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ADDRESSES AND CONTRIBUTED ARTICLES Incendiaries in Modern Warfare1n2 By Arthur B. Ray UNION
CARBIDE A N D
CAREON
RESEARCH LABORATORIES, INC.,LONGISLAND CITY, N. Y.
(Concluded)
PABT11-INCENDIABY
DEVICES
It is beyond the scope of this article to go into great detail regarding the various mechanical devices which have been developed to carry incendiary materials and permit them to have an effective incendiary action. However, by means of general description and illustration the essential characteristics of all the types of devices developed by the warring nations will be given. The following classification of devices will be followed: Small arms ammunition. Shell. Trench mortar projectiles. Grenades and other hand devices. Aircraft bombs. Flame projectors. Miscellaneous SMALCARMSAMMUNITION Incendiary small arms ammunition, while carrying only a very small amount of material, has proved to be of the greatest value in effectively attacking highly flammable targets, such as aircraft, which are either filled with hydrogen or carry tanks of gasoline. Most of the incendiary ammunition is of the regular calibers and fits the standard machine guns, but a special size, 11 mm., which can carry more incendiary material has been successfully used and is highly recommended. There are two classes of bullets which may have an incendiary effect-real incendiary bullets which may, or may not, begin to function before impact, and tracer incendiary bullets which begin t o function a t the instant of expulsion or shortly after and which, primarily intended as an aid in directing aim, may have considerable incendiary action, provided the target i s struck before the bullet ceases to trace. The types of incendiary materials used-whXte phosphorus and special oxidizing agent-combustible mixtures-have been previously discussed. As has been pointed out, the phosphorus is ignited by friction and the other mixtures are either ignited directly by the flare from the propellant or by a more sensitive primer which has been ignited by the propellant or by percussion. The type of bullet which carries phosphorus is shown in Fig. 1.8 When the bullet is fired the heat generated by friction quickly melts the fusible alloy from the vent and the molten phosphorus flows out and immediately ignites. The regular caliber bullet carrying the tracer-incendiary mixture of barium peroxide and magnesium previously discussed is shown in Fig. 2. A 11-mm. bullet carrying the mixture of barium nitrate, magnesium, and charred linseed oil with an igniting composition of red lead and magnesium is shown in Fig. 3. This larger bullet is very effective, in fact, it is claimed that balloons can be ignited by i t at 1600 yards. These three types of bullets were generally used. The German perforating tracer-incendiary bullet, shown in Fig. 4, carried an incendiary material stated to consist of:
.
Per cent Strontium nitrate 75 Magnesium 13 Aluminium 3 Iron 6 Resinous material 3 1 Presented before the Division of Industrial Chemists and Chemical Engineers a t the 58th Meeting of the American Chemical Society, Philadelphia, Pa., September 2 t o 6. 1919. 2 This article is published by permission of the Chief of the Chemical Warfare Service. 8 Dimensions in this and other illustrations are given in niiilimeters except where otherwise indicated.
The primer which was pressed in lightly was stated to consist of: Potassium permanganate Iron filings
Per cent 56 to 58 45 to 42
The German armor-piercing incendiary bullet shown in Fig. 5 which proved t o be especially effective against airplanes carry. ing protected gasoline tanks is interesting. The primer or igniting composition which is ignited upon impact consists of magnesium, potassium chlorate, and antimony sulfide. T h e incendiary charge consists of magnesium, aluminium, barium chlorate, sulfur, and a little nitrocellulose. The advantage of this bullet is that the burning composition in front of and around the armor-piercing core of steel is more likely to ignite gasoline, for example, from a perforated tank than if the composition were in a complete container which may be broken away from t h e bullet bodily on impact.
