( 278 ) 



line v = b for mixtures of helium and hydrogen '), it is desirable to 

 subject the barotropic phenomena for the cases mentioned to a closer 

 examination. In this discussion for mixtures one component of which 

 is a gas with feeble attraction, we shall again restrict ourselves 

 and suppose that in the considered cases at the considered temperatures 

 the second branch of the plaitpoint curve (van Laar, These Proc. 

 May '05 p. 37;, starting from ƒ£,, does not make its influence felt, 

 so that three phase equilibria do not yet make their appearance. 



§ 2. The course of the barotropic phenomena for binary mixtures, 

 one component of which is a gas tohose molecules exert only a feeble 

 attraction. 



In this discussion we shall have to distinguish the cases a, b, and 

 c mentioned in § 1. 



a. In this case a plait starting from v = b and closed towards 

 the side of the large v's, appears for 7\ m ^> T^> Tj,, which plait 

 we have called gas-gasplait in Suppl. N°. 15, March '07, p. 793. If 



&„<&„, then e p i will be > — for T> T h/jh (see Coram. N". 96* 



p. 504); at T= Tbph a barotropic plaitpoint occurs (cf. Suppl. N°. 15 

 March '07 PI. I, fig. 1); at T <^ Tt, p i s we find a barotropic nodal 

 line on the gas-gasplait (cf. Suppl. NM5, PI. I, fig. 2). At T= 1\ 

 the gas-gasplait passes into an obliquely crossing gas liquid plait. A 

 barotropic nodal line will exist on it (see fig. 1) till it disappears 

 under the three phase triangle, and so passes into the not absolutely 

 stable region. As mentioned in $ 1 we shall not give the description 

 of what happens when three phase equilibria have appeared. In the 

 same way we shall for the present disregard more complicated cases, 

 as the appearance of two barotropic nodal lines on the gas-gasplait, 

 three on the obliquely crossing plait etc., till further investigation 

 may teach that these cases are possible. 



If b„ > b xl , the plait coming from v = b may reach the side x = 0, 

 and pass into an oblique plait without it being necessary that a 

 barotropic tangent chord occurs. 



b. For b, t <^f> u a barotropic plaitpoint will occur at Tb,A s ^> T^i 

 (cf. Suppl. N°. 15, March '07 p. 798). This barotropic plaitpoint, 

 and also at Tb p u > 7 7 > Td u i the barotropic tangent chord, may 



!) This follows also from van Laar's fig. 22, Arch. Teyler (2) 10 (1907) p. 38 

 with the mentioned estimations on the critical temperature and pressure of helium 

 (cf. p. 275 note 2) and on the suppositions made (cf. These Proc. Dec. '06 p. 509 

 and 510). 





