1683 
curve (A,) smaller than for (A), for (A,) smaller again than for 
(A,), ete. 
Further it appears from table 1 that the curves of R go towards 
higher pressures and lower temperatures; of this group the curves 
(B), (Le) and (R,) are drawn. It appears from the direction of the 
_aP i 
arrow in table 1 that the absolute value of 7 for the curves 
é 
A,4,A,... R,R,R, increases from left to right. The curves of group 
R are situated, therefore, with respect to one another and to the 
curves of group A, as is drawn in fig. 1. 
When we draw with the aid of the series ¢ and d and the direc- 
tion of the arrows, also the curves of the other groups, then we 
find fig. 1. Herein is only one curve drawn of each of the groups 
Ba, Bs, S, C and 7. 
Consequently we find a P,7-diagram with five bundles of curves; 
each of the groups of signs Rk, b= B, + Bs, S and C of the series 
of signs a produces a bundle of curves in the P,7-diagram, the 
groups of signs A and 7’ produce together one single bundle only. 
AV <0 and An <0 [series e and /|. We obtain the same P,7- 
diagram as in fig. 1, with this great difference, however, that we 
have to change mutually the stable and metastable parts of the 
curves from fig. 1. Consequently we have to draw the dotted lines 
in fig. 1 and to dot the drawn lines. 
AV >O and Ay <0 {series g and Zl. It follows at once from 
series g and / that the curves of group A go, starting from the 
invariant point, towards lower pressures and temperatures, it is 
apparent from the direction of the arrow in table I that those curves 
must be situated with respect to one another as the curves (A), 
(A,) and (A,) in fig. 2. Further it appears from series g and / 
that the curves of group Z go towards higher pressures and tempe- 
ratures, it appears from the direction of the arrow in table I that 
those curves must be situated with respect to one another and to 
the curves of group A, as the curves (f,), (R,) and (#,) in fig. 2. 
When we draw, however, in the P,7-diagram also the curves of 
the other groups, then we find fig. 2. Herein only one curve is 
drawn of each of the groups B, B, S, C and 7. 
Now we find again a P,7-diagram with five bundles of curves, 
each of the groups of signs Rk, B= B, + Bi, S and C of series a 
produces again a bundle of curves; the groups of signs A and 7’ 
produce again together one bundle. 
108 _ 
Proceedings Royal Acad. Amsterdam, Vol. XVIIL. 
