Period of homogeneous oscillations in the ferroin-catalyzed Zhabotinskii system

Abstract

This work is primarily an experimental investigation of the ferroin‐catalyzed Zhabotinskii system [malonic acid (MA), sulfuric acid,sodium bromate, traces of bromide ions, and ferroin]. We measure the transmittance as a function of time at 546 nm. The emphasis is placed on the properties of the period of homogeneous oscillations. It is found that T depends on the initial concentrations of reactants: T (s) = C [BrO− 3]−1.6 0 [H2SO4]−2.7 0 [MA]−0.27 0 s (mol dm−3)4.57. The period is not perfectly constant. We investigate the conditions which favor irregularities: Low concentrations of BrO− 3, H2SO4, or MA; high concentrations of catalyst or reaction products. The irregularities in the period of homogeneous oscillations are of direct interest for our understanding of the formation of waves in the distributed system. Also, we find bifurcations in which a transition from steady‐state to full‐blown oscillations is observed. Such bifurcations may be due to an unstable limit cycle or to a saddle‐node transition. We discuss the saddle‐node case in terms of the Bautin model. Finally, two steady states are observed. One of them has not been reported previously: In this state, the catalyst is mostly oxidized (blue). The oxidized steady state occurs at low [MA]0. Under the same conditions of low [MA]0, the distributed system exhibits both oxidizing (blue) and reducing (red) waves. This interesting new observation shows how much the ferroin‐catalyzed Zhabotinskii system is still underinvestigated.