20 BULLETIN 72, U. S. DEPARTMENT OF AGRICULTURE. 
chloride has an effect on the yield, as is evidenced by the data for 
cooks 128 and 137. Both cooks employed 20 pounds of caustic soda 
per 100 pounds of wood, but the former used 5 pounds of sodium 
chloride in addition. The yields from the two cooks were identical. 
The use of sodium chloride appeared to improve the qualities of the 
pulps somewhat, but they were much inferior to sulphate pulps at 
similar yields. The few advantages attending the use of sodium 
chloride preclude the possibility of this modification of the soda 
process being of commercial value. 
Table 7. — Effect of sodium chloride (NaCl) used in conjunction with caustic soda (NaOH) 
on the yield of pulp. 
Weight of chips charged (bone-dry basis) pounds. . 0. 910 to 1. 043 
Water in chips per cent. . 15. 1 to 22. 
Causticity of liquor charge (disregarding NaCl) do 96. to 97. 2 
Duration of cooking at zero gauge pressure hours. . 0. 1 
Maximum gauge pressure per square inch pounds. . 90 
Total duration of beater treatment (at light brush only) hours. . 2 
Liquor charge, na- 
Chemicals charged 
per 100 pounds 
Initial vol- 
Duration of cook- 
tions. 
of chips (bone- 
dry basis). 
ume of 
digester 
ing. 
Yield of 
crude 
Cook 
No. 
liquors per 
pound of 
pulp 
(bone- 
chips 
At maxi- 
dry 
NaOH. 
NaCl.i 
NaOH. 
NaCl.i 
(bone-dry 
basis). 
Total. 
mum 
gauge 
pressure. 
basis). 
Grams 
Grams 
per liter. 
perliter. 
Pounds. 
Pounds. 
Gallons. 
Hours. 
Hours. 
Per cent. 
118 
44.2 
28.6 
15.0 
10.0 
0.420 
3.0 
2.5 
73.9 
122 
41.1 
20.0 
20.0 
10.0 
.600 
4.0 
3.5 
63.5 
128 
49.2 
12.0 
20.0 
5.0 
.500 
6.0 
5.3 
58.9 
137 
36.3 

20.0 

.662 
6.0 
5.3 
58.9 
72 
35.2 

20.0 

.681 
3.0 
2.3 
71.6 
(P. L.— 138, S. L.— 176.) 
i The values shown represent common table salt and not the pure chemical. 
EFFECTS OF SULPHUR. 
Cooks using " flowers of sulphur" and caustic soda as the cooking 
chemicals produced pulps almost identical with those resulting from 
the sulphate process. The addition of sulphur undoubtedly im- 
parted to the pulps the resistance to wear and strength not obtainable 
by the soda process alone. These cooks, however, were character- 
ized by the same disagreeable odor as the sulphate cooks, and this 
modification of the soda process seems to have no particular tech- 
nical advantage over the sulphate process except in the matter of 
control of the cooking liquors. 
EFFECTS OF VARYING THE PRESSURES OR TEMPERATURES OF COOKING. 
In the sulphate process, as in the soda process, the digester pres- 
sures represent the pressure of saturated steam, since no other 
gases are present in sufficient quantity to affect the pressure. This 
