STUDY OF CERIUM(4)-THALLIUM(1) REACTION AND ANALYSIS OF THALLIUM(1) MIXTURES BY KINETIC DIFFERENCES

The uncatalyzed cerium(IV)-thalllum(I) reaction in 0.125M sulfuric acid exhibits an extremely slow but measurable rate in the dark, while in room light, the rate of disappearance of cerium(IV) increases, presumably because of thallium(I)-catalyzed photoreduction. Catalysis by manganese(III) was so effective that photometric titration of thallium(I) with cerium (IV) titrant was possible. Two types of thallium-metal ion mixtures can be analyzed on the basis of kinetic differences alone. In the first type, metal ions such as iron(II) react rapidly with the cerium(IV) titrant in the absence of catalyst before thallium-reacts significantly. Then the catalyst is added and the thallium(I) is titrated with cerium(IV). In the second type of mixture, the catalyst is added at the start, and thallium(I) reacts rapidly with the cerium(IV) titrant before the other metal ions or reducing agents react significantly. The reducing agents studied were mercury(I), arsenic(III), and chromium(III). Theoretical calculations indicate the reactions of these substances with cerium(IV) should be negligible, but weak catalysis by manganese(III) apparently causes significant reaction above equivalent concentrations. © 1968, American Chemical Society. All rights reserved.