code: def SG(self):
          r'''Specific gravity of the mixture, [dimensionless]. 
          
          For gas-phase conditions, this is calculated at 15.6 °C (60 °F) and 1 
          atm for the mixture and the reference fluid, air. 
          For liquid and solid phase conditions, this is calculated based on a 
          reference fluid of water at 4°C at 1 atm, but the with the liquid or 
          solid mixture's density at the currently specified conditions.
  
          Examples
          --------
          >>> Mixture('MTBE').SG
          0.7428160596603596
          '''
          return phase_select_property(phase=self.phase, s=self.SGs, l=self.SGl, g=self.SGgf SG(self):
          r'''Specific gravity of the mixture, [dimensionless]. 
          
          For gas-phase conditions, this is calculated at 15.6 °C (60 °F) and 1 
          atm for the mixture and the reference fluid, air. 
          For liquid and solid phase conditions, this is calculated based on a 
          reference fluid of water at 4°C at 1 atm, but the with the liquid or 
          solid mixture's density at the currently specified conditions.
  
          Examples
          --------
          >>> Mixture('MTBE').SG
          0.7428160596603596
          '''
          return phase_select_property(phase=self.phase, s=self.SGs, l=self.SGl, g=self.SGg)
docs: r'''Specific gravity of the mixture, [dimensionless]. 
          
          For gas-phase conditions, this is calculated at 15.6 °C (60 °F) and 1 
          atm for the mixture and the reference fluid, air. 
          For liquid and solid phase conditions, this is calculated based on a 
          reference fluid of water at 4°C at 1 atm, but the with the liquid or 
          solid mixture's density at the currently specified conditions.
  
          Examples
          --------
          >>> Mixture('MTBE').SG
          0.7428160596603596