Nitro Explosives: A Practical Treatise by P. Gerald Sanford

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~Bellite~ is the patent of Mr Carl Lamm, Managing Director of the Roetebro
Explosive Company, of Stockholm, and is licensed for manufacture in
England. It consists of a mixture of nitrate of ammonia with di- or
tri-nitro-benzol, it has a specific gravity of 1.2 to 1.4 in its granulated
state, and 1 litre weighs 800 to 875 grms. Heated in an open vessel,
bellite loses its consistency at 90 deg. C., but does not commence to separate
before a temperature of 200 deg. C. is reached, when it evaporates without
exploding. If heated suddenly, it burns with a sooty flame, somewhat like
tar, but if the source of heat is removed, it will cease burning, and
assume a caramel-like structure. It absorbs very little moisture from the
air after it has been pressed, and if the operation has been performed
while the explosive is hot, the subsequent increase of weight is only 2
per cent. When subjected to the most powerful blow with a steel hammer
upon an iron plate, it neither explodes nor ignites. A rifle bullet fired
into it at 50 yards' distance will not explode it. Granulated bellite
explodes fully by the aid of fulminating mercury. Fifteen grms. of bellite
fired by means of fulminate, projected a shot from an ordinary mortar,
weighing 90 lbs., a distance of 75 yards, 15 grms. of gunpowder, under the
same conditions, throwing it only 12 yards. A weight of 7-1/2 lbs. falling
145 centimetres failed to explode 1 grm. of bellite.

Various experiments and trials have been made with this explosive by
Professor P.T. Cleve, M.P.F. Chalon, C.N. Hake, and by a committee of
officers of the Swedish Royal Artillery. It is claimed that it is a very
powerful and extremely safe explosive; that it cannot be made to explode
by friction, shock, or pressure, nor by electricity, fire, lightning, &c.,
and that it is specially adapted for use in coal mines, &c.; that it can
only be exploded by means of a fulminate detonator, and is perfectly safe
to handle and manufacture; that it does not freeze, can be used as a
filling for shells, and lastly, can be cheaply manufactured.

~Securite~ consists of 26 parts of meta-di-nitro-benzol and 74 parts of
ammonium nitrate. It is a yellow powder, with an odour of nitro-benzol. It
was licensed in 1886. It sometimes contains tri-nitro-benzol, and
tri-nitro-naphthalene. The equation of its combustion is given as

C_{6}H_{4}(NO_{2})_{2} + 10(NH_{4}NO_{3}) = 6CO_{2} + 22H_{2}O + 11N_{2}

and, like bellite and roburite, it is claimed to be perfectly safe to use
in the presence of fire damp and coal dust.[A] The variety known as
Flameless Securite consists of a mixture of nitrate and oxalate of ammonia
and di-nitro-benzol.

[Footnote A: See paper by S.B. Coxon, _North of Eng. Inst. Mining and
Mech. Eng._, 11, 2, 87.]

~Kinetite.~--A few years ago an explosive called "Kinetite"[A] was
introduced, but is not manufactured in England. It was the patent of
Messrs Petry and Fallenstein, and consisted of nitro-benzol, thickened or
gelatinised by the addition of some collodion-cotton, incorporated with
finely ground chlorate of potash and precipitated sulphide of antimony. An
analysis gave the following percentages:--

Nitro-benzol, 19.4 per cent.
Chlorate of potash, 76.9 per cent.
Sulphide of antimony nitro-cotton, 3.7 per cent.

[Footnote A: V. Watson Smith, _Jour. Soc. Chem. Ind._, January 1887.]

It requires a very high temperature to ignite it, and cannot, under
ordinary circumstances, when unconfined, be exploded by the application of
heat. It is little affected by immersion in water, unless prolonged, when
the chlorate dissolves out, leaving a practical inexplosive residue.[A] It
was found to be very sensitive to combined friction and percussion, and to
be readily ignited by a glancing blow of wood upon wood. It was also
deficient in chemical stability, and has been known to ignite
spontaneously both in the laboratory and in a magazine. It is an orange-
coloured plastic mass, and smells of nitro-benzol.

