PRODUCING SODA PULP FROM ASPEN. 15 



unseasoned wood free from knots to be 26.68 pounds. The samples 

 ranged from 23.6 to 31.4 pounds per cubic foot. 



As a rule the test material was sound, but some of the logs had 

 decayed hearts. The material was peeled by means of a carpenter's 

 drawknife; all decayed portions on the outside of the pieces and all 

 protruding knots were chopped off. Tins cleaned wood was then 

 sawed into disks five-eighths inch thick in the direction of the grain. 

 Butts, tops, and all disks containing decay or other defects were 

 culled. 



The remaining sound disks were split with the grain into chips 

 1 inch to 6 inches by one-fourth inch by means of a special guillo- 

 tine chipping machine. All knots were culled. The chips were 

 then seasoned to constant air-dry weight, thoroughly mixed and 

 screened to remove sawdust and dirt, and finally stored in cans to 

 await the cooking tests. 



COOKING CHEMICALS AND SOLUTIONS. 



In ordinary mill practice the soda cooking liquors are made as 

 described on page 4. The freshly causticized solution contains 

 caustic soda (NaOH) for the most part, but a small amount of soda 

 ash (sodium carbonate, Na 2 C0 3 ) still remains uncausticized. Various 

 impurities are also present, but these are considered to have no 

 effect in cooking. 



In the experiments the cooking solutions were made by dissolving 

 fused caustic soda, 76 per cent * sodium oxide (Na 2 0), in water. 

 The resulting solution was similar to the solutions used in commer- 

 cial practice so far as caustic soda and soda ash are concerned, and 

 there is no reason to believe that the results should be different in 

 any way from those which would have been obtained by the use of 

 commercial liquors of the same concentration and causticity. 



EFFECTS OF VARIATIONS IN THE COOKING CONDITIONS. 



The influence of the variable cooking condition in each group of 

 tests on resultant yields and properties of pulps and consumption 

 of cooking chemicals is shown graphically in figures 4 to 15. 2 The 

 same results in greater detail are given in Tables 10 to 14 of the 

 appendix. While, in general, the tests were carried out in accord- 

 ance with the plan which has been described, minor departures could 

 not be avoided, and the location of certain points on the diagrams 

 are more or less affected by such variations. For this reason the 

 tabulated data should be consulted for the exact conditions of each 

 cook. 



1 Manufacturer's analysis. 



2 The numerals opposite each platted point on the curves are the serial numbers of the cooks. (See 

 Tables 10 to 14.) 



