Nitro Explosives: A Practical Treatise by P. Gerald Sanford
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P. Gerald Sanford >> Nitro Explosives: A Practical Treatise
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~Kieselguhr Dynamite.~--The material generally consists of 75 per cent. of
nitro-glycerine and 25 per cent. of the infusorial earth kieselguhr. The
analysis is very simple, and may be conducted as follows:--Weigh out about
10 grms. of the substance, and place over calcium chloride in a desiccator
for some six to eight days, and then re-weigh. The loss of weight gives
the moisture. This will generally be very small, probably never more than
1 per cent., and usually less.
Mr James O. Handy, in order to save time, proposes to dry dynamite in the
following manner. He places 1 grm. of the material in a porcelain crucible
1 inch in diameter. The crucible is then supported at the bottom of an
extra wide-mouthed bottle of about 600 c.c. capacity. Air, which has been
dried by bubbling through strong sulphuric acid, is now drawn over the
surface of the sample for three hours by means of an ordinary aspirator.
The air should pass approximately at the rate of 10 c.c. per second. The
tube by which the dry air enters the bottle extends to within 1 inch of
the crucible containing the dynamite. An empty safety bottle is connected
with the inlet, and another with the outlet of the wide-mouthed bottle.
The first guards against the mechanical carrying over by the air current
of sulphuric acid from the acid bottle into the sample, whilst the second
prevents spasmodic outbursts of water from the exhaust from reaching the
sample. The method also gave satisfactory results with nitro-glycerine.
The dry substance may now be wrapped in filter paper, the whole weighed,
and the nitro-glycerine extracted in the Soxhlet apparatus with ether. The
ether should be distilled over at least twenty-four times.
I have found, however, that much quicker, and quite as accurate, results
may be obtained by leaving the dynamite in contact with ether in a small
Erlenmeyer flask for twenty-four hours--leaving it overnight is better--
and decanting, and again allowing the substance to remain in contact with
a little fresh ether for an hour, and finally filtering through a weighed
filter, drying at 100 deg. C., and weighing. This gives the weight of the
kieselguhr. The nitro-glycerine must be obtained by difference, as it is
quite useless to evaporate down the ethereal solution to obtain it, as it
is itself volatile to a very considerable extent at the temperature of
evaporation of the ether, and the result, therefore, will always be much
too low. The dry guhr can, of course, be examined, either qualitatively or
quantitatively, for other mineral salts, such as carbonate of soda, &c. An
actual analysis of dynamite No. 1 made by the author at Hayle gave--
Moisture, 0.92 per cent.; kieselguhr, 26.15 per cent.; and nitro-
glycerine, 72.93 per cent., the last being obtained by difference.
~Nitro-Glycerine.~--It is sometimes desired to test an explosive substance
for nitro-glycerine. If an oily liquid is oozing from the substance, soak
a drop of it in filter paper. If it is nitro-glycerine it will make a
greasy spot. If the paper is now placed upon an iron anvil, and struck
with an iron hammer, it will explode with a sharp report, if lighted it
burns with a yellowish to greenish flame, emitting a crackling sound, and
placed upon an iron plate and heated from beneath, it explodes sharply.
If a few drops of nitro-glycerine are placed in a test tube, and shaken up
with methyl-alcohol (previously tested with distilled water, to see that
it produces no turbidity), and filtered, on the addition of distilled
water, the solution will become milky, and the nitro-glycerine will
separate out, and finally collect at the bottom of the tube.
If to a solution of a trace of nitro-glycerine in methyl-alcohol, a few
drops of a solution, composed of 1 volume of aniline, and 40 volumes
sulphuric acid (1.84) be added, a deep purple colour will be produced.
This colour changes to green upon the addition of water. If it is
necessary to determine the nitro-glycerine quantitatively in an explosive,
the scheme on page 213 may be followed. Ether is the best solvent to use.
Nitrogen should be determined in the nitrometer.
