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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 22. No. 8
Ethylene Oxide and Ethylene Dichloride Two New Fumigants' J. M. RUSS,Jr. CARBIDE AND CARBON CHEMICALS CORPORATION, 30 EAST4
2 ST., ~ NEW ~ YORK,N. Y.
Fumigation is of great economic benefit. ManufacH E increasing importreated. The forced circulaturers, fruit packers, grain handlers, and warehousetance of fumigation as tion of air over the surface of men have been able to eliminate great losses caused by the liquid aids greatly in the a means of insect coninsect damage. Furthermore, expensive refrigeration vaporization of the fumigant. trol has created a demand for processes may be supplanted by fumigation, a cheaper fumigants which can be easily I n addition to being a good and more effective means of preventing insect damage and safely handled without fumigant, the ethylene dito stored goods. injury to the materials exchloride mixture has other Although only recently made available, the use of posed, a n d w h i c h c a n b e uses. It is an excellent solthe ethylene dichloride-carbon tetrachloride, ethylene applied under varying convent for oils and fats and, oxide, and Carboxide is already established in many ditions. Many compounds b ei n g non-inflammable, i s industries. These materials offer a choice of fumihave insecticidal properties used as a s p o t - r e m o v i n g gants which are adaptable to fumigation under widely but are limited in their use compound. It makes, therevarying conditions. Separate rooms, apartments, and as fumigants because of some fore, an excellent combination storerooms can be fumigated without vacating other undesirable characteristics, fumigant and cleaning soluparts of the same building or inconvenience to other such as slow vaporization, tion. Furriers find i t partenants. In like manner expensive shutdowns in instability, corrosive action, ticularly suitable for fumifactory operations can be avoided. Foodstuffs can be odor, retentivity by various gating and c l e a n i n g f u r s . fumigated without fear of injury or serious contaminamaterials, difficulty of hanThe mixture is also used in tion. Finally, fumigation is made easy in many dling, great inflammability, the form of emulsions as a applications which would otherwise be difficult. or extreme toxicity to man. contact insecticide. By the proper choice of processes and fumigants W h i l e t h e e t h y l e n e diI n the course of an extenmuch of the damage and discomfort caused by insects chloride-carbon tetrachloride sive investigation of the possican be eliminated. m i x t u r e is a very useful ble use of a large number of fumigant and solvent, it is comDounds. the Bureaus of Entomology and Chemistry and Soils discovered that ethylene not adapted to universal fumigation as is the case with ethyldichloride and ethylene oxide are highly toxic to insects ene oxide. and have characteristics which make them desirable fumiEthylene Oxide gants. Both compounds are relatively non-toxic to man. Ethylene oxide is a colorless, mobile liquid, which boils Ethylene Dichloride a t 10.5' C. and is therefore a gas a t ordinary temperatures. Ethylene dichloride is a colorless liquid of ethereal odor, It has a specific gravity of 0.887 a t 7"/4" C., a molecular which boils at 83.7" C. It has a specific gravity of 1.27 a t weight of 44.031, and a freezing point of -140" C. The 2Oo/2O0 C. and weighs 10.4 pounds per gallon. It is an ex- liquid is soluble in water and organic solvents. It has a cellent solvent for oils and fats, but is insoluble in water. faint but distinct ether-like odor, which is easily recognized, The vapors of ethylene dichloride are approximately 3.5 and its vapors are approximately 1.7 times as heavy as air. times as heavy as air. The vapors exhibit remarkable penetration into dense maEthylene dichloride will burn, but it is rendered non- terials such as wheat flour. inflammable by the addition of approximately 25 per cent by Extensive experiments with various foodstuffs have shown volume of carbon tetrachloride. This non-inflammable mix- that no residual taste or odor is left with materials that have been in contact with the vapors of ethylene oxide. ture is a very useful fumigant. A dosage of 8 pounds of the ethylene dichloride-carbon Even the flavor of such a sensitive material as tobacco is tetrachloride mixture per 1000 cubic feet in an air-tight unaffected by fumigation with it. A dosage of 1 pound ethylene oxide per 1000 cubic feet vault a t 70" F. will kill, in 24 hours, clothes moths, carpet beetles, rice weevils, Indian meal moths, flour beetles, saw- of air in an air-tight vault a t 70" F. will, in 20 hours, kill toothed grain beetles, and bedbugs. However, for com- clothes moths, carpet beetles, rice weevils, Indian meal mercial fumigation a dosage of 14 pounds of the mixture moths, saw-toothed grain beetles, red-legged ham beetles, flour beetles, cockroaches, tobacco beetles, and bedbugs. per 1000 cubic feet is recommended. Successful