Now it will be evident how the formula describes the course taken 
by the three-phaseline. For in the 7w-projection we notice that in 
Oa *S=eL—«G, and that starting from O4, the fraction 
gradually increases and thus the possibility exists that it attains to 
Qes 
a value equal to —. 
vLS 
dP p : dP 
Then nie the maximum is attained ; oe then becomes negative 
' a 
and the line on the P7-projection falls to Op’). 
The question whether indeed a maximum occurs thus depends on 
the concentration ratios of the coexisting phases and those of the 
heat values. By means of another method we previously arrived 
at a similar result (see our first Communication). 
The three-phase line proceeds without a maximum or minimum 
if the component A which at each temperature has the highest vapour 
pressure, has a higher triplepoint temperature than B. es—er is 
then continuously negative, which prevents the numerator from 
becoming zero. The impossibility of a maximum is moreover directly 
evident by looking at the spacial figure for that case. 
3. In Fig. 2 the diagram (PT and 7) is drawn for a system 
in which occurs a compound’) on the. melting branch of which 
Is SUCCESSION Legt £9 — Te and er — ae. ds realised... In such 
ease that branch exhibits also two maxima and one minimum. 
A further remarkable fact is the occurrence of a point towards 
ar ; 8 : A 
Ree and moreover the maximum point of sublimation and the 
1) In the system p ClC;H, — p BraC;H, the maximum lies at about 76°. If by 
interpolation we calculate the composition of the coexisting phases at that tempe- 
rature we find approximately 
from which follows 
PSN QS, 
te ain?) Qs 
which is a rather low value for that ratio. 
*) For a detailed description of this class of three-phase lines compare v. D. WAALS- 
KonnstamM Le ; H. W. Baxkuurs RoozeBoom, These Proceedings 1905; G. H. 
LEOPOLD, Dissertation. Amsterdam 1906; A, Smizs, Zeitschr. f. physik. Chem. 
78, 708 (1912). 
