There is a long tradition in Nottingham of letting off small amounts of explosives as a lecture demonstration
[Demonstrator] ... and Potassium Chlorate is an endothermic compound
[Demonstrator] So we should have an evolution of energy
With explosives sitting on a plate of aluminium,
and under the aluminium is a coin,
and when the explosive goes off,
the pressure of the explosion pressing down on the coin makes an impression.
[explosion sound]
Like almost ... like a mould of the shape of the coin.
And this has been done for more than 50 years in Nottingham using all sorts of different coins.
[explosion sound]
So with a new British pound coin which has 12 sides
it seemed a real opportunity to try it with a new pound coin.
But there's a catch.
You can see it's made of two pieces - a brass coloured ring and the silver centre.
The coins which've been used up till now in this experiment have always been solid coins,
made of the same material all the way across.
When you're handling explosives in the UK you need a special license
and therefore, a former colleague, Mr. Jim Gamble came in because he has one of these licenses.
The experiment itself is really quite interesting.
It's the reaction of white phosphorus, which is the very reactive form of phosphorus, with potassium chlorate.
It is fantastically dangerous to mix white phosphorus with potassium chlorate.
But Jim has a special method of doing it, which is safe.
But even with Jim's method, once the chemicals are mixed, quite often they explode spontaneously.
But otherwise, you need something warm to set it off.
People say you can set it off with the warmth of your finger.
But if you did that you would no longer have a finger!
So Jim uses a long metal rod which is heated at one end.
[Jim Gamble] And, you can see by the length of this rod, I have some respect for that mixture.
So what happens is that when you touch the material with the warm rod, it reacts enormously quickly
almost in a millionth of a second.
[explosion sound]
So even with our high-speed camera, you don't see the stages of the reaction.
One minute it's there, the next second it's gone.
When you're in the room, there's a REALLY LOUD bang.
It can be quite frightening. When I listen to it, I put my fingers in both ears.
[explosion sound]
So what happens with an explosive like this one, which is called a detonating explosive - it goes off very fast.
[explosion sound]
The air that is surrounding everything doesn't have time to move out of the way.
Normally at this point,
as the shock wave is going downwards, the aluminium plate is pressed onto the coin
and it makes the impression.
Now in this case, it was decided to put the pound coin on a washer,
this is a metal ring with a hole in the middle.
So, the explosion happened, the metal plate was pressed down.
But now because the outside of the pound coin was supported by the washer and the centre wasn't,
the centre of the coin was blown right out.
As you watch the slow-motion, you can see the two bits flying apart.
I believe that this is a really good demonstration of the power of the explosion.
[Brady] That's the queen!
[Jim Gamble] Yes, right.
[Brady] She's on the metal.
[Jim Gamble] Similar - a little bit more central.
[Jim Gamble] We've got another impression of the coin.
[Jim Gamble] This time ... again we've dished it.
[Jim Gamble] See that's pressed up against the brick it was standing on. You've a nice impression of the brick.
Because it's rumoured and I've heard from quite strong authorities
that if you try and hit the centre out of the pound coin with a hammer, you can't do it.
But here, it's flown right out!
It also demonstrates the fantastically good metallurgy of the coin
because the centre comes out without any damage at all.
The unfortunate thing is you're not allowed to damage coins.
We were trying to get a nice 12 sided impression on the piece of metal.
So I hope we'll be forgiven.
In future, when we do this demonstration, we won't use pound coins.
I should stress that these experiments were done with MY pound coins.
So we haven't spent any university money on trying this demonstration.
[Fluorine video]... and the gas just touching it is enough to start the fire
[Fluorine video] Think of that - just the cold gas, setting things on fire!