Complexometric determination of mercury(II) with 2-imidazolidinethione as a selective masking agent

Abstract

A simple, rapid and selective complexometric method is proposed for the determination of mercury(II). Mercury(II) is first complexed with a known excess of EDTA and the surplus EDTA is back-titrated at pH 5.0–6.0 with lead nitrate, Xylenol Orange being used as indicator. 2-Imidazolidinethione is then added to displace EDTA from the Hg—EDTA complex quantitatively and the EDTA released is titrated with lead nitrate. Reproducible and accurate results are obtained for 2–75 mg of mercury, with a relative error of less than 0.3% and standard deviation of less than 0.04 mg.