February, *18] MOORE AND GRAHAM: TOXICITY OF KEROSENE 
73 
higher fractions. In some brands, notably E, the injury from this 
fraction was greater than from any of the other fractions. In con¬ 
sidering the emulsions it is apparent that the soap protected the plants 
from the most volatile portions until such time as it had evaporated, 
hence in emulsions the lower fractions of the oil were less injurious than 
the higher fractions which remained on the plants so long that they 
had an opportunity to penetrate after the emulsion had dried out. 
Some kerosenes can be used at a relatively high concentration with 
little or no injury to the plants, while other brands produce injury 
when as dilute an emulsion as 3 per cent is used. This is more inter¬ 
esting in that A and B, kerosenes from the same field, showed this 
decided difference. This is possibly due to impurities in B which are 
not present in the more highly refined A. The influence of using hard 
water in diluting the emulsion resulted in a greater injury to the plants 
than the spray of the same strength diluted with distilled water. 
The Toxicity of Vapor of Kerosene 
Inasmuch as Shafer 1 considers that it is the vapor of kerosene and 
similar compounds which kills insects when used as a contact spray, 
a study of the vapor of the different brands and their fractions was 
made. 
In testing the vapors the house-fly, Musca domestica Linn., was 
used. The flies were placed in flasks and the amount of material 
required to kill them in 400 minutes was determined as described in 
previous papers by one of us. 2 The results are shown in Table III. 
Table III— Number cc. of Oil per Liter Required to Kill in 400 Minutes 
Oil 
Unfractionated 
First Fraction 
Second Fraction 
Third Fraction 
A 
.006237 
.004158 
.004752 
* 
B 
.005454 
.00297 
.003267 
* 
C 
.00594 
.00297 
.001782 
* 
D 
.005346 
.003584 
.003584 
* 
E 
.006534 
.003861 
.00297 
* 
* Not killed in 400 min. in saturated atmosphere. 
From this table it is evident that only the lower fractions are capa¬ 
ble of killing the insects, the higher fractions not being sufficiently vola¬ 
tile to produce sufficient vapor to kill at ordinary temperatures. 
The amount of liquid of the second fraction which was necessary to 
kill the insects was far in excess of that which would volatilize and 
1 Shafer, G. D. How Contact Insecticides Kill, I and II. Tech. Bui. Mich. Agric. 
Exp. Sta. Bui. 11, 1911. 
2 Moore. Loc. cit. 
