LABORATORY EXPERIMENTS WITH CHEMICAL WARFARE AGENTS' WALTER KINTTOF (Translated from fhe German) Editor's Note: This is a continuation of a translation of a large portion of a German textbook by Walter Kinttof begun in the December, 1947, issue.
SMOKE AGENTS
ing agent is used in great quantities) which carry over When the sky is obscure as the result of very fine into the classificationgroup of chloride screens. liquid particles (diameter 1 X 10-3 to 1 X 10-6cm.) Phosphoric Acid Screening Agent floating in the air, in common language this is called In Experiment 1 we became acquainted with the a "fog," while, if solid particles are present, this is called a "smoke." We will drop this differentiation formation of phosphoric acid screens. The yellow and designate all artificial obscuring substances, re- phosphorus which is superheated combines very gardless of the physical state of their aerosols, as "arti- quickly with the oxygen of the air to produce a flame with the formation of phosphoric pentoxide (P206) ficialfogs." The artificial fogs have as their purpose that of which vaporizes and is converted by the humidity of P206-+ hiding from the sight of the enemy persons, buildings, the air according to the equation 3Hz0 movements, etc., for a short or long period. The 2H3P0~to droplets of phosphoric acid which represent suitability of the fog for this purpose depends on the the phosphoric acid smoke. Especially intensive is the cloud formation of the following factors: (I) the fog must have good camouphosphorus when i t is pressed in a liquid state above flaging capacity and covering capacity, i. e., its optical its ignition temperature through a fine spinarette into thickness must be as great as possible: (2) i t must be resistant both against heat and humidity (water con- the atmosphere. Suitable devices were constructed tent of the atmosphere, rains, etc.); (3) the fog-pro- especially after the World War to secure this effect. ducing device must be easy to handle and transport; Such an apparatus is the so-called "phoda blower" of and (4) the product must be very cheap so that, with the chemical firm Hugo Stoltzenberg, Hamburg. By small amount of material and expense, an intensive this device a large amount of yellow phosphorus, melted by steam and heated to 10O0C.,is blown by the screening effectmight be produced. The importance of artificial fog for air protection steam through fine spiuarettes into the atmosphere. (camouflage service) lies both in the possibility of Upon emerging into the atmosphere, the phosphorus screening important works (plants, railway stations, bums with a great flame forming a thick white screen. communication centers) and entire villages and in the We can imitate the great effect of this smoke producusage for camouflage from enemy flying squadrons tion by the following experiment, which explains also (simulation of screening and pasture, etc.). From the principles of the Stoltzenberg device. EXPERIMENT 21. In the test tube ( a of b) of the the tactical viewpoint fog may be used for both defen"Microphoda blower" are placed three rods of phossive and offensive purposes. According to their chemical compositions, the phorus of 5-6 cm. in length and of 3 4 mm. in diameter. screens may be classified as follows: acid, chloride, Then water is poured over them so that it almost comes up to the side tube. The container is then closed with and colored screens. a cork bored through and a capillary tube of copper, ACIDIC SCREENS and heated on a stand in'a water bath up to 70-80°C. All screens are designated acid in which the smallest particles consist of acids or their anhydrides. Their most important representatives are the screens produced from phosphoric acid. A less important role is played by titanic and silicic acid screens (as different from practice here. in America the titanic acid screen-
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Copyright vested in the Attorney General, pursuant to law, and published here by permission of the Attorney General in the public interest under License No. JA-1213, as was the article "Chemistry in War," by Frits.Haber, in our November issue, 1945.