SHELL Shell designed to have an incendiary action, range in size from, the small 37-mm. to the large 17.5-cm. shell. The smaller sizes were used with great success in attacking aircraft from the ground, and the larger calibers were used with moderate success against all sorts of flammable ground targets. Xhere are tracer shelr which have an incendiary action over a considerable portion of the trajectory and the incendiary shell proper which do not function as incendiary devices until the moment of bursting, when the incendiary material is ignited and usually expelled. A common type of tracer-incendiary shell carrying the red lead and magnesium composition and primer is shown in Fig. 6 . Shell of this type range in size from 37 mm. t o 11.5 cm., but only the 75-mm. and 3-in. sizes were produced by the United States. These shell were used principally for balloon incendiary purposes. They are usually fitted with time fuses which are set t o function considerably short of the target. The fuse charge ignites t h e primer which in turn ignites the incendiary mixture, and the incandescent products of the combustion are emitted from t h e shell through holes in the head. The smoke from this combustion leaves a definite trace of the projectile so that the laying of the piece may be corrected if the trajectory does not pass through the target. The hot gases have a very efficient incendiary action if the shell passes through the envelope of a balloon. These shell may begin to function when 50 yds. lrom the muzzle of the gun and continue this action for from 6 to 25 sec., depending upon their size. A tracer incendiary shell which differs from the type just described in that it is base-opening is shown in Fig. 7. This type of shell, carrying a mixture of magnesium, barium nitrate, and binder, was used by British and Germans. Strontium nitrate was used sometimes t o give a better tracing effect. T h e flash from the time fuse is transmitted through the central tube and ignites the small quantity of composition between the mill board washers. This fires the priming and the incendiary composition in the body. The base is blown out with the result that t h e flame is emitted through the base of the shell. This dame lasts for about 15 sec. and gives a tracing as well as incendiary effect. Shell designed for incendiary effect alone may contain ther-
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FIG.I-INCENDIARY
‘i-
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BULLET,.303 INCH
FIG 2-S.P.G. TRACER BULLET, . 3 0 3 INCH
FIG &-INCENDIARY
BULLET,
11 M M .
be the commercial product or a modified form containing, in some cases, manganese, copper, or lead oxide. It is usually compressed in the shells to prevent segregation. Our experiments with this type of shell, however, were not successful. We were unable t o get complete combustion of the thermite or to prevent excessive scattering when the shell exploded. The incendiary action of the very finely divided and widely scattered material was not thought satisfactory, so a shell containing the incendiary material in definite units was experimented with. A type of shell which contains units of thermite or an oxidizing agent-combustible mixture is shown in Fig. 9. The units held in perforated WT STEEL CrwE cases are ignited from the central tube and ex.TCUC€P hop(R)JmOl’l pelled from the front of the shell by the explosion of the charge in the base. The units are PFUMEP ~ p o 3 1 T I C 4 l large enough to have considerable incendiary effect. While this type of shell was not produced by the United States, i t was extensively used by FIG.4-PERFORATING AND TRACER BULLET FIG.&-INCENDIARY ARMOUR-PIERCING the Other warring nations‘ The USED IN AVIATIOI BULLET against aircraft a 7.7-cm. shell which on bursting scattered steel slugs and flaming incendiary mite, special oxidizing agent-combustible mixtures, sodium, units, called “flaming onions” by allied airmen. A 15-cm. Gerphosphorus, and flammable organic materials. The materials man shell used against ground targets with little success coni n some cases are present as small units which are ignited and tained twelve or more celluloid cylinders surrounded by white scattered when the shell functions. I n other cases the incen- phosphorus and imbedded in paraffin, as shown in Fig. 10. A diary material is present as a mass which is expelled and more rather complicated Italian shell scattered 35 incendiary units or less scattered when the shell fbnctions. For an intensive when it functioned. The largest incendiary shell used during the war was the 17.5incendiary action it is of course desirable t o have as large a quantity of incendiary material as possible in one place, and for this cm. German shell shown in Fig. 11. It contained, as shown, reason extensive experiments were made with a type of shell thermite and sodium, but despite its size was not especially which expelled but did not scatter its incendiary charge. effective. A typical small shell which carries thermite and an igniting A base-opening shell, which on functioning ignited and expelled a single large unit of incendiary material, was developed by us and expelling charge of the potassium perchlorate-magnesium mixture known as ophorite is shown in Fig. 8. This type of but not produced in quantity. The general observation regarding incendiary shell is that shell acts as a shrapnel shell scattering the hot metal and slag produced by the thermite reaction and is said to have been par- the small caliber tracer-incendiary type was quite effective ticularly effective against aircraft. The time interval necessary against aircraft but t h a t the larger type designed for use against for practically complete ignition of the thermite is obtained by ground targets was not as successful, primarily because of the the use of a beeswax plug between t h e igniting ophorite in the greater difficulty of igniting the type of ground targets in the central tube and ophorite in t h e base. The thermite used may war zone.
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FIG.
