Aqueous standard redox potentials are conventionally referred to that of the standard hydrogen electrode (SHE) as zero (IUPAC definition), in the absence of the knowledge of its absolute value. Recently, the author obtained its value (4.20 V) from a newly found linear dependence of redox potentials on ionization potentials. This has enabled now to express the potentials of standard reference electrodes in terms of the absolute values

Raji Heyrovska

English

Crossref

Absolute Potentials of Standard Reference Electrodes at 25 C

1ABSOLUTE POTENTIALS OF STANDARD 
REFERENCE ELECTRODES AT 25 0C
Raji Heyrovská*
Institute of Biophysics, Academy of Sciences of the Czech Republic,
135 Kralovopolská, 612 65 Brno, Czech Rep. Email: rheyrovs@hotmail.com
Paper presented at the International Conference on 
M odern Electroanalytical M ethods 2009, 
December 9 -13, Prague, Czech Republic
Dedicated to the M emory of Professor Jaroslav Heyrovský 
on the Occasion of the 50th Anniversary of the 
Nobel Prize for Polarography
Venue of the conference: 
Faculty of Science, Charles University, Prague, Czech Republic
Website: http://www.natur.cuni.cz/heyrovsky
Conference Proceedings: Chemicke Listy, 103 (2009) OP-10, s238 (Abstract in English)
*http://www.jh-inst.cas.cz/~rheyrovs
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21.INTRODUCTION
Thanks to Galvani (1737-1798) for his discovery of animal or bio electricity, 
and Volta (1745-1827), Davy (1778-1829) and Faraday (1791-1867) 
for their explorations of chemical electricity,
“Electrochemistry has been of growing importance in our lives”
A simple electrochemical cell is ”The lemon battery”
Electrodes: copper coin (+) and zinc nail (-) & Electrolyte: citric acid
Half cell redox reactions: (1) Cu++ + 2e- = Cu & (2) Zn = Zn++ + 2e- 
Overall reaction: Zn + Cu++ = Zn++ + Cu
In the absence of the knowledge of absolute redox potentials of elements, electrochemists deal 
with the ”potential difference”, E between the two electrodes.
In the case of the lemon battery, the cell voltage ~ 1V between Cu and Zn
(Note: The unit of potential is named volt, in honor of Volta.)
a) Volta & Napoleon, b) Lemon battery, c) Pacemaker           d) Graphene electrode 
    (1801)                                                      (Li battery, 2009)      (Solar cell) 2008
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32. THE STANDARD (Eo) AND ABSOLUTE (EOabs) POTENTIALS 
Since the absolute potentials, EOabs, of half cells are not known, the potential
of the ”standard hydrogen electrode, Eo (SHE) is chosen as 0” at all
temperatures: http://goldbook.iupac.org/S05917.html (Last update: 2009-09-07)
The standard redox potentials, Eo in aqueous solutions [1] of Cu and Zn
are +0.34 and –0.76 V with reference to Eo (SHE) = 0. The cell voltage
of the ”lemon battery” is the “difference”, E = (+0.34) – (-0.76) = 1.10 V.
To know the absolute redox potentials, EOabs = Eo + EOabs(SHE), 
one has to know the value of EOabs(SHE). 
Of the many attempts, notable ones are: Trasatti’s (1986) [2] by
theoretical calculations: 4.44 (+/-) 0.04V and Donald et al’s (2008) [3], by
electron capture on gaseous phase nano-drops: 4.20 (+/-) 0.4 V. 
Recently, the present author (2009) [4] found that E o varies linearly with
the ionization potentials (I) for many groups of elements, and the common
intercept at I = 0, EOabs(SHE) = EOI = 0 = 4.20 (+/-) 0.03 V”, (same as in [3]). 
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43. LINEAR DEPENDENCE OF AQ. STD. POTENTIALS (EO) 
ON IONIZATION POTENTIALS (I)   
[4]: Heyrovská, R.: Electrochem. & Solid State Letts., 12 (10) F29-F30, (2009)
The data in [1] have been used to plot Eovs I in Fig. 1 below, where
I = I (sum) is the sum of the 1st, 2nd, .. ionization potentials, as the
case may be, depending on the value of n, (ox + ne- = red). 
Eo = kaqI - EoI=0; absolute aq. redox potential = Eoabs = Eo + EoI=0 
EoI=0 = Abs. potl. of S.H.E. = 2.87 V (H-/H: halogens) & 4.20 V (H+/H: all others)
(Author: Raji Heyrovska, Brno Conference, 29-30 June 2009)
-5
-4
-3
-2
-1
0
1
2
3
4
0 20 40 60 80 100
Ionization potentials, I    /V
Fig. 2. Linear dependence of aq. std. potls. on I. 
A
q.
 
