1549 
sented in fig. 1 by points of evhbL; hence it is apparent that all 
properties are true again now, as long as the liquid of the equili- 
brium Z,LG is represented by a point of evhd L. 
Consequently the liquid is allowed to change its composition only 
starting from Z (fig. 1) up to the line eZ,; correspondingly on this 
line the equilibrium shows something particular; here the triangle 
Z,LG passes viz. into a straight line. 
In our previous considerations we have assumed everywhere that 
each point of a region (£,/) represents one single bivariant equi- 
librium (F,F,) only. This is also the case when we take in fig. 3 
a point of the region Z,L( between the curves 7a and 75; no more, 
however, when this point is situated between da and dy. Then it 
represents two equilibria 7,LG, which differ from one another by 
the composition of the liquid ZL. The liquid of the one equilibrium 
is situated in fig. 1 at the one side, that of the other equilibrium 
at the other side of the line dZ,. 
In fig. 4 each point of the region Z,LG, which is situated within 
evhbi represents two equilibria Z,LG; the liquid of the one equi- 
librium is situated in fig. 1 at the one side, that of the other equi- 
librium at the other side of the line eZ,. Also, however near to 
the point 7 we take this point within ev bi, yet it always represents 
two different equilibria. The point £ itself represents still two 
different equilibria; in the one equilibrium the liquid has the com- 
position, indicated by point Z in fig. 1; in the other equilibrium 
the liquid is situated somewhere on vq. 
Hence it is apparent that this property is true again when we 
take into consideration in fig. 3 the first condition and in fig. 4 
the second. 
After this discussion of some examples, we shall now consider 
the general case. For this we take the field 
(A) Bt Ln Ent? 
first in its whole extension, consequently without taking into con- 
sideration which parts are stable or metastable. When all phases 
have an unvariable composition, then nothing particular can take 
place on change of P and 7’; this is the case, however, when one 
or more phases with variable composition occur. We take from the 
equilibrium (°F) a complex X and we change the pressure at 
constant 7’ or the temperature under constant P. Now the phases of 
this complex change their composition; we may imagine that at a 
certain moment between them a phase-reaction becomes possible. 
This is the case e.g. when in a binary system two points coincide 
