Is Iodine Oxidation with Hydrogen Peroxide Coupled with Nucleation Processes?

Abstract

An intriguing step of the Bray-Liebhafsky oscillatory reaction, that is, iodine oxidation with hydrogen peroxide, was examined. This process is characterized by enormous stochasticity of reaction induction times in the presence of mild mixing. In the present investigations, it was found that even in the presence of mixing, stochasticity is seriously reduced with simple glass powder addition. Using transparent glass, standard deviations changed from 184.9 to 10.6 min for 19 °C, and from 128.2 to 1.9 min for 27 °C. Repeating experiments with amber glass further confirmed those results as standard deviations changed from the mentioned ones to 8.7 min for 19 °C and to 2.5 min for 27 °C. Inert glass particles enhanced heterogeneous nucleation of oxygen formed in chemical reactions. Together with the previous analysis of the involved kinetic barrier of the whole reaction, it is an additional strong evidence of a possible energetic coupling between nucleation of glass cavities and chemical reactions. Such processes are usually neglected and may considerably change the investigations of the reaction mechanisms in other complex systems. Reaction was followed by the potentiometric method at 19 and 27 °C. The adjusted stopped-flow titration method was used in order to confirm the high degree of iodine to iodate conversion in the presence of nucleation centers.