Preparation and Properties of Liquid Oxygen

Liquid Oxygen

"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. Oxygen comprises 20.8% by volume of the atmosphere of earth. We will perish without oxygen. It is vital to support life, however when pure oxygen 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 oxidising agent and is a common liquid oxidizer propellant for spacecraft rocket applications. Liquid Oxygen was also used extensively in making explosives, but usage has gone down due to a high rate of accidents.

Properties of Liquid Oxygen

Oxygen is often stored as a liquid, although it is used primarily as a gas. Liquid oxygen is termed as a cryogenic liquid. Liquid oxygen extremely cold in nature and has a pale blue color. Due to its cryogenic nature, the materials it touches to become extremely brittle. Liquid Oxygen may react violently with reactivity combustible materials and reducing agents. It can oxidize organic materials violently.

Liquid Oxygen has following Properties: Molecular Formula: O2, Molecular Weight: 31.999, Boiling Point (at 1 atm): -297.4°F (-183.0°C, 90oK), Freezing Point (at 1 atm): -361.9°F (-218.8°C, 54oK), 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.

Preparation of Liquid Oxygen

To make liquid oxygen, air, which is about 80% nitrogen, 20% oxygen and small amounts of the inert gases, is required. Liquid oxygen is obtained by the rapid expansion of high-pressure gaseous air that has been purified to remove carbon dioxide, and other high boiling substances. Submersing a copper coil into liquid nitrogen and blowing oxygen through it also prepares liquid oxygen. The oxygen supply has to be connected to the top of the copper coil with the help 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 that is placed inside. The cup is filled with liquid nitrogen to allow the maintenance of the Liquid Oxygen as it is produced.

Storing Liquid Oxygen

Storage of liquid oxygen requires special attention. As pressure and temperature play very important factors in the storage of liquid oxygen, the vessels used to store liquid oxygen 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. Container should be secured completely. Only properly specified equipment, which is suitable for Liquid Oxygen, its supply pressure and temperature should be used. Container should be kept below 50°C in a well-ventilated place. Store should be a no smoking zone. Liquid oxygen should not be permitted to come in contact with organic materials or flammable or combustible substances of any kind. It is highly advisable that people dealing with liquid oxygen should be thoroughly familiar with the properties and safety measures before they start dealing with liquid oxygen and the equipments associated with it. Depending on the usage of the liquid oxygen, special clothing suitable is available and only these should 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 trousers. 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 any thing 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. There is a child in me who feels very proud at the marvels of science but that child has a fear also in some corner of her heart…she is scared…who knows which discovery lead us to another Nagasaki and Hiroshima!