56 ANN! \I. REPORTS 01 DEPARTMEN1 "1 AGRICULTURE, 1951 
molecule have been synthesized and submitted for testing against 
insects. 
Respirator) Devices (»iNr Satisfactory Protection igainsl Organic 
Phosphates and Chlorinated Insecticides 
The cooperative program for the development of respiratory equip- 
ment to protect operators applying insecticide vapors, mists, ami 
(Iii-i- was continued bj Federal agencies and manufacturers. Under 
the leadership of Bureau chemists, respirator cartridges and filters 
and gas-mash canisters were developed that give satisfactory protec- 
tion against parathion, tetraethy] pyrophosphate, tetraethyl dithio- 
pyrophosphate, ethyl p-nitrophenyl benzene thionophosphate, Lindane, 
aldrin, and dieldrin. Ii was necessary to incorporate a special fume 
filter with the respirator cartridges for use against mists and sprays 
containing tetraethyl pyrophosphate. Activated charcoal was used 
in ilic cartridges for protection against the chlorinated compounds. 
mask canisters oj the type used for organic vapors, acia g 
fumes, and dusts are effective against all these insecticides. 
Method for Determining Particle Size of ierosol Devised 
A mechanical method was developed for collecting a sample of an 
aerosol on a microscope slide. It provides the insect icide indust ry wit h 
a uniform method of determining the average particle size of an 
aerosol. 
Systemic 4ction of Octamethyl Pyrophosphoramide Studied 
Studies were made on the absorption and movement <d" octamethyl 
pyrophosphoramide in several species of plant-. Octamethyl pyro- 
phosphoramide is one of the chemicals receiving attention because of 
their systemic ad ion. whereby t hey are absorbed by plant- in sufficient 
quantities t<» kill insects feeding on the plant-. The results <d" this 
year's experiments indicate that until more information is available 
on the health hazard involved, octamethyl pyrophosphoramide should 
not be used on food crops. 
Studies were made of the absorption and movement of octamethyl 
pyrophosphoramide in the plant. Experiments in which radioactive 
phosphorus was used a- a tracer indicated that the insecticide tends 
in move into the young, growing pan- of the plant, where it is most 
rapidly absorbed. The results were confirmed by chemical studies 
using i • colorimetric method of analysis developed bj Bureau 
chemists. 
Experiments on the rate of penetration of octamethyl pyrophos 
phoramide into leaf tissue showed thai under the experimental condi- 
tions about 90 percei ■ amount applied to the foliage could no 
• r be recovered bj washing the leaves oi bean plants after I s 
hours and rose lea ves r ft er 72 hours. 
In ;i stud) of the persistence of this compound in chrysanthemum 
plants, I inch cuttings were placed m an aqueous sol ut I allowed 
to take up the insect icide. The cutt ings were then planted and allowed 
to l-i<»\\ for 00 days i<> a height of 3 feet. \t the end of that time 
of octamethyl pyrophosphoramide -till could be detected in 
the growing tip oi the plants. 
