3206 
PROFESSOR ABEL'S CONTRIBUTIONS TO THE 
HISTORY OF EXPLOSIVE AGENTS * 
HE degree of rapidity with which an explosive substance 
undergoes metamorphosis, as also the nature and results 
of that metamorphosis, are, in the greater number of instances, 
susceptible of several modifications by variations of the circum- 
stances under which the conditions essential to chemical change 
are fulfilled. Gun-cotton furnishes an excellent illustration of 
the manner in which such modifications may be brought about. 
If a loose tuft or large mass of gun-cotton-wool be inflamed in 
open air by contact with, or proximity to, some source of heat, 
the temperature of which is about 135° C. or upwards, it flashes 
into flame with a rapidity which appears almost instantaneous, 
the change being attended by a dull explosion, and resulting in 
the formation of vapours and gaseous products, of which nitro- 
gen-oxides form important constituents. If the gun-cotton be 
in the form of yarn, thread, woven fabric, or paper, the rapidity 
of its inflammation in open air is reduced in proportion to the 
compactness of structure or arrangement of the twisted, woven, 
or pulped material ; and if it be conyerted by pressure into com- 
pact masses, solid throughout, the rate of its combustion will be 
still further reduced. If to a limited surface of gun-cotton, when 
in the form of a fine thread or of a compactly pressed mass, a 
source of heat is applied, the temperature of which is sufficiently 
high to establish the metamorphosis of the substance but not 
adequate to inflame the products of that change (carbonic oxide, 
hydrogen, &c.), the rate ef burning is so greatly reduced that 
the gun-cotton may be said to smoulder without flame ; the 
reason being that the products of change, which consist of gases 
and vapours, continue, as they escape into air, to abstract the 
heat developed by the burning gun-cotton so rapidly that it 
cannot accumulate to an extent sufficient to develop the usual 
combustion, with flame, of the material. For similar reasons, 
if gun-cotton be kindled in a rarefied atmosphere, the change 
developed will be slow and imperfect in proportion to the degree 
of rarefaction, so that, even if an incandescent wire be applied, 
in a highly rarefied atmosphere, to the gun-cotton, it can only 
be made to undergo the smouldering combustion, until the pres- 
sure is sufficiently increased by the accumulating gases to reduce 
very greatly the rate of abstraction, by these, of the heat neces- 
sary for the rapid combustion or explosion of the substance. If, 
on the contrary, the escape of the gases from burning gun- 
cotton be retarded, as by enclosing it in an envelope or bag of 
paper, or in a yessel of which the opening is loosely closed, the 
escape of heat is impeded until the gases developed can exert 
sufficient pressure to pass away freely by bursting open the 
envelope or aperture, and the result of the more or less brief 
confinement of the gases isa more rapid or violent explosion, 
and consequently more perfect metamorphosis of the gun-cotton. 
So, within obvious limits, the explosion of gun-cotton by the 
application of flame or any highly heated body is more perfect 
in proportion to the amount of resistance offered in the first 
instance to the escape of ihe gases ; in other words, in propor- 
tion as the strength of the receptacle enclosing the gun-cotton, 
and the consequent initial pressure developed by the explosion, 
is increased. Hence, while gun-cotton has been found too rapid 
or violent in its explosive action when confined in guns, and has 
proved a most formidable agent of destruction if enclosed in 
metal shells or other strong receptacles, it has hitherto been 
found comparatively harmless as an explosive agent if inflamed 
in open air or only confined in weak receptacles. Modifications, 
apparently slight, of the manner in which the source of heat is 
applied to explosive agents, when exposed to air under cir- 
cumstances in other respects uniform, suffice to modify the 
character of their explosions in a remarkable manner. Thus a 
modification of the position in which the source of heat is placed 
with reference to the body of a charge of gunpowder, which is 
only partially confined, suffices to alter altogether the character 
of the explosion produced. 
The product of the action of nitric acid upon glycerine, which 
is known as nitroglycerine or glonoine, appears to be susceptible 
of only two varieties of decomposition. Ifa sufficient source of 
leat be applied to some portion ofa mass of this liquid in open 
air, it will inflame and burn gradually without any explosive 
effect ; and even when nitroglycerine is confined, the develop- 
ment of its explosive foree by the simple application of flame or 
of other sources of heat, by the ordinary modes of operation, is 
* An abstract of a paper, by Prof. Abel, F.RS., Chemist to the War 
Department, in the Philosophical Transactions. 
