310 J. P- KUENEN. 



C2, at least not witli those some distance away frorn B. For a mixture 

 like the oiie in the figure tlie two critical points F and E must be far 

 apart froni each other and froni tlie critical point (not sliown in the 

 figure) whicli the mixture would hâve if it did not separate into two 

 phases of différent composition, but behaved like a single substance '). 

 With mixtures of maximnm, va])our-])ressnre and inrnimMiii critical tem- 

 pérature, such as etliane + nitrous oxide, which were discovered some 

 time ago, the loops between R and the critical point of ethane were 

 broader than the others but even there remained relatively narrow and 

 it was natural then to suppose tliat tins fact had greater generality 

 than now appears to be the case. The shape of the plaitpoint-curve and 

 ■ the great distance between B und C.^ in tins case might hâve suggested 

 the probability of broader loops, even without the confirmation by 

 experiment. 



If is unnecessary to indicate the shape and changes of the plait on 

 the ■'F-surface for mixtures of hydrochloric acid and methylether, as we 

 can refer the reader to Hartman'w thesis quoted above. 



As regards the experiments themselves 1 will only mention that the 

 methylether was prepared from pure methylalcohol and sulphuric acid, 

 and absorbed in sulphuric acid from which it was afterwards liberated 

 by water. I refrain from communicating ail the numerical data obtained 

 as no value can be attached to the results except cjualitative value. Mr. 

 W. G. RoBsoN assisted me during the whole of the investigation. 



The question what is the molecular condition of the mixtures seems 

 as yet hardly capable of satisfactory solution. The criteria which are 

 applied for this purpose with regard to single substances fail with mix- 

 tures. It was lately pointed ont by Kamerlin«h Onnes ^) that the law 

 of correspoiiding states cannot without further considération be applied 

 to mixtures and van deu, Waals' équation déviâtes too much from the 

 truth to be able to use it as a test for the existence of double molécules- 

 The formation of liquid above the boiling-point of methylether does not 

 prove that association lias taken place : a somewhat higli value of the 



') Compare van der "Waals, Kon. Ak. 27 Noveraber 1897. 



*) Kamerlingh Onnes. Kon. Ak. van Wet. 30 Juni 1900. In this paper mix- 

 tures without mutual association are called „ideal" mixtures: „norniar' mixtures 

 seems more in accordance with the common use of the two words. 



