Reference Electrodes:

So far you have seen that galvanic cells are composed of two half cells and their potential can be measured using instrument called potentiometer. One of the half-cells of galvanic cell is consisted of the solution under investigation and the indicator electrode. The potential of this half is varied in accordance with the Nernst equation and the activity of the relevant ion. To the potential of the cell as a whole to reflect the indicator half-cell potential it is necessary to keep the potential of the other half- cell a constant. As described previously, we call this second half-cell the reference electrode. In this sub-section, we are going to take up some reference electrodes which are commonly used in potentiometry. Other than before which you should know the features to be considered when constructing or selecting a reference electrode. Some important one are:

• A potential of the electrode should remain constant; even some current is passed through it.
• The potential should be reproducible.

• A electrode should be simply prepared from readily available materials.
• A potential of the electrode should not change along with temperature.
• It shall be cheap.