( 556 ) 
or = = constant, we might derive an equation analogous to (5) for 
& 
the y,v-surface; also for the z,v-surface by choosing the plane in 
such a way that: 
oy dw 
By Ov tot are MET 
or 2 = is constant. 
oy 
dy = 0 
If we take volumes lying within the limits of the «, v, y-surface 
under consideration, which we shall henceforth call surface of coexis - 
tence, then the homogeneous phase thought in such a volume, will 
be stable, as long as 
dw? 026 \2 
Py 05 Oy (sao) 0 ang oe (sa) 
Tiet ee Bed RS En AE 
Rd ” da? de? dey ox dy? ec 
du? Oa? 
In proportion as we move further from the sides of the surface 
Op sap. 
of coexistence, we approach the volumes, for which — gs 
dv Qe 
2 
The surface, for which on = 0, will for a ternary system take 
dv? 
the place of the curve which we have represented by CKC' for a 
binary mixture in fig. 2 (previous communication). 
But the stability will have ceased long before we have reached 
9 
— 
07g 
=='0. ‘For ‘such volumes. (==) co 2 
dz? 
whereas the condition of the stability is that this quantity be 
Bg 
dw Gee 
‚ which is equal to —-——+—.,, would be —oo 
oy? dw 
the volumes for which oy 
dv? 
05 
oy? 
positive. Also 
for such volumes, whereas the condition of stability is not only 
that this quantity be positive, but even that it have a value such 
that: 
Ce A SO EN, 
dy? Ou? (say) 
The conditions for stability increase therefore with the number 
