Nitro Explosives: A Practical Treatise by P. Gerald Sanford

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[Illustration: FIG. 41.--ORDINARY FORM OF LUNGE NITROMETER.]

The solution being all in the measuring tube, the pressure tube is again
slightly raised, and the tube containing the nitro-cotton solution shaken
for ten minutes with considerable violence. It is then replaced in the
clamp, and the pressure relieved by lowering the pressure tube, and the
whole apparatus allowed to stand for twenty minutes, in order to allow the
gas evolved to assume the temperature of the room. A thermometer should be
hung up close to the bulb of the measuring tube. At the end of the twenty
minutes, the levels of the mercury in the pressure and measuring tubes are
equalised, and the final adjustment obtained by slightly opening the tap
on the measuring tube (very slightly), after first adding a little
sulphuric acid to the cup, and observing whether the acid runs in or moves
up. This must be done with very great care. When accurately adjusted, it
should move neither way. Now read off the volume of the NO gas in cubic
centimetres from the measuring tube. Read also the thermometer suspended
near the bulb, and take the height of the barometer in millimetres. The
calculation is very simple.

EXAMPLE--COLLODION-COTTON.

0.6[A] grm. taken. Reading on measuring tube = 114.6 c.c. NO. Barometer--
758 mm. Temperature--15 deg. C.

[Footnote A: 0.5 grm. is enough in the case of gun-cotton.]

Since 1 c.c. NO = 0.6272 milligramme N, and correcting for temperature and
pressure by the formula

760 x (1 + _d_^{2}) (_d_ = .003665), for temperature 15 deg. = 801.78,[A]

then

(114.6 x 100 x 750 x .6272)/(801.7 x. 6) = 11.22 per cent. nitrogen.

[Footnote A: See Table, page 244.]

The nitrogen in nitro-glycerine may of course be determined by the
nitrometer, but in this case it is better to take a much smaller quantity
of the substance. From 0.1 to 0.2 grm. is quite sufficient. This will give
from 30 to 60 c.c. of gas, and therefore a measuring tube without a 100
c.c. bulb must be used.

EXAMPLE.

0.1048 grm. nitroglycerine taken gave 32.5 c.c. NO. Barometer, 761 mm.
Temperature, 15 deg. C.

Therefore,

(3.25 x 100 x 761 x .6272)/(801.78 x.1048) = 18.46 per cent. N. Theory =
18.50 per cent.

Professor Lunge has devised another form of nitrometer (Fig. 42), very
useful in the nitrogen determination in explosives. It consists of a
measuring tube, which is widened out in the middle to a bulb, and is
graduated above and below into 1/10 c.c. The capacity of the whole
apparatus is 130 c.c.; that of each portion of the tube being 30 c.c., and
of the bulb 70 c.c. The upper portion of the graduated tube serves to
measure small volumes of gas, whilst larger volumes are read off on the
lower part.

[Illustration: FIG. 42. FIG. 43. SOME NEW FORMS OF NITROMETER.]

F.M. Horn (_Zeitschrift fuer angewandte Chemie_, 1892, p. 358) has devised
a form of nitrometer (Fig. 43) which he has found especially useful in the
examination of smokeless powders. The tap H is provided with a wide bore
through which a weighed quantity of the powder is dropped bodily into the
bulb K. From 4 to 5 c.c. of sulphuric acid which has been heated to 30 deg. C.
are then added through the funnel T, the tap H being immediately closed.
When the powder has dissolved--a process which may be hastened by warming
the bulb very carefully--the thick solution is drawn into the nitrometer
tube N, and the bulb rinsed several times with fresh acid, after which
operation the analysis is proceeded with in the usual way.

Dr Lunge's method of using a separate nitrometer in which to measure the
NO gas evolved to the one in which the reaction has taken place, the gas
being transferred from the one to the other by joining them by means of
indiarubber tubing, and then driving the gas over by raising the pressure
tube of the one containing the gas, the taps being open, I have found to
be a great improvement.

