This presentation is on the Topic " Colloidal Sate" for the Chemistry Undergraduate students of Mumbai University.

1. Colloidal State
Dr. Pravin U. Singare
Department of Chemistry,
N.M. Institute of Science,
Bhavan’s College, Andheri (West)

2. Crystalloids
• size < 10-7 cm in diameter.
• solution of crystalloids is
called True solution.
• Particles can easily pass
through the membrane.
• Solution of crystalloids have
particles having both + ive
and – ive charges.
• eg: NaCl salt solution in
water
Colloids
• size between 10-5 to 10-7 cm
in diameter.
• solution of colloids is called
colloidal solution (Sol).
• particles can not pass
through the membrane.
• colloidal solution with
particles having either + ve
or – ive charge.
• Eg: gum, glue
The solution having particle size above 10-5 cm is called suspension

3. Colloidal Solution (Sol)
Colloidal system consists of
- Dispersed phase
- Dispersion medium
• Dispersion medium: is the medium in which
the colloidal particles are dispersed.
• Dispersed phase : colloidal particles which are
dispersed in dispersion medium form
dispersed phase.

4. Classification of colloidal solution
(Sol)
• Classification based on the dispersion medium
 Hydrosol: water is the dispersion medium
 Alcosol: alcohol is the dispersion medium
 Aerosol: air is the dispersion medium
 Benzosol: benzene is the dispersion medium
• Classification based on affinity between dispersed
phase and dispersion medium
 Lyophilic colloids
 Lyophobic colloids

5. Lyophilic Colloids
• affinity between dispersed
phase and dispersion medium
is more.
• Dispersed phase can not be
easily coagulated and the
coagulated dispersed phase
can be easily brought back to
the colloidal state.
• Reversible colloids
• More stable as compared to
lyophobic colloids.
• When water as a dispersion
medium it is called hydrophilic
colloids.
• eg: gum, starch
Lyophobic Colloids
• affinity between dispersed
phase and dispersion medium
is less.
• Dispersed phase can be easily
coagulated and the coagulated
dispersed phase can not be
easily brought back to the
colloidal state.
• Irreversible colloids
• Less stable as compared to
lyophilic colloids.
• When water as a dispersion
medium it is called
hydrophobic colloids.
• eg: arsenic sulphide sol,
antimony sulphide sol

6. Origin of charge on the colloidal
particles
• Self dissociation
• Nature of dispersion medium
• Preferential adsorption

7. Self dissociation
• This phenomenon can be explained by using
solution of soap in water as the dispersion
medium. The soap is the sodium or potassium
salt of long chain fatty acid which dissociate in
water to give ions
R-COONa R-COO- + Na+
R-COO- ions have affinity for each other hence
they will aggregate with each other to form
micelles of colloidal size (colloidal micelles).

8. • The micelles are formed in such a way that the
alkyl group having more affinity for each other
will come close while the negative charge will
point in outward direction.
• As a result the colloidal solution of soap will
develop negative charge on the surface.
• Different micelles will keep away from each
other due to repulsion between the like
charges.

9. R
COO
-
R
COO
-
R COO-
-OOC R
Colloidal soap micelles having negative charge

10. Nature of dispersion medium
• Depending on the dispersion medium, the
colloidal particles will get acquire on the
surface.
• This can be explained taking example of
proteins which are formed from amino acids
will get acquire charge in acidic and alkaline
medium.

11. • In acidic medium, amino (-NH2) group of
amino acid will accept proton from the
medium and become positively charged.
• H2N-R-COOH [H+] +H3N-R-COOH
(α-amino acid)
• Hence during electrophoresis of amino acid
solution in acidic medium, the solution will
move towards negative electrode.

12. • In alkaline medium, -COOH group of amino
acid will loose proton to the medium and
become negatively charged.
• H2N-R-COOH [OH-] H2N-R-COO-
(α-amino acid) -H2O
• Hence during electrophoresis of amino acid
solution in alkaline medium, the solution will
move towards positive electrode.

