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From: chi9@quads.uchicago.edu (Lucius Chiaraviglio)
Newsgroups: sci.chem,sci.bio
Subject: Re: osmosis - how is it caused?
Summary: Actually, wouldn't salts cause activity reductions of polar solvents?
Keywords: osmosis
Message-ID: <1990Oct27.035951.27558@midway.uchicago.edu>
Date: 27 Oct 90 03:59:51 GMT
References: <1990Oct22.110253.2277@newcastle.ac.uk> <4137@kitty.UUCP>
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Organization: Department of Biology at University of Chicago
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In article <4137@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes:
>In article <1990Oct22.110253.2277@newcastle.ac.uk>,
>william@lorien.newcastle.ac.uk (William Coyne) writes:
>> Does it have something to do with the salt forming temporary weak bonds
>> with the water molecules, so on the side of the membrane with the higher
>> concentration fewer water molecules will be free to cross the membrane.
>
>	No.  It is important to understand that osmosis is a colligative
>property of solutions in that the determining factors pertain solely to
>the number of molecules of solute in solvent (and thermodyamic factors),
>and are *independent* of actual chemical composition.

	I know what you're saying -- that hydration of ions is not required to
achieve osmotic effects -- but wouldn't charge-dipole interactions between
ions and water molecules enhance the osmotic effects by lowering the
concentration of free water to an extent beyond what they could accomplish by
simple displacement?

--
|   Lucius Chiaraviglio    |    Internet:  chi9@midway.uchicago.edu