A selective complexometric method is described for the determination of mercury(II) using sodium metabisulphite as a masking reagent. An excess of EDTA is added to mercury(II) solution containing associated diverse metal ions and the surplus EDTA is back titrated at pH 5-6 (hexamine buffer) with standard zinc sulphate solution using xylenol orange as indicator. An aqueous solution of sodium metabisulphite is then added to displace EDTA selectively from Hg-EDTA complex and the released EDTA is then titrated against the same standard zinc sulphate solution. Reproducible and accurate results are obtained in the range 4-100 mg of mercury with a relative error ? 0.26% and coefficient of variation ?0.40%. The method is useful for the analysis of mercury in complexes and alloy samples.

Shetty, P.Nityananda Shetty, A.N.2026-02-05ComplexomeIndian Journal of Chemical Technology, 2004, 11, 2, pp. 163-1650971457Xhttps://idr.nitk.ac.in/handle/123456789/279522004alloybufferedetic acidmercurymetal ionmethenaminereagentsodium metabisulfiteunclassified drugxylenexylenol orangezinc sulfateaccuracyacidityaqueous solutionarticleerrorreproducibilitytitrimetryA selective complexometric method is described for the determination of mercury(II) using sodium metabisulphite as a masking reagent. An excess of EDTA is added to mercury(II) solution containing associated diverse metal ions and the surplus EDTA is back titrated at pH 5-6 (hexamine buffer) with standard zinc sulphate solution using xylenol orange as indicator. An aqueous solution of sodium metabisulphite is then added to displace EDTA selectively from Hg-EDTA complex and the released EDTA is then titrated against the same standard zinc sulphate solution. Reproducible and accurate results are obtained in the range 4-100 mg of mercury with a relative error ? 0.26% and coefficient of variation ?0.40%. The method is useful for the analysis of mercury in complexes and alloy samples.