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 
-30 
»\, 
8 
1 
:« 
Ul 
Q. 
c/5 2.0 
^***» 
£_^ 
5 
s 
1.5 
~S* 
,10 
.20 .30 .40 
POUNDS NaOH PER POUND OF WOOD 
1 30 
d 
PC 
U 9S 
14 
"--»L 
w 
CO 
a 
CL p. n 
• 
15 
10* 
2 4 6 8 10 12 
DURATION AT MAX. PRESSURE-HOURS 
^3.5 
I 3.0 
d 
£ 2.5 
£ 2.0 
\ 
i 
>y 
'17 
f 2 * 
to 
\J 
^ 
^ 
60 
70 80 90 100 110 120 
MAX. PRESSURE-PDS. PER SQ. IN. 
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 
8 3.0 
2.5 
°- 2.0 
J 
L 
• 
/ 
25 
24 
26 
40 
Fig. 8, 
50 60 70 80 
CONCENTRATION NaOH- 
90 100 110 
•GRAMS PER LITER 
-Effects of cooking conditions on the strength 
of pulp. 
