ME. ABEL'S BESEAECHES ON GUN-COTTON. 



291 



Mean 2*46 per cent. 



carbon, by the method of operating last described. The results of all the combustions 



(eight in number), conducted with different samples of gun-cotton yam, were so 



remarkably uniform, that they were regarded as furnishing ample numerical data, with 



respect to this constituent element. The following were the proportions of hydrogen 



found : — 



2-41 per cent. 2-56 per cent. ^ 



2-46 „ 2-44 „ 



2-40 „ 2-47 „ 



2-55 „ 2-44 



Determination of Nitrogen. — ^The method of Dumas was employed for determining, 

 by volume, the proportion of nitrogen contained in gun-cotton. A rather wide com- 

 bustion-tube, about 82 centimetres long, was drawn out at one end so as to admit of 

 being connected with a carbonic acid apparatus provided with a regulating tap ; and was 

 fitted at the other end with the usual form of delivery tube. 5 centimetres of the 

 tube were first fUled with coarse porous fragments of oxide of copper, a layer of 3 cen- 

 timetres of fine oxide of copper followed, and then the very finely cut gun-cotton, mixed 

 with a large proportion of oxide of copper ; the mixture occupying about 25 centimetres 

 of the tube. The next 22 centimetres were filled partly with coarse porous oxide of 

 copper, and partly with finely powdered oxide ; a layer of 20 centimetres of reduced 

 copper followed, and finally, the tube was plugged with coarse porous oxide, occupying 

 a length of about 5 centimetres. The combustion was conducted very slowly, with the 

 usual precautions, pure carbonic acid being passed through the apparatus for the 

 requisite period before commencing, and at the conclusion. The gas collected was 

 found, in one instance only, to contain traces of nitric oxide, and this determination was 

 consequently rejected. The quantity of substance operated upon varied between 0-3006 

 grm. and 0-415 grm. The follovdng are the percentage proportions of nitrogen calcu- 

 lated from the corrected volumes of gas observed : — 



Description of 

 gun-cotton. Nitrogen found. 



Coarse yam, made f 13-36 per cent, 

 in 1863. . .113-79 



a3-44 „ 



Fine yam, made 

 in 1864. . . 



Medium yam, 

 made in 1864 



Description of 

 gun-cotton. 



Nitrogen found. 



a 3-60 percent. 

 13-68 



Coarse yarn, made 

 in 1864 . 



13-63 „ 



U3-79 „ 



13-78 



14-03 



14-20 „ 



Medium yarn, f 13-97 „ 



made in 1864. 1 13-73 „ 



The results of these eighteen analyses of various products from Waltham Abbey 

 ranged, therefore, between 13-36 and 14-60, and give the number 13-83 as the mean 

 percentage of nitrogen contained in the material. 



