The New International Encyclopædia/Air

AIR (Lat. aër, Gk. ἀήρ, aēr, irom ἂειν, aein, to blow). The mixture of gases forming the atmosphere of the earth. It consists essentially of 79.03 parts of nitrogen and 20.97 parts of oxygen, with varying small quantities of carbonic acid, ammonia, ozone, argon, helium, neon, krypton, and xenon (qq.v.), aqueous vapor. Certain chemical compounds, as common salt, ammonium nitrate, etc., as well as minute particles of animal, vegetable, and mineral matter, are also frequently found in the air. Early chemists called all gases airs. The chief properties of air and the phenomena they give rise to may be found treated under Atmosphere; Aërodynamics; Aërostatics; Barometer; Aëronautics, etc.