( 387 ) 



RoBSON one of the components is an anomalous substance. It is 

 almost orenerally accepted, especially because they do not follow 

 the law of the correspondent states, that alcohols when in the liquid 

 state possess complex molecules. At j-= 1, i. e. for pure alcohol, 

 the association into complex molecules is perfect or maximum. But 

 when jr is very small the dissociation into simple molecules is 

 nearly perfect. Under these circumstances the critical temperature 



"x 



is not determined by the course of — alone. 



The critical temperature would be proportional to this quantity, 

 if the molecules of alcohol also in a rarefied solution continued to be, 

 what they were in the dense state when the substance is taken pure. 



Now in general the critical temperature of smaller molecules will 

 be lower than that of more complex molecules. Starting from ethane 

 the temperature would have to rise considerably till it reached that 



of alcohol according to the course of — . In consequence of the dis- 



sociation of the alcohol molecules the course will be determined by 



f — , where f is smaller than unitv. If x is near unitv this factor 



too will not differ much from unity. For values of x which do not 

 exceed \, an idea of the value of this factor is obtained by equating 



it to . Now it is easy to see that even if — had no mini- 



1 + .<• ^ h, 



mum or maximum, there would be numerous cases, in which the 

 factor f causes such a maximum, and this would involve that there 

 was also a minimum. 



If the true interpretation of tlie phenomenon is to be found in 

 this, a course such as Kuenen and RoBSON have found for mixtures of 

 alcohol, can never be found if the substances do not associate. But 

 the reverse may not be stated. What appeared as a longitudinal plait 

 in KuENEX and Robson's experiments, was in reality nothing but 

 a somewhat modified transverse plait. The following phrase already 

 refers to such a modification : (Mol. Theorie p. 172) „Es zeigt sich 

 dann aber, dass in diesem Falle die beiden Falten auf ihre Bildungs- 

 weise anders angesehen werden mussen u. s. w." In the figure on 

 p. 173 the spinodal curve has, however, not been traced correctly. 

 The bulging to the right of P should not be there. It should be 

 replaced by a small isolated closed curve, which has separated from 

 the other parts at the minimum temperature. 



It is not without interest to remark that the mixture of ethane 

 and methylalcohol behaves so differently. To find the probable cause 



