50 
BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 
the summer time, when the temperature inside the house was 75° to 
80° F. Experiments 13, 19, 29, and 30 were made to decrease the 
dosage needed. All larvae were not killed in experiments 13 and 19, 
where the dosage was 1 pound disulphid to 100 cubic feet with long 
exposures, but all were killed in experiments 29 and 30, with 1 
pound to 85 cubic feet and a 24-hour exposure. 
Table XXVI is a summary of the carbon disulphid experiments. 
From these experiments it is seen that satisfactory results were 
obtained by using 1 pound of carbon disulphid to 80 cubic feet for 
24 hours or longer when the seeds were not over 5 feet deep. 
Table XXVI. — Fumigation of cotton seed with carbon disulphid. 
Dosage. 
Experi- 
Expo- 
Per cent 
larvae 
How seeds were 
ment 
placed. 
No. 
Pounds. 
Cubic 
feet. 
sure. 
killed. 
Hours. 
1 
102 
90 
100 
Seed in bags. 
2 
161 
48 
1100 
Do. 
11 
80 
42 
100 
Do. 
20 
so 
42 
, 100 
Seed in bulk, 5 feet deep. 
21 
80 
48 
100 
Do. 
22 
80 
48 
100 
Do. 
23 
80 
24 
100 
Do. 
29 
85 
24 
100 
Do. 
30 
85 
24 
100 
Do. 
26 
80 
12 
95 
Do. 
19 
100 
48 
94 
Do. 
13 
100 
168 
91 
Seed in bulk, 6 feet deep. 
10 
54 
24 
290 
Seed in bulk, 5 feet deep. 
9 
82 
48 
88 
Do. 
31 
90 
24 
85 
Do. 
27 
80 
15 
82.5 
Do. 
7 
102 
48 
80.5 
Do. 
32 
90 
24 
60 
Do. 
6 
161 
48 
51 
Do. 
5 
161 
23 
37 
Seed in bags. 
8 
124 
48 
17 
Seed in bulk, 5 feet deep. 
4 
161 
23 
13.3 
Seed in bags. 
1 Record doubtful. 
2 Larvae in corked vials. 
Hydrocyanic- Acid Gas. 
The fumigation of cotton seed with hydrocyanic acid gas proved 
very unsatisfactory, as the gas is so light that it will not penetrate 
the seed more than a few inches. In some of the experiments an 
earthenware crock containing the sulphuric acid was set directly on 
top of the seed pile and the cyanid lowered by a string from the 
outside in the usual way. The penetration was so poor that a 
special generator was designed. A section of 10-inch pipe 14 inches 
long was fitted with gas-tight caps on both ends and a lead inner 
pot to hold the acid. The generator was placed outside the house 
below the floor level and the gas conducted to the inside, where it 
was allowed to escape in the bottom of the fumigation chamber 
through perforated pipes. It was hoped that the penetration 
upward would be greater than downward, but there was very little 
difference. 
