Rat vs. Chemist

Not even a lab rat can be certain of a job anymore. West Virginia University chemist Kenneth Showalter has found a better way of negotiating a maze--one that takes advantage of the peculiar properties not of rats but of chemical waves. These occur in certain reactions that produce their own catalyst, just as a brush fire generates the heat needed to burn more brush, and they propagate indefinitely along a front that takes any path open to it--racing down straightaways, bending around obstacles, and dying out only when it reaches an unbreachable barrier. Belgian chemist Agnessa Babloyantz had predicted in 1991 that such a reaction wave would trace the shortest route through a maze, but until last February, when Showalter announced his results, nobody had proved the hypothesis experimentally. Showalter first soaked a polymer membrane in the chemicals that create the most distinct waves--malonic acid, bromate ions, sulfuric acid, and an iron catalyst. Then he cut the membrane into the shape of a maze. Finally he touched off the reaction in the lower left corner and tracked the wave’s progress. (The colors--red, green, yellow, and blue--show the position of the wave front at four successive intervals of time.) It was then a simple matter to trace the shortest route from the starting point to any point in the labyrinth. The wave, Showalter enthusiastically points out, automatically gives you the optimal path.