( 342 ) 
Kersom’s caleulations (p. 13) that tolerably small variations in the 
oe and ze 
Accurate observations for mixtures with still smaller compositions are 
therefore highly desirable. As the 7,,/, and also the coordinates of 
the critical plaitpoint, are known with less certainty than the 77,1 
and pp, 2 comparison of the theoretical and the experimental values 
values of « and 2 greatly influence the values of 
for these quantities is practically useless. 
Again from the preceding equations Pryi= paer, T)i= Tr to a 
‘first approximation, and 
Vepl — Ver = — en CL Mon +m ji (64) 
xp Lr — 9 RT am, RT’. | il u . . . e 
Hence the plaitpoint may lie either to the right or to the left of 
the critical point of contact; for positive « we have 
| | 
| Moy > 0 Moy = 0 | 
| 
| YE i 
RI Ee > mo. | Vepl =d les WET | Vapl > Drs TEM | 
| | 
RPh EM or) Bayt Vars TC EE Wes EE ] | 
es: | 
If the plaitpoint lies to the left of the critical point of contact, it 
may still lie either to the right or to the left of the apex, that is to 
say either on the descending or on the ascending branch of the 
border curve. In fact, according to (58) and (64) it lies: 
m?* 
1. to the right of the critical point of contact when m,, and RT: HM 
have the same signs, 
2. between the critical point of contact and the apex when 
k 
pees (SOA k m* 
(EE tm.) dm 0 or ODM, (EE mand 
3. to the left of the apex when 
ko, (Mm? : : 
My = En (Er A mo) SS 0 or 0 ee a (Fe ee ms) Je More 
In the p, v, 7-diagram the plaitpoint has no geometrical meaning. 
The expression that the coordinates of the critical point of contact 
and the plaitpoint satisfy the equation (44) gives, to the second 
approximation : 
1 m* 
2 2 
sek BR gece aoe EE af ike ao 
zpl 4 RTE ce siz m,) C (65) 
80 11 
dn en 
