416 
MINUTES OF PROCEEDINGS OF 
Thus 806 grains of powder produce 62 volumes or 1444*6 cubic inches 
of gas at 0° C., and 1 atmosphere pressure; and, consequently, 1 cubic 
inch, or 240 grains, will produce 430 cubic inches of gas at the same 
temperature and pressure. The temperature of the products occupying 
430 times the powder space will be 
473720 
130 
3644° 0., 
and the pressure. 
supposing the solid potash to occupy one-third and the gases two-thirds of 
the powder space, will be = x 430 (1 + *00366 x 3644) = 9250 atmo¬ 
spheres, or 62 tons per square inch. 
Exception may be taken that no heat is here allowed for the decomposi¬ 
tion of the nitre, nor for the latent heat of the gases evolved from it. But 
I may observe that, in all compounds containing nitrogen, the elements are 
very readily decomposed, and in some cases, such as nitrous oxide, heat is 
actually evolved by the separation of the atoms. The units of heat were 
obtained by Bunsen and Schischkoff with the gases expanded and much 
latent heat absorbed; but, in passing from the liquid to the gaseous state 
under great pressure, the law has been established that no latent heat is 
absorbed, and vice versa. We may therefore consider the temperature 
arrived at as not very different from that which exists at the moment of 
explosion, for any absorption of heat by decomposition would probably be 
more than counterbalanced by the heat which would be evolved if we were 
to reduce the 430 volumes to f- of a volume. 
It is possible that the temperature may even be higher, and the pressure 
deduced is by no means the limit which might be attained, but is rather to 
be considered a minimum than a maximum, seeing that the products may 
be in a still further state of decomposition than has been assumed; for it is 
well known that at a high temperature carbon will reduce potassa; the 
tendency also of potassium to pass into vapour is well known. It is possible 
therefore that in the presence of carbonic oxide, and at such a temperature, 
the elasticity of the two vapours of potassium and oxygen may be sufficient 
to cause decomposition, and thus we should have all the products in the 
state of vapour with a corresponding augmentation of pressure. 
This is not at all unlikely, for in the cases of gun-cotton and nitro¬ 
glycerine, the products of decomposition are much more dissociated by 
being exploded in a confined space than when burned in the air. In their 
case the products, being carbonic acid, carbonic oxide, nitrogen, and aqueous 
vapour, have no tendency to reunite, and can be recovered in the very state 
in which they were at the time of maximum pressure; but, in the case of 
gunpowder, one of the products is potassium or potassa, whose strong basic 
attraction causes recombination, so that none of the other products, nitrogen 
only excepted, can remain free until it is satiated. 
These considerations show, almost with absolute certainty, that the pro¬ 
ducts obtained by the combustion of powder are not the same as exist in 
the gun during the time of greatest action; and we thus get rid of a difficulty 
which would tend to prevent our accepting the high pressures which we 
shall see are obtained by experiment. 
Another consideration in favour of a possible high pressure is the limit 
to which the laws applicable to gases can be carried. At some point the 
liquid form would be assumed; and, though with low temperatures the 
