Fugacity coefficient of a gas

The fugacity coefficient of a gas is defined in a similar way to the activity coefficient, but it is based on the residual Gibbs energy ... 

So, for example, to determine the fugacity coefficient of a gas at 0°C at a pressure of 100 bars, we obtain the values for the critical temperature and pressure of this gas from the tables, we deduce the reduced temperature and reduced pressure. On the x-axis, at point Pr on the curve relative to TV on the... 

This relation allows us to calculate the fugacity coefficient of a gas from the state equation of a mixture and consequently its fugacity and chemical potential using expressions [8.15] and [8.13]. 

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