We have adopted this year, as the explosive for our torpedoes, trinitrotoluol, or TNT, in view of the enormous advantages that it offers in force, stability, etc., over guncotton. We have substituted, at the same time, for fulminate of mercury in the detonators a new explosive, hvdronitride of lead.
TNT or Trotyl.
TNT is obtained by the nitration of toluene, much the same as nitroglycerine is obtained by the nitration of glycerine.
Toluene is a liquid substance, colorless, boiling at no° C. and is obtained by the distillation of coal tar. It is the first homologue of benzene, which it much resembles. For this reason toluene is also called methyl benzene. It was discovered in 1838 by Pelletier and Walter. It is found also, in the literature of chemistry, under the name “toluol,” for which reason trinitrotoluene is also called “trinitrotoluol.”
It is to be noted that, during nitration, one or more atoms of hydrogen (H) are replaced by one or more radicals (N02).
Mononitrotoluene.—The mononitrotoluene is obtained industrially by treating toluene with a mixture of nitric acid at 40°
Baume and sulphuric acid at 60° Baume. The nitration takes place in cast-iron vessels, cylindrical in form, and furnished with rotating paddles to keep the mixture in constant motion. After three hours of this digesting, the mixture is precipitated in water. The precipitate is first washed with alkaline water, and then with pure water. This precipitate is mononitrotoluene.
Just as during the nitration of glycerine the temperature never should exceed 30° C., so also in the manufacture of mononitrotoluene it should not pass beyond 50° C. To avoid a rise of temperature, the nitration vessels should have interior coils with a circulation of a cooling medium or liquid.
Mononitrotoluene is a solid substance, melting at 51° C., and was discovered by Saint Claire Deville.
Mononitrotoluene is not employed as an explosive by itself, but only in some mixture, such as Sprengel’s explosives, Favier’s explosive, etc.
Dinitrotoluene.—This derivative of toluene is obtained by prolonging the action of the nitric acid on the toluene, or by treating mononitrotoluene with this acid. This last process is adopted in all explosive factories that have been visited.
Like the first derivative of toluene, this also is a solid substance, melting at 70° C., and is slightly soluble in hot water and alcohol.
The dinitrotoluene, also, is not employed by itself, but always in mixture. Triplastite is an explosive frequently used in mines. It is composed of dinitrotoluene and guncotton.
We have already had one opportunity of using this explosive (dinitrotoluene) in a progressive powder to augment the initial velocity of a projectile, and with very good success.
Trinitrotoluene.—Trinitrotoluene, finally, is obtained by the reaction of the mixed nitric and sulphuric acids upon hot dinitrotoluene. In actual practice it cannot be obtained directly by the action of acids on toluene, although so stated in some works on military chemistry.
Trinitrotoluene is the explosive par excellence, having been adopted by the majority of countries as the explosive charge in grenades, as well as in mines and torpedoes.
The first practical knowledge of this compound comes from Germany, where it is better known under the name of Trotyl. This abbreviation is the one adopted by our naval commission in Europe, and is the one which we will use henceforth.
Its first application as artillery ammunition dates from 1902.
Just as picric powders were given different names, so also trotyl has different designations.
German)^, in its military instructions, calls it trotyl; England, which adopted it in 1911, calls it TNT (trinitrotoluene) ; Spain, trytil; while others, as France, Italy, Turkey, etc., hold to the name trinitrotoluene. .
General Properties of Trotyl, and jrs Advantages over Guncotton as a Torpedo-Charge.
Trotyl is a definite chemical substance, crystalline, of a light yellow color which afterwards darkens to a deep brown, similar to picric acid. It is insoluble in cold water; undergoes no change in air; and can support, without inconvenience, the greatest variations in atmospheric temperature, between —20° and + 50° C.
The neutral properties of trotyl, it will be seen, give it great advantages over picric acid. The latter, in virtue of its acid properties, forms metallic compounds, that is, picrates, which are very sensitive to shock. Lyddite (picric acid) has thus a great rival for gun-ammunition.
Kept submerged in water for many years, it does not lose its explosive force. Nor does it happen, as in the case of guncotton, that the greater the percentage of water the less the explosive force. Even in inflammability it does not suffer.
By means of gentle heating one can melt trotyl upon an iron plate without igniting it. Violent heating produces ignition. It burns slowly, however, without exploding, and with a black flame rich in carbon, similar to that produced by kerosene. Who would care to make this experiment with guncotton?
