1220 
like in fig. 2 (II) so that the tangent X/Y besides meeting the curve 
alb in the point #, also intersects this in two other points. In har- 
mony with fig. 3 we find that the vertical line corresponding with the 
temperature 7'p must intersect the curve XN in two points above 
HF, and the horizontal line corresponding with the pressure Py must 
intersect this curve in two points at the left of # 
From a consideration of the straight lines whose direction differs 
but little from the tangent XFY it follows that their P,7-curves 
in tig. 3 must exhibit on the one branch proceeding from #,a point 
with a maximum temperature and one with a maximum pressure, 
and on the other branch, besides two similar points, also one with 
a minimum temperature and a minimum pressure. 
The deduction and further consideration of the other cases I must 
leave to the reader. 
We can also determine the course of the saturation lines under 
their own vapour pressure and of the boiling point lines of the 
solutions saturated with solid matter, which has been discussed in 
the previous communications, in a different manner. 
For the stability requires that if we convert a system, at a constant 
temperature, into another having a smaller volume the pressure. 
must increase; if converted into one with a greater volume the 
pressure must decrease. 
We may also perceive this in the following manner. At the pressure 
P exists the system SS which is converted at the pressure P+ dP 
into the system jS’. We represent the & of the system JS, at the 
pressures P and P+dP by Sp and €pyap, that of the system JS’ 
by Sp and Spyar- 
As at the pressure P the system S is the stable one, it follows 
that Cp < GO’ p. 
As at the pressure P+ dP S’ is the stable one it follows that. 
prap<Cprip. If we represent the volumes of S and S’ at the 
pressure P by V and J” the latter condition can also be expressed by : 
Cp WAR bp va. 
From this now follows in connection with the first condition : 
V dP <= VIR 
hence, V’ < V if dP is positive and V’ >V if dP is negative. 
„The volume V" of the system S’, is, at the pressure P+ dP, 
! 
! 
like WV’ + DE dP, in which a is negative ; from this now follows : 
V'< V if dP is positive and V">V if dP is negative. 