13. • At intermediate pH a solution of amino acid will
contain dipole ions having +ive charge at one
end and –ive charge at other end i.e
+H3N-R-COO-
+H3N-R-COOH [H+] H2N-R-COOH [OH-] H2N-R-COO-
(+ Charged ion) (α-amino acid) (- charged ion)
Acidic medium Alkaline medium
(intermediate pH)
+H3N-R-COO-
(dipole ion)

14. • This constitute an electrical neutral system
and the solution will not show any movement
under the influence of electric field.
• Such dipole ions having positive charge at one
end and negative charge at other end are
called Zwitter Ions.
• The pH at which dipole ions are formed, the
system of colloidal solution will become
neutral and does not show electrophoresis is
called isoelectric point.
• For example the isoelectric point of gelatin is
4.7 while that of haemoglobin is 7.0

15. Preferential adsorption
• Adsorption of the common ions from the
dispersion medium on the surface of colloidal
particles will results in existence of charge on
the surface of colloidal particles.
• Depending on the way of preparation of
colloidal solution, either + iv or – ive ions from
the dispersion medium will get adsorbed.

16. • For example silver iodide (AgI) sol is prepared
by mixing excess of KI to dilute solution of
AgNO3 .
AgNO3 + KI AgI + KNO3 + K+ + I-
• Due to added excess of KI, the solution will
contain K+ and I- ions.
• The AgI sol thus formed will adsorb I- ions
(common ions) on the surface.
• The AgI sol will acquire – ive charge.

17. AgI
-I
I-
-I
-I
-I
-I
I-
-I
Fig. 1. Negatively charged AgI sol

18. • Alternatively if silver iodide (AgI) sol is
prepared by mixing excess of AgNO3 to dilute
solution of KI.
AgNO3 + KI AgI + KNO3 + Ag+ + NO3
-
• Due to added excess of AgNO3, the solution
will contain Ag+ and NO3
- ions.
• The AgI sol thus formed will adsorb Ag+ ions
(common ions) on the surface.
• The AgI sol will acquire + ive charge.

19. AgI
Ag+
Ag+
+Ag
+Ag
Ag+
+Ag
Ag+
+Ag
Fig. 2. Positively charged AgI sol

20. • Similarly arsenic sulphide (As2S3) sol possesses
– ive charge due to preferential adsorption of
sulphide (S2- ) ions (common ions) arising due
to passage of excess of H2S gas.
2AsCl3 + 3H2S As2S3 + 6HCl + H+ + S2-
(arsenic trichloride)

21. Colloidal Electrolyte
• Colloidal electrolyte are long chain high
molecular hydrocarbons which undergoes
ionisation in polar solvent to form ions.
• For example C17H35COONa (Sodium Stearate)
C17H35COONa C17H35COO- + Na+
• At low concentration of sodium sterate
(colloidal electrolyte), the solution contain
simple long chain stearate ions (C17H35COO-
Na-)

22. • As the concentration is increased, the stearate
ions will aggregate together to form micelle of
colloidal size.
• The ions will aggregate in such a way that
lyophobic hydrocarbon end will attract each
other and will be away from the solution while
lyophilic end will be directed towards the
solution.
• Thus micelle is an organised aggregate of
colloidal electrolyte molecules.

23. • The concentration at which the micelles appear is
called Critical Micellization Concentration (CMC).
R
COO
-
R
COO
-
R COO-
-OOC R
Here R = C17H35

24. Concentration
Equivalent
conductance
A
B
C’
C
CMC
Fig. 3. Variation of electrical conductivity with the concentration of colloidal electrolyte

25. •Below CMC the stearate ions exist in the solution as simple
stearate ions C17H35COO- .
•As a result the conductivity of solution increases linearly with
square root of concentration which is represented by straight
line AB in the graph (Fig. 3).
•At CMC the stearate ions get associated into micelles of size
sufficient to be classified as colloids.
•As a result, at CMC the break appears in the curve (Fig.3).
•Under high voltage current, the curve rises from B to C’ (Fig.3)
indicating the rise in conductance due to formation of highly
conducting stearate ion micelles.

26. • While under low voltage current the fall in
conductance is observed from B to C as shown
in the graph (Fig.3).
• The fall in conductance at low voltage current
is due to the formation of ionic atmosphere
surrounding the stearate ion micelles (Fig.4).

27. Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Cathode Anode
- -
-
-
-
-
-
-
-
Stearate ion micelle (C17H35COO-)
Fig.4. Na+ ion atmosphere surrounding the stearate ion micelle

28. Helmholtz & Stern’s Concept of Electrical Double Layer
• According to this concept the solid colloidal particle
when brought in contact with polar dispersion medium
will acquire charge on its surface.
• The charge which is developed on the surface of
colloidal particle will influence the distribution of ions
in the near by polar dispersion medium.
• Generally the oppositely charged ions (counter ions)
are attracted towards the surface and co-ions of like
charge are repelled away from the surface into the
bulk of dispersion medium.

