Complexometric determination of mercury(II) using thioglycolic acid as indirect masking agent

A simple, rapid and selective complexometric method is proposed for the det ermination of mercury(II). Mercury(II) and other diverse associated metal i ons are first complexed with excess of EDTA and the surplus EDTA is back ti trated with standard zinc sulfate solution at pH 5.0-6.0 (hexamine buffer) using xylenol orange as indicator. A 1% aqueous solution of thioglycolic ac id is then added to displace EDTA from the Hg(II)-EDTA complex. The release d EDTA is titrated with standard zinc sulfate solution as before. Reproduci ble and accurate results are obtained in the range 5-84 mg of mercury with relative error of less than 0.21% and coefficient of variation (n = 6) not more than 0.34%. The interference of various ions was studied and the metho d was used for the analysis of mercury in its synthetic alloy mixtures and also in complexes.