( iÖ8 ) 



This isotherm of 210^ has the steepest course; with increase of 

 temperature the course becomes at first less steep, but at 240° a steeper 

 course seems to reappear, which is probably connected with the 

 change of direction which appears above 240°. 



The projection of the solubility curve and the plaitpoint curve on 

 the ^-.I'-plane is i-epresented in fig. 7, where the dotted curves represent 

 the vapourbranches. The projections of the two parts a/j and qh of 

 the plaitpointcurve are almost straigiit lines. If we examine the 

 course of the line qh, in order to see at what temperature this line 

 Avill meet tlie line for pure anthracpiinone, we shall find ± 800°. 



Lastly we find in fig. 8 the course of the molecular volumina of 



//ao 



T 



JfffO 



loo 



n 

 Ether. 



/ 

 \ 



0.1 



~!nr 



r/ 



X 



Fig. 8. 



7\y "öip "öjj 1 



Aulhraquinone. 



the saturated solutions. Here too we have two continuous branches, 

 each of them consisting of a liquid and a vapour branch, dq and cp 

 are the liquid branches and qe^ and i>e are the vapour branches, i) and 

 q denote the molecular volumina of the two critical saturated solutions. 

 The dotted vapourcurve qe runs on to the concentration 0.015, so that 

 from this figure also directly follows that at higlier temperatures and 

 larger volumina three phases may again be obtained with the con- 

 centration with which point p may be realized. Here too the curves 

 ci) and qe indicate clearly tlie phenomenon of retrograde solubility. 

 So the ijivestigation described here has furnished proof positive of 

 the general points of view which were prominent in the qualitative 



