PHOSGENE* KIRBY E. JACKSON Nashville, Tennessee
Phosgene was first prepared by John Davy i n 1812 by mixing equal volumes of carbon monoxide and chlorine, and exposing to bright sunlight. It has also been prepared by the ozidation of chlorinated hydrocarbons with chromic acid; the interaction of sulfur triom'de with chlorinnted hydrocarbons; the combination of carbon monoxide and chlorine in the presence of a solid catalyst. Due to its rapid hydrolysis in the presence of moisture
it cannot be ssuccessfIrlIy used in chenzical warjare i n misty or rainy weather. Iron and steel objects are quickly attacked and its toxicity i s a consequence of its hydrolysis. Phosgene was prepared in the United States by passing chkorine and carbon monozide over a carbon catalyst. Mazimum production was attained shortly after the signing of the Armistice when fifty-five tans was poduced per day.
RISTORY AND PREPARATION
glass tubes packed with glass wool (glass acting as a weak catalyst). Wilm and Wischin (5) introduced the constituent gases, employing a slight excess of chlorine, into a 10-liter flask and then into a second smaller one, both being exposed to sunlight. Emmerling and Lengyel (6) describe the oxidation of chloroform by means of a mixture of potassium dichromate and concentrated sulfuric acid. They assumed the reaction to be:
D
URING the years 1800-12 several investigators, including Gay-Lussac and Thenard (1) and Murray (2), published statements to the d e c t that carbon monoxide and chlorine were mutually inactive, but in 1812 John Davy (3) more carefully investigated their interaction. He mixed equal volumes of the two gases which had been dried over calcium chloride, in a vessel over mercury; in the dark there was no result but after exposure for about a quarter of an hour to bright sunlight the color of the chlorine had entirely disappeared. The gases contracted to half their former volume the remaining gas contained neither hydrogen chloride nor carbon dioxide. He found that it was absolutely necessary that the constituents should be dried, otherwise "it will contain a considerable admixture of the carbonic and muriatic acid gases, which are produced in consequence of the decomposition of hygrometrical water." Davy named this new gas phosgene from two Greek w o r d s + o s meaning "light" and -yews "to produceu-which signifies, formed by ligbt. It is also known as "carbonyl chloride" and "carbon oxychloride." The principal methods for the preparation of phosgene resolve themselves into the following chief groups:
1. The photochemical combination of carbon monoxide and chlorine. 2. The oxidation of chlorinated hydrocsarbons with chromic acid. 3. The interaction of sulfur trioxide or oleum with chlorinated hydrocarbons. 4. The comhination of carbon monoxide and chlorine in the presence of a solid catalyst. The photochemical comhination of carbon monoxide and chlorine has been the subject of several detailed investigations. Chapman and Gee (4) experimented on the action of light on mixtures of equal quantities of pure carbon monoxide and chlorine passing through *Published with the permission of the c h i d of the chemical Warfare Service.
2CHCls
+ 3 0 +2COCll + H 2 0 + Clz
but Erdmann (7)showed and Gri'Pard and Urbain (8) later confirmed that the reaction actually takes place as f~uows: 2CHCls
+ CrO* + 2 0 +2 C 0 C l ~+ CrOC1. + H.0
Schiitzenberger (9) prepared phosgene by warming a mixture of carbon tetrachloride and sulfur trioxide; Dewar and Cranston (10) by heating a mixture of chlorosulfuric acid and chloroform; Armstrong (11) by the action of sulfur trioxide on a number of compounds-chloroform, carbon distilfide, phosphorus pentachloride, hexachlorobeuzene, etc. Schiitzenberger (12) prepared phosgene by passing carbon monoxide and chlorine through a tube containing spongy platinum heated to 350' and Patern6 (13) constituent gases over animal charcoal, by Atkinson, Heycock, and Pope (14) found that the activated wood used in the British box respirator proved more effective as a catalyst than the activated bone charcoal prepared by the latter, Among other reactions of less importance that give rise to the formation of phosgene the following are cited: heating of carbon tetrachloride with zinc oxide (15), action of concentrated hydrochloric and nitric acids on carbon disulfide (16), decomposition of bistrichloromethyl oxalate (17), dry distillation of sodium trichloroacetate (18), passage of carbon monoxide and chlorine into a saturated solution of aluminum chloride in chloroform (1% heating of a mixture of phosphate rock and common salt in an atmosphere of carbon
622
dioxide (20), decomposition of chloropicrin a t its boiling point (21), autoxidation of trichloroethylene (22), passage of carbon monoxide through antimony pentachloride (23), passing carbon monoxide over glowing silver chloride (24), heating sodium with phosphorus pentachloride (25), the action of carbon monoxide on platinic chloride (26), heating of trichloromethyl formate (27), heating of coke, quicklime, and chlorine in an electric furnace (28), passage of carbon oxysulfide and chlorine through a red-hot porcelain tube (29). PHYSICAL PROPERTIES
