Nitro Explosives: A Practical Treatise by P. Gerald Sanford

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Dr Muehlhaeusen, working on these lines in the laboratory, prepared nitro-
starch which contained 10.96 and 11.09 per cent. of nitrogen. When in the
state of powder it is snow-white in colour; it becomes electrified when
rubbed; it is very stable, and soluble even in the cold in nitro-
glycerine. He has also prepared a tetra-nitro-starch containing 10.58 and
10.50 per cent. of nitrogen, by pouring water into a solution of starch in
nitric acid which had stood for several days. The substance thus produced
in the laboratory had all the properties of that prepared by the other
process.

The production of penta-nitro-starch is effected by adding 20 grms. of
rice-starch--previously dried at a temperature of 100 deg.C., in order to
eliminate all moisture--to a mixture of 100 grms. of nitric acid, specific
gravity 1.501, and 300 grms. of sulphuric acid, specific gravity 1.8 (some
tetra-nitro-starch is also formed at the same time). After standing in
contact with these mixed acids for one hour the starch has undergone a
change, and the mass may now be discharged into a large quantity of water,
and then washed, first with water, and finally with an aqueous solution of
soda. The yield in Dr Muehlhaeusen's experiments was 147.5 per cent.

The substance thus formed is now heated with ether-alcohol, the ether is
distilled off, and the penta-nitro-starch appears as a precipitate, whilst
the tetra-nitro-starch, which is formed simultaneously, remains in
solution in the alcohol. As obtained by this process, it contained 12.76
and 12.98 per cent. nitrogen, whilst the soluble tetra-nitro-starch
contained 10.45 per cent.

Hexa-nitro-starch is the product chiefly formed when 40 grms. of dry
starch are treated with 400 grms. of nitric acid, specific gravity 1.501,
and allowed to stand in contact for twenty-four hours; 200 grms. of this
mixture are then poured into 600 c.c. of sulphuric acid of 66 deg. B. The
result of this manipulation is a white precipitate, which contains
13.52-13.23 and 13.22 per cent. nitrogen; and consists, therefore, of a
mixture of penta- and hexa-nitro-starch.

The experiments undertaken with these substances demonstrated that those
prepared by precipitating the nitro-starch with strong sulphuric acid were
less stable in character or properties than those which were precipitated
by water or weak sulphuric acid. Dr Muehlhaeusen is of opinion that possibly
in the former case a sulpho-group may be formed, which in small quantity
may occasion this instability.

The following table shows the behaviour of these substances prepared in
different ways and under various conditions:--

__________________________________________________________________
| | |
| | SAMPLES. |
| |____________________________________________|
| | | | | | |
| | A. | B. | C. | D. | E. |
| Ignition-point |175 deg. C. |170 deg. C. |152 deg. C. |121 deg. C. |155 deg. C. |
| Stability |Stable |Stable |Unstable|Unstable|Unstable|
| Per cent. of N. | 11.02 | 10.54 | 12.87 | 12.59 | 13.52 |
| 96 per cent. alcohol| Sol. | Sol. | Insol. | Insol. | Insol. |
| Ether | Insol. | Insol. | Insol. | Insol. | Insol. |
| Ether-alcohol | Sol. | Sol. | Sol. | Sol. | Sol. |
| Acetic Ether | Sol. | Sol. | Sol. | Sol. | Sol. |
|_____________________|________|________|________|________|________|

These samples were prepared as follows:--

A. From 1 part nitric acid and 2 parts sulphuric acid (containing 70 per
cent. H_{2}O).
B. From 1 part nitric acid and water.
C. From 1 part nitric and 3 parts H_{2}SO_{4} (con.).
D. From 1 part nitric and 3.5 parts con. H_{2}SO_{4}.
E. From 1 part nitric and 3 parts con. H_{2}SO_{4}.

