Clifton College Scientific Society. 41 



ture : it is then dried in a warm room, and closely packed up, to 

 keep it dry, in earthenware jars, ready for use. 



To make it on a small scale it is best to distil one's own nitric 

 acid, from a mixture of equal parts of the strongest sulphuric 

 acid and dry saltpetre : tlien you obtain the nitric acid strong, and 

 you can easily tell that it is so by its becoming hardly at all 

 warm, when mixed with an equal volume of sulphuric acid. The 

 ordinary " strong " nitric acid becomes quite hot when mixed with 

 sulphuric acid. Into this mixture of nitric and sulphuric acid put 

 the cotton-wool to be made into gun-cotton, and leave it standing 

 for a quarter of an hour. Take it out then, and wash it well by 

 stirring it about in a beaker of cold water, pulling it apart well 

 and pouring more water over it, to get rid of every trace of the 

 acid, especially sulphuric acid, which, if left in the gun-cotton 

 after it is made, will decompose it again into ordinary cotton, and 

 thus make it useless. The cotton must be then well dried, by 

 squeezing it first in a cloth, and afterwards between blotting 

 paper, and finally drying it in the sun or in a warm room. 



Of gun-cotton, thus made, I have some here which I shall use 

 in my experiments. It ought (1) to dissolve in strong sulphuric 

 acid without blackening, as it would do if changed cotton were 

 present ; (2) it should be insoluble in a mixture of ether and 

 alcohol. {Experiment.) 



A temperature even below red heat is sufficient for igniting 

 gun-cotton, especially if it be S2)read out, when the flame spreads 

 much more quickly through it. [Experiments.) * 



Gun-cotton, when ignited, decomposes so speedily, that the 

 flame throughout appears instantaneous. [Experiment.) 



This flame, being so suddenly produced and so quickly over, is 

 capable of giving out very little heat, and, indeed, it is said that 

 one hundred charges of gun-cotton fired in a gun do not heat the 

 gun so much even as thirty rounds of j)owder. The small heat 

 given oft' by inflamed nitrocellulose is easily shown. {Experi- 

 ment.) t However, if the gun-cotton be at all damp, as it is apt 

 to become, being very hygroscopic, it will, when placed on the 

 hand with gunpowder and ignited, not only set fire to the powder, 

 but also burn the hand. {Experiment xuith damp gun-cotton.) 



When gun-cotton is burnt in the air, unconfined, an imperfect 

 combustion only results, and the poisonous substance cyanogen, 

 and also a little prussic acid (formed by the union of water with 



* (1.) Nitrocellulose was lighted with a spark and an ignited wire. (2.) Gun- 

 powder saturated with Greek fire, was shown not to ignite ; while some gun- 

 cotton ignited under the same circumstances. 



t (1). Gun-cotton did not communicate its flame to gunpowder. (2.) It was 

 ignited on the hand without burning it, or even giving off much warmth. 



