Fugacities with Cubic Equations of State

Fugacities of nonpolar/weakly polar mixtures, for both the liquid and vapor phases, are typically calculated with cubic EoS. Use of the SRK, PR, and vdW-711 EoS with Eq. 11.9.3 gives  

Lin and Daubert (1980) did an extensive study on the evaluation of fiigacities for hydrocarbon mixtures with the SRK and PR EoS. Their findings can be summarized as follows  

Because the calculation of fiigacities requires the evaluation of derivatives with respect to composition (Eq. 11.9.3), the obtained results are more sensitive to the accuracy of the k,j - and for the virial - values, than are total mixture properties, such as volume. (See Problem 11.51). 

We will return to interaction coefficients when we discuss high pressure vapor-liquid equilibrium, where they play a key role since they are involved in the calculation of both, vapor and liquid phase fiigacities. 

Evaluation of fiigacities with EoS is presented in die next Example. 

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