二溴对甲基偶氮磺褪色光度法测定铝合金中微量铬  

Photometric Determination Chromium in Aluminium Alloy by Color-fading Reaction of Dibromo-p-methylsulfonazo

作　　者：钟国秀[1,2] 黄清华 晏高华[1,2] 

机构地区：[1]湖北省机电研究设计院,武汉430070 [2]湖北工业大学,武汉430070 [3]湖北省建材研究设计院,武汉430071

出　　处：《理化检验（化学分册）》2009年第5期596-597,602,共3页Physical Testing and Chemical Analysis(Part B:Chemical Analysis)

摘　　要：在硝酸介质中，铬（Ⅵ）与二溴对甲基偶氮磺生成l：3物质的量比的稳定络合物，导致显色剂二溴对甲基偶氮磺吸光度降低，据此建立了褪色光度法测定铝合金中铬（Ⅵ）含量。对反应介质的种类和酸度、显色剂的用量、反应时间、共存离子的干扰等影响因素进行了试验并予以优化。在530nm波长测定时，铬（Ⅵ）的质量浓度在0．032-0．48mg·L^-1范围内，反应体系吸光度的降低值△A与铬（Ⅵ）浓度呈线性关系，表观摩尔吸光率为4．34×10^4L·mol^-1·cm^-1。用于直接测定铝合金中微量铬的含量，测定值与标准值相符。相对标准偏差（n=8）小于2％。A stable complex was formed by the reaction of Cr（VI） with dibromo-p-methylsulfonazo in the mole ratio of 1 to 3 in dil. HNO3 solution, leading to decrease of absorbance of dibromo-p-methylsulfonazo as color reagent. Influtential factors, including the kinds and concentration of acid in the reaction medium, amount of color reagent, time of reaction, and interference of co-existing ions, were studied and optimized. Linear relationship between the magnitude of decrease in absorbance at 530 nm and the mass concentration of Cr（Ⅵ） was obtained in the range of 0. 032-0. 48 mg·L^-1 , and value of apparent molar absorptivity found was 4. 34×10^4L · mol^-1 · cm^-1. The proposed method was used in the determination of Cr（Ⅵ） in aluminium alloy, the results obtained was checked quite well with the standard values, and values of RSD＇s （n=8） were less than 2. 0%.

关 键 词：二溴对甲基偶氮磺 铬 褪色光度法 铝合金 

分 类 号：O657.32[理学—分析化学]