PKODTJCING SODA PULP PKOM 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 for 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 mostly 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 vc 
mills. 
Species of wood. 
Yield per 
cord. 4 
Poplar: 
100 per cent domestic . 
Do 
Do. 
Do. 
59 per cent domestic, 41 per cent imported . 
100 per cent domestic 
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. 
4 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 . 
