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XIV. Contributions to the History of Explosive Agents . 
By F. A. Abel, Treas. Chem. Soc. 
Received March 9, — Read April 15, 1869. 
The 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 in- 
stances, susceptible of several modifications by variations of the circumstances 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 instan- 
taneous, the change being attended by a dull explosion, and resulting in the formation 
of vapours and gaseous products, of which nitrogen-oxides form important consti- 
tuents. 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 con- 
verted by pressure into compact 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 ade- 
quate to inflame the products of that change (carbonic oxide, hydrogen, &c.), the rate 
of burning is so greatly reduced that the gun-cotton may be said to smoulder without 
flame, as shown by me in a communication to the Royal Society in 1864*; 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 develope 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 rare- 
faction, 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 pressure is sufficiently increased by the accumulating gases to reduce very greatly the 
rate of abstraction, by these, of the heat necessary for the rapid combustion or explosion 
of the substance f. 
If, on the contrary, the escape of the gases from burning gun-cotton be retarded, as 
* Proceedings of the Royal Society, vol. xiii. p. 213. t Ibid. p. 205 . 
MDCCCLXIX. 3 U 
