2. Sieve Analysis
This test is performed to determine The
percentage of different grain sizes contained
within a soil
Is performed to determine the distribution of a
coarse ,large-sized particles, and the
hydrometer method is used to determine the
distribution of the fine particles.
PURPOSE
9. ➔ Sedimentation is a method of
separating entities based on their
particle size
➔ It’s the process where a solid
material gets deposited from a
state of suspension or solution, in
a fluid.
Sedimentation
analysis
10. ➔ Sedimentation method is used for particle sizes
ranging from 1 micrometer to 200 micrometers.
➔ There are 3 commonly used methods:
1. Andreasen pipette
2. Balance
3. Hydrometer
➔ All these methods depend on the idea that the
terminal velocity of a particle in fluid is directly
proportional to its size.
Methods
11. ● The Andreasen apparatus consists of a 200 mm graduated
cylinder which can hold up to 500ml of suspension fluid.
● A pipette is located at the center of the cylinder and its held in
position by a ground glass stopper so that its tip coincides with
the zero level.
● A three way tap allows fluid to be drawn into a 10ml reservoir
which can then be emptied into a beaker of centrifuge tube.
12. ● Allow a homogenous suspension to settle in a cylinder, take
samples from the settling suspension at a fixed horizontal level
over intervals of time.
● Each sample will contain a representative sample of the
suspension, all of which have settled below the level of the
sampling point.
● The concentration of solid in a sample is taken at a time t.
● This concentration is expressed as a percentage of the initial
concentration, gives us the percentage of particles whose falling
velocity are equal to or less than x/t. Substitution in the equation
below gives us the corresponding stokes' diameter.
Procedure
13. Stoke’s diameter is defined as the diameter of the
sphere that would settle at the same rate as the
particle
14. ● The equipment required are simple to use and
inexpensive.
● You can measure a wide range of sizes with
accuracy and the results can be reproduced,
increasing it’s reliability.
Advantages &
Disadvantages
15. ● Sedimentation analyses must be carried out at concentrations
which are low enough for interactive effects between particles
to be negligible. This is so that the terminal velocities can be
assumed to be equal to those of the isolated particles.
● Careful temperature control is necessary to suppress
convection currents
● Large particles create turbulence, causing them to slow down
and get recorded as undersized.
● Particles have to be completely insoluble in the suspending
liquid.
Advantages &
Disadvantages
