Polarography is an electroanalytical technique invented by Jaroslav Heyrovsky in 1922. It involves using a dropping mercury electrode and measuring the current in the solution at different applied potentials to generate a current-voltage curve called a polarogram. There are four main types of current measured: residual, migration, diffusion, and limiting current. The construction includes a dropping mercury electrode, supporting electrolyte, mercury reservoir, and capillary tube. Polarography can be used for qualitative and quantitative analysis of samples without separation and allows analysis of small amounts of inorganic and organic substances.

1. Polarography
Presented by : Ajay Hage and
Ganesh Ghuge

2. Content
• Introduction
• Principle
• Types of current
• Construction and working
• Half wave potential
• Ilkovic. Equation
• Application

3. Introduction
• Discovered by Jaraslove Heyrosky in 1922,
• Who received Nobel prize in chemistry in 1952.
• The term polarography is applied to the
current voltage curve when dropping mercury
electrode is used and indicator electrode.
• This method comes under the category of
voltammetry techniques.

4. Principle:
• Polarography can be applied by increasing
negative potential between polorisable. and
depolrisable. electrode.
• Current voltage curve is recorded in sigmoid
shape
• The instrument which is use which is known
as polarograp.
• The current voltage curve is recorded which is
known as polarogram.
• Polarogram

5. Polarogram:

6. Types of current :
1. Residual current
2. Migration current
3. Diffusion current
4. Limiting current

7. 1. Residual current:
• It is the sum of the faradic current and
condenser current.
• Current produced by traces of the impurities
or reduction of the impurities.
• Condenser Current produced by Helmholtz
double layer.
• Residual current is denoted by (ir).

8. 2: Migration current
• Migration current is due to cation from
the bulk of the solution towards the
Cathod due to diffuse force.
• This current is due to migration of
oxidizable and reducible ion which is
proportional to the potential gradient.
• This can be removed by the addition of
supporting electrolyte solution.

9. 3 : Diffusion current
• Diffusion current is due to actual diffusion of
eletroreduciable ion from the bulk of sample
to the surface of the mercury droplet due to
concentration gradient.
• Various factors can be affected by the
diffusion of current.

10. 4: limiting current.
• Beyond a certain potential the current
reaches a steady value called as limiting
current.
• At this point the rate of diffusion of ion
is equal to rate of reduction.
• State of electrode is said to be
concentration polarised.

11. polarography apparatus:

12. Construction and working:
1. Dropping mercury electrode.
2. Supporting electrolyte.
3. Mercury pooled
4. Capillary tube.

13. Dropping mercury electrode:
• The indicator electrode is use for the analyte of
sample in the response of potential.
• Dropping mercury electrode is use as indicater
electrode.gradully increasing negative potential
can be applied easily.
• Known as working electrode.
• The basic principles of this dropping mercury
electrode is to control mercury flow through the
capillary closed the neddle valve.

14. Drop of mercury:

15. Advantages
• It provides a smooth and fresh surface for the
reaction.
• Mercury forms amalgam with most metals.
• Mercury has high hydrogen overvoltage.
• Each drop remains unaffected and does not
contaminated by the deposit ed metals.
• It useful the range of +0.4 to -1.8 volt.

16. Disadvantages:
• Surface area of drop of mercury has never
constant.
• Mercury has a poisonous.
• Applied voltage produces change in
surface tension and change in drop size.

17. Capillary tube:
• The capillary is glass tube and internal
diameter is 20-50u and connect ed to
mercury reservoir.
• By adjusting the height of the reservoir the
drop time can also adjusted.
• The drop size depends on the bore size of the
capillary.

18. Mercury pooled:
• A large pooled of mercury at bottom of the cell
is a anode and act as reference electrode.
• Saturated calmol electrode is also use.
• By connecting the pooled of mercury.

19. IIkovic equation
• The diffusion current at the SAME is given by
llkovic equation:
• id= 607n c m t
• Various factors can affect the llkovic equation.
• The quantities of mass ,and time will vary with
the capillary and the pressure of the mercury.

20. Half wave potential:
• Half wave potential is defined as the difference
between the total current to the total residual
current which is equal to the one half of the
limiting current.
• This can be obtained from theCVC.
• This can be mainly use for the identification of
the substance.

21. Application :
• Qualitative and quantitative analysis.
• Turbid and colour sample will be analysed.
• Mixture of sample will be analysed or
without separation of sample will be
analysed.
• Inorganic and organic sample can be
analysed.
• Small amount of sample can be analysed.

22. Thanks