code: def Bvirial(self):
          r'''Second virial coefficient of the gas phase of the chemical at its
          current temperature and pressure, in units of [mol/m^3].
  
          This property uses the object-oriented interface
          :obj:`thermo.volume.VolumeGas`, converting its result with
          :obj:`thermo.utils.B_from_Z`.
  
          Examples
          --------
          >>> Chemical('water').Bvirial
          -0.0009596286322838357
          '''
          if self.Vmg:
              return B_from_Z(self.Zg, self.T, self.P)
          return Nonf Bvirial(self):
          r'''Second virial coefficient of the gas phase of the chemical at its
          current temperature and pressure, in units of [mol/m^3].
  
          This property uses the object-oriented interface
          :obj:`thermo.volume.VolumeGas`, converting its result with
          :obj:`thermo.utils.B_from_Z`.
  
          Examples
          --------
          >>> Chemical('water').Bvirial
          -0.0009596286322838357
          '''
          if self.Vmg:
              return B_from_Z(self.Zg, self.T, self.P)
          return None
docs: r'''Second virial coefficient of the gas phase of the chemical at its
          current temperature and pressure, in units of [mol/m^3].
  
          This property uses the object-oriented interface
          :obj:`thermo.volume.VolumeGas`, converting its result with
          :obj:`thermo.utils.B_from_Z`.
  
          Examples
          --------
          >>> Chemical('water').Bvirial
          -0.0009596286322838357