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Bray-Liebhafsky reaction

The Bray-Liebhafsky reaction is a chemical clock first described by W. C. Bray in 1921 and the first oscillating reaction in a stirred homogeneous solution. He investigated the role of the iodate (IO3-), the anion of iodic acid in the catalytic conversion of hydrogen peroxide to oxygen and water by the iodate. He noticed that the concentration of iodine molecules oscillated and that oxygen did build up pulsating.

An increase in temperature reduces the cycle in the range of hours. This oscillating reaction consisting of free radical on non-radical steps was investigated further by his student H. Liebhafsky hence the name Bray-Liebhafsky-Reaction. It is interesting to note that during this period most chemists rejected the phenomenon and tried to explain the oscillation by invoking heterogeneous impurities.

A fundamental property of this system is that hydrogen peroxide has a redox potential which enables the simultaneous oxidation of iodine to iodate:

5 H2O2 + I2 → 2 IO3- + 2 H+ + 4 H2O

and the reduction of iodate back to iodine:

5 H2O2 + 2 IO3- + 2 H+ → I2 + 5 O2 + 6 H2O

Between these two reactions the system oscillates causing a concentration jump of the iodide and the oxygen production

The net reaction is

2 H2O2 → 2 H2O + O2

necessitating a catalyst and IO3-

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Bray-Liebhafsky_reaction". A list of authors is available in Wikipedia.
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