How to Make Liquid Oxygen

We usually think of oxygen in its gaseous state, as it is the air that we breathe, which helps us perform our daily functions. Liquid oxygen is oxygen cooled below -182.96 °C. It was first 'discovered' by a French chemist, Raoul Pierre Pictet. Oxygen was first liquefied in a stable state by Polish scientists Zygmunt Wróblewski and Karol Olszewski.

Understanding Liquid Oxygen

While liquid oxygen (LOX) sounds like a very difficult compound, it is quite easy to make it. Normal air consists of two main gases, nitrogen and oxygen. Both these gases liquefy at very low temperatures. To cool these gases to such low temperatures, the air is compressed and cooled, then allowed to expand again. By repeating this process over and over again, we have to get these two gases cooled to -196 °C, which is the boiling point of liquid nitrogen. Thus, we see that the boiling point of liquid nitrogen is lower than that of liquid oxygen. The liquid so formed at -196 °C is a combination of nitrogen and oxygen. To separate the two, the liquid is slightly heated to a temperature between -196 °C and -182.96 °C, where nitrogen becomes gaseous again, while oxygen still remains liquid.

Liquid Oxygen Uses

Industrial Uses
Since oxygen is a well-known gas, liquid oxygen is also used for similar combustion-related purposes. It is used in combination with liquid hydrogen and kerosene as an oxidizing propellant in spacecraft rocket application due to its high specific impulse. Many modern rockets and space shuttles also use liquid oxygen. It was also used as a propellant in the first Intercontinental Ballistic Missiles (ICBMs), but its use was discontinued because it is a cryogenic (of a very low temperature) liquid and needs to be replenished too often. It was also used to prepare oxyliquit explosives. LOX is also used in steel production. Oxygen is stored in its liquid form when it is used as a fuel component in oxy-acetylene torches.

Health and Medicinal Uses
It is also used in various vitamin supplements. Sprays containing liquid oxygen are used on cuts and bruises, and to reduce itchiness. For people suffering from respiratory diseases, liquid oxygen therapy is used.

Physical and Chemical Properties

• Molecular Formula: O2
• Molecular Weight: 31.999
• Boiling Point @ 1 atm: -297.4°F (-183.0°C, 90.19 K)
• Freezing Point @ 1 atm: -361.9°F (-218.8°C, 50.5 K)
• Density, Gas @ 68°F (20°C), 1 atm: 0.0831 lb/scf
• Density, Liquid @ BP, 1 atm: 71.23 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
• Solubility in Water @ 77°F (25°C), 1 atm: 3.16% by volume
• Expansion Ratio, Liquid to Gas, BP to 68°F (20°C): 1 to 860
• Latent Heat of Vaporization: 2934 BTU/lb mole

Thus, we can see that oxygen is a utile element not only in gaseous state but also in liquid state!