Dr Muehlhaeusen is of opinion that these compounds may be turned to
practical account in the production of good smokeless powder. He
recommends the following proportions and method. Six grms. of nitro-jute
and 2 grms. of nitro-starch are mixed together, and moistened with acetic
ether. These ingredients are then worked together into a uniform mass, and
dried at a temperature ranging between the limits 50 deg. to 60 deg. C. He has
himself prepared such a smokeless powder, which proved to contain 11.54
per cent. of nitrogen, and was very stable. Further details of Dr
Muehlhaeusen's work upon nitro-starch can be found in _Dingler's
Polytechnisches Journal_, paper "Die hoehren Salpetersaeureaether der
Staerke," 1892, Band 284, s. 137-143, and a Bibliography up to 1892 in
_Arms and Explosives_, December 1892.

M. Berthelot gives the heat of formation of nitro-starch as 812 cals. for
1 grm., and the heat of total combustion as equal to 706.5 cals. for 207
grms., or for 1 grm. 3,413 cals. The heat of decomposition could only be
calculated if the products of decomposition were given, but they have not
as yet been studied, and the quantity of oxygen contained in the compound
is far from being sufficient for its complete combustion. Berthelot and
Vieille found the average velocities for nitro-starch powder, density of
charge about 1.2, in a tin tube 4 mm. external diameter, to be, in two
experiments, 5,222 m. and 5,674 m. In a tin tube 5.5 mm. external
diameter, the velocity was 5,815 m., and in lead tube 5,006 m. (density
1.1 to 1.2). The starch powder is hygroscopic, and is insoluble in water
and alcohol. When dry it is very explosive, and takes fire at about 350 deg.
F. Mr Alfred Nobel has taken out a patent (Eng. Pat. No. 6,560, 88) for
the use of nitro-starch. His invention relates to the treatment of nitro-
starch and nitro-dextrine, for the purpose of producing an explosive
powder, to be used in place of gunpowder. He incorporates these materials
with nitro-cellulose, and dissolves the whole in acetone, which is
afterwards distilled off. A perfect incorporation of the ingredients is
thus brought about.

~Nitro-Jute.~--It is obtained by treating jute with nitric acid. Its
properties have been studied by Messrs Cross and Bevan (_Jour. Chem.
Soc._, 1889, 199), and by Muehlhaeusen. The latter used for its nitration an
acid mixture composed of equal parts of nitric and sulphuric acids, which
was allowed to act upon the jute for some time. He found that with long
exposure, i.e., from three to four hours in the acids, there was a
disintegrating of the fibre-bundles, and the nitration was attended by
secondary decomposition and conversion into products soluble in the acid
mixture. Cross and Bevan's work upon this subject leads them to conclude
that the highest yield of nitrate is represented by an increase of weight
of 51 per cent. They give jute the empirical formula C_{12}H_{18}O_{9} (C
= 47 per cent. H = 6 per cent., and O = 47 per cent.), and believe its
conversion into a nitro compound to take place thus:--

C_{12}H_{18}O + 3HNO_{3} = C_{12}H_{15}O_{6}(NO_{3})_{3} + 3H_{2}O.

This is equivalent to a gain in weight of 44 per cent. for the tri-
nitrate, and of 58 per cent. for the tetra-nitrate. The formation of the
tetra-nitrate appears to be the limit of nitration of jute-fibre. In other
words, if we represent the ligno-cellulose molecule by a C_{12} formula,
it will contain four hydroxyl (OH) groups, or two less than cellulose
similarly represented. The following are their nitration results:--

Acids used.--I. HNO_{3} sp. gr. 1.43, and H_{2}SO_{4} = 1.84 equal parts.
II. 1 vol. HNO_{3}(1.5), 1 vol. H_{2}SO_{4}(1.84).
III. 1 vol. HNO_{3}(1.5), 75 vols. H_{2}SO_{4}(1.84).

I. = 144.4; II. = 153.3; III. = 154.4 grms.; 100 grms. of fibre being used
in all three cases.

Duration of exposure, thirty minutes at 18 deg. C.

The nitrogen was determined in the products, and equalled 10.5 per cent.
Theory for C_{12}H_{15}O_{6}(NO_{3})_{3} = 9.5 per cent. and for
C_{12}H_{15}O_{6}(NO_{3})_{4} = 11.5 per cent. These nitrates resemble
those of cellulose, and are in all essential points nitrates of ligno-
cellulose.

