Na2EDTA滴定法测定粗二氧化碲中铅含量

建立了用氢溴酸消除锑、砷、锡干扰,用硫酸将铅形成硫酸铅沉淀,再用EDTA络合滴定法测定粗二氧化碲中铅量的方法。试样用硝酸、盐酸溶解,用硫酸沉淀铅,氢溴酸消除锑、砷、锡的干扰后,过滤分离其他共存元素,以乙酸-乙酸钠缓冲溶液溶解硫酸铅沉淀,在pH=5.0～6.0时,以二甲酚橙作指示剂,用Na_2EDTA溶液滴定溶液中铅含量。实验结果表明,氢溴酸加入量为15mL,酒石酸加入量为10mL,沉淀体积为50～60mL,沉淀时间1h以上时,方法相对标准偏差(RSD)在0.10%～1.1%,加标回收率为97.1%～102%,满足粗二氧化碲中铅量的生产控制检测要求。

Determination of lead in crude tellurium dioxide by Na2EDTA titration method

A method for the determination of lead in crude tellurium dioxide was established: the interference of antimony, arsenic and tin is eliminated by hydrobromic acid, lead is precipitated by sulfuric acid, then the content of lead in tellurium dioxide is determined through EDTA complexometric titration method. The sample is dissolved by nitric acid and hydrochloric acid, lead is precipitated by sulfuric acid. The interference of antimony, arsenic and tin is eliminated by hydrobromic acid, other coexisting elements are separated by filtration. Lead sulfate is dissolved in acetic acid sodium acetate buffer solution. The content of lead in the solution was titrated with Na2EDTA solution using xylenol orange as indicator at pH5.0 ~ 6.0. The results indicate that the amount of hydrobromic acid and tartaric acid added shall be 15 ml mL and 10 mL respectively, the precipitation volume shall be about 50 to 60 ml and the precipitation time shall be more than 1 hour. The relative standard deviation (RSD) of the method is 0.10% - 1.13%, and the recovery rate of standard addition is 97.1% - 101.7%. The method meets the requirements of the detection of lead content in crude tellurium dioxide during the production control.