The lesson this table teaches is, that it is almost impossible to nitrate cellulose in small quantities, and get uniform results, when the nitration is carried on at high temperatures. As regards the solubility of pyroxyline, Parks found that nitro-benzene, aniline, glacial acetic acid, and camphor, dissolved in the more volatile solvents methyl-alcohol and alcohol-ether, were much the best solvents for producing a plastic, as they are less volatile, and develop greater solvent action under the influence of heat. Nitro-benzene gives a solution that is granular; it seems to merely convert the pyroxyline, and not to dissolve it; but on the addition of alcohol, a solution is at once obtained, and the granular appearance disappears, and the solution becomes homogeneous. The acid mixture and the method of nitrating have much to do with the action of the various solvents, so also has the presence of water.

Dr Schupphaus found that propyl and isobutyl alcohols with camphor were active solvents, and the ketones, palmitone, and stearone in alcohol solution, also alpha- and beta-naphthol, with alcohol and anthraquinone (diphenylene diketone) in alcoholic solution, and also iso-valeric aldehyde and its derivatives, amyliden-dimethyl and amyliden-diethyl ethers.

August Sayer (U.S.P., No. 470,451) finds diethyl-ketone, dibutyl-ketone, di-pentyl-ketone, and the mixed ketones,[A] methyl-ethyl, methyl-propyl, methyl-butyl, methyl-amyl, and ethyl-butyl ketones are active solvents of pyroxyline; and Paget finds that although methyl-amyl oxide is a solvent, that ethyl-amyl oxide is not.

[Footnote A: Ketones are derived from the fatty acids by the substitution of the hydroxyl of the latter by a monad positive radical. They thus resemble aldehydes in constitution. The best-known ketone is acetone CH{3}CO.CH{3}. Mixed ketones are obtained by distilling together salts of two different fatty acids. Thus potassic butyrate and potassic acetate form propyl-methyl-ketone—

C(C{2}H{5})H{2} CO.CH{3}]

The solvents of pyroxyline can be divided into general classes—First, those which are solvents without the aid of heat or solution in alcohol; second, those that are solvents when dissolved in alcohol. These solvents are those which also develop a solvent action when heated to their melting point in combination with pyroxyline.

Mr W.D. Field groups the solvents of pyroxyline into classes thus: Two of the monohydric alcohols; compound ethers of the fatty acids with monohydric alcohols, aldehydes; simple and mixed ketones of the fatty acid series. These four classes include the greater number of the solvents of pyroxyline. Those not included are as follows:—Amyl-nitrate and nitrite, methylene-di-methyl ether, ethidene-diethyl ether, amyl-chloracetate, nitro-benzene and di-nitro-benzene, coumarin, camphor, glacial acetic acid, and mono-, di-, and tri-acetin.

Richard Hale uses the following solvent:—Amyl-acetate, 4 volumes; petroleum naphtha, 4 volumes; methyl-alcohol, 2 volumes; pyroxyline, 4 to 5 ounces to the gallon of solvent. Hale used petroleum naphtha to hasten the drying qualities of the varnish, so that it would set on the article to be varnished before it had a chance to run off. It is, however, the non-hygroscopic character of the solvent that makes the varnish successful. This formula is very largely used for the production of pyroxyline varnish, which is used for varnishing pens, pencils, &c., also brass-work and silver-ware.

The body known as oxy-cellulose[A] is formed by the action of nitric acid upon cellulose when boiled with it. The quantity formed is about 30 per cent. of cellulose acted upon. When washed free from acid, it gelatinises. It is then soluble in dilute alkalies, and can be reprecipitated from solution by alcohol, acids, or saline solutions. Messrs Cross and Bevan assign to it the formula C_{18}H_{26}O_{16}. It dissolves in concentrated sulphuric acid, and with nitric acid forms a nitro body of the formula C_{18}H_{23}O_{16}3(NO_{2}), which is prepared as follows:—The gelatinous oxy-cellulose is washed with strong nitric acid until free from water, and is then diffused through a mixture of equal volumes of strong sulphuric and nitric acids, in which it quickly dissolves. The solution, after standing for about an hour, is poured in a fine stream into a large volume of water, by which the "nitro" body is precipitated as a white flocculent mass. The product, after drying at 110 deg. C., was found upon analysis to contain 6.48 per cent. nitrogen.

[Footnote A: "On the Oxidation of Cellulose," by C.F. Cross and E.J. Bevan, Jour. Chem. Soc., 1883, p. 22.]

MISCELLANEOUS NITRO-EXPLOSIVES.

Nitro-Starch.—It is only recently that, by means of the process introduced by the "Actiengesellschaft Dynamit Nobel," it has been possible to make this explosive upon the manufacturing scale. Nitro-starch has been known since 1883, when Braconnot discovered it, and called it xyloidine. Its formula is C_{6}H_{8}O_{3}(NO_{3})_{2}, but Dr Otto Muehlhaeusen has lately succeeded in preparing higher nitrated compounds, viz.:—

(_a._) C_{6}H_{7-1/2}O_{2-1/2}(NO_{3})_{2-1/2}.

(_b._) C_{6}H_{7}O_{4}(NO_{3})_{3}.

Or doubling the molecule of starch:—

Nitrogen. i. Tetra-nitro-starch C_{12}H_{16}O_{6}(ONO_{2})_{4} 11.11 per cent. ii. Penta-nitro-starch C_{12}H_{15}O_{5}(ONO_{2})_{5} 12.75 " iii. Hexa-nitro-starch C_{12}H_{14}O_{4}(ONO_{2})_{6} 14.14 "

He regards them as true ethers (esters) of nitric acid. Thus on treatment with sulphuric acid, these compounds yield NO{3}H, the residue O.NO{2} thus appearing to be replaced by the sulphuric acid residue. On treatment with a solution of ferrous chloride, nitric oxide and "soluble" starch are regenerated. On shaking with sulphuric acid over mercury, all the nitrogen is split off as NO.

Tetra-nitro-starch is prepared upon the large scale as follows:—A quantity of potato-starch is taken and exposed in some suitable desiccating apparatus at a temperature of 100 deg. C. until all the moisture which it contains is completely driven off. It is then reduced to a fine powder by grinding, and dissolved in nitric acid of specific gravity 1.501. The vessel in which this solution is accomplished is made of lead, and must be provided with two jackets, cooled by means of water. It should further be fitted with a screw-agitator, in order to keep the nitric acid circulating freely. The charge of starch is introduced through an opening in the cover of this digesting vessel, and the proportions of acid to starch are 10 kilogrammes of starch to 100 kilos. of acid. The temperature is kept within the limits 20 deg. to 25 deg. C. When the solution of the starch is complete, the liquid is conducted into a precipitating apparatus, which is also provided with a cooling jacket, for the purpose of regulating the temperature. The bottom of this vessel is double and perforated, and here is placed a layer of gun-cotton to act as a filter. This vessel is filled with spent nitro-sulphuric acid obtained as a waste product from the nitro-glycerine manufactory, and the solution of starch in nitric acid is sprayed into it through an injector worked by compressed air, whereby the nitro-starch is thrown down in the form of a fine-grained powdery precipitate.

