May 15, 1879] 



NATURE 



67 



RECENT CONTRIBUTIONS TO THE HISTORY 

 OF D ETON A TING AGENTS ', 



III. 

 "M OBEL has observed that if, instead of making use of the most 

 explosive form of gun-cotton, or trinitrocellulose, a lower 

 product of nitration of cellulose (the so-called soluble or collodion 

 gun-cotton) is added to nitro-glycerine, the liquid exerts a pecu- 

 liar solvent action upon it, the fibrous material becoming gela- 

 tinised while the nitro-glycerine becomes at the same time fixed, 

 the two substances furnishing a product having almost the 

 characters of a compound. By macerating only from 7 to 10 

 per cent, of soluble gun-cotton with 90 to 93 per cent, of nitro- 

 glycerine, the whole becomes converted into an adhesive plastic 

 material, more gummy than gelatinous in character, from which, 

 if it be prepared with sufficient care, no nitro-glycerine will 

 separate even by its exposure to heat in contact with bibulous 

 paper, or by its prolonged immersion in water, the components 

 being not easily susceptible of separation, even through the 

 agency of a solvent of both. As the nitroglycerine is only 

 diluted with a small proportion of a solidifying agent which is 

 itself an explosive (though a somewhat feeble one), this blasting 

 gelatine, as Nobel has called it, is more powerful not only than 

 dynamite, but also than the mixture of a smaller quantity of 

 nitro-glycerine with the most explosive gun-cotton, as the liquid 

 substance is decidedly the most violent explosive of the two. 

 Moreover, as nitro-glycerine contains a small amount of oxygen 

 in excess of that required for the perfect oxidation of its carbon 

 and hydrogen constituents, while the soluble gun-cotton is de- 

 ficient in the requisite oxygen for its complete transformation 

 into thoroughly oxidised products, the result of an incoporation 

 of the latter in small proportion with nitro-glycerine, is the 

 production of an explosive agent which contains the proportion 

 of oxygen requisite for the development of the maximum of 

 chemical energy by the complete burning of the carbon and 

 hydrogen, and Lence this blasting gelatine should, theoretically, 

 be even slightly more powerful as an explosive agent than pure 

 nitro-glycerine. 



That such is the case has been well established by numerous 

 experiments, but although this blasting gelatine may be deto- 

 nated like dynamite by means of small quantities of confined 

 detonating composition, when it is employed in strongly-tamped 

 blast -holes, or under conditions very favourable to the develop- 

 ment of great initial pressure, it behaves very differently from 

 that material, or other solid though plastic preparations of nitro- 

 glycerine, if the attempt is made to detonate it when freely 

 exposed to the air or only partially confined . It not only needs 

 a much more considerable amount of strongly confined detonat- 

 ing composition than dynamite and similar preparations do, to 

 bring about a detonation with it under those conditions ; but 

 when as much as fifteen or twenty grains of confined fulminate 

 are detonated in direct contact with it, although a sharp explo- 

 sion occurs, little or no destructive action results, and a con- 

 siderable portion of the charge operated upon is dispersed in a 

 finely-divided condition. 



In comparing the effects of these nitro-glycerine preparations 

 with each other and with compressed gun-cotton and prepara- 

 tions of it, by detonating equal quantities quite unconfined upon 

 iron plates, the results appear to establish great superiority, in 

 ptoint of violence, of action, or destructive effect, of the more 

 rigid explosive agents (the gun cotton preparations). Thus, 

 employing iron plates I inch thick (supported upon an anvil with 

 a central cavity), and 4 oz. of each material unconfined, the 

 charges being all about the same diameter, exploded by deto- 

 nators of equal strength, and simply resting upon the upper 

 surface of the plate, compressed gun-cotton produced a 

 considern'^l ? indentation of the upper surface of the plate, 

 and long cracks in the lower surface ; a species of nitrated 

 gun-cotton, called tonite, produced a much shallower in- 

 dentation, though still a very marked one, but did not 

 crack the lower surface. Dynamite produced only a very 

 slight impression upon the plate, and none could be detected by 

 the eye on the plate upon which the blasting gelatine was 

 exploded. The difficulties, brought out by past experience, 

 which attend the contrivance of really comparative tests of the 

 explosive power of such substances as those under discussion, is 

 well exemplified by the foregoing results, which were influenced 



^ Weekly Evening Lecture at the Royal Institution, Friday, March 21, 

 1879. By Professor Abel, C.B., F.R.S. Revised by the Author. Continue* 

 from p. 45. 



to the maximum extent by the physical characters of the several 

 substances when thus applied, in a perfectly unconfined condi- 

 tion, so that the particles were free to yield to the force of the 

 initiative detonation in proportion to their mobility. But, for this 

 very reason, these experiments afford excellent illustration of the 

 extent to which the development of detonation and the sharpness 

 of its transmission through the mass is influenced not only by the 

 inherent sensitiveness of the substance to detonation, but also by 

 the degree of proneness of their particles to yield mechanically 

 to the force of a blow as applied by an initiative detonation. 

