for pharmacy students

1. GURUNANAK INSTITUTE OF
PHARMACEUTICAL SCIENCE AND
TECHNOLOGY

2. NON-AQUEOUS TITRATION
PRESENTED BY
•Sumel Ashique. Roll No-80
•Sumit Saha. Roll No-81
•Supratim Das. Roll No-82
B.pharm,2nd yr,3rd sem,Sec-B

3. CONTENTS. . .
Non-Aq. Solvents
Water Interference
Levelling Effect and Differentiating Effect
Principles of Non-Aq. Titration
 Prep. and Standarization of HClO4

4. • DEFINITION:
In which titration of weakly acidic or weakly basic
substances are carried out using non-aqueous solvent so; as to get sharp
end point.
• SOLVENT SYSTEM:
Mainly four types of solvents are used in non-aqueous
titration.
Aprotic solvent
Protogenic solvent
Protophilic solvent
Amphiprotic solvent

5. Aprotic Solvents:
They are chemically inert ,neutral substances.
Examples: Benzene, Toluene etc.
Protogenic Solvents:
They are acidic substances and exert a levelling effect
on bases.
Examples: HCL ,H2SO4 etc.
Protophilic solvents:
They are basic in character and react with acids to
form solvated protons.
Example:NaOH,KOH etc.

6.  Amphiprotic solvents:
They consist of liquids, alcohols and weak organic
acids,which are slightly ionised and combine with both protophilic and
protogenic properties.
Example: H2O, CH3COOH etc .
Water Inference in Non-Aqueous Titration:
 Non-aqueous titration mainly carried out between
weakly acidic and weakly basic substances.
 Weak acid and weak base in aqueous solution e.g in
presense of H2O.Here water due to its amphiprotic nature it acts as a
strong acid and the titration takes place between strong acid ( H2O) and
weak base .So the exact end point can not be found properly.

7. Basic Principles Behind Non-Aqueous Titration :
Formation of Onium Ion:
CH3COOH → CH3COO- + H+
HClO4 → ClO4- + H+
CH3COOH2
+ +ClO4
-
The titration of weak bases are done with HClO4 in acetic acid because in
presence of HClO4 ;Acetic acid reacts with HClO4 and produce Onium Ion which
act a strong acid.so that the titration takes place between strong acid and weak
base.

8.  Formation of Acetate Ion:
C5H5N+CH3COOH →C5H5NH+ +CH3COO_ (Acetate Ion)
When pyridine dissolved in CH3COOH it produce Acetate ion which acts
as a strong base in the solution.

9.  Levelling solvents:
In strong protophilic solvent,all acids act as if they
were of similar strength.Similarly in strong protogenic solvent
all bases act as if they were of similar strength.Solvents which
act in this way are known as levelling solvents.
 Differentiating solvents:
The weak acid and weak bases are differentiating
solvents.

10. Indicators used in non-aqueous
titrations :
Crystal violet:
0.5% w/v solution in glacial acetic acid.
Colour change : violet to greenish yellow
 Methyl red:
0.2% w/v solution in di-oxane
Colour change : yellow to red
Thymol blue:
0.2%w/v methanol
Colour change : yellow to blue

11. Preparation and standarization
of 0.1(N)HClO4 acid:
• Preparation:
Slowly add 72% HClO4 8.5 ml →Glacial acetic acid 900 ml with
continious mixing → add 30 ml of acetic anhydride →
𝑣𝑜𝑙𝑢𝑚𝑒 𝑚𝑎𝑘𝑒 𝑢𝑝 𝑡𝑜 1 𝑙𝑖𝑡 𝑤𝑖𝑡ℎ 𝑔𝑙𝑎𝑐𝑖𝑎𝑙 𝑎𝑐𝑒𝑡𝑖𝑐 𝑎𝑐𝑖𝑑 →
𝑠𝑡𝑎𝑛𝑑 𝑓𝑜𝑟 24 ℎ𝑜𝑢𝑟𝑠.
• Standarization:
Potassium hydrogen phatalate is used as standarization agent.
0.5 ml potassium hydrogen phatalate + 25 ml glacial acetic acid in a 100
ml conical flsk → 𝑤𝑎𝑟𝑚 𝑡𝑜 𝑑𝑖𝑠𝑠𝑜𝑙𝑣𝑒 → 𝑐𝑜𝑜𝑙𝑒𝑑 →
𝑡𝑖𝑡𝑟𝑎𝑡𝑒 𝑤𝑖𝑡ℎ 0.1 𝑁 𝐻𝐶𝑙𝑂4

12. Role of acetic anhydride in non-aqueous titration:
Acetic anhydride absorbs moisture so that the strength of
HClO4 remains same.
Role of HClO4 in the titration between weak-bases
and acetic acid:
Acetic acid itself is a weak acid and the titration between
weak base and weak acid will not give exact end point.But in
presence of HClO4 , CH3COOH produce Onium ion which acts as
a strong acid.Now the titration occurs between strong acid and
weak base,so the exact end point will find soon.

13. REFFERENCE…
Titration in non-aqueous solvents; Practical
Pharmaceutical Chemistry ;Beckett A.H.,Stenlake
J.B. ;page no-165,166,167;CBS publication;
Fourth edition-part one.