CAPTAIN NOBLE AND ME. F. A. ABEL ON FIEED GUNPOWDER. 
105 
Since p, v, and t are, in the case of permanent gases, connected by the equation of 
elasticity and dilatability, 
pv=Rt (5) 
(where R is a constant and t is reckoned from absolute zero), t will be known if p, v , 
and R be known. 
Now if we assume a = *6, it follows that in the combustion of 1 gramme of powder 
(gravimetric density =1) the gaseous products will, if the powder entirely fill the 
chamber in which it is placed, occupy a space of *4 cub. centim. But we know that, 
at 0° C. and under a barometric pressure of 760 millims., the gaseous products of 
1 gramme occupy a space of about 280 cub. centims. Hence at 0° C., if the gaseous 
products are compressed into a space of *4 cub. centim., we have a pressure of 700 
atmospheres; and since absolute zero = — 274° C., we have, in the equation ^> 0 v 0 =Rf 0 , 
the values ^ o =700, w 0 =-4, t 0 =2 74; 
.-. R=-^^ =1-0218. 
Hence (5) becomes 
pv=V0218t (6) 
Now under the above conditions, but at the temperature of explosion, we have from 
Table VIII. ^) = 6400 atmospheres, and, as before, v = *4. Therefore 
t= 
6400 x -4 
1-0218 
=2505; 
( 7 ) 
and this is the temperature of explosion reckoned from absolute zero. Subtracting 274° 
from this temperature to reduce the scale to Centigrade, we have temperature of explo- 
sion =2231° C. 
If we assume a=-65, the temperature of explosion deduced in the same way would be 
1950° C. ; but this temperature, as we shall shortly show, would be somewhat too low. 
We have now three points to consider: — 
1. Is this temperature a probable one] and can any direct experimental facts be 
adduced to corroborate this theoretical deduction ? 
2. What is the mean specific heat of the solid or liquid products which the above 
temperature implies ] and 
3. Can any corroboration be given to the high rate of expansion of the solid residue 
implied by assuming the value of a as =-6 ] 
With regard to the direct estimation of the temperature of explosion, we have made 
several experiments with the view of obtaining this result, by ascertaining the effects of 
the heat developed on platinum. For example, in experiment 78 we introduced into the 
charge of R. F. G. a coil of very fine platinum wire and also a piece of thin sheet plati- 
num. After the explosion the sheet platinum was found much bent, but unmelted ; but 
on examination with a microscope there were evident signs of a commencement of fusion 
on the surface, and a portion of the fine platinum wire was found welded on to the sheet. 
MDCCCLXXV. p 
