MR. ABEL’S RESEARCHES ON GUN-COTTON, 
201 
which are formed from portions of seed-husk adhering to the cotton, and from small 
quantities of gum-like and other substances still retained within the fibre, escape com- 
plete removal from the gun-cotton, although the larger proportion passes into solution 
during the treatment with acids and upon the subsequent digestion in an alkaline bath. 
It need scarcely be stated that the proportion of these substances, existing in the finished 
gun-cotton, varies with the description and quality of cotton employed, with the duration 
of the digestion in acids, and the degree of perfection of the purifying processes to which 
the material has been submitted. They are discovered by treatment of the gun-cotton 
with alcohol, and no specimen has yet been examined by me which has been found 
entirely free from them, while comparatively considerable proportions have been found 
to exist in a few specimens from Hirtenberg and jStowmarket. 
A description of the nature of these impurities, as far as it could be determined, has 
been given in the previous memoir*. They possess acid characters, and their origin 
leaves no room to doubt that they are less simple and definite, and therefore less stable 
in their characters, than are the products of the action of nitric acid at low temperatures 
upon pure cellulose. 
It has been argued by Schrotter, Redtenbacher, and Schneider in their official 
report upon Yon Lenic’s gun-cotton, that an incomplete conversion of cellulose into the 
most explosive gun-cotton may be one cause of the want of stability observed in the 
early products of manufacture (at Bouchet, &c.) ; and consequently the existence in 
gun-cotton of a proportion of the third class of impurities above specified should, accord- 
ing to these chemists, give rise to, or promote a tendency to spontaneous change in the 
material. On the other hand, Pelouze and Maury consider it probable that a gun-cotton 
will be the more liable to spontaneous change the further it is removed in composition 
from the cellulose type, and that products prepared by prolonged immersion in large 
proportions of very concentrated acids will therefore be more liable to spontaneous 
ignition than the gun-cotton prepared by a brief immersion in less concentrated acids. 
No experimental data are given in support of either opinion. 
The discordant results furnished by the heat-experiments just described, and the facts 
established by investigating the composition of the gun-cotton operated upon, led to the 
institution of a very considerable number of experiments with the view of ascertaining, 
if possible, whether the establishment of change in gun-cotton by its exposure to high 
temperatures has to be ascribed to the instability of trinitrocellulose itself, or whether 
it is to any extent ascribable to the injurious influence of less permanent bodies existing 
as impurities in the ordinary product of manufacture. 
A careful comparative examination was instituted of the effects of exposure, under 
equal conditions, to 100° C. upon a number of samples in portions of which the matters 
soluble in ether and alcohol had been determined. One gramme of each sample was 
first dried in a water-bath at a temperature of 50° C. ; it was then introduced loosely 
into a small flask having a neck about 220 millims. in length, and immersed in boiling 
water, the first indications of the disengagement of nitrous acid being afterwards care- 
* Transactions Royal Society, vol. clvi. p. 285. 
