Overvoltage. Discussion

J. W. Richards, A. J. Allmand, U. R. Evans
1914 Transactions of the Faraday Society  
communicated) : I fail to see exactly what Professor Richards has proved in his Paper. The experimental results could of course have been predicted with certainty beforehand. With an arrangement such as he employed, in which presumably hydrogen and oxygen were the sole products of electrolysis, no ozone or other oxidizing material being formed and concentration changes being negligible, then with an excess of heat produced irreversibly in the cell, the chemical work done by the current must
more » ... he current must necessarily correspond to the total energy change associated with the combination of hydrogen and oxygen to form liquid water (present as dilute sulphuric acid), and this, as Professor Richards points out, means a consumption of 1-48 to 1.49 volts (heat of reaction per gram-equivalent about 34,180 calories). Energy corresponding to 1-23 volts is absorbed in the reversible decomposition of the solution, and energy corresponding to 0.25 to 0.26 volt taken up directly as heat from the cell, If it were not for the heat produced in the electrolyte and (irreversibly) at the electrodes, the cell mentioned would cool during the electrolysis, and the volts absorbed would be considerably less than his theoretical value of 1-49. Nor do his results shed any light on the question of the nature of overvoltage-as to whether this complex phenomenon is due merely to ohmic resistance, as he suggests, or whether it is associated with the doing of chemical work, followed by the degradation of the chemical energy to heat energy. The balance of evidence at present, more particularly work done in Foerster's laboratory at Dresden, appears to me to favour the second hypothesis.
doi:10.1039/tf9140900310 fatcat:74p2ccs77fcxjhbsl6tznlulii