Muehlhaeusen obtained a much lower yield, and probably, as pointed out by
Cross and Bevan, a secondary decomposition took place, and his products,
therefore, probably approximate to the derivatives of cellulose rather
than to those of ligno-cellulose, the more oxidisable, non-cellulose, or
lignone constituents having been decomposed. In fact, he regards his
product as cellulose penta-nitrate (C_{12}H_{16}O_{5}(ONO_{2})_{5}). The
_Chemiker Zeitung_, xxi., p. 163, contains a further paper by Muehlhaeusen
on the explosive nitro-jute. After purifying the jute-fibre by boiling it
with a 1 per cent. solution of sodium carbonate, and washing with water,
he treated 1 part of the purified jute with 15 parts of nitro-sulphuric
acid, and obtained the following results with different proportions of
nitric to sulphuric acids:--

Yield Ignition Nitrogen.
per cent. Point.
Experiment I.-- 1. HNO_{3} 1. H_{2}SO_{4} 129.5 170 deg. C. 11.96%
" II. " 2. " 132.2 167 deg. C. 12.15%
" III. " 3. " 135.8 169 deg. C. 11.91%

An experiment made with fine carded jute and the same mixture of acids as
in No. II. gave 145.4 per cent. nitro-jute, which ignited at 192 deg. C., and
contained 12 per cent. nitrogen. This explosive is not at present
manufactured upon the large scale, and Messrs Cross and Bevan are of
opinion that there is no very obvious advantage in the use of lignified
textile fibre as raw materials for explosive nitrates, seeing that a large
number of raw materials containing cellulose (chiefly as cotton) can be
obtained at a cheaper rate, and yield also 150 to 170 per cent. of
explosive material when nitrated, and are in many ways superior to the
products obtained hitherto from jute.

~Nitro-mannite~ is formed by the action of nitric acid on mannite, a
hex-acid alcohol closely related to sugar. It occurs abundantly in manna,
which is the partly dried sap of the manna-ash (_Fraxinus ornus_). It is
formed in the lactic acid fermentation of sugar, and by the action of
nascent hydrogen on glucose and cellulose, or on invert sugar. Its formula
is C_{6}H_{8}(OH)_{6} and that of nitro-mannite C_{6}H_{8}(NO_{3})_{6}.
Mannite crystallises in needles or rhombic prisms, which are soluble in
water and alcohol, and have a sweet taste. Nitro-mannite forms white
needle-shaped crystals, insoluble in water, but soluble in ether or
alcohol. When rapidly heated, they ignite at about 374 deg. F., and explode at
about 590 deg. F. It is more susceptible to friction and percussion than
nitro-glycerine, and unless pure it is liable to spontaneous
decomposition. It is considered as the nitric ether of the hexatomic
alcohol mannite. It is formed by the action of a mixture of nitric and
sulphuric acids upon mannite--

C_{6}H_{8}(OH)_{6} + 6HNO_{3} = C_{6}H_{8}(NO_{3})_{6} + 6H_{2}O.

Its products of explosion are as shown in the following equation:--

C_{6}H_{8}(OH)_{6} = 6CO_{2} + 4H_{2}O + 3N_{2} + O_{2}.

Its percentage composition is as follows:--Carbon, 15.9 per cent.;
hydrogen, 1.8 per cent.; nitrogen, 18.6 per cent.; and oxygen, 63.7 per
cent. Its melting point is 112 to 113 deg. C., and it solidifies at 93 deg.. When
carefully prepared and purified by recrystallisation from alcohol, and
kept protected from sunlight, it can be kept for several years without
alteration.

Nitro-mannite is more dangerous than nitro-glycerine, as it is more
sensitive to shock. It is intermediate in its shattering properties
between nitro-glycerine and fulminate of mercury. It explodes by the shock
of copper on iron or copper, and even of porcelain on porcelain, provided
the latter shock be violent. Its heat of formation from its elements is
+156.1 calories. It is not manufactured upon the commercial scale.

