( 866 ) 
phase pressure would have to increase very rapidly in the neigh- 
bourhood of the critical end-point. 
au 
b. In the case of retreat of the plaitpoint line, a would be 
ap 
negative in the critical end-point both for the plaitpoint line and for 
the three-phase pressure; and as the three-phase pressure would 
dp. oe 
certainly resume its usual course at lower temperatures a positive 
q 
the three-phase pressure would necessarily present a maximum. 
r 
dp 
c. In thé case of retreat = of the three-phase pressure in the 
d 
neighbourhood of the critical end-point could vary between a very 
: ee ae : 
small value (e.g. for butane + aniline: Gee 12.5 atm. per degree) 
; 
to infinite (e.g. for isobutane + metylalcohol); the plaitpoint tempera- 
ture of this system does not appreciably vary between 10 and 70 atm.). 
So the latter possibility would wrongly have been considered as 
impossible by vaN DER WAALS’). 
We have hardiy any data as yet concerning the value of the three- 
phase pressures, which would enable us to test these results. Only 
a few observations of SCHREINEMAKERS *) about the system water + 
phenol can be used for this purpose: they have been rendered in 
table I. 
LAS EE sE 
dp. 
p in mm of \—— inmm of mercury 
t 
mercury | per degree 
99-8 29 
226 
38.9 AS 
S230 
49 A 62 
| 4.05 
50.3 QA 
5.16 
6.5 126 
6.66 
60.1 150 
7.44 
64.4 | 182 | 
| 105 
11.2 | 251 
1452, 
75.0 294. 
1) These Proc. X p. 193. 
2) These Proc. Ill p. 1. Ztschr. phys. Ch. 35 p. 459 (1900) 
