ME. ABEL'S EESEAECHES ON GTJN-COTTON. 287 



be judged at present, however, from the general properties of the products, the differ- 

 ence observed when the larger or the smaller proportion of acid is used, is not of 

 sufficient importance to render necessary the consumption of the larger quantity of acid 

 in the manufacture. 



2. The following experiment was instituted with a portion of one of the specimens of 

 gun-cotton from Stowmarket, which had been found to contain 11-5 per cent, of matter 

 soluble in ether and alcohol (after removal of the portion soluble in alcohol only). The 

 gun-cotton, having been perfectly dried and carefully weighed, was digested for three 

 hours with mixed nitric and sulphuric acids, of the kind always employed. It was after- 

 wards submitted to long-continued washing with distilled water ; precautions being taken 

 to prevent mechanical loss. The dry gun-cotton was found to have increased in weight 

 0-3 per cent. But the original gun-cotton contained 1'71 per cent, of mineral matter, 

 while, after having been digested with acids and washed, it furnished only 1-01 per cent, 

 of ash. The difference between these numbers had therefore to be added to the increase in 

 weight which the gun-cotton sustained by this second treatment with acids, which con- 

 sequently amounted to 1 per cent. The substance now no longer contained any appre- 

 ciable amount of soluble matter. Assuming that the soluble gun-cotton originally 

 existing in the sample was either one of those whose composition has been determined 

 by Hadow, 



(GisH^aOis, 8NG2, or G.^ii^O,,, 71^ 0,), 



the increase sustained by the imperfect sample, if completely converted into the most 

 explosive and insoluble product, should have amounted in the one instance to 0-61 per 

 cent, and in the other to 1-29 per cent. Considering that neither of these substances 

 would be likely to exist alone in the imperfectly converted material, the actual increase 

 of 1 per cent., sustained by the gun-cotton, must be regarded as a close approximation 

 to the theoretical proportion of imperfectly converted gun-cotton, and proves decisively 

 that, on the one hand, the treatment of the cotton with the acids had not in the first 

 instance been quite perfect, while on the other a further digestion of imperfectly con- 

 verted gun-cotton with acids will convert soluble gun-cotton which it contains, into the 

 most explosive or insoluble variety. 



Determination of the carbon, hydrogen, and nitrogen contained in gun-cotton. — The 

 difficulties which attend the application of the ordinary analytical methods to deter- 

 mining the composition of so highly explosive a substance as pyroxylin, need scarcely be 

 dwelt upon. Several special methods of proceeding have been pointed out by different 

 experimenters ; and others have been elaborated in the course of these researches ; but 

 even the most simple and perfect require great care and some experience in their em-, 

 ployment, for the attainment of trustworthy results. The following is a brief account 

 of the most successful methods tried for determining the carbon, hydrogen, and nitro- 

 gen, and of the results which each has furnished. 



In the majority of instances the specimens of gun-cotton analyzed were ordinary pro-' 

 ducts of manufacture. The material operated upon was always purified as far as pos- 



2 r2 