s
ta
n
da
rd
.
 
po
te
n
tia
ls
 
(v
s
 
S
.
H
.
E
.
), 
Eo
 
 
 
 
/V
Aq. Gp.(i), Cu, Ag, Au, Tl, n = 1
Gp.(ii), F, Cl, Br, I, n = 1
Gp.(iii), H, Li$, Na, K, Rb, Cs, n = 1
Gp.(iv), Ge, Sn, Pb, Se, Pd, n = 2
Gp.(v), Fe, Co, Ni, Cd, n = 2
Gp.(ix), N, P, Cr, Ga, n = 3
Gp.(vii), O, S, Te, n = 2
Gp.(viii), Be, Mg, Ca, Sr, Ba, Ra, n = 2
Gp.(xi), B, Al, Sc, Y, La, n = 3
Gp.(xii), Ti, Zr, n = 4
Gp.(vi), Mn, Zn, n = 2
Gp.(x),Al$, Eu, n = 3
(Tl, n = 1), Cu, Pb, Cd, Zn, Mn, Ba (n = 2),
Al (n = 3): $E1/2 (J. H. & D.I., 1935)
- - - , Cu, Ba, n = 2, E1/2
(i)
(ii)
(iii)
(iv)
(v)
(vii)
(viii)
(x)
(xi)
Lineární (Gp.(v), Fe, Co, Ni, Cd, n = 2)
Lineární (Gp.(ix), N, P, Cr, Ga, n = 3)
Lineární (Gp.(vi), Mn, Zn, n = 2)
Lineární (Gp.(x),Al$, Eu, n = 3)
Lineární (Gp.(viii), Be, Mg, Ca, Sr, Ba, Ra,
n = 2)
Lineární (- - - , Cu, Ba, n = 2, E1/2)
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54. ABSOLUTE POTENTIALS OF SHE AND OTHER ELEMENTS
The straight lines in Fig. 1 follow the simple equation, 
Eo = kaqI – EoI=0   and   Eoabs = Eo + EoI=0 (= kaqI)                        (1a,b)
                                             
where kaq is the slope, “EoI=0 = EOabs (SHE)” and Eoabs is the absolute redox
potential of elements (see Eq. 1b).
For Gp. VIIA (halogens, (1/2)X2/X-), EoI=0 = 2.87 (+/-) 0.01 V, and for 
the others, EoI=0 = 4.20 (+/-) 0.03 V, which correspond to the (1/2)H2/H-
and H+/H redox
 
