( 831 ) 
temperatures which draw near to 7, the equilibrium 2,3 will have 
become the main plait, and the sheet 2,1 must be considered as a 
branch plait and then the hidden plaitpoint belongs to this sheet, and 
the plaitpoint lying on the branch Q, ?., and the hidden plaitpoint 
form together a pair. 
So at the temperature of the splitting up of the spinodal line the 
points forming this pair must still be a certain distance apart. At 
higher temperature, in the drawing at 7’ of P.7, they coincide. A 
consequence of this transformation of the lefthand part to a branch 
plait, and reversely of the righthand part to a main plait is among 
other things that at higher temperatures on the lefthand side the 
metastable and the unstable branch of 2,5 form a line which pro- 
ceeds continuously, with a minimum pressure on the side of 2, and 
a maximum pressure on the side of 1, whereas these branches have 
for the equilibrium 2,1 the intricate shape known of a branch plait, 
and on which a hidden plaitpoint then occurs. 
The three-phase-pressure is represented by the dotted line Q,'Q, Q, Q,’ 
in fig. 43. The branch QQ, is the vapour branch. With regard to 
some particulars, a difference must be made depending on whether 
the Ast component, viz. that for which 7, < 7;,, has also the 
smallest value of 6. But as far as these and other particulars are 
concerned, it is perhaps better to wait if direct experimental inves- 
tigation yields data for this. 
With regard to the p,x-projection of the plaitpoint line and the three- 
EL Y i i dP . 
phase-line it suffices to state that if — — 0, also — = 0. While 
eG 10 
moreover a maximum for P,; can occur on the side of the 2nd com- 
dn 
ponent, if ——- — 0. 
Gh 
And now in conclusion this remark. If the three-phase-pressure 
begins above 7%, it depends on the following circumstance whether 
double retrograde condensation occurs or not. Let us think the well- 
known looplike p,a-curve drawn at Zg. If now the three-phase- 
pressure appears on the upper sheet in a point that les lower than 
the critical point of contact, it must occur at higher temperature. 
In the other case not. 
