cf preparing and employing Gun-cotton. 545 



tions which he considers favourable to nitration, and thinks he 

 has obtained a gun-cotton which offers great resistance to de- 

 composition. 



We shall not discuss the theoretical value of this assertion, 

 but it seems inadmissible. It is, on the contrary, probable that 

 a gun-cotton would decompose the more easily the further it 

 varied from the type cellulose, and therefore the more nitrated. 

 In any case General von Lenk asserts that the gun-cotton made 

 by his method explodes at a temperature of 136° C, and resists 

 any lower temperature. This is an important point in the dis- 

 cussion, and one which we have made the object of numerous 

 experiments. 



These experiments were first made with assay flasks, closed or 

 not, which were immersed in a bath of boiling water. 



All the specimens thus heated to 100° were decomposed in 

 a longer or shorter time, and a few minutes were sufficient in all 

 cases to exhibit a disengagement of nitrous vapour. 



The decomposition takes place in various different ways, which 

 cannot be reproduced at will. 



Four different modes of decomposition at a temperature of 100° 

 may be noted, each characterized by the disengagement of ni- 

 trous fumes. 



1. The gun-cotton detonates violently. 



2. It decomposes without detonation, leaving a white pulve- 

 rulent residue, which is acid, quite soluble in water, and con- 

 tains no nitrogen ; it forms about half the weight of the gun- 

 cotton. 



3. It leaves a yellow amorphous inexplosive residue, partially 

 soluble in water, and reducing tartrate of copper and potass 

 like grape-sugar. 



4. It gives a slight residue, about 8 to 10 per cent, of its 

 weight, of a black substance, like carbon. In this case the flask 

 is entirely lined with a yellow powder, which dissolves com- 

 pletely in the alkalies with a considerable disengagement of 

 ammonia. (This seemed to be ulmate of ammonia.) Acids pre- 

 cipitate from this solution a dirty yellow substance which is 

 also soluble in alkalies. The carbonaceous residue itself, though 

 it is little altered, disengages ammonia when treated with potass. 

 This production of ammonia by the mere action of heat on a 

 substance formed of nitric acid and ammonia is a remarkable 

 fact. 



Other experiments, made on various gun-cottons at tempera- 

 tures of 90° and then at 80°, gave exactly the same results, 

 except that the phenomena of decomposition, instead of appear- 

 ing after a few minutes, only showed themselves after some hours. 



At 60° and even at 55° gun-cotton is decomposed. After 



