Nov. 26, 1917 
Hydrocyanic-Acid Gas as a Soil Fumigant 
423 
In the concentration of 0.0156 gm. of sodium cyanid per liter (equiva¬ 
lent to 0.0046 per cent of hydrocyanic-acid gas over the solution) many 
of the flies were dead at the end oiiyi hours; the others, being apparently 
normal, were freed. A second series of experiments with hydrocyanic- 
acid gas was made on the following insects: Phylloxera {Phylloxera 
vastatrix ), tree hoppers {Stictocephala festina), leaf hopper {Agallia sp.), 
houseflies (Musca domestica), beetles (Diabrotica soror), with the results 
given in Table II. 
Table II .—Effect of hydrocyanic-acid gas on insects 
[Time of exposure one hour] 
Sodium 
Approxi¬ 
mate con¬ 
Effect on insects experimented upon. 
cyanid 
per liter. 
centration 
of gas above 
liquid. 
Phyllox¬ 
era. 
Leaf 
hoppers. 
House¬ 
flies. 
Beetles. 
Gm. 
1. 0 
Per cent. 
O. 3 
Dead... 
Dead... 
Dead... 
Dead. 
. 5 
• 1 5 
...do_ 
...do- 
...do.... 
Do. 
•25 
•075 
...do_ 
... do_ 
...do- 
Do. 
. 125 
•0375 
...do_ 
...do_ 
...do.... 
Do. 
.0625 
. 0187 
...do_ 
...do_ 
...do_ 
Alive. 
. 0312 
.0093 
...do_ 
...do_ 
...do.... 
Do. 
.0156 
. 0046 
...do_ 
.. .do.... 
...do- 
Do. 
. 0078 
.0023 
...do_ 
...do_ 
10 per 
Do. 
.0039 
. 0011 
Alive... 
Alive... 
cent 
alive. 
Alive... 
Alive. 
A concentration of approximately 0.0046 per cent hydrocyanic-acid 
gas in the atmosphere within the test tube was the minimum point of 
toxicity to flies in both experiments. For beetles a gas eight times as 
strong—that is, 0.037 P er cent of hydrocyanic-acid gas—is necessary to 
cause death. 
GERMINATION TESTS WITH HYDROCYANIC-ACID GAS SOLUTIONS 1 
Tests were made on alfalfa (Medicago sativa ), turnip (Brassica rapa ), 
com (Zea mays), and lettuce (Lactuca sativa) seed to determine the 
effect of hydrocyanic-acid gas solutions on germination. Glass tumblers 
were used as containers for the solution, the seeds being placed in the 
glass on swings which just touched the surface of the water. The 
tumblers were sealed with paraffined paper held in place with a rubber 
band. The temperature of the room throughout the experiment ranged 
from 19.5 0 to 24 0 C. Fifteen dilutions of the hydrocyanic-acid gas solu- 
1 One point should be noted in this entire series of experiments—viz, the possibility of a very slight excess 
of sulphuric add in the solution of hydrocyanic-add gas. With these experiments it was the intention to 
use just enough sulphuric acid to combine with the sodium and free all the hydrocyanic-acid gas. In some 
cases all the add might not have been neutralized and possibly would of itself cause some injury, or the 
sodium sulphate, one of the products resulting from the reaction of sulphuric add with sodium cyanid, 
might also have some action on the plant. 
