A Simple and Rapid Complexometric Determination of Thallium(III) using Mercaptoethane as Demasking Agent
A simple, rapid and selective complexometric method is proposed for the determination of thallium(III), using mercaptoethane(EtSH) as demasking agent. The sample solution containing Tl(III) is first complexed with excess EDTA and the surplus EDTA is removed by titration at pH 5–6 with zinc sulphate solution using xylenol orange as indicator. EtSH solution is then added to displaceEDTAselectively fromTl-EDTAcomplex. Thallium is determined indirectly by titration of releasedEDTA with zinc sulphate solution. Reproducible and accurate results are obtained in the concentration range 4–80mg of thallium with a relative error≤±0.6% and relative standard deviation≤0.7%. The method is successfully applied to the determination of Tl(III) in its synthetic alloy compositions and complexes, and waste-water samples.
KEY WORDS: Complexometric determination, thallium, demasking agent, mercaptoethane.
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