fumigation with the ethylene dichloride mixture For commercial fumigation, however, a dosage of 2 pounds depends to a large extent upon the method of application. per 1000 cubic feet is recommended. Although the conBecause of its relatively slow rate of vaporization, the liquid centrated vapors of ethylene oxide are inflammable, concensurface exposed should be large. This can be accomplished trations lethal to insects can be used with safety, since the by placing the mixture in shallow pans and allowing it to lower limit of inflammability is 3 per cent by volume or 3.67 evaporate or in certain cases, provided the walls or floor are pounds per 1000 cubic feet. Mixtures in air of ethylene oxide and carbon dioxide in unfinished, the fumigant may be sprayed on the walls or floor of the fumigation chamber. I n other instances the the ratio of 1 part of ethylene oxide to 7.5 parts or more liquid may be sprayed or poured upon the material being of carbon dioxide by weight are non-inflammable. Furthermore, ethylene oxide and carbon dioxide have practically Presented before the Division of Agricul1 Received May 21, 1930. the same vapor density and do not tend to separate or stratify. tural and Food Chemistry a t the 79th Meeting of the American Chemical Therefore, to eliminate possible dangers arising from an overSociety, Atlanta, Ga., April 7 to 11, 1930.
T
August, 1930
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
dose of ethylene oxide, it is advisable to use carbon dioxide with ethylene oxide for fumigation. Carbon dioxide has also proved to be of material aid in killing insects. Cotton and Young (5) determined that the presence of carbon dioxide increases the insecticidal action of ethylene oxide by causing an acceleration of the respiratory actions of insects. A dosage of 1 pound ethylene oxide and 7.5 pounds carbon dioxide per 1000 cubic feet is approximately equivalent to a dosage of 2 pounds ethylene oxide alone. Cotton (6)has shown that carbon dioxide causes a decrease in the adsorption of fumigants by various materials. This effect is especially apparent in vacuum fumigation, where the adsorption of fumigants is usually great. For example, in the fumigation of raw peanuts a dosage of 3.5 pounds ethylene oxide and 28 pounds carbon dioxide per 1000 cubic feet will give the same result as 7 pounds ethylene oxide used alone. Carbon dioxide is non-injurious to materials met with in fumigation. It is available as a liquid in cylinders under pressure and can also be obtained as a solid in the form of carbon dioxide snow or blocks of the compressed snow. Solid carbon dioxide is volatile and therefore must be used within a certain limit of time. The solid is of special benefit in certain instances, such as in the fumigation of grain and when it is desired to lower the temperatures of a material being fumigated. It has been found possible to mix liquid ethylene oxide and liquid carbon dioxide without reaction between the components. This mixture is stable and can be stored indefinitely in cylinders without deterioration of its insecticidal properties. It eliminates the necessity of handling two separate materials. This mixture is being marketed under the trade-mark “Carboxide.” Carboxide cylinders are equipped with eductor tubes for easy and rapid withdrawal of the fumigant. The mixture issues from the cylinder as a liquid which is atomized to a fine mist. Vaporization of the mist requires only a few minutes, thereby making available the maximum concentration of fumigant in a very short time. The availability of Carboxide in various-sized cylinders eliminates the necessity of measuring apparatus and makes the application of the fumigant extremely simple. When a number of cylinders are required they may be distributed throughout the space to be fumigated and the fumigant released from the cylinders in the order of their location with respect to the exit, the cylinder farthest from the exit being released first. When spaces are to be fumigated, it is usually desirable to introduce the fumigant through piping, using either small heavy-walled copper tubing or iron pipe. Under certain conditions, in vacuum fumigation, it may be preferable to vaporize the fumigant by passing it through a copper coil immersed in hot water. Vault Fumigation
The efficiency of fumigation depends largely upon temperature, concentration of fumigant, time of exposure, and nature of the material treated. The most favorable and economical conditions prevail where the temperature is above 70” F. and the effective concentration of fumigant can be maintained for the time required to give effective results on the particular material being treated. These conditions can be best maintained in vaults or rooms which are specially equipped for fumigation. When speed is essential vacuum vaults can be used. When speed is not important and space is available, atmospheric vaults are satisfactory for most materials. Some materials, however, because of their dense nature, are best fumigated under vacuum.
