796 



Fig. 3. 

 Dj the least volatile; D.i less volatile than B and C'; 

 B more volatile than C ; A very volatile. 



Tlie piirticularity is here that the eutectio liquid-vapour lines 

 referring to the foexistence with D, -\- D,, merge continuously 

 into each other in the points p and p^, which are therefore two 

 double critical endpoints. 



In these two points the two critical endpoint curves, that of Z), 

 and of Z),, intersect. 



9''' C''/.sv'. Just as in the preceding case two double critical end- 

 points can present themselves, when besides the ternary compound, 

 also tlie component C with A exhibits critical endpoints. We then 

 get a structure as given in fig. 4. 



The double-critical endpoints Pj and P„ are the points of inter- 

 section of two critical endpoint curves. 



For one critical endpoint curve the ternary compound Z), occurs 

 as solid phase, and for the other the component 6'. Of course the 

 corresponding continuous eutectio liquid vapour lines pass through 

 the two points of intersection. It has further been assumed in this 

 figure that just as in the preceding case a binary compound Z), is 

 formed from the ternary compound at a temperature above the 

 critical endpoint p. If in the binar}' system A — B also critical end- 

 points occur, two double critical endpoints may arise also on that 

 side of the ti-iangle, wliicli we need not specially indicate here. 



