Mixing An operation in which two or more components (in a separate or roughly mixed condition) are treated so that each particle lies as nearly as possible in contact with a particle of each of the other ingredients.

1. MIXING
Dr.Ahmad A.Yosef
Industrial Pharmacy
4th Stage
Lecture 2

2. Mixing
An operation in which two or more components (in a separate or
roughly mixed condition) are treated so that each particle lies as
nearly as possible in contact with a particle of each of the other
ingredients.
Ideal Or Perfect Mixing
When each particle lay adjacent to a particle of the other component
(i.e. each particle lies as closely as possible in contact with a particle
of the other component)
Random mixing
A mix where the probability of selecting a particular type of particle is
the same at all positions in the mix, and is equal to the proportion of
such particles in the total mix

3. OBJECTIVES OF MIXING:
1. To achieve a physical mixture.
2. To bring a physical change.
3. To achieve a dispersion.
4. To promote a chemical reaction.
1) Simple physical mixture:
Producing a blend of two or more miscible liquids or two or more
uniformly divided solids
2) Physical change:
Producing a change that is physical as distinct from chemical
3) Dispersion:
Dispersion of two immiscible liquids (Emulsion)
4) Promotion of reaction:
Activate, promote and control a chemical reaction so ensuring a uniform
product.

4. NEED OF MIXING
• It is a unit operation for tablet, capsule b/c many
ingredients are used, so mixing is required.
• Single material (potent e.g. 0.2ϻg) which is difficult to
handle so we add ingredients which Is mixed

5. TYPES OF MIXTURES
1)POSITIVE MIXTURE:
• Spontaneous and irreversible mixing (i.e. requiring no
energy input for mixing)
• Separation…..Requires energy
2) NEGATIVE MIXTURE
• Mixtures that require a higher degree of mixing along
with the expenditure of energy for mixing
• Separation….. Without energy
3) NEUTRAL MIXTURE
• Static in behavior (No tendency to mix spontaneously,
nor segregate when mixed)
• Both mixing and segregation occurs with expenditure of
energy.

6. TYPES OF MIXING
1. Liquid mixing or fluid mixing
2. Powder mixing or solid mixing
3. Semi-solid mixing

7. A) FLUID/LIQUID MIXING
Mixing process may be easy for some fluid and difficult for
others. Following three parameters gives necessary
knowledge about basic requirement of fluid for mixing.
1. Flow characteristics.
2. Mixing mechanisms.
3. Mixing equipment.

8. FLOW CHARACTERISTICS:
The fluid may flow freely or flow with resistance. They show
different flow characteristics, they may be classified as,
Newtonian fluid
Non –Newtonian fluid
1) PLASTIC/BINGHAM FLOW
2) PSEUDO-PLASTIC FLOW
3) DILATANT FLOW

9. MECHANISM OF MIXING
Four types of mechanism are involved in mixing of fluids.
1. Bulk transport mixing.
2. Turbulent mixing.
3. Laminar mixing.
4. Molecular diffusion.

10. FLOW PATTERN DURING MIXING
Mixing occurs due to the resultant effect of 3 components
acting on liquid:
1. Tangential / Circular component
2. Radial component
3. Axial / Longitudinal component

11. MIXING EQUIPMENTS
Batch mixing
Mixing a specific and limited quantity of material
1. Impellers
2. Air jet
3. Fluid jet
Continuous mixing
Equipment used for both are different. The two
components are common in the equipment used for batch
and continuous mixing processes which are;
1. Tank of suitable size to hold material.
2. Means of supply of energy to the system so as to
enhance the speed of mixing.

12. a) IMPELLER
• Impellers are mixing devices that provide a definite flow
pattern in liquid during mixing, moving at various
speeds.
• Liquids are mixed usually by impellers, which produce
shear forces for inducing the necessary flow pattern in
the mixing container.
CLASSIFICATION
Impeller exists in different forms.
1. Propeller 2. Turbine 3. Paddles

13. b) AIR JETS
Air jets or other inert gas jets are effectively used for
mixing purpose with fluid of the following characteristics;
1. Having low viscosity
2. Non foaming
3. Non-reactive with gas employed
4. Non-volatile in nature

14. c) FLUID JETS
In this device, the pumping operation is used to transfer
the liquid into the mixing tank.
MECHANISM
1. In this case the fluids are pumped through nozzle
which permits good circulation of material through the
tank.
2. The fluid jets in this operation behaves like propeller in
that they produce turbulent flow in the direction of their
axis, while differ from propeller b/c they don't produce
tangential flow themselves.
3. They may also operate simply by pumping the liquid
from the tank and back into the tank through the jet.

15. CONTINUOUS MIXING
Continuous mixing may be accomplished in two ways.
• By using tubes or pipes
• By using mixing chamber

16. B) POWDER MIXING
• Powder mixing may be regarded as an operation in
which two or more than two solid substances in
particulate form intermingled in mixer by continuous
movement of particles.
• It is an example of neutral mixture and is one the most
common operation employed during preparation of
different formulation like powder, tablets, capsules etc

17. MECHANISM OF POWDER MIXING
Mixing of powder is generally carried out by one of the
following mechanism or their combination.
1. Convective mixing
2. Shear mixing
3. Diffusive mixing

18. EQUIPMENTS FOR SOLID MIXING
1. Tumbling mixer
2. High shear mixture or granulator
3. Agitator mixer , includes
a) Ribbon mixer
b) Planetary mixer
c) Nautamixer
Planetary mixer
Nautamixer

19. C) SEMI-SOLID MIXING
MECHANISM:
• It has been found that, in mixing an insoluble powder with, a liquid, a
number of stages can be observed as the liquid content is increased
a) Pellet & powder state
• Addition of small amount of liquid to a bulk of powder causes the solids to
ball up and form small pellets.
b) Pellet state
• Further addition of liquid results in the conversion of more dry powder to
pellets
c) Plastic state
• As the liquid content is increased further the character of the mixture
changes markedly.
d) Sticky state
• Continual incorporation of liquid causes the mixture to attain the sticky
state; the appearance become paste like, the surface is shiny and the
mass adheres to solid surface.
e) Liquid state (semisolid state)
• Eventually the addition of liquids result in a decrease of consistency until a
fluid state is reached

20. Statistical evaluation
Objectives
1. To compare the efficiency of two or more mixing
operations.
2. To compare the efficiency of two or more equipment.
3. To follow the mixing process with time.
4. To optimize processing parameters
5. To investigate the mechanism of mixing in a given
piece of equipment

21. Applications of solid mixing
1. Involved in the preparation of many types of
formulations.
2. It is also an intermediate stage in the production of
several dosage forms.
3. Wet mixing in the granulation step in the production of
tablets and capsules.
4. Dry mixing of several ingredients ready for direct
compression as in tablets.
5. Dry blending of powders in capsules, dry syrups and
compound powders.
6. Production of pellets for capsules