code: def rhol(self):
          r'''Liquid-phase mass density of the chemical at its current
          temperature and pressure, in units of [kg/m^3]. For calculation of this
          property at other temperatures and pressures, or specifying manually
          the method used to calculate it, and more - see the object oriented
          interface :obj:`thermo.volume.VolumeLiquid`; each Chemical instance
          creates one to actually perform the calculations. Note that that
          interface provides output in molar units.
  
          Examples
          --------
          >>> Chemical('o-xylene', T=297).rhol
          876.9946785618097
          '''
          Vml = self.Vml
          if Vml:
              return Vm_to_rho(Vml, self.MW)
          return Nonf rhol(self):
          r'''Liquid-phase mass density of the chemical at its current
          temperature and pressure, in units of [kg/m^3]. For calculation of this
          property at other temperatures and pressures, or specifying manually
          the method used to calculate it, and more - see the object oriented
          interface :obj:`thermo.volume.VolumeLiquid`; each Chemical instance
          creates one to actually perform the calculations. Note that that
          interface provides output in molar units.
  
          Examples
          --------
          >>> Chemical('o-xylene', T=297).rhol
          876.9946785618097
          '''
          Vml = self.Vml
          if Vml:
              return Vm_to_rho(Vml, self.MW)
          return None
docs: r'''Liquid-phase mass density of the chemical at its current
          temperature and pressure, in units of [kg/m^3]. For calculation of this
          property at other temperatures and pressures, or specifying manually
          the method used to calculate it, and more - see the object oriented
          interface :obj:`thermo.volume.VolumeLiquid`; each Chemical instance
          creates one to actually perform the calculations. Note that that
          interface provides output in molar units.
  
          Examples
          --------
          >>> Chemical('o-xylene', T=297).rhol
          876.9946785618097