Calomel Electrode saturated

Potentials were measured at room temperature relative to an aqueous calomel electrode saturated with NaCl, using a rotating platinum electrode data for R = H complexes from reference 13, all other data from references 5 and 9. 

Potentials measured in DMF solutions vs. Ag/AgCl electrode in an aqueous 0.10 M LiCl solution. b Potentials measured in acetonitrile solutions at room temperature tn. an aqueous calomel electrode saturated with Nad. c The difference in potentials measured with techniques (a) and (b) was estimated as -0.03 V, i.e. potentials in DMF may be estimated by adding 0.03 V to the corresponding values measured in acetonitrile. d Potentials measured in CH2C12 us. saturated calomel electrode. 

The standard potential (E°) for this reaction is +0.268 V. If the cell is saturated with KCI at 25°C, the potential is +0.241 V. A calomel electrode saturated with KCI is called a saturated calomel electrode, abbreviated S.C.E. The advantage in using saturated KCI is that [Cl ] does not change if some liquid evaporates. 

Predict the value of E for a calomel electrode saturated with KC1, given that E° for the calomel electrode is 0.268 V. (Your answer will not be exactly the value 0.241 used in this book.)... 

S.C.E., saturated calomel electrode A calomel electrode saturated with KCI. The electrode half-reaction is Hg2Cl2(.v) + 2e 2Hg(/) + 2C1-. 

For most potentiometric measurements, either the saturated calomel reference electrode or the silver/silver chloride reference electrode are used. These electrodes can be made compact, are easily produced, and provide reference potentials that do not vary more than a few mV. The silver/silver chloride electrode also finds application in non-aqueous solutions, although some solvents cause the silver chloride film to become soluble. Some experiments have utilised reference electrodes in non-aqueous solvents that are based on zinc or silver couples. From our own experience, aqueous reference electrodes are as convenient for non-aqueous systems as are any of the prototypes that have been developed to date. When there is a need to exclude water rigorously, double-salt bridges (aqueous/non-aqueous) are a convenient solution. This is true even though they involve a liquid junction between the aqueous electrolyte system and the non-aqueous solvent system of the sample solution. The use of conventional reference electrodes does cause some difficulties if the electrolyte of the reference electrode is insoluble in the sample solution. Hence, the use of a calomel electrode saturated with potassium chloride in conjunction with a sample solution that contains perchlorate ion can cause dramatic measurements due to the precipitation of potassium perchlorate at the junction. Such difficulties normally can be eliminated by using a double junction that inserts another inert electrolyte solution between the reference electrode and the sample solution (e.g., a sodium chloride solution). 

Calomel electrodes Saturated (SCE) Normal (NCE) decinormal 0.241 (2) 0.280(1) 0.333(7) Mercurous bromide, iodide, iodate, acetate, oxalate electrodes Aqueous and mixed (with alcohols or dioxane)... 

NHE Normal Hydrogen Electrode (a + =1) SHE Standard Hydrogen Electrode (< + =1 ) SCE Saturated Calomel Electrode (saturated KCl) SSCE Saturated Salt Calomel Electrode (saturated NaCl) NCE Normal Calomel Electrode (1 M KCl) MSRE Mercury(l) Sulfate Reference Electrode... 

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