KINETICS OF THE HOMOGENEOUS REACTION BETWEEN CERIUM(IV) AND MERCURY(I) IONS IN AQUEOUS PERCHLORIC-ACID

The reaction between Ce(IV) and Hg2(2+) in 1 M (M = mol dm-3) HClO4 at 25-degrees-C has been shown to be catalysed by light, glass and metallic mercury. The kinetics were therefore studied in Teflon vessels in the dark. The addition of Hg2+ ions to mercury(I) stock solutions avoided the formation of colloidal mercury through the disproportionation of Hg2(2+). When these precautions were taken, the reaction was found to be much slower than reported by previous workers. The rate was first order in Ce(IV) but zero order in Hg(I), and the activation energy was 125 kJ mol-1.