GUN-COTTON AND GUNPOWDER. 233 
are generated they cool so that their mutual action is prevented. The amount 
of reaction between the first. products of decomposition will depend on their 
temperature and on the time during which they are maintained at that tem- 
perature. 
The experiment of bursting a loaded shell cannot be said to present the 
same circumstances as those which prevail when the explosive material is used 
in a fire-arm; for, in the first place, that part of the charge which burns after 
the rupture of the shell and the consequent expansion of the contained gases 
does not burn under pressure; and, in the second place, the products even of 
that portion of the combustion which antecedes the rupture of the shell are 
not kept together at a high temperature as long as they are in the barrel of a 
gun. If the cylinder used by Lieutenant von Karolyi had been of such 
strength as to resist bursting, and the gases have been allowed to escape into 
the exhausted vessel through a small vent, the circumstances would have been 
more nearly approximated to those which occur in practice with fire-arms. 
For the purpose of determining what is actually produced in the case pf the 
firing of a gun, the most satisfactory plan would seem to be to screw the muz- 
zles of a number of loaded musket barrels into a sufficiently strong and _air- 
tight vessel, and, their vents being securely closed and the whole apparatus 
exhausted by the air-pump, to fire them in suceession by the galvanic current, 
and then examine the products according to the method followed by Lieutenant 
von Karolyi. 
In the barrel of a gun, especially when loaded with a heavy projectile, the 
products of combustion remain under pressure and at a high temperature for a 
comparatively long time, and the products of the explosion of Lieutenant von 
Karolyi’s cylinders are such that, under these conaitions, we would expect 
them to decompose each other. Thus in the case of gunpowder, sulphate of 
potash was produced, together with unconsumed charcoal, sulphur, and various 
combustible gases. Now we know that sulphate of potash, kept at a red heat 
in contact with such reducing agents, will part with its oxygen, and be con- 
verted into the sulphide. 
Lieutenant von Karolyi finds mere traces of the sulphide of potassium 
among his products, but, on the other hand, the residue left in the barrel of a 
fire-arm after its discharge is found to consist mainly of this salt. This cir- 
cumstance does not show conclusively that sulphide of potassium is the chief 
solid product of the explosion, for it may have a special tendency to accumu- 
late on the walls of the gun, being deposited on the cold metal from a state of 
vapor; but the amount of its deposition makes it probable that it constitutes 
no inconsiderable proportion of the products of combustion. 
Some years ago Captain Rodman made certain experiments, in the course 
of which he exploded gunpowder in shells of great strength, which had in’ 
them small vents through which the resultant gases could make their escape ; 
this escape, however, requiring a measurable length of time. I obtained, by 
the kindness of Captain Rodman, some of the solid residue left in the shell 
after these explosions; but, when it reached me, it was in a moist and deli- 
quesced condition, and had apparently suffered decomposition by exposure to 
the atmosphere. When acted upon by dilute hydrochloric acid it evolved a 
large amount of carbonic acid gas, and when treated with distilled water and 
the liquor filtered, small precipitates only were produced by acid solutions of 
chloride of copper and of chloride of barium, so that but little sulphur was 
present either as sulphide or as sulphate. The only way in which I could 
account for such a condition of things was by supposing that the mass had 
originally contained sulphur in combination as sulphide of potassium, and that 
this, by the action of the moisture and carbonic acid of the atmosphere, had 
been transformed into carbonate. 
