THE STERILIZING ACTION OF GASEOUS ETHYLENE OXIDE

Transcription

1 THE STERILIZING ACTION OF GASEOUS ETHYLENE OXIDE I. EEVIEW i BY CHARLES E. PHILLIPS AND SATJL KATE (Received for publication April 8th, 1949) Sterilization is most often accomplished by the use of steam under pressure in an autoclave, or by the use of some chemical agent in liquid form. Less commonly used methods include boiling in water, dry heat, radiation or ultrafiltration. Relatively little attention, however, appears to be given the possibility of utilizing a bactericidal gas or vapor, even though such practice was in use before the turn of the century. At that time formaldehyde and, to a lesser degree, sulfur dioxide were widely used to disinfect sick rooms following a contagious illness. This practice, however, declined after it was shown that the treatment, as usually carried out, was often ineffective, and as the belief grew that it was probably unnecessary. Much of the interest in disinfecting gases died at this time. Recently, considerable research has been carried out on the use of triethylene glycol and propylene glycol vapors to reduce the bacterial count of air. This practice differs both from the older work with formaldehyde vapor and from the work discussed here on ethylene oxide vapor, in that the glycols are used only in air purification and not for the sterilization of solid materials. If we define a sterilizing gas as one which will sterilize not only the air, but also all surfaces and objects within an en- 1 Prom the laboratories of the Biological Department, Chemical Corps, Camp Detrick, Frederick, Md. On leave of absence from Camp Detrick. Present address: Department of Medicine, University of Chicago, Chicago 37, HI. closed space, the glycols are excluded since they have almost no effect on contaminated surfaces or solid objects. Our interest in disinfecting gases arose when we had occasion to attempt the sterilization of a number of objects which could not be treated successfully by the more common techniques. Many metallic objects together with wood, paper, leather, plastics, wool and foodstuffs presented particularly difficult problems in achieving sterilization without damage to the object being treated. An ideal sterilizing agent for such materials would be a noncorrosive and nondamaging gas which would diffuse through all types of porous substances, which could easily be removed by aeration following treatment, and which could effectively destroy all forms of microorganisms at ordinary temperatures. Other desirable features would include rapid action, low toxicity to human beings, nonflammability, ease of storage and handling and ready availability. Preliminary investigation of a considerable number of compounds indicated that ethylene oxide possesses many of these desired characteristics. This compound in particular was subjected to considerable study in this laboratory and is still being investigated. These studies are being reported in subsequent papers in this series. A search of the literature revealed that the bactericidal properties of ethylene oxide have been noted by a number of investigators, particularly those work- 70 AM.J.HYO., 1949, VOL. 50 : PP

2 STERILIZING ACTION OF GASEOUS ETHYLENE OXIDE. I 71 ing in the foodstuff industry where ethylene oxide was widely used as an insecticide. Recently, a few papers have appeared on this subject outside the patent and foodstuff literature, but books and reviews dealing with disinfection or sterilization rarely mention this compound, and its potential usefulness as a sterilizing agent appears not to be well known. It, therefore, seemed advisable in the first paper of this series to collect and summarize the information available on the bactericidal activity of ethylene oxide, together with other pertinent information on its chemical and biological properties, potential hazards and methods for analysis. Properties of ethylene oxide General. Bpoxy compounds contain two carbon atoms and an oxygen atom linked together in a 3-membered ring. As would be expected, such compounds are very reactive. Ethylene oxide, CH CHj, the simplest epoxy com- \ / pound, is widely used as an intermediate in chemical synthesis, and is readily available, in tank car quantities, in the United States. Ethylene oxide (specific gravity /4 C) boils at 10.8 C and freezes at C. It is thus a gas at ordinary temperatures and pressures, but one quite easily liquefied. The liquid is colorless, has a rather pleasant ethereal odor, and is soluble in all proportions in water and in the usual organic solvents. It can be obtained as a liquid in low-pressure steel cylinders or in sealed glass bottles. Small quantities of the liquid can be stored conveniently and safely in tightly capped bottles in a dry-ice chest. Storage in an electric refrigerator should not be attempted, however, because any ethylene oxide vapor escaping from the flask might form an explosive mixture which could be set off by the motor. Flammability. Ethylene oxide is vigorously flammable and the vapors form explosive mixtures with air in all proportions from 3 per cent to 80 per cent by volume. Whenever more than very small volumes are handled, this potential danger must be kept in mind. The explosion hazard is eliminated, however, when the vapors are mixed with more than 7.15 times their volume of carbon dioxide (1). A commercial product is available under the trade name Carboxide, 8 which contains 10 per cent ethylene oxide and 90 per cent CO. This product can be mixed with air in any proportion without forming an explosive mixture. Insecticidal activity. The biological activity of ethylene oxide was first noted by Cotton and Roark () in 198. They found it a powerful insecticide, active against a great number of insect pests. Mixing carbon dioxide with the ethylene oxide increased its effectiveness and also eliminated the fire hazard (3). In the years following 198, the use of ethylene oxide for insect fumigation rapidly became so widespread that, in 1935, a bibliography of references to its insecticidal properties (4) contained over 185 entries. No attempt will be made to review this literature. It is interesting to note that ethylene oxide concentrations ranging from 3. to 3 mg per liter were required to kill a variety of insect pests (, 5). Considerably higher concentrations are required to kill bacteria, as is indicated in table 1. Bacteriological activity. The first reference to the antibacterial properties of s Carbide and Carbon Chemicals Corporation, Passaic, N. J.

