THE TECHNOLOGIST. [J as. I, 1865. 



PROPERTIES AND USES OF GUN-COTTON. 259 



it is proposed to devote the remainder of this paper to a hrief considera- 

 tion of Lenk's method of preparation, and the results which have thus far 

 been arrived at, chiefly in Austria, regarding its application for military 

 and mining purposes. 



Hadow showed that by the action of nitro-sulphuric acid "on cotton, 

 several distinct compounds could be obtained. In proper gun-cotton 

 three equivalents of hyponitric acid should be substituted for three 

 equivalents of hydrogen of the cotton, but it often happened that from 

 one to six or more atoms were replaced and substituted, giving rise to 

 substances of varying composition, and less stable and, therefore, more 

 liable to undergo change or even spontaneous decomposition. This, 

 it was shown, depended upon inattention to certain parts of the process, 

 such as relative proportions of the acids, their strength and their tem- 

 perature at the time that the cotton was immersed, the time it remained 

 in contact with the acids, as well as imperfect subsequent washing. The 

 process of Baron von Lenk is founded upon the strictest attention to 

 these minutiae ; and although, in principle, his process is identical with 

 that of Schonbein, in detail it is essentially different, and produces an 

 uniform gun-cotton, whilst the result of the latter was frequently 

 variable in composition and properties. "Without entering into minute 

 detail, the Austrian plan of preparation is of this kind : — The first object 

 is to purify the cotton as far as can be, and for this purpose, in whatever 

 form used, it is boiled with potash, carefully washed, and dried. A 

 mixture of one part (by weight) of nitric acid, pure and strong, and 

 three of sulphuric acid is then made ; when this mixture is cold, the jars 

 containing it are put into cold water, and the cotton immersed in the 

 acids for forty-eight hoars • it is then taken out, and, after draining away 

 the acid, is dried in a centrifugal machine. It is then moved about in 

 water and washed until all acidity is removed, put into frames and 

 placed in a stream of water for two or three weeks, again treated with an 

 alkali, and again immersed in the stream for several days ; on removal it 

 is dried at a temperature below 212°. Von Lenk finishes the pre- 

 paration by steeping the gun-cotton in a solution of silicate of potash ; 

 this, by the majority of English chemists, is considered needless. 



Ihe properties of this gun-cotton are, that it does not differ in 

 appearance from ordinary cotton ; in moist situations it absorbs six or 

 Beven per cent, of water, but in a dry situation it parts with all, except 

 two per cent, which is normal ; and it may be preserved for any length 

 of time in a moist state, but dried possesses, without deterioration, the 

 usual properties. Gun-cotton ignites at about 300° F., burning with a 

 bright flash and large body of flame, with no smoke, and leaving no 

 residue, differing in these respects widely from gunpowder, which 

 demands a temperature between 500° and 600° for ignition. 



Many attempts have been made at various times to diminish the 

 rapidity of the burning of gun-cotton ; and the credit of overcoming this 

 difficvdty is due to Baron von Lenk, who, by a simple mechanical 



