返滴定法测定氯化钾无氰镀镉溶液中氯化镉

摘要

A method for analyzing cadmium chloride in cyanide-free potassium chloride cadmium plating bath was established by means of back titration.Coordination agent in the plating bath was oxidized by ammonium persulfate under the conditions of strong acidity and heating,for making the cadmium ions release from its complexes.Al3 + and tin(Ⅳ) impurities were masked by sodium fluoride,and Fe3+ impurity was masked by triethanolamine.Excessive EDTA standard solution was added for coordinating Cd2+,using Eriochrome Black T as indicator,thereby the EDTA was back titrated by zinc sulfate standard solution under pH ≈9.3 condition,then the cadmium chloride concentration was calculated by differential subtraction.The relative average deviation of determination result was 0.19％ and the recovery was 98.03％.%制定了氯化钾无氰镀镉溶液中氯化镉的返滴定分析方法,在强酸性和加热条件下用过硫酸铵氧化镀液中的配位剂,使镉离子从配合物中释放出来.用氟化钠掩蔽Al3+和Sn4杂质,用三乙醇胺掩蔽Fe3+杂质.加入过量的EDTA标准溶液配位Cd2,在pH≈9.3的条件下,以铬黑T作指示剂,用硫酸锌标准溶液返滴定EDTA,用差减法计算镀液中氯化镉的质量浓度.结果表明,测定结果的相对平均偏差为0.19％,回收率为98.03％.