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Physics. — "The P-T-X-spacial figure for a system of tivo com- 

 ponents which are miscible in the solid or liquid crystalline 

 state in all proportions." By Prof. A. Smits. (Communicated 

 by Prof. J. D. van der Waals). 



When we project the spacial figure mentioned in the title above 

 it appears that its most remarkable feature is this that three two 

 sheet surfaces must intersect viz. the vapour-liquid sheet, the vapour- 

 mixed-crystal sheet, and the liquid-mixed-crystal sheet, of which we 

 know that for the simplest case, i.e. for the case that these sheets 

 possess neither maximum nor minimum, they show great resemblance 

 in form. 



To examine how this intersection takes place we consider first of 

 all a /j-cr-figure for a temperature below the triplepoint temperature 

 of the two components. 



If we call as is usual, the component with the highest vapour 

 tension (and the lowest triple-point temperature) A, this p-d'-diagram 

 has a shape as indicated in fig. 1. 



On line a c b we find the mixed-crystal phases, which coexist with 

 the vapour phases, which lie on the line a d b. 



Between these two curves lies the region for vapour -j- mixed- 

 crystal, G + F, and above the line a c b the region for the mixed- 

 crystals F, and under a d b the region of the vapour G. If now 

 we choose a temperature above the triple-point temperature of A, 

 but below that of B, and if we assume for a moment that at the 

 temperature considered A is found in a solid, so supersolidified 

 state, we get a p-x-tiguve as indicated by afbga in fig. 2, which 

 is quite analogous to that represented in fig. 1. 



Solid A, however, being metastable at this temperature, part of 

 this ^Ki'-figure will be metastable on the ^4-side, and now the question 

 rises what stable equilibria will take the place of these metastable 

 equilibria. 



This is immediately seen when we imagine the case, that the two 

 components are liquid at the temperature considered, and so B occurs 

 in superliquefied state. 



In this case we should find a ^-«-figure as indicated by cldgc, 

 where we notice that d lies below b, and c above a, b and c 

 denoting the vapour tension of metastable states of A and B. 



The line eld indicates here the liquid phases coexisting with 

 vapour phases on egg. 



The p-.v-figure afbga being metastable on the side of A and 

 cldgc being metastable on the side of B, it is at once evident thai 



