1686 
first curve of group A to the last curve of group 7. This direction 
of tbe arrow is in accordance with (16). 
The corresponding P,T-diagram is easily found now; it is drawn 
in fig. 3; three curves are drawn of group A, of each of the other 
groups only one curve is drawn. The P,7-diagram shows this 
peculiarity that all curves are situated within two of the four 
quadrants; it follows from table 2 that this is the case for each of 
the four P,7-diagrams. The bundle A + 7'sbows here the peculiarity 
Fig. 3. 
that it is divergent, as well in the direction of pressure as of tem- 
perature, and that it contains two succeeding curves, which make 
with one another an angle which is larger than 90°. 
In all our considerations we have supposed up to now that the 
last group of the series of signs (19) is negative; it may of course 
also be positive. In order to consider this case we omit-the group 
T from (19) and therefore also from (20) so that it disappears also 
from the tables 1 and 2. Now it is evident that again we obtain 
the same P,T-diagrams which we have above, but that in those 
the curves of group 7 are missing. Consequently in the figs. 1 
and 2 there is no more a bundle which is divergent in direction of 
pressure, and in fig. 3 no bundle which is divergent as well in 
direction of pressure as of temperature. 
We represent the isentropical reaction, which may occur between 
the phases of an invariant point, by: 
a, FP, + ak, eed apBp heere + GntoP ne =0 AV; 0. (21) 
and the isovolumetrical reaction by: 