In order to precipitate 100 kilos. of the acid solution of starch, it is necessary to employ 500 kilos. of spent nitro-sulphuric acid. As it is precipitated the nitro-starch collects on the gun-cotton filter, and the acid liquor is run off through a tap placed beneath the perforated double bottom of the vessel, and of course below the filter pad. The precipitated starch is further cleansed from acid by repeated washings and by pressure, until all trace of acidity has been eliminated, and the substance exhibits a neutral reaction. The next step is to treat the nitro-starch with a 5 per cent. solution of soda, in contact with which it is allowed to stand for at least twenty-four hours. The product is then ground up until a sort of "milk" or emulsion is obtained, and lastly treated with a solution of aniline, so that when pressed into cake, it contains about 33 per cent. of water, and 1 per cent. of aniline.

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

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

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

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

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

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

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

These samples were prepared as follows:—

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

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

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

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

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

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

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

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

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

The nitrogen was determined in the products, and equalled 10.5 per cent. Theory for C{12}H{15}O{6}(NO{3}){3} = 9.5 per cent. and for C{12}H{15}O{6}(NO{3}){4} = 11.5 per cent. These nitrates resemble those of cellulose, and are in all essential points nitrates of ligno- cellulose.

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

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

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

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

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

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

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

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

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

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

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



CHAPTER IV.

DYNAMITE AND GELATINES.

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

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

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

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

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

(a.) Charcoal.

(b.) Gunpowder or other nitrate, or chlorate mixture.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

It has been observed that a dynamite made with wood sawdust can be moistened and then dried without marked alteration, and from 15 to 20 per cent. of water may be added to cellulose dynamite without depriving it of the power of exploding by strong detonator (this is similar to wet gun-cotton). It is, however, rendered much less sensitive to shock. With regard to the power of No. 1 dynamite, experiments made in lead cylinders give the relative value of No. 1 dynamite, 1.0; blasting gelatine, 1.4; and nitro-glycerine, 1.4. The heat liberated by the sudden explosion of dynamite is the same as its heat of combustion,[A] and proportionate to the weight of nitro-glycerine contained in the mixture. The gases formed are carbonic acid, water, nitrogen, and oxygen.

[Footnote A: Berthelot, "Explosives and their Power."]

The "explosive wave" (of Berthelot) for dynamite is about 5,000 metres per second. At this rate the explosion of a cartridge a foot long would only occupy 1/24000 part of a second, while a ton of dynamite cartridges about 7/8 diameter, laid end to end, and measuring one mile in length, would be exploded in one-quarter of a second by detonating a cartridge at either end.[A] Mr C. Napier Hake, F.I.C., the Inspector of Explosives for the Victorian Government, in his paper, "Notes on Explosives," says: "The theoretical efficiency of an explosive cannot in practice be realised in useful work for several reasons, as for instance in blasting rock—

"1. Incomplete combustion.

"2. Compression and chemical changes induced in surrounding material.

"3. Energy expended in cracking and heating of the material which is not displaced.

"4. The escape of gas through the blast-hole and the fissures caused by the explosion.

"The useful work consists partly in displacing the shattered masses. The proportion of useful work obtainable has been variously estimated at from 14 to 33 per cent. of the theoretical maximum potential."

[Footnote A: C.N. Hake, "Notes on Explosives," Jour. Soc. Chem. Ind., 1889.]

Among the various forms of dynamite that are manufactured is carbo- dynamite, the invention of Messrs Walter F. Reid and W.D. Borland. The base is nitro-glycerine, and the absorbent is carbon in the form of burnt cork. It is as cheap as ordinary dynamite, and has greater explosive force, seeing that 90 per cent. of the mixture is pure nitro-glycerine, and the absorbent itself is highly combustible. It is also claimed that if this dynamite becomes wet, no exudation takes place.

Atlas powder is a dynamite, chiefly manufactured in America at the Repanno Chemical Works, Philadelphia. It is a composition of nitro-glycerine, wood-pulp, nitrate of soda, and carbonate of magnesia. This was the explosive used in the outrages committed in London, by the so-called "dynamiters." Different varieties contain from 20 to 75 per cent. of nitro-glycerine.

The Rhenish dynamite, considerably used in the mines of Cornwall, is composed of 70 parts of a solution of 2 to 3 per cent. of naphthalene in nitro-glycerine, 3 parts of chalk, 7 parts of sulphate of barium, and 20 of kieselguhr.

Kieselguhr dynamites are being largely given up in favour of gelatine explosives. The late Colonel Cundill, in his "Dictionary of Explosives," gives a list of about 125 kinds of dynamites. Many of these, however, are not manufactured. Among the best known after the ordinary No. 1 dynamite are forcite, ammonia dynamite, litho-fracteur, rendock, Atlas powder, giant powder, and the various explosive gelatines. They all contain nitro- glycerine, mixed with a variety of other substances, such as absorbent earths, wood-pulp, nitro-cotton, carbon in some form or other, nitro- benzol, paraffin, sulphur, nitrates, or chlorates, &c. &c.

Blasting Gelatine and Gelatine Dynamite.—The gelatine explosives chiefly in use are known under the names of blasting gelatine, gelatine dynamite, and gelignite. They all consist of the variety of nitro- cellulose known as collodion-cotton, i.e., a mixture of the penta- and tetra-nitrates dissolved in nitro-glycerine, and made up with various proportions of wood-pulp, and some nitrate, or other material of a similar nature. As the gun-cotton contains too little oxygen for complete combustion, and the nitro-glycerine an excess, a mixture of the two substances is very beneficial.

Blasting gelatine consists of collodion-cotton and nitro-glycerine without any other substance, and was patented by Mr Alfred Nobel in 1875. It is a clear, semi-transparent, jelly-like substance, of a specific gravity of 1.5 to 1.55, slightly elastic, resembling indiarubber, and generally consists of 92 per cent. to 93 per cent. of nitro-glycerine, and 7 to 8 per cent. of nitro-cotton. The cotton from which it is made should be of good quality. The following is the analysis of a sample of nitro-cellulose which made very good gelatine:-

Soluble cotton 99.118 per cent. Gun-cotton 0.642 " Non-nitrated cotton 0.240 " Nitrogen 11.64 " Total ash 0.25 "

The soluble cotton, which is a mixture of the tetra- and penta-nitrates, is soluble in ether-alcohol, and also in nitro-glycerine, and many other solvents, whereas the hexa-nitrate (gun-cotton), C_{12}H_{14}O_{4}(ONO_{2})_{6}, is not soluble in the above liquids, although it is soluble in acetone or acetic ether. It is very essential, therefore, that the nitro-cotton used in the manufacture of the gelatine explosives should be as free as possible from gun-cotton, otherwise little lumps of undissolved nitro-cotton will be left in the finished gelatine. The non-nitrated or unconverted cotton should also be very low, in fact considerably under 1/2 per cent.

The nitro-cotton and the nitro-glycerine used should always be tested before use by the heat test, because if they do not separately stand this test, it cannot be expected that the gelatine made from them will do so. It often occurs, however, that although both the ingredients stand this test separately before being mixed, that after the process of manufacture one or other or both fail to do so.

