oe oh, ape 
| a, vs vs Uys 
[9 Ys Ys Yarr: | =O 
When we bear in mind, however, the compositions of the phases 
F.E, then it appears that (13) expresses, that it must be possible 
that between the phases a reaction of the form: 
NE A APS oe ee dan U 
consequently a phase-reaction occurs. Then the equilibrium is an 
equilibrium Eg and consequently it is situated in the P, 7-diagram 
on a curve Ep, viz. on a turning-line of the region 4. 
Therefore we find: 
‘in an equilibrinm of m components in » phases under constant 
P the temperature is maximum or minimum, when between the 
phases a phase-reaction can occur’. 
Consequently in a binary system 7’ is maximum or minimum 
when the two phases have the same composition; in a ternary 
system when the 3 points which represent the phases, are “situated 
on a straight line; in a quaternary system when the 4 phases may 
be represented by 4 points of a plane; ete. 
Now we have still to examine when 7’ is a maximum and when 
it is a minimum. For this we have to determine A7. We take the 
equations (7) in which all the terms with AP must be omitted now. 
When we add the equations after having multiplied the first by 
À,, the second by 4,, etc, then we find with the aid of (8) and 
(13): 
3 (aH). AT 4 QZ) LZ) 4+ oee OD 
or at first approximation: 
Dany ALTE {ese Vee ae 
Herein is: 
20H) = J, eee Ee 
consequently the increase of entropy which occurs at the reaction: 
AB Ea Wey Sy a ey eek 
Further is: 
Bis? 2) == Ze ees 
or, as it follows from the values of d?Z, etc.: 
