( 'i51 ) 



1 



ail aiiioiiiil (»r ahoiil atmosphere \\ ill keep siicli a |»liase iii e(|iii- 



lihriiiiii, at least as far as the |)rcssurc is coiiceriKMl. And a cause 



which accounts for a dilference of pressure of ahoiil — - almosi^here 



accounts also for considerable (htfereiiees in density as the critical 

 isolherinal runs nearly horizontally in (lie nei<;lil)ourliood of llie 

 critical point. 



A return to the time when wc thoutiht to exphiin a thiiiij,' hv 

 speakinii' of solubility and insolubility, seems not to be desirable to me. 



Chemistry. — ''(hi tJte possihle forms of tlw iiu'lUmjpoint-riirrc 

 foi' huxd-ij iiiidiires of U-oinOi'ithoiis .siihsttti/ri's.'" ]>y J. J. 

 VAN Laar. (Communicated by Prof. H. W. Bakhuis Moozkboom). 



1. The occurrence of so called "eHtertic points''' in nwltiiKj point- 

 curves does not seem to agree with the su])})Ositi()n oï perfect isoioorpliy 

 of the two solid comjionents and of their mixtures. This fact has 

 been repeatedly pointed out. It has been assumed that an inter- 

 ruption in tlie curve rejiresenting the solid mixtures (as in iig. 1 of 

 the plate) can only occur for isodimorplious substances, and that the 

 series of mixtures in the case of isomorphous substances was necessaril}- 

 to be uninterrupted (as in fig. 2). 



Lately Stortenbeker ^) expressed again the same idea and this induced 

 me to subject the question to a closer investigation. In the following 

 paper I hope to show that an interruption in the series of the 

 mixtures can very well occur even for perfectly isomorphous sub- 

 stances. In order to do this wi^ must keep in vie^v that — especially 

 in the solid condition — unstahle phases may occur, and that in all 

 occurring cases it is possible to trace the meltingpoint-cnrve conti- 

 nuoushj through the eutectic point. Only the stable conditions which 

 generally lie above the eutectic point are liable to be realized, so the 

 series of the mixtures is interru[)ted only practically. 



Prof. Bakhuis Roozeboom has expressed the idea of |)rolonging 

 the me]tingi)oint-curve l)eyond the eutectic point already before; 

 the way lujwever in which we must think this to be performed is 

 indicated inaccurately in the figure of an earlier pajier of Stortenbeker '■•). 



1) Ueber Liicken in der Mischungsreilie bei isomorphen Substanzen, Zeitschrift 

 fur Ph. Ch. 43, G29 (1903). 



') Ueber die Lösliclikeit von hydralicrten Mischkrystallcn, Z. f. l^h. Ch. 17, 

 645 (1895). 



