Fugacities in a mixture of real gases

The definition of partial pressures (10.24) applies both to real and perfect gases. 

We have already seen (10.34) that in a mixture oi perfect gases. i=l4 T) + RT Q.p.  

Again we see that this equation preserves the general form of the equation for perfect gases, with the fugacities replacing partial pressures. For example, for a binary mixture, for which the equation of state is (11.26), we have by comparing (11.32) with (11.67) 

The arguments of the preceding paragraph apply without alteration to the case of a mixture. Thus, just as for a single gas, the fugacity may be calculated from (c/. 11.59). 

We only require to know the partial molar volumes as a function of pressure to evaluate the fugacity of each component at a given temperature. We can use either directly determined values or an equation of state such as that derived from the van der Waals equation in 4 of 

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