The nonequilibrium electromotive force. I. Measurements in a continuously stirred tank reactor

Based on a statistical thermodynamic theory, it has been predicted [J. Keizer, J. Chem. Phys. 82, 2751 (1985)] that at nonequilibrium steady states the electromotive force (EMF) of an electrochemical cell will differ from the local equilibrium value given by the Nernst equation. We describe here experiments designed to test this prediction for aqueous solutions of Fe2+ and Fe3+ in sulfate buffer. Using a continuously stirred tank reactor driven by a peristaltic pump, a feed solution containing Fe2+ and Fe3+ was mixed with a second feed solution containing the oxidant sodium peroxydisulfate Na2S2O8. The reaction leads to a steady nonequilibrium mixture, which at acidic pH in sulfate buffer is composed of Fe2+ and the ferric sulfate complexes FeSO+4 and Fe(SO4)−2. The EMF of this half‐cell was measured vs a saturated calomel reference electrode as a function of residence time in the reactor. These potentials were compared to the Nernst potential calculated on the basis of the concentration ratio of Fe2+ to ...

[1]  J. Rush,et al.  Pulse radiolytic studies of the reaction of perhydroxyl/superoxide O2- with iron(II)/iron(III) ions. The reactivity of HO2/O2- with ferric ions and its implication on the occurrence of the Haber-Weiss reaction , 1985 .

[2]  J. Keizer.  Dissipation and fluctuations in nonequilibrium thermodynamics , 1976 .

[3]  B. Parsons,et al.  Appearance of sulphatoferric complexes in the oxidation of ferrous sulphate solutions. A study by pulse radiolysis , 1973 .

[4]  A. Bard,et al.  Electrogenerated chemiluminescence. 41. Electrogenerated chemiluminescence and chemiluminescence of the Ru(2,21 - bpy)32+-S2O82- system in acetonitrile-water solutions , 1982 .

[5]  F. Fairbrother,et al.  Book reviewA text-book of quantitative inorganic analysis: A. I. Vogel: (including elementary instrumental analysis). 3rd Ed. Longmans, Green, London, 1962. Pp.xxx + 1216 70s. , 1963 .

[6]  J. Keizer.  Theory of rapid bimolecular reactions in solution and membranes , 1985 .

[7]  W Geiseler,et al.  Three steady state situation in an open chemical reaction system I. , 1977, Biophysical chemistry.

[8]  J. Keizer.  Reversibility, work, and heat at nonequilibrium steady states , 1984 .

[9]  H. Hanley,et al.  A thermodynamics for a system under shear , 1982 .

[10]  Joel Keizer,et al.  Statistical Thermodynamics of Nonequilibrium Processes , 1987 .

[11]  Joel Keizer,et al.  The nonequilibrium electromotive force. II. Theory for a continuously stirred tank reactor , 1987 .

[12]  I. Epstein.  Oscillations and chaos in chemical systems , 1983 .

[13]  David Jou,et al.  Recent Developments in Nonequilibrium Thermodynamics: Fluids and Related Topics , 1986 .

[14]  Gilbert N. Lewis,et al.  Thermodynamics and the free energy of chemical substances , 1923 .

[15]  Joel Keizer,et al.  Nonequilibrium thermodynamics and the stability of states far from equilibrium , 1979 .

[16]  Joel Keizer,et al.  Fluctuations, stability, and generalized state functions at nonequilibrium steady states , 1976 .

[17]  J. Keizer,et al.  Spatially nonlocal fluctuation theories: Hydrodynamic fluctuations for simple fluids , 1982 .

[18]  Joel Keizer,et al.  Heat, work, and the thermodynamic temperature at nonequilibrium steady states , 1985 .

[19]  Joel Keizer,et al.  Thermodynamics at nonequilibrium steady states , 1978 .