Subject: question about solvation

From: Ioana Cozmuta <[email-masked]>
Date: Sun, 15 Dec 2002 19:24:29 -0800 (PST)

Hi,

I have a very basic question on which I would like to
have an answer from someone experienced who has a clear understanding.
I've looked it up in various books but

I have two sets of experimental data for oxygen and water vapor
permeabilities, respectively. The oxygen permeabilities are expressed in
cm^3*mm/m^2*day*atm while the water vapor in g*mm/m^2*day. If I use the
definition of permeability as being the product between the solubility and
the diffusion coefficient of the gas in a medium then I get that for
oxygen the solubility is expressed in cm^3/m^3*atm while for water vapor
it is expressed in g/m^3.
By definition the solubility is the limit, when pressure goes to zero, of
the ratio of the gas concentration versus its partial pressure (Henry's
law). Thus it should be expressed in
volume_of_gas(STP)/volume_of_matrix*partial pressure.

Is there usually a difference that is accounted for in experiments that I
am not aware of  and explains the different units for solubility?
Also what is the conceptual difference between Henry's constant and
solubility?

I am sorry if this question is trivial but it bothers me since a while and
I would like to have an expert chemist answer on this (my background is
not chemistry).

Thank you in advance,
Ioana

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