~Gelatine Compounds.~--The simplest of these compounds is, of course,
blasting gelatine, as it consists of nothing but nitro-cotton and nitro-
glycerine, the nitro-cellulose being dissolved in the glycerine to form a
clear jelly, the usual proportions being about 92 per cent. of nitro-
glycerine to 8 per cent. nitro-cotton, but the cotton is found as high as
10 per cent. in some gelatines. Gelatine dynamite and gelignite are
blasting gelatines, with varying proportions of wood-pulp and saltpetre
(KNO_{3}) mixed with a thin blasting gelatine. The method of analysis is
as follows:--Weigh out 10 grms. of the substance, previously cut up into
small pieces with a platinum spatula, and place over calcium chloride in a
desiccator for some days. Reweigh. The loss equals moisture. This is
generally very small. Or Handy's method may be used. The dried sample is
then transferred to a small thistle-headed funnel which has been cut off
from its stem, and the opening plugged with a little glass wool, and round
the top rim of which a piece of fine platinum wire has been fastened, in
order that it may afterwards be easily removed from the Soxhlet tube. The
weight of this funnel and the glass wool must be accurately known. It is
then transferred to the Soxhlet tube and exhausted with ether, which
dissolves out the nitro-glycerine. The weighed residue must afterwards be
treated in a flask with ether-alcohol to dissolve out the nitro-cotton.
But the more expeditious method, and one quite as accurate, is to transfer
the dried gelatine to a conical Erlenmeyer flask of about 500 c.c.
capacity, and add 250 c.c. of a mixture of ether-alcohol (2 ether to 1
alcohol), and allow to stand overnight. Sometimes a further addition of
ether-alcohol is necessary. It is always better to add another 300 c.c.,
and leave for twenty minutes or so after the solution has been filtered
off. The undissolved portion, which consists of wood-pulp, potassium
nitrate, and other salts, is filtered off through a linen or paper filter,
dried and weighed.
~Solution.~--The ether-alcohol solution contains the nitro-cotton and the
nitro-glycerine in solution.[A] To this solution add excess of chloroform
(about 100 c.c. will be required), when the nitro-cellulose will be
precipitated in a gelatinous form. This should be filtered off through a
linen filter, and allowed to drain. It is useless to attempt to use a
filter pump, as it generally causes it to set solid. The precipitated
cotton should then be redissolved in ether-alcohol, and again precipitated
with chloroform (20 c.c. of ether-alcohol should be used). This precaution
is absolutely necessary, if the substance has been treated with ether-
alcohol at first instead of ether only, otherwise the results will be much
too high, owing to the gelatinous precipitate retaining very considerable
quantities of nitro-glycerine. The precipitate is then allowed to drain as
completely as possible, and finally allowed to dry in the air bath at 40 deg.
C., until it is easily detached from the linen filter by the aid of a
spatula, and is then transferred to a weighed watch-glass, replaced in the
oven, and dried at 40 deg. C. until constant in weight. The weight found,
calculated upon the 10 grms. taken, gives the percentage of nitro-
cellulose.
[Footnote A: If the substance has been treated with ether alone in the
Soxhlet, the nitro-glycerine will of course be dissolved out first, and
the ether-alcohol solution will only contain the nitro-cellulose.]
~The Residue~ left after treating the gelatine with ether-alcohol is, in
the case of blasting gelatine, very small, and will probably consist of
nothing but carbonate of soda. It should be dried at 100 deg. C. and weighed,
but in the case of either gelignite or gelatine dynamite this residue
should be transferred to a beaker and boiled with distilled water, and the
water decanted some eight or ten times, and the residue finally
transferred to a tarred filter and washed for some time with hot water.
The residue left upon the filter is wood-pulp. This is dried at 100 deg. C.
until constant, and weighed. The solution and washings from the wood are
evaporated down in a platinum dish, and dried at 100 deg. C. It will consist
of the potassium nitrate, and any other mineral salts, such as carbonate
of soda, which should always be tested for by adding a few drops of nitric
acid and a little water to the residue, and again evaporating to dryness
and re-weighing. From the difference in weight the soda can be calculated,
sodium nitrate having been formed. Thus--
Na_{2}CO_{3} + 2HNO_{3} = 2NaNO_{3} + CO_{2} + H_{2}O.
