NES 
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lies at a greater distance from the second component, and if the 
deviation of the surface u from a plane surface is more considerable. 
The succession of the values of the pressures p,, p, and p, involves 
that the condition y, — y,=90, which would lead to: 
ld 
Ses ae | 
Ry) =e, a 
e A] 
cannot be fulfilled, for in that case the factor of w, would be less 
than unity, and the equation: 
yen 
| = 2, ie 
Page) ame 
with constant value of w',, and w',, would then in fact represent a 
line through the summit of the triangle; but a line outside the 
triangle. But we will return to this condition presently. 
These nodal envelopes have an analogous significance as that of 
the lines of force in the magnetic field. In the same way as 
the tangents of the lines of force determine the direction of the force, 
but not its intensity, so the tangents of the envelopes determine the 
direction in which the second phasis is to be found; but they do not 
indicate the distance between the points 1 and 2. This distance, 
however, is perfectly determined if also both branches of the curves 
of equal pressure and triangle OXY are drawn. Then we find the 
second phasis which coexists with a given liquid phasis, by drawing 
in the point representing the liquid phasis the tangent to the nodal 
envelope of that point; the point of intersection of this tangent and 
the vapour branch for the pressure of the liquid phasis represents 
the second phasis. If we do this for all points of the same nodal 
envelope then we get a new locus, which we may call conjugated 
curve of the nodal envelope. In order to give the equation of this 
conjugated curve we must be able to express v, and y, as functions 
of x, and y, and we must substitute these functions in the equation 
of the envelope. In general, however, we are not able to do this, 
not even in the case that the second phasis is a rare gas phasis. 
Only in the case that u’, and w’,, may be considered as constants it can 
easily be executed. If we write the equation of the envelope as follows : 
wey pe 3 
( a, y Ji oa o( Y, y' ls Jp 
ee CE or Fe et 
which only may be admitted for constant value of u’, and w',, , and 
if we take into account that: 
gi 
