Blasting the middle from a coin – Periodic Table of Videos


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] [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] [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!

100 thoughts on “Blasting the middle from a coin – Periodic Table of Videos”

  1. Please do a video on Pb(NO3)2 + NaHCO3. The result, Pb(OH)2, has some special traits as it won't react with Acetic acid, although it's a base with acid. I made this substance at school one day and would like to see you do a video on it.

  2. "We used my pound coin, so we didn't use any university money" Don't you get paid by the university? (it's a joke relax people!)

  3. This were his last words before he was arrested and sentenced for life because of vandalism of government property.

  4. Don't know about the UK. But there are laws that permit the usage of coins like this one for education purposes.

  5. This Guy's the Nutty Professor (and I'm sure a genius).  Love his experiments and his sense of humor.  This is the kind of Guy you want teaching you Science.

  6. The £1 coin is like the Toonies we have here, except it's the reverse. Nickel on the outside and aluminum bronze on the inside.

  7. I was under the impression that white phosphorus ignites spontaneously in air?

    Armstrongs mixture uses red phosphorous which does the same thing.

  8. Just use a Euro Coin, you guys aren't using them, so it'll probably be ok to do over there!
    Besides, no one has a monopoly over the euro coins, so I highly doubt anyone will persecute you.

  9. I prefer see these explosions on my screen than un my room. I am afraid the melted P + K ClO3 explode sponteanously!

  10. For what it's worth, I think it's a myth that it's illegal to damage coins – Edinburgh Zoo has a machine for pressing coins flat, with a whole screed about the history of this belief next to it!

  11. How much energy released per gram?
    This is definitely greater than 1 kilo-Joule, if not at least a Mega-Joule.

    However, this could be tiny in comparison to Kim Jong-un's Hydrogen bomb.

  12. You should use currency from outside GB. That way any governing authority will be outside the jurisdiction. For example the Secret Service can't get at you in England if you damage US coins.
    The US Secret Service is the "money police" in the US. If you are counterfeiting in the US, it's not the FBI that comes after you, it's the Secret Service.

  13. 0:33 I've always wanted to see this clip of Col. Shaw. You can really see how far that iron rod bent – almost double – as it smacked him on the head.

  14. I can't believe the prof has a knighthood but no explosives or firearms licence, how is he supposed to go into battle?

  15. yes. sure. you havn't spent any university money. because you used a 1 pound coin from your pocket.
    but i guess you also paid everybody from your own pocket, and bought the metal plates and the explosives from your own pockets.

  16. You most certainly CAN remove the center of a pound coin with a hammer and punch. Very easily in fact. Putting it back is another matter.

  17. And now for the £64,000 Question.

    White phosphorus is pyrophoric, which means it spontaneously combusts when it comes in contact with air. How were they able to do this experiment?

  18. In the states, it is also illegal to destroy currency, unless done for the sake of education. Is this not so in the UK?

  19. The Canadian two dollar coin commonly referred to as the, "toonie," was introduced in 1996. It is difficult to find one of the original batch from 1996 these days, but there's a trick where if you freeze it then smack it with a hammer, the inner and outer rings separate. The Royal Canadian Mint fixed this in 1997, after the error in the first batch was noticed. Also fun fact. The picture on the front side of the toonie is of a polar bear, but it can also look like a dinosaur when viewed sideways, or a group of penguins when viewed upside down. These were intentional artistic decisions, I used to be friends with the daughter of the artist who designed the toonie.

  20. Under Section 10 of the 1971 Coinage Act – No person shall, except under the authority of a licence granted by the Treasury, melt down or break up any metal coin which is for the time being current in the United Kingdom or which, having been current, has at any time after 16th May 1969 ceased to be so.
    but it is a cool experiment.

  21. You can easly separate the two parts of the coin by pressing a bit on it's sides, with a vice. It doesn't really require much force

  22. Excellent video, as always. However, I am shocked that (a) this quantity of explosives and (b) use in an academic setting, requires a license. Note, I don't have any knowledge that it is different anywhere else. I just find it amazing.

  23. What if one uses a nearly complete enclosed environment – where the gasses can come out one way – but the pressure on the master (coin) is perfect.

  24. The metal impression look like the time when the royal mint struck the pattern coin on a lead plate. It is very intersting !

  25. Nitrogen triiodide (spelled right?) might do the same thing also. I could not tell you though. That is just because I would not trifle with such a chemical.

  26. There is no law against defalcating a coin unless you try to pass it on.
    in recent years some university brat set fire to a note in front of a homeless person. The police did not charge him for it. It was either in Oxford or Cambridge.

  27. you're allowed to deface currency for the purposes of scientific demonstration, it's a lawful excuse for a charge of currency defacement.

  28. Red Phosphorus and Potassium Chlorate is just as dangerous. A friend of mine (now deceased) lost an eye when, in his teens, he mixed the two in a plastic spoon.

  29. I met Colonel Shaw when he performed the most wonderful experiments at Stanford University. Then we brought some beer to his hotel room.

  30. What's interesting is that US dimes, quarters and half dollars are made from three layers (a center core of pure copper, with the outer layers being 25% nickel, 75% copper). Before the blanks are cut out, the sheets are "explosively bonded" together.

    So that should be the next test-see if you can bond three layers with the same technique used here.

  31. So when they weld sheets of metal together for construction projects do they use a much more powerful explosive? I know they use a greater quantity. Why does it weld in the latter, but with the coin, the metal plate only deforms without any welding taking place.

  32. The reaction of the much less reactive red phosphorus is also violent and dangerous This mixture is called Armstrong powder.

  33. so even chemists cant make a tiny bit of explosive powder without a license? oi! You got a loicense for that, mate?!
    if only you were muslim, then they wouldnt question you about it.

  34. I just don't get will you used this particular explosive, there are a few others as fast as this mixture but safer, probably even using some milligrams of nitroglycerin would be safer, if someone knows the answer i'd really like to hear it

  35. Martyn: White phosphorus and potassium chloride are fantastically dangerous to mix.

    Me: where can I get some of both.

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