Period-Doubling Route to Chaos in the Hydrogen Peroxide−Sulfur(IV)−Hydrogen Carbonate Flow System

Both simulations and experimental results show that a period-doubling route leads from simple pH oscillations through period 2 and period 4 cascades to chaos in an aqueous H 2 O 2 −sulfur(IV)−HCO 3 - flow system by varying either the removal rate of CO 2 from the reaction mixture or the flow rate. Windows of stable period 3 oscillations are also found in the wide chaotic region calculated in the [H 2 O 2 ] 0 −[SO 3 2- ] 0 plane. An autocatalytic production of H + during the oxidation of sulfur(IV) by H 2 O 2 is responsible for the positive feedback, while a H + consuming negative feedback is provided by the relatively slow reversible formation of CO 2 (HCO 3 - + H + ⇋ CO 2 + H 2 O) and its controlled escape from the surface of the reaction mixture. Protonation of SO 3 2- also contributes to the removal of the free H + . Such a multichannel negative feedback appears to be the clue to the chaotic dynamical behavior. This seems to be the simplest known chaotic chemical reaction system.