Physics. — “On the Critical Quantities in the Case of Association, 
when the Molecular Attraction is considerably Increased on 
Dissociation of the Molecules to the Isolated Atoms, also in 
Connection with the Critical Quuntities of Mercury’. II. (Con- 
clusion). By Dr. J. J. van Laar. (Communicated by Prof. H. A. 
LORENTZ). 
(Communicated at the meeting of June 26, 1920). 
§ 9. General Relation for the Degree of Dissociation x 
of the Double Molecules. 
If Z is the thermodynamic potential of the mixture of double and 
single molecules, then it may assumed to be known that’) 
Zn Gant. — fp ae + pe + RT (n, log n, + n, log n,), 
when n, and n, represent the number of molecules resp. of the 
single and the double molecules, and C, and C, are given by 
C,=— hk, T (log T—1) + (,), — T (51), 
C,= —k, T (log T—1) + ©), — T @,). 
In this &, and &, are the capacities of heat at infinitely large 
constant volume, (e,), and (e,), the constants of energy, (s,), and (s,), 
the constants of entropy of the components. 
With equilibrium between the two components we have: 
u =D Os es, ee 
OZ 
when u, and uw, represent the two molecular potentials (viz. g, =a 
i 
0Z 
and fi, == or) of the components. [u,‚ refers, therefore, in mercury 
n, 
to 200,6 Gr., uw, on the other hand to 2 x 200,6 Gr. he Now 
0 
= = 4. RT (1 + log (n,+n,)) + RT log c, | 
u, = C, — : + RT(L + log (n, + n,)) + RT loge, 
as 6.2. Ee (n, logn, +n, log n,)=1 + log (n‚ dn) + log —_—-=1+ 
ms ER 
1) Cf. among others Arch. Teyrer (2) 11, gième Partie, p. 1—97 (1908). 
