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Re: Aquatic Plants Digest V3 #964

> From: IDMiamiBob at aol_com
> Subject: Re: CO2 and agitation
> Paul sears points out:
> > 	The 350 ppm in air is 350 ppm by volume, which is the normal way
> >  of expressing it with gases.  The concentrations in the tank are by weight.
> >  If I recall correctly, the equilibrium concentration of CO2 in water in
> >  contact with the atmosphere is something like 0.5 to 1 ppm, so if we
> >  have 15 ppm in the water, that would require several thousand ppm in
> >  the air for equilibrium.
> I'm not sure, but I suspect that if you counted the dissolved gases in the 
> water, about 350 ppm would turn out to be CO2.

	No.  CO2 is quite a bit more soluble in water than are oxygen, 
nitrogen or argon.  By "more soluble", I mean that for the same partial
pressure in the air, there will be more of it in the water.  These are
very rough numbers, but CO2 at 350 ppm (volume) in the air gives about
1/2 ppm (by weight) in the water.  Oxygen at 200000 ppm in the air gives
about 8 ppm in the water.

Paul Sears        Ottawa, Canada