The New Gresham Encyclopedia Part 15

_Propellant Explosives._--The chief propellants arc nitrocellulose, also called nitrocotton or guncotton, and nitroglycerine.

_Nitrocellulose._--The chief sources of cellulose are wood and cotton. When cotton is plentiful, nitrocellulose is made as follows. Cotton-waste is hand-picked to get rid of string, wood, &c.; it is opened out by a teasing-machine, which tears off small portions at a time, and the cotton is then dried to about 0.5 per cent moisture content. The cotton is then nitrated with 'mixed acid'--a mixture of about 16 per cent nitric and 75 per cent sulphuric acid and about 8 per cent water--at 15 to 25 C. After the nitration, the acid is removed and the nitrocotton boiled up in water to stabilize it. Generally nitrocotton contains about 12 to 13 per cent of nitrogen. Wet nitrocotton is quite safe although it can be detonated, but dry nitrocotton is very dangerous. To-day, paper is usually made from wood-pulp, and when the cotton supplies of Germany were stopped during the European War, nitrocellulose had to be made from wood-pulp via a form of paper crepe prepared by the Germans from the pulp. For propellant purposes the nitrocotton is 'gelatinized', either alone or mixed with nitroglycerine, and is then worked up into different forms, such as wire, rods, grains, or tape, when it becomes controllable at will, so that the firing is not dangerous.

_Nitroglycerine._--Mixed acid, containing 41 per cent nitric acid and 57.5 per cent sulphuric acid, is brought to 22 C. by cooling coils of brine, and pure glycerine is injected into the acid at such a rate that no glycerine acc.u.mulates unchanged, and that the temperature is kept between 15 and 22 C. When all the glycerine has been added, the liquid is allowed to stand, and the nitroglycerine rises to the surface. It is run off to the wash-house, where it is washed free from acid and settled. The process is a dangerous one, and great care must be taken at every stage of the manufacture. The floors of the plant must be free from grit and dirt, no acc.u.mulation of liquid should be allowed anywhere, special clothing and rubber boots must be worn, no metallic implements may be used, and the plant should not be handed over for repairs except under the supervision of a responsible person. Nitroglycerine, when absorbed in a porous earth called 'Kieselguhr', is called dynamite. Kieselguhr, or simply guhr, absorbs twice its weight of nitroglycerine; cork charcoal absorbs nine times its weight. Dynamite cartridges are generally exploded by detonators.

_Preparation of Cordite; Nitrocellulose Tape (N.C.T.); Ballist.i.te; &c._--For cordite, the nitrocotton, freed from moisture, is mixed with nitroglycerine, and the paste or the cotton itself, if N.C.T. is to be made, is incorporated into a uniform dough with ether and alcohol. Some mineral jelly is added to render the explosive more stable. The dough is pressed through different sizes of dies according to the product desired.

For rifle powder fine cords are used; for artillery, thicker cords or flat ribbons of varying thicknesses are required. The cords or tapes from the dies are cut into suitable lengths, the solvents driven off, and the products blended to obtain uniform ballistic quality. For ballist.i.te the nitrocellulose is beaten up with nitroglycerine in water. The paste is freed from water, dried, and worked into horn-like sheets by means of rollers.

_High Explosives; Picric Acid._--At the outbreak of the European War the chief high explosive of the Entente Powers was lyddite (in France, melenite), also called trinitrophenol or picric acid. It is a bright-yellow solid, melting-point 122 C., sparingly soluble in water, and forms easily exploded metallic salts. It is now displaced by trinitrotoluene. Picric acid is made from phenol or carbolic acid. Phenol is obtained from coal-tar, or made synthetically from benzene. The phenol is sulphonated with strong sulphuric acid, and the phenol-sulphonic acid resulting is nitrated with strong nitric acid at about 100 C. Picric acid separates, and is washed free from mineral acid and dried. It may also be made from benzene without converting it into phenol thus: The benzene is chlorinated and gives chlorbenzene. This is nitrated into dinitrochlorbenzene, and is then treated with caustic soda to give dinitrophenol. This is then further nitrated into trinitrophenol or picric acid. Picric acid has a high melting-point, it must be used pure, is dissolved by water, it attacks metals forming dangerous compounds, and requires troublesome plant for its manufacture. Hence it has been displaced by more suitable substances, notably by trinitrotoluene.

