Nitrogen
A gas discovered by Rutherford in 1772. It is extensively diffused in nature, forming about four fifths of the atmosphere, in which it plays the important part of diluting the oxygen and adapting it to the conditions of life. It is an important element of the vegetable kingdom, entering in considerable quantity into many of its compounds. It is supplied to plants by ammonia and nitric acid. Our food is largely composed of nitrogen, and it forms 16 per cent of the tissues of the animal body. Nitrogen is not found in any of the mineral formations of the earth's crust, except in some varieties of coal. See ATMOSPHERE; OXYGEN; AMMONIA.