Nitrogen (N2), when cooled, condenses at -320.4°F (-195.8°C or 77.36 K) and freezes at -345.9°F (-209.8°C or 63.17 K). Or, to reverse the order, solid nitrogen melts to form liquid nitrogen at -345.9°F, which boils at -320.4°F Liquid nitrogen is used in a wide range of cryogenic applications.
The Scottish physician Daniel Rutherford discovered nitrogen in 1772. It is the fifth most abundant element in the universe and makes up about 78% of the earth’s atmosphere, which contains an estimated 4,000 trillion tons of the gas. Nitrogen is obtained from liquefied air through a process known as fractional distillation.
The largest use of nitrogen is for the production of ammonia (NH3). Large amounts of nitrogen are combined with hydrogen to produce ammonia in a method known as the Haber process. Large amounts of ammonia are then used to create fertilizers, explosives and, through a process known as the Ostwald process, nitric acid (HNO3).
Nitrogen gas is largely inert and is used as a protective shield in the semiconductor industry and during certain types of welding and soldering operations. Oil companies use high-pressure nitrogen to help force crude oil to the surface. Liquid nitrogen is an inexpensive cryogenic liquid used for refrigeration, preservation of biological samples and for low temperature scientific experimentation.