16 



BULLETIN 72, U. S. DEPARTMENT OF AGRICULTURE. 



form of soft chips. The chips did not break up during the washing 

 operation, but were readily pulped by beater treatment. The pulp 

 was strong, tough, and resistant to wear. When larger amounts of 

 caustic soda were employed the pulp tended to be soft, fuzzy, and 

 less strong, while for smaller amounts it was harsh and brittle. (See 

 cooks 39 and 40, Table 6.) In the second series of tests (Table 4) 

 the conditions were such that all of the pulps were overcooked if 

 considered for kraft papers. 



The higher the amount of caustic soda employed, the lighter in 

 color was the pulp. The extremes for the first series of tests were 

 brown in the case of cook 31 and light gray in the case of cook 60. 

 For the second series of tests the color change was less noticeable. 



EFFECTS OF VARYING AMOUNTS OF SODIUM SULPHIDE. 



The effects of varying the amount of sodium sulphide were shown 

 by three series of tests employing different amounts of caustic soda 

 and of sodium sulphate. The cooking conditions and resultant yields 

 are given in Table 5. 



TABLE 5. Effect of varying amounts of sodium sulphide (Na 2 S) on the yield of pulp. 



Weight of chips charged (bone-dry basis) pounds. . 0. 996 to 1. 043 



Water in chips per cent. . 11. to 16. 



Initial volume of digester liquors per pound of chips (bone-dry basis) gallons. . 0. 662 to 0. 683 



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. . 0, l, or 2 



FIRST SERIES.i 



SECOND SERIES. i 



THIRD SERIES. 



(P. L 138.) 



1 The Mississippi wood (shipment L-3&) was used for the first series and the Louisiana wood (shipment 

 L-176) for the second and third series. 



2 With a few minor exceptions, the Na2SO4 amounted to one-half of these values for the first and third 

 series and to two-thirds of these values for the second series. 