[Footnote A: Col. Cundill, R.A., "Dict. of Explosives," says: "If,
however, it be exposed to moist and dry air alternately, the chlorate
crystallises out on the surfaces, and renders the explosive very
sensitive."]

~Tonite No. 3~ contains 10 to 14 per cent. of nitro-benzol (see Tonite).
Trench's Flameless Explosive contains 10 per cent. of di-nitro-benzol,
together with 85 per cent. of nitrate of ammonia, and 5 per cent. of a
mixture of alum, and the chlorides of sodium and ammonia.

~Tri-nitro-Toluene.~--Toluene, C_{7}H_{8}, now chiefly obtained from coal-
tar, was formerly obtained by the dry distillation of tolu-balsam. It may
be regarded as methyl-benzene, or benzene in which one hydrogen is
replaced by methyl (CH_{3}), thus (C_{6}H_{5}CH_{3}), or as phenyl-
methane, or methane in which one hydrogen atom is replaced by the radical
phenyl (C_{6}H_{5}), thus (CH_{3}C_{6}H_{5}). Toluene is a colourless
liquid, boiling at 110 deg. C., has a specific gravity of .8824 at 0 deg. C., and
an aromatic odour. Tri-nitro-toluene is formed by the action of nitric
acid on toluene. According to Haeussermann, it is more advantageous to
start with the ortho-para-di-nitro-toluene, which is prepared by allowing
a mixture of 75 parts of 91 to 92 per cent. nitric acid and 150 parts of
95 to 96 per cent. sulphuric acid to run in a thin stream into 100 parts
of para-nitro-toluene, while the latter is kept at a temperature between
60 deg. to 65 deg. C., and continually stirred. When the acid has all been run in,
this mixture is heated for half an hour to 80 deg. C., and allowed to stand
till cold. The excess of nitric acid is then removed. The residue after
this treatment is a homogeneous crystalline mass of ortho-para-di-nitro-
toluene, of which the solidifying point is 69.5 deg. C. To convert this mass
into tri-nitro derivative, it is dissolved by gently heating it with four
times its weight of sulphuric acid (95 to 96 per cent.), and it is then
mixed with 1-1/2 times its weight of nitric acid (90 to 92 per cent.), the
mixture being kept cool. Afterwards it is digested at 90 deg. to 95 deg. C., with
occasional stirring, until the evolution of gas ceases. This takes place
in about four or five hours.

The operation is now stopped, the product allowed to cool, and the excess
of nitric acid separated from it. The residue is then washed with hot
water and very dilute soda solution, and allowed to solidify without
purification. The solidifying point is 70 deg. C., and the mass is then white,
with a radiating crystalline structure. Bright sparkling crystals, melting
at 81.5 deg. C. may, however, be obtained by recrystallisation from hot
alcohol. The yield is from 100 parts di-nitro-toluene, 150 parts of the
tri-nitro derivative. Haeussermann states also that 1:2:4:6 tri-nitro-
toluene can be obtained from ordinary commercial di-nitro-toluene melting
at 60 deg. to 64 deg. C.; but when this is used, greater precautions must be
exercised, for the reactions are more violent. Moreover, 10 per cent. more
nitric acid is required, and the yield is 10 per cent. less. He also draws
attention to the slight solubility of tri-nitro-toluene in hot water, and
to the fact that it is decomposed by dilute alkalies and alkaline
carbonates--facts which must be borne in mind in washing the substance.
This material is neither difficult nor dangerous to make. It behaves as a
very stable substance when exposed to the air under varying conditions of
temperature (-10 deg. to +50 deg. C.) for several months. It cannot be exploded by
flame, nor by heating it in an open vessel. It is only slightly decomposed
by strong percussion on an anvil. A fulminate detonator produces the best
explosive effect with tri-nitro-toluene. It can be used in conjunction
with ammonium nitrate, but such admixture weakens the explosive power; but
even then it is stated to be stronger than an equivalent mixture of
di-nitro-benzene and ammonium nitrate. Mowbray patented a mixture of 3
parts nitro-toluol to 7 of nitro-glycerine, also in the proportions of 1 to
3, which he states to be a very safe explosive.

