Nitrogen makes up around 80% of the air and is found in many organic and inorganic compounds. It is colourless and odourless, and is only slightly soluble in water. Liquid nitrogen boils at approximately −196 °C and solidifies at −210 °C. After noble gases, nitrogen is the most inert element, combining with almost no other elements.
Liquid nitrogen is essential in various industrial applications and is obtained by fractional distillation from liquid air. It is most commonly used for cooling and refrigeration. It is also used to create inert atmospheres that prevent oxidation, for example in the food industry to prevent or delay bacterial proliferation, and in the metallurgical industry to cut and weld metals without introducing impurities. Finally, it is used to prepare base compounds for fertilisers and surfactants.
