SOFTWOOD DISTILLATION 227 



man to anticipate the demand and to develop a special market for his 

 products, which are sold to a large extent as specialties. At the 

 present time there is a gradually increasing belief among chemical 

 engineers that the destructive method of distillation is wrong to a 

 large extent in its fundamental principles. This belief has caused the 

 development of many new processes. However, the plants operating 

 by the destructive method have been and are still operating on a com- 

 mercial basis, whereas, those based upon the distillation of steam and, to 

 a less extent, those using extraction by solvent baths, have largely failed 

 to survive the fluctuating market conditions. Many of the failures are 

 no doubt due to the lack of real knowledge of the possibilities of each 

 system followed, a lack of knowledge of the market possibilities and the 

 failure to keep accurate cost data. 



With the development of the softwood distillation industry, there 

 has been a gradual sorting out of the species which can be profitably 

 utilized on a commerical scale. The principal requirement is that the 

 wood be sufficiently rich in resin and that there be as much " lightwood " 

 as possible. Lightwood generally consists of stumps and logs after the 

 bark and sapwood have rotted off and is characterized by high resin 

 content. Longleaf pine is the most satisfactory species used and is the 

 same tree which is tapped for rosin and spirits of turpentine as described 

 in the Chapter on Naval Stores. Cuban {Pinus heterophylla) and short- 

 leaf (Pinus echinata) pines are also used, but only to a limited extent. 

 Several experimental and commercial plants have been constructed to 

 utilize Norway pine in the Lake States and Douglas fir and western 

 yellow pine and larch in the West. These have generally proven unsat- 

 isfactory, however, for general commercial development because the low 

 average resin content, the comparatively high cost of obtaining the raw 

 material, and the fluctuations in the values for the products did not 

 permit a sufficient latitude for profitable development. Many of the 

 experiments on these woods have been tried out with specially selected 

 specimens and although these experiments have in some cases proven 

 that the products could be extracted on a commercially profitable basis, 

 in actual practice on large operations it has been impossible to secure a 

 sufficient quantity of wood of equally high resinous or " fatty " con- 

 stituents. 



DESTRUCTIVE DISTILLATION 



The destructive distillation of resinous woods is carried out at the 

 present time chiefly in the South along the South Atlantic and Gulf 