Phosgene therefore attacks iron and steel objects and is useful as a destructive agent. It is apparent that phosgene has no military utility in misty or rainy weather. Phosgene reacts with a number of metallic elements, especially on heatiig, to give the chloride of the metal and carbon monoxide. Many of the more reactive elements-potassium, sodium, etc.-react a t ordinary temperatures but the less active only upon warming (34). It has also been found that phosgene is capable of exciting the emission of surface electrons from sodium and potassium (35). With aluminum halides ~hoseene forms comnlexes ', (36); with metallic oxides tce pure anhydrous c h h d e s are formed (37); sulfides are very reactive with phosgene giving the chloride of the metal and carbon oxysulfide (38). Davy (3) noted that phosgene reacts with ammonia and since then numerous products of side reactions have been studied by many investigators. The primary amines react with phosgene violently with the liberation of much heat, the products depending, to a great extent, on the conditions of the experiment. By passing the vapor of phosgene through a solution of the amine in an inert solvent, urea is almost always formed. With secondary amines the formation of carbamyl chloride generally takes place, while with aliphatic tertiary amines there is no action. With aromatic tertiary amines there is only slight activity except in the presence of anhydrous aluminum chloride, when the Friedel-Craft reaction takes place with the formation of a considerable amount of acid chloride or ketone. Phosgene reacts with phenol in two different ways, depending upon the relative amounts of the two reacting substances. With one molecule of phenol to one of phosgene, phenyl chloroformate is formed; with two molecules of phenol to one of phosgene, phenyl carbonate is formed. For this reason phenol in the form of its sodium salt was first used b y the Allies in their early masks for the absorption 6f phosgene. Hexamethylenetetramine (urotropin) was used for the same purpose and proved more effective. Numerous reactions between phosgene and other organic compounds have been studied; and this reagent is employed in the manufacture .of organic dyestuffs, and some pharmaceutical products:
At low temperatures, phosgene is a clear, colorless liquid boiling a t 8.2'/756 mm. (30); hence, in warm weather it assumes the form of a vapor, unless under pressure. It does not freeze until the temperature of - 118°C. (31) is reached, so that under all ordinary conditions i t exists in liquid or gaseous form. In the vapor phase phosgene is a colorless gas. The liquid is heavier than water, having a specific gravity of 1.432 a t 0°/4' (6). The specific heat of phosgene is 0.243 calorie per gram (32) which is less than one-fourth that of water. The molecular weight of phosgene is 98.92; thus one liter of the vapor under standard conditions weighs 4.41 grams, the vapor density compared with air is 3.416 (which is 1.4 times that of chlorine). It therefore "hugs the ground" more tenaciously than chlorine and fills such places as ravines, trenches, dug-outs, etc. Its vapor pressure ranges from zero a t -183' (b.p. liquid oxygen) to 752 mm. a t 8.2" (reported b.p. phosgene). The higher the vapor pressure of a gas, the higher is the concentration of that gas that may be contained in a given amount of air. The molecular heat of evaporation between 0' and 8' is calculated as approximately 5500 calories (14). The heat of vaporization of phosgene is approximately 56 calories per gram, while that of water is 537 calories per gram. Thus nearly ten times as much heat is required to vaporize a given quantity of water as is required to vaporize an equal quantity of phosgene. With its high vapor pressure, low specific heat, and low heat of vaporization it is no wonder that phosgene is %onpersistent." Phosgene in the liquid state readily,dissolves a number of substances which are otherwise difficult to get into solution, and, for this reason, is a &itable DETECTION liquid for the determination of molecular weights by boiling-point alteration. The molecular elevation Phosgene is easily detected qualitatively by aspiratconstant was found to be 29 by Beckmann and Junker ing the gas suspected of containing it through a satu(30). rated aaueous solution of aniline. After two hours' ~, standing the diphenylurea is filtered off and identified CHEMICAL PROPERTIES by its melting point (39). If the precipitate is washed At ordinary temperatures, and in the absence of with water and dried a t 70' the weight gives a commoisture, phosgene is a fairly stable compound; a t paratively accurate idea of the amount of phosgene 503O it dissociates to the extent of 67%; a t 553', 80%; present. A variation of this method for quantitative a t 603", 91%; and a t 800°, 100% (33). It rapidly estimation, which gives more accurate results, consists hydrolyzes in the presence of even atmospheric mois- in treating the precipitate of s-diphenylurea by the ture, especially a t somewhat elevated temperatures. Kjeldahl process, estimating the amount of ammonia \~
