182 
‘potential energy — Ny) and N’ condensed to a crystal (potential 
energy = N’y’). 
For the vapour molecules we make again the assumptions I and 
IL of section I. As regards the atoms in the erystal our assumption 
will be, that 
Ill. In the calculations the motions of the atoms in the crystal 
are to be ignored *). 
The {y} weight of the condition (N‚N’) is then found to be 
OAL AVAL 1 path fake fee! | 
ya (XL Y4Z)-6NVN, (VW 2 Kn)®N (42.2nV M* POR), (78 
re ETT ren) m)eN (4rr,27 QR), (78) 
where 
K=E—S(Ny IN!) ee = eee 
On the other hand the entropy and energy of the system are 
given by the equations 
oe V 
S=2+ni\C log T + Rlog—+ x) Han's, « « (80)*) 
n 
B=al(CT $0) 4 Ad... 7 re 
The condition of equilibrium is given by 
Slog tyj=—0.. 2. .5 so 
with the conditions 
dio dix), JN 4 dN. = On (83) 
This yields an equation for NV’ as a function of V and K; sub- 
stituting 
al 
Ron nr VEN. 
he 
we find 
log p= —** 4 blog T + a - «> 
zs 
where « has the same meaning as @, in (46). The corresponding 
thermodynamic calculation gives 
1) This assumption is again meant not as a physical hypothesis, but as an 
approximation in the calculations. (Comp. note 5, 8 1). It comes to neglecting 
i dT for the solid (comp. M. Pranck, Thermodynamik, 4 Aufl., § 288, comp. 
0 
(270) in the thermodynamic deduction of the vapour-pressure formula for low 
temperatures. 
2) Properly speaking the last term should be #/s’; but with PrancK we neglect 
