( 188 ) 



We may also express this as follows : the locus for w,f = gets 

 outside the connodal line only on tlie vapour side. 



If the plaitpoint curve had only cut a portioji out of the 

 ascending part of the three-phase line, lö^j would still have been 

 positive in r/, and the locus ?r,y = would run quilc round the 

 connodal line near the plait. 



Fig. 4. 



If we return to fig. 4, we see that when we exceed the concen- 

 tration 5,7 mol. 7o> the line for soUd-jïuid sinks more and more into 

 the metastable and unstable region so that the portion remaining in 

 the stable region becomes steeper and steeper, and when at last the 

 concentration of the second critical end-point has been reached the 

 three-phase line and the line for soVid-jluid touch each other in the 

 point q. As is to be seen from the figure, this concentration lies 

 between 9,4 and 13 mol. "/j. 



When the concentration of anthraquinone becomes still greater, 

 the upper branch of the line for solid-fiuid will even have to change 

 its direction entirely, for this branch must possess a point where 

 the tangent is vertical, and this point must move to smaller pressures 

 for greater anthraquinone concentrations, till at last it will enter 

 the metastable region, at which moment the liquid branch of the 

 line solid-fluid runs to the right from the beginning. 



Before this moment has been reached, and so when the point 

 where v.c/ = still lies in the stable region, the phenomenon of 

 retrograde solidification above the threephase line, must make its 

 appearance, wdiich has not been found as yet, and \v'\\\ soon be the 

 subject of an investigation. 



Amsterdam, June 1911. Anorg. Chem. Lab. of the University. 



