( 637 ) 
All this is rendered still more conspicuous, when we project a 
space-representation, in connexion with fig. 1 and of some successive 
p, x-sections. In fig.1 D, and PD, represent the vapourpressure- 
curves of the two components; AM is the threephasepressure-curve, 
which terminates abruptly in M, where the gaseous phase 8 coin- 
cides with the liquid phase 1 (which consists for the greater part 
of ethane), because it meets there the critical curve C,C,, that is 
to say the curve of the plaitpoints P. Beyond JM there is coexi- 
stence only between the jlwid phase 3,1 and the phase 2, which 
consists principally of alcohol. It is the equilibrium between these 
latter phases, of which in fig. 2 the 7, r-representation is projected 
at different pressures. (The dotted houndary-curve O corresponds with a 
pressure inferior to the critical pressure of the second component, and 
superior to that of the first one). The 7. x-representation of fig. 3 
corresponds, at the (variable) threephase-pressure, with the threephase- 
equilibrium unto J/. In fig. 4 the indicated space-representation is 
drawn, which will be clear now without the least difficulty *). For 
the different higher pressures the corresponding 7’, x-sections are 
drawn in that representation. 
Remark. From C, (see fig. 1) to the maximum at 126°, where 
a and 6 coincide, and also from the minimum at 26°, where 6 and 
e coincide, to the lowest temperatures, increase of pressure will 
lower the critical temperature Q, and these critical points will be 
upper critical points in the 7’, 2-sections at constant pressure (see 
fig. 2). On the other hand, from the maximum at 126° to the 
minimum at 26° increase of pressure will raise the critical tempe- 
rature, and the designed critical points will be Lower critical points. 
That increase of pressure favours the mixing, as is clear from 
fig.1 and from the p,z-representations — as well in the case of 
an upper critical point, as of that of a lower one — is also in 
agreement with the 7’ 2-representation of fig. 2. For in the case of 
an upper critical point (see also fig. 5) a point A, situated within 
the boundary-curve will come — when the pressure is increased, by 
a) 
! aT . A 
which 7, will be removed to the lower point 7’), (for aan negative, as 
Pp 
we saw above) — without the new boundary-curve. And the same 
; ; si ke dT 
will be obviously the case for a lower critical point, where a 
jo 
is positive. 
1) This space-representation (without the 7, w-sections) has been already pro- 
jected independently by Mr. Bicuyer; but is not inserted in his communication. 
(These Proceedings of 28 Jan. 1905). 
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