MICROMERITICS & PRECIPITATION

Micromeritics is the science and technology of small particles.
Precipitation is the process of separation of the solid substance from a solution:

1. MICROMERITICSMICROMERITICS
&&
PRECIPITATIONPRECIPITATION
Dr. Asra Hameed Dr. Asra Hameed
Pharm.D (JUW) Pharm.D (JUW)
[email protected][email protected]

2. CONTENTS :
MICROMERITICS :
Definition & Origin of the term
“MICROMERITICS”
Applications
Factors affecting the flow
properties of powders
Particle size analysis
Particle size reduction
Bulk density
True density
Porosity
Importance of particle size

3. MICROMERITICS:
Micromeritics is the science and technology
of small particles.
 The knowledge and control of the size of
particles is of importance in pharmacy.
 The size, and hence the surface area of a
particle, can be related to the physical,
chemical & pharmacologic properties of
drugs.
Clinically, the particle size of a drug can
affect its release from dosage forms that
are administered orally, parenterally,
rectally & topically.
The successful formulation of suspensions,
emulsions & tablets; both physical stability
& pharmacologic response also depends
on the particle size achieved in the product.

4. Origin:
The term was created by. J. M. Dalla Valle in
his book MICROMERITICS THE
TECHNOLOGY OF FINE PARTICLES.
It was derived from the Greek word for: small
and part.
The size range which he covered in the book
was from 10−1 to 105 micrometers.
 Anything smaller than this but bigger than a
molecule were referred to at the time as
colloids but are now often referred to as
nano particles..

5. Applications:
Release & dissolution
Particle size & surface area influence the release
of a drug from a dosage form that is
administered orally, rectally parenterally &
topically. Higher surface area brings about
intimate contact of the drug with the
dissolution fluids in vivo & increases the drug
solubility & dissolution.
Absorption & drug action
Particle size & surface area influence the drug
absorption & subsequently the therapeutic
action. Higher the dissolution, faster the
absorption & hence quicker & greater the drug
action.

6. Applications:
Physical stability
Micromeritic properties of a particle i.e the
particle size in a formulation influences the
physical stability of the suspensions &
emulsions. Smaller the size of the particle,
better the physical stability of the dosage
form owing to the brownian movement of the
particles in the dispersion.
Dose uniformity
Good flow properties of granules & powders are
important in the manufacturing of tablets &
capsules. The distribution of particles should
be uniform in terms of number & weight.

7. Factors affecting the flow properties
of powders:
1.Particle’s Size and
Distribution
 2.Particle Shape &
texture
 3.Surface forces
 4.Flow Activators

8. Particle’s size & Distribution:
There is certain particle size at which
powder’s flow ability is optimum.
Coarse particles are more preferred than fine
ones as they are less cohesive.
 The size distribution can also be altered to
improve flow ability by removing a
proportion of the fine particle fraction or by
increasing the proportion of coarser
particles, such as occurs in granulation.

9. Particle Shape & texture:
Particle’s Shape:
 Generally, more spherical particles have
better flow properties than more irregular
particles. Spherical particles are obtained
by spray drying, or by temperature cycling
crystallization. - Flow activators are
commonly referred as glidants.
- Flow activators improve the flow ability
of powders
by reducing adhesion and cohesion.
e.g. talc, maize starch and magnesium
stearat
Particle's texture:
particles with very rough surfaces will be
more cohesive and have a greater
tendency to interlock than smooth
surfaced particles.

10. Surface Forces:
Reduction of electrostatic charges can
improve powder flow ability. Electrostatic
charges can be reduced by altering process
conditions to reduce frictional contacts.
Moisture content of particle greatly affects
powder’s flow ability.
Adsorbed surface moisture films tend to
increase bulk density and reduce porosity.
Drying the particles will reduce the
cohesiveness and improve the flow.
Drying the particles will reduce the
cohesiveness and improve the flow.

11. Flow activators:
Flow activators are commonly referred
as glidants.
Flow activators improve the flow ability
of powders by reducing adhesion and
cohesion.
e.g. talc, maize starch and magnesium
stearat

12. Methods for determining particle size:
1- Optical microscopy
(range: 0.2 –100 um):
The microscope eyepiece is
fitted with a micrometer by
which the size of the
particles may be estimated.
3.0 Instrumentation
Several important features
are visible:
Lenses
Eyepieces (oculars)
Light source
Camera

13. Methods for determining particle size:
2- Sieving (range: 40-
9500μm):
Standard sized sieves are available to cover a
wide range of sizes. These sieves are designed
to sit in a stack so that material falls through
smaller and smaller meshes until it reaches a
mesh which is too fine for it to pass through.
The stack of sieves is mechanically shaken to
promote the passage of the solids.
The fraction of the material between pairs of
sieve sizes is determined by weighing the
residue on each sieve.
The result achieved will depend on the
duration of the agitation and the manner of the
agitation.

