14 BULLETIN 80, U. S. DEPARTMENT OF AGRICULTURE. 



"opened up'' in a swing-hammer shredder running at low speed 

 and without a cage, so that the largest lumps after shredding were 

 about hazelnut size. This was done to facilitate sampling and 

 increase the accuracy- of the dry-weight determinations. The 

 shredded pulp was weighed and sampled (sample D) for determin- 

 ing the dry weight. It was then mixed with water and further 

 opened up in a 25-pound Hollander-style beater, with the roll well 

 off the bedplate so that no real beating could take place, and was 

 pumped from the beater to a 200-gallon stock tank at the head of the 

 screening system, where it was diluted with water to a known volume. 

 This mixture was then screened by means of a 6-plate diaphragm 

 screen with slots 0.009 inch wide. The screenings which went over 

 the plates were then collected, weighed, and sampled (sample E), as 

 described for the crude pulp. The screened, unbleached pulp which 

 went through the screen slots, mixed with a large amount of water, 

 was run to a water extractor and concentrated. Afterwards it was 

 pumped to the paper machine stuff chest, made up to a known volume 

 with water, pumped to the machine screen (diaphragm type, 0.012 inch 

 slots), and run out on a 15-inch Fourdrinier paper machine (see PL I), 

 into a sheet 10 inches wide by about 0.010-0.011 inch thick. The 

 rolls of the screened, unbleached pulp thus secured were stored await- 

 ing the tests to determine its properties for winch samples G to R 

 were taken. Where the screenings were so large in amount as to 

 preclude accuracy of sampling the crude unscreened pulp, such pulp 

 was screened without the preliminary pressing, shredding, etc., and 

 the screened pulp was collected on a 70-mesh sieve, pressed, shredded, 

 weighed, and sampled for the yield determinations. The pulp was 

 then screened again and made up into a sheet as described. 



The methods used for determining dry weights, yields, quality 

 of pulps, and composition of liquors are given in the appendix. 



TEST MATERIALS USED. 



WOOD. 



The test material consisted of 3 1 logs of aspen (Populus tremuloides, 

 Michx.) cut from representative trees growing intermixed with 

 wliite birch near Rhinelander, Wis. The trees were of seed growth 

 and had attained an average height of 44 feet, with straight, clear 

 lengths of about 22 feet from which the logs were cut. 



The ages of the logs varied from 28 to 42 years, as determined by 

 counting the annual rings. The logs were fairly free from knots, 

 considering the size of the trees and the species. Volume-weight 

 determinations on 36 samples, representative of the whole shipment, 

 showed the average bone-dry weight per cubic foot of green or 



