Tlie a{)peai'ance ot' a iiiiiiiiuiiiii is nol a priori ('xcliided; tlie general 

 i'onilitioiis now pass iiilo : 



So it is not exidenl, \\\\\ llie appearance of a niiniiniini slionld 

 eoincide with a\,^ <^ r/, r/,, '). 



Even for (t'\., ^ r/j ('^, a niinimuni can very well present itself. 



Tn fact tliei'e arc ol)jeclions lo assnniin<i- that <i'\., <i<i^(i.,, for this 

 supposition leads when the lemperalnre becomes lower to partial 

 mixability ■') and this phenomenon [)robably does not appear for 

 normal substances ^). 



The following however holds good for a possible minimum : 



a, + a, - 2a,, > {h^ + />, - 2^,) 7" , SO 



'^1 + ''. - 2''i. > 0. 

 For 'all temperatures excluding partial mixability, we lind thus 

 when a minimum appears 



l/a^ rt, < a^.^ < V, (rtj -[- a J. 

 71 = 3. 



The equation A3 = has a double root 1 = 0, so we obtain the 

 following series of signs : 



or 



II 



1) VAN DER Waals. I^roceedings, Amsterdam, Oci. 1002, p. 244. 

 -) VAN DKR Waals. Clonhnuïtiil II, p. 43. However in the ijediiction it lias been 

 supposed lliert! lliat Upq ■= ^/^ {hp -\- hq). 



3) VAN DER Waals. Slatique des Fluides, p. 32. 



