NON AQUEOUS TITRATION
madhuri poulkar
Introduction
Non aqueous titration is the titration of
substances dissolved in solvents other than
water. or
Non aqueous titration is the titration in which
is carried out in non aqueous solvent i.e.
solvents other than water.
Ex : acetone,formic acid,ethylene
diamine,chloroform etc
NEED OF NON AQUEOUS TITRATIONS
we need to perform an acid-base titration in non-
aqueous solvent due to:
The analyte is too weak acid or a base to be titrated in
H2O
Reactants or products are insoluble in H2O
Reactants or products react with H2O
Titration in H2O doesn’t allow a sharp end point but
in a non aqueous solvent with a stronger base than
OH- it is possible to get an sharp end point
ADVANTAGES OF NON AQUEOUS TITRATIONS
1) Organic acids and bases that are insoluble in water are
soluble in non-aqueous solvent.
2) Organic acid, which is of comparable strength to
water, can be titrated easily in non-aqueous solvent.
Bases also follow the same rules.
3) A non-aqueous solvent may help two are more acids
in mixture. The individual acid can give separate end
point in different solvent.
4) By the proper choice of the solvents or indicator, the
biological ingredients of a substance whether acidic or
basic can be selectively titrated.
DISADVANTAGE
Temperature ,moisture,co2 should be control.
Solvents are expensive.
Volatile solvents can polute environment
Indicator must be prepare in non aquous medium.
TYPES OF SOLVENTS
The solvents are divided into 4 groups
1. Aprotic solvents
2. Protophilic solvents
3. Protogenic solvents
4. Amphiprotic solvents
APROTIC SOLVENT
Aprotic solvent are most important solvent in this titration.
This solvent are chemically inert.
Neither acidic nor basic (inert solvent).
They have low dielectric constant and do not react with
either
acid or base and therefore do not favour ionization.
The most important examples of aprotic solvent are
Chloroform
Benzene
Dioxan
Ethyl acetate
AMPHIPROTIC SOLVENT
Amphiprotic solvent are those solvent they work as a
both mean protogenic or protophillic.
It means Amphiprotic solvent are acidic and basic in
nature.
And they are accept the proton and donate the proton.
For examples:-
Alcohols and weak organic acids
PROTOGENIC SOLVENT
Protogenic solvent are acidic in nature and they can
donate the proton.
Used to dissolved basic analyte.
They have high dielectric constant and ionised
Examples of Protogenic solvent are:
Glacial acetic acid, formic acid
PROTOPHILIC SOLVENT
Protophillic solvent are basic in nature.
Which possess a high affinity for proton.
Used to dissolved acidic analytes.
Examples:- Amines and ketone. Pyridine,
ethylenediamine,
Estimation of Sodium Benzoate :- Sodium
Benzoate :
Formula : C7H5NaO2 Mol. Wt. 144.1 Sodium Benzoate
contains not less than 99.0 per cent and not more than
100.5 per cent of C7H5NaO2, calculated on the dried
basis.
Description : A white, crystalline or granular powder or
flakes; odourless or with a faint odour; hygroscopic
Assay Procedure :
1.Weigh accurately about 0.25 g of Sodium Benzoate
2. dissolve in 20 ml of anhydrous glacial acetic acid, warming to
50º if necessary.
3. Titrate with 0.1 M perchloric acid, using 0.05 ml of 1-
naphtholbenzein solution as indicator. Carry out a blank
titration.
4.Record the burette reading .repeat the titration for three time
Equivalent: 1 ml of 0.1 M perchloric acid is equivalent to
0.01441 g of C7H5NaO2.
ESTIMATION OF EPHEDRINE-
HYDROCHLORIDE
Ephedrine-Hydrochloride(C10H15NO.HCl) •
Ephedrine: It is an alkaloid & weak organic base
obtained from species of Ephedra.
Halogen acid salt of ephedrine is freely soluble in water
compare to plain form of it.
Therapeutic Uses: Bronchial Asthma, Nasal
Decongestion, Hypotension, Mydriatic, CNS stimulant
etc.
Theory: Titration of halogen acid salt of bases in acetic acid
against perchloric acid includes, addition of mercuric acetate
(which is undissociated in acetic acid solution) to a halide salt
replaces the halide ion (they are too weakly basic to react
quantitively with acetous perchloric acid) by an equivalent
quantity of acetate ion, which is a strong base in acetic acid
2R.NH2.HCl (halogen acid salt of base) ⇌ 2RNH3+ + 2Cl−
(CH3COO)2 Hg (undissociated) + 2Cl− → HgCl2 (undissociated)
+ 2CH3COO−
2CH3COOH2+ + 2CH3COO− ⇌ 4CH3COOH
Assay: Dissolve about 500 mg of Ephedrine HCl
accurately weighed in 25ml of acetic acid. Add 10 mL of
mercuric acetate and 2 drops of crystal violet indicator
and titrate with 0.1 N perchloric acid to an emerald-
green (bluish-green) endpoint. Each ml of 0.1 N
perchloric acid is equivalent to 20.17 mg of
C10H15NO.HCl