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JANUARY, 1948
(Thermometer!) Then the apparatus is taken outdoors and the. rubber blower is put to work. By this means the liquid phosphorus is pressed through the capillary copper tube and comes out from the nozzle and ignites in the air, thus producing an enormous cloud (Fig. 2). Use: The phosphoric acid cloud is especially valuable for its strong camouflaging capacity-20 mg. per cm. makes objects invisible from a distance of 5-6 meters. On the other hand, there are a nupber of disadvantages. Due to the strong hygroscopic nature of the phosphoric acid, the clond condenses into drops, becomes heavy, and sinks quickly to the ground. Also the danger of the phosphorus ,(fire, wounds; toxicity) limits its use considerably as a screening agent. .The production of phosphoric acid clouds by means of the Stoltzenberg phoda blower is dependent on the existence of a steam power plant, and therefore it can be taken into consideration only for the Navy. S u l f u ~ i cAcid Screen Agent
Sulfuric acid clouds aye formed by combining the moisture of sulfuric acid with sulfuric anhydride (SO8). The SO3 may be volatilized from its solution in concentrated sulfuric acid, or chlorosnlfonic acid vapor may be hydrolized by the water vapor of the air. A particularly noticeable effect is secured by using a solution of sulfuric anhydride in chlorosulfonic acid. The evaporation of the screening agent can occur ' either as a result of mechanical or chemical means. The cloud-producing devices used in the following experiments correspond in general to the smokespraying device in which the necessary pressure is furnished by compressed gases which can be produced also in the interior of the apparatus by chemical means, and the "cloud lime device." Moreover, in warfare, the volatilization of acid agents may be made to take place through using the escaping gases of motors, i. e., airplanes.
FIGURE 3 , ( ~ ~ ~ ~ with t ~ common, ~ - con~ ~ centrated sulfuric acid. ~ ~ ~ ~ l t ~ ? )
Production of Smoke Screens from S u l f u ~ i cAcid by Chemical Means:
EXPERIMENT 23. In a 250-cc. suction flask place a layer of white sand 1 cm. thick. Above this add a layer of granulated quicklime (granulated in a mortar. Eye protection!). Close the flask by means of a Perforated stopper with a funnel having a glasscock. The funnel is charged with 50 cc. of fuming sulfuric acid (65 Per Cent anhydride content) or, better, a solution of 0°C Part thereof in one Part chlorosulfonic acid, ,NOWadd the acid dropwise from the funnel which is covered e t h a glass plate ( ~ i4).~ .
Production of Sulfuric Acid Clouds by Mechanical Means:
EXPERIMENT 22. (This is an outdoor experiment.) In a 150-cc. filter flask is placed 50 cc. of fuming sulfuric acid with 30 per cent or, better still, 65 per cent free anhydride, or 50 cc. of chlorosufonic acid (cf. Exp. 24), or 50 cc. of a solution of 50 g. of fuming sulfuric acid with 65 per cent anhydride content in 50 cc. of chlorosulfonic acid. The flask is connected by means of a one-hole rubber stopper to a Pfaul's sprayer (ten liter per hour capacity) and attached to the suction pipe is a rubber blower, by means of which the acid in the tube is forced out and is dispersed from its fine nozzle (Fig. 3). Result: During the dispersion of the fuming sulfuric acid or chlorosulfonic acid or a mixture of these two as a result of the release of the anhydride SOa, a thick white clond of sulfuric acid or sulfuric acid and hydrochloric acid is produced, which causes a strong irritating cough. This can be avoided by using a handkerchief (preferably a wet one) held to the mouth
Result: The quicklime reacts so strongly, even increasing to a red heat with the fuming sulfuric acid, that the sulfuric trioxide evaporates from the solution and eventually, mixed with chlorosulfonic acid vapors, it leaves through the side tube of the flask in the form of a dense smoke cloud. EXPERIMENT 24. In the bulb of a special retort of which the delivery tube terminates in a Liebig condenser, introduce 100 cc. of pyrosulfuric acid (fuming sulfuric acid with 50 per cent free anhydride content) or 80 g. of codmon fuming sulfuric acid with 65 per cent anhydride content. Then the inlet tube provided with a ground-in piece is set up, and dried hydrogen chloride (produced by dropping concentrated sulfuric acid on bone-dry sodium chloride) from the connected
