INDUSTRIAL FUMIGATION AGAINST INSECTS 33 



directly proportional to the carbon disulfide content, and they should 

 be used accordingly. 



The vapors of carbon disulfide are poisonous to human beings if 

 breathed for an extended period. Exposure to light concentrations 

 may induce a feeling of giddiness, which, however, will quickly pass 

 when the person affected comes into the fresh air. 



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 disulfide. 



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. 



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. The mixture of air with ethylene di- 

 chloride vapor is 1.2552 times as heavy as air at the same temperature 

 and pressure (77° F., 29.9 inches). 



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 trichloro- 

 ethylene. A mixture of 3 volumes of ethylene dichloride with 1 vol- 

 ume of carbon tetrachloride or trichloroethylene is free from fire hazard 

 under ordinary conditions, and is an effective fumigant when used at 

 the rate of 14 pounds per 1,000 cubic feet of space, unless the vault is 

 filled with absorbent material, when a heavier dosage is required. 



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. 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 treating 

 grains and seed, but should not be used for foodstuffs with high fat 