FIG. 9-6-IN. (15.3-CM1 INCENDIARY SHELL
7-1NCENDURY-TRACER 75-Mu. SHELL
FIG.10-15-CM. INCENDIARY SHELL
TRENCH MORTAR PROJECTILES Trench mortar projectiles such as the 3-in. and 4-in. Stokes’ bombs and the 8-in. Liven’s drums were used to destroy grass, shrubbery, or camouflage which might act as a Screen for enemy movements; to clean out woods; to demoralize the enemy during a gas projector attack, and to indicate the range in night projector attacks. The Stokes’ bombs loaded with phosphorus had little incendiary effect. When loaded with about 7.5 lbs. of slightly compressed thermite and the explosive igniter, “ophorite,” and exploded in the air by time fuse arrangement they were more effective. Obviously the best results were obtained when the explosion took place near the target SO that it was struck by the particles of hot or even molten metal and slag. Experimental work carried out at Hanlon Field, A. E. F., resulted in the development of an improved type of Stokes’ bomb which scattered larger units of very hot metal. No other incendiary material has been satisfactorily employed in Stokes’ bombs. The &in. Liven’s drum shown in Fig. 12 usually contained balls of cotton or jute waste and a special flammable liquid. The spontaneously flammable liquid previously discussed was developed primarily for use in these drums. The liquid generally used, however, consisted of a light and a heavy oil. The 1
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FIG.8-77-MM, INCENDIARY SHELL
FIG. 11--17.5-CM. MINENWERFER INCENDIARY SHELL
light oil is readily ignited by the flash from the explosive charge and the heavy oil gives the long burning desired. A mixture of light and heavy petroleum distillates gave satisfactory results. Soaking the cotton or jute balls in a chlorate solution and carefully drying in vacuum before putting them in the oil mixture caused them to burn with a fiercer flame when ignited. The units may also be soaked in molten “solid oil” and the oil allowed to solidify on them. This treatment results in more Oil being carried with them when they are expelled. These drums are fitted with an impact fuse which causes them to explode on landing. The oil saturated incendiary units are ignited by the flash from the explosive charge or take fire spontaneously if the special spontaneously flammable liquid is used and burn vigorously for sometime over an area approximately 50 yds. in diameter. The incendiary effect produced is good.
GRENADESA N D OTHER SMALL DEVICES While the use of incendiary grenades is limited, such armament is considered very valuable. Small portable incendiary devices can be used to set fire readily to flammable materials which it is desired to get rid of in either defensive or offensive operations. Several types of devices were used, such as real grenades filled with phosphorus or thermite, cans filled with flam-
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mable liquid and fitted with igniting and exploding devices, and paper or metal tubes filled with the oxidizing agent-combustible type of mixtures. Grenades, usually made of sheet metal, containing white phosphorus and fitted with an exploding device, were of course used principally for producing smoke, but the burning phosphorus scattered by the explosion had some incendiary effect, particularly in dug-outs. The phosphorus-filled grenades were widely used by all armies, and their incendiary effect, although incidental, was not lost sight of. Grenades containing thermite were used widely and proved to be very valuable for destroying or rendering useless guns and other material which had t o be abandoned in retreat, for destroying airplanes which were forced to land in enemy territory, for igniting flammable liquids which had been thrown into dug-outs by any means or which had been sprayed over an objective by a flame projector. When aviators used these grenades t o destroy airplanes after forced landing, one was placed on the gas tank, and one on delicate parts of :he motor. The delayed action fuse allowed time for the men to place themselves at a safe distance. Automobiles and tractors which it was necessary to abandon were also easily destroyed in a similar manner. The breech mechanism of guns was effectively sealed by the molten iron produced by the thermite reaction. A successful type of thermite grenade is shown in Fig. 13. In loading this grenade the thermite is moistened with sodium silicate, 1amped into the sheet iron container, one end of which is open, and baked. ,r m g ' 2 k A ~ r I ,/'W M R Y I I I I The hole is bored ,snmDawmo in the center of the block and the cover is crimped on the container. The bag of aluminium-barium per&mma&Dt oxide igniter from which the strands of quick match - luccNoiIs*y extend is inserted and the percussion firing plug --.fmrrw AND put in place so &aSnNS cMQ6E that a piece of Bickford fuse in the plug is connected with the quick match. The charge of thermite weighs about 600 g. The Germans made use of small portable inFIG. MARK I LIVENSINCENDIARY PROJECTIV3 cendiary devices which usually consisted of tubes of metal or pasteboard filled with an oxidizing agent-combustible type of mixture and fitted with a friction igniting device. One kind of device contained 1670 g. of incendiary material of the following composition: PJi.0'
