INDUSTRIAL FUMIGATION AGAINST INSECTS 31 



Carbon disulphide ranges in cost from about 6 cents a pound in 

 500-pound lots to 30 cents a pound in 1-pound lots. 



CARBON TETRACHLORIDE 



Carbon tetrachloride is a colorless, volatile liquid having a boiling 

 point of 170° F. Its vapors are noninflammable, and therefore it 

 is sometimes recommended as a fumigant in place of carbon disul- 

 phide. 



It is not very effective when used alone against insects that infest 

 stored products and should be chosen only when no other fumigant 

 will do. Its chief use is for mixing with more toxic fumigants to 

 reduce the fire hazard. 



To be at all effective, it must be used at a temperature of 75° F. or 

 higher, and at the rate of at least 30 pounds per 1,000 cubic feet of 

 space. It is applied by pouring it into the evaporating pan of the 

 vault. The vapors of carbon tetrachloride have an anesthetic effect 

 when breathed by man. Although they are not quickly toxic, it is 

 not safe to remain for any length of time in a strong concentration of 

 the gas. 



The cost of carbon tetrachloride ranges from about 5.8 cents per 

 pound in large quantities to 10 cents per pound in small lots. 



ETHYLENE DICHLORIDE 



Ethylene dichloride is a colorless liquid with an odor similar to 

 that of chloroform. It has a boiling point of 183.2° F., and on ex- 

 posure to air it evaporates, forming a gas that is more than three times 

 as heavy as air. It is an effective fumigant in gastight vaults, but 

 owing to its high boiling point it should be used at a temperature 

 of at least 70° F. and preferably somewhat higher. 



The vapors of ethylene dichloride are slightly inflammable. It 

 is therefore customary to use this fumigant in combination with 

 some noninflammable chemical, such as carbon tetrachloride or 

 trichloroethylene. A mixture of 3 volumes of ethylene dichloride 

 with 1 volume of carbon tetrachloride or trichloroethylene is free 

 from fire hazard under ordinary conditions, and is an effective fumi- 

 gant when used at the rate of 14 pounds per 1,000 cubic feet of 

 space. 



This fumigant is applied by pouring it or forcing it under pres- 

 sure into the evaporating pan of the vault. A small fan blowing 

 on the surface of the liquid insures a more rapid vaporization of the 

 fumigant and hastens its killing action. 



The vapors of ethylene dichloride have an anesthetic effect upon 

 man, and although it is safe to use in small quantities, one should 

 not be exposed to a heavy concentration of the gas for more than 

 a very brief period without a gas mask. 



The mixture of ethylene dichloride and carbon tetrachloride or 

 trichloroethylene has no corrosive action on metals or any bleaching 

 or staining action on textiles of any sort. It is suitable for treat- 

 ing grains and seed, but should not be used for foodstuffs with a 

 high fat content, for they are likely to retain a disagreeable odor 

 and taste after fumigation. 



Ethylene dichloride can be purchased separately or already mixed 

 with carbon tetrachloride or trichloroethylene. Alone or mixed 



