CARBONIC OXIDE

or CARBON MONOXIDE (CO), a gas formed during combustion when the exce of oxygen is not sufficiently large. It is found in chimney gases, in the gases of blast furnaces, and in the vapors arising from volcanoes. It is prepared in the laboratory by the action of concentrated sulphuric acid on oxalic acid, an equal volume of carbon dioxide also being roduced. Carbon monoxide is a colore , odorle gas slightly lighter than air. It is slightly soluble in water and burns with a pale blue flame to form carbon dioxide; this flame may sometimes be observed near the top of a coal fire when there is incomplete combustion in the lower part of the grate, or when the carbon dioxide first formed is turned into carbon monoxide by pa ing over a heated ma of coal. CO is a very poisonous gas, and is particularly dangerous in coal mines, where it is sometimes formed in small quantities.