DISTILLATION OF STUMPWOOD. 29 



came so violent when a temperature of about 300° C. was reached that 

 the distillation could practically be completed without further heat- 

 ing, and in less time than the richer wood with continued heating. 



It was necessary, therefore, in distilling the " bull pine " to watch 

 the oil-bath thermometer carefully in running up the temperature 

 for destructive distillation and turn off the heater flame when this 

 period was reached. The reaction progresses so rapidly that the dis- 

 charge of gas and vapors may exceed the otherwise ample condenser 

 capacity, and loss of distillate result from imperfect condensation. 

 The difference in behavior is due to the fact that the richer wood con- 

 tains a much greater ratio of rosin to cellulose. The heat set free 

 during decomposition of the wood substance is more than offset by 

 that required to effect decomposition of the rosin in such wood, and 

 additional heat must be supplied to insure the decomposition of rosin 

 and the distillation of the products. 



The fact that in the destructive distillation of nonresinous woods 

 enough heat above a certain temperature is developed to complete the 

 distillation without the application of heat from outside sources, 

 necessitates the installation of larger condensers in the distillation 

 of nonresinous woods than are needed in the distillation of resinous 

 woods. When the exothermal reaction begins, it proceeds so rapidly 

 that the condensers, which in the earlier stages were large enough to 

 condense all condensable material, can no longer do so, and a loss of 

 valuable products occurs if the condensers are too small to meet all 

 the requirements that may be placed upon them during the exother- 

 mal period. 



Yields. 



The yields of crude products obtained in the retort distillation, and 

 of the refined turpentine and pine oil for each sample, are given in 

 Table 14. A summary of these tabulations, giving the average re- 

 covery from the various grades of wood distilled, is given in Table 19. 



