Electrolytic cell reaction which would not occur spontaneously otherwise. A galvanic cell can be considered an electrolytic cell acting in reverse. While electrolytic cells convert electrical energy into chemical energy, galvanic cells convert chemical energy into electrical energy. Galvanic cells are often used in batteries. Michael Faraday defined the cathode of a cell as the electrode to which cations (positively charged ions, like silver ions Ag) flow within the cell, to be reduced by reacting with electrons (negatively charged) from that electrode. Likewise he defined the anode as the electrode to which anions (negatively charged ions, like chloride ions Cl) flow within
Saturated calomel electrode Saturated calomel electrode The Saturated calomel electrode (SCE) is a reference electrode based on the reaction between elemental mercury and mercury(I) chloride. It has been widely replaced by the silver chloride electrode, however the calomel electrode has a reputation of being more robust. The aqueous phase in contact with the mercury and the mercury(I) chloride (HgCl, "calomel") is a saturated solution of potassium chloride in water. The electrode is normally linked via a porous frit to the solution in which the other electrode is immersed. This porous frit is a salt bridge. In cell notation the electrode is written as: