CONDENSATION AND CRITICAL PHENOMENA. 275 



second plait. The theory may predict to a certain extent 

 the various possible cases that may occur, but very little 

 experimental work has as yet been done in this direction. 

 Konowalow and Alexejeff's researches must be mentioned 

 in this connection. Konowalow gives his results as curves 

 in the / .v diagram, Alexejeff uses .r t curves. Both 

 these diagrams are closely connected with the/ / diagram, 

 because all three may be looked upon as sections of, and 

 curves on, a surface, the p x t surface. We might con- 

 veniently call that surface a "border surface" as it contains 

 the phenomena of condensation, including the critical phe- 

 nomena, for mixtures of two given substances. 



The p t X surface is obviously not the only border 

 surface possible. Any three of the four quantities p v t 

 and X may be chosen as co-ordinates for a surface of that 

 kind. A set of v x border curves (of which fig. 3 is an 

 example) would together give the v x t border surface, and 

 so on. 



The same variety of choice exists if we want to represent 

 by a surface the condition of mixtures when homogeneous, 

 i.e. outside (or inside) the border curves. Bliimcke has 

 studied the properties of the / v x surfaces for mixtures. 

 None of these surfaces however gives the co-existing phases 

 by a simple geometrical construction as Van der Waals' -^ 

 surface does, and as long as the experimental data are so 

 few as they are at present, it is highly advisable to take 

 that surface as a guide and translate as it were its properties 

 into any two or three dimensional diagrams which seem 

 useful for our special purpose. 



BIBLIOGRAPHY. 



L. Cailletet. Experiences sur la compression des melanges 

 gazeux. Coiiiptes Rendiis, 90, pp. 210-11. 



L. Cailletet and P. Hautefeuille. Recherches sur la li- 

 quefaction des melanges gazeux. Comptes Rendus, 92, pp. 

 901-4. 



S. V. Wroblewskl Ueber das Verhalten der flussigen atmos- 

 pharischen Luft. Wiedemann s Annalen, 26, pp. 134-44. 



