code: def _Tension(T):
      
      if 248.15 <= T <= Tc:
          Tr = T/Tc
          return 1e-3*(235.8*(1-Tr)**1.256*(1-0.625*(1-Tr)))
      else:
          raise NotImplementedError("Incoming out of bound")
docs: Equation for the surface tension
  
      Parameters
      ----------
      T : float
          Temperature, [K]
  
      Returns
      -------
      σ : float
          Surface tension, [N/m]
  
      Notes
      ------
      Raise :class:`NotImplementedError` if input isn't in limit:
  
          * 248.15 ≤ T ≤ 647
          * Estrapolate to -25ºC in supercooled liquid metastable state
  
      Examples
      --------
      >>> _Tension(300)
      0.0716859625
      >>> _Tension(450)
      0.0428914992
  
      References
      ----------
      IAPWS, Revised Release on Surface Tension of Ordinary Water Substance
      June 2014, http://www.iapws.org/relguide/Surf-H2O.html