Kjelstrup et al. recently applied non-equilibrium thermodynamics to analyze the thermodynamic relationships for thermo-electrochemical effects in certain electrochemical cells [Electrochim. Acta 99 (2013) 166-175]. The present paper considers whether one can extend such relationships to establish equivalence between certain non-equilibrium thermodynamic properties, such as transported entropies, and equilibrium thermodynamic properties, such as partial molar entropies. If so it would enable the use of thermo-electrochemical measurements to determine certain quantities that have heretofore been considered "un-measurable", such as partial molar entropies of ions in solution. It would also provide a unifying principle between non-equilibrium thermodynamics and reversible thermodynamics, and it could lead one to consider the possibility of an additional law or principle of thermodynamics. (C) 2013 Elsevier Ltd. All rights reserved.