( 1'9 ) 



The liJic /'<'/, wliicli pai'lly coincides willi llio T-axis, is (lic vtipour 

 pressure curve of solid antIir;i([niiione, and dij tiial of Ii(piid antiira- 

 qiiinone. c/A is the nielliniipoiiil-curvo, wliicli (as van dkm Waals ^) 

 lias proved) marks the direction of (he three phase curve near 

 the meltiiigpoint d. These last three curves are drawn here schema- 

 tically. 



The main resnlt represented by Ihis y>-/-lignre is this that by the 

 meetiiig of plaitpointcnrve and three phase curve a part of the latter 

 has vanished or ratlier has become imaginary, and in (he examined 

 system that part that contains the maximum. 



The plaitpointcnrve is metastable between p and q and therefore 

 still to be realized, but this is not the case with the three [iliase 

 curve. However it appeared to me that at temperatures between p 

 and q, w\\\\ concentrations" greater than those of |)oint ry, three jihases 

 could temporarily appear together, if (hey had originated at a tem})e- 

 rature above 247^ and if afterwards the system in ecpiilibrium had 

 quickly cooled do\vu to less than 247^. The three ])Iiases however 

 were not in ecpiilibrium wow, for at a constant temperature a slight 

 change in volume proves to cause a great change in pressure. 



The liquid therefore, though in contact with solid anthraquinone, 

 was supersaturated ; it w^as very viscous and jtassed very slowly, 

 at times not until after an hour, to the stable condilion of solid lliiid, 

 under secretion of solid anthraquinone. 



Fig. 2 gives a number of />-v-sections for diircrent temperatures, 

 the pressure being given in atmospheres and the concentration in 

 1 mol. total of the mixture. 



We may immediately point ou( here that all (he lines in (his 

 figure joining poiids of e((ual value, as plai(poin(s (/), li<piids coexis- 

 (ing w'\\\\ vapour and solid andiraquinone (r), vaj)onr coc\is(iiig wi(h 

 liquid and solid andiraquinone [c), are all |)rojec(i()ns on (he />-,/•- 

 plane of curves, \\hicli occur in (he yy-j'-Z-surface '"'). 



The l)ranclies r„ y> and c^ />, an liicli |)ass in(o each odier cond- 

 nuously, reprcseiK (he series of liquids and vajiours which if we 

 come from a lower (emperature, coexist widi solid andiiacpiinone. 

 In y>, (he poin( of conlluence of (he (wo branches, we lia\e tlic first 

 |K>in(, where a satiwdU'd soludon reaches i(s cridcal condidon. This 

 takes place a( a concentration 0,015, tenqierature 20.'3^ and pressure 

 43 atin. If we pass on to higher tcm|>era(ures a stable solnlioji is 

 impossible over the range of tem])erature 203^ — 247", and instead we 



1) These Proc. VI p. 230. 



2) If the plaitpointfiii've has a maximum, it must possess a maximum also in 

 fig. '1. In the ^./;-p^ojec(ion on the contrary no niaxinuiin occurs. 



