pH-oscillations in a closed chemical system of CaSO3-H2O2-HCO3(-)

Long-lasting large amplitude periodic change of the pH is measured in an aqueous suspension of CaSO(3)-H(2)O(2)-HCO(3)(-) at 2.0-10.0 °C in a closed reactor. The amplitude can be as large as 2 pH units between pH 5 and 7. The observed phenomenon is explained and simulated by taking into account a slow dissolution of CaSO(3), which serves as a continuous supply of HSO(3)(-) for a H(+)-producing autocatalytic composite reaction between H(2)O(2) and HSO(3)(-). Protonation of HCO(3)(-) to form CO(2) in a reversible reaction provides for the necessary negative feedback in H(+)].