J56 MANUFACTURE OF CHARCOAL IN CHARCOAL KILNS (PITS) 



(b) Non-acid hemlock tannage, oak tannage, and union tannage (^ 3 hemlock bark, Vs oak bark) 

 consists of: — 



1. Treating (coloring) the hide, to begin with, to weak solutions of 4 to 13 per cent of tannin, 

 during 10 to 15 days. 



2. Gradually increasing, during the next 150 days, the concentration of the liquors. If a hide is 

 at once hung in a strong liquor, its outer layers only are tanned. The hide will not swell, 

 and the inner layers will fail to be impregnated. 



VI. The operations finishing the process of manufacture are :- Washing; scouring -off the so-called 

 bloom; stuffing (which means bathing in grease); drying; dampening and rolling under pressure; re-drying; 

 glossing on a brass bed by brass rollers. 



PARAGRAPH XXXIV. 

 MANUFACTURE OF CHARCOAL IN CHARCOAL KILNS (PITS). 



(A) DISTILLATION OF WOOD. The destructive distillation of wood, conducted under reduced 

 admission of air, yields chemically the following proportion of substances: — 



1. Twenty-five per cent of non- condensable gases, viz.: — 



carbon, monoxide marshgas propene 



carbon dioxide acetylene ethylene 



2. Forty per cent of condensable vapors, viz. : — 



acetone, furfurol acetic acid crotonic acid 



methyl alcohol formic acid capronic acid 



methylamine butyric acid propionic acid 



3. Ten per cent of tarry liquid, viz. : - 



tar xylol cresol pyrene 



creosote cumol phlorol chrysene 



toluol methol naphthalene paraffine 



4. Twenty-five per cent of solid residue, viz. :- 



charcoal inorganic salts 



(B) THE KILN OR PIT PROCESS. In the kiln process of destructive distillation of wood, the sub- 

 stances given above under 1, 2, and 3 are allowed to escape unused. 



Modern technology succeeds in condensing and utilizing several of these substances by the process 

 described in the next following paragraph (XXXV). 



Still, the majority of the charcoal commercially used is produced by the old and wasteful charcoal kiln. 



(C) CHARACTERISTIC QUALITIES OF CHARCOAL:- 



1. Charcoal has per cubic foot a larger heating power than wood. A ton of charcoal, in modern 

 machines, generates 2,000 horse -power. 



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



3. Its freedom from sulphur and phosphates makes it valuable 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 but one species and but one assortment of wood at a time. 



