The laboratory manual details a course on practical pharmaceutical analysis, comprising three experiments focused on the estimation of aspirin via UV spectrometric method, assay of milk of magnesia using back titration, and assay of ferrous fumarate with oxidation-reduction titration. Each experiment includes principles, reagents, procedures, and calculations integral to pharmaceutical analysis. This resource is prepared by Md. Imran Nur Manik from the Department of Pharmacy at the University of Rajshahi, Bangladesh.

1. Laboratory Manual
Course: 410
Subject: Practical- Pharmaceutical Analysis-II
Prepared By
Md. Imran Nur Manik
M.Pharm
Department of Pharmacy
University of Rajshahi
Rajshahi-6205, Bangladesh
Available at
Essential Pharma documents
www.pharmacydocs.blogspot.com

2. 1
Sl. No. Date Name of the experiment Page No.
01 06.02.12
Estimation of aspirin in a preparation by UV-spectrometric
method.
02 – 03
02 07.02.12 Assay of milk of magnesia from the supplied sample. 04 – 07
03 08.02.12 Assay of ferrous fumerate from the supplied sample. 08 – 11

3. 2
Experiment No. 01 Date: 06.02.12
Name of the experiment: Estimation of aspirin in a preparation by UV-spectrometric
method.
Principle:
UV Spectroscopic method is one of the instrumental analytical methods. It is widely used
in industry research and in the clinical evaluation of many pharmaceuticals. It is relatively
quick process.
The principle of UV spectrophotometer is based on the Beer-Lambert law. This law states
that absorbance or optical density is directly proportional to the concentration. The law is
valid only for dilute solution.
By UV spectroscopic method we can either find out the amount of drug or chemical
present in the sample by taking absorbance of standard substance and sample.
Amount of the substance =
dardsofAbsorbance
dardsofAmountsampleofAbsorbance
tan
tan
Reagent:
0.1 N NaOH solution: For preparing 500 ml 0.1 N NaOH solution, 2 gm of NaOH is
taken in a 500 ml volumetric flask and the volume make up to the mark by adding distilled
water.
This solution is used as blank solution and solvent for preparing standard and sample
solution.
Procedure:
Preparation of standard solution:
1. 150 mg of standard aspirin was dissolved in 0.1 N NaOH in a 100 ml volumetric
flask and the solution was made 100 ml. No filtration was required for this solution.
2. 1 ml of prepared solution was taken in a volumetric flask and made the volume
100 ml with 0.1 N NaOH. This solution was used as standard solution. The final
concentration of this solution would be 15 g/ml.
Preparation of sample solution:
3. The supplied tablet was grinded into powder in a mortar and the powder was
divided into two equal portions. One portion of powder which was equivalent to 150 mg of
aspirin was taken in a 100 ml volumetric flask. After addition of 40–60 ml 0.1 N NaOH
solution, the flask was heated in water bath at 37–40C for 30 minutes.
4. Then the solution was cooled and by adding 0.1 N NaOH solution, it was made up
to 100 ml. The prepared solution was filtered.
Md.
Imran
Nur
Manik

4. 3
5. Again, 1 ml of filtered solution was taken in a volumetric flask and made the
volume 100 ml with 0.1 N NaOH. This solution was used as sample solution. The final
concentration of this solution also would be 15 g/ml.
6. Absorbance was taken for standard and sample solution at 292 nm.
Data:
Absorbance of blank solution, a =
Absorbance of standard solution, b =
Absorbance of sample solution, c =
Calculation:
Amount of sample =
b
c 150
mg
Tablet weight = mg
mg of aspirin powder contains = mg aspirin
” ” ” ” = ”
= (P) mg of aspirin
Potency =
 
300
100P
=
= %
Result:
The potency of supplied aspirin tablet was %.
Comments:
Md.
Imran
Nur
Manik

5. 4
Experiment No. 02 Date: 07.02.12
Name of the experiment: Assay of milk of magnesia from the supplied sample.
Principle:
Back titration is frequently used when a reaction proceeds slowly or when the substance
to be assayed does not give a distinct, sharp end point with an indicator by direct titration.
Back titration or Residual titration is carried out by dissolving the substance under
examination in an accurately measured quantity of standard solution in excess or by heating
the reaction mixture.
To know the volume of the analyte solution, a known excess (100% to 200%) of the
reagent is added. The reaction mixture is heated or kept sometimes so that the reaction is
complete. Then, the unreacted reagent is determined by titration with another suitable
standard reagent.
The Milk of Magnesia is dissolved in an accurately measured excess of 1 N H2SO4
solution to ensure complete neutralization of all the Mg(OH)2 with the formation of the
soluble MgSO4.
The excess acid is then determined by residual titration with 1 N NaOH using methyl red
as indicator.
Knowing the amount of the reagent consumed, the quantity of the analyte is calculated by
stoichiometric calculation.
The reaction which takes place when the milk of magnesia is dissolved and upon residual
titration are as follows:
Mg(OH)2 + H2SO4  MgSO4 + 2H2O
H2SO4 + 2NaOH  Na2SO4 + 2H2O
1 ml of 1 N H2SO4 = 29.17 mg of Mg(OH)2
The percent of Mg(OH)2 present in the sample can be calculated from the following
formula:
     10042


sampletheofweight
sampleofweightmEqNNaOHofmlNSOHofml
The USP requires that milk of magnesia contains not less than 7% and not more than
8.5% of Mg(OH)2.
Md.
Imran
Nur
Manik

