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Re: CO2 and O2 and time
Well, we've learned a thing or two now(I have) but the poor newbie who
asked(and started all this) is likely thinking what is all this about!?
I must add that "time" also plays a large, often ignored, role in adding,
removing, binding,equalizing of pressures etc any chemical in a tank. It
will take some time for this "to happen" in the real applied world so when
adding CO2 on a continuos basis, this doesn't reflect this theory of partial
pressures well. Dan's comments seem to be right in this regards IMO. Proof
is in the Pudding. I know the Wet/dry's work very well and have a very
small, perhaps nonexsistant, effect. It would take time to remove or drive
off the gas once the system was out of "balance". It does not happen
instantly. A lot can happen in a few moments.
Regards,
Tom Barr -who still get humbled by this planted tank thing<g>
>
>I believe George was referring to the relationship between O2 and CO2 when
>both are *in solution*. Henry's law pertains to the relationship of a
>dissolved gas in proportion to its pressure in a gaseous state. In fact,
>Henry's Law actually proves that George is right, since the addition of CO2
>to water does not change the concentration of O2 in solution.
>
>> At equilibrium, water will contain these gasses in the
>> following levels:
>[snip]
>> Suppose then you add some CO2 to the system so that the
>> air now contains 77% N2, 18% O2, and 5% CO2. The total pressure remains the
>> same. The water will now contain the following:
>>
>> N2 585.2 mm Hg
>> O2 136.8 mm Hg
>> CO2 38.0 mm Hg
>
>Since CO2 is being added to the water via a pressurized tank, the partial
>pressure in the atmosphere has little to do with it. Unless you change the
>partial pressure of the O2 in the air above the water (which isn't gonna
>happen in someone's house where their aquarium is), its concentration in the
>water will not be affected by the addition of CO2 via a pressurized tank.
>
>Dan Dixon