滴定法连续测定铅锌矿中铅锌铜

铅锌矿样经盐酸和硝酸溶解后,以硫酸为沉淀剂,使铅与硫酸形成硫酸铅沉淀,锌和铜留在溶液中。过滤后,用乙酸-乙酸铵缓冲溶液溶解硫酸铅沉淀,以二甲酚橙为指示剂,EDTA标准溶液滴定铅。分取两份滤液,一份用于测定锌,另一份用于测定铜。测定锌时以氢氧化物沉淀分离铁、锰等金属离子后,在pH 5.5乙酸-乙酸钠缓冲液中,硫脲存在下,以二甲酚橙为指示剂,用EDTA标准溶液滴定锌。另一份滤液中铜采用碘化钾-硫代硫酸钠滴定法测定。方法用于铅锌矿样品中铅、锌和铜的测定,测定值与国家标准方法的测定值一致,测定结果的相对标准偏差在0.042%～0.088%之间。

Continuous determination of lead,zinc and copper in lead-zinc mine by titration

The lead-zinc ore sample was dissolved with hydrochloric acid and nitric acid. Then, the sulfuric acid was added to react with lead ions to form lead sulfate precipitate, while zinc and copper remained in the solution. After filtration, the lead sulfate precipitate was dissolved with acetic acid-ammonium acetate buffer solution. The content of lead was titrated with EDTA standard solution with xylenol orange as indicator. Two parts of filtrate were sampled for the determination of zinc and copper, respectively. During the determination of zinc, iron and manganese ions were firstly precipitated and separated in hydroxide. Then, the content of zinc was determined by titration with EDTA standard solution in acetic acid-sodium acetate buffer solution at pH 5.5 in the presence of thiourea with xylenol orange as indicator. The content of copper in another filtrate was determined by potassium iodide-sodium thiosulfate titration. The proposed method was applied to the determination of lead, zinc and copper in lead-zinc ore samples. The results were consistent with those obtained by national standard method. The relative standard deviations (RSD,n=6) were between 0.042% and 0.088%.