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JOURNAL OF CHEMICAL EDUCATION
gas generator (suction flask with dropping funnel) is passed into it until no more absorption occurs (recognizable by the decrease of temperature in the reactor flask as well as by the exit of hydrogen chloride vapors from the adapter). Then the gas-inlet piece is replaced by the ground-in piece combined with a thermometer, and then it is distilled over a wire screen into the adapter provided with a calcium chloride tube. The fraction from 155 to 165'C. is collected separately. Result: Hydrogen chloride combines with sulfuric trioxide to form an acid which fumes strongly in the air, that is, chlorosulfonic acid which boils at 155'C. under atmospheric pressure. See Figure 5. Properties: Chlorosulfonic acid is a water-clear liquid having a specific gravity of 1.776 at 2G°C. which boils at 155OC. under 760 mm. pressure, and at 7475'C. under 19 mm. pressure, and forms a dense cloud in the air,. The formation of a cloud from the acid depends on the reaction with water vapor of the air producing drops of sulfuric acid and hydrochloric acid. (Tactical use in smoke shells!) With liquid water chlorosulfonic acid reacts with explosive violence forming sulfuric and hydrochloric acids. Chlorosulfonic acid dissolves sulfur trioxide in any stage. Material is immediately destroyed by it. I t produces on the skin bums similar to those caused by concentrated sulfuric acid. In organic chemistry chlorosulfonic acid is used as a very active sulfurating reagent. EXPERIMENT 25. (Analysis of chlorosulfonic acid.) By means of an eye dropper provided with a long capillary tube, a small quantity (approximately 0.3 'to 0.5 g.) of chlorosulfonic acid is poured into a tared bulb with a stem sealed by flame, and the weight of chlorosulfonic acid is determined. Then the bulb is broken under 100 cc. of distilled water which is contained in a 200-cc. vertical cylinder provided with a perforated rubber stopper. This is then shaken until the cloud is completely dissolved. By means of a pipet 20 cc. of the resulting solution is put into each of two beakers and titrated with N/10 KOH using phenolphthalein as indicator for total acid and with N/10 AgNOa in nitric acid solution for HCI (retitration of excess AgNOa with N/10 silver ammonia solutioh by using a drop of ferric sulfate solution as indicator, Fig 6). Result: One mol of chlorosulfonic acid is decomposed by water into one mol of sulfuric acid and one mol of hydrochloric acid
Of the substances for the production of smokes from sulfuric acid. the most effective is a mixture of chlorosulfonic acid'and sulfur trioxide, here added in the form. of pyrosulfuric acid. I t is caUed "smoke acid." The sulfuric acid clouds excel because of their comparatively long persistency, considerably surpassing those produced from phosphoric acid. Sulfuric acid drops stay suspended in the air due to their slight hygroscopicity and do not increase as much because of moisture from atmospheric humidity as do the phosphoric acid drops. Therefore, they do not become so heavy and remain suspended in the air for a longer period. Sulfuric acid clouds have an unpleasant effect on the respiratory organs and skin. As much as 10 mg. per cubic meter causes an irksome coughing irritation from which one can be protected by holding a wet handkerchief over the mouth and nose. Thirty milligrams per cubic meter gives such a good screening that in ,daylight, from a distance of 5-6 meters, nothing can be seen. Besides this the sulfuric acid clouds are excellent due to their considerable inexpensiveness, that is, 1 kg. of smoke acid costs approximately five cents. Recently they have been used for prevention of frost in springtime on plantations. Probably the main role is due to the heat formed by the combination of sulfur trioxide with water vapor of the air.
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Titanic Acid and Silicic Acid Smoke Screens
These are formed by dispersing titanium or silicon tetrachloride and reacting these dispersions with the humidity of the air according to the equations TiClr 2Hz0 = TiO* 4HC1 and SiCL 2H20 = SiOz 4HC1. When ammonia is simultaneously dispersed, their covering capacity becomes increased because besides TiOz or SiOz ammonium chloride is also formed. The clouds are harmless F ~ c u n s6 but expensive, therefore they cannot compete with phosphoric acid and sulfuric acid clouds despite their good screening properties.
