636 
MR. H. B. DIXON ON CONDITIONS OF CHEMICAL CHANGE 
occupied about two seconds in passing down the length of 500 millims. occupied by the 
gases in the eudiometer. In three other experiments measured quantities of aqueous 
vapour w T ere added short of saturation ; in the last two experiments the aqueous 
vapour was at maximum tension, and the sides of the eudiometer were wet. Before 
each explosion the mercury in the gauge was brought to the mark 229 on the scale, 
which indicated a pressure of 533 millims. of mercury on the air in the closed limb. 
The following table gives the quantities of aqueous vapour in each experiment, the 
readings of the pressure gauge, and the pressures corresponding to those readings. 
Table IV.—Pressures produced by the explosion of carbonic oxide and oxygen with 
varying quantities of steam. 
No. 
Tension of 
carbonic oxide 
and oxygen. 
Tension of 
aqueous vapour. 
Reading of 
pressure gauge 
before explosion. 
Reading of 
pressure gauge 
after explosion. 
Increase of 
pressure 
registered in 
gauge. 
Temperature of 
gases. 
Length of 
column of 
gases exploded. 
millims. 
millims. 
millims. 
° c. 
1 
200 
Trace 
229 
236 
29 
33 
500 
2 
•) 5 
Trace 
236-2 
30 
33-2 
500 
3 
87 
249-2 
87 
33 
505 
4 
9-4 
249-6 
89 
33-5 
505 
5 
55 
15 
249-4 
88 
34 
514 
6 
5 5 
38 
252-6 
105 
33-3 
524 
7 
55 
40 
55 
252-6 
105 
34 
525 
These experiments show very plainly the increased rapidity of the propagation of 
the explosion produced by the addition of steam to the mixture of carbonic oxide and 
oxygen. With the exception of the 5th experiment the pressures registered mount 
up regularly with the increase of aqueous tension in the eudiometer. 
During the last three years several most interesting and ingeniously devised series 
of experiments have been brought before the French Academy of Sciences by MM. 
Berthelot and Vieille, and by MM. Mallard and Le Chatelier on the velocity of 
explosion of gases. They have shown the velocity to be far in excess of the rates 
previously assigned. The old determinations of Bunsen gave for the velocity of 
explosion of electrolytic gas 34 metres per second, and for carbonic oxide and oxygen 
1 metre per second. These numbers must be multiplied a thousandfold. MM. 
Berthelot and Vieille * have shown that the explosion of any particular mixture of 
gases in a tube begins slowly, increases in velocity, and finally gives rise to an “ ex¬ 
plosive wave,” which is propagated at a uniform rate. This rate is independent of the 
pressure and the diameter of the tube, but varies when different explosive mixtures 
are used. The experiments were made on different explosive mixtures in a tube 
40 metres long. They found the velocity of the explosive wave to be a close 
approximation to the mean velocity of translation of the molecules in the gaseous 
products of combustion calculated from the formula of Clausius. 
* Comptes Rendus, xcv., 151, 
