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:
- 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.
 
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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' ???