29. Cl-
H+
Cl-
H+
H+
H+
H+
H+
S2-
S2-
S2-
H+ Cl-
Cl-
H+
Cl-
H+
H+
Cl-
H+
H+
Cl-
Cl-
Cl-
As2S3
Charge on colloidal
surface
Oppositely charged
counter ions
Electrical Double
Layer
Diffused mobile Layer
of mixed charges
Dispersion
medium
2AsCl3 + 3H2S As2S3 + Cl- + H+
(arsenic trichloride)
A
B
C
Fig.5.

30. • This leads to the formation of an electrical
double layer which consist of rigidly fixed layer
of charge on the solid surface (here S2- ions)and
nearby the surface (in the dispersion medium)
there may be practically immobile layer of
oppositely charged counter ions (here H+ ions)
(Fig.5).
•Further that in the bulk of dispersion medium
there exist the diffused mobile layer of charges
which may have sign same or opposite that on
the adsorbed layer (here H+ and Cl- ions) (Fig.5).

31. • There exist a difference of potential between fixed electrical
double layer and diffused mobile layer of charges. This
potential is called Zeta potential.
• In the fig. 5. point A represent potential developed on the
surface of solid. Point B represent potential developed in fixed
part of double layer. Point C represent potential developed in
the bulk of dispersion medium.
• From the graph it is clear that fall of potential between A to B
is always sharp, while the fall in potential from point B to C is
gradual. This total fall in potential AC = AB + BC is called Zeta
potential (ζ) which is the fall in potential between fixed electrical
double layer and diffused mobile layer of charges (Fig.5).
• If ‘d’ is the thickness of electrical double layer, ‘ϭ’ is the amount
of charge /cm3, ‘D’ is the dielectric constant of the medium, the
Zeta potential is given by the equation
ζ = 4πϭd
D

32. Electrokinetic Effect
• When the diffused mobile layer of mixed
charges (formed in liquid dispersion medium)
is separated from the fixed part of the double
layer (formed on the solid surface) with the
help of an electric field, some effects are
observed at solid-liquid interface which is
known as electrokinetic effect.

33. Electrophoresis
• Due to the presence of electrical charge on the
colloidal particles, they migrate towards one of
the electrode when the sol (solution of colloidal
particles) is subjected to electric field.
• This migration of colloidal particles (dispersed
phase) under the influence of electric field
towards proper electrode is called
electrophoresis or cataphoresis.

34. +
-
Reservoir tube
Electrode
Sol
Electrolyte
Moving boundary
•The apparatus for electrophoresis is called Burton Tube which consist of a U-
shaped tube fitted with a stopcock at the bottom (Fig.6).
• A funnel shaped reservoir tube is attached to the back side of U-shaped
tube.
• A small quantity of suitable electrolyte having density less than that of sol is
placed in the U-shaped tube.
• The sol is then introduced in the U- shaped tube through the funnel shaped
reservoir tube.
•Since the electrolyte is lighter than sol, the added sol will displace the
electrolyte upward forming the sharp boundary in the two arms of the U-
shaped tube.
Fig. 6. BURTON TUBE

35. • When the electrodes are immersed in the electrolyte and
are connected to the suitable source of potential, all
colloidal particles will move towards one of the electrodes.
• If the colloidal particles are negatively charged the
boundary will rise towards positively charged electrode
and fall on negative side of the electrode.
• If colloidal particles are positively charged the reverse
phenomenon is observed.
• From the direction of movement of boundary it is possible
to detect the rate at which the colloidal particles migrate
in presence of electric field.

36. •This migration of colloidal particles in presence of
electrical field is expressed in terms of electrophoretic
mobility (µ) .
• Electrophoretic mobility (µ) is defined as the distance
travelled by the colloidal particles in one second
under the potential gradient of 1 Volt/cm.
• The electrophoretic mobility (µ) is related to Zeta
potential (ζ) by the equation
ζ = 4πµƞ
D
here ƞ is the viscosity of dispersion medium
and D is the dielectric constant of dispersion
medium

37. Application of Electrophoresis
Since the different colloidal particles in a mixture
migrate at different rates, the process of
electrophoresis can be used for
• Removal of dust and smoke particles present in the
effluent gases.
• Deposition of metal i.e. Electroplating.
• Analysis of mixtures of proteins eg. Proteins of
human blood like albumin, α- globulin, β-globulin
have their characteristic electrophoretic mobilities.

