SUITABILITY OF LONGLEAF PINE FOR PAPER PULP. 11 



All things considered, cooks 147 and 148, which may also be classed 

 with those of medium severity, gave the best results. These two 

 cooks were made under almost duplicate cooking conditions, approxi- 

 mately as follows: Caustic soda and sodium sulphide charged per 100 

 pounds of chips, 15 and 7.5 pounds, respectively; initial concen- 

 tration of caustic soda in digester liquor, 26.5 grams per hter; initial 

 volume of digester liquor per pound of chips, 0.68 gallon; total 

 duration of cooking, 3.5 hours, of which 2.8 hours for cook 147 and 

 3.0 hours for cook 148 were at a maximum gauge pressure of 100 

 pounds per square inch. 



The crude pulps were slightly raw and contained some soft chips, 

 which, however, broke up in the beater. The pulp from cook 148 

 was hydrated during the beating treatment to such an extent that the 

 paper made from it had a parchment-hke appearance, the individual 

 fibers being scarcely distinguishable from each other. This paper 

 had good wearing properties and was very tough, with a strength 

 factor of 0.77. The pulp from cook 147 was not subjected to so 

 long a beating treatment, and the resulting paper was not parch- 

 mentized to the same extent as that from cook 148. It had a strength 

 factor of 0.71, however, was very tough, and showed good wearing 

 properties. The yield from cook 148 was 48.4 per cent, or 1,718 

 pounds per solid cord, and from cook 147, 49.1 per cent, or 1,743 

 pounds per solid cord. 



EFFECTS OF BEATING. 



The mechanical treatment given a kraft pulp has as important 

 an influence on the properties of the resulting paper as the cooking 

 treatment itself. A crude pulp which appears to be of little value 

 can be made into strong high-grade paper if the proper beater treat- 

 ment is employed, while the best pulps can easily be ruined by 

 improper beating. The use of koUergangs or edge runners preUmi- 

 nary to actual beating, or of stone roUs and bedplates in the beaters, 

 and the determination by successive tests of the refining and beating 

 treatments best adapted for a particular pulp undoubtedly would 

 have resulted in papers of much better quahty than those obtained. 

 Nevertheless, many of the experimental papers were equal or superior 

 to commercial kraft papers. 



The effect of different beater treatments was shown by a single 

 series of tests on some of the crude pulp from cook 71 (Table 1). 

 Separate portions of the pulp were treated in the 1 -pound beater 

 for periods of 0.5, 1, 2, 3, and 4 hours with the roU at light brash. 

 The papers resulting from treatments of 2 hours or less were soft and 

 weak, and had poor wearing properties, but for the longer periods the 

 papers were firm and tough, with good wearing properties. Under 

 the 4-hour treatment the fibers became hydrated, and a parchment- 

 hke paper resulted. The fibers of longleaf pine when reduced by the 

 sulphate process seem to take up water and to become hydrated very 



