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three-phase-temperature lies between the melting-points of the pseudo-* 
components. 
Now on this assumption, the solid phase possesses everywhere more 
of the polymer B than the coexisting liquid phase, and if in the 
unary system a transition point occurs, the course of the curves of 
inner equilibrium must be as indicated by kl 3 , S t S t and S^S % . 
If the curve met the melting-point line of B, monotropy alone 
would be possible, as for enantiotropy reversal of the thermal sign 
would have to take place in this case, which is very improbable here. 
Experimental confirmation. 
It is clear that this theory requires that every substances which 
shows a transition point, must consist of two different kinds of mole¬ 
cules, which are in equilibrium at every temperature. 
So if we consider the substance HgJ 2 , the red modification oi 
which passes into the yellow one at 127°, we must assume two 
different kinds of molecules, the former of which gives rise to the 
formation of red, and the other to that of yellow HgJ 2 . 
The investigation of this substance, which was carried out in 
collaboration with Mr. S. C. Boxhorst chem. cand. has led to a 
very remarkable result. 
That it would appear that working quickly, the substance would 
betray its binary character, was expected, but that we should find 
here that case which I already mentioned, but considered as an 
exception, was highly surprising. 
For the sake of clearness the observed phenomena will be dis¬ 
cussed here in connection with the schematic fig. 4, in which a 
means yellow and $ red HgJ t . 
At 327° the red phase passes into the yellow one, which new 
phase remains intensely yellow up to about 380>; on further heating 
we observed that this phase assumed a red colour, at first hardly 
perceptibly, but then more and more pronounced, and that it becomes 
a dark red liquid at the melting-point temperature 255°,4. 
This phenomenon, which also appeared with very slow rise of 
the temperature, was studied in different ways with the naked eye \ 
and by means of the microscope, when it appeared that this change 
of colour takes place continuously , and is not owing to a second 
transition-point. 
This continuous change of colour between comparatively narrow 
limits of temperature made it therefore probable that above the 
point of transition the curve for the solid inner equilibria at first 
