1681 
Now we apply the rules /¢* and /® to the series of signs (19) 
and the rules //¢ and //® to the series of signs (20); viz. 19) is 
the series of signs of the isentropical-, (20) that of the isovolume- 
trical reaction. In the foregoing table the results are summarised. 
In table I line a represents the series of signs of the isentropical 
reaction and line 5 that of the isovolumetrical reaction. In order to 
indicate that a curve goes, starting from the invariant point, towards 
higher or lower pressures, we write at the beginning of a rule AP 
and further under each group a positive or negative sign; a positive 
sign indicates that AP is positive, or in other words that the curves 
go towards higher pressures; a negative sign indicates that AP is 
negative, therefore, that the curves go towards lower pressures. 
The lines, beginning with A7, indicate whether a curve goes, 
starting from the invariant point, towards higher or lower tempe- 
ratures. A positive sign indicates that A7’ is positive, therefore, that 
the curves go towards higher temperatures; a negative sign indicates 
that AZT’ is negative, therefore, that the curves go towards lower 
temperatures. 
When we take A70 [rules ¢ and g| then, in accordance with 
{* the curves of the groups A, 4,, B, and C go towards lower 
pressures, those of the groups FR, S and 7’ towards bigher pressures. 
This is expressed by the signs in series ¢ and g. 
For AV <0 [rule e and 7) we find with the aid of /® the series 
of signs e and 7. 
It is evident that in the rules ¢ and g [viz. AV > 0) all signs 
are tbe opposite and in the series e and 7 (viz. AV <0] all signs 
are the same as in the series of signs a. 
With the aid of //* and //® we find from series } the series 
d, f, h and 4. The series d and k [viz. Ay > 0] have the same 
signs, the series f and A [viz. Ax <0] have the opposite signs as 
the series of signs 0. 
As it follows from (17), the arrows in the lower line of the table 
. dP 
indicate the direction in which the absolute value ON ae increases 
for the different curves. Consequently it increases from curve (A,) 
to the last curve of group Be; it decreases from the first curve of 
group Bs to the last curve of group ~Z. 
Table I represents the four possible cases, viz. AV >O and 
Ay > 0 in series c and d; AV <0 and Ay <0 in series e and /; 
AV>O and Ay <0 in series g and h; AV <0 and Ay > 0 in 
series 7 and 4. The last rule / is true for each of those four cases. 
Now we can easily deduce the P,7-diagram for each of those cases. 
