VOLATILITY OF ORGANIC COMPOUNDS AS AN INDEX 

 OF THE TOXICITY OF THEIR VAPORS TO INSECTS ^ 



By W11.LIAM Moore, ^ 

 Head of Section of Research in Economic Zoology, Minnesota Agricultural Experiment 



Station 



INTRODUCTION 



In a previous paper ' the writer pointed out the relationship between 

 the toxicity of various benzene derivatives and their boiling points, 

 citing the literature. The question arose whether a similar relationship 

 of boiling point and toxicity existed among other volatile organic com- 

 pounds. Early in the work it was discovered that boiling point was 

 merely a convenient general index of the volatility of the compound and 

 that the real relationship was probably between toxicity and volatility. 

 It was at first thought that this relationship existed only with compounds 

 having an action on lower organisms similar to that of chloroform and 

 ether, but it was soon found to have a wider range of application. 



METHOD OF EXPERIMENTATION 



In general, the same methods were employed as in the previous work.' 

 In order to hasten the rate of diffusion of the vapor throughout the 

 flask, the piece of filter paper, with the chemical to be tested, was sus- 

 pended in the center of the flask by means of a fine wire. The lead foil 

 covering the stoppers was attacked by some of the acids used in the expe- 

 riments, making it necessary in these cases to coat the stoppers with 

 collodion. Many of the chemicals produced anesthesia, and, although 

 the flies shovved no signs of life, they recovered upon being removed 

 from the flask. A new method was therefore employed in determining the 

 amount of the chemical necessary to kill in 400 minutes. Flasks contain- 

 ing varying quantities of the chemical were started and all were stopped 

 400 minutes later. These exposed to the smaller doses usually revived; 

 with slightly stronger doses only a partial revival was noticed; while the 

 larger quantities of the chemical resulted in death. In this manner the 

 actual amount necessary to kill in 400 minutes was determined. 



In studying the volatility 0.5 c. c. of the liquid was spread over a 

 ground-glass plate and the time necessary for this quantity to evaporate 

 noted. Solids were powdered, and i gm. was spread out on the glass to 



1 Published, with the approval of the Director, as Paper No. 66 of the Journal Series of the Minnesota 

 Agricultural Exi)eriment Station. 



* The author wishes to express his thanks to Dr. R. A. Gortnerand Dr. A. D. Hirschf elder for suggestions 

 as to various chemicals to test and for samples of many of these chemicals, to Dean Frankforter and the 

 School of Chemistry for certain other chemicals, and to S. A. Graham for considerable of the routine work 

 of the investigation. 



' Moore, William. The toxicity of various benzene derivatives to insects. In Jour. Agr. 

 Research, v. 9, no. 11, p. 371-381. 1917. 



Journal of Agricultural Research, Vol. X, No. 7 



Washington, D. C. Aug. 13, 1917 



jk Key No. Minn. 7 



100303°— 17 4 (365) 



