GUN COTTON 323 itensity, it burns in the open air inexplosively. If ignited by a powerful flame, it flashes like gunpowder; but if ignited by a fulminate, it detonates with tremendous violence. This " sympathetic " quality, by virtue of which the total combustion seems to follow the character of the ignition, is difficult to explain, and also presents some anomalies. According to Mr. Abel, about five grains of fulminate of mercury is required to produce detonation ; but ten times that quantity of chloride of nitrogen, rongly confined, is required to produce the ime result, while 350 grains of nitro-glyce- le, exploded in contact with massive gun cotton, fails to produce any other result than the mechanical disintegration of the mass. The rate at which detonation is propagated along a >w of gun-cotton disks has been investigated >y Mr. Abel and Capt. A. Noble, who found it be about 18,000 feet a second. A sound wave would travel through such a mass with less than one fourth of this velocity, and such rapidity of transmission seems explicable only on the assumption that ignition is carried along le surface by the expanding gases, driven by their tension. The products of combustion of cotton vary with the conditions under which it is exploded. They consist of varying >roportions of carbonic oxide, carbonic acid, gas, nitric oxide, nitrogen, and water, analyses by Lieut. Von Karolyi of the sian army gave, by volume : CONSTITUENTS. I. II. Carbonic oxide 28-55 28-95 Carbonic acid . 19-11 20-82 Marsh gas 11-17 7-24 Nitric oxide 8-83 8-56 12-67 CarkTn . 1-85 1-82 Aqueous vapor 21-93 25-34 8-16 Total... 100-00 100-00 The first analysis is that of gases obtained by exploding the cotton in vacuo, and the second ~)y exploding it in strong iron tubes placed in mortar. Many attempts have been made to ibstitute gun cotton for gunpowder in mili- tary operations. A brief examination of the jhenomena of explosions will show that it can lever be advantageously used as an agent for the propulsion of projectiles. In the explosion of all detonating compounds the conversion of the solid or liquid material into elastic gases is so rapid that it may be regarded as practically, though not strictly, instantaneous. The sub- sequent expansion of these gases by their elas- tic force must be the motive power of the shot; and at the instant of concussion this is so great, in the case of gun cotton confined in a small receptacle, that no material can withstand it, unless the chamber be much larger than the bulk of the gun cotton. If the explosive en- ergy be reduced by using a large chamber, or by mixing the compound with some inert ma- terial, then the total elastic effort is no greater than that of gunpowder. It can be rendered serviceable in this relation only by depriving it of the very excess of energy which can alone give greater velocity to a projectile ; and there is no probability that any means can be em- ployed to compensate for this loss of energy, as may be done with gunpowder. As a bursting charge for hollow projectiles, the destructive efficiency of gun cotton is very great; but ex- perience has shown its extreme liability to ex- plode prematurely by the shock of the dis- charge. Its detonation in contact with hard materials shatters or disintegrates them. Wood and rock are completely pulverized by it, while hollow projectiles are often blown into innu- merable fragments. But these effects extend to a small distance only from the centre of ex- plosion, and at the distance of a few feet the effect is no greater than that obtained from gunpowder. The use of gun cotton in blasting is favored by its indifference to water, and by its great explosive effect, estimated by Combes and Flandin to be fourfold, by S6guier sixfold, and b.y Tamper double that of gunpowder. These estimates are based upon practical ex- periment. They indicate a saving in practice by the use of shallower bore holes. But the relative costliness of gun cotton, the danger of premature explosions in charging holes, its varying quality, its liability to spontaneous de- composition, and its too rapid combustion, which gives it a tendency to shatter or pulverize ra- ther than lift and loosen the rock, have proved great obstacles to its use. Many of these ob- jections have been obviated, it is asserted, by the manufacture of compound gun cotton above described, and by the admixture of less explosive or non-explosive substances, such as common cotton. Extensive and successful use was made of gun cotton in the quarries of Co- morn and in the removal of the ancient walls of Vienna. In the former case, the cotton was wound in solid cylinders; in the latter the cylinders were hollow. Punshon, an English manufacturer, claims that he makes an article of definite explosive power in grades, suited to any use, the quality of each grade being uni- form. He also asserts that his gun cotton prep- arations will not explode or decompose spon- taneously, and can be stored or transported without danger. In these preparations, the gun cotton is coated with a powder of sugar, or potash or other salts, which separates the fibres. By changing the quality of this pow- der the desired grade of exploding force is ob- tained. Bleekrode found that gun cotton, when moistened with an inflammable liquid, like carbon sulphide, ether, benzine, or alcohol, and ignited by the electric spark or otherwise, does not explode, but burns slowly. Hence he recommends that when stored it should be covered with such a liquid, which could be re- moved by evaporation. A new variety of gun cotton is made by immersing cotton for 15 minutes in a saturated solution of chlorate of potassa. It is chemically more allied appa j
