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From: bl@hplabsb.UUCP (Bruce T. Lowerre)
Newsgroups: net.misc,net.sci
Subject: Re: Helium Balloons
Message-ID: <3737@hplabsb.UUCP>
Date: Fri, 10-Oct-86 12:34:26 EDT
Article-I.D.: hplabsb.3737
Posted: Fri Oct 10 12:34:26 1986
Date-Received: Sat, 11-Oct-86 04:31:44 EDT
References: <520@zen.BERKELEY.EDU>
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Organization: Hewlett-Packard Laboratories
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Summary: Yes
Xref: ucbvax net.misc:314 net.sci:221

In article <520@zen.BERKELEY.EDU>, mikel@cory.Berkeley.EDU (Mike Liang) writes:
> [POP!]
> 
> I just opened up my dead helium ballon of two days to breath in and speak like
> like Donald Duck today and it didn't work.  Does the helium mutate or diffuse
                                                                        ^^^^^^^
> out of the balloon and regular air diffuse in or what?

Yes.  Diffusion takes place across a membrane from a higher concentration to a
lower concentration.  The rate of diffusion is affected by the mass of the
molecules.  Diffusion goes in both directions, i.e., the helium molecules
(which are identical to helium atoms) diffuse out and air molecules (diatomic)
diffuse in.  However, since the helium is much lighter than the air molecules,
the helium diffuses out at a higher rate than the air diffuses in.  So, your
balloon shrunk and filled with air.