818 
PROFESSOR H. B. DIXON ON THE MOVEMENTS 
values for the specific heats of steam and carbonic acid at high temperatures. For 
the purpose of comparison, the results obtained by Mallard and Le Chatelier, by 
Berthelot and Vieille, and those calculated by Chapman are printed in parallel 
columns in the fbllowiug table :— 
Table I.—Mean Sjjecilic Heat of Diatomic Gases (N, 2 ; ‘^c.) at Constant Volume. 
Temperature. 
Mallard 
and 
Le Chatelier. 
Berthelot 
and 
Vieille. 
) 
D. L. Chapman. 
0° C. 
4-8 
4-75 
0“_1000° 
5-4 
4‘75 
— 
0°_2000° 
6-0 
5 • 4 
7-45 
0°—.3000° 
6-C 
7-0 
7-56 i 
0°_4000° 
7-2 
8 * 6 
7*67 
0°_5000° 
7-8* 
10-2 
_ 7 • 7 8 
Mean Specific Heat of Steam. 
0° 
5 • 6 
_ 
_ 
0°_1000 
8-9 
— 
— 
0°_2000° 
12-2 
16-2 
8-7 
0^—3000° 
15-5 
18-1 
11-9 
0°—4000° 
18-7 
20-0 
14-3 
Mean Specific Heat of CC\. 
0° 
6-3 
6-4 
_ 
0°—1000° 
11-1 
— 
0°_2000° 
13-6 
19-1 
— 
0°_3000° 
Dissociation 
20 • 6 
1 
1 
(}n the other hand, D. Clerk! contends that in an explosion of gases, combustion 
is not completed instantaneously, the products of combustion are cooling while the 
unburnt particles are still combining, and therefore the maximum temperature 
reached never coincides with the theoi'etical temperature calculated for instantaneous 
combustion. The spreading of the flame throughoiit the vessel, i.e., the inflammation 
of the whole mass of gas, is not coincident with the moment of maximum tempera¬ 
ture and pressure. On exploding mixtures of coal-gas and air, and of hydrogen and 
air, in a closed vessel, and registering the pressure with a Bichards’ indicator, Clerk 
conies to the conclusion that neither dissociation of the products of combustion, nor 
a rise in the specific heats, can account foi- the tall of the observed pressures beloM' 
those calculated. This fall must be accounted for by the gradual inogress of the 
combustion. 
Concerning the rise in the specitic heat of carbonic acid there can, I think, be 
* Direct experiments made liy Mallakd and Le Chateliei: on the explosion of CoNj + 0^ give the 
mean specific heat of CO and of Nj at 4200° as 10, and at 2500° as 7'5. ‘ Recherches,’ p. 27(5. 
t ‘Proc. Inst. Civil Engineers,’ vol. 85 (1886). 
