182 
MR. ABEL’S RESEARCHES ON GUN-COTTON. 
on account of the variations in the gun-cotton itself, and partly because different expe- 
rimenters have examined the products of its metamorphosis at different stages. 
The accounts published by De Luca, Bonet, and Blondeau, between 1861 and 1865, 
of their investigations into the changes which gun-cotton undergoes spontaneously, 
include nearly all the results previously described in one or other of the published 
papers on this subject. 
The following is a general statement of the changes which gun-cotton, preserved in 
bottles partly or perfectly closed, has been obseryed to undergo by exposure to light, 
and of the nature of the products of decomposition. 
In the first instance nitrous vapours make their appearance, the atmosphere in the 
vessel becoming sometimes of a deep orange tint. The gun-cotton acquires considerable 
acidity, exhibits a peculiar pungent odour, and gradually contracts, so that it eventually 
occupies only a small proportion of the original volume. During this period a consi- 
derable proportion of nitric acid accumulates in the mass, and the decomposition proceeds 
after a time with increased rapidity, especially if the vessel be exposed to sunlight. The 
contracted gun-cotton gradually becomes more or less friable, its explosiveness is notably 
reduced, it yields a highly acid extract to water, in which, besides nitric acid, small pro- 
portions of glucose, of formic and oxalic acids, and of cyanogen have been detected. The 
material sometimes contracts to such an extent as to form a very compact somewhat hard 
mass, but in general it ultimately passes over with more or less rapidity into a brownish 
gum-like mass, 'which at first is rendered very porous by the evolution of gas-bubbles, 
and which becomes lighter in colour and friable after a time. This ultimate product of 
the decomposition of gun-cotton has been found to contain glucose and oxalic acid in 
considerable proportions, besides a gum-like substance, formic acid, cyanogen, and an 
organic acid which by some observers is considered to possess novel characters, while 
Divers believes that he has identified pectic and parapectic acids in the product of a 
decomposed specimen*. The amorphous mass has also been found to evolve ammonia 
when heated with a solution of potassic hydrate. 
In some instances the gun-cotton is described as having undergone other intermediate 
changes, but the greatest discrepancies exist between the observations of even the most 
practised experimenters regarding the periods within which the decomposition of gun- 
cotton has become manifest, and the conditions under which the changes have occurred. 
* The observations of Divers regarding the occurrence of the pectic acids among the products of decompo- 
sition of - gun-cotton, have been confirmed by the results of examination of a very large number of specimens 
obtained by the decomposition of gun-cotton at high temperatures under various conditions. The reactions of 
pec-tie and of para- and meta-pectie acids have been so frequently obtained that these substances must be 
regarded as general products of the gradual decomposition of gun-cotton. On the other hand, although thq 
most careful search has frequently been made for glucose, only two instances of its existence were established 
by the fermentation test. It appears probable that the reduction of cupric salt from an alkaline solution has 
in many instances been accepted as a sufficient indication of the presence of glucose, while, in reality, this 
reaction has been furnished by the pectic acids produced. Small quantities of cyanogen have on several occasions 
been detected among the products of very gradual decomposition of gun-cotton by heat. 
