CHEMICAL FRONT INITIATION AND PROPAGATION IN THE BROMATE-FERROIN REACTION

The initiation and propagation of chemical wave fronts in the bromate- ferroin reaction is considered numerically using a two- variable model derived from a reduced version of the FKN mechanism. The results indi cate that for a given initial concentration of bromide ion, there is a critical size for the region in which the wave is initiated and that this critical size increases with [Br-](0). For successful wave initia tions, an approximately constant-form travelling reaction wave develop s, but the wave speed does not approximate to a constant value in gene ral, indicating that care is required when using experimental data to estimate diffusion coefficients. These observations are also fully con sistent with the experimental observations that initiation becomes pos sible in this reaction after some initiation period that depends inver sely on [BrO3-] and [H+](2), the concentrations of bromate and H+ ions , and logarithmically on [Br-](0). Initiation becomes more difficult a s the space dimension of the system is increased. Analytical estimates based on the assumption of high [Br-](0) suggest that the critical si ze scales as [Br-](1/4)(0) and that the critical size for 1D, 2D and 3 D domains goes in the ratio 1:1/root 2:1/root 3.