This video is being released on Christmas Day.

We haven't made a Christmas video for a long time...

...so we're going to make up for it by lots of Christmas videos.

What I want to show you are some of the presents that I've been sent...

... by you YouTube viewers, and I've collected on my travels around the UK, around the world.

And they've all got something really quite interesting and chemical about them...

...and some of them have got really nice stories.

So let's begin with this one.

This looks like a sort of biscuit that you might get in a café - health food.

But it's actually solid and quite heavy. It was given to me in one piece but it broke in my luggage.

And it is the deposit that is formed inside an enormous wine barrel.

I visited a vineyard where they make wine, which belongs to the president of the Swiss Academy of Sciences, so he can really entertain in style.

And we sat among these huge barrels - big enough for somebody to get inside.

On each table there were lumps of this material.

So I must say in this case I had to ask for some, rather than being given it as a complete gift, but I told him I thought it would make an interesting YouTube video.

Now, I haven't tested this myself.

He told me that it was tartaric acid, though it might be a tartrate.

Tartaric acid is an interesting molecule because it was one of the first that was discovered to demonstrate left-handed and right-handed forms.

But I don't know whether the people who discovered it, discovered it in wine or somewhere else.

But I was amazed that you should have things like this inside a wine barrel.

And if you look, it's really quite thick.

So it's not just some tiny deposit.

[Brady]: Is this like... this is a bad thing? This ruins the wine? Is this like a waste product? Or...

[Professor]: I think that tartaric acid is a waste product, but a small amount of it stays in the wine and gives part of the flavour.

The flavours of wine are made up from a whole series of different compounds.

So you need just a pinch of this, a bit of that, and so on.

So if there was no tartaric acid at all, it wouldn't taste the same.

[Brady]: Was your host surprised when you asked to keep it?

[Professor]: I'm not sure. I'll have to ask him when I see him next.

He's a space scientist, astrophysicist. So I think deposits in wine barrels are not his area of science.

So, this is my present for the first day of Christmas.

And there are lots more to come for all twelve days of Christmas.

And some days have more than one present.

[laughter]

Oh my God!

I think it's absolutely disgusting! [laughs]

Eww! [laughs]

Ugh!