The nitro-cotton most suitable for gelatine making is that which has been finely pulped. If it is not already fine enough, it must be passed through a fine brass wire sieve. It will be found that it requires to be rubbed through by hand, and will not go through at all if in the least degree damp. It is better, therefore, to dry it first. The percentage of nitrogen in the nitrated cotton should be over 11 per cent. It should be as free as possible from sand or grit, and should give but little ash upon ignition, not more than 0.25 per cent. The cotton, which is generally packed wet in zinc-lined wooden boxes, will require to be dried, as it is very essential indeed that none of the materials used in the manufacture of gelatine should contain more than the slightest trace of water. If they do, the gelatine subsequently made from them will most certainly exude, and become dangerous and comparatively valueless. It will also be much more difficult to make the nitro-cotton dissolve in the nitro-glycerine if either contains water.

In order to find out how long any sample of cotton requires to be dried, a sample should be taken from the centre of several boxes, well mixed, and about 1,000 grms. spread out on a paper tray, weighed, and the whole then placed in the water oven at 100 deg. C., and dried for an hour or so, and again weighed, and the percentage of moisture calculated from the loss in weight. This will be a guide to the time that the cotton will probably require to be in the drying house. Samples generally contain from 20 to 30 per cent. of water. After drying for a period of forty-eight hours, a sample should be again dried in the oven at 100 deg. C., and the moisture determined, and so on at intervals until the bulk of the cotton is found to be dry, i.e., to contain from 0.25 to 0.5 per cent. of moisture. It is then ready to be sifted. During the process of removing to the sifting house and the sifting itself, the cotton should be exposed to the air as little as possible, as dry nitro-cotton absorbs as much as 2 per cent. of moisture from the air at ordinary temperatures and average dryness.

The drying house usually consists of a wooden building, the inside of which is fitted with shelves, or rather framework to contain drawers, made of wood, with brass or copper wire netting bottoms. A current of hot air is made to pass through the shelves and over the surface of the cotton, which is spread out upon them to the depth of about 2 inches. This current of air can be obtained in any way that may be found convenient, such as by means of a fan or Root's blower, the air being passed over hot bricks, or hot-water pipes before entering the building. The cotton should also be occasionally turned over by hand in order that a fresh surface may be continually exposed to the action of the hot air. The building itself may be heated by means of hot-water pipes, but on no account should any of the pipes be exposed. They should all be most carefully covered over with wood-work, because when the dry nitro-cotton is moved, as in turning it over, very fine particles get into the air, and gradually settling on the pipes, window ledges, &c., may become very hot, when the slightest friction might cause explosion. It is on this account that this house should be very carefully swept out every day. It is also very desirable that the floor of this house should be covered with oilcloth or linoleum, as being soft, it lessens the friction.

List shoes should always be worn in this building, and a thermometer hung up somewhere about the centre of the house, and one should also be kept in one of the trays to give the temperature of the cotton, especially the bottom of the trays. The one nearest to the hot air inlet should be selected. If the temperature of the house is kept at about 40 deg. C. it will be quite high enough. The building must of course be properly ventilated, and it will be found very useful to have the walls made double, and the intervening space filled with cinders, and the roof covered with felt, as this helps to prevent the loss of heat through radiation, and to preserve a uniform temperature, which is very desirable.

The dry cotton thus obtained, if not already fine enough, should be sifted through a brass sieve, and packed away ready for use in zinc air-tight cases, or in indiarubber bags. The various gelatine compounds, gelignite, gelatine dynamite, and blasting gelatine, are manufactured in exactly the same way. The forms known as gelatine dynamite differ from blasting gelatine in containing certain proportions of wood-pulp and potassium nitrate, &c. The following are analyses of some typical samples of the three compounds:—

Gelatine Blasting Gelignite. Dynamite. Gelatine.

Nitro-glycerine 60.514 71.128 92.94 per cent. Nitro-cellulose 4.888 7.632 7.06 " Wood-pulp 7.178 4.259 ... " Potassium nitrate 27.420 16.720 ... " Water ... 0.261 ... "

The gelignite and gelatine dynamites consist, therefore, of blasting gelatine, thickened up with a mixture of absorbing materials. Although the blasting gelatine is weight for weight more powerful, it is more difficult to make than either of the other two compounds, it being somewhat difficult to make it stand the exudation and melting tests. The higher percentage of nitro-cotton, too, makes it expensive.

When the dry nitro-cotton, which has been carefully weighed out in the proportions necessary either for blasting gelatine or any of the other gelatine explosives, is brought to the gelatine making house, it is placed in a lead-lined trough, and the necessary quantity of pure dry nitro- glycerine poured upon it. The whole is then well stirred up, and kept at a temperature of from 40 deg. to 45 deg. C. It should not be allowed to go much above 40 deg. C.; but higher temperatures may be used if the nitro-cotton is very obstinate,[A] and will not dissolve. Great caution must, however, be observed in this case. The mixture should be constantly worked about by the workman with a wooden paddle for at least half an hour. At a temperature of 40 deg. to 45 deg. the nitro-glycerine acts upon the nitro-cotton and forms a jelly. Without heat the gelatinisation is very imperfect indeed, and at temperatures under 40 deg. C. takes place very slowly.

[Footnote A: Generally due to the nitro-cotton being damp.]



The limit of temperature is 50 deg. C. or thereabouts. Beyond this the jelly should never be allowed to go, and to 50 deg. only under exceptional circumstances.

The tank in which the jelly is made is double-lined, in order to allow of the passage of hot water between its inner and outer linings. A series of such tanks are generally built in a wooden framework, and the double linings are made to communicate, so that the hot water can flow from one to the other consecutively. The temperature of the water should be about 60 deg. C. if it is intended to gelatinise at 45 deg. C., and about 80 deg. if at 50 deg. C.; but this point must, of course, be found by experiment for the particular plant used. An arrangement should be made to enable the workman to at once cut off the supply of hot water and pass cold water through the tanks in case the explosive becomes too hot.



The best way to keep the temperature of the water constant is to have a large tank of water raised upon a platform, some 5 or 6 feet high, outside the building, which is automatically supplied with water, and into which steam is turned. A thermometer stuck through a piece of cork and floated upon the surface of the tank will give the means of regulating the temperature.

When the jelly in the tanks has become semi-transparent and the cotton has entirely dissolved, the mixture should be transferred to the mixing machine. The mixing machines are specially designed for this work, and are built in iron, with steel or bronze kneading- and mixing-blades, according to requirements.

A suitable machine for the purpose is that known as the Nito-Universal Incorporator, shown in Fig. 30, which has been specially constructed by Messrs Werner, Pfleiderer, & Perkins, Ltd., after many years' experience in the mixing of explosive materials, and is now almost exclusively adopted in both Government and private factories. Mr George M'Roberts'[A] mixing machine, however, which is shown in Fig. 31, is still used in some factories for dynamite jelly.

[Footnote A: See Jour. Soc. Chem. Ind., 1890, 267.]

If it is intended to make gelignite, or gelatine dynamite, it is at this point that the proper proportions of wood-pulp[A] and potassium nitrate should be added, and the whole well mixed for at least half an hour, until the various ingredients are thoroughly incorporated.

