IEC TR 62456:2007

TECHNICAL IEC
REPORT TR 62456
First edition
2007-03
An electrochemical reference system
for use in different solvent media –
The decamethylated ferricinium/ferrocene
redox couple
Reference number
IEC/TR 62456:2007(E)
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TECHNICAL IEC
REPORT TR 62456
First edition
2007-03
An electrochemical reference system
for use in different solvent media –
The decamethylated ferricinium/ferrocene
redox couple
© IEC 2007 ⎯ Copyright - all rights reserved
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– 2 – TR 62456 © IEC:2007(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
AN ELECTROCHEMICAL REFERENCE
SYSTEM FOR USE IN DIFFERENT SOLVENT MEDIA –
THE DECAMETHYLATED FERRICINIUM/FERROCENE
REDOX COUPLE
FOREWORD
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The main task of IEC technical committees is to prepare International Standards. However, a
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IEC 62456 which is a technical report, has been prepared by subcommittee 65D: Analysing
equipment, of IEC technical committee 65: Industrial-process measurement and control.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
65D/125/DTR 65D/127/RVC
Full information on the voting for the approval of this technical report can be found in the report
on voting indicated in the above table.

TR 62456 © IEC:2007(E) – 3 –
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until the
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related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

– 4 – TR 62456 © IEC:2007(E)
INTRODUCTION
The proposal of this technical report is justified by the difficulties met by electrochemists,
electroanalysts, corrosionists, and biologists when electrode potentials measured in different
non-aqueous or aqueous-organic solvents with reference to the familiar, commercially
available, and very dependable, aqueous Saturated Calomel Electrode (SCE) are to be
physically inter-compared on some “inter-solvental scale” of electrode potentials. These
difficulties are caused by the occurrence of two basic extrathermodynamic factors, namely, the
primary medium effect [1] on electrode potentials and the liquid-junction potentials between
different solvent media. This report details the use of the half-wave potential of the
ferricinium/ferrocene redox couple or the decamethyl derivatized ferricinium/ferrocene redox
couple as the basis of a reference electrode system useful to compared measured electrode
potentials to the aqueous saturated calomel electrode when used in various solvent systems.
For an acceptable approach to the solution of the above problem, superseding earlier attempts
[2], Strehlow and co-workers [3], [4] proposed to use the redox couple ferricinium|ferrocene (in
terms of its “half-wave potentials”, or “formal redox potentials”, obtainable from voltametric
experiments in different solvents with the same supporting electrolyte and against the same
working reference electrodes), for which, based on an extended experimental evidence, they
assessed an “invariancy of potential” to within about ±15 mV in a dozen different solvents,
assuming the above redox couple to be unaffected by solvent interactions. Principles and
reasons for this choice were expounded in detail [3], [4] and need not be repeated
...