方法要点伍德合金中含锡12.5%,铅25%,镉12.5%,Bi 50%.试样以盐硝混合酸溶解后,锡以SnCl_4形式存在,加入5毫升4%氯化钠溶液.以增加氯离子浓度,使Sn~(4+)更稳定的存在于溶液中。Sn~(4+)在pH=1时水解,故加入过量的EDTA,将锡、铅、镉,铋全部络合,在pH5～6时加入NH_4F,释放Sn-EDTA中的EDTA,以铅盐返滴求出锡含量。在pH0.8～1.5时用EDTA直接滴定铋,当溶液中存在C1~-时,铋常生成BiOCl沉淀,此沉淀在滴定中被EDTA慢慢滴定,不影响分析结果。若在测定铋、铅、镉的溶液中 Method points Wood containing tin 12.5%, lead 25%, cadmium 12.5%, Bi 50% sample dissolved in salt and pepper mixed acid, tin SnCl_4 form, adding 5 ml of 4% sodium chloride solution to increase The chloride ion concentration makes Sn ~ (4+) more stable in the solution. Sn ~ (4+) is hydrolyzed at pH = 1, so an excessive amount of EDTA is added to complete the complexation of tin, lead, cadmium and bismuth. At pH5 ~ 6, NH4F is added to release EDTA in Sn- Back drop to find the tin content. Bismuth is titrated directly with EDTA at pH 0.8 ~ 1.5. When there is C1 ~ - in the solution, bismuth often forms BiOCl precipitate. The precipitate is slowly titrated by EDTA in the titration without affecting the analysis result. If the determination of bismuth, lead, cadmium solution