On the Analysis of Bodies containing Nitric Acid. 427 



0'015 cubic inch; leaving 



'^'96 cubic inches of nitric oxide =1*594 grains NO.,, and 

 which correspond to 



2'869 grs. nitric acid, or 53' 1 3 per cent, of the nitrate ofpotash. 

 Four consecutive experiments made in this manneryielded — 



53-13 



53-14 



53-73 



53-29 



Mean .... 53-32 

 or leaving out the third experiment, 53-19. 



The calculated per-centage of nitric acid in nitrate of potash, 

 the acid being represented by 6*75, and the potash by 5-8992, 

 is 53-36*. 



In order further to determine whether the presence of organic 

 matter would interfere with the liberation of the nitric oxide, 

 the experiment was repeated with the addition of three grains 

 of cotton wool, which was first dissolved in the sulphuric acid ; 

 the result was 53-24. 



Other nitrates are analysed in the same manner. For salts 

 in powder, which it is difficult to pass through mercury with- 

 out loss, I cut a quarter-inch glass tube into little cylinders 

 for them, of half an inch long, and close up the ends with 

 thin paper fastened with gum. In the analysis of numerous 

 samples of crude nitrates, the residue, which is azote, may be 

 taken as a constant quantity, and the jar graduated in such a 

 manner that the volume of gas may be read off at once as the 

 per-centage of nitric acid. 



Preparation of Gun-Cotio?i. — The cotton I employed was 

 fine Sea Island. It was first thoroughly carded, and then 

 bleached, by boiling in caustic soda, and steeping in solution 

 of bleaching powder ; then caustic soda again, and afterwards 

 weak nitric acid. It was well washed and beaten in a bag 

 with water after each operation. When burnt, 10,000 parts 

 left 9 of ashes. It was considered to be lignine, nearly pure. 



The cotton, dried and carded after bleaching, was exposed 

 in parcels of 10 grains each, for several hours, to the heat of 

 a steam-bath, and each parcel was immersed, while hot, in an 

 ounce measure of the following mixture: — 



One measure sulphuric acid, spec, grav., 1*840. 



Three n)easures of pale lemon-coloured nitric acid, of 1-517. 

 After one hour it was washed in successive portions of water, 

 till no tjace of acid remained, and dried in the open air. 



* By Thomson's numbers the per-centage of nitric acid in nitre is 52*94; 

 by Berzeliufl, 53*44. 



