428 Mr. W. Crum on the Composition of Gun-Cotton. 



30 grs. of bleached cotton wool, dried at 65" F., became, 

 after bein<r some hours in a steam bath, 



28'32 grs., and lost, therefore, S-Q per cent, of water. It 

 increased to 



51 'OS 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 r33 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 com- 

 mencement 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. 



The 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 I found reason to believe that 

 it still contained a portion of unaltei'ed cotton. With a view 

 to saturate that portion, it was immersed a second time, and 

 for twenty-four hours, in the same mixture of acids, but with- 

 out yielding any greater quantity of nitric acid. 



An immersion of one hour in nitric acid alone gave a belter 

 result. It lost in weight by this second process 0*47 per cent. 

 It was litde altered in appearance, but after being dried in the 

 open air, it lost in the air-pump only 0*69 per cent., instead 

 of r33, as in the former case. It is this substance of which I 

 shall now relate the analysis. 



Ashes in Gun-Cot ton. — Sixteen grains of gun-cotton were 

 dissolved in nitric acid. The solution being evaporated by 

 degrees, and burnt to ashes, left 0*035 gr. of a reddish ash, 

 or 0-22 per cent. 



Nitric Acid in Gun-Cotton. — In this process the same ap- 

 paratus is employed as for nitrate of potash. About 6 grains 

 of the gun-cotton, containing a known quantity of water, is 

 collected into a ball — squeezed between the finger and thumb 

 to free it as much as possible from air — and let up into the 

 jar, over the mercurial trough. 125 grains of sulphuric acid 

 are added to it. Nitric acid is liberated, and, being acted 

 upon by the mercury, produces nitric oxide. After one hour, 

 when about three-fourths of the whole gas has been evolved, 

 and the gun-cotton is entirely dissolved, 50 grains of water 

 are added. In another hour the increase of gas ceases; in a 

 few hours more its boundary is noted, then treated with sul- 

 phate of iron, and the residue measured. It consists of azote 



