1. COLLOIDAL
SYSTEMS
Dr. L.T.M. Muungo

2. INTRODUCTION
A colloid is a substance microscopically
dispersed throughout another substance.
The word colloid comes from a Greek word
kolla, which means glue thus colloidal
particles are glue like substances. These
particles pass through a filter paper but not
through a semipermeable membrane.
Colloids can be made settle by the process
of centrifugation.

3. The colloidal system consist of two phases:
A dispersed phase ( A discontinuous phase )
A dispersion medium ( A continuous phase )
The dispersed-phase particles have a diameter of
between approximately 1nm – 0.5um .
Such particles are normally invisible in an optical view,
though their presence can be confirmed with the use of
an ultramicroscope or an electron microscope.

4. Homogenous mixtures with a dispersed phase in
this size range may be called colloidal
aerosols, colloidal emulsions, colloidal
foams, colloidal dispersions, or hydrosols.
If the dispersed phase is solid and the dispersion
medium is liquid then it is called colloidal
suspension but if the dispersed phase and
dispersion medium both are in liquid state then it
is known as colloidal emulsion.

5. The dispersed-phase particles or droplets are
affected largely by the surface chemistry present in
the colloid.
Some colloids are translucent because of
the Tyndall effect, which is the scattering of
light by particles in the colloid.
Other colloids may be opaque or have a slight
color.
Colloidal solutions (also called colloidal
suspensions) are the subject of interface and
colloid science.
This field of study was introduced in 1861
by Scottish scientist Thomas Graham.

6. . Examples of colloids are silver solutions, milk,
synthetic polymers and blood etc.
Blood Milk

7. Inter-Particle Interactions

8. forces play an important role in the interaction of
colloid particles:
1) EXCLUDED VOLUME REPULSION:
IN LIQUID THEORY STATE:
In liquid state theory, the 'excluded volume' of a molecule
is the volume that is inaccessible to other molecules in
the system as a result of the presence of the first
molecule.
The excluded volume of a hard sphere is eight times its
volume—however, for a two-molecule system, this
volume is distributed among the two particles, giving the
conventional result of four times the volume.

9. 2) ELECTROSTATIC INTERACTION :
Colloidal particles often carry an electrical charge and
therefore attract or repel each other. The charges of
both the continuous and the dispersed phase, as well as
the mobility of the phases are factors affecting this
interaction.
3) VAN DER WAALS FORCE : van der Waals
force (or van der Waals interaction), is the sum of the
attractive or repulsive forces between molecules other
than those due to covalent bonds, the hydrogen bonds,
or the electrostatic interaction of ions with one another
or with neutral molecules or charged molecules

10. 4) STERIC FORCES :
Steric effects arise from the fact that each
atom within a molecule occupies a certain
amount of space. If atoms are brought too
close together, there is an associated cost
in energy due to overlapping electron
clouds (Pauli or Born repulsion), and this
may affect the molecule's preferred shape
(conformation) and reactivity.

11. Types of Colloids

12. TYPES OF COLLOIDS:
Classification of Colloids is based
on Physical State of Dispersed
Phase and Dispersion Medium:

15. Classification of Colloids based
on Nature of Interaction
Between Dispersed Phase and
Dispersion Medium:
Lyophilic Colloids
Lyophobic Colloids
Association colloids

16. Lyophilic Colloids
• Lyophilic colloids are liquid loving colloids (Lyo means
solvent and philic means loving).
 Ease of Preparation:
• As these colloids are liquid loving, their solutions are
easy to prepare and can be prepared directly by mixing
colloid with liquid.
 Stability:
• Lyophilic sols are relatively stable as strong forces of
interaction exist between colloidal particles and liquid.

17. Reversibilty:
If large quantity of liquid is added to
precipitations or the colloidal solution is
stirred properly lyophilic sols can regain
their original state.
This shows that lyophilic sols are also
reversible in nature.

