the large supply of lightwood now available.* 

 Lightwood is often charred by the ground fires 

 which run through the pine forests. 



Turpentine Orcharding 



The oldest and most approved method of obtain- 

 ing rosin and turpentine depends on making inci- 

 sions in the living tree and . collecting the oleore- 

 sinous exudate. This general operation is known 

 as "orcharding." The turpentine is recovered from 

 the crude gum by distillation and the non-volatile 

 rosin is purified by a simple process of straining 

 while still in a molten condition. 



The "gum spirits of turpentine" so obtained are 

 always taken as the highest standard of quality, 

 since they are not contaminated by those decom- 

 positions products formed during certain other 

 treatments of resinous woods. The orcharding 

 method is simple and requires but little outlay for 

 apparatus. The exhausted trees are available 

 for lumber, and the choice of areas for orcharding 

 is now usually made with this end in view. On 

 the other hand, the yield from a single tree is 

 small, the average being 10-12 pounds of crude 

 gum per annum (Herty, J. Ind. Eng. Chem., Jan. 

 1913, p. 67). This necessitates the exploitation 

 of a very large number of trees and any but the 

 most careful methods of orcharding result in rapid 

 devastation of a forest. 



Destructive Distillation 



The aim in this process is to heat the richer 

 grades of pine in closed retorts at progressively 

 higher temperatures in order to first liberate the 

 volatile oils of the wood in a comparatively un- 

 changed condition and finally to decompose the 

 rosin and the wood into a series of products which 

 are for the most part volatile at high temperatures. 



*A. Tschirch, in "Die Harze and die Harzbe- 

 halter," second edition, describes the increased 

 accumulation of rosin in a wounded or dead tree 

 as a pathological process carried on by minute 

 organisms. 



8 



