THE TOBACCO BEETLE. 55 
FUMIGATION. 
Fumigation is now generally employed as a means of destroying 
certain classes of insects, and is a standard remedy against insects 
which damage stored products and those infesting mills and fac- 
tories. , 
The tobacco beetle has been found to be exceedingly resistant to 
fumigants. Numerous experiments have shown that it is necessary 
to use much stronger dosages of fumigants in treatment of this 
beetle than are employed usually against other insects. The insula- 
tion afforded by the pupal cells and by the compactness of food sub- 
stances seems to protect the contained larvee or pupe from the action 
of the fumigant. In many instances only a small percentage of the 
tobacco-beetle larvee survives treatment, but adults transforming 
from these small numbers serve to reinfest tobacco if it is kept for 
any length of time. 
The properties and characteristics of the various chemicals used 
for fumigation should be thoroughly understood in every particular 
by the operator in order that necessary precautions may be taken 
and the work properly done. ‘The treatment is simple, however, 
easily applied, and fairly effective. 
FUMIGATION WITH HyYDROCYANIC-ACID GAS. 
In generating hydrocyanic-acid gas in fumigation sodium cyanid 
(NaCN), or potassium cyanid (KCN), sulphuric acid (H,SO,), 
and water are necessary. The hydrocyanic-acid gas, which is the 
killing agent, is produced by the action of the sulphuric acid (diluted 
with water) on the sodium or potassium cyanid. The cyanid is 
usually employed in the crystal form. It .is now sold in molds 
weighing 1 ounce each. When small quantities are used, this form 
is best, as it avoids the trouble and danger of weighing. A high 
grade of cyanid should be used for fumigation, as the presence of 
adulterants greatly reduces the amount of hydrocyanic-acid gas 
evolved. Potassium cyanid should be guaranteed to be 98 or 99 
per cent pure. A high grade of sodium cyanid should be used 
which is guaranteed to contain not less than 51 per cent cyanogen. 
Commercial sulphuric acid, sp. gr. 1.84 or 66° Baumé, which is 
approximately 93 per cent pure, is commonly used for fumigation. 
DANGER ATTENDING USE. 
Hydrocyanic-acid gas and the chemicals employed to produce it are 
extremely dangerous, and as hydrocyanic-acid gas is fatal to human 
beings uf breathed in any quantity considerable care is necessary in 
ats use. Sodium cyanid and potassium cyanid are violent and fatal 
poisons if taken internally, and sulphuric acid produces burns when 
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