10 
BULLETIN 72, U. S. DEPARTMENT OF AGRICULTURE. 
rubbed or crumpled for a long time without becoming fuzzy, tearing, 
or showing signs of wear at the place of friction. The papers had also 
a soft, smooth, greasy, leather-like feel, and were light brown in color, 
like the imported kr.aft papers. The yields were rather low for 
sulphate kraft pulps. For cook 77 the yield was 45.3 per cent, or 
1,609 pounds per solid cord, and for cook 141, 44.2 per cent, or 1,569 
pounds per solid cord. Under still more severe cooking treatments 
longleaf pine pulps become very soft and gradually lose their strength 
and wearing properties. (See autoclave tests, p. 14-24.) 
MEDIUM! COOKING TREATMENTS. 
The above-mentioned cooks show approximately the higher and 
lower limits of yield in the production of pulps and papers of good 
quality. However, the better quality of wrapping papers resulted 
from pulps having the lower yields, and in attempting to secure this 
better quality, but with higher yields than were obtained for cooks 77 
and 141, cooks 85, 98, and 146 were made. For cook 85 the amounts 
of chemicals and the initial concentrations were decreased from the 
corresponding conditions for cook 77, while the duration of cooking 
and the pressure remained practically the same; for cook 98 a further 
decrease was made in the amounts of chemicals and in the concen- 
trations, but the duration of cooking was increased; for cook 146 the 
amounts of chemicals and the duration were practically the same as 
for cook 85, but the concentrations were decreased while the pressure 
was increased. The cooking conditions, given in full in Table 1, are 
briefly summarized in Table 2. The resultant papers were in each 
case of good quality, being tough and resistant to wear, but they were 
in general not so strong as those from pulps produced under more 
severe cooking treatments. The strength factors for cooks 85, 98, 
and 146 were 0.87, 0.56, and 0.68, respectively. There is little doubt, 
however, that these values could be increased considerably by 
employing beating and other refining treatments better adapted for 
these particular pulps than the treatments given them. The yields 
obtained were quite high, cook 85 yielding 52 per cent, or 1,846 
pounds per solid cord; cook 98, 51.8 per cent, or 1,839 pounds per 
solid cord; and cook 146, 54.9 per cent, or 1,949 pounds per solid cord. 
Table 2. — Condensed summary of cooking conditions for cooks 77, 85, 98, and 146. 
Liquor charge, initial 
Chemicals per 100 
pounds of chips 
Duration of cooking. 
Maximum 
Cook No. 
(bone-dry basis). 
Total. 
At maxi- 
mum gauge 
pressure. 
pressure 
NaOH. 
Na^S. 
NaOH. 
NasS. 
inch. 
77 
Grams per 
liter. 
44.6 
36.0 
28.8 
26.5 
Grams per 
liter. 
22. 3 
18.0 
14.4 
13.2 
Pounds. 
20.0 
15.0 
12.0 
15.0 
Pounds. 
10.0 
7.5 
6.0 
7.5 
Hours. 
3.0 
3.0 
5.0 
3.0 
Hours. 
2.3 
2.5 
4.3 
2.3 
Pounds. 
90 
85 
90 
98 
90 
146 
100 