[Footnote A: Most of the wood-pulp used in England is obtained from pine-trees, but poplar, lime, birch, and beech wood are also used. It is chiefly imported as wood-pulp. The pulp is prepared as follows:—The bark and roots are first removed, and the logs then sawn into boards, from which the knots are removed. The pieces of wood are afterwards put through a machine which breaks them up into small pieces about an inch long, which are then crushed between rollers. These fragments are finally boiled with a solution of sodium bisulphite, under a pressure of about 90 lbs. per square inch, the duration of the boiling being from ten to twelve hours. Sulphurous acid has also been used. Pine-wood yields about 45 per cent. and birch about 40 per cent. of pulp when treated by this process. The pulp is afterwards bleached and washed, &c.

Birch. Beech. Lime. Pine. Poplar. Cellulose 55.52 45.47 53.09 56.99 62.77 per cent. Resin 1.14 0.41 3.93 0.97 1.37 " Aqueous extract 2.65 2.47 3.56 1.26 2.88 " Water 12.48 12.57 10.10 13.87 12.10 " Lignine 28.21 39.14 29.32 26.91 20.88 "]

The following analysis of woods is by Dr H. Mueller:—These mixing machines can either be turned by hand, or a shaft can be brought into the house and the machine worked by means of a belt at twenty to thirty revolutions per minute. The bearings should be kept constantly greased and examined, and the explosive mixture carefully excluded. When the gelatine mixture has been thoroughly incorporated, and neither particles of nitrate or wood meal can be detected in the mass, it should be transferred to wooden boxes and carried away to the cartridge-making machines to be worked up into cartridges.



The application of heat in the manufacture of the jelly from collodion- cotton and nitro-glycerine is absolutely necessary, unless some other solvent is used besides the nitro-glycerine, such as acetone, acetic ether, methyl, or ethyl-alcohol. (They are all too expensive, with the exception of acetone and methyl-alcohol, for use upon the large scale.) These liquids not only dissolve the nitro-cellulose in the cold, but render the resulting gelatine compound less sensitive to concussion, and reduce its quickness of explosion (as in cordite). They also lower the temperature at which the nitro-glycerine becomes congealed, i.e., they lower the freezing point[A] of the resulting gelatine.

[Footnote A: It has been proposed to mix dynamite with amyl alcohol for this purpose. Di-nitro-mono-chlorhydrine has also been proposed.]

The finished gelatine paste, upon entering the cartridge huts, is at once transferred to the cartridge-making machine, which is very like an ordinary sausage-making machine[A] (Fig. 33). The whole thing must be made of gun-metal or brass, and it consists of a conical case containing a shaft and screw. The revolutions of the shaft cause the thread of the screw to push forward the gelatine introduced by the hopper on the top to the nozzle, the apex of the cone-shaped case, from whence the gelatine issues as a continuous rope. The nozzle is of course of a diameter according to the size of cartridge required.

[Footnote A: G. M'Roberts, Jour. Soc. Chem. Ind., 31st March 1890, p. 266.]



The issuing gelatine can of course be cut off at any length. This is best done with a piece of hard wood planed down to a cutting edge, i.e., wedge-shaped. Mr Trench has devised a kind of brass frame, into which the gelatine issuing from the nozzle of the cartridge machine is forced, finding its way along a series of grooves. When the frame is full, a wooden frame, which is hinged to one end of the bottom frame, and fitted with a series of brass knives, is shut down, thereby cutting the gelatine up into lengths of about 4 inches.

It is essential that the cartridge machines should have no metallic contacts inside. The bearing for the screw shaft must be fixed outside the cone containing the gelatine. One of these machines can convert from 5 to 10 cwt. of gelatine into cartridges per diem, depending upon the diameter of the cartridges made.

After being cut up into lengths of about 3 inches, the gelatine is rolled up in cartridge paper. Waterproof paper is generally used. The cartridges are then packed away in cardboard boxes, which are again packed in deal boxes lined with indiarubber, and screwed down air tight, brass screws or zinc or brass nails being used for the purpose. These boxes are sent to the magazines. Before the boxes are fastened down a cartridge or so should be removed and tested by the heat test, the liquefaction test, and the test for liability to exudation. (Appendix, p. 6, Explosives Act, 1875.) A cartridge also should be stored in the magazine in case of any subsequent dispute after the bulk of the material has left the factory.

The object of the liquefaction test is to ensure that the gelatine shall be able to withstand a fairly high temperature (such as it might encounter in a ship's hold) without melting or running together. The test is carried out as follows:—A cylinder of the gelatine dynamite is cut from the cartridge of a length equal to its diameter. The edges must be sharp. This cylinder is to be placed on end on a flat surface (such as paper), and secured by a pin through the centre, and exposed for 144 consecutive hours to a temperature of 85 deg. to 90 deg. F., and during such time the cylinder should not diminish in height by more than one-fourth of an inch, and the cut edges should remain sharp. There should also be no stain of nitroglycerine upon the paper.

The exudation test consists in freezing and thawing the gelatine three times in succession. Under these conditions there should be no exudation of nitro-glycerine. All the materials used in the manufacture of gelatine explosives should be subjected to analytical examination before use, as success largely depends upon the purity of the raw materials. The wood-pulp, for instance, must be examined for acidity.

Properties of the Gelatine Compounds.—Blasting gelatine is generally composed of 93 to 95 parts nitro-glycerine, and 5 to 7 parts of nitro- cellulose, but the relative proportions of explosive base and nitro- glycerine, &c., in the various forms of the gelatine explosives do not always correspond to those necessary for total combustion, either because an incomplete combustion gives rise to a greater volume of gas, or because the rapidity of decomposition and the law of expansion varies according to the relative proportions and the conditions of application. The various additions to blasting gelatine generally have the effect of lowering the strength by reducing the amount of nitro-glycerine, but this is sometimes done in order to change a shattering agent into a propulsive force. If this process be carried too far, we of course lose the advantages due to the presence of nitro-glycerine. There is therefore a limit to these additions.[A]

[Footnote A: Mica is said to increase the rapidity of explosion when mixed with gelatine.]

The homogeneousness and stability of the mixture are of the highest importance. It is highly essential that the nitro-glycerine should be completely absorbed by the substances with which it is mixed, and that it should not subsequently exude when subjected to heat or damp. It is also important that there should be no excess of nitro-glycerine, as this may diminish instead of augment the strength, owing to a difference in the mode of the propagation of the explosive wave in the liquid, and in the mixture. Nitro-glycerine at its freezing point has a tendency to separate from its absorbing material, in fact to exude. When frozen, too, it requires a more powerful detonation to explode it, but it is less sensitive to shock. The specific gravity of blasting gelatine is 1.5 (i.e., nearly equal to that of nitro-glycerol); that of gun-cotton (dry) is 1.0.

Blasting gelatine burns in the air when unconfined without explosion, at least in small quantities and when not previously heated, but it is rather uncertain in this respect. It can be kept at a moderately high temperature (70 deg. C.) without decomposition. At higher temperatures the nitro-glycerine will partially evaporate. When slowly heated, it explodes at 204 deg. C. If, however, it contains as much as 10 per cent. of camphor, it burns without exploding. According to Berthelot,[A] gelatine composed of 91.6 per cent. nitro-glycerine and 8.4 per cent. of nitro-cellulose, which are the proportions corresponding to total combustion, produces by explosion 177CO_{2}+ 143H_{2}O + 8N_{2}.

[Footnote A: Berthelot, "Explosives and their Powers."]

He takes C{24}H{22}(NO{3}H){9}O{11} as the formula of the nitro- cellulose, and 51C{3}H{2}(NO{3}H){3} + C{24}H{22}(NO{3}H){9}O{11} as the formula of the gelatine itself, its equivalent weight being 12,360 grms. The heat liberated by its explosion is equal to 19,381 calories, or for 1 kilo. 1,535 calories. Volume of gases reduced temperature equals 8,950 litres. The relative value[A] of blasting gelatine to nitro- glycerine is as 1.4 to 1.45, kieselguhr dynamite being taken as 1.0.

[Footnote A: Roux and Sarran.]



CHAPTER V.

NITRO-BENZOL, ROBURITE, BELLITE, PICRIC ACID, &c.

Explosives derived from Benzene—Toluene and Nitro-Benzene—Di- and Tri-nitro-Benzene—Roburite: Properties and Manufacture—Bellite: Properties, &c.—Securite—Tonite No. 3.—Nitro-Toluene— Nitro-Naphthalene—Ammonite—Sprengel's Explosives—Picric Acid— Picrates—Picric Powders—Melinite—Abel's Mixture—Brugere's Powders— The Fulminates—Composition, Formula, Preparation, Danger of, &c.— Detonators: Sizes, Composition, Manufacture—Fuses, &c.

The Explosives derived from Benzene.—There is a large class of explosives made from the nitrated hydro-carbons—benzene, C{6}H{6}; toluene, C{7}H{8}; naphthalene, C{10}H{8}; and also from phenol (or carbolic acid), C{6}H{5}OH. The benzene hydro-carbons are generally colourless liquids, insoluble in water, but soluble in alcohol and ether. They generally distil without decomposition. They burn with a smoky flame, and have an ethereal odour. They are easily nitrated and sulphurated; mono, di, and tri derivatives are readily prepared, according to the strength of the acids used. It is only the H-atoms of the benzene nucleus which enter into reaction.

Benzene was discovered by Faraday in 1825, and detected in coal-tar by Hofmann in 1845. It can be obtained from that portion of coal-tar which boils at 80 deg. to 85 deg. by fractionating or freezing.[A] The ordinary benzene of commerce contains thiophene (C{4}H{4}S), from which it may be freed by shaking with sulphuric acid. Its boiling point is 79 deg. C.; specific gravity at 0 deg. equals 0.9. It burns with a luminous smoky flame, and is a good solvent for fats, resins, sulphur, phosphorus, &c. Toluene was discovered in 1837, and is prepared from coal-tar. It boils at 110 deg. C., and is still liquid at 28 deg. C.

[Footnote A: It may be prepared chemically pure by distilling a mixture of benzoic acid and lime.]

The mono-, chloro-, bromo-, and iodo-benzenes are colourless liquids of peculiar odour. Di-chloro-, di-bromo-benzenes, tri- and hexa-chloro- and bromo-benzenes, are also known; and mono-chloro-, C_{6}H_{4}Cl(CH_{3}), and bromo-toluenes, together with di derivatives in the ortho, meta, and para modifications. The nitro-benzenes and toluenes are used as explosives. The following summary is taken from Dr A. Bernthsen's "Organic Chemistry":—

SUMMARY. ____________ C_{6}H_{5}(N0_{2}) Nitro-benzene. Liq. B.Pt. 206 deg. C. C_{6}H_{4}(NO_{2})_{2} Ortho-, meta-, and para- di-nitro-benzenes. Solid. M.P. 118 deg., 90 deg., and 172 deg. C. C_{6}H_{3}(NO_{3})_{3} S.-Tri-nitro-benzene. Solid. M.P. 121 deg. C. ____________ C_{6}H_{4}(CH_{3})NO_{2} Ortho-, meta-, and para- nitro-toluenes. B.P. 218 deg., 230 deg., and 234 deg. C, Para compound solid. ____________ C_{6}H_{3}(CH_{3})_{2}NO_{2} Nitro-xylene. Liquid. ____________ C_{6}H_{2}(CH_{3})_{3}NO_{2} Nitro-mesitylene. Solid. ____________ C_{6}H_{3}(CH_{3})(NO_{2})_{2} Di-nitro-toluenes. ____________ C_{6}H_{4}Cl(NO_{2}) Nitro-chloro-benzenes. C_{6}Br_{4}(NO_{2})_{2} Tetra-bromo-di-nitrobenzene. ____________

The nitro compounds are mostly pale yellow liquids, which distil unchanged, and volatilise with water vapour, or colourless or pale yellow needles or prisms. Some of them, however, are of an intense yellow colour. Many of them explode upon being heated. They are heavier than water, and insoluble in it, but mostly soluble in alcohol, ether, and glacial acetic acid.

Nitro-benzene, C_{6}H_{5}(NO_{2}), was discovered in 1834 by Mitscherlich. It is a yellow liquid, with a melting point of +3 deg. C. It has an intense odour of bitter almonds. It solidifies in the cold. In di-nitro-benzene, the two nitro groups may be in the meta, ortho, or para position, the meta position being the most general (see fig., page 4). By recrystallising from alcohol, pure meta-di-nitro-benzene may be obtained in long colourless needles. The ortho compound crystallises in tables, and the para in needles. They are both colourless. When toluene is nitrated, the para and ortho are chiefly formed, and a very little of the meta compound.

Nitro Compounds of Benzene and Toluene.—The preparation of the nitro derivatives of the hydrocarbons of the benzene series is very simple. It is only necessary to bring the hydrocarbon into contact with strong nitric acid, when the reaction takes place, and one or more of the hydrogen atoms of the hydrocarbon are replaced by the nitryl group (NO_{2}). Thus by the action of nitric acid on benzene (or benzol), mono-nitro-benzene is formed:—

C_{6}H_{6} + HNO_{3} = C_{6}H_{5}.NO_{2} +H_{2}O. Mono-nitro-benzene.

By the action of another molecule of nitric acid, the di-nitro-benzene is formed:—

C_{6}H_{5}.NO_{2} + HNO_{3} = C_{6}H_{4}(NO_{2})_{2} + H_{2}O. Di-nitro-benzene.

These nitro bodies are not acids, nor are they ethereal salts of nitrous acid, as nitro-glycerine is of glycerine. They are regarded as formed from nitric acid by the replacement of hydroxyl by benzene radicals.

Mono-nitro Benzene is made by treating benzene with concentrated nitric acid, or a mixture of nitric and sulphuric acids. The latter, as in the case of the nitration of glycerine, takes no part in the reaction, but only prevents the dilution of the nitric acid by the water formed in the reaction. Small quantities may be made thus:—Take 150 c.c. of H_{2}SO_{4} and 75 c.c. HNO_{3}, or 1 part nitric to 2 parts sulphuric acid, and put in a beaker standing in cold water; then add 15 to 20 c.c. of benzene, drop by drop, waiting between each addition for the completion of the reaction, and shake well during the operation. When finished, pour contents of beaker into about a litre of cold water; the nitro-benzol will sink to the bottom. Decant the water, and wash the nitro-benzol two or three times in a separating funnel with water. Finally, dry the product by adding a little granulated calcium chloride, and allowing to stand for some little time, it may then be distilled. Nitro-benzene is a heavy oily liquid which boils at 205 deg. C., has a specific gravity of 1.2, and an odour like that of oil of bitter almonds. In the arts it is chiefly used in the preparation of aniline.

Di-nitro Benzene is a product of the further action of nitric acid on benzene or nitro-benzene. It crystallises in long fine needles or thin rhombic plates, and melts at 89.9 deg. C. It can be made thus:—The acid mixture used consists of equal parts of nitric and sulphuric acids, say 50 c.c. of each, and without cooling add very slowly 10 c.c. of benzene from a pipette. After the action is over, boil the mixture for a short time, then pour into about half a litre of water, filter off the crystals thus produced, press between layers of filter paper, and crystallise from alcohol. Di-nitro-benzene, or meta-di-nitro-benzene, as it is sometimes called, enters into the composition of several explosives, such as tonite No. 3, roburite, securite, bellite.

Nitro-benzene is manufactured upon the large scale as follows:—Along a bench a row of glass flasks, containing 1 gallon each (1 to 2 lbs. benzene), are placed, and the acids added in small portions at a time, the workmen commencing with the first, and adding a small quantity to each in turn, until the nitration was complete. This process was a dangerous one, and is now obsolete. The first nitro-benzene made commercially in England, by Messrs Simpson, Maule, and Nicholson, of Kennington, in 1856, was by this process. Now, however, vertical iron cylinders, made of cast-iron, are used for the nitrating operation. They are about 4 feet in diameter and 4 feet deep, and a series are generally arranged in a row, at a convenient height from the ground, beneath a line of shafting. Each cylinder is covered with a cast-iron lid having a raised rim all round. A central orifice gives passage to a vertical shaft, and two or more other conveniently arranged openings allow the benzene and the mixed acids to flow in. Each of these openings is surrounded with a deep rim, so that the whole top of the cylinder can be flooded with water some inches in depth, without any of it running into the interior of the nitrator. The lid overhangs the cylinder somewhat, and in the outer rim a number of shot- holes or tubes allow the water to flow down all over the outside of the cylinder into a shallow cast-iron dish, in which it stands. By means of a good supply of cold water, the top, sides, and bottom of the whole apparatus is thus cooled and continually flooded. The agitator consists of cast-iron arms keyed to a vertical shaft, with fixed arms or dash-plates secured to the sides of the cylinder. The shaft has a mitre wheel keyed on the top, which works into a corresponding wheel on the horizontal shafting running along the top of the converters. This latter is secured to a clutch; and there is a feather on the shaft, so that any one of the converters can if necessary be put either in or out of gear. This arrangement is necessary, as riggers or belts of leather, cotton, or indiarubber will not stand the atmosphere of the nitro-benzole house. Above and close to each nitrator stands its acid store tank, of iron or stoneware.

The building in which the nitration is carried out should consist of one story, have a light roof, walls of hard brick, and a concrete floor of 9 to 12 inches thick, and covered with pitch, to protect its surface from the action of the acids. The floor should be inclined to a drain, to save any nitro-benzol spilt. Fire hydrants should be placed at convenient places, and it should be possible to at once fill the building with steam. A 2-inch pipe, with a cock outside the building, is advisable. The building should also be as far as possible isolated.

The acids are mixed beforehand, and allowed to cool before use. The nitric acid used has a specific gravity of 1.388, and should be as free as possible from the lower oxides of nitrogen. The sulphuric acid has a specific gravity of 1.845, and contains from 95 to 96 per cent. of mono- hydrate. A good mixture is 100 parts of nitric to 140 parts of sulphuric acid, and 78 parts of benzene; or 128 parts HNO_{3}, 179 of H_{2}SO_{4}, and 100 of benzene (C_{6}H_{6}). The benzene having been introduced into the cylinder, the water is turned on and the apparatus cooled, the agitators are set running, and the acid cock turned on so as to allow it to flow in a very thin stream into the nitrator.

Should it be necessary to check the machinery even for a moment, the stream of acid must be stopped and the agitation continued for some time, as the action proceeds with such vigour that if the benzene being nitrated comes to rest and acid continues to flow, local heating occurs, and the mixture may inflame. Accidents from this cause have been not infrequent. The operation requires between eight to ten hours, agitation and cooling being kept up all the time. When all the acid is added the water is shut off, and the temperature allowed to rise a little, to about 100 deg. C. When it ceases to rise the agitators are thrown out of gear, and the mixture allowed some hours to cool and settle. The acid is then drawn off, and the nitro-benzene is well washed with water, and sometimes distilled with wet steam, to recover a little unconverted benzene and a trace of paraffin (about .5 per cent. together). At many English works, 100 to 200 gallons, or 800 to 1,760 lbs., are nitrated at a time, and toluene is often used instead of benzene, especially if the nitro-benzene is for use as essence of myrbane. The waste acids, specific gravity 1.6 to 1.7, contain a little nitro-benzene in solution and some oxalic acid. They are concentrated in cast-iron pots and used over again.

Di-nitro Benzene is obtained by treating a charge of the hydrocarbon benzene with double the quantity of mixed acids in two operations, or rather in two stages, the second lot of acid being run in directly after the first. The cooling water is then shut off, and the temperature allowed to rise rapidly, or nitro-benzene already manufactured is taken and again nitrated with acids. A large quantity of acid fumes come off, and some of the nitro- and di-nitro-benzol produced comes off at the high temperature which is attained, and a good condensing apparatus of stoneware must be used to prevent loss. The product is separated from the acids, washed with cold water and then with hot. It is slightly soluble in water, so that the washing waters must be kept and used over again. Finally it is allowed to settle, and run while still warm into iron trays, in which it solidifies in masses 2 or 4 inches thick. It should not contain any nitro-benzol, nor soil a piece of paper when laid on it, should be well crystallised, fairly hard, and almost odourless. The chief product is meta-di-nitro-benzene, melting point 89.8, but ortho-di-nitro-benzene, melting point 118 deg., and para-di-nitro, melting point 172 deg., are also produced. The melting point of the commercial product is between 85 deg. to 87 deg. C.

Di-nitro-toluene is made in a similar manner. The tri-nitro-benzene can only be made by using a very large excess of the mixed acids. Nitro- benzene, when reduced with iron, zinc, or tin, and hydrochloric acids, forms aniline.

Roburite.—This explosive is the invention of a German chemist, Dr Carl Roth (English patent 267A, 1887), and is now manufactured in England, at Gathurst, near Wigan. It consists of two component parts, non-explosive in themselves (Sprengel's principle), but which, when mixed, form a powerful explosive. The two substances are ammonium nitrate and chlorinated di-nitro-benzol. Nitro-naphthalene is also used. Nitrate of soda and sulphate of ammonium are allowed to be mixed with it. The advantages claimed for the introduction of chlorine into the nitro compound are that chlorine exerts a loosening effect upon the NO_{2} groups, and enables the compound to burn more rapidly than when the nitro groups alone are present.

