[Gk. nitron, nitre; and gennao, I produce.] The gaseous element which forms nearly four-fifths of the atmosphere. When alone or uncombined it does not possess any very active properties. In the air it serves to dilute the oxygen, which by itself would be too strong in its effects on life. Nitrogen is a colorless and transparent gas. It has neither smell nor taste, and it will not readily combine with other elements. It is very slightly soluble in water, and it is neither combustible nor a sup porter of combustion, a lighted taper plunged into a jar containing nitrogen being at once extinguished. It forms many most important compounds, such as nitric acid, ammonia, and cyanogen.