ME. ABEL’S EESEABCHES ON &ITN-COTTON. 
233 
the very gradual effect of a high temperatures (90°-100°) upon the pure gun-cotton. 
The introduction of considerable quantities of saline matter into gun-cotton necessarily 
gives rise to the production of smoke and to some deposition of solid residue, upon the 
explosion of the substance, and although the amount of both these products would then 
still be very trifling as compared with those of a corresponding character resulting from 
the explosion of gunpowder, it is inadvisable that they should be unnecessarily increased. 
It therefore appears preferable to limit the extent of impregnation of gun-cotton with 
sodic carbonate to 1 per cent.* It has been abundantly demonstrated by the experi- 
ments detailed and by one instituted upon a more considerable scale, to be presently 
described, that even the introduction of one-half that proportion of sodic carbonate into 
gun-cotton serves to afford it sufficient protection under conditions of exposure to heat 
exceeding in severity and duration any which the material would have to encounter if 
substituted for gunpowder in all directions. 
III. Protective action of Water . — In one of the earlier experiments on the effects of 
exposure of gun-cotton to 100° (experiment 124, Table VII.), it was found that the 
accidental introduction of a very small quantity of water into the vessel containing the 
gun-cotton, afforded most perfect protection to the material, which exhibited no signs of 
change during sixteen hours’ exposure to 100°, and had not sustained any loss in weight 
at the close of the experiment. This power possessed by water (or aqueous vapour) of 
preserving gun-cotton from decomposition at high temperatures f is remarkably at variance 
with the influence exerted by moisture, if confined together with gun-cotton under pro- 
tracted exposure to bright daylight 1 and sunlight, in which case there appears no doubt, 
from the results which have been described, that the aqueous vapour operates in deter- 
mining to a slight extent the decomposition of the material. 
Further illustrations, though less striking than the one above quoted, were furnished 
of the protective effect of aqueous vapour, by the comparative tardiness with which 
certain samples of gun-cotton containing more than the ordinary proportion of hygro- 
scopic moisture underwent change by exposure to high temperatures {vide experiments 
38, 39, and 40). This preservative power of water has received the fullest demonstration 
from the results of a considerable number of experiments, the nature of which is fairly 
represented by the following examples. 
Experiment 150. — A hank of gun-cotton was suspended in the upper part of a capa- 
cious flask containing distilled water tinted with litmus. The water was maintained in 
rapid ebullition for several hours, the greater portion of the steam condensed in the 
neck of the flask and upon the gun-cotton, returning to the body of water. At the con- 
clusion of the experiment the tint of the litmus (compared with a standard) had not 
been affected in the slightest, and the gun-cotton was perfectly neutral and unaltered. 
* It is scarcely necessary to observe that this carbonate is selected for introduction into the gun-cotton 
because, while its solubility affords the means of its uniform distribution through a mass of material, it possesses 
no tendency to increase the hygroscopic properties of the latter. 
t See also pp. 199 and 200. 
