[Footnote A: Tonite No. 1 was patented by Messrs Trench, Faure, and
Mackie, and tonite Nos. 2 and 3 by Trench alone.]
Tonite is extensively used in torpedoes and for submarine blasting, also for quarries, &c. Large quantities were used in the construction of the Manchester Ship Canal. Among its advantages are, that the English railways will take tonite on the same footing as gunpowder; it is a very dense material; if wetted it can easily be dried in the sun; it very readily explodes by the use of a proper detonator; while it burns very slowly and without the least danger; the cartridges being waterproofed, it can be employed in wet bore holes, and it can be tamped with water; and finally, as it contains sufficient oxygen to oxidise the carbon, no carbonic oxide (CO) gas is formed, i.e., its detonation is perfect. It is a very safe explosive to use, being little susceptible to either blows or friction.
Not long ago, a committee, composed of Prof. P. Bedson, Drs Drummond and Hume, Mr T. Bell, one of H.M. Inspectors of Coal Mines, and others, in considering the problem whether the fumes produced by the combustion of tonite were injurious to health, carried out a series of experiments in coal mines for this purpose. The air at the "intake" was analysed, also the air of the "return," and the smoky air in the vicinity of the shot holes. The cartridge was surrounded by the flame-extinguishing mixture, and packed in a brown paper bag. During the first experiment nineteen shots were fired (= 6.29 lbs. tonite). The "return" air showed only a trace of carbonic oxide gas (CO). At the second experiment thirteen shots were fired (= 4.40 lbs. tonite), and analysis of the air of the "return" showed that CO was present in traces only, whilst the fumes contained only 1.9 to 4.8 parts per 10,000.
~Dangers in connection with the Manufacture of Guncotton, &c.~—Of all the nitro compounds, the least dangerous to manufacture are gun-cotton and collodion-cotton. The fact that the Stowmarket Factory is within five minutes' walk of the town shows how safe the manufacture of this explosive is regarded. With the exception of the nitration and the compression into blocks or discs, the whole process is worked with a large excess of water, and the probability of an explosion is thus reduced to a minimum. Among the precautions that should, however, be taken, are—first, the careful extraction of the resinous and soluble substances from the cotton before nitration, as it was shown many years ago by Sir F.A. Abel that the instability of the gun-cotton first manufactured in England and Austria was chiefly due to these compounds. They are generally removed by boiling the cotton in a soda solution.
The actual nitration of cotton is not a dangerous operation, but the operations of wringing in the hydro-extractors, and washing the nitro- cotton after it leaves the first centrifugal machine, are somewhat so. Great care should be taken that the wrung-out nitro-cotton at once comes in contact with a large excess of water, i.e., is at once immersed entirely in the water, since at this stage it is especially liable to decomposition, which, once started, is very difficult to stop. The warmer the mixture and the less water it contains, the more liable it is to decomposition; hence it is that on warm and damp days the centrifugal machines are most likely to fire. The commencement of decomposition may be at once detected by the evolution of red fumes. Directly the gun-cotton is immersed in the large quantity of water in the beater and poacher it is safe.
In order that the final product may be stable and have good keeping qualities, it is necessary that it should be washed completely free from acid. The treatment in the beater and poacher, by causing the material to assume the state of a fine pulp, in contact with a large quantity of water, does a good deal to get rid of the free acid, but the boiling process is absolutely necessary. It has been proposed to neutralise the free acid with a dilute solution of ammonia; and Dr C.O. Weber has published some experiments bearing upon this treatment. He found that after treatment with ammonia, pyroxyline assumed a slightly yellowish tinge, which was a sure sign of alkalinity. It was then removed from the water, and roughly dried between folds of filter paper, and afterwards dried in an oven at 70° C. After three hours, however, an explosion took place, which entirely destroyed the strong copper oven in which the nitro- cotton (about one oz.) had been drying. The explosion was in some respects remarkable. The pyroxyline was the di-nitro-cellulose (or possibly the penta-nitro?), and the temperature was below the igniting point of this material (40° C. would have been a better temperature). Dr Weber determined the ignition point of his di-nitro-cellulose, and found it to be 194° to 198° C., and he is therefore of opinion that the explosion was due to the treatment of the partially washed material with ammonia. A certain quantity of ammonium nitrate was probably formed, and subsequently dried upon the nitro-cellulose, in a state of very fine subdivision. The faintest trace of acid would then be sufficient to bring about the explosive ignition of the ammonium nitrate.
