# Carbon dioxide in liquid and gaseous phases with liquid water

Zuzana Sediva
What are the differences between carbon dioxide solubility (miscibility, reaction) in liquid water when in gaseous (<38 bar) and liquid (>38 bar) phase? The temperature in my experiments is usually between 0 and 5°C. The stirring speed is around 500 rpm.
Is the solubility given apart from pressure and temperature by the co2-water interface?
Is there more phase - interface for the reaction between water and CO2 in the gaseous phase? According to Henry's law for real gases (including a Poynting correction), the solubility should rise with the fugacity of the vapor. How is it however, when the carbon dioxide is liquid? More CO2 should dissolve at higher pressures (CO2 in liquid phase), however the liquid CO2 - liquid water interface should be harder to achieve than the gaseous CO2-liquid water interface. Thank you very much.

Mentor
Doesn’t the Poyntong correction apply only to the fugacity of the liquid? Are you considering non-ideality of the vapor phase mixture?

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Zuzana Sediva
@ Chestermiller
Yes, the Poynting correction is at the Henry's constant for CO2 in the water solvent:
x_CO2=f_CO2/(H*exp^(V_co2 in water*(p-p_w))/(RT)), where H is the Henry constant for CO2 in water;

My question is more, how does CO2 and water interact when CO2 is gaseous and when liquid? Is there actually more dissolved at lower pressures because gas is more accessible to water than liquid CO2 or the other way around? The law above is clear until CO2 is gaseous. When CO2 is liquid, what happens?

Mentor
@ Chestermiller
Yes, the Poynting correction is at the Henry's constant for CO2 in the water solvent:
x_CO2=f_CO2/(H*exp^(V_co2 in water*(p-p_w))/(RT)), where H is the Henry constant for CO2 in water;

My question is more, how does CO2 and water interact when CO2 is gaseous and when liquid? Is there actually more dissolved at lower pressures because gas is more accessible to water than liquid CO2 or the other way around? The law above is clear until CO2 is gaseous. When CO2 is liquid, what happens?
The non-ideal phase equilibrium behavior of mixtures at high pressures and with aqueous ionic solutions is too extensive to be covered in detail here. I refer you to Introduction to Chemical Engineering Thermodynamics by McCabe and Smith for a complete treatment.