MODELING OF A SILVER ION PERTURBED BELOUSOV-ZHABOTINSKII OSCILLATOR

There has been much recent study of the reaction Ag+ + Br- → AgBr (reaction O6) and its relevance to the silver ion perturbed Belousov-Zhabotinskii reaction; the mechanistic interpretation of the so-called non-bromide-controlled oscillations, and the refutation of that interpretation, depend quite strongly on whether this reaction effectively removes bromide from the solution. Our work examines the effect of silver bromide precipitation on two modified Oregonator models, with a variety of rate constants of (O6). We show that, if the reaction O6 is assumed slow, bromide control can be maintained, but at the expense of having very high supersaturation of AgBr monomers. If reaction O6 is fast, no bromide-controlled oscillations occur while there is a significant concentration of silver ion. A more involved precipitation model with recent experimentally determined rate constants also shows that the Oregonator will not give bromide-controlled oscillations during the time when silver ion is in high concentration. Furthermore, the simulations indicate that the relatively high rate of the bromide production reaction O5 predicts a fast disappearance of the silver ions which contradicts the experimental results. It is concluded that models which include the "non-bromide-controlled" oscillations as perturbed bromide-controlled oscillations are thus far incomplete and that modification of these models should be considered. © 1990 American Chemical Society.