towards / or mm, draws near to the point m,. This is represented 
by dm,. The point 6 of fig. 4 corresponds with the homonymous 
one of fig. 3; it is, therefore, that point of the saturation line under 
its Own vapour pressure in which the side liquid-gas of the three- 
phase triangle meets this saturation line. The points d and 4 divide 
the branch J/dbm of the saturation line under its own vapour 
pressure into three parts. 
On distilling the liquid d a complex + L is formed which tra- 
verses the complex distillation curve dm, ; the pressure therefore 
falls from Pa to the minimum pressure P,, and the liquid itself tra- 
verses the curve dbm. As the pressure gets nearer P,,, the liquid 
and the solid substance /’ will be left behind more and more in 
that proportion in which the vapour m, can be formed from them; 
at the last moments of the distillation we notice the solid matter 
and the liquid to disappear simultaneously. 
Let us now take a liquid ¢ of the branch J/d. On distillation of 
this liquid, a complex /’-+ L is formed which traverses the complex 
distillation curve proceeding from c towards /. The pressure, there- 
fore, falls from ZP, to the minimum pressure P„ and the liquid itself 
traverses the branch chm. The nearer the pressure gets to P,, the less 
liquid will be retained in the complex which finally will practi- 
cally consist of the solid substance /’ only. 
Let us now take a liquid s of the branch dé; this on distillation 
forms a complex /’+ L which traverses the complex distillation 
curve sf. Hence, the pressure falls from P; to Pf and the liquid 
itself proceeds along the curve sbf; the liquid s is, therefore, con- 
verted into the liquid f at first with separation of solid matter which 
is then again redissolved. 
We notice from this that the point d is a point of demarcation 
and insuch a manner that all the liquidum distillation curves which 
meet the saturation line under its own vapour pressure between 
d and M do not leave the heterogeneous region, whereas those 
meeting this curve between d and / abandon that region. 
If we take a distillation temperature higber than the maximum 
sublimation point but lower than the minimum melting point of the 
substance / the saturation- and vapour-saturation curve under their 
own vapour pressure will have a form as in fig. 7 (I). All liquidum 
distillation curves which meet this saturation curve abandon the 
heterogeneous region. I must leave the consideration of the other 
cases to the reader. : 
(To be continued). 
