Nitro Explosives: A Practical Treatise by P. Gerald Sanford

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~Estimation of Acetone.~--Kebler (_Jour. Amer. Chem. Soc._, 1897, 19, 316-
320) has improved Squibb's modification of Robineau and Rollins' method.
The following solutions are required:--

(1.) A 6 per cent. solution of hydrochloric acid.

(2.) A decinormal solution of sodium thiosulphate.

(3.) Alkaline potassium iodide solution prepared by dissolving 250 grms.
of potassium iodide in water, made up to a litre; dissolving 257 grms. of
sodium hydroxide (by alcohol) in water, likewise made up to a litre. After
allowing the latter to stand, 800 c.c. of the clear solution are added to
the litre of KI.

(4.) Sodium hypochlorite solution: 100 grms. of bleaching powder (35 per
cent.) are mixed with 400 c.c. of water: to this is added a hot solution
of 120 grms. of crystallised sodium carbonate in 400 c.c. of water. After
cooling, the clear liquid is decanted, the remainder filtered, and the
filtrate made up to a litre; to each litre is added 25 c.c. of sodium
hydroxide solution (sp. gr. 1.29).

(5.) An aqueous solution of the acetone, containing 1 or 2 per cent. of
acetone.

(6.) Bicarbonated starch solution prepared by treating 0.125 grm. of
starch with 5 c.c. of cold water, then adding 20 c.c. of boiling water,
boiling a few minutes, cooling, and adding 2 grms. of sodium bicarbonate.

To 20 c.c. of the potassium iodide solution are added 10 c.c. of the
diluted aqueous acetone, an excess of the sodium hypochlorite solution is
then run in from a burette and well shaken for a minute. The mixture is
then acidified with the hydrochloric acid solution, and while agitated, an
excess of sodium thiosulphate solution is added, the mixture being
afterwards allowed to stand a few minutes. The starch indicator is then
added, and the excess of thiosulphate re-titrated. The relation of the
sodium hypochlorite solution to the sodium thiosulphate being known, the
percentage of acetone can be readily calculated.[A]

[Footnote A: See "The Testing of Acetone," Conroy, _Jour. Soc. Chem.
Ind._, 31st March 1900, vol. xix.]

Dr S.J.M. Auld has recently (_Jour. Chem. Soc._, Feb. 15, 1906, vol. xxv.)
worked out a volumetric method for the estimation of acetone, depending on
the formation of bromoform, and its subsequent hydrolysis with alcoholic
potash. The hydrolysis is probably expressed thus--

3CHBr_{3} + 9KOH + C_{2}H_{5}OH = 3CO + C_{2}H_{4} + 9KBr + 7H_{2}O

as it has been shown by Hermann and Long that exactly 3 volumes of carbon
monoxide to 1 of ethylene are evolved. The residual potassium bromide is
estimated by means of standard silver nitrate solution. Bromoform is
specially suitable for this purpose for several reasons. It is very
readily formed by the action of bromine and potash on acetone, and
although very volatile in steam, it is not liable to loss due to its own
evaporation. Further, its high molecular weight and large percentage of
bromine conduce to accurate results, 58 grms. of acetone being responsible
for the formation of 357 grms. of KBr. The method of carrying out the
analysis is as follows:--

A known quantity of the solution to be tested, containing acetone to the
extent of 0.1 to 0.2 grm., is pipetted into a 500 c.c. round-bottom flask,
diluted with a little water, and mixed with 20 to 30 c.c. of a 10 per
cent. solution of caustic potash. The flask is connected with a long
reflex condenser, and is also fitted with a dropping funnel containing a
solution of bromine in potassium bromide (200 grms. of Br and 250 grms. of
KBr to 1 litre of water). The bromine solution is allowed to flow into the
mixture until it has acquired a faint yellow tinge, the flask and its
contents being then heated on the water bath at about 70 deg. C. for half-an-
hour. Bromine solution is added drop by drop until the slight coloration
is permanent, excess of bromine being got rid of by boiling for a minute
or two with a little more caustic potash. The mixture is then distilled
until the distillate is free from bromoform, halogen being tested for in
the usual manner. Water is added to the contents of the flask if
necessary. It may be here observed that no acetone can be detected in the
distillate by means of the mercuric oxide test, and free bromine is also
absent. The condenser having been washed out with a little alcohol, in
order to remove any traces of bromoform which may have collected, the
distillate and washings are mixed with 50 c.c. of alcohol and sufficient
solid caustic potash to make an approximately 10 per cent. solution. The
mixture is then heated on the water bath under a reflux condenser until
the bromoform is completely decomposed. This generally occupies about
three-quarters of an hour. The liquid is allowed to cool, evaporated to
smaller bulk if necessary, and exactly neutralised with dilute nitric
acid. It is then diluted with water to 500 c.c., and an aliquot part
titrated with N/10 silver nitrate solution, using potassium chromate as
indicator; 240 parts of bromine correspond to 58 parts of acetone. The
complete analysis can be performed in one and a half to two hours. It is
imperative that the bromine used should be pure, as crude bromine
frequently contains bromoform. The method is suitable for the estimation
of acetone in wood-spirit, the spirit being diluted to 10 times its
volume, and 5 c.c. of this solution employed for the determination. For
example--