Potassium nitrate Srilfur Carbon
Per cent 62 5 27.0 10.5
This material burns rapidly with a lively flame and gives off quantities of white smoke. The stated purpose of this device was to chase the enemy out of their shelters by a great development of flames and smoke. In actual practice it readily serves either as an incendiary or smoke-producing device, depending on circumstances. Its name, Brand-rohren, however, indicates the greater incendiary action. Other tubes of different sizes
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and containing different incendiary mixtures were used. Some use was made by the French of a can which contained about 3 liters of a petroleum oil mixture and was fitted with a friction exploding and igniting 777prrn device. In operation the device weighing about 71bs. was armed . /gn/ter and thrown into trench or dug-out. It was reported to be quite effective. With the idea of developing a device which would have both the advantagks of the thermite grenade against metal and FIG.13-THERMITE GRENADE the advantages of the oil device against flammable material a combination thermite-solid oil grenade was experimented with. The thermite used in these experimental devices was found to be advantageously bound with celluloid-about 4 per cent by weight being used dissolved in a suitable solvent, such as acetone. Solid oil prepared as previously described was satisfactory. The arrangement of the materials is shown in Fig. 14. The grenade is fired by withdrawing the safety pin and releasing the bouchon firing handle as is done with all American grenades. The spit of the fuse ignites the booster which sets off the igniter and thermite in turn. The resulting molten iron and slag
rndEh& FIG.14-TIXERXITE-SOLID
OIL GRZNADE
readily penetrates the grenade case, a t the same time igniting the celluloid case and the solid oil. The mass burns with a large hot flame for about 4 min. This device was not produced because it was thought that the all-thermite grenade previously described would be of more value under the conditions then existing.
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FIG.16-INCENDIARY
ZEPPELIN
BOMB
AIRCRAFT BOMRS
It was early recognized that bombing by means of aircraft is of the greatest military importance, and it was also early recognized that incendiary bombs possessed great potential destructive power. It is interesting to recall that during the first raid over London on May 31, 1915, one German airship dropped four 200-lb. explosive bombs, twenty small explosive grenades, and ninety incendiary bombs. This armament was clearly designed to affect the maximum amount of damage t o life and property in a populous town and indicates the importance attached to incendiary bombs. Later, incendiary bombs were extensively used by the allied airmen with considerable success. The bombs developed and used since 1915 may be divided into three classes: (1) large bombs known as “intensive type” which burn practically in situ, (2) large bombs known as “scatter type” which on functioning scatter widely a number of incendiary units, and (3) small unit bombs which can literally be rained down upon a target. It is generally conceded that the scatter type is the least effective. Obviously the kind of bomb
-r
ica5W-4
FIG.16-GERMAN
AEROPLANE INCENDIARY BOMB
which can be most effectively used will depend upon the kind of target to be attacked. Grain crops, forests, and other rela-
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tively highly flammable targets which occupy a considerable area are best attacked by small unit or the scatter type bombs which permit a wide scattering of the incendiary materials. On the other hand, towns, factories, storehouses, ammunition depots, and similar targets are best attacked by intensive type bombs which burn with a large fierce flame. The intensive type bombs developed comprise a large variety of models and carry practically all types of incendiary materials. The most satisfactory incendiary filling consists of thermite or other great heat evolving mixture and a larger amount of a highly flammable material. The first bombs dropped from German Zeppelins were of the intensive type. They weighed 20 lbs. each,and, as shown in Fig. 15, contained benzine, thermite, and ignition mixture, and were wrapped with tow rope impregnated with tar and barium nitrate. A percussion fuse served to cause the first ignition. These rather crude bombs were dropped from airships only. A rater type of bomb dropped from German airplanes as well as airships, shown in Fig. 16 weighed either 10 or 20 lbs. The main filling in these bombs was a pasty mixture of benzine and paraffin, or paraffin and potassium perchlorate. The central tube contained a mixture (composition “A”) of aluminiumC iron filings, and barium nitrate which 6,0*D was ignited on impact (fuse not shown) and served to heat up and ignite the other materials. The black powder explosion was intended to disrupt the sheet iron casing and scatter