OXYGEN

(Yunanca köken — orijinale bakınız.) This important clement was discovered in 1774, by Dr. Priest ley. It has been termed dephlogisticated air, vital air, and empyreal air. As it forms a component part of many of the acids, it was termed, at the framing of the new nomenclature, oxygen gas. There are several compounds of oxygen which, when exposed to heat, are decomposed, and yield the gas in a state of purity: of these the best is chlorate of potash; but as that salt is expensive, we generally resort to black oxide of manganese, which, at a dull-red heat, gives out a considerable quantity of tolerably pure oxygen Oxygen gas is colourle , tastele , and inodorous; it is electro-negative, and therefore, when compounds containing it are electrically decomposed, it always appears at the positive surface. It is a little heavier than atmospheric air, in the proportion, that is, of 11 to 10; 100 cubical inches gas.weighing 34'6 grains. It is not absorbed by water, and is neither acid nor alkaline. It has a powerful attraction for most of the simple substances, especially for the electropositive bodies: the act of combining with it is called oxidation. The compounds thus formed are divided into acid* and oxides: among the latter are the alkalis, and almost all salifiable bases. Oxidation is often attended with the evolution of he at and light, as in all proce es of combustion in atmospheric air: sometimes it is slow, and unattended with such phenomena, as in the gradual rusting of metals. Oxygen is a most powerful supporter of combustion; it constitutes one fifth of the bulk of the atmosphere, and is the principle which enables combustible bodies to hum in it. The product of combustion, that is, the oxide or acid, is sometimes itself gaseous, as when charcoal, by burning, is converted into carbonic acid; or it is liquid, as hydrogen, by combustion, produces water; or it is solid, as when iron, hy burning, produces oxide of iron. Oxygen gas is also e ential to respiration; that is, to the evolution of carbonic acid from the blood. [s. 884]