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[APD] Long- vs Short- Term Membrane Exposure

Are there permeable membranes that will pass molecules as large as O2 and
CO2 without passing the more diminutive H2O?

I'm not too sure a reference solution would remain so if the osmotic
pressure across the membrane is maintained during long- term exposure. Some
consideration to "individualized" reference solutions might have to be
acknowledged if the membrane is to be used for monitoring the system
continuously. In such a case, the reference can be a carbonate solution of
the same strength as the tank's tested "total alkalinity", with the
"reference" being the known _type_ of the alkalinity's source, keeping
dilution to a minimal range.

...noticed that people were concerned about the effects of "distillation
dilution" in the "drop test" method (though I think matching strengths might
be as handy there, too), but of all the considerations for membranes I've
seen in passing I may have missed a mention of this one...


David A. Youngker
jaafaman at comcast_net

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