酸性锡锌合金镀液中硫酸锌的分析方法

摘要

为了解决柠檬酸对EDTA容量法测定锌的干扰问题,制定了测定酸性锡锌合金镀液中硫酸锌的新方法.加双氧水将Sn(Ⅱ)和Fe(Ⅱ)分别氧化成Sn (Ⅳ)和Fe (Ⅲ),然后用氟化钠掩蔽锡离子及铝杂质,用三乙醇胺掩蔽铁杂质,用二甲基二硫代氨基甲酸钠掩蔽铜杂质.在pH=10的条件下以铬黑T作指示剂,用EDTA标准溶液滴定锌.测定结果的相对平均偏差为0.17％,回收率为99.59％～ 100.41％.%A novel method for analyzing the content of zinc sulfate in an acidic Sn-Zn alloy electroplating bath was established to eliminate the interference of citric acid to the determination of Zn by volumetric method using EDTA.Sn(Ⅱ)and Fe(Ⅱ) are oxidized to Sn(Ⅳ) and Fe(Ⅲ) by hydrogen peroxide,and then Sn(Ⅳ) and A1 impurities are masked by sodium fluoride,Fe(Ⅲ) by triethanolamine and Cu impurities by sodium dimethyldithiocarbamate.Zn ions are titrated by standard EDTA solution with Eriochrome Black T as indicator at pH 10.The method has a relative average deviation of 0.17％ and a recovery ranging from 99.59％ to 100.41％.