equilibria resply. 
Hence, the voltage of the ”lemon battery” is the “difference in the absolute
potentials of Cu (4.2+0.34) and Zn (4.2-0.76)”, E = 4.54 – 3.44 = 1.10 V.
The Eo values in [1], based on Eo (SHE) = 0, have now been converted [4]
into the absolute redox potentials, EOabs for many elements of the
Periodic table. These values are given in Table 1 (from [5]) in slide 6 below.
Table 2 in slide 7 gives  the values of Eo [6] and Eoabs, the absolute potential,
of some standard reference electrodes.
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6Table 1. Absolute aqueous redox potentials, Eoabs = E0SHE=0 + Eoabs(SHE) (in V) of elements, ZX, where Z is the
atomic number, Eoabs(SHE) = 2.87 (+/- 0.01) V for gp. VIIA and 4.20 (+/- 0.03) V for the others. E0SHE=0 data are 
from [3]. The values of n in the redox, O + ne = R are at the head of the columns or in brackets next to E0abs.
Elec.struc. ZX Eoabs Elec.struc.
ZX Eoabs Elec.struc.
ZX Eoabs Elec.struc.
ZX Eoabs
Gp.IA: s1 n=1 Gp.IB: s1 n=1 Gp.IIA: s2 n=2 Gp.IIB: s2 n=2
1s1 1H 4.20
[He]2s1 3Li 1.16 [He]2s2 4Be 2.23
[Ne]3s1 11Na 1.49 [Ne]3s2 12Mg 1.84
[Ar]4s1 19K 1.28 [K]3d10 29Cu 4.72 [Ar]4s2 20Ca 1.36 [Ca]3d10 30Zn 3.44
[Kr]5s1 37Rb 1.28 [Rb]4d10 47Ag 5.00 [Kr]5s2 38Sr 1.31 [Sr]4d10 48Cd 3.80
[Xe]6s1 55Cs 1.28 [Cs]4f145d10 79Au 6.03 [Xe]6s2 56Ba 1.28 [Ba]4f145d10 80Hg 5.05
[Rn]7s1 87Fr [Fr]5f146d10 111Rg [Rn]7s2 88Ra 1.28 [Ra]5f146d10 112Cn
Gp.IIIA: s2p1 n=3 Gp.IIIB: s2d1 n=3 Gp.IIIB: s2fxd1 n=3 Gp.IIIB: s2fxd1 n=3
[Be]2p1 5B 3.35 [Ba]5d1 57La 1.82 [Ra]6d1 89Ac 2.07
[Mg]3p1 13Al 2.53 [Ba]5d04f2 58Ce 1.86 [Ra]6d2 90Th 2.37(4)
[Zn]4p1 31Ga 3.67 [Ca]3d1 21Sc 2.17 [Ba]5d04f3 59Pr 1.85 [Ra]6d15f2 91Pa 2.74(4)
[Cd]5p1 49In 3.86 [Sr]4d1 39Y 1.83 [Ba]5d04f4 60Nd 1.88 [Ra]6d15f3 92U 2.54
[Hg]6p1 81Tl 5.45 [Ba]5d1 71Lu 1.82 [Ba]5d04f5 61Pm 1.91 [Ra]6d15f4 93Np 2.41
[Cn]7p1 113Uut [Ra]6d1 103Lr 2.07 [Ba]5d04f6 62Sm 1.90 [Ra]6d05f6 94Pu 2.20
Gp.IVA: s2p2 n=2 Gp.IVB: s2d2 n=4 [Ba]5d04f7 63Eu 2.21 [Ra]6d05f7 95Am 2.13
[Be]2p2 6C 4.72 [Ba]5d04f8 64Gd 1.92 [Ra]6d15f7 96Cm 2.14
[Mg]3p2 14Si 3.39 [Ba]5d04f9 65Tb 1.89 [Ra]6d05f9 97Bk 2.19
[Zn]4p2 32Ge 4.45 [Ca]3d2 22Ti 3.01 [Ba]5d04f10 66Dy 1.91 [Ra]6d05f10 98Cf 2.27
[Cd]5p2 50Sn 4.06 [Sr]4d2 40Zr 2.50 [Ba]5d04f11 67Ho 1.87 [Ra]6d05f11 99Es 2.20
