INDUSTRIAL FUMIGATION AGAINST INSECTS 



37 



tion obtained. By means of a bypass from the exhaust to the multi- 

 ple gas-inlet system the vacuum pump can be utilized to circulate the 

 gas in the tank. This feature is now standard equipment with some 

 tanks. 



The use of a vaporizer in connection with a vacuum chamber in- 

 creases its efficiency by insuring the entrance of the fumigant in a 

 gaseous state. The most common type of vaporizer consists of a steel 

 tank in which steam is generated by means of electric heating elements. 

 A copper coil, through which the fumigant is conducted, runs through 

 this steam-heated tank and is so designed that the fumigant is in 

 gaseous form by the time it reaches the vacuum chamber. If carbon 



Figure 28. — End view of vacuum equipment shown in figure 27. Tank at left 

 closed and under fumigation. Tank at right nearly loaded with 43,000 

 pounds of Turkish tobacco. These tanks will treat all incoming tobacco 

 placed in this storage establishment. Note end of cylindrical accumulator 

 on top of tank at right. 



disulfide is used, a specially designed vaporizer is required, since it 

 must be mixed with carbon dioxide before it is admitted to the 

 fumigating chamber. 



In some vacuum outfits an accumulator tank (fig. 27) is utilized to 

 vaporize and heat the fumigant before drawing it into the vacuum 

 chamber. It consists of a tank with a heating coil into which the 

 dosage is drawn, and in which it can be held until ready for use. 



Hydrocyanic acid, chloropicrin, methyl bromide, and mixtures of 

 carbon dioxide with ethylene oxide, methyl formate, and carbon di- 

 sulfide are used in vacuum fumigation. The dosage required de- 

 pends on the type and quantity of the commodity to be fumigated, its 

 temperature, and the length of exposure. 



