PRODUCING SODA PULP FKOM ASPEN. 



45 



parison between the amounts of bleaching powder required for pulps from poplar 

 (including aspen) and for other pulps: 



Table 7. — Amount of bleaching powder required Jor commercial pulps. 



Kind of pulp. 



Bleaching 



powder per 



100 pounds 



of pulp. 





Pounds. 

 18-25 

 12-15 

 10-15 



15-25 

 14-20 







Sulphite spruce 



Sulphite poplar 



The individual fibers in aspen soda pulp are of the following dimensions: 1 Length, 

 from 0.67 to 1.49 mm., averaging 0.99 mm.; breadth at the middle, from 0.01 to 0.03 

 mm., averaging 0.02 mm. ; approximate thickness of cell walls, 0.002 mm. ; ratio of length 

 to breadth, 50:1. The fibers are slender, gradually tapering to needle-pointed ends. 

 They are pliable and mpstly curved, although many are nearly straight. While 

 sometimes twisted and often swollen in nodes, with slight constrictions, they are 

 never badly tangled or knotted . Aspen fibers tend to be more nearly circular in cross 

 section than those from conifers. Other distinguishing characteristics are the medium 

 length of the fibers and the presence, except in ' ' overcooked " pulps, of remnants of the 

 larger wood vessels and parenchymatous tissue. The vessel walls have closely packed 

 bordered pits with hexagonal contour, and the inside walls are not marked with spiral 

 thickenings, as is the case with some species. The vessel ends have open pores without 

 gratings, which distinguishes aspen pulp from that of the tulip tree or yellow poplar 

 sold in European markets under the name "Amerikanische Aspenzellulose." 2 



YIELDS. 



The yields reported by a number of American soda-pulp mills operating on aspen 

 and other woods-are given in Table 8. 



Table 8. — Yields of soda pulps reported by various mills. 3 



Species of wood. 



Yield per 

 cord.* 



Poplar: 



100 per cent domestic . 

 Do 



Do. 

 Do. 



59 per cent domestic, 41 per cent imported . 



100 per cent domestic 



Do. 



Pounds. 

 1,000 

 1,040 

 1,050 

 1,050 

 1,075 

 1,102 

 1,139 

 1,144 

 1,153 

 1,161 

 1,170 

 1,191 

 1,200 

 1,209 



1 The dimensions and characteristics were determined microscopically from 52 separate fibers from the 

 26 different cooks made in these experiments. No effort was made to select extremely long or extremely 

 short fibers. See also photomicrographs of pulps, Plates II to VII. 



2 Litchauer, Zentr. f. d. Oesterr.-ung. Papierindustrie, p. 822, vol. 23, 1905. 



3 Each value is the report of 1 mill, received during the period 1907-1909. 



* On the percentage basis the yields of soda pulp from poplar also vary widely. Reid (Jr. Soc. Chem. 

 Ind., pp. 273-276, vol. 5, 1886) reports a yield of 41 per cent. De Cew (Jr. Soc. Chem. Ind., pp. 561-563, vol. 

 26,1907) cites a yield of 44 per cent, or 1,150 pounds per cord, from large-tooth aspen. Sindall(Paper Tech- 

 nology, p. 201, 2d ed. 1910) mentions a yield of 52 per cent, which is unusually high for commercial 

 practice. 



33 per cent domestic, 67 per cent imported . 



100 per cent domestic 



59 per cent domestic, 41 per cent imported. 



100 per cent domestic 



91 per cent domestic, 9 per cent imported . . 



100 per cent domestic 



90 per cent domestic, 10 per cent imported. 



