[Jewelry making - Article 01322] - [Orchid] Why Hydrofluoric acid is so dangerous

[John Donivan]

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    It struck me that many people, myself included, say, "Be careful
    with that" or even "Don't even go there" with regard to HF without
    really saying why. The why is very important to know - it could save
    your life. 

    Fluorine is the most reactive element on Earth by far. It reacts with
    almost everything. A stream of water will burn with a bright flame in
    a fluorine atmosphere. There is a group of chemists called "The
    Fluorine Martyrs" who died, were blinded or otherwise injured trying
    to isolate it as an element. Henri Moissan, who also discovered
    Moissanite, won the 1906 Nobel prize for finally doing it. The
    chemistry of HF gets complex petty fast, but in an aqueous solution
    it's a weak acid, meaning that it doesn't dissociate into ions very
    much, more specifically it doesn't form Hydronium ions as much as the
    strong acids, Hydronium ions being what Ph paper is testing for -
    acidity. This is essentially accurate, though of course it's also a
    stripped down version. Hcl dissociates at a theoretical 100%, by
    contrast. Other important weak acids are phosphoric acid and boric
    acid. What this means in lay terms is that it's not dangerous so much
    because of it's acidity per se (though of course that counts, too),
    it's dangerous because of what it is - an incredibly reactive
    fluorine compound. 

    But wait, there's more.. Osmosis is the ability of atoms and
    molecules to squeeze between the spaces between other atoms and
    molecules. Desalinization of sea water uses a membrane that permits
    the small water molecules to pass through, but not the large salt
    molecules. This is also why helium balloons deflate overnight. If you
    imagine your skin as a wire mesh of, say, 1/4" grid (6mm or so), then
    sulfuric acid is a marble - it will just sit on top. The tiny HF
    molecule is rice, and will just pour right through your skin as
    though it wasn't there at all. This is again, essentially accurate,
    though there's more to it, also. Hydrogen bonding and stuff. So, if
    you spill HF on your skin, it goes right through it, and then once it
    gets inside it begins to react aggressively with everything it finds,
    most importantly Calcium. Spilling some on your finger can rot the
    bone underneath in minutes. More importantly it takes calcium out of
    your body chemistry, creating a chemical imbalance that quickly leads
    to chemical shock and death, even with agressive treatment. Medical
    treatment for HF exposure is massive injections of calcium gluconate
    for that very reason. 

    It's (largely) not the acid, it's the fluorine that gets you. Be
    very careful if you use it - inhaling fumes is the same, but worse. 

http://www.donivanandmaggiora.com
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