Mol. wt. = 106 = 170
(170 - 106 = 64) and _x_ = (106 x _d_)/64
where _x_ equals grms. of sodium carbonate in residue, and _d_ equals the
difference in weight of residue, before and after treatment with nitric
acid.
The nitro-glycerine is best found by difference, but if desired the
solutions from the precipitation of the nitro-cellulose may be evaporated
down upon the water bath at 30 deg. to 40 deg. C., and finally dried over CaCl_{2}
until no smell of ether or chloroform can be detected, and the nitro-
glycerine weighed. It will, however, always be much too low. An actual
analysis of a sample of gelatine dynamite gave the following result:--
Nitrocellulose (collodion) 3.819 per cent.
Nitro-glycerine 66.691 "
Wood-pulp 16.290 "
KNO_{3} 12.890 "
Na_{2}CO_{3} _Nil._
Water 0.340 "
This sample was probably intended to contain 30 per cent. of absorbing
material to 70 per cent. of explosive substances. Many dynamites contain
other substances than the above, such as paraffin, resin, sulphur, wood,
coal-dust, charcoal, also mineral salts, such as carbonate of magnesia,
chlorate of potash, &c. In these cases the above-described methods must of
course be considerably modified. Paraffin, resin, and most of the sulphur
will be found in the ether solution if present. The solution should be
evaporated (and in this case the explosive should in the first case be
treated with ether only, and not ether-alcohol), and the residue weighed,
and then treated on the water bath with a solution of caustic soda. The
resin goes into solution, and is separated by decantation from the
residue, and precipitated by hydrochloric acid, and collected on a tarred
filter (dried at 100 deg. C.), and dried at 100 deg. C. and weighed. The nitro-
glycerine residue is treated with strong alcohol, decanted, and the
residue of paraffin and sulphur washed with alcohol, dried, and weighed.
To separate the paraffin from the sulphur the residue is heated with a
solution of ammonium sulphide. After cooling the paraffin collects as a
crust upon the surface of the liquid, and by pricking a small hole through
it with a glass rod the liquid underneath can be poured off, and the
paraffin then washed with water, dried, and weighed. Sulphur is found by
difference. Mr F.W. Smith (_Jour. Amer. Chem. Soc._, 1901, 23 [8],
585-589) determines the sulphur in dynamite gelatine as follows:--About 2
grms. are warmed in a 100 c.c. silver crucible on the water bath with an
alcoholic solution of sodium hydroxide, and where the nitro-glycerine is
decomposed, the liquid is evaporated to dryness. The residue is fused with
40 grms. of KOH and 5 grms. of potassium nitrate, the mass dissolved in
dilute acetic acid and filtered, and the sulphates precipitated in the
usual way. If camphor is present, it can be extracted with bisulphide of
carbon after the material has been treated with ether-alcohol. In that
case the sulphur, paraffin, and resin will also be dissolved. The camphor
being easily volatile, can be separated by evaporation. Let the weight of
the extract, freed from ether-alcohol before treatment with bisulphide of
carbon, equal A, and the weight of extract after treatment with CS_{2} and
evaporation of the same equal B; and weight of the residue which is left
after evaporation of the CS_{2} and the camphor in solution equal C, the
percentage of camphor will be A - B - C. The residue C may contain traces
of nitro-glycerine, resin, or sulphur.
Camphor may be separated from nitro-glycerine by means of CS_{2}. If the
solution of camphor in nitro-glycerine be shaken with CS_{2}, the camphor
and a little of the nitro-glycerine will dissolve. The bisulphide solution
is decanted, or poured into a separating funnel and separated from the
nitro-glycerine. The two solutions are then heated on the water bath to
20 deg. C. and then to 60 deg. C., and afterwards in a vacuum over CaCl_{2} until
the CS_{2} has evaporated from them. The camphor evaporates, and leaves
the small quantity of nitro-glycerine which had been dissolved with it.
