Both nitrogen and phosphorus are essential to life and, accordingly, are used in fertilizers, which provide the nitrates and phosphates needed to make plants grow. Nitrogen is also used to provide an inert atmosphere in the production of glass and the annealing of steel, and liquid nitrogen is employed as a refrigerant in the storage of food and of medical samples, such as blood.
Although by far the widest use of phosphorus is in the production of fertilizers, it is also used in fireworks and explosives, and phosphorus sulphide is to be found on the sides of boxes of safety matches. Further compounds are used in steels and in radiation shields in nuclear reactors.
Arsenic, antimony and bismuth are all used in alloys. All three are used in type metals, where the presence of the arsenic makes the metal easier to cast and of increased hardness; and are again combined in solder, where their low melting points are essential. Arsenic also improves the sphericity of lead shot, and its toxic compounds are used in herbicides and insecticides. Both arsenic and antimony are semiconductors and are used in the manufacture of electronic components.
