1317 
From these relations between the four variables w, y, P and 
T follows: 
{(w—a) r + (y—B) 3} de Hede + (y—B) dy = AdP — BAT (5) 
w—al)s + (y—B'd de Hees} (y—B) dy = A'dP — BAT (6) 
(8—8) de = (a—al) dy ae on EE) 
If from this we wish to deduce the relation between dP and dT 
we may divide (5) by (6). In consequence of (4) we get: 
Ba Ad P— BdT 
TE Me a os Sr! 8) 
or after reduction : 
dP Keay a ea) 4 (8) 
ais (a'—a) V + (c#—a') v + («—a) v' - 
which corresponds with formula (4). 
Hence, as we have seen above, if we choose the exact conditions, 
we can compel the complex /-+ #” to traverse the sublimation 
curve a" D, the four-phase curve D S and the melting point curve 
Sd". We will now investigate which conditions of the complex 
F+ IF’ are represented by points situated outside these curves. We 
distinguish therein different cases. 
1. The complex PF + #” has a congruent sublimation line, four- 
phase line and melting point line. 
Let us first introduce the complex F+ F’ in a point of the 
sublimation curve so that #4 #’ + G@ is formed. From a conside- 
ration of what happens on supplying or withdrawing heat or on a_ 
change in volume we deduce: at the right of and below the line 
a'D are situated the regions + G and F’ + G, at the left of and 
above curve a'D is situated the region + F’. 
Acting in a similar manner with points of the other curves we 
find : 
at the left of and above a'D/Sd" is situated the region + JF’. 
at the left of and below a" Dare situated the regions / + Gand #” + G 
BN A saat ae Na Rar >»  » » L2+4+0+Gand f’+L+4+G6 
Na ean at are Ole 3 mee es SY F4 L and F'+ L. 
Let us enter the region F+2+G from a point of the fourphase 
curve in a horizontal direction. We then, at a constant pressure, 
raise the temperature of the system #-+ 2+ G. The liquid and 
the vapour of this system then traverse a part of the boiling point 
and vapour boiling point curve of the substance J’. 
If we enter the region “+ L + G from a point of the four- 
phase curve in a vertical direction we then, at a constant tempera- 
86 
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Proceedings Royal Acad. Amsterdam. Vol. XV. 
