1. A colorless, odorless, inert gaseous element constituting approximately one percent of earth's atmosphere, from which it is commercially obtained by fractionation for use in electric light bulbs, fluorescent tubes, and radio vacuum tubes and as an inert gas shield in arc welding. atomic number 18; atomic weight 39.948; melting point -189.3°C; boiling point -185.9°C. see table at element.

1. A chemical element (symbol ar) with an atomic number of 18.

1. A colorless, odorless gas occurring in the air (of which it constitutes 0.93 per cent by volume), in volcanic gases, etc.; -- so named on account of its inertness by Rayleigh and Ramsay, who prepared and examined it in 1894-95. symbol, A; at. wt., 39.9. argon is condensible to a colorless liquid boiling at -186.1° C. and to a solid melting at -189.6° C. it has a characteristic spectrum. no compounds of it are known, but there is physical evidence that its molecule is monatomic. weight of one liter at 0° C. and 760 mm., 1.7828 g.

1. A name given by lord Rayleigh and professor William Ramsay to a new constituent of the atmosphere discovered by them in 1894. it is an inodorous gas, singularly inert chemically.
2. A gaseous element having, in the pure state as a gas, a density of 19.96 (H=1) and an atomic weight of 39.6.

1. a colorless and odorless inert gas; one of the six inert gases; comprises approximately 1% of the earth's atmosphere