Aug. I3.I9I7 Volatility of Organic Compounds 371 



condensed upon reaching their finer divisions. If the compound is very- 

 volatile, it will evaporate and readily pass out of the insect, while if very 

 slightly volatile it will remain in the insect, and will penetrate the tissues 

 and produce the poisonous reactions which lead to the insect's death. 

 In higher animals, when the compound is taken into the lungs, it is 

 rapidly removed by the blood and carried to all parts of the body, giving 

 it an opportunity to react chemically with the tissues. For this reason 

 the toxicity of volatile organic compounds is more closely correlated with 

 the chemical composition when introduced into the higher animals, 

 while in insects toxicity is more closely associated with volatility than 

 with chemical composition. 



SUMMARY 



In general, the toxicity of a volatile organic compound is correlated 

 closely with its volatility. 



A decreasing volatility is accompanied by an increased toxicity. 



The boiling point of the chemical is a general index of its volatility. 



Compounds with boiling points of 225° to 250° C. are usually so 

 slightly volatile that they do not produce death except after very long 

 exposures. 



The structure of the respiratory system of the insect is probably 

 responsible for the remarkable influence of volatility on the toxicity of 

 the vapor of volatile organic compounds. 



