562 
is reached; the vapour branch is, of course, only attained at a 
much higher temperature (point 3) when on the threephase line, 
vy = 0.50; the three-phase line is then almost sure to have passed 
the minimum 7. 
From this figure it is readily observed how little the behaviour 
of the mixture «= 0.50 conveys the idea of a single substance. For 
it is evident from this figure how not only all the sharp demar- 
cations have vanished but how peculiar retrograde phenomena 
(between 7’, and 3) complicate the ‘behaviour. Direct stoechio- 
metric criteria no longer exist for such a compound; it is only 
recognisable from the general connexion of the phenomena’). ; 
6. It is not our intention to discuss the course of the three-phase 
line in all possible systems with formation of mixed crystal, but it 
is still of importance to devote some attention to the case that a 
maximum or a minimum appears in the sections of the spacial 
figure. 
In Fig. 6 is drawn the ease where in the 7'e-sections appears a 
maximum for the equilibrium S—L, not, however, for the equili- 
brium £—G. Such a maximum often gives rise to doubt: does it 
indicate a compound or not? A further discussion of this question 
will be postponed to a future communication, but here it is important 
to know the three-phase line of this type of system. 
In Fig. 6 we notice how, starting 
in O4, the three-phase line rises, 
for the concentration fraction in (2) 
has a positive value, this rises and can 
attain the value where equation (3) is 
satisfied; the maximum 7’ then appears. 
The numerator of equation (2) now 
obtains a negative value. - As pre- 
sently xz will become — zs the concen- 
tration fraction increases very strongly 
and before #7 becomes = rs the deno- 
minator in equation (2) becomes zero, 
dP ; ‚dp it 
so that = becomes == o (point ee then again becomes positive. 
a 
Soon x7, now becomes = xs as represented by point /. This point 
) Vel. H. R. Kruyr, Algemeene Theorie en bizondere Ervaring (Amsterdam 
1916). 
