NITROGEN (symbol, N; equiv. 14; sp. gr. 0.9713) derives its name from the Greek words nitron, niter, and to produce, in consequence of its being an essential constituent of that salt. It is frequently termed (note (Gr. a, priv., roe, life), especially by the French chemists, in consequence of its being a gas incapable of supporting life, and for the same reason the German chemists term it (" choking substance"). It was discovered by Rutherford in 1772. Long regarded as a "permanent" gas, it was liquefied by Cailletet in 1878.
Nitrogen is a colorless, tasteless, inodorous, permanent gas, which in its appearance in no way differs from the atmospheric air, of which it is the main ingredient. It is somewhat lighter than atmospheric air, 100 cubic in. at F., and barometer 30 in., weighing 30.119 grains, while the same volume of air weighs 30.935 grains. It is char acterized rather by negative than by positive properties. It is not combustible, nor is it a supporter of combustion (a lighted taper being immediately extinguished if immersed in this gas); it is not respirable, although it is not positively poisonous; for when it is mixed with respirable gases (as with oxygen in atmospheric air) it may be breathed with out injury. It is very sligthly soluble in water, and hence may be collected over that fluid. Its combining powers arc very slight, and although it unites with oxygen, hydrogen, chlorine, and many other substances, the union is never effected by the direct action of the elements on one another, hut only by complicated processes, and many of the result ing compounds are of an exceedingly unstable nature.
Nitrogen is one of the most widely diffused elementary substances. It forms about four4ifths of the bulk of the atmosphere; for air, after having been freed from the small quantities of carbonic acid and aqueous vapor which it contains, consists, according to the experiments of Dumas and Boussingault, of 20.81 per cent of oxygen and 79.19 per cent of nitrogen by volume, or 23.01 of oxygen and 76.99 of nitrogen by weight; the two gases in this case being uniformly mixed, but not in chemical combination with one another. it occurs, however, in combination with oxygen in the form of nitric acid
in various nitrates, which are found as natural products in many parts of the globe. In combination with hydrogen it is abundantly found as ammonia, and com bined with oxygen, hydrogen, and carbon, and sometimes additionally with sulphur and phosphorus, it forms the most important constituents of the solids and fluids of the ani mal body, and occurs in many vegetable products, especially in the alkaloids, such as morphia, strychnia, quinia, etc.
The ordinary methods of preparing and exhibiting this gas are based upon the removal of the oxygen from atmospheric air. This may be done: (1) By setting fire to a small piece of phosphorus placed in a capsule that floats on the water of the pneumatic trough, and by inverting a glass-receiver filled with air over it. The phosphorus combines with the oxygen of the air to forum phosphoric acid, which dissolves in the water, while the nitrogen is left, and must be transferred to another vessel. (2) By placing a stick of phos phorus in a jar of air which over Water. In two or three days there will be the same results as in the former eipertment—viz., phosphoric acid and nitrogen. (3) Or by passing air through a tube containing heated copper filings, which absorb the oxygen. In the above cases carbonic acid is present, which may be removed by passing the gas through a solution of potash. Pure nitrogen may be directly obtained by the action of chlorine gas on a solution of the nitrogenous substance, ammonia.
Nitrogen forms with oxygen no less than 5 distinct compounds, containing, respect ively, 1, 2, 3, 4, and 5 equivalents of oxygen, with 1 equivalent of nitrogen, These com pounds are thus named and constituted: Protoxide of nitrogen (known also as nitrous oxide and laughing gas), NO; hinoxide (or deutoxide) of nitrogen (known also as nitric oxide), nitrous acid, NO,; hyponitric acid (known also as peroxide of nitrogen), nitric acid, NO,.