( 505 ) 

 know in how far the properties of Jle and H 8 create that possibility. 



§3. Barotropic phenomena at the compression of a mixture o f definite 



concentration. What will take place in this case is easy to be derived from 

 the foregoing survey of the different equilibria which are possible at a 

 same temperature. For the further discussion we have to trace the 

 isomignic line, the line of equal concentration [x = const.) for this 

 mixture, and to examine the section with the connodal curve, the 

 successive chords, and finally again with the connodal curve. 



In the description of the barotropic phenomena we shall confine 

 ourselves to the more complicated case, that at the T considered 

 both a higher and a lower barotropic tangent-chord occur, after 

 which it will be easy to survey the phenomena when only one 

 barotropic tangent-chord appears. 



To distinguish the different cases we must divide the liquid branch 

 of the connodal curve at T into an infra- {x = to x = x^T , lower 

 barotropic concentration of the liquid phase at T), inter- (ximt to xh, s t) 

 and supra- {x = xibsT to x — x p i )-barotropic part, and the gasbranch 

 into the three corresponding pieces falling within and on either side 

 of the region between the two barotropic tangent-chords (the lower 

 bix and the higher b s j) at that temperature. 



Whether the phenomena of retrograde condensation attend those 

 of the barotropic change of phase or not depends on this : whether 

 both barotropic concentrations of the gas phases fall below the plait- 

 point concentration or not. 



Let us restrict ourselves in this description to the case that this 

 complication does not present itself or let us only consider mixtures 

 for which x <^ x p i . On compression the first liquid accumulates in the 

 lower part of the tube for x <^ x g uT and for xr ^> x ^> x g b 8 T) and in the 

 higher part for x f ,i, s T^> x^> x g uT- On further compression, when 

 MgbiT ^> < v ibsT , change of phase will take place once for mixtures of 

 the concentration x, so that x g b s T ^> x ^> a gbil or xib 8 T^>^^>^lUTl 

 it will take place twice for mixtures of the concentration x, so 

 that XgUT ^> x ^> 'VibsT- So the last remains of the gasphase will 

 vanish above for x^xmt and for x p i^> x^> xib 8 T, and below for 

 •'7/;.sY , ^> x^> 'i-'ibiT ■ 'f it is possible that over a certain range of 

 temperature the barotropic tangent-chords get so far apart that 

 %ibiT ^> AgbiT, change of phase will again take place once for these tem- 

 peratures for mixtures of the concentration x, so that x^bsT ]> x ^> xi^t 

 or XgUT > x > XibiT ■ 



This description will, of course, only be applicable to He and H, 

 when the suppositions mentioned prove to be satisfied. 



