Semi-automatic catalytic titration of metal ion mixtures and its application to metallurgical samples

Abstract

The semi-automatic catalytic titration of several metal ions and binary mixtures of iron(III) with copper(II), nickel or manganese(II) is described. The 4,4′-dihydroxybenzophenone thiosemicarbazone/hydrogen peroxide system was used in the presence of EDTA or EGTA as inhibitors with copper(II) as catalytic titrant. Two sample aliquots are necessary for the analysis of binary mixtures. In one, both metals are titrated in the presence of EDTA; in the other, only copper, nickel or manganese is titrated with EGTA or EDTA if a masking agent for iron(III) (triethanolamine or fluoride) is added. The iron/metal ratios tolerated range from 1:14 to 13:1 for the 0.2–3.0 μmol range, the relative standard deviation being 1–2%. The method was applied to metallurgical samples with good results.