24 



BULLETIN "72, U. S. DEPAKTMENT OF AGEICULTUEE, 



Table 10. — Effect of varying initial concentrations on the yield of pulp. 



Weight of chips charged (bone-dry basis) pounds. . 0. 964 to 1. 031 



Water in chips per cent. . 10. 4 to 24. 4 



Causticity of liquor charge do 52. 8 to 53. 6 



Su.phidity of liquor charge do 27. 2 to 27. 5 



Duration "of cooking, total hours. . 3. 



Duration of cooking, at zero gauge pressure do 0. 1 



Duration of cooking at maximum gauge pressure do 2.0 to 2.5 



Maximum gauge pressure per square inch pounds. . 90 



Total duration of beater treatment (at light brush only) hours. . 2 



First Second 

 Chemicals charged per 100 pounds of chips (bone-dry basis): series, series. 



NaOH poimds. . 15. 12. 



NajS do.... 7.5 6.0 



NasSO, do. ... 7. 5 6. 



All sodium compounds as KazO do 21.8 17.5 



FIRST SERIES. 



Cook 

 No. 



Liquor charge, initial concentrations. 



Initial volume 



of digester 



liquors per 



pound of chips 



(bone-dry basis). 



Yield of 



crude pulp 



(bone-dry 



basis). 



NaOH. 



NaiS. 



NasSOi. 



All sodium 



compounds 



asNajO. 



89 

 90 

 91 

 93 

 94 

 95 

 96 

 97 



Grams 

 per liter. 

 60.0 

 45.0 

 36.0 

 30.0 

 25.7 

 22.5 

 20.0 

 18.0 



Grams 

 per liter. 

 30.0 

 22.5 

 18.0 

 15.0 

 12.9 

 11.2 

 10.0 

 9.0 



Grams 

 per liter. 

 30.0 

 22.5 

 18.0 

 15.0 

 12.9 

 11.2 

 10.0 

 9.0 



Grams 

 per liter. 

 87.2 

 65.1 

 52.1 

 43.6 

 37.4 

 32.7 

 29.0 

 26.1 



Gallons. 

 0.300 

 .400 

 .500 

 .600 

 .-00 

 .800 

 .900 

 1.000 



. Per cent. 

 47.9 

 53.3 

 55.2 

 58.6 

 61.3 

 64.4 

 66.4 

 66.9 



SECOND SERIES. 



112 



72.0 



- 36. 



36.0 



104.9 



0.200 



51.0 



100 



49.7 



24.8 



24.8 



72.0 



.290 



51.1 



101 



36.0 



18.0 



18.0 



52.2 



.400 



52.3 



105 



28.8 



14.6 



14.4 



42.2 



.500 



.56.0 



114 



24.0 



12.0 



12.0 



35.0 



.600 



62.6 



106 



20.6 



10.3 



10.3 



30.0 



.700 



60.6 



107 



18.0 



9.0 



9.0 



26.2 



.800 



66.0 



108 



16.0 



8.0 



8.0 



23.3 



.900 



67.4 



115 



14.4 



7.2 



7.2 



21.0 



1.000 



67.3 



110 



12.0 



6.0 



6.0 



17.5 



1.200 



67.8 



111 



10.3 



5.1 



5.1 



15.0 



1.400 



67.4 



(P. L.— 138, S. L.— 176.) 



When the concentration of all sodium chemicals expressed as 

 NagO was varied from 26.1 to 87.2 grams per liter (first series of 

 tests) the resultant yield decreased from 66.9 to 47.9 per cent. The 

 best results, considering both yield and quahty of pulps, were obtained 

 from cooks 91 and 93, using NajO concentrations of 52.1 and 43.6 

 grams per Uter, respectively. Pulps produced from cooks having 

 lower concentrations were brittle and lacked strength and wearing 

 properties. In the second series of tests, using somewhat smaller 

 amounts of chemicals, the higher concentrations afforded the better 

 results. The best pulp vnth. regard to strength and wearing proper- 

 ties was that obtained from cook 112, using a NajO concentration of 

 104.9 grams per Hter. The pulps obtained when using a concen- 

 tration of 35 grams per liter or less were quite brittle, and had little 

 strength and poor wearing properties. 



