1690 
VI for an arbitrary pair of reaction-equations, bowever the same as 
that of the isentropical reaction. lt causes, therefore, which stands 
to reason, the same P,T-diagramtype. 
The only difference is, that the isentropical reaction still defines 
at the same time which curves go in the same direction of pressure, 
and the isovolumetrical reaction defines which curves go in the same 
direction of temperature. 
14. Another deduction of the P, 7-diagramty pes, 
In previous communications we have already deduced in different 
ways the P,7-diagramtypes. A new deduction follows from the 
previous considerations in chapter (13). 
Using the properties 1 and 2 we found: 
the series of signs of the isentropical reaction defines the P,7- 
diagramtype and besides which curves go in the same direction of 
pressure ; 
the series of signs of the isovolumetrical reaction defines the P,7™- 
diagramtype and besides which curves go in the same direction of 
temperature. 
Hence we may deduce now, that the series of signs of each other 
reaction, which occurs between the phases of the invariant point, 
defines also the P, 7-diagramty pe. 
In order to show this we take the arbitrary reactions: 
plain Se IRA ne leet irate pew a 0 a) (225) 
mM FS ew Mat oh to ——= Okee = eo) 
Herein /, and m, are positive, both are written in such order of 
succession, that we have 
De: ee tye 
= +> 
Mn+2 
In each of those ee a definite change in volume and entropy 
occurs; we may, therefore, deduce from them the isentropical and 
isovolumetrical reaction, as is shown in the previous chapter. We 
write them: 
GF Baks are == 0h OAV GO ee  N(20) 
0,7, ua, +... + Unpogntelnte=0 0; An . (27) 
In communication VI we have seen that all pairs of reaction- 
equations, which we can deduce from a given pair, have the same 
series of signs; (24) has, therefore, the same series of signs as (26). 
As the P,7-diagramtype is defined by the series of signs of (26), 
it is, therefore, also defined by the series of signs of (24). 
