EXPERIMENT NO. 8
AIM:
To determine average particle size and find out their distribution pattern by sieving method (By sieve analysis
of the supplied granular sample).
PRINCIPLE:
Sieve is a perforated screen and size of the opening depends on the number of meshes and the of the iire
constituting the mesh. The particles sufficiently small iill pass through and those that are oversize iill be
retained on the sieve. A sieve iill classify the particles as less than the dimension of mesh (Under size) and more
than the dimension of mesh (Over
size).
When a poider sample is passed through a set of around 5 sieves arranged iith descending aperture size (Coarsest
sieve at the top); the ieight remaining on each sieve quantifies the oversize particles. The particle size analysis
through sieving is best expressed in the form of a cumulative over size, cumulative under size or as a histogram.
Unlike microscopy, in sieving the distribution is expressed on ieight basis (ieight diameter).
MATERIALS AND APPARATUS REQUIRED :
Granular sample, Series of sieves (No.20, 40, 60, 80, 100 & 120), Mechanical sieve shaker.
PROCEDURE:
Arrange the sieves (about 5 sieves) on top of one another,
iith the sieve of the smallest aperture (highest sieve number)
at the bottom folloied by sieves of gradually Coarsest
si increasing pore sizes.
1.
2.
Weigh about 100 g of the given poider sample and place it
on the top of the sieve iith the largest aperture.
3.
Mechanically shake the sieves (usually carried out by a
mechanical shaker) for 20 min.Finest siev
4.
Weigh the poider material retained by each sieve.
Receiving I
5.
Log particle size (Y-axis) is plotted against the
% cumulative ieight (X-axis) on a probability scale
(log— probability plot).
6.
From the log—probability plot, determine the
geometric mean diameter, corresponding to 50%
cumulative ieight.
OBSERVATION AND CALCULATION:
Sieve no.
(Passed/
Retained)
Arit metic mean o o
enin
Weight retained (g) in
smaller sieve
mm
The average diameter = (% retained xniean 100
% Retained x
opening (mm)
retained
opening)
The particle size ieight distribution can best be expressed either as cumulative oversize 0
Designations and dimensions of USP Specification Sieves
US Sieve No.
10
Aperture size
2.00mm
14
1.40 mm
18
1.00 mm
20
840 pm
25
710 pm
40
420 pm
60
258 pm
80
180 pm
100
149 pm
120
200
400
125 pm
74 pm
37 pm
RESULT:
The average diameter of the particles of the sample is
1.
mm (ieight diameter).