( 1^0 ) 



anthraqniiione ooiicentrations of 0.1 and 0.2 mol. V^, it is note- 

 worthy that, whereas the point where the border line for liquid- 

 vapour possesses a vertical tangent, so where vi,, = 0, still lies in 

 the stable region, the line Ibi- solid-fluid under the thi-ee-i)hase line 

 already shows a maximum pressure and a maximum temperature 

 in the stable region, from which follows that we find here ix double 

 retrograde phenomenon. 



At the same temperature retrograde condensation and retiograde 

 solidification may namely be successively observed with increase or 

 decrease of volume, (See fig. 3 of the communication "On retro- 

 gressive vapour lines" in the Proceedings of this Meeting p. 180). 



At the concentration 0.3 mol. Vp the letrograde condensation has 

 just disappeared, but tlie i-etrograde solidification under the three- 

 phase line continues to exist. This phenomenon of relrograde solidi- 

 fication must also exist above the three-phase line, but the point 

 where the upmost bi-anch of the line soUd-jiuid possesses a vertical 

 tangent lies at such high pressures that up to now no retrograde 

 solidification has been found above the three-phase line. 



If we now consider the {PT)j; section corresponding to the con- 

 centration 0.9 mol. %» i- e. (he concentration of the first critical 

 end-point, we notice that the line for .solid-jhdd passes for the 

 second time through the border line with this concentration, and 

 that in such a way that the upper section takes place at about 46 

 atmospheres, from which follows tliat the same phenomenon must 

 be found already for smaller anthraquinone concentrations, as was 

 found indeed. 



A consequence of this second meeting is this that the rigiitliand 

 branch of the line for solid-fluid no longer runs on uninterruptedly, 

 but is stopped by the three-phase line, where it becomes metastable 

 resp. unstable, as was already shown schematically in fig. 2, after 

 which it appears again in the stable region at lower pressure. 



For the concentration 1.3 mol. 7o the first branch of the three- 

 phase line is still cut, and the line for solid-fluid just shows still 

 a pressure maximum in the stable region, but it is so faint, that 

 we may be justified in saying that this is the greatest anthraquinone 

 concentration, at which this pressure-maximum still occurs in the 

 stable region. 



So up to this moment the meeting of the solid-fluid line with the 

 three-phase lines has taken place in the points where lu,/ is neg., 

 but for greater concentrations this is changed. 



If we now consider the concentration 1.9 ?>?c/. •;,,, we observe that 

 h e line for solid-Jiuid has already got detached from the first branch 



