm). Beer's Law is obeyed in the total concentration range of 0～3×10 -5 mol/L. On the basis of testing thirteen kinds of coexisting ionic disturbance, the hardness of water of six samples was determined. The results are very consistent with EDTA titrimetric analysis.