(48 ) 



is given in fig. 4a. Kuenen met with it, among others, in the case 

 of mixtures of C^Hg with ethyl- and some higher alcohols. Also 

 triethjlamine with water is a well-known instance. 



This case is evidently found, when the plaitpoint curve CjC, of fig. 2 

 assumes the shape drawn in fig. 3. We may namely imagine that 

 when the two curves d Cj and CqA approach each other, a deviation 

 from the straight course may be found on the left side of C^C^, 

 specially if b^ should not be = b,, by which the point C\ would 

 therefore be shifted to the left, to the side of the small volumes. At 

 all events the anomaly of one of the two components can give 

 rise to the occurrence of this second principal type, as I showed in 

 a preceding paper. 



From the shape of the different spinodal curves it is obvious that 

 from Ci the temperatures first increase, as far as the point of contact 

 at R^. The temperature is then T' (see fig. 3<2). But between R^ and 

 RJ, where the plaitpoint curve is again touched by one of the 

 spinodal curves, the temperature decreases, and so also the pressure, 

 so that in the ^;, T-diagram of fig. 3a the line R^ R,' runs back 

 again, as in fig. la the line R^ A and in fig. 2a the line R^ A, having 

 in this case two cusjjs in i?, and RJ. 



Here the points between R^ and RJ, and also those on d R^ and 

 C^RJ in the neighbourhood of R^ and RJ can again not be realized, 

 and the consequence will be the occurrence of a three phase 

 equilibrium^). 



As I already observed in one of my previous papers (I.e. p. 646), 

 after the two liquid phases 1 and 2 have coincided in the neigh- 

 bourhood of the point R\, here too, separation of the two liquid 

 phases must take place again — provided the temperature be sufficiently 

 lowered — and this will take place in the neighbourhood of the 

 point, where one of the spinodal curves in R, touches the plaitpoint 

 curve Co A. This is also represented in the jh T-diagram of fig. Sa. 



When comparing figs. 1, 2 and 3, we see clearly the connection 

 between the three principal types and their transition into each other. 

 The connection is given by the different course of the two plaitpoint 

 cui-ves in figs. 1 and 2, which (see fig. 3) may pass continuously 

 into each other with changed circumstances of critical data of the 

 two components. 



1) Gf. VAN DER Waals, Gontinuital II, p. 187, and These Proceedings V, 

 p. 307-11 Oct. 25, 1902. 