~Faversham Powder.~--One of the explosives on the permitted list (coal
mines) is extensively used, and is manufactured by the Cotton Powder Co.
Ltd. at Faversham. It is composed of tri-nitro-toluol 11 parts, ammonium
nitrate 93 parts, and moisture 1 part. This explosive must be used only
when contained in a case of an alloy of lead, tin, zinc, and antimony
thoroughly waterproof; it must be used only with a detonator or electric
detonator of not less strength than that known as No. 6.

~Nitro-Naphthalene.~--Nitro-naphthalene is formed by the action of nitric
acid on naphthalene (C_{10}H_{8}). Its formula is C_{10}H_{7}NO_{2}, and
it forms yellow needles, melting at 61 deg. C.; and of di-nitro-naphthalene
(C_{10}H_{6}(NO_{2})_{2}), melting point 216 deg. C. There are also tri-nitro
and tetra-nitro and [alpha] and [beta] derivatives of nitro-naphthalene.
It is the di-nitro-naphthalene that is chiefly used in explosives. It is
contained in roburite, securite, romit, Volney's powder, &c. Fehven has
patented an explosive consisting of 10 parts of nitro-naphthalene mixed
with the crude ingredients of gunpowder as follows:--Nitro-naphthalene, 10
parts; saltpetre, 75 parts; charcoal, 12.5 parts; and sulphur, 12.5 parts.
He states that he obtains a mono-nitro-naphthalene, containing a small
proportion of di-nitro-naphthalene, by digesting 1 part of naphthalene,
with or without heat, in 4 parts of nitric acid (specific gravity 1.40)
for five days.

Quite lately a patent has been taken out for a mixture of nitro-
naphthalene or di-nitro-benzene with ammonium nitrate, and consists in
using a solvent for one or other or both of the ingredients, effected in a
wet state, and then evaporating off the solvent, care being taken not to
melt the hydrocarbon. In this way a more intimate mixture is ensured
between the particles of the components, and the explosive thus prepared
can be fired by a small detonator, viz., by 0.54 grms. of fulminate.
Favier's explosive also contains mono-nitro-naphthalene (8.5 parts),
together with 91.5 parts of nitrate of ammonia. This explosive is made in
England by the Miners' Safety Explosive Co. A variety of roburite contains
chloro-nitro-naphthalene. Romit consists of 100 parts ammonium nitrate and
7 parts potassium chlorate mixed with a solution of 1 part nitro-
naphthalene and 2 parts rectified paraffin oil.

~Ammonite.~--This explosive was originally made at Vilvorde in Belgium,
under the title of the Favier Explosive, consisting of a compressed hollow
cylinder composed of 91.5 per cent. of nitrate of ammonia, and 8.5 per
cent. of mono-nitro-naphthalene filled inside with loose powder of the
same composition. The cartridges were wrapped in paper saturated with
paraffin-wax, and afterwards dipped in hot paraffin to secure their being
water-tight. The Miners' Safety Explosives Co., when making this explosive
at their factory at Stanford-le-Hope, Essex, abandoned after a short trial
the above composition, and substituted di-nitro-naphthalene 11.5 per cent.
for the mono-nitro-naphthalene, and used thin lead envelopes filled with
loose powder slightly pressed in, in place of the compressed cylinders
containing loose powder. The process of manufacture is shortly as
follows:--132-3/4 lbs. of thoroughly dried nitrate of ammonium is placed
in a mill pan, heated at the bottom with live steam, and ground for about
twenty minutes until it becomes so dry that a slight dust follows the
rollers; then 17-1/2 lbs. of thoroughly dry di-nitro-naphthalene is added,
and the grinding continued for about ten minutes. Cold water is then
circulated through the bottom of the pan until the material appears of a
lightish colour and falls to powder. (While the pan is hot the whole mass
looks slightly plastic and of a darker colour than when cold.) A slide in
the bottom of the pan is then withdrawn, the whole mass working out until
the pan is empty; it is now removed to the sifting machine, brushed
through a wire sieve of about 12 holes to the inch, and is then ready for
filling into cartridges. The hard core is returned from the sifting
machine and turned into one of the pans a few minutes before the charge is
withdrawn.

