Hydrometer Method of Sedimentation Analysis for Particle Size Distribution
Hydrometer method is a popular method to determine particle size distribution. The He in the pipette method is not constant here; It keeps varying
What is sedimentation analysis?
Sedimentation analysis is based on Stoke’s law.
If sphere is falling in a medium of infinite extent, it’s velocity has been increased due to the gravity effect. After some times forces get balanced and it attains a constant velocity known as the terminal velocity
What are the different methods?
• Pipette Method
• Hydrometer Method
Procedure for Hydrometer Method
The He in the pipette method is not constant here. It keeps varying.
• Here it is not required to draw the sample like in pipette method, we can directly take the specific gravity of the solids using the hydrometer.
• This device works on the principle of buoyancy
Corrections to the hydrometer readings
Meniscus correction Cm
• The correction is positive.
• If the temperature is greater than 27deg then positive
• If the temperature is lesser than 27deg then negative correction.
Deflocculating agent correction Cd
• The correction is negative.
• Sedimentation analysis for particle size analysis is done by pipette and hydrometer method
• Sedimentation analysis is based on Stoke’s law
• There are limitation to Stoke's law
• We assumed the particles are spherical in shape but in practical clay is flaky in shape.
• We have assumed the medium has no boundaries and infinite but we perform the test in a finite medium and there exist many spheres