1204 
Al Hr, — @) r+ (y, 8) sh cos @ + Hw, —@) 8 Hy, —8) tf sin ¢ 
BC—AD 
in which A= — v therefore positive or negative. 
From this it follows that d7’ will be „il when (9) is nil, therefore 
when the line drawn through 4 coincides with the tangent X/Y in 
F at the boiling point line passing through this point, or what 
amounts to the same thing, at the saturation line under its own 
aT = dg . (10) 
vapour pressure. We now distinguish fwo cases. 
Vv. The saturation lines under their own vapour pressure are 
now situated as in fig. 14(1); we now imagine, in this figure, the 
tangent drawn on to the saturation line under its own pressure, 
passing through #. As in fig. 1 we will eall this XY. The point 
corresponding with the point D of fig. 1 is, of course, situated in 
fig 14(1) on the vapour line correlated to the saturation line under 
its own vapour pressure which passes through the point /. Hence 
it is situated, as in fig. 1 to the left of the line VAN. 
If now we move in fig. 14(1) from / towards that side of the 
line NN where the point D is situated, then, as follows from (10), 
the temperature increases starting from EF; when moving towards 
the other side of the line X/Y the temperature decreases from 4 
After the previous considerations in regard to Fig. 1 it is evident 
that this agrees with fig. 14 (T+. If in this figure we imagine a line 
drawn from / towards that side of XA} where the point D is 
situated this will come into contact with one of the exphased satu- 
ration lines under their own vapour pressure. As each of these curves 
belongs to a definite constant temperature differing, of course, from 
curve to curve, the temperature in this point of contact is a maximum 
one. If now in fig. 2 we imagine the pressure axis to be replaced 
by the temperature axis we again obtain a curve like «£”5 with 
a maximum temperature between « and 4. If in fig. 14 (1) we turn 
the line passing through /# until it coincides with NA}, the curve 
al”) of fig. 2 is transformed to curve cf”’d of this figure. 
Should the case oeeur that in / the saturation line under its own 
vapour pressure becomes curved away from JD, we obtain curves 
as in fig. 3 in which we must again imagine the pressure axis to 
be replaced by the temperature axis. 
V<v. The saturation lines under their own vapour pressure are 
no longer situated as in fig. 14(J); we may, however, easily imagine 
them from this figure if we suppose the point / to lie on the line 
MAM, between J/ and M,. From a consideration of this figure it 
then follows that, starting from #, the temperature decreases towards 
that side of the line NFN where the point D is situated and 
