The calomel electrode is a type of reference electrode used in electrochemistry. It consists of mercury in contact with a paste of mercurous chloride (Hg2Cl2) and a potassium chloride solution. This setup provides a stable and well-defined electrode potential, making it useful for measuring the voltage in various electrochemical cells. Calomel electrodes are commonly used in pH measurements and other electrochemical applications. They are known for their reliability and ease of use. However, due to the toxicity of mercury, alternative reference electrodes, such as the silver/silver chloride electrode, are sometimes preferred in modern applications.