64 
■ large propoitiOD Of this compound, and the pure substance itself, wen- worked 
out, but do large batches wore made. The toxicity of this compound apparently 
disappears rather rapidly utter application to foliage, perhaps 1 
volatility. 
Fundamental studies of the characteristici of oil emulsions, t<> develop specifi- 
cations for the preparation and mode of application of the be* le in- 
BecticidaJ preparations of this nature, have been continued at the laboratory ar 
Wooster, Ohio. Particular attention was paid to the development of meat 
estimating oil deposits, as insect iridal ellicacy is primarily dependent upon the 
quantity of oil that adheres to the foliage of a sprayed plant, in previous 
yean it was found possible to recover and measure highly refined mineral-oil 
deposits, but the method is tedious, and it fails with vegetable oils; SO atten- 
tion was turned to laboratory methods, and in some cases it was found DOC 
to predict the oil deposits on chrysanthemum foliage by means of experiments 
made with paraffined plates. Studies have also been made to lind other ln- 
secticidal materials which, when added to oil emulsions, would dissolve in the 
oil phase and enhance its insecticidal or OYidda] effect, particular attention 
being directed to oil-soluble combinations of nicotine. Two promising t>p 
materials were found, namely, a combination of nicotine with beta-naphthol and 
the nicotine salts of the halogcnated fatty acids. 
At Manhattan, Kans., a study was begun of several problems connected with 
the fumigation of Hour mills and Hour products. Determinations of the con- 
centration of hydrocyanic acid gas in typical fumigations were made, ami the 
superiority of fumigating the milling machinery rather than the mill as a 
whole was demonstrated. The importance of maintaining a high vacuum in 
connection with vacuum fumigation <>f flour products was demonstrated. The 
great effect the load of dour has in absorbing the hydrocyanic acid, hence 
requiring larger dosages than the size of the chamber would seem to indicate, 
was shown. 
In connection with experiments conducted in cooperation with the Bureau 
of Plant Industry to determine the effect of washing on the removal of spray 
residues on apples, numerous analyses wore required, many being made in. 
replicate to furnish data for statistical study of variations. Two special e 
of the variation to be expected among the apples in a sample were mad. 
individual apples from an unwashed lot being run at Washington, D 
100 groups Of 2 apples from a washed lot being run at "Wemucheo. Wash. The 
r lot showed an extreme variation from O.OTH* to 0.214 around a mean of 
0.140 grain per pound, and the latter lot a range from 0.000 to 0.060 around a 
mean of 0.028. 
Considerable work was done on the determination of spray rosidu. 
rotenone and nicotine deposited by sprays containing derris, cube, and various 
nicotine mixtures. The red colorimet ric test tor rotenone previously dev- I 
proved fairly suitable Cor following the loss of derris deposit after spraying, 
and the nicotine could also be determined satisfactorily. 
A Btudy was made of the lead and arsenic content of n chewing to! 
and T snuffs, requiring the development of satisfactory methods of analysia 
In the Bamples analyzed, the lead content ('( the chewing t" 
from 0.025 to 0.610 grain per pound, and of the snuffs from 
grain per pound. The arsenic content proved in some cases to be higher than 
was expected on the basis that had arsenate had been used, but tins may 
have been due to the additional use of other arsenical-. 
A new line of work was undertaken in the form of an investigation of 
ory materials used to improve the -(ability or ease i'i Application of 
Insecticides. Stress Was laid upon the study of wetting and spreading agents. 
At the College Park, Md., station a study of the sulphated higher alcohols. 
which have recently come into prominence as suggested aids in the removal 
of spray residue from fruit, was undertaken, and it was found that. whereas 
they do not break down immediately in acid solutions as tin* BOaps do, they 
do undergo hydrolysis and hence should be freshly prepared. At Washington, 
D I !., a phy8iCOChemlca] study of wetting and Spreading power was begun. 
making USe of measurements of surface tension ami interfacial tension against 
:i standard petroleum oil. Detailed studies were made ^t some soap solutions, 
from which the great dependence of wetting power on concentration and on 
the ratio of alkali to fatty add Is easily >een. Numerous commercial wetting 
.■iLTents have been studied, ami the claims for some of them shown to be 
extravagant in the course of this work two qualitative methods of visually 
demonstrating moderate differences in wetting and spreading power were de 
