PRODUCING SODA PULP FROM ASPEN. 



21 



Increasing the pressure and increasing the initial concentration 

 beyond a certain point both increased the strength of the pulp. 

 This effect is apparently contradictory to that found for the other 

 two groups of tests and may possibly be due to the high tempera- 

 tures and high concentrations which would tend to cause a physical 

 change in the cellulose with in- 

 crease of the cementing effect 

 mentioned previously. 



Curves showing the influence 

 of cooking conditions on the 

 strength of pulp are given in 

 figure 8. 



3.5 



- 3.0 



2.5 



(A 2.0 



1.5 





8 















\ 1 























7*-~-~ 





£ 



& 

















~4* 







.10 



.20 .30 .40 



POUNDS NaOH PER POUND OF WOOD 



i 3.b 



1 30 

 d 



at 



W 2 5 



















I6~~ 





14 



^13 



« 









W 



B 



c 2.0 



« 



• 

 15 









10 







2 4 6 8 10 12 

 DURATION AT MAX. PRESSURE-HOURS 



3.5 



3.0 



X 2.5 



a- 2.0 











i 



>y 



'IT 







22 







liS 











\2 





20 











60 



70 80 SO 100 110 120 

 MAX. PRESSURE-PDS. PER SQ.IH. 



EASE OP BLEACHING. 



The chief purposes of bleach- 

 ing are (1) to produce a white 

 pulp and (2) to destroy any non- 

 cellulose materials which tend 

 to make the pulp less durable. 

 The more nearly the original 

 pulp approaches to pure cellu- 

 lose the less is bleaching re- 

 quired. However, difficulty of 

 bleaching is occasioned not only 

 by the presence of ligneous mat- 

 ters, but also by coloring mat- 

 ters absorbed in the cell walls 

 from the "black liquors" and 

 by the residual cooking chem- 

 icals which the leaching and 

 washing treatments have failed 

 to remove. In the latter case 

 a certain amount of bleach is 

 neutralized by reactions with 

 the other chemicals. 



Curves expressing the effects 

 of varying the cooking condi- 

 tions on the ease of bleaching, as measured by the amount of bleach 

 required to bring the pulps to a standard white color, are shown in 

 figure 9. These curves show that under the conditions of cooking the 

 residual ligneous matters are the most important factor in determin- 

 ing the amount of bleach required, since the more thorough cooking pro- 

 duces pulps that are more easily bleached. The decrease in amount of 



3.5 



S 3.0 



£ 2.5 



°- 2.0 



40 50 60 70 30 90 100 110 

 CONCENTRATION NaOH -GRAMS PER LITER 



Fig. 8. — Effects of cooking conditions on the strength 

 of pulp. 















J 



L 













s 



/ 







26 





25 





24 







