1272 
It follows from (10) that: 
aor a—a 
r, tus,)de,+(s,-+ut,)dy,+ gr: +A )dP— ne Bey? dT+- 
( 1 Kad 1 1 waak Jil ! 
- (26) 
+4Cdw,°*+ Dde,dy, +3 Edy, + 0 | 
We may easily calculate what is represented in (15) and (16) by 
A, B, C, D and Z. R and R’ contain only terms which are in- 
finitely small with respect to those, which have been written down 
already. When we subtract (15) from (16) and when we put for 
the sake of abbreviation: 
$ r,dx,? + s,dxv,dy, + 
Kh 
Edit KK . 68 ye 
then we find: 
Vi—e vv H,—y -4.,,. K 
(es =e = dP — En — ‘an ———=f" (18) 
ad, gd Gr bmm’ uit, 
Herein A contains only terms which are infinitely small with 
respect to dP, dT, dx,*, dx, dy, and dy,”. Now between the phases 
FF, F’ and G we imagine a reaction to take place, at which the 
unity of quantity of vapour is generated. Let AV, be the increase 
of volume, 4H, the increase of entropy at this reaction. When we 
put as first approximation in (18) Rk" = 0, then follows: 
AV,.dP—AH,.dT=K . RC 
Hence follows with the aid of (14): 
AH 
Ae. == 2 AY MP AS eee 
AV, is a thousand times larger than AV; consequently the 
coefficient of dP is generally positive; it is apparent from (17) that 
K is also positive. Therefore we find dP >O or: the pressure is 
a minimum in 7, As d7’= AW dT is ze consequently the 
temperature is in 7 maximum or minimum. 
Now we consider the P,7-diagram. The equilibrium AHF’ 
is represented by a curve; as on this curve the conversion of one of 
the solid substances takes place into the two others, or reversally, 
we call this curve the conversion-curve. It follows from (14) that 
on increase of 7’ the pressure can as well increase as decrease. 
The equilibrium-curve /’-+ FH "+ G coincides with the conversion- 
curve; it covers this curve, however, only partly. As the pressure 
is a minimum in its terminatingpoint 7, it proceeds starting from r 
towards higher pressures. Through this point r moreover go the 
