ME. ABEL’S EESEAECHES ON GUN-COTTON. 
229' 
very faint nitrous vapours were observed after two hours’ exposure ; these did not 
increase at all, but disappeared entirely after continuation of the heating for four hours 
longer. When the tube had been heated for six days the point was opened, and gas 
escaped under considerable pressure. The tube was again closed and heated for nine 
days, six hours daily ; upon afterwards opening it, gas escaped only under slight pressure. 
It was again heated to 100° for seven days, when the tube was accidentally fractured by 
the effects of a neighbouring explosion. At this time the gun-cotton had become 
darkened in some places and had an acid reaction, but exhibited little other signs of 
change. 
Several experiments were conducted with gun-cotton containing considerably larger 
proportions of sodic carbonate than the samples previously employed, for the purpose of 
obtaining data with regard to the progressive changes resulting from the protracted 
exposure of “ alkalized ” gun-cotton to heat. The results obtained are fairly represented 
by the following selected experiments. 
Experiment 146. — 6-5 grms. of AValtham Abbey gun-cotton were impregnated with 
0-45 grm. of sodic carbonate. The air-dry specimen was exposed to 100° (for five to six 
hoars daily), being loosely packed in a narrow-necked flask. Small weighed quantities 
of the sample (from 007 to OT grm.) were removed from the flask for examination each 
morning before heat was again applied. The darkening, always produced by heating 
gun-cotton with an alkalized substance, commenced upon the first day’s exposure to heat, 
but no other effect was noticed ; after six days’ exposure the gun-cotton was still 
slightly alkaline, the coloration having gradually increased, until some parts exhibited 
a brown tint. In other respects the substance was unchanged. After the ninth day’s 
heating the gun-cotton was found to be quite neutral. About one-fifth of the speci- 
men was then removed for examination. Water extracted the colouring-matter entirely, 
and a brown solution was obtained, in which sodic nitrate and nitrite were readily 
detected. The liquid also reduced cupric salts slightly. The gun-cotton itself had not 
suffered any change in explosiveness or strength of fibre, nor had. the solubility in ether 
and alcohol increased appreciably. 
The exposure of the sample to 1 00° C. was continued for seven days longer. On the 
sixth day a small portion was examined and found still to be neutral. On the seventh 
day, the atmosphere in the flask was found to have an acid reaction, though no nitrous 
vapours were perceptible. 
Upon determining the weight of the gun-cotton (with deduction of the portions used 
during the experiment), it was found by calculation that the loss which it had sustained 
during exposure to heat for 100 hours {in sixteen days) was greater than would have been 
caused by the complete expulsion of carbonic acid from the carbonate employed. The 
aqueous extract was highly coloured, the gun-cotton being left almost colourless. Sodic 
nitrate and nitrite existed plentifully in the liquid, and the latter reduced cupric oxide 
in an alkaline solution. The washed gun-cotton was found, as might have been anti- 
mdccclxvii. 2 i 