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Smoke Screens From Salts
Of the many inorganic salts only two are suited for smoke screens. They are ammonium chloride a n d , zinc chloride. They are used as such for smoke production directly or are formed by reaction. As to importance, they are not inferior to the smokes produced from acids. Having the same good screening properties, their handling is considerably simpler. In the form of smoke candles of various sizes they can be transported anywhere. Ammonium Chloride Smokes Production by sublimation:
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EXPERIMENT 26. Heat 2 g. ammonium chloride
JANUARY, 1948 over a direct flame in a copper dish 6 cm. in diaineter. Result: Ammonium chloride sublimes with heat, forming smoke (sublimation point 325'C.). EXPERIMENT 27. To produce considerable ammonium chloride smoke, a fuel mixture must be used whereby a largP quantity of ammonium chloride can be evaporated in a comparatively short time. Two and five-tenths grams of dextrose or potato starch is well mixed in a porSelain dish with 3.5 g. potassium chlorate and filled in a smoke candle can. In the center of the mixture we make a hole with a glass rod, then "Ignit" is filled in the cavity so made and ignited with a stormproof match. Result: A mixture of carbohydrate and potassium chlorate burns when ignited properly, with the formation of considerable heat (Fig. 7). EXPERIMENT 28. In a porcelain dish 4 g. of ammonium chloride, 2.5 g. of potato starch, and 3.5 g. of potassium chlorate are well mixed by means of a spatula, and the whole mixture packed into a 10-g. smoke candle can and pressed in. Then'the mixture is ignited out of doors in the above-described manner.
Result: A burning fuel mixture of a carbohydrate and potassium chlorate will cause ammonium chloride to sublime for smoke formation. Production by addition of ammonia and hydrochloric acid:
EXPERIMENT 29. (Wet method.) The formation 'of ammonium chloride smokes can often be observed in laboratories when bottles containing hydrochloric'acid and ammonia are left open or when the bottles are brought close to each other. To make this formation of a cloud more dense, use the apparatus which consists 'of two suction flasks each provided with a gas inlet tube connected in series. In one of the bottles put concentrated hydrochloric acid (37 per cent) and in the other one concentrated ammonia (35 per cent) close to the ends of the inlet tubes. Now flow air through them by means of a rubber blower (Fig. 8). Result: Vapors of ammonia and hydrochloric acid unite to form an ammonium chloride cloud according to NHIOH HCl = Hs0 NHaCI. EXPERIMENT 30. (Dry method.) Provide two test tubes with short glass tubes drawn to a fine bore. Fill one of the tubes with a mixture of 5 g. of ammonium chloride and 4 g. of calcium oxide, the other one with 7 g. potassium bisulfate and 3 g. of sodium chloride. Set
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both tubes in a double test tube holder. The necks oi the tubes are directed against each other. By simultaneous heating of both tubes, hydrogen chloride is
generated in one of the tubes and ammonia in the other. At the exit of the nozzles a cloud of ammonium chloride is formed. See Figure 9. Zinc Chloride ~ m o k i - ~ e r g e r Mixture
EXPERIMENT 31. In a copper dish 2 g. of zinc chloride is heated over the flame of a blast burner. Result: Zinc chloride sublimes a t a high temperature (sublimation point 730°C.). EXPERIMENT 32. Two cubic centimeters of carbon tetrachloride and approximately 4 cc. of silver nitrate' solution are shaken in a test tube after closing the mouth of the tube with the thumb. Result: Carbon tetrachloride does not react with the silver nitrate solution. In that compound the chlorine is in organic combination, that is, i t does not form ions with water. EXPERIMENT 33. On the bottom of a test tube drop one drop'of carbon tetrachloride, add