12 



BULLETIN 72, U. S. DEPARTMENT OF AGRICULTURE. 



quickly. For all of the semicommercial tests previously mentioned 

 (Table 1) this effect, indicated by the smooth, greasy feel of the wet 

 paper stock, was obtained with from 2 to 4 hours' beater treatment. 



WOOD REQUIRED FOR 1 TON OF PULP. 



It has been shown that sulphate kraft pulps of fairly good strength 

 and toughness can be obtained from longleaf .pine with yields (bone- 

 dry basis) as high as 61 per cent, or 2,170 pounds per solid cord * in 

 case of wood as heavy as that tested. For the production of the 

 best grades of wrapping papers, which equal or excel in quality the 

 imported sulphate kraft papers, the yield of pulp would be approxi- 

 mately 51 per cent, or 1,800 pounds (bone-dry) per solid cord. This 

 is equal to a ton (2,000 pounds) of nominally air-dry pulp. 2 How- 

 ever, it should be remembered that for wood either lighter or heavier 

 than that on which this calculation is based the amount required per 

 ton of pulp would be correspondingly greater or less, unless the differ- 

 ences in weight were due to resin alone. 3 



COMPARISON OF THE SODA AND SULPHATE PROCESSES. 



Table 3 contains the record of the semicommercial soda tests. 

 The best results in both yield and quality were obtained in the case of 

 cook 152. This cook employed 20 pounds of caustic soda per 100 

 pounds of wood at an initial concentration of 79.7 grams per liter and 

 5 hours' cooking at 110 pounds gauge pressure, the total duration 

 being 6 hours. The resulting paper was very strong (strength factor 

 0.90) and the feel and wearing properties were also exceptionally 

 good for a soda pulp. The yield was 48 per cent, or 1,704 pounds 

 per solid cord. 



TABLE 3. Record of semicommercial tests using the soda process. 



1 Weighing 3,550 pounds; see p. 6. 



2 Standard moisture content of 10 per cent or 100 pounds air-dry weight equals 90 pounds bone-dry 

 weight. 



3 The average specific gravity (oven-dry weight, green volume) of all of the longleaf pine from Louisiana 

 in the shipment from which the two test logs were taken, including bolts cut higher up in the trunks of the 

 same trees and material from several additional trees, was 0.528. (See Forest Service Circular 213, Mechan- 

 ical Properties of Woods Grown in the United States, 1913, Table 1. ) This is equal to a weight per cubic 

 foot of 33 pounds in comparison with the 35.5 pounds obtained for the two butt logs. 



