Complexometric determination of indium(III) using 2-mercaptoethanol as masking agent

An indirect complexometric method is described for the determination of In( III) in the presence of other metal ions and anions using 2-mercaptoethanol as the masking agent. In(III) and other metal ions are initially complexed with an excess of EDTA and the surplus EDTA titrated back with standard zi nc sulfate solution at pH 5.0-6.0 (hexamine) using xylenol orange as indica tor. A known excess of aqueous 10% 2-mercaptoethanol solution is then added to release the complexed EDTA from In- EDTA complex and is then titrated w ith zinc sulfate solution to the same sharp end point. Accurate and reprodu cible results are obtained for 2.3-46 mg of In(III). The effects of various cations and anions are also studied. The method is applied for the determi nation of In(III) in artificial mixtures corresponding to alloy composition s.