The ammonite is filled into the metallic cartridges by means of an
archimedian screw working through a brass tube, pushing off the cartridges
as the explosive is fed into them against a slight back pressure; a cover
is screwed on, and they then go to the dipping room, where they are dipped
in hot wax to seal the ends; they are then packed in boxes of 5 lbs. each
and are ready for delivery. The di-nitro-naphthalene is made at the
factory. Mono-nitro-naphthalene is first made as follows:--12 parts of
commercial nitrate of soda are ground to a fine powder, and further ground
with the addition of 15 parts of refined naphthalene until thoroughly
incorporated; it is then placed in an earthenware pan, and 30 parts of
sulphuric acid of 66 deg. B. added, 2 parts at a time, during forty-eight
hours (the rate of adding H_{2}SO_{4} depends on the condition of the
charge, and keeping it in a fluid state), with frequent agitation, day and
night, during the first three or four days, afterwards three or four times
a day. In all fourteen days are occupied in the nitration process. It is
then strained through an earthenware strainer, washed with warm water,
drained, and dried. For the purpose of producing this material in a
granulated condition, which is found more convenient for drying, and
further nitrification, it is placed in a tub, and live steam passed
through, until brought up to the boiling point (the tub should be about
half full), cold water is then run in whilst violently agitating the
contents until the naphthalene solidifies; it can then be easily drained
and dried. For the further treatment to make di-nitro-naphthalene, 18
parts of nitro-naphthalene are placed in an earthenware pan, together with
39 parts of sulphuric acid of 66 deg. B., then 15 parts of nitric acid of 40 deg.
B. are added, in small quantities at a time, stirring the mixture
continually. This adding of nitric acid is controlled by the fuming, which
should be kept down as much as possible. The operation takes ten to twelve
days, when 100 times the above quantities, taken in kilogrammes, are
taken. At the end of the nitration the di-nitro-naphthalene is removed to
earthenware strainers, allowed to drain, washed with hot water and soda
until all acid is removed, washed with water and dried. The di-nitro-
naphthalene gives some trouble in washing, as some acid is held in the
crystals which is liable to make its appearance when crushed. To avoid
this it should be ground and washed with carbonate of soda before drying;
an excess of carbonate of soda should not, however, be used.

~Electronite.~--This is a high explosive designed to afford safety in coal
getting. This important end has been attained by using such ingredients,
and so proportioning them, as will ensure on detonation a degree of heat
insufficient under the conditions of a "blown-out" shot, to ignite fire
damp or coal dust. It is of the nitrate of ammonium class of permitted
explosives. It contains about 75 per cent. of nitrate of ammonium, with
the addition of nitrate of barium, wood meal, and starch. The gases
resulting from detonation are chiefly water in the gaseous form, nitrogen,
and a little carbon dioxide. It is granulated with the object of
preventing missfires from ramming, to which nitrate of ammonium explosives
are somewhat susceptible. This explosive underwent some exhaustive
experiments at the experimental station near Wigan in 1895, when 8 oz. or
12 oz. charges were fired unstemmed into an admixture of coal dust and 10
per cent. of gas, without any ignition taking place. It is manufactured by
Messrs Curtis's & Harvey Ltd. at their factory, Tonbridge, Kent.

~Sprengel's Explosives.~--This is a large class of explosives. The
essential principle of them all is the admixture of an oxidising with a
combustible agent at the time of, or just before, being required for use,
the constituents of the mixture being very often non-explosive bodies.
This type of explosive is due to the late Dr Herman Sprengel, F.R.S.
Following up the idea that an explosion is a sudden combustion, he
submitted a variety of mixtures of oxidising and combustible agents to the
violent shock of a detonator of fulminate. These mixtures were made in
such proportions that the mutual oxidation or de-oxidation should be
theoretically complete. Among them are the following:--

1. One chemical equivalent of nitro-benzene to equivalents of nitric acid.

2. Five equivalents of picric acid to 13 equivalents of nitric acid.

3. Eighty-seven equivalents of nitro-naphthalene to 413 equivalents of
nitric acid.

4. Porous cakes, or lumps of chlorate of potash, exploded violently with
bisulphide of carbon, nitro-benzol, carbonic acid, sulphur, benzene, and
mixtures of these substances.

