190 
MR. ABEL’S RESEARCHES ON GUN-COTTON. 
depression was more considerable ; but at the expiration of twelve months’ exposure to. 
strong daylight and sunlight, it was only 115 millims. in the dry bulb-tube, and 220 
millims. in the bulb-tube enclosing water. During the ensuing winter months the 
development of gas was again very trifling, though it continued to be greater in the 
tube which enclosed water. After two years’ exposure to light the mercury was expelled 
from this tube, but the depression of the mercury in the dry tube amounted only to 340 
millims., and after the third year’s exposure the extent of depression in the latter was 
660 millims. Neither of the specimens had undergone any alteration in appearance 
after exposure for three years and four months. They were then removed from the 
bulbs, and the following were the results of their examination. 
Gun-cotton from the dry tube. 
Slightly altered in explosiveness and 
strength of fibre. Slightly pungent odour, 
0-77 per cent, extracted by water. Aqueous 
solution very faintly acid, contained a mi- 
nute quantity of nitric acid, no oxalic acid, 
reduced cupric salts slightly : 2 7' per cent, 
of soluble gun-cotton. 
Gun-cotton from the tube which 
enclosed water. 
Not greatly changed in explosiveness or 
strength of fibre. Odour more pungent 
than in the other sample, T4 per cent. 
| extracted by water. Aqueous solution 
| faintly acid, contained a small quantity of 
I nitric acid, no oxalic acid, reduced cupric 
[ salts : 39*7 per cent, of soluble gun-cotton. 
These four experiments show that — 
1. Gun-cotton in an ordinarily dry condition undergoes very slow change indeed when 
freely exposed in closed vessels (either containing air or with air excluded) to strong 
daylight and to the light and heat of the sun, the effects upon the material, during 
upwards of three years’ exposure, being to diminish its explosiveness somewhat by the 
reduction of a portion of the trinitrocellulose to lower cellulose-products. The material, 
when purified by washing in alkaline water after this very severe exposure to light, is 
still gun-cotton possessing useful explosive properties, and exhibiting no greater tendency 
to change than the original material. 
2. If the space in which the gun-cotton is enclosed be kept saturated with aqueous 
vapour, the substance undergoes decidedly more rapid and considerable change, though, 
even under these circumstances, gun-cotton prepared according to the system now in use 
is much less rapidly decomposed, by severe exposure to light than has been the case with 
specimens of gun-cotton previously experimented upon. 
Samples of gun-cotton which had been submitted to a less perfect purification than 
usual, afforded indications of being somewhat more rapidly affected by prolonged expo- 
sure to strong daylight and sunlight. 
Experiment 5. — A quantity of gun-cotton, after removal from the acids, was exposed 
to the purifying effects of flowing water for one day only, and was afterwards submitted 
to treatment with the hot alkaline bath as usual. 19-85 grms. of this sample were 
introduced into a dry bulb-tube from which the air was exhausted over mercury, and 