Placed on a cherry-red plate, trotyl burns slowly. Its great insensibility to shock, friction, and pressure makes it particularly appropriate for a military explosive. The shock produced by an 8-mrn. rifle-bullet, with a velocity of 850 meters at 20 m. distance, going through a block of cast trotyl, does not cause the slightest alteration in it.
The pressure supported by trotyl in making up charges is 3,000 kg. per sq. cm. The friction and attrition produced by a steel saw has no influence whatever upon it. This is a very common operation in the manufacture of trotyl. Trotyl can also be turned in a lathe, like a block of wood.
Making a technical comparison as to the resistance to shock of different explosives, detonated by the percussion test in an impact testing machine, the hammer weighing 2 kg., we have:
Dry guncotton explodes at a height of.................... 5 cm.
Wet guncotton explodes at a height of.................. 50 cm.
Picric acid explodes at a height of.......................... 20 cm.
Trotyl explodes at a height of................................ 80 cm.
Comparing the foregoing, we see that the insensibility of trotyl is four times greater than that of picric acid, and twice as great as that of the 20 per cent wet guncotton used in torpedo warheads.
Trauzl’s Lead Block.
By the above comparison we can also see the great sensitiveness of dry guncotton, used as the priming charge in our torpedoes.
The density of loose trotyl is 0.75; of cast trotyl, as used in charges, 1.61; and of compressed trotyl, 1.50. The greatest density to which guncotton can be compressed is from 1.36 to 1.40, containing 18 per cent to 20 per cent of water, a great density in the compression constituting a grave peril.
Pure trotyl melts at 8o.°6 C., with considerable increase in volume, but without decomposition. Its specific gravity, when recrystallized in alcohol and dried, is 1.7, the same as of picric acid.
From all this we can deduce that a 45-cm. torpedo whose charge is no kg. of guncotton will contain, in the same volume, 127 kg. of trotyl. As a factor of density we have, as a consequence, the lessening of the distance from the center of
explosion of the charge in relation to the object destroyed, which gives a greater effect to the charge.
Section After Firing.
Comparing again the two explosives used to-day in our navy in torpedo-charges, let us note more differences as to the velocity of detonation and force of explosion, important factors from the military point of view.
Section Before Firing.
Let 11s determine experimentally the velocity of propagation of the detonation, by measurement in an iron tube.
Trotyl (compressed) ............................... 7.620 m. per sec.
Wet guncotton ........................................ 5.228 m. per sec.
Dry guncotton ......................................... 6.383 m. per sec.
Now it is known that the greater the velocity of detonation of a high explosive, the greater will be its effect. Our trials of the explosive force of trotyl have turned out most favorably. It produced in the Trauzl spherical block of lead (40 cm. in diam.), with a charge of 50 grams, an excavation of 1485 cc., and with 20 per cent wet guncotton, 1400 cc. From these trials we conclude that the effect or explosive force of 45-cm. torpedoes charged with trotyl is much greater than that of the same charged with guncotton, for the following reasons :
1. Ability to increase the weight of charge in given space.
2. Diminution of distance from center of explosion.
3. Greater velocity of detonation.
4. Greater explosive force.2 ?
The chemical stability of trotyl is “ unlimited ”; on the contrary we all know the instability of guncotton and the dangers attendant upon its decomposition. In addition to regular inspections for both, we still have, in the case of guncotton, the special conditions of its care, preservation, and storing in magazines.
Loaded torpedoes, carried on board during action, constitute a serious danger. Trotyl, as a charge, lessens this. A projectile detonated in contact with a charge is almost certain to explode it. This will happen with any kind of torpedo-charge. But in the case of trotyl, its slight sensitiveness prevents this explosion, if the projectile explodes a little way from it. For the same reason splinters are not dangerous to trotyl charges. A torpedo, with a detonator in place, constitutes a danger, because the shock of splinters can produce a detonation. Guncotton charges are more sensitive and detonate more easily.
2 General E. M. Weaver, U. S. A., in the preface to his Military Explosives, 3d Edition, states that TNT will not stand the shock of impact, and therefore passes from the class of shell-fillers. He states that its relative explosive force is 119,000 lbs. per sq. in., as compared with that of picric acid 135,800 lbs., and of Explosive D 124,600 lbs.; and also that it is more sensitive to shock than Explosive D.—R. E.
