196 
ME. ABEL’S RESEAECHES ON GUN-COTTON. 
end ; the other extremity of the tube was constricted, then exhausted and filled with 
nitrogen, these operations being repeated three times ; the tube was afterwards sealed 
and heated to 100° C. in a water-bath. After forty-five minutes faint red vapours were 
observed. In another quarter of an hour the colour of the vapours was very deep ; in a 
short time nitrous acid began to condense in the cool part of the tube. After continuing 
the heat for 1^ hour longer, the coloured vapours had entirely disappeared. The gun- 
cotton had become highly bleached, and in the upper extremity of the tube it was par- 
tially converted into the gummy substance. Nitric oxide escaped when the tube was 
opened. 
Experiment 25. — A sample of gun-cotton impregnated with about 0-4 per cent, of 
alkaline carbonate, was exposed to 100° in an exhausted sealed tube, for the purpose of 
collecting the gases evolved. When the tube had been heated six hours daily for five 
days, it was opened under mercury, and the gas, which escaped under considerable pres- 
sure, collected. The tube was again closed and heated for two days, when gas was once 
more collected from it. The experiment was interrupted, after the gun-cotton had been 
further heated for two days, the tube being fractured by the effects of an explosion in its 
vicinity. The collected gases were found to consist of 50 2 per cent, of carbonic acid, 
4‘7 per cent, of nitric oxide, and 45 per cent, of nitrogen. 
These experiments, in which the gun-cotton was submitted to the influence of 100° C. 
under the most severe conditions, appear to indicate that nitric peroxide or nitrous acid 
is liberated by the first decomposition of the gun-cotton, and at once establishes a 
further destructive action upon the substance, becoming reduced to nitric oxide, nitro- 
gen being eventually liberated by complete reduction of the latter*. The extent of 
surface of gun-cotton presented to the action of heat, and of the liberated acid, appears 
to exert, as might be anticipated, an important influence upon the change. Exposure 
of fine gun-cotton thread to heat under the same conditions as those which were safe 
with coarse yarn gave rise to explosions, due possibly to the increased pressure of gas 
in the tubes, but more probably, judging from their great violence, to the sudden decom- 
position of the gun-cotton at a particular period. The characters exhibited by the pro- 
ducts of decomposition of gun-cotton obtained in experiments 20 and 24, were similar 
to those already described by other chemists, and have been referred to in the preceding 
parts of this paper. 
II. Experiments in vessels open to the air . — The following experiments, conducted 
with considerably larger quantities of gun-cotton than before employed, were made with 
the view* of obtaining, at one time, several distinct data regarding the decomposition of 
gun-cotton at 100° C. Direct evidence was sought of the development of heat in gun- 
cotton upon continued exposure to that temperature. The period was carefully noted 
when decomposition was first indicated by the disengagement of nitrous acid, after com- 
mencement of the experiment. In some instances, the loss of weight sustained by the 
* Similar results were observed in experiment 109. 