[Hg]6p2 82Pb 4.08 [Ba]4f145d2 72Hf 2.64 [Ba]5d04f12 68Er 1.88 [Ra]6d05f12 100Fm 2.24
[Cn]7p2 114Uuq [Ra]5f146d2 104Rf [Ba]5d04f13 69Tm 1.88 [Ra]6d05f13 101Md 2.50
Gp.VA: s2p3 n=3 Gp.VB: s2d3 n=3 [Ba]5d04f14 70Yb 1.98 [Ra]6d05f14 102No 3.00
[Be]2p3 7N 5.68 [Ba]5d14f14 71Lu 1.90 [Ra]6d15f14 103Lr 2.20
[Mg]3p3 15P 3.70
[Zn]4p3 33As 4.44 [Ca]3d3 23V 3.95
[Cd]5p3 51Sb 4.4 [Sr]4d3 41Nb 3.10
[Hg]6p3 83Bi 4.52 [Ba]4f145d3 73Ta
[Cn]7p3 115Uup [Ra]5f146d3 105Db
Gp.VIA: s2p4 n=2 Gp.VIB: s2d4 n=3 Gp.VIIA: s2p5 n=1 Gp.VIIB: s2d5 n=2
[Be]p4 8O 5.42 [Be]2p5 9F 5.74
[Mg]3p4 16S 3.75 [Mg]3p5 17Cl 4.23
[Zn]4p4 34Se 4.09 [Ca]3d4 24Cr 3.44 [Zn]4p5 35Br 3.94 [Ca]3d5 25Mn 3.02
[Cd]5p4 52Te 3.06 [Sr]4d4 42Mo 4.00 [Cd]5p5 53I 3.41 [Sr]4d5 43Tc 4.60
[Hg]6p4 84Po 2.8 [Ba]4f145d4 74W 4.08(4) [Hg]6p5 85At 3.07 [Ba]4f145d5 75Re
[Cn]7p4 116Uuh [Ra]5f146d4 106Sg [Cn]7p5 117 [Ra]5f146d5 107Bh
Gp.VIIIA: s2p6 Gp.VIIIB: s2d6 n=2 Gp.VIIIB: s2d7 n=2 Gp.VIIIB: s2d8 n=2
1s2 2He
[Be]2p6 10Ne
[Mg]3p6 18Ar
[Zn]4p6 36Kr [Ca]3d6 26Fe 3.76 [Ca]3d7 27Co 3.92 [Ca]3d8 28Ni 3.94
[Cd]5p6 54Xe [Sr]4d6 44Ru 5.24(8) [Sr]4d7 45Rh 4.96(3) [Sr]4d8 46Pd 5.12
[Hg]6p6 86Rn [Ba]4f145d6 76Os 4.89(4) [Ba]4f145d7 77Ir 5.36(3) [Ba]4f145d8 78Pt 5.39
[Cn]7p6 118Uuo [Ra]5f146d6 108Hs [Ra]5f146d7 109Mt [Ra]5f146d8 110Ds
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7Table 2. Absolute potentials, E0abs of reference
electrodes at 25 0C (in V)
Ref. Electrodes E0(SHE= 0) E0abs
Hydrogen (SHE) 0.00 4.20
Calomel:
NCE: Hg/Hg2Cl2, KCl (1M) 0.28 4.48
SCE: Hg/Hg2Cl2, KCl (sat'd) 0.24 4.44
Silver /  silver chloride:
Ag/AgCl, KCl (0.1M): 0.29 4.49
Ag/AgCl, KCl (sat'd): 0.20 4.40
Ag/ AgCl, NaCl (sat'd): 0.20 4.40
Mercury /  mercury oxide: 
Hg/ HgO, NaOH (0.1M): 0.17 4.37
Mercury /  mercurous sulfate:
Hg/Hg2SO4, H2SO4 (1M): 0.67 4.87
Hg/ Hg2SO4, K2SO4(sat'd):0.65 4.85
Silver /  silver sulfate:
Ag/Ag2SO4, H2SO4 (1M): 0.71 4.91
Ag/ Ag2SO4, K2SO4(sat'd): 0.69 4.89
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8Fig. 2. Absolute potentials, E0abs of reference electrodes versus standard 
potentials, E0 (ref. electrode), (SHE = 0)
4.10
4.20
4.30
4.40
4.50
4.60
4.70
4.80
4.90
5.00
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80
E0 (ref. electrodes), (SHE = 0)
E0
a
bs
 
