Incendiaries in Modern W arfare1,2
5 which proved to be especially effective against airplanes carry
ing protected gasoline tan k s is interesting. T h e primer or ig
niting com position which is ignited upon im p act consists of m agnesium , potassium chlorate, and antim ony sulfide. The incendiary charge consists o f m agnesium , alum inium , barium chlorate, sulfur, and a little nitrocellulose. T h e advantage of this bu llet is th a t th e burning com position in front of and around th e armor-piercing core of steel is more lik ely to ignite gasoline, for exam ple, from a perforated tank th a n if the com position were in a com plete container which m ay be broken aw ay from the b u llet b od ily o n im pact.
Sh e l l
Shell designed to h ave an incendiary action , range in size from th e sm all 37-mm. to th e large 17.5-cm. shell. T he sm aller sizes were used w ith great success in attack ing aircraft from the ground, and th e larger calibers were used w ith m oderate success against all sorts of flam m able ground targets. T here are tracer shell which h a v e an incendiary action over a considerable portion of th e trajectory and th e incendiary shell proper which do not function as incendiary devices until th e m om ent of bursting, w hen the incendiary m aterial is ignited and usually expelled.
A com m on typ e of tracer-incendiary shell carrying th e red lead and m agnesium com position and primer is show n in Fig. 6.
Shell of this ty p e range in size from 37 m m . to 11.5 cm ., b u t only th e 75-m m . and 3-in. sizes were produced b y th e U n ited States.
T hese shell were used principally for balloon incendiary purposes.
T h ey are usually fitted w ith tim e fuses which are set to function considerably sh ort of th e target. T he fuse charge ignites the primer which in turn ignites th e incendiary m ixture, and the incandescent products of th e com bustion are em itted from, the shell through holes in th e head. T he sm oke from th is combus
tion leaves a definite trace of th e projectile so th a t the laying of th e piece m ay be corrected if the trajectory does not pass through the target. T he h o t gases have a very efficient incen
diary action if the shell passes through th e envelope of a balloon.
T h ese shell m ay begin to function w hen 50 yds. from th e muzzle of the gun and continue this action for from 6 to 25 sec., depend
ing upon their size.
A tracer incendiary shell which differs from the ty p e just described in th a t it is base-opening is show n in F ig. 7. This type o f shell, carrying a mixture of m agnesium , barium nitrate, and binder, w as used b y B ritish and Germans. Strontium nitrate w as used som etim es to give a better tracing effect. T he flash from th e tim e fuse is transm itted through th e central tube and ignites the sm all qu antity o f com position betw een th e mill board washers. T h is fires th e priming and th e incendiary com
position in th e b od y. T h e base is blow n out •with th e result th a t th e flam e is em itted through th e base of th e shell. This flam e la s ts for abou t 15 sec. and gives a tracing as well as incen
diary effect.
Shell designed for incendiary effect alone m ay contain
ther-Aun., 1921 T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 715
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F io . 1— In c e n d ia r y Bu l l e t, .303 Inc h Fig 2 — S .P .G . Tr a c e r Bu l l e t, Fig 3 — In c e n d ia r y Bu l l e t, I I Mm. .303 Inc h
be th e commercial product or a m odified form containing, in som e cases, m anganese, copper, or lead oxide. I t is usually com pressed in the shells to prevent segregation. Our experim ents with th is ty p e of shell, how ever, were n o t suc
cessful. W e were unable to g e t com plete com bustion of the therm ite or to prevent excessive scattering when the shell exploded. T h e incen
diary action of the very finely divided and w idely scattered m aterial was not th ou gh t satisfactory, so a shell containing th e incendiary m aterial in definite un its was experim ented w ith.
A type of shell which contains un its of ther
mite or an oxidizing agent-com bustible mixture is shown in F ig. 9. T h e u n its held in perforated cases are ignited from the central tu b e and ex
pelled from th e front of th e shell b y th e explo
sion of the charge in th e base. T h e un its are large enough to h ave considerable incendiary effect.
