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Thread: Helium solubility

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    Banned Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del's Avatar
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    Helium solubility

    Ah... my addled brain needs a little help here.

    I'm in a slow paced discussion about breathing gasses and have been confronted with an opinion that, 'helium, being a less soluble gas than N2, won't bend you as easily and is so a safer gas to dive deep on.'

    It doesn't ring true to me, and as it's the Australia Day long weekend, I need the truth to be pointed out...

    please?

    cheers

    Andy

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    Re: Helium solubility

    Quote Originally Posted by Andy Del  View Original Post
    Ah... my addled brain needs a little help here.

    I'm in a slow paced discussion about breathing gasses and have been confronted with an opinion that, 'helium, being a less soluble gas than N2, won't bend you as easily and is so a safer gas to dive deep on.'

    It doesn't ring true to me, and as it's the Australia Day long weekend, I need the truth to be pointed out...

    please?

    cheers

    Andy
    Surely the question isn't solubility here but speed of diffusion.

    Also, whenever somebody says solubility, "soluble in what?" It's less lipid-soluble than nitrogen, which is why it's less narcotic than N2.

    However, being much smaller (atomic mass 2 vs 28 for N2), it diffuses in and out of things faster.

    David

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    Re: Helium solubility

    & will rip through things with more devastating effects than N2. So I would say a helium is not safer, but it has its place.

    Quote Originally Posted by David Pye  View Original Post
    Surely the question isn't solubility here but speed of diffusion.

    Also, whenever somebody says solubility, "soluble in what?" It's less lipid-soluble than nitrogen, which is why it's less narcotic than N2.

    However, being much smaller (atomic mass 2 vs 28 for N2), it diffuses in and out of things faster.

    David

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    RBW Member nigelh has much to be proud of nigelh has much to be proud of nigelh has much to be proud of nigelh has much to be proud of nigelh has much to be proud of nigelh has much to be proud of nigelh has much to be proud of nigelh has much to be proud of nigelh has much to be proud of nigelh has much to be proud of nigelh has much to be proud of nigelh's Avatar
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    Re: Helium solubility

    At 303°K/1ATM mol fraction solubilities are
    N2 1.108e-5 mols/mol
    He 6.978e-6 so less mols/mol

    Remember 1 mol of gas is roughly the same volume. (PV=nRT)

    The problem is speed. You gas on fast and gas off fast so miss a short stop on helium and it is the equivalent of a bigger stop on nitrogen. Helium is less forgiving.
    Last edited by nigelh; 24th January 2009 at 17:55. Reason: rework as my original post was junk

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