1 c.c. NO gas at 0 deg. and 760 mm.
Equals 0.6272 milligrammes (N) nitrogen.
" 1.343 " nitric oxide.
" 2.820 " (HNO_{3}) nitric acid.
" 3.805 " (NaNO_{3}) sodium nitrate.
" 4.523 " (KNO_{3}) potassium nitrate.

~Champion and Pellet's Method.~--This method is now very little used. It
is based upon the fact that when nitro-cellulose is boiled with ferrous
chloride and hydrochloric acid, all the nitrogen is disengaged as nitric
oxide (NO). It is performed as follows:--A vacuum is made in a flask,
fitted with a funnel tube, with a glass stopper on the tube; a delivery
tube that can also be closed, and which dips under a solution of caustic
soda contained in a trough, and the end placed under a graduated tube,
also full of caustic soda. From 0.12 to 0.16 grm. cotton dissolved in 5 to
6 c.c. of sulphuric acid is allowed to flow into the flask, which contains
the ferrous chloride and hydrochloric acid, and in which a vacuum has been
formed by boiling, and then closing the taps. The solution is then heated,
the taps on the delivery tube opened, and the end placed under the
collecting tube, and the NO evolved collected. The NO gas is not evolved
until the solution has become somewhat concentrated. Eder substituted a
solution of ferrous sulphate in HCl for ferrous chloride. Care must be
taken that the flask used is strong enough to stand the pressure, or it
will burst.

The same chemists (_Compt. Rendus_, lxxxiii. 707) also devised the
following method for determining the NO_{2} in nitro-glycerine:--A known
quantity of a solution of ferrous sulphate of previously ascertained
reducing power is placed in a flask, acidified with hydrochloric acid, and
its surface covered with a layer of petroleum oil. About .5 grm. of the
nitro-glycerine is then introduced, and the flask heated on the water
bath. When the sample is completely decomposed, the liquid is heated to
boiling to remove nitric oxide, and the excess of ferrous sulphate
ascertained by titration with standard permanganate; 56 of iron (Fe)
oxidised by the sample correspond to 23 of NO_{2} in the sample of
nitro-glycerine.

~The Schultze-Tieman Method~ for determining nitrogen in nitro-explosives,
especially nitro-cellulose and nitro-glycerine.--The figure (No. 44) shows
the general arrangement of the apparatus. I am indebted for the following
description of the method of working it to my friend, Mr William Bate, of
Hayle. To fill the apparatus with the soda solution, the gas burette is
put on the indiarubber stopper of basin W, and firmly clamped down. Then
the taps A and C are opened, and B closed. When the burette is filled with
soda solution half-way up the funnel Y, A and C are closed, and B opened.
The arrows show the inlet and outlet for the cooling water that is kept
running through the water jacket round the nitrometer tube. To collect the
gas, raise the nitrometer off the rubber stopper, and place the gas tube
from the decomposition apparatus in the glass dish W and under the opening
of the nitrometer.

[Illustration: Fig. 44. SCHULTZE-TIEMAN APPARATUS.]

For the estimation of nitrogen in nitro-cellulose take .5 to .65 grm., and
place in the decomposition flask _f_ (Fig. 45), washing in with about 25
c.c. of water by alternately opening clips D and E. The air in the flask
is driven out by boiling, whilst the air is shut off by the tube _i_
dipping into the basin W, which is filled with the soda lye, and tube K is
placed in the test tube R, which contains a few c.c. of water. As soon as
all the air is completely driven out, clips D and E are closed, and the
gas jet is taken away. (This flask must be a strong one, or it will
burst.) Into test tube R, 25 c.c. of concentrated solution of
protochloride of iron and 10 to 15 c.c. concentrated hydrochloric acid are
poured, which are sucked up into the developing flask _f_ by opening clip
E, air being carefully kept from entering. The clip E is now closed, and
tube _i_ is put underneath the burette, and the development of NO gas is
commenced by heating the contents of the flask _f_. When the pressure of
the gas in the flask has become greater than the pressure of the
atmosphere, the connecting tube begins to swell at _i_, whereupon clip D
is opened, and the boiling continued with frequent shaking of the bulb,
until no more nitrous gas bubbles rise up into the soda lye, the
distilling over of the HCl causes a crackling noise, the clip D is closed,
and E opened. The burette is again put hermetically on the indiarubber
stopper in basin W, and the apparatus is left to cool until the water
discharged through P shows the same temperature as the water flowing
through (into the cooling jacket) Z. If the level of the soda solution in
the tube X is now put on exactly the same level as that in the burette by
lowering or elevating the tube X as required, the volume of NO obtained in
c.c. can be read off within 1/10 c.c., and the percentage of nitrogen
calculated by the usual formula.

