CHARCOAL 



237 



produce both less charcoal and a product of lower quality for general 

 utility purposes. For certain specialized purposes in metallurgical work, 

 however, a charcoal derived from mixed hardwoods and softwoods 

 is sometimes preferred. Charcoal made from willow and other light- 

 weight woods has been in great demand for the manufacture of certain 

 forms of explosives, filtering purposes and disinfectants. Experiments 

 have shown that the volume of charcoal is only about 50 per cent to 60 

 per cent of that of the original air-dry wood, and the weight only about 

 19 per cent to 25 per cent of the original weight of wood used. 



Photograph by U. S. Forest Service. 



FIG. 63. A charcoal pit near Elk Neck, Cecil Co., Maryland, ready to be covered with 

 grass, leaves, etc., and soil preparatory to burning. Beech, birch, maple, hickory and 

 the oaks make the best charcoal because of their great density. 



On a large operation in Virginia where pits containing about 35 cords 

 of white and red-oak wood were used, an average of about 30 bu. to the 

 cord were secured. In southern Pennsylvania where a mixture of oaks 

 and yellow pine were used in open-air pits, a yield of 30 bu. was secured. 

 It is generally regarded that this is an average yield when the better 

 hardwoods and more dense soft woods are used. 



The yields from the beehive and other forms of prepared kilns are 

 obviously much greater, because of the increased efficiency in operation. 

 An investigation of the yields of 25 hardwood distillation plants in New 



