36 
BULLETIN 80, TJ. S. DEPARTMENT OF AGRICULTURE. 
"When varying the durations and the pressures of cooking and the 
initial concentrations, the amounts of soda ash per ton of pulp were 
affected by yields alone, and the minimum amount is employed under 
conditions which give the maximum yields. Increased durations, 
pressures, and concentrations 
afford decreased yields, and 
the amount of soda ash per 
ton of pulp consequently is 
increased. The platted point 
for cook 10 is not on the curve, 
due to the initial digester 
liquors for this cook having 
had about 3 per cent lower 
causticity than the other cooks 
in this group of tests. Lower 
causticities involve the use of 
a greater amount of soda ash 
for the same amount of caustic 
soda. 
BLEACHING POWDER. 
600 
500 
ft. 400 
_i 
3 
o- 300 
a 
ua 200 
u 
2 wq 
19 
|8 
7 
J 
5 
.20 .30 .40 
POUNDS NaQK PER POUND OF WOOD 
500 
z 
?400 
uj 300 
a. 
w 200 
100 
400 
\ 
\ 
\ 
X 
s ^ 
(4 
13 
■—2!? 
10 
1 
2 4 6 8 10 12 
OURATiQN AT MAX. PSESSURE- HOURS 
o 
ft. 300 
200 
100 
! 
r 
V 
, 2 > 
20~~""-< 
J9 
^ 
>n 
60 
70 80 90 100 110 120 
MAX. PRESSURE-PDS. PER SO. IN. 
200 
100 
40 50 60 70 80 90 100 110 
CONCENTRATION NaOH-GRAMS PER LITER 
Fig. 19.— Effects of cooking conditions on amount of 
bleaching powder employed per ton of pulp. 
cent available chlorine, and losses in 
are disregarded. 
The curves in figure 19 show 
that increasing the amounts 
and concentrations of caustic 
soda and the durations and 
pressures of cooking result in 
all cases in decreasing the 
amounts of bleaching powder 
consumed. 
Yields do not influence the 
calculations, since the con- 
sumption per ton of bleached 
pulp depends on the per cent 
of bleach required and the 
bleaching losses. The ordi- 
nates for the curves represent 
bleaching powder of 35 per 
making the bleaching solutions 
COMBINED COST OF WOOD AND CHEMICALS PER TON OF PULP. 
The curves in figure 20 show costs for certain items in producing 
a ton of bleached pulp (2,000 pounds air-dry basis) as influenced by 
variations in the cooking conditions. Curves marked A represent 
cost of wood alone; curves B, cost of wood and soda ash; and curves C, 