formed calorimetrically by means of Nessler's solution (4.0). A more sensitive qualitative test is that with p-phenetidine (41). The phosgene-suspected material is dissolved in benzene and to the solution is added one drop of p-phenetidine; a turbidity due to the presence of s-di-(4-ethoxypbeny1)weaindicates the presence of phosgene. The best method of estimating phosgene in a mixture of gases is by absorption (42). Atmospheric moisture decomposes phosgene comparatively slowly, and acid solutions retard absorption. The method which has been found best is to pass a known volume of the gas (2 to 3 liters) in 8 to 10 hours through 10 cc. of 10 N sodium hydroxide solution dissolved in 50 cc. 95% alcohol. After the passage of the gas the solution is evaporated on the water bath and the sodium chloride formed estimated in the usual way. The accuracy of the method depends on the absence of hydrogen chloride or chlorine in the gas, if the phosgene is contaminated with these gases the analysis is correspondingly more difficult.
secondary, since it has been impossible to detect the absorption of phosgene into the blood stream. Exposure to i t results in a variety of changes in the organism, in addition to the development of pulmonary edema. Thus, gassing has a definite influence on the respiration, heart beat, temperature, concentration of the blood, the water content of the lungs and other tissues, the chloride content of the blood and tissues (with resulting changes in chloride excretion by way of the kidneys), the number of red and white cells of the blood and the respiratory function of the blood, leading to dyspnea and partial asphyxia. Acidosis is present a t times, and there is a distinct influence on protein metabolism. The picture presented by phosgene shows that acute gas poisoning may be divided into three stages (44). In the first stage, which lasts from five to eight hours, there is usually a very significant dilution of the blood; during this period pulmonary edema develops. In the first part of this period the temperature may fall markedly; in the latter part of the period there is a greatly accelerated pulse, accompanied by a rise in PHYSIOLOGICAL PROPERTIES temperature considerably above the normal. The Phosgene has an odor "more suffocating than that second stage, which reaches its maximum between of chlorine and it occasions a very painful sensation in five and twenty-four hours, is characterized by a very the eyes" (3). The odor has been described as that of marked concentration of the blood. In this period musty hay, green apples, or green corn. There is also a the temperature may be well maintained, or there may more or less distinct odor of hydrochloric acid, as well be a distinct drop below normal. If the temperature is well maintained, the condition of the individual is as a sour taste, due to hydrolysis. The toxic action of phosgene results from its hy- considered good; on the other hand, if the temperature suddenly falls, the outcome is usually fatal. The third drolysis: stage is characterized by a readjustment to normal COCL H20-+2HC1 + CO. conditions with respect to both concentration of the Phosgene passes over the trachea and bronchi and blood and temperature. destroys the epithelium of the smaller bronchia and It is usually assumed that pulmonary edema is the bronchioles, and especially the alveoli, the walls of cause of death in gas poisoning. While i t is true that which are everywhere damaged. The toxic action of pulmonary edema and changes in blood concentration phosgene is slower than that of chlorine, probably are intimately related in gas poisoning, the direct because, to produce its effects, it must undergo chemical cause of death is the extreme concentration of the blood change; this fact bas earned for phosgene the name of rather than the presence of the fluid in the lungs. having a delayed action. Death is caused by something more than simple Since as little as 1 mg. per liter may be lethal if the inability of the blood to absorb oxygen, by something exposure lasts more than a few minutes, and is quite more than a physical obstacle in the lungs. It is quite capable of producing casualties, it can readily be seen logical, therefore, to assume that blood concentration that even in cold weather and a slight wind, effective is immediately responsible for death. Blood concentramilitary concentrations of phosgene m,ay be secured as a tion means a failing circulation, an inefficient oxygen result of the great toxicity and the wide margin be- carrier, oxygen starvation of the tissues; fall of temperatween the theoretical possible concentratton and the ture, and, finally, suspension of vital activities. lethal dose. It is the most effective of the pulmonary TREATMENT irritants for it bas been found that for a 30-minute exposure 3 mg. per liter of chlorine, 