What is the difference between the different reference electrode for ph meter?
Commonly used reference electrode calomel electrode and silver / silver chloride electrode two categories. The calomel electrode has the advantages of stable potential and good reproducibility, but also has the disadvantages of large temperature hysteresis, failure to be used under high temperature (<70 ° C), and toxicity of the electrode material.
Silver / silver chloride reference electrode is not only easy to prepare, stable potential, good reproducibility, and the electrode structure is firm, the temperature hysteresis is small, when the temperature changes quickly reach equilibrium potential at a new temperature, and can be at high temperature Under use. However, silver / silver chloride electrode is more soluble in concentrated potassium chloride solution, so in the external reference electrode solution (usually 3.3mol / L potassium chloride solution), silver chloride should be added in advance to be saturated, otherwise The silver chloride coating on the reference electrode is dissolved, making the potential unstable. The capillary reference electrode is a special fabrication of a silver / silver chloride reference electrode that sinters a silver / silver chloride reference electrode in the middle of a glass capillary and fills the working medium between them.
This reference electrode not only has a stable potential but also can effectively prevent the change of the reference potential caused by the contamination of the external reference solution and is therefore more suitable for use under high temperature and continuous testing conditions.