Will soda dissolve your teeth? The short answer is 'no,' and the longer answer is, 'no, of course not.' And yet there is a rumor, and has been for decades, that a nail dropped in coca cola will be dissolved in a few days — which led to the widespread idea that the soda would dissolve teeth, too. The truly weird part is that there is a scientific underpinning to this myth.
As a kid, I first read that a nail dropped in soda would be completely dissolved in a week in a humor book about junk food. The humorist actually said that such a demonstration had been put on at his school, and the teacher told the students that drinking soda would dissolve their teeth. That should teach me to trust humorists. I'm not a science snob. I've believed what I know, retroactively, is silly science. But even to me, and even at a young age, it seemed to me that a person who drank so much soda that their teeth were exposed to it for a cumulative week's worth of time would have bigger health problems than dissolved teeth. However, I never thought about the actual nail. Search anywhere on the internet and you can find it's not true.
Why did anyone ever think it was? Well, the credit in this case goes to Cornell, where a professor named Clive McCay testified before the House of Representatives that a human tooth left in Coca Cola will dissolve overnight. He meant it as a way of illustrating that coke causes cavities. This was cunning of McCay, since it's easier for a representative to get hold of a nail than a human tooth. However, as the rumor spread, it gained different spins. A human tooth would dissolve, and so people were rotting their teeth. Metal would dissolve and so people were exposing themselves to dangerous chemicals. Some rumors said that steak would dissolve, and so would the human stomach. The culprit was supposed to be the phosphoric acid, citric acid, and carbonic acid in coke.
What's unfair to the poor, underrepresented international company, is that coke did not get its fearsome reputation because it was harsh, but because it was gentle. Vinegar, lemon juice, and cranberry juice all have a lower pH value - being more acidic - than even the lowest values given for coke. Which is why coke was used, by some, to remove rust stains from metal. Even weak acids corrode metal. Often even plain water will do damage. Carbon dioxide combines with water to create carbonic acid - this happens in carbonated drinks as well. The acid helps oxygen grab on to the metal, which liberates electrons and changes the entire structure of the metal to rust. This is why carbon dioxide increases in the atmosphere lead to 'acid rain' that eats away at structures. The thing is, acids will eat away at rust, often faster than they will at metal. A strong enough acid will grab oxygen right off of the rust molecules. Commercial rust cleaners have strong acids in them, but they require attention so they don't corrode metal as well, and aren't always on hand. So people would sometimes put rusty nails or other metal in coca cola for some time to dissolve the rust without dissolving the nails themselves. Even a long soak in coke will leave a nail in need of a little scrubbing to get the last of the rust off, but it won't hurt the nail in the least. People who weren't in on the trick noticed coca cola taking off rust, and figured it would dissolve a nail as well. Coke, in part, got this reputation not because it will dissolve nail, but because it won't.
The official site, though, recommends actual rust cleaners for all your home care needs. The good news? You still can use coke to glaze a ham.
Top Image: Spiff
Via Snopes, eHow, How Stuff Works, and Antique Engines.