0.8 mg. of chloroIf, in spite of intensive treatment in the first stage, picrin, and 0.36 mg. of phosgene are approximately the blood becomes markedly concentrated, and a equivalent (43). Were it not for the fact that the notable fall in temperature takes place, the condition mask affords complete protection no army could stand must be considered very serious, and if the patient is against it. To the end of the war its use continued to left untreated, he will surely die. At this point infusion of a solution is carried out. The essential treatment, produce casualties when gas discipline was relaxed. From an extensive investigation of the acute effects in this stage, is to diminish, if possible, the degree of of gassing, i t is quite evident that the detrimental blood concentration, and it has been found by experiinfluence of phosgene is confined to the respiratory ence that it matters little how this is done. Thus, the tract and that all other effects must be regarded as purpose may be accomplished by the infusion of salt
+
solution, by oral administration of water, or even by large scale because it had never been necessary to intraperitoneal injection of salt solution. Probably make any considerable quantity of it. The French and one-half of the patients in a serious condition in this English passed oxygen through a gas producer filled stage of blood concentration may he saved by one of with coke, the oxygen combining with the carbon, these procedures. giving carbon monoxide. Obviously the great heat of ' Since edema and a highly concentrated blood lead to reaction of oxygen and carbon must be carried away deficiency of oxygen in the tissues, the problem of the by the water rapidly enough to insure the life of the relation of oxygen to the treatment of gas poisoning is converter. Plant engineers conceived the idea of using presented. Oxygen treatment alone in gas poisoning a mixture of carbon dioxide and oxygen. The union of does not save life. This follows from the fact that carhon dioxide with carbon to form carbon monoxide oxygen administration does not change the concentra- is a reaction in which heat is absorbed; therefore, by tion of the blood, which is the direct cause of death. using the mixture of the two gases, the heat of the one When, however, the concentration of the blood is reaction was absorbed by the other. In this way a restored to a more nearly normal condition, the addi- constant temperature could be maintained, and the tion of oxygen administration to the treatment is of production of carbon monoxide was greatly increased. obvious benefit, since under these circumstances the Carbon dioxide was prepared by the combustion of blood regains its normal respiratory functions. coke; the gas was washed and then absorbed in a solution of potassium carbonate; and subsequently MANUFACTURE freed by heating. In Germany and the United States the war-time The phosgene plant a t Edgewood Arsenal included production of phosgene was based on the combination a carbon dioxide plant, having a daily capacity of 125,of carbon monoxide with chlorine, using carbon as a 000 cu. ft. of pure carhon dioxide and an oxygen plant catalyst. In France and Italy the early war-time with a capacity of 200,000 cu. ft. per day, which, in production was based on the action of sulfuric acid on combination with four producers gave a daily procarbon tetrachloride; later on they changed to the duction of 400,000 cu. ft. of carbon monoxide. Phosgene was then prepared by passing the mixture of carbon monoxide-chlorine process (45). Phosgene, prior to the war, was manufactured in carbon monoxide and chlorine over a carbon catalyzer. Germany in the works of the Bayer Company. The In this reaction much heat is generated so it was plant was capable of producing about thirty tons per necessary to cool to a definite temperature. The month. The method employed does not appear to be an reaction is practically complete and the phosgene is economical one; the carbon monoxide was prepared liquefied by passing through condensing coils immersed by passing carbon dioxide over wood charcoal contained in refrigerated brine. Phosgene was shipped overseas in gas-filled m d e s and the resulting carhon monoxide in large quantities in wrought-iron drums containing was washed with sodium hydroxide. The carbon 1700 pounds, as well as in standard-caliber gas shells, monoxide and chlorine were bubbled through Woulff Stokes' mortar bombs, and Liven's projector bombs. bottles and, a t a short distance from the point of mixing, The capacity of the Edgewood plant a t the time it were passed downward through a layer of about 20 closed, shortly after the signing of the Armistice, cm. of prepared charcoal. By regulating the mixture was forty tons per twenty-four hours. Two additional so that there was a slight excess of carbon monoxide, units were nearing completion, which would have the phosgene was obtained with 0.25% to 0.5% of brought the total capacity to eighty tons-per twentychlorine. Stress was laid upon the method of