This slide is about small particles. You will find here introduction about micromeritics, its fundamental and derived properties.

1. Micromeritics

2. Presented by-
MUH1903003F
Mst. Jannatul Mawa
ASH1903001M
Nazmul Huda Nabil
ASH1903004M
Niladry Datta
BKH1903007F
Alima Khatun
ASH1903008M
Khandaker Abir Hasan
ASH1903010M
Md. Ismail Hosen
ASH1903011M
Saifur Rahaman
ASH1903015M
Milon Kumar Sarkar

3. 1
2
3
4
Topics
Introduction of micromeritics
Importance of micromeritics in
the field of pharmacy
Fundamental properties of particle
I Particle size and size distribution
II Particle shape
III Particle volume
IV Particle surface area
Derived properties
I Particle density

4. 4
Introduction
What is micromeritics?
The science and knowledge of small particles is
known as micromeritics.
It is the study of fundamental and derived
properties of individual as well as a collection of
particles.
The name micromeritics was given by Dalla Valle.
 Micromeritics deals with –
 Particle size and size distribution
 Methods of determining particle size
 Particle shape and surface area
 Pore size
Unit : Micrometer or 10-6 m

5. Importance
2
3
Drug release and dissolution
Particle size and surface area influence the release
of a drug from a dosage form that is administered
orally, rectally, parenterally and topically.
Absorption and drug action
Particle size and surface area influence the drug
absorption and the therapeutic action. The higher
the dissolution, the faster the absorption.
Physical stability
The particle size in a formulation, influence the
physical stability of the suspension and emulsion.
The smaller the size of the particle, the better the
physical stability of the dosage form.
1

6. Importance
4
5
6
Dose uniformity
Particle size and shape also governs flow properties of
powders and granules in tableting. The distribution of
particles should be uniform in terms of number and
weight.
Flowability
Granulation technique convert powder into granule of
uniform size to increase flow property.
Compressibility
Small particle size enhance compressibility.
7 Others
Small particle size enhances mixing, drying and
extraction of pharmaceutical formulations.

7. Properties
1 Fundamental Properties
a. Particle size and size distribution
b. Particle shape
c. Particle surface area
d. Particle volume
e. Particle number
2 Derived Properties
a. Density of particles
I. Bulk density
II.Granular density
III.True density
b. Flow properties of particles
c. Porosity
d. Bulkiness

8. FUNDAMENTAL
PROPERTIES

9. Particle Size 9
Any collection of particles is usually polydisperse.
It is therefore necessary to know not only the size of a certain particle, but
also how many particles of the different size exist in the sample.
Particle size is related to the shape and surface area of individual particle.
5 0.0110
Increase in Particle Size
Decrease in flow properties

10. 10

11. Particle Shape
 According to their shape particles are divided into two groups.
1.Symmetrical particle
2.Asymmetrical particle

12. Particle Shape
Symmetrical particle
The particle having specific crystal shape can be expressed in term of their
diameter known as symmetrical particle.
For example: Spherical shape.
Advantage:
 If we know the diameter of spherical particle we can easily determine its
surface area and volume.

13. Particle Shape
Asymmetrical particle
The particle which have no specific crystal shape known as asymmetrical particle.
As the asymmetry of particle increases then the surface area and
volume of the particle also become complex to be determined.
In order to determine their surface area and volume four different
types of equivalent diameter are used. i.e.
• Surface diameter
• Volume diameter
• Projected diameter
• Stokes diameter

14. Expression of Particle in Diameter
The size of a sphere is readily expressed in terms of its diameter.
Surface diameter, ds, is the diameter of a sphere having the same surface
area as the asymmetric particle.
r
ds = 4r2
 Volume diameter, dv, is the diameter of a sphere having the same volume
as the asymmetric particle.
r
dv =
4
3
r3

15. Expression of Particle in Diameter
Projected diameter, dp, is the diameter of a sphere
having the same observed area as the asymmetric
particle.
Stokes diameter, dst, is the diameter which describes
an equivalent sphere undergoing sedimentation at
the same rate as the asymmetric particle.

