204 
MR. ABEL’S RESEARCHES ON GUN-COTTON. 
(deposited upon the fibre by the hard water in which the material had been washed) 
than other samples. There was consequently present in such specimens a larger amount 
of matter capable of neutralizing acid, if liberated by the action of heat, than in others ; 
and therefore the period would be proportionately delayed, in those instances, when 
the development of free acid would first become evident. The Stowmarket samples had 
been submitted to the “ silicating ” process, which consists in impregnating the gun- 
cotton with a dilute solution of soluble glass, afterwards drying it, and finally washing it 
in spring- or rain-water. The result of this treatment is that small proportions of alka- 
line and earthy carbonates are deposited upon the fibre in addition to what it would 
acquire by simple long-continued exposure to running water. This circumstance tends 
to explain why the Stowmarket gun-cotton experimented with, though generally much 
more seriously affected by protracted exposure to 100° C. than the Waltham Abbey 
samples, appeared to resist change in several instances for much longer periods than the 
latter. 
The proportion and nature of the mineral matters in gun-cotton may, therefore, as 
shown by those experiments, exert a very notable effect upon the behaviour of the mate- 
rial when exposed to high temperatures. But the results of subsequent experiments 
have demonstrated most decisively that the influence which the presence of earthy or 
alkaline carbonates, mechanically distributed in small proportion through a mass of 
gun-cotton, exerts upon the effects produced by exposure to heat, is in many instances 
not confined to a simple delay of the indications of change furnished by the development 
of acid ; it may also manifest itself in much more important directions, namely, by 
actually retarding and even considerably limiting, if not altogether preventing, the spon- 
taneous decomposition of the gun-cotton itself. These effects are of such evident import- 
ance in connexion with the question of the stability of gun-cotton, that they have been 
made the subject of extensive experimental inquiry, the results of which will be given 
under a special head. 
3. The different behaviour of the samples of gun-cotton operated upon in the foregoing 
experiments cannot be ascribed to differences in the proportions of matter soluble in 
ether and alcohol present in them. The four samples (experiments 41, 45, 47, 52) which 
withstood to the greatest extent the action of heat, contained 1-8, 2, 2T, and 2*31 per 
cent, of soluble matter, which numbers represent the lowest, the mean, and almost the 
highest proportions of soluble matter in the Waltham Abbey gun-cotton. Again, some 
samples of Waltham Abbey products, containing identical proportions of soluble matter, 
behaved very differently, as may be seen by comparing experiments 41 and 42, 45 and 
46, 51 and 52. The want of connexion between the proportion of matter soluble in 
ether and alcohol, and the stability of the sample, is perhaps even more strikingly 
demonstrated by results obtained with specimens of Stowmarket and Hirtenberg 
products. Samples containing equal proportions of soluble matter, as in experiments 
56 and 57, 59 and 60, 65 and 72, behaved very differently, while others, in which the 
amount of soluble matter differed very considerably, exhibited similar behaviour upon 
