Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 3, 1802).djvu/348

326&#93; 3^6] OXY them, if taken by persons subieft to the jaundice, immediately afier coming from the tepid bath, will tend to restore their natural co- lour: — we have had no experience of its medicinal etFects. OX-TONGUE, theCoMMON, or Lang-pe-boeuf, Picris echioiilcs, h. an indigenous plant, growing on the borders of corn-fields, and flow- ering in the months of July and August. — When young, this ve- getable affords an agreeable pot- herb : its juice is milky, and not too acrid. OXYD, a term, in the anti- phlogistic system of chemistry, de- noting those compound bodies vhicli are formed by the decompo- si tion of (UT/^t'/z-o^fli, either by means of metals, of certain other sub- stances. All oxydes are the basis of some jnetallic bodies, the most remarka- ble of which, were formerly known under the name of calcfs (or wagi- steiyes, if dissolved in acids), and have received their present appel- lation from the acidilying principle _ wlfich they are believed to contain. jVIetals are converted into oxj/des by combustion, and by solution in acids : but, many of them acquire this form, by the a6tion of the at- mosphere alone ; though they as- sume it with greater facility, when the latter is aided by moisture. — During the process of conversion into oxydes, metals are divested of their lustre ; and, after increasing considerably in weight, they exhi- bit an earthy appearance. — Specu- lative chemists have, therefore, lately conjedured, that all earths are metaLic oxydes, and that they are all susceptible of redu6lion to a metallic state, provided there be any matter for •hich oxygen has OXY more powerful eleSive attraction than that, by which it is kept in combination with the bases of such supposed oxydes. As this opinion, hou'ever, is unsupported by actual proof, it cannot b? admitted in the present system of chemistry. OXYGEN, is a term inventecj by the French chemists, and at present employed to express the acidifying priuciple. Oxygen is considered as an ele- mentary sonietldng, utterly inca-» pable of decomposition ; nor will it admit of being exliibited by it- self, or of being produced in its simple state : for, at the moment of its becoming free, it unites with the light, and caloric, or heat of the surrounding medium, and thus forms what has been severally de- nominated vital-air, Jire-air, de- phlogisticatcd ox pure-air, and la«t- ly. Oxygen-gas. The peculiar cha- racter of this elastic fluid was first developed by Dr. Priestley, whose experiments have been con- firmed, and the properties of gas- oxygen fully explained, by Lavoi- sier, Cavendish, and other il- lustrious chtmical philosophers. — ■ From their discoveries it appears, that this uncompounded invisible matter can be known only in its combinations ; that it forms a con- stituent part of the atmospheric air, in which it exists in the propor- tion of 27 or 28 parts to 100. Farther, oxygen may be sepa- rated not only from tl.e atroospherbi but also from water ; from all acids ; aiid also from vegetables exposed to the rays of the sun. By this natural p'ocess, a considerable portion of it is evolved from the leaves of plants during their per- spiration, in consequence of solar heat : thus, when oxygen is car-