_Trinitrotoluene_ (_T.N.T._).--This compound may now be made in a continuous plant. Mononitrotoluene is put in at one end of the plant and comes out as trinitrotoluene. Mixed nitric and sulphuric acid is put in at the end where the T.N.T. is obtained, and emerges, where mononitrotoluene is put in, as waste acid. T.N.T. in the past has also been made discontinuously thus: The toluene is nitrated by mixed acid into either mono- or dinitrotoluene, which is then trinitrated. The conversion into mononitrotoluene was used in the United Kingdom, France, Germany, Canada, and America; the conversion into dinitrotoluene was used in Italy. The T.N.T. emerges liquid, and is pa.s.sed over a rotating drum internally cold water cooled. A knife strips the thin congealed skin of T.N.T. off. This T.N.T. is only grade 3, and for conversion into grade 1 it must be purified. Formerly this was done by means of an organic solvent, but this dangerous and expensive method has been displaced by treatment either with phenol or sodium sulphite, which gives a grade 1 product. T.N.T. is a very pale yellow solid, melting-point 80.2 C., and therefore, melted by hot water, almost insoluble in water, burns quickly in the air, is inert, and comparatively safe to handle. It has displaced picric acid owing to its superiority, physically and chemically, over that substance.

_Tetryl or C.E._ (_Composition Exploding_).--Tetryl, also called tetranitrodimethylaniline, or more correctly trinitrophenylmethylnitramine, is a powerful high explosive, and is thus obtained. One part of dimethylaniline is dissolved in 10 parts of strong sulphuric acid, and the solution allowed to flow into strong nitric acid. The temperature should be kept below 40 C., else decomposition may occur. After nitration the yellow tetryl separates out, and is filtered off and water-washed till free from acid. It is then dried in hot-air stoves. Tetryl is much more dangerous than T.N.T., and is also more poisonous to handle. No other nitro-bodies were made in England on the large scale during the European War, but on the Continent, owing to the scarcity of raw materials, dinitrobenzene, dinitrotoluene, and nitronaphthalenes, and even less important nitro-bodies, were made. Their manufacture is similar to that of those already described. Probably none of these nitro-bodies so pressed into use is as good as T.N.T.

_Detonating Substances._--Though modern explosives are not easily exploded by a blow, they are sensitive to shock of given intensity, and lesser or different shocks will not suffice. The 'detonator' to produce the shock is set into the explosive. A complete sh.e.l.l carries two detonators. One, in the percussion cap, sets off the propellant charge which expels the projectile; the other, in the fuse in the nose of the sh.e.l.l, is ignited by the discharge of the gun, and detonates the high-explosive filling at a set interval after the discharge of the sh.e.l.l. Therefore, the sh.e.l.l can be exploded either in its flight when it is used as shrapnel sh.e.l.l, or on its arrival at its objective when it can be used for small-calibre artillery sh.e.l.l for field-guns, &c., or after its arrival when it is used for heavy howitzer and armour-piercing sh.e.l.l for destroying entrenched works, armoured forts, or ships. The manufacture of detonators is a very dangerous and delicate operation. Some substances (the copper acetylides) explode by a scratch, some (nitrogen iodide) by the touch of a feather or the tread of a fly, some explode even in solution when poured from one vessel into another (diazobenzeneperchlorates). Mercury fulminate is more often employed in the detonator, and is prepared from mercury, alcohol, and nitric acid. It is expensive, and most modern detonators consist of lead azide or salts of styphnic acid, with a layer of T.N.T. in a narrow aluminium cylinder.

The following is a list of the more important explosives, the different groups not being mutually exclusive:--

COAL-MINE EXPLOSIVES

_American._

Aetna Coal-mine Powder A, B, C: nitroglycerine explosive.

Black Diamond: 2A, 3A, 6L.F are nitroglycerine explosives; 5, 7, 8, ammonium nitrate explosives.