[Illustration: FIG. 45.--Decomposition Flask for Schultze-Tieman Method.]

The solution of protochloride of iron is obtained by dissolving iron
nails, &c., in concentrated HCl, the iron being in excess. When the
development of hydrogen ceases, it is necessary to filter warm through a
paper filter, and acidify filtrate with a few drops of HCl. The soda
solution used has a sp. gr. of 1.210 to 1.260; equals 25 deg. to 30 deg. B. The
nitro-cellulose is dried in quantities of 2 grms. at 70 deg. C. during eight
to ten hours, and then three hours in an exiccator over H_{2}SO_{4}. The
results obtained with this apparatus are very accurate. The reaction is
founded upon that of MM. Champion and Pellet's method.

~The Kjeldahl Method of Determining Nitrogen.~--This method, which has
been so largely used by analysts for the determination of nitrogen in
organic bodies, more especially perhaps in manures, was proposed by J.
Kjeldahl,[A] of the Carlsberg Laboratory of Copenhagen. It was afterwards
modified by Jodlbauer, of Munich,[B] and applied to the analysis of nitro-
explosives by M. Chenel, of the Laboratoire Centrale des Poudres, whose
method of procedure is as follows:--0.5 grm. of the finely powdered
substance is digested in the cold with a solution of 1.2 grm. of phenol
and 0.4 grm. phosphoric anhydride in 30 c.c. of sulphuric acid. The
mixture is kept well shaken until the solution is complete. From 3 to 4
grms. of zinc-dust is then cautiously and gradually added, the temperature
of the mass being kept down until complete reduction has been effected.
Finally, 0.7 grm. of mercury is added, and the process continued in the
usual way, according to Kjeldahl; that is, the liquid is distilled until
all the ammonia has passed over, and is absorbed in the standard acid. The
distillate is then titrated with standard ammonia.

[Footnote A: J. Kjeldahl, _Zeitschrift Anal. Chem._, 1883, xxii., p. 366.]

[Footnote B: Jodlbauer, _Chemisches Centralblatt_, 1886, pp. 434-484. See
also _Arms and Explosives_, 1893, p. 87.]

The NO_{2} group is at the moment of solution fixed upon the phenol with
the production of mono-nitro-phenol, which is afterwards reduced by the
action of the zinc-dust into the amido derivative. During the subsequent
combustion, the nitrogen of the amido-phenol becomes fixed in the state of
ammonia. M. Chenel is perfectly satisfied with the results obtained, but
he points out that the success of the operation depends upon the complete
conversion of the phenol into the mono-nitro derivatives. This takes place
whenever the organic compound forms a _clear solution_ in the cold
sulphuric acid mixture. Substances like collodion or gun-cotton must be
very finely divided for successful treatment. The following table shows
some of the results obtained by M. Chenel:--

______________________________________________
| | |
| | Total Nitrogen. |
| Substances Analysed. |______________________|
| | | |
| | Calculated. | Found. |
| |_____________|________|
| | | |
| Saltpetre (KNO_{3}) | 13.86 | 13.91 |
| | | 13.82 |
| | | 13.73 |
| | | 13.96 |
| Ammonium nitrate | 35.00 | 35.31 |
| | | 34.90 |
| | | 34.96 |
| Barium nitrate | 10.72 | 10.67 |
| | | 10.62 |
| Nitro-glycerol | 18.50 | 18.45 |
| Di-nitro-benzol[A] | 16.67 | 16.78 |
| | | 16.57 |
| Para-nitro-phenol | 10.07 | 10.03 |
| Picric acid[A] | 18.34 | 18.42 |
| | | 18.43 |
| Ammonium picrate | 22.76 | 22.63 |
| | | 22.67 |
| Di-nitro-ortho-cresol | 14.14 | 14.10 |
| | | 13.98 |
| Tri-nitro-meta-cresol | 17.28 | 17.57 |
| | | 17.27 |
|_______________________|_____________|________|

[Footnote A: Dr. Bernard Dyer obtained 18.39 per cent. for picric acid and
16.54 per cent. for di-nitro-benzol.--_Jour. Chem. Soc._, Aug. 1895.]

