48 BULLETIN 1298, TJ. S. DEPARTMENT OF AGRICULTURE 
Alphanaphtylamine, aluminum fluoride, aluminum sulphate, potas- 
sium bromate, potassium permanganate, salol, sodium aluminate, 
and sodium sulphocarbolate seemed to check all the molds except 
those causing the neutral gray discolorations, but they did not 
control the wood-destroying fungi. 
Potassium permanganate colored the pulp a dark brown, but the 
wood-destroying fungi bleached out this color. 
PRESERVATIVES RECOMMENDED FOR MILL APPLICATION 
Of the preservatives reported upon, sodium fluoride shows the 
highest antiseptic effectiveness and the fewest objectionable features 
for mill application. Cost is the main objection to it. Borax is a 
close second. 
Boric (boracic) acid is equal or somewhat superior to borax, but 
its greater cost throws it out of competition. 
A combination of naphthalene and cymene in the proportions rec- 
ommended above, promises to be nearly as effective as sodium fluo- 
ride, and is very much cheaper. 
Sodium dinitrophenolate, applied at the rate of 2 pounds per ton, 
appears very promising. In antiseptic efficiency it is equal to any- 
thing tried, but the yellowish chemical discoloration it causes may 
render the pulp objectionable for some purposes. This stain, how- 
ever, readily washes out, although it may leave the pulp somewhat 
browner than normal. 
Sodium dichromate did not seem to give quite as good results as 
the four substances just mentioned. Its antiseptic efficiency varied 
rather too widely in the tests, and its tendency toward browning of 
the pulp was rather marked, particularly when applied at a rate of 
32 pounds per ton. 
Preservative solutions should be applied at the press roll, in which 
case the retention is about 70 per cent for a 5 per cent solution. The 
loss of chemical in the white water must be compensated for in order 
to get the necessary actual concentration in the pulp. There is no 
danger of the treated pulp sticking to the rolls. 
Preservative solutions can not be effectively applied to pulp in 
storage, either before or after infection has taken place. Any 
method of dipping or spraying that would be satisfactory would not 
be economically feasible. It thus appears a much simpler matter to 
prevent the development of molds and decay than to stop it. 
Aside from technical difficulties in application the deciding factor 
in the commercial use of smy chemical is its cost, and this fact has 
not been lost sight of in this investigation. 
On the assumption that the pulp normally leaves the wet machine 
one-third dry, the cost of various chemicals per ton of air-dry pulp, 
at the market prices of July 9, 1923, would be as follows: 
Cost 
per ton 
of pulp 
Borax, 80 pounds per ton, at 5}4 cents per pound $4. 20 
Boric acid, 80 pounds per ton, at 10 cents per pound 8. 00 
Crude cymene, 6 pounds per ton, at 634 cents per pound, and crude naph- 
thalene, V/% pounds per ton, at 3 cents per pound . 42 
Sodium fluoride, 48 pounds per ton, at 8% cents per pound 4. 20 
Sodium dinitrophenolate, 2 pounds per ton, at 40 cents per pound (for 
dinitrophenol) . 80 
Sodium dichromate, 16 pounds per ton, at 8 cents per pound 1. 28 
