( 806 ) 
d d 
closed line round the second point of intersection of = = Oand ke —0. 
AX U 
27 
14. At a temperature higher than =e of the minimum critical 
temperature, there is positive pressure in the double point. For 
the double point continually proceeds in the same direction; so 
da 
da b 
ag es constantly decreases during this movement and now the 
pee Vv 
da 
expression : 
da dan * 
pee poe 5 
MRT 27 de 1 dx 27 1 n\? 
= == SS SS = = 
MRT. 8 db db 8 2 
a— 2a — 
dx da 
2 
has a value O for n=O and n=2, a maximum for n nk be- 
2 
tween n=—=1 (the 2 of the minimum critical temperature) and x = 5 
€ 
‘ 1 
the righthand member is, therefore, greater than 7 and, so MR mn 
2 
so that the pressure in the double point is positive. For x mn 
double point lies exactly at 7= 7} or v = 3d, so in the point of 
d 
= where this line, which then has split up, has its tangent 
Vv 
//v-axis. At still higher temperature the double point of p gets on 
d 
the vapour branch of En — 0, and disappears at the temperature at 
U 
ee db Heen 
which = = MKT for x=, as is indicated in fig. 9. So long as 
& av 
the double point continues to lie on the liquid branch, that branch 
of the isobar, which comes from «= «,,v — 0, passes through the 
: dp 
double point, meets the vapour-branch of = =0 at larger x, where 
v 
its tangent becomes //v-axis, and then runs back to a point of the 
line «=v, for greater value of v than that of the maximum pressure 
on the straight line mentioned. The other branch of the loop-isobar 
comes from a point of this line with smaller pressure than the 
maximum pressure, and having passed the double point it remains at 