The other portion is the nitro-glycerine, now free from CS_{2}. The two
are weighed and their weights added together, and equals the nitro-
glycerine present. There is a loss of nitro-glycerine, it being partly
evaporated along with the CS_{2}. Captain Hess has shown that it is equal
to about 1.25 per cent. This quantity should therefore be added to that
found by analysis. Morton Liebschutz, in a paper in the _Moniteur
Scientifique_ for January 1893, very rightly observes that the variety of
dynamites manufactured is very great, all of them having a special
composition which, good or bad, is sometimes of so complicated a nature
that the determination of their elements is difficult.
The determination of nitro-glycerine in simple dynamite No. 1 is easy; but
not so when the dynamite contains substances soluble in ether, such as
sulphur, resin, paraffin, and naphthalene. After detailing at length the
methods he employs, he concludes with the observation that the knowledge
of the use of acetic acid--in which nitro-glycerine dissolves--for the
determination of nitro-glycerine may be serviceable. Mr F.W. Smith[A]
gives the following indirect method of determining nitro-glycerine in
gelatine dynamite, &c. About 15 grms. of the sample are extracted with
chloroform in a Soxhlet apparatus, and the loss in weight determined. In a
second portion the moisture is determined. A third portion of about 2
grms. is macerated with ether in a small beaker, the ethereal extract
filtered, and the process of extraction repeated three or four times. The
united filtrates are allowed to evaporate spontaneously, and the residue
warmed gently on the water bath with 5 c.c. of ammonium sulphide solution,
and 10 c.c. of alcohol until the nitro-glycerine is decomposed, after
which about 250 c.c. of water and sufficient hydrochloric acid to render
the liquid strongly acid, are added, and the liquid filtered. The
precipitate is washed free from acid, and then washed through the filter
with strong alcohol and chloroform into a weighed platinum dish, which is
dried to constant weight at 50 deg. C. The contents of the dish are now
transferred to a silver crucible, and the sulphur determined. This amount
of sulphur, deducted from the weight of the contents of the platinum dish,
gives the quantity of substances soluble in chloroform with the exception
of the nitro-glycerine, moisture, and sulphur. The amount of the former
substances _plus_ the moisture and sulphur, deducted from the total loss
on extraction with chloroform, gives the quantity of nitro-glycerine.
Nitro-benzene may be detected, according to J. Marpurgo, in the following
manner:--In a porcelain basin are placed two drops of liquid phenol, three
drops of water, and a fragment of potash as large as a pea. The mixture is
boiled, and the aqueous solution to be tested then added. On prolonged
boiling nitro-benzene produces at the edge of the liquid a crimson ring,
which on the addition of a solution of bleaching powder turns emerald-
green. And nitro-glycerine in ether solution, by placing a few drops of
the suspected solution, together with a drop or two of aniline, upon a
watch-glass, evaporating off the ether, and then adding a drop of
concentrated sulphuric acid to the residue, when, if nitro-glycerine is
present, the H_{2}SO_{4} will strike a crimson colour, due to the action
of the aniline sulphate upon the nitric acid liberated from the nitro-
glycerine.
[Footnote A: "Notes on the Analysis of Explosives," _Jour. Amer. Chem.
Soc._, 1901, 23 [8], 585-589.]
~Tonite.~--The analysis of this explosive is a comparatively easy matter,
and can be performed as follows:--Weigh out 10 grms., or a smaller
quantity, and boil with water in a beaker, decanting the liquid four or
five times, and filter. The aqueous solution will contain the nitrate of
barium. Then put the residue on the filter, and wash two or three times
with boiling water. Evaporate the filtrate to dryness in a platinum dish.
Dry and weigh. This equals the Ba(NO_{3})_{2}. If the sample is tonite No.
