  The technique presented here for the measurement of electrical conductivity
is based on the principle that the current converges on a small disk electrode.
Most of the ohmic resistance therefore lies within a narrow region surrounding
the disk. If the reference electrode is kept outside this zone, the potential
difference between the working and the reference electrode includes practically
all ohmic potential drops occurring in the solution. Moreover, this ohmic drop
can be related to the conductivity of the solution by an analytical expression
derived by Newman. At sufficiently high overpotentials, the rate of charge
transfer is limited by the conduction of current from the bulk solution to the
electrode. In this regime, the current varies linearly with the electrode
potential and the conductivity of the solution can be estimated from the slope
of the voltammogram using Newman's expression. The electrochemical reaction
used for measuring conductivity of solutions of salts is the cathodic reduction
of water and that used for aqueous acids is the cathodic reduction of hydrogen
ions. The technique has been used to measure conductivity of several common
aqueous electrolytes. A good agreement is found between the present technique
and the conventional technique based on AC impedance analysis.
