METHODS OF PRODUCTION. 9 



and in the forest be placed at 50 per cent of this, a very conservative 

 estimate, there are 8,000,000,000 board feet, or approximately 

 8,000,000 cords of wood (on a basis of 40 per cent unoccupied space 

 in a cord), available for the recovery of turpentine and rosin and the 

 manufacture of paper, acetate of lime, wood alcohol, oxalic acid, etc. 

 From this class of material from 1 to 10 gallons of crude turpentine 

 per cord are recovered under the present practice, the average 

 recovery being 3 gallons per cord. 



Pine wood also yields from 3 to 15 or 20 per cent of rosin, while 

 exceptionally rich lightwood may yield from 30 to 35 per cent. 

 The average rosin yield of good lightwood is probably between 12 

 and 18 per cent. Assuming low yields of turpentine and rosin, a 

 calculation shows that it is possible to recover from the wastes of the 

 yellow-pine lumber industry (including dead-and-down timber) as 

 much or more turpentine, rosin, and rosin oils as are now produced 

 by the ordinary methods of turpentining from the living tree. The 

 profitable utilization of mill wastes in this way would add mate- 

 rially to the wealth of the South and help to conserve its timber 

 resources. 



METHODS OP PRODUCTION. 



Wood turpentine can be recovered from any of the coniferous 

 woods. Those which have been found to contain sufficient resin to 

 justify working them are the long-leaf yellow pine, of the South, the 

 Norway pine of the Central North, and the Douglas fir of the North- 

 west. The methods by which wood turpentine is recovered may be 

 appropriately divided into three classes, (a) destructive distillation 

 methods, (b) steam distillation methods, (c) extraction with solvents. 



DESTRUCTIVE DISTILLATION. 



In the destructive distillation method wood exceptionally rich 

 in turpentine, and rosin (generally termed " lightwood" or stumps) 

 is loaded into retorts holding one or more cords each, and slowly 

 heated at a low temperature until all the turpentine and other low- 

 boiling oils are driven off and condensed, when the oils are directed 

 to other receiving vessels, and the distillation of the wood continued 

 until nothing remains in the retort but charcoal. In conducting this 

 process it is important that the temperature of the retort should 

 not rise above 200 C. until all turpentine in the wood has been driven 

 off, otherwise the wood is decidedly charred and the turpentine is 

 contaminated with other materials from which it can not be subse- 

 quently purified. Industrially, it has been found impracticable 

 until very recently to prevent such contamination, and for this reason 

 destructively distilled turpentine has certain characteristic properties 

 which distinguish it from turpentine prepared in other ways. The 



