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eurves of equal pressure, namely that one for which p = p,,, touches 
the (X-axis. 
In the following chapter we will give some indications concerning 
the course of the curves of constant pressure for the vapour phases 
in this case, and in the general case. Let us return to that purpose 
to equation II of p. 3 of this communication. 
Db. Displacement of the curves of equal pressure with 
variation of the pressure. 
We have already observed that the projection of the connodal curve 
of a Gsurface, construed for a certain value of p coincides with the 
projection of the curves, for which the pressure is equal to p, and 
that therefore all laws, which hold for the connodal curve, also apply 
to the curves of equal pressure. 
If in the equation: 
a O76. 7 05 | 
Vo, UP = (z,—2,) On, + (¥,—Y;,) Ow,0y, | du, + 
a le, Dir Sarde re) se | dy, 
we choose the values of dv, and dy, such, that 
de, ae dy, dl 
ee eae 
where ZL represents the length of a line, connecting the point P,, 
whose coordinates are v, and y, with the point P,, representing the 
phasis coexisting with P, and whose coordinates are x, and y,.. Be 
further d/ the length of a line, whose projections are dv, and dy, 
then the point w, + dz,,y,-+ dy, lies between the points P, and P,. 
It lies therefore in what we may call the heterogeneous region. The 
above equation may then be written : 
dp | 076 de, 2 075 Ox, dy, 076 dy, *} 
v., — = Li 2 — = ler . 
gh | Bel | ag a dl \( dl ) NE eel = | 
The second member of this equation is positive for the points of 
the connodal curve, as the ¢-surface lies above the tangent plane for 
all phases which may be realised. If the point P, represents a 
Wes hs dp 5 
liquid phasis, then #,, is positive, and therefore 5 also positive. 
When the pressure increases the liquid branch is displaced in such 
a way, that it moves towards the side of what was before the 
heterogeneous region. This rule for a ternary system is equivalent 
