[Jewelry making - Article 01417] - Re: [Orchid] Why Hydrofluoric acid is so dangerous

[Helen Hill]

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Hi John,

    That was a very thorough and good explanation of the hazards
    associated with hydrofluoric acid. However, your definition of
    osmosis wasn't strictly accurate. Osmosis isn't the "ability of atoms
    and molecules to squeeze between the spaces between other atoms and
    molecules". A) atoms and molecules can't "squeeze" through spaces
    like a squid or octopus - atoms and molecules are the size they are
    and can't make themselves smaller. B) Osmosis is actually and
    specifically the diffusion of water molecules (although since I was
    at Uni, it seems to have been expanded to include the diffusion of
    any fluids). 

    The definition of diffusion being the movement of molecules from a
    region of high concentration to a region of low concentration, across
    a selectively permeable membrane (we used to say semipermeable but it
    changed to selectively permeable as "semi" was misleading). Thus, the
    definition of osmosis is the movement of water molecules from a
    region of high water concentration (or low solute concentration) to a
    region of low water concentration (or high solute concentration)
    across a selectively permeable membrane. The process by which HF
    enters the skin is more one of absorption but you're right, it will
    get in there and cause havoc with your body chemistry (something I
    know a bit about, having had to be admitted to hospital two years ago
    in hypovolaemic shock due to the electrolyte imbalance caused by the
    primary Addison's disease I was subsequently diagnosed with - not
    something I wish to repeat in a hurry!). 

Sorry to split hairs.

Helen
UK
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