1318 
ture, lower the pressure of the system F+ 2-+G; the liquid and 
the vapour of this system then traverse a part of the saturation- and 
vapour saturation curve of the substance / under its own vapour 
pressure. 
The same applies if we enter the region #” + L+G from a 
point of the four-phase curve. In order to find the limitation of the 
different regions we draw in fig. 1 the sublimation curve a K, the 
three-phase curve KF and the melting point curve /d of the compound 
F’ and the same curves a’K’, K’F” and F’ d’ of the compound LP’. 
We will assume that / and #’ also melt with increase in volume. 
The curves Fe and Kf have the same significance as the homony- 
mous curves in fig. 3 (III); the same applies to the curves fe’ and 
K’f’. The question now arises: where are these curves situated in 
regard to the corresponding curves of the complex /’+ F7. 
Fig. 1. 
Let us first take a pressure so high that / and #” as well as 
their complex /’+ F’ have a melting point. Now, as is well known, 
the mutual melting point of “+ F” is situated lower than than of 
each of the components individualiy. A horizontal line intersecting 
the three melting point lines must therefore intersect the melting 
point line of + 2” at lower temperature than the two other 
melting point lines. 
