The Kinetics of Bromate-Cerium(III) and -Iron(II) Reactions

The bromate-cerium(III) and -iron(II) reactions in acidic media were examined with special reference to their induction periods and reaction rates. In the bromate-cerium(III) reaction, the induction period is followed by a burst of cerium(IV) formation and then a gradual formation of cerium(IV). In the bromate-iron(II) reaction, a slow decrease occurs only in acidic media, even without bromate, so it may differ from the decrease in the tris(1,10-phenanthroline)iron(II) concentration based on the oxidation by bromate. It was interpreted as the dissociation from [Fe(phen)3]2+ to [Fe(phen)2]2+ and phen. This is the induction period for iron(III) formation, which follows as the burst. The induction period and the rates of cerium(IV) or iron(III) formation can be interpreted on the basis of the mechanism for the Belousov oscillatory and the present redox reactions proposed by Noyes and his co-workers.