( 334 ) 
Now we may again write for the equation of the connodal line 
0 = (vor) —2 B! (vor) + PPE VE ere 
To the first approximation along this curve 
dij 2m,, AT, 2e Lua ge 
a gal == IN. 7. El 2 F : he (37) 
dv? mn, Rpm, RI, k,,ae—m,, 
and this expression has the opposite sign to 7%, 4,,a—m*,,. Here 
therefore we distinguish only two cases. 
dr P 
ARTE hee Pe alan F „<0, i.e. the connodal line turns its 
av 
concave side towards the v-axis (fig. 14); 
dx : 
Dee eR a Ne EM 13 a > 0O and the connodal line is convex to 
LU 
the v-axis (fig. 15). 
9. The critical point of contact. 
The characteristic of the critical point of contact is that there the 
two phases with which the condensation begins and ends coincide. 
If er, pr, and v7, represent the elements of that point we have there 
D= o7,—017% 9 =0, Hpi prin =—Vand zun 
and from (33) it follows that 
RT m,, 
OT, Sa Se ae 
; mo + RT; m,, 
BT Py a> AT > EE 
that is to say to the first approximation the composition at the critical 
point of contact is the same as at the plaitpoint (cf. 26). The diffe- 
rent cases which may occur now follow. 
A glee eile eee im tiea) 
a). T>T 3 er, is negative and there is no connodal line inside 
the region that can be observed. This corresponds to the position of 
the border curve in figs. 5 and 11. 
6b) T= Tr; e7.=0 and the formula (30) represents a connodal line 
which touches the v-axis. 
ce) T< Tr; xr, >O0 and there is a connodal line in the région of 
positive 2, (see also figs. 6 and 12). 
DAR Dragen el 
a) F> Tr; er, >0 and the connodal line lies entirely within 
the region that can be observed; (figs. 1, 3. 7 and 9). 
b) T=T,; er, =—=0 and the connodal line touches the v-axis ; 
ce) P< T,; er, >0 and the connodal line can only be completed 
eaf ae 
