ON THE APPLICATION OF GUN-COTTON TO WARLIKE PURPOSES. 15 
gun-cotton, and of several specimens of gun-cotton-twist papers, according 
to the prescribed method, were sufficiently uniform to furnish reliable com- 
parative results; but the liability of the glass tube to fracture during the 
application of heat, by the water present, led to the abandonment of this 
method of proceeding in favour of the following more simple one. A capa- 
cious glass globe, fitted with a stopcock and copper wires passing to the 
interior, is attached to an air-pump, which is also in communication with the 
upper end of a barometric tube. A weighed quantity of the gun-cotton is 
wrapped round a platinum wire, stretching from one copper wire in the globe 
to the other. The globe, being again attached to the air-pump, is exhausted 
until the mercury in the tube stands at about 29 inches, The gun-cotton is 
then inflamed by the aid of a voltaic current, and the depression of the column 
of mercury is noted when the apparatus has thoroughly cooled, By this 
method, perfectly concordant indications were obtained in employing dif- 
ferent specimens of the Austrian gun-cotton, and of products prepared ac- 
cording to the precise method for producing the most explosive gun-cotton, 
which had furnished proper results when examined synthetically *, 
Experiments have been made with quantities of cotton-wool varying 
from one to two ounces, to ascertain how far‘the long-protracted contact (for 
forty-eight hours) of the cotton with the mixed acids, as prescribed in the 
Austrian system, is essential to the complete conversion of the cotton-wool 
into the most explosive gun-cotton. The products obtained by immersion 
of the cotton even for thirty minutes were found to be almost perfectly con- 
verted; the volumes of gas furnished by them and their synthetical exami- 
nation showed, however, that they still probably contained small quantities 
of unconverted cotton, Continuous immersion for twenty-four hours was 
found in all cases to furnish products completely up to the theoretical standard. 
Considering that the quantity of cotton immersed in one quantity of acid 
in the actual process of manufacture is much more considerable than that with 
which these experiments could be made, and that it is in the form of skeins 
of a somewhat compact roving or yarn, it appears a safe and not unnecessary 
precaution, in order to ensure perfect uniformity, to submit the cotton to as 
long a period of immersion as that adopted in Austria. 
A considerable increase in outlay being involved in the employment, on a 
manufacturing scale, of a nitric acid of any specific gravity higher than 1:5, 
comparative experiments have been made on the production of gun-cotton 
with acid of that specific gravity, and of the spec. grav. 1:52 prescribed in the 
Austrian system, both acids being mixed with the proper proportion of 
strong sulphuric acid. In all the experiments, the resulting products were 
found to be identical in their nature. Considering therefore that, accord- 
ing to the directions laid down, the mixed acids are only to be employed for 
the treatment of one quantity of cotton, there appears to be no advantage 
derivable from the employment of nitric acid of a higher specific gravity 
than 1:5. 
Several experiments have been instituted for the purpose of ascertaining 
whether the rejection of the acids as of no further value, after the immersion in 
them of one quantity of cotton, was likely to be indispensable to the produc- 
tion of uniform results, In one instance, four equal quantities of the same 
* In carrying on experiments to test the mode of examination, some interesting results 
were obtained bearing importantly upon the influence exerted over the rapidity and nature 
of decomposition of the gun-cotton by its position relatively to the source of heat, and by 
other variable conditions. These results have led to experiments now in progress. 
_t Asample of the nitric acid employed at Hirtenberg was collected on the spot ; its spe- 
cific gravity was found to be 1°515, 
