This document provides an overview of conductometry. It discusses how conductometry measures the conductance of electrolyte solutions using a conductivity cell and conductometer. It describes different types of conductivity cells and how conductometric titrations work by measuring changes in conductance during titrations. Examples of various acid-base titrations are given. Conductometric titrations can be used to analyze many different samples and have advantages like not requiring indicators. Applications include measuring water pollution, food analyses, and more.

1. Conductometry
PRESENTED BY:-
Miss.- Harshada R. Bafna.
M. Pharmacy.(Q.A.)

2. Introduction.
Conductivity cell.
 Conductometric titrations.
 Applications
Content’s -
2

3. 3Introduction
 Determination of conductance of an electrolyte solution by
conductometer is called as Conductometry.
 Instrument used for to measure conductance of solution is
known as conductometer.
What is conductivity/conductance……………?
 Conductivity is the ability of a solution, a metal or a gas to
pass an electric current.
 In solutions the current is carried by cations and anions
whereas in metals it is carried by electrons.

4. 4How is conductivity measured…………?
 Conductivity may be measured by applying an alternating
electrical current (I) to two electrodes deep in a solution.
 Measuring the resulting voltage (V). During this process.
 The cations travel to the negative electrode,
 The anions travel to the positive electrode and the solution acts
as an electrical conductor.

5. 5What is conductivity of solution ----------?
 Conductivity is typically measured in aqueous solutions of
electrolytes.
 Electrolytes are substances containing ions, i.e. solutions of
ionic salts or of compounds that ionise in solution.
 The ions formed in solution are responsible for carrying the
electric current.
 Electrolytes include acids, bases and salts and can be either
strong or weak.
 Strong electrolytes are substances that are fully ionised in
solution.
 Weak electrolytes are substances that are not fully ionised in
solution.

6. 6Instrumentation
 For determination of conductance of electrolyte solution
conductivity cell and conductometer are required.
1. Conductivity cell -
 It is Made of Pyrex or quartz and are fitted with two platinum
electrodes.
 It Should be placed in vessel containing water to maintain
constant temperature.
 Types of Conductivity cell :
1. Wide mouthed cell
2. Cell for reactions producing precipitation
3. Dip type cells

7. 71. Wide mouthed cell
 It is wide mouth bottle with bark cork having holes for passing
two platinum wires of 1 sq. cm. size is used.
 It is used for Low conductance measurement .
2. Cell for reactions producing precipitation
 In that electrodes are tightly set in the perpex lid which is
provided with opening for the stirrer and tip of the burette.
 Magnetic stirrer is used for stirring the solution.
 It is used for precipitating type of conductance

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3. Dip type cells
 In this a wide bore glass tube of corning glass are fixed copper
wire.
 The tipe of which have two platinum plates of 1sq. cm in a size
fixed at 1 cm. the terminal of copper wire are taken out for
connections.
 The position of wire is fixed in glass tube by rosin

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2. Conductometer :
 The conductance measurements are
made by using conductivity bridge.
 The conductometers are made
using wheatstone bridge circuit.
 In this cell is placed in one arm of
the wheatstone bridge circuit ab and
resistance R1 composed the arm ac.
 D stands for detector is either
galvanometer, earphone.
 A source of alternating current (V)
with a frequency of 50-60 Hz is
used in the circuit by connecting b
and c.

10. 10Conductometric titrations
 Conductometric titration is a laboratory method of quantitative
analysis used to identify the concentration of a given analyte in a
mixture.
 Principle -
 During a titration process, one ion is replaced with another and the
difference in the ionic conductivities of these ions directly impacts
the overall electrolytic conductivity of the solution.
 It can also be observed that the ionic conductance values vary
between cations and anions.
 Finally, the conductivity is also dependant upon the occurrence of
a chemical reaction in the electrolytic solution.

