How is pure oxygen extracted/manufactured?
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To go into deeper detail on u/veespike’s excellent explanation – air is a mixture of gases, roughly 70% Nitrogen, 20% Oxygen, and then some CO2, methane, and other random gases. Just like water melts and freezes at given temperatures, gasses will melt and freeze at given temperatures and each one is unique and different.
So if take a jar of room temperature air and start cooling it down really, really cold, like 200 degrees below zero, at a certain point the CO2 will liquify and fall out of the air like rain drops. I can pour out the liquid CO2 and now I have a a cup of liquid CO2 and jar of air without any CO2 gas. I can keep cooling it further and then the nitrogen will liquify and I can pour that out and have a glass of CO2, a glass of nitrogen, and a jar of whatever’s left in the air.
If I do this right, I can get a glass of liquid oxygen and only liquid oxygen.
I used examples, but Oxygen liquifies at around -294F. Nitrogen is -320F and CO2 is -109F.
So if I cooled air to -108F it’s just cold air. One more degree down and the CO2 ‘rains’ out as liquid CO2. If I kept removing heat the temperature would stay the same for bit but the CO2 would all rain out. Once the CO2 is gone the temperature will fall again until -294F when the Oxygen rains out, and Nitrogen at -320F.
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