This document discusses non-aqueous titration, which involves titrating weakly acidic or basic substances using non-aqueous solvents to obtain a sharp endpoint. It describes the different types of non-aqueous solvents that can be used, including aprotic, protophilic, protogenic, and amphiprotic solvents. The document also discusses how solvent properties affect acidity and outlines methods for titrating weak acids and bases via potentiometric or indicator methods. Key indicators and solvents used for titrating each are provided.

1. 1
NON AQUEOUES TITRATION
BY
Dr. Suman Pattanayak
Associate Professor
Department of Pharma Analysis & QA.
Vijaya Institute of Pharmaceutical Sciences for Women
M. Pharm/ I Sem
Advance Pharmaceutical Analysis

2. CONTENT
 Introduction
 Types Of Solvents
1. Aprotic solvents
2. Protophilic solvents
3. Protogenic solvents
4. Amphiprotic solvents
 Non Aqueous Titration Of Weak Acids
 Non Aqueous Titration Of Weak Bases

3. INTRODUCTION
Definition
Non aqueous titration are those in
which titration of weakly acidic or basic
substances are carried out using non aqueous
solvents so as to get sharp end point.
 Non aqueous solvents the disadvantages of poor
solubility and weak reactivity.
 Moisture and corbondioxide should be avoided
using non aqueous procedures.
 Moisture should be held to less than 0.05%.
 Standerdisation &titration should be carried out
as far as possible at the same temperature.

4.  In non aueous solvents the acidity is decreases in
the following order
HCIO4> HBr>H2SO4>HCI>HNO3
o HCl in water…….strongly acidic
o HCl in acetic acid……weakly acidic
o Acetic acid in water……weakly acidic
o Acetic acid in ammonia….strongly acidic

5. Types of solvents
The solvents are divided into 4 groups
1. Aprotic solvents
2. Protophilic solvents
3. Protogenic solvents
4. Amphiprotic solvents

6. Aprotic solvents(inert solvents)
 Aprotic solvents are neutral, chemically inert
substances such as benzene and chloroform.
 They have a low dielectric constant, do not react
with either acids or bases and therefore do not
favor ionization.
 The picric acid gives a colorless solution in
benzene or toluene which becomes yellow on
adding aniline shows that picric acid is not
dissociated in benzene or toluene solution.
 This type of solvents neither accept or donate
protons
Ex:-Benzene , dioxan ,

7. Protophilic solvent
 Basic in character and react with acids to form
solvated proton
HB + Sol. ⇌ Sol.H+ + B-
Acid + Basic solvent ⇌ Solvated proton + Conjugate base of
acid
 A weakly basic solvent has less tendency than a
strongly basic one to accept a proton.
 Similarly a weak acid has less tendency to donate
protons than a strong acid.
 As a result a strong acid such as perchloric acid
exhibits more strongly acidic properties than a weak
acid such as acetic acid when dissolved in a weakly
basic solvent.

8. Protogenic solvents
 Acidic in nature and donte protons
 Ex:- sulphuric acid , formic acid, propionoic acid
,acetic anhydride etc.
 They have high dielectric constant and ionised
 Because of their strength and ability to donate
protons.

9. Amphiprotic solvents
 Have both protophilic and protogenic properties.
 This can acept or donate protons.
 Ex:-water , alcohols, acetic acid
CH3COOH ⇌ H+ + CH3COO-
 Here the acetic acid is functioning as an acid.
 If a very strong acid such as perchloric acid is dissolved in acetic
acid, the latter can function as a base and combine with protons
donated by the perchloric acid to form protonated acetic acid., an
onium ion”
HClO4 ⇌ H+ + ClO4
-
CH3COOH + H+ ⇌ CH3COOH2
+ (onium ion)
 Since the CH3COOH2
+ ion readily donates its proton to a base, a
solution of perchloric acid in glacial acetic acid functions as a
strongly acidic solution.

10.  When a weak base, such as pyridine is dissolved in
acetic acid, equivalent amount of acetate ions are
produced which have more tendency to acept
protons.
 Therefore, to titrate a solution of a weak base in
acetic acid with perchloric acid in acetic acid, and
obtain a sharp endpoint.
HClO4 + CH3COOH ⇌ CH3COOH2
+ + ClO4
-
onium ion
C5H5N + CH3COOH ⇌ C5H5NH+ + CH3COO-
Acetate ion
CH3COOH2
+ + CH3COO- ⇌ 2CH3COOH
Burette conical flask
Adding HClO4 + C5H5N ⇌ C5H5NH+ + ClO4
-

11. DETERMINING END POINT
A. Potentiometric titration
B. Indicator method
A. Potentiometric titration :
 potentiometric method for the detection of the equivalence point
 The end point is determined by using indictor electrode(glass
electrode) and reference electrode(saturated calomel electrode)

12. Indicator method:
Crystal violet
(0.5 per cent in glacial acetic acid) violet blue-green yellowish-
green
α-Naphtholbenzein
(0.2 per cent in glacial acetic acid)
blue or blue-
green
orange
dark-
green
Oracet Blue B
(0.5 per cent in glacial acetic acid)
blue purple pink
Quinaldine Red
(0.1 per cent in methanol)
magenta
-------
almost
colour
less
Indictor Basic Neutral Acidic
Color changes
Thymol Blue yellow blue

13. Non Aqueous Titration of weak Bases
 Solvents used in the titration of weak bases;
Neutral solvents :
Ex: -
alcohol,chloroform,benzene,chlorobenzene
Acidic solvents:
Ex:-formic acid,glacial acetic
acid,propionic acids
 Titrant used in the titration of weak basess:
Ex:-Perchloric acid
 Indicatores used in the titration of weak bases
Ex:-oracat blue ,crystal violet,1-
naphtholbenzein(weak bases)
methyl red,methyl orange & thymol blue(stronger bases)

14.  Many weakly acidic substances (aicohol or aprotic solvent)can
be titrated in an appropiate non aqueous solvents with a
sharp end point .
Ex:- acidic halides, acids,amino acids,
enols(barbiturates,xanthines), phenols, pyrroles
sulphonamides etc,.
1) Solvents used in the titration of weak acids:
Ex:-Ethylenediamine,n-butylamine,morpholine
2) Titrant used in the titration of weak acids:
Ex:-sodium methoxide, lithium methoxide,
potasium methoxide ,tetrabutyl ammonium hydroxide etc.
3) Indicatores used in the titration of weak acids
Ex:-azo violet.thymol blue,thymolphthalein.,O-
Nitro aniline
Non Aqueous titration Of weak acids

15. REFERENCES:
Textbook of QUANTITATIVE CHEMICAL
ANALYSIS : VOGEL’S
PHARMACEUTICAL TITRIMETRIC
ANALYSIS:
A.A NAPOLEON