PYROLIGNEOUS ACID, WOOD (METHYL) ALCOHOL, AND THEIR MANUFACTURE 169 



PARAGRAPH XXXV. 

 PYROLIGNEOUS ACID, WOOD (METHYL) ALCOHOL, AND THEIR MANUFACTURE. 



(A) RAW MATERIALS. These are, preferably, broad-leafed species- beech, maple, birch-which 

 must be thoroughly seasoned. Birch is inferior to beech and maple. Elm imparts to the product an 

 undesirable odor. 



Heavy material is preferable, it is said, to small stuff. 



(B) DISTILLATION. The process consists in a dry distillation of the wood, differing from the 

 charcoal kiln process merely by preventing the resulting gases from escaping. 



The distillation takes place in large horizontal iron cylinders, usually over 40 feet long by 6 feet in 

 diameter, into which the wood is run on steel trucks. After closing the cap of the cylinders (admission 

 of air reduces the output of pyroligneous acid) the cylinders are slowly heated to a red heat. The gases 

 forming are led, by long worm pipes, through a condenser. 



Not all of the gases formed allow of condensation. The uncondensable gases are conducted to the 

 fire room. 



At the bottom of the cylinder, tar is forming and is let out frequently by a system of pipes into a 

 collecting basin. Conifers yield more wood-tar than do hardwoods. 



(C) FURTHER TREATMENT. The gases, condensed to a liquid a large proportion of which is water, 

 are conducted to the still house. 



The main components of the liquid are wood-tar (heaviest), pyroligneous acid (medium weight) con- 

 taining wood-vingear and wood-alcohol, and wood-oil (lightest). 



By gravity alone, these constituents are separated, to begin with, the liquid flowing from one tank 

 into the other. 



All containers must be made either of wood or of copper. 



The pyroligneous acid, freed from wood-tar and from wood-oil, is then treated with lime. Lime 

 neutralizes the pyroligneous acid, by forming acetate of lime, and frees the wood -alcohol. 



The neutralized liquid is then distilled, wood-alcohol going over first, water next, and acetate of lime 

 remaining as a syrup. This syrup is boiled down, in open pans, to the consistency of a sugar, the grey 

 acetate of lime of commerce. 



(D) THE PLANT. The plant consists of two buildings: - 



\. The retort house contains a series of iron retorts which can be opened and sealed at either end. 

 Cars loaded with dry wood enter at one side; cars loaded with glowing charcoal are drawn from the 

 other side, after the lapse of 48 hours. The charcoal cars are allowed to cool in a double set of air-proof 

 sheet iron sheds. Immediately above the retorts are found the open pans in which the acetate of lime 

 is condensed. 



II. The still house, situated at a safe distance from the retort house, contains the main condenser, a 

 series of wooden tanks and a number of copper stills. Its basement is used for a barrelling room. 



(E) OUTPUT. One cord of air- dry beech yields 2,000 pounds of liquids, 14 gallons of tar, and 

 1,000 pounds (50 bushels of 20 pounds each) of charcoal, worth 5c to 6c per bushel. 



The 2,000 pounds of liquids furnish 190 pounds of acetate of lime (worth 9',2C per pound, and 9 gallons 

 of 96 per cent wood-alcohol, worth 50c per gallon. 



(F) USE. Acetate of lime is used in the manufacture of acetone, gunpowder, acetic acid, and of 

 the salts of acetic acid. 



Wood -alcohol is used largely in the manufacture of varnishes, dyes, celluloid, and especially for 

 denaturizing the true ethyl- alcohol. It is poisonous. 



22 



