PRODUCTION OF SULPHITE PULP FROM SPRUCE. Dit 
decrease in the amount of bleach consumed, as indicated by the curve. 
This is rather surprising when one considers that the yield of screened 
pulp increased almost 5 per cent, while the bleach decreased from 22 to 
11 percent. This must be due to the more uniform cooking occurring 
at the lower temperatures so that broken up, uncooked shives did not 
consume bleach. The values for strength are fairly regular (Table 3), 
probably as a result of the use of an improved style of beater in this 
series. As would be expected, they show an increase in strength 
with decrease in temperature. 
Photomicrographs of the pulps produced in cooks 90, 92, 97, and 
100 are shown on Plates IX, X, XI, and XII. Cook 90, which was 
made with a high temperature, contains much lignified fiber and is 
not very uniform; while cook 100, which was made at a low tempera- 
ture, seems to be well cooked and has fibers nearly all of the same 
length. 
SUMMARY OF RESULTS. 
1. These experiments have demonstrated that a standard color 
can be used with which to match the color of the liquor in the digester 
to determine when a cook is finished. A cook can be duplicated at 
any time by comparison with this standard. 
2. The limit to which the combined SO, can be decreased to obtain 
good cooking seems to be about 1 per cent. Below this there is a 
rapid darkening of the pulp produced, and an increase in the screen- 
ings and bleach consumed. 
3. When the temperature and total SO, are kept constant, the yield 
of screened pulp increases somewhat with increase in the combined 
SO,, because of the more thorough cooking. Consequently, less 
screenings are obtained. 
4. When the temperature and total SO, are kept constant, a de- 
crease in the amount of combined SO, causes quicker cooking action, 
so that a cook can be finished in less time. 
5. An increase in the total SO, causes a decrease in the cooking 
~ period, other factors remaining constant. 
6. The screenings and color of the pulp remain constant as the 
total SO, is decreased to about 5 per cent, after which there is a rapid 
increase in both of these factors. 
7. The higher the total SO,, the easier it is to bleach the pulp, 
other factors being the same. 
8. The amount of screenings decreases as the temperature is lowered, 
because of the more even cooking obtained at the lower tempera- 
tures. 
9. The bleach is reduced as the temperature is decreased, while the 
yield of pulp increases. 
