Demonstrations have been my thing for a long time. I’ve done scores of different ones – quiet ones, loud ones, small ones, big ones, smelly ones, coloured ones. You name it. But all most people remember are the fiery ones. The great Jearl Walker, who wrote the Amateur Scientist column at Scientific American for many years and who wrote a Socratic physics textbook “The Flying Circus of Physics” (consisting only of questions) once said that the only demonstrations anyone remembers are the ones in which the audience imagine that the lecturer might be killed. Bassam Shakashiri, one of the American masters of the lecture demonstration replied, rather too earnestly, that this was completely the wrong approach.
But the fact is that we thrive on drama, and fires and fireworks are pretty central to the kinds of things that chemists play with to attract attention. Even in my rather low-key show “How the Zebra got its Stripes” which has only four demos in about 45 minutes, I light a small bit of “fun cotton”.
So it brings you down to earth when you hear of a really bad accident.
Last night I got an email from an acquaintance who drew my attention to a rather sensationalist article from Bild in Germany, about a 23 year old student who suffered very serious injuries during a demo lecture.
During a lecture titled “Feuer und Flamme, Schall und Rauch” – Fire, Flame, Noise and Smoke, the title of an excellent history of the Demonstration Lecture by Fritz Kreissl and Otto Krätz – the 23 year old student who was one of the speakers, had a metal container filled with aluminium powder and potassium chlorate blow up in her hand, accompanied by a huge flame. This seems to have happened as she sprinkled the mixture over a Bunsen flame. If these details are correct then one can only surmise that as the did it, the stream of powder ignited and the flame travelled back into the container, setting it off.
An appalling accident.
It is a stark reminder to us of the fragility of the little kinetic trap that we so often sit in. We are often only a few tens of kJ away from disaster, and we forget this at our peril.
So if you’re doing demos out there, remember that in many of these experiments you are Riding the Tiger – organize your bench – keep things well apart – and play a defensive game. Never forget that mixtures of fuels and oxidizers are always dangerous. As I know to my own cost, there’s a fine line between theatre and disaster.