Physical Pharmacy
SOLUBILIZATION
By
Abdul-Wahhab Khedr
Demonstrator of Pharmaceutics & Industrial
Pharmacy
Definition:
• Solubilization is the process of bringing into solution
substances which are insoluble or sparingly soluble
in water.
• Methods of Solubilization:
1) The use of mixed solvents (blending and Co-solvency).
2) The use of surface active agents (Micelle formation).
3) The use of hydrotropic salts e.g. iodine and potassium
iodide.
4) Complex formation e.g. caffeine and barbiturate.
Determination of Solubility of Benzoic acid
• Procedure:
1. In a glass bottle, add 0.5 gm benzoic acid & 20 ml
distilled water.
2. Shake for 10 min and set aside for another 10 min.
3. Filter the contents of the bottle, take 10 ml of the
filterate and titrate with 0.1 N NaOH using Ph.Ph. as
indicator (3-5 dps).
4. The End Point is determined by the appearance of the
first permanent faint pink colour.
5. Repeat the above steps using surfactant solutions
(1%, 3%, 5%, 7%) instead of distilled water and
determine the end points.
Procedure
E.P = Volume of titrant used
0.1 N
NaOH
Filter
20 ml dist. Water or sample soln
10 ml of
filterate
0.5Shake
gm
benzoic
acid
Set
aside
for
for10
10min
min
3 dps
Ph.Ph
Calculation of Solubility
E.P  F 1000
So lub ility 
(g / l)
10
Factor (F): is the amount of benzoic acid (in grams) neutralized by
1 ml of titrant (0.1 N NaOH).
Calculation of Factor (F):
+ NaOH
1 mole benzoic acid ≡ 1 mole NaOH
122 gm
≡ 1000 ml 1 M NaOH
122 gm
≡ 1000 ml 1 N NaOH
122 /10
≡ 1000 ml 0.1 N NaOH
F
≡ 1 ml 0.1 N NaOH
+ H2O
F
122
 0.0122
10 1000
Calculation of Solubility
E.P  0.0122 1000
So lub ility 
(g / l)
10
Results:
Surfactant Concn
E.P
Solubility (g/l)
1%
3%
5%
7%
Then draw the relationship between surfactant concn (on x-axis)
and solubility (on y-axis).