The percentage of water (from 18 per cent to 20 per cent) in guncotton charges, necessary to reduce their sensitiveness, is an inconvenience. When in store, the water in the charges slowly deposits itself in the lower_ part of the charge, forming strata of different density, which condition sometimes results in partial detonations. The compression of guncotton in single blocks should therefore be abandoned, as the dislocation of water is easier, and irregular densities will ensue.
The partial mine and torpedo explosions that occurred in the Russo-Japanese War are attributed to this irregular density in the charges. England, as a consequence, immediately abandoned the compressing of guncotton into a single block.
In charges of trotyl, the total mass is homogeneous, and does not absorb moisture, dispensing entirely with any inspection for this cause.
The Technical Requisites Trotyl Should Satisfy for
Military Use. .
The chemical purity of trotyl is one of the principal factors favorable to its military application, and for this reason it ought to fulfil a series of technical specifications.
Trotyl, being a product of nitration, can contain as impurities both nitric and sulphuric acid.
Determination of Nitric Acid.—In order to determine the presence of this acid we must resort to a most sensitive reagent— diphenylamine.
Boil 10 grams of trotyl with 50 cc. of distilled water. Filter the cooled solution, adding fresh water to make up 50 cc. Take 5 cc. of this and dissolve it in a porcelain dish with 0.1 cc. of a solution of sulphuric diphenylamine (1: 100) and 20 cc. of concentrated sulphuric acid. After five minutes the liquid, in its reaction, becomes violet, if nothing is wrong, and this reaction ought not to be stronger than the reaction obtained with a standard solution that contains 0.004 nitric acid per litre.
The standard solution is prepared as follows: 0.640 grams of potassium nitrate are dissolved in 1000 cc. of distilled water, and 10 cc. of this are again diluted in 1000 cc. of water.
Determination of Sulphuric Acid.—Boil 10 grams of trotyl in 250 cc. of distilled water. Leave it to cool and filter it. Draw
off 100 cc. of the previously filtered solution and acidulate it with some drops of hydrochloric, and precipitate it with a solution of barium chloride (1: 10). There will result the formation of a precipitate.' This calculated in SO;! ought not to exceed .05 gram in 100.
Foreign Substances.—Dissolve 50 grams of trotyl in 200 cc. of hot benzol, and filter. The weight of the residue from this filtration ought not to exceed 0.10 grams in 100. The resulting ashes from calcination ought not to exceed 0.9 grams in 100.
The nitrogen determined by Kjedahl’s apparatus ought not to be less than 18.30 per cent.
Point of Solidification.—Trotyl, previously dried, is placed 30 mm. from a Bunsen burner, and melted in a test tube. The amount of melted trotyl should be sufficient to cover the thermometer bulb for 2 cm. During cooling the degree of temperature should be observed, noting that before complete solidification, the thermometer rises a little, after remaining steady.
The temperature of solidification ought not to be below 79.“5 C., which corresponds to the fusing-point of pure trotyl (8o.°6 C.).
The temperature correction indicated by the thermometer is made after the following formula:
n(T-t)
6300 ’
signifying—
K=correction in degrees.
« = number of degrees of the thermometer above the melted mass.
T—t — difference between temperature of air and of fusion.
Density.—For cast trotyl the density ought not to be less than 1.6; and for compressed, not less than 1.5. This should be determined by the flask method or the relation between weight and volume.
Moisture.—Place two samples of the pulverized trotyl in a furnace at 50° C. After four hours the difference in weight ought not to be greater than 0.1 per cent.
Bleiazid or Nitridide of Lead.
Lp to the present time, fulminate of mercury has always been used for detonators in torpedo-charges. The fulminate alone was first used in military pyrotechnics. Afterwards it was mixed with other explosive nitrates, such as trotyl, picric acid, tetranitromethylaniline, etc., in order to increase the force of the initial impulse.
In navies, principally, the fact that fulminate of mercury is very porous and cannot explode when wet is a great inconvenience. That is, its easy absorption of moisture, due to its porosity, makes it decrease in density.
This new explosive (nitridide of lead) was introduced two years ago in military-explosive work, thanks to the labors of that eminent German chemist Dr. Lothar Wohler of Darmstadt, who applied it to detonators.
Bleiazid, a German word made up of Btei (lead) and azoe (nitrogen), has the chemical formula PbN„. It is a derivative of lead and hydrazoic acid.3 It may be called lead hydronitride.
