Geology Reference
In-Depth Information
(4.1) If slurry is not formed, but a viscous paste, use a pycnometer
having a larger volume. See No. (1.1) under the Section “Test
Specimen.”
Note 1 —For some soils containing a significant fraction of or-
ganic matter, kerosene is a better wetting agent than water
and may be used in place of water for oven-dried specimens. If
kerosene is used, the entrapped air should only be removed by
use of an aspirator. Kerosene is a flammable liquid that must
be used with extreme caution.
(5) Deairing the Soil Slurry —Entrapped air in the soil slurry can
be removed using either heat (boiling), vacuum or combining heat
and vacuum.
(5.1) When using the heat-only method (boiling), use a duration of
at least 2 h after the soil-water mixture comes to a full boil. Use
only enough heat to keep the slurry boiling. Agitate the slurry as
necessary to prevent any soil from sticking to or drying onto the
glass above the slurry surface.
(5.2) If only a vacuum is used, the pycnometer must be continually
agitated under vacuum for at least 2 h. Continually agitated means
the silt/clay soil solids will remain in suspension, and the slurry is in
constant motion. The vacuum must remain relatively constant and be
sufficient to cause bubbling at the beginning of the deairing process.
(5.3) If a combination of heat and vacuum is used, the pycnometers
can be placed in a warm water bath (not more than 40°C) while ap-
plying the vacuum. The water level in the bath should be slightly be-
low the water level in the pycnometer. If the pycnometer glass becomes
hot, the soil will typically stick to or dry onto the glass. The duration
of vacuum and heat must be at least 1 h after the initiation of boiling.
During the process, the slurry should be agitated as necessary to
maintain boiling and prevent soil from drying onto the pycnometer.
(6) Filling the Pycnometer with Water —Fill the pycnometer with
deaired water by introducing the water through a piece of small-
diameter flexible tubing with its outlet end kept just below the sur-
face of the slurry in the pycnometer or by using the pycnometer
filling tube. If the pycnometer filling tube is used, fill the tube with
water, and close the valve. Place the tube such that the drainage
holes are just at the surface of the slurry. Open the valve slightly
to allow the water to flow over the top of the slurry. As the clear
water layer develops, raise the tube and increase the flow rate. If
the added water becomes cloudy, do not add water above the cali-
bration mark or into the stopper seal area. Add the remaining
water the next day.
(6.1) If using the stoppered iodine flask, fill the flask, such that the
base of the stopper will be submerged in water. Then rest the stop-
per at an angle on the flared neck to prevent air entrapment under
the stopper. If using a volumetric or stoppered flask, fill the flask to
above or below the calibration mark depending on preference.
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