20 



BULLETIN 620, U. S. DEPARTMENT OP AGRICULTURE. 



only about 0.5. per cent. This probably is due to a decrease in the 

 amount of hydrolysis of the cellulose occurring under 120° C. The 

 screenings decreased with the temperature. The explanation for this 

 is that with the higher temperature the cooks are finished before the 



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120 160 



PARTS BLACK 



10 20 30 44 46 48 50 



DURATION OF COOK - HOURS YIELD OF UNSCREENED 



PULP - PERCENT 



i +• ■— — 



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YIELD OF SCREENED PULP - PERCENT 



12 3 4 5 

 SCREENINGS - PERCENT 



TO 20 30 40 50 

 BLEACH - PERCENT 



Fig. 10.— Effect of varying the temperature of cooking. 



inner portions of some of the larger chips are thoroughly cooked, while 

 the smaller ones are probably overcooked. The lower temperatures 

 with their longer cooks insure a more even cooking and therefore 

 produce less screenings. Decrease in the temperature produced a 