SHE Hg/HgO Ag/AgCl calomel Hg/Hg-ous-sulf Ag/Ag-sulf ada7Ř
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9J A R O S L A V  H E Y R O V S K Ý
“The trends of polarography”
*Nobel Lecture, December 11, 1959
*Fig. 8. Polarographic spectrum showing seven cations in the solution, [8].
                                                  Cu,     Pb,      Cd,       Zn,      Mn,     Al,      Ba
*1959: E1/2 (vs  SCE) [7]:             0.00, -0.37, -0.62, -1.00, -1.40, -1.64, -1.94 V  
#2009: E1/2,abs (SCE = 4.44) [4]:  4.44,   4.07,  3.82,   3.44,  3.04,  2.80,   2.50 V  
 
 
#[4]: Raji Heyrovská, December 11, 2009
Note: Differences between E1/2 and E0 are discussed in [9]. 
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10
ACKNOWLEDGEMENTS
The author thanks the Institute of Biophysics for institutional grant Nos. AV0Z50040507 and AV0Z50040702 of 
the ASCR and the Organizers of MEM 2009 conference for the opportunity given to present the above new 
results of research.
LITERATURE
 
Pictures on slide 1 (Webpages last accessed: 28 Nov. 2009)
 
a) Volta and Napoleon:
 http://chem.ch.huji.ac.il/history/volta.htm 
b) Lemon battery: http://www.hilaroad.com/camp/projects/lemon/1lemon_meter.jpg 
c) Pace maker: 
http://regulatoryoverlord.com/blog/2009/04/10/the-medical-device-industry-and-the-role-of-cdrh/
d) Graphene electrode: http://pubs.acs.org/doi/abs/10.1021/nl072838r
1. Bard, A.J., et al.: Standard potentials in aqueous solutions, Marcel
Dekker, 1985, NY. 
2. Trasatti, S.: Pure & Appl. Chem. 58 (1986) 955.
3. Donald, W.A., et al.: J. Am. Chem. Soc. 130 (2008) 3371.
4. Heyrovská, R.: Electrochem. & Solid State Letts., 12 (10) F29-F30
(2009).
5. Heyrovská, R.: ECST, 25 (2010) 159.
6. Potentials of Common Reference Electrodes, http://www.consultrsr.com/resources/ref/refpotls.htm#nce
(last accessed: 24th November 2009). 
7. Heyrovský, J., and Kuta, J., Principles of Polarography, Publishing House of the ASCR, Prague, 1965. 
8. http://nobelprize.org/nobel_prizes/chemistry/laureates/1959/heyrovsky-lecture.pdf 
9. Lingane, J.J.: J. Am. Chem. Soc. 61 (1939) 2099.
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1ABSOLUTE POTENTIALS OF STANDARD REFERENCE ELECTRODES AT 25 0CRaji Heyrovská*Institute of Biophysics, Academy of Sciences of the Czech Republic,135 Kralovopolská, 612 65 Brno, Czech Rep. Email: rheyrovs@hotmail.comPaper presented at the International Conference on M odern Electroanalytical M ethods 2009, December 9 -13, Prague, Czech RepublicDedicated to the M emory of Professor Jaroslav Heyrovský on the Occasion of the 50th Anniversary of the Nobel Prize for PolarographyVenue of the conference: Faculty of Science, Charles University, Prague, Czech RepublicWebsite: http://www.natur.cuni.cz/heyrovskyConference Proceedings: Chemicke Listy, 103 (2009) OP-10, s238 (Abstract in English)*http://www.jh-inst.cas.cz/~rheyrovsNature Precedings : doi:10.1038/npre.2010.4354.1 : Posted 19 Apr 201021.INTRODUCTIONThanks to Galvani (1737-1798) for his discovery of animal or bio electricity, and Volta (1745-1827), Davy (1778-1829) and Faraday (1791-1867) for their explorations of chemical electricity,“Electrochemistry has been of growing importance in our lives”A simple electrochemical cell is ”The lemon battery”Electrodes: copper coin (+) and zinc nail (-) & Electrolyte: citric acidHalf cell redox reactions: (1) Cu++ + 2e- = Cu & (2) Zn = Zn++ + 2e- Overall reaction: Zn + Cu++ = Zn++ + CuIn the absence of the knowledge of absolute redox potentials of elements, electrochemists deal with the ”potential difference”, E between the two electrodes.In