( 060 ) 



paper: Contibution to the knowledge of the p, x- and i\\ep, TMines 1 ,, 



at least when we take the maxima of pressure very much higher 

 and the minima very much lower, so that on the left side the figure 

 intersects itself twice. The detachment of the two binodal curves then 

 takes place in a very intricate way by means of a series of modifications, 

 which I shall, however, omit, with a view to the available space. 

 So, for this I must refer to the lectures which I am arranging for 

 publication as mentioned in the beginning of my preceding commu- 

 nication, though certainly some time will elapse before they see 

 the light. 



Physics. "Contributions to the knoioledge of the ^-surface of 



Van der Waals. XIII. On the conditions f or the sinking and 

 again rising of a gas i>lia.«> in the liquid phase for binary 

 mixtures, (continued). By Dr. W. H. Kkesom. Communication 

 N°. 96 c from the Physical Laboratory at Leiden. (Communi- 

 cated by Prof. H. Kamerlingh Onnes). 



(Communicated in tbe meeiing of January 20, 1907). 



§ 6. Conditions for the occurrence of barotropic plaitpoints for 

 mixtures with M t = 2 M v v kl = 8 v k „. Now that it had appeared in 

 § 5 (These Proc. p. 510), that there exists a barotropic plaitpoint 3 ) 

 on the assumptions mentioned there, first of all the occurrence of 

 barotropic plaitpoints with MJM l = 2 1 vj Ci 'vk 1 = 7s was subjected to 

 a closer investigation, partly also on account of the importance of 

 these considerations for mixtures of He and H 2 3 ). The barotropic 

 plaitpoints given in table I respectively for the ratio of the critical 



>) These Proc. VIII, p. 200. 



2 ) The proof that this barotropic plaitpoint really lies on the gas-liquid plait, is in 

 connection with the discussion of the longitudinal plait. In a following Gomm. 

 by Prof. Kamerlingh Onnes and me on this latter subject, the treatment of 

 which was postponed for the present as stated in Gomm. N°. 96^, the proof 

 in question will be included. 



3 ) To enable us to judge in how far this last assumption is in accordance with 

 what is known about mixtures of He and H 2 , the following remark may follow 

 here, in the name of Prof. Kamerlingh Onnes too, (cf. Gomm. N° 96b § 4, Dec. 

 '06 p. 506) on b (cf. van der Waals, These Proc. Jan. "07, p. 528) and a for 

 helium: It proved in the preliminary experiment described in Gomm. N°. 96a that 

 on analysis the liquid phase contained at least (some He has evaporated from 

 it during the drawing off of the liquid phase) about 3 % He, the gas phase at 

 least (a very small quantity of liquid has been drawn along with the gas phase 

 being blown off) about 21% H 2 (estimations of the corrections which for the 

 reasons mentioned ought to be applied to the results of the analysis make 

 it probable that they will not considerably influence the results derived here [added 

 in the English translation]). Let us put the density of liquid hydrogen boiling under 



