ME. ABEL'S EESEAECHES ON GUN-COTTON. 289 



to oxidize minute portions of carbon separated from the gun-cotton, when the whole 

 tube was raised to a red heat at the close of the operation. The proportion of reduced 

 copper employed was so regulated, that a considerable quantity remained unoxidized at 

 the conclusion of the experiment. Great care was required in the application of heat 

 to the parts of the tube containing the moist gun-cotton, there being otherwise consi- 

 derable risk of its fracture by the water expelled from the heated substance. 



The following are the results of eight carbon determinations made by this method in 

 different specimens of gun-cotton manufactured in 1863. The quantities of material 

 operated upon ranged from 0-2634 grm. to 0*4115 grm. 



Mean =24 -42 per cent. 



Method III. — ^A weighed quantity of gun-cotton, moistened as in the preceding 

 experiments, was placed in a capacious strong Bohemian glass tube, sealed at one end ; 

 a small quantity of oxide of copper was introduced into the tube just in front of the 

 gun-cotton. The other extremity of the tube was now constricted, and was sealed when 

 the air in the tube had been exhausted. Heat was then carefully applied to the sealed 

 tube untn the gun-cotton had undergone slow combustion, and the oxide of copper was 

 afterwards shaken to that part of the tube where a minute carbonaceous deposit had 

 been left by the gun-cotton. The tube was placed in a gas-furnace and connected at 

 one end with an apparatus for delivering pure air and oxygen, and at the other with a 

 long combustion-tube, in a separate furnace, containing layers of oxide of copper and 

 porous reduced copper, to which were attached a large chloride-of-calcium tube and the 

 potassa-apparatus. The two Bohemian tubes were connected by a narrow india-rubber 

 tube, about 12 centimetres long, fitted with a screw clamp, so that communication 

 between the tubes could be cut ofi" or gradually increased. The long tube having been 

 raised to a red heat, the point of the sealed tube which was enclosed in the caoutchouc 

 connexion was broken, and the confined gases were allowed to pass gradually over the 

 heated oxide of copper and metal. When no further escape of gas from the tube took 

 place, the other extremity, connected with the apparatus for delivering air, was broken, 

 and the whole of the products of decomposition of the gun-cotton were gradually con- 

 veyed into the heated tube. Pure oxygen was finally passed through the apparatus, 

 and the tube in which the gun-cotton had been burned was heated to redness. 



The gun-cotton for these experiments was taken from various products of Waltham 

 Abbey manufacture obtained in 1863 and 1864; the quantity employed varied between 

 0-2257 grm. and 0-39 grm. The following proportions of carbon were obtained : — 



