Thioacetamide as a releasing agent for the complexometric determination of thallium(iii) in its synthetic alloys and complexes

A simple and selective complexometric method for the determination of thallium is proposed, based on the masking ability of thioacetamide 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 zinc sulphate solution at pH 5-6 (hexamine buffer) using xylenol orange as the indicator. A 0.8% aqueous solution of thioacetamide is then added to displace EDTA from the TI(III)-EDTA complex. The released EDTA is titrated with standard zinc sulphate solution as before. Reproducible and accurate results are obtained for 0.018 - 0.371 mol L^-1(3.79mg - 75.91mg) of Tl(III) with relative error less than ±0.43% and coefficient of variation not more than 0.26%. The interference of various ions was studied and the method was used for the analysis of thallium in its synthetic alloy mixtures and also in complexes.