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Chemistry. A- The P,T,X-spacial representation of the system 
ether-anthraquinone .” By Prof. A. Smits. (Communicated by 
Prof. J. D. van der Waals). 
As the type ether-anthraquinone occurs so frequently, and the 
spacial figure of the substances belonging to this system deviates so 
greatly from the P,7 T ,X-representation given by Bakhuis Roozeboom 
on account of the very different state of the two components at the 
same temperature, it seemed desirable to me to draw up a spacial 
representation of the system ether-anthraquinone. 
The figures 1, 2, and 3 now give us a view of this P,7",Xspaeial 
representation taken from different sides, and may contribute to 
facilitate the insight into the peculiarities of this system. 
In fig. 1 the plane a, l, /, k, s, h , g represents the p,#-section 
corresponding with the critical temperature of the component ether, 
which is thought on the left. 
So the point a indicates the critical pressure of pure ether, and 
the line a l the unsaturated liquids containing anthraquinone, which 
coexist with the vapours on the line ag. 
The three-phase-pressure line g,l,s, on which the equilibrium 
between vapour g, saturated liquid /, and solid anthraquinone s lies, 
forms the upper boundary of the two-phase equilibrium between 
solid anthraquinone and vapour, the vapour phases of which lie on 
the vapour line h,g, and the solid phases coexisting with them on hs. 
The line g Is is at the same time the lower boundary of the 
equilibrium between liquid and solid anthraquinone just as of that 
between liquid and vapour, and If or the meltingpoint isotherm 
indicates the liquid phases, and sk the solid phases. 
As van der Waals showed, the lines hg and //are two branches 
of one and the same curve, which possesses a partly metastable, 
partly unstable intermediate portion between g and /. If we wish 
to have a name for the whole curve, solubility-isotherm is convenient. 
If we now proceed to higher temperatures, i. e. in a direction 
normal to the just discussed p, ^-section to the left, the principal 
change is this that the lines la and ga pass continuously into each 
other, and the liquid-vapour region moves a little to the right as 
the lines not only get detached from the axis but the vapour and 
liquid points g and / move also to greater anthraquinone concentrations. 
The point where the continuous transition between liquid and 
vapour takes place lies on the plaitpoint curve a pq b, which connects 
the critical point of ether with that of anthraquinone, and running 
on the liquid-vapour surface connects the points of maximum pres¬ 
sure m the different p,a?-sections. 
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