Primings therefor and Shell Charged therewith.
Year: 1885

page_text: Primings therefor and Shell Charged therewith.
I, ALEXANDER MELVILLE CLARK, of the firm of A. M. and Wm. Clark, of
53, Chancery Lane, in the County of Middlesex, Fellow of the Institute of Patent
Agents, do bereby declare the nature of this Invention (a communication to me
from abroad by Eugène Turpin, of 2 Rue Jouffroy, Paris, France, Chemist and in
what manner the same is to be performed, to be particularly described and.
ascertained in and by the following statement :-
This Invention relates to the employment of trinitro-phenol of commerce as an
explosive and detonating substance for charging mines projectiles and other uses.
Trinitro-phenol, or Picric Acid, alone, has never hitherto been proposed for use as
an explosive substance without the aid of an oxidizing agent. Picric acid itself
has always been considered as an imperfect body, incapable of constituting an
efficient explosive, inasmuch as it contains hardly one half of the oxygen necessary
for its complete combustion. It has therefore been proposed to mix with it from
forty to fifty-five per cent of some oxidizing substance such as chlorates nitrates,
chromates, nitric acid etc. In this case, however, it has been recognised that the
picric acid might displace the nitric and chloric acids from their salts, and thus
cause spontaneous explosions. Owing to these considerations the employment of
these dangerous mixtures have been rejected, and they have never come into
practical use. It has then been proposed to use only the salts formed by Picric
acid, and the bases, that is to say, Picrates, mixed with an oxidizing agent. Picric
acid has therefore, never been used alone that is to say, without being conjoined
with an active substance. I have, however, discovered that, contrary to all the
adopted theories, Picric acid alone, that is to say, neither mixed nor combined with
any active substance and such as it is found in commerce, is one of the most
powerful and valuable explosives that can be conceived. Its explosive force is
greater than that of compressed gun-cotton, and the different forms of dynamite.
Its insensibility to shock, as well as its stability are also very remarkable. I have
found that the maximum force of explosives of this kind, contrary to what has

page_text: been believed, does not coincide with the chemical formule, which correspond to
complete combustion, but on the contrary with the combustion which yields
carbonic oxide. On this novel theory therefore, the maximum of power may be
obtained with nothing near the maximum sensibility, which admits of obtaining
results hitherto unlooked for. It is generally admitted that the power of explosives
is proportionate to the heat disengaged, which has always led chemists to employ
the oxidizing agent, and preferably in excess, in order to obtain complete combustion.
This, however, was a grave mistake, as the oxygen necessary to form carbonic acid
could produce a double volume of carbonic oxide, which would produce a much
more considerable amount of work, and which is far from being compensated by
the increase in value of the temperature which is produced in the case of the
formation of carbonic acid. As regards the carbonic oxide this need not be
considered, as its conversion into carbonic acid takes place immediately it is
projected into the air, by the action of the flame of the explosion, and at the
expense of the oxygen of the air. I have found that when picric acid alone,
without any admixture is fired by means of an initial detonator of sufficient power,
it is capable of producing the most violent bursting effects, for which reason it is
proposed to apply it for Industrial and military uses, by the novel means, and
processes hereinafter described.
This application is the more important, as hitherto an explosive for military uses
possessing the following properties found in Picric-acid alone has never been
obtained viz 1st Absolute chemical stability, that is to say, non-susceptibility
of spontaneous decomposition or of elementary change. 2nd Absolute physical
stability, that is to say, non-susceptibility of congelation, exsudation, liquefaction
or evaporation. 3rd Absolute insensibility to the most extreme variations of
atmospheric temperature. 4th Capability of being preserved for an indefinite
period 5th Perfectly non-hygrometric. 6th Perfect security in manufacturing,
manipulation, and transport. 7th Little, or no capability of ignition in the open
air. 8th Greater power of dispersing earth than either gun cotton or dynamite.
9th Shattering properties equal, if not superior, to those possessed by other violent
explosives. 10th Insensibility, or at least inexplosibility, on the ball striking-
and 11th Insensibility (when used in shells) to the shock of the discharge of the
cannon.
