( 636 ) 
Chemistry. — “On the different forms and transformations of 
the boundary-curves in the case of partial miscibility of two 
liquids.” By J. J. van Laar. (Communicated by Prof. H. W. 
BakKnuis RoozrBoom. 
(Communicated in the meeting of March 25, 1905). 
1. In a preceding communication) I showed, that when one of 
the two components of a binary mixture is anomalous, the 7, z- 
representation of the spinodal curve, and consequently also that of 
the connodal curve, the so-called saturation- or boundary-curve 
w=f(T), can assume different forms, which are indicated there. It 
depends principally only on the value of the critical pressure of the 
normal component, with regard to that of the anomalous component, 
which of the different forms may occur with a definite system of 
substances. 
An aflirmation of the theory, developed by me, that is to say 
of the cases and transformations deduced by me from the general 
equations, is found in the circumstance, that these cases and trans- 
formations may be realised im quite the same succession with one and 
the same. substance, and this by external pressure. In the same way 
as with dijferent normal substances as second component the form 
drawn in fig. 7 Le., presents itself at relatively low critical pressures 
(with regard to that of the anomalous component), and that of fig. 2 
le. at relatively high critical pressures — the form of fig. 7 may be 
realised at relatively low external pressure, and that of fig. 2 at 
relatively high external pressure, whereas at intermediate pressures 
all the transitional cases again will return in just the same succession. 
2. For that purpose we but have to look at the p,7-diagram 
of the eritical curve for ethane and methylalcohol, as projected 
by KueNeN *) in consequence of his experimental determinations (com- 
pare fig. 1). We see, namely, immediately from the form of the curve, 
departing from C, (the higher critical temperature, that of CH,OH), 
which indicates the pressures, at which for different temperatures 
the two coexistent phases coincide, and above which we have 
consequently perfect homogeneity, that according to the value of the 
pressure one critical point « may occur (at the pressures 1 and 2), 
two viz. a and b,c (at 8), three, viz. a, b and c (at 4), again two, that 
is to say (a,b) and c (at 5), and finally again one, viz. c (at 6). (also 
compare fig. 2). 
1) These Proceedings of 28 Jan. 1905. 
2) Phil. Mag. (6) 6, 637—653, specially p. 641 (1903). 
