THE most widely studied oscillatory chemical reaction is the catalytic oxidation of a variety of organic compounds by acidic bromate - the Belousov-Zhabotinsky reaction. Babu et al.1 have reported that the gallic acid, bromate, sulphuric acid and cobalt (II) system showed oscillatory behaviour. They claim that the two key steps are the oxidation of cobalt (II) by bromate to cobalt (III), and the reduction of the latter by gallic acid (GA), that is, they regarded the chemical process as a Belousov-Zhabotinsky-type oscillatory reaction. Redox potential data on the Co3+/Co 2+ (1.81 V), BrO3-/Br- (1.44 V) and BrO3-/Br2 (1.51 V) systems, imply that the reduction of bromate by cobalt (II) is highly unfavourable thermodynamically which made us sceptical about the suggested steps. We report here our preliminary investigations mostly on the GA-BrO3--H 2SO4 system which attempted to unravel this problem. One of our first experiments showed that chemical oscillation occurred even in the absence of a catalyst. This unexpected finding indicated novel perspectives regarding chemical oscillators.
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