186 
ME. ABEL’S KESEARCHES ON GUN-COTTON. 
results corresponding very nearly with those required by the formula G 18 H 23 0 15 7N0 2 , 
the compound C, or collodion gun-cotton, of which the composition was determined by 
Hadow. It was, moreover, readily soluble in a mixture of ether and alcohol, and 
furnished a good collodion-film. It is most probable, therefore, that a deficiency in the 
strength of the acids employed in its production had led to the manufacture, in this 
instance, of soluble and less explosive gun-cotton by Messrs. Hall. A specimen of this 
material, after having been very carefully washed, was dried and enclosed by me in a 
stoppered bottle, in which it has remained exposed to diffused daylight for upwards of 
three years. A piece of litmus-paper, enclosed with the gun-cotton, exhibited faint 
signs of reddening within three months after the first exposure, and within twelve 
months it was bleached. At this time the gun-cotton possessed a faint but decided 
cyanic odour ; no nitrous vapours were perceptible within the bottle, either then or at 
any more recent period up to the present time, though the odour of the gun-cotton has 
now become more pronounced, and is indicative of nitrous acid. The substance has 
at present a marked acid reaction ; it has not as yet altered either in explosiveness, 
strength of fibre, or other properties, but the odour and slight development of acid are 
undoubted indications that the material which for sixteen years was preserved in a 
moist condition in the dark without any apparent change, has during three years’ expo- 
sure to light furnished slight indications of spontaneous change. It was a specimen of 
gun-cotton prepared by Messrs. Hall in 1847, and preserved by Percy since that year 
in a stoppered bottle, exposed to light, which had gradually become converted into a 
light-brown semifluid gum-like mass, described by Hofmann as having exhibited all the 
properties of ordinary gum, and as being interspersed with crystals of oxalic acid. It 
is therefore not improbable that the specimen of Messrs. Hall’s manufacture above 
referred to may, by long-continued exposure to light, eventually furnish more im- 
portant indications of spontaneous change than have hitherto been developed in it. 
There can be little doubt that the quality of cotton operated upon by Messrs. Hall 
in the production of the specimens above referred to (and certainly in the instance of that 
examined by me), was considerably inferior to that of the material employed by me in 
1846, and the character of the gun-cotton produced demonstrates that the conditions 
essential to the production of the most explosive material were not fulfilled by the method 
of manufacture pursued by those gentlemen in 1847. It is equally certain that the great 
importance of as complete a purification as possible of the cotton employed and of the 
product obtained was not fully recognized at that period, and that consequently, although 
a small laboratory operation carefully conducted according to the prescribed directions 
might furnish a pure product of great stability, the operations of manufacture had not 
been established with the precision essential to the attainment of satisfactory results. 
The following are the results obtained up to the present time by exposure to light, 
under various circumstances, of gun-cotton prepared and purified according to Yon 
Lenk’s directions. 