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I n vacuum fumigation greater dosages of fumigant are required to give good results in the short period of exposure. The dosage of fumigant will depend upon the material treated and the available time of exposure. For example, in the fumigation of dried raisins, a dosage of 20 pounds of Carboxide per 1000 cubic feet will give a complete kill in hour, while 10 pounds of Carboxide require ll/z hours. For the treatment of dried beans a dosage of 20 pounds Carboxide per 1000 cubic feet will give a complete kill in l/Z hour while 10 pounds require 1 hour for the same result. I n atmospheric vaults the forced circulation of warm air aids greatly in the penetration of the fumigant into dense materials. Heating of the air can be accomplished by means of units heated by steam, hot water, or completely enclosed electric elements. Circulation of the air in the vault may be accomplished by a fan connected by means of a shaft through the wall or ceiling to a motor outside the vault. It is preferable to place the heating and circulating apparatus near the roof of the vault to conserve space. The dosages of fumigant and time of exposure in atmospheric vaults depend upon the material treated. For example, dried fruits in bags can be fumigated successfully with 10 pounds Carboxide per 1000 cubic feet in 12 hours, while flour in bags requires 20 pounds for 16 to 24 hours. Carboxide can be used for the fumigation of all materials in vacuum or atmospheric vaults. It is particularly well suited for vacuum fumigation owing to the beneficial effect of the carbon dioxide in decreasing adsorption of the ethylene oxide by the material treated. No data are available on the use of the ethylene dichloride mixture in vacuum fumigation. Doubtless the dosages of fumigant required would be so great that complete removal of the vapors from the fumigated material would be difficult. The ethylene dichloride mixture can be used in atmospheric vaults for the fumigation of many materials such as furs, clothing, furniture, bedding, rugs, and certain foodstuffs, including grain. For ready reference a table of dosages and time of exposure for various materials when using Carboxide and the ethylene dichloride mixture in an air-tight vault a t 70” F. is given below. The dosages are based on the space in an empty vault with no allowance for the space-taken up by the material being treated. Dosage a n d T i m e of Exposure Using Carboxide a n d E t h y l e n e Dichloride Mixture ETHYLENE DICHLORIDE-CARBON TETRACHLORIDE MIXTURE
CARBOXIDE MATERIAL
Atmomhere
I
Vacuum
I
Dried fruits Cereals in cartons Brans, rice, corn, I and other grain in bags Flour i n 1 0 0 pound bags Tobacco in bales Candy in cartons N u t meats Almonds and peanuts in shells Clothing f u r s, furnitdre, a n d rugs
1
I
Lbs./l000
Lbs./1000
I
I
10
12-16
20
1
20 20 16 20
16-24 16-24 16 12-16
20
1 2 I1/z
10
12-16
20 20
1
30
4
30
4
16
1
1
22
24
14
24
28 24 Notrecommended Not recommended Not recommended Not recommended 14
24
Grain Fumigation
Insect control in grain is of particular importance because of the investment involved and the potential damage which can be caused by insect activity. Insects destroy grain and, in so doing, bring about a rise in the temperature of the grain which eventually results in fermentation; this, being a progressive action, will finally end in actual carbonization
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INDUSTRIAL AND ENGINEERING CHEMISTRY