The insensibility of Picric acid-by itself, is due to the excess of Carbon which
it contains, and for this reason I have found that it is absolutely necessary to
avoid the admixture of any oxidizing substance, as it considerably increases its
sensitiveness, as well as greatly reduces its power. It is thus as will be seen, in
those very properties which have always led to its rejection, that I have found
those elements of value which have enabled me to apply it for the various purposes
mentioned. Picric acid, unmixed, attains its maximum sensitiveness to priming;
this property being very slight when it is in the form of fine-powder; although
but slightly sensitive to shock, its sensitiveness may be still further reduced by
different means, which admirably adapt it for, and, in fact, are indispensable to, its
use if it is desired to obtain satisfactory results.
These processes consist (1.) in compressing the picric acid, in order to increase its
density, and, at same time, lessen its sensitiveness, contrary to what is the case
with gun-cotton, it being well known that gun cotton in a flocculent form is not
exploded by a priming, whereas it explodes readily when compressed. (2) By
agglomerating it (and at same time moulding it to various forms) with an aqueous
solution of gum arabic, or some fatty body, such as heavy oils, fats, etc; which
have the property of rendering picric acid insoluble, and then allowing it to dry if
necessary. (3) Collodion jelly diluted in the proportion of from three to five per
cent in a mixture of alcohol, and ordinary ether, may also be used to agglomerate
the picric acid to lessen its sensitiveness, and adapt it for being moulded into any
form. Blocks thus obtained will explode in a closed chamber, with primings of
from one, to three grammes of fulminate. The maximum of insensibility is
obtained when in the cast state, which is one of the best modes of employment.

page_text: In this case it will resist, in the open air, the explosion of a priming composed of
three grammes of fulminate inserted in the cast mass, but it explodes perfectly in
a closed chamber, such as a shell, for example, as will be hereinafter explained.
Cast picric acid behaves much like wet gun cotton, that is to say, it may be
exploded even under water, with a priming of picric acid in dry powder; which
is itself primed with 1.5 grammes of fulminate. Very powerful explosions, may,
in this manner,
be obtained. Cast picric-acid perfectly resists the shock produced
by the firing of a cannon, when contained in a projectile, having an initial velocity
of six-hundred metres and produces destructive effects of a kind hitherto unknown.
The following is the process of casting the picric acid. The acid is fused in a
vessel provided with a false bottom heated to +130° to 145° C. by a current of
steam under pressure, or simply by the circulation of a liquid heated to the desired
temperature, such as oil, chloride of zinc, glycerine, etc. The melted picric acid is
run into moulds of a form corresponding to that of the blocks required, or it may
be run into the projectiles themselves, which should be heated to a constant tempe-
rature of about 100° in order to prevent too rapid solidification. The importance
of the application of this method is considerable. It has been observed that in
large projectiles at a high velocity, ordinary powder if in small grains, sometimes
ignites through the friction which results from its settling down, in consequence of
the initial shock, whereas if it is in the form of compressed blocks it resists ignition.
For this reason, it is preferred to employ for hollow projectiles picric acid, in com-
pressed powder, agglomerated after pressure, or preferably cast, it thus attaining
a density of 1.6 to 1.7. This latter mode of use is also more convenient, as it
enables the explosive to be cast in receptacles of any form having small orifices,
such as shells, torpedoes tubes, moulds, etc. When required for producing explo-
sions in the open air, for blowing up rails, walls, etc for military purposes, it is
preferable to employ the picric acid in dry powder which is firmly packed into the
cartridge case of tin, copper, or pasteboard, and a priming tube, inserted well into
the material, as in the case of gun-cotton or dynamite. The priming of the picric
acid may be effected by the three following means;-(a) By the direct employment
of a priming of 1.5 grammes of fulminate of mercury which answers well for picric
acid in dry powder. (b) By employing an intermediate priming of picric acid
in powder, primed by the fulminate, which is very suitable when using cast, or
agglomerated picric acid. (c) By dispensing with the fulminate, and employing a
sufficiently large charge of ordinary quick-burning powder enclosed in a strong
tube, and made to burst inside the charge of picric acid. This last method is
of especial importance in connection with artillery.