No. 1 covers the explosive known as _Hellhoffite_, and No. 2 is really
oxonite, and No. 4 resembles rack-a-rock, an explosive invented by Mr S.R.
Divine, and consisting of a mixture of chlorate of potash and nitro-
benzol. Roburite, bellite, and securite should perhaps be regarded as
belonging to the Sprengel class of explosives, otherwise this class is not
manufactured or used in England. The principal members are known as
_Hellhoffite_, consisting of a mixture of nitro-petroleum or nitro-tar
oils and nitric acid, or of meta-di-nitro-benzol and nitric acid;
_Oxonite_, consisting of picric and nitric acids; and _Panclastite_, a
name given to various mixtures, proposed by M. Turpin, such as liquid
nitric peroxide, with bisulphide of carbon, benzol, petroleum, ether, or
mineral oils.

~Picric Acid, Tri-nitro-Phenol, or Carbazotic Acid.~--Picric acid, or a
tri-nitro-phenol (C_{6}H_{2}(NO_{2})_{3}OH)[2:4:6], is produced by the
action of nitric acid on many organic substances, such as phenol, indigo,
wool, aniline, resins, &c. At one time a yellow gum from Botany Bay
(_Xanthorrhoea hastilis_) was chiefly used. One part of phenol (carbolic
acid), C_{6}H_{5}OH, is added to 3 parts of strong fuming nitric acid,
slightly warmed, and when the violence of the reaction has subsided,
boiled till nitrous fumes are no longer evolved. The resinous mass thus
produced is boiled with water, the resulting picric acid is converted into
a sodium salt by a solution of sodium carbonate, which throws down sodium
picrate in crystals.

Phenol-sulphuric acid is now, however, more generally used, and the
apparatus employed for producing it closely resembles that used in making
nitro-benzol. It is also made commercially by melting carbolic acid, and
mixing it with strong sulphuric acid, then diluting the "sulpho-
carbolic"[A] acid with water, and afterwards running it slowly into a
stone tank containing nitric acid. This is allowed to cool, where the
crude picric acid crystallises out, and the acid liquid (which contains
practically no picric acid, but only sulphuric acid, with some nitric
acid) being poured down the drains. The crude picric acid is then
dissolved in water by the aid of steam, and allowed to cool when most of
the picric acid recrystallises. The mother liquor is transferred to a tank
and treated with sulphuric acid, when a further crop of picric acid
crystals is obtained. The crystals of picric acid are further purified by
recrystallisation, drained, and dried at 100 deg. F. on glazed earthenware
trays by the aid of steam. It can also be obtained by the action of nitric
acid on ortho-nitro-phenol, para-nitro-phenol, and di-nitro-phenol (2:4
and 2:6), but not from meta-nitro-phenol, a fact which indicates its
constitution.[B]

[Footnote A: O. and p. phenolsulphonic acids.

C_{3}H_{4}(OH).SO_{3}H + 3HNO_{3} = C_{6}H_{2}(NO_{2})_{3}OH + H_{2}SO_{4}
+ 2H_{2}O. (Picric acid).]

[Footnote B: Carey Lea, _Amer. Jour. Sci._, (ii.), xxxii. 180.]

Picric acid crystallises in yellow shining prisms or laminae having an
intensely bitter taste, and is poisonous. It melts at 122.5 deg. C., sublimes
when cautiously heated, dissolves sparingly in cold water, more easily in
hot water, still more in alcohol. It stains the skin an intense yellow
colour, and is used as a dye for wool and silk. It is a strong acid,
forming well crystallised yellow salts, which detonate violently when
heated, some of them also by percussion. The potassium salt,
C_{6}H_{2}(NO_{2})_{3}OK, crystallises in long needles very slightly
soluble in water. The sodium, ammonium, and barium salts are, however,
easily soluble in water. Picric acid, when heated, burns with a luminous
and smoky flame, and may be burnt away in large quantity without
explosion; but the mere contact of certain metallic oxides, with picric
acid, in the presence of heat, develops powerful explosives, which are
capable of acting as detonators to an indefinite amount of the acid, wet
or dry, which is within reach of their detonative influence. The formula
of picric acid is

