See also Nitrogen on Wikipedia, and the disclaimer.

Ni′trogen is an elementary gas which in the free state forms nearly four fifths by volume of our atmosphere.  In combination with other elements, nitrogen is a necessary constituent of all plants and animals, and it forms a very large number of important compounds, both natural and artificial.  Its presence in the atmosphere was discovered in 1772 by Rutherford, at that time professor of botany in the University of Edinburgh.  It was more particularly investigated soon after by Priestley, Scheele, Cavendish and Lavoisier.  It is a colorless, tasteless, odorless gas, and was formerly regarded as permanent and incondensable; but it can be liquefied at a sufficiently low temperature.  Nitrogen is slightly lighter than atmospheric air, and is fourteen times as heavy as hydrogen.  It is but slightly soluble in water, one hundred volumes of water at ordinary temperature dissolving only one and a half volumes of nitrogen.

While nitrogen is a constituent of all plant and animal organisms and of many important compounds, it is, in a free state, rather inert toward other elements and does not readily enter into direct combination with them.  It is not combustible, nor does it act in the atmosphere as a supporter of combustion, as a lighted taper plunged into a jar of nitrogen will at once be extinguished.  Nitrogen is not poisonous, since it is breathed freely along with oxygen by all animals; but it cannot support life, and an animal placed in it will die from suffocation for want of the oxygen necessary for breathing.  Its function in the atmosphere seems to be mainly that of diluting the oxygen with which it is there associated.  Although nitrogen forms about 79.1 per cent. of the total volume, and 77 per cent, of the total weight, of the atmosphere, the free gas cannot be taken up by plants directly, but it is combined with other elements through the agency of certain bacteria that exist in nodules on the roots of leguminous plants, that is, those that are related to clover, peas etc.  Other plants, particularly grasses and grains which require much nitrogen, are dependent upon the combined nitrogen of the soil; hence nitrogenous fertilizers, such as dried blood, ammonium salts and nitrates, as well as ordinary manures, are important in agriculture for use on soils containing insufficient nitrogen.  Two of the important compounds of nitrogen are nitric acid and ammonia.  This element also is an essential constituent of the proteids or albuminoids, which make an important part of our food, as well as of the alkaloids, most of the dyes and a host of other natural and artificial compounds.