NON AQUEOUS

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