( 793 ) 



tines of the unsplit mixtures belonging to the phases lying on them. 



Whereas in the ease, that at a temperature comparatively little 

 lower also the other side of the «//-surface is reached by the origin- 

 ally closed plait, the difference of the second gas phase with a liquid 

 phase is still not very conspicuous, this may become very clear for 

 the case of § 2, to which we have now got at last, that viz. with 

 decreasing temperature a plait comes from the side v = b x on the 

 «/'-surface, and the plait appears for the first time as longitudinal 

 plait. Now we may again call PBDF the branch of the first gas 

 phase, PACE the branch of the second gas phase. It will certainly 

 be obvious to speak of gas phases when all the parts of the plait are 

 found above the critical temperatures of the unsplit mixtures, and 

 we shall decidedly have to speak of two gas phases, when the 

 second branch of the connodal curve is intersected all over its length 

 by isomignic lines on which beyond this plait no splitting up occurs, 

 or if it is at most touched by one of them in the point v = b. For 

 then it is beyond doubt that the final point of that branch must be 

 called a gas phase. 



Possibly also phases between the isomignic line of the critical 

 point of contact, the line v = b x and the second gas branch belong 

 to the second gas phase. 



§ 5. The surface of saturation for equilibria on the gas-gasplait 

 In fig. 3, 4 and 5 the sections T= const, of the p, T, ,r-surface ot 

 saturation for equilibria on the gas-gasplait have been schematically 

 drawn for a mixture in which one component is a gas without, or 

 almost without cohesion, in fig. 3 and 4 for temperatures higher 

 than the critical temperature of the first component, in fig. 5 for 

 this last temperature. 



In these figures too the division of a gas phase into two gas 

 phases, and the transition of a part of the gas region into the liquid 



region at T= Tfa is clearly set forth. The curve is the 



locus of the plaitpoints. 



In a following communication, in which the properties of the 

 if'-surface for such mixtures will be further discussed, T, .u-sections 

 etc. will be drawn of this surface of saturation. At the same time 

 it will then have to appear in how far retrograde unmixing of a 

 phase into two other phases is to be expected. 



That one of these phases may be called a second gas phase, 

 appears in § 4. 



§ 6. On tin- conditions which must I»' fulfilled that limited mis- 



