Nitro-Explosives: A Practical Treatise Part 17

_Emmensite_ is the invention of Dr Stephen Emmens, of the United States.

The Emmens "crystals" are produced by treating picric acid with fuming nitric acid of specific gravity of 1.52. The acid dissolves with the evolution of red fumes. The liquid, when cooled, deposits crystals, stated to be different to picric acid, and l.u.s.trous flakes. These flakes, when heated in water, separate into two new bodies. One of these enters into solution and forms crystals unlike the first, while the other body remains undissolved. The acid crystals are used mixed with a nitrate.

Emmensite has been subjected to experiment by the direction of the U.S.

Secretary for War, and found satisfactory. A sample of Emmensite, in the form of a coa.r.s.e powder, was first tried in a pistol, and proved superior in propelling power to ordinary gunpowder. When tested against explosive gelatine, it did very good work in shattering iron plates. It is claimed for this explosive that it enjoys the distinction of being the only high explosive which may be used both for firearms and blasting. This view is supported by the trials made by the American War Office authorities, and shows Emmensite to be a useful explosive both for blasting and as a smokeless powder. Its explosive power, as tested, is 283 tons per square inch, and its specific gravity is 1.8.

Abel proposed to use picric acid for filling sh.e.l.ls. His _Picric Powder_ consisted of 3 parts of saltpetre, and 2 of picrate of ammonia.

_Victorite_ consists of chlorate of potash, picric acid, and olive oil, and with occasionally some charcoal. It has the form of a coa.r.s.e yellowish grey powder, and leaves an oily stain on paper, and it is very sensitive to friction and percussion. The composition is as follows:--KClO_{3} = 80 parts; picric acid, 110 parts; saltpetre, 10 parts; charcoal, 5 parts. It is not manufactured in England. _Tschiner's Powder_ is very similar to Victorite in composition, but contains resin. A list of the chief picric powders will be found in the late Colonel J.P. Cundill, R.A.'s "Dictionary of Explosives."

CHAPTER VII.

_a.n.a.lYSIS OF EXPLOSIVES._

Kieselguhr Dynamite--Gelatine Compounds--Tonite--Cordite--Vaseline-- Acetone--Scheme for a.n.a.lysis of Explosives--Nitro-Cotton--Solubility Test-- Non-Nitrated Cotton--Alkalinity--Ash and Inorganic Matter--Determination of Nitrogen--Lunge, Champion and Pellet's, Schultze-Tieman, and Kjeldahl's Methods--Celluloid--Picric Acid and Picrates--Resinous and Tarry Matters-- Sulphuric Acid and Hydrochloric Acid and Oxalic Acid--Nitric Acid-- Inorganic Impurities--General Impurities and Adulterations--Pota.s.sium Picrate, &c.--Picrates of the Alkaloids--a.n.a.lysis of Glycerine--Residue-- Silver Test--Nitration--Total Acid Equivalent--Neutrality--Free Fatty Acids--Combined Fatty Acids--Impurities--Oleic Acid--Sodium Chloride-- Determination of Glycerine--Waste Acids--Sodium Nitrate--Mercury Fulminate--Cap Composition--Table for Correction of Volumes of Gases, for Temperature and Pressure

~Kieselguhr Dynamite.~--The material generally consists of 75 per cent. of nitro-glycerine and 25 per cent. of the infusorial earth kieselguhr. The a.n.a.lysis 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 pa.s.s 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 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 quant.i.tatively, for other mineral salts, such as carbonate of soda, &c. An actual a.n.a.lysis 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 quant.i.tatively 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 a.n.a.lysis 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 gla.s.s 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 gla.s.s 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, pota.s.sium 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 quant.i.ties 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 C., until it is easily detached from the linen filter by the aid of a spatula, and is then transferred to a weighed watch-gla.s.s, replaced in the oven, and dried at 40 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 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 C.

until constant, and weighed. The solution and was.h.i.+ngs from the wood are evaporated down in a platinum dish, and dried at 100 C. It will consist of the pota.s.sium 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 to 40 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 a.n.a.lysis 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 C.), and dried at 100 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 p.r.i.c.king a small hole through it with a gla.s.s 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 pota.s.sium nitrate, the ma.s.s 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 C. and then to 60 C., and afterwards in a vacuum over CaCl_{2} until the CS_{2} has evaporated from them. The camphor evaporates, and leaves the small quant.i.ty 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 quant.i.ty should therefore be added to that found by a.n.a.lysis. 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 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 quant.i.ty 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 quant.i.ty 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-gla.s.s, 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 a.n.a.lysis of Explosives," _Jour. Amer. Chem.

Soc._, 1901, 23 [8], 585-589.]

~Tonite.~--The a.n.a.lysis of this explosive is a comparatively easy matter, and can be performed as follows:--Weigh out 10 grms., or a smaller quant.i.ty, 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 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 a.n.a.lysis 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 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 pa.s.ses through a sieve having holes of the size of No. 8 wire gauge, but not through one with holes No. 14 wire gauge.

[Ill.u.s.tration: 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 gla.s.s 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 gla.s.s 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 gla.s.s 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 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 F., and a melting point of 86 F. It is obtained during the distillation of petroleum, and consists mainly of the portions distilling above 200 C. It boils at about 278 C.