August, 1928
INDUSTRIAL AND ENGINEERING CHEMISTRY
805
Ethylene Oxide as a Fumigant' R. T. C o t t o n and R. C. Roark BUREAU OF ENTOMOLOGY AND BUREAUOB CHEMISTRY AND SOILS, WASHINGTON, D. C.
D
URIiYG the course of an investigation of several aliphatic compounds to determine their value as fumigants, it was discovered that the vapors of ethylene oxide are highly toxic to insects. I n so far as the writers are aware, there are no previous references to the use of this material as an insecticide. Properties of Ethylene Oxide
Ethylene oxide is made from ethylene chlorohydrin (CH1OHCH7C1) and potassium hydroxide solution. At ordinary temperatures it is a colorless gas; a t low temperatures it is a mobile colorless liquid, boiling a t 10.5' C. The specific gravity of liquid ethylene oxide is 0.887 a t 7'/4O C. The empirical formula is CzH40,and the structural formula is l H < . The molecular weight is 44.031. It is miscible with 0
/
CHz
water in all proportions and is soluble in the usual organic solvents. On heating it unites with water to form ethylene glycol (CHzOHCH20H). Ethylene oxide is very reactive and combines with all compounds having a labile hydrogen atom, such as water, alcohol, ammonia, and acids. The concentrated vapors of ethylene oxide are inflammable, but concentrations lethal to insects can be used with safety. Ethylene oxide is not highly toxic to man, but when inhaled for a long time it produces a cyanosis, which, however, is counteracted by the use of carbon dioxide gas. Availability a n d Cost
Owing to lack of knowledge regarding the usefulness of ethylene oxide, there has been no demand for it, and consequently it is quoted a t a rather high figure. The writers were able to purchase it in small quantities at a cost of $2.00 per pound. It is now commercially available and could undoubtedly be made to sell for from 50 cents to 75 cents per pound. Experimental
Preliminary tests in half-liter Erlenmeyer flasks containing 200 grams of wheat indicated that about 20 mg. per liter constituted the minimum lethal dose for specimens of the rice weevil under those conditions. Tests on a larger scale were conducted in a 500-cubic foot fumigation vault. Insects in cotton-stoppered glass vials were placed in the vault. The fumigant was applied by pouring it into a shallow trough near the top of the vault or by allowing it to escape into the vault from a small cylinder containing the fumigant in liquid form under pressure. A dosage of 1 pound per 1000 cubic feet of space for 20 hours proved to be 100 per cent lethal to specimens of the clothes moth, Tineola biselliella; the carpet beetles, Attagenus piceus and Anthrenus vorax; the rice weevil, Sitophilus oryza; the Indian meal moth, Plodia interpunctella; the saw-toothed grain beetle, Oryzaephilus surinamensis; the red-legged ham beetle, Necrobia rujpes; and the flour beetle, Tribolium confusum. For commercial fumigation work it is recommended that I Presented as part of the Symposium on Insecticides and Fungicides before the Division of Agricultural and Food Chemstry a t the 75th Meeting of the American Chemical Society, St. Louis, Mo., April 16 to 19, 1928.
the fumigant be used a t the rate of 2 pounds per 1000 cubic feet of space. For comparative purposes tests were made in the same vault with the vapors of carbon disulfide and carbon tetrachloride. The results of these tests are given in Table I. Table I-Relative Toxicity of the Vapors of Ethylene Oxide Carbon DisulBde, and Carbon Tetrachloride to Various Insdcts Infesting Stored Goods MINIMUM TEMPERA- LETHAL FUMIGANT EXPOSURE TURE DOSE Hours F. Lbs./l000 cu. f!. Ethylene oxide 24 70 1 Carbon disulfide 24 70 1 I/¶ Carbon tetrachloride 24 85 30
The data in Table I indicate that the vapors of ethylene oxide are somewhat more toxic to stored-product insects than are those of carbon disulfide and about thirty times as toxic as those of carbon tetrachloride. Effective a t Low T e m p e r a t u r e s
Owing to its low boiling point ethylene oxide is effective at comparatively low temperatures. The experiments above reported were conducted in a vault without artificial heat, the temperature during the experiment ranging from 60 O to 75' F. Penetration
Tests in the 500-cubic foot vault indicate that this fumigant has excellent powers of penetration. Insects buried in overstuffed furniture, sealed in packages of cereals, and buried in jars of rice were killed with ease. Effect u p o n Commodities
I n order to study the effect of the gas upon commodities, foodstuffs of various types, clothing, furniture, and metals were placed in a vault and fumigated for 24 hours at a dosage of 2 pounds per 1000 cubic feet. No deleterious effect was noticeable. Foodstuffs, such as nut meats and dried fruits, were unaffected, and no foreign taste or odor was discernible immediately after removal from the fumigation chamber. No liquid foods were treated. G e r m i n a t i o n Tests
Germination tests with fumigated wheat indicate that seeds for planting purposes should not be fumigated with ethylene oxide since the vapors seriously affect the germination. Vacuum Fumigation
Preliminary: tests in a vacuum fumigation tank indicate that it can be successfully used for this type of fumigation. Japanese Synthetic Fertilizer Factory-A new synthetic fertilizer factory which will be operated by the Haber-Bosch method is to be erected in Japan. It is reported that the output of the factory will be approximately 30,000 tons of pure nitrogen per year. This development may have a far reaching effect, since Japanese fertilizers would naturally be at a great advantage in Asia, from the standpoint of transportation costs, over those from more distant countries.
