Complexometric determination of thallium(III) using ethanethiol as a selective masking agent

Abstract

A complexometric method based on the selective masking property of ethanethiol towards palladium(II) is proposed. In presence of diverse metal ions, palladium(II) is complexed with excess EDTA and the surplus EDTA is backtitrated with standard zinc sulphate solution at pH 5-5.5 (acetic acid-sodium acetate buffer) using xylenol orange as indicator. An excess of a 0.1% aqueous solution of ethanethiol is then added to displace EDTA from Pd(II)-EDTA complex. The released EDTA is titrated with the same standard zinc sulphate solution as before. Reproducible and accurate results are obtained in the concentration range of 0.5-14.26 mg of palladium with relative error of ±0.40% and coefficient of variation not exceeding ±0.34%. The effect of diverse ions is studied. The method has been used for the determination of palladium in its complexes, catalysts and synthetic alloy mixtures.