16. Particle Size Distribution 16
The particle size distribution in a powder may be quantified by one of the
following two ways.
1. Number particle size distribution
In this technique we count the number of particle in specific size range.
The number of particle are usually calculated by microscopic technique.
2. Weight particle size distribution
In this technique we weight the particle in specific size range. The
weight of the particle is usually calculated by sedimentation or
sieving method.

17. Particle Size Distribution
Frequency Distribution Curve
If the number or weight of particle is plotted against
their size range a frequency curve is obtained. This
curve is known as frequency distribution curve.
Such frequency curve can give a visual representation
of the distribution which an average diameter can not
achieve.
It is possible that two or more sample have the same
diameter but different frequency distribution.

18. Particle Volume 18
 Volume is the quantity of three-dimensional space enclosed by a closed surface.
• SI unit: Cubic meter
• SI base units: 1 m3
• Dimension: L3
 There are some particle volume such as:
1.Bulk volume
2.True volume
3.Void volume
4.Tapped volume
5.Granular volume

19. Particle Volume
1. Bulk volume
Bulk volume is the total volume of void and solid material.
Solid volume is the volume occupied by the solid material
only, i.e. not including porosity.
Mathematically, Vbulk = Vvoid + Vsolid
2. True volume
True volume is the volume of the particles excluding the inter
and intra particulate spaces in a powder.
True volume = Bulk volume – Void volume

20. Particle Volume
3. Void volume
The volume of the pores or space between particles is known as void volume.
Void volume = Bulk volume – True volume
4. Tapped volume
The apparent powder volume obtained under standard conditions of tapping.
5. Granular volume
Granular volume is the volume of powder itself and volume of intra particulate
spaces.

21. Particle Surface Area
 The surface area of a solid particle is a measure of the total
area that the surface of the particle occupies.
 Surface area of a sphere is given by-
S = d2
While its volume is given by-
V =
d3
6
 Spherical particles have minimum surface area and better
flow properties.
 Particle size and surface area inversely related to each other.
As the particle size decreases, surface area increases which
in turn increases the solubility and dissolution .
d
S = d2

22. Particle Surface Area
 The more asymmetric a particle, the greater is the surface area per unit volume.
 If particle shape is not spherical, then
Surface Area = sdp
2 = ds
2
Here,
s = Surface area factor
ds = Equivalent surface diameter
dp = Projected diameter
 Surface of particle area can be determined by –
a. Adsorption method
b. Air permeability method

23. Particle Surface Area
The Specific Surface
The specific surface is the surface area per unit volume (Sv) or per unit weight (Sw).
Sv =
Surface area of particles
Volume of particles
Sw =
Surface area of particles
Weight of particles

24. DERIVED
PROPERTIES

25. Particle Density
Density is universally defined as the weight per unit volume (w/v).
Based on method of determination, three types of densities can be distinguished.
1. True density
2. Granule density
3. Bulk density

26. Particle Density
1. True density
It is the density of the actual solid material devoid of free spaces and is
defined as the ratio of the given mass of a powder and its true volume.
True density =
True mass
True volume
The true density of a powder may be determined by the following methods:
a. Liquid displacement method
b. Gas displacement method

27. Particle Density 27
Granule density is the ratio of the mass of
the granular powder and the volume
occupied by the granular material
together with its intraparticle spaces.
Granule density =
Mass of the granular powder
Granule volume
Granule density is determined by the
displacement of mercury.
2. Granule density

28. Particle Density
3. Bulk density
Bulk density of a powder is determined as the ratio
of the mass of the powder and its bulk volume.
Bulk density =
Mass of the powder
Bulk volume

29. Particle Density
Comparison Between Densities of Tablet Granulations

30. Conclusion
Knowledge and control of the size and the size range of particles have profound
importance in pharmacy. Size, shape and surface area of particles can be
related in a significant way to the physical, chemical and pharmacologic
properties of a drug. And, micromeritics is the study of fundamental and
derived properties of individual as well as collection of particles.