PRODUCING SODA PULP FEOM 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. This 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 x 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.) 
