1186 
each series of signs is a representation of both diagrams. Consequently 
a certain relation must exist between the two diagrams ; we shall show : 
a P,7-diagramtype can be considered as a schematical reaction- 
diagramtype of the corresponding concentration-diagramtype; and 
reversally: a concentration-diagramtype can be considered as a 
schematical representation of the corresponding P, 7-diagramty pe. 
When we take e. g. the P,7-diagramtype of fig. 2 (ID. Hence it 
is apparent that the curves (1) and (2) are situated at the one side, 
curves (3) and (4) at the other side of curve (5). We may express 
this by 
(OUSE Sier list 4. ee 
This relation (51) expresses however also, that in the monovariant 
equilibrium (5) =1 +2 43 +4 a reaction occurs of the form: 
IR Bede Me eee EN 
This reaction expresses that a complex of the phases 1 and 2 
can pass into a complex of the phases 3 and 4 and reversally, the 
quantitative proceeding of this reaction, however, does not show 
itself in (52). We may deduce this quantitative proceeding from the 
concentration-diagram [fig. 1 (II)]; herein it is determined by the 
ratio of the parts into which the diagonals 12 and 34 divide one 
another. As 52 represents the proceeding of the reaction schematically 
only, we shall call for this reason 52 a schematical reaction. 
Now it is evident in what way we can contemplate a P,7- 
diagram as a schematical reactiondiagram. For this we first change 
the meaning of the curves; in the P,7-diagram a curve, e. g. curve 
(/,) represents the temperatures and pressures under which the 
monovariant equilibrium (/,) = #, +... Hope can occur; now we 
assume that this curve (/) represents nothing else but the phase 
F,. [In fig. 2 (II) curve (1) represents therefore, the phase 1, curve 
2 the phase 2, ete.|. Now the diagram is no more a P,7-diagram; 
it is also not a econcentration-diagram, for, although we represent 
in it the 7 + 2 phases, their compositions do not show themselves. 
It is a schematical reactiondiagram only. 
Now it follows from the previous: each phase divides the other 
into two groups; each of those groups represents a complex of phases 
and in such a way that both the complexes may be converted 
mutually. 
In the reactionequation the phases of the one complex are situated 
at the one side, those of the other complex at the other side of the 
reaction-sign. 
Let us apply these considerations to fig. 2 (ID, which we consider 
