Method improvement for the determination of copper in copper-lead alloy by iodometry
HAO Lu1,2, FENG Zhenhua1,2
1. BGRIMM MTC Technology Co., Ltd., Beijing 102628, China; 2. Beijing Key Laboratory for Evaluation and Testing of Metallic Mineral Resources, Beijing 102628, China
Abstract：Cu-Pb alloy contains antimony, tin and other elements, which have interference with the determination of copper by iodometry. In order to determine the copper content in Cu-Pb alloy accurately, the iodometry was improved. The sample was dissolved with tartaric acid-nitric acid. The formation of lead chloride and lead bromide precipitates was avoided. Meanwhile, the hydrolysis of antimony and tin was inhibited. The interference elements such as antimony and tin in sample were removed by adding 5 mL of hydrobromic acid in perchloric acid-sulfuric acid system. 3 mL of glacial acetic acid was added to control the pH of solution at 3-4. Ammonium hydrogen fluoride was added to mask iron. Potassium iodide was added to react with copper(Ⅱ), and the iodine precipitated was titrated with sodium thiosulfate standard titration solution using starch as the indicator. Near the stoichiometric point, 7 mL of potassium thiocyanate solution was added to release the iodine which was adsorbed on the surface of cuprous iodide precipitate. The determination method of copper content in Cu-Pb alloy by iodometry was established. The results showed that the improved method could eliminate the influence of coexisting elements on the determination results. The content of copper in Cu-Pb alloy was determined according to the experimental method. The relative standard deviations (RSD, n=11) were between 0.18% and 0.25%. The recoveries were between 98.85% and 100.10%.
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