Front dynamics of pH oscillators with initially separated reactants

Abstract

The spatiotemporal dynamics of the Landolt-type pH oscillators are studied both numerically and experimentally with initially separated reagents in space. This configuration results in an A + B → oscillator front type system with localized patterns. The generic Rabai model of the pH-oscillators predicts the formation of an asymmetric acidic domain at the interface of the two zones loaded by different sets of chemicals. This asymmetry is caused by the initial conditions rather than the difference in the diffusivities of the components. As the influence of the negative feedback process increases, this acidic zone becomes to be localized around the interface. At some point, the acidic zone bifurcates, a less acidic zone separates and starts to move forward the oxidant rich zone. In a limited domain of parameters, spatiotemporal oscillations are found due to the instability of the main acidic zone. The appropriate conditions for the development of this periodic behavior is characterized by simulations. The numerically predicted phenomena are supported by experiments performed with the bromate–sulfite–ferrocyanide and with the hydrogen peroxide–sulfite–ferrocyanide systems, except the oscillatory phenomena.