Determination of indium and thallium in indium-thallium alloys

The thallium-indium alloys were dissolved in sulphuric acid (1 + 1). In this medium thallium remained in the univalent state and could be determined directly, without a separation, by an oxidation-reduction titration with potassium bromate. The indium was determined directly with an EDTA titration. Ascorbic acid was added to maintain the thallium in the univalent state, which did not interfere. Ascorbic acid also masked any interfering tervalent thallium by effectively reducing it to the univalent state. Sharp end-points were obtained for both titrations, which were carried out in the temperature range of 50-95 degrees . The method offers excellent precision and accuracy.