pharmaceutics

1. GURUNANAK INSTITUTE OF
PHARMACEUTICAL SCIENCE AND
TECHNOLOGY

2. PROPERTIESOFPOWDER(P0R0SITY
)
PRESENTED BY
•Sumel Ashique. Roll No-80
•Sumit Saha. Roll No-81
•Supratim Das. Roll No-82
B.pharm,2nd yr,3rd sem,Sec-B

3. CONTENTS. . .
Porosity and its evaluation tests
 True Density
Bulk Density
Numerical problems and solutions
Bulkiness
Flow properties of powders
Factors affecting on flow properties

4. Porosity:
The porosity or voids is defined as
the ratio of the void volume to bulk volume.
𝜀 =(VB −𝑉P )/ Vb
=1- Vp / Vb
Void volume = Vb – Vp
Porosity is expressed in percent, 𝜀 × 100
Vb=Bulk volume
Vp=True volume

5. Problems:
I. A sample of calcium oxide powder with a true density of
3.203 and weighing 131.3 gm was found to have a bulk
volume of 82cm3 when placed in a 100 ml graduated cylinder
.calculate the porosity.
The volume of the particle is (131.3g /3.203gcm-3 ) =41cm3
𝜀 =(vb- vp)/ vb
=(82-41)/ 82
=0.5× 100=50%

6. Densities of Powders:
It is defined as the mass per unit
volume.
Types of density:
There are three types of densities based
on the determination method :
 True Density.
 Bulk Density.
 Granule Density.

7.  True Density (𝝆):
Defined as the volume of the pores
and voids within the sample.
 Bulk Density (𝝆b)
Defined as the volume of all of the
pores within the sample.
 Granule Density(𝝆g)
Defined as the ratio of the mas of the
granular powder and granule volume.

8. Bulkiness:
The reciprocal of bulk density
is known as the bulkiness or
specific bulk volume.
• It increases with a decreases in
particle size.
• It may get reduced since the
smaller particles may shift
between the larger ones.

9.  Flow properties:
Flow properties of powder is in an
important parameter in the production of
pharmaceutical dosage forms. It may be free
flowing or may have poor flow.
Reasons of poor flow:
• Cohesiveness between particles due to
van der waals, electrostatic forces.
• Adhesion between the particles and the
container wall.
• Friction between particles.

10. Test to evaluate the flow ability
of a powder
Carrs Compressibility Index:
A volume of powder is filled into a graduated glass
cylinder and repeatedly tapped a known duration.The volume of
powder after tapping is measured.
Carrs Index (%) = Tapped density- Bulk density
Bulk density =Weight/bulk volume
Tapped density=Weight/ true volume

11. Relationship between powder flowability and %
compressibility:
• Flow Description Compressibility
Excellent flow 5-15
Good 16-18
Fair 19-21
Poor 22-35
Very poor 36-40
Extremely poor > 40

12. Hausner Ratio:
H.ratio =Tapped density / Bulk density
• It is related to inter particle friction.
• Values less than 1.25 indicates good flow ( coarse
spheres) and greater than 1. 5 indicates poor flow .(
flakes)
• Between 1.25 and 1.5 added glidant normally improves
flow.
• > 1.5 added glidant does not improve flow.

13. Factors affecting the flow properties of powders
• Particle size distribution: ↑ the average particle size improves the flow
properties due to reduction in the cohesive forces.
• Particle shape and texture: spherical particles have better flow ability
as compared to irregular particles.
• Surface forces: Reduction of electrostatic charges can improve powder
flow ability .Drying of particles will reduce the cohesiveness and ↑
𝑓𝑙𝑜𝑤.
• Addition of fines: presence of small portion of fines in a powder may
improve the flow properties.
• Flow activators:↑
𝑡ℎ𝑒 𝑓𝑙𝑜𝑤𝑎𝑏𝑖𝑙𝑖𝑡𝑦 𝑏𝑦 𝑟𝑒𝑑𝑢𝑐𝑖𝑛𝑔 𝑎𝑑ℎ𝑒𝑠𝑖𝑜𝑛 𝑎𝑛𝑑 𝑐𝑜ℎ𝑒𝑠𝑖𝑜𝑛.

14. REFFERENCE…
Micromeritics and powder Rheology ;Physical
Pharmacy; S.P Agarwal, Rajesh Khanna; page no-
38,39,40,.41,42,43,44,45;CBS publishers; Second
edition.