ON THE APPLICATION OF GUN-COTTON TO WARLIKE PURPOSES. 9 
which receives six skeins of known weight. The jars are then weighed, 
_ some of the mixed acids being added if necessary, to bring the proportion 
of acids up to 104 Ibs. to 1 lb. of cotton. 
The jars are set aside for forty-eight hours in a cool place ; in summer they 
should be placed in cold water. When that period has elapsed, the acid is 
separated from the cotton as far as possible by means of a centrifugal machine, 
as before described. The men working the machine are protected from the 
fumes of the acids by a wooden partition. The acids removed from the 
cotton are not used again in the preparation of gun-cotton. 
The skeins of gun-cotton are at once removed from the centrifugal machine 
to perforated receptacles, which are immersed in a stream, where they are 
allowed to remain at least three weeks. Each skein is afterwards separately 
rinsed in the stream to remove mechanical impurities, and the water is then 
separated by the centrifugal machine. 
The gun-cotton is next submitted to treatment with a solution of carbonate 
of potassa, as in the preliminary process, and again washed after the alkaline 
liquid has been expressed. When the skeins have been allowed to dry 
tolerably by simple exposure to air, they are placed in a large wooden tub 
containing a solution of silicate of soda, the temperature of which is about 
15°C. This solution should have a specific gravity of 1-072, and is prepared 
as required from a solution of spec. grav. 1-216. The cotton remains one 
hour in the solution of silicate of soda, which is supposed to exercise two 
functions :— 
(a) That of protecting the cotton by acting as a varnish upon the fibres. 
(6) That of retarding its combustion. 
Upon removal of the gun-cotton from the bath of water-glass, the liquid is 
partly expressed by hand, and afterwards more fully by means of the centri- 
fugal machine. The skeins must then be thoroughly dried. They are 
afterwards immersed in running water for five or six hours, and each skein 
subsequently washed by hand. The water having been extracted by the 
centrifugal machine, the gun-cotton is removed to the drying-house, where it 
remains eight or ten days. Its manufacture is then completed. 
The gun-cotton is packed in ordinary deal boxes lined with paper, and kept 
in dry magazines until required to be made into cartridges, &c. 
Well-organized arrangements are employed for mixing the sulphuric and 
nitric acids, immersing the cotton, and for conducting the various other opera- 
tions connected with the manufacture. 
II.—On the Composition, and some Properties, of Specimens of Gun-cotton pre- 
pared at the Austrian Government Works. By F. A. Anut, F.R.S. 
(4) Several specimens of gun-cotton prepared at the Imperial Factory at 
Hirtenberg near Vienna*, being the descriptions manufactured for cannon, 
for shells, and for small arms, were submitted to chemical examination, to 
determine the following points :— 
(a) The proportion of hygroscopic moisture existing in them, under 
normal conditions, 
(6) The composition of the different specimens of gun-cotton. 
(c) The proportion and nature of their mineral constituents. 
(5) I. The proportion of moisture expelled from the samples of gun-cotton, 
* Several of these specimens were taken from ammunition, &c., which were being used 
at the time, for experimental practice, by the Austrian authorities, 
