NATURE OF THE PROCESS. 263 



There is no example of carbon combining di- 

 rectly with oxygen at common temperatures, but 

 numerous facts show that hydrogen, in certain states 

 of condensation, possesses that property. Lamp- 

 black which has been heated to redness may be 

 kept in contact with oxygen gas, without forming 

 carbonic acid ; but lamp-black, impregnated with 

 oils which contain a large proportion of hydrogen, 

 gradually becomes warm, and inflames sponta- 

 neously. The spontaneous inflammability of the 

 charcoal used in the fabrication of gunpowder has 

 been correctly ascribed to the hydrogen which it 

 contains in considerable quantity ; for during its 

 reduction to powder, no trace of carbonic acid 

 can be detected in the air surrounding it; it is 

 not formed until the temperature of the mass has 

 reached the red heat. The heat which produces 

 the inflammation is therefore not caused by the 

 oxidation of the carbon. 



The substances which undergo eremacausis may 

 be divided into two classes. The first class com- 

 prehends those substances which unite with the 

 oxygen of the air, without evolving carbonic acid ; 

 and the second, such as emit carbonic acid by ab- 

 sorbing oxygen. 



When the oil of bitter almonds is exposed to the 

 air, it absorbs two equivalents of oxygen, and is 

 converted into benzoic acid ; but half of the oxygen 

 absorbed combines with the hydrogen of the oil, 



