三价铬钝化液中铁杂质的分析方法

Method for analysis of iron impurity in a trivalent chromium passivation bath

利用钛铁试剂(邻苯二酚-3,5-二磺酸钠)与三价铁离子在p H=10之下的特效显色反应,用分光光度法测定三价铬钝化液中铁杂质的质量浓度。以钝化液底色作为参比,用1 cm比色皿,在波长500 nm处测定显色溶液的吸光度。本法测定结果的相对平均偏差为0.58%,回收率为97.7%～100%,满足监控三价铬钝化液的要求。

The mass concentration of iron impurity in a trivalent chromium passivation bath is analyzed by spectro- photometric method based on the specific color development reaction of disodium 1,2-dihydroxybenzene-3,5-disulfonate （also called Tiron） with Fe3＋ ions at pH 10. The absorbance of the chromogenic solution is determined using a 1 cm cuvette at a wavelength of 500 nm with the blank passivation bath as reference. The method has a relative average deviation of 0.58% and a recovery ranging from 97.7% to 100%, meeting the requirement of monitoring and control of trivalent chromium passivation bath.