INDUSTRIAL FUMIGATION AGAINST INSECTS 



35 



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 disulphide 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 modern vacuum outfits an accumulator tank is utilized to 

 vaporize and heat the fumigant before drawing it into the vacuum 



Figure 32. — End view of vacuum equipment shown in figure 31. Tank at left closerl 

 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 establish- 

 ment. Note end of cylindrical accumulator on top of tank at right. 



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, ethylene oxide-carbon dioxide 

 mixture, methyl formate-carbon dioxide mixture, and carbon cli- 

 sulphide-carbon dioxide mixture are used in vacuum fumigation. 

 The dosage required depends on the commodity to be fumigated 

 and the length of exposure. 



PROCEDURE 



The commodity to be fumigated is first loaded into the vacuum 

 chamber, the doors are tightly closed, and a vacuum of about 28 or 



