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The apex A property of a Fluid Mixture represented by the junction point of Vapour Liquid Equilibrium (VLE) area on PT diagram of Fluid Mixture (see Fig. 1).


It is characterized by pseudo-critical temperature  

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and pseudo-critical pressure 
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bodyp_c--uriencoded--P_%7Bpc%7D
.

Supercritical carbon dioxide - WikipediaImage RemovedImage Added

Fig. 1Schematic PT diagram with Vapour Liquid Equilibrium and Pseudo-Critical Point (Tpc, pPpc).


The simplest estimate of estimate  (also called Linear Blending Rule) of Pseudo-Critical Point 

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body--uriencoded--( T_%7Bpc%7D, \, pP_%7Bpc%7D )
 is the mole fraction weighted average of the critical temperature 
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body--uriencoded--\%7B T_%7Bc, i%7D \%7D
 and  critical pressure 
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body--uriencoded--\%7B P_%7Bc, i%7D \%7D
 of fluid components (which are pure substances) :

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anchorKXETTTpc
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T_{pc} = \sum_i x_i \, T_{c,i}
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pP_{pc} = \sum_i x_i \, pP_{c,i}

where

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bodyx_i

mole fraction of the 

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bodyi
-th mixture component

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body--uriencoded--T_%7Bc,i%7D

critical temperature of the 

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bodyi
-th mixture component

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body--uriencoded--

p

P_%7Bc,i%7D

critical pressure of the 

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bodyi
-th mixture component


There are other no-linear methods to blend the components  to estimate the 
Pseudo-Critical Point but many engineering applications use 

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anchorTpc
 and 
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anchorppc
 as the seed and then fit the values to match lab test data.


In case the fluid composition is not known one can use empirical 
Pseudo-Critical Point Correlations to assess the Pseudo-Critical Point.

See also

...

Natural Science / Physics / Thermodynamics / Thermodynamic system 

...

Pseudo-Critical Point (Tpc, pPpc) ][ Pseudo-Critical Temperature (Tpc) ][ Pseudo-Critical Pressure (Ppc)]Pseudo-Critical Point Correlations @model ]

[ Critical Point (Tc, pPc) ][ Сritical Temperature Temperature  (Tc) ][ Critical Pressure (pPc) ]