Re: [APD] Estimative Index for CO2 Dosing - Bah!

[Jerry Baker <jerry at bakerweb_biz>]

gbooth at frii_com wrote:
> Someone mentioned CO2 equilibrium values.  This was beat to death back in
> the 90s and the theoretical value for CO2 equilibrium was 0.485 PPM (at a
> specific temperature, etc).  However wonderful that theoretical number is,
> the practical value is around 2-3 PPM.  Resolution was never reached on
> why there was a difference but it was probably due to either
> A) biological respiration (bacteria, algae, plants, fish) keeping ahead of
> diffusion to the atmosphere,
> 2) the contrarian nature of aquarium water.

I'm not afraid to be wrong, so someone correct me if I am here. My 
understanding of Henry's Law is that the calculation should go something 
like this:

CO2: 0.0314 molar percent in the atmosphere and a solubility constant of 
1/29.76 mol/l.

   0.000314 atm
-----------------  =  1.05x10^-5 mol/l * 44010 mg/mol = 0.464 mg/l
29.76 atm/(mol/l)

Oops. Last time I accidentally only moved the decimal over 4 places 
instead of 5.

This is for water at 25°C (77°F), which is very near what most of us are 
probably using.

You could use this and 1479 mg/l as saturation to construct your own 
curve with some certainty.

-- 
Jerry Baker


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