430 
Journal of Agricultural Research 
Vol. XI, No. 9 
Table VI.— Hydrocyanic-acid gas generated in a compact clay-bam soil 
Depth of 
generator. 
Charge 
of sodium 
cyanid. 
Distance of test 
from generator. 
Time elapsing 
after 
fumigation. 
Results. 
Inches. 
24 
Ounces. 
*9 
Inches. 
18 
i minute.... 
No trace of hydrocyanic-acid gas. 
24 
19 
18 
14 hours. 
Do. 
24 
19 
6 
Do. 
24 
19 
Directly at 
.do. 
0.48 per cent of hydrocyanic- 
acid gas. 
0.144 per cent of hydrocyanic-' 
acid gas. 
24 
19 
generator. 
.do. 
60 hours. 
At the top of the hole where the generator had been inserted there 
was no odor of gas at any time during or after the generation. The only 
trace of hydrocyanic-acid gas, except directly at the generator, was just 
6 inches from the generator, and even at this point it was much below 
the point of toxicity to insects. This experiment showed definitely 
that heavy soils are very impervious to this gas. 
Work was now begun on sandy soil. A box 2 feet deep, 20 inches wide, 
and 2 feet 4 inches long was filled with moist sand, the generator being 
placed near the bottom and at one end of the box. Table VII gives the 
results. 
Table VII.— Hydrocyanic-acid gas generated in loose , sandy soil 
Depth of 
generator. 
Charge 
of sodium. 
Distance of test 
from generator. 
Time elapsing 
after fumigating. 
Results. 
Inches. 
20 
Ounces. 
12 
Inches. 
18 
i minute.... 
0.12 per cent of hydrocyanic- 
acia gas. 
0.3 per cent of hydrocyanic- 
20 
12 
18 
16 hours. 
20 
12 
18 
64 hours. 
acid gas. 
Faint trace. 
By comparing the first and second reading it will be seen that several 
hours are required for the gas to diffuse even a short distance in the sdil. 
When the gas was first generated the odor was very noticeable near the 
generating box and also when the box was emptied after taking the 
last of the three readings. The gas, which is temporarily absorbed by 
the water, is given off again as the partial pressure in the soil atmos¬ 
phere decreases. 
The water in the soil takes up large quantities of gas and retains it in 
solution a long time, so that, even though the concentration of gas in any 
soil might not be great enough to be fatal to insects on a short exposure, 
yet with the longer periods of time which we seem to have in soil work, 
there is a possibility of a smaller dose being effective than would be the 
case where the gas escapes more quickly. 
LABORATORY STUDY OF SOIL ABSORPTION 
From the above experiment it was seen that the gas was either being 
absorbed by the soil moisture, adsorbed 1 by the soil particles, or that 
it reacted chemically with the soil constituents. 
