1. Place a freshly filled reference electrode of the same type (i.e. SCE) in a small beaker containing a saturated solu tion of potassium chloride/silver chloride solution. You must assume that the fresh electrode is at the correct potential.
2. Place the reference electrode (i.e. SCE) to be tested in the same beaker as the fresh reference electrode.
3. With a 3 1/2 digit voltmeter, measure the potential difference between the two reference electrodes. Or use a Model 273 Potentiostat with the reference to be tested hooked up as the working electrode. With the cell switch set to external, the potential (E) reading is the potential difference of the two electrodes.
4. If you measure more than 40 mVpotential difference between the two reference electrodes, we recommend you renew the filling solution and replace the Vycor frit.
The frit should be replaced periodically, anyway. The trick to getting the frit on correctly is to turn the electrode while gently applying heat.
SCE [Saturated Calomel Electrode]............................ 242 mV
SSCE [Sodium Saturated Calomel]........................... 236 mV
AgCl/Ag [1 M KCl /sat'd AgCl]................................. 222 mV
AgCl/Ag [sat'd KCl /sat'd AgCl].............................. 197 mV
Hg/HgSO4, [sat'd HgSO4]. ........................................ 616 mV
Cu/CuSO4, [sat'd CuSO4] ..........................................300 mV