MB. ABEL'S RESEAECHES ON GUN-COTTOX. 298 



necessary), but has been prepared from cotton separated from foreign matters as far as 

 it is possible by the ordinary method of purification adopted. 



2. Ample proof has been furnished, by most extensive and rigorous experiments, of 

 the invariable existence in the purified gun-cotton (as produced by the most complete 

 action of the strongest acids upon cotton-wool, purified by treatment with alkali and 

 washing) of notable proportions of substances which owe their existence to the presence 

 of foreign matters remaining in the cotton fibre after its ordinary purification, and also 

 of products resulting from the less perfect action of nitric acid upon small portions of 

 the cellulose. 



3. Although these two varieties of impurities were extracted as far as possible by 

 repeated digestion and washing with ether and alcohol, from the pyroxylin analyzed, 

 their perfect removal from the fibre, by the application of any feasible method of puri- 

 fication, is extremely difficult, if not impossible. 



4. The existence of even small proportions of these impurities in a sample of 

 pyroxylin will have the effect of raising somewhat the percentage of carbon, obtained 

 by analysis of the substance, above that which would be furnished by the pure material, 

 and also, consequently, of reducing to a trifling extent the propoi'tion of nitrogen 

 obtained, below the theoretical requirement. 



A proof of this is furnished by the analytical results obtained with specimens of the 

 matter soluble in ether and alcohol, which had been extracted from Waltham Abbey 

 gun-cotton. 



These results are as follows: — 



Carbon. Hydrogen. Nitrogen. 



Specimen 1 30-60 2-91 



Specimen 2 < 



^ I 29-28 11-85 



Mean results furnished by the gun-cotton] ^a.-i c cy.Ac: -i o.oq 



after digestion with ether and alcohol .J 



It is believed that the foregoing circumstances must be admitted to account perfectly 

 for the slight variations exhibited, among themselves, by the numerous analytical results 

 which have been quoted. The whole of the carbon-percentages obtained by the most 

 trustworthy method of analysis (Method IV.) are somewhat higher, and the great 

 majority of the results of the nitrogen determinations are a little lower than required 

 by the formula 



r H- 



^«{3Noj^5, or Ci,Hi,0„3N2 05. 



On the other hand, making even very full allowance for errors of analysis, and 

 assuming for an instant the possibility that the substance analyzed could be an abso- 

 lutely pure product, the individual as well as the mean results of the carbon, hydrogen, 

 and nitrogen determinations, are far more closely in accordance with those theoretical 

 requirements, than with the percentage results which should be furnished by a pure 

 MDCCCLXVI. 2 s 



