Figure 13-14.—ASTM hydrometer.
Figure 13-15.—Dispersion cup and stirrer.
will need 30 to 50 grams of air-dry material. When the
flocculating (adhering to each other in clusters) should
sample is mostly sand, you will need approximately 75
be used. After it has soaked for approximately 16 hours,
to 100 grams.
the soil-water slurry is transferred to the dispersion cup
First, place the sample in an evaporating dish. Then
(fig. 13-15) and is mixed for 1 to 10 minutes depending
pour a solution of water (distilled or demineralized) and
on the plasticity of the soil.
a dispersing agent, such as sodium hexametaphosphate,
over the sample to make a soil-water slurry. Only
Next, you transfer the soil-water suspension to a
enough water to submerge the sample completely and
1,000-milliliter (mL) sedimentation cylinder and add
enough dispersing agent to keep the soil particles from
distilled or demineralized water to fill the cylinder to the
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