Saturday, 9 February 2013

Advantages and disadvantages of dropping mercury electrode.

Some of the advantages of dropping mercury electrode(DME) are as follows:

  • Mercury form amalgam with most metals.
  • Mercury has a high hydrogen overvoltage.
  • It provides a smooth, fresh surface for the reaction.
  • Each drop remains unaffected and does not become contaminated by the deposited metal.
  • Diffusion equilibrium is readily established at mercury-solution interface.
Some of the disadvantages of dropping mercury electrode(DME) are as follows:
  • It is poisonous so care should be taken in its handling.
  • Surface area of a drop of mercury is never constant.
  • Applied voltage produces changes in surface tension and hence change in drop size.
  • Mercury has limited applications in analysis of more positive potential range.
Following care must be taken while using dropping mercury electrode:
  • Pure and triple distilled mercury should be used in DME
  • Tip of DME should be always immersed in water when not in use.
  • Tip of DME should be cleaned by dipping in nitric acid.
  • The DME assembly should be mounted vertical on a heavy stand to be free from vibrations.
  • It is essential to use clean and dust  free tubing while setting the DME.
  • There should be sufficient mercury in reservoir so that the pressure changes are negligible.