857 
(er Hy, 5] de Here) s + (y,—8) 1 dy = 0. (13) 
: . dy À 
We thus find a definite value for —; at the same time it appears 
ae 
from (13) that in point / the saturation line under its own vapour 
pressure and the liquidum line of the heterogeneous region LG 
meet each other. It further appears from (13) that the tangent to 
the saturation line in # under its own vapour pressure and (he line 
which connects the points # with the vapour phase are conjugated 
diagonals of the indicatrix in point £. (The same applies, of course 
to the boiling point line of the saturated solutions). 
If accidentally, not only the liquid but also the vapour still has 
the composition /’, therefore, when not only «=a and y=, but 
dy Nn EG 
also ¢, == a andy, — 8, then De becomes indefinite. 
In this case, however a maximum or minimum vapour pressure 
appears in the ternary system LG; we will refer to this later. 
From (6) and (7) we deduce for rs =a and y=8: 
(BC—AD) aT 
A 
This relation determines the change in temperature d7Z’ around 
point F; this is always differing from O unless one chooses de and 
dy in such a manner that the second member of (14) becomes nil. 
According to (13) this signifies that, starting from /’, one moves 
over the tangent to the liquidum line of the heterogeneous region L(, 
We now choose de and dy along the line which connects the 
point £ with the vapour phase; for this we put: 
de =(e,—a)di and dy=(y,—p)dA . . . . (15) 
We then obtain from (14) 
(BC—AD) dT = (V—v) (a, —a)? r + 2 (@,—a@) (y,— 8) s + (y,— 8)? § dd (16) 
v, which A obtains 
= {(v,—a)r + (y,—@) si} de + wr, —a@)s + (y,—8) dy (14) 
In this we have replaced A by the value V- 
fora == a) ard “y= 8: 
Let us investigate the sign of: 
K= BC — AD = (Hr) C — (V—v») D. 
Now, C is the increase in volume when a quantity of vapour is 
generated from an indefinitely large quantity of liquid; D is the 
increase in--entropy in this reaction. Hence so long we are not too 
close to temperatures at which critical phenomena occur between 
liquid and vapour, C is as a rule large in regard to (V—v); H—7 
and D are quantities of about the same kind. If now V <2, then 
K is for certain positive; if, however, V > v, then K is, as arule, 
