VOLATILE PRODUCTS. 



Besides a certain amount of tar, and the inflammable gases which, as has 

 "been stated, are utilized as fuel in the charcoal manufacture, even the smoke has 

 proved of considerable value. It contains methylic alcohol, which also distils 

 over from the retort in a liquid form, accompanied by acetic acid. This crude 

 distillate is known as " wood vinegar," and is redistilled and rectified over quick- 

 lime, yielding " wood-spirit" (crude methylic alcohol). The acid portion is then 

 saturated with slaked lime, so as to form a solution of calcium acetate, which is 

 evaporated, the salt being used in the manufacture of acetic acid and metallic 

 acetates, especially that of lead, as as a step towards the formation of white lead. 



Dr. Hough describes a charcoal iron-smelting factory in Michigan, where a 

 cord of wood yields forty-two bushels of charcoal, worth 7 cents per bushel, or 

 $2.99 cents per cord, besides 2,800 cubic feet of " smoke," valued at over 30 cents, 

 and the inflammable gas which supplies three-fourths of the fuel consumed. The 

 "smoke" yields two gallons of wood-spirit, worth 85 cents (3s. 4|d.) per gallon 

 in the Chicago market, and 200 Ib. of acetate of lime, worth 2| cents (l^d.) per 

 Ib. in Philadelphia. Thus the " smoke " for which 30 cents (Is. 3d.) are paid, 

 yields $6.70 (1 6s. 9d.) the total yield of a cord of wood being $9.69 (1 18s. 8d.) 

 These products are best obtained from dry hard woods, especially beech. 



TAR AND PITCH. 



The mixture of heavy non-volatile hydrocarbons known as tar, though 

 obtained in small proportions in the destructive distillation of all kinds of wood, 

 is yielded mainly by the roots, boles, branches, and waste timber of pines, 

 especially Pinus palustvis, P. sylvesh is, and P. pinaster. It is mainly imported 

 from the southern United States, from Archangel, and from Blo^ and other 

 Baltic ports. 



The pitch pine (P. palustris) covers extensive tracts, and springs up spon- 

 taneously in the disused cotton fields of the Southern States, while the Scots 

 pine (P. sylvestris) forms enormous forests in the North of Europe and in 

 Siberia. The preparation of tar is still virtually the same as that described 

 by Theophrastus. A hole is dug in the side of the bank in which billets of 

 wood are heaped up and covered closely with turf or earth, a fire is then 

 kindled from below, and the slow combustion causes the tar to exude from 

 the wood and flow out from the heap into barrels placed below to receive it. 

 On distillation, tar yields wood vinegar, creosote, and oil of tar, leaving a residue 

 of pitch. The black, brittle, glossy solid which we know as pitch, and which is 

 mainly home manufactured, is usually obtained by simply boiling the tar, so as 

 drive off the volatile oils. 



TURPENTINE, RESIN, ETC. 



In addition to being our chief sources of tar and pitch, the firs are the 

 exclusive commercial source of the oleo-resin known as turpentine. This is a 

 solution of a resin in a volatile oil which exudes from incisions made in the stems 

 of these trees. On distillation it yields from 14 to 16 per cent, of colourless 

 essential oil, known as oil or spirits of turpentine (Ci H 16 ), the residue being 

 resin or colophony (the formula of which is probably C w H 62 O 04 ). The greatest 

 quantity of turpentine imported is the produce of the pitch pines (Pinus 



