164 
contains” not only the expression V,/ N,/... N;/, but also the 
“symmetry-numbers” of the molecules 6,, 6,,..., 6; (comp. e.g. (6) 
$ 3). These, therefore, influence the dissociation-equilibrium (comp. $ 8). 
Accordingly the numerical vulue of the chemical constant of a 
molecule should depend not only on its mass and moment of inertia, 
but also on the “symmetry-number” of the molecule. 
The question whether any of the cases of dissociation-equilibrium 
or evaporation which have been investigated numerically, speak in 
favour of or against this modification, we shall leave to others who 
are more familiar with the experimental side of the question. 
§ 1. Fully excited and non-excited degrees of freedom. 
The thermodynamic theory of the dissociation-equilibrium considers 
the molecules as having constant specific heats in the range in question, 
i.e. possible changes of the specific heats are left out of account in 
the calculations. If they were taken into account, the expressions for 
the entropy and energy of the gasmixture would not have the special 
form, which is essential for the definition of the “chemical constant” *). 
In a kinetical theory of the dissociation-equilibrium analogous 
assumptions or approximations must therefore be admitted, if a 
kinetie interpretation of the chemical constant is aimed at. 
We shall make the following assumption in our calculations: 
I. The translational motions of the molecules as also their rotations *) 
(with the exception of those referred to under II) will be considered 
entirely free from any limitations depending upon quanta *) (“fully 
excited degrees of freedom”). 
Il. On the other hand the following motions will be assumed 
to be absent ‘) (“non-excited degrees of freedom): 
a. The rotation of di-atomic molecules about the axis of symmetry 
and all rotation of mon-atomic molecules. 
1) Compare the expressions for the energy and entropy in § 5 and in M. PLANCK, 
Thermodynamik §§ 237 — 241. 
2) We therefore exclude for the special object of our theory these cases, in which 
a rotation happens to be in the intermediate state of being “partially excited”, as 
these would introduce a variable specific heat (Comp. Nernst. Theor. u. exp. 
Grundlagen d. neuen Wärmesatzes, p. 136 bottom p. 137 top). 
3) Le. we approximate for these degrees of freedom all summations over succes- 
sive quanta-steps by the corresponding f fan dp; comp. “addit notes 1”. 
4) ie. for these degrees of freedom we confine ourselves in our calculation of 
the sum to the lowest quantum-stage. 
