What’s that smell?

A school playground joke from my childhood concerns a new deodorant called “vanish”. It makes you invisible, so that no one can see where the smell is coming from.

But how can we seriously get rid of bad smells? One way, which makes the manufacturers of air fresheners a lot of money, is to mask it with a more pleasant smell. Another, considerably less expensive, is to bind the aroma molecules to a solid surface so that they are no longer floating around in the air.

It is to the credit of the ancient Egyptians that they were the first to discover (or, at least, to describe the discovery on a papyrus around 1500 B.C.E.) a material that could efficiently capture odour molecules. It was activated charcoal – that is, charcoal that has been heated to a sufficiently high temperature that its surface becomes very adept at holding on to odour molecules, and which has been reduced to a very fine powder so that its particles have a very large total surface area.

The Egyptians used activated charcoal to overcome the smell of putrefying wounds. It has since found many other chemical and medical uses, including the one favoured by Australian bushwalkers of chewing on a bit of wood from a burnt-out tree to relieve the symptoms of indigestion or dyspepsia.

The one that really appeals to me, however (and which stimulated this post) is its use in anti-flatulence underpants (e.g. http://www.myshreddies.com/ ). Surely worth an IgNobel Prize; oh, yes, the original invention got one.


IMAGE: Myshreddies.com. For another image that is rather too tasteless for me to consider using it.

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