(1.) Three c.c. of a solution containing 9.61 per cent. acetone gave
1.7850 grm. KBr. Acetone found = 9.66 per cent.

(2.) Ten c.c. of a solution containing 0.96 per cent. acetone gave 0.5847
grm. KBr. Acetone found = 0.95 per cent.

~Nitro-Cotton.~--The first thing upon opening a case of wet cotton, or in
receiving a sample from the "poacher," that requires to be determined is
the percentage of water that it contains. It is best done by weighing out
about 1,000 grms. upon a paper tray, which has been previously dried in
the oven at 100 deg. C. for some time, and become constant in weight. The
trayful of cotton is then placed in a water oven, kept at 100 deg. C., and
dried as long as it loses water. The loss gives the percentage of water.
It varies from 20 to 30 per cent. as a rule in "wet" cotton.

OUTLINE SCHEME FOR THE ANALYSIS OF NITRO-EXPLOSIVES
_______________________________________________________________________
| |
| Exhaust dried substance with Anhydrous Ether in Soxhlet's Fat |
| Extraction Apparatus. |
|_______________________________________________________________________|
| |
| _Solution_--Divide into two parts ~A.~ and ~B.~ |
|_______________________________________________________________________|
| |
| ~A.~ |
| |
| Allow ether to evaporate spontaneously. Dry residue in vacuo over |
| H_{2}SO_{4} and weigh. Equals nitro-glycerine, resin, camphor, and |
| paraffin. |
| |
| The nitro-glycerine in this residue may be decomposed by heating |
| with a solution of alcoholic potash. Water may then be added, and the |
| alcohol evaporated off on the water bath. From this solution the |
| resin may be precipitated by HCl, filtered off, dried, and weighed. |
| Solution containing the paraffin is treated with AmS solution and |
| heated. On cooling the paraffin separates, and may be separated. |
| Residue may be shaken with CS_{2} to remove camphor. |
|_______________________________________________________________________|
| |
| ~B.~ |
| |
| Add phenol-phthalein and titrate with alcoholic potash, 1 c.c. normal |
| KHO = .330 grm. _resin_, and add considerably more KHO. Evaporate, |
| dissolve residue in water, shake with ether, and separate. |
|_______________________________________________________________________|
| |
| _Ethereal Solution_ evaporated leaves paraffin. |
|_______________________________________________________________________|
| |
| _Aqueous Solution_-- |
| Add bromide, acidify with HCl, separate any resin and precipitate, |
| filtrate with BaCl_{2} BaSO_{4} x .1373 = Sulphur. |
|_______________________________________________________________________|
| |
| _Residue_-- |
| Dry, weigh, and exhaust with water preferably in Soxhlet. |
|_______________________________________________________________________|
| | |
| _Solution_-- | _Residue_-- |
| Contains metallic | Dry, weigh, and agitate an aliquot part with |
| nitrates, chlorates, | with H_{2}SO_{4} and Hg in nitrometer. If |
| soluble carbonates, | nitro-cellulose is present, treat remainder of |
| the sum of which | residue with ether-alcohol. |
| (except AmCO_{3}) |________________________________________________|
| can be determined by | |
| evaporating down at | _Solution_-- |
| 100 deg. C. to dryness | Evaporate and weigh. Residue consists of |
| and weighing. | soluble nitro-cellulose. |
| Nitrates can be |________________________________________________|
| determined by | |
| | _Residue_-- |
| | Dry and weigh and determine hexa-nitro- |
| | cellulose in nitrometer, if present. Exhaust |
| | remainder with acetic ether. |
| |________________________________________________|
| | | |
| | _Solution_-- | _Residue_-- |
| | Hexa-nitro-cellulose | Dry and weigh, ignite |
| | (Gun cotton). | and reweigh. Loss = |
| | | _Cellulose_. |
| | |_________________________|
| | | |
| | | Residue consists of |
| | | sawdust, charcoal, |
| | | coal, chalk, guhr, |
| | | or mineral matter, &c. |
|______________________|______________________|_________________________|

