24 



BULLETIN 72, U. S. DEPARTMENT OF AGRICULTURE. 



TABLE 10. Effect of varying initial concentrations on the yield of pulp. 

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



Water in chips per cent. . 16. 4 



Causticity of liquor charge do 52. 8 



SUiphidity of liquor charge do 27. 2 



Duration of cooking, total hours. . 



Duration of cooking, at zero gauge pressure do 



Duration of cooking at maximum gauge pressure do 2. 



Maximum gauge pressure per square inch pounds. . 



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



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



NaOH pounds. 



Na 2 S do... 



Na 2 S0 4 do... 



All sodium compounds as Na 2 O do. . . 



to 24. 4 

 to 53. 6 

 to 27. 5 

 3.0 

 0.1 



to 2.5 

 90 

 2 



First Second 

 series, series. 

 15. 12. 

 7. 5 6. 

 7.5 6.0 

 21.8 17.5 



FIRST SERIES. 



SECOND SERIES. 



(P. L. 138, S. L. 176.) 



When the concentration of all sodium chemicals expressed as 

 Na 2 O 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 quality of pulps, were obtained 

 from cooks 91 and 93, using Na 2 O concentrations of 52.1 and 43.6 

 grams per liter, 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 with regard to strength and wearing proper- 

 ties was that obtained from cook 112, using a Na 2 O concentration of 

 104.9 grams per liter. 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. 



