Explosions: How We Shook the World Page #5

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as a source of carbon, like the charcoal in gunpowder

and by nitrating it, he added oxygen and nitrogen

from the acid actually into the molecules of the cotton,

rather than just being in neighbouring grains.

We must make sure the temperature remains cool.

So I'm going to put a thermometer in so we can measure the temperature.

- Do you want to help?

- I do. What temperature should I watch out for?

OK, it mustn't go above 18 degrees centigrade.

I'm going to adjust this. Could you give me an update?

- It's at 21 at the moment.

- Right.

- I don't want to scare anybody.

- No, it's OK. What we'll do,

we'll just cool it down a bit. OK.

So what temperature are we now?

- It's down to 19.

- OK, well, we need to get it a bit cooler.

- We're down to 18.4.

- OK.

What's the danger if the temperature starts rising?

We want to keep control of this reaction.

I'm very conscious of this.

- That's OK.

- I know battery acid's quite horrifically dangerous and if that's just as dangerous.

It's much... These are very concentrated acids,

so we've got to be extremely careful.

'The nitration reaction changes the cotton chemically so that now,

'just like in the gunpowder mix, there are carbon, nitrogen

'and oxygen atoms, an explosive reaction waiting to happen,

'but in this substance they're actually all in the same molecule,

'so much closer together than in gunpowder.

'Schonbein had accidentally created a much more efficient explosive.'

So this is it, our nitrocellulose, or guncotton as it's known.

- That's right.

- I mean, now we've washed the acid off and dried it,

it feels exactly like cotton wool.

Just like we started with.

The only difference with this one, compared to the cotton wool,

is that we've got the oxygen actually linked to the fuel.

So because we've changed every single molecule

of the cotton to guncotton,

- then it's going to go exactly the same every time?

- Yes.

- Go on, then.

- Right. Are you ready?

I'm more than a little intrigued.

Stand back.

- I am already.

- Ready?

That gives off a lot of heat.

Heat, light, lots of gas being given out and then you can just have

a look, and there's sort of black bits there, that's the carbon.

So it hasn't fully oxidised.

So there's not enough oxygen for all the carbon that's in the molecules,

- so we're just left with some carbon.

- That's right.

That's a very, very rapid burnout. Whoof.

Like with the gunpowder when you just set it on fire,

it's unconfined, so you don't get an explosion,

you just get this rapid burning.

It all goes up into the atmosphere and it's all disappeared as gases

and that's what you're left with.

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