1868. | its Claims as a New Industrial Agent. 153 
explosive. A burning match may be introduced into it without 
producing any explosion; the match may be made to ignite the 
liquid, but combustion will cease as soon as the match ceases to 
burn. Nitro-glycerine may even be burned by means of a cotton- 
wick or a strip of bibulous paper, as oil from a lamp, and as harm- 
lessly. It remains fixed and perfectly unchanged at 212° Fah.; if 
heated to about 360°, however, it explodes. Kopp says that it may 
be volatilized by a regulated heat without decomposition, but if it 
boils, detonation becomes imminent, and hence, when it is dropped 
on a metal plate which is hot enough to cause it to boil it will 
decompose with a somewhat violent detonation. A plate not actually 
red-hot will cause this change ; if, however, the plate be red-hot, a 
drop of nitro-glycerine falling on it will immediately take fire and 
burn like a grain of gunpowder. At temperatures below from 48° 
to 45° Fah., it becomes a glassy crystalline mass, but is otherwise 
unchanged. It was crystallized nitro-glycerine which exploded on 
the Town Moor of Newcastle. Notwithstanding the great quantity 
of oxygen which is contained in this substance, and the powerful 
affinity which phosphorus and potassium have for that element, 
they have no effect on nitro-glycerme. If prepared perfectly pure 
it is totally devoid of any tendency to volatilize, and it may be kept 
for an indefinite period of time without showing any proneness to 
spontaneous decomposition. 
Nitro-glycerine may be decomposed with the greatest of ease by 
treatment with caustic potash, which resolves it into glycerine and 
nitric acid. This is certainly the most effectual means of rendering 
it permanently harmless, although there are other substances which 
will bring about its decomposition without any explosion. The 
extraordinary power exerted by nitro-glycerine during its explosion 
is undoubtedly the most interesting property which this substance 
possesses. The practical utilization of this explosive power was at 
first thought impossible, because it was observed that a spark would 
not produce any explosion at all, and that a blow from a hammer 
or some similar instrument would only produce a detonation that 
was limited exclusively to the part struck. In using all other 
ordinary explosives, such as gunpowder and gun-cotton, it is prac- 
tically necessary to employ fire, either as a spark or a flame, and as 
this would be of no use in the case of nitro-glycerine, some other 
mode of exploding it had to be resorted to. Mr. Nobel, who was 
the first person to demonstrate the possibility of using nitro-glycerine 
as a new industrial agent, hit upon the method now universally 
adopted, namely, percussion, or rather concussion. When a quan- 
tity of nitro-glycerine is spread in a thin layer over the surface of 
a hard stone, an anvil, or other metallic mass, and then percussed, 
or sharply struck with a hammer, only that portion actually struck 
explodes or detonates, so that percussion pure and simple is prac- 