38. Electro-osmosis
• For negatively charged colloidal particles, the dispersion
medium will have positively charge, while for positive charge
colloidal particles, the dispersion medium will have negative
charge.
• As a result if the colloidal particles are maintained stationary,
the dispersion medium would move under the influence of
electrical field.
• This movement of dispersion medium under the influence of
electrical field toward suitable electrode is called electro-
osmosis.

39. z
x
y
P1 P2
T1 T2
•The apparatus for electro-osmosis consist of a vessel having capillary tubes T1
and T2 divided into three compartments (X, Y & Z) by using a porous partition
membranes P1 and P2 (Fig.7).
• The colloidal solution (sol) is placed in compartment X.
• The compartments Y and Z are filled with the same dispersion medium as that
of sol.
• The porous partition membrane prevents electrophoresis but will allow the
dispersion medium to pass through it.
• As a result when the potential is applied between the electrodes placed near
the membranes, the level of dispersion medium will found to rise in one arm
of capillary tube while in the other arm of capillary tube the level of
dispersion medium will fall.
+ -
Fig.7 Electro-osmosis

40. • For positively charged colloidal particles, the dispersion medium would
be negatively charged and hence the movement of dispersion medium
will be from compartment Z to compartment Y(as in the figure 7) .
• While for negatively charged colloidal particles, the dispersion medium
would be positively charged and hence the movement of dispersion
medium will be from compartment Y to compartment Z.
• In both the cases the level of dispersion medium will fall in one arm of
the capillary tube and will rise in other arm of the capillary tube.
• This flow of dispersion medium under the influence of electric field is
called electro-osmotic flow.
• The pressure required to counter balance the electro-osmotic flow is
called electro-osmotic pressure (P) which is related to Zeta potential
(ζ) by the equation
ζ = Pπr2
2DE
Here P is the electro-osmotic pressure in N/m2; r is the radius of the
capillary tube in cm; D is the dielectric constant of the medium; E is
the applied potential in electrostatic unit

41. Streaming Potential
• It is a mechanical effect in which potential is
developed due to movement of dispersion
medium across the stationary dispersed phase
(colloidal particles).
• Streaming potential is exactly reverse of electro-
osmosis.
• In electro-osmosis flow of liquid dispersion
medium take place due to potential applied, while
in streaming potential, the potential is developed
due to flow of liquid dispersion medium.

42. • When two compatible Calomel electrode are kept on
the two side of the porous partition membrane (Fig.7),
the streaming potential (S) developed due to forced
movement of liquid dispersion medium across the
membrane can be measured.
• The streaming potential (S) and Zeta potential
(ζ) are related by the equation
ζ = 4πƞkS
PD
here k is the specific conductance of a liquid dispersion
medium, ƞ is the viscosity of dispersion medium, D is
the dielectric constant of the medium and P is the
pressure applied to cause the flow of liquid dispersion
medium.

43. Sedimentation potential (Dorn Effect)
• If a colloidal solution is kept undisturbed for a
long time, the colloidal particles will tend to fall
down (settle down) due to gravitational force.
• The gravitational force will cause heavier particles
to settle at relatively lower portion of the vessel
while the lighter particles will settle at the top.
• Such distribution is called sedimentation and the
potential developed between the upper and
lower layer is called sedimentation potential or
Dorn effect.

44. • Sedimentation potential is a mechanical effect
in which the potential is developed due to
movement of colloidal particles (dispersed
phase) with respect to stationary dispersion
medium.
• Sedimentation potential is reverse of
electrophoretic effect.
• In electrophoresis the colloidal particles
(dispersed phase) move due to potential
applied, while in sedimentation potential, due
to movement of colloidal particles (dispersed
phase) the potential is developed.