18. Lyophobic Colloids
Lyophobic colloids are liquid hating colloids (Lyo means
solvent and phobic means hating).
Ease of Preparation:
As these colloids are water hating, their solutions are easy to
prepare and cannot be prepared directly by mixing colloid
with liquid. Special methods are employed to prepare
lyophobic solutions.
Stability:
Lyophobic sols are less stable as weak forces of interaction
exist between colloidal particles and liquid.

19. Reversibilty:
Lyophobic colloids do not regain
their original state as coagulated
mass cannot be dispersed into
colloidal form.
This shows that lyophobic solutions
are also irreversible in nature.

20. Association colloids
• These are the colloids which behave as normal strong
electrolytes at low concentrations but exhibit colloidal
properties at higher concentrations due to the formation of
aggregated particles.
• The aggregated particles thus formed are called micelles.
• The associated colloids are usually formed by surfactants
(surface active agents) like soaps and synthetic detergents.
• These agents form micelles when present in solution at a
concentration greater than critical micellar concentration
(CMC).

21. Methdos of preparation colloids
DISPERSION METHOD

22. Dispersion Methods
• In dispersion methods, colloidal particles
are obtained by breaking large particles of a
substance in the presence of a dispersion
medium. Since the solsformed are
unstable, they are stabilized by adding
mechanical energy input.
• Dispersion method in the preparation of
colloids can be done by crushing the large
suspension’s particles into small in size.

23. Dispersion Method
• In these methods, the bigger particles of a
substances are broken down to form smaller
particles of colloidal dimensions thus obtained
are stabilized by the addition of certain
stabilizing agents. Some important dispersion
methods are as follows:

24. I. Mechanical Dispersion Method
• In this method, the dispersion of the coarse
material (whose colloidal solution is to be
prepared) is carried out in a machine called
colloid mill.
• Colloid mill - It consists of two heavy steel discs
separated by a little gap. The gap may be
adjusted according to the particle size desired.
The two discs rotate at high speed (about 8000
revolutions per minute) in the opposite direction.

25. I. Mechanical Dispersion Method
• A suspension of the substance in water is
introduced into the mill. The coarse particles
present in the suspension are grinded to the
particles of colloidal dimensions and get
dispersed in water to form a sol. Finer
dispersion can be obtained by adding an inert
diluents which prevents the colloidal particles
to grow in size.

26. I. Mechanical Dispersion Method
• Mechanical dispersion is also called direct
dispersion. It is a method of making a colloid
by crushing or milling a given solid and the
powder produced is dispersed into a given
dispersing medium.
• Examples : Making of sulphur sol with the use
of glucose as diluents.

27. I. Mechanical Dispersion Method
• The diagram shows the mechanical dispersion
method.

28. II. Electrical Dispersion Method
• Also known as “Bredig arch method “
• Is a method of preparing colloids, especially
metallic sols. In this method, two metallic
wires functioning as electrodes are immersed
into water, then on both ends of wires is given
a strong enough electric current to be
evaporated and then it is dispersed into water
to form a metallic sol.

29. II. Electrical Dispersion Method
• In this method, an electric are is struck between
the two electrodes of the metal (whose colloidal
solution is to be prepared) immersed in the
dispersion medium (say water).
• The dispersion medium is cooled by surrounding
it with a freezing mixture. High temperature of
the arc vaporizes some of the metal. The vapour
condenses to the particles of colloidal size on
cooling. The colloidal particles thus formed get
dispersed in the medium to form a sol. of the
metal.

30. II. Electrical Dispersion Method
• This method is used for the preparation of sols
metals such as gold, silver, platinum etc.
Electtrical Dispersion Method

31. III. Peptization Dispersion
• The process of converting aprecipitate into a
colloidalsol by shaking it with thedispersion
medium, in thepresence of a small amountof
electrolyte
• Electrolyte = Peptizing agent
• This method is used to convert a freshly
prepared precipitate into a colloidal sol

32. III. Peptization dispersion
• In this method, a freshly prepared precipitate
of the substance is made to pass into the
colloidal state by the addition of a suitable
electrolyte. The process of dispersing a freshly
prepared precipitate into colloidal form by
using a suitable electrolyte is called
peptization. The electrolyte added is called
peptizing agent.

