609 
of oe re, at which minimum value of (7%), can occur with a 
(Ti), (Tr), 
rather high degree of approximation. But the uncertainty, or rather 
our ignorance of the value of / prevents a sharp determination. 
What precedes is of use at least in so far that it gives the reason 
why in the first experimental investigation about binary mixtures, 
for which the value of 7) differed so little for the two eomponents, 
minimum (7%), was of such frequent occurrence. 
Let us now proceed to the determination of the value of wv at 
which the plaitpoint coincides with the critical point for the mixture 
taken as homogeneous. For this mixture the p, T-tigure is not rounded, 
but the vapour and the liquid branch touch each other in the plait- 
point; they also touch the p,7-line of the plaitpoints and the p,7- 
oe re 
line of the critical points. From = ad follows : 
2dT 1 dp da 
Tde p dx ade 
1 
and with — == b (rs), if we neglect the variation of (rs) follows: 
P 
dT 1 dp db 
Tde p dx ee bda 
ee. En 
If we put par!” we find by division : 
1 da 
ade 2—fy By et 
Rn eet 
b dx 
as I assumed already before but without a rigorous proof, and 
without demonstrating that on account of the probable variability of 
(rs) the relation only holds with a high degree of approximation. 
If we have two componerts for which the value of f does not 
differ much, 7, which will probably lie between f, and f,, will 
not differ much either. For the mixture water-ether Jr may be put 
= 7 approximately, at least not far from the ether side, hence we 
must determine w from the equation : 
2 (a,,—4,) + 2e (a,+a, —2a,,) Ze 
a, + 2 (a,, a,) & + (a, +a,—2a,,) a jan 
En 5 2 (6,,—9,) + 22 (6, +6,—26,,) 
6 b, + 2 (6,,—8) e+ a? (6, + b,—26,,) 
40 
Proceedings Royal Acad. Amsterdam. Vol. XV. 
