168 FUMIGATION METHODS 
far as combustion is concerned. ‘The gas is non-ex- 
plosive when used at or below 0.25 gramme potassium 
cyanide per cubic foot of space enclosed, other condi- 
tions being normal. We have asked Dr. H. W. 
Wiley, Chief of the Bureau of Chemistry, United 
States Department of Agriculture, for his opinion re- 
garding this matter, and quote the following letter 
from him: 
‘“Cyanogen gas, or hydrocyanic acid gas, mixed 
with air or oxygen, forms an explosive mixture, but I 
should not think that in the proportions you mention, 
viz., 0.25 gramme of potassium cyanide for each cubic 
foot of air space, it would produce an atmosphere 
which would be explosive. Hydrocyanic acid, how- 
ever, is combustible and could be mixed with air, I 
presume, so as to form an explosive mixture. I have 
looked over the authorities, but can find no mention 
of explosive properties. 
‘* The danger of hydrocyanic acid, in my opinion, ts 
not from tts explosive properties, but from its highly pot- 
sonous nature. Small quantities of hydrocyanic acid 
gas inhaled are extremely poisonous, and are apt to 
produce fatal results. Jt would be equivalent to instant 
death for any one to enter a building filled with it. 
‘‘While I do not think there would be danger of 
an explosion in the proportions you mention (0.25 
gramme), I would advise great circumspection in the 
introduction of a light, unless it be an incandescent 
electric light, enclosed in an air-tight globe. Such 
lights should always be used where there is any danger 
of explosion.’’ 
Practical application.—The following testimonials 
