Re: Bubbling plants

George Booth repled to Jim Kostich:

>> Another possibility along this line of thought is that the water might
>> well continue dissolving O2, but be dumping some other gas
>> simultaneously to "make room".
>No, each gas has its own soluability (partial pressure).  One type
>will not leave to make room for another.
>> The above is all based on my assumption that the maximum solubility of
>> each of the gases involved is limited by the presence of other gases
>> already dissolved - an assumption which makes sense to me,
>That is incorrect.  Many fish stores continue to advise against CO2
>injection "because it will reduce the oxygen available to the fish".
>It just doesn't work that way.

I disagree with this analysis. Addition of any gas will lower the partial
pressures of other gases. A liquid in equlibrium with a mixed gas
atmosphere can hold exactly 1 atmosphere of mixed gas. If we increase the
amount of one gas by a diffusion scheme like our CO2 "reactors" we increase
its partial pressure, therefore the total partial pressures of the other
gasses will be reduced.

Imagine an aquarium with half of the surface exposed to air and half
exposed to CO2. In this case the average atmosphere above this tank is 50
percent CO2, 10 percent O2, and 40 percent N2. Obviously the partial
pressures of N2 and O2 will be reduced.

In this case since a continuous transport of the the gases from one
atmosphere to the other will be established the partial pressures in the
liquid will also be affected by how efficiently each gas diffuses
into/outof the liquid, I don't know if different gases have different
diffusion rates into a liquid or not, however I suspect so, since this is
"sorta" how a gas chromatograph works.

Anyway not to worry, the partial pressures of CO2 that we are using are so
low that not much O2 or N2 leaves.