When Chenel endeavoured to apply Jodlbauer's modification of Kjeldahl's
process to the examination of the tri- and tetra-nitrated naphthalenes, he
found that good results were not obtainable, because these compounds do
not dissolve completely in the cold sulphuric acid. It may, however, be
used if they are previously converted into the naphthylamines, according
to the plan proposed by D'Aguiar and Lautemann (_Bull. Soc. Chim._, vol.
iii., new series, p. 256). This is rapidly effected as follows:--Twelve
grms. of iodine are gradually added to a solution of 2 grms. of phosphorus
in about 15 or 20 c.c. of bisulphide of carbon, this solution being
contained in a flask of 250 c.c. capacity. The flask and its contents are
heated on the water bath at 100 deg. C. with constant attention, until the
last traces of the carbon bisulphide have distilled away. It is then
cooled, and the iodide of phosphorus is detached from the sides of the
flask by shaking, but not expelled. The next step is to add about 0.5 to
0.6 grm. of the substance that is to be analysed, after which 8 grms. of
water are introduced, and the flask is agitated gently two or three times.
As soon as the reaction becomes lively, the contents of the flask are well
shaken. It is usually finished about one minute after the addition of the
water. The flask is now cooled, and 25 c.c. of sulphuric acid, together
with 0.7 grm. of mercury, are gradually added; hydriodic acid (HI) forms,
and the temperature of the flask must be raised sufficiently to expel it.
The remaining part of the operation is as in the ordinary Kjeldahl
process.

M. Chenel has found this process the best for the analysis of the nitro-
naphthalenes, and for impervious substances like collodion or gun-cotton.
Personally, I have never been able to obtain satisfactory results with
this process in the analysis of nitro-cellulose, and I am of opinion that
the process does not possess any advantage over the nitrometer method, at
any rate for the analysis of gun-cotton.

Table giving the Percentages of Nitrogen and Oxide of Nitrogen in Various
Substances used in or as Explosives:

Name FORMULAE NITROGEN NO_{2}
per cent. per cent.

Nitroglycerine C_{3}H_{5}(ONO_{2})_{3} 18.50 = 60.70
Hexa-nitro-cellulose C_{12}H_{14}O_{4}(ONO_{2})_{6} 14.14 = 46.42
Penta-nitro-cellulose C_{6}H_{8}O_{5}(ONO_{2})_{5} 11.11 = 36.50
Nitro-benzene C_{6}H_{5}NO_{2} 11.38 = 37.39
Di-nitro-benzene C_{6}H_{4}(NO_{2})_{2} 16.67 = 54.77
Tri-nitro-benzene C_{6}H_{3}(NO_{2})_{3} 19.24 = 63.22
Nitro-toluene C_{7}H_{7}NO_{2} 10.21 = 33.49
Nitro-naphthalene C_{10}H_{7}NO_{2} 8.09 = 26.53
Di-nitro-naphthalene C_{10}H_{6}(NO_{2})_{2} 12.84 = 42.12
Nitro-mannite C_{6}H_{7}(NO_{3})_{6} 23.59 = 77.37
Nitro-starch C_{6}H_{8}O_{4}(HNO_{3}) 6.76 = 22.18
Picric acid
(Tri-nitro-phenol) C_{6}H_{2}OH(NO_{2})_{3} 18.34 = 60.15
Chloro-nitro-benzene C_{6}H_{3}Cl(NO_{2})_{2} 13.82 = 45.43
Ammonium nitrate NH_{4}NO_{3} 35.00 =
Sodium nitrate NaNO_{3} 16.47 =
Potassium nitrate KNO_{3} 13.86 =
Nitric acid HNO_{3} 22.22 =
Barium nitrate Ba(NO_{3})_{2} 10.72 =

