Spatial bistability, oscillations and excitability in the Landolt reaction

Abstract

The spatio-temporal dynamics of the iodate–sulfite reaction (Landolt reaction) is investigated in a one-side-fed gel reactor. In these conditions, the system can generate spatial bistability, oscillations and excitability, even though in a well-stirred open reactor only steady-state bistability can be observed. Different experiments to probe the origin of the observed spatio-temporal instabilities are discussed. The reaction is mainly auto-activated by protons. The different observations globally support that the oscillatory behaviors are the result of long-range activation, through the rapidly diffusing protons. Such a source of temporal instability has only been recently discovered. This is the second experimental example for such a mechanism. Phase diagrams are established as a function of the ratio and the value of the input concentrations of iodate and sulfite. Remarkably, the stability limits of the steady spatial states and the spatio-temporal oscillatory state organize in a cross-shaped phase diagram, a topology commonly observed in open well stirred systems.