apparatus was supported in a horizontal position 

 by resting the flanges in two concrete yokes. The 

 4 in. outlet of the tee was turned upward to act 

 as a dome for the collection of steam and turpen- 

 tine vapor; this arm was also used for charging and dis- 

 charging. The digester was equipped with thermo- 

 meter pocket, pressure gage, and relief line con- 

 trolled by a needle valve and leading to a glass con- 

 denser. An internal stirring device, consisting of a 

 small shaft fitted with arms, allowed mixing of the 

 contents of the digester when desired. As .con- 

 densation was too great when the digester was 

 heated by live steam, heat was furnished by two 

 large circular gas burners. 



Manipulation 



The manipulation was much the same in all the 

 experiments. For the preliminary extraction, from 

 one to two kilograms of resinous chips were pjaced 

 in the digester and covered with a measured volume 

 of alkaline liquor, containing the desired amount of 

 NaOH or Na 2 CO 3 . It was found that considerable 

 space had to be left for steam collection on account 

 of the tendency towards foaming. The top flange 

 was then securely bolted in place, all necessary 

 connections were made and the burners started. 

 In about an hour there was evidence of pressure 

 and the relief line was opened to permit steam 

 distillation of the volatile oils. The burners were 

 controlled to maintain a fixed, low pressure (be- 

 tween 15 and 30 pounds) for extraction of the rosin. 



Agitation was carried on continuously or inter- 

 mittently to prevent local overheating and to facili- 

 tate solution of the rosin. Continuous stirring 

 tended to fray the chips and render them less 

 suitable for pulping. 



The turpentine fractions were in most cases 

 isolated every fifteen minutes during the relieving 

 period. Curves are given showing the rate of 

 evolution of the volatile oils and the changes in 

 refractive index and specific gravity during the 

 course of distillation for typical experiments. 



After the preliminary treatment no longer yielded 

 turpentine in measurable amounts, the burners 



29 



