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Re: CO2 reactor problem

>Subject: Re: CO2 reactor problem
>Craig wrote
>Until a few weeks ago, I was using DIY yeast CO2 which was being pumped into
>a DIY counter-current flow reactor in my sump run by a powerhead. I asked
>the group why I was getting a pocket of air in the reactor that would not
>dissolve and the response was that all the gas coming out of the yeast was
>not CO2, and so the reactor had to be periodically vented of these other
>gases. Well, now I'm using a CO2 canister and I'm still getting the same gas
>pocket. My flow is only 2 bubbles per second and it seems that the reactor
>(although it has massive turbulence and gas/water mixing) is unable to keep
>up with CO2 input. So are there still a lot of non-water soluble gases in
>bottled CO2? I wouldn't think so, but let me know if I'm wrong.
The gas in your CO2 canister is entirely CO2, but it doesn't stay that way
when it is in contact with the water.  The water is in equilibrium with the
air, and so it will have oxygen and nitrogen dissolved in it.  If the water
is in equilibrium with atmospheric air at 760 mm Hg pressure---one
atmosphere---, the partial pressure for O2 will be 160 mm Hg, and the
partial pressure of N2 will be 600 mm Hg.  Initially, inside the bubble of
CO2, the partial pressures of these gasses will be 0, and the partial
pressure of CO2 will be equal to the atmospheric pressure---760 mm Hg.  N2
and O2 will diffuse into the CO2 bubble from the water as the CO2 diffuses
out.  At equiblirium, you will have a bubble, whose composition will be the
same as that of atmospheric air.  So, not to worry.  You do have pure CO2
in the canister, and it is all getting into the water.  The bubble that is
left is from gasses that were in the water that have diffused into the CO2

Paul Krombholz, in Central Mississippi, where we are getting
drought-busting rains, starting yesterday.  At least 2 inches, so far.  The
frogs love it!