3 7 CHARLES R. PHILLIPS AND SAUL KAYE TABLE 1 Sterilization conditions for gaseous ethylene oxide Sterilizing conditions Material treated Contaminant Ethylene oxide concentration (mg per liter)*, Temperature (Fahrenheit) Exposure time (hours) Source Moist cotton Moist sugar Cut tobacco Sand, starch Bread Spices, dry foods Dry gums Surgical supplies Pancreatin Spices Bakery equipment Glass, paper and cloth Soil Growths on agar slants 48 test organisms Thermophyllic bacteria Aerobic spores Mold spores Mold spores B. anthracoides spores Yeasts, fungi A. In vacuum chambers , , B. In tight containers , approx..05f under Gross and Dixon (7) Gross and Dixon (7) Gross and Dixon (7) Yesair and Williams (15) Kirby et al. (8) Griffith and Hall (10, 16, 17) Griffith and Hall (16, 17) Griffith and Hall (19) Griffith and Hall (18) Baer (0) Kirby et al. (8) Velu et al. (6) Roberts et al. (7) Whelton et al. (4) * Milligrams per liter are equivalent to ounces per 1,000 cubic feet. Thus, concentrations expressed in these units can be directly applied to both metric and English systems of measure. t Ethylene oxide alone admitted to vacuum chamber and held for 10 minutes. Air then slowly admitted. ethylene oxide appears to be a patent application filed in 199 by Sehrader and Bossert (6). In this patent, granted in 1936, it is claimed that "pests and germs of all kinds'' are destroyed by the use of alkylene oxides in conjunction with CO, though no supporting data are presented. Both ethylene oxide and propylene oxide are given as examples of alkylene oxides found to be effective. In 1933, Gross and Dixon (7) applied for a patent on a "Method of Sterilizing," in which ethylene oxide was the active agent. This patent, granted in 1937, disclosed considerable experimental evidence on the effectiveness of this chemical. The authors claimed to have tested it against 48 different microorganisms, most of them pathogenic in nature, imbedded in moist cotton, against moist (10 per cent H O) sugar crystals containing thermophylic bacteria, and

