AZA 0857 PARTICLE SIZE SEDIMENTATION (HYDROMETER METHOD)

Description

Particle Size Sedimentation Hydrometer Method – Azalab

The Particle Size Sedimentation (Hydrometer Method) is a laboratory procedure used for determining the grain size distribution of fine soils, particularly those that are smaller than 75 microns in diameter such as silts and clays. Offered by Azalab, this method is essential in geotechnical engineering, soil mechanics, civil construction, and environmental research to understand the behavior of cohesive soils.

The hydrometer method measures the relative density of a soil-water suspension at different depths and times, using the principle of sedimentation based on Stokes’ Law. As the soil particles settle, the hydrometer records changes in the suspension density, helping determine the percentage of particles of various sizes. AZALAB

Particle size analysis of soils:
Hydrometer method
This equipment is used to determine the quantitative
size distribution of very fine particle in soils such as clay
and silt.
The complete set comprises:
! Sedimentation Cylinder, 1000 ml capacity (6 pieces) with rubber bungs.
! Soil Hydrometer, 151H, range 0.995 to 1.038g/ml with div. 0.001 Glass Tank, dimensions: 600x300x380 mm
! Heater complete with thermostat, circulation unit. 230V Single Phase 50Hz 1000W
! Glass Thermometer, range -10 to 50° C., Sub-div. 0.5° C.
! Beaker, Borosilicate Glass, 250 ml capacity
! Sodium Hexametaphosphate, 1000 g
! High Speed Stirrer, 4000 R.P.M, complete with baffle cup, for dispersing soil
particles in water.

What Is Included in the Apparatus?

• Hydrometer (151H or ASTM Type): Measures relative density (g/L) of soil suspension

• 1000 ml Sedimentation Cylinder: Borosilicate glass cylinder for soil-water mix

• Thermometer: For water temperature correction (typically 0–50°C range)

• Dispersing Agent: Usually sodium hexametaphosphate (user-supplied)

• Measuring Cylinder and Stirring Rod: For consistent sample preparation

• Timing Device: Digital stopwatch for sedimentation tracking

How the Hydrometer Method Works

This method is based on the principle that soil particles of different sizes settle at different rates in a liquid. A representative soil sample is mixed with a dispersing agent and placed in a sedimentation cylinder. Over time, the hydrometer measures the density of the soil suspension at regular intervals (e.g., 2 minutes, 5 minutes, 1 hour, etc.). AZALAB

Each reading provides information about the fraction of particles still suspended in the liquid at that time, allowing precise calculation of the grain size distribution for particles smaller than those measurable by sieving. AZALAB+PRACTICAL SIZE

Applications

• Geotechnical Investigations: Determines soil classification for foundation and earthwork designs

• Soil Mechanics Education: Widely used in universities for academic demonstration

• Civil Engineering: Essential for road, embankment, and dam construction analysis

• Environmental Testing: Classifies sediments in lakes, rivers, and wetlands

Specifications Table

Frequently Asked Questions (FAQ)

Q1: What is the hydrometer method used for?
A: It is used to determine the grain size distribution of fine soils (silt and clay) through sedimentation analysis.

Q2: How accurate is the hydrometer method compared to sieve analysis?
A: It is more accurate for particles smaller than 75 microns, which cannot be classified reliably using sieves.

Q3: Is this method suitable for sandy soils?
A: No, it is specifically intended for fine-grained soils. Coarse particles settle too quickly for accurate hydrometer measurement.

Q4: What standards does this method follow?
A: It complies with IS 2720 Part IV, ASTM D422, and BS 1377.

Q5: Does the apparatus include a dispersing agent?
A: No, but sodium hexametaphosphate can be easily sourced separately for accurate dispersion.