34 ANNUAL BEPOBTS OF DEPARTMENT OF AGRICULTURE, 1953 
potatoes, peaches, Sugar beets, sorghum, cottonseed oil, soil, and calf 
pellets. 
Corrosive Properties of Aerosol Spray Eliminated 
By dissolving schradan in carbon tetrachloride and washing it with 
a dilute sodium carbonate solution, Bureau chemist- have found that 
they can eliminate the corrosive properties of this insecticide on 
greenhouse aerosol containers. Schradan has become an important 
greenhouse insecticide because of its effectiveness against otherwise 
resistant spider mites. Its eorrosiveness, however, had become a seri- 
ous problem because of variation in its pilot plant production. Dif- 
ficulty encountered because of the deposition of insoluble crystalline 
material on the walls of aerosol containers holding schradan was 
eliminated by placing the aerosol mixture in a large pressure tank and 
filtering it when transferring it to the small containers. 
Three-Hour Exposure to Lindane Vapor Kills Nonresistant 
House Flies 
House flies of a nonresistant strain were killed after 3 hours of 
exposure to lindane vapor regardless of the ventilation. Studies 
with this material were continued because of the widespread sale of 
lindane thermal generators. The concentration of lindane vapor 
in the air of rooms where these devices were in operation varied 
greatly because of differences in ventilation. In one set of te-t- a 
concentration of about 0.2 microgram of lindane per liter of air was 
found by analysis in a closed room, while the concentration was only 
about 0.015 microgram per liter when windows and doors were open. 
Experimental Aerosol Valves Tested 
Xew types of experimental aerosol valves designed by various 
manufacturers for the domestic trade were tested for leakage, particle 
size delivered, and delivery rate. Suggestions were made for remedy- 
ing faults in the valves. The commonest cause of trouble is deteriora- 
tion and failure of rubber components of the valves. The most satis- 
factory material for this purpose thus far tested is a synthetic rubber 
of about G5 durometer hardness. 
INew-Type Respirators Tested Against Poisonous Aerosols 
A number of new respirators were tested for protection against 
sprays and dusts of maiathion, Svstox, schradan, DMC, Aramite, 
p-chloropheny] 2>-chlorobenzenesulionate, aldrin, and dieldrin. Spe- 
cial fume filters in combination with chemical cartridges are necessary 
to protect against sprays and dusts of nialathion, Svstox, and schra- 
dan. Other than nialathion, Svstox, and schradan, all the materials 
wcic removed by the usual paper-type filters and chemical cartridges. 
Several new type- of respirators failed to reduce 1 he concentration 
of the organic phosphorus insecticide- satisfactorily because of the 
small surface area of their filters. Gas mask canisters commonly used 
in greenhouses for protection against aerosols containing organic 
phosphorus compounds, when tested against schradan, SystOX, EPN, 
and nialathion, reduced the vapor concentration below 1 p. p. m. 
