METHODS OF PRODUCTION. 



11 



by the steam (which, as has been said, is difficult to secure) coupled 

 with the smaller quantity of vapor to be condensed. Further, the use 

 of steam under pressure is questionable, as the terpenes are readily 

 polymerized at high temperatures. On the other hand, it is rela- 

 tively certain that owing to the difficulty of securing contact, the usual 

 steam process in fixed retorts does not remove all turpentine from the 

 wood, and an apparatus or process which will insure contact of the 

 steam with all of the wood will give higher yields of turpentine. In 

 this connection, the use of a rotating retort immediately suggests 

 itself, and several plants claim to obtain larger yields with these. 

 Distillation under reduced pressure, if found practicable, undoubtedly 

 offers several important advantages, among which are the distilla- 

 tion of turpentine at low temperature, thus reducing the tendency to 

 polymerization, penetration of the wood by steam, and distillation 

 of the turpentine from the interior of the pieces of wood. 



Prolonged heating is .exceedingly costly, and with proper equip- 

 ment is needless, as it has been demonstrated that turpentine may be 

 removed in from two to three hours, when proper penetration of the 

 wood by the steam is secured. The steam process is particularly 

 applicable for the utilization of mill wastes, such as slabs and saw- 

 dust, and has found its greatest development in connection with the 

 sawmills of the South. 



The following diagram shows the products of the steam distillation 

 of wood and the utilization of the extracted chips:" 



Resinous wood.. 



(hogged and 

 steam dis- 

 tilled) 



Distillate. 



Chips. 



Water. 



Crude oils 



(fractionated) 



Destructively distilled (see p. 10). 

 Wasted or burned. 



fSteam wood turpentine (GO to 80 per 



< cent). 



IPine oils (20 to 40 per cent). 



Paper pulp. 



gSSJSMfti-a^lgs?? ,r<> ""n*-"*-- 



Sodium carbonates 



Digested with caustic 



soda and drained 



E 



(C structively distilled) {^^ (aee p . 10) . 

 EXTRACTION WITH SOLVENTS. 



Finally, turpentine may be recovered from wood by dissolving it 

 in a volatile or nonvolatile solvent, or in an alkali. Extraction with 

 volatile solvents is but little employed, and deserves more consider- 

 ation than it has received. The economical working of solvent 

 processes is dependent primarily on the possibility of a practically 

 complete recovery, at a minimum cost, of the large quantities of 

 solvent which are required to saturate the wood for extraction. 

 Fortunately the solvent can be almost entirely recovered. The 

 products obtained by the use of volatile solvents of low boiling point 

 are of high quality; the rosin is clean and bright, while the turpentine 

 is comparatively free from materials produced in the extraction. 



