PRODUCING SODA PULP FROM ASPEN. 



19 



The more thorough cooking resulting from the higher initial con- 

 centrations of caustic soda produced lighter-colored pulps, although 

 the lower limit of {he cooking condition in these tests was considerably 

 above the minimum for successful cooking. 



While the several curves shown in figure 5 indicate for each group 

 of tests more or less change in the " parts black" color ratings or the 

 depth of color, the hues of the 

 pulps were not materially- 

 affected. 



1000 



OCCURRENCE OF SHIVES. 



Shives are most numerous 

 in pulps from the less severe 

 cooks and are entirely absent 

 from those thoroughly cooked. 

 The shives curves (fig. 6) bear 

 some resemblance to those for 

 the yields of screenings, but 

 shives disappear from the pulps 

 only under somewhat more 

 severe cooking conditions than 

 those which reduced the yield 

 of screenings to zero. At the 

 point of maximum yield of 

 screened pulp the cooking has 

 progressed far enough for the 

 fibers to become more or less 

 separated from each other, but 

 not completely so, since some 

 of them still remain in groups 

 (shives) small enough to pass 

 the screen slots. But as the 

 cooking becomes more severe 

 the fibers are entirely sepa- 

 rated, and the resulting pulp 

 is free from shives. In gen- 

 eral, increasing the amount of 

 temperature of cooking, or the 

 liquor decreases the "shiviness" 



800 



600 



400 



.200 



1 



\\ 

















\ 

















V 



's 











• 





\ 



















W-, 



1 



& — 1 



£— * 







.10 



.20 .30 .40 

 POUNDS NaOH PER POUND OF WOOD 



:800 

 i 



600 

 i 



400 



; 200 



"\ 

















\ 



\ 

















\ 



















\}4 



13 



n 



10 







2 4 6 8 10 12 

 DURATION AT MAX. PRESSURE-HOURS 



60 



70 80 80 100 110 120 

 • MAX. PRESSURE- PDS. PER SQ.IN. 



Fig. 6.- 



50 60 70 80 90 100 110 

 CONCENTRATION NaOH-GRAMS PER LITER 



-Effects of cooking conditions on the occur- 

 rence of shives in pulp. 



caustic soda, the duration or the 

 initial concentration of the digester 

 of the pulp. 



ASH CONTENT. 



The curves in figure 7 indicate that increasing the thoroughness 

 of cooking within certain limits decreases the ash content of the pulp; 

 outside of these limits the ash content may be increased. 

 • Since the normal amount of ash in aspen wood is not over three- 

 quarters of 1 per cent, the high amounts in the pulps produced 



