( 279 ) 



occur both on the plait starting from v = b and on that starting 

 from ,v = (figs. 2 and 3). If in the homogeneous double plaitpoint 

 the isobar should run parallel to the .r-axis. T^u would coincide 

 with Tdpi ■ For T < Td,,i a barotropic chord exists on the obliquely 

 crossing plait, just as in case (a) 1 ). 



For 6,, > b lu as in this case for a, the existence of barotropic 

 tangent chords is not required. 



c. If b tt < b u , a barotropic plaitpoint will make its appearance for 

 r J\.h<C 7*, and > Tkmi at lower temperatures a barotropic tangent 

 chord is found on the plait starting from x = and closed on the 

 side of the small v's, and at T <C Tkm on the obliquely crossing plait 

 (fig. 4). For b 3i ^>b u as for a and b. 



In fig. 5 the course of the spinodal curves (continuous) and of the 

 connodal curves (lines consisting of dashes) on the tp-surfaee for the 

 unity of weight has been more fully represented for a case c. The 

 figure has been construed with a view to mixtures of helium and 

 hydrogen. In this we adopted the hypotheses mentioned in Comm. 

 N°. 96--, Dec. '06, p. 509 and 510, and put for hydrogen 7/,=: 32,3, 

 ^=14.2, for helium 7^=1,3, 6 M He = £ &mh s (p. 275 note 2) 5 ). 

 The volume v is expressed in the theoretical normal volume of a 

 molecular quantity as unity. The point K m has been calculated 

 according to van dkh Waals Cont. II, p. 43. The spinodal curves 

 have been constructed as in Suppl. N°. 15, March '07, p. 788. 

 Pu is the barotropic plaitpoint, calculated in the way indicated in 

 Comm. N°. 96 c , Dec. '06, p. 510. Further the plaitpoint curve 

 K x K m calculated according to the equation given by van Laar, 



') In the light of our present knowledge of the behaviour of mixtures and divested 

 of the considerations which are incompatible with it (cf. p. 274 footnote 1) the 

 phenomenon deemed possible by Jamin, G. R. 96 (1883) p. 1451, Journ. phys. (2) 

 2 J 883) p. 383, would be described as follows: On compression of a gas above a 

 suitable quantity of liquid (see p. 281 note 2), this liquid is made to dissolve at first 

 under plaitpoint circumstances after which on further pressing in of the gas 

 into the thus formed homogeneous phase a phase richer in the least volatile 

 component (called by Jamin liquid, by us in certain cases, cf. Suppl. No. 15, 

 March '07, § 4, second gas phase) may separate above the phase which is richer 

 in the most volatile component. If this phenomenon could be realized, we should 

 have to deal with a case b for a temperature T > T,t f i, and in which the line 

 EQ (see fig. 6) intersects the plait starting from v = b in such a way that for 



the intersected connodal tangent chords i > — . 



3 J However, on account of the uncertainty which s^ill prevails about Ti-He and 

 picll<; and in view of the probability that a\m < ^ania a<m (see p. 280) it is 

 still to be considered as quite possible that He— H 2 belongs to case (6), as was 

 supposed in Suppl. N°. 15. 



