铜-锌合金镀液中锌的分析方法

Analysis Method of Zinc in Cu-Zn Alloy Plating Bath

用铬黑T作指示剂分析氰化物镀铜-锌合金镀液中的锌,在传统的测定方法中,需要使用剧毒氰化物和抗坏血酸抑制Cu2+离子的生成。为了消除氰化物的污染,研究了用三乙醇胺取代氰化钾的方法,三乙醇胺与Cu+离子生成稳定的络合物,在抗坏血酸存在的条件下,Cu+离子不能转变为Cu2+离子。测定时加甲醛破坏游离氰化钠,以铬黑T作指示剂,在pH=10的条件下用EDTA滴定锌。测定结果的相对平均偏差为0.71%,回收率为101.3%～101.9%。

During the conventional zinc element determinations in cyanide Cu-Zn alloy plating bath,eriochrome black T was used as an indicator,and virulent cyanide and L-ascorbic acid were employed to inhibit the formation of Cu^2＋ ions.In order to eliminate the pollution of cyanide,a method substituting triethanolamine for potassium cyanide was studied.Triethanol-amine could form a stable complex with Cu^＋ ions.With the presence of L-ascorbic acid,Cu^＋ ions could not be changed to Cu^2＋ ions.In the analysis process,zinc ions were titrated by using EDTA under condition of pH 10 with addition of formaldehyde to destroy free cyanide beforehand and eriochrome black T as an indicator.The results show that the relative average deviation of this method was 0.71% and the recovery was 101.3%～101.9%.