Not only does this exciting reaction change from green to blue to purple to red, in less than a minute, but then it repeats the four color sequence continuously for over an hour! This very famous reaction is known as the Belousov-Zhabotinsky Reaction, or simply the B-Z reaction.
We thought it might be interesting to see if our sensors could be used to detect the repeating behavior of the chemical reaction. Some of the most interesting results came by using a Stainless Steel Temperature Probe. The results can be seen in these Logger Pro 3 graphs. The first graph shows 20 minutes of data collection, and about 30 cycles of the oscillating reaction. In the second graph, we have zoomed in on 2 cycles, and show where each of the colors appear.
Temperature of the B-Z reaction over 20 minutes
Temperature and color changes of the B-Z reaction over two minutes
These data suggest that the mechanism exhibits a net exothermic process, followed by a somewhat smaller endothermic process, yielding a gradually increasing temperature. What would data from an ORP Sensor, Colorimeter, or pH Sensor look like for this reaction? Try it for yourself!
Flinn Scientific (800-452-1261 or www.flinnsci.com) sells a kit containing all the solutions and instructions needed for this reaction. Order the Fantastic Four-Color Oscillator Chemical Demonstration Kit (order code AP4833). If you wish to prepare your own solutions, instructions can be found in Bassam Shakhashiri’s Chemical Demonstrations: A Handbook for Teachers of Chemistry, University of Wisconsin Press: Madison; 1985; Volume 2, pp 257-261. A very thorough explanation of the reaction mechanism can also be found in the Shakhashiri book.