( 817 ) 
confined to values of w between ‘x,), and (v,),, when (,), denotes 
the value of x for which on the righthand side of the closed dotted 
curve the tangent is normal to the «z-axis, and in the same way 
(v,)g the same thing on the lefthand side. 
For a section between (x,), and (w,), the modification remains 
restricted between the two values of 7’ which are determined by the 
closed dotted curve of fig. 39 for the temperature. Outside these values 
of « and 7’ the upper sheet is, if not quite unmodified, yet of the 
usual shape. If we call the concentration of the vapour phase 2,, 
and that of the coexisting liquid phase z,, this usual shape of the 
upper sheet is determined by the equation : 
d5 
v,, dp =(a#, — «,)| — | de, + 1, dT. 
Cok. 
2 
2 
And if it were our purpose to determine the situation of the sheet 
of the three-phase-pressure with respect to the metastable and un- 
stable sheet of the coexisting equilibrium between vapour and liquid, 
the above equation might serve this purpose. For along the circum- 
aa. 
dT 
known. Thus to give an example, this quantity is positive in the 
lower part on the right hand of Q,. And v,, being positive and 
v,—a@, negative, we find from: 
dp \ _ Op 
(Ge) + Gr), 
d, 0 
(F)<(55)- Hence in the righthand part the sheet of the three- 
123 Te 
phase-pressure lies below the metastable sheet — which, however, 
might be considered as having been known beforehand from the 
shape of a p‚z-line at constant temperature for the equilibrium 
vapour-liquid. In the lefthand part the sheet of the three-phase- 
pressure lies on the other hand above the metastable sheet. 
In a section normal to the «z-axis just through Q, the sheet of 
the three-phase-pressure begins at Q, touching the metastable sheet, 
and in a section just through Q, there is contact at the end. But 
it would lead us too far to include all the metastable and unstable 
sheets in our consideration. To examine what the shape is of the 
stable part of the liquid sheet inside the dotted ring, and so of the 
upper part of the surface of saturation is, however, very necessary 
indeed. 
If we take two points of the dotted ring lying on a level and if 
we call the value of x for the point lying on the right z, and for 
ference of the closed dotted curve of fig. 39 the value of is 
