Simulations of the Iodine Interphase Transport Effect on the Oscillating Bray−Liebhafsky Reaction

Abstract

The effect of the iodine interphase transport originated from physical processes, such as pressure decrease, vigorous stirring, and/or an inert gas bubbling, on the dynamics of the oscillating Bray-Liebhafsky reaction is studied. Some new experiments were made at 60 °C that confirmed the possibility of suppressing oscillations by means of the iodine vapor removal from the reaction solution. It has been proved that the iodine vaporization is governed by the first-order kinetics with respect to the concentration of aqueous iodine, and a critical rate constant for iodine escape causing inhibition of the oscillatory mode was determined. The experiments were confronted with the models proposed by Kolar-Anic ´and Schmitz with co-workers. Both the models studied reflect the observed phenomenon. A simulation based on the latest model shows very good semiquantitative agreement with experiment, needing only a minor modification of the rate constants suggested by Kolar-Anic ´et al.

Oxygen Production in the Oscillatory Bray−Liebhafsky Reaction

“…A recent simulation, 9 based on the models proposed by Kolar-Anic and Schmitz with co-workers, 10,11 complemented by the physical process of iodine interphase transport shows very good semiquantitative agreement with experiments. Buchholtz and Broecker 12 could show that in their CSTR experiments, when there was no gas phase above the solution, no oscillations could be observed in the BL system at a high flow rate.…”

“…2,23 The equilibrium solubility of oxygen at this temperature is 0.00126 M. 2 We were familiar with previous observations that oscillations in the batch BL system monitored potentiometrically can be suppressed by rapid stirring. 3,[7][8][9] Therefore, we tried to find the limit of stirring above which oscillations in the rate of oxygen evolution disappear ( Figure 4). The number of oscillations ranged from 15 to 17 at stirring rate from 50 to 300 rpm.…”

The time dependence of molecular iodine emission from <i>Laminaria digitata</i>

“…In addition there can be production of O 2 by the reaction of H 2 O 2 with HOI at higher acidity (Valent et al, 1998;Schmitz, 2001):…”

Computational Simulation of Bray-Liebhafsky (BL) Oscillating Chemical Reaction

“…However, one process might be faster than the other during a short interval. Processes (B) and (C) alternately dominate over the whole system and result in the concentration of iodine and the rate of oxygen gas evolution change periodically [9][10][11][12]. Although the overall stoichiometry of the BL reaction seems to be simple, it is not easy to describe the mechanism.…”

“…On the other hand, the concentration of oxygen becomes supersaturated and the degree of super-saturation depends on the experimental conditions, such as the concentrations of reactants and temperature. There are several papers of the analysis of mechanism of BL reaction [8,11,14,15]. Matsuzaki [12] proposed a mechanism involving I 3 -; the question is how to verify it by experiment.…”