( 187 ) 
But in general the quantity (wr) Wijde Ur, ) Will cause a 
modification in the course of the value of the pressure which is 
very slight. The value of the pressure depending principally on the term 
Ya 
ny) ; : : d 
We will consider more closely this last quantity, which represents 
d vod dp 
the limiting value of — — for y,=0 or y,=1, for a binary 
p dy, ; ‘ 
mixture and which for a ternary system is to be augmented with 
t 
VG ES 
(7,—2,), 1 2 
ay, 
5 . ’ . . Yay. 
We have found before the following value for >: 
Yi. 
gat Ag) LI) ale “1 
I Ch Yi) = de ne ae ye En 
From this value we deduce, if we set y, —=0 and x, = 
9 
0 
Var Ui (e an —1)—a,(e"™ ty) eh 1 
— — = ae 
Lt staa Br 
ny) La (ef * —1) 
where w‚, and w,, have the values they have in the point whose 
coordinates are #, ==, and y,—0. This value, which for 2, == 0 
d 3 . 2 3 p Ae pe 
is equal to e “"—1, has for «, —1 the final value e #* “" —1, 
and varies fluently with increasing «,; and now the way in which 
1 dp 
—-— varies depends upon the relation between u’, and w,. This 
p dy, 
value may have reversed its sign, either from negative to positive 
or from positive to negative. The quantity u, — tt, represents the 
variation of g for the motion along the hypothenuse towards the 
summit of the triangle in the same way as wu’, represents the varia- 
tion for the motion along the N-axis towards the summit. If there- 
fore 7, for the summit is lower than (7%), then w',, is positive, 
and if 7, for the summit is higher than (7), then wy — us, is 
negative. 
It is not superfluous to point out in how high a degree the value 
i ,dp oe fess 
geen depends on the value of u’, , if it represents the initial 
p dy, | 
direction of a curve of equal pressure for a binary system. According 
: : , : pe : . 
to our former observations this value is equal to e “—1. If we 
1 dp yy, ae 
also draw the vapour curve, then — =>, and soit is equal to: 
Pp dy, Ys 