NOTE.--Camphor is found by difference. Sulphur is only partially soluble
in ether. It is better, therefore, to extract some of the original
substance with water, and treat residue with alcoholic KHO. Add bromide,
acidify, and precipitate as BaSO.

~The Solubility Test.~--The object of this test is to ascertain, in the
case of gun-cotton, the percentage of soluble (penta and lower nitrates)
cotton that it contains, or in the case of soluble cotton, the quantity of
gun-cotton. The method of procedure is as follows:--Five grms. of the
sample which has been previously dried at 100 deg. C., and afterwards exposed
to the air for two hours, is transferred to a conical flask, and 250 c.c.
ether-alcohol added (2 ether to 1 alcohol). The flask is then corked and
allowed to digest, with repeated shaking, for two or three hours. The
whole is then transferred to a linen filter, and when the solution has
passed through the filter, is washed with a little ether, and pressed in a
hand-screw press between folds of filter paper. The sample is then
returned to the flask, and the previous treatment repeated, but it will be
sufficient for it to digest for one hour the second time. The filter is
then again pressed first gently by hand, then in the press, and afterwards
opened up and the ether allowed to evaporate. The gun-cotton is then
removed from the filter and transferred to a watch-glass, and dried in the
water oven at 100 deg. C. When dry it is exposed to the air for two hours and
weighed. It equals the amount of gun-cotton and unconverted cotton in the
5 grms. The unconverted cotton must be determined in a separate 5 grms.
and deducted.

The method of determining the soluble cotton now used in the Government
laboratories is as follows:--Fifty grains of the nitro-cotton are
dissolved in 150 c.c. of ether-alcohol, and allowed to stand, with
frequent shakings, in a 200 c.c. stoppered measure for six hours; 75 c.c.
of the clear solution are then drawn off by the aid of a pipette and
evaporated in a dish on the water bath, and finally in the water oven at
120 deg. F. (49 deg. C.), until constant in weight. The weight found equals the
quantity of soluble cotton in the 75 c.c., which, multiplied by 4, equals
the percentage, thus: Suppose that 2.30 grains was the weight found, then

(2.3 x 150)/75 = 4.6 in 50 = 9.20 per cent.

A method for the determination of soluble nitro-cellulose in gun-cotton
and smokeless powder has been published by K.B. Quinan (_Jour. Amer. Chem.
Soc._, 23 [4], 258). In this method about 1 grm. of the finely divided dry
sample to be analysed is placed in an aluminium cup 1.9 inch in diameter
and 4-1/8 inch deep. It is then covered and well stirred with 50 c.c. of
alcohol, 100 c.c. of ether are then added, and the mixture is stirred for
several minutes. After removing the stirrer, the cup is lightly covered
with an aluminium lid, and is then placed in the steel cup of a
centrifugal machine, which is gradually got up to a speed of 2,000
revolutions per minute, the total centrifugal force at the position
occupied by the cups (which become horizontal when in rapid rotation) is
about 450 lbs. They are rotated at the full speed for ten to twelve
minutes, and the machine is then gradually stopped. By this time the whole
of the insoluble matter will be at the bottom of the cup, and the
supernatant solution will be clear. It is drawn off to within a quarter of
an inch of the bottom (without disturbing the sediment), with the aid of a
pipette.

