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Question

What is the construction and working of dropping mercury electrodes?


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Solution

Dropping mercury electrode:

  • The dropping mercury electrode (DME) is a working electrode that is made up of mercury.

Construction of DME:

It is made up of three components:

  • Capillary
  • Mercury reservoir vessel
  • Standing tube with adjacent stopcock

Working of DME:

  • The dropping mercury electrode (DME) is polarizable and can act as an anode as well as a cathode.
  • The pool of mercury acts as a counter electrode, i.e., it will act as an anode if DME is the cathode or vice-versa.
  • The counter electrode is non-polarizable. To the analyte solution placed in a glass beaker, supporting electrolyte such as KCl is added.
  • Pure nitrogen/hydrogen gas is bubbled through the solution, to take out oxygen.
  • Then gradually increasing voltage is applied to the polarographic cell, typically by going to a more negative decomposing potential and current is recorded.

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