COMPLEXOMETRIC DETERMINATION OF CADMIUM USING 2-MERCAPTOETHANOL AS MASKING REAGENT

A complexometric method for the determination of cadmium(II) in presen ce of other metal ions is described based on the selective masking abi lity of 2-mercaptoethanol towards cadmium(II). Cadmium and other ions in a given sample solution are initially complexed with excess of EDTA and the surplus EDTA is titrated with lead nitrate solution at pH 5.0 -6.0 (hexamethylentetramine), using xylenol orange as indicator. A kno wn excess of 2-mercaptoethanol solution (10% alcoholic) is then added, the mixture is shaken well and the released EDTA from the Cd-EDTA com plex is titrated against standard lead nitrate solution. The interfere nces of various ions are studied and the method is applied to the dete rmination of cadmium in its complexes. Reproducible and accurate resul ts are obtained for 3.5-25 mg of Cd with relative errors less than or equal to 0.65% and standard deviations less than or equal to 0.06 mg.