[fizzling]
I was talking to one of my students, and mentioned how years ago,
one of my coworkers had put a Coke can in a lab chiller, and it had blown up,
and the bits had damaged the pump of the chiller.
And then I suddenly thought, what would happen if we put a Coke can in liquid nitrogen?
So late last night, I went out and bought two cans of coke.
This was a first for me - I've never bought cans of coke, and I've never tasted any.
-[Brady] You've never tasted Coca Cola? -I've never tasted Coca Cola.
-One little sip? -Not a sip.
-Are you allergic to it, or...? -No, no, it just doesn't appeal to me.
And now I've got to this age, I don't want to spoil my record.
I might be the oldest non-Coke drinker in the world!
[Brady laughs]
There's not coke in there, is there?
No.
Then I persuaded Neil that it was worth doing.
[fizzling]
As you can expect, when the can was dropped in, the nitrogen started boiling, a lot.
What I was interested in is that CO₂ is quite soluble in cold liquid,
but it's not soluble in ice, or it's poorly soluble.
So, of course, what should happen is that when the Coke freezes,
the CO₂ should come out, as a gas, and the pressure should go up.
At the same time, because ice is less dense than liquid, the liquid in the Coke can should expand.
But because liquid nitrogen is pretty cold, the CO₂ may well solidify,
so the effect will be less than if it was a gas.
So what I was suspecting is that the can would break... I hoped, quite spectacularly.
And the first time we did it was quite exciting, because the can split before all the Coke had frozen.
A slit, almost as if it had been cut by a knife, appeared in the side of the can,
and the Coke... came out.
And, of course, as soon as the liquid, which, Coke is mostly water, and some sugar,
as soon as it came in contact with the liquid nitrogen, it froze.
But there was much bubbling, so it froze into a sort of froth.
A bit like a water-ice.
In the end, what came out looked like an artwork!
And I persuaded great dear Neil that we should watch it melting.
And I got quite excited going back and looking at it!
[Brady] The professor was more excited by the melting than anything we did all day.
[Dr. Poliakoff] The second can, which, we did rather better with- better lighting, things like that -
was very disappointing.
Because it froze completely before the can split.
And the can split again, but everything inside was solid, so nothing came out.
What was quite interesting is that when you look through the slit,
the ice, instead of being a solid lump, was in much smaller pieces.
[ice cracking]
Not quite like sand, but quite powdery.
That didn't surprise me, because I've known for many years
that if you put ice in liquid nitrogen, it does crack.
Finally, Brady thought we ought to be fair, and we ought to do Pepsi, as well as Coke.
-[Brady] Have you tried Pepsi? -I haven't tried Pepsi, either.
-Okay. -I include them as the same sort of thing.
Unfortunately, the machine we've got only sells bottles of Pepsi.
So freezing a plastic bottle of Pepsi, we expected it to have split in much the same way.
[hissing]
But in fact, it was very disappointing, because the bottle froze completely without splitting at all.
I got bored and left.
[ice cracking]
Brady and Neil couldn't restrain themselves from tasting the frozen Pepsi, but I kept my pledge.
It's nice and warm, but I suppose gold color also gives you a feeling of warmth,
so it may be partly psychological.
The reason why the bank has got this store, is because not only the Bank of England,
but other central banks, like to keep some of their money reserves in gold.