Issued November 5, 1907. 



United States Department of Agriculture, 



FOREST SERVICE CIRCULAR 114. 

 GIFFORD PINCHOT, Forester. 



WOOD DISTILLATION. 



By W. C. GEER, Expert. 



[NOTE. The Forest Service has received many inquiries about the commercial dis- 

 tillation of hardwoods and softwoods and the quantity of the products obtained. It has 

 been impossible to answer these inquiries by letter as fully as desired, and the growing 

 need of a popular publication which would briefly state a few facts on wood distillation 

 has been strongly felt. For this reason this circular has been compiled. It is not 

 intended to be technical in nature or to contain the results of original investigations, 

 but rather to furnish a few facts concerning the wood distillation industry as it now 

 stands in this country. Circulars of a more technical character and dealing with 

 concrete problems in wood distillation will follow.] 



INTRODUCTION. 



There are two distinct processes for obtaining valuable products 

 from wood by distillation destructive distillation and steam dis- 

 tillation. In the destructive process the wood fiber is .broken down 

 and new compounds are formed, but in the steam process this is not 

 properly the case. In both processes the volatile compounds of the 

 wood are vaporized. 



In destructive distillation heat is applied below the wood-containing 

 vessel, which has a comparatively small pipe as its only outlet. The 

 heat vaporizes the volatile compounds, such as water and turpentine, 

 and breaks down the nonvolatile compounds, such as cellulose and 

 the wood gums; it forms a number of new compounds, usually of a 

 simpler chemical nature, and these in turn are vaporized with the 

 water and turpentine, leaving a residue of charcoal. The decomposi- 

 tion of the wood in this process is exceedingly complicated and is not 

 yet fully understood. 



In steam distillation, which is much simpler, the wood is chipped 

 and placed in a closed receptacle into which steam is blown from a 

 boiler, and the volatile compounds which are not chemically united 

 with the rest are vaporized and carried out of the retort with the 

 steam. Though in practice the wood, is often so much overheated 

 that the wood fiber is slightly decomposed, and though it is quite 

 possible to carry the overheating so far that the process becomes one 



9678 No. 11407 



