THE HISTORY OF EXPLOSIVE AGENTS. 
507 
were required to accomplish the result attained by 0-32 grm. of either of the confined 
fulminates, or by 2 grms. of the mercuric fulminate, unconfined by any strong envelope 
(p. 499). 
With the view of ascertaining whether the relative power of different explosive agents 
to accomplish the detonation of gun-cotton appears to be in direct proportion to the re- 
lative mechanical effects of their explosion (i, e. to the work performed by them upon a 
body placed in contact with them), a series of experiments was instituted with the object 
of comparing this particular action of the several explosive materials. 
A thin and uniform copper sheet was cut up into square pieces of equal dimensions, 
and these were similarly supported at their comers only. Equal quantities of the four 
different explosive agents, the mercury- and silver-fulminates and the chloride and iodide 
of nitrogen, were employed ; in the case of the two former the weights were directly 
determined, but in the case of the latter they were estimated as accurately as possible 
by the methods given at pages 504 and 506. In some experiments the fulminates were 
placed in direct contact with the copper, in others, with the view of comparing them 
accurately with the iodide of nitrogen, they were placed upon thin cards which rested 
upon the sheet copper. The iodide of nitrogen was always used in this way, but as for 
obvious reasons the chloride of nitrogen could not be thus employed, it was placed in 
very thin watch-glasses which rested upon the copper sheet. The force brought to bear 
upon the copper support was obviously not diminished to any important extent by the 
expenditure necessitated in the fracture of the thin glass surface. 
The following are the results deduced from repeated experiments with a series of dif- 
ferent proportions of the several explosive agents. 
The mechanical effect of the explosion of silver-fulminate in small quantities, freely 
exposed to air, was decidedly greater than that of the other three substances when ex- 
ploded under the same conditions. 0 - 07 grm. (1 grain) of this fulminate produced a 
deep and very sharply defined indentation in the copper sheet. A corresponding quan- 
tity of the iodide of nitrogen, made to cover about the same surface of the sheet metal, 
produced a decidedly less deep and more rounded indentation. The explosion of an 
equal quantity, and even more than double that amount, of chloride of nitrogen, with 
its surface freely exposed to air, did not even break the thin watch-glass which contained 
it ; if, however, similar quantities of the liquid were covered with a thin layer of water, 
their mechanical action upon the copper was decidedly greater than that of the exposed 
iodide. 0‘07 grm. (1 grain) of mercuric fulminate, freely exposed, produced no effect 
whatever upon the copper sheet, but if enclosed in a thin case of sheet metal, its mecha- 
nical action was greater than that of silver-fulminate when exposed to air. 1 grm. 
(15 - 5 grains), 1*62 grm. (25 grains), and 3-24 grms. (50 grains) were exploded without 
producing any indentation upon the copper, provided that the little heap was inflamed 
by the application of a heated body to some portion of their exposed surfaces ; but if the 
source of heat was situated at the base of the heap, being entirely enclosed by the fulmi- 
3 y 2 
