This document discusses amperometry and biamperometry, focusing on their principles, instrumentation, experimental conditions, and procedures for titration, which involves measuring current changes during chemical reactions. Amperometry measures the concentration of electroactive substances via current generated at an electrode, while biamperometry employs two identical microelectrodes and a small applied potential for titration. Both methods offer advantages such as rapid endpoint detection and reduced interference from foreign salts.

1. AMPEROMETRY
AND
BIAMPEROMETRY
Presented by : Medha Thakur
MSc Chemistry,
S.N.D.T university

2. Contents
AMPEROMETRY
 Introduction
 Principle
 Instrumentation
 Titration Cell
 Indicator Electrode
 Experimental Condition
 Titration Procedure & Curves
 Advantages
BIAMPEROMETRY
• Introduction
• Instrumentation
• Titration Curves
• Application

3. INTRODUCTION
• Amperometry is a general term for techniques, whereby the
concentration of an electroactive substance is measured by
the current which results from its reaction at an electrode.
• Amperometric titration are those in which amperometry is
used to follow concentration changes and thus to detect
equivalent points of titrations.

4. PRINCIPLE
• the limiting current in polarography is independent of the applied voltage
impressed upon a D.M.E. (or other indicator) is proportional to the
concentration of the electroactive material in solution.
• This is the Fundamental principle of amperometric titration.
• the end point is the point of intersection of the two lines, giving the change
of current before and after the equivalence point.
• the current which passes through the titration cell between an indicator
electrode (e.g. DME) and the appropriate reference electrode (e.g. S.C.E.) is
measure as a function of the volume of the titrating solution.

5. INSTRUMENTATION
It is relatively simple and consist of the following:
• an emf source such as a battery or a power supply
• a potential regulating device,
• a microammeter or galvanometer,
• an electrolysis and titration cell,
• indicator electrodes, reference electrode and salt
bridge,
• a titrant delivery device such as burette or a
micro burette and stirrer.
The electrical circuit is similar to that in polarogrphs.
The only difference is in the cell.

6. 1) TITRATION CELL
• An excellent and inexpensive titration cell consist of
• a Pyrex glass 100 cc flat or round bottomed flask as
shown in fig.
• The burette, N2 inlet tube, DME and the salt
bridge are fitted into the neck by means of a rubber
stopper.
• The salt bridge is connected to a reference
electrode (SCE).

7. 2) INDICATOR ELECTRODES
• Normally DME is used as the indicator electrode
However it cannot be used at high positive potentials
(above 0.4v w.r.t. S.C.E.) because of oxidation of Hg.
• Hence above +0.4v upto 1.1v a rotating platinum
micro electrode is used.
• The diffusion current is not steady if a stationary Pt
electrode is used.

8. EXPERIMENTAL CONDITION
• cell is maintained at a fairly constant temperature during the titration.
• It is advantageous to store the reagent beneath an atmosphere of inert gas.
• not necessary if the regent solution has concentration 10-20 times the
concentration.
• If the analyte is electro-reducible, supporting electrolyte is added to eliminate the
migration current.
• If the reagent is electro-reducible & the analyte not, then addition of supporting
electrolysis is not required
• A maxima suppressor may be added. If the polarographic characteristic of the
analyte & the reagent are not known.

9. TITRATION PROCEDURE
The general procedure is as follows:
• A known volume of the solution under test is placed in the titration cell. which is then
assembled with the burette, DME, N2 inlets etc.
• The electrical connections are completed (DME at cathode and SCE or Hg pool as anode) and
the dissolved O2 is removed by passing pure N2 for 15 min.
• The voltage is adjusted to the desired value & the initial id value is noted.
• A known volume of reagent is run from a semi-microburette, N2 bubbled in for 2 min.The
current & burette reading are both noted.
• The procedure is repeated until sufficient readings have been obtained to permit the end point
to be determined as the intersection of the two linear parts of the graph.

10. TITRATION CURVES
• fig. A, B & C are most common types of curves
encountered in amperometric titration.The
slight rounding off in the vicinity of the
equivalence point is due to the solubility of
the ppt.
• For each amperometric titration the applied
voltage is adjusted to the value between X
andY as shown in fig. A’-C’.

11. Curves
• In fig. A, only the material being titrated is
reduced and gives a diffusion current [For
e.g. Pb [II] ions titrated oxalate or sulphate
ions]
• the current decrease upto the end point.
After the end point the current is fairly
constant.

12. Continue
• In fig. B, Reagent is reduced, analyte is
not.
• [e.g. sulphate ions titrated with Ba [II] or
Pb [II] ions].
• Thus current is constant upto the end
point but rises steadily after the end
point.

13. Continue..
• In fig. C, both analyte and the titrating
reagent are reduced and give diffusion
currents and a sharpV shaped curve is
obtained.
• [for e.g. Pb ions titrated with dichromate ions,
Ni [II] with dimethyl glyoxime]
• Thus current decreases upto the end point &
then rises steadily after the end point.

14. ADVANTAGES
• The titration can usually be avoided out rapidly, since the end point is found
graphically.
• can be carried out at dilutions[10-4M] at which visual or potentiometric
titrations no longer yield accurate results.
• Foreign salts may frequently be present without interference, usually added
as the supporting electrolyte in order to eliminate migration current.
• The results of the titrations are independent of the characteristic of capillary.
• temperature need not be known, it is kept constant during the titration.

15. BIAMPERO
METRY
UNIT-1

16. INTRODUCTION
• These is a modification of the amperometric method.
• In this method, two identical stationary microelectrodes, immersed
in a well stirred solution of the sample are used, instead of the SCE
and the DME.
• A small potential [say 0.01 to 0.1v] is applied between the two
electrodes
• Reversible oxidation to reduction system be present either before
or after the end point.
• also sometimes called as the dead stop end point technique.

17. INSTRUMENTATION
• A simple apparatus suitable for
biamperometry is shown in fig. is
• A pair of identical microelectrode (E&F)
are used
• 3v battery or 2v accumulator, M is a micro
ammeter, P is potentiometer to control the
potential
• The potential is set between 10-100 mv.

18. TITRATION CURVES
• fig. a,b,c the three types of titration curves that are commonly encountered.
• Curve in fig. a is observed when both the reactants are reversible w.r.t. the electrode curves.
• in fig. b & c are obtained when only one of the reactant exhibits reversible behavior.
• The titration of Fe [II] with Ce [IV] is an e.g. of fully reversible system.

19. APPLICATIONS
• Bimperometric titration method has been widely applied to titrations
involving I2, it is also useful with reagents such as Br2,Ti [III], Ce [IV].
• An important use is the titration of H2O with KFR.
• The principle advantage of the method is its simplicity. No reference
electrode is require & the only instrument needed is a simple voltage
divider.