( 336 ) 
Physics. — Dr. J. E. VerscHarreLT: “Contributions to the knowledge 
of VAN per Waais’ y-surface. VIL The equation of state and 
the w-surface in the immediate neighbourhood of the critical 
state for binary mixtures with a small proportion of one of 
the components.” (Continued). Communication n°. 81 from the 
physical Laboratory at Leiden, by Prof. H. KAMERLINGH ONNES. *) 
(Communicated in the meeting of Sept. 27, 1902). 
10. The border curve and the connodal line in special cases. 
1. When m,, = 0, ie. pr B=h,, Tra, all isotherms intersect one 
another nearly at the critical point (pre, VT) as we have seen in $ 3; 
according to the equations (26), (27) and (28) the plaitpoint coincides 
in that case with this critical point. Besides from (31) it follows that 
d*p : d*p 
Pam this value however belongs to a only to the first approx- 
imation (i.e. at the critical point itself), or the border curve is a 
parabola of a higher degree than the second. In fact we find in 
this case: 
pes 1e A Mm Mao \m ont a ien d 
gl gta ge), ge gan 
Meso 9 Maa Mag 
1 m,,m 
11 $1 
Pa PTR S| os we ee 5; 
ELT 
and therefore the border curve to the first approximation becomes a 
parabola of the fourth degree; the equation of that parabola is: 
Met 1 M,, Ma, : 
P—PTk=——, 00 a (v—v x) ’ 
M 3 Mao 
The connodal line, however, remains a parabola of the second 
a 2} 
. a*: 
degree, on which en 
dv? Tr ka 
2. A second remarkable case is that where 27)m,,-+-m?,,—0; for 
then the term p,—prz disappears from the expression for g? (equation 
23), so that p becomes of the first order with respect to p,—pTk. 
We then find : 
1 (m,,m 0,.—PTk m i 2 mm 
a a 01 ‘3 11 m , 1 t ot Paul 01 NEZ 01 40 a 
en Eer a m RTim,,\ 3 0 EN a 
Ol 30 
and 
5 2 2 
ae en AD Moos OPE 
Mao Me Ne Zei 5 RTE nn 
BART. _ MMM Ì mn (Roem), 
11 12 x 
a, fd ym, DMs, x 
1) Comp. Proceedings Royal Acad. of Sciences Sept. 1902. 
