Liquid nitrogen

Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4. Liquid nitrogen is often referred to by the abbreviation, LN2
The inert properties of nitrogen make it a good blanketing gas in many applications. Nitrogen blanketing is used to protect flammable or explosive solids and liquids from contact with air. Certain chemicals, surfaces of solids, and stored food products have properties that must be protected from degradation by the effects of atmospheric oxygen and moisture. Protection is achieved by keeping these items in a nitrogen atmosphere. "Inerting" or "padding" are other terms used to describe displacement of air and nitrogen blanketing.
Refineries, petrochemical plants and marine tankers use nitrogen to purge equipment, tanks and pipelines of dangerous vapors and gases (for example, after completing a pipeline transfer operation or ending a production run) and to maintain an inert and protective atmosphere in tanks storing flammable liquids.
Materials become hard and brittle when cooled by to very low temperatures. This property permits the removal of “flash” or “fins” on cast plastics and rubber. The castings are cooled by liquid nitrogen and the flash broken off by mechanical action.