Learned Societies. 513 
system of manufacture, by prolonged exposure to tem- 
peratures, considerably exceeding those which are ex- 
perienced in tropical climates, is very trifling in comparison 
with the effects of heat upon gun-cotton, and it may be so 
perfectly counteracted by very simple means, which in no 
way interfere with the essential qualities of the material, 
that the storage and transport of gun-cotton presents no 
greater danger, and is, under some circumstances, attended 
with much lessrisk of accidentthanisthecase with gunpowder. 
7. Perfectly pure gun-cotton, or trinitro-cellulose, resists to 
a remarkable extent the destructive effects of prolonged 
exposure to temperatures even approaching 100 deg. C., and 
the lower nitro-products of cellulose (soluble gun cotton), 
are at any rate not more prone to alteration when pure. 
The incomplete conversion of cotton into the most explo- 
sive products does, therefore, not of necessity result in the 
production of a less perfectly permanent compound than 
that obtained by the most perfect action of the acid mix- 
ture. 8. But all ordinary products of manufacture contain 
small proportions of organic (nitrogenised) impurities of 
comparatively unstable properties, which have been formed 
by the action of nitric acid upon foreign matters retained 
by the cotton fibre, and which are not completely separated 
by the ordinary, or even a more searching process of puri- 
fication. It is the presence of this class of impurity in 
gun-cotton which first gives rise to the development of free 
acid when the substance is exposed to the action of heat; 
and it is the acid thus generated which eventually exerts 
a destructive action upon the cellulose products, and thus 
establishes decomposition, which heat materially accele- 
rates. If this small quantity of acid developed from the 
impurity in question be neutralised as it becomes nascent, 
no injurious action upon the gun-cotton results, and a great 
promoting cause of the decomposition of gun-cotton by 
heat is removed. This result is readily obtained by uni- 
formly distributing through gun-cotton a small proportion 
of a carbonate ; carbonate of soda, applied in the form of 
solution, being best adapted to this purpose. The depo- 
sition of carbonates of lime and magnesia upon the fibre 
of gun-cotton, either by its long-continued immersion in 
flowing spring water, or by its subjection to the so-called 
“silicating ” process adopted by von Lenk, exerts a similar 
protective effect, which, however, is necessarily very variable 
in its extent, as the amount of carbonate thus introduced 
into a mass of gun-cotton is uncertain; moreover, as it is 
