A pH-Regulated Chemical Oscillator:  The Homogeneous System of Hydrogen Peroxide−Sulfite−Carbonate−Sulfuric Acid in a CSTR

Periodic oscillations in both pH and the potential of a platinum electrode have been observed in the H 2 O 2 −Na 2 SO 3 −Na 2 CO 3 −H 2 SO 4 system using a continuous-flow stirred tank reactor. This homogeneous system was studied at 25 °C over a wide range of concentrations and flow rates. Phase diagrams delineating the behavior of the system under various conditions have been obtained. The main features of the experimental results have been duplicated by a computer simulation based on a proposed model. Positive feedback in H + is provided mainly by the autocatalytic oxidation of HSO 3 - by H 2 O 2 . The main process for negative feedback in H + is the dehydration of H 2 CO 3 to CO 2 . Simulations predict a period-doubling route to chaos, which is also suggested by experimental results. The effects of carbonate and acid impurities in the Na 2 SO 3 source and of atmospheric CO 2 are both simulated and discussed.