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 larvae or pupse from the action 

 of the fumigant. In many instances only a small percentage of the 

 tobacco-beetle larva? 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 loork properly done. The treatment is simple, however, 

 easily applied, and fairly effective. 



Fumigation with Hydrocyanic-acid Gas. 



In generating hydrocyanic-acid gas in fumigation sodium cyanid 

 (NaCN), or potassium cyanid (KCN), sulphuric acid (H 2 S0 4 ), 

 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° Baume, which is 

 approximately 93 per cent pure, is commonly used for fumigation. 



DANGER ATTENDING USE. 



Hydro cyanic- acid gas and the chemicals employed to produce it are 

 extremely dangerous, and as hydrocyanic-acid gas is fatal to human 

 beings if breathed in any quantity considerable care is necessary in 

 its use. Sodium cyanid and potassium cyanid are violent and fatal 

 poisons if taken internally, and sulphuric acid produces burns when 



