code: def Z(self):
          r'''Compressibility factor of the chemical at its current phase and
          temperature and pressure, [dimensionless].
  
          Examples
          --------
          >>> Chemical('MTBE', T=900, P=1E-2).Z
          0.9999999999079768
          '''
          Vm = self.Vm
          if Vm:
              return Z(self.T, self.P, Vm)
          return Nonf Z(self):
          r'''Compressibility factor of the chemical at its current phase and
          temperature and pressure, [dimensionless].
  
          Examples
          --------
          >>> Chemical('MTBE', T=900, P=1E-2).Z
          0.9999999999079768
          '''
          Vm = self.Vm
          if Vm:
              return Z(self.T, self.P, Vm)
          return None
docs: r'''Compressibility factor of the chemical at its current phase and
          temperature and pressure, [dimensionless].
  
          Examples
          --------
          >>> Chemical('MTBE', T=900, P=1E-2).Z
          0.9999999999079768