( 647 ) 
075 cae 
Ow? Ps T y 
Ors OW Op 
Ox? Ov? <i Ordu 
stead of the thermodynamic potential the free energy is used, and 
not w,p and 7, but z, v and 7’ are the independent variables. 
As we have further in the case of normal components e. g 
2 
which corresponds with the condition — )= 0,1) when in- 
0g 0g 
CS 5 Art 
n, Hij 
On, 05 ; AA 
we have also nes Cann and the above-mentioned condition may 
av U 
be replaced by 
Òu, 2 
Sl 
Ow 
Now 
fi dw a 
fu, =C,— (e — 2 =) + RT log (le), 
Hij 
where C, is a pure function of the temperature, whereas w is 
given by 
o =| pdv — pr. 
Ou, 
The condition — = 0 is therefore identical with 
Ue 
do RT ò 
Ue — 
Ou? l—2 ; 
or 
io) 
RP a (Va) eee en ate se OT 
(la) (1) 
from which I also started in my preceding communication ’). 
2 
rr . . . w 
Now the difficulty arises, that the exact calculation of NE leads 
av 
to rather complicated expressions, so that vaN DER Waars contented 
himself most times with approximations. These consisted in this, that 
in the liquid state at sufficiently low temperatures 1st p was omitted 
5 . a € . . 
by the side of —, 2nd terms of order v—6 were neglected against 
5 
those of order v. 
Starting namely from the equation of state of vAN DER WAALS 
1) Compare van per Waats, Cont. II, p. 137. 
1) These Proc. 28 Jan. 1905. 
