(559) 
(dw dp 7 
lt ra ibaa ae 5 KAN 
dp 
dv,2 
bes ( a2 \2— ve ey ep — 2 
ay dry dv, 5 dw dn dv, dy, Or, jp 
de” Sy dw pin eles dr du dw a 
i) as dv? a3 — dur? wate 
a RD 2 
ry ED, 
Oa” dw 
Ov,” 
Ee dw AW TP 
4 Py dv, 02, dv, dy, 
tf Ee dary dy a oy 
AM ay thea bo AE 
Le 
7 amas ay _ \an an) 
a? dw 
dv,” 
ay Os Op 
EE a 
ae bra an 
df 
numerator of the second term being equal to d , and as p and 
w/ p 
dy, being equal to — dp, and the 
io must be equally great for coexisting phases, the above equation 
dz 
cannot be satisfied without the factor of dy,” being 0. As we saw 
before, we reduce this factor to the criterion for the limit of 
the unstable and stable phases; and the surface of coexistence 
and the spinodal surface have therefore an element in common. 
As a rule these two surfaces will not only touch each other in 
one point, but we shall be able to give a continuous series of points 
of contact, so a curve along which the surface of coexistence 
envelopes the spinodal surface. The latter case has already been 
discussed in our former communication, when at equal temperature 
and variable pressure every time another mixture was in plaitpoint 
circumstance. The case that they touch each other only in one 
point occurs when we can form a mixture of the three components 
31% 