W hile this ty p e of shell w as n o t produced b y the U n ited States, it was exten sively used b y the other warring nations. T h e Germans used i6Minns
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m ite, special oxidizing agent-com bustible m ixtures, sodium, phosphorus, and flammable organic m aterials. T h e materials in some cases are present a s sm all un its which are ignited and scattered w hen th e shell functions. In other cases th e incen
diary material is p r e s e n ta s a m ass which is expelled and more or less scattered w hen th e shell functions. For an intensive incendiary action it is of course desirable to have as large a quan
tity of incendiary m aterial as possible in one place, and for th is reason extensive experim ents were m ade w ith a typ e of shell which expelled bu t did not scatter its incendiary charge.
A typical sm all shell which carries therm ite and an igniting and expelling charge of the potassium perchlorate-magnesium mixture known a s ophorite is show n in Fig. 8. T h is ty p e of shell acts as a shrapnel sh ell scattering th e h o t m etal and slag produced b y the therm ite reaction and is said to h a v e been par
ticularly effective again st aircraft. T h e tim e interval necessary for practically com plete ignition o f the therm ite is obtained b y the use of a beeswax plug betw een th e igniting ophorite in th e central tube and ophorite in th e base. T h e therm ite used m ay
against aircraft a 7.7-cm . shell which on burst
ing scattered steel slugs and flam ing incendiary units, called "flaming onions” b y allied airmen. A 15-cm. Ger
m an shell used against ground targets w ith little success con*
tained tw elve or more celluloid cylinders surrounded b y w hite phosphorus and imbedded in paraffin, as show n in F ig. 10. A rather com plicated Italian shell scattered 35 incendiary un its when it functioned.
T h e largest incendiary shell used during the war was th e 17.5- cm. German shell shown in Fig. 11. I t contained, as shown, therm ite and sodium, b u t despite its size was not especially effective.
A base-opening shell, which on functioning ignited and expelled a single large un it of incendiary m aterial, w as developed b y us bu t n ot produced in quantity.
T h e general observation regarding incendiary shell is th a t th e sm all caliber tracer-incendiary ty p e w a s quite effective against aircraft b u t th a t th e larger ty p e designed for use again st ground targets w as not as successful, prim arily because of the greater difficulty of igniting th e ty p e o f ground targets in the war zone.
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I n c e n d i a r y S h e l l
Tr e n c h Mo r t a r Pr o j e c t i l e s
Trench m ortar projectiles such a s th e 3-in. and 4-in. S tok es’
bombs and th e 8-in. L iven ’s drum s were used to d estroy grass, shrubbery, or camouflage w hich m ight a c t as a screen for enem y m ovem ents; to clean ou t woods; to demoralize th e enem y during a gas projector attack , and to indicate the range in nigh t pro
jector attack s.
T h e S tok es’ bom bs loaded w ith phosphorus h ad little incen
diary effect. W hen loaded with abou t 7.5 lbs. of slig h tly com pressed therm ite and th e explosive igniter, “oph orite,” and ex ploded in th e air b y tim e fuse arrangem ent th ey were more effective. O bviously th e b est results w ere obtained when the explosion took place near th e target so th a t it w as struck b y the particles of h o t or even m olten m etal and slag. Experim ental work carried ou t a t H anlon Field, A. E . F ., resulted in th e d e
velopm ent of an unproved type of S tok es’ bom b which scattered larger units of very h ot m etal. N o other incendiary m aterial h a s been satisfactorily em ployed in S tok es’ bom bs.
T h e 8-in. L iven ’s drum show n in F ig. 12 usually contained balls of cotton or ju te w aste and a special flam m able liquid.
T he spontaneously flammable liquid previously discussed was developed prim arily for use in these drum s. T h e liquid gen
erally used, however, consisted of a lig h t and a h eavy oil. T he
ligh t oil is readily ignited b y the flash from the explosive charge and th e h eavy oil gives th e long burning desired. A mixture of ligh t and h ea v y petroleum d istillates gave satisfactory results.
