1590 
We take a point X in a concentration-diagram, e.g. in fig. 1 (ID; 
we imagine this point so close to the side 13, that it is situated 
within each of the triangles 148, 123, and. 153. It appears from the 
position of this point that it may represent: the invariant equili- 
brium 1+2+3+4-+5 or one of the monovariant equilibria : 
(2) = 1458, (5) —1423 and (4)=1258 or one of the bivariant 
equilibria: 148, 123 and 153. 
Now we may put the question: which of those seven equilibria 
will ocenr? Before answering this question in general, we shall 
first elucidate it by an example. 
It is evident that the equilibrium 12345 can only occur at the 
temperature 7’, and under the pressure P, of the invariant point; 
the occurrence of the other equilibria follows from the corresponding 
P, T-diagram | fig. 2 (II)]. Hence it is apparent that the complex X 
is converted into the equilibrium (2) = 1453, when we choose P 
and 7 in such a way that they are represented by a point of 
curve (2); it is converted into the equilibrium (5) = 1423 when P 
and 7’ are represented by a point of curve (5) and into the equili- 
brinm (4) = 1253, when P and 7 are represented by a point of 
curve (4). 
We shall call the part of the P, 7-diagram, situated between two 
succeeding curves a “space”; space (1) (2) means, therefore, that 
part of the P,7-diagram which is situated between the curves (1) 
and (2). 
As is apparent from fig. 2 (II) from the complex \ the equilibrium 
143 will result when P and 7’ are represented by a point of the 
spaces (1) (2) or (1) (5), it is converted into 128, when P and 7 
are represented by a point of space (4) (5) and into 153 when 
Pand T are represented by a point of the spaces (2) (3) or (3) (4). 
As the equilibrium 12345 can occur only at 7, and under P,, 
we leave this further out of consideration. Then it appears that 
the complex Y can be converted into three monovariant and three 
bivariant equilibria, and that the chosen P and 7’ define which of 
those equilibria shall occur. 
We go in fig. 2 (ID starting from curve (2) e.g. towards the left; 
when we write the six equilibria mentioned above, in the order 
of succession, in which they follow one another in fig. 2 (ID), then 
we find® (2) 135°) 123) (hy 1342). 
It appears from the position of the equilibria, that in the P,7- 
diagram : 
1. these equilibria do not cover one another neither completely 
nor partly ; 
