¢ 4440) 
the case if Po > Ts. Also in this case, however, the possibility 
remains that on the lefthand side the intersection takes place in 
points of the lower sheet. But the latter must iake place if Pa, > Th. 
And in the transition of the point of intersection of the upper sheet 
to the lower sheet we meet with the complication which I am now 
going to discuss, but which will perhaps be easier to understand, 
when I shall discuss the properties of the p,a-sections of the surface 
of saturation, so sections at constant temperature. 
If we think such a p,«-section at a temperature only little lower 
than 7, the upper branch has, leaving the line of the equilibrium 
between the two liquids out of consideration, the known shape with 
a minimum and a maximum between z, and z,, because the three- 
phase-pressure exists, P., being < 7. The third phase then lies on 
the lower branch at 2, < #,<a,, and if at higher temperatures 
ne ae oP: the value of ey is then already positive. At at 
IT, tel oS é y positive. At a tempe- 
rature somewhat above 7, the p‚z-curve has got detached from the 
d 
axis (v= 0), and has a point where En od, and 80 vi, 0 BR 
Hi 
then the point 1 still lies on the lower sheet. Now we might suppose 
and I have held this opinion myself, and 1 think I have given 
diagrams in accordance with this view, that on further rise of the 
temperature the critical point of contact for the equilibrium 215 
would proceed so far towards greater value of a, that it would 
coincide with the coexisting vapour phase, but that then at the same 
time this third coexisting phase would be critical point of contact 
for the equilibrium 3,1, to render it possible for the metastable branches 
to be contained in the heterogeneous region. If this were possible 
the third phase would have come on the upper sheet at still 
higher temperature — and in this case there would be no question 
of complication. But that this concurrence of circumstances cannot take 
place we see when we examine its signification. First of all | observe 
that we cannot put that v,, = 0 coincides with v,, = O without proof, 
and that “else we get other complications” cannot be accepted as a 
proof. But we may also directly see that v,, — 0 cannot exist in the 
; =O, dv, 
same point as v,, = 0. Then — — — {| — | = 0 would have to hold, 
Uit, da, pT 
: V,—2, dv, 
and at the same point also ii | = 0. Or the fanvenmie 
L,—2, de Jor 
the isobar in the point wv, would have to pass both through the 
point «, and through the point a,, and this isobar would have to be 
at the same time the isobar of these two jatter points, and the three points 
