Chaotic pH Oscillations in the Sulfur(IV)−Hydrogen Peroxide−Marble Flow System

A self-accelerating oxidation of sulfur(IV) by hydrogen peroxide in an unbuffered aqueous solution in the presence of solid marble has been utilized to develop an oscillatory system in a continuous-flow stirred tank reactor. First, a model was constructed from the component reactions: (1) H 2 O 2 + HSO 3 - → H + + SO 4 2- + H 2 O; (2) CaCO 3 + H + → Ca 2+ + HCO 3 -; (3) HSO 3 - ↔ H + + SO 3 2-; (4) CO 2 (aq) + H 2 O ↔ H + + HCO 3 -; (5) CO 2 (aq) → CO 2 (gas). Simulations based on the kinetics of reactions 1−5 predicted regular pH oscillations, bursting, and chaotic responses. Most of the simulated phenomena were found experimentally in the vicinity of the predicted conditions. The parameters of the experimental oscillations also agree well with their calculated counterparts.