( 182 } 



edlj having a positive value, tlie quantity ?t'.,/ must be negative in 

 that point. 



From this it follows again, what also graphically appears a necessity, 

 that in this case lOsf does not pass through zero once, but twice, 

 before the critical end-point q is reached, and I will at once add 

 that this also follows from the course of the determined (PJ!,/ )x-lines, 

 as will appear from the following communication. 



In this way we come to the conclusion that the locus ?/.y=rO 

 gels outside the plait only on the vapour side of the latter. 



So on the vapour branch of the second half of the three-phase 

 region state (6) is succeeded by state (6a) : 



+ + - + 



— ^ '■ («Ja) 



{ws — a,,) vif, — {xi — .x.j) Vsf 

 + ■ +■ + + 



In this change the numerator has passed through zero and has 



changed its sign (has become pos.), so that now T -j^ is negative. 



Now on approach of the plait the point is indeed reached where 

 yr.s7= and then becomes j)ositive, so that we then get state (8), 

 but the second member of the numerator can never predominate, 

 because the positive value of ?^Vƒ remains too small for this ; moreover, 

 as we remarked just now, for ether-anthraquinone we meet here 

 with the case that w,f soon passes through zero again, so tliat this 

 quantity has become negative again before the second critical end- 

 point q is reached. 



In the immediate neighbourhood of this point the signs are as 



d.v 

 indicated in {Cvi) and so 7' ,y will be — cc in the point q. 



So tlie projection of the li<iui(l and the vapour lines of the interrupted 

 three-phase region will have a shape as has been indicated in the 

 figures 2 and 3 of the preceding communication ''On retrogressive 

 welting-yoint lines" . ^) 



In the case that the plaitpoint curve only takes a part out of the 

 ascending branch of the three-phase line, this projection cannot 

 undergo any essential modifications for the reasons mentioned above. 

 It is true that Wsf is then positive in the critical end-point q, but 

 this can never give rise to a change of the sign of the numerator. 



Amsterdam, June 1911. Anorg. Chem. Laboratory 



of the University. 



1) These Proc. p. 170. 



