Timbers. 



520 



[December 1909. 



Pure acetic acid is also prepared from 

 the acetate of lime by distilling it with 

 sulphuric acid. 



Wood alcohol is used very largely for 

 technical purposes. It is a useful solvent, 

 and is widely applied for producing 

 form-aldehyde, for "denaturing" ordi- 

 nary alcohol, and in the coal-tar dye 

 industry. 



Products from soft wood.— When "soft" 

 woods, i.e., resinous woods, such as 

 those obtained from the various pines, 

 are destructively distilled, the sub- 

 stances obtained are as follows : — (1) in- 

 flammable gas ; (2) light oils ; (3) pyro- 

 ligneous acid ; (4) tar ; (5) charcoal. The 

 pyroligneous acid so manufactured is 

 inferior in quality to that afforded by 

 hard woods. The principal fraction is 

 the " light oil " which is usually collected 

 in two portions, of which the lower 

 boiling one is a kind of crude turpentine 

 oil. This is a dark red oil of unpleasant 

 odour, but after suitable treatment and 

 fractionation it yields a nearly colour- 

 less spirit of characteristic odour, which 

 is used as a substitute for ordinary 

 turpentine oil. (Compare this Bulletin, 

 1906, 4. 215.) The best yields of products 

 in this process are obtained from the 

 heart wood. 



Steam Distillation of Wood. 



Besides the method of destructive dis- 

 tillation described above, a process of 

 distillation with steam is gradually 

 finding extended use for obtaining valu- 

 able products from waste pine wood. 

 This process only occasions the separ- 

 ation of volatile products (turpentine oil) 

 already pre-existent in the wood. 



Pine-tree stumps, saw-mill waste, and 

 sometimes pine timber itself are cut into 

 chips and placed in a vertical retort 

 fitted with a steam injection pipe. 

 Through this pipe saturated or super- 

 heated steam is blown in, and turpentine 

 oil, which is readily volatilised, passes 

 out of the retort and collects with the 

 water in a receiver, where it may be 

 readily separated. 



The residual wood, after drying a 

 short time in the air, is suitable for 

 fuel. The crude turpentine is rectified 

 from a copper still, and yields a slightly 

 yellow spirit of an agreeable odour 

 which is readily saleable at a price 

 slightly below that of ordinary turpen- 

 tine oil. 



Electric Process for the Distil- 

 lation of Wood. 



It is stated that a new electric process 

 has been evolved recently in British 

 Columbia for the utilisation of waste 

 wood, and that the process combines 



destructive distillation with a primary 

 distillation of the free turpentine oil 

 contained in the wood. An experimental 

 plant has been set up at Vancouver, 

 B. C, where waste firewood is obtain- 

 able from local saAV-mills, and the elec- 

 tricity from water-power at a low cost. 



The wood is filled into oblong cans 

 constructed to fit into special retorts, the 

 brickwork of which is permeated with 

 wrought-iron strips, through which 

 passes a current of 110 volts. The 

 temperature of the vessel, as measured 

 by direct reading pyrometers, rises 

 from 75° C. at the start to 130° C, when 

 turpentine oil begins to volatilise. The 

 current is then shut off. radiation from 

 the brickwork sufficing to complete the 

 distillation. By the time the temper- 

 ature of the can has risen to 150° C, 

 on the outside and 205° C. in the interior, 

 the turpentine oil has been nearly all 

 removed. It is collected by condensa- 

 tion with cold water as in the ordinary 

 process. The rosin contained in the 

 wood melts and runs down to the bottom 

 of the vessel and out through perfor- 

 ations, and is collected in the bottom 

 of the retort. 



The can containing the wood is now 

 removed from the turpentine oil retort 

 into an adjoining still, where the heat- 

 ing is continued, and the wood resi- 

 duum is destructively distilled as pre- 

 viously described. In this Avay the 

 fresh set of products, charcoal, wood- 

 tar, etc., is obtained quite separate 

 from the turpentine oil and rosin of 

 the first distillation. 



It is stated that by this process the 

 following yields are obtained per 1,0001b. 

 of wood from British Columbia coast 

 fir :- 



Turpentine ... ... 6'7 galls. 



Rosin 168*0 lb. 



Tar oil ... ... 5*1 galls. 



Tar 68-0 lb. 



Charcoal 323'0 lb. 



The charcoal obtained is said to be of 

 good quality, tough, and suitable for 

 special purposes. 



Owing to the absence of cheap supplies 

 of raw material, wood distillation is not 

 widely practised in the United Kingdom, 

 but the distillation of sawdust, scrap- 

 wood, spent tan and similar materials 

 is carried on to a small extent. 



In many of the Colonies and Depen- 

 dencies large tracts of forest exist fre- 

 quently containing trees of little value 

 as timber, and these might well be used 

 in this way, where the products of distil- 

 lation, and especially the charcoal, are 

 marketable locally. In Canada, wood dis- 