45. Electrophoresis Sedimentation
potential
Electro-
osmosis
Streaming
potential
Type of
effect
Electrical effect Mechanical
effect
Electrical
effect
Mechanical
effect
What is
applied?
Potential is
applied
Mechanical
force
Potential is
applied
Mechanical
force
What will
move?
Dispersed phase
(colloidal
particles)
Dispersed
phase
(colloidal
particles)
Dispersion
medium
Dispersion
medium
What will
remain
stationary
?
Dispersion
medium
Dispersion
medium
Dispersed
phase
(colloidal
particles)
Dispersed
phase
(colloidal
particles)
What is
the result?
Migration of
dispersed phase
Potential is
developed
Migration
of
dispersion
medium
Potential is
developed

46. Donnan Membrane Equilibrium
•The Donnan membrane equilibrium arises when a
salt solution containing large non diffusible ion is
separated from a salt solution like NaCl containing
diffusible ions by means of porous partition
membrane.
• At equilibrium, it is expected that the diffusible
ion should get equally distributed on both side of
the membrane.
•However in practice the distribution is unequal.
•This was shown by Donnan and hence named as
Donnan membrane equilibrium.

47. • Consider NaCl solution of initial
concentration C1 separated from the salt
solution of NaR having initial concentration
C2 by means of semipermeable membrane.
• In NaR salt solution, R- is the large non
diffusible ion.
• When diffusion take place, consider X gm of
Na+ and X gm of Cl- ions are diffused from
LHS (compartment I) to RHS (compartment
II).
• As a result, at equilibrium conc. of Na+ and
Cl- ions in LHS is decreased by X. Hence
conc. of Na+ and Cl- ions in LHS will be (C1-
X).
• While at equilibrium, the conc. of Na+ and
Cl- ions in RHS will increase by X. Hence
conc. of Na+ ions in RHS which was C2
initially will now be (C2+X) and conc. of Cl-
which was 0 initially will now be X.
• Conc. of R- at equilibrium will be C2 which
will remain same as that of initial
concentration (remain unchanged).
LHS (I) RHS (II)
Initial
Conc.
Equilbrium
Conc.
Na+ Cl- Na+ Cl-
R -
C1 C1 C2 C2 0
(C1 - X)(C1 – X) (C2 + X) C2 X
Semipermiable
membrane

48. According to chemical thermodynamic at equilibrium, the chemical
potential of NaCl on both side of the membrane must be same. The
chemical potential µ is given by the equation
µ = µo + RTlna ------------(1)
here µo is the standard chemical potential and ‘a’ is the activity of the
chemical species.
Therefore µ NaCl (I) = µ NaCl (II)
µo + RTlna NaCl (I) = µo + RTlna NaCl (II)
a NaCl (I) = a NaCl (II)
a Na
+
(I) . aCl
-
(I) = a Na
+
(II) . aCl
-
(II) --------- (2)
For dilute solutions, the activities ‘a’ can be replaced by molar
concentration. Therefore eq. (2) will be
[Na+
(I)] . [Cl-
(I)] = [Na+
(II)] . [Cl-
(II)]
(C1-X) . (C1-X) = (C2+X) . (X)
C1
2-2C1X +X2 = C2X +X2
C1
2 = C2X + 2C1X
C1
2 = X(C2 + 2C1)
C1 . C1 = X(C2 + 2C1)

49. C1 = X --------------(3)
(C2 + 2C1) C1
The term X/C1 in eq.(3) indicates the fraction of NaCl that diffuses
across the membrane from LHS to RHS.
If the concentration of NaCl to be equal on both side of the
membrane, it is necessary that X/C1 should be 1/2.
From eq. (3) X/C1 will be 1/2 only if concentration C2 of non-
diffusible (R-) ion = 0.
But the concentration C2 of non-diffusible (R-) ion = 0 is not
possible.
Hence equal concentration (i.e. equal distribution) of diffusible
salt on both side of the membrane is also not possible.
This is due to the presence of non-diffusible (R-) ion on other side
of the membrane.
Thus it can be said that in presence of non-diffusible (R-) ion on
other side of the membrane, the distribution of diffusible ions
across the membrane is also affected.

50. • This effect of non-diffusible ions can be minimised when C1 >>>> C2
i.e. by taking the concentration of diffusible ions (C1) much greater
than the C2 which is the concentration of non-diffusible (R-) ion.
Under such conditions when C1 >>>> C2, the concentration of C2
will be negligible small in comparison to C1 and hence eq.(3) will be
reduced to
C1 = X
(2C1) C1
1 = X
2 C1

51. Emulsions
• The colloidal solutions in which both the
dispersed phase and dispersion medium are
immiscible liquids are called emulsions.
• Emulsions are classified in to two types
Oil in Water (O/W) type emulsions
Water in Oil (W/O) type of emulsions

