1. Objectives Definition of mixing Objectives of Mixing Types of Mixtures
Mechanisms of Mixing PH

2. Most Commonly used operation in daily life.
Mixing:
Most Commonly used operation in daily life.
Used in food, Plastic, Glass, Paint, Paper, fertilizer Industries.
In Pharmaceutical Industry :
Liquids, Viscous Liquids, Semi – solids & Solids require Mixing. PH

3. Introduction A true solution : An emulsion: A solution:
In Pharmaceutical Industry generally Mixing is Carried out
to obtain.
A true solution :
When two miscible liquids are mixed together
An emulsion:
when two immiscible liquids are mixed in presence of emulsifying agent .
A solution:
when Solid is dissolved in a Vehicle. PH

4. A Suspension: An ointment : A powder:
when an insoluble solid is mixed with a
vehicle in presence of a suspending agent.
An ointment :
When a solid or liquid is mixed with a semisolid base
A powder:
When two or more solid substances are mixed
together PH

5. Definition
Mixing is a process in which two or more than two components are mixed in such a way that each particle of any one ingredient lies as nearly as possible to the adjacent particle of other ingredient. PH

6. Objectives of Mixing
To ensue uniformity of composition between mixed ingredients
To enhance the Physical or chemical reactions PH

7. Type of Mixtures Positive Mixtures Negative Mixtures Neutral MixturesPH

8. Positive Mixtures Mixed by diffusion Process No energy required
Do not create any problem
Eg :- Two gases or two miscible liquids. PH

9. Negative Mixtures Difficult to prepare.
Required a higher degree of Mixing & external force
Tendency to separate out unless they are continuously
stirred.
Eg: Suspensions & Emulsions. PH

10. Neutral Mixtures Static in their behaviour
No tendency to mix spontaneously
Do not separate out easily.
Eg:- Pastes, Ointments , Mixed powder etc. PH

11. Mechanisms of Mixing Convective Mixing Shear Mixing Diffusive MixingPH

12. Convective Mixing: Shear Mixing: Diffusive Mixing:
Transfer of groups of adjacent particles from one place to another within the mixture.
Shear Mixing:
Shear forces created within the mass of the material by using agitator arm
Diffusive Mixing:
When materials tilted, gravitational forces cause the upper
layers to slip & diffusion of individual particles take place PH

13. Objectives Liquid mixing Sub groups of liquid mixing
Stages of liquid mixing
Equipment of Liquid mixers:
Shaker mixers
Propeller mixers PH

14. Sub Groups of Liquid Mixing
Mixing of liquids in liquids
Mixing of two miscible liquids
Eg: solutions
Mixing of two immiscible liquids
Eg: emulsions PH

15. Mixing of Liquids and Solids
Liquids and soluble solids
eg : solutions
Liquids and insoluble solids
eg : suspensions PH

16. Mixing of Liquids and Liquids
Stages of mixing:
Localized mixing:
Shear is applied to the particles of the fluid
General movement:
Takes all the particles of the bulk through the nearing zone to produce uniform product PH

17. Small scale preparation of emulsion
Suitable apparatus: mortar & pestle
Shear forces produced
General movement also produced
Two stages of preparation of emulsions:
Primary emulsion
Secondary emulsion PH

18. Mixing of liquids & soluble solids
These are homogeneous mixtures
eg: solutions PH

19. Mixing of Liquids & Insoluble Solids
These are heterogeneous mixtures
eg: suspensions
Suitable apparatus for small scale preparation:
Mortar & pestle PH

20. Equipment for Liquid Mixing
Shaker mixers
Propeller mixers
Turbine mixers
Paddle mixers PH

21. Shaker mixers Limited use in industries:
Reasons: Variable mixing efficiency Changes in viscosity Constructional characters like use of baffles
Oscillatory movement : for small scale work
Rotary movement : for large scale work PH

22. Propeller mixers Mostly widely used in industries:
For liquids of low viscosity
Not suitable for viscous liquids like glycerin, castor oil etc.,
Size of propeller small as compared to container PH

23. Propeller mixers Propeller rotates at a very high speed up to 8000 rpm
Undesirable vortex formation & entrapment of air are resulted due to high speed of propeller
Can be avoided by number of ways shown in the diagram PH

