1. Lab 7– Powder Micromeritrics
Physical Pharmacy
Lab 7– Powder Micromeritrics

2. Particle size analysis
Powder flow

3. Particle Size Analysis
Microscopy
Sieving
Sedimentation techniques
Optical and electrical sensing zone method
Laser light scattering techniques
(Surface area measurement techniques)

4. Particle size

5. Sieve method
Sieve analysis is performed using a nest or stack of sieves where each lower sieve has a smaller aperture size than that of the sieve above it.
aperture size or mesh size (or sieve number).
The mesh size is the number of wires per linear inch.

6. Sieve method
Sieve diameter dA: The width of the minimum square aperture through which the particle will pass (see text and

7. Advantages
Easy to perform
Wide size range
Inexpensive
Disadvantages
Known problems of reproducibility
Wear/damage in use or cleaning
Irregular/agglomerated particles
Rod-like particles : overestimate of under-size
Labour intensive

8. Procedure Instruments
Analytical Sieves
Analytical balance
Weigh about 50 gm of the given granules on analytical balance.
Switch on the analytical sieve machine, set the amplitude at 1 and the time of mechanical vibration on 5 minutes.
Add the given amount of the powder granules to the coarsest sieve on the top and push start to initiate mechanical vibration.

9. 4. After the vibration have stopped, weigh the granules or powder in each of the sieves with recording its corresponding number and particle size. 5. Calculate the percentage weight of powder at each of the size ranges by the following equation: % Retained =
weight in the sieve number x
X 100
total weight

10. 6. Make a table as follows
7. Build a histogram using Microsoft Excel or graph paper, between particle size of different sieves and % retained

11. Powder Micrometrics & Flow
General factors that affect flow powders
Size
Shape
porosity
Density
Humidity

12. Angle of Repose
The maximum angle possible between the surface of pile of non-cohesive (free-flowing) material and the horizontal plane.
Related to the interparticulate friction and resistance to flow

13. Different angles of reposes can be obtained for the same powder because of the differences in the way the samples were handled.

14. Procedure ( Angle of repose)
Take a certain amount of powder and Form the angle of repose on a fixed base, the base should be free of vibration
Vary the height of the funnel to carefully build up a symmetrical cone powder. Care should be taken to avoid vibration as the funnel is moved.
The funnel height should be maintained approximately 2-4 cm from the top of the powder pile as its us being formed in order to minimise the impact of falling powder on the tip of the cone.
Determine the angle of repose by measuring the height of the cone of the powder and calculating the angle of repose from the following equation: