Nitro-Explosives: A Practical Treatise Part 12

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 quant.i.ties 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 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 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 gla.s.s 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 quant.i.ty 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 pa.s.sage 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 c.o.c.k 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 c.o.c.k 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 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 quant.i.ty 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 quant.i.ty 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 was.h.i.+ng 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 ma.s.ses 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, and para-di-nitro, melting point 172, are also produced. The melting point of the commercial product is between 85 to 87 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 circ.u.mstances of roburite in coal mines, is yet of so p.r.o.nounced 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'

a.s.sociations, 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 a.n.a.lysis 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 a.s.serted 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 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 ca.n.a.l runs through the centre, separating the chemical from the explosive portions of the works, and the Lancas.h.i.+re and Yorks.h.i.+re Railway runs up to the doors. Besides sending large quant.i.ties 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 C., and of ammonium nitrate as 1,130 C., whereas that of blasting gelatine is as much as 3,220 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 Rotebro 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 C., but does not commence to separate before a temperature of 200 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 a.s.sume 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 sh.e.l.ls, 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. c.o.xon, _North of Eng. Inst. Mining and Mech. Eng._, 11, 2, 87.]

~Kinet.i.te.~--A few years ago an explosive called "Kinet.i.te"[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 a.n.a.lysis 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 circ.u.mstances, 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 ma.s.s, 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 C., has a specific gravity of .8824 at 0 C., and an aromatic odour. Tri-nitro-toluene is formed by the action of nitric acid on toluene. According to Haussermann, 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 to 65 C., and continually stirred. When the acid has all been run in, this mixture is heated for half an hour to 80 C., and allowed to stand till cold. The excess of nitric acid is then removed. The residue after this treatment is a h.o.m.ogeneous crystalline ma.s.s of ortho-para-di-nitro- toluene, of which the solidifying point is 69.5 C. To convert this ma.s.s 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 to 95 C., with occasional stirring, until the evolution of gas ceases. This takes place in about four or five hours.

The operation is now stopped, the product allowed to cool, and the excess of nitric acid separated from it. The residue is then washed with hot water and very dilute soda solution, and allowed to solidify without purification. The solidifying point is 70 C., and the ma.s.s is then white, with a radiating crystalline structure. Bright sparkling crystals, melting at 81.5 C. may, however, be obtained by recrystallisation from hot alcohol. The yield is from 100 parts di-nitro-toluene, 150 parts of the tri-nitro derivative. Haussermann states also that 1:2:4:6 tri-nitro- toluene can be obtained from ordinary commercial di-nitro-toluene melting at 60 to 64 C.; but when this is used, greater precautions must be exercised, for the reactions are more violent. Moreover, 10 per cent. more nitric acid is required, and the yield is 10 per cent. less. He also draws attention to the slight solubility of tri-nitro-toluene in hot water, and to the fact that it is decomposed by dilute alkalies and alkaline carbonates--facts which must be borne in mind in was.h.i.+ng the substance.

This material is neither difficult nor dangerous to make. It behaves as a very stable substance when exposed to the air under varying conditions of temperature (-10 to +50 C.) for several months. It cannot be exploded by flame, nor by heating it in an open vessel. It is only slightly decomposed by strong percussion on an anvil. A fulminate detonator produces the best explosive effect with tri-nitro-toluene. It can be used in conjunction with ammonium nitrate, but such admixture weakens the explosive power; but even then it is stated to be stronger than an equivalent mixture of di-nitro-benzene and ammonium nitrate. Mowbray patented a mixture of 3 parts nitro-toluol to 7 of nitro-glycerine, also in the proportions of 1 to 3, which he states to be a very safe explosive.

~Faversham Powder.~--One of the explosives on the permitted list (coal mines) is extensively used, and is manufactured by the Cotton Powder Co.

Ltd. at Faversham. It is composed of tri-nitro-toluol 11 parts, ammonium nitrate 93 parts, and moisture 1 part. This explosive must be used only when contained in a case of an alloy of lead, tin, zinc, and antimony thoroughly waterproof; it must be used only with a detonator or electric detonator of not less strength than that known as No. 6.

~Nitro-Naphthalene.~--Nitro-naphthalene is formed by the action of nitric acid on naphthalene (C_{10}H_{8}). Its formula is C_{10}H_{7}NO_{2}, and it forms yellow needles, melting at 61 C.; and of di-nitro-naphthalene (C_{10}H_{6}(NO_{2})_{2}), melting point 216 C. There are also tri-nitro and tetra-nitro and [alpha] and [beta] derivatives of nitro-naphthalene.

It is the di-nitro-naphthalene that is chiefly used in explosives. It is contained in roburite, securite, romit, Volney's powder, &c. Fehven has patented an explosive consisting of 10 parts of nitro-naphthalene mixed with the crude ingredients of gunpowder as follows:--Nitro-naphthalene, 10 parts; saltpetre, 75 parts; charcoal, 12.5 parts; and sulphur, 12.5 parts.

He states that he obtains a mono-nitro-naphthalene, containing a small proportion of di-nitro-naphthalene, by digesting 1 part of naphthalene, with or without heat, in 4 parts of nitric acid (specific gravity 1.40) for five days.

Quite lately a patent has been taken out for a mixture of nitro- naphthalene or di-nitro-benzene with ammonium nitrate, and consists in using a solvent for one or other or both of the ingredients, effected in a wet state, and then evaporating off the solvent, care being taken not to melt the hydrocarbon. In this way a more intimate mixture is ensured between the particles of the components, and the explosive thus prepared can be fired by a small detonator, viz., by 0.54 grms. of fulminate.

Favier's explosive also contains mono-nitro-naphthalene (8.5 parts), together with 91.5 parts of nitrate of ammonia. This explosive is made in England by the Miners' Safety Explosive Co. A variety of roburite contains chloro-nitro-naphthalene. Romit consists of 100 parts ammonium nitrate and 7 parts pota.s.sium chlorate mixed with a solution of 1 part nitro- naphthalene and 2 parts rectified paraffin oil.

~Ammonite.~--This explosive was originally made at Vilvorde in Belgium, under the t.i.tle of the Favier Explosive, consisting of a compressed hollow cylinder composed of 91.5 per cent. of nitrate of ammonia, and 8.5 per cent. of mono-nitro-naphthalene filled inside with loose powder of the same composition. The cartridges were wrapped in paper saturated with paraffin-wax, and afterwards dipped in hot paraffin to secure their being water-tight. The Miners' Safety Explosives Co., when making this explosive at their factory at Stanford-le-Hope, Ess.e.x, abandoned after a short trial the above composition, and subst.i.tuted di-nitro-naphthalene 11.5 per cent.

for the mono-nitro-naphthalene, and used thin lead envelopes filled with loose powder slightly pressed in, in place of the compressed cylinders containing loose powder. The process of manufacture is shortly as follows:--132-3/4 lbs. of thoroughly dried nitrate of ammonium is placed in a mill pan, heated at the bottom with live steam, and ground for about twenty minutes until it becomes so dry that a slight dust follows the rollers; then 17-1/2 lbs. of thoroughly dry di-nitro-naphthalene is added, and the grinding continued for about ten minutes. Cold water is then circulated through the bottom of the pan until the material appears of a lightish colour and falls to powder. (While the pan is hot the whole ma.s.s looks slightly plastic and of a darker colour than when cold.) A slide in the bottom of the pan is then withdrawn, the whole ma.s.s working out until the pan is empty; it is now removed to the sifting machine, brushed through a wire sieve of about 12 holes to the inch, and is then ready for filling into cartridges. The hard core is returned from the sifting machine and turned into one of the pans a few minutes before the charge is withdrawn.