IN GASES: HYDROGEN, CARBONIC OXIDE, AND OXYGEN. 
637 
v=29-354 
where r is the absolute temperature, calculated on the assumption that the molecules 
contain all the heat disengaged in. the reaction, and a is the mean density of the gases 
remaining after combustion. 
The rate of explosion and the calculated velocity of the gaseous molecules agree 
fairly well in the case of hydrogen and the simpler hydrocarbons exploded with 
oxygen. For instance, they find the velocity of explosion of electrolytic gas to be 
2810 metres per second, the “theoretical velocity” being 2831 metres per second. 
But with carbonic oxide the velocity observed is only 1090 metres per second, the 
calculated velocity being 1940. This gas they consider, therefore, to be an exception 
to the general rule. When, however, a mixture of carbonic oxide and hydrogen is 
exploded with oxygen, they find the observed velocity of explosion to approximate to 
the calculated velocity, and explain the fact by supposing the hydrogen to com¬ 
municate to the carbonic oxide a law of detonation analogous to its own. With 
mixtures of carbonic oxide and nitrous oxide, a similar divergence between the cal¬ 
culated and observed velocities of explosion is found, whereas with hydrogen and 
other gases containing hydrogen, exploded with nitrous oxide, there is a very close 
agreement between the observed and calculated velocities. Berthelot and Vieille 
dried the explosion tube before each experiment, and employed dry gases. In their 
experiments with hydrogen and oxygen they found that the rate of the explosive 
wave was independent of the material of the tube, and of its diameter above 5 millims. 
The velocity was the same whether the tube was curved or straight. The maximum 
velocity was attained only after the explosion had travelled between 50 and 500 
millims. from the spark. The “variable state” preceding the regime of the explosive 
wave differed according to the strength of the spark employed to fire the mixture. 
The velocity of explosion was determined by making the flame break two thin strips 
of tin, stretched across the explosion tube near either end, each strip forming part 
of one of the circuits of a Boulenge chronograph. A grain of fulminate was folded 
in the strips to ensure their being broken by the flame. Berthelot and Vieille 
have published no experiments oil the duration of the variable state preceding the 
establishment of the explosive wave with carbonic oxide and oxygen. 
Measurement of the initial velocity of explosion of carbonic oxide and oxygen. 
To determine directly the initial velocity of explosion of carbonic oxide and oxygen 
from the point of ignition, with varying quantities of aqueous vapour, the following 
apparatus was employed :— 
A is a brass pipe of 13 millims. internal diameter soldered into a metal trough, so that 
each end projected a short distance from the end of the trough. To one end of the brass 
tube the firing piece B was cemented. This consisted of a short thick glass tube in 
which were sealed two platinum wires connected with the secondary coil of a large 
