Behaviour of the mercury, mercuric oxide electrode in alkaline solutions in the temperature range 298–363 K

Abstract

Electromotive-force measurements of mercury, mercuric oxide electrodes against the silver, silver chloride and the hydrogen electrodes in mixed KCl + NaOH solutions have been made in the range 298–363 K. After digesting the crystals of HgO, bias potentials between the electrodes never exceeded 0.2 mV; they were much smaller between electrodes having HgO of the same colour. The thermodynamics of the reaction HgO(c)+ H2(g)= Hg(1)+ H2O were established; the ΔS values obtained differ from those reported in thermodynamic tables. In the experimental temperature range, pKw was also determined with good precision and this allowed the calculation of the standard potential of the mercury, mercuric oxide electrode having the electrode reaction 2e + HgO(c)+ H2O(l)= Hg(l)+ 2OH–(aq).