二溴对甲基偶氮磺褪色光度法测定铬青铜中铬

Discoloring spectrophotometric determination of chromium in chromium bronze with dibromo-p-methylsulfonazo

基于0．6mol／L硝酸介质中，显色剂二溴对甲基偶氮磺与铬（Ⅵ）的褪色反应，建立了测定铬青铜中铬（Ⅶ含量的褪色光度分析方法。讨论了吸收光谱、酸度、试剂用量、时间、络合物组成、干扰离子等因素的影响，确定了反应的最佳条件。在25mL溶液中，铬（Ⅵ）量在0．8～12μg范围内符合比尔定律，表观摩尔吸光系数为4．34×10^4L·mol^-1·cm^-1.方法可用于直接测定铬青铜中铬（Ⅶ的含量，结果与二苯基碳酰二肼光度法（DPC）相符，其相对标准偏差（RSD）在0．97％～1．02％之间。

A sensitive spectrophotometric method was developed to determine chromium（Ⅵ） in chromium bronze on the basis of discoloring reaction of chromium（VD-dibromo-p-methylsulfonazo system in 0.6 mol/L HNO3 medium. Some factors such as absorption spectra,acidity, dosage of reagent, time, composition, interference of coexisting ions on the reaction were discussed, and the optimal reaction conditions were established. Beer＇s law was obeyed in the range of 0. 8-12 μg/25 mL for chromium（Ⅵ） with an apparent molar absorptivity of 4.34× 10^4 L· mol^-1· cm^-1. The proposed method could be directly used in the determination of Cr（Ⅵ） in chromium bronze,and the results were in good agreement with those of diphenlycarbazide spectrophotometry （DPC）. The relative standard deviation is 0.97%-1.02%.