Calculating dissolved Co2

[Jarred Awesome]

Hello Everyone,

I’m by no means a chemist, but I have been trying to learn a little bit about it, for a project I’m working on.

I don’t know where else to ask, so I figured this forum might be a good place.

I have an aquarium, and I am trying to calculate how much co2 is dissolved in the tank.

If I understand properly, I can permanently put an upside down cup in the water, and use Henry’s Law to figure this out.


Attached you can find a drawing of my set up.



I can also use Antoine’s equation compensate for temperature 

Here is what I came up with, but I don’t have enough knowledge to know if I’m doing this properly can someone see if I am doing this properly?

I took the temp of water, the applied Antoine Equation to get the Vapour Pressure in the cup. (Not sure if that’s what I am supposed to do)

I then took the PPM measured in the cup, and the result from the Antoines equation And applied it to this: PA=(ppm/PV)x10e6, in order to get the partial pressure.

I then applied the result into Henry’s law to get the result in M/L,

Then multiplied it by 44010 to get the readily as ppm

Here is the raw math.

co2 in  cup = 195PPM
Water temp in aquarium = 27 C

Antoine Equation(with constants from water put in):

10^(a-b/(T+c))
10^(7.94917-1657.462/(27+227.02)
=19.887130064 mmHg


Ppm to Partial Pressure

Partial Pressure = PPM/10^6*Vapor Pressure
(195/10^6)*19.887130064
=0.039687554121637006 mmHg

Then Henry’s law
    kh = 29.95
    c = pa/kh
    ppm = c*44010 
Dissolved gas = Partial Pressure / Henry's constant
039687554121637006 / 29.95
=000129907122206828293 M/L

Then converting m/L into ppm
mmHg * Mollar Mass of given Gas
000129907122206828293 * 44010

Rounded that gives me 5.71ppm if co2 in the aquarium.

My hope is someone can tell me if my my math and implantation is correct?