1208 
acf is in equilibrium. If ¢ represents the vapour in equilibrium with 
the liquid a, a vapour between a and c will be in equilibrium with 
a liquid between a and 5. If each liquid is united with the vapour 
with which it is in equilibrium, these conjugation lines not only 
occupy the strip eaZ, and faZ but also a part situated between 
ba and curve ca outside this field. 
We have taken the point of intersection a of ZFZ, and the curve 
fe between Hand Z; it is evident that it may also be situated at 
the other side of #. 
We now imagine drawn in fig. 5 a set of straight lines passing 
through F and for each one its conjugated vapour curve ; these latter 
all pass through the point D. Among these there is one that also 
passes through the point / At the maximum sublimation point of 
the compound / the vapour in equilibrium with solid # has the 
composition /’ and the liquid which then, of course, is present in 
an infinitely small quantity only, a composition A’ (fig. 5). We can 
observe this also by other means. We imagine then in fig. 1, besides 
the boiling point lines of the solutions saturated with #, also drawn 
their appertaining vapour lines; one of these passes through the 
point #’ so that at a definite P and 7’ a vapour exists of the same 
composition as / which can be in equilibrium with solid / and a 
liquid. This liquid is represented by the point A’ of the boiling 
point line of the pressure /, appertaining to the vapour point £. 
In fig. 1 and 5 this point is represented by A. Hence, the equili- 
brium solid A+ vapour / + liquid A occurs; we are therefore, 
at the upper sublimation point of the compound /’, therefore, in the 
point A of the sublimation line ak of fig. 4. 
If now in fig. 5 we turn the line ZFZ,, until it passes through 
the point A, its conjugated vapour curve will pass through the 
points D and £. 
We have noticed above that the straight line ZFZ,, and its con- 
jugated vapour line can have a point of intersection a (fig. 5). As 
in this case the vapour a, the liquid 4 and the solid substance F 
are situated on a straight line, it follows from (11) that: 
dP_ (re) B— (¢—0) ere Cao 
dT (we) A — (a —u) C (ere) V + (a—2) V, 4+ (we) v 
(13) 
so that the same relation applies as if the three phases belong to a 
binary system. 
If, on one of the straight lines ZFZ,, the points a and 6 of fig. 
5 coincide, the solid substance 4 is in equilibrium with a liquid 
and a vapour which both have the same composition. This is the 
