Selective complexometric titration of lead in the presence of large amounts of interfering ions

Abstract

A method is proposed for the selective complexometric determination of lead, with sulphuric acid and barium chloride being used as the masking agent. To a solution containing lead and other cations, an excess of ethylenediaminetetracetic acid (EDTA) is added, the excess of EDTA is then back-titrated at pH 5–6, with zinc nitrate and the mixed indicator Xylenol Orange-cetylpyridinium bromide. In order to decompose the lead-EDTA complex, H₂SO₄ and BaCl₂ are added and the liberated EDTA is again back-titrated with zinc nitrate. The interference of various cations has been studied. The procedure has been successfully utilised for the analysis of various lead-containing alloys such as bronzes, ounce metal, solders and tin- and lead-based alloys. The method is simple and rapid and the lead-EDTA complex decomposes at room temperature.