6. 5
Reagent and their preparation:
1. 1 N 250 ml H2SO4 solution: 6.78 ml of 98.08% of conc. H2SO4 was taken into 100
ml of water in a 250 ml volumetric flask and then add water up to mark 250 ml.
2. 1 N 100 ml Na2CO3 solution: 5.3 gm of Na2CO3 was taken into 7 ml of distilled
water in a 100 ml volumetric flask. Finally volume was adjusted up to mark by adding
distilled water.
3. 1 N 250 ml NaOH solution: 10 gm of NaOH was taken into 125 ml of distilled water
in a 250 ml volumetric flask. Finally volume was adjusted up to mark by adding distilled
water.
Standardization of 1N H2SO4 solution by 1 N Na2CO3 solution:
i. 10 ml of Na2CO3 was taken in a conical flask. 1-2 drops of methyl red indicator was
added to it.
ii. The titration was performed using 1 N H2SO4 solution which was previously kept on
burette. When the yellow color disappeared, addition of H2SO4 was stopped and red color
appeared.
iii. The experiment was repeated for three times.
Data for standardization of H2SO4 solution:
No. of
observation
Volume of Na2CO3
(V1 ml)
Volume of H2SO4
solution (ml)
Difference
(ml)
Mean
volume
(V2 ml)IBR FBR
1 10
2 10
3 10
Calculation of strength of H2SO4 solution:
We know that, V1S1 = V2S2 Here, V1 = 10 ml
S2 =
2
11
V
SV
S1 = N
V2 = ml
= S2 = ?
= N
Md.
Imran
Nur
Manik

7. 6
Standardization of 1 N NaOH by H2SO4:
i. 10 ml H2SO4 was taken in a conical flask and 1-2 drops of methyl red indicator was
added to it.
ii. The titration was performed using 1 N NaOH solution which was preciously kept on
burette. When the red colour disappeared, addition of NaOH was stopped and yellow colour
appeared.
iii. The experiment was repeated for three times.
Data for standardization of NaOH solution:
No. of
observation
Volume of H2SO4
solution
(V1 ml)
Volume of NaOH
solution (ml)
Difference
(ml)
Mean
volume
(V2 ml)IBR FBR
1 10
2 10
3 10
Calculation of strength of NaOH solution:
We know that, V1S1 = V2S2 Here, V1 = 10 ml
S2 =
2
11
V
SV
S1 = N
V2 = ml
= S2 = ?
= N
Procedure for sample preparation and titration:
i. 5 ml of milk of magnesia was taken in a conical flask.
ii. 25 ml of 1 N H2SO4 solution was added to it.
iii. After solution is complete, methyl red indicator 1-2 drops were added.
iv. The excess acid was titrated with 1 N NaOH which was previously kept on
burette. When yellow colour appeared, addition of NaOH solution was stopped.
v. The experiment was done for two times.
Md.
Imran
Nur
Manik

8. 7
Data for standardization of Na2S2O3:
No. of
observation
Volume of added
H2SO4 solution
(V1 ml)
Volume of NaOH
solution (ml)
Difference
(ml)
Mean
volume
(V2 ml)IBR FBR
1 25
2 25
Calculation of percentage of Mg(OH)2:
=
     100
02917.042


sampletheofweight
NNaOHofmlNSOHofml
=
     100
02917.0


sampletheofweight
= 100
5
02917.0


= %
Result:
The percentage of Mg(OH)2 present in sample was %.
Comments:
Md.
Imran
Nur
Manik

