PRODUCTION" OF SULPHITE PULP FROM SPRUCE. 



15 



yield of screened pulp increases as the combined S0 2 is increased to 

 1 per cent, but beyond this remains constant. The amount of 

 bleaching powder necessary to bring the pulp to a standard white 

 decreases as the combined S0 2 is increased to about 1 per cent, but 



80 120 160 200 10 20 30 44 46 48 50 



PARTS BLACK DURATION Of COOK- HOURS YIELD OF UNSCREENED 



PULP - PERCENT 



1 







J_ # 1 — ,, 



— t , — 





- 



._. 



. 



-j-p 







4 i| 



4. 





! 



ir 





r 1 — _ — 



■1 





»/ . 1 1_ _ 



Pr - \ 



===" "k- 







\ !k. 



V ^ C 



.... . j ., .... 



^^ 



= > 



— i — i — i— — i — — i — 









]— . 





42 44 46 48 SO 



YIELD OF SCREENED PULP -PERCENT 



12 3 4 5 

 SCREENINGS-PERCENT 



10 20 30 40 SO 

 BLEACH-PERCENT 



Fig. 8. — Effect of varying the amount of combined S0 2 in the cooking liquor. 



any increase beyond this point does not produce any further change 

 in color. 



The amount of combined S0 2 does not seem to hare much influence 

 on the different factors studied, provided it is over 1 per cent, but 

 any decrease below this caused marked changes in the character and 



