MR. ABEL'S RESEARCHES ON GUN-COTTOK 301 



and the product was to a considerable extent soluble in ether and alcohol. In another 

 experiment, a still more soluble product was obtained by immersion for only three 

 minutes. Experiments 6 and 7 indicate that, the quantity of acid used being limited, 

 digestion for twelve hours is scarcely sufficient to ensure the maximum attainable increase 

 of weight ; and the results of experiments 3 and 4, compared with those of 1 and 2, 

 indicate that under equal conditions, the result obtained by immersion for twenty-four 

 hours is quite equal to that furnished by more protracted digestion. This observation 

 is fully borne out by the results of manufacturing operations, as pointed out in the first 

 part of this memoir. There is no doubt that an actual loss of product, though only 

 slight, is sustained by prolonging the contact of the acids with the gun-cotton much 

 beyond the period necessary for its perfect production. 



Experiment 9 shows that a very brief treatment of cotton with a warm acid-mixture 

 effects its conversion into insoluble gun-cotton as completely as a long-continued treat- 

 ment with cold acids (the proportion of the latter being limited). This experiment was 

 made for the purpose of ascertaining whether, with the employment of the strongest 

 acids, heat exerted a similar influence upon the character of the product to what it does 

 when weaker acid-mixtures, or mixtures of saltpetre and sulphuric acid are employed. 

 This is evidently not the case, for the product obtained was as slightly soluble as the 

 general products of manufacture at Waltham Abbey. It was also found that a few 

 minutes' immersion in a warm acid-mixture converted an imperfect product, obtained by 

 a few minutes' treatment with cold acids and containing much soluble matter, into a 

 gun-cotton of the ordinary kind. 



The following results were obtained by submitting samples of cotton-yarn (taken from 

 ordinary supplies for the manufacture of gun-cotton) to treatment with the usual mixture 

 of acids, the cotton having previously been boiled in an alkaline bath and washed ; after 

 which treatment it still retained a very few fragments of seed. 



In all these experiments a considerable excess of acids (about 60 parts to 1 of cotton) 

 was employed. They afford decided evidence of the influence which the quality of the 

 cotton employed must exert upon the quantity of product obtained even in a laboratory 

 operation ; and show that the results furnished, under most favourable circumstances, by 

 cotton of ordinary commercial quality, fluctuate between 78 and 81 per cent., never quite 

 reaching the latter number. The results also point, as did some of those obtained with 

 the purer cotton, to a tendency of the gun-cotton to dissolve in the acid-mixture when 

 the immersion is continued for a very long period. Both results (experiments 13 and 



MDCCCLXVI. 2 T 



