This message is in MIME format.  The first part should be readable text,
  while the remaining parts are likely unreadable without MIME-aware tools.

---1463809521-1605815049-1268319915=:27632
Content-Type: TEXT/PLAIN; charset=UTF-8
Content-Transfer-Encoding: QUOTED-PRINTABLE



On Thu, 11 Mar 2010, Russell McMahon wrote:

> > > > I'm trying to understand an aspect of the simultaneous diffusion
> > > > (effusion?*) =C2=A0of several gases through a permeable membrane be=
tween two
> > > > spaces.
>=20
> > Isn't this 'osmosis' ??
>=20
> Not technically  - osmosis is the special case, but essentially the same =
thing.
>=20
> > You might want to look up chromatography
>=20
> I've already looked up many many many things :-).
> The question is not HOW it works from a descriptive point of view or
> what happens but how the existence of a particular fraction of a given
> gas is "known" about by the same gas on the other side of the
> membrane. I can calculate WHAT happens but need to know why.
> It would make sense if gases of equal molar fraction or molecular
> number were interchangeable in the target gas, but the explanations
> claim that it is the moles of the actual gas that count.
>=20
> eg if I contrive two gases A & B of equal molecular number.
> If the partial pressure of A is equal on both sides of the membrane
> then no diffusion of A will occur. No problem.

Yes problem. You still get diffusion, but the rate in both directions=20
makes it appear as though nothing is happening. Try adding a radioative=20
marker to gas A on one side of the membrane.

> But according to what I read if there is A on one side and B on the
> other both with equal partial; pressures then both will diffuse in
> opposite directions until the partial pressures of each is balanced.
> The rate at which this balancing will occur will almost always be
> unequal between the two cases as a given membrane / gas combination
> has a species specific rate constant.

Regards
Sergio Masci
---1463809521-1605815049-1268319915=:27632
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

---1463809521-1605815049-1268319915=:27632--