Hi Chris/Ivan, memories a bit crusty now! However there are lots of really interesting reactions like this. This is a bit spooky as on Sunday I was going though a big pile of papers on the subject which had been lying undisturbed in a black sack for years with the intention of recycling them. Nearly as strange as the day I went into a second hand bookshop and suddenly wondered if they had a copy of "Order Out of Chaos", then to turn round and see one on the shelf!
I looked at 2 reactions : hydroxylamine in nitric acid and the same again but with potassium thiocyanate added. I think I posted a couple of pics on the doomed free energy thread but I've included them again.
The hydroxylamine/nitric acid travelling wave was first discovered by accident by a friend at Swansea. (He was investigating basic reactions in nitric acid for BNFL for the Purex process)
At least it wasn't tax payers money we were wasting
On returning from the student bar one afternoon he noticed that the homogeneous solution
he had left in a spec cell on the side had separated into two layers. Not unusual perhaps, but the top layer was getting bigger! It took a while to find someone to show and by this time there was just a homogeneous solution. For quite some time it was put down to one beer too many as he couldn't get it to do it again!
Eventually it was established that it wasn't a figment of his imagination and I carried on the studies
In BZ
type reactions you get the reactions occurring homogeneously causing the whole solution to change colour. In the case of the travelling waves I was looking at the reaction occurs at a moving front which you can cause to move down (never succeeded in making it go up) in a test tube or spectrophotometer cell. You can also initiate them in a petri dish and get them to move outwards forming quite intricate patterns.
The basis for all these reactions is the same - you need a feedback mechanism to keep the reaction going. In the case of the system I was studying nitrous acid is formed which is a catalyst for its own formation sustaining the propagation of the wave. Some of the systems are more complicated with several interlinked reactions going on, all feeding each other. As the name of the thread suggests there can be a build up of concentrations until a tipping point is reached and another reaction occurs.
The mathematical modelling is clever and requires the normal kinetics of the homogeneous reaction to be known and then to translate how they can explain the rate at which the wave moves. You end up with lots of simultaneous differential equations. The localised concentrations and temperature effects can lead to some really spectacular patterns.
I think it's the study of these sorts of reactions that have gone a long way towards the development of chaos theory and is probably being used in the predictions of climate change and potential tipping points.
Now, useless! Takes envelope and extracts one small handful of smites and points them in the direction of the Wily One. Remembers the "Thou Shalt not Smite" vow and puts them back in the envelope.
Seem to have gone on a bit but it's not often the subject arises, about once every 20 years or so ..
