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> From: Sean Murphy <gonefishn at geocities_com>
> Subject: RE: CO2 and O2 
> 2) In nature CO2 does not follow Henry's Law because of the way it
> combines with any cations in natural waters.

	It doesn't combine with cations.  It will react with OH- or
CO3--, but the dissolved CO2 still obeys Henry's law.

>  This means that CO2 is
> dissolved more like a salt then a gas in our tanks.  

	There is dissolved CO2 and there is HCO3- in our tanks.  That
is what the pH/KH/CO2 tables are all about.

> 3) When CO2 does not follow Henry's Law it does not affect the
> saturation level of O2 which does follow Henry's Law.  If you injected
> N2 (a gas which follows Henry's Law) into your tank you could force out
> the O2 but not by injecting CO2 at the levels that we can.  

	The amount of each gas dissolved depends on the partial pressure
of each gas in the atmosphere in contact with the water.  If one bubbles
a gas through water in sufficient quantity, the water "sees" only that gas,
and it will sweep everything else out.  In general, this will not be easy
to do, because of the large surface area of water in our tanks that is
(we hope) exposed to the air.

Paul Sears        Ottawa, Canada

Finger ap626 at freenet_carleton.ca for PGP public key.