198 
ME. ABEL’S RESEARCHES ON GUN-COTTON. 
These results indicated, — 
(1) That sufficiently protracted exposure to 100 P C. under conditions unfavourable to 
the rapid expulsion of the nitrous acid developed by the first action of the heat upon 
the gun-cotton, ensures the complete destruction of the original properties of this sub- 
stance, and its conversion into a variety of volatile and fixed products. 
(2) That the rapidity and violence of the decomposition resulting from the combined 
action of heat and of the acid generated, is regulated by the quantity of gun-cotton 
operated upon. 
(3) That, as shown by experiments 28 and 29, conducted with coarse and fine yam 
manufactured in precisely the same manner, the mechanical condition of the gun-cotton 
exerts an important influence over the rapidity of decomposition at 100° (a point also 
indicated by the results of experiments in sealed tubes). 
(4) That a very important difference may exist between the behaviour of different 
samples of gun-cotton, even if operated upon in precisely the same manner, quantities, 
and mechanical conditions. This is illustrated by comparing experiments 30 and 31 
(conducted with Austrian gun-cotton), with experiment 28, and with a considerable 
number (18) of precisely similar experiments instituted with different samples of Wal- 
tham Abbey gun-cotton, in not one of which was an explosion brought about by long- 
continued exposure of equal quantities (6‘5 grms.) to 100° C. The two specimens of 
Austrian gun-cotton differed very greatly in composition from all the products of manu- 
facture prepared at Waltham, according to Von Lena’s system; and it will be shown 
presently that this circumstance may serve to account for the exceptional proneness of 
these specimens to very violent decomposition under the particular conditions of the 
above experiments. 
It need perhaps scarcely be stated that the temperature-observations in these experi- 
ments (and others still to be described) were instituted more with the view to afford a good 
means of registering the comparative rapidity of decomposition of different specimens of 
gun-cotton operated upon under equal conditions, than with the idea of attempting to 
ascertain the actual moment of development of heat and progressive rise of temperature 
in a mass of gun-cotton. Such observations could only be correctly made with much 
larger quantities of gun-cotton, so confined as to prevent the escape of heat from the 
interior, and are therefore impracticable on the score of danger. A considerable 
number of these thermometric observations, which unquestionably recorded close ap- 
proximations of the actual rise in temperature of the interior of the mass of badly con- 
ducting gun-cotton, showed that, when the temperature passes 110° to 112° C., the deve- 
lopment of heat proceeds with great rapidity, so that very speedily the rise of the thermo- 
meter does not keep pace with the heating of portions of the gun-cotton in close proxi- 
mity to it, and therefore the explosion of the mass appears to occur at a temperature 
considerably lower than the actual exploding point of gun-cotton. 
In continuation of the heat-experiments, several samples of gun-cotton from Waltham 
Abbey and Stowmarket, weighing 3 grms. each, in an air-dry condition, were exposed to 
