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1. SPREADING COEFFICIENT, ADSORPTION AT LIQUID INTERFACES
HYGIA INSTITUTE OF PHARMACY
Ghaila road, Prabandh Nagar, Lucknow 226020
Topic-
Subject- Physical Pharmaceutics BP302T
Submitted By-
Anoop Kumar Dwivedi
Roll No-2108950500015
B.Pharm 2nd Year,3rd Sem
Under supervision Of-
Mrs.Reema Yadav
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2. Contents
• Spreading coefficient
• Work of adhesion
• Work of cohesion
• Factor ,Application
• Adsorption at liquid interfaces
• Adsorbent and Adsorbate
• Factor,Application
• Conclusion
• Refrences
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3. Spreding Coefficient:-
In two immiscible liquid when we placed
first’s liquids drop on the surface of other it
will spread as a film.
And the ability of one liquid to spread over
another liquid is calculated as spreading
coefficient.
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4. • Spreading coefficient (s) is the difference
between the work of adhesion and work
of cohesion.
• S= Wa-Wc
• S=spreading coefficient
• Wa=work done of adhesive force
• Wc=work done of cohesive force
• Generlly spreading occurs when
adhesive force is more than cohesive
force-
• Wa>Wc
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5. Work of adhesion:-
• Adhesive force:- It applied on the different
nature’s liquid.
eg- oil /water
• Cohesive force :- It applied on the same nature’s
liquid.
eg- oil/oil, water/water
consider the liquid drop with surface tension
gamma(ᵧlv)and the solid surface with surface
tension ᵧsv . 5

6. • When the liquid drop adhere to solid
surface it form surface tension ᵧsl.
• .
• The work of adhesion is simplyfy the
difference between surface tension of
liquid/vapour and solid/vapour and that of
the solid/liquid.
• Work of adhesion given to the following
equation-
• Wa= ᵧsv + ᵧlv- ᵧsl
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7. Work of cohesion
• When a consider a liquid cylinder with unit
cros section area, this liquid is sub divided
into two cylinder,two new surface are form.
• The two new area will have a surface
tension of 2 ᵧlv
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8. • Spreading coefficient (s) is the difference
between work of adhesion and work of
cohesion-
• S = Wa-Wc
• S = ᵧsv+ ᵧlv- ᵧsl-2 lv
• S = ᵧsv- ᵧlv- ᵧsl
• S = ᵧsv-(ᵧlv+ ᵧsl)
• ᵧlv =serface tension of spreading liquid.
• ᵧsv = serface tension of sublayer liquid.
• ᵧls = interfacial tension.
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9. Factor affecting spreading
coefficient
• Fatty acid and alcohols have high
spreading coefficient .
• As non polar chain length increase in an
acid or alcohol spreading coefficient
decrease.
• Propionic acid and ethyl alcohol having
high spreading coefficient.
• Liquid petroleum do not spread on water.
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10. Application of spreading
coefficient
• Absorption of medicament from
creams,lotions,etc.
• Stabilization of emulsion.
• Coating of tablets.
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11. Adsorption at liquid interfaces
• Adsorption is defined as the deposition of
some molecule or ions(molecular species)
onto the surface of liquid.
It is divided mainly two parts-
1) Positive adsorption
2)Negative adsorption (absorption)
Positive adsorption:-
• Molecule deposit on the surface of liquid.
• Surface free energy and surface tension
decresed.
• Molecule settle down on surface.
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12. Negative adsorption(absorption)
• Molecule does not deposit on the surface,it
mix with the liquid.
• Surface free energy and surface tension
increase.
• Molecules mixed with liquid.
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13. Adsorbent and adsorbate
• The solid on the surface of which gas or a
liquid molecules accumulate is called
adsorbent .
• The substance (gas or liquid) whose
molecule accumulate on the solid surface
is called adsorbate.
• Non adsorbed gas is called adsorptive.
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14. Types of adsorption
• Physical adsorption:-
• This adsorption is multi-layered process.
• Reversible,rapid,weak and non-specific.
• The removal of the adsorbate from the adsorbent
being known as desorption.
• Chemical adsorption:-
• Irreversible ,stronger, specific and may require an
activation energy and therefore be slow.
• This types of adsorption is almost a single- layered
phenomenon.
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15. Factors affecting adsorption
• Temperature
• Temperature The amount adsorbed
• pH
• Ionization The amount adsorbed
• Solute concentration
• The concentration of the solute The
amount adsorbed
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16. Applications of adsorption
• Adsorption used in the removal of colouring
matter.
•
• Adsorption used in dyeing.
•
• Adsorption used in chromatography.
• Adsorption used in gas masks.
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17. Conclusion
• When the spreading coefficient is
positive,oil is expected to spread over
water. whereas a negative spreading
coefficient indicated that oil will not spread
over water.
• Adsorption occur by the method of positive
and negative adsorption.
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18. Refrences
• Hajare.A Ashok ,`A test book of physical
pharmaceutics-1’ first (1st ) edition ,Nirali
prakashan,2018,pg no [3.7-3.10].
• Martin’s Sinki J. patrick,A test book of
physical pharmaceutics science “5th edition,
lippincott william ,pg no-[239-243]
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