46 BULLETIN 1298, U. S. DEPARTMENT OF AGRICULTURE 
washed pulp may be left somewhat darker than normal. About 14 
pounds of ground wood and 22 pounds of sulphite were treated with 
sodium dinitrophenolate at the laboratory; 430 pounds of ground 
wood were treated at the mill. From 1 to 2 pounds of chemical per 
ton preserved the pulp from decay for periods up to 16 months, but 
did not prevent all molding. Up to six months these concentrations 
proved highly efficient. On sulphite, 3 pounds per ton almost 
perfectly preserved the pulp for 24 months. Concentrations of 4 
pounds and higher are somewhat more effective, but they color the 
pulp rather too yellow. 
Sodium dichromate is a reddish-brown substance readily soluble in 
cold water, yielding an orange-yellow solution. When applied at the 
rate of about 30 pounds per ton it immediately stains the pulp a 
slight yellow, and the discoloration, on standing, becomes brownish, 
darkening the pulp somewhat. Although classed as a poison, 
sodium dichromate is not considered dangerous to handle. About 
45 pounds of ground wood and 11 pounds of sulphite were treated 
with this preservative at the laboratory; 230 pounds of ground wood 
were treated at the mills. The addition of 8 pounds of chemical 
per ton at one mill preserved the pulp for seven months. From 14 to 
28 pounds of chemical per ton at another mill permitted only slight 
molding in 16 months. The laboratory results were not so good. 
Ten pounds per ton preserved the pulp for three months but failed 
in six months. (PI. XIV, fig. 2.) From 20 to 33 pounds per ton 
kept it in rather good condition for 6 months, but failed in 13 
months. The sulphite pulp held up better than ground wood. 
COMMENTS ON OTHER CHEMICALS 
Beta naphthol (1 pound per ton) failed, under a severe laboratory 
test, to preserve ground wood for as long as 13 months, but 6 pounds 
per ton almost perfectly preserved sulphite pulp for 2 years. Because 
this substance is but slightly soluble in water, it was applied in sus- 
pension. Dusting the dry chemical on the pulp may prove a better 
procedure. 
Copper acetate gave unfavorable results when used at the rate of 10 
pounds per ton. Thirty-seven pounds per ton gave rather good 
results. It browns the pulp considerably. 
Copper acetoarsenite (Paris green) gave efficient protection when 
used at a rate of 7 pounds per ton. It is too poisonous to handle, 
however, and gives a deep green surface discoloration to the pulp. 
Copper sulphate at a rate of 78 pounds per ton gave considerable 
protection. 
Diclilorobenzol was highly effective in the excessive amounts em- 
ployed, and further tests should be made at lower concentrations. 
It was used in the form of a crude oil, but dilute emulsions in water 
probably can be easily made. It is volatile, and the odors are oppres- 
sive in a closed space but not particularly poisonous. It is used in the 
crystalline form as a very effective insecticide in herbaria, etc. 
Dinitrochlorohenzol proved very effective when applied at the rate 
of 6 pounds per ton, but on account of its highly poisonous properties 
it can not be recommended as a pulp preservative. 
Lysol (96 pounds per ton) protected the pulp from decay but per- 
mitted severe molding. 