52. • Oil in Water (O/W) type of emulsions means
the dispersed phase is oil while dispersion
medium is water.
• Water is the continuous phase while oil is the
discontinuous phase.
• Eg. Milk

53. • Water in Oil (W/O) type of emulsions means
the dispersed phase is water while dispersion
medium is oil.
• Oil is the continuous phase while Water is the
discontinuous phase.
• Eg. Cold creams

54. water
Oil
W/O Type
(Stable emulsion)
O/W Type
(Stable emulsion)
(Unstable
emulsion)
• The emulsion which consist of Oil dispersed in Water or
Water dispersed in Oil are unstable because both the
emulsions will soon separate in two layers (Upper Oil
layer and lower water layer).
• Therefore a third substance called emulsifier or
emulsifying agent is added to stabilise an emulsion.

55. • A long chain organic compounds with polar
functional groups for eg. Soap will work as a good
emulsifying agent.
•Such emulsifier get adsorbed at the interface
between the dispersed droplets and dispersion
medium in the form of mono-molecular layer in
such a way that polar end (hydrophilic end) of
emulsifier will dip in Water while the hydrocarbon
chain being hydrophobic will dip in Oil.
•It results in bringing of two liquids (Oil & Water) in
intimate contact with each other, thereby reducing
the surface tension and stable emulsion is
obtained.

56. Surfactants
• Surfactants are the substance which when
added to the solvent reduces the surface
tension at the solution interface.
• The surface tension decreases because the
concentration of the solute at the surface of a
liquid is more than in the bulk of the solution.
• So surfactants are also called surface active
agents.

57. • According to Gibb’s adsorption equation
= - C . dγ
RT dC
Here S is the excess of concentration of solute/cm2 of the
surface as compared to that in the bulk of solution.
C is the equilibrium concentration of solute
= rate of change of surface tension with concentration
R is the molar gas constant
T is the temperature in kelvin.
dγ
dC
S

58. Case l
• If by addition of solute to a
solvent, the surface tension
of the solution decreases
i.e. dγ/dC in the above
equation becomes – ive,
then in such case, S
becomes + ive indicating
higher concentration of
solute at the surface than
that in the bulk of solution.
Such solutes are called
surface active agents or
surfactants.
Case ll
• If by addition of solute to a
solvent, the surface
tension of the solution
increases i.e. dγ/dC in the
above equation becomes +
ive, then in such case, S
becomes - ive indicating
decrease in concentration
of solute at the surface than
that in the bulk of solution.
Such solutes are called
surface inactive agents.
S = - C . dγ
RT dC

59. • Surfactants are divided in to three classes
1. Anionic surfactants: eg. Sodium cetyl sulphate
C16H33SO4
-Na+ in which the surface activity is
due to the anions.
2. Cationic surfactants: eg. Cetyl trimethyl
ammonium bromide C16H33N(CH3)3
+Br-
in which the surface activity is due to the
cations.
3. Non-ionogenic surfactants: eg. Cetyl
polyglycol ether C16H33(OCH2-CH2)n-OH whose
molecules can not undergo dissociation.

60. Surfactants used in detergents, pesticides and food
industries
(Industrial application of surfactants)
For industries manufacturing food products,
detergents and pesticides formulations, the
products manufactured are generally a mixture of
water and water insoluble compounds like fats,
proteins, grease and toxic chemicals. To such
product mixture, low concentration of added
surfactants will change the surface properties of
the liquid. Hence the surfactants find a wide range
of applications in such industries.

61. • Surfactants when used in detergents will help to
improve wetting of cloth fibres and spreading of
detergents.
• It will also help to produce and control foam formation
and modify the viscosity.
• Many manufactured food are in the state of emulsion
or have been in emulsified state during manufacturing.
Eg.: butter and butter cream (W/O type of emulsion),
ice cream, milk (O/W type of emulsion).
• For such food emulsions, small quantity of surfactants
are used as a emulsifying agent where they help to
improve the shelf storage of food products by
promoting the air retention properties of food mixture.

62. • For an oil soluble pesticides, oil in water
emulsions are widely used which helps in getting
oil soluble pesticides in a water mixture.
• This helps in the active pesticide ingredients
being applied as a water spray.
• Surfactants when added to such oil in water
pesticide emulsions will improve the emulsifying,
spreading and wetting properties of pesticides.
• Thus small amount of pesticides can be applied
on the larger surface with almost the same effect
as that of applying larger amount of pesticides.