(529 ) 
According to these observations the first mixture has its critical 
point (B) at nearly 18° C., the third at 6° C. *). 
In the case of water and nicotine?) Hupson (Z. f. Ph. Ch. 47, 
p. 113) has observed the complete isolated plait. But here a hydrate 
is formed, being decomposed continually, when the temperature rises. 
The theory of the phenomenon remains however formally the same: 
everywhere, where a pretty considerable variaton in the value of 
v presents itself — whatever should be the cause of it — the 
existence of such a plait may be expected — as soon as the required 
conditions are satisfied. 
Still another example is found in mixtures of carbonic-acid and 
nitrobenzol (Bicuner), which makes it probable, that CO, in iguid 
state is an associative liquid. Indeed, there exist important reasons 
in the thermal behaviour of that substance which would confirm 
that supposition. 
AreN has observed, that CH,Cl and pyridine mix in every pro- 
portion, but that the combination, which is soon formed. is nearly 
unmixable with both components. In this case again there is found a 
lower critical point, for both plaits — i.e. for that, formed by CH,CI 
and the combination, and for that, formed by pyridine and the 
combination. 
It is a matter of course that the existence of a lower critical 
point necessarily determines that of an wpper one. With rise of 
temperature the /iquid mixture approaches more and more to a 
gaseous one, where of course miscibility in every proportion takes 
place. (How the plait can transform itself there, and pass into the 
transversal plait, lies entirely without the plan of this inquiry). 
Inversely we can not always conclude from the existence of an 
upper critical point to that of a lower one, because — even, when 
the connodal curve begins to contract downward — the case of 
fig. 6 can occur. 
But this is certain, that when an wpper critical point is found 
at ordinary temperatures, we have always to deal with the point C, 
and not with A, the latter always lying (see fig. 2) in the ease of 
mixtures of water and a normal (or anomalous) substance below 
—90° C., and in the case of mixtures of two normal substances 
(compare § 3) at most some thirty degrees below 0° C. 
Nearly always there may therefore be expected the case of fig. 4, 
1) Kuenen (Phil. Mag. [6] 6, p. 637—653 (1903)) could however not confirm 
the existence of a lower critical point for diethylamine. In an earlier Memoir 
Kuenen has found also a lower critical point for mixtures of C,H, and ethyl 
isopropyl and butyl-alcohol, 
