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Michael: You’ve probably heard of acids. They’re sour, they’re corrosive, and you really don’t want them in a papercut. But inside chemistry labs, chemists also work with what they call superacids. Which are... exactly what they sound like. They’re incredibly corrosive and very dangerous, but they also might hold the keys to things like creating better plastics and to fighting smog in cities worldwide.

Acids are molecules that easily become negatively charged, whether that means easily gaining a negatively charged electron or easily losing a positively charged hydrogen ion. And stronger acids become negatively charged more easily than weak acids.

The pH scale is the most common way of measuring an acid’s strength, based on the concentration of active hydrogen ions when the acid is mixed with water. Every time the pH drops by 1, hydrogen ions are ten times more common and the acid is ten times more reactive. Lemon juice, for example, has a pH of about 2, which means that there’s one hydrogen ion donated for every hundred other molecules in the juice. And stomach acid, with a pH of 1, gives one hydrogen ion for every ten other molecules.

The pH scale only really works down to 0, where there’s one hydrogen ion for every molecule in the solution. Below that, and for acids that aren’t mixed with water, chemists use something called the Hammett acidity function, which is kind of a way of describing what pH a really strong acid acts like it has. Even if there aren’t actually that many hydrogen ions floating around.

Using the Hammett acidity function, we can say that pure sulfuric acid, a kind of acid that’s used in lots of industrial processes, acts like it has a pH of -12! You’ll never find something as powerful as pure sulfuric acid out in nature, since it’s so strong that it violently reacts with pretty much anything it touches — including water. But in chemistry labs, sulfuric acid is just the beginning.

Chemists call anything stronger than pure sulfuric acid a superacid. Superacids were first described back in 1927 by scientists at Harvard, but superacid research really got going back in the 1960s, mainly thanks to a chemist named George Olah. Olah won the 1994 Nobel Prize in chemistry for his research into carbocations, a type of molecule that has a carbon atom with a positive charge. They’re important in the production of some plastics and high-quality gasolines.

Olah found that one of the best ways to make carbocations is to put organic molecules, which have lots of carbon, next to superacids. His discoveries make it easier for researchers to study plastic-making.

Other researchers have also found some superacids that bond really well with nitrogen oxides, gases made of both nitrogen and oxygen that are released in car exhaust, become smog, and lead to acid rain. These scientists think they’ll be able to stop nitrogen oxides before they reach the atmosphere by running the car exhaust past the superacid first.

Superacids get so strong because a lot of them are made by mixing an existing strong acid with another acid that involves the super-reactive element fluorine. The fluorines end up bonded to lots of hydrogen, but they’ll drop the hydrogen in favor of just about anything else. So as soon as another molecule wanders too close, the fluorines lose all their hydrogens and bond with the new molecule instead -- pretty much no matter what it is.

One of the best-known superacids is one called magic acid. It might sound like some kind of illegal drug cocktail, but magic acid is actually used to break up lower-quality gasolines into carbocations so that they can form more complicated bonds and make the kind of high-quality gasoline that racecars use. Magic acid is a combination of three very strong acids, and it acts like it has a pH of -23. That’s a hundred billion times more powerful than pure sulfuric acid! But it’s still not the strongest superacid ever made.

That honor goes to fluoroantimonic acid -- a mixture of just two of the acids used to make magic acid -- which acts like it has a pH of -28. That’s ten thousand times stronger than magic acid, ten million billion times stronger than pure sulfuric acid, and a million billion trillion times stronger than concentrated hydrochloric acid — an acid that’s already strong enough to give you very severe burns.

So fluoroantimonic acid wouldn’t just burn human skin. It would eat through skin and bones and anything else it might touch -- and that’s after it eats right through just about any container you might try to put it in and almost any liquid you try to dilute it with. The only way to store these sorts of substances is with teflon.

Teflon is already made out of molecules with super-strong carbon-fluorine bonds, so it won’t even bow to fluoroantimonic acid. No one’s found a specific use for such a fantastically strong acid yet, but chemists are actively looking for one. But unless you have teflon-lined bottles lying around, it’s probably a good idea to just stay away from superacids. You know what? Even if you do have teflon bottles. Just stay away.

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