557 



Chemistry. — ''The occurrence of an upper critical point of 

 mixing at the coexistence of two mixed crystal phases" \^y 

 Prof. A. Smtts and C. A. Lobry de Bruyn. ^Communicated 

 by Prof. J. D. van der Waals). 



1. When examining the system K CI ^ — Na CI Kurnakow and 

 Zemczuznyi ^) found that as Fig. 1 shows, a continuous melting-point 

 line occurs here with a temperature minimum at dr 664°, and that 

 after the solidification a transformation still makes its appearance 

 in different mixtures. 



qoo 



8oó 



joo' 

 6od 

 Soo' 



/ 



goo' 



Joo 



boo' 



Soo 



^ /o io Jo I/O so bo 70 So go foo 



Fig. 1. 



The existence of these transformations (which is chiefly of interest 

 here) has appeared in two ways. In the first place from the curves 

 of cooling and in the second place from the fact that, as was first 

 found by Ostwald") and Beketoff ''), and afterwards confirmed 

 by Kurnakow and Zemczuznyi, the heat of solution of a mixture 



1) Z. f. anorg. Ghem. 52, 186, (1907). 



2) Journ. prakt. chem. 35, 8 (1882). 



3) Z. f. anorg. chem. 40, 855 (1904). 



36* 



