(aS) 
we find a differential equation, which differs from the one treated 
p. 124 in so far that x,, y,, dv, and dy, are substituted for 
B, Yo dx, and dy,, and that —w',, and —w',, are substituted for 
wr ande. In the integral found there the same substitutions must 
of course be performed. So we find: 
a wy Pas 1 mae fede ab 
EEEN Ree nine 221 
1—wz,—y, dan 
P1 PM ; 
——l ——_—] 
or vs ( P3 ae C Ys ( v2 ) 
ln lier 
This equation may also be written in the following form: 
Ka heh He DaTEbE babe 
a PL Gs 7. [AV td nn 
For C,=0, we have also «,=0, and the Y-axis is therefore the first 
of the envelopes, just as was the case for the liquid phases. For C,—= a 
we have y,—O and 1—7,—y,—0. The last of the envelopes is 
therefore also here the N-axis and the hypothenuse. Though the 
equation of the two series of envelopes is different, the course is in 
many respects analogous. These envelopes also touch the hypothenuse 
in their beginning and touch the X-axis in their final point. They 
have a tangent parallel to the Y-axis, and the locus of the points 
where this is the case, is found from the equation: 
rt, = 0 
1e En 
or 1e, = y, ——-—— 
le ©" 
Pais rots 
or le, = y, fay os tas 
Pear it 
This locus coincides with the vapour branch of the curve of press- 
ure p,. This nodal envelope has a conjugated curve, which is again 
a nodal envelope with greater value of the constant, just as is the 
case for the liquid phases. 
Before we proceed to the discussion of the nodal envelopes in more 
complicated cases, namely in those in which a maximum pressure 
occurs either on the sides of the triangle or for a point inside the 
triangle, we will make some general observations about peculiar points 
of these curves, which, however, only apply to the case that the 
second phasis is a rare gas phasis. 
. aH, a M 
From the equation : = ann 
Nore aan By at Tae 
Ya Yi a4 U 
