Silver/silver chloride and mercury/mercurous sulfate standards electrodes confiability

The present work proposes a procedure for the metrological evaluation of reference electrodes. The procedure determines the potential, relative to the standard hydrogen electrodes, and the isothermal temperature coefficient for these electrodes. High surface area half cells, 0.469 M silver/silver chloride/potassium chloride (Ag/AgCl/KCl) and (0.5 M gel) mercury/mercurous sulfate/1 M sulfuric acid/potassium sulfate (Hg/Hg2SO4/1 M H2SO4/K2SO4) were used for these cells. For 0.469 M Ag/AgCl/KCl, the measured potential showed <1 mV difference from theoretical value and isothermal temperature coefficient close to the thermodynamic value. The potential for (0.5 M gel) Hg/Hg2SO4/1 M H2SO4/K2SO4 showed a difference of 19 mV from the theoretical value without salt bridge. The estimated salt bridge value should be between 13.95 mV and 27.90 mV.