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Complexometric Determination Of Thallium(III) By Using �?�?�?�?�?�?�?�?Mixed Masking�?�?�?�?�?�?�?�? Method

Nityananda A.Shetty, P.Parameshwara, J.Karthikeyan, Prakash Shetty

A simple and selective complexometric method for the determination of thallium in presence of other metal ions is proposed based on the selective masking ability of thiouracil towards thallium(III). Thallium present in a given sample solution is first complexed with a known excess of EDTA and the surplus EDTA is titrated with standard lead nitrate solution at pH 5-6(hexamine) using xylenol orange as the indicator. A 1 % aqueous solution of thiouracil is then added to displace EDTA from the Tl(III)-EDTA complex. The released EDTA is titrated with standard lead nitrate solution. Reproducible and accurate results are obtained for 3mg to 95mg of Tl (III) with relative error less than ± 0.26% and coefficient of variation not more than 0.35%. The interference of various ions are studied. This method is used for the analysis of thallium in its synthetic alloy mixtures and also in complexes.