72 CARBONIC OXIDE. 



required whether the carbon is burnt in a few seconds, 

 or slowly combined with oxygen by the gradual pro- 

 cess of decay. If we were to try to combine six 

 grains of carbon with twenty grains of oxygen, we 

 should find that only sixteen grains of the oxygen 

 would combine with the charcoal, and the remaining 

 four grains of oxygen would be left unchanged. 



127. When we try to burn charcoal so that it shall 

 get less oxygen than is requisite to convert it into 

 carbonic acid, we find that it is possible to do so, but 

 that the gas produced is not carbonic acid. Carbon 

 and oxygen are able to combine together in more 

 than one proportion ; and consequently, though 

 when carbon is burnt in the air, or where it can get 

 abundance of oxygen, it always forms carbonic acid, 

 yet when burnt so that it cannot combine with a suffi- 

 cient quantity of oxygen to form that gas, it forms a 

 different compound containing less oxygen, which is 

 called carbonic oxide. 



128. This compound is a transparent colorless 

 gas, like carbonic acid, and resembles it also in being 

 totally unfit to support animal life; indeed, it appears 

 to be far more dangerous than carbonic acid when 

 taken into the lungs, even though considerably di- 

 luted with common air. It extinguishes flame, as 

 might be expected, but it is itself combustible, burn- 

 ing with a pale blue flame, and at the same time is 

 converted into carbonic acid, in consequence of 

 having acquired more oxygen from the air in which 

 it has burnt. 



