The influence of the starch indicator on front waves in the iodate–arsenous acid system with applied electric fields

Abstract

The effects of the addition of a starch indicator to propagating reaction fronts in the iodate–arsenous acid system are considered, both experimentally and by the analysis of a model based on the Dushman–Roebuck kinetic scheme equipped with the complexation reaction between starch, I₂ and I₃⁻. Both the experiments and the model show that the starch affects front propagation by slowing the waves down, with an increasing reduction in speed as the starch concentration is increased. This changes the magnitude of the electric field that has to be applied in order to achieve changes in the local stoichiometry. Contrary to the experimental observations, the model shows that the boundaries between the different reaction outcomes are the same, when expressed in terms of the dimensionless parameter ψ = E/v (where E and v are dimensionless versions of the field strength and propagation velocity), as in a previous study by Forštová et al. (J. Phys. Chem., 2000, 104, 9136) where the effects of starch were not included.