44 



NATURE 



\_May 8, 1879 



violently, even when only a particle of the mass is subjected to a 

 sufficient disturbing influence, has been exploded without the 

 usual demonstrations of force, by the transmitted effect of a 

 detonation of mercuric fulminate. In these instances the violence 

 of the concu-sion produced by the initiative detonation was only 

 just bordering on that required for the development of detonation, 

 and it appears probable that only some small portion of the mass 

 operated upon was in a condition or position favourable to the 

 action of the initiative blow. The remainder of the mass would 

 then be dispersed by the gases developed from the detonated 

 portion ; in some instances the particles would be inflamed at the 

 moment of their dispersion, in others, they would even escape 

 ignition. 



Some experiments made in firing at masses of compressed gun- 

 cotton, differently arranged and of different thicknesses, with a 

 Martini- Henry rifle, at short ranges, afforded interesting confir- 

 mation of the correctness of the explanation given of the operation 

 of a bluw upon masses of explosive material under different 

 conditions. Disks of gun-cotton of the same density and dia- 

 meter, but differing in thickness, were fired at ; they were freely 

 suspended, and their distance from the marksman was in all in- 

 stances 100 yards. The thinnest disks were simply perforated by 

 the bullets ; somewhat thicker disks were inflamed by the impact 

 of the bullet, while still thicker disks, fired at under the same 

 conditions, were exploded. No instance of detonation was, 

 however, obtained. These differences in effect, obtained with 

 masses of different thickness and weight, are due to the differ- 

 ence in their power to resist mechanical motion when struck by 

 the bnllet, and in the different amount of resistance to penetra- 

 tion presented by the thin and the thicker disks. 



It has been explained that nitro-glycerine may be largely 

 diluted with inert solid matters without its sensitiveness to 

 detonation being reduced, while its detonation in open air 

 becomes very much facilitated, because the tendency of its 

 particles to yield to the force of a blow or detonation, is very 

 greatly diminished. But if a solid explosive agent is diluted with 

 inert stlid matter the case is different ; for in such a mixture of 

 the finely divided solid with non-explosive solid particles, there 

 must be a partial and sometimes a complete separation of the 

 particles of the explosive by the interposed inert particles with 

 which it is diluted ; hence the sensitiveness to detonation is 

 reduced, and its transmission by the particles is retarded or 

 altogether impeded, by a diminution of the extent of contact 

 between the substance to be detonated and the initiative detona- 

 tion, and by the barrier which the interposed non-explosive 

 particles oppose to the transmission of detonation. In experi- 

 ments made in this direction with finely divided gun-cotton, it 

 was found that although dilution with an inert solid, applied in 

 the solid jorm, reduced the sensitiveness of the material to deto- 

 nation, this was not the case when it was incorporated with a 

 salt soluble in water, the mixture being then compressed while in 

 the wet state. The compressed masses thus obtained were, when 

 dried, in a condition of greater rigidity than could be attained 

 by submitting undiluted gun-cotton to considerably more power- 

 ful pressure, because the crystallisation of the soluble salt used 

 as the diluent upon evaporation of the water, cemented the 

 particles composing the mass more rigidly together. The gun- 

 cotton was therefore presented in a form more capable of 

 resisting the mechanical action of a small charge of fulminate, 

 than a more highly compressed undiluted gun-cotton, and hence 

 the reduction in sensitiveness due to the detonation of the explosive 

 compound is nearly counterbalanced by the greater rigidity im-. 

 parted to the mass. If a soluble oxidising agent (a nitrate or 

 chlorate) be employed as the diluting material, the predisposition 

 to chemical reaction between it and the gun-cotton (which is 

 susceptible of some additional oxidation), appears to operate in 

 conjunction with the effect of the salt in imparting rigidity to the 

 mixture, thus rendering the latter quite as sensitive to the deto- 

 nating action of the minimum fulminate charge as undiluted gun- 

 cotton. Moreover, the interesting fact has been conclusively 

 established, that these compressed mixtures of gun-cotton with a 

 nitrate or a chlorate are much less indifferent to the influence of 

 detonating nitroglycerine than gun-cotton in its pure state, 

 chlorated and nitrated gun-cotton being detonated with certainty 

 by means of \ oz. of nitro-glycerine. 