somewhat the incendiary materials. The bombs were wrapped with tow rope as shown and then shellacked over. They were extenFIG, 17-INCENDIARY BOMB sively used and were fairly INTENSIVE TYP~ successful. A great many bombs of the intensive type were developed by the Allies. A 20-lb. bomb developed by the French and known as the “Chenard” is considered to be very effective. It contains as the principal incendiary material a mixture of rosin and celluloid, and is unique in that it is ignited while falling, so reaching the target in flames, The British early used with some success a bomb filled with gasoline which was ignited on impact by a Very cartridge. Other British bombs of this type filled with special oxidizing agent-combustible mixtures or, later, with thermite, were used, but the principal British bomb is the small unit bomb which will be described later. A 50-lb. intensive type bomb was developed by US which contained, as shown in Fig. 17, thermite and solid oil as the principal incendiary materials, and had an impact ignition mechanism held in the nose or the tail of the bomb, or both. As shown in Fig. 18,the bombs consist of two main parts-the steel nose and the sheet zinc body with the sheet iron vanes attached. The thermite bound with sodium silicate as previously described may be baked in sheet iron cans which are then placed in the nose or i t may be baked directly in the nose. The solid oil is run into the zinc body while warm and fluid and allowed t o harden. To protect the thermite from the oil a zinc plate is
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an incendiary material, consisting of cotton impregnated with a flammable liquid and a mixture of potassium perchlorate and paraffin. I t is interesting to note that the igniting and explosive material in this bomb is a sulfur-bound thermite, which when ignited in a confined space acts as a mild explosive as well as a great heat producer. A 50-lb. scatter type bomb developed by us is identical with the intensive type as far as outside dimensions are concerned. I t may contain units consisting of waste tied into balls and saturated with flammable liquid such as a mixture of crude turpentine and carbon disulfide. Or the units may consist of a core of solid oil held in a celluloid container or an oxidizing agent-combustible mixture, about which is wrapped waste impregnated with ammonium nitrate and coated over with a mixture of trinitrotoluene and naphthalene. The units are usually about 3 in. in diameter. When the bomb lands, ignition and ejection of the units are effected by an explosion of black powder in the nose. A simultaneous explosion of a smaller amount of powder in the rear disrupts the bomb casing and assists materially in the scattering of the units. While this type of bomb was developed it was not used because the small unit bombs or darts were considered more effective. A bomb similar to the one j u t described, in that balls of waste saturated with a flammable liquid were ignited and scattered, was developed by the Italians.
soldered over it. The body or rear casing is strengthened and the central tube held firmly in place by the steel cup, as shown in Fig. 17. Ignition may be effected by a black powder flash or by the bullet from the service -.... cartridge. The arrangement of the ignition mixture, which is slightly compressed to prevent segregation. is shown. When the bomb functions on landing. the thermite, being first ignited, serves to burn through the casing, and the immense amount of heat liberated quickly melts, volatilizes to a certain extent, and ignites the, oil which begins burning with a tremendous burst of flame which is most effective. The zinc casing is readily destroyed and thesolid oil continues to melt and spread the conflagration. The expressed opinion of those who have witnessed these bombs in action is that the incendiary materials are highly efficient and that any further developments should be directed toward the mechanical improvement of the bomb. Many varieties of the "scatter type" bomb have been developed. A 40-lb. air burst bomb filled with white phosphorus was used by the British against observation ballwns and ground targets. A rather inefficient 20-lb. bomb developed by the French functions on impact and ejects one or more ignited units of
Fie. 20 I N T B N S ~ TVPB Y B IBCBNDIABY DROPB o ~ a I I - B R ~ T ~ S X'MALL U ~ i T r v e I~ N E B N ~ ~ A Dnop RY Bme 111, IV A N D V-AYBR~EAN SXALL UNIT TvnB I N C B N I I ~ X Y D x O P Boaes V I - A ~ ~ S B L C ATHSRM1TB-SOLID N OD. I N C B N ~ A GSSNAOS ~Y VII-ANBBICAN SCATTBR TVPBINCBNDIAPY DRYBOMB 1-Axeetcm
A late model bomb used by the Germans, shown in Fig. 19, was designed to burst in the air and scatter forty-six small incendiary units. These units consisted of perforated zinc cylinders filled with about 50 g. of a nitrate-suliur-tar mixture which burned quickly with a small hat Ilame. While these various scatter type bombs are fairly effective against readily flammable targets, it is generally believed that the more recently developed, small unit bombs can be used to a better advantage. The British originated the idea of dropping a large number of small unit bombs instead of one large scatter type bomb, and developed the 6.5-oz. bomb shown with American bombs in Fig. 20. In principle this little bomb follows that of a mortar and projectile complete. It carries a cartridge very much like a shotgun shell which on impact sets down on the striker point in the base of the body thus causing the function-