24. Propeller mixers
Fig: 33.1 PH

25. Propeller mixers
Fig: 33.2 PH

26. Propeller mixers
Fig: 33.3 PH

27. Objective Turbine Mixers Paddle Mixers Homogenization HomogenizersPH

28. Turbine Mixers Consist of Circular disc impeller
Rotate at lower speed than propeller
Produce greater shear force than propeller
Used for liquid of high viscosity
Special application in preparation of emulsions PH

29. Fig : 34.1 PH

30. Paddle Mixers Paddles used as impellers
Rotate at low speed of 100 r.p.m
Paddles consist of blades attached to vertical shaft
Blades have large surface area
Effectively mix viscous liquids & semisolids PH

31. Paddle Mixers
Fig: 34.2 PH

32. Homogenization
Definition:- Process of conversion of coarse emulsion into colloidal state of uniform composition.
Uses:- Process used for the preparation of emulsions, suspensions etc. PH

33. Homogenizers Equipment used for the homogenization of emulsions
Principle:- Conversion Large globules in a coarse emulsion to smaller globules when passed through a narrow orifice under pressure PH

34. Various types of Homogenizers
Hand Homogenizer (Emulsifier)
Knaewood Mixer
Silver son– Mixer – Emulsifier
Colloid Mill PH

35. Emulsifier Most commonly used hand homogenizer
Reduction in the globular size increasers with the speed of pumping PH

36. Fig: 34.3 PH

37. Knewood Mixer Effective mixing machine
Effective mixing action because both beaters & axis rotate
producing Planetary action
Due to planetary action mixing of whole of the liquid is
affected Different types of beaters available PH

38. Fig: 34.4 PH

39. Colloid Mill Works on the principle of shearing
Consists of rotor & stator
Gap between rotor stator can be adjusted from
0.005 to cm
Rotor rotates at a speed of 3000 to 20,000 r.p.m. PH

40. Colloid Mill
Material already reduced to fine particles is fed through hopper
Material thrown outward in the mill by centrifugal action.
Material passes through narrow gap between rotor & stator
The size of the material is reduced
Fine particles collected from outlet. PH

41. Fig: 34.5 PH

42. Colloid mill
Fig: 34.6 PH

43. Advantages Useful for preparing pharmaceutical suspensions,
emulsions, lotions, ointments & creams.
Capable of producing particles in micron size.
Size reduction is always carried out in presence of a liquid. PH

44. Objectives Silver son - Mixer- Emulsifier Mixing of powders
Factors affecting Mixing of powders
Mechanisms of mixing. PH

45. Silverson Mixer – Emulsifier
Consists of emulsifying head which consists of number of blades & covered with fine mesh sieve.
Blades rotate at a very high speed to produce shearing action PH

46. Silverson Mixer – Emulsifier
The emulsifying head is rotated by means of motor & immersed in the liquids to be emulsified
The liquids to be mixed are sucked through fine mesh & subjected to vigorous mixing by high speed rotation of blades. PH

47. Silverson Mixer – Emulsifier
The mixed material is then expelled out with a great force.
Sucking in & forcing out of the liquid continuously goes on
In this way the liquids to be mixed are made to pass repeatedly through the emulsifying head PH

48. Silverson Mixer – Emulsifier
By this large size globules are effectively reduced to small
size globules.
Various sizes of mixers available
Mixing capacity varies form 9 liters to 9000 liters. PH

49. Silverson Mixer
Fig: 35.1 PH

50. Factors affecting mixing of powders
Particle size:- Particle size & particle size distribution is important
Difference in particle size can lead to segregation as smaller
particles will slide past the larger ones through the voids
between them. PH

51. Mixing of powders Powders are examples of neutral mixtures.
Powder mixing is quite different from liquid mixing.
Powder mixing is an operating in which 2 or more than two solids in particulate form are intermingled randomly in particles PH

52. Factors Affecting Mixing of Powders
Particle shape:
Spherical particles are easier to mix than irregular shaped particles
Risk of segregation is less from particles of
irregular shape
Better inter - locking properties
Compromise between the two is ideal for uniform mixing PH

53. Factors Affecting Mixing of Powders
Material Density:
Material with different densities are difficult to mix uniformly
Heavier particles have a tendency to slide down & settle at the bottom
Therefore it is necessary that the material should be of the same densities PH

