GUN-COTTON AND GUNPOWDER. 235 
binoxide of nitrogen diminishes as the pressure increases. Hence the deoxida- 
tion of nitrogen-compounds during the combustion takes place the more com- 
pletely the greater the work which the gun-cotton has to perform during its 
combustion. 
This circumstance suggested to me the idea of exposing the gun-cotton 
during its combustion to a determinate resistance, and regulated so that it just 
gives way at the moment the gun-cotton is completely burnt away. This 
condition led me to the experiment of placing a vessel filled with gun-cotton 
which offered the necessary resistance, in a 60-pr. mortar, which was then ex- 
hausted and the gun-cotton exploded by galvanism. s 
The resistance of the explosion vessels must be so chosen that the gas in 
the mortar, after explosion, has an excess of pressure of half an atmosphere, 
in order that it may subsequently be transferred to the measuring vessels. 
The explosion vessels which I used were made according to the directions 
of the late Lieutenant.Colonel Ebner, and consisted of hollow cast-iron cylin- 
ders closed at one end, while at the other was a nut through which the ar- 
rangement for a galvanic explosion passes. For this purpose the nut is pro- 
vided with an excavation in which is a thin platinum wire fastened on the one 
hand to the insulated copper wire, and on the other to the copper wire which 
passes directly through the nut. Outside the cover the wires are bent into 
knots, which, as previously mentioned, serve to support the cylinders and to 
complete the voltaic circuit. 
The weight of the gun-cotton whose gases shall fill the exhausted mortar 
of 5,216 cubic centimetres contents so that there shall be the tension above 
mentioned, I have empirically determined, and find that it is 10 grammes. 
The fact that 10 grammes of cotton somewhat compressed occupy a space of 
10.5 centimetres in length and 2 centimetres in diameter, determined the inter- 
nal dimensions of the cylinder. The thickness of the sides of the cylinder 
was also obtained from an empirical experiment, which showed that with a 
thickuess of 8 millimetres the cylinder just exploded with production of flame, 
and that thus, in accordance with the condition stated, the gun-cotton burns 
away the moment the cylinder burst. JI must here mention a peculiar cireum- 
stance which attracted my attention in determining the thickness of the side 
of the cylinder, and which serves to characterize gun-cotton. For the above 
investigation I successively filled, with gun-cotton cylinders 4, 6, and 8 milli- 
metres thick in the side and exploded them in a hole. Although the cylinders 
of 4 and 6 millimetres in thickness contained comparatively a larger charge, 
the pieces produced were considerably larger than those of the cylinder 8 mil- 
limetres in thickness. The former were often only split lengthwise, their cover 
and bottom remained unchanged, while the pieces of the cylinder of 8 milli- 
metres in thickness were scarcely larger than hazel-nuts. 
The above bursting vessels might also probably be constructed of glass. 
Very strong, thick glass tubes are taken, and at each end corks cemented in, 
one of which has been provided with a galvanic conduction and the small 
platinum wire. The length of the vessels and the thickness of their sides 
could then be regulated by the quantity of gas and the desired resistance. 
The qualitative analysis of the products of the combustion of gun-cotton 
under the circumstances described gave carbonic oxide, carbonic acid, nitrogen, 
marsh gas, and a trace of a sulphurous gas, (probably a bisulphide of carbon 
compound,) which, from its small quantity, escaped analysis and could only be 
detected by the smell. This probably arises from a small trace of sulphuric 
' acid adhering to the gun-cotton, which either was not removed in washing, or 
by subsequent treatment with potash remained as sulphate. 