Besides the nitro compounds already described, there are many others, but
they are of little importance, and are none of them made upon the large
scale. Among such substances are _nitro-coal_, which is made by the action
of nitric acid on coal; _nitro-colle_, a product which results from the
action of nitric acid on isinglass or gelatine, soaked in water. It is
then treated with the usual acids.

Another method is to place strong glue in cold water until it has absorbed
the maximum amount of the latter. The mixture is solidified by the
addition of nitric acid, nitrated in the usual way, and well washed.
Abel's _Glyoxiline_ is only nitrated gun-cotton impregnated with nitro-
glycerine. Nitro-lignine is only nitro-cellulose made from wood instead of
cotton; and nitro-straw is also only nitro-cellulose. The explosive known
as _Keil's Explosive_ contains nitro-glucose. Nitro-molasses, which is a
liquid product, has also been proposed, and nitro-saccharose, the product
obtained by the nitration of sugar. It is a white, sandy, explosive
substance, soluble in alcohol and ether. When made from cane sugar, it
does not crystallise; but if made from milk sugar, it does. It has been
used in percussion caps, being stronger and quicker than nitro-glycerine.
It is, however, very sensitive and very hygroscopic, and very prone to
decomposition. Nitro-tar, made from crude tar-oil, by nitration with
nitric acid of a specific gravity of 1.53 to 1.54. Nitro-toluol is used,
mixed with nitro-glycerine. This list, however, does not exhaust the
various substances that have been nitrated and proposed as explosives.
Even such unlikely substances as horse dung have been experimented with.
None of them are very much used, and very few of them are made upon the
manufacturing scale.

CHAPTER IV.

_DYNAMITE AND GELATINES._

Kieselguhr Dynamite--Classification of Dynamites--Properties and
Efficiency of Ordinary Dynamite--Other Forms of Dynamite--Gelatine and
Gelatine Dynamites, Suitable Gun-Cotton for, and Treatment of--Other
Materials used--Composition of Gelignite--Blasting Gelatine--Gelatine
Dynamite--Absorbing Materials--Wood Pulp--Potassium Nitrate, &c.--
Manufacture and Apparatus used, and Properties of Gelatine Dynamites--
Cordite--Composition and Manufacture.

~Dynamite.~--Dynamite consists of nitro-glycerine either absorbed by some
porous material, or mixed with some other substance or substances which
are either explosives or merely inert materials. Among the porous
substances used is kieselguhr, a silicious earth which consists chiefly of
the skeletons of various species of diatoms. This earth occurs in beds
chiefly in Hanover, Sweden, and Scotland. The best quality for the purpose
of manufacturing dynamite is that which contains the largest quantity of
the long tubular _bacillariae_, and less of the round and lancet-shaped
forms, such as _pleurosigmata_ and _diclyochae_, as the tube-shaped diatoms
absorb the nitro-glycerine better, and it becomes packed into the centre
of the silicious skeleton of the diatoms, the skeleton acting as a kind of
tamping, and increasing the intensity of the explosion.

Dynamites are classified by the late Colonel Cundill, R.A., in his
"Dictionary of Explosives" as follows:--

1. Dynamites with an inert base, acting merely as an absorbent.

2. Dynamites with an active base, i.e., an explosive base. No. 2 may be
again divided into three minor classes, which contain as base--

(_a._) Charcoal.

(_b._) Gunpowder or other nitrate, or chlorate mixture.

(_c._) Gun-cotton or other nitro compound (nitro-benzol, &c.).

The first of these, viz., charcoal, was one of the first absorbents for
nitro-glycerine ever used; the second is represented by the well-known
Atlas powder; and the last includes the well-known and largely used
gelatine compounds, viz., gelignite and gelatine dynamite, and also tonite
No. 3, &c.

