How Is Liquid Nitrogen Made?
By Ronny Kalyango
Nitrogen is an element found in the atmosphere that exists in both liquid and gaseous form and has an extremely low boiling point of minus 196 degrees Celsius (384.8 degrees Fahrenheit). Natural nitrogen is usually gaseous, which poses no harm and has no distinctive smell. Liquid nitrogen is dangerous as it expands when exposed to high temperatures. To make gaseous nitrogen into liquid form requires normal air. Liquid nitrogen can be produced in low or large quantities.
Air Compression
Air compression is one of the methods of obtaining liquid nitrogen. Under normal atmospheric pressure, nitrogen molecules are usually far apart, but when put under pressure, they come together. Nitrogen, being an extremely cold element, starts heating up and the temperatures rise.
Cooling
After compression, the gas is left for a while and as it cools it expands. The temperatures surrounding it are absorbed. This nitrogen gas is compressed again and again until a liquid element is produced.
Freezing
Liquid nitrogen can also be produced using a freezing device called a cryocooler. For this method, no air compression is necessary. You can obtain liquid nitrogen under the normal atmospheric pressure. Gaseous nitrogen is pumped into a flask, which is called a dewar, a name that is derived from its inventor, James Dewar. This is a special vacuum flask used to store the gaseous nitrogen. The cryocooler then cools the nitrogen until it turns into liquid.
Handling Liquid Nitrogen
Liquid nitrogen has a low boiling point and it expands even at normal room temperature. This can lead to explosions and it should therefore be stored in a dewar which has to be loosely fitted. This reduces any chances of pressure collecting in the flask. Dewars are designed to enable effective storage and transportation of the liquid nitrogen. There are some special gloves called cryo gloves that should be worn all the time while handling liquid nitrogen.
References
Writer Bio
Based in Kampala, Uganda, Ronny Kalyango has been writing since 2008. He has written for "Uganda Trends" magazine and "Daily Monitor" newspaper. He works as a features writer for Gulu Publishers, a news agency. Kalyango has a Bachelor of Arts in literature from Makerere University.