854 
a constant pressure it disappears at an elevation of temperature only. 
From all tuis it follows that most of the diagrams described above 
which occur at a constant temperature on reduction of pressure 
will also. as a rule, form at a constant pressure by an elevation of 
temperature. At a constant temperature, the liquid and the gas of 
the three-phase equilibrium /'+ L + G each proceed along an 
isothermic-polybaric curve which we have called the saturation line 
of / under its own vapour pressure and the vapour line appertaining 
thereto. 
Under a constant pressure, the liquid and the gas of the three- 
phase equilibrium #4 1+ G each proceed along a polythermic- 
isobaric curve. As these solutions saturated with / can, at a given 
pressure, be in equilibrium with vaponr and consequently boil at 
that temperature we will call these lines the boiling point line of 
the solutions saturated with / and the vapour line appertaining 
thereto. 
The saturation line of /’ under its own pressure may be circum- 
phased [fig. 7 (I) and 11 (I)|) as well as exphased [fig. 12 (I) and 
13 (I)|. The same applies to the boiling point line of the solutions 
saturated with #, with this difference, however, that fig. 13 (1) 
does not occur. The saturation line of # under its own vapour 
pressure exhibits a pressure maximum and minimum; the boiling 
point line of the solutions saturated with /” a temperature maximum 
and minimum. These are, however, so situated that the arrows. of 
the figs. 7 (1), 11 (U) and 12 (I) should point in the opposite 
direction. 
We will refer later to these curves in various respects. 
We can also unite these boiling point lines with their correlated 
vapour lines for different pressures, in a same plane. We then 
obtain a diagram analogous to fig. 14 (I) in which the arrows, 
however, must point in the opposite direction. If the pressure axis 
is taken perpendicularly to the plane of drawing, the spaceal 
representation gives two planes, namely the boiling point plane of 
the solutions saturated with / and the correlated vapour plane. 
We will now consider still in another way the saturation lines 
under their own pressure and the boiling point lines of the liquids 
saturated with a solid substance. 
We assume that a solid substance / of the composition a, 8, and 
1) The number (1) placed behind a figure signifies that a figure from the first 
communication is intended. 
