A bloody story

Roses are red, violets are blue... actually, when you think about it, it's a load of rubbish. Roses are any old colour, and violets are, well, violet. The clue's in the name. But one thing that is, without doubt, red is blood. Its colour is its most dramatic quality. And yet the reason it's red is often given wrongly.

'Ah yes,' someone will wisely observe. 'Blood is red because of the iron in it. Like rust.' Well, yes, red blood cells are mostly haemoglobin, and the key characteristic of that interesting compound is four iron atoms. But as far as the colour goes it's pure coincidence. Find out why - and much more about haemoglobin - in the latest Royal Society of Chemistry podcast on haemoglobin. Click here to listen...