I saw an advert on the TV at the weekend for Arm & Hammer Enamel Care Toothpaste, and as I have sensitive teeth, I was paying attention.

Arm & Hammer Enamel Care Toothpaste, we are told, is very good for sensitive teeth because it contains "liquid calcium", which apparently is very good for filling up the small holes that cause sensitive teeth.

Here I spotted a flaw. Thanks to the unique way in which the British education system is funded, I have a chemistry degree. I'm not going to pretend this makes me a genius, it just means I was good at remember things about chemistry for 6 weeks in 1995. But anyway.

Calcium is a metal. More specifically it is an alkaline earth metal. I forget exactly what this means, but all you need to know is that calcium is a metal.

What you also need to know is that calcium has a melting point of 842 degrees Centigrade. This means that liquid calcium is very hot. Hot enough to turn bone to ash.

Pretty much anyone will tell you that boiling water has a temperature of 100 degrees Centigrade. It's also worth bearing in mind that the tip of a lit cigarette is approximately 700 degrees Centigrade.

I don't know what's worse. The idea that Arm & Hammer want to burn me alive with liquid metal, or that they can't be bothered to say that what the toothpaste really contains is a liquid solution of calcium citrate. Which is an entirely different thing.