Care must be taken that the solution thus withdrawn is perfectly clear.
About 10 to 15 c.c. of colloid solution and a film of insoluble matter
remain at the bottom of the cup; these are stirred up well, the stirrer is
rinsed with ether-alcohol, about 50 c.c. of fresh ether-alcohol are added;
the mixture is again treated in the centrifugal apparatus for about eight
minutes; the whole washing process is then repeated until all soluble
matter has been removed. This may require about seven or eight (or for
samples with much insoluble matter ten or twelve or more) washings, but as
the extraction proceeds, the period of rotation may be somewhat reduced.
After extraction is completed, the insoluble matter is transferred to a
Gooch crucible with the usual asbestos pad, dried at 100 deg. C., and weighed.
The residue may, if wished, be dried and weighed in the aluminium cup, but
then it cannot be ignited. The whole time for an analysis exclusive of
that required for drying, is from one to two hours--average time, 1-1/4
hour. The results are satisfactory both as to accuracy and rapidity.
Acetone-soluble nitro-cellulose may be determined by the same method.

~The Unconverted or Non-nitrated Cotton.~--However well the cotton has
been nitrated, it is almost certain to contain a small quantity of non-
nitrated or unconverted cotton. This can be determined thus:--Five grms.
of the sample are boiled with a saturated solution of sodium sulphide, and
then allowed to stand for forty-eight hours, and afterwards filtered or
decanted, and again boiled with fresh solutions of sulphide, and again
filtered, washed first with dilute HCl and then with water, dried, and
weighed. The residue is the cellulose that was not nitrated, plus ash, &c.
It should be ignited, and the weight of the ash deducted from the previous
weight.

Acetone, and acetic-ether (ethyl-acetate) may also be used as solvents for
the nitro-cellulose. Another process is to boil the gun-cotton, &c., in a
solution of sodium stannate made by adding caustic soda to a solution of
stannous chloride, until the precipitate first formed is just
re-dissolved. This solution dissolves the cellulose nitrates, but does not
affect the cellulose. Dr Lunge found the following process more
satisfactory in the case of the more highly nitrated products:--The
reagent is an alcoholic solution of sodium-ethylate prepared by dissolving
2 to 3 grms. of sodium in 100 c.c. of 95 per cent. alcohol, and mixing the
filtered solution with 100 c.c. of acetone. It has no effect upon
cellulose, but decomposes nitro-cellulose with the formation of a reddish
brown compound, which is soluble in water. In the determination, 5 grms.
of gun-cotton are heated to 40 deg. or 50 deg. C. on the water bath with 150 c.c.
of the reagent, the liquid being shaken at intervals for twenty to thirty
minutes; or the mixture may be allowed to stand for a few hours at the
ordinary temperature. The brown-red solution is decanted from the
undissolved residue, and the latter washed with alcohol and with water, by
decantation, and then on the filter with hot water, to which a little
hydrochloric acid is added for the final washings. For ordinary work this
cellulose is dried immediately and weighed, but in exact determinations it
is washed with alcohol, again treated with 50 c.c. of the reagent, and
separated and washed as before. The cellulose thus obtained, gives no
trace of gas in the nitrometer, and duplicate determinations agree within
0.1 to 0.2 per cent. when the weight of unchanged cellulose amounts to
about 0.2 grm. Gun-cotton, which is completely soluble in acetone,
contains only traces of cellulose, and when as much as 0.85 per cent. is
present it does not dissolve entirely. This method is not applicable to
the determination of cellulose in lower nitrated products, and Dr Lunge
attributes this to the fact that these being prepared with less
concentrated acid invariably contain oxy-cellulose.

~Alkalinity.~--Five grms. of the air-dried and very finely divided sample
are taken from the centre of the slabs or discs, and digested with about
20 c.c. of N/2 hydrochloric acid, and diluted with water to about 250
c.c., and shaken for about fifteen minutes. The liquid is then decanted,
and washed with water until the washings no longer give an acid reaction.
The solution, together with the washings, are titrated with N/4 sodium
carbonate, using litmus as indicator.

~Ash and Inorganic Matter.~--This is best determined by mixing 2 or 3
grms. of the nitro-cotton in a platinum crucible with shavings of
paraffin, heating sufficiently to melt the paraffin, and then allowing the
contents of the crucible to catch fire and burn away quietly. The
temperature is then raised, and the carbonaceous residue incinerated,
cooled, weighed, &c., and the percentage of ash calculated. Schjerning
proceeds in the following way:--He takes 5 grms. of the nitro-cotton in a
large platinum crucible, he then moistens it with a mixture of alcohol and
ether, in which paraffin has been dissolved to saturation, and filtered
and mixed with one-fourth of its volume of water. Some fragments of solid
paraffin are then added, and the ether set on fire. Whilst this is in
progress the crucible is kept in an oblique position, and is rotated so
that the gun-cotton may absorb the paraffin uniformly. The partially
charred residue is now rubbed down with a rounded glass rod, and the
crucible is covered and heated for from fifteen to twenty minutes over the
blow-pipe, the lid being occasionally removed. The residue is soon
converted into ash, which is weighed, and then washed out into a porcelain
basin and treated with hydrochloric acid heated to 90 deg. C. The oxide of
iron, alumina, lime, and magnesia are thus dissolved, and the silica
remains as insoluble residue. The rest of the analysis is conducted
according to the well-known methods of separation. The percentage of ash
as a whole is generally all that is required.

