( 260 ) 
III. The two critical end-points lie on the branch SM (points p. 
and q 2 from fig. 1), so between melting point and maximum subli¬ 
mation point. The liquid branch of the two-phase region of p coexisting 
with solid intersects the line for x = 1 / 2 twice, once in the melting- 
point S (Fig. 3), and the second time in a point b, which lies between 
S and p. In the same way the vapour branch of the region of q 
intersects the middle phase twice, in the maximum sublimation point 
M and in a point lying between M and q. In b and S the compound 
exists by the side of liquid of equal concentration under the three- 
phase pressure; in the points of intersection of the vapour branch 
with x — 7 S by the side of vapour of equal concentration, with which 
then a liquid of other concentration coexists. The line which in this 
case indicates the equilibrium between liquid and gas for the concen¬ 
tration of the compound passes through S and M, but also through 
the two other points , of intersection of liquid and vapour branch 
with x = 7s, and through a point c of the critical line, which is, 
therefore metastable there. 
T 
T 
Fig. 4. 