the case of the lemon battery, the cell voltage ~ 1V between Cu and Zn(Note: The unit of potential is named volt, in honor of Volta.)a) Volta & Napoleon, b) Lemon battery, c) Pacemaker           d) Graphene electrode     (1801)                                                      (Li battery, 2009)      (Solar cell) 2008Nature Precedings : doi:10.1038/npre.2010.4354.1 : Posted 19 Apr 201032. THE STANDARD (Eo) AND ABSOLUTE (EOabs) POTENTIALS Since the absolute potentials, EOabs, of half cells are not known, the potentialof the ”standard hydrogen electrode, Eo (SHE) is chosen as 0” at alltemperatures: http://goldbook.iupac.org/S05917.html (Last update: 2009-09-07)The standard redox potentials, Eo in aqueous solutions [1] of Cu and Znare +0.34 and –0.76 V with reference to Eo (SHE) = 0. The cell voltageof the ”lemon battery” is the “difference”, E = (+0.34) – (-0.76) = 1.10 V.To know the absolute redox potentials, EOabs = Eo + EOabs(SHE), one has to know the value of EOabs(SHE). Of the many attempts, notable ones are: Trasatti’s (1986) [2] bytheoretical calculations: 4.44 (+/-) 0.04V and Donald et al’s (2008) [3], byelectron capture on gaseous phase nano-drops: 4.20 (+/-) 0.4 V. Recently, the present author (2009) [4] found that E o varies linearly withthe ionization potentials (I) for many groups of elements, and the commonintercept at I = 0, EOabs(SHE) = EOI = 0 = 4.20 (+/-) 0.03 V”, (same as in [3]). Nature Precedings : doi:10.1038/npre.2010.4354.1 : Posted 19 Apr 201043. LINEAR DEPENDENCE OF AQ. STD. POTENTIALS (EO) ON IONIZATION POTENTIALS (I)   [4]: Heyrovská, R.: Electrochem. & Solid State Letts., 12 (10) F29-F30, (2009)The data in [1] have been used to plot Eovs I in Fig. 1 below, whereI = I (sum) is the sum of the 1st, 2nd, .. ionization potentials, as thecase may be, depending on the value of n, (ox + ne- = red). Eo = kaqI - EoI=0; absolute aq. redox potential = Eoabs = Eo + EoI=0 EoI=0 = Abs. potl. of S.H.E. = 2.87 V (H-/H: halogens) & 4.20 V (H+/H: all others)(Author: Raji Heyrovska, Brno Conference, 29-30 June 2009)-5-4-3-2-1012340 20 40 60 80 100Ionization potentials, I    /VFig. 2. Linear dependence of aq. std. potls. on I. Aq. standard. potentials (vs S.H.E.), Eo    /VAq. Gp.(i), Cu, Ag, Au, Tl, n = 1Gp.(ii), F, Cl, Br, I, n = 1Gp.(iii), H, Li$, Na, K, Rb, Cs, n = 1Gp.(iv), Ge, Sn, Pb, Se, Pd, n = 2Gp.(v), Fe, Co, Ni, Cd, n = 2Gp.(ix), N, P, Cr, Ga, n = 3Gp.(vii), O, S, Te, n = 2Gp.(viii), Be, Mg, Ca, Sr, Ba, Ra, n = 2Gp.(xi), B, Al, Sc, Y, La, n = 3Gp.(xii), Ti, Zr, n = 4Gp.(vi), Mn, Zn, n = 2Gp.(x),Al$, Eu, n = 3(Tl, n = 1), Cu, Pb, Cd, Zn, Mn, Ba (n = 2),Al (n = 3): $E1/2 (J. H. & D.I., 1935)- - - , Cu, Ba, n = 2, E1/2(i)(ii)(iii)(iv)(v)(vii)(viii)(x)(xi)Lineární (Gp.(v), Fe, Co, Ni, Cd, n = 2)Lineární (Gp.(ix), N, P, Cr, Ga, n = 3)Lineární (Gp.(vi), Mn, Zn, n = 2)Lineární (Gp.(x),Al$, Eu, n = 3)Lineární (Gp.(viii), Be, Mg, Ca, Sr, Ba, Ra,n = 2)Lineární (- - - , Cu, Ba, n = 2, E1/2)Nature Precedings : doi:10.1038/npre.2010.4354.1 : Posted 19 Apr 201054. ABSOLUTE POTENTIALS OF SHE AND OTHER ELEMENTSThe straight lines in Fig. 1 follow the simple equation, Eo = kaqI – EoI=0   and   Eoabs = Eo + EoI=0 (= kaqI)                        (1a,b)                                             where kaq is the slope, “EoI=0 = EOabs (SHE)” and Eoabs is the absolute redoxpotential of elements (see Eq. 1b).For Gp. VIIA (halogens, (1/2)X2/X-), EoI=0 = 2.87 (+/-) 0.01 V, and for the others, EoI=0 = 4.20 (+/-) 0.03 V, which correspond to the (1/2)H2/H-and H+/H redox equilibria resply. Hence, the voltage of the ”lemon battery” is