碘酸钾滴定法测定铝铜中间合金中锡

采用氢氧化钠、过氧化氢溶解试样后，加入盐酸，在隔绝空气的条件下，以氯化汞为催化剂，采用次亚磷酸钠将高价锡还原至二价，将溶液冷却至10℃以下，用碘酸钾滴定法测定了铝铜中间合金中锡的含量。实验表明，在滴定前加入5mL250g/L的硫氰酸铵溶液与Cu(I)生成硫氰酸亚铜沉淀可消除铜的干扰，而其它共存杂质元素不干扰测定。方法对与铝铜中间合金基体相同的铸造铝合金标准样品中的锡元素进行多次测定，测定结果与认定值相符，相对标准偏差在1.5%～3.6%(n=8)之间，相对误差在0.0%～1.6%之间。

Determination of tin in aluminum-copper intermediate alloy by potassium iodate titration

After the sample was dissolved with sodium hydroxide and hydrogen peroxide, hydrochloric acid was added. Under anoxic conditions, the high-valence tin was reduced to divalent by sodium hypophosphite with mercuric chloride as catalyst. Then the content of tin in aluminum-copper intermediate alloy was determined by potassium iodate titration after the sample solution was cooled to below 10℃. The experiment showed that, the interference of copper could be eliminated by adding 5 mL of 250 g/L ammonium thiocyanate to form cuprous thiocyanate precipitate with copper (Ⅰ) before titration. Meanwhile, the other coexisting impurities had no interference with the determination. The proposed method was applied to determination of tin several times in certified reference material of casting aluminum alloy, which had the same matrix with aluminum-copper intermediate alloy. The results were consistent with the certified values. The relative standard deviations (RSD, n=8) were between 1.5% and 3.6%, and the relative error was between 0.0% and 1.6%.