1233 
a particularity, when two phases of a binary system have the same 
concentration; this only occurs, when the components satisfy definite 
conditions. To allow of a third phase having also the same compo- 
sition, still more special conditions, hardly ever to be expected, must be 
fulfilled. Although this does not prove the absolute impossibility of 
such a point, we see at once that it is highly improbable, and in 
any case that it cannot occur in general. 
Until now, no single example has been experimentally investigated ; 
it seemed, therefore, important to prove with some system the exactness 
of the above considerations. We chose the system carbon disulphide- 
methylaleohol. 
The principal thing is to show that-in the ¢, a-diagram the curve 
indicating the concentration of the vapour, runs as is drawn in 
figure 1. This gives the change of composition, which the three 
| phases — permanently remaining in equili- 
T brium — undergo by rise of temperature, 
or, as we may also express it, the ¢,a- 
projection of the triple curve. At low 
temperatures, the order of the phases is 
L,GL,; G and ZL, become equal at a 
certain temperature after which the order 
is GL,L,; at this peculiar temperature, 
the G-curve cuts the Z,-¢urve. 
This is the cause of another particu- 
x larity, which may also be considered as 
Fig: 1. a characteristic of these systems. The 
p‚v-diagram must have the form of fig. 2 at low temperatures.— 
when the order is L,GL,—, and that of fig. 3 at higher ones, as 
is easily seen graphically. The transition between these is formed 
p P 
Fie 2 Pig. 3, 
