ME. ABEL’S EESEAKCHES ON GUN-COTTON. 
183 
In some instances the first signs of decomposition were observed after exposure of the 
gun-cotton to daylight for several years, in others a few days’ exposure sufficed to establish 
the change. Some observers state that the material has been preserved in the dark for 
very protracted periods without change, others {e.g. quite recently De Luca and Blondeau) 
show that, even in the dark, gun-cotton undergoes decomposition within a comparatively 
short period. Such conflicting observations afford convincing proof of great variations 
in the composition or degree of purity of the materials experimented upon. 
The exposure of gun-cotton to heat has, by most observers, been found to accelerate 
its decomposition considerably ; but here again great discrepancies are presented by dif- 
ferent accounts of 'the behaviour of the material under the influence of different tempe- 
ratures; thus, its spontaneous explosion has been brought about in some instances by 
brief exposure to a degree of heat which, in others, has only produced a comparatively 
very gradual decomposition. 
The most interesting and important of recent observations upon the influence of heat 
on the stability of gun-cotton are those described by Pelouze and Maury in their recent 
report upon Baron Yon Lena’s system of manufacturing gun-cotton, and upon the com- 
position and properties of the products which it furnishes. They describe a number of 
results obtained with specimens of gun-cotton which, it is to be inferred, were all pro- 
duced according to Von Lena’s directions, and which, therefore, provided these were 
strictly adhered to, and such an adherence ensured the uniformity of the products, should 
have furnished reliable data regarding the powers of purified gun-cotton to resist the 
destructive effects of heat. The principal results arrived at by Pelouze and Maury are 
as follows : they found that all specimens which were heated to 100° C. became decom- 
posed in more or less time ; a few minutes’ exposure to that temperature sufficed in every 
instance to determine the evolution of nitrous vapours. They describe the results of de- 
composition as susceptible of variation at will ; either the gun-cotton might he brought 
to explode, or the various forms of decomposition already described by other chemists 
might be established ; or finally, it might be made to furnish simply a small black residue 
presenting the appearance of carbon, from which ammonia might be disengaged. Iden- 
tically the same results were obtained by exposing specimens of gun-cotton to tempera- 
tures of 90° and 80° C., with this difference, that the phenomena of decomposition, 
instead of appearing in a few minutes, were not exhibited until after the lapse of several 
hours. It is further stated that pyroxylin is decomposed at 60° C. (I40°F.), and even at 
50° C. (1.22° F.) ; after the lapse of several days dense vapours filled the vessel containing 
the specimens, but no explosions of gun-cotton occurred in the experiments conducted at 
those temperatures. Great stress is laid, however, upon an instance of explosion which 
occurred with a specimen of gun-cotton prepared according to Yon Lena’s process, 
immediately upon its coming into contact with the metal of an oil-bath, the temperature 
of which was only 47° C. (116 0- 6 F.) at the time. Pelouze and Maury afterwards refer 
to the instances of spontaneous decomposition of gun-cotton at ordinary temperatures 
observed by other chemists, and to certain specimens, among a number prepared at 
2 c 2 
