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From: doug@ndcheg.UUCP (Doug Price)
Newsgroups: sci.bio,sci.physics
Subject: Re: check your figures
Message-ID: <293@ndcheg.UUCP>
Date: Thu, 8-Oct-87 12:27:22 EDT
Article-I.D.: ndcheg.293
Posted: Thu Oct  8 12:27:22 1987
Date-Received: Sun, 11-Oct-87 03:15:14 EDT
References: <1617@culdev1.UUCP>
Organization: Univ. of Notre Dame
Lines: 31
Summary: xenon/oxygen
Xref: mnetor sci.bio:705 sci.physics:2448

In article <1617@culdev1.UUCP>, drw@culdev1.UUCP (Dale Worley) writes:
> doug@ndcheg.UUCP (Doug Price) writes:
> > Since xenon
> > is 4.56 more dense than air at 21 C, I wonder how you can keep a homogenous
> > mixture of xenon/O2 without going to zero gravity?
> 
> Using the Maxwell-Boltzman distribution to examine how the density of
> xenon and, say, oxygen vary with altitude:
> 
> 	density is proportional to exp[ - m g h / k T ]
> 
> 	where m = mass of atom/molecule, g = earth's accelleration, h =
> 		altitude, k = Boltzman's constant, T = absolute temperature
> 
> you can figure out that the density of xenon varies with altitude only
> a little more than the density of oxygen does, and the difference in
> densities varies about as fast.  Remember, nonzero temperature tends
> to keep things stirred up!  (but it's significant only if they have a
> *real* small mass)

  What I meant was that since xenon is more dense than oxygen, it would
settle towards the bottom of the storage vessel when gravity is present.
It is known that mixtures of gases will separate if their densities vary
by a large amount and if there is no strong intermolecular forces to keep
the mixture homogeneous.  Linde (producer of laboratory gases) recommends
that cylinders containing such mixtures be rolled around prior to use so 
the gases are well mixed. > 

                                Doug Price  U. of Notre Dame
                ..!iuvax!ndmath!ndcheg