By Sunil Bhardwaj

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Rotating platinum micro electrode have following advantages over Dropping mercury electrode (DME)

1. The electrode is simple to construct.

2. The rotating platinum micro electrode can be used at positive potential upto +0.9 volt whereas DME is working in pot. range of -2 volt to +0.4 volt. Therefore scope is very wide

3. The diffusion current (which is proportional to the concentration of ions reduced at the cathode) is 20 times larger than in the case of DME. The large current obtained allows small concentration of metal ions to be measured with greater accuracy. Hence the use of rotating platinum micro electrode makes the amperometric method more sensitive and accurate.

Polarography

The addition of the titrant instalments, dilutes the experimental solution to a certain extent. Due to the dilution of the solution the observed current is smaller. Hence the observed current is multiplied by the correction factor,$$ \text {Correction Factor} = \frac { V+v }{ V } $$Where, V = Volume of the original solution
v = Volume of instalment of titrant.

To minimise the effect of dilution the titrant should be at least 20 times more concentrated than the solution being titrated. As the volume of the titrant added is small therefore micro burette is used to ensure correct addition.

The diffusion current values are found after each addition of the titrant. The graph is plotted. Id V/S Volume of the titrant. From the graph, the end point of the titration and subsequently the concentration of the reducible species present in the solution can be found out by using, $$ N_1 \times V_1 = N_2 \times V_2 $$

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