C_{6}H_{2}|(NO_{2})_{3}
|OH.

which shows its formation from phenol (C_{6}H_{5}OH.), three hydrogen
atoms being displaced by the NO_{2} group. The equation of its formation
from phenol is as follows:--

C_{6}H_{5}.OH + 3HNO_{3} = C_{6}H_{2}(NO_{2})_{3}OH + 3H_{2}O.

According to Berthelot, its heat of formation from its elements equals
49.1 calories, and its heat of total combustion by free oxygen is equal to
+618.4 cals. It hardly contains more than half the oxygen necessary for
its complete combustion.

2C_{6}H_{2}(NO_{2})_{3}OH + O_{10} = 12CO_{2} + 3H_{2} + 3N_{2}.

The percentage composition of picric acid is--Nitrogen, 18.34; oxygen,
49.22; hydrogen, 1.00; and carbon, 31.44, equal to 60.26 per cent. of
NO_{2}. The products of decomposition are carbonic acid, carbonic oxide,
carbon, hydrogen, and nitrogen, and the heat liberated, according to
Berthelot, would be 130.6 cals., or 570 cals. per kilogramme. The reduced
volume of the gases would be 190 litres per equivalent, or 829 litres per
kilogramme. To obtain a total combustion of picric acid it is necessary
to mix with it an oxidising agent, such as a nitrate, chlorate, &c. It has
been proposed to mix picric acid (10 parts) with sodium nitrate (10 parts)
and potassium bichromate (8.3 parts). These proportions would furnish a
third of oxygen in excess of the necessary proportion.

Picric acid was not considered to be an explosive, properly so called, for
a long time after its discovery, but the disastrous accident which
occurred at Manchester (_vide_ Gov. Rep. No. LXXXI., by Colonel (now Sir
V.D.) Majendie, C.B.), and some experiments made by Dr Dupre and Colonel
Majendie to ascertain the cause of the accident, conclusively proved that
this view was wrong. The experiments of Berthelot (_Bull. de la Soc. Chim.
de Paris_, xlix., p. 456) on the explosive decomposition of picric acid
are also deserving of attention in this connection. If a small quantity of
picric acid be heated in a moderate fire, in a crucible, or even in an
open test tube, it will melt (at 120 deg. C. commercial acid), then give off
vapours which catch fire upon contact with air, and burn with a sooty
flame, without exploding. If the burning liquid be poured out upon a cold
slab, it will soon go out. A small quantity carefully heated in a tube,
closed at one end, can even be completely volatilised without apparent
decomposition. It is thus obvious that picric acid is much less explosive
than the nitric ethers, such as nitro-glycerol and nitro-cellulose, and
very considerably less explosive than the nitrogen compounds and
fulminates.

It would, however, be quite erroneous to assume that picric acid cannot
explode when simply heated. On the contrary, Berthelot has proved that
this is not the case. If a glass tube be heated to redness, and a minute
quantity of picric acid crystals be then thrown in, it will explode with a
curious characteristic noise. If the quantity be increased so that the
temperature of the tube is materially reduced, no explosion will take
place at once, but the substance will volatilise and then explode, though
with much less violence than before, in the upper part of the tube.
Finally, if the amount of picric acid be still further increased under
these conditions, it will undergo partial decomposition and volatilise,
but will not even deflagrate. Nitro-benzene, di-nitrobenzene, and mono-,
di-, and tri-nitro-naphthalenes behave similarly.

The manner in which picric acid will decompose is thus dependent upon the
initial temperature of the decomposition, and if the surrounding material
absorb heat as fast as it is produced by the decomposition, there will be
no explosion and no deflagration. If, however, the absorption is not
sufficient to prevent deflagration, this may so increase the temperature
of the surrounding materials that the deflagration will then end in
explosion. Thus, if an explosion were started in an isolated spot, it
would extend throughout the mass, and give rise to a general explosion.

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