Ø At present oxygen is produced in industry from liquid air. Rectification-fractional distillation of liquid air allows to separate oxygen, nitrogen, and noble gases in large amounts. To liquefy gaseous oxygen it is cooled below critical temperature (-118°С) and then strongly compressed.
To liquefy the air is compressed up to 100 atm. Gas temperature grows simultaneously. Hot compressed air is passed through a refrigerator where it is cooled to the room temperature. Then, the gas pressure is decreased to 10 atm and its temperature is decreased by 30°С due to expansion (this physical phenomenon is referred to as Joule-Thompson effect). Repeted compression-expanding cycles allow to achieve a liquid state of air. Since O2 has higher tboiling (-183°С), compared with N2 (-196°С) therefore N2 is evaporated at distillation first and pure oxygen remains in a liquid phase.
Ø Electrolysis of water(especially pure oxygen is produced)
• О2 is stored and transported at the pressure of 150 atm in blue balloons made of steel, with the inscription “Oxygen” in black.
Notwithstanding its low boiling point (about — 190 °C), liquid air can be stored at atmospheric pressure for quite a long time in the Dewar flasks.