4 STERILIZING ACTION OF GASEOUS ETHYLENE OXIDE. I 73 against moist cut tobacco. They claimed complete sterilization in all cases. It was claimed also that ethylene oxide homologues and solutions of ethylene oxide in water and other solvents are bactericidal. The exact exposure times, concentrations and conditions under which Gross and Dixon claimed effective sterilization appear in table 1, together with a similar summarization of the experimental data from the other articles covered in this review. The authors describe a vacuum chamber set-up but do not specifically state whether or not in all their tests the chamber was evacuated before the ethylene oxide was admitted. The Gross and Dixon patent is interesting not only because of the broadness of its claims but also because the authors present a theory as to the mechanism of the action of ethylene oxide sterilization. They state that in the presence of moisture, ethylene oxide is converted to some extent into ethylene glycol and that this conversion is necessary for sterilization to take place. All claims in their patent specifically mention the use of ethylene oxide in the presence of moisture. The authors of this review present an alternative alkylation theory for the mechanism of the action of ethylene oxide in the second paper of this series, which follows in this journal. In the fourth paper they will deal with the question of moisture in some detail. Kirby, Atkin, and Frey (8), in 1936, reported on the use of ethylene oxide to control molds commonly found in bakeries. They eliminated mold spores from equipment and also successfully treated in a vacuum chamber loaves of bread which were inoculated with mold spores before being wrapped in waxed paper. The chamber was evacuated and then ethylene oxide was introduced until a rise in pressure of % 0 atmosphere was noted. The chamber was then brought to atmospheric pressure by the admission of filtered air. This paper contains the first mention of vacuum sterilization to treat food after it has been packaged, and thus to reduce the chance of recontamination before use. The main commercial application of ethylene oxide for sterilizing purposes appears to have followed the discovery (9) that spices were often a source of spoilage in foods to which they had been added. Hall (10), James (11), McBride (1), and Yesair and Cameron (13) in 1938, and Smith (14) and Yesair and Williams (15) a few years later all published on various aspects of the use of ethylene oxide to sterilize or '' practically sterilize" spices. Yesair and Williams also tested ethylene glycol as a bactericide and found it much less active than ethylene oxide. This test caused them to doubt that the action of ethylene oxide depended upon its conversion to the glycol, as Gross and Dixon (7) had suggested. They claimed, however, that they obtained better sterilization of spices when a beaker of water was placed in their vacuum sterilization chamber. On the basis of this evidence, Yesair and Williams supported the earlier claim that better results were obtained in the presence of moisture. Griffith and Hall applied for a patent in 1937, which was issued (16) in 1940 and reissued (17) in 1943, on the use of ethylene oxide in a vacuum chamber to sterilize spices and other materials. Similar patents were obtained by the same authors for the sterilization of pancreatin (18) and colloid materials (19). Baer (0) applied for in 1938, and was granted in 1941, a patent covering the vacuum sterilization of organic products such as foods and particularly

5 74 CHARLES R. PHILLIPS AND SAUL KAYE spices. His patent is of particular interest because he claims, in contradiction to Gross and Dixon (7) and Yesair and Williams (15), that it is highly undesirable to have substantial amounts of moisture present in the spices during sterilization. The usual procedure in sterilization of spices consists of placing them in a vacuum chamber and evacuating to 8 or to 9 inches of mercury. Ethylene oxide is then introduced into the evacuated chamber for the desired exposure period. It, in turn, is then evacuated and replaced by air. Several successive evacuations and readmissions of air may be performed to remove all traces of the fumigant. The various concentrations, temperatures and exposure times in these published recommendations vary considerably, as indicated in table 1. This method of sterilizing spices has been successfully put to use on a commercial scale for the last 10 years by McCormick and Company of Baltimore, Md., who report little, if any, difficulty with the process (1). They achieve remarkable penetration of the ethylene oxide with this technique. Packaged spices are treated while inside the individual boxes in which they are to be sold, which in turn are packed in heavy paper cartons sealed for shipping. Spice can also be treated inside heavy wooden barrels, with the heads already inserted for shipping. It is claimed that with the vacuum treatment, ethylene oxide penetrates through any type of container provided that it "breathes" or is not hermetically sealed. Other reports on practical applications of ethylene oxide sterilization within the food industries may be found in the work of Angla () who reported that ethylene oxide prevented the fermentation of grape, lemon, orange and tomato juices, and in the work of Mrak (3) and Welton, Phaff, Mrak and Fisher (4) who reported the usefulness of ethylene oxide in preventing the spoilage of dried fruits. In the latter paper it was shown that yeasts and molds were actually killed, not merely inhibited, and it was mentioned that bacteria were more resistant, particularly spore formers such as Bacillus subtilis. Propylene oxide was stated to be active also, but to a lesser degree than ethylene oxide. A patent by Baerwald (5), applied for in 1944 and issued in 1945, covered the sterilization of dried fruits or other foodstuffs packed in cellophane or similar materials. Ethylene oxide, usually in solution to lower its vapor pressure, was admitted to the food product before packaging. After packaging, it would evaporate, exercise its sterilizing action and diffuse out through the wrapping before the product reached the consumer. Among the few papers referring to applications of ethylene oxide sterilization outside of the foodstuff industry is that of Velu, Lepigre and Bellocq (6) who reported in 194 that glass, metal and cloth surfaces containing the extremely resistant spores of Bacillus anthracoides were readily sterilized by exposure to ethylene oxide. These authors visualized the sterilization of infected clothes and other articles by means of ethylene oxide, and even discussed the possibility of treating entire railroad cars in chambers built over the tracks. Salle and Korzenovsky (7) in 194 investigated the advantages offered by vacuum sterilization with germicidal gases as opposed to admitting the gases into a closed container at atmospheric pressure. They originally included formaldehyde, methyl bromide, methyl

