August, *18] 
MOORE: CHLORPICRIN FUMIGATION 
357 
86 per cent in spite of innumerable mechanical losses. Attention is 
called to the analyses of two samples of acid arsenate. No. 12 was 
produced in the preliminary work and No. H 1-7 drawn from a mix¬ 
ture of seven different laboratory batches prepared for spraying experi¬ 
ments. 
Acid calcium arsenate is soluble in water but practically insoluble 
in lime water, which indicates that its safe application necessitates an 
admixture with Bordeaux or strong milk of lime. It contains a high 
percentage of arsenic and may serve in many instances as a substitute 
for acid lead arsenate during the present emergency. Experiments 
to test its efficiency are in progress. 
FUMIGATION WITH CHLORPICRIN 1 
r 
By William Moore, Division of Entomology and Economic Zoology, Minnesota 
Agricultural Experiment Station 
Introduction 
The discovery that chlorpicrin, although a rather volatile compound, 2 
is extremely toxic to insects naturally raised the question as to its 
possible use in the fumigation of grain and clothing. Its value as a 
fumigant to destroy the clothes louse [Pediculus humanus ( vestimenti )] 
and its eggs has been repotted. 3 Molecule for molecule it is about 283 
times as toxic as carbon bisulphide, which is now in common use as a 
fumigant of clothing and grain. Carbon bisulphide has the disadvan¬ 
tage of being very explosive. The use of chlorpicrin under normal 
conditions is without danger, although when heated it may be exploded. 
Carbon bisulphide, although it has a very disagreeable odor, does not 
deter people from entering a room containing large quantities of the 
vapor, and illness and even death may result. 
Owing to the severe irritation to the eyes, nose, and throat produced 
by even very small quantities of the vapor of chlorpicrin in the air, 
no one would ever enter a room until all the vapor had escaped. One 
of the chief advantages of carbon bisulphide in the fumigation of grain 
is that its vapor is about 2.5 times heavier than air and is thus able to 
sink down through a large mass of grain. Chlorpicrin vapor is about 
twice as heavy as that of carbon bisulphide. With these advantages 
in mind the following experiments are of interest. 
1 Published, with the approval of the director, as paper No. 114 of the Journal 
Series of the Minnesota Agricultural Experiment Station. 
2 Moore, Wm., Volatility of Organic Compounds as an Index of the Toxicity of 
their Vapors to Insects, Jour, of Agr. Research, vol. X, No. 7, 1917, pp. 365-371. 
3 Moore,Wm., The Control of the Clothes Louse [Pediculus humanus (vestimenti)], 
Jour, of Lab. & Clin* Medicine, vol. Ill, No. 5, 1918, pp. 261-268. 