In the year 1867 Nobel produced dynamite by absorbing the nitro-glycerine
in an inert substance, forming a plastic mass. In his patent he says:
"This invention relates to the use of nitro-glycerine in an altered
condition, which renders it far more practical and safe for use. The
altered condition of the nitro-glycerine is effected by causing it to be
absorbed in porous unexplosive substances, such as charcoal, silica,
paper, or similar materials, whereby it is converted into a powder, which
I call dynamite, or Nobel's safety powder. By the absorption of the nitro-
glycerine in some porous substance it acquires the property of being in a
high degree insensible to shocks, and it can also be burned over a fire
without exploding."

Ordinary dynamite consists of a mixture of 75 per cent. of nitro-glycerine
and 25 per cent. of kieselguhr. The guhr as imported (Messrs A. Haake &
Co. are the chief importers) contains from 20 to 30 per cent. of water and
organic matter. The water may be very easily estimated by drying a weighed
quantity in a platinum crucible at 100 deg. C. for some time and re-weighing,
and the organic matter by igniting the residue strongly over a Bunsen
burner. Before the guhr can be used for making dynamite it must be
calcined, in order not only to get rid of moisture, but also the organic
matter.

A good guhr should absorb four times its weight of nitro-glycerine, and
should then form a comparatively dry mixture. It should be pale pink, red
brown, or white. The pink is generally preferred, and it should be as free
as possible from grit of all kinds, quartz particles, &c., and should have
a smooth feeling when rubbed between the finger and thumb, and should show
a large quantity of diatoms when viewed under the microscope. The
following was the analysis of a dried sample of kieselguhr:--Silica,
94.30; magnesia, 2.10; oxide of iron and alumina, 1.3; organic matter,
0.40; moisture, 1.90 per cent.

The guhr is generally dried in a reverberatory muffle furnace. It is
spread out on the bottom to the thickness of 3 or 4 inches, and should
every now and then be turned over and raked about with an iron rabble or
hoe. The temperature should be sufficiently high to make the guhr red hot,
or the organic matter will not be burnt off. The time occupied in
calcining will depend of course upon the quality of the guhr being
operated upon. Those containing a high percentage of water and organic
matter will of course take longer than those that do not. A sample of the
calcined guhr should not contain more than 0.5 per cent. of moisture and
organic matter together.

After the guhr is dry it requires to be sifted and crushed. The crushing
is done by passing it between iron rollers fixed at the bottom of a cone
or hopper, and revolving at a moderate speed. Beneath the rollers a fine
sieve should be placed, through which the guhr must be made to pass.

The kieselguhr having been dried, crushed, and sifted, should be packed
away in bags, and care should be taken that it does not again absorb
moisture, as if it contains anything above about five-tenths per cent. of
water it will cause the dynamite made with it to exude. The guhr thus
prepared is taken up to the danger area, and mixed with nitro-glycerine.
The nitro-glycerine used should be quite free from water, and clear, and
should have been standing for a day or two in the precipitating house. The
guhr and nitro-glycerine are mixed in lead tanks (about 1-1/2 foot deep,
and 2 to 3 feet long), in the proportions of 75 of the nitro-glycerine to
25 of the guhr, unless the guhr is found to be too absorbent, which will
cause the dynamite to be too dry and to crumble. In this case a small
quantity of barium sulphate, say about 1 per cent., should be added to the
guhr. This will lessen its absorbing powers, or a highly absorptive sample
of guhr may be mixed with one of less absorptive power, in the proportions
found by experiment to be the best suited to make a fairly moist dynamite,
but one that will not exude.

The mixing itself is generally performed in a separate house. In a series
of lead-lined tanks the guhr is weighed, placed in a tank, and the nitro-
glycerine poured on to it. The nitro-glycerine may be weighed out in
indiarubber buckets. The whole is then mixed by hand, and well rubbed
between the hands, and afterwards passed through a sieve. At this stage
the dynamite should be dry and powdery, and of a uniform colour.