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T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
ing of the cap which simultaneously ejects the cartridge and causes ignition of the incendiary charge. This charge is the special flaming thermite previously described. The little bombs are loaded into containers which are hung underneath the airplanes in such a manner that they may be released as desired. Each container may carry 144 or 272 bombs, depending upon its size. The number of these bombs which can be camed by one airplane runs from 860 carried by a De Haviland 4 up to 16.000 carried by aHandleyPage V type. It is amarent that bv .^ formation flying the Frc 21--GSah(~~"WEX" P O R T A B L E T V P EF L A M E PROlPCTOR bombs can literally he rained down upon a large area 01 target and practically cover it with a sheet of flame. And it is claimed hy the British that since the terminal velocity of the bombs is such as to cause them topenetrate heavy roof constructions they can be used most effectively against towns and factories, prelerahly in conjunction with large, high-explosive bombs. There is some question, however, as to the real efficiencyof the incendiam material employed. Following the Britisb idea we have developed two types of small bombs or darts, as they are called by us. One type intended primarily for use against crops and forests has no great peuetrating power and burns with a very large flame. It carries the oxidizing agent-combustible mixture especially dcveloped
PIC. 22--H*v
PLAlaB
cux
for it, which has been previously described. in an elongated 12-gage shotgun shell and functions on impact by reason of a simple firing device. The other type, intended primarily for use against building constructions, has sufficient penetrating
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power to pierce the roof, and carrier B sufficient amount of incendiary material t o be effective. The incendiary material is the efficient thermite-solid oil combination. previously discussed, held in a zinc container. Neither of these darts was produced in quantity. Both are shown in Fig. 20.
FLAME PROJECTORS Devices for projecting flaming liquids were originated by the Germans and used early in the war with considerable success, which was due, however, more to the demoralizing etfect than to the actual destructive power. Flame projectors have since been developed by the Allies and used to some extent. The principle of dl flame projectors i s the same. U m U y a suitable flammable liquid contained in a metal reservoir of greater or less capacity is put under heavy pressure hy a compressed gas in a steel cylinder connected to the reservoir, generally through a reducing valve designed to maintain a given pressure in the reservoir. The liquid is forced out of the reservoir through a pipe dtted with B valve and terminated by a nozzle of suitable diameter which directs the stream towards the enemy. The liquid is ignited either at theend of the by meanS FIG.2 3 - - " L ~ - r l m ~ d PORTABLE ' &*MB PROlBCTOR of attached igniting devices, or, where it is projected on the earth, by means of incendiary grenades which are thrown into the area played upon by the stream. The flammable liquids and igniting devices used have been previously discussed. The propellant gases ~enerallyused are nitrogen, hydroqen. carbon dioxide, and air, each of which have certain advantages and disadvantages. Absolutely dry carbon dioxide, owing to the fact that it can be readily liquefied and compressed into small volume. is recommended very strongly. Liquefied or compressed flammable hydrocarbon gases are unsatisfactory because of their physical characteristics. In some cases the gas is charged directly into the cylinder with the liquid. but this is not considered a satisfactory practice. The compressed gas is usually carried in a separate cylinder. The pressures which it is possible to employ depend largely
Pia. 24-"Lawne~cs'' I i ~ l P sPaOlEcio~BEING. PIRI?:D S B O I
CBOUWO
upon the diameter of the nozzle. The longest throw possible is desired, and the characteristics of the liquid, the diameter 01the nozzle, and the pressure are all adjusted to this end. With a given liquid and size of nozzle the length of throw increases
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regarding the most important of them are given in the, tabulation which follows: DATARGDAXDINC PORTADLRFLAICFIIOJBCTP*.S German French Italian British American Dedg"*tio" We= Pa 1 ) . S.. F. Lawrence Boyd No. 5 Weight charged, Ibr. tM $3 4n 66-70 70 capacity, Sal. 2.5 3.0 1.5 3-3.6 4.76 Propellant Nitrogen Air Air Clrboo HydcoDioxide zen Working prenruie, Ihr persq, tn. 288 iin 240 240 . Ixa.ofoonie.in. 0.24 0.3~-0.48 m i Range of projection, it. 8n-inn 88 83 12,; I I-;
__ ___
Fro.