purifying four hours. Phosgene was also manufactured in the the carbon catalyst. Wood charcoal was treated with government plant operated by the Oldbury Electrohydrochloric acid and other acids until perfectly free chemical Company having a capacity of ten tons per from soluble ash, the acid was washed out, and the day. The Bound Brook, New Jersey, plant of the charcoal dried in vacuum. The phosgene was liquefied Frank Hemingway, Inc., had a capacity of five tons per day; this was sent overseas mostly in bu1.k (47). by cooling with ice and salt (46). The method of manufacturing phosgene employed USE IN THE FIELD a t Edgewood Arsenal was worked out in the labdkatory Because of the high boiling point of phosgene it of the Oldbury Electrochemical Company. Of the raw materials necessary for the manufacture of phos- could not be used alone in gas cylinders even during gene, the chlorine was provided a t first by purchase the summer months, but when it was mixed with from private plants, but later through the Edgewood chlorine no difficulty was experienced. The percentage chlorine plant. After a suffiaent supply of chlorine of phosgene in the mixture was suffidently high to was assured the next question was how to obtain an secure the many advantages which it possesses over adequate supply of carbon monoxide. Instructions chlorine; e. g., it is about eight times more toxic, much from Europe were to the effect that the carbon mon- less reactive, and possesses the delayed effect. Very interesting light is thrown on the first phosgene oxide could be best made by first producing oxygen from liquid air and using pure oxygen in a small cloud gas attack by Maj. Barley, D.S.O., Chemical water-cooled producer to make pure carbon monoxide. Adviser to the British Second Army (48). It appears A method for this gas had not been developed on a that in November, 1915, the French captured a prisoner
who had attended a gas school in one of the factories of valve, partly to prevent re-breath'mg exhaled air and the Interessen Gemeinschaft. Here lectures explained partly to prevent the deterioration of the alkali of the that a new gas was to be used against the British mask by carbon dioxide. The protection was later forces, many thousands of casualties were expected, further increased by the addition of hexamethyleneand an attack would follow, which, correcting the tetramine, and this mask was known as the PH helmet. errors of the fist effort a t Ypres, would lead to the This increased the protection more than threefold'capture of the Channel ports. Efforts were a t once to 1000 parts per million of air. In the American Expeditionary Force i t was found made to obtain information on gas preparation by the Germans in front of the British sectors. A sergeant- (49) that gas was responsible for 70,552, or 31.4%, major was captured on the morning of December 16th of all casualties entered in the hospitals. Nearly oneand he revealed the date and front on which the cyl- half of the gas casualties were caused by unknown inders were installed. About 35,000 British troops gases; many of them by combinations of two or more were found to he in the direct line of the gas, but, gases, thus rendering i t impossible to attribute the owing to the timely warning and to the protection which direct cause to a known gas. Phosgene was responsible had recently been adopted, very few casualties were for 6834 casualties and of them 66 died. The number of experienced. The Germans had prepared a huge in- days lost by men in hospital from phosgene gassing fantry attack, and used a new type of gas shell on this was 311,040; the average number of days for each case occasion. Massed German troops received huge casu- was 45.5. It is not necessarily the primary purpose in war to alties owing to the preparation of the British and the kill but, on the contrary, to incapacitate for the time failure of the gas attack. During the summer of 1915 it became evident that being, until the objective is gained. To hospitalize phosgene-chlorine mixtures would be used in gas attacks a man it has been estimated that six men are required and it was therefore necessary to provide protection for attendance, thereby reducing by just that many against them. The hypo helmet, which offered no those who might otherwise bear arms. Mustard, protection against phosgene, was soaked in an alkalme "the king of the war gases," was responsible for 27,711 sodium phenolate solution containing glycerol, and this casualties, more than four times as many as phosgene, new form of impregnation created the P helmet. It with 599 deaths (nearly ten times as many as phosgene protected against 300 parts of phosgene in a million accounted for), but with only 271,993 days lost as of air. Since the impregnating solution attacked contrasted with 311,040 days lost due to phosgene. flannel, two layers of flannelette were used. The helmet Thus, a t least in some respects, it would appear that was further improved by the addition of an expiratory phosgene was more dective than mustard.
