# Conductometry – Pharmaceutical Analysis 1 B. Pharma 1st semester

Conductometry

Contents

• Conductometry

• Principle involved

• Measurement of conductivity

• Pros and cons of conductometric titrations

• Precautions to be taken

• Procedure

• Comparison of potentiometry vs conductometry

• Applications

Objectives

By the end of this
session, students will be able to:

• Define conductometry

• Define and explain the principle involved in
conductometric titrations

• Discuss the pros and cons Conductometry

• Explain precautions to be taken for conductometric
titrations

• Brief the applications of conductometric titrations

Conductometry

• Measurement of conductivity of a solution

• Due to mobility of cations and anions towards respective
electrodes

• Conductivity (C) is inversely proportional to resistance
(R) of a solution

C = 1/R

• Unit of conductivity is mhos or ohms-1

• Conductivity of a solution depends upon-

o
Number of ions (concentration)

o
Charge of ions

o
Size of ions

o
Temperature

• Resistance of a solution is given by

R = E/I

Where E = potential difference

I = current which flows through

Unit of resistance (R) is ohms

Potential difference (E) is volts

Current (I) is amperes

• Resistance of a solution depends upon length (l) and cross
resistance (a) of the conductor through which conductivity takes place

R = ρl/a

• ρ is specific resistance

Specific resistance
(ρ)
is the resistance offered by a substance of 1cm length and 1 sq.cm
surface area, Unit of measurement is ohm cm

Specific
conductivity (kv)
is the conductivity offered by a substance of 1cm length
and 1 sq.cm surface area, Unit of measurement is mhos cm-1

Equivalent
conductivity (λv)
is the conductivity of a solution containing equivalent
weight of the solute between electrodes 1 cm and 1 sq.cm, Unit of measurement
is mhos cm-1

• Molar conductivity
(μv)
is the conductivity of a solution containing molecular weight of the
solute between electrodes 1 cm apart and 1 sq.cm surface area

• Molar conductivity = specific conductivity x volume of
solution containing one molecular weight of the electrolyte

Measurement
of Conductivity

• Conductivity may be measured by applying an alternating
electrical current (I) to two electrodes immersed in a solution and measuring
the resulting voltage (V)

• Cations migrate to the negative electrode, the anions to
the positive electrode and the solution acts as an electrical conductor