PEODUCING SODA PULP FEOM 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 

 gauge ." A sample of this 



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Fig. 3.— Typical graphic log of cook. (Cook 24.) 



(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 



