Formation of Chromium(III) Dithizonate Complex and Its Ion-pair Solvent Extraction

Abstract

Reactions of Cr (III) with dithizone (H₂dz) in acetone and of Cr (VI) with diphenylthiocarbazide in 10% (v/v) acetone-water mixture were investigated. The complex formed by these reactions is the 1: 1 cationic complex of Cr (III) with dithizone, [Cr (Hdz)]²⁺, which has an absorption maximum at 525 nm (molar absorptivity, ε = 2.95 x 10⁴ dm³. mol^-1. cm^-1) in acetone and at 530 nm (ε = 2.85 x 10⁴ dm³. mol^-1. cm^-1) in water. The complex reacted with dodecyl sulfate ion (ds^-) to form an ion-pair of [Cr (Hdz)] (ds) ₂, which was extracted into butyl acetate and isobutyl metyl ketone. But, it was not extracted into chloroform and benzene. The extracted ion-pair has an absorption maximum at 530 nm (ε = 2.85 x 10⁴ dm³. mol^-1. cm^-1) in butyl acetate. The partition coefficient, P= { [Cr (Hdz)] (ds) ₂} (o)/{ [Cr (Hdz)] (ds) ₂ }, was determined as 10^0.54 between water phase and butyl acetate phase.