PRODUCING SODA PULP FROM ASPEN. 
13 
employed, and were held constant at this value during the remainder 
of the cook. At the end of the cooking period the top relief vent 
was opened and the digester pressure quickly " relieved" until 
" blowing pressure" was reached, when the vent was closed, the two 
blow-off valves were opened, and the digester was emptied under 
blowing pressure with „ 
the assistance of a steam 
ejector in the blow-off 
line. 
The pulp was caught 
in the blow pit, where 
it was washed with three 
or more 50-gallon appli- 
cations of hot water. 
After the blowing and 
after each successive 
washing the pulp was 
allowed to drain, and the 
drainings were pumped 
to the black-liquor stor- 
age tank. The washing 
operations were contin- 
ued until the last drain- 
ings were of a specific 
gravity lower than 1 .003 
at 22° C. Inasmuch as 
the top relief pipe emp- 
tied into the blow pit, it 
was possible to collect 
the small amount of 
relief liquors, together 
with the black liquors, 
in the storage tank, 
where the volume of the 
whole was read off on 
the graduated tank 
A i i.,i • Fig. 3.— Typical graphic log of cook. (Cook 24.) 
gauge. A sample of this 
(sample C) was secured for analysis, and the amount and character 
of the recovered chemicals determined. (Fig. 2.) 
After the last washing the crude pulp in the blow pit was drained 
as dry as possible and, by means of scoops, removed to a strong linen 
bag inclosed in a perforated metal cylinder. The pulp in this form 
was then placed under a 70-ton, knuckle-joint, power press. After 
being pressed to about 30 per cent bone dry the pulp was next 
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