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) (25) (26)
GAY-Luss~c AND TAENARD, Rechcches-fihysco-chimigue, 2, 150 (1811). M ~ R ANicholson's Y, Jownal, 30,227 (1811). DAVY,JORN, Phil. Trans., 102,144(1812).
CRAPMAN AND GEE, 3. Chem. Soc., 99, 1726-39 (1911). WILMAND WISCHIN,Ann., 147,150 (1868). EMMERLING AND LENGYEL, Ann. S24#$'~.,7,101-7 (1869). ERDMANN, Ber., 26, 19904 (1893). GRIGNA~D AND URBAIN, Comfit. rend., 169, 17-20 (1919). SCHOTZENBERGER, ibid., 69,352 (1869). DEWARAND CRANSTON, Chem. Neu's. 20,174-5 (1869). ARMSTRONG, Bey., 3, 730 (1870). SCK~~TZENBERGER, Bull. soc. ckim., [2] 10, 188 (1868). PAT ERN^, Gem. chim. itel., 8,233 (1878). ATKINSON,HEYCOCK, AND POPE, I. Ckem. Sac., 117, 141026 (1920). SCH~~TZENBERGER, Comfit. rend., 66, 747 (1868). BERZELIUS AND MARCET, Gilbert's Ann., 48,161 (1814). CAROURS, Ann. ckim. fihys., [3] 19, 352 (1847). E HENRY, Ber., 12, 1845 (1879). PLOVNIKOV, 3. RUSS.Phys. Chem. Soc., 48, 457 (1916). PLOVNIKOV, Ckem. News, 112,267 (1915). GARDNERAND FOX,J.Chcm. Soc., 115,1188(1919). ERDMANN, J.prakt. Chem., [2] 85,78(1912). HOPMANN, Ann., 70, 139 (1849). GBBEL,J . firakt. Chem., [I] 6,388 (1835). GUSTAVSON, Ber., 3, 990 (1870). SCH~~TZENBERGER, Ann. St&.. 8,242 (1870).
(27). HENTSCHEL, 3 . pakt. Ckem., [2] 36,101,214 (1887). 2.elegepu. Clhm.., 19,1775 (1906). (28) MICHALSKI, (29) EMMERLING AND LENGYEL, Bw., 2,546-8 (1869). (30) BECHMANN AND JUNKER, Z . anolp. Ckem., 55,370 (1907). (31) ERDMANN, Ann., 362,148 (1908). (32) SHIVER, J. CHEM. EDUC., 7,99 (1930). (33) BODENSTE~N AND DURRANT, Z. fihysik. C h m . , 61, 437 (1908). (34) Bereelius' Jakresberichte, Fort. Phys. Wiss., 16,162 (1837). (35) HABER AND JUST, Ann. Phys., [4] 36; 608 (1911). (36) BAUD,Comfit. mend., 140,1688 (1905). ibid., 152,87 (1911). (37) CHAUVENET, (38) CHAUVENEI., ibid., 152, 1250 (1911). ibid., 168,773 (1919). (39) KLINGAND SCHNITZ, (40) KUNGAND SCRNITZ, ibid., 168,891 (1919). Ber. deut. pharm. Ges., 3,213 (1893). (41) SCHOLEEIN, (42) BERTHOLET, Bull. soc. ckim., [N.S.],13, 9 (1870). (43) VEDDER, "Medical aspects of chenii~alwarfare," The Williams & Wilkins Co., Baltimore, 1925, p. 83. (44) UNDERHILL, J . Am. Med. Assoc., 73,686 (1919). (45) KONGWAWW, Z. ges. Schiess-Sfirengstoffw,,22, 152 (1929). (46) NORRIS, Ind. Eng. Ckem., 11,828 (1919). (47) HERTY, i6id.. 11,9 (1919). (48) LEFEBURE, "The riddle of the Rhine," The Chemical Foundation, Inc., New York City, 1929, p. 46. "A comparative study of world war casualties (49) GILCHRIST, from gas and other weapons," U. S. Government Printing ofice, 1928, p. 21.
The attention of correspondents is directed to the change of address of the editorial office, which is now located at Kent Chemical Laboratory, The Universit of Chicago. The business and publication offices remain at the plant of the ~ a c z ~ r i n t i nCompany g at Easton, Pennsylvania.
