The effect of tartaric acid on the kinetics of the oxidation of uranium (IV) by thallium (III) in aqueous perchloric acid

Abstract

The kinetics of the oxidation of uranium (IV) by thallium (III) in the presence of tartaric acid was investigated in aqueous perchloric acid solutions. Increases in initial rate with increasing tartaric acid concentrations were observed, along with departure from the second-order rate law. The orders with respect to uranium (IV), thallium (III), tartaric acid, and hydrogen ion were found to be 0·93, 0·05, 0·37 and −0·91, respectively. Thallium (III) in the presence of tartaric acid was shown to be stable by polarography, yet in kinetics experiments with Tl(III) in excess over uranium (IV), the reaction stopped because the Tl(III) was consumed. The oxidation of U(IV) by oxygen of the air is catalysed by the presence of tartaric acid, but this reaction is negligibly slow compared to the U(IV)Tl(III)-tartaric acid reactions. The presence of U(VI), and Tl(I) were shown to have no effect on the reaction kinetics. A mechanistic interpretation has been developed to account for the observed results.