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If on compression the deposition of solid C failed to appear in 
the vapour coexisting with solid B, the solubility-isotherm acg,/, 
shows that in this case a metastable three-phase equilibrium between 
vapour, liquid, and solid B might occur, the coexisting phases of 
which are indicated by the points g,, /,, and d. 
The figure also shows that if the vapour that coexists with solid 
C could be compressed without solid B being formed, a metastable 
three-phase equilibrium between vapour, liquid, and solid e might 
appear, indicated by the points g,, /,, and e. 
If we now think the third component A added, and placed in 
the third angle of the base of the trilateral prism, and if we assume 
that the chosen temperature lies above that of the first critical end- 
points in the systems 4B and AC, it is possible that the stable 
ternary V, X-figure simply consists of two isothermal solubility 
surfaces which intersect along a line which originates in the point c. 
Along this ternary solubility isotherm solid B + solid C+ vapour 
coexist. Now it is clear that a two-sheet liquid-vapour surface extends 
within the said solubility surfaces, which begins on the binodal vapour 
and liquid line in the plane for LC. The two sheets of this liquid- 
vapour-surface will continuously merge into each other in space, 
and this continuous transition takes place on the critical isotherm, 
the projection of which on the LC-plane is indicated by the line A4, 
When the said liquid-vapour-surface lies entirely inside the two 
isothermal solubility surfaces, no critical phenomena can occur in 
stable condition, and in this case no particularities occur. Now we 
know that at temperatures lower than those assumed here stable 
liquid equilibria must occur, and this must also happen when we 
raise the temperature, and in this way approach the eutectic tempe- 
rature of the system 5L—C. With decrease of temperature we shall 
see liquid appear as stable phase, because then the liquid-vapour- 
surface extends more quickly in space than the solubility surfaces. 
The consequence of this is that at a certain temperature the three- 
phase solubility isotherm for Sg + Sc + G just touches the liquid- 
vapour-surface. So at this moment Sg + So + L + G must be able 
to coexist for the first time, from which follows that this contact 
must take place in a point of the critical isotherm of the liquid- 
vapour surface so that liquid and vapour are identical there, and a 
critical phenomenon makes its appearance. 
In connection with this the following things may be remarked. 
Starting from the pairs of points g,,/, and g,,/, two continuous 
curves pass over the liquid-vapour-surface, the former of which 
indicates the vapours and liquids coexisting with solid B, and the 
13 
Proceedings Royal Acad. Amsterdam. Vol. XV. 
