A gaseous compound of oxygen and carbon, consisting by weight of 75 of the former, and 100 of the latter. Its spec. grav. is 0.9569. Carbonic oxide may be procured by subjecting to a strong heat in a retort or gun-barrel, a mixture of an earthy carbonate and metallic filings; the most convenient mixture is equal parts of dry chalk, and iron or zinc filings; it is given out also in large quantities from brick kilns, and may be seen burning with a dark blue flame. It is, when respired, fatal to animal life.