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When we know of each phase of the invariant equilibrium ^(.I'^O) 

 the entropy, the volume ami the composition, then with the aid 

 of (12) and (J 4) we may define the isovolu metrical and isentropical 

 reaction quantitativel3^ Consequently we are able to draw exactly 

 the direction of the different monovariant curves in the /^,7'-diagram, 

 we call it a quantitative P, 7-diagram. 



When we only now both reactions (jualitatively, then we can 

 define only whether the monovariant curves proceed, starting from 

 the invariant point towards higher or. lower temperatures and towards 

 higher or lower pressures; but then their situation with respect to 

 one another is still undefined; this we call a (pialitative P, 7-diagram. 



We take for example the reactions: 



F,^F,:^F, + f\\-F, A/7>0 A.r=0 ' 



K-\-F, + P\:^F, + F, AH=0 AF>0 



of a ternary invariant equilibrium. The first is, according to the 



supposition £\V=0, the isovolumetrical reaction and it takes place, 



according to the supposition A H ^ from left to right on addition 



of heat. It appears from A i/ = and AT'^^0 that the second 



one is the isentropical reaction and that the volume increases from 



lef to right. 



In accordance to our former considerations, now we have : 



F, + F,:^F,-^F,-\-F, A//>0 AF=0 



{F,){F,){F,) I {F,){F,) 



.... (19) 

 towards lower T \ towards higher T 



Further we have : 



F,-\-F,-^F,:^F, + F, LB = AF>0 



{F,){F,) I {F,)iF,){F,) 



.... (20) 

 towards higher P j towards lower P 



In accordance to our previous notation, herein is : 



{F,) = F,A-F, + F, + F, , (FJ=F, + F,i^F,-^F,, etc. 



Now we know qualitatively the P, T-diagram ; we know viz. that 

 from the invariant point curve (F",) is going towards higher 7' and 

 lower P; curve {F,) goes towards higher T and at the same time 

 towards higher P, etc. 



Inversely we can also find from a qualitative P, 7-diagram the 

 qualitative isovolumetrical and isentropical reaction. When we know 

 f.i. that the curves {F^) and {F,) go towards higher temperatures 

 and (i^j) (F^) and (F^) towards lower temperatures, then we have 

 to construe (19) in the inverse direction viz. from the bottom to the 

 top, in order to (ind the isovolumetrical reaction. 



