(3) 
diseussion has enabled me to give a more precise and accurate form 
to some of the equations and to some of the quantities occurring in 
them. In these cases I shall discuss some properties more extensively, 
concerning which I had else confined myself to refer to Cont. IL. 
From a theoretical point of view the relation between p, , and y, 
at given temperature is not more important than that between »,, 7, 
and y, or between v,, 7, and y,. But even for a simple substance 
the experimental investigation concerning the maximum pressure has 
first been executed, and only in these later years it has been followed 
by an investigation concerning the densities. In the same way we 
may expect, that also for a ternary system the experiment will occupy 
itself in the first place with the determination of the pressure, and 
that the investigation as to the densities of the phases coexisting with 
other phases, will follow later. The surface representing for all tem- 
peratures the pressure as function of the composition of a binary 
mixture has been called by me “surface of saturation”. We might 
call for a ternary system the surface whose properties we are about 
to investigate “surface of saturation for a given temperature”. Wherever 
it is not ambiguous I shall speak simply of “surface of saturation” 
In the following considerations we will take triangle OXY in a 
horizontal plane; the direction in which the pressure is laid off is 
then vertical. We represent the maximum pressures of the three com- 
ponents by p,, p, and p, where we choose the indices in such a way that 
Ie OER NES 
If 7 > T, for one of the components, then the surface of satu- 
ration does not reach the corresponding angle and the corresponding 
maximum pressure does not exist any longer. 
a. Curves of equal pressure. 
For curves of equal pressure, we have dy ==0, and equation 11 
is reduced to: 
05 05 
(eme) Oa, TF (Ya) Oa Òy, at 
0*5 en | 
a (v,— Blan ‘Oy, + (y¥,— En dy, —— Ue 
The projection of these curves is of course the same as the 
projection of the connodal curve of the &-surface construed for this 
pressure. We have discussed this projection in our first communi- 
cation p. 461. If p is chosen such that p, <p <p. the two 
branches of this projection cut the two sides of the triangle adjacent 
i a 
