Mr. Crum on the Analysis of Nitrates, and on Explosive Cotton. 165 



would interfere with the liberation of the nitric oxide, the experiment 

 was repeatod with the addition of three grains of cotton wool, which was 

 first dissolved in tho 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 without loss, I cut a quarter- 

 inch glass tube into little cylinders for them, of half an inch long, and 

 closed up the ends with thin paper fastened with gum. In the analysis of 

 numerous samples of crude nitrates, the residue, which is azote, may bo 

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

 tho volume of gas may be read off at once as tho per centage of nitric acid. 



Prepaeation of Gun-Cotton. — The cotton I employed was fine Sea 

 I -land. 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 

 Ik a ten in a bag with water after each operation. When burnt, 10,000 

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



The cotton, dried and carded after bleaching, was exposed in parcels 

 of ten grains each, for several hours, to the heat of a steam-bath, and 

 each parcel was immersed, while hot, in one ounce measure of the follow- 

 ing mixture : — 



One measure Sulphuric Acid, spec, grav., 1*840. 



Three measures of pale lemon coloured Nitric Acid, of 1*517. 



After one hour it was washed in successive portions of water, till no trace 

 of acid remained, and dried in the open air. 



Thirty grains of bleached cotton wool, dried at 65° Fahr. became, after 

 being some hours in a steam-bath, 28*32 grs., and lost, therefore, 5*6 per 

 cent, of water. It increased to 51*08 grs. when made into gun-cotton, 

 and dried in the open air. Dried further in vacuo, over sulphuric acid, 

 it was reduced to 50*40 grs., and lost therefore 1*33 per cent, of water. 



100 of dry cotton produced 

 177*9 of dry gun-cotton. 



The gun-cotton thus prepared is whiter, but less transparent, than the 

 original bleached wool. It appears to be little liable to change, but a 

 slight elevation of temperature causes a commencement of decomposition, 

 and the colour becomes more or less brown. It is much less tenacious 

 than cotton wool. Dissolved in nitric acid, and tested with chloride of 

 barium, it gives no indication of sulphuric acid. 



Tho increase of weight above stated is the greatest I have been able to 

 obtain ; and I had completed its analysis in the manner I shall describe, 

 when T 1 '< uinil reason to believe that it still contained a portion of unaltered 

 cotton. With a view to saturate that portion, it was immersed the 