~ ~ - A x B I I I C & NP o % T * ~ L B T v p n F ~ k x 6PP.OJBCTOB
as the pressure increases up to a definite point, beyond which the stream of liquid is broken up into drops and the length of projection is decreased. For a five-sirteenths~in.nozzle an average working pressure with a moderately heavy liquid i s around 250 lbs. per sq. in. and the projection obtained may be over 100 ft. Both portable and large stationary machines have been employed. The portable type projectors, carried on the backs of the operators by means of suitable straps and pads, contain from 2 to 5 gal. of liquid, have 3 projection of from 60 to 125 it., and may he emptied of liquid by continuous discharge in less than 20 see. They are used by attacking parties and are usually operated 50 as to throw a number of shots or jets of liquid in-
Fie. 2 E - G r a ~ m
Sr~rrowanu Twa FLAMS PROJBCTOA L'SED sox T n r ~ c nDBBBNS&
stead of a continuaus stream. This method of operation prolongs the actual period during which they can be used as weapons, which even under the best conditions, is very short. A great many portable projectors differini: considerably in many respects have been developed. Some comparative data
The German "Wex" Flammenwerfer showqin Fig. 21 is a late type differing from earlier types chiefly in shape. :It has a detachable nozzle from which fact it gets it? name ["Wex!'. from u'echselbarer-interchangeable). This model has a toroidshaped oil container, as can be seen, which is made of,steel 1.5 mm. thick. The gas container is a steel sphere which fits inside the ring of the oil container and has a volume of about 0.1 cu. it. Ignition is effected by means of a to& deyice at the nozzle' which is automatically ignited by the pressure of the releasen liquid and which continues to burn while the liquid is being discharged. The French P-3 model has separate oil and gas, containers and an igniting device attached to the nozzle which is set off by the operator. Other French projectors differ considerably in design and some early ones had no igniting device but deppnded upon incendiary grenades to ignite the projected oil. The British projector known as the "EIny Flame Gun" (Fig. 22) is unique in that the oil and propellant (carbon dioxide) are contained in the same reservoir. Ignition is effected by a device at the nozzle consisting of a slow burning mixture inserted in a metal holder. This mixture is ignited by an electric detonator, the battery case which furnishes the current being clipped on to any convenient part of s-*-m:za, the apparatus. This form of ignition "- -'is said to be excellent. The machine. although possessing some undesirable features, gives very good results. '~~,". ,~~ The British Lawrence projector (Fig. 23) carries a separate carbon dioxide container inside the oil container, and has practically the same electrically ignited ignition device as the Hay projector. The type and range of projection is shown in Fig. I,IX 24. This projector has maregoodand fewer bad features than any other yet produced. The American projector, as finally developed, possesses some differences of design from any other models. It has double oil containers for convenience in carrying and a separate PlO. Zi-G*Rm*N SNCSYDI. propellant cylinder as shown in Fig. .-R,.ue 25. Hydrogen is used as the propellant gas and is also used ior producing a pilot light for ignilion of the liquid a t the nozzle. The large stationary type of projectors designed primarily for trench defense carried considerably more liquid than the portable type and were capable of a much longer projection. This increased projection Iange is obtained by using a nozzle with larger orifice and operating under P higher pressure. In some models a number of liquid containers are connected to a manifold with the propellant gas cylinders connected to each container. By this arrangement the apparatus is made more mobile because the units are not so heavy.
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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
A large “Flammenwerfer” used by the Germans for trench defense shown in Fig. 26 contained about 45 gal. of liquid. The propellant gas was nitrogen held in the two small cylinders, and the igniting device was similar to that used on the portable type projectors. The French I,-1 projectors consisted of three liquid containers connected to a manifold, three compressed air cylinders, and the necessary valves and projecting nozzle. The total volume of liquid was about 33 gal., the duration of projection 15 sec., and the maximum range of projection 180 ft. The utility of these machines was considered very limited. The large machines designed by the British for use in emplacements, tunnels, or trenches had a maximum range of projection of 100 yds. Eighty gallons of liquid held in four tanks were projected by means of compressed “deoxygenated air.” The ignition device was similar to that used on the portable projectors previously described. The development of large projectors was not pushed by us because the general usefulness of the machines was questionable. MISCELLANEOUS DEVICES Besides the devices such as have been described, which were more or less generally used, a number of special devices were designed for particular uses.
Vol. 13, No. 8
Among these was a very ingenious device used by German spies for causing fires in the cargo of ships. It was called an “incendiary blue pencil’’ because of its similarity in appearance to an ordinary blue marking pencil. The construction is shown in Fig. 27. In operation the spy nicks the “pencil” with a knife so as ‘tobreak the point of the glass bulb filled with concentrated sulfuric acid and then inserts i t vertically into the flammable material-cotton, sugar, etc. The sulfuric acid begins to trickle down into the reservoir and in time is siphoned over into the potassium chlorate with a resulting incendiary action. A large number of mysterious fires in vessels a t sea were traced to these “pencils.” Incendiary cans or boxes were used as a means of defense (n dissipating gases in dug-outs and deflecting gas waves. The heat generated by the devices produced air currents which effectively caused the desired. results. Special devices were attached to the gasoline tanks of airplanes, by means of which quick destruction couId be effected in case the machines were forced down in enemy territory. Then there were well worked out schemes for rendering trenches absolutely impregnable by forcing oil and gas through underground pipes t o special outlets concealed in front, causing its ignition there when the occasion demanded, and so “producing a regular inferno through which no one could pass!”