We had the good fortune to be present at the first lecture of Dr. Wohler, accompanied by numerous practical experiments, at a formal meeting of the United Societies of German Chemists.
3 This is undoubtedly HNS, called by Curtino hydronitrous acid. Authority, Mendeleef. Some translators call it hydronitric acid—but it is believed they do so incorrectly—also hydrazoic acid and azoimide. It is hydrazine
H H
\ /
N —N '
/ \
H H •
in which three atoms of H are replaced by N, giving
N —N
\ /
N
I
H •
and for this reason the name hydrazoic acid most clearly defines it.—G. W. Patterson.
Nitrohydric acid or hydrazoic acid, NsH, is very explosive itself and forms highly explosive salts. It furnishes a remarkably great volume of gas. It has not as yet received any important practical application. JVisse/s Explosive Materials, D. Van Nostrand Company, 1898.—R. E.
Concerning the discovery of hydrazoic acid in 1890 by Curtino, the illustrious chemist Bertholet says: “ It is one of the most notable and long-wished-for discoveries of the present epoch.”
Hydrazoic acid is a violent and very sensitive explosive, that explodes when exposed to intense light. Nevertheless it is capable of practical use.
Specialists in military explosives persevered in their research of the compounds of this acid until they arrived at the lead hydronitride. Leading in this crusade were the eminent chemists Bertholet, Vieille, Noelting, Dennsted, and finally Wohler.
The latter, in his lecture, practically demonstrated the greater velocity of reaction, in the detonation of lead hydronitride, over fulminate of mercury, as well as its superior resistance to moisture. This assurance of lead hydronitride resisting moisture, without losing its detonating effect, made it rapidly adopted as a detonator.*
In its natural state the sensitiveness of lead hydronitride to shock is the same as that of fulminate of mercury. Compressed, it is less sensitive in this regard than the fulminate. Its force of detonation, however, is twice as great. Hydronitride of lead holds its detonating properties, even when compressed at 6000 kg. per sq. cm., while fulminate loses this property at 700 kg. Lead hydronitride resists high temperatures better than its rival. It is insoluble in water, of a white color, and dust-like in appearance.
In making detonators, tetranitromethylaniline, or “ tetryl ” (not to be confounded with “trotyl”), is added to both fulminate of mercury and lead hydronitride. Tetryl is the abbreviation for tetranitromethylaniline. It is a yellow explosive substance, insoluble, stable like trotyl, and is obtained industrially by the nitration of dimethylaniline.
‘That this material is to any extent in practical use as yet is considered doubtful, as there are many features about it that require considerably more experimentation. For example, the size of its crystals determines its sensitiveness. Cases are on record where even under water large crystals spontaneously explode, involving the whole mass in contact. Very fine crystals of it are less sensitive than fulminate, but to make it a practical material may involve a larger share of experiment than this paper would indicate.— G. W. Patterson.
Explosive Charge of Trotyl for Torpedoes. Composition and Construction.
I have given a description of the explosives that compose the charges of trotyl. We are now going to show how the whole charge is made up.
The charge of trotyl, like that of guncotton, is composed of detonator, primer, and explosive charge properly so-called.
The Detonator.—The detonator is composed of 1 gram of nitride of lead and 1.7 grams of tetryl. The manufacture is a
Sketch
shobfhxg
Position, of printer •trv the charge.
- "Trc^rvsvevsc sectioj-u of tl)e U.J9J7CV
PUn upper
j3C4.rt of the ohccrgc. Sb owilntf the fositioft of ttje pYLyner.
1
Hoff yvya.r\ f~ ? (redya-wn./)
secret, and its invention is protected by patents. The detonator is 7.5 mm. in diameter, and 50 mm. in length. In the acceptance tests of detonators not one should be permitted to fail, after being left eight days in air that is saturated with moisture, and afterwards detonated in an impact machine. All should detonate with a fall of hammer of 81 cm., equal in practice to a torpedo-speed of 4 meters per sec. The firing-point which causes the detonation ought to enter 15 mm., more or less, into the interior of the detonator.
A fulminate of mercury detonator is unable to satisfy the above requirements of moisture absorption.
Primer Charge.—The primer charge is composed of trotyl, compressed to a density of 1.5, having a cylindrical form with a diameter of 12 cm. and a height of 17 cm. Its upper part is in the shape of an ogival, as shown in our sketch. The compression of this charge is made at 2000 kg. per sq. cm.