3, and contains di-nitro-benzol, treat first with ether to dissolve out
this substance. Filter into a dish, and evaporate off the ether, and weigh
the di-nitro-benzol, and afterwards treat residue with water as before.
The residue is dried and weighed, and equals the gun-cotton present. It
should then be treated with a solution of ether-alcohol in a conical
flask, allowed to stand some three hours, then filtered through a weighed
filter paper, dried at 40 deg. C., and weighed. This will give the gun-cotton,
and the difference between this last weight and the previous one will give
the collodion-cotton. A portion of the residue containing both the gun-
cotton and the soluble cotton can be tested in the nitrometer, and the
nitrogen determined.
~Cordite.~--This explosive consists of gun-cotton (with a little
collodion-cotton in it as impurity), nitro-glycerine, and vaseline--the
proportions being given as 30 per cent. nitro-glycerine, 65 per cent. gun-
cotton, and 5 per cent. vaseline. Its analysis is performed by a
modification of the method given for gelatines. Five grms. may be
dissolved in ether-alcohol in a conical flask, allowed to stand all night,
and then filtered through a linen filter. The residue is washed with a
little ether, pressed, and dried at 40 deg. C., and weighed. It equals the
gun-cotton. The solution contains the nitro-glycerine, soluble cotton, and
vaseline. The cotton is precipitated with chloroform, filtered off, dried,
and weighed. The two ether-alcohol solutions are mixed, and carefully
evaporated down in a platinum dish upon the water bath at a low
temperature. The residue is afterwards treated with strong 80 per cent.
acetic acid, which dissolves out any nitro-glycerine left in it. The
nitro-glycerine is then obtained by difference, or the method suggested to
me privately by Mr W.J. Williams may be used. The residue obtained by
evaporation of the ether-alcohol solution, after weighing, is treated with
alcoholic potash to decompose the nitro-glycerine, water is added and the
alcohol evaporated off. Some ether is then added, and the mixture shaken,
and the ether separated and evaporated, and the residue weighed as
vaseline.
The moisture should, however, be determined by the method devised by Mr
Arthur Marshall, F.I.C., of the Royal Gunpowder Works, Waltham Abbey,
which is carried out as follows:--The cordite or other explosive is
prepared in the manner laid down for the Abel heat test, that is t say, it
is ground in a small mill, and that portion is selected which passes
through a sieve having holes of the size of No. 8 wire gauge, but not
through one with holes No. 14 wire gauge.
[Illustration: FIG. 40.--MARSHALL'S APPARATUS FOR MOISTURE IN CORDITE.]
The form of apparatus used is shown in Fig. 40. It consists of an
aluminium dish A, having the dimensions shown, and the glass cone B
weighing not more than 30 grms. Five grms. of the cordite are weighed into
the aluminium dish A. This is covered with the cone B, and the whole is
accurately weighed, and is then placed upon a metal plate heated by steam
from a water bath. It is left upon the bath until all the moisture has
been driven off, then it is allowed to cool for about half-an-hour in a
desiccator and is weighed. The loss in weight gives accurately the
moisture of the sample. For cordite of the original composition, one
hour's heating is sufficient to entirely drive off the moisture; for
modified cordite containing 65 per cent. of gun-cotton, two hours is
enough, provided that there be not more than 1.3 per cent. of moisture
present.
If the proportion of nitro-glycerine be higher, a longer heating is
necessary. The aluminium dish must not be shallower than shown in the
figure, for if the distance between the substance and the edge of the
glass cone be less than half an inch, some nitro-glycerine will be lost.
Again, the sample must not be ground finer than stated, else some of the
moisture will be lost in the grinding and sieving operations, and the
result will be too low. In order to be able to drive off all the moisture
in the times mentioned, it is essential that the glass cone shall not fit
too closely on the aluminium dish, consequently the horizontal ledge round
the top of the dish should be bent, so as to render it slightly untrue,
and leave a clearance of about 0.02 inch in some places. If these few
simple precautions be taken, the method will be found to be very accurate.
