code: def rho(self):
          r'''Mass density of the chemical at its current phase and
          temperature and pressure, in units of [kg/m^3].
  
          Utilizes the object oriented interfaces
          :obj:`thermo.volume.VolumeSolid`,
          :obj:`thermo.volume.VolumeLiquid`,
          and :obj:`thermo.volume.VolumeGas` to perform the
          actual calculation of each property. Note that those interfaces provide
          output in units of m^3/mol.
  
          Examples
          --------
          >>> Chemical('decane', T=550, P=2E6).rho
          498.67008448640604
          '''
          return phase_select_property(phase=self.phase, s=self.rhos, l=self.rhol, g=self.rhogf rho(self):
          r'''Mass density of the chemical at its current phase and
          temperature and pressure, in units of [kg/m^3].
  
          Utilizes the object oriented interfaces
          :obj:`thermo.volume.VolumeSolid`,
          :obj:`thermo.volume.VolumeLiquid`,
          and :obj:`thermo.volume.VolumeGas` to perform the
          actual calculation of each property. Note that those interfaces provide
          output in units of m^3/mol.
  
          Examples
          --------
          >>> Chemical('decane', T=550, P=2E6).rho
          498.67008448640604
          '''
          return phase_select_property(phase=self.phase, s=self.rhos, l=self.rhol, g=self.rhog)
docs: r'''Mass density of the chemical at its current phase and
          temperature and pressure, in units of [kg/m^3].
  
          Utilizes the object oriented interfaces
          :obj:`thermo.volume.VolumeSolid`,
          :obj:`thermo.volume.VolumeLiquid`,
          and :obj:`thermo.volume.VolumeGas` to perform the
          actual calculation of each property. Note that those interfaces provide
          output in units of m^3/mol.
  
          Examples
          --------
          >>> Chemical('decane', T=550, P=2E6).rho
          498.67008448640604