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Re: CO2

> Date: Tue, 22 Jul 1997 03:41:45 -0400
> From: "Jeff K" <jeff1908 at net-gate_com>
> Reading a description of an Aqualine CO2 reactor in That Fish Place's
> catalog, I came across the following:
> It spoke of its 1.45 meters of contact travel "Allowing diffusion of 100g
> CO2 with 10KH"

The reactor has a plastic casting inside which acts like a giant
corkscrew -- the CO2 bubbles enter at the bottom and spiral up,
diffusing into the water as they go.  I suppose there might be 1.45
meters of travel inside ... 

> I thought I had a basic understanding of the CO2/pH/KH relationship,
> but now I'm lost.. Is there something missing here? How does CO2
> diffusion relate to KH (besides pH)? Shouldn't they be talking about a
> time period and/or water quantity? Perhaps grams per liter per hour?

Yes, a rate would be more useful.  Perhaps this is just a translation
error. Or general marketing garble. 

BTW, the instructions that came with the one I bought where in
French. Not being well versed in French, I managed to break it before
I got it working. 

> Also, I don't remember reading anything about temperature. Wouldn't
> temperature affect water's ability to hold CO2?

IMHO, not to a significant degree. 

> Finally, how does water's CO2 concentration affect further diffusion?
> My gut tells me the process slows as concentrations rise.

That's correct. 

> If I'm right, would the addition of an inverted, CO2 filled bottle be
> a good indicator of concentration? It's diffusion rate would seem to
> indicate preexisting levels.

Kind of, but there is another process involved that will mess this up.
Since diffusion is based on relative concentrations of gases and
diffusion constants, as CO2 diffuses into the water from the bottle,
other gases will diffuse into the bottle from the water.  Soon the
atmosphere in the bottle is only partially CO2 and you'll notice not
much diffusion happening.  For this reason, "bell jar" type diffusers
need to be burped every so often.