( 519 ) 
If we use the equation of var per Waals: 
Sn, RES va 
Lam v—b vy? 
then we obtain: 
w = Xn, . RT log (» — b) +5 — — RT Ln, . log Zn, — pv *). 
Supposing now, that in the case “of liquids the external pressure p 
(or the vapour-tension} can be neglected with respect to the mole- 
. a . u . 
cular pression — , the equation of van DER Waars may be written: 
v 
a an, RT 
oo ob 
and the expression for @, when in the same manner pv is omitted 
. 
a . 
by the side of — , passes into 
v 
PO oy ard a 
oO Zn, KT log tm, log Xn, , 
la 
or 
= T a 
o = 2n, . RT log +—, 
vi v 
that is to say into 
“Gt 
mn a 
o = RT log — 
/t v 
2 
when Yn, = 1. For — we find consequently : 
av 
2 
Po GE RP 0? ; a 
Ou? TEE Te ok Ow? a or’ 
by which the equation (3) of the projection of the locus of the points 
of inflection on the 7, z-plane passes into 
0° a 0? a 
WSS ie Mlt 
( Z) Fe 5) uy Or?  v? | 
or into 
» 
1 If D= fw), ten (par still gives a term ne | oe . But this term may be 
v—h 
regarded as independent of w, and so can be added to the temperature function Cj. 
36 
Proceedings Royal Acad. Amsterdam, Vol, VII. 
