492 
MR. F. A. ABEL’S CONTRIBUTIONS TO 
the application of slight disturbing impulses of a mechanical or chemical nature, would 
appear at first sight only to a small extent susceptible of modifying influences similar to 
the above. The direct application of but little heat, or the production of a slight 
increase of temperature by gentle friction or pressure, or by the development of chemical 
action in some very small portions of the mass, suffices to explode the chloride or 
iodide of nitrogen, or silver-fulminate ; and the explosion of one particle clevelopes an 
impulse so greatly in excess of that required to disturb the chemical equilibrium 
existing among the molecules of the mass, that instantaneous decomposition ensues 
throughout. The great proneness to change of these substances when exposed to a 
slight disturbing influence, is illustrated by the fact that a concussion imparted to the 
air in a spacious apartment in which the iodide of nitrogen has been placed, by means 
of a small explosion or detonation, or even by the violent slamming of a door, suffices to 
bring about the explosion of that substance. But even if these bodies be so confined 
that an initial resistance is offered to the escape of the gaseous products of their explo- 
sion, the violence of the detonation is greatly increased, the development of explosive 
force being restricted to the instant of rupture of the envelope by the compressed gases. 
Thus the violence of explosive force exerted by a small quantity of silver-fulminate, con- 
fined in a case of stout sheet metal, is very decidedly greater than if a corresponding 
quantity be enclosed in metal foil, or freely exposed to air and inflamed in the same 
manner. The violence of explosion of iodide of nitrogen has been found to be very 
decidedly increased by enclosing it in an evelope or shell of plaster of Paris, or, better 
still, in a case of sheet metal, Avhile the chloride of nitrogen explodes with but compa- 
ratively little violence unless it is confined. The reputation which this substance has 
enjoyed of being the most violent explosive body known, appears to have been due to 
the fact that experiments on its explosion have always been conducted with a covering 
of water upon the material. Three or four drops (about 0T4 grm. = 2 grains) placed 
in a watch-glass covered only with a thin layer of water, explode with a sharp report 
when touched with turpentine, and almost pulverize the glass ; but similar quantities, 
of which the upper surfaces were exposed to air, have been repeatedly exploded in 
watch-glasses without breaking the latter. 2 grms. of the chloride, contained in a watch- 
glass, and covered with a thin layer of water, were placed upon a small solid cylinder of 
hard papier mache which rested upon paving. A violent explosion was produced by 
touching the chloride with turpentine, the watch-glass was pulverized and dispersed, and 
the cylinder was greatly shattered, fragments being projected in all directions. 4 grms. 
of the chloride, with the upper surface exposed to air and placed upon a similar cylinder 
of papier mache, produced a comparatively very feeble explosion ; the watch-glass was 
broken, but the cylinder was not in the slightest degree affected, and remained undis- 
turbed in its original position. A repetition of the experiment with 4 grms. of the 
chloride, enclosed by a thin layer of water, produced complete disintegration of the 
cylinder. It appears from these results that in the case of the chloride of nitrogen, 
the decomposition of which is of an instantaneous character, the resistance offered at the 
