( 201 ) 



liquid and solid phase for the case that the last is a dissociable 

 combination. 



Some of the points mentioned in what follows had already been 

 given by him ^), but it was not till now that they could be 

 combined into a connected whole through the knowledge obtained 

 during the last time (see inter alia the preceding paper). 



1. For the case that two substances A and B enter into a com- 

 bination, I shall distinguish three cases. 



1^* that the vapour tension of the combination lies between that 

 of the components, (fig. 1). 



2"^ that the vapour tension of the combination is smaller than 

 that of the components, (fig. 2). 



S'*^ that the vapour tension of the combination is greater than 

 that of the components, (fig. 3). 



2. If we bear in mind that for the case that the combination 

 does not dissociate, a |>ci'-section for the system A-\-AB-{-B is to 



be considered as a junction of the tw^o systems ^4 -}--l^a,nd .4j5-{--^*' 

 it is not difficult to combine the ^>-a:-sections for the system A -}- AB -{- B 

 for different temperatures into one diagram. 



If we first examine case 1, where the vapour tension of AB lies 

 between that of the components, it may be observed, that in the 

 system A -\- AB, A is the substance with the higher and AB that 

 with the lower vapour tension, whereas in the system AB-\-B, AB 

 has the higher and B the low^er vapour tension. Bearing this in 

 mind, we get, led by the diagrams given by me before ^), to fig. 1, 

 in which the hatched regions a m EE^ I, EE^ e e^ e^ dc^ c^ c, dc' E'E\ e' 

 and E'E\ I' l\l' ^l\a' m\m' ^m\m' indicate the vapours and liquids wiiicli 

 coexist with solid phases {A, AB, AB and B) at different tempera- 

 tures. We shall call these regions henceforth the three phase regions ; 

 they have as base the line which joins the points E with E^ res- 

 pectively E' with E\ and are bounded on one side hy a vapour 

 line and on the other side by a liquid line. The latter has ah-eady 

 been called solubility curve before. At and below the eutectic 

 temperature the p-.c-section is simplest and it consists for each of the 

 two systems of two lines representing the vapours which can coexist 

 with solid A or solid AB respectively with solid AB or solid B. 

 Such a p-.?j-section is found in the lines k o (jo E\ h', where it must 

 be expressly stated that o go and goE\ do not form a continuous 

 curve, but are two separate branches, which cut at go. 



1) Rec. Trav. chim. 5, 335 (1886). 



2) These Proc. Vol. VI, p. 484. 