Carbonite: nitroglycerine 26, barium nitrate 4, pota.s.sium nitrate 29, wood-meal or starch flour 40, calcium carbonate 0.25.

Du Pont Permissible: nitroglycerine, ammonium nitrate, common salt.

Eureka: nitroglycerine and hydrated salt.

Mon.o.bel: ammonium nitrate, nitroglycerine, wood-meal, alkali chloride.

Red H1-7: ammonium nitrate explosives.

Trogan Coal Powder: contains nitrostarch.

_Austrian and Hungarian_.

Chlorat.i.t: during war was used in coal-mines.

Dynammon: ammonium nitrate, pota.s.sium nitrate, red charcoal.

Pannomite: nitroglycerine, collodion cotton, ammonium nitrate, dextrin, glycerine, nitrotoluene, alkali chloride.

t.i.tanite: Ammonium nitrate, trinitrotoluene, curc.u.ma charcoal.

_Belgian_.

Alsilite: ammonium nitrate, trinitrotoluene, ferrosilicon-aluminium, salt.

Baellnite: ammonium-nitrate, trinitrotoluene.

Densite: alkaline nitrates, trinitrotoluene, dinitrotoluene, and ammonium chloride.

Favier Explosives: mixtures in varying proportions containing ammonium nitrate, nitronaphthalene, paraffin, and resin; higher nitrated naphthalenes, pota.s.sium nitrate, and tetryl may be present.

Manufactured by the French Government as Explosifs N or Favier or Grisounites. Grisounites-couche for coal-mines have theoretical explosion temperatures of 1500 C., Grisounites-roche of 1900 C.

Ammonite, Westfalite, Bellite, Roburite are explosives of this type; other ammonites, Bellite Nos. 2 and 4, Faversham powder, and negro powder have ammonium or sodium chloride added.

_British._

Ammonite: Favier type; ammonium nitrate 75, dinitronaphthalene or other nitro-body, salt 20.

Bellite: ammonium nitrate and metadinitrobenzene; salt and starch may be added.

Bobbinite: the only gunpowder explosive allowed in England, not allowed in foreign mines; alkali nitrate, carbohydrates, wax may be added.

Shatters coal less than high explosives.

Cambrite: a n.o.bel carbonite plus 8 per cent of a cooling agent.

Denaby Powder: ammonium nitrate, alkali nitrate, T.N.T., ammonium chloride.

Dyn.o.bel: nitroglycerine 15, collodion cotton 0.5, nitro-body 3, ammonium nitrate 46, wood-meal 5.5, salt 29.5, magnesium carbonate 0.5.

Limit charge, 18 to 30 ounces. Swing of ballistic pendulum, 2.35 inches.

Monarkite: ammonium and sodium nitrate, nitroglycerine, nitrocotton, starch, mineral jelly, salt.

Mon.o.bel: ammonium nitrate, nitroglycerine, wood-meal, salt, alkali chloride, magnesium carbonate; nitro-body may be present.

Negro Powder: Grisounite type; ammonium nitrate 88, T.N.T. 10, graphite 2.

Rex Powder: nitroglycerine 12, salt 20, wood-meal 8, ammonium nitrate 60. Charge, 20 ounces. Swing of pendulum, 2.61 inches.

Rippite (Super): nitroglycerine, nitrocotton, pota.s.sium nitrate, borax, alkali chloride.

Roburite: ammonium nitrate 61, T.N.T. 16, salt 23.

Stomonal: nitroglycerine, ammonium nitrate, sodium nitrate, wood-meal, wheat-flour, salt, ammonium oxalate.

Thames Powder. Similar to above.

_Danish._

Aerolite: ammonium nitrate 78.1 per cent, pota.s.sium nitrate 7.5 per cent, sulphur 8.75 per cent, tar 2.5 per cent, sago-meal 1.25 per cent, manganese dioxide 1.25 per cent, resin 0.6 per cent.

Poudre Blanche Cornil: ammonium nitrate, alkali nitrate, nitronaphthalene, lead chromate.