6 
into the digester or autoclave, the amounts of each chemical per 
pound of chips (bone-dry basis) was in the desired proportion, and 
the concentration of chemicals in the digester liquor (including the 
water in the chips) was of the desired degree. For soda cooks the 
procedure was similar, except that caustic soda was the only chemical 
to be taken into consideration. The general procedure in conducting 
the tests was as follows : 
The chips to be used for a cook were sampled and weighed. By 
means of the sample the amount of moisture in the chips and the 
equivalent bone-dry weight of the charge were determined. The chips, 
together with the cooking liquors, were then charged into the auto- 
clave or digester, and the vessel closed. After a cook was completed 
the crude pulp obtained was washed thoroughly, pressed to remove 
water, shredded, weighed, and sampled for determining its equivalent 
bone-dry weight. The pulp was then mixed with water and treated 
in a Hollander-style beating engine 1 with the roll barely touching 
the bedplate (light brush) until the soft chips in the pulp had 
become disintegrated into fibers and the wet fibers had a smooth, 
slippery feel. The beater roll was then pressed hard down on the 
bedplate (stiff brush), and the beating operation continued until 
the pulp was suitable for making wrapping paper, as determined by 
its "feel." The beaten pulp was then screened through the slots 
(0.012 inch width) of a diaphragm pulp screen. In all cases the 
screenings obtained were so small hi amount that they were dis- 
regarded in the yield calculations. The semicommercial pulps were 
run over a Pusey and Jones 15-inch Fourdrinier paper machine into 
rolls of dry paper, while the autoclave pulps were made up into sheets 
on a small hand mold. The papers thus produced contained the 
experimental pulps alone, without the addition of any other materials. 
DETERMINATION OF YIELDS AND PROPERTIES. 
The yield of pulp (bone-dry basis) is usually expressed as a per- 
centage of the bone-dry weight of the chip charge, both weights 
being determined as explained above. When yields per cord are 
given they are based on a "solid cord" containing 100 cubic feet of 
clear wood (green volume) having a bone-dry weight of 35.5 pounds 
per cubic foot; 2 or 3,550 pounds per cord. 
The strengths of the papers from the semicommercial pulps were 
determined by means of a Mullen paper tester, five "pop tests" being 
made on double thicknesses of each paper. The value is expressed 
as a "strength ratio," which is the average of the five test values in 
pounds per square inch divided by the average sheet thicknesses 
1 A 25-pound Emerson beater was used for the semicommercial tests and a 1-pound Noble and Wood 
beater for the autoclave tests. Both makes were equipped with steel fly bars and steel bedplate bars. 
2 This was the average bone-dry weight of the two butt logs of long leaf pine from Louisiana, the 
material used in the tests for which yields per cord are given. 
