Under the direction of M. von Arx, experiments with dynamite have been lately undertaken in Switzerland, with the view especially to investigate what degree of dangor is offered by it in transportation. Already the first blasting experiments gave proof of the extraordinary power of this explosive. The explosion took place in from two to four minutes. Two and a half cartridges detached a mass of six and a half cubic meters of hard rock in a bore hole of I'll meters depth and three centimeters diameter; and in another experiment, three and a half cartridges, when exploded in a hole of 1*32 meters depth, loosened a mass of seventy-one cubic meters. Similar results were obtained in cast and wrought iron, and in water. A cartridge that was allowed to explode in the river Aare, threw a large volume of water to a considerable hight. In order to investigate the danger of spontaneous explosion, the dynamite was first subjected to chemical analysis. In treating it with alcohol, 76'6 per cent of nitro-glycer-in were extracted, while a solid residuum of a reddish white color was left, that consisted chiefly of silica, and small admixtures of lime, oxide of iron, and alumina. The priming of the copper fusee was found to consist of fulminate of mercury. The effective portion of dynamite is consequently the nitro-gly-cerin, while the other substances serve merely to diminish the danger of spontaneous decomposition. A blasting material of this kind may explode by great variations of temperature, by intense solar rays, shocks, electricity, and spontaneous decomposition. This last mentioned possibility must yet be referred to experimental investigation. However, the experiments have furnished very satisfactory results in regard to the other influences. Dynamite was not acted* upon by steam, and when not inclosed was consumed slowly in the firs, but when inclosed, it exploded with considerable force. The effect of light was experimented upon by a mirror, the dynamite burning in its focus with light puffings, without explosion, and when exposed to a jess concentrated light, no effect was found to take place. The experiments which were undertaken in order to examine the effect of concussion proved that explosion will only take place when the material is placed between two very hard surfaces, and when the shock is very powerful. However, if concussion takes place between iron and stone, explosion is rarely produced, and never so between iron and wood. Inclosed dynamite explodes easier, but the intensity of the shock must in all cases be great. It was also thought of importance to examine whether the dynamite would explode by lightning. It was for this reason exposed to the discharge sparks of a large Leyden jar, and those of a powerful induction apparatus. As, however, explosion ensued in no instance, from the experiments the experts drew the conclusion that the transportation of dynamite is not attended with any danger. Changes of temperature, strong heat, even fire, and intensely concentrated solar rays do not produce explosion, so long as the material itself is not inclosed in vess.ds possessing great powers of res'stance. And, while it will decompose by shocks, these will scarcely ever be intense enough to offer real danger. As regards spontaneous decomposition, there is nothing known about the new blasting material ; however, it is evident that the earthy admixture must prevent a rapid decomposition, and only allow a gradual and slow one. Taken all in all, the dynamite offers considerably less danger than nitroglycerin, and, since it is nearly equal to it in explosive power, there is no reason why the latter composition should not soon be replaced by the former.
This article was originally published with the title "On Experiments with Dynamite" in Scientific American 21, 21, 330 (November 1869)