How Is Liquid Oxygen Made?

Oxygen

One of the Earth's most abundant chemical elements is oxygen, which makes up about a fifth of the air's volume. Oxygen is needed to sustain life. Energy needed for the life process is created in plants and animals when oxygen combines with other chemicals. Plants make oxygen through a process called photosynthesis. Their cells take energy from the sun and make sugar from carbon dioxide and water. A byproduct of this process is oxygen, which is then released into the air. Most fuels need oxygen to burn, and in turn heat is released back into the atmosphere. Oxygen can be found in the air, water and in the Earth's crust. The chemical symbol for Oxygen is the letter "O."

People need oxygen to breathe, but it has many other uses. It can be used in manufacturing, such as when making steel in a method known as the basic oxygen process. Oxygen is used to help welders fuel their torches. Oxygen can also be made into liquid and used for purposes such as making liquid rocket fuel. It can also be combined with other chemicals to make explosives. Liquid oxygen is called LOX.

Ordinary oxygen makes up about 20 percent of the atmosphere. It is made up of two oxygen molecules that are fused together. The symbol for ordinary oxygen is O2. It is odorless, colorless and tasteless. When pressure is applied to ordinary oxygen, it will liquefy at high temperatures. When the pressure is 730 pps (pounds per square inch), it will liquefy at 118.8 degrees C. When the oxygen exceeds that temperature, it cannot be liquefied. The pressure and temperature at which oxygen liquefies is referred to as its critical temperature and pressure. When liquefied, oxygen becomes magnetic and can be confined within the poles of a strong magnet.

Liquid oxygen is made commercially through a distillation process. The nitrogen will boil before the oxygen, and as the nitrogen boils away, the liquid air remains with a higher concentration of oxygen. When stored, it is placed in steel tanks at a pressure more than a hundred times greater than that of the atmosphere.