54. Factors Affecting Mixing of Powders
Particle attraction:
Materials with different surface charges can lead to segregation
This effect increases as the size of the particle decreases
Particles with same electrostatic charges lead to aggregation of powder PH

55. Factors Affecting Mixing of Powders
Proportion of powders to be mixed:
Relative proportions of materials to be mixed play an important role
Easy to mix equal quantities of two powders
In cases of a smaller quantity of one powder with larger quantity of another - they are to be mixed in ascending order of their weight PH

56. Mechanisms of mixing Convective mixing:
Mixing of powders is generally achieved by a combination of one or more of the following mechanisms
Convective mixing:
Takes place by the bulk transfer of groups of particles from one part of powder bed to another by means of blades or paddles PH

57. Mechanisms of mixing Shear mixing: Diffusive mixing:
Take place due to setting up of slip planes within the mass of the material
Diffusive mixing:
Occurs when random movement of particles within a powder bed cause them to change their relative positions in relation to one another PH

58. Objectives Equipment used for mixing of powders Tumbler Mixers
Agitator Mixers PH

59. Equipment used for Mixing of powders
Tumbler Mixers
Agitator mixers PH

60. Tumbler Mixers Construction:
Consists of metallic vessels which are rotated on their
axis at a slow speed.
The mixing vessel are made up of stainless steel & have
doors for loading and unloading of the materials.
Tumbler mixers are available in a variety of shapes and
sizes PH

61. Tumbler Mixers
They are Y-cone blender, cubical blender, double cone blender, V-shaped mixer and cylindrical tumbler mixer.
Y-cone, cubical and double cone blender are most popular. PH

62. Tumbler Mixers Y-cone blender has three arms projecting in different
directions
Cubical blender has a cubical shape while the double
cone blender consists of a shallow drum with two conical
ends. PH

63. Tumbler Mixers Working:
Materials to be mixed are loaded into the mixing vessel which is rotated at a slow speed by means of an electric motor.
Due to slow speed of rotation, the material is raised
along the sides of the vessel PH

64. Tumbler Mixers The powder then tumbles down & mixing occurs.
Vessel should not be rotated at high speed.
Because the powder material shall be held along with the side of the vessel by centrifugal force & shall not fall down.
Hence no mixing take place . PH

65. Tumbler Mixers
The vessel is allowed to rotate for the required period of time .
These mixers are commonly used for mixing of powders
and granules during tabletting PH

66. Fig: 36.1 Tumbler Mixers PH

67. Fig: 36.2 PH

68. Fig:36.3 PH

69. Fig: V-Cone Blender PH

70. Agitator powder mixers
Construction:
The agitator powder mixer consists of a stationary vessel in which a central shaft with helical blades is fitted.
The shaft is rotated by means of an electric motor. PH

71. Agitator powder mixers
Working:
The material to be mixed is loaded into the vessel and the blades are allowed to rotate at a slow speed .
The blades produce a continuous cutting and shuffling motion and cause the powder material to flow in rotational as well as transverse direction.
Any powder agglomerates in the material are broken down by the shearing action that develops between the moving blade and trough.
Agitated powder mixers are quite suitable for blending free flowing materials having components of preferably the same size and density. PH

72. Fig: 36.5 Agitated Power MixerPH

73. Fig: 36.6 Agitator powder mixerPH

74. Objectives 1. Mixing of semisolids
2. Equipment used for semisolid mixing
- Planetary mixer
Sigma blade mixer
Triple roller mill PH

75. Mixing of Semisolids
Process involved depends on the properties of materials.
Many semisolids form neutral mixtures.
Show little tendency of segregation.
Major problem is poor flow characteristics.
So diffusive & convective mixing is not possible.
Hence mixers with high mixing capacity are generally
employed. PH

76. Equipment used for semi solid mixing
Planetary mixers
Triple roller mill PH

77. Fig: 37.1 Planetary Mixer PH

78. Fig : 37.2.Schematic Diagram of Planetary MixerPH

79. Planetary Mixers Construction: Also called as change-can mixers
Consists of mixing paddles fixed on the rotating arm.
Arm rotates about its own axis and also travels in a circular path around the mixing vessel.
Movement is alogous to that of planes.
Various size and shapes of paddles available.
The paddle is shaped to the size of the vessel. PH

