Statistics for A complexometric method for the determination of mercury(II) in presence of other metal ions is described based on the selective masking action of 1-propane thiol towards mercury(II). Mercury(II) present in a given sample solution is first complexed with an excess of EDTA and the unreacted EDTA is titrated against lead nitrate solution at pH 5-6 (hexamine buffer) using xylenol orange as the indicator. A 0.8% aqueous solution of 1-propane thiol is then added to displace EDTA from the Hg(II)-EDTA complex. The released EDTA is titrated with standard lead nitrate solution as before. Reproducible and accurate results are obtained for 4-85 mg of mercury(II), with relative error less than ±0.23% and coefficient of variation not more than ±0.41%. The effects of various ions were studied. The method is used for the analysis of mercury(II) in its synthetic alloy mixtures and also in complexes.