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Preparation and Properties of Liquid Oxygen

Preparation and Properties of Liquid Oxygen

Perhaps a layman could only think of oxygen as the most essential thing, which sustains life. Let us learn more about oxygen in its liquid form, including its properties and method of preparation.
Anju Shandilya
Last Updated: Apr 9, 2018
"What oxygen is to the lungs, such is the hope to the meaning of life", these words of Emil Brunner precisely explain about the importance of oxygen in our life. It comprises 20.8% by volume of the atmosphere of Earth. We will perish without this element. It is vital to support life, however, when its pure form is inhaled at pressures greater than 2 or 3 atmospheres, one will suffer from dizziness, vomiting, tiredness, light-headedness, mood changes, euphoria, confusion, muscular twitching, burning or tingling sensations, and loss of consciousness. That is why someone has rightly said that excess of anything is bad. Liquid oxygen is also a very powerful oxidizing agent and is a common propellant for spacecraft rocket applications. It was also used extensively in making explosives, but its usage has gone down, due to a high rate of accidents.


Oxygen is often stored as a liquid, although it is used primarily as a gas. Liquid oxygen is termed as a cryogenic liquid. It is extremely cold in nature and has a pale blue color. Due to its cryogenic nature, the materials it touches to become extremely brittle. It may react violently with combustible materials and reducing agents. It can oxidize organic materials violently.
  • Molecular Formula: O2
  • Molecular Weight: 31.999
  • Boiling Point (at 1 atm): -297.4°F (-183.0°C, 90.19K)
  • Freezing Point (at 1 atm): -361.9°F (-218.8°C, 50.5K)
  • Critical Temperature: -181.8°F (-118.4°C)
  • Critical Pressure: 729.1 psia (49.6 atm)
  • Density, Gas @ 68°F (20°C), 1 atm: 0.0831 lb/scf
  • Specific Gravity, Gas (air=1) @ 68°F (20°C), 1 atm: 1.11
  • Specific Gravity, Liquid (water=1) @ 68°F (20°C), 1 atm: 1.14
  • Specific Volume @ 68°F (20°C), 1 atm: 12.08 scf/lb
  • Latent Heat of Vaporization: 2934 BTU/lb mole
  • Expansion Ratio, Liquid to Gas, BP to 68°F (20°C): 1 to 860
  • Solubility in Water @ 77°F (25°C), 1 atm: 3.16% by volume

To make liquid oxygen, air, which is about 80% nitrogen, 20% oxygen, and small amounts of the inert gases, is required. It is obtained by the rapid expansion of high-pressure gaseous air, that has been purified to remove carbon dioxide, and other high boiling substances. It can also be prepared by submerging a copper coil into liquid nitrogen and blowing oxygen through it. The oxygen supply has to be connected to the top of the copper coil, with the help of rubber tubing. Liquid nitrogen is added to the can, which begins cooling of the coils. This nitrogen is boiled till the heat is removed from the can. To catch the Liquid Oxygen, a large test tube is placed in the cup, which is placed inside.


Storage of liquid oxygen requires special attention. As pressure and temperature are very important factors, the vessels used to store it, should be designed according to ASME codes. The piping design that will be used, has to follow codes issued by the American National Standards Institute (ANSI). There should be no use of oil or grease. Liquid Oxygen should be segregated from flammable gases and other flammable materials in store. The container should be secured completely. Only properly specified equipment, which is suitable for its supply pressure and temperature, should be used. Container should be kept below 50°C, in a well-ventilated place. The storage area should be a no-smoking zone. The stored content should not be permitted to come in contact with organic materials or flammable and combustible substances of any kind. It is highly advisable that people dealing with it, should be thoroughly familiar with the properties and safety measures, before they start dealing with it. Depending on its usage, special clothing is available, and these should only be used. The recommended personal protective equipment for handling cryogens includes a full-face shield over safety glasses, loose-fitting thermal insulated gloves, long sleeve shirts, and pants. Safety shoes are highly recommended for people who are responsible for the storage and movement of the containers.

With the growth of scientific discoveries in modern era, it is quite possible that we will not need anything for our survival and it can also happen that in the days to come, there will be absolutely no need of oxygen. Till that day comes it is this central force, which ignites the life force in our lungs. Liquid Oxygen has many medical and scientific usages, however, it is upon us to use it safely and sensibly.