34 BULLETIN 1296, U. S. DEPARTMENT OF AGRICULTURE 
Very little drying seems to have occurred during storage, except 
in the case of a few laps at the top of the piles before they were inter- 
piled with the decayed commercial ground wood. The average 
moisture for the 81 representative laps sampled at the time of the 
last inspection was approximately 71 per cent, varying for the in- 
dividual specimens between 41 and 81. There were only 17 laps 
below 65 per cent, and 64 between 65 and 80 per cent. 
COMMERCIAL TESTS AT MILL 
Preservative tests, made at two Wisconsin mills, involved approxi- 
mately 2,900 and 4,300 pounds of ground-wood pulp. In both 
cases the preservative was sprayed on the pulp on the wet machine. 
The results of the tests are recorded in Table 13. 
Test A. — At one of the mills 18 preservatives that had appeared 
promising in earlier laboratory tests were used in varying concentra- 
tions with the object of checking them under mill conditions. Several 
of the substances were further diluted in order to determine the 
minimum quantity effective under commercial conditions. 
The treating solutions flowed from a barrel set on a platform about 
4 feet 6 inches above the suction box on the wet machine. The 
barrel was connected to a pipe which was perforated with holes three- 
sixty-fourths inch in diameter and one-half inch apart from center 
to center, the pipe extending along the stretch roll 2 inches above it. 
All pipes were copper. A strip of cloth 5 inches wide hung from the 
perforated pipe and brushed against the pulp. The perforations 
were turnea upward about 45° from the horizontal, thus causing the 
chemical always to flow to the pulp by way of the cloth. 
After treatment the commercial laps were piled in a moist basement 
under the wet-machine room and surrounded by the regular stock. 
(See PI. XIII, fig. 2.) In computing the amount of chemical applied 
it is assumed that 70per cent was retained in the pulp as it came from 
the wet machine. From 25 to 60 pounds of pulp, oven-dry weight, 
were treated with each concentration of preservative. 
Test B. — This test at the second mill included five of the most 
promising preservatives: Boric 1 acid, sodium borate (borax), sodium 
dichromate, sodium dinitrophenolate, and sodium fluoride. The 
solutions were made up in cold water, with the exception of borax 
and boric acid, which go into solution much more quickly in warm 
water. 
The solutions, strained through fine wire mesh, were added to the 
pulp at the top press roll by dripping from a three-eighth-inch brass 
pipe perforated with one sixty-fourth-inch holes spaced three-fourths 
inch apart from center to center. This pipe extended the full width 
of the machine, and was connected with a clean 50-gallon barrel. 
There were two globe valves in the line for regulation of flow. The 
barrel was hung from the ceiling, so that the solution had a minimum 
head of 2 feet. It was slightly tilted to one side, and a clean-out 
hole provided. The rate of flow of the solution was adjusted as 
closely as possible by preliminary trials with the intention of setting 
the second valve at a fixed point and moving only the first, as a cut-off. 
In actual practice, however, it was found necessary to regulate the 
second valve from time to time, according to flow judged by the eye. 
The tendency of the small holes in the pipe to plug was not particularly 