NATURE 
[ Aug. 18, 1870 
difficult and very uncertain. 
to a sudden concussion, such as is produced by a smart though 
not very violent blow from a hammer upon some rigid surface 
on which the nitroglycerine rests, the latter explodes with a 
sharp detonation, just as is the case with gun-cotton. Only that 
portion of the explosive agent detonates which is immediately 
between the two surfaces brought into sudden collision ; the con- 
finement of this portion between the hammer and the support, 
combined with the instantaneous decomposition of the portion 
struck, prevent any surrounding freely exposed portions from 
being similarly exploded by the detonation. A similar result is 
obtained if any explosive compound or mixture be submitted to 
a sufficiently sharp and violent blow, but the tendency of sur- 
rounding particles to become inflamed by the dctonation is in 
direct proportion to the rapidity of explosive action of the sub- 
stances. The practical difficulties and uncertainty which attend 
attempts to develop the explosive force of nitroglycerine by the 
agency of flame or the simple application of any highly heated 
body, even when the material is confined in strong receptacles 
(such as iron shells or firmly tamped blast-holes), appeared fatal 
to any useful application of the powerful explesive properties of 
this substance, until M. Alfred Nobel’s persevering labours to 
utilise nitroglycerine, eventually resulted in the discovery of a 
method by which the explosive power of the liquid could be de- 
veloped with tolerable certainty. M. Nobel first employed gun- 
powder asa vehicle for the application of nitroglycerine. By 
impregnating the grains of gunpowder with that liquid, he added 
considerably to the destructive force of the powder when exploded 
in the usual way in closed receptacles. M. Nobel’s subsequent 
endeavours to apply nitroglycerine fer se were based upon the 
belief that its explosion might be effected by raising some por- 
tion of a quantity of the liquid to the temperature necessary for 
its violent decomposition, whereupon an initiative explosion 
would be produced which would determine the explosion of any 
quantity of the substance. 
The circumstance that nitroglycerine, or any preparation of 
that substance, may be violently exploded when freely exposed 
to air, by the explosion in contact with it of a small confined 
charge of gunpowder, or of a detonating substance, while other 
modes of explosion by the application of heat or flame, which 
have been described by M. Nobel, only develop explosion under 
special conditions, points to a decided difference between the 
action of the two modes of ignition, and appears to indicate that 
it is not simply the heat developed by the chemical change of the 
gunpowder or detonating powder which determines the explosion 
of the nitroglycerine. An experimental investigation of this 
subject has Jeft no doubt on my mind that the explosion of nitro- 
glycerine through the agency of a small detonation is due, at any 
rate in part, to the mechanical effect of that detonation, and that 
this effect may operate in exploding the nitroglycerine, quite 
independently of any direct action of the heat disengaged. 
The readiness and certainty with which gunpowder, gun- 
cotton, and other explosive substances may be detonated through 
the agency of a blow from a hammer or a falling body, are 
regulated by several circumstances ; they are in direct proportion 
to the weight of the falling body, to the height of its fall, or the 
force with which it is impelled downwards, to the velocity of its 
motion, to the mass and rigidity, or hardness, of the support or 
anvil upon which the body falls ; to the quantity and mechanical 
condition of the explosive agent struck, and to the ready explo- 
sibility of the latter. Thus a sharp blow from a small hammer 
upon an iron surface will detonate gunpowder with yery much 
greater certainty than the simple fall of a heavy hammer, or than 
a comparatively weak blow from the latter. It is very difficult, 
by repeated blows applied at very brief intervals, to ignite gun- 
cotton, if placed upon a support of wood or lead, both of whieh 
materials yield to the blow, the force set into operation by 
that blow being transferred through the explosive agent and 
absorbed in work done upon the material composing the 
support. If, however, the latter be of iron, which does not 
yield permanently to the blow of the hammer, the detonation of 
these substances is readily accomplished. If the quantity of ex- 
plosive agent employed be so considerable as to form a thick 
layer between the hammer and support, the force applied appears 
to be to so great an extent absorbed in the motion imparted to 
the particles of the comprehensible mass, that its explosion is 
not readily accomplished ; and if the material be in a loose or 
porous condition (as, for example, in a state of powder or of 
loose wool), much work has to be accomplished in moving 
particles of the mass through a comparatively considerable space, 
But if the substarice be submitted ~ 
