PRODUCING SODA PULP FROM ASPEN. 23 



Table 4. — Effect of concentration on bleaching losses (autoclave tests). 1 



Cook 

 No. 



Concentra- 

 tion of 

 NaOH. 



Yield of 



total crude 



pulp. 



Yield of 

 screenings. 



Bleach 

 required. 



Loss on 

 bleaching. 



1 

 2 

 4 



Grams per 

 liter. 

 80 

 50 

 30 



Per cent. 

 41.10 

 44.23 

 46.97 



Per cent. 



0.10 



.03 



.07 



Per cent. 

 15.4 

 14.7 

 15.8 



Per cent. 

 3.92 

 4.08 

 4.68 



.20 .30 .40 



POUNDS NaOH PER POUND OF WOOD 



i Each cook employed seven hours' duration at 110 pounds pressure per square inch. The caustic soda 

 charged amounted to 0.25 pound per pound of wood. For complete information see appendix, Table 15. 



These data indicate that increasing the concentration reduces the 

 loss en bleaching, hence the curve in figure 10 has been drawn to show 

 such an effect. This is sub- 

 stantiated by the fact that 

 varying the amount of chemi- 

 cal and the duration and pres- 

 sure of cooking in each case 

 showed a reduction in the 

 bleaching losses as the severity 

 of cooking increased, and that 

 most of the other curves for 

 the effect of concentration 

 (especially the yield, shives, 

 and bleach-required curves) 

 show more severe cooking with 

 the higher concentrations. 



The relatively large amount 

 of loss in the case of cook 23 

 does not seem to be warranted 

 in view of the well-cooked con- 

 dition of the pulp. However, 

 the comparatively high strength 

 of the pulp indicates an abnor- 

 mal condition. 



The loss in weight of a pulp 

 during bleaching is due prima- 

 rily to the removal of the col- 

 ored ligneous matters and to 

 the partial destruction of the 

 cellulose itself. The latter is 

 especially liable to occur if the 

 bleaching treatments are severe, or if the cooking treatments have left 

 the cellulose in an easily oxidized condition, so that it is either dis- 



2 4 6 8 10 12 

 DURATION AT MAX. PRESSURE-HOURS 



\ 



c 

















s 



2i 



>- 



< 



'" < 



l" . 



17 





i 



|20 









60 



70 80 90 100 110 120 

 MAX.PRESSURE-PDS.PER SQ.IN. 







( 



, 25 







< 



21 



i 



26 



r 







i 



'24 







40 



SO 60 70 80 90 100 110 

 CONCENTRATION NaOH-GRAMS PER LITER 



-Effects of cooking conditions on the bleach- 

 ing loss. 



