290 



MR. ABEL'S EESEAHCHES ON GUN-COTTON. 



Mean 24-15 per cent. 



Method IV. — The gun-cotton was reduced, by cutting, to an extremely fine state of 

 division, and mixed when dry as intimately as possible with a very large proportion of 

 chromate of lead, in the first few experiments, and of finely-divided oxide of copper in 

 the remainder. Long layers of oxide of copper and porous reduced copper were 

 employed as usual, and at the close of the combustion a current of pure oxygen, and 

 finally pure air, was passed through the tube. With care and some experience, the 

 combustion of the substance was brought perfectly under control by this comparatively 

 simple method of proceeding ; in a few instances, however, the operation was terminated 

 prematurely by the stopping up of the tube, in consequence of the explosive combustion 

 of a small accumulation of the finely-divided gun-cotton. 



The following are the results obtained in carbon determinations with different 

 specimens by this method. (The quantity of substance varied between 0-2263 grm. 

 and 0-4839 grm.) 



Coarse yam, made in 1863. 

 Carbon found. 

 24-88 per cent. 24-36 per cent. 

 24-04 „ 24-67 



Coarse yarn, made in 1864. 



Carbon found. 



24-67 per cent. 24-37 per cent. 



Medium yam, made in 1864. 



Carbon found. 



24-54 per cent. 24-46 per cent. 



24-69 „ 24-70 



24-87 „ 24-61 



24-76 „ 24-78 



Fine yarn, made in 1864. 

 Carbon found. 



24*34 per cent. 24-39 per cent. 



24-39 „ 24-66 



24-21 „ 24-23 



24-31 „ 24-75 



Mean result of 28 determinations=24-57 per cent. 



The several mean results arrived at by the four different methods employed for deter- 

 mining the carbon in gun-cotton, manufactured by Von Lenk's process, are 24-02, 24-42, 

 24-15, and 24-57 ; the mean of 49 determinations is therefore 24-29. But the results, 

 upon the accuracy of which the most perfect reliance is to be placed, are unquestionably 

 those furnished by the fourth method, which ranged between 24-04 and 24-88 per cent., 

 the mean being 24-57 per cent. 



Determination of Hydrogen. — The hydrogen was determined at the same time as the 



