24 BULLETIN 309, U. S. DEPART ME XT OF AGRICULTURE. 
liberated during the cooking, there is usually more pressure within 
the digester than the pressure corresponding to the temperature of 
the charge, and since this false pressure is usually unknown it seems 
preferable to employ temperature as the control. 
The results of the tests are shown in Table VII. 
Table VII. — Results of trials of four cooks of zacaton pulp. 
Cook. 
Fiber. 
Relation of 
b one-dry 
fiber. 
Causticity 
of waste 
solution. 
Caustic. 
Wet. 
Bone dry. 
Consumed 
by grass. 
Relation of 
excess. 
Relation of 
consumed 
to added. 
Per cent. 
Pounds. 
No. 11 
Pounds. 
686 
815 
715 
730 
22.8 
20.0 
20.1 
19.8 
156 
163 
143 
144 
Per. cent. 
50.4 
49.7 
47.0 
46.3 
Per cent. 
Per cent. 
Per cent. 
Per cent. 
Xo. 12 
35.3 
38.2 
38.7 
12.0 
11.5 
11.4 
8.1 
8.7 
8.9 
59 
56 
56 
No. 13 
No. 14 
The average yield of fiber at 90 per cent bone dry is 43 per cent of 
the air-dry grass, which would average 80 per cent bone dry. 
The excess caustic soda, 8.1 to 8.9 per cent of the bone-dry grass, 
is doubtless higher than is necessary, and it would indicate that less 
soda could have been employed in the cooking. 
Pulp charges from the four cooks were remarkably similar in 
appearance and feeling; they drained and washed with great ease, a 
property not shared by the pulp of many plants and a fact of great 
importance in a commercial sense, because of the necessity of washing 
out and recovering the spent soda, 
On screening the pulp charges through a No. 10 cut screen there 
remained undercooked screenings to the extent of 2.05 per cent of 
the bone-dry pulp, or 1 per -cent of the bone-dry grass. The screened 
stock bleached easily and to a satisfactory color with the equivalent 
of 12.7 per cent of commercial bleaching powder. 
After washing free from bleach residues, the stock was given four 
hours' medium brushing in a beating engine (fig. 13) and furnished with 
24 per cent of clay, 1.8 per cent of resin size, and 2 per cent of alum. 
At the close of the beating operation the charge was whitened by 
the addition of a small amount of blue or blue and red color, to offset 
the residual yellow tint invariably present in all bleached stocks. 
The finished stock was run through a Jordan refiner and to a 
30-inch Fourdrinier machine speeded to 85 feet per minute. Although 
the stock w T as a little too "free'' to get the maximum felting of the 
fiber it acted very well on the machine and gave a machine-finished 
sheet of good appearance and quality. Physical tests of this sheet, 
designated as Xo. 76, in connection with those of sheet No. 41 are 
given in Table VIII. 
