ME. ABEL’S EESEAECHES ON GUN-COTTON. 
189 
the bulb, and its exposure continued for a further period of two years. The effects upon 
this specimen of more than one year’s exposure in a confined space to strong daylight, 
frequent sunlight, and considerable heat radiated from the wall during the summer 
months, were as follows : — the gun-cotton had a somewhat pungent odour, in which, 
however, nitrous acid could not be recognized ; its reaction was decidedly, though not 
powerfully, acid ; the strength of its fibre and its explosiveness had not become affected. 
By exhaustion with boiling water it furnished a somewhat acid liquid, which contained 
a very small quantity of organic matter ; a yellowish tinge was imparted to it by addition 
of potassic hydrate, but it did not reduce cupric salts. 
After treatment with water, the gun-cotton was carefully exhausted with the usual 
mixture of ether and alcohol, and was found not to furnish a higher proportion of extract 
than the original material. 
The remainder of this sample, after further exposure in the bulb-tube for two years 
(i. e. upwards of three years from the commencement of the experiment), had not altered 
in appearance, and was found to be in the following condition. 
There was scarcely any perceptible odour in the tube on removing the extremity from 
the mercury ; and the gun-cotton itself, when extracted from the bulb, had decidedly less 
odour than when examined two years previously. 
It was still highly explosive, and the toughness of its fibre had very slightly diminished. 
Water extracted only T3 per cent, of soluble matter; the extract had a faint acid reac- 
tion ; a minute quantity of nitric acid was detected in it, but no oxalic acid ; and it exerted 
to a very slight extent a reducing action upon cupric salts. The gun-cotton yielded 25 - 5 
per cent, of soluble product to the mixture of ether and alcohol. 
Experiments 3 and 4. — It was considered very probable that the gradual metamorphosis 
sustained by gun-cotton upon exposure to sunlight would be attended by the disengage- 
ment of gaseous products, and that the rate of generation of these might furnish an 
indication of the comparative rapidity with which different specimens were affected. 
With this view two bulb-tubes, similar to those used in the experiments just described 
(the stems being 812 millims. long and 10 millims. in diameter), were respectively charged 
with 15 grms. of air-dry gun-cotton of the same manufacture as used in the preceding 
experiments. These tubes were then carefully exhausted over mercury, by means of a 
long narrow glass tube inserted into them, and extending from the mouth of the tube to 
within the bulb. The column of mercury in each tube was thus raised to within 16 
millims. and 17 millims. of the height of the barometer. A small quantity of water 
was afterwards passed up into one of the tubes, so as to form a layer upon the mercury 
3 - 5 millims. in height. These bulb-tubes were exposed in the middle of October 1863, 
side by side, in the position already described. 
During exposure to light for the first four (autumn and winter) months, the depression 
of the mercury was not considerable in either instance, but it was nearly twice as great 
in the bulb-tube which enclosed water as in the other (88 millims. in the latter and 
31 millims in the former). During the next six months (from spring to autumn) the 
MDCCCLXVII. 
2 D 
