( 572 ) 



but tliev are more (•(implicated, heeanse here the (•()m|)Onents mav 

 combine. 



Now tVdiii a chemical |ii>iiit of view it is of the liiiiheyt impor- 

 tance to examine also these more complicated phenomena, in order 

 to obtain in this way a ijeneral insight into the phenomena of equi- 

 librium for the case that compounds are raised to high temperatures, 

 and placed under such a pressure that critical |)henomena are found 

 with saturated solutions. As vet any insight into this was wanting. 



Hy bringing the results of my investigation on ether-anthraqninone 

 ill connection with the cases lately discussed by me in a paper: 

 "Contribution to the knowledge of the PX and tlie PT-lines for the 

 case that two substances enter into a combination which is disso- 

 ciated ill the liipiid anil the gas phase" '), I have succeeded in 

 arriving at a clear (Miuccplioii of (he abo\e mentioned plienomf^iia. 



In all the cases which 1 shall shortly discuss here, I start from 

 the supi)Ositioii that the compound under consideration is miscible 

 with both components in tliiid state in all proportions. On the whole 

 our knowledge as to this is exceedingly slight, nor is (here the least 

 certainty on this head for the substances which I shall adduce here 

 as examples. 



2. First of all 1 shall consider the case, that two substances 

 A and B yield a dissociajiug compound A„, B„, the melting point of 

 which lies above the critical temperature oi' (he substance A. This 

 case is met with in (he system CaO— ('O.^. If now the solubility of 

 the compound A,„ I5„ in A is still slight a( the critical temperature 

 of A, the continuous plaitpoint curve, A\hicli starts at the critical point 

 of A (C()J and terminates in the critical point of 1! (Cat )) will meet 

 the solubility curve of A„, B„ ((kCOj) in fluid A (C().J in two points. 

 That the point /> exists has already been demonstrated by Dr. Büchner"); 

 in temperature this point lies only slightly above 31°, the solubilitv 

 of CaCO, in tliiid CO, being still very slight at this temperature 



This case has been represented in Fig. J . The upper half of this 

 diagram contains the projection of the spacial figure on the PT-plane; 

 the lower half represents the [projection of the tiro phase regions 'j 

 coe.ftstiiKj vith sdJid siihst'Uice, and the plaitpoint curve. The com- 

 bination of these two projections seems to me the simplest way of 



1) These Proc, June 1ÖÜ5, p. 20U. 



») Thesis for the doctorate, IÜ(>. (1905). 



'•) At lirst I ^uve the iiaiiu> of flirei' phasv regions to tliese regions because, 

 though they imlicate only two pliases, a third coexists witli tliem. It seems, 

 liowever, better to me \.o »pcA\i o{ two phase j-egions coexisting icith solid substance, 

 which term I shall use licnceforth. 



