Silver Chloride Electrode - Applications

Applications

Commercial reference electrodes consist of a plastic tube electrode body. The electrode is a silver wire that is coated with a thin layer of silver chloride, either physically by dipping the wire in molten silver chloride, or chemically by electroplating the wire in concentrated hydrochloric acid.

A porous plug on one end allows contact between the field environment with the silver chloride electrolyte. An insulated lead wire connects the silver rod with measuring instruments. A voltmeter negative lead is connected to the test wire. The reference electrode contains potassium chloride to stabilize the silver chloride concentration.

The potential of a silver:silver chloride reference electrode with respect to the standard hydrogen electrode depends on the electrolyte composition.

Notes to the Table: (1) The table data source is, except where a separate reference is given. (2) E_lj is the potential of the liquid junction between the given electrolyte and the electrolyte with the activity of chloride of 1 mol/kg.

The electrode has many features making is suitable for use in the field:

• Simple construction
• Inexpensive to manufacture
• Stable potential
• Non-toxic components

They are usually manufactured with saturated potassium chloride electrolyte, but can be used with lower concentrations such as 1 mol/kg potassium chloride. As noted above, changing the electrolyte concentration changes the electrode potential. Silver chloride is slightly soluble in strong potassium chloride solutions, so it is sometimes recommended the potassium chloride be saturated with silver chloride to avoid stripping the silver chloride off the silver wire.