( 795 ) 



more, favourable for mixtures of helium and neon 1 ) than for those o. 

 helium and hydrogen. 



For mixtures of helium and water the ratios for the above assumed 

 «He and />n,. are such that for them limited miscibility in the gas 

 state is to be expected, if the suppositious mentioned in § 2 are to 

 be applied. 



The coefficients of viscosity and of conduction of heat (cf. Comm. 

 N°. 96c, Febr. '07 p. 660 footnote 2) admit a value of b lh . which 

 is still somewhat though only little higher ; this might render 

 it possible to realise the said phenomenon perhaps also for the other 

 pairs of substances mentioned, especially when we bear in mind 

 that its appearance is not excluded for 7\ m <^ T^ (cf. p. 794 footnote!). 



The experimental investigation of these mixtures has beeu taken 

 in hand in the Leiden Laboratorv. 



(Communicated in the meeting of March 30). 



§ 7. The shape of the spinodal curves and of the plaits for the 

 case that the moUcules of one component exert some, though still 

 feeble attraction. With very small value of the mutual attraction 

 a la of the molecules of the two components, in connection with the 

 feeble attraction a a , of the molecules of one component inter se, the 

 spinodal curve will with decreasing temperature extend more and 

 more on the if> surface as in PI. I fig. 1 from the side of the small 

 v's, come into contact with the line x = at T=^T/ Cr , and then 

 cross from the line v = b to the side x = in two isolated branches 2 ). 

 We leave here out of account what takes place at lower temperatures 

 when the spinodal curve approaches and reaches the side,r = l too. 



To examine what shape the spinodal curve can have with greater 

 attraction of the most volatile component, we shall avail ourselves 

 of the suppositions introduced in § 2 and also applied in § 6 con- 



i) Cf. Ramsaf and Travers, Phil. Trans. A. 197 (1901) p. 47 for data con- 

 cerning refractive power and critical temperature of neon. 



dTxpl 



2 ) Here ■ > for ' x = 0. We see here that Verschaffelt's conclusion 



dx 



(These Proc. March 1906 p. 751) concerning the maximum temperature in the 



plaitpoint curve for mixtures, for which the component is indicated by a point 



from the region OHK (see fig. 2) must be supplemented by the possibility that 



he branch of the plaitpoint curve starting from the first component, goes to infinite 



pressures. 



54 



Proceedings Royal Acad. Amsterdam. Vol. IX. 



