The Cook Book

Recipe for the week of September 2 - 8

Belousov's Brew

Visitors to the Kitchen keep requesting real recipes, so to launch the fall season we'll offer up quite a few. Our main topic this week is perhaps the most celebrated real application of cellular automata: the Belousov-Zhabotinsky oscillating chemical reaction. This Petri dish experiment produces spiral wave dynamics strikingly similar to those generated by excitable CA rules such as the Greenberg-Hastings Model and Cyclic Cellular Automaton. The following simple prescription comes from Rubin Aliev of Duke University:

BZ Reaction

0.2 M Malonic Acid
0.3 M Sodium Bromate
0.3 M Sulfuric Acid
.005M Ferroin

Combine to form a solution. Add approximately 5 mL of the solution to a Petri dish, 6 cm in diameter, so that the thickness of the layer is 0.5 -1 mm. Watch until colorful spatio-temporal patterns emerge. In thicker layers there is an interference of hydrodynamic flows with the reaction.

Professor Aliev has a charming BZ site. Highlights include an mpeg movie of a real reaction that we sampled for this week's soup, a nice explanation of the chemistry, and a snapshot and

colorful biography

of the discoverer. Here's a teaser from the bio:

'Maybe the first interest in chemistry arose in Boris' mind when he together with his elder brother tried to compose a bomb to kill the Czar. Making bombs must be an interesting activity for teenagers.'

Some additional movies of real BZ chemistry are available from Science Magazine. But next to Aliev's, the best web site on related matters comes from James Baird at Brown University, whose Circadian page includes his own more detailed recipe and one by Arthur Winfree. Baird makes connections between the reaction and periodic biological phenomena such as cricket chirps and human heartbeats. For the orally fixated, there's even a tempting formula for Cricket cookies, though we suspect our readers might prefer some Real Recipes here in the Kitchen.

The Chef was particularly amused to find the following exam problem at Professor Baird's site. Presumably the T is a key to the correct response.

9. (5) In a discussion of the Belusov-Zhabotinsky oscillating reaction in a book on chaos by Nina Hall it is stated: 'The problem was that [the reaction was not real because] chemists assumed that such behavior-where a reaction couldn't make up its mind which way to go, refusing to settle down to an energetically stable state-contravened the second law of thermodynamics.' This statement is strange because

How do you like that answer in light of our first Kitchen recipe ever, which described a 'very stable steady state of spirals' ???

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