Carbonic Oxide — Chambers's Encyclopaedia

Carbonic Oxide is the lower oxide of Carbon (q.v.), and is represented by the formula $\text{CO}$ . It consists of 12 parts by weight of carbon and 16 parts of oxygen. It does not occur naturally, but may be observed burning with a pale-blue flame in fireplaces 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, $CO_2$ ; and this gas rising up through red-hot coal or carbon, $C$ , has part of its oxygen abstracted by the carbon, and two molecules of carbonic oxide, $CO$ , are produced, which taking fire on the top of the coals, burn with the characteristic blue flame, abstracting more oxygen from the air, and re-forming carbonic acid, $CO_2$ . Carbonic oxide can be prepared for experimental purposes by heating in a retort a mixture of oxalic acid, $H_2C_2O_4$ , and sulphuric acid, $H_2SO_4$ , when the latter abstracts the water from the oxalic acid, and the other elements, $C_2O_3$ , escape as carbonic acid, $CO_2$ , and carbonic oxide, $CO$ . On passing the mixed gases through a solution of potash, $KOH$ , the carbonic acid is retained as carbonate of potash, $K_2CO_3$ , whilst the carbonic oxide remains as gas. Carbonic oxide is a transparent, colourless gas, with an oppressive odour. It is rather lighter than air, its specific gravity being only .968. In this it differs very markedly from Carbonic Acid (q.v.). For many years it resisted all attempts to liquefy it, but at last, on December 2, 1877, it yielded to the modern methods of combined cold and pressure. 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 enters into many compounds known to the organic chemist, such as urea. It is used in Siemens's and other 'producer' gases, of which it is a principal ingredient; and is the most important reducing agent in blast-furnace processes.