PEOFESSOR H. B. DIXON ON THE RATE OF EXPLOSION IN GASES. 147 
On diluting the electrolytic gas with hydrogen the rate of explosion was found to 
increase, and to approximate to the calculated velocity of the sound-wave. The 
mixtures were made by bringing the electrolytic gas from the cell, and the hydrogen 
from a holder, into a sulphuric acid wash-bottle through two tubes of the same size 
dipping side by side beneath the liquid. By regulating the flow of hydrogen the 
bubbles of each gas could be kept passing at an ecpial rate. In this way a mixture 
containing three volumes of hydrogen to one volume of chlorine was passed into the 
explosion tube. The correctness of the mixture was checked by collecting and 
analysing a sample of the gas escaping from the end of the tube. By passing the 
hydrogen at half the rate a mixture containing approximately two volumes of 
hydrogen to one of chlorine was obtained. While the addition of diluent hydrogen 
to the electrolytic gas makes little difference in the calculated rates, the observei^l 
velocities of explosion increased appreciably. On the assumption that the heat of 
combination of hydrogen and chlorine is 22,630 calories, the calculated and observed 
velocities are as follow :— 
Table XXXVIII. — Rate of Explosion of Hydrogen and Chlorine with addition 
of Hydrogen. 
Mixture. 
Ho + CL 
H.+ Clj 
H, + CL 
Berthelot’s 0 . 
1571 
1.581 
1589 
Rate of explosion 
1729 
1849 
1—1 
CO 
■ 1 
V 
1830 
1832 
1832 
These experiments show that in the explosion of hydrogen and chlorine as in the 
explosion of hydrogen and oxygen, in ecjuivalent proportions, the rate falls below tbn 
calculated velocity of the sound-wave, but on diluting the gases the calculated and 
observed velocities come together. This divergence at the highest temperature may 
be explained either by the dissociation of the hydrochloric acid or by a rise in its 
specific heat.''' As I have shown, we have direct evidence of some dissociation. On 
the other ha,nd, the physical properties of hydrochloric acid more nearly resemble 
those of carbonic oxide and the elementary gases than those of steam or cai’bonic 
acid; we should expect, therefore, that the specific heat of hydrochloric acid should 
remain as constant as that of carbonic oxide at high temperatures. 
* MM. Mallard and Lii Chatelier conclade from their experiments that some dissociation occurs 
when equal volumes of hydrogen and chlorine are exploded. When excess of hydrogen is added they 
find no dissociation. 
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