Volumetric analysis, also known as titrimetric analysis, is a quantitative analysis technique that determines the concentration of an unknown substance by titrating it with a solution of known concentration. The key steps are: (1) adding a known volume of the titrant of known concentration to the titrate of unknown concentration until the endpoint is reached, as indicated by a pH indicator; (2) recording the titrant volume used; and (3) calculating the concentration of the titrate based on the reaction stoichiometry and volumes added. Common types of titrations include acid-base titrations, redox titrations, and precipitation titrations. Proper indicator selection based on the relative acid/base strengths is

1. VOLUMETRIC ANALYSIS
{TITRIMETRICANALYSIS}
By Aman Kakne

2. ANALYTICAL CHEMISTRY
It is the branch of chemistry which deals
with the analysis of substances. It is mainly
divided into two parts.
(1) Qualitative Analysis
(2) Quantitative Analysis

3. QUALITATIVE ANALYSIS
It is primarily concerned with the identification of the
constituents present in a chemical substance or mixture
of substances.
QUANTITATIVE ANALYSIS
It is primarily concerned with the exact determination
of the quantity of constituents present in a chemical
substance or a mixture of substances.

4. INTRODUCTION TO VOLUMETRIC ANALYSIS
Volumetric analysis is also known as titrimetric analysis.
Volumetric analysis is a mode of quantitative analysis which
is based on the determination of the volume of a solution of
known concentration (standard) required to react quantitatively
with a solution of the substance to be analysed.
The process of finding out the volume of the standard
solution required to react completely with a known volume of
solution under analysis is known as titration.

6. EQUIPMENT
The key equipment used in a titration are:
• Burette
• Burette Stand
• Measuring cylinder
• White tile – used to see colour change in the solution
• Pipette
• pH indicator
• Conical Flask

7. TERMS IN VOLUMETRIC ANALYSIS
 Titrate: The substance to be determined is termed as the
titrate.
 Titrant: The substance of known concentration is termed as
titrant.
 Titration: The process of determining the volume is termed as
titration.
 End point: The point at which the reaction is complete is
termed as the end point.
 Indicator: Some auxiliary substance which is used to detect
the end point of the titration is termed as the indicator.
 Standard solution: The solution of known concentration is
termed as the standard solution.

8.  PRIMARY STANDARD
A standard solution can be obtained by dissolving a
definite weight of a substance having purity called a
primary standard in a definite volume.
 SECONDARY STANDARD
A secondary standard is a standard that is prepared in
the laboratory for a specific analysis .
It is usually standardized against a primary standard.

9. CONCENTRATIONS TERMS IN VOLUMETRIC ANALYSIS
In volumetric analysis, the various concentration
terms are used.
 Normality
 Molarity
 Molality
 Weight Percent
 Equivalent weight
 Strength

10. CLASSIFICATION OF TITRATION
 Acid- Base Titration: When the neutralisation reaction is
involved, then the titration is termed as acid-base or
neutralisation titration.
NaOH + HCl NaCl + H2O
 Redox Titration: These are involving oxidation reduction
reactions.
10FeSO4 + KMnO4 + H2SO4 5Fe2(SO4)3 + K2SO4 +
2MnSO4 + 8H2O
 Precipitation Titration: These involve the formation of the
precipitate. Precipitation of silver cations with halide is
widely used in this analysis.
AgNO3 + NaCl AgCl + NaNO3

11. Complexometric titration: When formation of stable
complex is the reaction involved, certain organic reagents
such as Ethylene diamine tetra acetic acid (EDTA) forms a
stable complex with various metal ions and is thus used
for analysis of these metal ions.
 Non-aqueous titration: When the reaction occurs in non-
aqueous solvents it means organic solvents, this is mainly
used for analysis of very weak acids and bases
Diazotisation : These titrations involve the diazotisation
reactions.

13. ACID–BASE TITRATION
The reaction between acids and bases are termed as neutralisation
reactions. These reactions take place rapidly and it becomes possible to
find equivalence points of such titrations. Hence such acid- base
titrations have been possible.
It has been possible to divide these titrations into:
1. Acidimetry: The titrations of substances which act as bases under
the conditions of titrations with standard acid are termed as
acidimetry.
2. Alkalimetry: The titrations of substances which act as acids under
the conditions of titrations with standard base are termed as
alkalimetry.
In acidimetry – alkalimetry, the reactions involve neutralisation
with the formation of salt and water.
NaOH + HCl NaCl + H2O

14. ACIDIMETRY
In acidimetry, a known volume of an alkaline
substance or a base is put into a conical flask. This solution
is then titrated against a standard solution of an acid taken
in burette till an equivalent quantity of acid is added to the
alkali.
The point at which the acid and base are added in
equivalent amounts is termed as the equivalent point.
If both the acid and alkali are strong electrolytes, the
resulting solution would be neutral and is having pH7. On the
other hand, if acid or base or both acid and base are weak
electrolytes, the salt formed gets hydrolysed to a certain
extent and the resulting solution would be slightly acidic or
alkaline at the equivalence point and pH will not be seven.

