Mixing CO2 with Air under pressure

[mahoodlum]

Hello folks - I hope this is the right area to post...

I brew beer at home, and air, more correctly, the O2 in air causes oxidation and ruins beer. In order to prevent it, many home brewers use stainless steel containers that can be pressurised with CO2.

The commonly accepted wisdom is that a squirt of CO2 is let into the container to pressurise it up to say 20 psi. A pressure release valve is then pulled to "expel air" dropping the pressure a little.

My query is this - how does CO2 mix with air under pressure in the vessel? Does it form a layer underneath the O2 in "air" or do the two gasses mix. What is the explanation behind the answer?

Hugely grateful to you for the answer, since I have been relatively uncomfortable with the explanation that the CO2 forms a "layer" to protect the beer. I personally don't think it's that simple surely?

Thanks :)

 

[Borek]

Most likely they mix perfectly and all you can get with the procedure described is dilution (less O₂ left, but it is still present). Repeat several times for best results.

 

[astrokreng]

Hello there,

I can provide some insight into the process of mixing CO2 with air under pressure. When CO2 is added to a container of air under pressure, it will displace the air and create a layer of CO2 on top. This is because CO2 is denser than air and will naturally sink to the bottom of the container, pushing the lighter air molecules upwards.

However, this does not mean that the CO2 and air are completely separated. In fact, they will mix to some extent due to diffusion and molecular movement. This means that there will still be some oxygen present in the layer of CO2, albeit in lower concentrations.

The reason why this process is effective in protecting your beer from oxidation is because the layer of CO2 acts as a barrier, preventing the oxygen from coming into contact with the beer. This is similar to how a layer of oil can prevent water from seeping into it.

I hope this explanation helps to clarify any doubts you may have. The process may seem simple, but it is based on scientific principles of gas behavior and diffusion. If you have any further questions, please don't hesitate to ask. Thank you for your interest in understanding the science behind your brewing process.