CARBONIC OXIDE is a compound of one atom of carbon and one atom of oxygen, is represented by the symbol CO, and has the atomic weight 18. It does not occur natu rally, but may be observed burning with a pale-blue flame in fire-places and stoves, especially in frosty weather. During the combustion of the fuel at the lower part of the grate, the oxygen of the air unites with the carbon of the fuel to form carbonic acid and this gas rising up through red-hot coal or carbon (C), has part of its oxygen abstracted by the carbon, and two atoms of C. 0. (CO) arc produced, which, twang fire on the top of the coals, burn with the characteristic blue flame, abstracting more oxygen from the air, and re-forming carbonic acid C. 0. can be prepared for experimental purposes by heating a mixture of oxalic acid (HO, and sulphuric acid in a retort, when the latter abstracts the water from the oxalic acid, and the other elements (C202) escape as carbonic acid and C. 0. (CO). On passing the
mixed gases through a solution of potash (KO), the carbonic acid is retained as carbonate of potash whilst the C. 0 remains as gas. C. 0. is a transparent, colorless gas, a little lighter than air, being 067, and has never been liquefied nor solidified. It burns with a blue flame, but is a non-supporter of combustion, and at once extinguishes a lighted candle introduced into it. It is very poisonOus, and even when largely diluted with air, if inhaled, it produces a sensation of oppression and tightness of the head, and ultimately acts as a narcotic poison. It does not take part in any natural phenomena, nor is it put to any use in the arts and manufactures, and in these respects, affords a striking contrast to carbonic acid, which has so many duties to perform in nature and in the arts.