208 
ME. ABEL’S EESEAECHES ON GUN-COTTON. 
other hand, that the closing up of the fibres resulting from the solution (or gelatiniza- 
tion), but imperfect removal from the gun-cotton of the soluble portions, may, in the 
above experiment, have imparted to the material increased powers of resisting decom- 
position at a high temperature. 
Experiments 83-87. — Four specimens of gun-cotton, containing small proportions of 
imperfectly converted material, were thoroughly saturated with a very weak solution of 
pure soluble gun-cotton (or collodion), then at once removed from the liquid and dried. 
The mechanical condition of the gun-cotton was not perceptibly altered by this treat- 
ment. These specimens w r ere exposed to 100° C., together with portions of the original 
samples (all of them being for this purpose packed lightly and uniformly in small flasks). 
In every instance the prepared gun-cotton resisted the action of heat for a much longer 
period than the unprepared material. The former exhibited the first very faint indica- 
tions of disengagmg of nitrous acid between twelve and fourteen hours after the first 
exposure, while the unprepared specimens evolved nitrous acid after one hour to l h 30 m 
exposure. 
It would appear therefore from these experiments that the addition of less perfectly 
converted gun-cotton to the ordinary product does not have the effect of promoting its 
decomposition at 100° C., but that, on the contrary, when applied as indicated above, it 
renders the material considerably less susceptible of change, probably because the fibres 
are partially sealed, or in some other way mechanically protected by the treatment with 
dilute collodion. That the partial or complete closing of the fibre does exert an im- 
portant influence upon the power of gun-cotton to resist the action of heat was demon- 
strated by 
Experiment 88. — An ordinary sample of dry gun-cotton was allowed to remain for 
eighteen hours in a confined space together with an open vessel containing the ether- and 
alcohol-mixture. It was afterwards dried and exposed to 100° C., side by side with a por- 
tion of the sample in its original condition. The latter exhibited signs of decomposi- 
tion within two hours, the sample which had been exposed to the action of the vapour 
only exhibited faint signs of change after eighteen hours’ exposure. 
Experiment 89. — A specimen of Stowmarket gun-cotton containing a large proportion 
of matter extractable by ether and alcohol was washed with alcohol only, and its 
behaviour at 100° was afterwards compared with the original gun-cotton. The washed 
gun-cotton resisted the action of heat only slightly longer than the original gun-cotton, 
but it was observed that the washing had effected the separation of much of the earthy 
carbonates mechanically attached to the fibre, and hence was deprived, by the alcoholic 
treatment, both of a protective and a destructive element. A portion of the washed 
gun-cotton was afterwards exhausted as far as possible with ether and alcohol. By this 
treatment the fibre was much disintegrated, and upon exposure of the insoluble gun- 
cotton to 100° C., it exhibited signs of decomposition much more speedily than the 
original gun-cotton. The ethereal extract was evaporated, and the dry product was 
exposed for thirty hours (during six days) to 100° C. No indications of nitrous acid 
