22 
BULLETIN -80, U. S. DEPAKTMEBTX OF AGBICULXUBE. 
bleach required was very rapid up to the point where shives were 
eliminated; beyond this point the effect was less marked. It must 
not be assumed, however, that the shives alone necessitated the larger 
amounts of bleach. The presence of shives indicates an incomplete 
cooking reaction and implies that considerable ligneous matter may 
remain in the other (completely separated) fibers. 
The effect of severity of the 
cooking conditions is especially 
noticeable in the curves for the 
tests varying the amount of 
caustic soda and the duration 
of cooking, since certain of the 
pulps produced in these tests 
were less thoroughly cooked 
than any of those from the 
other groups. 
30 
20 
9 
^^-4 — U-4 
.10 
.20 .30 AQ 
POUNDS NaOH PER POUND OF WOOD 
30 
V 
\I5 
«^W 
13 
i 2 
-v 
2 4 6 8 10 12 
DURATION AT MAX. PRESSURE-HOURS 
^0 
10 
n 
(22 
^21 
20 
19 ' 
SO 
70 80 90 100 110 120 
MAX. PRESSURE-PDS. PER SQ. IN. 
20 
LOSS ON BLEACHING. 
The curves showing the 
losses on bleaching as affected 
by the varying cooking condi- 
tions are given in figure 10. 
As would be expected, the loss 
decreased with thoroughness 
of cooking. In the tests vary- 
ing the amounts of chemical 
and the durations of cooking 
the rate of decrease in bleach- 
ing loss with greater severity 
of cooking was fairly constant, 
but it is probable that if the 
cooking conditions were ex- 
tended for higher values than 
those used the curves would 
approach parallelism with the horizontal axis. Such an effect was 
obtained for the tests in which the cooking pressures were varied. 
It is not reasonable to believe that more severe cooking would result 
in pulps which would suffer no loss whatever on bleaching. 
The platted points for the tests in which the initial concentrations 
were varied are so few in number and so irregular in location that 
they give little indication of the influence of this factor. However, 
additional information is obtained from some earlier tests of the Forest 
Service, summarized in Table 4. 
20 
40 50 60 70 80 90 100 110 
CONCENTRATION NaOH -GRAMS PER LITER 
Fig. 9.— Effects of cooking conditions on the ease of 
bleaching. 
26 
k 5 
24 
'23 " 