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Types of Conductometric titration……
1. Acid – Base OR Neutral Titration :
a) Strong acid –Strong base
Example: HCL vs NaOH
b) Strong acid – Weak base
Example : HCL vs NH4OH
c) Weak acid –Strong base
Example : CH3COOH vs NaOH
d) Weak acid –Weak Base
Example : CH3COOH vs NH4OH
2. Precipitation titrations.

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1. STRONG ACID- STRONG BASE
 Fall in conductance due to replacement of high conductivity
hydrogen ions by poor conductivity of sodium ions.
 Rise in conductance due to increase in hydroxyl ions.

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2. Strong acid- weak base :
 Fall in conductance due to replacement of hydrogen by
ammonium ions .
 Conductance remain constant due to supression of NH40H
by NH4CL.

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3.Weak acid –Strong base:
 Initial decrease in conductance followed by increase
due to NaOH
 Steep rise due to excess of NaOH

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4. Weak acid- weak base:
 Increase in conductance due to excess of CH3COOH
 Constant conductance due to supression of NH4OH by
CH3COOH

16. 16Precipitation titrations
 A reaction may be made the basis of a conductometric
precipitation titration provided the reaction product is sparingly
soluble or is a stable complex.
 The solubility of the precipitate (or the dissociation of the
complex) should be less than 5%.
 The addition of ethanol is sometimes recommended to reduce
the solubility in the precipitations

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Advantages of Conductometric titrations
 Does not require indicators since change in conductance is
measured by conductometer.
Suitable for coloured solutions.
 Since end point is determined by graphically means accurate
results are obtained with minimum error.
 Used for analysis of turbid suspensions, weak acids, weak bases,
mix of weak and strong acids.
 Temperature is maintained constant throughout the titration.
 This method can be used with much diluted solutions

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Dis-advantages of Conductometric titrations
 Increased levels of salt in solutions masks the conductivity
changes in such cases it does not gives accurate results.
 Applications of conductometric titrations to redox systems is
limited because, high concentration of hydronium ions in the
solutions tends to mask the change in conductance.

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Application of Conductometric titrations
1. Check water pollution in rivers and lakes
2. Alkalinity of fresh water
3. Salinity of sea water (oceanography)
4. Deuterium ion concentration in water- deuterium mixture
5. Food microbiology- for tracing micro organisms
6. Tracing antibiotics
7. Estimate ash content in sugar juices
8. Purity of distilled and de - ionised water can determined
9. Solubility of sparingly soluble salts like AgCl, BaSo4 can be
detected
10. Determination of atmospheric so2.
11. Estimation of vanillin in vanilla flavour.

20. 20 Conductance: (C)
It implies the ease with which the current flows through conductor,
thus the conductance is reciprocal to resistance.
C= I/R
Specific resistance: (ρ)
 It is the resistance offered by a substance of 1cm length and
1sq.cm surface area
 Unit of measurement is ohm cm
R ∞ l ⁄ A
Resistance : (R)
It is measure of the conductors opposition to the flow of electric
charge .
R =1/G

21. 21Specific conductance : (K)
Conductance of the body of uniform length(l) &uniform area cross
section(A)
K =1 ⁄ R × 1 ⁄ A
 Molar conductance : (^)
Conductance of a solution containing 1 mole of the solute in 1000 cm
of the solution which placed between two parallel electrodes which
are 1 cm apart
^ = 1000 ⁄ C
 Equivalent conductance : (^eq)
Specific conductance of the solution containing 1gm equivalent of
solute in 1000cm3 of solution.
^ eq =1000k ⁄ Ceq

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Reference
1. A Textbook of Pharmaceutical Analysis (volume – I) by DR A
V Kasture, DR H N More, DR K R Mahadik, DR S G
Wadodkar, Nirali Prakashan, Pg.no. 214-223.
2. A Textbook of Pharmaceutical Analysis by David. G. Watson,
Churchill Livingstone, Pg.no. – 68.
3. www.google.com.

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Thank You.