The discovery of the phenomenon is credited to
Boris Belousov. In 1951, while trying to find the non-organic analog to the
Krebs cycle, he noted that in a mix of
potassium bromate,
cerium(IV) sulfate,
malonic acid, and
citric acid in dilute
sulfuric acid, the ratio of concentration of the cerium(IV) and cerium(III) ions oscillated, causing the colour of the solution to oscillate between a yellow solution and a colorless solution. This is due to the cerium(IV) ions being reduced by malonic acid to cerium(III) ions, which are then oxidized back to cerium(IV) ions by bromate(V) ions. Belousov made two attempts to publish his finding, but was rejected on the grounds that he could not explain his results to the satisfaction of the editors of the journals to which he submitted his results. Soviet biochemist
Simon El'evich Shnoll encouraged Belousov to continue his efforts to publish his results. In 1959 his work was finally published in a less respectable, nonreviewed journal. After Belousov's publication, Shnoll gave the project in 1961 to a graduate student,
Anatol Zhabotinsky, who investigated the reaction sequence in detail; however, the results of these men's work were still not widely disseminated, and were not known in the West until a conference in
Prague in 1968. A number of BZ cocktails are available in the chemical literature and on the web.
Ferroin, a
complex of
phenanthroline and
iron, is a common
indicator. These reactions, if carried out in
petri dishes, result in the formation first of colored spots. These spots grow into a series of expanding concentric rings or perhaps expanding spirals similar to the patterns generated by a
cyclic cellular automaton. The colors disappear if the dishes are shaken, and then reappear. The waves continue until the reagents are consumed. The reaction can also be performed in a
beaker using a
magnetic stirrer.
Andrew Adamatzky, a computer scientist in the
University of the West of England, reported on liquid logic gates using the BZ reaction. The BZ reaction has also been used by Juan Pérez-Mercader and his group at
Harvard University to create an entirely chemical Turing machine, capable of recognizing a
Chomsky type-1 language. Strikingly similar oscillatory spiral patterns appear elsewhere in nature, at very different spatial and temporal scales, for example the growth pattern of
Dictyostelium discoideum, a soil-dwelling
amoeba colony. In the BZ reaction, the size of the interacting elements is molecular and the time scale of the reaction is minutes. In the case of the soil amoeba, the size of the elements is typical of single-celled organisms and the times involved are on the order of days to years. Investigators are also exploring the creation of a
"wet computer", using self-creating "cells" and other techniques to mimic certain properties of
neurons. ==Chemical mechanism==