The Ozone-Iodine-Chlorate Clock Reaction

Abstract

This work presents a new clock reaction based on ozone, iodine, and chlorate that differs from the known chlorate-iodine clock reaction because it does not require UV light. The induction period for this new clock reaction depends inversely on the initial concentrations of ozone, chlorate, and perchloric acid but is independent of the initial iodine concentration. The proposed mechanism considers the reaction of ozone and iodide to form HOI, which is a key species for producing non-linear autocatalytic behavior. The novelty of this system lies in the presence of ozone, whose participation has never been observed in complex systems such as clock or oscillating reactions. Thus, the autocatalysis demonstrated in this new clock reaction should open the possibility for a new family of oscillating reactions.

Statistical evaluation of an electrochemical probe for the detection of chlorate

“…Simpler spectrophotometric methods for chlorate detection are, in theory, amenable for field use. These methods are generally based on bleaching the color of a dye species [6,[11][12][13][14] or the catalyzed generation of colored triiodide anion [15][16][17][18] in the presence of chlorate. The color change may be visible to the naked eye or with the aid of very simple instrumentation, permitting development of a lightweight system that requires little or no power to operate.…”

The Chlorate-Iodine-Nitrous Acid Clock Reaction

“…Reaction (18) has been used in our model for the chlorate-iodine clock reaction [1] with k = 7 L mol −1 s −1 , and in the model for the ozone-iodine-chlorate clock reaction [3] with the same rate constant used here ( k = 20 L mol −1 s −1 ).…”

“…This additional H + in the rate law for Reation (4) has been used before in the model for the ozone-iodine-chlorate clock reaction [3] . For Reaction (18), the additional H + in the rate law can be justified by the same argument, considering the protonation of ClO 3 − and HIO 2 , and has also been used in the model for the ozone-iodine-chlorate clock reaction [3] . In the case of Reaction (17) it was very critical to introduce a square dependence on H + to obtain the qualitative agreement shown in Figure 4 .…”

“…Because UV light can generate small amounts of ozone from dissolved oxygen in water, we investigated the possibility that an ozone solution could substitute for light and trigger the chlorate-iodine clock reaction. In fact, we were able to show that the ozone-iodine-chlorate clock reaction exists and the initial step is the reaction between ozone and iodide [3] . In this same work [3] we have also shown that not all oxidant species, as for example H 2 O 2 , were able to react in such way to produce the autocatalysis which results in the clock reaction behavior.…”

“…This new chlorate-iodine-nitrous acid clock reaction opens a new opportunity to find an oscillating system containing chlorate or nitrous acid species, in both cases an unprecedented finding. The possibility to find out an oscillating reaction based on this new clock reaction is greater than in the case of the ozone-iodine-chlorate clock reaction [3] because a nitrous acid solution is much easier to work than the unstable ozone solution.…”