The drying of gun-cotton or collodion-cotton is also a somewhat dangerous operation. A temperature of 40° C. (104° F.) should not be exceeded, and thermometers should be placed in the nitro-cotton, and the temperature frequently observed. An electric alarm thermometer is also a useful adjunct to the cotton drying house. Great care must also be taken that there are no exposed hot-water pipes or stoves in the drying house, as the fine gun-cotton dust produced by the turning or moving of the material upon the shelves would settle upon such pipes or stoves, and becoming hot, would be very sensitive to the least friction. The floor also should be covered with linoleum or indiarubber. When hot currents of air are made to pass over the surface of gun-cotton, the gun-cotton becomes electrified. It is important, therefore, to provide some means to carry it away. Mr W.F. Reid, F.I.C., was the first to use metal frames, carriers, and sieves, upon which is secured the cloth holding the gun-cotton, and to earth them.
The compression of gun-cotton into blocks, discs, &c., is also attended with considerable risk. Mr O. Guttmann, in an interesting paper upon "The Dangers in the Manufacture of Explosives" (Jour. Soc. Chem. Ind., No. 3, vol. xi., 1892), says: "The compression of gun-cotton into cartridges requires far more care than that of gunpowder, as this is done in a warm state, and gun-cotton even when cold, is more sensitive than gunpowder. When coming out of the centrifugal machines, the gun-cotton should always pass first through a sieve, in order to detect nails or matches which may by chance have got into it. What has been said as to gunpowder presses applies still more to those for gun-cotton, although the latter are always hydraulic presses. Generally the pistons fit the mould perfectly, that is to say, they make aspiration like the piston of a pump. But there is no metal as yet known which for any length of time will stand the constant friction of compression, and after some time the mould will be wider in that part where the greatest compression takes place. The best metal for this purpose has proved to be a special steel made by Krupp, but this also is only relatively better; for pistons I prefer hard cast iron. If the position of the moulds and pistons is not exactly the same in all cases, what the Germans call 'Ecken' (English 'binding') will take place, viz., the mould will stand obliquely to the piston, and a dangerous friction will result." "Of course, it is necessary to protect the man working the hydraulic valves during compression. At Waltham Abbey they have a curtain made of ship's hawsers, which is at the same time elastic and resistant." Mr Guttmann has found that a partition wall 12 inches thick, made of 2-inch planks, and filled with ground cinders, gives very effective protection. A door in this partition enables the workman to get to the press, and a conical tube penetrates the wall, enabling the man to see the whole work from a safe standpoint. The roof, or one side of the building, should be of glass, so as to give the explosion a direction.
~Trench's Fire-extinguishing Compound~ is manufactured by the Cotton Powder Company at Faversham, and is the invention of Mr George Trench, F.C.S., the manager of the Company. The object of the invention is to surround the cartridges of tonite, when used in coal mines, with a fire- extinguishing compound. If a charge of tonite, dynamite, or gelatine dynamite is put inside a few ounces of this mixture, and then fired, not the least trace of flame can be observed, and experiments appear to show that there is no flame at all. The compound consists of sawdust impregnated with a mixture of alum and chlorides of sodium and ammonia. Fig. 22 shows the manner of placing the tonite cartridge in the paper bag, and surrounding it with the fire-extinguishing compound, aa. The attachment of the fuse and detonator is also shown.
[Illustration: FIG. 22.—TRENCH'S FIRE-EXTINGUISHING CARTRIDGE.]