The formula of chloro-di-nitro-benzol is C{6}H{3}Cl(NO{2}){2}. The theoretical percentage of nitrogen, therefore, is 13.82, and of chlorine 17.53. Dr Roth states that, from experiments he has made, the dynamic effect is considerably increased by the introduction of chlorine into the nitro compound. Roburite burns quickly, and is not sensitive to shock; it must be used dry; it cannot be made to explode by concussion, pressure, friction, fire, or lightning; it does not freeze; it does not give off deleterious fumes, and it is to all intents and purposes flameless; and when properly tamped and fired by electricity, can be safely used in fiery mines, neither fine dust nor gases being ignited by it. The action is rending and not pulverising. Compared to gunpowder, it is more powerful in a ratio ranging from 2-1/2 to 4 to 1, according to the substance acted upon. It is largely used in blasting, pit sinking, quarrying, &c., but especially in coal mining. According to Dr Roth, the following is the equation of its decomposition:—

C_{6}H_{3}Cl(NO_{2})_{2} + 9HN_{4}NO_{3} = 6CO_{2} + 20N + HCl.

In appearance roburite is a brownish yellow powder, with the characteristic smell of nitro-benzol. Its specific gravity is 1.40. The Company's statement that the fumes of roburite were harmless having been questioned by the miners of the Garswood Coal and Iron Works Colliery, a scientific committee was appointed by the management and the men jointly for the purpose of settling the question. The members of this committee were Dr N. Hannah, Dr D.J. Mouncey, and Professor H.B. Dixon, F.R.S., of Owens College. After a protracted investigation, a long and technical report was issued, completely vindicating the innocuousness of roburite when properly used. In the words of The Iron and Coal Trades' Review (May 24, 1889), "The verdict, though not on every point in favour of the use in all circumstances of roburite in coal mines, is yet of so pronounced a character in its favour as an explosive that it is impossible to resist the conclusion that the claims put forward on its behalf rest on solid grounds."

Roburite was also one of the explosives investigated by the committee appointed in September 1889 by the Durham Coalowners' and Miners' Associations, for the purpose of determining whether the fumes produced by certain explosives are injurious to health. Both owners and workmen were represented on the committee, which elected Mr T. Bell, H.M. Inspector of Mines, as its chairman, with Professor P.P. Bedson and Drs Drummond and Hume as professional advisers. The problem considered was whether the fumes produced by the combustion of certain explosives, one of which was roburite, were injurious to health. The trial comprised the chemical analysis of the air at the "intake," and of the vitiated air during the firing of the shots at the "return," and also of the smoky air in the vicinity of the shot-holes. Five pounds and a half of roburite were used in twenty-three shots. It had been asserted that the fumes from this explosive contained carbon-monoxide, CO, but no trace of this gas could be discovered after the explosion. On another occasion, however, when 4.7 lbs. of roburite were exploded in twenty-three shots, the air at the "return" showed traces of CO gas to the extent of .042 to .019 per cent. The medical report which Drs Hume and Drummond presented to the committee shows that they investigated every case of suspected illness produced by exposure to fumes, and they could find no evidence of acute illness being caused. They say, "No case of acute illness has, throughout the inquiry, been brought to our knowledge, and we are led to the conclusion that such cases have not occurred."

Manufacture.—As now made, roburite is a mixture of ammonium nitrate and chlorinated di-nitro-benzol. The nitrate of ammonia is first dried and ground, and then heated in a closed steam-jacketed vessel to a temperature of 80 deg. C., and the melted organic compound is added, and the whole stirred until an intimate mixture is obtained. On cooling, the yellow powder is ready for use, and is stored in straight canisters or made up into cartridges. Owing to the deliquescent nature of the nitrate of ammonia, the finished explosive must be kept out of contact with the air, and for this reason the cartridges are waterproofed by dipping them in melted wax. Roburite is made in Germany, at Witten, Westphalia; and also at the English Company's extensive works at Gathurst, near Wigan, which have been at work now for some eighteen years, having started in 1888. These works are of considerable extent, covering 30 acres of ground, and are equal to an output of 10 tons a day. A canal runs through the centre, separating the chemical from the explosive portions of the works, and the Lancashire and Yorkshire Railway runs up to the doors. Besides sending large quantities of roburite itself abroad, the Company also export to the various colonies the two components, as manufactured in the chemical works, and which separately are quite non-explosive, and which, having arrived at their destination, can be easily mixed in the proper proportions.

Among the special advantages claimed for roburite are:—First, that it is impossible to explode a cartridge by percussion, fire, or electric sparks. If a cartridge or layer be struck with a heavy hammer, the portion struck is decomposed, owing to the large amount of heat developed by the blow. The remaining explosive is not in the least affected, and no detonation whatever takes place. If roburite be mixed with gunpowder, and the gunpowder fired, the explosion simply scatters the roburite without affecting it in the least. In fact, the only way to explode roburite is to detonate it by means of a cap of fulminate, containing at least 1 gramme of fulminate of mercury. Secondly, its great safety for use in coal mines. Roburite has the great advantage of exploding by detonation at a very low temperature, indeed so low that a very slight amount of tamping is required when fired in the most explosive mixture of air and coal gas possible, and not at all in a mixture of air and coal dust—a condition in which the use of gunpowder is highly dangerous.

Mr W.J. Orsman, F.I.C., in a paper read at the University College, Nottingham, in 1893, gives the temperature of detonation of roburite as below 2,100 deg. C., and of ammonium nitrate as 1,130 deg. C., whereas that of blasting gelatine is as much as 3,220 deg. C. With regard to the composition of the fumes formed by the explosion of roburite, Mr Orsman says: "With certain safety explosives—roburite, for instance—an excess of the oxidising material is added, namely, nitrate of ammonia; but in this case the excess of oxygen here causes a diminution of temperature, as the nitrate of ammonia on being decomposed absorbs heat. This excess of oxygen effectually prevents the formation of carbon monoxide (CO) and the oxides of nitrogen."

The following table (A), also from Mr Orsman's paper, gives the composition of five prominent explosives, and shows the composition of the gases formed on explosion. The gases were collected after detonating 10 grms. of each in a closed strong steel cylinder, having an internal diameter of 5 inches.

With respect to the influence of ammonium nitrate in lowering the temperature of explosion of the various substances to which it is added, it was found by a French Commission that, when dry and finely powdered, ammonium nitrate succeeds in depreciating the heat of decomposition without reducing the power of the explosive below a useful limit. The following table (B) shows the composition of the explosives examined, and the temperatures which accompanied their explosion.

