32 - College of Forestry 



of the charcoal without admission of oxygen, the charcoal 

 after the heating process is completed in the oven retorts is 

 left in the cars and drawn into the first cooling oven and left 

 for 24 hours. This is of the same type and construction as 

 the charring oven. The cars containing charcoal are then 

 drawn into second coolers where they remain for 24 hours; 

 then left in the open air 48 hours, so that there is a period 

 of 9G hours which lapses between the time of the completion 

 of the heating process and the time when the charcoal is 

 loaded on the cars. It must remain on the freight cars at 

 least 12 hours before shipment so that 108 hours lapse to the 

 time of final shipment. This precaution is taken to prevent 

 fire, which frequently causes the loss of charcoal and cars in 

 transit. 



Distillation. 



Although many changes have been introduced in the 

 manner in which the wood is heated for distillation pur- 

 poses, very few changes have been made within the last 

 twenty years in the refining of the crude distillate. 



In the modern oven retort operation the process requires 

 from 23 to 26 hours for completion, When the wood is 

 rolled in trucks into the ovens, the doors are hermetically 

 sealed and the fires are started underneath. In from one to 

 two hours the wood is sufiiciently heated up so that waier 

 distillation takes place. This distillate contains about 2 per 

 cent acid. Then the '"' green gas " comes free for about five 

 to six hours. 



It is considered desirable to heat up the wood gradually 

 and also to let it cool off gradually at the end of the process. 

 The exothermic process, that is, that part of the process in 

 which the wood fibers break down under the intense heat, 

 does not take place until the temperature is run up to about 

 300 degrees Fahrenheit. In about six hours after closing the 



