( 542 ) 
in which T l is the temperature of the triple point 0 A . 
The vapour pressure I\ at the temperature T % is the sum of the 
partial pressures of the components p A and pn : 
P 3 =PA + PB 
for which we may write 
P, = {\-x L ) Pt 9 4- PB .(2) 
if Pt 2 represents the vapour pressure of liquid A at that temperature. 
If now we call Pp the vapour pressure of A at its triple point 
and use van der Waals’ well known formula for the saturated 
vapour pressure we may write 
,Pk _ , T k -T, 
PTi T 
By subtraction we get: 
Pt~ j T, 
If now we substitute the value found in (1) for P, 1 
/— (®s— 
P T , = P Tt e « 
thus writing (2) in this form: 
f?h( X S-*L) 
P, = (1 —a L ) P Tl e V -f pB 
If now case I a (maximum pressure) is to occur, the three-phase line must 
rise from Oa to higher values of P and therefore P, ]> Pi v The 
chance of seeing this case realised in a certain system, therefore depends 
on P 2 having as great as possible a value in regard to Pj\ and relation 
T i 
(3) shows us when this will be the case. For th'e first term — and 
9 
xs —xl will then be characteristic. The value of xs — X L is indicated 
by the difference in initial direction of the branches of the melting 
point lines for solid and liquid and this difference is determined 
T 
precisely by — l ). When therefore we pay special attention to %s — X L> 
!J Compare van Laar, Zeitschr. f. physikal. Chem. 64, 257 (1908). 
