( 242 ) 



If we suppose that the .two critieal [)hases witli which the sohd 

 body can coexist, and wliicli differ considerablv in concentration foi- 

 anthraqninone and etlier, approacli each other, the two separate 

 parts of the T,.r tigure and also that of tlie y>, ,i' figure and that of 

 the [), 7' figure will approach each other. At the point of contact the 

 two parts of the T, ,v figure, and that of the />, ,r figure will intersect 

 at an acute angle. If we continue this inodificatioJi further, the 

 two upj)er branches of these figures have joined, forming one con- 

 tinuous curve; in the same way the two lower branches. Then the 

 2>, 7'curve shows a maximum. The existence of this maximum three- 

 phase-pressure has already been demonstrated and discussed by me 

 on the occasion of former investigations by prof. Bakhiis Ro<»/;kho()M '). 

 We find again the result obtained before, no\\- under the followiiig form: 



•t'j 'i'l ^S »'^'i '*'»• ■''2 



which means, that if we write for that special point of the three- 

 phase-pressure : 



^ , dp l^w 



the value of L ir would be 0. 



If we now examine the course of the .r,T curve for the three- 

 phase-pressure more closely, making use of the fornuda on p. 241, 

 or what comes to the same thing according to the fornuda of 

 Verslag 1897, Deel r>, p. 4ill, it ai)pears, that other complications 

 may occur : and thai il is not perfectly accurate to say that the 

 />,7' curve on the side of the anlhra{{uinone is an ascending curve, 

 till the triple jminl of this substance has been reached. Then we can 

 also account for the asymmetric behaviour of the y>, 7\'urve. It ascends 

 from the trifde |»oint of ether and descends on the other side. 



In this consideration we shall denote by Xd, xi and .Vg the concen- 

 tration of the vapour, of the liquid and of the solid body. In the 

 same way we shall use f^/, ei and eg ; then we get for a \ery small 

 quantity of the admixture : 



{.>-d—.Vs)(vi — v.,) — {.ri—.i's) (cd—v,) 



1) Verslag Koii. Akad. Amsterdam, 1885, 3e reeks, Deel 1, pag. 380. 

 -) The more accurate value of the numerator of the last fraction is : 



(.'W - .';) \U (1 "•'•>■) f A/j .Vs] — (.'7— .'•«) [r.l (1 - •'•</) + >n .'V/| 

 In this we have, liowever, disregarded the heat of rarefaction. 