of the grain. Even slight damage due to insect infestation or fermentation affects the market value of grain. Fumigation is the most economical method of insect control in grain. It is effective in killing all forms of insect life and, in contrast with mechanical and heat-t,reating methods, does not involve great power costs and loss of grain. By the proper choice of fumigants this process can be carried out without any deleterious effect on the grain. Aside from temperature, the most important factors intluencing the effectiveness of a good grain fumigant are diffusion and distribution of the fumigant. Tests have shown that diffusion of gases in grain is very slow because of the dense nature of the material. Other experiments have shown that diffusion is hindered by adsorption and absorption of the fumigant by the grain. Therefore, for effective fumigation provisions must be made for proper distribution of the fumigant in the grain to insure proper diffusion. The most effective method of distribution thus far developed involves the mixing of the fumigant with the grain as it enters a bin. When a liquid fumigant is used in deep bins, the loss due to evaporation in falling to the lower depths necessitates the use of quantities in excess of the theoretical amounts. The amount of fumigant lost depends upon several factors, such as temperatures, height of fall, and the rate of displacement of air in the bin by grain. It is therefore difficult to calculate the quantities of liquid fumjgant needed for effective treatment under these varying conditions. The ideal grain fumigant is one which offers a minimum of hazard and can be buried in the grain before vaporizing. These conditions are met by a mixture composed of ethylene oxide absorbed in solid carbon dioxide. In the ratio of 1 part by weight of ethylene oxide to 8 parts of finely pulverized solid carbon dioxide, a semi-solid mass is formed which can be gradually introduced into the grain stream entering a bin. Volatilization of the ethylene oxide does not occur to any appreciable extent until all solid carbon dioxide has passed into the gaseous state, by which time the mixture is well imbedded in the grain. The mixture is of such nature that comparatively little solid carbon dioxide is vaporized in the fall to the lower depths of deep bins. Variations in temperature, height of fall, and rate of air displacement do not materially affect the quantities of mixture required. The application of the mixture can be made without disagreeable effects on the operator. The application of the mixture involves preparation in small batches and introduction into the bin a t intervals timed with the rate of grain flow. The mixture is prepared by placing a weighed quantity of crushed solid carbon dioxide in a container and adding to it the proper quantity of ethylene oxide. The solid carbon dioxide absorbs the liquid ethylene oxide and a slushy product is obtained. The mixture should be introduced into the bin by shaking or scooping from the container, or by means of a machine feeder. At no time should the mixture be directly handled, even with gloves, because it is extremely cold and the cold liquid is absorbed by leather and fabrics. The size of the batches is determined by the size of the bin and the rate a t which it is filled. It should be assumed that proper diffusion will not take place through a column of more than 2 feet. Each batch should be gradually introduced, rather than dumped in all at once. The mixture of ethylene oxide and solid carbon dioxide kills the insects and at the same time cools the grain. The cooling effect is important because it either halts or decreases fermentation. The extent to which the grain is cooled depends upon the quantity of the mixture used. A combination of the cooling effect and the chemical action of the mixture may be responsible for the sweetening of musty grain, which has been observed in several instances.
