This is a really beautiful chemical reaction and everyone that I have shown this reaction to from the ages of 5 and up have loved it. The BZ reaction is an example of an oscillating reaction, which in the recipe that I use contains Cerium and Iron ions. These give it a great range of colours from yellowy-green to blueish to a reddy-purple and back again. A very good explanation of what is going on and a recipe (Experiment 1) can be found at http://ed.augie.edu/~gjhonsbr/BZ_lab.html
I usually scale this recipe down to a total volume of 300ml.
Great fun can be had by pouring the mixture into test tubes once it has started oscillating and seeing if they stay synchronized. Also the mixture can be poured into a shallow dish, you then see "wisps" of different colours forming.
If you look hard above the reaction mixture when you have first mixed the solutions you sometimes see a brown colour, this is bromine. Also, the reaction generates carbon dioxide gas which can be seen as bubbles forming on the sides of the reaction vessel (note that this reaction should be done in an open topped vessel to prevent an accident occurring).
Some drugs are poorly absorbed because they are not very soluble. As a proof of principle experiment I once designed a polymer to solve this problem. To exemplify this approach I took Phenytoin, which is known to be soluble under alkaline conditions but insoluble under acidic conditions. If phenytoin is taken by mouth, when it reaches the stomach it floculates and becomes very insoluble. This is reported to lead to variable pharmacokinetics. It was reasoned that if the Phenytoin could be added to a biodegradable polymer which would release the drug over time and remain soluble across a wide pH range, that absorption of the free drug would become smoother and more predictable. This was found to be the case.
pH 2 is acidic, pH 7 is neutral, pH 12 is basic. The stomach produces hydrochloric acid which is acidic. Vinegar is a house hold product which is acidic, water is neutral when not contaminated, and oven cleaning fluid is often made up of sodium hydroxide which is very basic.
Picture shows a comparison of the solubility of free Phenytoin and polymer bound Phenytoin at pH 2, pH 7 and pH12. There is twice as much Phenytoin in the polymer samples.
This video sequence has been cut right down to show the addition and then three cycles of the reaction.Each cycle actually takes longer than is shown here (only about 1 in 40 frames shown), but the reaction can keep cycling for more than an hour.
Click on picture to download (256KB)
Chemistry can be fun and beautiful, it is also of great importance to everyone, even if you do not know it. All life is driven by the core sciences of chemistry and physics, every cell in your body is a little chemical factory with millions of chemical reactions going on all the time. Also, modern life would be quite different without continued chemical research and development. Can you imagine a life without plastics, just look around you, how many of the objects you see are made entirely from natural materials? One thing we should all consider is what we will do when oil supplies run out at some point in the future, most of these modern materials originate from oil feed stocks and alternatives will have to be found. Just imagine how heavy a mobile phone or computer would be with casing made of entirely of wood or metal!
Below you can find two example of chemistry in action. The first is an example of a beautiful and fascinating reaction, and the second is an example of how chemistry can be used to make a drug soluble which is otherwise insoluble in the stomach.
Index to further Chemistry Corner pages:
Where did it all start.......fun, flames and smells