15. ALKALIMETRY
In alkalimetry , a known volume of an acidic substance is
taken into a conical flask. This solution is then titrated against
a standard solution of an alkali or base taken in a burette till
an equivalent quantity of alkali or base is added to the acid.
The point at which the acid and base are added in
equivalent amounts is termed as the acid equivalence point.
The pH of the resulting solution will be 7 if both acid and
base are strong electrolytes. The pH of the resulting solution
will be less or greater than 7 if acid or base both acid and
base are weak electrolytes.

16. INDICATORS
Acid-base indicators:
These are the indicators which are used in acid-base titration
to locate their equivalence point. These indicators have one
colour solution while an altogether different colour in alkaline
solution.
The colour change of an acid-base indicator is not sudden but
takes place within a small range of pH value. This range is
called the pH range of an indicator.

17. Indicator Colour on acidic
side
Range of colour
change
Colour on basic
side
Methyl violet Yellow 0.0-1.6 Violet
Bromophenol blue Yellow 3.0-4.6 Blue
Methyl orange Red 3.1–4.4 Yellow
Methyl red Red 4.4–6.3 Yellow
Litmus Red 5.0–8.0 Blue
Bromothymol blue Yellow 6.0–7.6 Blue
Phenolphthalein Colourless 8.3–10.0 Pink
Alizarin yellow Yellow 10.1–12.0 Red

18. Acid–base titration is performed with a bromothymol
blue indicator, when it is a strong acid – strong base titration,
a phenolphthalein indicator in weak acid – strong base
reactions, and a methyl orange indicator for strong acid –
weak base reactions.
If the base is off the scale, i.e. a pH of >13.5, and the acid
has a pH > 5.5, then an Alizarine yellow indicator may be
used.
On the other hand, if the acid is off the scale, i.e. a pH of <0.5,
and the base has a pH < 8.5, then a Thymol Blue indicator
may be used.
INDICATORS USED

19. An acid-base titration using phenolphthalein as the indicator. The
conical flask contained solution that just reached the endpoint.
Before starting the titration a suitable pH indicator must be
chosen. The equivalence point of the reaction, the point at which
equivalent amounts of the reactants have reacted, will have a pH
dependent on the relative strengths of the acid and base used. The
pH of the equivalence point can be estimated using the following
rules:
•A strong acid will react with a strong base to form a neutral
(pH = 7) solution.
•A strong acid will react with a weak base to form an acidic
(pH < 7) solution.
•A weak acid will react with a strong base to form a basic (pH > 7)
solution.
METHOD

20. When a weak acid reacts with a weak base, the
equivalence point solution will be basic if the base is stronger
and acidic if the acid is stronger. If both are of equal strength,
then the equivalence pH will be neutral. However, weak acids
are not often titrated against weak bases because the colour
change shown with the indicator is often quick, and therefore
very difficult for the observer to see the change of colour.
The point at which the indicator changes colour is called
the end point. A suitable indicator should be chosen, preferably
one that will experience a change in colour (an end point) close
to the equivalence point of the reaction.
METHOD

21. First, the burette should be rinsed with the standard
solution, the pipette with the unknown solution, and the conical
flask with distilled water.
Secondly, a known volume of the unknown concentration
solution should be taken with the pipette and placed into the
conical flask, along with a small amount of the indicator chosen.
The known solution should then be allowed out of the
burette, into the conical flask. At this stage we want a rough
estimate of the amount of this solution it took to neutralize the
unknown solution. The solution should be let out of the burette
until the indicator changes colour and the value on the burette
should be recorded. This is the first (or rough) titration volume
and should be excluded from any calculation.
METHOD

22. METHOD
At least three more titrations should be performed,
this time more accurately, taking into account roughly where
the end point will occur. The initial and final readings on the
burette (prior to starting the titration and at the end point,
respectively) should be recorded. Subtracting the initial volume
from the final volume will yield the amount of titrant used to
reach the end point. The end point is reached when the
indicator just changes colour permanently.

23. An acid-base titration
using phenolphthalein
as the indicator. The
conical flask contained
solution that just
reached the endpoint

24. TITRATION OF WEAK ACID
The pH of a weak acid solution being titrated with a strong
base solution can be found at different points along the
way.
These points fall into one of four categories:
initial pH
pH before the equivalence point
pH at the equivalence point
pH after the equivalence point