( 792 ) 



Every phase which cannol be brought on the connodal curve 

 through this operation, or if it can, comes on the gas branch, will 

 have to be called a gas phase, every phase which is made to lie on 

 the liquid branch through isomignic expansion is a liquid phase; 



Besides the phases lying between the connodal and the spinodal 

 curve which isomignically may be brought on the liquid branch of 

 the connodal are metastable liquid phases. 



Besides the isothermic and isomignic compression without splitting 

 there is another operation already mentioned in ^ 3, which may 

 help us to form an opinion about the similarity of different phases, 

 viz. the isopiestic and isothermic mixing. ') With regard to this 

 phases which have been obtained by isopiestic admixing- without 

 splitting from phases of which it has been ascertained that they are 

 to be called liquid phases, must be called liquid phases until in 

 another way. (e. g. because no splitting takes place with isomignic 

 compression and expansion) they have been proved to have passed 

 into gas phases. s ). 



Proceeding to the case that the plait from higher temperature 

 appears as a closed plait on the «//-surface, as long as the plaitpoint 

 which first comes into contact with the side with decrease of tem- 

 perature, lias not yet come into contact, and with decrease of tem- 

 perature the plait has not yet reached ;i mixture which on splitting- 

 behaves as a simple substance, and for which the distinction in 

 liquid state and gas state is therefore fixed, we shall have to con- 

 sider that branch of the connodal curve on the side of this plait- 

 point, which passes into that of the gas phase at lower temperature, 

 as belonging to the ordinary gas phase, whereas the branch which 

 passes into the liquid branch at lower temperature may be looked 

 upon as a second gas phase, and we are the more justified in doing 

 so as the temperature should lie further above the critical tempera- 



!) With the continuous isothermic and isopiestic mixing of two similar phases 

 a and b the case may present itself (divided plait in the case of minimum crit. 

 temp.), that an intermediate phase c of the other kind is obtained. So in general 

 we cannot conclude to the similarity of c from the isothermic and isopiestic mixing 

 of similar a and b. 



2) This criterion is particularly of application to the retrograde condensation 

 ^2nd kind. For then phases on the connodal curve between the plaitpoint and the 

 critical point of contact are liquid phases, phases on the p-curve through the plait- 

 point and phases with the same x as the critical point of contact just the transi- 

 tions to gas phases. The phases within the triangle bounded by these two lines 

 and the connodal curve are also to be considered as liquid phases. 



Here we abstract from the small uncertainties which would be caused in these 

 definitions when capillarity ought to be taken into account. |_Added in the translation J. 



