ME. ABEL'S EESEAKCHES ON GUN-COTTON. 281 



by treatment with mixed nitric and sulphuric acids, while the products of ordinary 

 manufacture have been employed in the analytical experiments. 



The loosely spun cotton-wool from which these products are obtained varies some- 

 what in purity, even after the preliminary treatment with alkali and washing which 

 it undergoes previous to conversion. The material, as supplied to Waltham Abbey 

 by the cotton-spinners, always contains seed fragments, which are only very partially 

 removed by the purifying process, but are in most instances completely dissolved or 

 mechanically removed during the processes of conversion and purification. The puri- 

 fied cotton is always considerably inferior in whiteness to the converted material. The 

 loss sustained by the cotton in the treatment with potassic carbonate and subsequent 

 washing, ranged between 5 and 10 per cent. An average sample of the cotton used 

 was submitted to analysis after having been purified in the usual manner. It con- 

 tained 0-044 per cent, of ash, and the following percentage proportions of carbon and 



hydrogen : — 



Found. Cellulose. 



Carbon ...... 44-26 44-44 



Hydiogen .... 6-05 6-17 



Oxygen .... 49-69 49-39 



Hygroscopic moisture existing in gun cotton. — The amount of water absorbed and 

 retained by gun-cotton under normal atmospheric conditions is very uniform ; the 

 average proportion is 2 per cent. ; and although gun-cotton will gradually absorb as 

 much as 6 per cent, of water if exposed for a sufficient period to a very moist confined 

 atmosphere, the proportion which it retains upon re-exposure to open air rarely exceeds 

 2 per cent. This amount is rapidly reabsorbed by gun-cotton, after perfect desiccation 

 in vacuo over sulphuric acid. 



Mineral constituents of gun-cotton. — The proportion of mineral constituents (or ash) 

 in gun-cotton has been carefully determined in a large number of products of manu- 

 facture. The mode of operation consisted in thoroughly moistening the dried and 

 weighed gun-cotton (about 4 grms.) in distilled water, and then projecting it, in small 

 fragments, into a deep platinum vessel of known weight heated to low redness. The 

 decomposition of the gun-cotton under these conditions is so gradual, that there is no 

 risk of the mechanical dispersion of any of the ash. After the combustion of the gun- 

 cotton was completed, the temperature of the vessel was raised sufficiently to bum off' 

 minute quantities of carbon which had separated during the slow combustion. The 

 variation in the amount of ash obtained from different samples of gun-cotton manu- 

 factured at the same works was but slight; 1 per cent, was the average proportion 

 existing in gun-cotton manufactured at Waltham Abbey. A few samples examined 

 contained a somewhat higher proportion, and some specimens, obtained from Hirten- 

 berg, furnished an average proportion of nearly 2 per cent. An analysis of the ash in 

 these instances indicated that the gun-cotton had been submitted to the " silicating " 

 treatment adopted by Lenk. The ash furnished by gun-cotton not thus treated con- 



