BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 45 
The commercial synthesis of the pyrethroids is now being investi- 
gated. If the process proves feasible, the United States will no longer 
be dependent on imports of pyrethrum flowers, which have amounted 
to as much as 20,000.000 pounds in 1 year. Pyrethrum is a strategically 
important material, which is now obtained entirely from foreign 
sources. Owing to the need for large quantities by the armed forces 
during the war, there was a critical shortage of pyrethrum for agri- 
cultural uses. Although many synthetic organic insecticides have 
been developed in recent years, prior to the synthesis of these pyre- 
throids, no satisfactory substitute for pyrethrum insecticides had 
been found for certain uses. 
Chemical Methods for Parathion Developed 
A method has been developed for purifying parathion in order to 
obtain material for use as a standard in analytical work or other in- 
vestigations. Technical parathion is washed with petroleum ether 
and then dissolved in ethyl ether. The ether solution, after being 
washed with 10-percent sodium carbonate solution, is passed through 
a short column of adsorbent clay and diatomaceous earth. The re- 
sulting oil is taken up in a mixture of petroleum ether with ether and 
crystallized by chilling. The purified product is an odorless, yellow 
oil, which crystallizes readily in needles that melt at 6° C. 
A polarographic method of analysis has been developed for the assay 
of technical parathion and formulations containing it. Electrolysis 
is carried out at 25° ±0.5° C. in an acetone-water solution with 0.05N 
potassium chloride as the electrolyte and 0.01 percent of gelatin as 
the suppressor. A saturated calomel electrode is used as the reference 
electrode. About 10 milligrams of parathion is needed for final 
analysis. 
Insecticidal Amide Isolated from Prickly-Ash 
An insecticidal compound has been isolated from the bark of the 
southern prickly-ash tree and identified as X-isobutyl-2,8-dode- 
cadienainide. This amide, which has been named "herculin," is simi- 
lar chemically to affinin, an insecticidal compound previously isolated 
from the roots of Heliopsis Jongipes (A. Gray) Blake, a Mexican her- 
baceous plant known locally as chilcuague. It is unusual to find con- 
stituents similar from both chemical and insecticidal standpoints in 
plants of such different types. 
Three other species of Heliopsis occurring in the United States were 
shown to have insecticidal properties, and studies are under way to 
determine their active constituents. 
These studies were conducted with funds authorized under the 
Eesearch and Marketing Act of 1946. 
Diluents for Insecticides Sought in Agricultural Waste Products 
A number of agricultural waste products, including nutshells, seed 
hulls, and bark and other residues from forest and field crops, have 
been tested for potential usefulness as diluents for insecticide dusts. 