14. Methods for determining particle size:
3-Sedimentation
The tendency for particles in
suspension to settle out of the
fluid in which they are
entrained, and come to rest
against a barrier.
It is the deposition or
accumulation of sediment.
In this method large particles
settle down rapidly while
smaller particles take some
time to settle down, so
sedimented particles are taken
out by the tube from the bottom
and remaining are the fine
particles.

15. Methods for determining particle size:
4-ELUTRIATION
The process of separating
the lighter particles
from the heavier ones
by means of an upward
direction.
the process of elutriating
is to purify, separate, or
remove (ore, for
example) by washing,
decanting, and settling.

16. Size Reduction
Four commonly used methods
for size reduction:
Compression
Impact
Attrition
Cutting

17. Size reduction equipment
Size reduction equipment is
divided into crushers, grinders,
ultra fine grinders, and cutting
machines
Crusher (coarse and fine, Jaw
crushers etc) do the heavy work
of breaking large pieces of solid
material into small lumps.
Grinders(intermediate and fine,
Attrition mills, Hammer mills,
impactors) reduce crushed feed to
powder. The product from an
intermediate grinder might pass a
40-mesh screen; most of the
product from a fine grinder would
pass a 200-mesh screen with a
74mm opening.

18. Size reduction equipment
An ultra fine grinder
(Fluid-energy mills,
Hammer mills with
internal classification etc)
accepts feed particles no
larger than 6mm and the
product size is typically 1
to 5m m.
Cutters(Knife, cutters ,
dicers, slitters)give
particles of definite size
and shape, 2 to 10mm in
length.

19. Bulk Density
Bulk density is a property of
powders, granules and other
“divided” solids, especially
used in reference to mineral
components (soil), chemical
substances, (pharmaceutical)
ingredients, foodstuff etc.
It is defined as the mass of
particles of the material divided
by the total volume they occupy.
Bulk density=mass/volume as a Bulk density=mass/volume as a
wholewhole
The sum of the two gives the bulk
volume:
Vb = Vgr + VpVb = Vgr + Vp

20.  True density
The density of the
particles that makeup a
powder or particulate
solid, in contrast to bulk
density, which measures
the average density of a
large volume of the
powder in a specific
medium (usually air).
It is defined as the mass
of particles of the
material divided by the
true volume of particles.
True density=mass/real volumeTrue density=mass/real volume

21. Porosity
Porosity is a measure of the
void spaces in a material,
and is measured as a
fraction, between 0–1, or as
a percentage between 0–
100%.
The porosity is defined as the
ratio of the pore volume to
the bulk volume, for
example,

22. Importance of particle size
BY SIZE REDUCTION;BY SIZE REDUCTION;
Increase the surface area of drugs
Easier & uniform mixing
Rate of drying is enhanced
Increase stability of emulsion
Increase rate of adsorption
Physical appearance improved
(ointments, paste & creams).
Stability of some drugs increase in powder
form & decrease in solution form
Powder drugs are easily administered than
solid dosage form.
In suspension, cake form which quickly
redisperse upon shaking.

24. Contents
Precipitation:
Definition of the term
“PRECIPITATION”
Process of precipitation
Precipitate
Precipitant
Supernatant liquid
Applications

25. PRECIPITATION
Precipitation occurs through a
chemical reaction that forms an
insoluble compound out of two
or more soluble compounds.
Precipitation is the process of Precipitation is the process of
separation of the solid separation of the solid
substance from a solution:substance from a solution:
 Either by altering the
substance to an insoluble form,
Or by altering the solvent
composition to lessen the
solubility of the substance in it.

26. Process Of Precipitation
Precipitation Reactions occur when
cations and anions of aqueous
solutions combine to form an
insoluble ionic solid, called a
precipitate.
The most important method for
precipitation is by displacement
reaction taking place in the
solution,
 In which more active metal
displace inactive or less active
metal.

27. Precipitate
When the reaction occurs in a
liquid, the solid formed is called
the Precipitate.
Precipitant
A substance that causes a
precipitate to form when it is
added to a solution or
suspension.
Supernatant liquid
The liquid remaining above the
solid is in either case called the
supernate or supernatant.

28. Applications
It is used for:
The separation of metal ions in aqueous
solution
The analysis of metal ions in aqueous
solution
The preparation of some of the substance
The Purification of some of the substance

29. Applications
Separation
The precipitate forms
because the solid
(AgCl) is insoluble in
water.
That is true for all
precipitates - the
solids
are insoluble in
aqueous solutions.

30. Applications
Preparation
White lotion is prepared by
precipitation
Purification
The process of recrysallization is to
be done in purification.
In which impure solid is absorb in the
suitable solvent at increased
temperature.
After cooling, much of impurities
remain absorbed in the solvent
while the purified solid is
precipitated.