the “difference in the absolutepotentials of Cu (4.2+0.34) and Zn (4.2-0.76)”, E = 4.54 – 3.44 = 1.10 V.The Eo values in [1], based on Eo (SHE) = 0, have now been converted [4]into the absolute redox potentials, EOabs for many elements of thePeriodic table. These values are given in Table 1 (from [5]) in slide 6 below.Table 2 in slide 7 gives  the values of Eo [6] and Eoabs, the absolute potential,of some standard reference electrodes.Nature Precedings : doi:10.1038/npre.2010.4354.1 : Posted 19 Apr 20106Table 1. Absolute aqueous redox potentials, Eoabs = E0SHE=0 + Eoabs(SHE) (in V) of elements, ZX, where Z is theatomic number, Eoabs(SHE) = 2.87 (+/- 0.01) V for gp. VIIA and 4.20 (+/- 0.03) V for the others. E0SHE=0 data are from [3]. The values of n in the redox, O + ne = R are at the head of the columns or in brackets next to E0abs.Elec.struc. ZX Eoabs Elec.struc.ZX Eoabs Elec.struc.ZX Eoabs Elec.struc.ZX EoabsGp.IA: s1 n=1 Gp.IB: s1 n=1 Gp.IIA: s2 n=2 Gp.IIB: s2 n=21s1 1H 4.20[He]2s1 3Li 1.16 [He]2s2 4Be 2.23[Ne]3s1 11Na 1.49 [Ne]3s2 12Mg 1.84[Ar]4s1 19K 1.28 [K]3d10 29Cu 4.72 [Ar]4s2 20Ca 1.36 [Ca]3d10 30Zn 3.44[Kr]5s1 37Rb 1.28 [Rb]4d10 47Ag 5.00 [Kr]5s2 38Sr 1.31 [Sr]4d10 48Cd 3.80[Xe]6s1 55Cs 1.28 [Cs]4f145d10 79Au 6.03 [Xe]6s2 56Ba 1.28 [Ba]4f145d10 80Hg 5.05[Rn]7s1 87Fr [Fr]5f146d10 111Rg [Rn]7s2 88Ra 1.28 [Ra]5f146d10 112CnGp.IIIA: s2p1 n=3 Gp.IIIB: s2d1 n=3 Gp.IIIB: s2fxd1 n=3 Gp.IIIB: s2fxd1 n=3[Be]2p1 5B 3.35 [Ba]5d1 57La 1.82 [Ra]6d1 89Ac 2.07[Mg]3p1 13Al 2.53 [Ba]5d04f2 58Ce 1.86 [Ra]6d2 90Th 2.37(4)[Zn]4p1 31Ga 3.67 [Ca]3d1 21Sc 2.17 [Ba]5d04f3 59Pr 1.85 [Ra]6d15f2 91Pa 2.74(4)[Cd]5p1 49In 3.86 [Sr]4d1 39Y 1.83 [Ba]5d04f4 60Nd 1.88 [Ra]6d15f3 92U 2.54[Hg]6p1 81Tl 5.45 [Ba]5d1 71Lu 1.82 [Ba]5d04f5 61Pm 1.91 [Ra]6d15f4 93Np 2.41[Cn]7p1 113Uut [Ra]6d1 103Lr 2.07 [Ba]5d04f6 62Sm 1.90 [Ra]6d05f6 94Pu 2.20Gp.IVA: s2p2 n=2 Gp.IVB: s2d2 n=4 [Ba]5d04f7 63Eu 2.21 [Ra]6d05f7 95Am 2.13[Be]2p2 6C 4.72 [Ba]5d04f8 64Gd 1.92 [Ra]6d15f7 96Cm 2.14[Mg]3p2 14Si 3.39 [Ba]5d04f9 65Tb 1.89 [Ra]6d05f9 97Bk 2.19[Zn]4p2 32Ge 4.45 [Ca]3d2 22Ti 3.01 [Ba]5d04f10 66Dy 1.91 [Ra]6d05f10 98Cf 2.27[Cd]5p2 50Sn 4.06 [Sr]4d2 40Zr 2.50 [Ba]5d04f11 67Ho 1.87 [Ra]6d05f11 99Es 2.20[Hg]6p2 82Pb 4.08 [Ba]4f145d2 72Hf 2.64 [Ba]5d04f12 68Er 1.88 [Ra]6d05f12 100Fm 2.24[Cn]7p2 114Uuq [Ra]5f146d2 104Rf [Ba]5d04f13 69Tm 1.88 [Ra]6d05f13 101Md 2.50Gp.VA: s2p3 n=3 Gp.VB: s2d3 n=3 [Ba]5d04f14 70Yb 1.98 [Ra]6d05f14 102No 3.00[Be]2p3 7N 5.68 [Ba]5d14f14 71Lu 1.90 [Ra]6d15f14 103Lr 2.20[Mg]3p3 15P 3.70[Zn]4p3 33As 4.44 [Ca]3d3 23V 3.95[Cd]5p3 51Sb 4.4 [Sr]4d3 41Nb 3.10[Hg]6p3 83Bi 4.52 [Ba]4f145d3 73Ta[Cn]7p3 115Uup [Ra]5f146d3 105DbGp.VIA: s2p4 n=2 Gp.VIB: s2d4 n=3 Gp.VIIA: s2p5 n=1 Gp.VIIB: s2d5 n=2[Be]p4 8O 5.42 [Be]2p5 9F 5.74[Mg]3p4 16S 3.75 [Mg]3p5 17Cl 4.23[Zn]4p4 34Se 4.09 [Ca]3d4 24Cr 3.44 [Zn]4p5 35Br 3.94 [Ca]3d5 25Mn 3.02[Cd]5p4 52Te 3.06 [Sr]4d4 42Mo 4.00 [Cd]5p5 53I 3.41 [Sr]4d5 43Tc 4.60[Hg]6p4 84Po 2.8 [Ba]4f145d4 74W 4.08(4) [Hg]6p5 85At 3.07 [Ba]4f145d5 75Re[Cn]7p4 116Uuh [Ra]5f146d4 106Sg [Cn]7p5 117 [Ra]5f146d5 107BhGp.VIIIA: s2p6 Gp.VIIIB: s2d6 n=2 Gp.VIIIB: s2d7 n=2 Gp.VIIIB: s2d8 n=21s2 2He[Be]2p6 10Ne[Mg]3p6 18Ar[Zn]4p6 36Kr [Ca]3d6 26Fe 3.76 [Ca]3d7 27Co 3.92 [Ca]3d8 28Ni 3.94[Cd]5p6 54Xe [Sr]4d6 44Ru 5.24(8) [Sr]4d7 45Rh 4.96(3) [Sr]4d8 46Pd 5.12[Hg]6p6 86Rn [Ba]4f145d6 76Os 4.89(4) [Ba]4f145d7 77Ir 5.36(3) [Ba]4f145d8 78Pt 5.39[Cn]7p6 118Uuo [Ra]5f146d6 108Hs [Ra]5f146d7 109Mt [Ra]5f146d8 110DsNature Precedings : doi:10.1038/npre.2010.4354.1 : Posted 19 Apr 20107Table 2. Absolute potentials, E0abs of referenceelectrodes at 25 0C (in