6 STERILIZING ACTION OF GASEOUS ETHYLENE OXIDE. I 75 formate, ethylene oxide and carbon disulfide in their study, but when a few preliminary tests showed that only formaldehyde sterilized within hours they did no further work with the other compounds. With formaldehyde the presence of a vacuum was shown to be necessary if any penetration and sterilization of porous substances were to be achieved. Ludin and Kane (8) tested in 194 the effect of various gases upon the sterilization of inoculated threads imbedded in various upholstery materials. They stated that ethylene oxide either alone or in 1-in-l mixture with carbon dioxide was a germicidal fumigant. In l-in-7 and l-in-9 mixtures of ethylene Animal Guinea pig Rat TABLE Toxicity of inhaled ethylene oxide to small animals Effect Lethal Intermediate Tolerable Lethal Intermediate Ethylene oxide concentration (mg per liter)* oxide and carbon dioxide, however, they failed to achieve sterility under their test conditions. Roberts and co-workers (9) showed in 1943 that soil in enclosed containers could be sterilized with ethylene oxide. Hansen and Snyder (30) reported recently on the use of gaseous ethylene and propylene oxides for the routine laboratory sterilization of various culture media, especially those, such as pea straw, which are damaged by autoclaving. Toxicity. Ethylene oxide, while toxic, is less so than many other fumigants, so that workers using it for insecticidal purposes do not usually use a gas mask (31). In general, its toxic limits are Exposure time (minute*) 5 (approx.) (intermittent) Several hours Source (33) (33) (33) (33) (3) (3) Tolerable (intermittent) (3) Mouse Lethal Tolerable 440 (intermittent) * Or ounces per 1,000 cu. ft.

7 76 CHARLES B. PHILLIPS AND SAUL KATE about the same as those of ammonia. Three major studies (3, 33, 34) of its toxicity to small animals have been reported. The data from these are summarized briefly in table. Stehle, Bourne and Lozinsky (3) were interested mainly in determining whether or not the compound had any possible application as an anesthetic. It was too toxic for that purpose. Waite, Patty and Yant (33) believe that the hazard to health is mainly due to low concentrations of ethylene oxide which may be endured for periods long enough to cause marked irritation of the respiratory system. These workers state that ethylene oxide, though it does not possess a distinct odor in these low concentrations, is sufficiently irritating to give warning of its presence. Greaves- Walker and Greeson found that 0 mg/1 of ethylene oxide produced a definite irritating action on the nasal passages within 10 seconds. A concentration of 4 mg/1 was slightly irritating to the nasal passage but produced no after-effects. The odor was similar to that of acetic acid. Zernik (35) attempted the uncertain task of extrapolating the results of animal tests to lethal dosages for man. He estimated that an exposure of 0.5 mg/1 for 1 hour would be objectionable, but the same concentration for a day would be dangerous. He considered 1.0 mg/1 sufficient to cause sickness and death after a number of hours of inhalation. At least two cases appear in the literature of accidental poisoning in man by ethylene oxide. Blackwood and Erskine (36) report cases in 6 men who became ill while working in a ship compartment adjacent to one being fumigated with Carboxide. Recently, a brief report appeared in Industrial Hygiene News Letter (37) of 10 women workers who were overcome by ethylene oxide which was being used as a disinfectant in a California food plant. Further information on the latter instances was obtained from the State of California Department of Public Health (38). In neither of these events was the exact concentration of ethylene oxide known. In both of them the gross symptoms of the persons affected included headaches, nausea, vomiting and respiratory irritation. No permanent ill effects occurred.* Analysis of ethylene oxide Because of its widespread use as a fumigant against insect pests, considerable work has been published on analytical methods for ethylene oxide in air. The most successful of these depend upon the hydrolysis of the compound. This, contrary to prevalent opinion (7), is not rapid unless catalyzed (39). With water alone, ethylene glycol is very slowly formed, according to equation (1) below. In the presence of hydrogen ion this reaction proceeds more rapidly. (1) H C H S O H C OH In concentrated salt solution hydrolysis proceeds rapidly and ethylene chlor- 4 Since this review was written, eases of accidental blistering of the skin due to exposure to ethylene oxide vapor have occurred in this laboratory. While the liquid when spilled on the skin evaporates rapidly causing no damage, very bad burns occurred when rubber shoes were donned by laboratory workers immediately after they had been sterilized by ethylene oxide vapor. Apparently the vapor had dissolved in the rubber, and diffused out against the skin. No such incidents have occurred with similar articles of clothing aired until free of vapor before being worn. The accident is being studied further.

