SUITABILITY OF LONGLEAF PINE FOB PAPEB PULP. 21 
was determined by actual test. The digester pressures, therefore, 
correspond to the temperatures of saturated steam; and values of 
each may be converted into the other by means of standard steam 
tables. 
Table 8 shows the effect on yield of variations of pressure from 40 
to 140 pounds per square inch. As the pressures increased, the 
yields decreased. Cook 45, with a pressure of 40 pounds per square 
inch, resulted in a product so much undercooked that no. pulp could 
be prepared from it. The yield, of course, was very high. Cook 46, 
using a pressure of 140 pounds per square inch, resulted in 50 per 
cent yield. For intermediate pressures the yields were correspond- 
ingly higher. 
Table 8. — Effect of varying pressures on the yield of pulp. 
Weight of chips charged (bone-dry basis) pounds. . . 1. 000 to 1. 005 
Water in chips, per cent. . 10. 4 to 11. 
Causticity of liquor charge do 53.5 
Sulphidity of liquor charge do 27. 4 
Initial volume of digester liquors per pound of chips (bone-dry basis) gallons. . . 0. 667 to 0. 680 
Duration of cooking, total hours. . 3. 
Duration of cooking at zero gauge pressure do 0. 1 
Duration of cooking at maximum gauge pressure do 2. to 2. 3 
Total duration of beater treatment (at light brush only) do — or 1 
Liquor charge, initial con- 
centrations. 
Chemicals charged per 100 
pounds of chips (bone-dry 
basis). 
Yield of 
Cook 
No. 
Maximum 
crude 
All 
sodium 
All 
sodium 
gauge 
pressure. 
pulp 
(bone-dry 
basis). 
NaOH. 
Na^S.i 
com- 
NaOH. 
Na^S.i 
com- 
pounds 
pounds 
as NasO. 
as NaaO. 
Grams 
Grams 
Grams 
per liter. 
per liter. 
per liter. 
Pounds. 
Pounds. 
Pounds. 
Pounds. 
Per cent. 
45 
21.3 
10.6 
30.8 
12.0 
6.0 
17.4 
40 
( 2 ) 
42 
21.1 
10.6 
30.6 
12.0 
6.0 
17.4 
80 
61.3 
39 
21.2 
10.6 
30.7 
12.0 
6.0 
17.4 
90 
60.2 
41 
21.1 
10.6 
30.6 
12.0 
6.0 
17.4 
120 
54.0 
46 
21.3 
10.6 
30.8 
12.0 
6.0 
17.4 
140 
50.0 
1 The same values apply to the Na 2 SO< used. 
(P. L.— 138, S. L.— 3 6.) 
2 Wood not cooked; no pulp prepared. 
Pulps produced with the higher pressures were stronger and had 
better wearing properties than those resulting from the lower pres- 
sures. With lower pressures the pulps became more and more 
brittle and gradually lost their soft, pliable, leather-like feel. The 
pulps resulting from the lower pressures were the more brown in 
color. 
The best pressure conditions for these tests seemed to be from 100 
to 140 pounds per square inch. If larger amounts of chemicals had 
been employed, pulps of the same yield and properties would prob- 
ably have resulted from pressures of 80 to 100 pounds per square 
inch. 
