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Potentials of Common Reference Electrodes

RESOURCES > REF ELECTRODES > POTENTIALS

The following tables give the potentials of several commonly used reference electrodes. Various filling solutions are listed where data was available. Note that the nature and concentration of the filling solution can dramatically change the potential! When you look through the scientific literature, be sure the author has specified the filling solution!

If you are confused about converting from one reference electrode to another, read our explanation or use our calculator. 

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Notes:

  1. In some cases, two slightly different potentials are listed for the same electrode/filling solution.  Some of the values are 'standard potentials' or potentials of cells without liquid junction. Other values ('LJ' in tables, below) are for cells which include a liquid junction potential.
  2. Values in italics have been calculated from the suitable (LJ or non-LJ) potentials in these tables. Other values have been taken directly from the reference cited.

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Calomel:

Hg2Cl2(s) + 2e- == 2Hg(liq) + 2Cl-

 

Potential @ 25°

Liq
Jct ?

LIT
REF

vs. NHE

vs. SCE

Hg/Hg2Cl2, KCl (0.1M)

0.3337

0.0925

  

1,3

0.336

0.092

LJ

2

Hg/Hg2Cl2, KCl (1M)
NCE (Normal Calomel)

0.2801

0.0389

  

1,3

0.283

0.039

LJ

2

Hg/Hg2Cl2, KCl (3.5M)

0.250

0.006

LJ

2

Hg/Hg2Cl2, KCl (sat'd)
SCE (Sat'd Calomel)

0.2412

0

  

1,3

0.244

0

LJ

2

Hg/Hg2Cl2, NaCl (sat'd)
Bard  calls this SSCE

0.2360

-0.0052

  

1

Potentials at other temperatures are also available online.

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Silver / silver chloride:

AgCl(s) +e- == Ag(s) + Cl-

 

Potential @ 25°

Liq
Jct ?

LIT
REF

vs. NHE

vs. SCE

Ag/AgCl, KCl (0.1M)

0.2881

0.047

 

3

Ag/AgCl, KCl (3M)

0.210

-0.032

 

10

Ag/AgCl, KCl (3.5M)

0.205

-0.039

LJ

2

Ag/AgCl, KCl (sat'd)

0.197

-0.045

  

1

0.199

-0.045

LJ

2

0.1988

-0.042

 

2

Ag/AgCl, NaCl (3M)

0.209

-0.035

LJ

8

Ag/AgCl, NaCl (sat'd)

0.197

-0.047

LJ

3

Ag/AgCl,Seawater

0.25

0.01

  

9

More information about the Ag/AgCl Ref. Electrode.

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*f Mercury / mercury oxide: 

HgO(s) + H2O + 2e- == Hg(liq) + 2OH-

 

Potential @ 25°

Liq
Jct ?

LIT
REF

vs. NHE

vs. SCE

Hg/HgO, NaOH (0.1F)

0.165

-0.076

  

3

Hg/HgO, NaOH (1F)

0.140 ?

-0.101 ?

  

3

Hg/HgO, KOH (20%)

0.098

?

?

6

More information about the Hg/HgO Ref. Electrode is available.
A mercury/mercury oxide electrode is commercially available from
Koslow Scientific.

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Mercury / mercurous sulfate:

Hg2SO4 + 2e- == 2Hg(liq) + SO4-2

 

Potential @ 25°

Liq
Jct ?

LIT
REF

vs. NHE

vs. SCE

Hg/Hg2SO4, H2SO4 (0.5M)

0.68

0.44

  

1

0.682

0.441

  

3

Hg/Hg2SO4, H2SO4 (1M)

 

 

 

 

Hg/Hg2SO4, K2SO4(sat'd)

0.64

0.40

  

1

0.658
@ 22°C

0.414
@ 22°C

LJ

2

0.65

0.41

  

3

Abbreviated "MSE" - unspecified sulfate concentration.
A mercury/mercurous sulfate electrode is commercially available from
Koslow Scientific.

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Copper-copper sulfate:

Cu+2 + 2e- == Cu(s)

 

Potential @ 25°

Liq
Jct ?

LIT
REF

vs. NHE

vs. SCE

Cu/CuSO4 (sat'd) 

+0.316

0.074

LJ

7

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Non-Aqueous:

Ag+ + e- == Ag(s)

 

Potential @ 25°

Liq
Jct ?

LIT
REF

vs. NHE

vs. SCE

Ag/AgNO3 (0.01M) in MeCN

-na-

0.3
vs aq SCE

LJ

3

Ag/AgNO3 (0.1M) in MeCN

-na-

0.36
vs aq SCE

LJ

4

MeCN = acetonitrile

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REFERENCES:

(1) "Electrochemical Methods: Fundamentals and Applications", AJ Bard & LR Faulkner, John Wiley & Sons, NY (2000). See the table on inside back cover.
(2) "Electrochemistry for Chemists, Second Edition", DT Sawyer, AJ Sobkowiak, J Roberts, Jr., John Wiley & Sons, NY (1995). See Section 5.2.
(3) "Handbook of Analytical Chemistry", L Meites, ed., McGraw Hill, NY (1963). See Sect 5.
(4) Calculated assuming 60 mV change from 0.01M value.
(5) "Reference Electrodes, Theory and Practice", DJG Ives & GJ Janz, Academic Press, NY (1961).
(6) http://www.koslow.com/meroxide.html
(7) "Reference Electrodes (Half-Cells)", J Lichtenstein, Materials Performance, Oct., 2001, p.68.
(8) http://www.bioanalytical.com/products/ec/faqele.html#Ref_Type
(9) http://www.corrosion-doctors.org/References/Potential.htm
(10) EP Friis, JET Anderson, LL Madsen, N Bonander, Per Moller, J Ulstrup, Electrochim. Acta, 43 (1998), 1114-1122.

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