33. III. Peptization Dispersion
• In peptization, the larger particles is dispersed
into smaller particles in a colloidal size by
adding a particular electrolyte which acts as a
dispersing agent.
• For example, sediment of Al(OH)3 will change
into a colloid by adding a solution of AlCl3 ;
NiS will charge into sol when it is added into
H2S; and sediment of AgCl will charge into a
colloid by adding a solution of ammonia.

34. IV. Homogenization
• Homogenization is a process for preparing
something to become homogeneous. In this
preparation, a particular emulsifier is usually
added to emulsify the fat particles in milk or
cream so that the milk or cream form a stable
colloid. In this process, skim milk powder is
often used and it is conducted in a
homogenization device.

35. Summary of Dispersion Method
• Dispersion method - larger particles of a substance
(suspensions) are broken into smaller particles. The
following methods are employed.
• There are 4 ways using dispersion method :
1. Mechanical Dispersion Method - the substance is
first ground to coarse particles.
2. Electical Dispersion Method - is used to prepare
sols of platinum, silver, copper or gold.
3. Peptization Dispersion - The process of
converting a freshly prepared precipitate into
colloidal form by the addition of suitable
electrolyte
4. Homogenization - is any of several processes used
to make a chemical mixture the same throughout.

36. APPLICATIONS OF
COLLOIDS

37. OVERVIEW
What are colloids?
Applications of colloids
Pharmaceutical apllications.
Industrial applications
Other applications
Conclusion.

38. INTRODUCTION

39. DEFINITION
Colloidal System is
the heterogenous biphasic system
 dispersed phase ranges within 1-10
angstrom to few micrometres in
dimensions.
differs from other heterogenous and
homogenous solutions in terms of the size
of dispersed phase.

40. APPLICATIONS OF COLLOIDS
Colloids play an important role in pharmacy,in
our daily life and in industries.
A few of the important applications of colloids
are listed below.

41. PHARMACEUTICAL
APPLICATIONS

42. PHARMACEUTICAL APPLICATIONS
THERAPY
Colloidal system are used as therapeutic
agents in different areas.
Colloidal medicines being finely divided, are
more effective and are easily absorbed in
our system.
Penicillin and streptomycin .
EYE LOTIONS:
• Argyrol and protargyrol

43. PHARMACEUTICAL APPLICATIONS
COLLOIDAL SULPHUR:
Absorbed efficiently in colloidal forms.
COLLOIDAL COPPER:
In treatment of cancer.
COLLOIDAL GOLD:
Diagnostic agent for paresis.
COLLOIDAL MERCURY:
In treatment of syphilis.

44. PHARMACEUTICAL APPLICATIONS
NATURAL COLLOIDS
Plasma protein.
COLLOIDAL ELECTROLYTES.
Increase solubility,stability and taste of
compounds,in lyophillic colloids.
STABILITY OF DRUGS:
lyophobic colloids.
and prevent flocculation .

45.  gelatin coating over tablets
and granules.
 For protection.
DISSOLUTION AND
ABSORBTION:
 Both enhance due to huge
surface area.
 sulphur colloid.

46. PHARMACEUTICAL APPLICATIONS
TARGETED DRUG DELIVERY:
Liposomes.
Vessicles of phospholipids.
As a drug carrier to promote controlled
release of drug in body.
Taken up by the liver and spleen.

47. APPLICATIONS IN FOOD INDUSTRY:
 Many of our foods are
colloidal in nature.
 Milk is an emulsion of
butterfat in water
protected by a protein,
casein.
 Salad dressing, gelatin
deserts, fruit jellies.
 Ice cream & Bread.

