code: def rhos(self):
          r'''Solid-phase mass density of the chemical at its current temperature,
          in units of [kg/m^3]. For calculation of this property at
          other temperatures, or specifying manually the method used
          to calculate it, and more - see the object oriented interface
          :obj:`thermo.volume.VolumeSolid`; each Chemical instance
          creates one to actually perform the calculations. Note that that
          interface provides output in molar units.
  
          Examples
          --------
          >>> Chemical('iron').rhos
          7869.999999999994
          '''
          Vms = self.Vms
          if Vms:
              return Vm_to_rho(Vms, self.MW)
          return Nonf rhos(self):
          r'''Solid-phase mass density of the chemical at its current temperature,
          in units of [kg/m^3]. For calculation of this property at
          other temperatures, or specifying manually the method used
          to calculate it, and more - see the object oriented interface
          :obj:`thermo.volume.VolumeSolid`; each Chemical instance
          creates one to actually perform the calculations. Note that that
          interface provides output in molar units.
  
          Examples
          --------
          >>> Chemical('iron').rhos
          7869.999999999994
          '''
          Vms = self.Vms
          if Vms:
              return Vm_to_rho(Vms, self.MW)
          return None
docs: r'''Solid-phase mass density of the chemical at its current temperature,
          in units of [kg/m^3]. For calculation of this property at
          other temperatures, or specifying manually the method used
          to calculate it, and more - see the object oriented interface
          :obj:`thermo.volume.VolumeSolid`; each Chemical instance
          creates one to actually perform the calculations. Note that that
          interface provides output in molar units.
  
          Examples
          --------
          >>> Chemical('iron').rhos
          7869.999999999994