 Thus, although in comparing two substances of similar physical 

 characters, compressed gun-cotton and compressed nitrated gun- 

 cotton or tonite, the superiority of the piu-e compound over the 

 mixture, in point of sharpness and violence of action, is well 

 illustrated, a comparison of the result furnished by the weakest 

 of the four explosive agents tried, viz., tonite, with that of the 

 substance which should be superior to all the others in explosive 

 force (i.e. the blasting gelatine) demonstrates the important in- 

 fluence which the comparatively great rigidity of the mass in the 

 one case exerts in favouring the completeness and sharpness oi 

 its detonation in open air, and the great disadvantage under 

 which the other explosive is applied, arising out of the plastic 

 and therefore readily yielding nature of the material. But if, 

 by exposure to a moderate degree of cold, this plastic nitro- 

 glycerine preparation is made to freeze, its detonation upon an 

 iron plate produces an indentation, as well as a destructive effect 

 upon the lower surface of the plate, very decidedly greater than 

 those furnished by the corresponding amount of pure com- 

 pressed gun cotton. Similarly, the effect produced by the deto- 

 nation of dynamite upon a plate of the kind used, is but little 

 inferior to that of gun-cotton, and decidedly greater than that of 

 tonite, if it is employed in the frozen condition. 



A series of experiments has been made with cylinders of lead 

 having a central perforation I '3 inch in diameter extending to a 

 depth of 7 inches and leaving solid metal beneath of a thickness 

 ranging from 3*5 to 55 inches, according to the size of the 

 cylinders used. These furnished results of considerable interest 

 as illustrating the action of these several detonating agents. 

 Charges of i'2S oz. of each explosive substance were used 

 throughout the experiments, and were placed at the bottoms of 

 the holes. By the detonation of the charges the cylindrical 

 holes in the lead were enlarged into cavities of a pear shape (and 

 sometimes approaching the spherical form) of various diameters ; 

 in some instances the metal was besides partially torn open in a 

 line from the bottom of the charge-hole to the circumference of 

 the lower face of the cylinder ; and in the case of some of the 

 gun-cotton charges, the fissure in the metal in this direction 

 was complete, the base of the block being separated from the 

 remainder, in the form of a cone. In the first place the portions 

 of the holes above the charges were simply left open ; in the 

 subsequent experiments they were filled up to a level with the 

 upper surface, with dry, fine, loose sand, or with water. The 

 dimensions of the cylinders were increased in successive experi- 

 ments until, in the case of every one of the explosives used, the 

 mass of metal was sufficiently great to resist actual fracture at the 

 base of the cylinder. Under the condition of these experiments, 

 more or less considerable resistance being opposed to the mecha- 

 nical dispersion of the plastic explosi\e substances, their detona- 

 tion was greatly facilitated, though even then, the holes in the 

 lead blocks being left open to the air, some amount of the 

 blasting gelatine evidently escaped detonation ; the widening 

 of the upper part of the charge-hole, in experiments of this 

 nature made with the gelatine, indicated that detonation was trans, 

 mitted to small portions dispersed in the first instance and in the act 

 of escaping from the block. In all the experiments, whether the 

 holes were left open or filled with sand or water, the effect pro- 

 duced upon the base of the block by the detonation of compressed 

 gun-cotton, was considerably more violent than with the other 

 explosive agents, indicating a sharpness of action which was 

 only shared by the blasting gelatine when used in a frozen state 

 in one of these experiments. The dimensions of the cavities 

 produced by the gelatine were, at the largest part, considerably 

 greater than those produced by the dynamite and nitrated gun- 

 cotton (tonite), and slightly greater than those of the gun-cotton 

 charges; but in the latter, the fracture of the base of the 

 cylinder gave rise in most of the experiments to an escape of 

 force, so that in these cases the effects of the detonation could 

 not be well compared by measurements of the cavities. When 

 the gelatine was converted by freezing into a rigid mass its 

 superiority in explosive force even over compressed gun-cottott 



