LaMotte SOIL TEXTURE UNIT 1067 - Manual (Page 2)

3. Use the pipet (0372) to add 1 mL of *Texture Dispersing Reagent
(5644PS) to the sample in Soil Separation Tube “A”. Dilute to line
45 with tap water.
4. Cap and gently shake for two minutes, making sure the soil sample
and water are thoroughly mixed.
The sample is now ready for separation. The separation is accomplished by
allowing a predetermined time for each fraction to settle out of the
solution. Be sure that you continue to gently shake the separation tube up
to the time of the first separation (Step 5).
5. Place Soil Separation Tube “A” in the rack. Allow to stand
undisturbed for exactly 30 seconds.
6. Carefully pour off all the solution into Soil Separation Tube “B”.
Return Tube “A” to the rack. Allow Tube “B” to stand undisturbed for
30 minutes.
7. Carefully pour off the solution from Soil Separation Tube “B” into
Soil Separation Tube “C”. Return Tube “B” to the rack.
8. Add 1 mL of Soil Flocculation Reagent (5643PS) to Soil Separation
Tube “C”. Cap and gently shake for one minute.
9. Place the Soil Separation Tube “C” in the rack and allow to stand
until all the clay in suspension settles. This may require up to 24
hours.
NOTE: Unless there is further use of the clay sample for air drying and study
as described later, it is not necessary to wait for the suspension to settle.
Due to the colloidal nature of clay in solution and its tendency to swell
and form a gel, the portion of clay remaining in Tube “C” is not used to
determine the clay fraction present in the soil. The clay fraction is
calculated by adding the sand and silt fractions and subtracting this total
from the initial volume of soil used for the separation.
EXAMPLE:
Tube “A” Sand 2 Initial Volume 15
+Tube “B” Silt +8 Total “A” & “B” -10
Total “A” & “B” 10 Clay 5
10. Read Soil Separation Tube “A” at top of soil level. To calculate
percentage sand in the soil, divide reading by 15. Multiply by 100.
Record as % sand.
11. Read Soil Separation Tube “B” at top of soil level. To calculate
percentage silt in the soil, divide reading by 15. Multiply by 100.
Record as % silt.