Indirect complexometric determination of mercury(II) using sodium chloride as selective masking agent

A simple and accurate complexometric method is proposed for the determination of mercury(11) using sodium chloride as the selective masking agent in the presence of diverse metal ions and anions. Mercury(II) is first complexed with a known excess of EDTA and the surplus EDTA is then titrated with standard zinc sulfate at pH 5.0-6.0 (hexamine) using xylenol orange as the indicator. An excess of 10% sodium chloride is then added and the released EDTA is titrated with zinc sulfate solution. The method works well in the range from 2 to 235 mg of mercury(II) with relative error +/-0.45% and standard deviation less than or equal to0.90 mg. The method is applied for the determination of mercury in its alloys.