48. INDUSTRIAL
APPLICATIONS

49. NON-DRIP PAINTS:
 All paints are colloidal
dispersions of solid pigments
in a liquid medium.
 paints also contain long-
chain polymers.
 At rest, the chains of
molecules are coiled.
 stress is applied with a paint
brush, the coiled molecules
straightened.
 This renders the paint ‘non-
drip’.

50. INDUSTRIAL APPLICATIONS
Sewage disposal:
Colloidal particles of the dirt, mud etc. carry
electric charge.
the colloidal particles are coagulated when
sewage water is passed through the plates
kept at a high potential.
the suspended matter gets removed.

51. INDUSTRIAL APPLICATIONS
 Cleansing action of
soap:
Soap solution is
colloidal in nature.
 It removes the dirt
particles either by
adsorption or by
emulsifying.

52. OTHER APPLICATIONS
 Photography:
A colloidal solution of
silver bromide in gelatin
is applied on glass
plates or celluloid films
to form sensitive plates
in photography.

53. OTHER APPLICATIONS

54. OTHER APPLICATIONS
Clarification of Municipal water:
 The municipal water contains colloidal
particles.
Alum which yield ions, Al3+ is added to water
to coagulate the negatively charged clay
particles.
Al3+ + 3H2O ---- Al(OH)3 + 3H+
Al(OH)3 + 4H2O + H+ ----- Al(OH)3(H2O)4

55. OTHER APPLICATIONS
Artificial Kidney machine:
The human kidneys purify the blood by
dialysis through natural membranes.
The toxic waste products such as urea and uric
acid pass through the membranes
 colloidal-sized particles of blood proteins
(haemoglobin) are retained

57. OTHER APPLICATIONS
 The phenomenon of
the scattering of light
by the sol particles is
called Tyndall effect.

59. CONCLUSION:
• A knowledge of colloid chemistry is essential
to understand some of the various natural
phenomena around us.
• Colloids make up some of our modern
products.
• Dialysis,life saving treatment.

60. QUESTIONS?

61. PHARMACEUTICAL APPLICATION OF COLLOIDS:
• Some important application of colloids are
discussed below:

62. 1. THERAPY:
• Colloidal material are used for a variety of
pharmaceutical application including therapeutic &
diagnostic agents, drug delivery system.
• Example: copper colloids ( anti cancer) & mercury
colloids ( anti syphilis).

63. 2.DRUG PREPARATION:
• Drug substances may also be prepared as
colloidal sized particles to improve
bioavailability or therapeutic activity
.Example: colloidal sulphur etc.

64. 3.TABLETS COATING:
• Colloidal dispersion of gelatin is used in coating over
tablets & granules which upon drying leaves uniformly
dry film over them & protect them from adverse
condition of the atmosphere.

65. 4.MEDICINES:
• Most of the medicines are colloidal such as Calcium &
Gold are administered by injections to raise the vitality
of human system.

66. 5.FOOD ITEMS:
• Large numbers of food particles which we use
in our daily life are colloidal in nature.
• Example: Milk, butter, & ice cream etc

67. 6.NUCLEAR MEDICINES:
Colloidal dispersion containing radioactive
isotopes are being used as diagnostic &
therapeutic agents in nuclear medicines.
Example: Colloidal gold is made by reducing a
solution of AgCl either by treatment with
ascorbic acid.

68. THANK YOU!

69. Study Questions
• Define the following terms:
[continuous phase , Homogenous mixtures , Heterogenous, etc]
• Respond to the following questions:
 State and describe the types of inter-particle interactions in a pharmaceutical system
 State and explain the characteristic classification of colloidal system based on physical components
 State and describe different methods of colloidal preparations
• Group work discussional questions:
 Describe the pros and cons of colloidal systems as drug carrier and delivery system
 Describe the various pharmaceutical and therapeutical applications colloidal system can be used
 Describe the mechanisms involved in colloidal drug carrier and delivery entities for therapeutical effects