6 —
Electrochemical Techniques
If a solution forms part of an electrochemical cell, the potential of the cell, the current flowing through
it and its resistance are all determined by the chemical composition of the solution. Quantitative and
qualitative information can thus be obtained by measuring one or more of these electrical properties
under controlled conditions. Direct measurements can be made in which sample solutions are compared
with standards; alternatively, the changes in an electrical property during the course of a titration can be
followed to enable the equivalence point to be detected. Before considering the individual
electrochemical techniques, some fundamental aspects of electrochemistry will be summarized in this
section.
Definitions
Electrochemical Cell
A pair of electrodes (metallic or otherwise) in contact with an electrolyte solution.
Galvanic or Voltaic Cell
An electrochemical cell which spontaneously produces current (or energy) when the electrodes are
connected externally by a conducting wire.
Electrolysis or Electrolytic Cell
An electrochemical cell through which current is forced by a battery or some other external source of
energy.
Half-cell Reactions
Oxidation or reduction reaction occurring at an electrode (Table 6.1).
Anode
The electrode at which oxidation occurs.
Cathode
The electrode at which reduction occurs.