THE SUITABILITY OF AMERICAN WOODS EOR PAPER PULP 11 
EXPERIMENTAL PROCEDURE 2 
EQUIPMENT 
In the course of the Forest Service experiments several digesters 
were used for making the cooks. In Figure 1 is shown the lead- 
lined digester which was used until 1911. From 1911 to 1916 the 
same equipment, with the lead lining removed, was used for the 
alkaline cooks only, the equipment shown in Figure 2 being used 
for the sulphite cooks. Since 1916 the equipment shown in Figures 3 
and 4 has been used for the sulphite cooks and that in Figures 5 
and 6 for the alkaline cooks. All these digesters held between 
60 and 70 gallons, and all gave similar results. All were stationary 
with the exception of the one shown in Figures 3, and 4, which could 
be revolved on trunnions to obtain positive circulation. In all 
the digesters except the earliest, indirect heat as well as direct steam 
Fig. 2.— Digester used for sulphite cooks from 1911 to 1916, inclusive 
was supplied in order to overcome the excessive radiation character- 
istic of small-sized apparatus. By that means condensation was 
obtained comparable in amount to that in commerical equipment. 
The chipper used was of the usual disk type but of laboratory size. 
Figure 7 shows the semicommercial beater used, and Figure 8 the 
combination 12-inch cylinder and Fourdrinier paper machine on 
which the paper samples were made. Operating in conjunction 
with the paper machine was a Jordan refining engine of laboratory 
size, so that the results obtained were comparable to mill practice. 
CONDUCT OF TESTS 
The chips, cut five-eighths along the grain, were carefully screened 
to remove sawdust, bark, large pieces, and large knots. Before 
charging, the moisture content of the wood was determined and the 
quantities of cooking chemicals and the volume of liquor were calcu- 
lated from the oven-dry weight of the wood. During cooking, 
2 Tests on chemical pulps only. For experiments on mechanical pulps see Thickens, J. H., and 
McNaughton, G. C, ground-wood pulp. Dept. Agr. Bui. 343, p 151, illus., 1916. 