If compressed gun-cotton is diluted by impregnating the mass 

 with a liquid, or with a solid which is introduced into the mass 

 in a fused state, its susceptibility of detonation is reduced to a 

 very much greater extent than by a corresponding quantity of a 

 sohd inert body, incorporated as such with the gun-cotton, the 



cause being the converse of that which operates in preventing a 

 reduction of the sensitiveness to detonation of nitro-glycerine by 

 its dilution with an inert solid. In this case the explosive liquid 

 envelopes the solid diluent, and remains continuous throughout, 

 occupying the spaces which exist between the solid particles ; 

 hence detonation is readily established and transmitted. But in 

 the case of the solid explosive the diluent, which is liquid, or 

 at any rate is introduced into the mass in the liquid state, 

 envelopes each particle of the solid, so that a filn« of inert 

 material surrounds each, isolating it from its neighbours, and 

 thus opposing resistance to the transmission of detonation, which 

 is proportionate to the original porosity or absorbent power of 

 the mass. 



While compressed gun-cotton, in the air-dry state, is detonated 

 by 2 grains of mercuric fulminate imbedded in the material, its 

 detonation by 15 grains, applied in the same manner, becomes 

 doubtful when it contains 3 per cent, of water, over and above 

 the 2 per cent, which exists normally in the air-dry substance. 

 Specimens which had been impregnated with oil or soaked in 

 melted fat and allowed to cool could not be detonated by means 

 of 15 grains of fulminate. These diluted samples of gmn-cotto» 

 could only be detonated by adding very considerably to the 

 power of the initiative detonation ; 100 grains of confined ful- 

 minate generally failed to detonate gun-cotton containing from 

 10 to 12 per cent, of water, and if the amount reached 17 per 

 cent., 200 grains of fulminate were needed to insure its detona- 

 tion. 



But moist or wet compressed gun-cotton is decidedly more 

 susceptible of detonation by (dry) compressed gun-cotton itself 

 than by mercuric fulminate. 



Thus ICX3 grains of dry gun-cotton, detonated through the 

 agency of the ordinary fulminate fuze, suffice to detonate wet 

 gun-cotton containing 17 per cent, of water, though this result is 

 somewhat uncertain. If the diluting agent amounts to 20 per 

 cent., detonation is not certain with less than l oz. of dry gun- 

 cotton, and if the compressed material be completely saturated 

 with water (i.e., containing 30 to 35 per cent.), 4 oz. of the air- 

 dry substance, applied in close contact, are needed to insure its 

 detonation. 



Detonation is transmitted through tubes from dry compressed 

 gun-cotton to a moist disk of the material with the same facility 

 as to the dry substance ; and this is also the case with regard to 

 the propagation of detonation from one mass of moist gun-cotton 

 to another, in open air, all the pieces being ranged in a row, in 

 contact with each other, provided that the piece first detonated 

 does not contain less water than the others to which detonation 

 is transmitted. 



Gun-cotton containing 12 to 14 per cent, of water is ignited 

 with much difficulty on applying a highly heated body. As it 

 leaves the hydraulic press upon being converted from the pulped 

 state to masses having about the density of water, it contains 

 about IS per cent, of water ; in this condition it may be throw* 

 on to a fire or held in a flame without exhibiting any tendency to 

 burn ; the masses may be perforated by means of a red-h«t iron 

 or with a drilling tool, and they may with perfect safety be cut 

 into slices by means of saws revolving with great rapidity. If 

 placed upon a fire and allowed to remain there, a feeble flame 

 flickers over the surface of the wet gun-cotton from time to time 

 as the exterior becomes sufficiently dry to inflame; and in this 

 way a piece of compressed gun-cotton will bum away very 

 gradually indeed. A pile of boxes containing in all 6 cwt. of 

 gun-cotton, impregnated with about 20 per cent, of water, when 

 surrounded by burning wood and shavings in a wooden building 

 was very gradually consumed, the gun-cotton burning as already 

 described when the surfaces of the masses became partially dried. 

 Quantities of wet gun-cotton of 20 cwt. each, packed in one 

 instance in a large, strong wooden case, and, in the other, in a 

 number of strong packing cases, have been placed in small maga- 

 zines, very substantially constructed of concrete and brickwork. 

 Large fires were kindled around the packages in each building, 

 the doors being just left ajar. The entire contents of both 

 buildings had burned away, without anything approaching ex- 

 plosive action, in less than two hours. This comparatively great 

 safety of \\ et gun-cotton, coupled with the fact that its detonation 

 in that condition may be readily accomplished through the 

 agency of a small quantity of dry gun-cotton, which, through 

 the medium of a fulminate fuse or detonator, is made to act as 

 the initiative detonating agent, gives to gun-cotton important 

 advantages over other violent explosive agents for purposes which 

 involve the employment of more or less considerable quantities 



