巴氏合金中锡的测定常采用碘量法、络合滴定法,碘量法中常用的还原剂有纯铅、纯镍、纯铁、纯铝或次亚磷酸钠等。在用金属还原剂还原锡时,铜、锑、砷等离子也被还原成细粉元素状态,当有10mg以上铜、50m巳以上锑及5mg以上的砷将使终点不易判别。此时,宜用次磷酸钠作还原剂,还原速度快,终点明显,文献介绍,铜仅被还原至一价,滴定前加入硫氰酸盐使其生成CuCNS沉淀,即使大量铜存在也不影响测定。但我们在实验中发现,铜含 Babbitt determination of tin in the commonly used iodine method, complexometric titration, iodine method commonly used reductant pure lead, pure nickel, pure iron, pure aluminum or sodium hypophosphite and so on. In the reduction of tin with a metal reductant, copper, antimony and arsenic ions are also reduced to a fine powder state. When there is more than 10 mg of copper, more than 50 m of antimony and 5 mg or more of arsenic will make the end point difficult to discriminate. At this point, it is appropriate to use sodium hypophosphite as a reducing agent, the reduction speed, the end point significantly, the literature describes the copper was only reduced to a monovalent, thiocyanate before titration to generate CuCNS precipitate, even if the presence of large amounts of copper does not affect Determination. However, we found in experiments that copper is contained