Pharmaceutical Analysis

Chapter 5

Complexometry

INTRODUCTION

Werner first observed that each atom is surrounded by the maximum number of small which is collectively called as complex. The technique involves the titrating the metal ions with complexing agent which is commonly known as the ligands. The formed coloured complex is used to detect the end point of the titration.

PRINCIPLE

The main principle is the reaction between the ligand and the metal ion to form a complex. The metal ion acts as Lewis acid and the ligand acts as Lewis base which is the complexing agent:

 

M⁺² + Ln (MLn)⁺²

 

Examples:	Ag+ + 2CN− Ag(CN)2−
Cu+2 + 4NH3 Cu(NH3)4+2
Metal ion ...