2012: Advent Chemistry: Hydrogen Fluoride

by on December 17, 2012

Speaking of things that are very good at what they do, let’s take a gander at hydrogen fluoride. This one doesn’t need a picture, because it’s just H-F, one hydrogen and one fluorine. (I have a terrible habit of spelling it flourine, but it is not in fact a baking ingredient.)

When it’s dissolved in water it dissociates, falling apart to give H+ and F. This is an excellent acid and is called hydrofluoric acid. Hydrofluoric acid is interesting. At high concentrations (lots of HF in not very much water) it’s a very strong, powerful acid. At low concentration (lots of water with not very much HF) it’s a weak acid and doesn’t dissociate very well, but it’s a fantastic solvent.

HF doesn’t just dissolve plastic. It dissolves glass, so it has to be stored and used in specialised containers.

It also dissolves people. Hydrofluoric acid can eats its way straight through bone. A horror story is told about a research assistant who spilt a drop of hydrofluoric acid on his finger and didn’t realise until it had gone all the way through, leaving him with an unusual piercing and a wonderful way to break the ice at parties.

Luckily, because it’s so hard to handle safely, you are highly unlikely to ever come into contact with HF. Please don’t worry about it. There’s no way you’re going to get it randomly spilt on you unless you work in a lab where they use it, and if you do work in that kind of lab, you’ll already know.

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