In guncotton charges the primer is indispensable, but experi-
than cast trotyl, the detonation is transmitted with more facility and regularity to the main charge. Our sketch shows clearly the arrangement and position of the primer.
The Charge Proper.—The explosive charge, as shown in our sketch, is composed of five parts: an upper one, which takes the exact shape of the upper inside part of the head of the torpedo; a central part in the form of an oblong block; and others that
surround the central part. The division of the charge, as well as the number of component parts, has no effect whatever on the explosive force of the war-head.
The upper part of the charge has set in it the primer, which is completely fixed to it, the whole forming one block only.
In the manufacture of the block the following is the procedure:
The trotyl is melted in a copper flask in a vapor bath. It is afterwards poured into small flasks, all alike, and cooled until it is about at the solidifying point of the trotyl. It is then compressed into a cast-iron mold of the exact configuration and dimensions desired, and in the determined position of the primer charge. The melted liquid trotyl is then poured into the form, the low temperature of which prevents further melting. At the end of twelve hours draw the block out of the form, the block being by this time completely solidified.
The casting of the remaining parts is simple. Bring the form to the exact conformation of the blocks; melt enough trotyl; distribute it into the forms, and leave it. For the first few hours it is necessary to stir it, so that it does not crystallize and form air bubbles within the mass.
In order that the component parts of the charge shall be protected, the whole charge is electroplated 8 with a copper carton covering, whose thickness varies from i/io to 2/10 of a mm. This sheet forms a metallic envelope of chemically pure copper, and adheres closely to the trotyl. As an embellishment, the copper is chemically treated, producing the effect of vieux cuivre.
Loading and Unloading.—The loading and unloading of the torpedo war-head is most easy. Each block is pierced with two threaded holes, reinforced at these points by the copper electroplate. The handles which accompany the war-head permit withdrawal when necessary, with the greatest facility, by merely screwing them into the holes.
Care and Preservation of Charges and Detonators.—No especial precautions whatever are necessary relative to the care of trotyl charges. Their chemical stability is unlimited. Atmospheric temperature has no influence whatever on the charges,
" After the rigid specifications required for TNT, the wisdom of this procedure of copper plating it, using a liquid bath that is usually acid, seems somewhat questionable.—G. W. Patterson.
and it is thus practicable to keep them in any kind of magazine or storeroom.
It is advisable, however, to avoid high temperatures, in the interest of conservation, observing also the fusing-point of trotyl (8o.°6 C.). High temperature expands the copper envelope of the charge, causing it to lose its adherence. This results in a loss of the effective military value of the envelope. A temperature of 45° C. as a maximum should be the standard practice.
In case of accident to the ship or flooding of storerooms, the trotyl charges suffer nothing of their explosive power, even if months under water.
The detonators (of PbNe) ought to be cared for only as ordinary detonators.
The foregoing shows us that chemistry applied to the military art marches in these last years with gigantic strides. A few years ago the rudiments of chemistry were scarcely necessary to a comprehension of military pyrotechnics; to-day this subject cannot be studied without the most profound research into this science.
Editor’s Note.—Germany, Russia and Brazil are reported to have adopted TNT for mines and torpedoes.
Density.—As crystals this is .8 to i.o; melted, it is 1.5; and treated in special manner, it reaches 1.62. A pressure of 18 tons per square inch can be used when its density becomes 1.7. Picric acid can be subjected to 5 tons per square inch pressure, but its density fused or melted is high, 1.65.
Comparisons with Other High Explosives.—Picric acid or shimose stains the skin yellow, is very poisonous and difficult to work with, while it forms metallic salts that are very explosive and far more dangerous than the acid itself. The alkali picrates-are practically as violent as fulminate of mercury. TNT is still under investigation in the United States. It does not stain the skin; is non-poisonous; forms no metallic compounds; is absolutely nonhygroscopic and perfectly stable, both physically and chemically; is not sensitive to blow, shock, or fire; when heated gradually it volatilizes with an explosion; however, it lacks sufficient oxygen for complete comb’ustion.
Authorities.—C. E. Bichel, Rivista di Artigliera e Genio, I. Rudeloff.
The detonator—hydronitride of lead—has not been experimented with to any extent as yet, but possibly does offer a field if the results given in the article are accurate and the result of exhaustive experiments. It is not believed that as yet it is in practical use to any extent. As Mr. Patterson notes, however, its sensitiveness is too non-uniform as yet to make one certain of it.