The Latimer, Pitzer, and Slansky (LPS) calculation of the absolute electrode potential of the standard calomel electrode (StdCE) involves a sequence of processes in which the metals Hg and Na appear. Let Hg be the ``first'' metal and Na the ``second'' metal. The substitution of 21 other metals M for Na as the second metal leads to an array of remarkably self‐consistent values. With 16 uni‐ and divalent second metals M, the LPS potential of the StdCE falls in the range of +0.523 v to +0.693 v (with the Gibbs‐Stockholm sign convention) with a mean of +0.599 v and a standard deviation of 0.043 v. The constancy of these values is shown to be thermodynamically reasonable. The LPS method is then generalized to obtain the absolute electrode potentials of 22 other standard electrodes (SMeE) by substituting 22 other ``first'' metals Me for Hg. The generalized LPS absolute potentials of the 22 SMeE's can be converted to that of the StdCE by (1) a simplest, (2) a more refined calculation procedure. The simplest generalized LPS potential of the StdCE is strongly dependent on the choice of the first metal Me, the more refined potential is independent of this choice and agrees with the values obtained above with Hg as first metal.

A conceptual experiment is set up by which it is shown that the LPS potential or any of the generalized LPS potentials of the StdCE can be interpreted operationally as linear combinations of conceptually observable potentials differences, all potentials being taken in ``pieces of the same kind of metal'' (to use Gibbs' phrase). This experiment suggests that the LPS potential of the StdCE is equivalent to the measurable outer or volta potential difference in a free space gap between mercury and electrolyte, when the two phases are in electrical contact. The discrepancy between the LPS calculated value and Klein and Lange's experimental value for this volta PD is discussed, and an experimental value of —98.3 kcal obtained for the standard free energy of hydration of the sodium ion.

Topics
Free energy, Electrical components, Electrolytes, Electrochemical potential, Volta potentials
1.
Latimer
,
Pitzer
, and
Slansky
,
J. Chem. Phys.
7
,
108
(
1939
).
Google Scholar
Crossref
Search ADS
 
2.
M. L.
Huggins
,
J. Chem. Phys.
5
,
143
(
1937
).
Google Scholar
Crossref
Search ADS
 
3.
J. Willard Gibbs, Collected Works (Yale University Press, New Haven, Connecticut), Vol. I, p. 429;
J. A. Christiansen and M. Pourbaix, Comptes Rendes of the XVII Conference of the I.U.P.A.C. (held at Stockholm in 1953) (Paris, 1954), pp. 82–84;
A. J.
 
deBethune
,
J. Electrochem. Soc.
 
102
,
288C
(
1955
);
Google Scholar
Crossref
Search ADS
 
T. S.
Licht
 and
A. J.
deBethune
,
J. Chem. Educ.
34
,
433
(
1957
). The Gibbs‐Stockholm electrode potential V has a sign opposite to that of Latimer’s4 oxidation half‐reaction potential E and, unlike E, remains sign‐invariant when the direction of the half‐reaction is reversed. The half‐reaction free energies are therefore ΔG = +nFV for oxidations and ΔG = −nFV for reductions.
Google Scholar
Crossref
Search ADS
 
4.
W. M. Latimer, Oxidation Potentials (Prentice‐Hall, Inc., Englewood Cliffs, 1952), second edition.
5.
W. M.
Latimer
,
J. Chem. Phys.
23
,
90
(
1955
).
Google Scholar
Crossref
Search ADS
 
6.
E. A.
Guggenheim
,
J. Phys. Chem.
33
,
842
(
1929
).
Google Scholar
Crossref
Search ADS
 
7.
G. Herzberg, Atomic Spectra and Atomic Structure (Prentice‐Hall, Inc., Englewood Cliffs, 1937).
8.
Reference 4, pp. 15 and 16.
9.
This is the standard enthalpy of Mn+(g) less that of M(g) as tabulated by W. M. Latimer.4
10.
C. B.
Kazda
,
Phys. Rev.
26
,
643
(
1925
).
Google Scholar
Crossref
Search ADS
 
11.
Reference 4, page 23.
12.
H. B. Michaelson, Handbook of Chemistry and Physics (The Chemical Rubber Publishing Company, Cleveland, Ohio, 1954), thirty‐sixth edition, pp. 2342–4.
13.
G. N. Lewis and M. Randall, Thermodynamics (McGraw‐Hill Book Company, Inc., New York, 1923).
14.
J. Willard Gibbs, Collected Works (Yale University Press, New Haven, Connecticut, 1949), Vol. I, pp. 332, 333, 342, 370, 429.
15.
E.
Lange
,
Z. Elektrochem.
55
,
76
(
1951
).
Google Scholar
 
16.
P.
Van Rysselberghe
, Report of the C.I.T.C.E.’s Commission on Electrochemical Nomenclature and Definitions (German text by E. Lange),
Z. Elektrochem.
58
,
530
(
1954
).
Google Scholar
 
17.
R. Parsons, in J. O’M Bockris, Modern Aspects of Electrochemistry (Academic Press, Inc., New York, 1954), Chap. 3.
18.
Alternatively, the gap distance Na′‐NaCl‴ can be oscillated mechanically and the potentiometer leads adjusted until the alternating current in Cu′ and Cu‴ induced by the oscillations is reduced to zero. The potential difference should be the same. The period of the oscillations should be not less than the time of relaxation of the oxidation‐reduction reaction at the Na″, NaCl‴ interface.
19.
O.
Klein
 and
E.
Lange
,
Z. Elektrochem.
43
,
570
(
1937
).
Google Scholar
 
20.
H.
Strehlow
,
Z. Elektrochem.
56
,
119
(
1952
).
Google Scholar
 
21.
A. J.
deBethune
 and
J. J.
Perez
,
Am. J. Phys.
24
,
584
(
1956
).
Google Scholar
Crossref
Search ADS
 
22.
Reference 17, Chap. 2.
23.
W.
 
Nernst
,
Z. Physik. Chem.
 
4
,
129
(
1889
);
Google Scholar
 
W.
Nernst
,
Ber.
30
,
1547
(
1897
).
Google Scholar
Crossref
Search ADS
 
24.
P.
 
Rüetschi
,
Z. Elektrochem.
 
60
,
29
(
1956
);
Google Scholar
 
P.
Rüetschi
,
J. Electrochem. Soc.
104
,
176
(
1957
).
Google Scholar
Crossref
Search ADS
 
25.
R. Fowler and E. A. Guggenheim, Statistical Thermodynamics (Cambridge University Press, London, 1952), p. 488.
This content is only available via PDF.
© 1958 American Institute of Physics.
1958
American Institute of Physics
You do not currently have access to this content.