キレート及び沈殿滴定における接触指示系としての芳香族アミン及びジアミン類の組み合わせ効果

概要

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Catalytic indication methods for detecting the endpoint of the EDTA titration of Mn^<2+> and the precipitation titration of halide ions (Cl^-, Br^-, and I^-) have been developed. As indicator reaction the coupling reaction of p-phenylenediamine (I) and m-aminophenol (II) catalyzed by traces of Mn^<2+> in 0.4 M hydrogen-carbonate solution containing 0.06 % hydrogen peroxide and that of (I) and m-phenylenediamine(III) catalyzed by traces of Ag^+ are utilized. In contrast to oxidation products of single amine substrate, the absorption maximum of these coupling products shows a bathochromic shift and the solution turns instantaneously reddish violet (I-II) or violet (I-III) by the action of the metal ion catalyst. A mixed o-toluylene-diamine and (II) indicator system is also useful for catalytic titration of Mn^<2+>. This catalytic method has been applied to the substitution titration of Zn^<2+>, Cd^<2+>, and Pb^<2+>. In catalytic precipitation titration of halide ions, Br^- and I^- are titrated in aqueous solution, while Cl^- is determined in non-aqueous or mixed solvent, i. e. methanol or 50 % acetone. Milligram amounts of metal ions (Mn^<2+>, Zn^<2+>, Cd^<2+>, Pb^<2+>) and halide ions (Cl^-, Br^-, I^-) are determined with the relative standard deviation of 0.1 %,
1983-06-05