8 STERILIZING ACTION OP GASEOUS ETHTLENE OXIDE. I 77 hydrin is formed as indicated in equation (). () HjC O + Cl- + H O H C Cl >H OH- A detailed study of the kinetics of these reactions has been made by Bronsted, Kilpatrick and Kilpatrick (40). Deckert (41, 4), Lubatti (43, 44, 45), and others (46, 47, 48) have based their published analytical methods upon equation (). Concentrated solutions of NaCl, KCNS, CaCl, MgBr, and LiCl in standardized acid have been proposed as collecting and hydrolyzing solution (). In this laboratory, slightly modifying published methods, a collection solution is used which is nearly saturated (49 to 53 per cent) with MgBr and which contains exactly 0.1 N H SO 4. Measured amounts of this solution are placed in two gas-collecting bubblers which are then mounted in series. The air being analyzed is drawn through these bubblers in carefully measured volumes. The solutions are allowed to stand for at least 3 minutes, after which time hydrolysis is complete and the Mg(0H) so liberated is neutralized by the sulfuric acid. The collection solutions are then transferred quantitatively to Erlenmeyer flasks where the amount of acid consumed in the reaction is determined by titration with standardized NaOH, using methyl orange as an indicator. Each ml of 0.1 N H SO 4 consumed is equal to 4.4 milligrams of ethylene oxide. A number of qualitative methods have been developed for use in the rapid detection of ethylene oxide in air (49, 50, 51). Most of these depend upon the hydrolysis by salt solutions, with the presence of phenolphthalein serving to indicate the formation of alkali. These tests are quite effective at high concentrations of ethylene oxide; the color develops slowly, however, at concentrations around 10 mg per liter or lower. SUMMARY Ethylene oxide, a gas at ordinary temperatures and pressures, has been noted by various workers to be bactericidal. A review is presented of the information available in the literature on this subject, together with other pertinent information on the insecticidal properties of ethylene oxide, on its flammability and toxicity and on available analytical methods for this compound. REFERENCES 1. Jones, G. W., and Kennedy, R. E. Extinction of ethylene oxide fumes with carbon dioxide. Indust. Eng. Chem., 1930, US: Cotton, R. T., and Roark, R. C. Ethylene oxide as a fumigant. Indust. Eng. Chem., 198, 0: Cotton, R. T., and Young, H. D. The use of carbon dioxide to increase the insecticidal efficiency of fumigants. Proe. Entomol. Soc. Washington, 199, 31: Young, H. D., and Busbey, R. L. References to the use of ethylene oxide for pest control. U. S. Dept. Agric. Bureau of Entomol. and Plant Quarantine, April Balzer, A. I. Insect pests of stored rice and their control. U. S. Dept. Agric. Farmers Bull. no. 1906, Schrader, H., and Bossert, E. Fumigant composition. U. S. Patent,037,439 (1936). 7. Gross, P. M., and Dixon, L. F. Method of sterilizing. IT. S. Patent,075,845 (1937). 8. Kirby, G. W., Atkin, L., and Frey, C. N. Recent progress in "rope" and mold control. Food Industries, 1936, 8: , 470, Jensen, L. B., Wood, I. H., and Jansen, C. E. Swelling in canned chopped hams.

