CALOMEL ELECTRODE

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CALOMEL ELECTRODE

 It is a secondary reference electrode. It consists of a glass tube at the bottom of which is kept, Hg2Cl2, and a solution of KCl. A Pt wire is dipped into the Hg layer used for making electrical contact. 

The side tube is used for making electrical contact with the salt bridge. The electrode is represented as Hg| Hg2Cl2| KCl. Electrode reaction is represented as : 

  2Hg + 2 Cl    ---->       Hg2Cl2 + 2 e-

The potential of the electrode depends upon the concentration of KCl solution.

 Electrode potential if saturated calomel electrode (SCE) is 0.2422V.

Determination of electrode potential (E⁰) using calomel electrode 

The electrode whose potential is to be found out is connected with a saturated calomel electrode through a salt bridge internally and the emf of the cell is determined using a potentiometer. 


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