Formation of Aqueous Complex of Chromium (III) Reduced from Chromium (VI) with Tannic Acid

Abstract

The formation of aqueous complexes of chromium (III) with tannic acids which was reduced from chromium (VI) by this acid was studied by solvent extraction methods. Chromium (VI) was reduced by this acid rapidly, furthermore, it was found that the reduced chromium (III) formed aqueous complexes with this acid. The formation constants of these aqueous complexes were calculated by following solvent extraction methods. Although the chromium (III) in 1 mol dm-3 sodium perchlorate solutions was extracted by trioctylphosphine oxide (TOPO) into hexane, the extraction of chromium (III) was worse when the tannic acid was added in this system. By this experimental results, when the number of tannic acid in the aqueous complex of chromium (III) was four, the complex was most stable and the formation constant of this complex was calculated to be 1011.