June ii, 1917 
Toxicity of Benzene Derivatives to Insects 
377 
less toxic than in the benzene ring. Para configurations seem to be 
more toxic than ortho configurations, while the only meta derivative 
tried was less toxic than either. Although certain relationships exist 
between chemical composition and toxicity, they are not as striking or 
as constant as might be expected. 
BOILING POINTS AND TOXICITY 
In working over the results, the author noticed a relationship between 
the boiling point of the chemical and its toxicity. As many of the com¬ 
pounds bore no guaranty of purity, the boiling points of several were 
determined and a curve plotted, showing the chemicals in order from 
the lowest boiling point to the highest. In comparison, a curve of 
toxicity of these compounds was plotted, as shown in figure 3. The 
curves show strikingly that the higher the boiling point the more toxic 
is the chemical. Exceptions are to be noted, which may be due to the 
r 61 e played by chemical composition in either raising or lowering the 
toxicity; but, in general, the curve is an increase of toxicity with an 
increase in the boiling point. Benzaldehyde shows a break in the curve, 
possibly owing to a specific action of the aldehyde. The low boiling 
point of furfural (96° C.) may account for its toxicity being less than 
would be expected from its chemical composition. Carbon bisulphid, 
having the lowest boiling point (47 0 G.), lower than any of the benzene 
derivatives tested, is likewise the least toxic of all the compounds. 
The explanation of the relationship of boiling point to toxicity has 
not been ascertained. Whether the introduction of a certain element 
or group causes an increase in toxicity incidental to an increase in the 
boiling point or whether it is the relationship of boiling point to vapor 
pressure and volatility is not known. 
BOILING POINT AND LIPOID SOLUBILITY 
Another interesting observation is the relationship between boiling 
point and lipoid solubility. To test the lipoid solubility of the com¬ 
pounds, cephalin was extracted from the brain of an ox by Hirsch- 
felder’s method (2). 
Ox brain was covered with three volumes of alcohol, shaken up two or three times, 
and the excess of alcohol then poured off and squeezed out gently through linen, 
care being taken to avoid great force in wringing out the alcohol, as this tends to break 
up the brain tissue into very finely divided particles which pass through the filter. 
The residue is then covered with three volumes of ether, shaken vigorously, and 
filtered first through cotton and then through filter paper. The clear filtrate thus 
obtained is evaporated to dryness over a water bath and a yellow residue remains. 
The cephalin so prepared was placed in capsule heads of 0.08 c. c. 
capacity and introduced into 1 c. c. of the chemical to be tested. It 
was found that benzene boiling at 78.5° C., toluene at 107.5 0 C., and 
xylene at 130° C. dissolved several capsules of cephalin until it finally 
