# Volumetric Analysis

Volumetric analysis is an analytical method of estimating the concentration of a substance in a solution by adding exactly the same number of equivalents of another substance present in a solution of known concentration.

**Simple titrations**

The aim of simple titration is to find the concentration of an unknown solution with the help of the known concentration of another solution.

Let us take a solution of a substance

*A*of unknown concentration. We are provided with the solution of another substance*B*whose concentration is known (*N*_{1}). We take a certain known volume (*V*_{2}liter) of*A*in a flask and start adding*B*from burette to*A*slowly till all the*A*is consumed by*B*. This can be known with the aid of suitable indicator, which shows color change after the complete consumption of*A*. Let the volume of*B*consumed be*V*_{1}liter. According to the law of equivalents, the number of equivalents of*A*would be equal to the number of equivalents of*B*. Therefore,*N*

_{1}

*V*

_{1}=

*N*

_{2}

*V*

_{2}, where

*N*

_{2}is the concentration of

*A*.

Thus using this equation, the value of

*N*_{2}can be calculated.There are two types of simple titrations: (a) acidâ€“base titrations and (b) redox titrations.

**Iodimetry**

This titration involves free iodine. Such direct estimation of iodine is called iodimetry. This involves the titration of iodine solution with known sodium thiosulphate solution, whose normality is

*N*. Let the volume of sodium thiosulphate used be*V*liter.Equivalents of

*I*_{2}= Equivalents of Na_{2}S_{2}O_{3}used =*N*Ã—*V*Moles of

Mass of free

*I*_{2}in the solution**Iodometry**

This is an indirect method of estimation of iodine. An oxidizing agent is made to react with excess of solid KI. The oxidizing agent oxidizes I

^{âˆ’}to I_{2}. This liberated iodine is then made to react with Na_{2}S_{2}O_{3}solution of normality*N*. Let the volume of thiosulphate solution required be*V*liter.Oxidizing agent (

*A*)+ Reduced form of oxidizing agent

Equivalents of

*A*= Equivalents of I_{2}= Equivalents of Na_{2}S_{2}O_{3}used =*N*Ã—*V*Equivalents of A =

*N*Ã—*V*Let the

*n*-factor of*A*in its reaction with KI be*x*, thenMass of

*A*consumed = (where*M*_{A}is the molar mass of*A*)