V)Ref. Electrodes E0(SHE= 0) E0absHydrogen (SHE) 0.00 4.20Calomel:NCE: Hg/Hg2Cl2, KCl (1M) 0.28 4.48SCE: Hg/Hg2Cl2, KCl (sat'd) 0.24 4.44Silver /  silver chloride:Ag/AgCl, KCl (0.1M): 0.29 4.49Ag/AgCl, KCl (sat'd): 0.20 4.40Ag/ AgCl, NaCl (sat'd): 0.20 4.40Mercury /  mercury oxide: Hg/ HgO, NaOH (0.1M): 0.17 4.37Mercury /  mercurous sulfate:Hg/Hg2SO4, H2SO4 (1M): 0.67 4.87Hg/ Hg2SO4, K2SO4(sat'd):0.65 4.85Silver /  silver sulfate:Ag/Ag2SO4, H2SO4 (1M): 0.71 4.91Ag/ Ag2SO4, K2SO4(sat'd): 0.69 4.89Nature Precedings : doi:10.1038/npre.2010.4354.1 : Posted 19 Apr 20108Fig. 2. Absolute potentials, E0abs of reference electrodes versus standard potentials, E0 (ref. electrode), (SHE = 0)4.104.204.304.404.504.604.704.804.905.000.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80E0 (ref. electrodes), (SHE = 0)E0abs SHE Hg/HgO Ag/AgCl calomel Hg/Hg-ous-sulf Ag/Ag-sulf ada7ŘNature Precedings : doi:10.1038/npre.2010.4354.1 : Posted 19 Apr 20109J A R O S L A V  H E Y R O V S K Ý“The trends of polarography”*Nobel Lecture, December 11, 1959*Fig. 8. Polarographic spectrum showing seven cations in the solution, [8].                                                  Cu,     Pb,      Cd,       Zn,      Mn,     Al,      Ba*1959: E1/2 (vs  SCE) [7]:             0.00, -0.37, -0.62, -1.00, -1.40, -1.64, -1.94 V  #2009: E1/2,abs (SCE = 4.44) [4]:  4.44,   4.07,  3.82,   3.44,  3.04,  2.80,   2.50 V    #[4]: Raji Heyrovská, December 11, 2009Note: Differences between E1/2 and E0 are discussed in [9]. Nature Precedings : doi:10.1038/npre.2010.4354.1 : Posted 19 Apr 201010ACKNOWLEDGEMENTSThe author thanks the Institute of Biophysics for institutional grant Nos. AV0Z50040507 and AV0Z50040702 of the ASCR and the Organizers of MEM 2009 conference for the opportunity given to present the above new results of research.LITERATURE Pictures on slide 1 (Webpages last accessed: 28 Nov. 2009) a) Volta and Napoleon: http://chem.ch.huji.ac.il/history/volta.htm b) Lemon battery: http://www.hilaroad.com/camp/projects/lemon/1lemon_meter.jpg c) Pace maker: http://regulatoryoverlord.com/blog/2009/04/10/the-medical-device-industry-and-the-role-of-cdrh/d) Graphene electrode: http://pubs.acs.org/doi/abs/10.1021/nl072838r1. Bard, A.J., et al.: Standard potentials in aqueous solutions, MarcelDekker, 1985, NY. 2. Trasatti, S.: Pure & Appl. Chem. 58 (1986) 955.3. Donald, W.A., et al.: J. Am. Chem. Soc. 130 (2008) 3371.4. Heyrovská, R.: Electrochem. & Solid State Letts., 12 (10) F29-F30(2009).5. Heyrovská, R.: ECST, 25 (2010) 159.6. Potentials of Common Reference Electrodes, http://www.consultrsr.com/resources/ref/refpotls.htm#nce(last accessed: 24th November 2009). 7. Heyrovský, J., and Kuta, J., Principles of Polarography, Publishing House of the ASCR, Prague, 1965. 8. http://nobelprize.org/nobel_prizes/chemistry/laureates/1959/heyrovsky-lecture.pdf 9. Lingane, J.J.: J. Am. Chem. Soc. 61 (1939) 2099.Nature Precedings : doi:10.1038/npre.2010.4354.1 : Posted 19 Apr 2010

AbstractAqueous standard redox potentials are conventionally referred to that of the standard hydrogen electrode (SHE) as zero (IUPAC definition), in the absence of the knowledge of its absolute value. Recently, the author obtained its value (4.20 V) from a newly found linear dependence of redox potentials on ionization potentials. This has enabled now to express the potentials of standard reference electrodes in terms of the absolute values.</jats:p

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Absolute Potentials of Standard Reference Electrodes at 25 C

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