~Analysis of Celluloid.~--The finely divided celluloid is well stirred, by
means of a platinum wire, with concentrated sulphuric acid in the cup of a
Lunge nitrometer, and when dissolved the nitrogen determined in the
solution in the usual way. To prevent interference from camphor, the
following treatment is suggested by H. Zaunschirm (_Chem. Zeit._, xiv.,
905). Dissolve a weighed quantity of the celluloid in a mixture of ether-
alcohol, mixed with a weighed quantity of washed and ignited asbestos, or
pumice-stone, dry, and disintegrate the mass, and afterwards extract the
camphor with chloroform, dry, and weigh: then extract with absolute
methyl-alcohol, evaporate, weigh, and examine the nitro-cellulose in the
nitrometer.

~Picric Acid and Picrates.~--Picric acid is soluble in hot water, and to
the extent of 1 part in 100 in cold water, also in ether, chloroform,
glycerine, 10 per cent. soda solution, alcohol, amylic alcohol, carbon
bisulphide, benzene, and petroleum. If a solution of picric acid be boiled
with a strong solution of potassium cyanide, a deep red liquid is
produced, owing to the formation of potassium iso-purpurate, which
crystallises in small reddish-brown plates with a beetle-green lustre.
This, by reaction with ammonium chloride, gives ammonium iso-purpurate
(NH_{4}C_{8}H_{4}N_{5}O_{6}), or artificial murexide, which dies silk and
wool a beautiful red colour. On adding barium chloride to either of the
above salts, a vermilion-red precipitate was formed, consisting of barium
iso-purpurate. With ammonio-sulphate of copper, solutions of picric acid
give a bright green precipitate. Mr A.H. Allen gives the following methods
for the assay of commercial picric acid, in his "Commercial Organic
Analysis":--

~Resinous and Tarry matters~ are not unfrequently present. They are left
insoluble on dissolving the sample in boiling water. The separation is
more perfect if the hot solution be exactly neutralised by caustic soda.

~Sulphuric Acid, Hydrochloric Acid, and Oxalic Acid~, and their salts are
detected by adding to the filtered aqueous solution of the sample
solutions of the picrates of barium, silver, and calcium. These salts are
readily made by boiling picric acid with the carbonates of the respective
metals and filtering: other soluble salts of these methods may be
substituted for the picrates, but they are less satisfactory.

~Nitric Acid~ may be detected by the red fumes evolved on warming the
sample with copper turnings.

~Inorganic Impurities and Picrates of Potash and Sodium~, &c., leave
residues on cautious ignition.

~General Impurities and Adulterations~ may be detected and determined by
shaking 1 grm. of the sample of acid in a graduated tube with 25 c.c. of
ether, the pure acid dissolves, while any oxalic acid, nitrates, picrates,
boric acid, alum, sugar, &c., will be left insoluble, and after removal of
the ethereal liquid, may be readily identified and determined. For the
detection and determination of water and of oxalic acid, 50 c.c. of warm
benzene may be advantageously substituted for ether. Sugar may be
separated from the other impurities by treating the residue insoluble in
ether or benzene with rectified spirit, in which sugar and boric acid
alone will dissolve. If boric acid be present, the alcoholic solution will
burn with a green flame. Mono- and di-nitrophenic acids lower the melting
point (122 deg. C). Their calcium salts are less soluble than the picrate, and
may be approximately separated from it by fractional crystallisation, or
by precipitating the hot saturated solution of the sample with excess of
lime water. Picric acid may be determined by extracting the acidulated
aqueous solution by agitation with ether or benzene, and subsequently
removing and evaporating off the solvent. It may also be precipitated as
the potassium salt.

~Potassium Picrate~ [KC_{6}H_{2}(NO_{2})_{3}O]. When a strong solution of
picric acid is neutralised by carbonate of potash, this salt is thrown
down in yellow crystalline needles, which require 260 parts of cold or 14
parts of hot water for their solution. In alcohol it is much less soluble.

