Hydrometer Analysis of Fines Testing objectives: To determine the distribution of fine soil particles by a sedimentation process using a hydrometer . Using this test the grain size distribution for soils containing appreciable amount of fines is obtained.

What is a Hydrometer? Device used to determine directly the specific gravity of a liquid Consists of a thin glass tube closed at both ends Large bulb contains lead shot to cause the instrument to float upright in liquid. Scale is calibrated to indicate the specific gravity of the liquid.

Required Test Equipment Mixer Scale Hydrometer Jar Scale Deflocculating Solution

Measure Sample Collect 50 g of fine from mechanical sieving procedure 1 ft3

Deflocculating Stage Add sample to 125 ml of 40g/L sodium hexometaphosphate (deflocculating solution) Allow to soak for at least 12 hours

Mix sample with spatula to dislodge settled particles

Sample Preparation Pour sample into mixing cup Use distilled water to rinse beaker

Sample Preparation Add distilled water to the soil in mixer cup to make it about two-thirds full. Mix using mixer for two minutes

Sample Preparation Pour the mix into the second graduated 1000-cc cylinder. Make sure that all of the soil solids are washed out of the mixer cup. Fill the graduated cylinder with distilled water to bring the water level to 1000 cc mark

Starting the Test Seal the jar or simply place hand over end and rotate about 60 times. Set the jar on the bench and record the time. This is time (t=0) on your data sheet. Take a hyrdometer reading and temperature reading at prescribed intervals. After each reading the hydrometer is put into the transparent cylinder