328 
PROFESSOR H. B. DIXON ON THE MOVEMENTS 
Table 11.— Velocity of Reflexion-Waves in Gaseous Explosions. 
iMixture of gases. 
Velocity of detonation- 
wave in metres per second. 
Velocity of reflexion- 
wave in metres per second. 
Ratio of velocities. 
2H., + Oo 
2820 
1538 
1-83 
H., + N.>0 
2305 
1383 
1-67 
2CO-t-Oo 
1676 
1078 
1-56 
C-.N. + 0.. 
2728 
1230 
2 • 22 
CoNo + 20., 
2321 
1129 
2-06 
2C.,H., + 50., 
2391 
1133 
2-11 
Although the formula for the velocity of sound in gases is strictly valid for small 
displacements oidy, nevertheless it ajjpeared of interest to calculate from the observed 
velocities of these reflexion-waves what temperature they indicated in the gas on 
the assuinjotion that they were propagated as sound-waves. Of course, to calculate 
tlie temperature from the velocity of sound it is necessary to know the ratio of the 
speciflc heats y, and since in the case of carbonic acid and steam this ratio is very 
doubtful, a corresponding uncertainty must exist in the temperature calculated. But 
in the case of cyanogen burning to carbonic oxide the products of combustion, 
carljonic oxide and nitrogen, are similar to air, and their speciflc heats either do not 
alter, or do not alter greatly with rise of temperature. The velocity of sound in such 
a gas would therefore give an apjjroximation to the temperature. 
Now the velocity of the reflexion-waves in cyanogen exploded with its own volume 
of oxygen is 1230 metres per second. Assuming y to be unaltered by rise of 
temperature, and tlie velocity of sound in air at 0° C. to be 333 metres per second, 
the temperature of tlie gas where the reflexion-wave was measured is given by the 
formula : 
where v is the velocity of sound, and dy and d the densities of the gas and air 
respectively under the same conditions. If, on the other hand, we assume (with 
Le Chatelier) that the speciflc heat at constant volume of diatomic gases rises with 
tlie temperature and liecomes 7 at the temperature of this experiment, then the 
ratio y falls to D2'J, and the formula becomes : 
In the case of cyanogen exploded vTth twice its volume of oxygen the flrst 
reaction probably consists in the liurning of the cvanogen to carbonic oxide, which 
