Abstract: The oxidation of CD-4 with [CO^Ⅲ(NH₃)₅Cl]²⁺(Ox) catalyzed by Fe(CN)₆^3-(Ox′) was investigated in HAc-NaAc buffer solution by means of initial rate method. The empirical rate equation is:The regeneration of Fe(CN)63- is regarded as the rate-determing step. The rate cons" tant(298K) and activation parameters have been evaluated. The results obtained with TEPPD instead of CD-4 or Fe(CN)₆^4- instead of Fe(CN)₆^3- suport the suggested regeneration mechanism.The empirical rate equation of direct oxidation of CD-4 or TEPPD with [Co^Ⅲen₂Cl₂]⁺ has been formulated. The activation energy was measured. The rate-determing step may be the oxidation of PPD to S⁺.The experimental results of oxidation of PPD with [Co^Ⅲ(NH₃)₆]³⁺ [Co111en₃]³⁺; [CO^Ⅲ(NH₃)₅Cl]²⁺(Ox) and [Co^Ⅲen·Cl₂]⁺ showed that the oxidizing ability of the Co(III)-complexes decreases with their substitution inertness.

Key words: Cobalt (Ⅲ)-complexes, oxidation, kinetics, p-phenylene-diamines, superadditive oxidation mechanism