EXPERIMENTAL WORK. 



15 



increased. Every effort should be made to have the steam carry as 

 large a proportion of turpentine as is practicable. It is evident that 

 if the proportion obtaining in refining can be had in steaming from the 

 wood, steam consumption can be greatly reduced and the cost of 

 equipping the plant and of making turpentine considerably lowered. 

 Experiments are being conducted with this object in view. The ex- 

 perience and observations of the Bureau of Chemistry indicate that 

 this condition can best be secured by relieving periodicaUy from the 

 retort. After the removal of the easily freed oils, which are very 

 largely obtained in the first half hour of steaming without pressure, 

 the valve in the outlet pipe to the condenser may be closed and the 

 chips subjected to 40 to 50 pounds of steam pressure for from 20 to 

 30 minutes, when the outlet valve may be opened for an equal 

 period, maintaining the pressure all the tune. This steaming and 

 relieving may be alternated until it is no longer profitable to steam 

 the chips. 



PULP-COOKING DATA. 



An additional quantity of water was placed in the digester with the 

 chips and the alkali solution to distill off all the turpentine. Thus, 

 during the early stages of the cooking, while the turpentine was being 

 steamed off, the cooking of the fiber was conducted at low pressure 

 with a dilute alkali solution. The concentration of the alkali solution 

 increased gradually through the distillation of water and turpentine, 

 until for the final stage the cooking was conducted in a 20 to 27 

 per cent alkali solution. During the steaming period the pressure 

 never exceeded 50 pounds, while the digester was closed and did not 

 fall below 25 to 35 pounds during relieving. 



All of the cooking data so far as they relate directly to the produc- 

 tion of pulp have been brought together in Table 2. 



TABLE 2. Cooking data. 



