Analysis of the bromate-ferroin clock reaction

Abstract

The bromate-ferroin clock reaction is studied experimentally and the dependence of the clock or induction timet _cl on the initial concentration of various reactants determined. Particular attention is paid to the dependence oft _{cl cl} on the initial bromide ion concentration [Br⁻]₀. An analytical theory is also derived based on a subset of the Field-Körös-Noyes mechanism. This analysis reveals several features, including exponential decay of [Br⁻] during the induction period followed by a super-exponential decay in the actual clock event, a linear relationship betweent _cl, and ln[Br⁻] over a wide range of [Br⁻]₀, but departures from this at higher (and lower) concentrations. These features are all confirmed essentially quantitatively by the experimental results. The theory also predicts, and the experiments confirm, that there is a critical bromide ion concentration marking the end of the induction period. This study then provides a firm basis from which to interpret and predict the behaviour of this system in a wider range of experimental situations (such as the reaction-diffusion waves in unstirred media).