9 78 CHARLES K. PHILLIPS AND SAUL KAYE Indust. Eng. Chem., 1934, 6: Hall, I. A. Sterilized spices: new factor in food quality control. Food Industries, 1938, 10: 44-45, James, L. H. Seducing the microbial content of spices. Food Industries, 1938, 10: 48-49, McBride, B. S. Automatic equipment for space fumigation. Food Industries, 1938, 10: Tesair, J., and Cameron, E. J. Present status of the sterilization of spices. The Canner, 1938, 86: Smith, H. W. Treated spices reduce spoilage. Food Industries, 1940, 1: Yesair, J., and Williams, O. B. Spice contamination and its control. Food Besearch, 194, 7: Griffith, C. L., and Hall, L. A. Sterilization process. U. S. Patent,189,947 (1940). 17. Idem. Sterilization process. U. S. Patent Ee.,84 (1943). 18. Idem. Sterilization of pancreatin. U. S. Patent,189,948 (1940). 19. Idem. Sterilizing colloid materials. V. S. Patent,189,949 (1940). 0. Baer, J. M. Method of fumigation of organic products. U. S. Patent,9,360 (1941). 1. McCormiek and Co. Personal Communication Angla, B. Sur 1 'emploi des 1 'oxyde d 'e'thylene en denologie. Compt. Bend. Acad. Agr. France, 1939, 5: Mrak, E. M. The deterioration of dates. Eept. Ann. Date Growers Inst. (Coachella Valley, California), 1941, 18: Whelton, E., Phaff, H. J., Mrak, E. M., and Fisher, C. D. Control of microbiological food spoilage by fumigation with epoxides. Food Industries, 1946, 18: Baerwald, F. K. Food preservation method. U. S. Patent,370,768 (1945). 6. Velu, H., Lepigre, A., and Bellocq, P. Action bactgricide de 1'oxyde d'fithylene a l'fitat gazeux. Bull. Acad. M6d. (Paris), 194, 1X6: Salle, A. J., and Korzenovsky, M. The effect of a vacuum on the destruction of bacteria by germicides. Proc. Soc. Exper. Biol. and Med., 194, SO: Ludin, B., and Kane, H. J. The germicidal action of gases. Unpnblished report. Division of Bedding Laboratory, N. Y. State Dept. of Labor, Eoberts, J. L., Allison, L. E., Prickett, P. S., and Eiddle, K. B. Preliminary studies on soil sterilization with ethylene oxide. Jour. Bact., 1943, 45: Hansen, H. N., and Snyder, W. C. Gaseous sterilization of biological materials for use as culture media. Phytopathology, 1947, 37: Brown, E. W. Carboxide gas: a new insecticidal fumigant for bedbugs and cockroaches. U. S. Naval Medical Bulletin, 1933, 31: Stehle, E. L., Bourne, W., and Lozinsky, E. tjber die pharmakologische Wirkung von Athylenoxyd. Arch. Exper. Path, und Pharm., 194, 104: Waite, C. P., Patty, F. A., and Yant, W. P. Acute response of guinea pigs to vapors of some new commercial organic compounds. IV. Ethylene oxide. TJ. S. Public Health Eeports, 1930, 45: Greaves-Walker, W. J., and Greeson, C. E. The toxicity of ethylene oxide. Jour. Hyg., 193, 3: Zernik, F. tjber Aethylenoxyd. Giftwirkung, Verwendung, Schutzmassnahmen. Gasmaske, 1933, 5: Blackwood, J. D., and Erskine, E. B. Carboxide poisoning. U. S. Naval Med. Bull., 1938, 36: Anon. Industrial Hygiene Newsletter, 1947, 7: No. 3, Abrams, H. K. Dept. of Public Health, State of California. Personal communication, Bodforss, S. Die Athylenoxyde. Ihre Darstellung und Eigenschaften. Stuttgart, 190, pp Bronsted, J. N., Kilpatrick, M., and Kilpatrick, M. Kinetic studies on ethylene oxides. Jour. Amer. Chem. Soc. 199, 51: Deckert, W. Bestimmung des Athylenoxyds bei Durchgasungen mit athylenoxydhaltigen Praparaten. Ztschr. anal. Chem., 1930, 8: Idem. Zur massanalytischen Athylenoxydbestimmung. Ztschr. anal. Chem., 1937, 109: Lubatti, O. F. Determination of ethylene oxide. Jour. Soc. Chem. Indust., 193 SI: T.

10 STERILIZING ACTION OF GASEOUS ETHYLENE OXIDE. I Idem. Determination of fumigants. III. Microdetennination of ethylene oxide and hydrogen cyanide. Jour. Soc. Chem. Indust, 1935, 54: 44-46T. 45. Idem. Determination of fumigants. XIV. Besidual ethylene oxide in wheat. Jour. Soc. Chem. Indust., 1944, 63: T. 46. Burns-Brown, W. Determination of fumigants. VI. Purity of commercial ethylene oxide in cylinders. Jour. Soc. Chem. Indust., 1936, 55: 31-35T. 47. Idem. Application of fumigants to ships and warehouses. V. Distribution of ethylene oxide in barges containing dried fruit. Jour. Soc. Chem. Indust., 1937, 56: 116-1T. 48. Kerckow, F. W. Analytische Bestimmung von Athylenoxyd. Ztschr. anal. Chem., 1937, 108: Deckert, W. Des Gasrestnachweis bei Athylenoxyddurchgasungen (T-Gas). Ztschr. angew. Chem., 193, 45: Leroux, L. La detection des gaz et des vapeurs toxiques. Bev. d'hyg. Med. Prev., 1935, 57: Heering. Die Anwendung von Indikatoren zur Erkennung giftiger Gase und Dampfe. Gasmaske, 1936, 8: