28 BULLETIN 1313, U. S. DEPARTMENT OF AGRICULTURE 
Many of the fumigants and combinations of fumigants which 
operated successfully in glass jars and in the presence of wheat in 
bottles, boxes, and barrels gave disappointing results when used on a 
large scale. A mixture, in equal proportions by weight, of ethylene 
bromide and carbon tetrachloride, used at the rate of 16 pounds per 
1,000 cubic feet, was successful when applied to weevils in wheat in a 
box, but this mixture, even with the addition of 50 per cent more 
carbon tetrachloride, was ineffective when used in box cars. This 
is probably explained by the facts that in a box car the weevils may 
be in the grain at a much greater depth than in a small box or barrel 
and that the grain is much more Fe hitly packed. Also, a box car is 
not a tight container and the vapors of the fumigant may not be 
long retained. 
The most successful fumigants used in the box-car tests were ethyl 
formate in combination with carbon tetrachloride (12.1 pounds each 
er 1,000 cubic feet) and ethyl acetate (12.5°® pounds per 1,000 cubic 
Foot) in combination with carbon tetrachloride (25 pounds per 1,000 
cubic feet). 
FIRE HAZARD FROM FUMIGANTS 
The vapor pressures of ethyl acetate and carbon tetrachloride are 
very close for all temperatures up to their boiling points (Table 9, 
Mio): 
TABLE 9.—Vapor pressures of ethyl acetate and carbon tetrachloride 
Observed vapor Observed vapor 
pressure ! pressure ! 
Temper cea pe —————————— 
ature atur 
Ethyl Carbon ° Ethyl Carbon 
acetate? | tetra: acetate ?| tetra 
chloride chloride 
2X G2 mm mm. na OF m m 
—20 6. 55 9. 92 40 186. 20 210. 90 
—10 12. 95 18. 81 50 282. 20 309. 00 
0 24. 30 33. 08 60 415. 40 439. 00 
10 42. 70 55. 65 70 596. 30 613. 80 
20 72. 80 89. 55 80 832.70 | 4 836.35 
30 | 118.70 | 139.60 
1 Sydney Young. The vapor-pressures, specific volumes, heats of vaporization, and critical constants 
of 30 pure substances. Jn Sci. Proc. Roy. Dublin Soc., n. s. (1909-10), 12:374-448. 
2 Boiling point at 760 millimeters, 77.15° C. 
3 Boiling point at 760 millimeters, 76.75° C. 
4 Calculated. 
A mixture of 3 volumes of carbon tetrachloride and 2 volumes of 
ethyl acetate (equivalent to 72.5 per cent carbon tetrachloride and 
27.5 per cent ethyl acetate by weigh is noninflammable at ordinary 
temperatures. Moreover, in this mixture the vapors of the two 
components tend to separate but very slightly, thus making the 
mixture safe from fire hazard. ~ 
On the other hand, carbon disulphide has a much higher vapor 
pressure than carbon tetrachloride at ordinary temperatures, thus 
making mixtures of these compounds unsafe. The experiments of 
the Underwriters Laboratories at Chicago (Grain Dealers Journal, 
December 10, 1921, vol. 47, p. 798) show that a mixture of 75 per 
cent carbon tetrachloride ee 25 per cent carbon disulphide by vol- 
6 A mixture of ethyl acetate and carbon tetrachloride containing 334 per cent by weight of the acetate 
will flash slightly at ordinary temperatures but will not continue to burn. 
