10(5 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
the absolute humidity very low, it may be necessary after one or two 
hours exposure to lightly sprinkle the trench with water to increase the 
atmospheric moisture thus raising the hydrocyanic acid concentration. 
In fumigating houses or greenhouses it is sufficient to spread out the 
flakes or granular material on newspaper since there is usually sufficient 
atmospheric moisture to decompose the calcium cyanide. In some 
cases damp papers or a moist flower basin might be used but if too much 
water is used the flakes become wet and the calcium cyanide decomposes 
to ammonia and other compounds and the amount of hydrocyanic acid 
evolved will be small. If the flakes are placed in buckets or jars and 
water poured over them a solution of calcium cyanide will be formed 
which does not give off hydrocyanic acid any more rapidly than a 
similar solution of sodium cyanide. 
Dust Mixtures Containing Calcium Cyanide 
In view of the nature of calcium cyanide, it is at once apparent that if 
the dust is to be diluted for dusting purposes, the diluent should be dry 
unless the dilution is made at the time the dust is applied. Combinations 
with sulphur, lime, talc, or clay may be used providing the material is 
dry. Combinations with acid materials such as dusts containing nico¬ 
tine sulphate would completely destroy the calcium cyanide. Nico¬ 
tine dusts containing moisture also represent an incompatible mixture. 
Summary 
Calcium Cyanide is a crude cyanide which reacts with atmospheric 
water vapor producing hydrocyanic acid. 
Calcium Cyanide in contact with a quantity of water forms a solution 
and does not liberate its hydrocyanic acid. 
If the moisture is just sufficient to wet the material a different re¬ 
action occurs with the production of ammonia and other little known 
compounds. 
The success of calcium cyanide dust for the control of insects depends 
upon exposing the insects to a high concentration of hydrocyanic acid 
gas for a very short time. 
Calcium cyanide dust should not be mixed with other materials which 
contain moisture or acids. 
President A. G. Ruggles : The next paper is by Albert Hartzell and 
F. A. Lathrop. 
