silversilverkloridelektroder

The silver–silver chloride electrode, often abbreviated as Ag/AgCl electrode, is a common reference electrode used in electrochemistry. It provides a stable and well-defined potential in chloride-containing aqueous solutions, making it suitable for a wide range of measurements including potentiometry and pH sensing.

Construction and design: The electrode consists of a silver metal substrate (wire or bar) coated with a thin layer of silver chloride (AgCl). It is immersed in an electrolyte containing chloride ions, typically potassium chloride (KCl). Many commercial Ag/AgCl electrodes are sealed with a filling solution of saturated KCl and feature a porous junction or frit to connect the internal solution with the outside sample solution.

Principle and potential: The potential arises from the redox couple AgCl(s) + e− ⇌ Ag(s) + Cl−. The electrode potential depends on the chloride ion activity in the surrounding solution and can be described by E = E° − (RT/F) ln a(Cl−). At 25°C, the potential is commonly cited as about +0.22 V versus the standard hydrogen electrode (SHE) in saturated KCl, with small shifts depending on chloride concentration and temperature.

Applications and maintenance: Ag/AgCl electrodes are widely used as reference electrodes in pH meters, electrochemical experiments, and corrosion studies. The stability of the potential relies on a stable chloride environment and proper maintenance of the filling solution. Exposure to light, high oxidizing conditions, or changes in chloride concentration can alter performance, so replacement or resealing may be necessary over time.

Variants and considerations: There are simple Ag/AgCl wire electrodes and sealed reference electrodes with KCl fillings. Temperature, chloride concentration, and junction design influence potential stability and drift, making awareness of solution chemistry important for accurate measurements.