Soaking th e cotton or ju te balls in a chlorate solution and care
fully drying in vacuum before pu ttin g them in th e oil mixture caused them to burn w ith a fiercer flame w hen ignited. The u n its m ay also be soaked in m olten "solid o il” and th e oil al
low ed to solid ify on them . T h is treatm ent results in more oil being carried w ith them w hen th e y are expelled.
T hese drum s are fitted w ith an im pact fuse w h ich causes them to explode on landing. T h e oil saturated incendiary units are ignited b y th e flash from the explosive charge or tak e fire spon
taneously if th e special sp ontaneously flam m able liq uid is used and b u m vigorously for som etim e over an area approxim ately 50 yd s. in diam eter. T h e incendiary effect produced is good.
Gr e n a d e s a n d Ot h e r Sm a l l De v i c e s
W hile th e use of incendiary grenades is lim ited, such arma
m ent is considered very valuable. Sm all portable incendiary devices can be used to se t fire readily to flam m able materials which it is desired to get rid o f in eith er defensive or offensive operations. Several typ es of devices w ere used, such as real grenades filled w ith phosphorus or therm ite, cans filled w ith
flam-Aug., 1921 T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 717 mable liquid and fitted w ith igniting and exploding devices,
and paper or m etal tub es filled w ith th e oxidizing agent-com bustible typ e of m ixtures.
Grenadjs, usually m ade of sh eet m etal, containing w hite phosphorus and fitted w ith an exploding device, were of course used principally for producing sm oke, bu t the burning phos
phorus scattered b y the explosion had some incendiary effect, particularly in dug-outs. T h e phosphorus-filled grenades were widely used by all arm ies, and their incendiary effect, although incidental, was n ot lost sight of.
Grenades containing therm ite were used w idely and proved to be very valuable for destroying or rendering useless guns and other m aterial which had to be abandoned in retreat, for destroying airplanes which were forced to land in enem y terri
tory, for igniting flam m able liquids which had been thrown into dug-outs by an y m eans or which had been sprayed over an ob
jective b y a flame projector. W hen aviators used these grenades to destroy airplanes after forced landing, one was placed on the gas tank, and one on delicate p arts of th e m otor. T h e delayed action fuse allow ed tim e for th e m en to place them selves a t a safe distance. A utom obiles and tractors w hich it was necessary to abandon were also easily destroyed in a sim ilar m anner. T he breech mechanism of gun s was effectively sealed by th e m olten iron produced b y th e therm ite reaction.
A successful ty p e of therm ite grenade is show n in Fig. 13.
In loading this grenade th e therm ite is m oistened w ith sodium silicate, tam ped into the sh eet iron container, one end of which is
open, and baked.
T h e hole is bored in th e center of the block and the cover is crim ped on the container.
T h e bag of alumi- nium-barium per
oxide igniter from which th e strands of quick m atch extend is inserted and th e percus
sion firing plug pu t in place so th a t a piece of Bickford fuse in the plug is con
nected w ith the quick m atch. The charge of therm ite weighs about 600 g.
T he Germans m ade use of sm all portable in
cendiary devices which usually consisted of tu b es of m etal or pasteboard filled with an oxidizing agent-com bustible typ e of mixture and fitted with a friction igniting device. One kind of device contained 1670 g. of incendiary material of th e following com position:
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This material burns rapidly w ith a lively flame and gives off quantities of w h ite sm oke. T h e sta ted purpose of th is device was to chase the enem y ou t of their shelters by a great develop
ment of flames and sm oke. In actual practice it readily serves either as an incendiary or sm oke-producing device, depending on circumstances. Its nam e, Brand-rohren, however, indicates the greater incendiary action . Other tub es of different sizes
and containing differ
en t incendiary m ix
tures were used.
