Abstract
Initial addition of iodide ion to the oscillatory bromate-cerium-malonic acid system produces a variety of phenome- na, depending on the initial iodide concentration. At moderately high and low [I-], the onset of oscillations is delayed, while
very high [I-] totally suppresses oscillation. In an intermediate range of iodide concentration, oscillations which are qualita- tively different from the hallde-free oscillations appear with a shorter than normal induction period. These oscillations are later superceded by the ordinary, halide-free oscillations. Our observations may be accounted for by a mechanism involving (a) the direct reduction of Ce(IV) to Ce(III) by iodide, (b) the iodide-catalyzed production of glyoxylic acid, which gives rise to the induced oscillations, and (c) eventual oxidation of iodide to iodate by brómate.