36 



BULLETIN 80, U. S. DEPARTMENT OF AGRICULTURE. 



When varying the durations and the pressures of cooking and the 

 initial concentrations, the amounts of soda ash per ton of pulp were 

 affected by yields alone, and the mmimuni amount is employed under 

 conditions which give the maximum yields. Increased durations, 



pressures, and concentrations 

 afford decreased yields, and 

 the amount of soda ash per 

 ton of pulp consequently is 

 increased. The platted point 

 for cook 10 is not on the curve, 

 due to the initial digester 

 liquors for this cook having 

 had about 3 per cent lower 

 causticity than the other cooks 

 in this group of tests. Lower 

 causticities involve the use of 

 a greater amount of soda ash 

 for the same amount of caustic 

 soda. 



600 



500 



a. 400 



o. 300 



uj 200 



100 



500 



400 



9 



"Ih- — ,t> s 



.20 .30 .40 

 POUNDS NaOH PER POUND OF WOOD 



uj 300 



M 200 



100 



400 



a. 300 



200 



m 



































\»I5 



















14 



a 



— 21L 



to 





1 



2 4 6 8 10 12 

 DURATION AT MAX. PRESSURE- HOURS 



100 



I 



c 

















V 



,*• 



















20"-~-< 



J9 



J8 



,17 





60 70 80 90 100 110 120 



MAX. PRESSURE-PDS. PER SQ. IN. 



200 



100 



40 50 60 10 80 90 100 IK) 

 CONCENTRATION NaOK-GRAMS PER LITER 



Fig. 19. — Effects of cooking conditions on amount of 

 bleaching powder employed per ton of pulp. 



cent available chlorine, and losses in 

 are disregarded. 



BLEACHING POWDER. 



The curves in figure 19 show 

 that increasing the amounts 

 and concentrations of caustic 

 soda and the durations and 

 pressures of cooking result in 

 all cases in decreasing the 

 amounts of bleaching powder 

 consumed. 



Yields do not influence the 

 calculations, since the con- 

 sumption per ton of bleached 

 pulp depends on the per cent 

 of bleach required and the 

 bleaching losses. The ordi- 

 nates for the curves represent 

 bleaching powder of 35 per 

 making the bleaching solutions 



COMBINED COST OF WOOD AND CHEMICALS PER TON OF PULP. 



The curves in figure 20 show costs for certain items in producing 

 a ton of bleached pulp -(2,000 pounds air-dry basis) as influenced by 

 variations in the cooking conditions. Curves marked A represent 

 cost of wood alone; curves B, cost of wood and soda ash; and curves C, 



