Kinetics and mechanism of palladium(II) catalyzed chromium(VI) oxidation of mercury(I) in aqueous sulphuric acid

The Cr-VI oxidation of Hg-I in an aqueous acid medium occurs to a modest ex tent only in presence of Pd-II and in H2SO4 above ca. 0.20 mol dm(-3). The reaction is first order in [Cr-VI] in the presence of Pd-II catalyst. The o rder in [Hg-I] is less than unity, whereas that in [Pd-II] is unity. Increa se in [H2SO4] accelerates the reaction rate. The added products, Cr-III and Hg-II, do not significantly effect the reaction rate. A mechanism involvin g HCrO4- and PdCl+ as the reactive species of oxidant and catalyst respecti vely, is proposed. The reaction constants involved in the mechanism have be en evaluated.