Vol. 22, No. 8
While perfect kills and an appreciable lowering of the temperatures have resulted, in completely enclosed bins, from a dosage of 2 pounds ethylene oxide and 14 pounds solid carbon dioxide per 1000 bushels of grain it is advisable to use an overdose rather than an underdose. It is t h e r e fore recommended that the dosage, in completely enclosed bins, should be 2.5 to 3 pounds ethylene oxide and 20 to 30 pounds solid carbon dioxide per 1000 bushels of grain. The heavier dosages should be used in bins of large diameter. Large-scale experiments in the fumigation of grain with the ethylene oxide-solid carbon dioxide mixture have been conducted in various localities under representative conditions. Bins varying in height from 25 to 100 feet and capacities from 2500 to 140,000 bushels of grain have been successfully and easily fumigated. The results have been more than satisfactory as 100 per cent kills of all grain insects have been obtained. When it is not practical to use the ethylene oxide-solid carbon dioxide mixture in the fumigation of small bins and freight cars, the ethylene dichloride-carbon tetrachloride mixture will give results comparable with those obtained with any liquid fumigant. A dosage of ll/z to 2 gallons of the mixture per 1000 bushels of grain will give good results in tight bins. The mixture can be applied by pouring on the grain stream entering a bin or on top of the grain in a freight car. Fumigation of grain in freight cars is at best uncertain because of the loose construction of the average car. It is very seldom that a perfect kill of all insects is obtained in freight cars; however, this type of fumigation is often justified because enough insects can be killed to prevent serious damage to the grain. The time of exposure in grain fumigation will depend upon whether the grain is to be moved immediately or stored. I n such tests as have been conducted with ethylene oxidesolid carbon dioxide mixture and the ethylene dichloridecarbon tetrachloride mixture the time of exposure has varied between 24 hours and 3 weeks. House and Apartment Fumigation Houses and apartments have been successfully fumigated with Carboxide and the ethylene dichloride-carbon tetrachloride mixture. Separate rooms and apartments can be fumigated without vacating other apartments in the same building. For this purpose Carboxide is superior to the ethylene dichloride mixture. I n tight spaces where the temperature can be maintained above 70" F., a dosage of 1 pound ethylene oxide and 7.5 pounds carbon dioxide, or 10 pounds Carboxide, per 1000 cubic feet for 10 to 16 hours will kill bedbugs, roaches, carpet beetles, silverfish, clothes moths, and mice. I n spaces which are not tight it is necessary to increase the dosage and time of exposure. While ethylene oxide and Carboxide and the ethylene dichloride mixture are not dangerously toxic to humans, overexposure to the concentrated vapors will cause severe nausea. For house, apartment, or any type of fumigation where the operator is liable to overexposure, it is advisable to wear a mask which will absorb organic vapors. Fumigation of Storerooms Storerooms in candy factories, hospitals, restaurants, storage warehouses, navy depots, and grocery stores have been fumigated successfully with ethylene oxide and carbon dioxide. Insects in packages of cereals, dried fruits, and flour can be killed when the proper conditions are observed. Overstuffed furniture has been successfully rid of live clothes moths and carpet beetles when fumigated in separate storage compartments.
August, 1930
I X D U S T R I A L AND ENGINEERING CHEJ4ISTRY
Carboxide is well suited to the fumigation of storerooms because of the variety of materials usually present and the ease of application. The method of application is similar to that used in vault fumigation. The dosage should be based on that material present which requires the greatest quantity of fumigant. Fumigation in Refrigerator Cars
It is sometimes necessary to fumigate in refrigerator cars. This is especially true in the dried-fruit industry, where sufficient vault capacity is not always available. This type of fumigation may not always be effective because of the loose construction of some cars. Carboxide is excellent for fumigation in refrigerator cars provided they we properly sealed. Before fumigation the cars should be sealed as effectively as possible. The drain pipes from the ice compartments are fitted with liquid seal caps, but these caps are generally clogged with dirt or else are subject to being jarred from position by moving of the car. The most effective method of sealing the drain pipes is to provide wooden plugs which
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can be inserted in the pipes for the duration of the treatment. Care must be taken, however, to remove the plugs after fumigation or else the compartments will eventually be flooded. The required quantities of fumigant can be introduced through the ice ports of a refrigerator car. Carboxide cylinders are of such sizes that one cylinder can be used for each car. The contents of a cylinder may be emptied into the ice compartment through a hose connected to the cylinder on the outside, or else the cylinder may be placed bodily in the compartment. The dosage for dried fruits should be 16 pounds of Carboxide per 1000 cubic feet for an exposure of 10 to 12 hours at 70” F. Literature Cited (1) Back, Cotton, and Ellington, J . Econ. EnlotnoL., 23, S o . 1 (1930). (2) Cotton, Ihid., 23, S o . 1 (1930). (3) Cotton and Roark, I b i d . , 20, 636 (1927). ( 4 ) Cotton and Roark, IND.Exc. CHEM.,20, 80: (1928). ( 3 Cotton and Young, Proc. Enfomol. Soc. Washington, 31, 97 (1929) (6) Hoyt, ISD. ENO.c.HElf., 20, 460 (1928). (7) Jones and Kennedy, Ibid., 22, 146 (1930).
