Describe the advantages and disadvantages of using a mercury drop electrode in polarography.

Answer: (1)The advantages of using mercury drop electrode in polarography

①The mercury drop drops continuously, the electrode surface adsorption of impurities is less, the surface is often kept fresh, and the reproducibility of the measured data is good:

②The superpotential of hydrogen on mercury is relatively large, and there will not be any hydrogen precipitation even if the potential of the mercury drop electrode is as negative as 1.3V, which makes it possible to carry out the polarographic analysis in the acidic solution;

③Many metals can form amalgam with mercury, which reduces the reduction potential of these metal ions on the mercury drop electrode, making it easier to electrolyze and precipitate;

④Mercury is easy to purify, and high purity of mercury can be obtained, which is one of the important conditions to ensure that the polarographic method has a very good reproducibility and accuracy.

(2) the disadvantages of using mercury drop electrode in the polarographic method

① mercury volatile and toxic;

② mercury can be oxidized, mercury drop electrode can not be used for the electrode than the Gan seek a positive potential;

③ mercury drop electrode on the residual current is larger, limiting the sensitivity of the determination.