Som e use was m ade b y the French o f a can which contained abou t 3 liters of a petroleum oil m ixture and was fitted w ith a friction exploding and ignitin g
Th erm ite device. In operation th e device w eighing abou t 7 lbs. w as arm ed I g n i t e r and throw n into trench or dug-out. It w as reported to be quite effective.
W ith th e idea of developing a device which would have b oth th e ad van tages of th e th erm ite gren- F io . 13—T h e r m i t e C r e n a d e ade against m etal and
the advan tages of the oil device against flammable m aterial a com bination thermite-solid oil grenade w as experim ented with. T he therm ite used in these experimental devices w as found to be a d van tageously bound with celluloid— abou t 4 per cen t b y w eight being used dissolved in a suitable solvent, such as acetone.
Solid oil prepared as previously described was satisfactory.
T h e arrangement of th e m aterials is show n in F ig. 14. T h e grenade is fired b y withdraw ing th e sa fe ty pin and releasing th e bouchon firing handle as is done w ith all Am erican grenades.
T he sp it of the fuse ignites the booster w hich se ts off th e igniter and therm ite in turn. T he resulting m olten iron and slag
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readily penetrates the grenade case, a t th e sam e time igniting the celluloid case and th e solid oil. T h e m ass burns w ith a large h o t flame for about 4 m in. T h is device w as n o t produced be
cause it was thou ght th a t th e all-therm ite grenade previously described would be of more value under th e conditions then existing.
71S T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y V ol. 13, N o. 8
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Fu ses. F lo . 15— In c e n d ia r y Ze p p e l i n Bomh
A i r c r a f t B o m b s
I t w as early recognized th a t bom bing b y m eans of aircraft is of the greatest m ilitary im portance, and it was also early rec
ognized th at incendiary bom bs possessed great potential destruc
tive power. I t is interesting to recall th a t during the first raid over London on M ay 31, 1915, one German airship dropped four 200-lb. explosive bom bs, tw en ty sm all explosive grenades, and ninety incendiary bombs. T his arm am ent was clearly designed to affect the m axim um am ount of dam age to life and property in a populous tow n and indicates the im portance attach ed to incendiary bom bs. Later, incendiary bom bs were exten sively used by the allied airmen w ith considerable success.
T h e bombs developed and used since 1915 m ay be divided into three classes: (1) large bombs known as “ intensive ty p e ” which burn practically in situ, (2) large bom bs known as "scatter ty p e” which on functioning scatter w id ely a number of incen
diary units, and (3) sm all unit bom bs which can literally be rained down upon a target. It is generally conceded that the scatter typ e is the least effective. O bviously thejkind of bomb
Fi g. 16— Ge r m a n Ae r o p l a n e In c e n d ia r y Bomb
which can be m ost effectively used will depend upon th e kind of target to be attack ed . Grain crops, forests, and other
rela-tively highly flammable targets which occu py a considerable area are best attacked by sm all unit or the scatter ty p e bombs which perm it a wide scattering of th e incendiary m aterials. On the other hand, tow ns, factories, storehouses, am m unition depots, and sim ilar targets are best attack ed b y intensive typ e bombs which burn w ith a large fierce flame.
T h e intensive ty p e bom bs developed comprise a large variety of m odels and carry practically all types of incendiary materials.
T he m ost satisfactory incendiary filling con sists of therm ite or other great h eat evolving m ixture and a larger am ount of a h igh ly flammable m aterial. T he first bom bs dropped from German Zeppelins were of th e intensive typ e. T h ey weighed 20 lbs. each and, as shown in F ig. 15, contained benzine, ther
m ite, and ignition m ixture, and were wrapped w ith tow rope im pregnated w ith tar and
barium nitrate. A percussion fuse served to cause the first ignition. T h ese rather crude bom bs were dropped from airships only. A later ty p e of bomb dropped from Germ an airplanes as well as airships, show n in Fig.
16 weighed either 10 or 20