~Ammonium Picrate~ is more soluble in water than the above, and sodium
picrate is readily soluble in water, but nearly insoluble in solution of
sodium carbonate.

~Picrates of the Alkaloids.~--Picric acid forms insoluble salts with many
of the alkaloids, and picric acid may be determined in the following
manner:--To the solution of picric acid, or a picrate, add a solution of
sulphate of cinchonine acidulated with H_{2}SO_{4}. The precipitated
picrate of cinchonine [C_{20}H_{24}N_{2}O(C_{6}H_{2}N_{3}O_{7})_{2}] is
washed with cold water, rinsed off the filter into a porcelain crucible or
dish, the water evaporated on the water bath, and the residual salt
weighed. Its weight, multiplied by .6123, gives the quantity of picric
acid in the sample taken.

~Analysis of Glycerine.~[A] Glycerine that is to be used for the
manufacture of nitro-glycerine should have a minimum specific gravity of
1.261 at 15 deg. C. This can be determined, either by the aid of a Sartorius
specific gravity balance, or by using an ordinary specific gravity bottle.
One of 10 or 25 c.c. capacity is very convenient.

[Footnote A: See also Sulman and Berry, _Analyst_, xi., 12-34, and Allen's
"Commercial Organic Analysis," vol. ii., part i.]

~Residue~[A] left upon evaporation should not be more than 0.25 per cent.
To determine this, take 25 grms. of the glycerine, and evaporate it at a
temperature of about 160 deg. C. in a platinum basin, and finish in an air
bath. Weigh until constant weight is obtained. Afterwards incinerate over
a bunsen burner, and weigh the ash.

[Footnote A: Organic matter up to .6 per cent. is not always prejudicial
to the nitrating quantities of a glycerine.]

~Silver Test.~ A portion of the sample of glycerine to be tested should be
put in a small weighing bottle, and a quarter of its bulk of N/10 silver
nitrate solution added to it, then shake it, and place in a dark cupboard
for fifteen minutes. It must be pronounced bad if it becomes black or dark
brown within that time (acrolein, formic, and butyric acids).

The German official test for glycerine for pharmaceutical purposes is much
more stringent, 1 c.c. of glycerine heated to boiling with 1 c.c. of
ammonia solution and three drops of silver nitrate solution must give
neither colour or precipitate within five minutes.

~Nitration.~ Fifty grms. of the glycerine are poured from a beaker into a
mixture of concentrated nitric acid (specific gravity 1.53) and sulphuric
acid (1.84), mixed in the proportions of 3 HNO_{3} to 5 H_{2}SO_{4} (about
400 c.c. of mixed acids). The mixed acids should be put into a rather
large beaker, and held in the right hand in a basin of water, and the
glycerine slowly poured into them from a smaller one held in the left. A
constant rotatory motion should be given to the beaker in which the
nitration is performed. When all the glycerine has been added, and the
mixture has been shaken for a few minutes longer, it is poured into a
separator, and allowed to stand for some time. It should, if the glycerine
is a good one, have separated from the mixed acids in ten minutes, and the
line of demarcation between the nitro-glycerine and the acid should be
clear and sharp, neither should there be any white flocculent matter
suspended in the liquid. The excess of acids is now drawn off, and the
nitro-glycerine shaken once or twice with a warm solution of carbonate of
soda, and afterwards with water alone. The nitro-glycerine is then drawn
off into a weighed beaker, the surface dried with a piece of filter paper,
and weighed; 100 parts of a good glycerine should yield about 230 of
nitro-glycerine. A quicker method is to take only 10 c.c. of the
glycerine, of which the specific gravity is already known, nitrate as
before, and pour into a burette, read off the volume of nitro-glycerine in
c.c. and multiply them by 1.6 (the specific gravity of nitro-glycerine),
thus: 10 grms. gave 14.5 c.c. nitro-glycerine, and 14.5 x 1.6 = 23.2
grms., therefore 100 would give 232 grms. nitro-glycerine. The points to
be noted in the nitration of a sample of glycerine are: the separation
should be sharp, and within half an hour or less, and there should be no
white flocculent matter formed, especially when the carbonate of soda
solution is added.

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