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Page:Popular Science Monthly Volume 21.djvu/801

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EXPLOSIONS AND EXPLOSIVES.

The latter dissolves the former, and the result is an elastic, gelatinous, semi-transparent mass, which is easily cut or torn apart, and shows no trace whatever of nitro-glycerine on handling. Its explosive properties are unaffected by contact with water, and in this respect it is the most useful of all the high explosives for military purposes. With the change in the physical condition of the two components comes also a change in the ease of explosion; these two bodies, each of itself highly explosive, form when united one which is quite the reverse. When unconfined, a primer of fifty grains of fulminate will cause the explosion of but a very small portion of a charge, the rest being torn in pieces; if, however, it be strongly confined, so that the blow of the fulminate exerts its whole force, which is propagated through the gelatine, it then explodes with a violence as great as that of nitro-glycerine, if not somewhat greater. This latter point has not been fully determined, but the probabilities are that the expansion of the constituents of the gelatine is more complete and is accompanied with more heat than is the case with nitro-glycerine alone. The gelatine freezes at 40° Fahr., and in this state is fired with no difficulty whatever, being in this respect much superior to dynamite. When subjected to a pressure of two hundred and fifty pounds to the square inch, no nitro-glycerine is separated; the union between the two constituents seems to be complete and definite. If subjected to the action of flame, it takes fire less readily than dynamite, but burns very much like it, with perhaps a greater strength of flame, as if urged by a bellows. When heated to 100° it softens, but does not become at all greasy, and there is no exudation of nitro-glycerine. Explosion by the application of heat takes place at about 420°; but it is found that by the addition of a small amount of camphor, say four per cent, it will bear an increased heat of 100° before explosion. Experiments made with the gelatine thus camphorated show that the camphor exercises no deleterious effect upon the strength of the material, while rendering it less like jelly, and more like that form of confection known as fig-paste. Six per cent of camphor may be added without harm, but any greater quantity materially diminishes the explosive effect. Portions of this gelatine, both pure and camphorated, have been subjected to a constant heat of 100° for more than six weeks, and no exudation of the dangerous nitro-glycerine has been observed. It will not explode under circumstances which ordinarily render certain the detonation of either nitro-glycerine or dynamite—that is to say,' a quantity of the gelatine will resist the shock of the detonation of another quantity placed within a very few feet of it; if very near, it may take fire and burn, but detonation will not ensue unless the two masses are almost in actual contact, and even then it will not always occur. It further possesses the property of permitting the impact of a ball from a gun without exploding, while both dynamite and gun-cotton may be readily detonated by a blow of this kind. All