9. 8
Experiment No. 03 Date: 08.02.12
Name of the experiment: Assay of ferrous fumerate from the supplied sample.
Principle:
Assay of ferrous fumerate is done by carrying out an oxidation-reduction titration method
using 0.1 N cerric ammonium sulfate [NH4(Ce) (SO4)2 . 2H2O] as a titrant and phenanthroline
ferrous complex as an indicator.
At the end of the titration color of the titration medium changes into bluish green color.
The supplied 0.1 N cerric ammonium sulfate solutions are previously standardized with
Na2S2O3 solution, which in turn was standardized by K2Cr2O7 solution.
1 ml of cerric ammonium sulfate = 16.99 mg of ferrous fumerate.
Reagent and their preparation:
1. 1 N 100 ml HCl solution: 8.5 ml 36.5% concentrated HCl (specific gravity 1.16) was
taken in a volumetric flask and added water q. s. to 100ml.
2. 0.1 N 250 ml Cerric ammonium sulfate solution: 16.5 gm of this reagent was taken
into 150 ml of distilled water in a 250 ml of volumetric flask, 7.5 ml of concentrated H2SO4
was added and the flask was shaken for dissolving. Then the solution was heated at 37-40C
at water bath until a fresh color of the solution was obtained. Finally volume was adjusted up
to the mark by adding distilled water.
3. 0.1 N 500 ml Na2S2O3 solution: 12.4 gm of Na2S2O3 was taken into 500 ml
volumetric flask. About 300 ml distilled water was added and shake well to dissolve. After
that distilled water was added up to the mark.
4. 0.1 N 100 ml K2Cr2O7 solution: 0.49 gm of K2Cr2O7 was taken in a 100 ml conical
flask and mark up to with distilled water.
5. Kl solution: 10 gm of KI was taken into 100 ml volumetric flask and water was
added q. s. to 100 ml.
6. Starch solution: 0.2 gm of starch was taken into 100 ml of water and heated up to
complete the solution.
7. Phenanthroline complex: 0.7 ml of ferrous sulfate was taken into a 100 ml
volumetric flask and 1.5 gm of phenanthroline was added and water q. s. to 100 ml was
added.
Md.
Imran
Nur
Manik

10. 9
Standardization of 0.1 N Na2S2O3 solution by 0.1 N K2Cr2O7 solution:
i. 10 ml of K2Cr2O7 solution was taken in a conical flask. 2 gm of NaHCO3 and 3 gm of
KI was added to it and finally 5 ml conc. HCl was added.
ii. The conical flask was covered with a watch glass and kept for 5 minutes in a dark
place.
iii. The watch glass was washed down with distilled water and the solution was diluted
with about 50 ml of distilled water.
iv. The titration was performed by using 0.1 N Na2S2O3 solution which was previously
kept on burette. When light yellow color appeared, the addition of thiosulfate solution was
stopped and few drops of starch solution were added. It was again titrated with thiosulfate
solution until blue color disappeared.
v. The same experiment was done for three times.
Data for standardization of Na2S2O3:
No. of
observation
Volume of K2Cr2O7
(V1 ml)
Volume of Na2S2O3
solution (ml) Difference
(ml)
Mean
volume
(V2 ml)IBR FBR
1 10
2 10
3 10
Calculation of strength of Na2S2O3 solution:
We know that, V1S1 = V2S2 Here, V1 = 10 ml
S2 =
2
11
V
SV
S1 = N
V2 = ml
= S2 = ?
= N
Standardization of Cerric ammonium sulfate by Na2S2O3 solution:
i. 10 ml of cerric ammonium sulfate was taken in a 250ml conical flask and 15 ml KI
solution was added.
ii. The titration was performed by using 0.1 N Na2S2O3 solution which was previously
kept in burette. When light yellow color was appeared, addition of thiosulfate was stopped
and 1ml of starch solution was added as an indicator. It was again titrated with this thiosulfate
solution until blue color disappeared.
iii. The experiment was repeated for three times.
Md.
Imran
Nur
Manik

11. 10
Data for standardization of Cerric ammonium sulfate:
No. of
observation
Volume of cerric
ammonium sulfate
(V2 ml)
Volume of Na2S2O3
solution (ml) Difference
(ml)
Mean
volume
(V1 ml)IBR FBR
1 10
2 10
3 10
Calculation of strength of cerric ammonium sulfate:
We know that, V1S1 = V2S2 Here, V1 = 10 ml
S2 =
2
11
V
SV
S1 = N
V2 = ml
= S2 = ?
= N
Assay of ferrous fumerate in supplied sample by standard cerric
ammonium sulfate:
Procedure:
i. The supplied sample (i.e. average of 10 ferrous fumerate) was taken into a 50 ml
volumetric flask.
ii. 10 ml of 1 N HCl was added to it and then boiled until the solid substance dissolves
completely in a water bath.
iii. After cooling the volume was adjusted by adding distilled water.
iv. 25ml of resulting solution was transferred into a 250 ml conical flask and 3-4 drops of
phenanthroline complex was added and titrated against 0.1 N cerric ammonium sulfate until
bluish green color was appeared.
v. The experiment was repeated for two times.
Table for final titration:
No. of
observation
Volume of supplied
solution
(ml)
Volume of cerric
ammonium sulfate
(ml)
Difference
(ml)
Mean
(ml)
IBR FBR
1 25
2 25
Md.
Imran
Nur
Manik

12. 11
Calculation:
1 ml of cerric ammonium sulfate = 16.99 mg of ferrous fumerate
 of ” ” ” =
1.0
99.16 
” ”
= mg of ferrous fumerate
Now, 25 ml solution contains = mg of ferrous fumerate
 50 ” ” ” = ” ” ” ”
= (P) mg of ferrous fumerate
 Potency =
 
200
100P
=
= %
Result:
The potency of ferrous fumerate was %.
Comments:
Md.
Imran
Nur
Manik