Equations of state for representing pure component properties are compared, using very accurately smoothed experimental data and fitting the equation of state parameters for the optimal representation of densities and saturation properties (vapor pressure and saturated volumes). The optimization procedure takes into account the experimental errors. It is applied to data on methane, ethane, and ammonia. Four equations are compared: the Redlich-Kwong equation, the Redlich-Kwong-Fuller equation, the Ponce-Renon equation, and a new empirical modification of it.

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