Hydrometer Analysis

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  • Topic: Particle size distribution, Sieve analysis, Silt
  • Pages : 4 (866 words )
  • Download(s) : 321
  • Published : March 21, 2011
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Date: March 3, 2011

Hydrometer analysis is used to determine the grain-size distribution of a soil which is similar to the sieve analysis done in an earlier lab. Hydrometer analysis can be combined with the sieve analysis to determine the amounts (percents) of fines (silts and clays) in a sample.

The hydrometer analysis doesn’t require the soil to be passed through a series of sieves like in the sieve analysis. The analysis measures the rate of sedimentation. The larger the particle, the quicker it will fall out of sedimentation.

A dispersion mixture is used to help the soil particles into suspension. Because the dispersion mixture increases the specific gravity of the resulting liquid, a composite correction for the hydrometer reading must be applied. It is not possible to read the bottom of the meniscus when it is in a soil-water mixture so a correction must be applied for the variation of temperature of the liquid, and a meniscus correction.


To determine the particle size distribution of a fine-grained soil.


2 Sedimentation Cylinders (1000mL)
Hydrometer (152H)
Dispersing Agent (NaPO3)
Malt Mixer
Beaker (300mL)
Graduated Cylinder (100mL)
Rubber Stopper
Weight Scale (±0.1g)
Wash Bottle
Soil Sample
Jars (Designated Hydrometer Jar with the mixture; the other the Control Jar.)


* A fine grain soil was obtained and it’s soil description was recorded * A 50g sample was obtained
* The 50g sample was placed in mixer cup and mixed with the dispersing agent * Water was added to the half way mark of the...
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