Yesterday was the 5th of November, which means thousands — nay millions — of people in the UK spent last night looking up at drizzly skies going ‘Ooooh!’ and ‘Aaaah!’ at successive fireworks. It’s all thanks to a plot 400 years ago to blow up the Houses of Parliament (or is it?)
Now, hands up all the readers whose formative experiences as chemists involve burning things? Thought so — me too! One of my lecturers took this further than most, however, and used to bring home-made gunpowder into lecture theatres to compare to commercial bangers. There wasn’t much sleeping in HIS lectures — or people sitting on the front row.
So, fire, bangs, colours – what more could one want? Think of all that chemistry that’s going on… Thanks to a few excellent websites, I now know that strontium and lithium salts are responsible for red, calcium for orange, sodium for yellow, barium for green, copper for blue and iron is gold (eh?). The crackling showers of white sparks are created by titanium flakes: the noise is caused by the thin layer of oxide cracking as the metal inside melts. Thousands of years since they were first invented, gunpowder is still used to provide both the whizz of the flight and the bang of the subsequent explosion.
All this might seem pretty simple (C + S + KNO3) stuff, but I remember from Dr Ludman’s course just how complicated the reactions were — and how hard to balance in the homework! And all those tightly packed solids give off [relatively] vast volumes of gases in a splurge of energy and entropy.
So the next time you see some fireworks — real or not — spare a thought for the creative chemists with some of the best jobs in the world.
Neil Withers (Associate Editor, Nature Chemistry)