A reference electrode is an electrode whose potential remains constant, reproducible, and essentially independent of the composition of the test solution, provided that specified experimental conditions such as temperature and ionic strength are maintained. It is used in electrochemical measurements as a stable reference against which the potential of another electrode, generally an indicator electrode, can be measured. The potential of a reference electrode is known or well established under defined conditions, making it possible to determine the potential of the indicator electrode and thereby obtain information about the chemical composition of a solution. In potentiometric measurements, the potential difference between two electrodes is measured under conditions where practically no current is allowed to flow through the electrochemical cell. One electrode is the indicator electrode, which responds to the activity or concentration of the analyte, while the other is the reference electrode, which provides a stable and constant potential. The measured cell potential is therefore related mainly to the potential of the indicator electrode. This relationship forms the fundamental basis of potentiometry. An ideal reference electrode should possess several important characteristics. Its potential should be constant and highly reproducible. It should be insensitive to the composition of the solution being analysed, except for unavoidable effects such as changes in junction potential. The electrode should be reversible and establish equilibrium rapidly. Its internal construction should provide a stable electrical contact with the test solution. It should also have a low temperature coefficient so that moderate changes in temperature do not produce significant variations in its potential. In addition, the reference electrode should not contaminate or react significantly with the sample. Reference electrodes generally consist of a reversible electrode system in contact with a solution containing a fixed concentration of the relevant ions. A porous frit, ceramic junction, or salt bridge provides ionic contact between the internal reference solution and the sample while maintaining electrical continuity. The liquid junction permits ions to migrate between the two solutions and completes the electrochemical circuit. The standard hydrogen electrode is the primary reference electrode against which the potentials of other electrodes are conventionally measured. It consists of a platinum electrode in contact with