ME. ABEL’S EESEAECHES ON GUN-COTTON. 
247 
“ silicated ” gun-cotton in the two other boxes (2 and 3). Moreover, this gun-cotton, 
though exposed to heat for two months longer than the unsilicated gun-cotton (in No. 1 
box), was found upon examination to have evolved considerably less acid. 
(6) The gun-cotton which had been uniformly impregnated with only O' 3 per cent, of 
sodic carbonate furnished no signs whatever of development of heat up to the period 
when the experiment was interrupted, having been, at that time, exposed for ten months 
to a heated atmosphere, the temperature of which ranged, for seven hours daily during 
seven months, between 54° and 55°. It is much to be regretted that a careful examina- 
tion of the contents of this box after so prolonged and severe an exposure to heat was 
prevented by an accident. 
(7) The condition of the gun-cotton after exposure to heat in the three boxes first 
removed was very similar. Although the material was found to be highly impregnated 
with nitric oxide and nitrous acid (the development of which there is every reason to 
believe had been very considerably promoted by the large metal surfaces of the boxes 
which were in close contact with the gun-cotton), the decomposition had not proceeded 
in any one of the boxes to such an extent as to produce an alteration in the explosive 
and other properties of the gun-cotton. When the latter had been purified from the 
free acid developed in it, no difference could be discovered between it and the original 
material, except that it had become slightly bleached. The gun-cotton from boxes 1 
and 2, after being purified by digestion in alkaline water and subsequent repeated 
washing in distilled water, was dried, repacked and returned to the hot-air chamber. It 
now contained no carbonates whatever by which the destructive effect of acid, if deve- 
loped, could be retarded or prevented ; but the boxes, each containing eleven pounds of 
this gun-cotton, were exposed to heat for three months, the temperature of the air ranging 
from 54° to 55°*5 for seven hours daily, and no indication whatever of development of 
heat was obtained in either instance. (The purified gun-cotton from boxes 3 and 4 was 
also repacked and returned to the chamber at later periods.) 
After the heat-experiments described above had been continued between eight and 
nine months, two barrels, fitted with tubes for thermometers, each containing about 
twenty-three pounds of gun-cotton which was neither “ silicated” nor impregnated with 
sodic carbonate, were placed in the chamber, the object being to obtain direct proof of 
the extent of influence exerted by the metal surfaces in the cases employed in the other 
experiments, upon the behaviour of the gun-cotton itself. 
Two other much smaller metal-lined cases, each containing about five pounds of gun- 
cotton, were also placed in the chamber at this time ; one of them was filled with a 
sample which had already been subjected to severe exposure to heat and had subse- 
quently been purified from acid, and the other was filled with disks prepared by com- 
pressing gun-cotton which had been reduced to pulp. Lastly, an ammunition case con- 
taining twenty-three pounds of gun-cotton, which was impregnated with a more con- 
siderable quantity of sodic carbonate than employed in the first experiment, was added 
to the contents of the chamber. The heating of the latter to 54°-55° was continued 
2 l 2 