~Examination of Nitrated Celluloses with Polarised Light.~--Dr G. Lunge
(_Jour. Amer. Chem. Soc._, 1901, 23 [8], 527) has formed the following
conclusions:--The most highly nitrated products appear blue in polarised
light, but those containing between 13.9 and 13.0 per cent. of nitrogen
cannot be distinguished from each other by polarisation. As the percentage
of nitrogen rises, the blue colour becomes less intense, and here and
there grey fibres can be observed, though not in proportion to the
increase in the nitrogen. Below 12.4 per cent. of nitrogen, the fibres
show a grey lustre, which usually appears yellow when the top light is cut
off. Below 10 per cent. of nitrogen, the structure is invariably partially
destroyed and no certain observations possible. It is only possible to
distinguish with certainty, firstly any unchanged cellulose by its
flashing up in variegated (rainbow) colours; and secondly, highly nitrated
products (from 12.75 per cent. N upwards), by their flashing up less
strongly in blue colours. The purple transition stage in the fibres
containing over 11.28 per cent. of N (Chardonnet) was not observed by Dr
Lunge.

~Determination of Nitrogen by Lunge Nitrometer.~--The determination of the
percentage of nitrogen in a sample of gun-cotton or collodion is perhaps
of more value, and affords a better idea of its purity and composition,
than any of the foregoing methods of examination, and taken in conjunction
with the solubility test, it will generally give the analyst a very fair
idea of the composition of his sample. If we regard gun-cotton as the
hexa-nitro-cellulose, the theoretical amount of nitrogen required for the
formula is 14.14 per cent., and in the same way for collodion-cotton,
which consists of the lower nitrates, chiefly, however, of the penta-
nitrate, the theoretical nitrogen is 12.75 per cent., so that if in a
sample of nitro-cotton the nitrogen falls much lower than 14 per cent., it
probably contains considerable quantities of the lower nitrates, and
perhaps some non-nitrated cellulose as well (C_{6}H_{10}O_{5})_{x}, which
of course would also lower the percentage of nitrogen.

The most expeditious method of determining the nitrogen in these nitro
bodies is by the use of Lunge's nitrometer (Fig. 41), and the best way of
working the process is as follows:--Weigh out with the greatest care 0.6
grm. of the previously dried substance in a small weighing bottle of about
15 c.c. capacity, and carefully add 10 c.c. of concentrated sulphuric acid
from a pipette, and allow to stand until all the cotton is dissolved. The
nitrometer should be of a capacity 150 to 200 c.c., and should contain a
bulb of 100 c.c. capacity at the top, and should be fitted with a Greiner
and Friederich's three-way tap. When the nitro-cotton has entirely
dissolved to a clear solution, raise the pressure tube of the nitrometer
so as to bring the mercury in the measuring tube close up to the tap. Open
the tap in order to allow of the escape of any air bubbles, and clean the
surface of the mercury and the inside of the cup with a small piece of
filter paper. Now close the tap, and pour the solution of the nitro-cotton
into the cup. Rinse out the bottle with 15 c.c. of sulphuric acid,
contained in a pipette, pouring a little of the acid over the stopper of
the weighing bottle in case some of the solution may be on it. Now lower
the pressure tube a little, just enough to cause the solution to flow into
the bulb of the measuring tube, when the tap is slightly opened. When the
solution has run in almost to the end, turn off the tap, wash down the
sides of the bottle, and add to the cup of the nitrometer; allow it to
flow in as before, and then wash down the sides of the cup with 10 c.c. of
sulphuric acid, adding little by little, and allowing each portion added
to flow into the bulb of the nitrometer before adding the next portion.
Great care is necessary to prevent air bubbles obtaining admission, and if
the pressure tube is lowered too far, the acid will run with a rush and
carry air along with it.

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