208 Chemistry. [Lecture 31. 



not as yet been able to disengage it from the 

 oxygen when united with it, and reduce it again 

 to its beautiful crystallized form ; yet it would 

 be rash to say that it never will be done. At 

 least, having advanced so far, we may venture to 

 say, that the making of diamonds would be a 

 much more rational object of pursuit than the 

 philosopher's stone, which so long occupied the 

 attention of mankind. 



Charcoal, however purified, is not, like the 

 diamond, a simple substance, for it is always 

 combined with some portion of oxygen, and is 

 therefore an oxide of carbon, or of diamond. 

 Lavoisier concluded that pure charcoal is com- 

 posed of about eighty-four parts diamond, or 

 pure carbon, and about thirty-six of oxygen. 



It has, however, still a strong attraction for a 

 super dose of oxygen, whence it is very com- 

 bustible, and by combustion in the open air, or 

 in oxygen gas, is converted into carbonic acid 

 gas. This accounts for its utility in reducing 

 the oxides, or calces, of metals, which, when 

 heated with charcoal, part with their oxygen to 

 it, and carbonic acid gas is formed, and the me- 

 tals are restored to their metallic state and lus- 

 tre. Charcoal may be obtained from all vege- 

 table and animal substances, and from fossils 

 of the bituminous kind. It is commonly pro- 

 cured by burning wood with a smothered heat, 

 and extinguishing it when red hot. 



Charcoal, unless heated, is in a great measure 



