This document provides an overview of complexometric titration and discusses the use of ethylenediaminetetraacetic acid (EDTA) as a complexometric indicator. It defines important terms like complexometric titration, complexometric indicator, and complexation. It explains that complexometric titration uses the formation of a colored complex to indicate the endpoint of a titration. EDTA is highlighted as a hexadentate ligand that can form stable complexes with small metal ions, causing a distinct color change used to determine the endpoint. The document notes that complexometric titration with EDTA allows for accurate determination of metal ions at low concentrations.

1. Lecture- 20
Subject – Pharmaceutical Analysis-I
Course – B. Pharm 1st Year
Faculty Name – Umesh Kumar

2. Important terms;
Complexometric titration: A titration based on the formation of
coordination complexes between a metal ion and complexing agent (or
chelating agent) to form soluble complexes.
Complexometric indicator: water soluble organic molecules that
undergoedefinite colour change in the presence of specific metal ions
and are used incomplexometric titrations.
Complex: a substance composed of two or more components capable
of an in- dependent existence.
Complexation: the association of two or more chemical species that
are capable of independent existence by sharing one or more pairs of
electrons.

3. Complexometric titration:
 Complexometric titration is a form of volumetric titration in which
the formation of a colored complex is used to indicate the end point
of a titration.
 Complex-forming reactions involving many metal ions can serve as
a basis for accurate and convenient titrations for such metal ions.
 These kinds of complex ion titration procedures referred to as
complexometric titrations, have high ac- curacies and offer the
possibility of determinations of metal ions at the millimole levels.
 Although this type of a chemical reaction can be classified as
a Lewis acid-base reaction, it is more commonly known as
a complexation reaction.

4. Conti……..
 As applied to chemical analysis, this definition is generally taken to
mean the bonding of a central metal ion, capable of accepting an
unshared pair of electrons with a ligand that can donate a pair of
unshared electrons.
 In a complexation reaction, the product of the reaction is termed
a complex.
 The species which donates the electron pairs by acting as a Lewis
base is known as a complexing agent or ligand, and the ion which
accepts the donated electrons, theLewis acid, is called the central
ion or central atom.

6. EthyleneDiamineTetraAcetic acid
 EDTA called as ethylenediaminetetraacetic
acid is a complexometric indicator consisting
of 2 amino groups and four carboxyl groups
called as Lewis bases.
 Edta is a hexadentate ligand because of its
competence to denote six pair of lonely
electrons due to the formation of covalent
bonds.
 Even the presence of small metal ions would
lead to a distinct change in the color. This
leads to the formation of a weak complex.

7. Conti…….
 Complexing agents are less soluble in water, and most of
them are free acids.
 They are used in volumetric Solutions. Before using them,
they are converted into sodium salts that are feasible in water.
 Since they are characterised with less solubility in water, they
are used for titration.
 Sometimes simple titration methods are used to determine the
simple metal ions present in water. But to determine the exact
number of metal ions present complexometric titration is
used, and it is conducted using EDTA.

8. To be continued in Next video