It is now ready to be made up into cartridges, and should be taken over to
the cartridge huts. These are small buildings surrounded with mounds, and
contain a single cartridge machine. Each hut requires three girls--one to
work the press, and two to wrap up the cartridges. The cartridge press
consists of a short cylinder of the diameter of the cartridge that it is
intended to make. Into this cylinder a piston, pointed with ivory or
lignum vitae wood, works up and down from a spring worked by a lever. Round
the upper edge of the cylinder is fastened a canvas bag, into which the
powdery dynamite is placed by means of a wooden scoop, and the descending
piston forces the dynamite down the cylinder and out of the open end,
where the compressed dynamite can be broken off at convenient lengths. The
whole machine should be made of gun-metal, and should be upright against
the wall of the building. The two girls, who sit at tables placed on each
side of the press, wrap the cartridges in parchment paper. From these huts
the cartridges are collected by boys every ten minutes or a quarter of an
hour, and taken to the packing room, where they are packed in 5-lb.
cardboard boxes, which are then further packed in deal boxes lined with
indiarubber, and fastened down air tight. The wooden lids are then nailed
down with brass or zinc nails, and a label pasted on the outside giving
the weight and description of the contents. The boxes should then be
removed to the magazines. It is well to take a certain number of
cartridges from the packing house at different times during the day, say
three or four samples, and to test them by the heat test. A sample cut
from a cartridge, about 1 inch long, should be placed under a glass shade,
together with water (a large desiccator, in fact), and left for some days.
A good dynamite should not, under these conditions, show any signs of
exudation, even after weeks.[A]

[Footnote A: For analysis of dynamite, see chapter on "Analysis," and
author's article in _Chem. News_, 23rd September 1892.]

~Properties of Kieselguhr Dynamite.~--One cubic foot of dynamite weighs 76
lbs. 4 oz. The specific gravity of 75 per cent. dynamite is, however,
1.50. It is a red or grey colour, and rather greasy to the touch. It is
much less sensitive to shock than nitro-glycerine, but explodes
occasionally with the shock of a rifle bullet, or when struck. The
addition of a few per cent. of camphor will considerably diminish its
explosive qualities to such an extent that it can be made non-explosive
except to a very strong fulminate detonator. The direct contact of water
disintegrates dynamite, separating the nitro-glycerine, hence great
caution is necessary in using it in wet places. It freezes at about 40 deg.
Fahr. (4 deg. C.), and remains frozen at temperatures considerably exceeding
that point. When frozen, it is comparatively useless as an explosive
agent, and must be thawed with care. This is best done by placing the
cartridges in a warming pan, which consists of a tin can, with double
sides and bottom, into which hot water (130 deg. Fahr.) can be poured. The
dynamite will require to be left in for some considerable time before it
becomes soft. On no account must it be placed on a hot stove or near a
fire, as many serious accidents have occurred in this way.

Frozen dynamite is a hard mass, with altered properties, and requires 1.5
grm. of fulminate instead of 0.5 grm. to explode it. Thawing may also
cause exudation of the nitro-glycerine, which is much more sensitive to
shock, and if accidentally struck with an iron tool, may explode. It is a
dangerous thing to cut a frozen cartridge with a knife. Ramming is even
more dangerous; in fact it is not only dangerous, but wasteful, to use
dynamite when in a frozen state.

Dynamite explodes at a temperature of 360 deg. Fahr., and is very sensitive to
friction when hot. In hot countries it should never be exposed to the rays
of the sun. It should, however, not be kept in a damp or moist place, as
this is liable to cause exudation. Sunlight, if direct, can cause a slow
decomposition, as with all nitro and nitric compounds. Electric sparks
ignite, without exploding it, at least when operating in the open air.

Dynamite, when made with neutral nitro-glycerine, appears to keep
indefinitely. Sodium or calcium carbonate to the extent of 1 per cent. is
often added to dynamite to ensure its being neutral. If it has commenced
to undergo change, however, it rapidly becomes acid, and sometimes
explodes spontaneously, especially if contained in resisting envelopes.
Nevertheless, neutral and well-made dynamite has been kept for years in a
magazine without loss of its explosive force. If water is brought into
contact with it, the nitro-glycerine is gradually displaced from the
silica (guhr). This action tends to render all wet dynamite dangerous.

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