code: def SGg(self):
          r'''Specific gravity of the gas phase of the chemical, [dimensionless].
          The reference condition is air at 15.6 °C (60 °F) and 1 atm 
          (rho=1.223 kg/m^3). The definition for gases uses the compressibility
          factor of the reference gas and the chemical both at the reference
          conditions, not the conditions of the chemical.
              
          Examples
          --------
          >>> Chemical('argon').SGg
          1.3795835970877504
          '''
          Vmg = self.VolumeGas(T=288.70555555555552, P=101325)
          if Vmg:
              rho = Vm_to_rho(Vmg, self.MW)
              return SG(rho, rho_ref=1.2231876628642968) # calculated with Mixture
          return Nonf SGg(self):
          r'''Specific gravity of the gas phase of the chemical, [dimensionless].
          The reference condition is air at 15.6 °C (60 °F) and 1 atm 
          (rho=1.223 kg/m^3). The definition for gases uses the compressibility
          factor of the reference gas and the chemical both at the reference
          conditions, not the conditions of the chemical.
              
          Examples
          --------
          >>> Chemical('argon').SGg
          1.3795835970877504
          '''
          Vmg = self.VolumeGas(T=288.70555555555552, P=101325)
          if Vmg:
              rho = Vm_to_rho(Vmg, self.MW)
              return SG(rho, rho_ref=1.2231876628642968) # calculated with Mixture
          return None
docs: r'''Specific gravity of the gas phase of the chemical, [dimensionless].
          The reference condition is air at 15.6 °C (60 °F) and 1 atm 
          (rho=1.223 kg/m^3). The definition for gases uses the compressibility
          factor of the reference gas and the chemical both at the reference
          conditions, not the conditions of the chemical.
              
          Examples
          --------
          >>> Chemical('argon').SGg
          1.3795835970877504