MANUFACTURE OF WOOD-VINEGAR. 231 



at the utmost, 68 per cent., of hydrogen about 5 per cent., and 

 of oxygen more than 26 per cent. 



With a distilling temperature of 464 F. there remains, of 100 

 parts of wood dried at 302 F., a residue of 50.8 parts of brands, 

 and with a distilling temperature of 518 F. 37 parts. 



With a temperature above 644 F. the result is black coal, the 

 quantity and composition of which vary according to the tempera- 

 ture. Between 644 F. and 810 F. remains 31.5 to 19 per cent, 

 of charcoal with a composition of from 75 to 81.6 per cent, of 

 carbon, 4.4 to 2 of hydrogen, and 20 to 15 of oxygen, and 0.5 to 

 1.1 of ash. 



At still higher temperatures the quantity of charcoal decreases 

 but little ; it amounts, for instance, at the melting point of bar- 

 iron, to 17.3 per cent., and at that of platinum, to 15. per cent. 

 The content of carbon, however, constantly increases until at the 

 last-mentioned temperature it reaches 96.5 per cent. 



Violette further confirmed the fact long known that the degree 

 of carbonization exerts a great influence upon the result, slow 

 carbonization yielding far more charcoal, than quick. 



The variety of wood also exerts an influence upon the yield of 

 charcoal. At 572 F. there were, for instance, obtained from 



Later on Violette found that the elementary composition of 

 these charcoals varied. There are contained, for instance, in char- 

 coal from 



Carbon. Hydrogen. Oxygen Ash. 



(and nitrogen). 



Oak .... 67.4 4.1 28.5 0.2 



Aspen .... 68.2 5.5 25.7 0.6 



Birch .... 71.1 4.5 23.5 0.7 



Ash .... 70.4 4.5 24.4 0.7 



These figures are, however, only correct for charcoal kept air- 

 tight after its preparation and immediately analyzed. Ordinary 

 charcoal contains at least 5 per cent, of hygroscopic water. 



