Belousov-Zhabotinskii reaction systems in the presence of Ag⁺

Abstract

Threshold values of [Ag⁺] for quenching (i) Br⁻ potential oscillation and (ii) redox potential oscillations + Br⁻ oscillations have been determined under aerobic and anaerobic conditions for the (a) malonic acid + Ce₄₊ + BrO₋₃ + H₂SO₄ system, and the (b) oxalic acid + acetone + Ce⁴⁺ + BrO⁻₃ + H₂SO₄ system. Similar experiments on the lower limit of BrO⁻₃ under aerobic/anaerobic conditions are reported. The results show that the mechanism of quenching, so far as the key steps are concerned, is expected to be the same in the two cases. Numerical simulations have been made on the basis of the Field, Körös and Noyes (FKN) mechanisms with the additional step Ag⁺ + Br⁻ ⇋ AgBr. The analysis shows that the experimental results can be explained quite well if the corresponding forward rate constant, k₆, is assumed to lie between 10⁴−10⁵ M⁻¹ s⁻¹, as has been suggested by Ruoff and others.