Chocolates That Bite Back

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Recently as I bit into a chocolate, I felt a strange tingling sensation in my tooth. I’d failed to notice that some of the foil wrapping was still stuck to the chocolate. The resulting unpleasant tingle was due to a modest electric shock. The combination of my amalgam dental filling and the aluminium foil, surrounded by saliva, made a very simple battery. When the foil touched my filling, a chemical reaction occurred. Since saliva is a moderately good conductor of electricity, an electric current flowed between the two different metals. People with the newer white fillings miss the tingle, since non-metals don’t conduct electricity.

You can experience a similar sensation if you put a copper wire and an iron nail into a lemon and touch them with the tip of your tongue.

In 1762, the Italian scientist Luigi Galvani showed that an electric current was produced when any two dissimilar metals were submerged in salt water. He demonstrated the electricity by stimulating the nerves in frog legs to make them twitch.

Some brave people have actually chomped into foil chocolates on purpose and in total darkness in front of a mirror. They claim to have seen tiny bursts of light as their teeth bit into the foil. Even though I love chocolates, that’s the kind of experiment I leave to others.

So next time you bite into a chocolate, be careful to remove all the wrapping, or it might bite back.