Carbonic Oxide, Or Carbon Monoxide, a gas containing one equivalent less of oxygen than carbon dioxide, being a combination of one equivalent each of carbon and oxygen - hence represented by the symbol CO. It contains 42.86 per cent, of carbon and 57.14 per cent, of oxygen. Its weight compared with air is 0'967. It is a product of imperfect combustion, and is generated in large fires in close furnaces in enormous quantities, mixed with carbonic acid gas and other gaseous products of combustion. By the introduction of atmospheric air to it while highly heated, it combines with another atom of oxygen, burning with a blue flame and becoming carbon dioxide. It is visible by night undergoing this change, as it meets the air when issuing from the tops of chimneys of large furnaces, indicating imperfect combustion within the furnace. In large iron establishments this gas is utilized by. causing it to burn with the fresh air admitted under the boilers of the steam engines, or in the chambers constructed for heating the air blown into the furnaces. If the flow of the gases be obstructed, or in any way irregular, explosions may result by sudden admission of oxygen or of atmospheric air to them when highly heated. When mixed with pure oxygen, carbonic oxide is by the electric spark converted into carbon dioxide with an explosion.

The oxide may be reobtained by passing the dioxide through tubes containing red-hot charcoal or metallic iron, which take up one atom of oxygen. - Carbonic oxide is a colorless gas, without smell or taste, but more irrespira-ble and poisonous than carbon dioxide. Its inhalation as it issues from furnaces sometimes causes immediate asphyxia to the workmen. It undergoes no change like carbonic acid gas under heavy pressures at the lowest temperatures; nor is it taken up by water like this gas, nor does it produce similar acid reactions in changing vegetable blues to red. Heat and electricity produce no change in it when alone; when mixed with carbonic acid gas, it may be separated and obtained pure by introducing quicklime or potash, which absorbs the higher oxide. Carbonic oxide may be obtained with facility by heating oxalic acid with five or six times its weight of oil of vitriol, and absorbing the carbonic acid gas by quicklime, as stated above. Cuprous chloride gradually absorbs carbonic oxide if agitated with it.