(N. Eq.=14.)

Nitrogen constitutes 79.19 per cent. of the atmosphere by measure, or 76.99 by weight. Sp. gr. 0.9713. It seems to act the part of a diluent in the air, counteracting the too stimulating properties of oxygen. Nitrogen forms acids with three and five equivalents of oxygen (No3 and No5); the salts known as the nitrites and the nitrates, especially the latter, are much used in medicine. With hydrogen it forms ammonia, with carbon it forms cyanogen, and enters into the composition of all the alkaloids, and many of the other most active medicinal principles, as morphia, quinia, and prussic acid. Water at the ordinary temperature dissolves about 1/50 of its bulk of nitrogen. It is rarely or never employed in its free state as a therapeutic agent.