Introduction:
The hydrometer test is an application of Stokes Law, which in essence states that larger particles fall more quickly in a suspending fluid, while finer particles remain in suspension longer. The time at which the hydrometer readings are taken determines the size of particle remaining in suspension, while the reading on the hydrometer determines the amount of that size.
Aim:
This test is performed to determine the percentage of different grain sizes contained within a soil. The mechanical or sieve analysis is performed to determine the distribution of the coarser, larger-sized particles, and the hydrometer method is used to determine the distribution of the finer particles.
Materials: Fine Grained Soil Sample (oven dried – Approximately 50 grams)
Apparatus :Hydrometer
Mechanical Mixer (Milkshake Maker)
Dispersing Agent
2 Graduated Cylinders and a Glass Beaker
Distilled Water Supply
Balance (0.01g accuracy)
Thermometer
Spatula
Hand Stirrer
Spray Bottle
Timer
Vernier Callipers
Procedure :Approximately 50g of dry soil was weighed and prepared.
The soil is mixed with distilled water to form a smooth thin paste in the mixer cup.
1-2 droplets of the dispersing agent are added from a pipette to the paste and the mixture is washed into the cup of the stirrer by using a spray bottle. Try not to lose any material.
The suspension is mixed using the milkshake maker for about 10 minutes.
While the suspension is being mixed, a graduated cylinder is filled with distilled water – This cylinder will be used to store the hydrometer in between readings.
After mixing, the specimen is washed into the 2nd graduated and enough distilled water is added to bring the level to the 1000cc mark.
The suspension is mixed using a hand stirrer
After stirring it for about 30 seconds (make sure it is well mixed),the hydrometer is inserted correctly.