摘要：

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。

关键词: 酸性铬蓝K, 显色反应, 硬度测定

Abstract:

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 Ca²⁺ and Mg²⁺ are of equal molar concentration. In addition, the best conditions are decided. The results show that Ca²⁺and Mg²⁺ with ACBK form 1∶1 complex in NH3H2O-NH4Cl　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.

Key words: acidic chrome blue K , chromogenic reaction, hardness determination