The Behavior of Indium(III) Complexes in Several Liquid-Liquid Distribution System. I. A Solvent Extraction Study of Indium(III) Complexes in Aqueous Perchlorate Media Containing Several Anionic Ligands

Abstract The stabilities of the indium(III) complexes in 4 m sodium perchlorate solutions with eight univalent anionic ligands have been studied at 25°C by using a TTA-chelate extraction method and a TBP adduct extraction method. The following conclusions have been reached. The stabilities of the indium(III) halide complexes are larger in this order; Cl−>Br−>I−; on the other hand, those of indium(III) complexes with the halate anions increase in the order: ClO3−<BrO3−<IO3−. The former forms more stable complexes than the latter. Thiocyanate ions form the most stable indium(III) complexes (the first to the fifth complexes), while nitrate ions form the least stable one (only the first complex). The values obtained by the TTA method are almost identical with those obtained by the TBP method. It was also concluded that although the TTA method could be applied to all the systems studied, it is more suitable for the examination of the lower complexes; the TBP method, on the other hand, could be used only for the systems in which an extractable third complex is formed, but it could give more accurate constants for the higher complexes. Thus, only a combination of these two methods can give all the equilibria in a system where many complexes are formed.