( 479 ) 



lliis closed plnil is our (»!' iiiiiiiiiiiiiii prcsstifc : slni'liim IVoiii this 

 poiiil llic pressure on lliis plail passes tliroii^li a iiiaxiiiiiiiii and a 

 iiiiniiniiiii siiecessi\elv and i-eaclies ils liiiiliest \aliie in llie I'eal plail- 

 poinl. hi olliei' words \\\o tlieoretical part of llie lieni erilieal cnrNc 

 iji llie yy,/-diaLii-ain shoidd lie helow the piaelical |)ait, as willi the 

 oilier aleolioU. This supposition seems so iiiiicli sini|>ler llian llie 

 opposite one thai I feel priniijiled to stale the lollow inu rule: ir/im 

 tin' llirci'-itlnlsi' ni't'ssiiri' is lifhi'ii'ii flic rilpoii/' jiiu'ssiiiu's af llit' coni- 

 jtDiit'iits fill' lli<'or<'tlc<il vnticiil ciirri' hi'iids (loii'iiirdrds. irlnn it /.v 

 li'iijlwr tiniii tin' riijunir jnu'ssiircs of tin' cinn jxini'iits (as with ellicr 

 and water \) ) the cnrri: hi'inis n jnciii-ds. 



Ill his hook on the "C\)iitiniiitv ' ') the author discusses the pro- 

 bable behaviour of the niixtiiros at liiuher lemperaliires. Apart from 

 a possible plailpoint on the side of the small \dliiiiies on the li(piid- 

 plait, there is no practical plait[)oiii1 left above J. Prof, van di'.k 

 Waai.s assumes that this condition will continue up t(t the critical 

 point of methvlalcohol. that the plait \\ ill close itself here, gradually 

 contract and ultimately (hsap|»ear either at the limiliiii:- li<piid-\ (iliime 

 or by its plailpoint nieetiiiii- with a possible li(piid plaitpoint. 



This expectation has not been realised by my experiments and 

 must ill itself be looked upon as improbable. The formation of the 

 li(piid-|>lait is ascribeil to the association of methylalcohol. Abo\-e a 

 certain temperature this abnormality has disappeared and in any case 

 at the critical point it is for most substances \-ery small, ('onsiderin^i- 

 the jj,reat diirerence between the critical temperatures of the two 

 coiislilnents of the mixture an admixture of etliaiK^ to methylalcohol 

 cannot but lower the ci-itical point, even if the mutual attraction 

 of the (Mmiponents were comparatix'ely ureal. As a matter of fact 

 methylalcohol seems to liaxc some associntioii left at the critical 

 point ■'). Ihil this association has the ellect of making- the mutual 

 attraction appear even smaller and thus increases the probal>ility of 

 a lowcriuii- of the critical lemperaliire by the addition of ethane. It 

 follows that the cross-plait has to apjiear on the j|'-Mirface in the 

 usual manner with fall of teiii|ioralure, with its plaitpoint turiii-d 

 towards the ethane side. 



in \ iew of the fact that at low lemperaliires there is a liipiid- 



•) KuENKN ami Ih^DsoN I. f. p. :!.-)l. 



2) Conlinuiliil II, )). lS<t voiv. 



■'•) Pi.vMSAY i^ SiiiKi.Ks, Zcilsclii'. Pliysik. (llieinic IT), p. 1 15. Nojjoily seems hi h;iv«« 

 c)l»sprvo(l as far as I know thai the coinparalively liigli value of the rrilical tomp- 

 eratiire of melliylalinliul may he e.xplaineii liy associalioii, as also tin- di-vialioii 

 tVom Kopp's law Uw llie boiling points of series of organic substances. 



