door in front, which can be tightly fastened. The top of the bat- 

 tery is often tiled and serves as a drying floor for acetate of lime. 

 The condensers are of copper, and are cooled by water. A "run," 

 from charging to recharging, takes twenty-four hours. 



The invention of the "oven" form of carbonizing vessel marked 

 a distinct forward step in wood distillation. Oven kilns are made 

 large enough to hold from two to four cars, which are run in on tracks, 

 each loaded with about 2 cords of wood. They are usually fired 

 separately, and the vapors pass over into the condensers either at 

 the side or at the end. In other respects they resemble the " retorts." 



PRODUCTS. 



Four crude products are obtained from each of these forms of car- 

 bonizing vessels: (1) Charcoal, which remains in the vessel; (2) a 

 noncondensible gas, which is carried off by suitable pipes; (3) an 

 aqueous liquor known as " pyroligneous acid;" and (4) wood tar, 

 which is condensed with the pyroligneous acid. 



The charcoal is cooled differently in the case of each distilling ves- 

 sel, though in all cases it is cooled for forty-eight hours. With Kilns, 

 it is allowed to cool before being removed; with the retorts, it is 

 shoveled into drums or cans and sealed from the air; and with the 

 ovens, the loaded cars are run out and closed in large coolers, which 

 are similar in form to the ovens. 



The gas from the kilns is piped back into the kiln furnaces, where 

 it serves to carbonize the wood. The gas from retorts and ovens 

 is burned under the boilers or under the retorts. 



The pyroligneous acid and the tar run off together from the con- 

 densers into vats, where the tar settles. The pyroligneous acid is 

 reddish brown in color and has a strong, characteristic, burnt-wood 

 odor. The tar, when in thin layers, is dark brown in color, and 

 has a bad odor. These two liquid products are refined by processes 

 which in general are the same for each of the three forms of carboniz- 

 ing apparatus. The processes differ somewhat, however, at the dif- 

 ferent plants. 



Dissolved in the tar are some of the valuable compounds of the 

 pyroligneous acid, while dissolved in the pyroligneous acid are some 

 tarry bodies. Both liquids are distilled m order to concentrate the 

 valuable substances, which are chiefly acetic acid and methyl, or wood, 

 alcohol. The concentrated liquid containing the acetic acid and 

 methyl alcohol is neutralized with lime and distilled from a " lime- 

 lee" still, giving (1) a residue which upon evaporation yields gray 

 acetate of lime, and (2) a distillate which upon refining^ yields the 

 various grades of wood alcohol. 



Some plants obtain a crude, brown, evil-smelling wood alcohol, of 

 82 per cent strength, which is sent to a refinery for further treatment; 

 others obtain a 95 to 99 per cent product without color or unpleasant 

 odor. Wood alcohol is ill-smelling only when impure as a result of 

 incomplete refining. 



Oven and retort plants which produce alcohol no purer than 82 per 

 cent secure about the following average yields from wood distillation 

 per cord of wood : 



Charcoal 45 to 52 bushels. 



Gray acetate of lime 180 to 225 pounds. 



Wood alcohol, 82 per cent 8 to 10 gallons. 



fCir. 114] 



