SOLID FUELS. 



WOOD CHARCOAL. 



Wood charcoal always contains quantities of hydrocarbons 

 which have resisted the action of heat. That called forest 

 charcoal, made by burning in heaps, is the most charged with 

 them ; that obtained from distillation of wood in retorts con- 

 tains less. 



The heat of combustion is very variable. According to 

 Berthier* commercial wood charcoal contains 10 per cent of 

 volatile matters and 2 per cent of ash (carbon 80 to 90, hy- 

 drogen 1.5-4). 



Pure wood charcoal was first tested calorimetrically by 

 Favre and Silbermann, and since then by several experi- 

 menters. To obtain it pure it was calcined strongly and 

 treated with chlorine to remove all traces of hydrogen. In 

 this state wood-charcoal produces under constant pressure 

 8080 calories, F. & S., or 8100 S.-K. & M.-D. ; with con- 

 stant volume Berthelot and Petit obtained 8137 calories. 



Several years ago Berthier pointed out that half-burnt 

 charcoal, charbon roux or Rothkohle, was superior in combus- 

 tible content to that perfectly burnt. Sauvage has confirmed 

 this, and gives the following results: 



and 

 cubic foot wood contained of combustible matter 908 parts. 



* Traite des essais par la voie seche, vol. I, p. 286. 



