16 
BULLETIN 12, U. S. DEPARTMENT OF AGRICULTURE. 
form of soft chips. The chips did not break up during the washing 
operation, but were readily pulped by beater treatment. The pulp 
was strong, tough, and resistant to wear. When larger amounts of 
caustic soda were employed the pulp tended to be soft, fuzzy, and 
less strong, while for smaller amounts it was harsh and brittle. (See 
cooks 39 and 40, Table 6.) In the second series of tests (Table 4) 
the conditions were such that all of the pulps were overcooked if 
considered for kraft papers. 
The higher the amount of caustic soda employed, the lighter in 
color was the pulp. The extremes for the first series of tests were 
brown in the case of cook 31 and light gray in the case of cook 60. 
For the second series of tests the color change was less noticeable. 
EFFECTS OF VARYING AMOUNTS OF SODIUM SULPHIDE. 
The effects of varying the amount of sodium sulphide were shown 
by three series of tests employing different amounts of caustic soda 
and of sodium sulphate. The cooking conditions and resultant yields 
are given in Table 5. 
Table 5. — Effect of varying amounts of sodium sulphide (Na 2 S) on the yield of pulp. 
Weight of chips charged (bone-dry basis) pounds. . 0. 996 to 1. 043 
Water in chips per cent . . 11. to 16. 
Initial volume of digester liquors per pound of chips (bone-dry basis) gallons. . 0. 662 to 0. 683 
Duration of cooking, total hours. . 3. 
Duration of cooking at zero gauge pressure". do 0. 1 
Duration of cooking at maximum gauge pressure do 2.0 to 2.5 
Maximum gauge pressure per square inch pounds. . 90 
Total duration of beater treatment (at light brush only) hours. . 0, 1, or 2 
FIRST 
SERIES 
1 
Liquor charge. 
Chemicals charged per 100 
pounds of chips (bone-dry 
basis). 
Initial concentrations. 
Yield of 
Cook 
No. 
pulp 
(bone- 
dry 
basis). 
All 
Caus- 
Sulphid- 
All- 
sodium 
ticity. 
ity. 
sodium 
NaOH. 
Na 2 S.2 
com- 
NaOH. 
Na £ S.2 
com- 
pounds, 
pounds, 
as Na 2 0. 
asXa 2 0. 
Grams 
Grams 
Grams 
per liter. 
per liter. 
per liter. 
Per cent. 
Per cent. 
Pounds. 
Pounds. 
Pounds. 
Per cent. 
31 
26.3 
13.1 
38.1 
53.6 
27.5 
15.0 
7.5 
21.7 
52.0 
34 
26.3 
26.3 
49.6 
41.1 
42.2 
15.0 
15.0 
28.3 
47.4 
35 
26.3 
43.9 
62. 4 | 32. 7 
56.0 
15.0 
25.0 
35.5 
44.5 
36 
26.3 
70.2 
88.0 23.2 
63.5 
15.0 
40.0 
50.0 
39.9 
37 
26.5 
88.3 
103.8 19.7 
67.5 
15.0 
50.0 
58.9 
40.3 
SECOND SERIES. 
133 
134 
139 
27.2 
27.2 
27.0 
1.8 
5.4 
9.0 
31.1 
34.4 
37.3 
67.7 
61.3 
56.1 
4.6 
12.6 
19.2 
15.0 1.0 1 17.2 
15.0 3.0 | 19.0 
15.0 5.0 20.7 
68.9 
67.6 
60.1 
THIRD 
SERIES 
i 
129 
35.3 
3.7 
39.4 
69.4 
7.4 
20.0 
2.1 
22.3 
64.3 
130 
35.9 
7.2 
43.0 
64.8 
13.3 
20.0 
4.0 
23.9 
53.7 
131 
36.0 
10.8 
46.3 
60.2 
18.5 
20.0 
6.0 
25.7 
49.7 
132 
36.0 
14.4 
49.6 
56.2 
23.1 
20.0 
8.0 
27.6 
47.7 
(P. L— 138.) 
1 The Mississippi wood (shipment L-36) was used for the first series and the Louisiana wood (shipment 
L-176) for the second and third series. 
2 With a few minor exceptions, the Na 2 SO< amounted to one-half of these values for the first and third 
series and to two-thirds of these values for the second series. 
