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A silver chloride electrode is a type of reference electrode, commonly used in electrochemical measurements. For example, it is usually the internal reference electrode in pH meters. As another example, the silver chloride electrode is the most commonly used reference electrode for testing cathodic protection corrosion control systems in sea water environments. The electrode functions as a redox electrode and the reaction is between the silver metal (Ag) and its salt — silver chloride (AgCl, also called silver(I) chloride). The corresponding equations can be presented as follows: : : or an overall reaction can be written: : This reaction is characterized by fast electrode kinetics, meaning that a sufficiently high current can be passed through the electrode with the 100% efficiency of the redox reaction (dissolution of the metal or cathodic deposition of the silver-ions). The reaction has been proven to obey these equations in solutions of pH values between 0 and 13.5. The Nernst equation below shows the dependence of the potential of the silver-silver(I) chloride electrode on the activity or effective concentration of chloride-ions: : The standard electrode potential E0 against standard hydrogen electrode (SHE) is 0.230V ± 10mV. The potential is however very sensitive to traces of bromide ions which make it more negative. (The more exact standard potential given by an IUPAC review paper is 0.22249 V, with a standard deviation of 0.13 mV at 25 °C.〔R.G. Bates and J.B. MacAskill, "Standard Potential of the Silver-Silver Chloride Electrode", Pure & Applied Chem., Vol. 50, pp. 1701—1706, http://www.iupac.org/publications/pac/1978/pdf/5011x1701.pdf〕) == 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.〔Detail of Making and Setting up a Microelectrode, University of Denver, http://carbon.cudenver.edu/~bstith/detailelectrode.doc (link is obsolete)〕 A porous plug on one end allows contact between the field environment with the silver chloride electrolyte.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 class="wikitable" 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「silver chloride electrode」の詳細全文を読む スポンサード リンク
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