A Composition of Gases. Volume Explosive. of Gas formed. CO{2}. CO. CH{4} N. &H. Per Per Per Per c.c. cent. cent. cent. cent. Gunpowder Nitre 75 parts Sulphur 10 '' 2,214 51.3 3.5 3.5 41.7 Charcoal 15 '' Gelignite Nitro-glycerine 56.5 parts Nitro-cotton 3.5 '' 4,980 25 7 ... 67 Wood-meal 8.0 '' KNO{3} 32.0 '' Tonite Nitro-Cotton 3,750 30 8 ... 62 Barium nitrate Roburite Ammonium nitrate, 86 parts Di-nitro-chloro-benzol 14 '' 4,780 32 ... ... 68 Carbonite Nitro-glycerine 25 parts Wood-meal 40 '' 2,100 19 15 26 ... Potas. nitrate 34 ''

B Original Percentage Final Explosive. Temperature NH{4}.NO{3} Temperature Co-efficient. added. Co-efficient. Nitro-glycerine 3,200 ... ... Blasting gelatine (8 per cent. gun-cotton) 3,090 88 1,493 Dynamite (25 per cent. silica) 2,940 80 1,468 Gun-cotton, 1 2,650 ... ... 2,060 90.5 1,450 Ammonium nitrate 1,130 ... ...

Bellite is the patent of Mr Carl Lamm, Managing Director of the Roetebro Explosive Company, of Stockholm, and is licensed for manufacture in England. It consists of a mixture of nitrate of ammonia with di- or tri-nitro-benzol, it has a specific gravity of 1.2 to 1.4 in its granulated state, and 1 litre weighs 800 to 875 grms. Heated in an open vessel, bellite loses its consistency at 90 deg. C., but does not commence to separate before a temperature of 200 deg. C. is reached, when it evaporates without exploding. If heated suddenly, it burns with a sooty flame, somewhat like tar, but if the source of heat is removed, it will cease burning, and assume a caramel-like structure. It absorbs very little moisture from the air after it has been pressed, and if the operation has been performed while the explosive is hot, the subsequent increase of weight is only 2 per cent. When subjected to the most powerful blow with a steel hammer upon an iron plate, it neither explodes nor ignites. A rifle bullet fired into it at 50 yards' distance will not explode it. Granulated bellite explodes fully by the aid of fulminating mercury. Fifteen grms. of bellite fired by means of fulminate, projected a shot from an ordinary mortar, weighing 90 lbs., a distance of 75 yards, 15 grms. of gunpowder, under the same conditions, throwing it only 12 yards. A weight of 7-1/2 lbs. falling 145 centimetres failed to explode 1 grm. of bellite.

Various experiments and trials have been made with this explosive by Professor P.T. Cleve, M.P.F. Chalon, C.N. Hake, and by a committee of officers of the Swedish Royal Artillery. It is claimed that it is a very powerful and extremely safe explosive; that it cannot be made to explode by friction, shock, or pressure, nor by electricity, fire, lightning, &c., and that it is specially adapted for use in coal mines, &c.; that it can only be exploded by means of a fulminate detonator, and is perfectly safe to handle and manufacture; that it does not freeze, can be used as a filling for shells, and lastly, can be cheaply manufactured.

Securite consists of 26 parts of meta-di-nitro-benzol and 74 parts of ammonium nitrate. It is a yellow powder, with an odour of nitro-benzol. It was licensed in 1886. It sometimes contains tri-nitro-benzol, and tri-nitro-naphthalene. The equation of its combustion is given as

C_{6}H_{4}(NO_{2})_{2} + 10(NH_{4}NO_{3}) = 6CO_{2} + 22H_{2}O + 11N_{2}

and, like bellite and roburite, it is claimed to be perfectly safe to use in the presence of fire damp and coal dust.[A] The variety known as Flameless Securite consists of a mixture of nitrate and oxalate of ammonia and di-nitro-benzol.

[Footnote A: See paper by S.B. Coxon, North of Eng. Inst. Mining and Mech. Eng., 11, 2, 87.]

Kinetite.—A few years ago an explosive called "Kinetite"[A] was introduced, but is not manufactured in England. It was the patent of Messrs Petry and Fallenstein, and consisted of nitro-benzol, thickened or gelatinised by the addition of some collodion-cotton, incorporated with finely ground chlorate of potash and precipitated sulphide of antimony. An analysis gave the following percentages:—

Nitro-benzol, 19.4 per cent. Chlorate of potash, 76.9 per cent. Sulphide of antimony nitro-cotton, 3.7 per cent.

[Footnote A: V. Watson Smith, Jour. Soc. Chem. Ind., January 1887.]

It requires a very high temperature to ignite it, and cannot, under ordinary circumstances, when unconfined, be exploded by the application of heat. It is little affected by immersion in water, unless prolonged, when the chlorate dissolves out, leaving a practical inexplosive residue.[A] It was found to be very sensitive to combined friction and percussion, and to be readily ignited by a glancing blow of wood upon wood. It was also deficient in chemical stability, and has been known to ignite spontaneously both in the laboratory and in a magazine. It is an orange- coloured plastic mass, and smells of nitro-benzol.

[Footnote A: Col. Cundill, R.A., "Dict. of Explosives," says: "If, however, it be exposed to moist and dry air alternately, the chlorate crystallises out on the surfaces, and renders the explosive very sensitive."]

Tonite No. 3 contains 10 to 14 per cent. of nitro-benzol (see Tonite). Trench's Flameless Explosive contains 10 per cent. of di-nitro-benzol, together with 85 per cent. of nitrate of ammonia, and 5 per cent. of a mixture of alum, and the chlorides of sodium and ammonia.

Tri-nitro-Toluene.—Toluene, C_{7}H_{8}, now chiefly obtained from coal- tar, was formerly obtained by the dry distillation of tolu-balsam. It may be regarded as methyl-benzene, or benzene in which one hydrogen is replaced by methyl (CH_{3}), thus (C_{6}H_{5}CH_{3}), or as phenyl- methane, or methane in which one hydrogen atom is replaced by the radical phenyl (C_{6}H_{5}), thus (CH_{3}C_{6}H_{5}). Toluene is a colourless liquid, boiling at 110 deg. C., has a specific gravity of .8824 at 0 deg. C., and an aromatic odour. Tri-nitro-toluene is formed by the action of nitric acid on toluene. According to Haeussermann, it is more advantageous to start with the ortho-para-di-nitro-toluene, which is prepared by allowing a mixture of 75 parts of 91 to 92 per cent. nitric acid and 150 parts of 95 to 96 per cent. sulphuric acid to run in a thin stream into 100 parts of para-nitro-toluene, while the latter is kept at a temperature between 60 deg. to 65 deg. C., and continually stirred. When the acid has all been run in, this mixture is heated for half an hour to 80 deg. C., and allowed to stand till cold. The excess of nitric acid is then removed. The residue after this treatment is a homogeneous crystalline mass of ortho-para-di-nitro- toluene, of which the solidifying point is 69.5 deg. C. To convert this mass into tri-nitro derivative, it is dissolved by gently heating it with four times its weight of sulphuric acid (95 to 96 per cent.), and it is then mixed with 1-1/2 times its weight of nitric acid (90 to 92 per cent.), the mixture being kept cool. Afterwards it is digested at 90 deg. to 95 deg. C., with occasional stirring, until the evolution of gas ceases. This takes place in about four or five hours.