a spatulaful of zinc powder, and fill the test tube along its length up to its radius with a layer of zinc powder. Stroingly heat the zinc starting a t the mouth of the slightly bent tube, and finally vaporize the carbon tetrachloride on the bottom of the tube. (Observe the color.) When the tube has cooled off, pour its contents on a wet a t e r and wash into another test tube using about 20 cc. of distilled water. To the filtrate add a few drops of nitric acid and one drop of silver nitrate solution. There is a white precipitate! Result: With heat zinc powder decomposes carbon tetrachloride releasing chlorine. The inorganic bound
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chlorine reacts with silver nitrate in aqueous solution as an ion forming silver chloride. The conversion of carbon tetrachloride by zinc powder has been used by the Frenchman Berger for the production of smoke mixtures. For starting the reaction, he added to the mixture of zinc and carbon tetrachloride sodium or potassium chlorate as a source of oxygen. For making denser smoke he added ammonium chloride and magnesium oxide. Above 200°C. the cohversiou of zinc and carbon tetrachloride occurs automatically with development of heat sufficient to sublime the zinc chloride. EXPERIMENT 34. In a beaker mix, to form a paste, 35 g. zinc powder, 9 g. sodium chlorate, 7 g. ammonium chloride, 8 g. magnesium oxide or magnesium carbonate, and 41 g. carbon tetrachloride. Twenty-five grams of this mixture is placed in a candle'box and ignited outdoors by Mox matches or "Ignit" or stormproof matches. Result: The mixture burns with the production of a dense white smoke: Berger mixture. The Berger mixture has a very good screening capacity. The substance is stored under cover (smoke candles) and can be kept for unlimited time and is safe against premature firing. In a small space there is considerable screening.power stored away. The ignition occurs by the most simple way. Only a concentration of msre than 100 mg. per cubic meter bas an effecton breathing. The production of smoke candles can occur in all sizes. To these advantages there is only one disadvantage, that is, due to the strong hygroscopicity of zinc chloride, the smoke screen can be upheld only for a comparatively short time. COLORED SMOKES
EXPERIMENT 35. In test tubes over open Bunsen
flames are heated small quantities of artificial indigo (indigopn), auramine, chrysodine orange, and paranitraniline red. Result: The above-named dyes sublime without decomposition. On that property of certain dyes (th'at they sublime below their decomposition point) is based the production of colored smokes which might be used to simulate fires (red), pastures (green), and the like. The heat necessary for the sublimation is produced by a carbohydrate-potassium chlorate fuel mixture. The following formulas can be used for the preparation of wellfunctioning colored smoke screens: Yellow smokes-2.5 g. glucose, 3.5 g. potassium chlorate, 3.5 g. auramine, 1.0 g. chrysoidin, and 5.0 g. kieselguhr or 2.5 g. glucose, 2.5 g. potassium chlorate, 2.5 g. auramine, and 2.5 g. kieselguhr. Red s m o k e 2 . 5 g. glucose, 2.0 g. potassium chlorate, 8.0 g. paranitraniline red, and 1.0g. kieselguhr. Blue s m o k e 4 . 0 g. indigotin (artificial indigo), 3.5 g. potassium chlorate,' 2.5 g. glucose, and 7.5 g. kieselguhr. Green smoke-2.6 g. indigotin, 1.5 g. auramine, 3.5 g. potassium chlorate, 2.6 g. glucose, and 2.5 g. kieselguhr. Note: In lieu of glucose, common potato starch can be used. The above mixtures are pressed into 10-g. smoke candles, covered with a carton paper disc provided with a hole in the center, and then closed with a can cover. The carton paper has the purpose of cooling off the evaporated dyestuffs and thereby liberating them. Ignition is by means of "Ignit." Result: By sublimation of the named dyestuffs by means of carbohydrate and potassium chlorate fuel mixtures, colored smokes are obtained.
