( 21 ) 
to the rule of Konowanow for a binary system, if this latter rule is 
duly extended. If on the other hand /, lies on the liquid sheet, 
dp 
then v,, and therefore also a is negative. This signifies that the 
( 
vapour branch of the eurves of equal pressure moves on towards 
the heterogeneous region if the pressure decreases, and on the other 
hand towards the region which at constant pressure belonged to the 
homogeneous region, if the temperature imereases. If the pressure 
is varied the two branches move, in such a way, that one of the 
branches retreats for the other. If there is not yet question of eri- 
tical phenomena, a point for which v,, =O does not yet exist, and 
the given rule holds without exceptions. For the case that no 
maximum pressure exists, the two branches of the projection of the 
curves of equal pressure consist of two curves, originating both 
in the same side of the rightangled triangle, and ending again in 
the same side. Every point on one of the branches has a conju- 
gated point on the other branch. We will eall the lines joining such 
a pair of conjugated points (coexisting phases) chords. The first of 
these chords have the direction of one of the sides of the rightangled 
triangle and the last the direction of the other side. If these two sides 
are the sides containing the right angle, then the chord turns over an 
angle of 90°. It oecurs however only as an exception that the chord 
is directed towards the origin in other points than the extremities. 
Afterwards we will return to this question. 
If a maximum pressure exists, the branches of the curves of equal 
pressure form closed curves near the phasis, whose pressure is maxi- 
mum. The liquid branch contracts if the pressure increases, and 
according to the rule, deduced above, it moves towards the branch of 
the vapour phases. This branch therefore must also form a closed 
curve round the point of maximum pressure and that a smaller one. 
For the limiting case, the curve for the liquid phases is an ellipse 
the curve for the vapour phases is also closed, but has other dimen- 
sions, and its axes have other directions and another ratio, in the 
limiting case, however, it must coincide with the ellipse of the liquid 
phases. At any rate therefore, the position of the liquid branches being 
given for increasing pressure we may immediately conclude to the 
relative position of the vapour branches. 
(To be continued.) 
