PSA Soil Sand Separates

Sand Separates

Environmental Soils and Biogeochemistry Characterization Laboratory

As part of Particle Size Distribution Analysis

Sand Separation

  1. Remove the sample from the shaker and pour through a Tyler no. 270 [300-mesh] sieve mounted on a ring stand.
  2. Place a funnel below the sieve and a 1 L cylinder below the funnel. Collect the silt and clay in the 1 L cylinder. Avoid using jets of water in washing the sample. Wash and rub all particles from the centrifuge bottle into the sieve. Continue to wash until the suspension volume in the cylinder is ~ 800 mL.  Sand and some of the coarse silt remain on the sieve. Rinse all
  3. Fill the cylinder to 1 L and cover with a 65-mm watch glass.
  4. Prepare a distilled water and dispersant blank to measure temperature fluctuations and contributions of the dispersant salts. Allow the cylinder to stand overnight to equilibrate the suspension with the room temperature.
  5. Weigh and mark a sand evaporation dish (a 400 ml beaker or quart canning jar works well) and record the weight.
  6. Wash the sand into the evaporation dish and dry the sand at 105°C overnight.
  7. Weigh the oven dried sand and beaker and record the weight.

To fractionate the sand

    1. Transfer the dried sand to a nest of sieves that has a top-to-bottom order of 1.0, 0.5, 0.25, 0.1, and 0.047 mm.
    2. Shake the sand for 3 min on a shaker that has 1.3 cm vertical and lateral movements and oscillates at 500 strokes min-1. Record the weight of each separate sand fraction (SWi ) to the nearest mg.
    3. Place sand fractions in labeled storage.

TW = Total weight (g), recorded to the nearest mg.

SWi = Weight of the sand fractions (1.0, 0.5, 0.25, 0.1, and 0.047mm)

Sand % = ∑ (SWi / TW) x 100

It is not uncommon when sieving the sand fraction to discover that some silt was included in the sand fraction. This value can be added back into the silt calculation after the sand separates are determined.

Determining the percentage by mass of the sand separates is especially important for any textural class that has sand in its name to determine the textural subclass. See the Soil Survey Manual (Soil Survey Staff, 1993).

References

Soil Survey Staff. 2004. Soil Survey Laboratory Methods Manual. pp 55-59. SSIR no. 42 Ver. 4. [See procedure 3A].

Soil Survey Staff. 1993. Soil Survey Manual. pp 136-140. USDA Handbook no. 18. Washington, DC.

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