Duplicate determinations do not differ more than 0.01 per cent.[A]
[Footnote A: "Determination of Moisture in Nitro-glycerine Explosives," by
A. Marshall, _Jour. Soc. Chem. Ind._, Feb. 29, 1904, p. 154.]
~The Vaseline~ (C_{16}H_{34}), or petroleum jelly, used has a flash-point
of 400 deg. F. It must not contain more than 0.2 per cent. volatile matter
when heated for 12 hours on the water bath, and should have a specific
gravity of 0.87 at 100 deg. F., and a melting point of 86 deg. F. It is obtained
during the distillation of petroleum, and consists mainly of the portions
distilling above 200 deg. C. It boils at about 278 deg. C.
~Acetone~ (CH_{3}CO.CH_{3}), or dimethyl ketone, is formed when iso-propyl
alcohol is oxidised with potassium bichromate and sulphuric. It is also
produced in considerable quantities during the dry distillation of wood,
and many other organic compounds. Crude wood spirit, which has been freed
from acetic acid, consists in the main of a mixture of acetone and methyl-
alcohol. The two substances may be roughly separated by the addition of
calcium chloride, which combines with the methyl-alcohol. On subsequent
distillation crude acetone passes over, and may be purified by conversion
into the bisulphite compound.
Acetone is usually prepared, however, by the dry distillation of crude
calcium or barium acetate.
(CH_{3}.COO)_{2}Ca = CH_{3}.CO.CH_{3} + CaCO_{3}.
The distillate is fractionated, and the portion, boiling between 50 deg. and
60 deg. C., mixed with strong solution of sodium bisulphite. The crystalline
cake of acetone sodium bisulphite, which separates on standing, is well
pressed, to free it from impurities, decomposed by distillation with
dilute sodium carbonate, and the aqueous distillate of pure acetone
dehydrated over calcium chloride. Acetone is a colourless, mobile liquid
of sp. gr. .792 at 20 deg. C., it boils at 56.5 deg. C., has a peculiar, pleasant,
ethereal odour, and is mixible with water, alcohol, and ether in all
proportions.
The acetone used in the manufacture of cordite should conform to the
following specification:--
SPECIFICATION FOR ACETONE.
1. The acetone to be not more than 0.802 specific gravity at 60 deg. F. When
mixed with distilled water it must show no turbidity, and must leave no
residue on evaporation at 212 deg. F. On distillation, four-fifths by volume
of the quantity taken must distil over at a temperature not exceeding 138 deg.
F. The residual matter left after this distillation must not contain,
besides acetone, any ingredient that is not a bye-product incidental to
the manufacture of acetone.
2. One c.c. of 0.10 per cent. solution in distilled water of pure
permanganate of potash, added to 100 c.c. of the acetone, must retain its
distinctive colour for not less than 30 minutes. This test should be made
at a temperature of 60 deg. F.
3. The acetone tested by the following method must not show more than
0.005 per cent. of acid, calculated to acetic acid:--
To 50 c.c. of the sample diluted with 50 c.c. of distilled water, with 2
c.c. of phenol-phthalein solution (1 gramme to 1,000 c.c. of 50 per cent.
alcohol) added as an indicator, add from a burette N/100 sodium hydrate
solution (1 c.c. 0.0006 gramme acetic acid), and calculate to acetic acid
in the usual manner.
The water used for the dilution of the acetone must be carefully tested
for acidity, and the pipettes used for measuring should not be blown out,
as it would be possible thus to neutralise nearly 2 c.c. of the soda
solution.
The presence of water in a sample of acetone may be detected by Schweitzer
and Lungwitz's method (_Chem. Zeit._, 1895, xix., p. 1384), which consists
in shaking together equal volumes of acetone and petroleum ether (boiling
point, 40 deg. to 60 deg. C.), when if present a separation of the liquid in
layers will take place.
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