The accompanying drawing illustrates the Invention as applied to the charging
of Shells, with cast (fused) or powdered Picric acid; and with or without a priming
of fulminate. The drawing represents a longitudinal vertical section of the shell.
A is the body, and B the plug, containing the priming, in the chamber D of which
plug may be placed a charge of quick burning powder, or Picric acid in powder.
In this latter case, a priming containing from 0.8 to 1 gramme of fulminate should
be attached to the fuse C. E. copper ring surrounding the base of the shell. The
chamber D is coned, and also the core which is used to form a cavity for its recep-
tion in the fused, or cast acid, to enable said core to be easily drawn out. It will
thus be seen that in order to produce the detonating explosion of the picric acid, or,
on the same conditions, that of the compressed gun cotton, or dynamite without
the use of fulminate, a cavity is moulded in the charge of compressed, agglomerated,
or cast, picric acid, to receive the screw plug, which terminates, at its inner end, in
a very strong, but brittle, chamber of cast steel, or iron, which is filled with very
violent gunpowder, or, preferably, with 25 grammes of a powder composed of
chlorate of potash, tar, and charcoal. The plug is closed by means of the fuse.
It will thus be seen that a strong priming of gunpowder is used instead of a
priming of fulminate, the only fulminate employed being that contained in the
artillery fuse. If it is desired to obtain, either in mines, or elsewhere, an explosion
without detonation of the picric acid, a small charge of powder should be employed,

page_text: either wrapped in paper, or contained in a waterproof bag, to be ignited by the
miner's fuse, the latter having no action upon the picric acid when unenclosed.
Under these conditions the picric acid may be employed in mining, and excavating
generally in the same manner as dynamite, and gun cotton. If the mine is dry, it
is sufficient to introduce the picric acid into the hole, either in powder, or in small
crystals, or agglomerated, or cast, and to prime it in one of the ways described. If
the mine is wet, or under water, the picric acid must be enclosed in a waterproof
envelope of metal, indiarubber, cloth, gummed taffetas, waterproof paper etc, and
primed with a strong priming of dry picric-acid in powder which is itself primed,
by means of a fulminate. The picric acid is almost completely insoluble in cold
water, and detonates freely with a priming of 1.5 grammes, if it is inoistened with
three per cent of water. As applied for military purposes, picric acid is suited for
charging hollow projectiles, land, submarine, aerial, and hand torpedoes, fougasses,
mines, trains, or primings, bursting cartridges etc. It may also be used for charging
bombs in pyrotechnic displays.
Having now particularly described, and ascertained the nature of the said
Invention, and in what manner the same is to be performed, I declare that what
I claim is
1st The employment, as an explosive agent for military and other uses, of the
trinitro-phenol, or picric acid, of commerce, unmixed with any oxidizing substance
whatever, as hereinbefore described for the purpose specified.
2nd The processes of preparing picric-acid for the purpose of lessening its sensi-
tiveness, and rendering it suitable for each of its several applications; consisting in
compressing it in a pulverulent condition; agglomerating, or moulding it in a melted
condition; as hereinbefore described for the purpose specified.
3rd The method of employing picric acid unmixed with any oxidizing agent by
fusing, and running it either into moulds, or into projectiles, maintained in a heated
condition during the filling as hereinbefore described for the purpose specified.
4th The method of priming the picric-acid, whether agglomerated, or fused, by
means of a priming composed of picric-acid in powder, and fulminate, as herein-
before described for the purpose specified.
5th A projectile charged with either compressed, agglomerated, or fused picric
acid, and in which the priming is effected without the use of fulminate, by means
of quick burning ordinary gunpowder, inserted in a tube, or envelope, suitable for
bursting in the midst of the charge of picric acid in a cavity provided for its
reception, as hereinbefore described, and represented in the accompanying drawing.
011
1005