370 



Journal of Agricultural Research 



Vol. X. No. 7 



TablS I. — Relation of the volatility of organic compounds to their toxicity 



DISCUSSION OF RESULTS 



Holt/ working with the cockroach, states that the toxicity of a volatile 

 organic compound increases as the boiling point increases, up to a certain 

 point, beyond which an increase in boiling point is accompanied by a 

 decrease in toxicity. In the writer's own work the results show an 

 increase in toxicity up to where the compound is so slightly volatile (b. p. 

 225° to 250° C.) as to be of no value. Holt used a fixed quantity of each 

 compound in uniform flasks, giving the time required as an index of 

 toxicity. Under such conditions a larger quantity of a high boiling point 

 compound than would volatilize was placed in the flask. Although such 

 compounds required longer to kill the cockroaches in Holt's flasks, the 

 amount of vapor which produced the death was much less than was con- 

 sidered to be the case. The apparent decrease in toxicity in his experi- 

 ments was really an increase, since the dose was greatly diminished, 

 although the period of time was increased. The question naturally 

 arises as to why the volatility of a chemical should be related to its 

 toxicity. The following seems to be a reasonable explanation. The 

 vapor present in the air is taken into the tracheae of the insects and is 



1 Holt, J. J. H. ths cockroach; its destruction and dispbrsal.' In I,ancet, v. 190, no. 4840, p. 

 1136-1137. 1916. 



