471 
Point 7, the saturation point of KCl + BaCl, .2H,O + Di 22 
” h, EE) ” EE) ” BaCl, ° 2H,O + Di22 + Dit 
NS ae 3 » 9» BaCl,.2H,O + CuCl,.2H,0-+ Di 
As the equilibria represented in fig. 2 only apply to one definite 
temperature 7’ and one definite pressure P, we have at 60° the 
following equilibria: 
. Invariant (P. 7) equilibria. 
binary : the point a, c and e. 
ternary : bn Oe. Vor Gand A 
. Monovariant (P. 7) equilibria. 
ternary : the curves ab, be, ed, de, ef, fg, gk and ka. 
quaternary : __,, go Ghekh. Ui sah, hi fr and 1d 
C. Divariant (P. 7’) equilibria. 
1. quaternary : the planes I, II, III, IV and V. 
A 
Ì 
vn 
3. quaternary: „ ele ande £: 
B 
ij 
2 
It is evident that between the Figs. 1 and 2 there exist transi- 
tion forms, which must occur between 40° and 60°. If we start 
from fig. 2 and lower the temperature, the saturation surface V gets 
smaller until at 57° the points g and # coincide. The saturation surface 
then has a triangular form of which one apex rests against the side 
plane W—CuCl,—-KCl of the tetrahedron. As in this apex the 
saturation surfaces I, 1V, and V meet, the equilibrium: 
Cu Cl2.2H20 + Dy22-+ Diy 
occurs in the ternary system KCl — CuCl, — Water at 57°. 
On lowering the temperature still further the saturation surface V 
becomes smaller still and surrounded by the saturation surfaces /, [// 
and JV to finally disappear in a point within the tetrahedron, so 
that the relations drawn in fig. 1 occur. The moment the saturation 
surface V disappears, or rather that it becomes metastable, the 
surfaces J, IL, IV, and V pass through one point so that only one 
single point of the surface V represents a stable solution. This then 
signifies that in the quaternary system occurs the invariant (2) equi- 
librium : 
Ba Clo.2H20 — Cu Cl2.2Ho0 + Di o2 + D1 + Solution. 
This as deduced from the thermic determinations, happens at 
+ 55.7°. 
Between the above 5 phases a phase reaction may take place at 
55.7°, on increase, or decrease of heat. 
