To perform this separation on air, it must be cooled to a very low temperature so that it liquefies. Once this is done, the air can be passed into the bottom of a fractionating column. This column slowly raises the temperature until the oxygen and nitrogen in the air are separate from one another. From there, two tubes separately pipe off the gases.This process can be repeated on the oxygen because in many cases, there are still trace amounts of argon found in the oxygen. Pure nitrogen, oxygen and argon can be removed from the air by the end of the final fractional distillation.
Regards.