693 



CHAPTER III. 



WOOD-CARBONISATION. 



Section I. — General Account. 



Whenever wood is burned, in the presence of air, it is 

 converted into gases with a small ash-residuum. If, however, 

 air is excluded and the wood heated to temperatures of 300° — 

 350° C. (570^ — 660° F.), it becomes converted into secondary 

 products, such as water, acetic acid, wood-alcohol, tar, carbon- 

 dioxide and monoxide, and hydrocarbons ; also into hydi'ogen 

 and a solid residuum, wood-charcoal. 



This decomposition of an organic body is termed dry 

 distillation, and in the case of Avood, carbonisation. 



Charcoal consists of carbon and the incombustible inorganic 

 constituents of wood : all charcoal also contains more or less 

 hydrogen and oxygen, which become the more reduced in 

 quantity the higher the temperature at which the wood is car- 

 bonised; consequently the percentage of carbon is then increased. 



As the secondary products absorb a not inconsiderable quantity 

 of carbon, and when charcoal is made in the forest some wood 

 is actually burned, the loss of combustible matter, according to 

 V. Berg, may be as high as 64%. This loss is, however, 

 compensated by the superiority of charcoal to wood as a com- 

 bustible and by its easier transportability. 



Charcoal is more effective than firewood, owing to the greater 

 intensity of the heat it gives off when burning, the greater 

 power of radiating heat which it possesses, the facility with 

 which it may be reduced in size before being used and 

 especially owing to its superiority for metallurgic processes 

 (greater uniformity in smelting, &c.). 



Theoretically, according to Grothe,* charcoal should yield 



* Die Brenn-rnaterialien u. Feutruiic'saiilageii. 



