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  • Nitrogen triiodide is a well-known compound

  • that has been used by chemical, pranksters since I don't know when.

  • When I was a schoolboy, I made some and it went off with an enormous bang

  • [Music]

  • When you make it, it comes out as a damp, rather dark coloured compound.

  • When you spread it out on the surface to dry, it dries relatively quickly and then becomes a so-called

  • contact explosive - if you touch it even very gently it can go off with a loud bang

  • So what we did was to put it on a warm surface,

  • Neil had a hot plate with a metal sheet on top to protect it.

  • And, it was put on a filter paper to dry.

  • Took quite a long time to dry - nearly half an hour.

  • But then he touched it off with a new tool that he's invented which he called a professor on a stick!

  • Like most chemical reactions, it needs some energy to set it off.

  • But this one is very little energy.

  • Physical energy just rubbing two crystals together is enough to get it going.

  • So it's rather like something that is about to over balance and you just need to give it a little push.

  • And the result was pretty dramatic.

  • [Music]

  • [Bang]

  • [Music]

  • [Bang]

  • [Music]

  • [Bang]

  • [Music]

  • So the chemistry is really quite simple

  • NI3 dissociates into nitrogen gas N2 and iodine.

  • And N2 has a very strong bond between the two nitrogen atoms.

  • So it releases a lot of energy very quickly.

  • And as it releases the energy of course it accelerates the reaction

  • and so it all goes off or nearly all goes off at once.

  • You also get a cloud of iodine vapor which is a sort of browny purple color.

  • In fact the unfortunate little professor disappears among the clouds and comes out covered in iodine.

  • Though, I managed to wash the iodine off the professor using sodium thiosulfate.

  • Occasionally, it will go off spontaneously like my sample in my locker at school.

  • Well my experience was that, like many people, I tried to make quite a large amount.

  • It was hidden in my locker so the teacher shouldn't find it and then it dried out.

  • When I opened the door, whatever I did was enough to set it off. So there was a big bang.

  • Fortunately I was not in any way hurt, but it was quite as lesson to me.

  • [Bang]

  • [Bang]

  • [Bang]

  • The chlorine compound nitrogen trichloride is a liquid and is far worse.

  • The French chemist Pierre Dulong who discovered it

  • lost an eye and two fingers or some people say three fingers when it exploded.

  • And when Humphrey Davy in London was trying to repeat the experiment, he got some glass in his eye,

  • then his assistant Michael Faraday tried it and injured his hand and one of his fingernails came off.

  • So nitrogen trichloride is a truly dreadful compound.

  • But, the triiodide, because it's a solid, has been used for many many years.

  • And in fact, we discovered in the archives here a really quite nice account of a debate between

  • two university teams - one from Nottingham and one from Swansea that took place in 1928.

  • One of the students Noel Cusa wrote an account.

  • So it begins quite formally.

  • There was an inter-varsity (between university) debate that year at Nottingham

  • It was held in the large theatre.

  • He then explains how the students were very badly behaved

  • shooting peas out of pea-shooters from their mouths at the audience in the front

  • and then on the people debating on the stage.

  • But what the people on the stage didn't know was that the pranksters were chemistry students,

  • and they had put nitrogen triiodide, which was damp, all over the stage.

  • So one of the people from Swansea got up

  • and was walking up and down the stage trying to calm everything down.

  • And then, it happened.

  • The nitrogen triiodide liberally spread earlier on the platform began to dry out

  • and each step of the Swansea man produced alarming crackles and bangs

  • until all those on the dais, that's the stage, disappeared up to their knees in a violet haze.

  • At this point, the proceedings were called off.

  • So you see, even a long time ago, students could be really badly behaved.

  • In fact, far more badly behaved than would be permitted nowadays at the University.

  • Obviously this is not the sort of reaction you should try at home,

  • because this compound is terribly unstable.

  • It is being used by people because even microscopic amounts make quite a loud bang.

  • And so it's particularly dangerous if you make a large amount of this material.

  • Even in the lab where we were working making this video,

  • we spilt some on the floor

  • [crackle]

  • [crackle]

  • and there were crackles for an hour or two afterwards.

  • Hi, you probably just heard the professor mentioned sometimes you can suffer a

  • premature detonation of your nitrogen triiodide.

  • We did experience such a problem, and we also captured it on video if you'd like to see it,

  • I'll include a link in the video description.

  • [spraying sound]

  • And while I have your attention, can I also just thank everyone who supports Periodic Videos on Patreon helping us go the extra mile.

  • Details about that can also be found down below the video.

Nitrogen triiodide is a well-known compound

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B1 nitrogen iodine compound behaved stage energy

Nitrogen Triiodide (touch powder) - Periodic Table of Videos

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    林宜悉 posted on 2020/03/27
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