104 FOREST UTILIZATION 



III. 10% of tarry liquid, viz.: 



tar cresol 



creosote phlorol 



toluol naphtalene 



xylol pyrene 



cumol chrysene 



methol paraffin 



IV. 25% of solid residue, viz. : 



charcoal inorganic salts 



B. The kiln process. 



In the kiln process of destructive distillation of wood, all of the 



above substances are allowed to escape unused, excepting the 



solid residue. 

 Modern technology succeeds in catching and utilizing several of 



the substances given under II and III, as appears from Section 



XXXV. 

 Still, the large majority of the charcoal commercially used is 



produced by the old and wasteful charcoal kiln. 



C. Characteristic qualities of charcoal. 



I. Charcoal has per cubic foot a larger heating power than 



wood. 



II. Owing to its lesser weight, it is very cheaply transported. 

 III. Its freedom from sulphur and phosphates makes it valu- 

 able for metallurgic work (Swedish charcoal iron). 



D. The work at the kiln. 



I. For use in kilns, wood must be thoroughly seasoned, free 



from heavy knots. The billets must have equal length. 



The kilns should be charged with one species and one 



assortment of wood only at a time. 

 II. The work consists of: 



(a) Preparation of ground near water by leveling and 



hoeing the soil, by removing roots and stones, 

 by raising the center of the circle to be occupied 

 by the kiln about 10 inches over its circumfer-: 

 ence. 



The diameter of the circle is from 15 feet to 30 

 feet usually. The best soil is loamy sand, 

 which secures proper regulation of the draft. 



The site should be protected from wind. Twigs 

 are woven into a wind screen on the windward 

 side, if necessary. 



(b) Erecting the "chimney" by placing three or four 



poles of even height at one foot distance from a 

 center pole, fastening them together to the cen- 

 tral pole by withes. 



The chimney is cylindrical if kiln is lighted from 

 above, pyramidal if kiln is lighted from below. 



