Grain-Size Analysis of Soil (Including Both Mechanical and Hydrometer Analyses) - Soil Properties: Testing, Measurement, and Evaluation - page 124

or demineralized water if necessary so that the cup is more than
half full. Stir for a period of 1 min.
Note 1 —A large-size syringe is a convenient device for han-
dling the water in the washing operation. Other devices in-
clude the wash-water bottle and a hose with nozzle connected
to a pressurized distilled water tank.
(4) Immediately after dispersion, transfer the soil-water slurry to
the glass sedimentation cylinder, and add distilled or demineral-
ized water until the total volume is 1,000 mL.
(5) Using the palm of the hand over the open end of the cylinder (or
a rubber stopper in the open end), turn the cylinder upside down
and back for a period of 1 min to complete the agitation of the slurry
(Note 2). At the end of 1 min set the cylinder in a convenient loca-
tion and take hydrometer readings at the following intervals of
time (measured from the beginning of sedimentation), or as many
as may be needed, depending on the sample or the specification for
the material under test: 2, 5, 15, 30, 60, 250, and 1,440 min. If the
controlled water bath is used, the sedimentation cylinder should be
placed in the bath between the 2- and 5-min readings.
Note 2 —The number of turns during this minute should be ap-
proximately 60, counting the turn upside down and back as
two turns. Any soil remaining in the bottom of the cylinder
during the first few turns should be loosened by vigorous shak-
ing of the cylinder while it is in the inverted position.
(6) When it is desired to take a hydrometer reading, carefully insert
the hydrometer about 20 to 25 s (seconds) before the reading is due
to approximately the depth it will have when the reading is taken.
As soon as the reading is taken, carefully remove the hydrometer
and place it with a spinning motion in a graduate of clean distilled
or demineralized water.
Note 3 —It is important to remove the hydrometer immediately
after each reading. Readings shall be taken at the top of the
meniscus formed by the suspension around the stem, since it is
not possible to secure readings at the bottom of the meniscus.
(7) After each reading, take the temperature of the suspension by
inserting the thermometer into the suspension.
(8) After taking the final hydrometer reading, transfer the sus-
pension to a No. 200 sieve and wash with tap water until the wash
water is clear. Transfer the material on the No. 200 sieve to a suit-
able container, dry in an oven at 230 ± 9°F (110 ± 5°C) and make a
sieve analysis of the portion retained, using as many sieves as de-
sired or required for the material, or upon the specification of the
material under test.