In this paper we report that sodium benzoate works as good inhibitor for SO 2 oxidation in pH range 4.02-5.25 in the presence of Ag(I). Based on the observed results following rate law given and a free radical mechanism have been proposed. d[S(lV)]/dt = (k 1 + k 2 [Ag(I)]) [S(lV)]/1 + B [Organics]

The results of the different carboxylic acids inhibited Co 2 O 3 catalysed autoxidation of S(IV) in alkaline medium have been shows that the reactions follow the free radical mechanism.