66 ANNUAL REPORTS 01 DEPARTMENT OP AGRICULTURE, 11 
compound has been referred to as furethrin and bas also been syn- 
thesized by Japanese chemists. Preliminary tests indicate ir is more 
toxic to houseflies than pyrethrins. A- was the experience with 
allethrin, it is more toxic when made with the natural chrysanthemum 
monocarboxylic acid than when the synthetic acid i> used. 
A crystalline Isomer of allethrin, isolated previously, was prepared 
in larger quantity and submitted for insecticida] tests. This isomer, 
which ha- been given the name alp ?ta-dl- trans isomer of allethrin, 
while less toxic than allethrin to houseflies, promises to he of val 
a Standard in the analysis of technical allethrin. 
Action of Parathion in Soil Determined 
A study of the behavior of parathion in soil indicated that volatili- 
zation account.- for the major part of the loss, but that a biological 
process also operates in it- removal. 
Inseetieidal Properties of Sehradan Studied 
A procedure was developed for the preparation of pure sehradan 
(octamethyl pyrophosphoramide) for use as a standard in analytical 
studies. This involved dissolving technical sehradan in chloroform, 
washing with dilute acid and base, decolorizing with charcoal, and 
distilling a fraction boiling at 118°-124° C./0.5 mm. 
Samples of canned peas that had been treated with sehradan during 
their growth were analyzed hut no sehradan was found in them. 
Experiments with chrysanthemums treated with sehradan showed 
thai the insecticide seems to concentrate in meristematic tissue and 
flowers. Study of the rate of penetration of sehradan into rose-leaf 
tissue indicated that about 50 percent of the amount deposited pene- 
trate- into the leaves in 6 hour-, and the greater part in 24 hours. The 
sehradan then remains in the leave- for several days. When this ma- 
terial was applied to the soil in which tomatoes were grown, it ap- 
peared in the fruits in proportion to the amount applied. 
Heliopsis Yields Several Toxic Substances 
In the investigation of the insecticidal constituents of American 
species of Heliopsis, further quantities of scabrin vein' isolated from 
//. helianthoides var. scabra root- and senl out for testing against 
\arious inseci species not previously tested with this material. The 
compound proved to he toxic to mealworms and sawtoothed grain 
beetles. It was not effective again si mustard beetles, cotton stainers, 
and Wi\ flour hectic-. In addition to scabrin, an oil toxic to insects 
was also obtained from this species of II , Jiopsis, The composition oJ 
t hi- oil i- being furi her si udied. 
No Translocation in Tomatoes of Parathion Residues in Soil 
Sin. lie- were completed during the year of residues accumulating 
from aerosol and -oil applications of parathion t<> vegetable crop-. 
In these experiments aerosols wen' applied at the rate of l gram of 
parathion per 1,000 cubic feet in a greenhouse in which tomatoes, 
cucumbers, and lettuce were growing. Parathion was also added to 
-oil in w Inch tomatoes were mow n at rates of 8 t<> L28 pounds an acre. 
