24 



HARDWOOD RECORD 



and maple, with the last preferred. The 

 wood is cut into cordwood lengths and allowed 

 to season for a year. According to the best 

 information, the amount of the products ob- 

 tained from green wood and from ordinary 

 drj' wood is not different, cord for cord, but 

 the higher water content of green wood dilutes 

 the distillate and necessitates more fuel for 

 the carbonization. E.\cessivo seasoning will 

 doubtless reduce the yield of valuable consti- 

 tuents. Body wood is better than slab wood. 

 Very small wood, such as thin edgings, car- 

 bonizes so rapidly that it must bo mixed with 

 larger pieces. The problem of the destructive 

 distilUition of sawdust has not yet been satis- 

 factorily solved. 



Wood is heated or carbonized in three 

 forms of apparatus; brick kilns, retorts and 

 ovens. 



The charring of wood is a process as old 

 as civilization. In the early days wood was 

 charred under sod in the old charcoal kiln, 

 which has been a familiar sight over a good 

 part of the world. The modern charcoal kiln 

 is so made that valuable vapors are con- 

 densed from the smoke, which in the old- 

 fashioned kiln escaped into the air and were 

 wasted. Kilns are now mainly used to pro- 

 duce charcoal for blast furnaces for pig 

 iron. They are made of brick, with a cir- 

 cular base, and divided approximately into 

 two semi-circular sections. They hold each 

 about 50 cords, and arc charged and dis- 

 charged by hand. The vapors are carried 

 off into condensers, where the condensable 

 ones arc liquefied. 



The name "retort" is given to a small 

 form of cylindrical vessel holding about 

 three-fourths of a cord. The retorts are set 

 horizontally in brickwork, in pairs, each pair 

 forming a "battery," and heated from be- 

 neath. They are filled and discharged from 

 a single door in front, which can be tightly 

 fastened. The top of the battery 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 charg- 

 ing to recharging, takes twenty-four hours. 



The invention of the "oven" form of car- 

 bonizing 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. ' ' 



Four crude products are obtained from 

 each of these forms of carbonizing ves- 

 sels: Charcoal, which remains in the vessel; 

 a noncondensable gas, which is carried off 

 by suitable pipes; an aqueous liquor known 

 as "pyroligneous acid;" and wood tartar, 

 which is condensed with the pyroligneous 

 acid. 



The charcoal is cooled differently in the 

 case of each distilling vessel, though in all 

 cases it is cooled for forty-eight hours. With 

 kUns, it is, allowed to cool before being re- 



moved; 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 carbon- 

 ize 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 condensers 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 prod- 

 ucts are refined by processes which in general 

 are the same for each of the three forms 

 of carboniziug apparatus. The processes dif- 

 fer somewhat, however, at the different plants. 



Dissolved in the tar are some of the valu- 

 able compounds of the pyroligneous acid, 

 while dissolved in the pyroligneous acid arc 

 some tarry bodies. Both liquids are distilled 

 in order to concentrate the valuable sub- 

 stances, which are chiefly acetic acid and 

 methyl, or wood alcohol. The couceutrated 

 liquid containing the acetic acid and meihy] 

 alcohol is neutralizeu 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 re- 

 fining yields the various grades of wood al- 

 cohol. 



Some plants obtain a crude, brown, evil- 

 smelling wood alcohol, of 82 per cent strength, 

 which is sent to a refinery for further treat- 

 ment; others obtain a 95 to 99 per cent prod- 

 uct 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 al- 

 cohol no purer than 82 per cent secure about 

 the following averages from wood distilla- 

 tion per cord of wood: 



Charcoal, bushels 45 to 52 



Gray acetate oi lime, pounds ISO to 225 



Wood alcohol, 82 per cent, gallons 8 to 10 



The lack of chemical supervision at thu 

 works makes statements of yield a little con- 

 fusing, since wood alcohol and acetate of 

 lime are variable in quality and the num- 

 ber of gallons and pounds may therefore 

 actually represent products of quite different 

 composition. 



Kiln plants obtain about the following 

 yield per cord of wood: 



Charcoal, bushels 45 to 52 



Acetate of lime, pounds go to 150 



Wood alcohol, 82 per cent, gallons 4 to 6 



These compounds have a variety of uses, 

 which may be briefly mentioned. Charcoal 

 is used in blast furnaces for the production 

 of pig iron, in copper and sugar refineries, 

 in the production of gunpowder, for fuel, 

 etc. Wood alcohol is sold under a variety 

 of trade names, such as "Columbian spirit" 

 and ' ' colonial spirit. " It is most widely used 

 as a solvent in the production of shellacs and 



varnishes. It is also used in hat making, 

 in perfumery, in the coal-tar dye industry, 

 in manufacture of formaldehyde, and for mix- 

 ing with grain alcohol to produce "dena- 

 tured " or " industrial ' ' alcohol. The acetate 

 t>f lime is a gray, finely crystalline body, which 

 is used in the manufacture of wood vinegar, 

 acetic acid, many commercial acetates, acetic 

 ether, acetone, and other products. From 

 the acetone may be produced iodoform and 

 chloroform. 



A number of receipts for the jjreparation 

 of denatured alcohol have been recently au- 

 thorized by Congress and established by the 

 Commissioner of Internal Revenue, so that 

 denatured alcohol, with its due admixture of 

 wood alcohol, is now a market article. The 

 wood distillation plants now in existence iu 

 the United States are able to produce prob- 

 ably 30,000,000 gallons of wood alcohol an- 

 nually. 



Denatured alcohol is now a competitor of 

 wood alcohol. At present the producers and 

 refiners of wood alcohol are in suspense as 

 regards the extent of the consumption of the 

 product for denaturing purposes. 



Several species of hardwood are distilled 

 by steam in order to obtain valuable es- 

 .sential oils. Sweet birch, for example, yields 

 "oil of wintergreen, " an oil used in medici- 

 nal preparations. Xo thorough study has yet 

 been made of this division of the subject, 

 but it is known that a small industry is 

 supported. 



Iron or steel retorts are used, varying in 

 capacity from 1 to 4 cords. They are either 

 vertical or horizontal. The vertical retorts 

 have their long axis upright, and are set 

 singly in brickwork with suitable flues, usu- 

 ally with the openings for charging and 

 discharging at the top and bottom. The fire- 

 box below is at one side, so that the heat 

 goes around the outside of the retort itself. 

 Few of these retorts are now in use. 



The horizontal retorts are similar to those 

 used in hardwood distillation. Though they 

 differ as to form, all are cylindrical steel 

 vessels set in batteries in brickwork and are 

 charged and discharged through doors at one 

 or both ends. The gases escape through 

 pipes to copper condensers. The firebox is 

 sometimes constructed to fire two retorts at a 

 time, though usually but one. 



Though there are a number of methods 

 which differ somewhat iu results, the five 

 products usually obtained are: Charcoal, a 

 uoneondensible gas, light oils, which are often 

 taken in two fractions, one of which is a 

 crude turpentine, tar, and pyroligneous acid. 

 At some plants the light oil vapor, which 

 volatilizes easUy, is led off into condensers 

 with the gas and pyroligneous acid, while 

 the tar, which is heavier, is drawn off at 

 the bottom; at others the entire volatile prod- 

 uct is driven off through a pipe at the top 

 and, after passing through the condenser, 

 is separated into the crude turpentine and 

 tar fractions. 



There is no more uniformity in heating 

 methods than in the form of the retorts. The 



