Deville has also showed that carbon monoxide was partly disso-
ciated into carbon and carbon dioxide (for the oxygen evolved or
set free combines with the undissociated carbon monoxide) at
temperatures of about 1,300° C, and from the results of later experi-
ments upon carbon dioxide he concludes that CO 2 is "strongly
dissociated at 1,200° C," to use his own words. As the actual
temperatures attained during combustion in explosion vessels
and engine cylinders is somewhere between 1,000° C. and 2,000° C,
it is quite reasonable to conclude that some of the products of
combustion, at least, cannot exist in a state of perfect chemical
combination, but that the undissociated and dissociated products
will exist together until the temperature falls sufiSciently for the
free elements of dissociation to recombine. The evolution of heat
during the recombination will evidently occur after maximum
temperature has been reached, and will cause the expansion curve
to then lie above the theoretical one.
Dissociation would then appear to consist of a suppression of
heat at the maximum temperature of explosion, and an evolution
of heat during the expansion stroke.
The exact amount of dissociation occurring forms a point of
controversy amongst different authorities at the present moment,
although there appears to be no doubt that dissociation does pre-
vent the attainment of very high temperatures during combustion.
It has previously been shown that with no dissociation, hydrogen
burning in oxygen would give a theoretical temperature of at
least 7,000° C, yet the experiments of Bunsen, Deville and others
show that even the temperature of 3,000° C. is not attained.
