SIR ANDREW NOBLE: RESEARCHES ON EXPLOSIVES. 
461 
predicted. At low densities the small charge burns much more slowly, has a large 
percentage of air to heat up, and, from the slow burning, parts with a much greater 
percentage of heat to the walls of the explosion vessel. 
The extraordinary rapidity with which the gases part with their heat may be 
appreciated if I mention that a charge of 32 grammes, giving rise to a pressure of 
close upon 8 tons (1219 atmospheres), parts with half of its heat to the walls of the 
explosion vessel in little more than half a second. 
Since, with the Norwegian ballistites, there is a slight departure from previous 
experience, and from the pressures indicated by multiplying the volume of gas by the 
heat generated for densities higher than 0"3, I have shown for these explosives both 
the curves derived from the actual observations and that which would result if the 
pressure were determined from the data to which I have referred. 
The next point we have to consider is : The data being as is shown in the tables 
and graphically in the plates, what temperature are we to assign to that generated 
by the explosion ? With the view of studying the question I resorted to two 
methods: (i.) Knowing with very considerable accuracy the units of heat (water 
gaseous) generated by the explosion, and having determined approximately the 
specific heat of the gases, the temperature of explosion should be given by the 
equation 
t _ gramme units of heat , . 
specific heat ’ ’ ' ' * ‘ ' *' 
(ii.) Knowing also with considerable accuracy the pressure at any given density, and 
knowing the pressure p 0 when the volume of gas generated is reduced to the tempera¬ 
ture of 0° C. and a pressure of 760 millims. of mercury, the temperature is given by 
the equation 
_ P-Po 
0-00367 xp 0 
( 2 ). 
With reference to equation (1), the specific heat of C0 2 is a very important factor 
in this determination, and the recent researches of Messrs. Holborn and Austin 
upon the specific heat of gases at constant pressure at high temperatures having 
apparently shown that the specific heats given by Mallard and Le Chatelier for 
temperatures above 100° C. are considerably too high, I have taken the figures 
given by these physicists, which, I may observe, up to temperatures of 800° C. are 
confirmed by Langen. 
The equation given by Holborn and Austin for the specific heat of C0 2 at 
constant pressure is 
Specific heat — 0-2028 + 0-000,128,40— 0-000,000,O50 2 , 
0 being the temperature. 
