ON THE APPLICATION OF GUN-COTTON TO WARLIKE PURPOSES. 19 
(14) d. Purification of the Gun-cotion.—At the expiration of forty-eight 
hours the jars were conveyed toa centrifugal machine, by which the principal 
quantity of acid was separated from the cotton. The machine employed at 
Hirtenberg for this purpose is made of copper, the one used by me was 
constructed entirely of iron, the sides of the revolving cylinder consisting of 
coarse iron-wire gauze, rendered sufficiently rigid by an iron framework. 
After each operation the machine was washed out with an abundant supply 
of water, and thus the corrosive action of the acids upon it has really been 
very trifling. The oxide dissolved by the acid when the skeins were placed 
in the machine was sufficient to colour the liquid, and also to stain the cotton 
in places, but these stains disappeared entirely in the first washing which 
the product received. The skeins were rapidly transferred, by means of 
an iron hook, to the machine, and the latter was then set in motion, at first 
slowly, and ultimately at a speed of 800 revolutions per minute. Within 
ten minutes the acid was so far separated from the cotton that the skeins 
were only damp. 
Some precautions were necessary in effecting the first transfer to water 
of the skeins, with acid still clinging to them. If they were simply thrown 
into water so that the latter would penetrate them only gradually, the heat 
resulting from the union of the free acids and the water immediately esta- 
blished a violent action of the nitric acid upon the cotton, quantities of nitrous 
vapours being disengaged, At Hirtenberg the gun-cotton, when taken from 
the machine, is quickly placed under a small caseade, where its saturation 
with water is effected with very great rapidity. As this arrangement was not 
attainable at Waltham Abbey, the skeins, directly they were removed from 
the machine, were plunged singly, as rapidly as possible, and moyed about 
violently, in a large body of water. They were then washed by hand in a 
stream until no acid taste whatever was perceptible in the cotton, and were 
afterwards immersed in the stream for a period of not less than forty-eight 
hours. For this purpose they were arranged in rows upon poles fixed in 
frames, which were so placed in the water that the skeins. were in a vertical 
position, the water circulating among them freely, The current of the 
stream used at Waltham Abbey (at the only available place for these ex- 
periments) was not so rapid as could have been desired, and the dryness of 
the season had rendered it unusually sluggish; still it was sufficient to 
afford a continual change of the water surrounding the cotton, The cha- 
racter of this water is by no means such as to render it specially fitted for the 
purification of the gun-cotton. The bed of the stream is always thickly 
covered with luxuriant vegetable growth, and the water itself is conse- 
quently so highly charged with vegetable matter, that, although light was 
excluded as far as possible from the cotton during its immersion, the skeins 
became covered in many places, within a few days, by vegetable growth, 
which in time attached itself so firmly to the cotton as to be very difficult 
of removal by hand-washing. 
The system of purification, as carried on at Hirtenberg, differs very consi- 
derably from that described in General Lenk’s process as patented in this 
country. At the above-named establishment, the gun-cotton is in the first 
instance left in the stream for three weeks and upwards; it is afterwards 
washed in a dilute solution of carbonate of potassa, again washed in water, 
dried, and then treated with a solution of soluble glass. After this treatment 
it is dried, washed for six hours in the stream, and finally by hand. 
In the patented process, it is directed that the gun-cotton in the first in- 
stance should be immersed in running water for forty-eight hours and up- 
" O24 
