PRODUCING SODA PULP PKOM 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 
6T^--L_ 6 ' s 
4« 
.10 
5 
4 
.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- 
\<s 
\ 
\«5 
! 
N 
V 
13 
! 
•N 
"V 
-12 
10 
2 4 S 8 10 12 
DURATION AT MAX, PRESSURE-HOURS 
SO 
70 80 90 100 110 120 
&ia.pREssyR>~PDs.pEa so. in. 
1 $ 
1" 
==4- 
L 
*» 
40 
50 60 70 80 30 100 110 
CONCENTRATION NaOH- GRAMS PER LITER 
Fig. 10.— Effects of 
solving conditions on the bleach- 
ins; loss. 
