Combustible Substances. 207 



never without it, also those of lead ; but the py- 

 rites is the only ore from which it can be ex- 

 tracted with profit. The combinations of the 

 sulphuric acid have been already noticed under 

 the article salts. 



4th. CARBON is the next of the simple com- 

 bustibles which demands our attention. The 

 principal forms under which this substance ap- 

 pears is the diamond, charcoal of wood, pit coal, 

 and carbonic acid, wherever it exists. Carbon, 

 however, forms a large proportion of all vege- 

 table matter, and even enters more or less into 

 the substance of most animal bodies. 



It is in the diamond alone, however, that car- 

 bon exists in a state of purity, and uncombined 

 with other matter. It is not, however, so easy 

 of combustion as charcoal, possibly from its 

 crystallized form, which may not admit of so easy 

 a separation of the parts. Charcoal takes fire at 

 a red heat. The diamond before it can be 

 burned must be exposed to a heat of not less 

 than 5000 in the focus of a powerful burning 

 glass. It is then by its union with oxygen con- 

 verted wholly into carbonic acid gas. Morveau 

 found that diamond, during its combustion, com- 

 bines with 4-592 parts of oxygen ; consequently 

 carbonic acid gas consists of about eighteen 

 parts of diamond, and about eighty-two of 

 oxygen. 



Though we have been successful, however, in 

 dissolving and analysing the diamond, we have 



