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



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



Species of wood. 



Yield per 

 cord. 



Poplar 11 per cent and pine 89 per cent 



Poplar 91 per cent and chestnut 9 per cent 



Poplar 75 per cent and gum 25 per cent 



Poplar 95 per cent and gum 5 per cent 



Poplar 12 per cent, pine SS per cent, and gum small amount 



Poplar 3 per cent, pine 25 per cent, and maple 72 per cent 



Poplar 32 per cent, pine 52 per cent, and hemlock 16 per cent 



Poplar 13 per cent, pine 1 per cent, and chestnut 86 per cent 



Poplar 7 per cent, pine 43 per cent, maple 45 per cent, and basswood 5 per cent 



Poplar 9 per cent, pine 34 per cent, maple 19 per cent, beech 19 per cent, other hard woods 19 



per cent 



Poplar 56 percent, maple 7 percent, and basswood 37 percent 



Poplar 40 per cent; birch, maple, beech, and basswood 



Poplar 30 per cent, Cottonwood 30 per cent; maple, buckeye, willow, and lime 10 per cent each. . 



Pounds. 



1,000 

 800 



1,000 



1,139 

 985 

 948 

 862 

 800 



1,014 



794 

 1,043 

 1,160 

 1,000 



The several yields were all determined from the amounts of wood consumed annu- 

 ally by each mill and the total production of pulp in the same time. The yields 

 represent air-dry, bleached pulp, except for a few of the mills which used coniferous 

 woods, together with the poplars. 



The experimental work of the Forest Service shows that yields of over 55 per cent 

 (bone-dry basis) of unbleached pulp (see Table 11) can be obtained. Even the lowest 

 yield of good unbleached pulp was not less than approximately 45 per cent. A yield 

 of 55 per cent amounts to over 1,450 pounds of bone-dry, unbleached pulp, or over 

 1,600 pounds of air-dry, bleached pulp,- per 100 cubic feet of solid wood. The average 

 12S-foot cord of peeled aspen contains approximately 90 cubic feet of solid wood, 1 

 and on this basis would produce 1,440 pounds of air-dry, bleached pulp. 



It seems evident, therefore, that considerably higher yields can be obtained from 

 aspen than are secured in commercial practice. One of the many reasons for the 

 lower yields of the commercial plants is probably the quality of the wood. 2 In the 

 Forest Sendee tests the wood used was clear and sound, all defective material having 

 been culled. 



USES. 



The principal use of soda poplar or aspen pulp is in the bleached form for such 

 papers as book, magazine, antique, coated, lithograph, map, card, cover, common 

 envelope, and writing; and wood blotting papers; also the soft, bulky papers some 

 times required for special purposes. In making these papers longer-fibered pulps, 

 that is, bleached rag or sulphite wood pulps, are mixed with the soda pulp in various 

 proportions up to 80 per cent of the whole. These other fibers are added mainly for 

 the purpose of strengthening the soda pulps, and their proportion in the mixture 

 depends upon the desired quality of the product. The use of considerable amounts 

 of soda poplar pulp is favored in some cases because it imparts to the sheet of paper a 

 bulkiness and opacity not readily obtainable with ordinary sulphite or rag pulp alone. 

 The addition of the long-fibered pulps tends to increase the cost of the products, 

 but gives them more lasting qualities. These mixed pulps lend themselves with 

 particular ease to the various paper-making operations, such as sizing, coloring, 

 beating, and running on the paper machine. 



The amount of various kinds of wood pulps used in the United States in 1909 and 

 1899 is shown in Table 9. 



1 Forest Service Bulletin 36 (rev. ed., 1910), p. 113, Woodman's Handbook, by II. S. Graves and E. A. 

 Ziegler; also "Factors influencing the volume of solid wood in the cord," by R. Zon, Forestry Quarterly, 

 p. 126. No. 4, vol. 1. 



2 In some earlier experiments by the Forest Service considerably lower yields were obtained, which were 

 attributed to the inferior quality of the wood. See Table 15. 



