IX.

Electrochemical Techniques

When a positive and a negative electrode are placed in a solution containing ions, and an electric potential is applied to the electrodes, the positively charged ions (cations) move toward the negative electrode, or cathode, and the negatively charged ions (anions) to the positive electrode, or anode. As a result, electric current flows between the electrodes. The strength of the current depends on the electric potential between the electrodes and the concentration of ions in the solution. Hence, this instrumental quantitative method, called conductometry, is often used to measure the ion concentration in a solution.

In a related technique, electrodes specially constructed to accept only specific ions are used to determine the sodium ion or calcium ion concentration or the pH of the solution being analyzed. Such ion-selective electrodes are important in several types of clinical analysis.

See also Chemical Reaction; Chemistry.