( 637 ) 
points of this curve, which is limited on both sides in this way, will 
coincide (and accordingly also the three points //,D, and C),and the 
whole coexistence-curve reduces to a single point (fig. 26). 
We shall prove the above in the following paragraphs. 
25. In the first place it may be observed that the equation of 
dissociation : 
go (ot &/ 2) Ab 
fs ian. PL Felt ae RT 
aa as @ 
Lê p+ ee 
now gives rise to an altogether different shape of B= f(v) for 7’ 
constant. If Ab is negative, the course is as in fig. 21, with a mini- 
mum in A/; for 4é positive the course is indicated by fig. 22. 
(LBRT . 
SS m 
This is at once evident when p + “/,2 is replaced by 
v—b 
the above equation, by which it becomes: 
Bg: De A STi (14) Ab 
rete Te RT ¢ v—b (v—b) raed a (5) 
For Ad negative the value of 8 will approach unity both for 
v= 6b and for v=o; whereas for Ab positive for v= 6 the value 
of B approaches zero on account of the exponential factor, which 
then becomes e-”. The transition of 8 from 1 (liquid state) to 
near 0 (solid state) takes place in the descending portion AB for 
Ab negative (fig. 21); on the other hand the transition of 8 from O 
(solid state) to near 1 (liquid state) will take place in the ascending 
part AB for Ad positive (tig. 22). As we saw in the preceding papers, 
the increase of 8 from the minimum J/ to 1 again, takes place for 
Ab negative in the vapour phase and large values of v. 
Now for Ab positive the change between A and B (fig. 22) will 
take place for small volumes only, when q, is not too large. For 
else evidently in consequence of the small value of the exponential 
Go 
factor e #7 — the index of which has now no longer the reversed 
+ 4/2) Ab 
sign of that of aw Ee ‚ but the same — the nearly asymp- 
totic course of OA will continue to the neighbourhood of great values 
of v, and the change of # will take place between A and B in the 
vapour phase. But this evidently prevents the isotherm from twice 
taking a turn (in consequence of the rapid decrease of «/,s (from the 
a 
value = WO the value 
a 2 
3 ae between the volumes v==b, (solid) and 