80. Working: Material is loaded in the vessel
Paddle is rotated at a slow speed .
The small clearance between the mixing vessel and
paddle provides a kneading and shearing action which ensures mixing of the material.
Intermittent scrapping also required to ensure perfect
and uniform mixing. PH

81. Fig: 37.3 Schematic Diagram of Tripple Roller MillPH

82. Triple Roller Mill
Various types of roller mills consisting of one or more rollers are commonly used.
In pharmaceutical industry Tripple roller mill is generally preferred for mixing ointments. PH

83. Construction:
Mill is fitted with 3 rollers which are made of hard abrasion resistant material
They are arranged in close proximity to each other.
They are rotated at different speeds
The rollers are mounted horizontally with very small gap in between.
Gap can be adjusted.
The material coming between the rollers is crushed depending on the gap and also sheared by the difference in their speeds. PH

84. Working: Materials to be mixed are fed in the hopper though the gap
Arranged to pass though the gap in between the rollers B and C where it is reduced in size.
Then the material is passed between the rollers C and D, where it is further reduced in size.
Smooth mixture is obtained . PH

85. Working
The Gap between rollers C and D is usually less that the gap between B and C.
After passing the material between rollers C and D, the smoothened mixture is continuously removed from roller D by means of scrapper E.
From there, it is collected in a receiver PH

86. Uses
Triple Rollers mill is often used for mixing of solid ingredients in semisolid base like Ointments PH

87. Objectives 1. What is meant by “Mixing” & “Homogenization”
2. Mixers used in mixing of liquids, solids and semisolids PH

88. Definition of Mixing Mixing: In pharmaceutical Industry:
A process in which two or more than components are
mixed in such a way that each particle of any one
ingredient lies as nearly as possible to the adjacent
particle of other ingredient.
In pharmaceutical Industry:
Process of mixing is used in the formulation of solutions,
emulsions, suspensions, powders, ointments and creams PH

89. Type of mixtures: Mechanisms of mixing:
1. Positive mixtures eg; Two miscible Liquids
2. Negative mixtures eg: Suspensions & Emulsions
3. Neutral mixtures eg: Pastes & ointments
Mechanisms of mixing:
Convective mixing
Shear mixing
Diffusive mixing PH

90. Liquid Mixing Mixing of liquids & liquids: Mixing of liquids & Solids:
Mixing of two miscible liquids Eg: Solutions
Mixing of two immiscible liquids Eg: Emulsions
Mixing of liquids & Solids:
Mixing of liquids & soluble solids Eg: Solutions
Mixing of liquids & insoluble solids Eg: Suspensions. PH

91. Liquid Mixing On small scale emulsions & suspensions can be prepared
by using mortar & pestle
Emulsions are prepared in 2 stages :
primary emulsion and
secondary emulsion. PH

92. Equipment used for liquid mixing
Propeller Mixers
Paddle Mixers
Shaker Mixers
Turbine Mixers PH

93. Propeller Mixer These are used for mixing liquids of low viscosity
Propeller rotates at a very high speed up to 8000 rpm
Turbine mixers used for liquids of low high viscosity and
rotate at lower speed than propellers
In paddle mixers, paddles rotate at low speed of 100rpm
Effectively mix viscous liquids & semisolids PH

94. Homogenization Definition: Various types of Homogenizers:
Process of conversion of coarse emulsion into colloidal
state of uniform composition.
Equipment used for this process – homogenizers
Various types of Homogenizers:
Hand Homogenizer
Silverson – mixer – emulsifier
Colloid mill PH

95. Principle involved in homogenizers
Conversion of large globules in a coarse emulsion to
smaller globules when passed through a narrow orifice
under pressure.
Colloid mill:
Used for preparing suspensions , emulsions lotions,
ointments and creams.
Widely used homogenizers are Silverson mixer- emulsifier
and colloid mill PH

96. Mixing of powders: Factors affecting mixing of powders
Particle size , particle shape , material density, particle
attraction, proportion of powders to be mixed.
Mechanisms of mixing :
Convective mixing , shear mixing, diffusive mixing PH

97. Equipment used for mixing of powders:
Tumbler mixers,
Agitator mixers,
Double cone mixer
Semisolid mixing:
Equipment used for semisolid mixing
Planetary mixer
Triple roller mill PH

98. Most commonly used mixers for mixing are semisolids
Planetary mixers & sigma blade mixers
Triple roller mill is often used for incorporating solid medicaments into ointment bases PH