[Jewelry making - Article 01426] - Re: [Orchid] Why Hydrofluoric acid is so dangerous

[John Donivan]

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>      Any idea what it might be? Any idea how dangerous it might be? I
>     had always assumed it formed a weak solution of hydrofluoric acid
>     when mixed with peroxide as it will eat through glass, but not
>     plastic. I never really considered it to be any more dangerous
>     than pickle or 

    Dave - Nope, nope, nope. There are supposedly HF free platinum
    devesters, which I've heard of, too, but a search came up empty...
    There's a post in the Orchid archives where Gesswein talks about it
    (1999), but they don't sho it on their site. There's also this: 

    A small shop may wish to consider a safer devesting agent for
    platinum investment as a substitute for hydrofluoric acid. Ask your
    tool supplier; there are many brand names. You can also mix your own
    substitute using the following formula (percent- ages are given by
    weight): 25 percent sodium hydroxide, 25 percent potassium
    hydroxide, and 50 percent deionized or distilled water. (The sodium
    hydroxide and the potassium hydroxide should be in pearl or flake
    form.) Combine all three solutions in a stainless steel container,
    and heat (do not boil) for 25 to 40 minutes. Be careful mixing,
    since the three ingredients will naturally heat up when combined. 

    I know nothing about that post personally, I'm just passing it on.
    HF is a gas, and becomes hydrofluoric acid when dissolved in water
    (FYI: HF + H2O -> H3O+ + F-). Meaning there's no solid unless it's
    frozen. As Jim said lately, it could be fluoride salts, similar to
    sodium bisulfate. All that stuff is proprietary, and it could be that
    research could figure out some things, but I personally don't know
    the answers. Tip: The above post is alkaline, a quick test will tell
    you if yours is acidic or basic - at least a start. 

http://www.donivanandmaggiora.com
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