( 541 ) 
Prof, van dkr Waahs (1. c. p. 490) has also taught us how to 
deduce an expression showing the relation between p,t an a. 
From the three equations 
V s dp — i ]Sdt = dM x p x + xsd 
Vudp — y]Ldt = dM l U l 4 - — M d l 2 \) 
VQdp — 1 = dM x [i x + XG* ( M ,fi s — ^iMi) 
as ns 
xl m 
. , xsiri L — + ^ 
Vs~T] = Vl) 
\ xl Vl ] 
| *« r e : 
This gives us a quite general expression for the three-phaseline 
in the systems described. It will, however, not be easy to arnve 
through ft to the desired elucidations. If, for instance, we wish to 
know when J will be equal to 0 the numerator thus becoming nought, 
the question first arising is what do iji *10 etc- really '®P 
Kohnstamm ') has rightly observed that such differences roust n* 
be simply called heat of condensation etc. because vl and ,s do 
not relate to the same mixture. And the second 
numerical value of those quantities in a system to be investigated 
is still much more difficult to answer. 
In order to get a first insight into these systems, I have taken 
another course though of less general applicability. We wdlseeho 
the pressure changes in regard to the triplet pressure of A, when 
the liquid phase has the composition « assummg hat « has a 
very small value, in other words that but a very small qnant.ty of 21 
"ThTfem^tum^, a, which that liquid is in 
a solid phase, the composition of which is * S , is found from Roth- 
mend’s formula *) for very dilute mixtures : 
T = T x + 0*5 — x i) . W 
1) Proc Kon. Akad. IX p. 647 (1907). 
2) Zeitschr. f. physikal. Chem. 24, 710 (1897), 
