OXYGEN. The properties Of this ineSi remarkable eleinentary body are best ktiethi in its elastic or aeriform state, in which it is termed Oxygen Gas. The disdovery of this importaiit subStance vitia Media by Dr. PtieStley in 1774, and somewhat later ifidepaiidentlY by Scheele. To this gas Dr. Priestley gave the name of dephlogisticated air, Scheele called it empyreal air, and Condorcet vital air. Lavoisier gave it the name of oxygen, which it still retains. Dr. Priestley first procured this gaseous body by heating the binoxide of mer cury in an air-jar over mercury, by means of a lens, and he afterWards obtitinfd it froth ether SubstatiCes. It is fed+ prepared if various ways, according to the purposes to Which it is intended to be applied.
Oxygen possesses great pdiver of cowibi nation with other eleinentary there being scarcely One with Which it is net knOwzi to combine either by direct union' or indirect chemical action. The conapouhda to which it gives rise by coinbining, foi example, with certain metals, and also indeed with sortie other bodieS, May be clidaed tinder the three heads of Oxides, Acids, and Alhdlies. Therd are many bodies which, by a moderate degree of oxidation, bectiine first Mid by an in creased degree, acid4 'such substances are charcoal, phosphorus, ehroniluin, &n.
Oxygeit Gas is deVoid of eolckit, taste, or smell. It 14 transparent and invisible. It possesses the mechanical properties of com mon air. It is Capable of being respired, and a given volume of it will support life much longer than an equal bulk of Comnieri air. It
is heavier than atmospheric air, 100 cubic inches at a medium temperature and pressure weighing 34.4 grains, whereas an equal volume of atmospheric air weighs 31 grains. It is but slightly soluble in water, teejnirizig about 27 time's its bulk for solution. Light has no effect upon this gaS. By heat, like all gaseous bodies, it is merely expanded. The most re markable property of oxygen gas is the facility and splendour with which bodies, when pre viously ignited, burn in it; substances which dc not undergo combnstion in the air, will readily do so, and With great brilliancy, in oxygen gas. Iron, for example, but very readily in it when previmisly made red-hot.
Until after the discovery of oxygen nothing was or could be known respecting the nature of the air, of Water; Or of earth, all of which; forrferly reCketted as eleintritart bedieR; now known to be borciiiblitid; arid to Contain oxygen aS one of their conatitnenta. It heti also thrown great and unexpected light on flail nature of combustion and reSpiratidn: The principal compounds which oxygen forms with taetitla and other elementiu-y bodies, are briefly under their re spective heads. To notice thO useful purposes ' stfbaerved in the arts by Oxygen is neithei necessary not possible ; since It takes part, iir some Way or other, with SterY coitibination and every process.