(CAREN) 
From this we deduce: 
Therefore a tangent of the nodal envelope parallel to the hypo- 
thenuse can only occur in the case that w, and w',, have different 
sign. 
All these relations apply only to the case that w',, and w',, may 
be equated to zero; and the given rules will require corrections when 
the temperature is increased and approaches one of the critical 
temperatures. If 7 has reached a value higher than (7%), for instance, 
and consequently the surface of saturation does not cover the whole 
triangle any more, the envelopes can no longer pass through the 
angle of the third component. Even without knowledge of the equation 
of the envelopes we can understand in the following way what 
peculiarity will then come into the shape of those curves. The 
surface of saturation has in the vertical plane containing the }’-axis, 
and also in that containing the hypothenuse still the shape of fig. 11, 
Cont. IL. The first curve of slope lies in the first mentioned ver- 
tical plane and consists of that part of the p curve of the figure 
mentioned which extends to the maximum, i.e. to the point C. All 
other points of this pressure-curve, as well those between C and P 
as those forming the lower branch, represent coexisting phases and 
belong to the conjugated curve of this curve of slope. The last of these 
curves of slope lies above the X-axis and above the hypothenuse, but 
above the hypothenuse it also extends only to the projection of the 
point of maximum pressure. Every intermediate nodal envelope has 
initially the shape of fig. 13, has also still a vertical tangent, but ends in a 
point (the projection of a plaitpoint) before it has reached the locus 
which represents the limit of the points above which the surface of 
saturation extends. Above such a limiting point of the nodal envelope 
the curve of slope of which it is the projection has reached its highest 
point. Before the limiting point however the course has been modified. 
In order to discuss this modification we will derive the second 
2, 
5 : : yy 
derivative function, namely rary From: 
5 
da eo 
mee IS follows 
dea, Ed, 
Ps gy — Crdi) dede) 
ey ’ 
de,” BA (z,—2,)° 
