INDIRECT COMPLEXOMETRIC DETERMINATION OF MERCURY USING POTASSIUM-IODIDE AS SELECTIVE MASKING AGENT

This paper describes a indirect complexometric method for the determin ation of mercury in the presence of co-ions, based on the selective ma sking ability of potassium iodide. To the mixture of mercury (II) and other metal ion solution, EDTA solution was added in excess of the met al ions present. The pH of the solution was adjusted to 5.0-6.0 using solid hexamine (10 +/- 2 g) and surplus EDTA was titrated with zinc su lfate solution using xylenol orange indicator. An excess of solid pota ssium iodide was then added to decompose the Hg-EDTA complex and the r eleased EDTA was titrated with standard zinc sulfate solution. Accurat e results were obtained for 4.5-80 mg (2.24 x 10(-5) M - 3.99 x 10(-4) M) of mercury with relative errors less than or equal to 0.4 %, stand ard deviations less than or equal to 0.07 mg. Sn(IV) and Au(III) inter feres but can be masked using sodium fluoride. The method can be appli ed in the analysis of mercury in its alloys and complexes.