SPECIFIC HEATS OF SOME COMPOUND GASKS. 591 
Thus, for instance, the molecules CH;,Cl, CH,Br and CH,I have the same energy 
absorbing power, from which it follows, with a high degree of probability, that the 
halogen atoms in these molecules, in spite of their great difference in mass, absorb the 
same share of the total energy. It is very improbable that if they did not, the 
redistribution of energy in the molecule on interchange of the halogens would result 
in the total capacity being unchanged. Similarly, we may infer from the behaviour 
of hydrogen, ethane, and propane that the chlorine atom may in some cases have the 
same energy absorbing power as the hydrogen it replaces. 
An instance of another kind of interchange that can be made without disturbing 
the distribution of energy, is seen in the case of the two propyl chlorides and the two 
dichlorethanes. Trusting to graphic formule the chemist explains the difference be- 
tween the two members of a pair as being due to a hydrogen changing places with a 
chlorine within the molecule, the configuration being in other respects unchanged. 
The relation of methyl acetate to ethyl formate is explained in a somewhat similar 
way, for if we write the formula of ethyl formate in the form CH,—CH,—O—CO—H 
—we can convert it into that of methyl acetate by interchanging CH, and CO. Thus 
it appears that, if we can trust graphic formule to give information of this kind, 
groups may be interchanged without disturbing 8. It would be of interest to earry 
out this point farther, and find whether one of the groups could be removed from the 
molecule, and the other put in its place without altering 8. Has, for instance, 
methyl-ethyl oxide, which would be obtained by replacing CO in either of the above 
by CH,, the same y? It is probable that valuable information on the status of the 
radicle might be got by the determination of @ for a number of suitably chosen com- 
pounds. 
It appears then that a single atom of hydrogen, oxygen or carbon can in many cases 
be replaced by chlorine, sulphur and silicon respectively, without disturbing the 
distribution of energy in the molecule, but in no case investigated can the replacement 
be repeated without bringing about a large increase in 8. Hence we conclude that 
an atom has not an intrinsic heat capacity which it carries with it unchanged into any 
gaseous molecule of which it forms part, but that it is affected by its neighbours. In 
other words f is not an additive quantity, for the configuration of the molecule plays 
a part in the distribution of energy. 
My experiments would not be inconsistent with the supposition that the configura- 
tion is the sole feature that fixes the distribution, but until more definite evidence is 
obtained—especially with regard to the physical significance of radicles—this must 
remain no more than a suggestion. 
It was pointed out many years ago by Naumann, when experimental evidence was 
seanty, that 6 divided by the number of atoms in the molecule was nearly equal 
to 33. If this held generally, it would be an important fact, for it would point to 
something of the nature of Borrzmann’s Theorem being true, and as the statement is 
sometimes quoted by writers, I have given the quotients in question in the fifth 
