Reference Electrode Potentials
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The calomel electrode is usually constructed from a platinum wire inserted into a a mixture of calomel (mercurous chloride, Hg</sub>2</sub >Cl2</sub >) and mercury with an electrolyte solution of KCl or NaCl. The relevant half equation is:
Hg<s>2Cl2 + 2e– == 2Hgliq + 2Cl–
Conditions | vs NHE | vs SCE | LJ | Reference |
---|---|---|---|---|
Hg/Hg2Cl2, KCl (0.1M) | 0.3337 | 0.0925 | - | 1,3 |
Hg/Hg2Cl2, KCl (0.1M) | 0.336 | 0.092 | Yes | 2 |
Hg/Hg2Cl2, KCl (1M) NCE (Normal Calomel) | 0.2801 | 0.0389 | - | 1,3 |
Hg/Hg2Cl2, KCl (1M) NCE (Normal Calomel) | 0.283 | 0.039 | Yes | 2 |
Hg/Hg2Cl2, KCl (3.5M) | 0.250 | 0.006 | Yes | 2 |
Hg/Hg2Cl2, KCl (sat'd) SCE (Sat'd Calomel) | 0.2412 | 0 | - | 1,3 |
Hg/Hg2Cl2, KCl (sat'd) SCE (Sat'd Calomel) | 0.244 | 0 | Yes | 2 |
Hg/Hg2Cl2, NaCl (sat'd) | 0.2360 | -0.0052 | - | 1 |
NOTES