OXYGEN (from Gk. 60s, oxys, sharp, quick, acid + --yevhs, -genes, producing, from ylyvegOaL, yignesthai, to become). A gaseous element iso lated by Priestley in 1774. Priestley's classical researches in pneumatic chemistry led him to the discovery that when red mercuric oxide is heated by the sun's rays it decomposes into a colorless gas, which be called 'dephlogisticated air,' and metallic mercury. A year later Scheele, in Sweden, independently discovered oxygen, giving it the name of 'empyreal air.' Shortly after wards Condorcet suggested the name of 'vital air.' Lavoisier, however, was the first definitely to establish the true character of oxygen, and it was he who first gave it its present name. See LHEMISTRY.
Oxygen exists uneombined in the atmosphere, to the extent of 21 per cent. by volume and more than 23 per cent. by weight. In combination, too, it is very abundant in nature, forming eight ninths by weight of all water and a considerable percentage by weight. of silica, alumina, and chalk, which are the three most abundant and widely distributed constituents of the earth's crust. It is further a normal component of nearly every rock and mineral, and of all animal and vegetable tissues and fluids. It is absorbed in large quantities from the atmosphere by animals and vegetables in the process of respiration, but plants also evolve it under the influence of sun light. Oxygen may be readily prepared by heat ing red mercuric oxide, by heating manganese dioxide to a red heat, or by heating potassium chlorate to 370' C. Commercially it was long made by heating manganese dioxide, either alone or together with potassium chlorate. The alter nate forniation and decomposition of alkaline manganates was originally proposed in 1866 by Tessie lotay, as a process of manufacturing oxygen for illuminating purposes. The process has been successfully employed in Europe and the United States. Rut more recently the alternate formation and decomposition of barium peroxide has been taken advantage of for the eominercial production of oxygen. This method, which was chiefly developed by the brothers Brin, consists in heating barium oxide to a dull red heat in a current of air, whereby it is converted into bari um peroxide, which at a still greater heat is decomposed again into barium oxide and free oxygen. This economic process is hieing worked
on a large scale in various places. Pictet, in 1901, announced the invention of an economical method for obtaining oxygen from the air.
Oxygen (symbol, 0; atomic weight, 16; see ATOMIC WEIGHTS) is a colorless, odorless, and ta.teless gas which has been condensed to a pale steel-blue. transparent liquid, boiling at —181.4° C. and freezing to a white solid at —235'1'. Com pared with air as unity. oxygen has a specific gravity of 1.1504, and it is the least refractive of all gases. Oxygen is slightly magnet ie. which property is diminished or temporarily suspended by elevation of temperature. When examined through thick layers, oxygen has a bluish tinge of color. It combine, directly with most of the elements. (See OxinEs.) It is sparingly soluble in water, and nearly all natural waters contain oxygen in solution which can he completely re moved by boiling in vaello. This dissolved oxy gen is the source from which fish obtain the oxy gen necessary to sustain life. In the pure state it may be inhaled, for a time, with impunity, and it even acts as a tonic or exhilarant. Its Iona eontinued respiration, however, is harmful. In pore oxygen bodies burn with much greater bril liancy than in common air. See COMBUSTION.
oxygen has 'wen used successfully to maintain air in a respirable as in diving bells, submarine vessels, etc., and its use has been sug gested for the revivifying of the atmosphere in public halls. It finds extensive application, in connection With hydrogen or illuminating gas, to produce the ,,xyllydrogen flame. I See O(YllYDRO. GEN 131.0WPIPE and DRUMMOND LIGHT.) It is also used in the bleaching of paper pulp. in the oxidation aml thickening of oils which are used in the manufacture of v:m•nisIh and oilcloths, for the purpose of hastening the maturing of spirits, or liquors, and in the manufacture of vinegar. See also OzoNF,..