Some New Features in Limekiln Construction1P2 By Richard I(. Meade 11-13
E. FAVETTEST.,
BALTIMORE, MARYLAND
It is not the purpose of the present paper to present any very logical treatment of the subject of lime burning, but rather t o touch on some points of limekiln design which are an improvement over common practice, and it is assumed that the reader is familiar with the general proposition of lime burning in both shaft and rotary kilns. As a preliminary to the discussion of various improvements to be desired in a limekiln, it may be well to give a short summary of what takes place in the burning of lime We have in limestone calcium carbonate and magnesium carbonate, mixed with certain other chemical compounds as impurities, such as silica, iron oxide, alumina, etc. When limestone is burned, the carbon dioxide passes off,and lime and magnesia remain to form commercial lime. To decompose calcium carbonate into lime and carbon dioxide, there will be required 1451 B. t. u. per lb. of lime formed. To decompose magnesium carbonate into magnesia and carbon dioxide, there will be required 1318 B. t. u. per lb. of magnesia. Hence, t o burn dolomitic lime containing 54 per cent lime and 46 per cent magnesia, there will be required 1380 B . t . u . This explains why a magnesian lime can be burned more easily than a high calcium lime. In designing a limekiln our object is to build a furnace in which the latent heat of the fuel is put to work to decompose the limestone. This is usually done by burning the fuel and passing the products of combustion through a body of the stone. In the case of the flame kiln, the transfer of heat from the gases to the stone takes place in the shaft of the kiln. It is not practical to transfer all of the heat from the gases to the limestone, and some of it is always carried out by the gases. Manifestly, as the transfer of heat goes on the gases are cooled; consequently the temperature of the gases when they leave the kiln is an indication of the thoroughness with which this transfer takes place. Usually the gases pass through the arches at from 2000’ t o 2500’ F. and leave the top of the kiln at from 400’ t o 700” F.
* Read at the 3;d Annual Convention of the National Lime Association, Hotel Commodore, New York, N. Y.,June 17, 1921. 2 Received June 29, 1921
As the heat is transferred t o the stone, the temperature of the latter increases gradually until a temperature of 1650” is reached, when no further increase of temperature occurs until the limestone has been completely converted to lime, when the temperature again rises. SOURCES OF HEATL O S S INCOMPLETE COMBUSTION O F FUEL-In order to bring about this transfer of heat most economically, the coal must, of course, first be completely burned. Two common losses which occur are from the unburned coal carried out of the furnace in the ashes and from the carbon only half burned, to form carbon monoxide instead of carbon dioxide.‘ HEAT CARRIED OFF BY GASES-It is well known that the rate of heat transfer is proportional to the difference between the gases and the material to be heated, other conditions remaining constant. Hence the gases entering the shaft should be at as high a temperature as is possible, consistently with the production of lime of proper quality. The greatest factor in determining the temperature of the products of combustion is the amount of air used for combustion. Thus, if we burn 1 Ib. of coal with just the quantity of air necessary for combustion, the gases produced will weigh about 11lbs. If we use twice as much air as is necessary, the products will weigh 21 lbs., etc. Now, manifestly, if we transfer the heat of 1 Ib. of coal t o 11 lbs. of gas the temperature of the latter will be much higher than if we transfer this quantity of heat to 21 lbs. of gas. There is another objection t o excess air. Some heat is always carried away by the gases leaving the kiln. This heat is proportional to the quantity and temperature of the gases. Eleven pounds of gas leaving the kiln a t 4OO’will carry off only about onehalf of the heat which would be carried off by 21 lbs. Similarly, 11 lbs. of gas leaving at 400’ F. will carry off only about one-half the heat which it would at 730’ F. To promote kiln efficiency, therefore, we must cut down to a minimum the excess,air used for combustion. Some excess is 1
One pound of carbon burhed t o carbon dioxide will produce 14,580
B . t. u.. one pound burned to carbon monoxide only 3173 B. t. u.
