Liquid nitrogen is nitrogen in a liquid state at an extremely low temperature. It is a colourless clear liquid. It is often referred to by abbreviation LN2 or LIN or LN and has the UN number 1977.
Liquid nitrogen is a cryogenic fluid that can cause rapid freezing on contact with living tissue. When appropriately insulated from ambient heat, liquid nitrogen can be stored and transported, for example in vacuum flasks. The temperature is held constant at 77 K by slow boiling of the liquid, resulting in the evolution of nitrogen gas. With the advent of pressurized super-insulated vacuum flasks has made liquefied nitrogen to be stored and transported over longer time periods with losses reduced to 2% per day or less.
What are the uses of Liquid nitrogen?
Liquid nitrogen has many uses both domestic and scientific based on its cold temperature.
Some examples are:
Freezing and transport of food products.
For branding cattle.
Cooling materials for easier machining or fracturing.
Used by dermatologists and surgeons in cryotherapy to remove skin abnormalities.
As a source of extremely dry nitrogen gas.
Coolant for superconductors, vacuum pumps, and other materials and equipment.
For molecular gastronomy preparation of unusual foods and beverages.
Used in medicine for cryopreservation of biological samples, such as sperm, eggs, and animal genetic samples.
Science projects, including liquid nitrogen ice cream, freezing flowers and then watching them shatter when tapped onto a hard surface, and making nitrogen fog.
Dangers of Liquid Nitrogen
Liquid Nitrogen can be extremely dangerous or deadly if not handled properly.
Because it boils so rapidly, the phase transition from liquid to gas can generate a lot of pressure very quickly.
Liquid nitrogen is cold enough to cause severe frostbite upon contact with living tissue.
Adding a lot of nitrogen to the air reduces the relative amount of oxygen. This can result in an asphyxiation risk. Cold nitrogen gas is heavier than air, so the risk is greatest near the ground.
