THE ROYAL ARTILLERY INSTITUTION. 
127 
ON SOME PHENOMENA EXHIBITED BY GUN-COTTON AND GUNPOWDER 
UNDER SPECIAL CONDITIONS OF EXPOSURE TO HEAT.* 
BY E. A. ABEL, E.R.S. 
[COMMUNICATED BY THE SECRETARY, R.A.I.] 
The experiments upon which I have been engaged for some time past, in 
connexion with the manufacture and properties of gun-cotton, have brought 
under my notice some interesting points in the behaviour of both gun-cotton 
and gunpowder, when exposed to high temperatures, under particular 
conditions. I believe that these phenomena have not been previously 
observed, at any rate to their full extent, and I therefore venture to lay 
before the Royal Society a brief account of them. 
Being anxious to possess some rapid method of testing the uniformity of 
products obtained by carrying out General von Lent's system of manufacture 
of gun-cotton, I instituted experiments for the purpose of ascertaining 
wdiether, by igniting equal weights of gun-cotton of the same composition, 
by voltaic agency, within a partially exhausted vessel connected with a 
barometric tube, I could rely upon obtaining a uniform depression of the 
mercurial column, in different experiments made in atmospheres of uniform 
rarefaction, and whether slight differences in the composition of the gun¬ 
cotton would be indicated, with sufficient accuracy, by a corresponding 
difference in the volume of gas disengaged, or in the depression of the 
mercury. I found that, provided the mechanical condition of the gun¬ 
cotton, and its position with reference to the source of heat, were in all 
instances the same, the indications furnished by these experiments were 
sufficiently accurate for practical purposes. Each experiment was made 
with fifteen grains of gun-cotton, which were wrapped compactly round the 
platinum wire; the apparatus was exhausted until the column of mercury 
was raised to a height varying from 29 inches to 29*5 inches. The flash 
which accompanied the deflagration of the gun-cotton was apparently similar 
to that observed upon its ignition in open air; but it was noticed that an 
interval of time always occurred between the first application of heat (or 
incandescence of the wire) and the flashing of the gun-cotton, and that 
during this interval there was a very perceptible fall of the column of 
mercury. On several occasions, when the gun-cotton, in the form of 
"roving," or loosely twisted strand, was only laid over the wire, so that it 
hung down on either side, the red-hot wire simply cut it into two pieces, 
which fell to the bottom of the exhausted vessel, without continuing to 
burn. As these results appeared to indicate that the effects of heat upon 
gun-cotton, in a highly rarefied atmosphere, differed importantly from those 
observed under ordinary circumstances, or in a very imperfect vacuum, a 
* Reprinted from the “Proceedings of the Royal Society,” with permission of the President 
and Council. 
[VOL. IV.] 
17 
