Selective complexometric determination of tin, with mercaptans as releasing agents

A method is proposed for selective complexometric determination of tin, mercaptans being used as releasing agents. To a solution containing tin and other cations, excess of EDTA is added and the surplus is back-titrated at pH 5-6 with lead nitrate (Xylenol Orange as indicator). Thioglycollic acid or mercaptopropionic acid is then added to decompose the tin-EDTA complex and the liberated EDTA is titrated with lead nitrate. The interference of various cations has been studied and the method has been employed for the estimation of tin in a variety of alloys.