@property<EOL><INDENT>def eos(self):<DEDENT>
return self.eos_in_a_box[<NUM_LIT:0>]<EOL>
r'''Equation of state object held by the chemical; used to calculate
        excess thermodynamic quantities, and also provides a vapor pressure
        curve, enthalpy of vaporization curve, fugacity, thermodynamic partial
        derivatives, and more; see :obj:`thermo.eos` for a full listing.

        Examples
        --------
        >>> Chemical('methane').eos.V_g
        0.02441019502181826