Effect of Priming-Coat Reduction and Special Primers upon Paint Service on Different Woods’ F. L. Browne FOREST PRODUCTS LABORATORY, X m ~ s o x -Wrs ,
Past efforts of chemists to make better house paints have been seriously hampered by the fact t h a t paint varies widely in its performance on different kinds of wood. Changes in paint composition t h a t otherwise would be advantageous have often proved impracticable because they accentuate the discrepancy in behavior on different woods. Disagreement about the best formula for the white base of house paint is largely due to this situation. From empirical exposure tests it appears t h a t t h e variable behavior of paint on different softwoods is due primarily to lack of specific adhesion between aged coatings and wood substance. Instead of wearing down from the surface, the coatings break up and fall off, starting
over the summerwood. The present paper reports empirical tests of certain modifications of painting practice t h a t have been supposed to improve durability of coatings over summerwood. The results indicate t h a t past recommendations have usually been based upon inadequate theory rather than upon sound experience. In the author’s opinion the problem of adhesion is a fundamental one that must be solved before substantial improvement in the serviceableness of house paints on wood can be achieved. With permanent adhesion between coatings and wood, variable paint behavior between woods and uncertain service on repainting would be eliminated, leaving the paint chemist free to build wear-resistant coatings on a firm foundation.
. . . . . . . .......
I
N 1924 the Forest Products Laboratory started an ex-
tensive series of exposure tests of painted wood, the object of which was to compare the behavior of coatings of typical house paints on wood surfaces of different kinds under normal conditions of exterior exposure ( 1 ) . Many technologists have been of the opinion (15,16) that such comparisons between woods are fair only if the primer is mixed with linseed oil and thinner-that is, reducedin proportions determined by the characteristics of the wood. The theory underlying this opinion is that some woods require a larger proportion of thinner in the priming coat than others in order to obtain maximum durability of the coating. Inquiry, however, revealed the fact that, although reasonable agreement exists among technologists about good practice in reducing white-lead paste paint or lead and zinc Received April 4, 1930. Presented before the Division of Paint and Varnish Chemistry a t the 79th Meeting of the American Chemical Society, Atlanta, Ga., April 7 to 11, 1930. 1
prepared paint for new exterior woodwork in general, there is no agreement either about the woods that require modification of this general practice or what that modification should be for specific woods. It mas therefore decided to begin the 1924 tests with the same reduction of the primer, which this paper will call the “standard” reduction, for all woods and then to start a second series of tests in 1925, using the woods on which less satisfactory paint service was expected, to see whether the durability of the coatings would be affected by changing the standard reduction of the primer or by using some of the special priming paints that have been suggested for such woods. Results of the 1924 tests are being published elsewhere (4, 5 ) . This paper presents the outcome of the 1925 tests. Woods Selected The woods for the 1926 tests were selected partly on the basis of observations after the first year of exposure of the
