Electrically Coupled Belousov-Zhabotinskii Oscillators: Experimental Observation of Chaos in a Chemical System and Identification of its Source in the Field-Noyes Equations

The Belousov-Zhabotinskii (BZ) reaction is by far the chemical oscillator that is best characterized experimentally and best understood mechanistically (Field et al. 1972; Field 1985; Field and Boyd, 1985). It is the metal-ion-catalyzed oxidation by bromate ion (BrO₃-) of any of a large class of organic materials in a strongly acidic, aqueous medium. In the experiments reported here, the Ce(IV)/Ce(III) couple is used as the metal-ion catalyst and acetylacetone (CH₃COCH₂-COCH₃), which we will refer to as AA, is used as the organic material to avoid bubble formation. All experiments were carried out in 2.73 M H₂SO₄ and in continuous-flow, stirred tank reactors (CSTR) driven by peristaltic pumps. The general behavior of oscillating chemical reactions in CSTR experiments has been reviewed by DeKepper and Boissonade (1985), and the detailed CSTR behavior of the BZ reaction with malonic acid has been described by DeKepper and Bar-Eli (1983).