Overview of Silver Chloride
Silver chloride is a white powder that is sensitive to light. When exposed to light, it turns black and is reduced to silver. It has a specific gravity of 5.56, a melting point of 455°C, and a boiling point of 1550°C. It is insoluble in water but soluble in concentrated hydrochloric acid and ammonia water.
Silver chloride is used in the production of traditional photographic films, photosensitive materials, and photographic paper.
Silver Chloride Electrode
Silver chloride is commonly used as an electrode material due to its excellent electrical properties: it exhibits a reversible reaction and provides stable and reproducible potentials. This makes it ideal for applications such as reference electrodes in electrochemical experiments and pH electrodes.
In biological tissues, the charge carriers are ions, while in the electrical circuits of measurement devices, the charge carriers are electrons. Therefore, effective charge transfer between ions and electrons at the interface between the electrode and skin is crucial for detecting bodily signals. Not all metals facilitate this reversible reaction and charge transfer easily, but silver chloride electrodes do. This makes them ideal for use in biological sensing electrodes.
Common methods of producing silver chloride layers include electrolyzing a silver surface in a chloride ion solution, immersing a silver substrate in molten silver chloride, or applying silver chloride paste to the object. The latter method does not require chemical treatment and avoids producing waste liquids.
In recent years, the use of silver chloride paste, which does not generate waste liquids from the plating process, has gained attention due to environmental concerns.
Silver Chloride Paste
Silver chloride paste is a conductive resin material that contains particles of silver (Ag) and silver chloride (AgCl), dispersed in a resin or solvent. When this paste is dried with heat, it forms conductive coating films and adhesive layers.
The paste form allows for easy adjustment of viscosity by adding diluents, making it suitable for application methods such as screen printing or dip painting.
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Applications
Electrocardiograph electrodes (electrodes for ECG)
Electromyocardiograph electrodes (electrodes for EMG)
Electroencephalograph electrodes (EEG electrodes)
Electrodes for blood glucose measurement (electrodes for SMBG, CGM, FMG)
