ELECTROCHEMICAL TECHNIQUES FOR CHARACTERIZING SOIL CHEMICAL-PROPERTIES

Electrochemical techniques are a category of methods used for the study of the composition and properties of a medium based on electrochemical reactions occurring at the electrode-solution interface. This chapter reviews the principles and applications of most important electrochemical techniques in soil science. The basic principle of electrochemical techniques is to convert one chemical parameter of a medium into an electrical parameter by an appropriate device, usually an electrode or an electrode pair, and then to measure this electrical parameter using an instrument. As in the case of electrical measurements, in electrochemical techniques four parameters can be utilized. The electrode potential may be a function of the composition of the solution. Techniques based on the measurement of this potential are called potentiometry. When an external voltage is applied to an electrode, an electrical current may flow through the circuit. Techniques utilizing this current-voltage relationship are called voltammetry. One can also measure the electrical resistance (conductance) between two electrodes in the medium, and such a technique is called conductometry. In all these techniques, the electrode is the site at which electrochemical reactions take place and is the key element in electrochemical analyses. Therefore, in the discussion the electrode potential at the electrode- solution interface when no current flows is first examined, and then the effect of current on electrode potential, electrode polarization, is discussed. © 1992, Academic Press, Inc.